Publications by authors named "Alex M Parker"

14 Publications

  • Page 1 of 1

A mini-thoracotomy approach for walking veno-arterial extracorporeal membranous oxygenation.

J Card Surg 2021 Apr 16;36(4):1569-1571. Epub 2020 Dec 16.

Department of Surgery, Division of Thoracic and Cardiovascular Surgery, College of Medicine, University of Florida, Gainesville, Florida, USA.

Fulminant myocarditis is a rapidly progressive myocardial inflammation that commonly requires advanced circulatory support therapies. We report our management of a 36-year-old gentleman with fulminant myocarditis who we managed with extracorporeal membranous oxygenation (ECMO) and subsequently durable bi-ventricular assist devices as a bridge to heart transplantation. The patient was admitted after a 1-week history of malaise with severe lethargy, jugular venous distension to greater than 10 cm, and troponin elevation to greater than 27 K. He was taken immediately for a heart catheterization which showed no obstructive coronary disease, and hemodynamics consistent with bi-ventricular failure. We proceeded with ECMO for hemodynamic support, utilizing a mini-thoracotomy for cannulation. A Protek Duo Rapid Deployment (LivaNova) was inserted via a modified Seldinger technique through the left ventricular apex, terminating in the ascending aorta. Percutaneous right IJ bicaval via a y-ed Avalon Elite (Getinge) was employed for venous drainage. This case highlights an alternate strategy for central walking veno-arterial ECMO in a patient presenting with fulminant myocarditis with a platform that minimizes upper/lower extremity over/under perfusion complications, while providing sternal sparring antegrade arterial flow with simultaneous ventricular unloading/venting.
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http://dx.doi.org/10.1111/jocs.15232DOI Listing
April 2021

The quest for noninvasive predictors of pulmonary vascular resistance in heart transplant candidates.

Pol Arch Intern Med 2020 10 29;130(10):826-827. Epub 2020 Oct 29.

Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, Florida, United States.

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http://dx.doi.org/10.20452/pamw.15656DOI Listing
October 2020

Hemodynamic effects of ivabradine use in combination with intravenous inotropic therapy in advanced heart failure.

Heart Fail Rev 2021 Mar 30;26(2):355-361. Epub 2020 Sep 30.

Division of Cardiovascular Medicine, University of Florida, Gainesville, FL, USA.

Intravenous inotropic therapy can be used in patients with advanced heart failure, as palliative therapy or as a bridge to cardiac transplantation or mechanical circulatory support, as well as in cardiogenic shock. Their use is limited to increasing cardiac output in low cardiac output states and reducing ventricular filling pressures to alleviate patient symptoms and improve functional class. Many advanced heart failure patients have sinus tachycardia as a compensatory mechanism to maintain cardiac output. However, excessive sinus tachycardia caused by intravenous inotropes can increase myocardial oxygen consumption, decrease coronary perfusion, and at extreme heart rates decrease ventricular filling and stroke volume. The limited available hemodynamic studies support the hypothesis that adding ivabradine, a rate control agent without negative inotropic effect, may blunt inotrope-induced tachycardia and its associated deleterious effects, while optimizing cardiac output by increasing stroke volume. This review analyzes the intriguing pathophysiology of combined intravenous inotropes and ivabradine to optimize the hemodynamic profile of patients in advanced heart failure. Graphical abstract Illustration of the beneficial and deleterious hemodynamic effects of intravenous inotropes in advanced heart failure, and the positive effects of adding ivabradine.
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http://dx.doi.org/10.1007/s10741-020-10029-xDOI Listing
March 2021

Patterns of emergency department utilization for LVAD patients compared with non-LVAD patients.

Int J Cardiol Heart Vasc 2020 Oct 14;30:100617. Epub 2020 Aug 14.

Division of Cardiovascular Medicine, University of Florida, Gainesville, FL, United States.

Background: Left ventricular assist device (LVAD) patients are vulnerable to over-utilization of resources.

Methods And Results: We explored the pattern of emergency department (ED) presentations of LVAD patients and their costs compared with non-LVAD heart failure patients. ED visits between 7/2008 and 7/2017 were reviewed to identify 145 LVAD patients, and 435 patients with known heart failure were selected using propensity score matching for age and sex. ED evaluation metrics, hospitalization cost, and length of stay (LOS) were analyzed. Although the most common ED presentations and their frequency differed between groups, few were LVAD specific. LVAD patients were more likely to have taken personal vehicles or be flown to the ED. They had similar times to triage, rooming, and physician evaluation compared with non-LVAD patients. However, LVAD patients were noted to have a shorter time from physician assessment to disposition (109.8 min vs. 177.0 min, p < 0.001) and, overall, LVAD patients had shorter ED LOS (6.33 vs. 9.82 hrs, p = 0.0001). For patients admitted, no significant difference was found between groups in hospital LOS (6.67 vs 6.58 days, p = 0.928) or total cost ($28,766 vs $21,524, p = 0.087).

Conclusion: Shorter disposition times without increases in LOS or costs may identify a created healthcare disparity among LVAD patients.
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http://dx.doi.org/10.1016/j.ijcha.2020.100617DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7452580PMC
October 2020

Reply: Advantage of leadless pacemaker over the conventional pacemaker in patients with left ventricular assist device.

Pacing Clin Electrophysiol 2020 10 22;43(10):1218. Epub 2020 Sep 22.

Division of Cardiology, Department of Medicine, University of Florida Academic Health Center, Gainesville, Florida.

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http://dx.doi.org/10.1111/pace.14057DOI Listing
October 2020

Severe COVID-19 After Recent Heart Transplantation Complicated by Allograft Dysfunction.

JACC Case Rep 2020 Jul 8;2(9):1347-1350. Epub 2020 Jun 8.

Division of Cardiovascular Medicine, Department of Medicine, University of Florida, Gainesville, Florida.

A 50-year-old male presented with atrial flutter 25 days after heart and kidney transplantation. Rejection was excluded, but he developed severe COVID-19 infection with cardiac allograft dysfunction. Despite continued corticosteroid and tacrolimus therapy, he remained aviremic. Respiratory and myocardial functions recovered after a week of mechanical ventilation. The cardiomyopathy was stress induced. ().
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http://dx.doi.org/10.1016/j.jaccas.2020.05.066DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7279732PMC
July 2020

Leadless pacemaker use in a patient with a durable left ventricular assist device.

Pacing Clin Electrophysiol 2020 09 27;43(9):1048-1050. Epub 2020 May 27.

Division of Cardiology, Department of Medicine, University of Florida Academic Health Center, Gainesville, Florida.

There is limited known safety and efficacy of leadless pacemaker device use in patients with durable left ventricular assist devices (LVADs). We present a case of a pacemaker-dependent LVAD patient with infection of permanent transvenous pacemaker who underwent successful implantation of Micra transcatheter pacing system (Medtronic).
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http://dx.doi.org/10.1111/pace.13937DOI Listing
September 2020

A giant mystery in giant cell myocarditis: navigating diagnosis, immunosuppression, and mechanical circulatory support.

ESC Heart Fail 2020 02 24;7(1):315-319. Epub 2019 Dec 24.

Division of Cardiology, University of California San Francisco, San Francisco, CA, USA.

Giant cell myocarditis is a rare but often devastating diagnosis. Advances in cardiac imaging and mechanical circulatory support have led to earlier and more frequent diagnoses and successful management. This disease state has wide variation in acuity of presentation, and consequently, optimal treatment ranging from intensity and type of immunosuppression to mechanical circulatory support is not well defined. The following case describes the management of a patient with an unusual presentation of giant cell myocarditis over a 10 year course of advanced heart failure therapies and immunomodulatory support. This case highlights emerging concepts in the management of giant cell myocarditis including sub-acute presentations, challenges in diagnosis, and treatment modalities in the modern era.
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http://dx.doi.org/10.1002/ehf2.12564DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7083393PMC
February 2020

The Importance of Extracardiac Muscle Mass in Heart Failure.

Authors:
Alex M Parker

Cardiology 2019 20;142(1):37-38. Epub 2019 Mar 20.

Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, Virginia, USA,

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http://dx.doi.org/10.1159/000497039DOI Listing
May 2019

Increased Pulmonary-Systemic Pulse Pressure Ratio Is Associated With Increased Mortality in Group 1 Pulmonary Hypertension.

Heart Lung Circ 2019 Jul 21;28(7):1059-1066. Epub 2018 Jun 21.

Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, VA, USA. Electronic address:

Background: Pulmonary arterial hypertension (PAH) is characterised by remodelling of the pulmonary vasculature leading to right ventricular (RV) failure. The failing RV, through interventricular uncoupling, deleteriously impacts the left ventricle and overall cardiac efficiency. We hypothesised that the ratio of the pulmonary artery pulse pressure to the systemic pulse pressure ("pulmonary-systemic pulse pressure ratio", or PS-PPR) would be associated with mortality in PAH.

Methods: We conducted a retrospective analysis of 262 patients in the National Institute of Health Primary Pulmonary Hypertension Registry (NIH-PPH). We evaluated the association between the PS-PPR and mortality after adjustment for the Pulmonary Hypertension Connection (PHC) risk equation.

Results: Among 262 patients (mean age 37.5±15.8years, 62.2% female), median PS-PPR was 1.04 (IQR 0.79-1.30). In the Cox proportional hazards regression model, each one unit increase in the PS-PPR was associated with more than a two-fold increase in mortality during follow-up (HR 2.06, 95% CI 1.40-3.02, p=0.0002), and this association of PS-PPR with mortality remained significant in the multivariable Cox model adjusted for the PHC risk equation, mean pulmonary artery pressure, and body mass index (BMI) (adjusted HR 1.81, 95% CI 1.13-2.88, p=0.01). Furthermore, PS-PPR in the upper quartile (>1.30) versus quartiles 1-3 was associated with a 68% increase in mortality after adjustment for these same covariates (adjusted HR 1.68, 95% CI 1.13-2.50, p=0.01).

Conclusions: Pulmonary-systemic pulse pressure ratio, a marker of biventricular efficiency, is associated with survival in PAH even after adjustment for the PHC risk equation. Further studies are needed on the wider applications of PS-PPR in PAH patients.
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http://dx.doi.org/10.1016/j.hlc.2018.05.199DOI Listing
July 2019

Plasma Volume and Renal Function Predict Six-Month Survival after Hospitalization for Acute Decompensated Heart Failure.

Cardiorenal Med 2017 Dec 3;8(1):61-70. Epub 2017 Nov 3.

Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, Virginia, USA.

Background: Plasma volume (PV) is contracted in stable patients with heart failure (HF) due to decongestion strategies. On the other hand, increased PV can adversely affect the trajectory of HF. We therefore examined the effects of increased percentage change in PV (%ΔPV), blood urea nitrogen (BUN), and %ΔPV stratified by BUN and glomerular filtration rate (GFR) on survival after discharge in patients hospitalized for acute decompensated HF (ADHF).

Methods: We used the Strauss-Davis-Rosenbaum formula to calculate the %ΔPV between baseline and hospital discharge in a cohort from the Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness trial (ESCAPE). Kaplan-Meier curves were constructed for survival over 6 months. Cox proportional hazards regression was used to obtain adjusted hazard ratios (HR) and 95% confidence intervals (95% CI) for the associations between survival after discharge and %ΔPV, BUN, and %ΔPV stratified by BUN and GFR.

Results: Of the 324 patients included in our study (age 56.1 ± 13.6 years, 26.5% female), those with increased or no %ΔPV at discharge were less likely to survive at 6 months compared with those having reduced %ΔPV (log rank, = 0.0093). Increased %ΔPV (HR 1.08 per 10% increase; 95% CI: 1.02-1.14) and increased BUN at discharge (HR 1.02 per mg/dL; 95% CI: 1.01-1.03) were independently associated with worse survival. Decreasing %ΔPV had a greater association with improved survival in patients with discharge BUN <31 mg/dL ( = 0.02) and discharge GFR >40 mL/min/1.73 m ( = 0.047).

Conclusions: Increased %ΔPV and BUN at discharge predicted worse 6-month survival in patients with ADHF. Decreased %ΔPV with low BUN or high GFR at discharge was associated with improved survival.
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http://dx.doi.org/10.1159/000481149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5757574PMC
December 2017

Decreased pulmonary arterial proportional pulse pressure is associated with increased mortality in group 1 pulmonary hypertension.

Clin Cardiol 2017 Nov 10;40(11):988-992. Epub 2017 Jul 10.

Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, Virginia.

Background: This study evaluated the utility of a novel index, pulmonary arterial (PA) proportional pulse pressure (PAPP; range 0-1, defined as [PA systolic pressure - PA diastolic pressure] / PA systolic pressure), in predicting mortality in patients with World Health Organization group 1 pulmonary hypertension (PH).

Hypothesis: Low PAPP is associated with increased 5-year mortality independent of a validated contemporary risk-prediction equation (Pulmonary Hypertension Connection [PHC] equation).

Methods: In a group of 262 patients in the National Institutes of Health Primary Pulmonary Hypertension (NIH-PPH) Registry, PAPP and the PHC risk equation were used to predict mortality during 5 years of follow-up using Cox proportional hazards models. Kaplan-Meier survival curves were used to compare mortality among PAPP quartiles, and significance was tested using the log-rank test.

Results: Patients in the lowest quartile (PAPP ≤0.47) had a significantly higher 5-year mortality than did patients in higher quartiles (log-rank P = 0.016). In a Cox model adjusted for the PHC equation, PAPP remained significantly associated with 5-year mortality (hazard ratio: 0.74 per 0.10 increase in PAPP, 95% confidence interval: 0.61-0.90). The χ statistic for the single PAPP covariate in this model was 8.8 (P = 0.003), which compared favorably with the χ statistic of 15.2 (P < 0.0001) for the multivariable PHC equation.

Conclusions: PAPP, an index of ventricular-arterial coupling, is independently associated with survival in World Health Organization group 1 PH. The use of this easily measurable index for guiding risk stratification needs further investigation.
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http://dx.doi.org/10.1002/clc.22752DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6490329PMC
November 2017

: A Validated Scoring System for Early Stratification of Neurologic Outcome After Out-of-Hospital Cardiac Arrest Treated With Targeted Temperature Management.

J Am Heart Assoc 2017 May 20;6(5). Epub 2017 May 20.

Department of Cardiovascular Medicine, University of Virginia, Charlottesville, VA

Background: Out-of-hospital cardiac arrest (OHCA) results in significant morbidity and mortality, primarily from neurologic injury. Predicting neurologic outcome early post-OHCA remains difficult in patients receiving targeted temperature management.

Methods And Results: Retrospective analysis was performed on consecutive OHCA patients receiving targeted temperature management (32-34°C) for 24 hours at a tertiary-care center from 2008 to 2012 (development cohort, n=122). The primary outcome was favorable neurologic outcome at hospital discharge, defined as cerebral performance category 1 to 2 (poor 3-5). Patient demographics, pre-OHCA diagnoses, and initial laboratory studies post-resuscitation were compared between favorable and poor neurologic outcomes with multivariable logistic regression used to develop a simple scoring system (). The score ranges 0 to 5 using equally weighted variables: (): coronary artery disease, known pre-OHCA; (): glucose ≥200 mg/dL; (): rhythm of arrest not ventricular tachycardia/fibrillation; (): age >45; (): arterial pH ≤7.0. A validation cohort (n=344) included subsequent patients from the initial site (n=72) and an external quaternary-care health system (n=272) from 2012 to 2014. The c-statistic for predicting neurologic outcome was 0.82 (0.74-0.90, <0.001) in the development cohort and 0.81 (0.76-0.87, <0.001) in the validation cohort. When subdivided by score, similar rates of favorable neurologic outcome were seen in both cohorts, 70% each for low (0-1, n=60), 22% versus 19% for medium (2-3, n=307), and 0% versus 2% for high (4-5, n=99) scores in the development and validation cohorts, respectively.

Conclusions: stratifies neurologic outcomes following OHCA in patients receiving targeted temperature management (32-34°C) using objective data available at hospital presentation, identifying patient subsets with disproportionally favorable ( ≤1) and poor ( ≥4) prognoses.
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http://dx.doi.org/10.1161/JAHA.116.003821DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524053PMC
May 2017

Analysis of the dynamics of assembly and structural impact for a histidine tagged FGF1-1.5 nm Au nanoparticle bioconjugate.

Bioconjug Chem 2009 Nov;20(11):2106-13

Department of Chemistry and Biochemistry and Kasha Laboratory Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306, USA.

Whether assembling proteins onto nanoscale, mesoscopic, or macroscropic material surfaces, maintaining a protein's structure and function when conjugated to a surface is complicated by the high propensity for electrostatic or hydrophobic surface interactions and the possibility of direct metal coordination of protein functional groups. In this study, the assembly of a 1.5 nm CAAKA passivated gold nanoparticle (AuNP) onto FGF1 (human acidic fibroblast growth factor) using an amino terminal His(6) tag is analyzed. The impact of structure and time-dependent changes in the structural elements in FGF1and FGF1-heparin in the presence of the AuNP is probed by a molecular beacon fluorescence assay, circular dichroism, and NMR spectroscopy. Analysis of the results indicates that a time-dependent evolution of the protein structure without loss of FGF1 heparin binding occurs following the formation of the initial FGF1-AuNP complex. The time-dependent changes are believed to reflect protein sampling of the AuNP surface to minimize the free energy of the AuNP-FGF1 complex without impacting FGF1 function.
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http://dx.doi.org/10.1021/bc900224dDOI Listing
November 2009