Publications by authors named "Terrance S Chua"

27 Publications

  • Page 1 of 1

Impact of time of onset of symptom of ST-segment elevation myocardial infarction on 1-year rehospitalization for heart failure and mortality.

Am Heart J 2020 06 19;224:1-9. Epub 2020 Mar 19.

National Heart Centre Singapore, Singapore, Singapore; Cardiovascular and Metabolic Disorders Program, Duke-National University of Singapore, Singapore, Singapore; The Hatter Cardiovascular Institute, University College London, London, UK; Cardiovascular Research Center, College of Medical and Health Sciences, Asia University, Taiwan; Yong Loo Lin School of Medicine, National University Singapore, Singapore, Singapore; Tecnologico de Monterrey, Centro de Biotecnologia-FEMSA, Nuevo Leon, Mexico. Electronic address:

Circadian patterns in ST-segment elevation myocardial infarction (STEMI) patients have been previously reported, but little is known about the impact of time dependence of symptom onset on long-term prognosis. Our study population consisted of 11,731 STEMI patients treated by primary percutaneous coronary intervention (PPCI), enrolled in the Singapore Myocardial Infarction Registry (SMIR). Analysis of STEMI incidence trends over the 24-hour period showed the highest rate of symptom onset in the morning, with the peak incidence at 09:00 am. Patients with symptom onset in between 00:00 am-5:59 am showed the highest prevalence of diabetes (P = .010) and anterior STEMI (P < .001) and had the longest ischemic time (P < .001). After adjusting for confounders, we found an association between time of symptom onset of STEMI and rehospitalization for heart failure (HF) at 1 year, with symptom onset between 06:00 pm-11:59 pm and 00:00 am-05:59 am having an estimated 30% to 50% higher risk of rehospitalization for HF at 1 year. Moreover, symptom onset remained a predictor of worse prognosis only in the subgroup of patients with symptoms lasting longer than 120 minutes. The results of this study demonstrate for the first time that rehospitalization for HF in STEMI patients treated with PPCI has a dependence on the time of onset of symptoms, with prolonged ischemia time playing a pivotal role. This may be an additional risk factor to identify those who warrant closer monitoring and more rigorous optimization of their treatment at follow-up, to improve their outcomes.
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http://dx.doi.org/10.1016/j.ahj.2020.03.011DOI Listing
June 2020

Prevalence of Brugada Syndrome in a Large Population of Young Singaporean Men.

Circulation 2020 01 13;141(2):155-157. Epub 2020 Jan 13.

Medical Classification Centre, Central Manpower Base (X.S., B.Y.Q.T., C.H.S., J.S.W.L., M.D., K.W., D.Y.Z.L., G.G.R.S., E.C.Y.L., C.K.W.K., T.J.Y., D.T.T.C.), Singapore Armed Forces.

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http://dx.doi.org/10.1161/CIRCULATIONAHA.119.043670DOI Listing
January 2020

Independent Predictors of Cardiac Mortality and Hospitalization for Heart Failure in a Multi-Ethnic Asian ST-segment Elevation Myocardial Infarction Population Treated by Primary Percutaneous Coronary Intervention.

Sci Rep 2019 07 11;9(1):10072. Epub 2019 Jul 11.

The Hatter Cardiovascular Institute, Institute of Cardiovascular Science, University College London, London, United Kingdom.

We aimed to identify independent predictors of cardiac mortality and hospitalization for heart failure (HHF) from a real-world, multi-ethnic Asian registry [the Singapore Myocardial Infarction Registry] of ST-segment elevation myocardial infarction (STEMI) patients treated by primary percutaneous coronary intervention. 11,546 eligible STEMI patients between 2008 and 2015 were identified. In-hospital, 30-day and 1-year cardiac mortality and 1-year HHF rates were 6.4%, 6.8%, 8.3% and 5.2%, respectively. From the derivation cohort (70% of patients), age, Killip class and cardiac arrest, creatinine, hemoglobin and troponin on admission and left ventricular ejection fraction (LVEF) during hospitalization were predictors of in-hospital, 30-day and 1-year cardiac mortality. Previous ischemic heart disease (IHD) was a predictor of in-hospital and 30-day cardiac mortality only, whereas diabetes was a predictor of 1-year cardiac mortality only. Age, previous IHD and diabetes, Killip class, creatinine, hemoglobin and troponin on admission, symptom-to-balloon-time and LVEF were predictors of 1-year HHF. The c-statistics were 0.921, 0.901, 0.881, 0.869, respectively. Applying these models to the validation cohort (30% of patients) showed good fit and discrimination (c-statistic 0.922, 0.913, 0.903 and 0.855 respectively; misclassification rate 14.0%, 14.7%, 16.2% and 24.0% respectively). These predictors could be incorporated into specific risk scores to stratify reperfused STEMI patients by their risk level for targeted intervention.
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http://dx.doi.org/10.1038/s41598-019-46486-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6624280PMC
July 2019

Sex Differences in 1-Year Rehospitalization for Heart Failure and Myocardial Infarction After Primary Percutaneous Coronary Intervention.

Am J Cardiol 2019 06 19;123(12):1935-1940. Epub 2019 Mar 19.

National University Heart Centre, National University Hospital, Singapore; Cardiovascular Research Institute, National University of Singapore, Singapore; Yong Loo Lin School of Medicine, National University of Singapore, Singapore. Electronic address:

It is unclear whether universal access to primary percutaneous coronary intervention (pPCI) may reduce sex differences in 1-year rehospitalization for heart failure (HF) and myocardial infarction (MI) after ST-elevation myocardial infarction (STEMI). We studied 7,597 consecutive STEMI patients (13.8% women, n = 1,045) who underwent pPCI from January 2007 to December 2013. Cox regression models adjusted for competing risk from death were used to assess sex differences in rehospitalization for HF and MI within 1 year from discharge. Compared with men, women were older (median age 67.6 vs 56.0 years, p < 0.001) with higher prevalence of co-morbidities and multivessel disease. Women had longer median door-to-balloon time (76 vs 66 minutes, p < 0.001) and were less likely to receive drug-eluting stents (19.5% vs 24.1%, p = 0.001). Of the medications prescribed at discharge, fewer women received aspirin (95.8% vs 97.6%, p = 0.002) and P2Y antagonists (97.6% vs 98.5%, p = 0.039), but there were no significant sex differences in other discharge medications. After adjusting for differences in baseline characteristics and treatment, sex differences in risk of rehospitalization for HF attenuated (hazard ratio [HR] 1.05, 95% confidence interval [CI] 0.79 to 1.40), but persisted for MI (HR 1.68, 95% CI 1.22 to 2.33), with greater disparity in patients aged ≥60 years (HR 1.83, 95% CI 1.18 to 2.85) than those aged <60 years (HR 1.45, 95% CI 0.84 to 2.50). In conclusion, in a setting of universal access to pPCI, the adjusted risk of 1-year rehospitalization for HF was similar in both sexes, but women had significantly higher adjusted risk of 1-year rehospitalization for MI, especially older women.
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http://dx.doi.org/10.1016/j.amjcard.2019.03.021DOI Listing
June 2019

A Population-wide study of electrocardiographic (ECG) norms and the effect of demographic and anthropometric factors on selected ECG characteristics in young, Southeast Asian males-results from the Singapore Armed Forces ECG (SAFE) study.

Ann Noninvasive Electrocardiol 2019 05 1;24(3):e12634. Epub 2019 Feb 1.

Medical Classification Centre, Central Manpower Base, Singapore Armed Forces, Singapore, Singapore.

Background: Routine use of pre-participation electrocardiograms (ECGs) has been used by the Singapore Armed Forces, targeting early detection of significant cardiac diseases. We aim to describe the impact of demographic and anthropometric factors on ECG variables and establish a set of electrocardiographic reference ranges specific to a young male multiethnic Southeast Asian cohort.

Methods And Results: Between November 1, 2009, and December 31, 2014, 144,346 young male conscripts underwent pre-participation screening that included a 12-lead ECG, demographic and anthropometric measurements. The Chinese population had the longest PR interval (146.7 ± 19.7 vs. 145.21 ± 19.2 in Malays vs. 141.2 ± 18.8 ms in Indians), QRS duration (94.5 ± 9.8 vs. 92.6 ± 9.7 in Malays vs. 92.5 ± 9.4 ms in Indians) and QTcB interval (408.3 ± 21.3 vs. 403.5 ± 21.6 in Malays vs. 401.2 ± 21.4 ms in Indians) (all p < 0.001). Body mass index (BMI) >25 kg/m and body fat >25% were independently associated with lower prevalence of increased QRS voltage on ECG. Systolic blood pressure of >140 mmHg or diastolic blood pressure of >90 mmHg independently increased the prevalence of increased QRS voltage on ECG.

Conclusions: Electrocardiographic parameters vary across different ethnicities and in comparison with international norms. In our population, diagnosis of increased QRS voltage by ECG is less prevalent with obesity and increased body fat. Further analysis of gold standard measurements for the diagnosis of LVH in our population is ongoing, to improve the accuracy of the ECG screening process.
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http://dx.doi.org/10.1111/anec.12634DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6931495PMC
May 2019

Platelet inhibition to target reperfusion injury trial: Rationale and study design.

Clin Cardiol 2019 Jan 17;42(1):5-12. Epub 2018 Dec 17.

The Hatter Cardiovascular Institute, Institute of Cardiovascular Science, University College London, London, UK.

Background: In ST-segment elevation myocardial infarction (STEMI) patients treated with primary percutaneous coronary intervention (PPCI), current oral P2Y12 platelet inhibitors do not provide maximal platelet inhibition at the time of reperfusion. Furthermore, administration of cangrelor prior to reperfusion has been shown in pre-clinical studies to reduce myocardial infarct (MI) size. Therefore, we hypothesize that cangrelor administered prior to reperfusion in STEMI patients will reduce the incidence of microvascular obstruction (MVO) and limit MI size in STEMI patients treated with PPCI.

Methods: The platelet inhibition to target reperfusion injury (PITRI) trial, is a phase 2A, multi-center, double-blinded, randomized controlled trial, in which 210 STEMI patients will be randomized to receive either an intravenous (IV) bolus of cangrelor (30 μg/kg) followed by a 120-minute infusion (4 μg/kg/min) or matching saline placebo, initiated prior to reperfusion (NCT03102723).

Results: The study started in October 2017 and the anticipated end date would be July 2020. The primary end-point will be MI size quantified by cardiovascular magnetic resonance (CMR) on day 3 post-PPCI. Secondary endpoints will include markers of reperfusion, incidence of MVO, MI size, and adverse left ventricular remodeling at 6 months, and major adverse cardiac and cerebrovascular events.

Summary: The aim of the PITRI trial is to assess whether cangrelor administered prior to reperfusion would reduce acute MI size and MVO, as assessed by CMR.
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http://dx.doi.org/10.1002/clc.23110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6436500PMC
January 2019

Long-Term Prognostic Value of Appropriate Myocardial Perfusion Imaging.

Am J Cardiol 2017 06 29;119(12):1957-1962. Epub 2017 Mar 29.

National Heart Centre Singapore, Singapore, Singapore; Duke-National University of Singapore Medical School, Singapore, Singapore.

Appropriate use criteria (AUC) for single-photon emission computed tomography myocardial perfusion images (SPECT-MPIs) were developed to address the growth of cardiac imaging studies. Long-term prognostic value of AUC in SPECT-MPI has not been tested in existing cohorts. We sought to determine the long-term prognostic value of MPI classified as appropriate. AUC was evaluated in a prospectively designed cohort of patients who underwent clinically indicated MPI. MPI studies were classified based on 2009 AUC for SPECT-MPI. Data regarding downstream coronary angiography (cath), revascularization and all-cause mortality, cardiac death, and nonfatal myocardial infarction (MI) were collected from national registries. Among n = 1,129 MPI scans that received an appropriate grading, 148 all-cause deaths, 109 MIs, 58 cardiac deaths, 152 caths, 113 revascularization procedures occurred over a mean follow-up period of 5.4 ± 1.2 years (0.9% cardiac death rate per year, 1.8% MI rate per year). Most of the scans were low-risk normal MPI scans (summed stress score ≤3; 74.1%). An abnormal scan was associated with higher rates of MI (19.5% vs 6.2%, hazard ratio 1.72, p = 0.017) and cardiac death (13.4% vs 2.3%, hazard ratio 2.12, p = 0.016). In conclusion, MPI scans classified as appropriate have long-term prognostic value, despite a high proportion of low-risk scans. This provides support for clinicians to consider the use of appropriate grading in addition to MPI scan results in patient management.
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http://dx.doi.org/10.1016/j.amjcard.2017.03.026DOI Listing
June 2017

Differential risk reclassification improvement by exercise testing and myocardial perfusion imaging in patients with suspected and known coronary artery disease.

J Nucl Cardiol 2016 06 11;23(3):366-78. Epub 2015 Sep 11.

National Heart Centre Singapore, 5 Hospital Drive, Singapore, 169609, Singapore.

Objective: The objective of this study is to compare the incremental prognostic and net risk reclassification value of exercise testing alone vs exercise myocardial perfusion imaging (MPI) for estimating the risk of death in patients with suspected and known coronary artery disease (CAD).

Methods: 6702 patients with suspected CAD and 2008 with known CAD had treadmill exercise MPI and were followed for 2.5 ± 0.9 years for the occurrence of all-cause death. The estimation of risk of death and net reclassification improvement (NRI) were examined in three models. Model 1: clinical variables; Model 2: model 1+Duke Treadmill Score; and Model 3: model 2+ MPI variables. Risk estimates were categorized as <1%, 1-3%, and >3% risk of death per year.

Results: In patients with suspected CAD, the global Chi-square for predicting risk of death increased significantly for Model 2 compared to Model 1 (74.78 vs 63.86 to (P = .001). However, adding MPI variables in Model 3 did not further improve predictive value (Chi-square 79.38, P = .10). In patients with suspected CAD risk, reclassification improved significantly in Model 2 over Model 1 (NRI = 0.12, 95% CI 0.02 to 0.22, P = .019), but not in Model 3 (NRI = 0.0009, 95% CI -0.072 to 0.070; P = .98). In contrast, in patients with known CAD Model 2 did not yield significant improvements for predicting risk and risk reclassification compared to Model 1. However, global Chi-square of Model 3 was significantly higher than that of Model 2 (30.03 vs 6.56, P < .0001) with associated significant reclassification improvement (NRI = 0.26 95% CI 0.067 to 0.46. P = .0084).

Conclusion: Risk reclassification by diagnostic testing is importantly influenced by baseline characteristics of patient cohorts. In patients with suspected CAD, NRI is predominately achieved by exercise variables, whereas in patients with known CAD, greatest NRI is obtained by MPI variables.
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http://dx.doi.org/10.1007/s12350-015-0253-xDOI Listing
June 2016

Intergenerational transfer of blood pressure knowledge and screening: a school-based hypertension awareness program in Singapore.

Glob Health Promot 2016 Mar 17;23(1):27-36. Epub 2014 Dec 17.

Singapore Heart Foundation, Singapore.

Objective: This study aims to examine the efficacy of a hypertension awareness education program in Singapore in reaching out to a wider population of diverse racial and intergenerational cohorts by dispatching grade five children as information intermediaries to their immediate and extended family members.

Method: After receiving structured instruction and training on blood pressure screening, students were requested to share knowledge gained in school with their family members at home and practice blood pressure measurement on family volunteers. We assessed pre- and post-program blood pressure knowledge change, attitude toward screening, and the diffusion of blood pressure information. One adult family member was also asked to complete a short survey at the program end.

Results: A comparison of the students' (final n = 3926) pre- and post-program survey data showed that knowledge and attitudes towards knowledge sharing improved after participating in the program. The post-program survey also revealed that students generally felt confident and displayed positive attitudes in performing blood pressure screening on family members. On average, each student practiced blood pressure measurement on 3.04 people. Female family members were more likely to be targeted for knowledge sharing and screening than male family members. The family members' survey revealed positive attitudes towards screening, but family members were not confident about getting their measurements done regularly.

Conclusion: The program met its objectives in raising the awareness of grade five children and provision of knowledge. It also met the larger objective of raising hypertension awareness in a wider population, especially those who otherwise might not directly receive health education and blood pressure screening.
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http://dx.doi.org/10.1177/1757975914555730DOI Listing
March 2016

Single-photon emission computed tomography myocardial perfusion imaging-assessed stress perfusion defect severity is associated with mortality independent of ethnicity in an Asian population.

J Nucl Cardiol 2014 Dec 28;21(6):1148-57. Epub 2014 Aug 28.

Department of Cardiology, National Heart Centre Singapore, Singapore, Singapore,

Background: Ischemic heart disease is growing by epidemic proportions in Asia. Among patients in Western populations with similar myocardial perfusion imaging (MPI) ischemia severity, ethnicity is independently associated with mortality. We aimed to determine the differential prognostic value of MPI abnormality severity among three major Asian ethnic groups.

Methods: From 16,921 consecutive patients, we used summed stress score to define increasing abnormal scan severity groups (minimal, mild, moderate, and severe) among Chinese, Indian, and Malay patients. We determined mortality from the national death registry. Using multivariable Cox regression models, we examined the association between ethnicity and mortality.

Results: Chinese patients were older than Indians or Malays. Annual all-cause death rates increased with increasing abnormal scan severity in all three ethnicities. After adjustment, ethnicity was not associated with mortality. With Chinese as the reference group, adjusted hazard ratio and 95% CI for Malays and Indians were 1.29 (0.95-1.77) and 1.06 (0.74-1.50) in the minimally abnormal scan group, and 1.20 (0.75-1.91) and 0.82 (0.47-1.45) in the severely abnormal scan group, respectively.

Conclusions: Mortality risk is related to the severity of scan abnormality and is independent of ethnicity in Asians. Our findings emphasize the continued utility of MPI in guiding risk stratification in Asia.
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http://dx.doi.org/10.1007/s12350-014-9988-zDOI Listing
December 2014

Myocardial contractile dysfunction associated with increased 3-month and 1-year mortality in hospitalized patients with heart failure and preserved ejection fraction.

Int J Cardiol 2013 Oct 19;168(3):1975-83. Epub 2013 Jan 19.

National Heart Centre Singapore, Singapore; Duke-NUS Graduate Medical School, Singapore, Singapore. Electronic address:

Background: There is a clinical need for a contractility index that reflects myocardial contractile dysfunction even when ejection fraction (EF) is preserved. We used novel relative load-independent global and regional contractility indices to compare left ventricular (LV) contractile function in three groups: heart failure (HF) with preserved ejection fraction (HFPEF), HF with reduced ejection fraction (HFREF) and normal subjects. Also, we determined the associations of these parameters with 3-month and 1-year mortality in HFPEF patients.

Methods: 199 HFPEF patients [median age (IQR): 75 (67-80) years] and 327 HFREF patients [69 (59-76) years] were recruited following hospitalization for HF; 22 normal control subjects [65 (54-71) years] were recruited for comparison. All patients underwent standard two-dimensional Doppler and tissue Doppler echocardiography to characterize LV dimension, structure, global and regional contractile function.

Results: The median (IQR) global LV contractility index, dσ*/dtmax was 4.30s(-1) (3.51-4.57s(-1)) in normal subjects but reduced in HFPEF [2.57 (2.08-3.64)] and HFREF patients [1.77 (1.34-2.30)]. Similarly, median (IQR) regional LV contractility index was 99% (88-104%) in normal subjects and reduced in HFPEF [81% (66-96%)] and HFREF [56% (41-71%)] patients. Multi-variable logistic regression analysis on HFPEF identified sc-mFS <76% as the most consistent predictor of both 3-month (OR=7.15, p<0.05) and 1-year (OR=2.57, p<0.05) mortality after adjusting for medical conditions and other echocardiographic measurements.

Conclusion: Patients with HFPEF exhibited decreased LV global and regional contractility. This population-based study demonstrated that depressed regional contractility index was associated with higher 3-month and 1-year mortality in HFPEF patients.
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http://dx.doi.org/10.1016/j.ijcard.2012.12.084DOI Listing
October 2013

Iliofemoral anatomy among Asians: implications for transcatheter aortic valve implantation.

Int J Cardiol 2013 Aug 21;167(4):1373-9. Epub 2012 Apr 21.

Department of Cardiology, National Heart Centre Singapore, Singapore.

Background/objectives: This study aims to examine iliofemoral anatomy and predictors of vessel size and tortuosity in Asian patients as transfemoral transcatheter aortic valve implantation (TAVI) may be limited by the smaller Asian physique.

Methods: Characteristics and vessel dimensions of 549 patients undergoing ultrasonography were reviewed. The minimal luminal diameter (MLD) along the iliofemoral vasculature of each side was identified and the larger of the two sides was used to determine suitability for transfemoral TAVI.

Results: The mean age was 66 ± 11 years (68% males). Mean iliac MLD was 7.6 ± 1.7 mm, females smaller than males (7.2 ± 1.7 vs 7.8 ± 1.7, p<0.001). Mean iliac MLD decreased with age: 7.9 ± 1.7 mm, 7.4 ± 1.9 mm and 7.3 ± 1.6mm for ages <70 years, 70-79 years and ≥ 80 years respectively (p=0.038). Mean femoral MLD was 7.0 ± 1.7 mm, females smaller than males (6.3 ± 1.5mm vs 7.3 ± 1.8mm, p<0.001). Females were more likely than males to have iliac and femoral MLD <6mm (20% vs 12%, p=0.019 and 34% vs 21%, p=0.001). Independent predictors of smaller iliofemoral dimensions were female gender, lower body surface area, diabetes mellitus, dyslipidemia and smoking history. Significant iliac tortuosity was present in 11.8%, more frequent in males than females (15% vs 6%, p=0.005), and in those with logistic EuroSCORE ≥ 15 than <15 (27% vs 10%, p=0.001).

Conclusions: This study establishes the mean iliac and femoral artery diameters in a cohort of relatively young Asian patients. Age and female gender were associated with smaller vessel dimension and several independent predictors of smaller vasculature and tortuosity were identified. These results have implications for TF TAVI in Asia.
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http://dx.doi.org/10.1016/j.ijcard.2012.04.001DOI Listing
August 2013

Correlation between clinical outcomes and appropriateness grading for referral to myocardial perfusion imaging for preoperative evaluation prior to non-cardiac surgery.

J Nucl Cardiol 2012 Apr;19(2):277-84

Department of Cardiology, National Heart Centre Singapore, Singapore, Singapore.

Background: In a previous study, we have found that referral to myocardial perfusion imaging(MPI) for preoperative evaluation of patients before non-cardiac surgery was the most common cause of inappropriate referral based on AHA/ACC Appropriate Use Guidelines, though 40% of scans graded as inappropriate had abnormal MPI results. The aim of this study was to correlate appropriateness grading with (1) the outcome of MPI scans, and (2) the clinical outcome of patients after surgery, so as to determine if the predictive value of MPI was related to appropriateness grading.

Methods: All consecutive patients referred to the MPI laboratory of our center from March 2009 to July 2009 for preoperative risk stratification were prospectively studied. Patients’ medical records and stress data were collected, and all imaging results were recorded. Based on appropriate use criteria (AUC), MPI studies were classified into appropriate, inappropriate, uncertain or unclassified. MPI studies were classified on the basis of their results into normal or abnormal scans. Primary clinical outcome measured was the occurrence of any major cardiac and cerebrovascular event during follow-up up to 90 days.

Results: There were 176 referrals for preoperative evaluation. 39.8% (n 5 70) of these referrals were graded as inappropriate. Based on AUC, referrals for MPI in intermediate- and high-risk groups with poor functional class were graded as appropriate, while referrals for MPI in low-risk and intermediate risk groups with normal functional class were graded as inappropriate referrals. The overall event rate was 6.25%. Cumulative death rate at 90 days was 1.7%, non-fatal MI 4%, and occurrence of stroke occurred in 0.6%. The primary outcome was higher in the intermediate group with poor functional class (13%) and high-risk group (64%) than the low-risk and intermediate risk groups with good functional class (4%). In the high-risk group, an abnormal MPI scan was associated with an extremely high event rate (50%) that was significantly greater than the event rate in patients with a normal MPI result (14%) (P 5 .01). Although 40% of preoperative low-risk and intermediate risk patients had an abnormal MPI result, their over all event rates were low (0 and 4%, respectively), with no difference in the rate of events between patients with normal and abnormal MPI scans in the inappropriate group.

Conclusions: In conclusion, in correlating the relationship between appropriateness grading by AUC with the outcome of MPI scans and subsequent event rates, we found that MPI results predicted outcome in appropriately tested patients, but not in patients whose tests were classified as inappropriate, in whom event rates were low, regardless of the results of testing. Our findings support the AUC recommendations for the selective role of testing in preoperative risk stratification,which use the type of surgery and functional class to determine the appropriateness of referral.
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http://dx.doi.org/10.1007/s12350-011-9462-0DOI Listing
April 2012

Prevalence of electrocardiographic abnormalities in an unselected young male multi-ethnic South-East Asian population undergoing pre-participation cardiovascular screening: results of the Singapore Armed Forces Electrocardiogram and Echocardiogram screening protocol.

Europace 2012 Jul 2;14(7):1018-24. Epub 2012 Feb 2.

Medical Classification Centre, Central Manpower Base, Singapore Armed Forces, 3 Depot Road, Singapore 109680.

Aims: Resting 12-lead electrocardiograms (ECGs) have been employed in the pre-participation evaluation of young asymptomatic subjects to detect pre-existing heart diseases. Although the incorporation of routine ECG in pre-participation screening remains controversial, there is increasing evidence that cardiomyopathies and ion channelopathies have ECG changes as the initial manifestation. The causes of sudden cardiac death in young people show significant geographical variation. We aim to determine the prevalence and spectrum of ECG abnormalities in a young male South-East Asian population.

Methods And Results: The Singapore Armed Forces Electrocardiogram and Echocardiogram (SAFE) protocol is an ECG-based pre-participation cardiac screening programme modelled after the Italian system. From October 2008 to May 2009, a total of 18 476 young male conscripts (mean age 19.5 years old, range 16-27) underwent mandatory pre-enlistment medical screening at a single medical facility. Subjects with abnormal ECG findings were classified into two groups: Group A had ECG changes that fulfilled a pre-specified checklist to screen for hypertrophic cardiomyopathy and were referred for transthoracic echocardiogram; Group B had other ECG abnormalities [such as Brugada pattern, Wolff-Parkinson-White (WPW) pattern, long QTc] and were referred for secondary screening at a tertiary institution. Of the 18 476 subjects screened, 7.0% (n= 1285) had ECG abnormalities. Of note, 19 (0.10%) had Brugada pattern, 25 (0.14%) had WPW pattern, and 31 (0.17%) had prolonged QT interval on ECG. The prevalence of ECG abnormalities was significantly higher in Chinese than in South Asians (7.2 vs. 5.7%, P= 0.003).

Conclusion: The prevalence of ECG abnormalities in a young, South-East Asian male population was 7.0%. There were significant ethnic differences, with ECG abnormalities more prevalent in Chinese than in South Asians (7.2 vs. 5.7%, P= 0.003). The inclusion of universal ECG, in addition to history and physical examination, may increase the sensitivity of a cardiovascular screening programme. Knowledge of the spectrum and prevalence of ECG abnormalities and disease conditions would be pivotal in designing customized screening programmes.
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http://dx.doi.org/10.1093/europace/eur424DOI Listing
July 2012

Comparing the use of cobalt chromium stents to stainless steel stents in primary percutaneous coronary intervention for acute myocardial infarction: a prospective registry.

Acute Card Care 2011 Dec;13(4):219-22

Department of Cardiology, National Heart Centre Singapore, Singapore.

Objectives: To determine clinical outcome and rates of target vessel revascularization (TVR) in patients undergoing primary percutaneous coronary intervention (PCI) for STEMI who were treated with cobalt-chromium stents compared to stainless steel bare metal stents (BMS).

Background: The newer generation cobalt chromium stents were reported to achieve lower rates of TVR compared with conventional BMS.

Methods: Consecutive STEMI cases admitted within 12 h of symptom onset and undergoing primary angioplasty and bare metal stent implantation 1 January 2002 and 31 December 2008 were identified. Primary outcomes were rates of clinically-driven TVR at six months as well as occurrence of major adverse cardiovascular events (MACE) either of all-cause death, repeat myocardial infarction or TVR at six months.

Results: 1030 cases with 1175 lesions (84% males) and median age of 58 years underwent primary PCI for STEMI in our registry. Overall procedural success rate was 98%. Stainless steel stents were inserted in 65% of the culprit lesions (stainless steel, n = 766 versus cobalt chromium, n = 264). Primary outcomes of TVR (3.5% in the stainless steel group and 3.4% in the cobalt chromium group, P = 0.93) and MACE (8.4% in the stainless steel group and 5.3% in the cobalt chromium group, P = 0.11) after six months were no different between the two groups. However, there were more deaths at 30 days in the stainless steel group compared to the cobalt chromium group (3.5% versus 0.4%, HR 4.04 (1.03-3.88), P = 0.04).

Conclusion: Both cobalt-chromium and stainless steel coronary stents were associated with similar and low risk of clinically-driven TVR.
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http://dx.doi.org/10.3109/17482941.2011.634011DOI Listing
December 2011

Percutaneous coronary intervention in Asians--are there differences in clinical outcome?

BMC Cardiovasc Disord 2011 May 23;11:22. Epub 2011 May 23.

National Heart Centre Singapore, Singapore.

Background: Ethnic differences in clinical outcome after percutaneous coronary intervention (PCI) have been reported. Data within different Asian subpopulations is scarce. We aim to explore the differences in clinical profile and outcome between Chinese, Malay and Indian Asian patients who undergo PCI for coronary artery disease (CAD).

Methods: A prospective registry of consecutive patients undergoing PCI from January 2002 to December 2007 at a tertiary care center was analyzed. Primary endpoint was major adverse cardiovascular events (MACE) of myocardial infarction (MI), repeat revascularization and all-cause death at six months.

Results: 7889 patients underwent PCI; 7544 (96%) patients completed follow-up and were included in the analysis (79% males with mean age of 59 years ± 11). There were 5130 (68%) Chinese, 1056 (14%) Malays and 1001 (13.3%) Indian patients. The remaining 357 (4.7%) patients from other minority ethnic groups were excluded from the analysis. The primary end-point occurred in 684 (9.1%) patients at six months. Indians had the highest rates of six month MACE compared to Chinese and Malays (Indians 12% vs. Chinese 8.2% vs. Malays 10.7%; OR 1.55 95%CI 1.24-1.93, p < 0.001). This was contributed by increased rates of MI (Indians 1.9% vs. Chinese 0.9% vs. Malays 1.3%; OR 4.49 95%CI 1.91-10.56 p = 0.001), repeat revascularization (Indians 6.5% vs. Chinese 4.1% vs. Malays 5.1%; OR 1.64 95%CI 1.22-2.21 p = 0.0012) and death (Indians 11.4% vs. Chinese 7.6% vs. Malays 9.9%; OR 1.65 95%CI 1.23-2.20 p = 0.001) amongst Indian patients.

Conclusion: These data indicate that ethnic variations in clinical outcome exist following PCI. In particular, Indian patients have higher six month event rates compared to Chinese and Malays. Future studies are warranted to elucidate the underlying mechanisms behind these variations.
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http://dx.doi.org/10.1186/1471-2261-11-22DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114787PMC
May 2011

Prevalence of hypertrophic cardiomyopathy on an electrocardiogram-based pre-participation screening programme in a young male South-East Asian population: results from the Singapore Armed Forces Electrocardiogram and Echocardiogram screening protocol.

Europace 2011 Jun 12;13(6):883-8. Epub 2011 Apr 12.

Medical Classification Centre, Central Manpower Base, Singapore Armed Forces, 3 Depot Road, Singapore 109680, Singapore.

Aims: Hypertrophic cardiomyopathy is a leading cause of sudden cardiac death (SCD) in young people in the USA. Pre-participation screening for athletes might reduce the incidence of SCD. In Singapore, military service is compulsory for all young able-bodied male citizens. The Singapore Armed Forces Electrocardiogram and Echocardiogram (SAFE) pre-participation screening protocol based on the Italian programme was introduced. This study evaluates the prevalence of hypertrophic cardiomyopathy (HCM) in a young male South-East Asian population.

Methods And Results: From October 2008 to May 2009, all male military conscripts underwent pre-participation screening. For all conscripts whose electrocardiogram (ECG) findings fulfilled any of these pre-specified criteria (Group A), direct referral for a transthoracic echocardiogram was mandatory. Conscripts with ECG findings other than pre-specified criteria (e.g. T-wave inversions, repolarization abnormalities) were referred for secondary screening by cardiologists (Group B), which could include echocardiography. Out of 18 476 subjects screened during the study period, 988 (5.3%) subjects were fast tracked for echocardiogram (Group A). Of them, there were three (0.3%) cases with severe abnormalities; there was one case each of HCM, bicuspid aortic valve with significant aortic valve regurgitation, and atrial septal defect with right ventricular systolic dysfunction. The patient with HCM had left axis deviation on ECG. None of the 215 patients who underwent echocardiography following cardiology consult (Group B) had HCM.

Conclusion: The prevalence of HCM in our young male population (mean age 19.5, range 16-27) using an ECG-based screening protocol was 0.005%; this appeared lower than published data from other geographical cohorts. Possible explanations include a later age of phenotypic manifestation in our population, limitations of the ECG criteria for screening, or a truly lower prevalence of HCM. More population-based longitudinal studies would be needed to ascertain the true prevalence of HCM in our South-East Asian population.
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http://dx.doi.org/10.1093/europace/eur051DOI Listing
June 2011

Long-term outcomes after coronary bare-metal-stent and drug-eluting-stent implantations: a 'real-world' comparison among patients with diabetes with diffuse small vessel coronary artery disease.

Coron Artery Dis 2011 Mar;22(1):96-9

National Heart Centre, Singapore, Singapore.

Background And Aim: Drug-eluting stents (DESs) have been reported to be more efficacious compared with bare-metal stents (BMSs) in reducing the need for target vessel revascularization (TVR). However, the long-term benefits for patients with diabetes with small vessel disease are less certain. We aim to determine the clinical outcome of patients with diabetes with diffuse small vessel coronary artery disease who undergo percutaneous coronary intervention.

Methods: This is a single-center prospective registry of all patients with diabetes with target lesions implanted with stents that were 2.25 mm or less in diameter and approximately 20 mm in total stent length between January 2002 and October 2008. Primary outcome was combined major adverse cardiovascular events: death, nonfatal myocardial infarction and TVR up to 5 years. Outcomes were adjusted for age, sex and cardiovascular risk factors.

Results: There were 544 patients (63% males, mean age 62±10 years) with 1010 lesions that were followed up for a mean duration of 3±2 years. Two hundred and thirty-nine patients (439 lesions) received BMS whereas 305 (571 lesions) received DES. DES lesions were longer (mean length 23.3±6.96 vs. 17.8±5.02 mm, P<0.001) than BMS lesions. Procedural success was similar for BMS and DES patients (86.2 vs. 86.6%, P=0.90). DES patients had less TVR at 6 months [3.9 vs. 9.2%, odds ratio (OR): 4.90, 95% confidence interval (CI): 1.53-15.65, P=0.007], 1 year (1 vs. 3.8%, OR: 8.01, 95% CI: 1.25-51.10, P=0.028) and 3 years (13.8 vs. 18.0%, OR: 5.50, 95% CI: 3.74-8.13, P=0.043). By 5 years, the primary outcome was lower in DES patients (21.6 vs. 28%, OR: 1.79, 95% CI: 1.14-2.80, P=0.011). Independent predictors of TVR at 6 months were above or equal to 59 years of age (OR: 0.95, 95% CI: 0.90-1.00, P=0.032) and use of glycoprotein-IIbIIIa inhibitors (OR: 0.02, 95% CI: 0.001-0.50, P=0.018). Stent length was not a significant predictor of TVR.

Conclusion: Our observational analysis suggests that DES seems to have short-term and mid-term advantages over BMS in reducing TVR and overall major adverse cardiovascular events. Percutaneous coronary intervention with DES may be considered as an option in these patients with limited revascularization options.
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http://dx.doi.org/10.1097/MCA.0b013e32834236d0DOI Listing
March 2011

Evaluation of the American College of Cardiology Foundation/American Society of Nuclear Cardiology appropriateness criteria for SPECT myocardial perfusion imaging in an Asian tertiary cardiac center.

J Nucl Cardiol 2011 Apr 24;18(2):324-30. Epub 2010 Nov 24.

Department of Cardiology, National Heart Centre, Mistri Wing, Third Hospital Avenue, Singapore 168752, Singapore.

Background: Appropriate use criteria (AUC) for SPECT MPI have been published to address concern about the growth of cardiac imaging studies and the effective use of imaging, but there is no published data on its role outside the United States.

Methods: All consecutive patients referred to the MPI laboratory of our center from February 16 to June 19, 2009 were prospectively studied. Patients' medical records and stress data were collected and all imaging results were recorded. Based on AUC, MPI studies were classified into appropriate, inappropriate, uncertain, or unclassified. MPI studies were classified on the basis of their results into normal or abnormal scans.

Results: There were 1,623 patients (mean age 61 years ± 11, 61% males). Most common indications for SPECT were evaluation of ischemic equivalent for coronary artery disease (CAD), risk assessment post-revascularization, and preoperative evaluation for non-cardiac surgery. 10% of referrals were classified as inappropriate, 5% uncertain, and 3% unclassified. Women (48.4% vs 40.6% for men, P = .063) and asymptomatic patients (50.2% vs 14.3% for symptomatic, P < .001) had a higher proportion of inappropriate studies. The preoperative group had the highest proportion of inappropriate studies (59%). Appropriate referrals had a higher proportion of abnormal SPECT results than inappropriate referrals (40% vs 27%, OR 2.08, 95% CI 1.56-2.77, P < .001).

Conclusions: The pattern of referrals for SPECT MPI in an Asian center appears to vary from published reports in the United States. Preoperative evaluation for low-risk surgery appears to be the most common source of inappropriate referrals in our institution. Inappropriate referrals have a higher proportion of normal studies, but 27% were still reported as abnormal.
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http://dx.doi.org/10.1007/s12350-010-9317-0DOI Listing
April 2011

Risk assessment models in acute coronary syndromes and their applicability in Singapore.

Ann Acad Med Singap 2010 Mar;39(3):216-20

National Heart Centre Singapore, Singapore.

Risk prediction models are critical in managing patients with acute coronary syndromes (ACS) as they identify high-risk patients who benefit the most from targeted care. We discuss the process of developing and validating a risk prediction model as well as highlight the more commonly used models in clinical practice currently. Finally we conclude by outlining the importance of creating a risk prediction model based on a Singapore population of ACS patients so as to further improve patient, hospital and research outcomes.
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March 2010

Improving door-to-balloon times in primary percutaneous coronary intervention for acute ST-elevation myocardial infarction: the value of an audit-driven quality initiative.

Ann Acad Med Singap 2008 Jul;37(7):568-72

Department of Emergency Medicine, Singapore General Hospital, Singapore.

Introduction: The study was designed to reduce door-to-balloon times in primary percutaneous coronary intervention for patients presenting to the Emergency Department with acute ST-elevation myocardial infarction, using an audit as a quality initiative.

Materials And Methods: A multidisciplinary work group performed a pilot study over 3 months, then implemented various process and work-flow strategies to improve overall door-to-balloon times.

Results And Conclusion: We developed a guideline-based, institution-specific written protocol for triaging and managing patients who present to the Emergency Department with symptoms suggestive of STEMI, resulting in shortened median door-to-balloon times from 130.5 to 109.5 minutes (P<0.001).
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July 2008

Improving access to outpatient cardiac care at the national heart centre--a partnership between specialists and primary care.

Ann Acad Med Singap 2008 Feb;37(2):151-7

Quality Management Department, Singapore Health Services Pte Ltd, Singapore.

Ensuring timely access to specialist care is an important indicator of the quality of a health service. Demand for cardiology outpatient appointments has grown considerably in the last decade, leading to increased waiting time for cardiology appointments at public hospitals. This paper examines the effectiveness of past and ongoing strategies initiated by the National Heart Centre, many of which were in collaboration with SingHealth Polyclinics, documents the lessons learnt, and provides a framework for approaching this problem. Instead of a simplistic approach where institutions react to long waiting times by growing capacity to meet demand, this paper emphasises the need to focus on the final intended outcome (timely diagnosis and treatment) rather than on a single performance indicator, such as waiting time. A broad systems approach at the national level is advocated, rather than piecemeal, uncoordinated actions by individual hospitals.
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February 2008

Pattern and outcome of subsidised referrals to cardiology specialist outpatient clinics.

Ann Acad Med Singap 2008 Feb;37(2):103-8

Department of Cardiology, National Heart Centre, Singapore.

Introduction: Increasing demand for public healthcare and access to specialist care has become a major concern. Characterising the referral pattern to a national centre's cardiology specialist outpatient clinics (SOCs) and the diagnostic outcomes may be useful in formulating referral guidelines to contain rising demand.

Materials And Methods: A prospective observational followup study was conducted of all consecutive new patient referrals to the cardiology SOCs of the National Heart Centre over a 1-month period. The records of these 1224 patients were reviewed following their first visit and again after 3 months of evaluation and investigation. Patients' demographics, referral sources, indications of referral, risk factors, provisional and final diagnoses were collected. Referrals from the top 2 volume sources (government polyclinics and hospital Emergency Department) accounted for 600 referrals. These subsidised referrals formed the study group for analysis.

Results: The mean age of referred patients was 56 +/- 15.2 years, with equal proportion of males and females. Most patients had known cardiac risk factors of hypertension (53.2%) and hyperlipidaemia (42.3%). Only 23% of referrals had significant cardiac abnormalities. Referrals for typical chest pain derived the highest yield whereas referrals for atypical chest pain, non-cardiac chest pain derived the lowest yield. Referrals for asymptomatic electrocardiogram (ECG) changes (except for atrial flutter/fibrillation) did not yield cardiac abnormalities. Multivariate analysis of chest pain referrals showed typical chest pain and hyperlipidaemia to be statistically significant predictors for coronary artery disease.

Conclusion: Referrals to cardiology outpatient specialist clinics should be based on the presence of patient symptoms, particularly that of typical chest pain. In asymptomatic patients, routine ECG screening did not appear to yield significant cardiac abnormalities.
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February 2008

Trends in mortality from acute myocardial infarction in the coronary care unit.

Ann Acad Med Singap 2007 Dec;36(12):974-9

National Heart Centre, Singapore.

Introduction: The treatment and outcome of acute myocardial infarction (AMI) has evolved greatly over the past few decades. We compared the mortality and complication rates of patients with AMI admitted to the Coronary Care Unit (CCU) in 2002 to previously reported data.

Materials And Methods: All data for AMI patients admitted to National Heart Centre CCU in 2002 were collected through the Singapore Cardiac Data Bank, including demographics, in hospital complications and mortality. These were compared to previous reports from the same institution in 1988, 1975 and 1967.

Results: A total of 516 cases with AMI were identified. A higher proportion of patients were aged >or=70 years in 2002 (31.8%) compared to 1988 (25%), 1975 (11%) and 1967 (5.6%). Acute percutaneous transluminal coronary angioplasty (PTCA) was performed in 250 of 516 (48%) patients in 2002. The overall in-patient and age-standardised mortality was 14.7% and 10% respectively, compared to 20.6% and 17% respectively in 1988 (P = 0.06). For the 250 patients who underwent acute PTCA, overall mortality was 5.2% compared to 24% in those who did not (P <0.001). Common in-hospital complications included heart failure (38%), non-sustained ventricular tachycardia (8%), atrial fibrillation (8%) and complete heart block (6%). Age, heart failure, bundle branch block and sustained ventricular tachycardia were associated with higher mortality by univariate analysis. On multivariate analysis, older age, heart failure and the absence of percutaneous intervention were independently associated with higher mortality.

Conclusion: In-hospital mortality for AMI patients admitted to the CCU declined from 1988 to 2002 despite a higher proportion of elderly patients. The introduction of new therapies including drugs and percutaneous intervention may have contributed to this decline.
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December 2007

Building collaboration in cardiac imaging.

Ann Acad Med Singap 2006 Oct;35(10):665-6

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October 2006

Systolic modeling of the left ventricle as a mechatronic system: determination of myocardial fiber's sarcomere contractile characteristics and new performance indices.

Mol Cell Biomech 2005 Dec;2(4):217-33

Bioengineering Division, School of Chemistry and Biomedical Engineering, College of Engineering, Nanyang Technological University, Singapore, 639798.

Background: In this paper, the left ventricle (LV) is modeled as a cylinder with myocardial fibers located helically within its wall. A fiber is modeled into myocardial structural units (MSUs); the core entity of each MSU is the sarcomeric contractile element. The relationship between the sarcomere unit's contractile force and shortening velocity is expressed in terms of the LV model's wall stress and deformation, and hence in terms of the monitored LV pressure and volume. Then, the LV systolic performance is investigated in terms of a mechatronic (excitation-contraction) model of the sarcomere unit located within the LV cylindrical model wall.

Methods: The governing equation of dynamics of the LV myocardial structural unit (MSU) is developed, involving the parameters of the series-elastic element (SE), the viscous element (VE) and the contractile element (CE). We then relate the MSU's force and displacement variables (in terms of SE, VE and CE parameters) to the LV pressure and volume, using the patient's catheterization-ventriculogram data. We thereby evaluate the MSU elements' parameters.

Results: We then determine the sarcomere (CE) 'force vs. shortening-velocity' characteristics as well as the power generated by the sarcomere (or CE) element. These are deemed to be important LV functional indices. When our computed sarcomeric peak-power is compared against the traditional LV contractility indices (by linear regression), a high degree of correlation is obtained.

Conclusions: We have provided herein, a LV systolic-phase (cylindrical geometry) model whose wall contains the myocardial fibers having sarcomere units. We have expressed the LV myocardial sarcomere's CE (force vs. shortening-velocity) characteristics in terms of the LV pressure-volume data. These CE properties express the intrinsic performance capacity of the LV. Hence, indices containing these properties are deemed to reflect LV performance. In this regard, our new LV contractility index correlates very well with the traditional LV contractility index dP/dt(max).
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December 2005

Left ventricular shape-based contractility index.

J Biomech 2006 15;39(13):2397-409. Epub 2005 Sep 15.

School of Mechanical and Aerospace Engineering, College of Engineering, Nanyang Technological University, Singapore 639798, Singapore.

This study develops contractility indices in terms of the left ventricular (LV) ellipsoidal geometrical shape-factor. The contractility index (CONT1) is given by the maximum value dsigma(*)/dt wherein sigma(*)=sigma/P, sigma is the wall stress, and sigma(*) is expressed in terms of the shape factor S (the ratio of the minor axis and major axis, B/A, of the instantaneous LV ellipsoidal model). Another contractility index (CONT2) is also developed based on how far apart the in vivo S at the start of ejection is from its optimized value, CONT2=(S(se)-S(se)(op))/S(se)(op), where S(se) refers to the value of S at the start of ejection, S(se)(op) is the derived optimal value of S(se) for which sigma* is maximum. The values of S(=B/A) were calculated from cineventriculographically monitored LV volume, myocardial volume and wall-thickness. Then both the contractility indices were evaluated in normal subjects, as well as in patients with mild heart failure and in patients with severe heart failure. The normal values of CONT1 and CONT2 are 8.75+/-2.30s(-1) and 0.09+/-0.07, respectively. CONT1 decreased in patients with mild and severe heart failures to 5.78+/-1.30 and 3.90+/-1.30, respectively. CONT2 increased in patients with mild and severe heart failures to 0.11+/-0.09 and 0.23+/-0.12, respectively. This implies that a non-optimal and less ellipsoidal shape is associated with decreased contractility (and poor systolic function) of the LV. CONT1 and CONT2 are useful as non-invasively determinable quantitative indices of LV contractility, to distinguish between normal and pathologic LVs.
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http://dx.doi.org/10.1016/j.jbiomech.2005.08.002DOI Listing
January 2007
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