Publications by authors named "Amy E Hackmann"

12 Publications

  • Page 1 of 1

Use of a Bluetooth tablet-based technology to improve outcomes in lung transplantation: A pilot study.

Am J Transplant 2020 12 13;20(12):3649-3657. Epub 2020 Jul 13.

Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Southern California, Los Angeles, California, USA.

The impact of remote patient monitoring platforms to support the postoperative care of solid organ transplant recipients is evolving. In an observational pilot study, 28 lung transplant recipients were enrolled in a novel postdischarge home monitoring program and compared to 28 matched controls during a 2-year period. Primary endpoints included hospital readmissions and total days readmitted. Secondary endpoints were survival and inflation-adjusted hospital readmission charges. In univariate analyses, monitoring was associated with reduced readmissions (incidence rate ratio [IRR]: 0.56; 95% confidence interval [CI]: 0.41-0.76; P < .001), days readmitted (IRR: 0.46; 95% CI: 0.42-0.51; P < .001), and hospital charges (IRR: 0.52; 95% CI: 0.51-0.54; P < .001). Multivariate analyses also showed that remote monitoring was associated with lower incidence of readmission (IRR: 0.38; 95% CI: 0.23-0.63; P < .001), days readmitted (IRR: 0.14; 95% CI: 0.05-0.37; P < .001), and readmission charges (IRR: 0.11; 95% CI: 0.03-0.46; P = .002). There were 2 deaths among monitored patients compared to 6 for controls; however, this difference was not significant. This pilot study in lung transplant recipients suggests that supplementing postdischarge care with remote monitoring may be useful in preventing readmissions, reducing subsequent inpatient days, and controlling hospital charges. A multicenter, randomized control trial should be conducted to validate these findings.
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December 2020

The Disparity Between Public Utilization and Surgeon Awareness of the STS Patient Education Website.

Ann Thorac Surg 2020 07 19;110(1):284-289. Epub 2019 Nov 19.

Society for Thoracic Surgeons Media Office, Chicago, Illinois.

Background: Many online resources currently provide healthcare information to the public. In 2015, the Society of Thoracic Surgeons (STS) created a multimedia web portal ( to educate the public regarding cardiothoracic surgery and provide an informative tool to which cardiothoracic surgeons could refer patients.

Methods: A patient education task force was created, and disease-specific content was created for 25 pathological conditions. After launching the website online, a marketing campaign was initiated to make STS members aware of its availability. Website visits were monitored, and an online survey for public users was created. An email survey was sent to STS members to evaluate awareness and content. Surveys were analyzed for effectiveness and utilization by both public users and STS member surgeons.

Results: From 2016 to 2018, the website had more than 1 million visits, with visits increasing yearly. Surveyed user ratings of the website were positive regarding quality and utility of the information provided. STS member response was poor (379 responses of 6347 emails), and 78.3% of responders were unaware of the website. Surgeon responders were positive about the content, though many still refrain from referring patients.

Conclusions: Online education for cardiothoracic surgery is seeing increased public use, with high ratings for content and utility. Despite aggressive marketing to STS members, most remain unaware of this website's existence. Those who are aware approve of its content, but adoption of referring patients to it has been slow. Improved strategies are necessary to make surgeons aware of this STS-provided service and increase patient referrals to it.
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July 2020

Successful rescue therapy with venovenous extracorporeal membrane oxygenation for re-expansion pulmonary oedema in a patient with one lung.

Eur J Cardiothorac Surg 2019 Mar;55(3):582-584

Division of Cardiac Surgery, Department of Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA.

Re-expansion pulmonary oedema following the drainage of pleural fluid is rare. We report a patient with 1 lung who developed life-threatening re-expansion pulmonary oedema following thoracentesis and was rescued with venovenous (VV) extracorporeal membrane oxygenation (ECMO), surviving to discharge 28 days later. An aggressive early rescue therapy with VV ECMO should be pursued for all types of acute lung injury regardless of patient age, comorbidities or transplant candidacy, given the likelihood of native lung recovery following ECMO support.
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March 2019

Selective Aortic Arch and Root Replacement in Repair of Acute Type A Aortic Dissection.

Ann Thorac Surg 2018 Feb 3;105(2):505-512. Epub 2017 Nov 3.

Department of Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, California. Electronic address:

Background: Controversy exists regarding the optimal extent of repair for type A aortic dissection. Our approach is to replace the ascending aorta, and only replace the aortic root or arch when intimal tears are present in those areas. We examined intermediate outcomes with this approach to acute type A aortic dissection repair.

Methods: Between March 2005 and October 2016, 195 patients underwent repair of acute type A aortic dissection. Repair was categorized by site of proximal and distal anastomosis and extent of repair. Mean follow-up was 31.0 ± 30.9 months. Kaplan-Meier analysis was used to assess survival. Multiple variable Cox proportional hazards modeling was utilized to identify factors associated with overall mortality.

Results: Overall survival was 85.1%, 83.9%, 79.1%, and 74.4% at 6, 12, 36, and 60 months, respectively. Eight patients required reintervention. The cumulative incidence of aortic reintervention at 1 year with death as a competing outcome was 3.95%. Multiple variable regression analysis identified factors such as age, preoperative renal failure, concomitant thoracic endograft, postoperative myocardial infarction and sepsis, and need for extracorporeal membrane oxygenation as predictive of overall mortality. Neither proximal or distal extent of repair, nor need for reintervention affected overall survival (proximal: hazard ratio 1.63, 95% confidence interval: 0.75 to 3.51, p = 0.22; distal: hazard ratio 1.12, 95% confidence interval: 0.43 to 2.97, p = 0.81; reintervention: hazard ratio 0.03, 95% confidence interval: 0.002 to 0.490, p < 0.01).

Conclusions: A selective approach to root and arch repair in acute type A aortic dissection is safe. If aortic reintervention is needed, survival does not appear to be affected.
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February 2018

Outcomes after mitral valve repair: A single-center 16-year experience.

J Thorac Cardiovasc Surg 2017 09 9;154(3):822-830.e2. Epub 2017 Feb 9.

Department of Surgery, Keck School of Medicine of USC, University of Southern California, Los Angeles, Calif.

Objective: To evaluate outcomes after mitral valve repair.

Methods: Between May 1999 and June 2015, 446 patients underwent mitral valve repair. Isolated mitral valve annuloplasty was excluded. A total of 398 (89%) had degenerative valve disease. Mean follow-up was 5.5 ± 3.8 years. Postoperative echocardiograms were obtained in 334 patients (75%) at a mean of 24.3 ± 13.7 months.

Results: Survival was 97%, 96%, 95%, and 94% at 1, 3, 5, and 10 years. Risk factor analysis showed age >60 years and nondegenerative etiology predict death (hazard ratio, 2.91; 95% confidence interval, 1.06-8.02, P = .038; and hazard ratio, 1.87; 95% confidence interval, 1.16-3.02, P = .010, respectively). Considering competing risks due to mortality, the cumulative incidence of reoperation was 2.8%, 4.2%, 5.1%, and 9.6% at 1, 3, 5, and 10 years. Competing risk proportional hazard survival regression identified nondegenerative etiology and previous cardiac surgery as predictors of reoperation, and posterior repair was protective (all P < .05). Cumulative incidence of progression of mitral regurgitation (2 or more grades) with mortality as a competing risk was 4.7%, 10.5%, 21.0%, and 35.8% at 1, 3, 5, and 10 years. Patients with previous sternotomy, repair or coronary artery bypass grafting, and concurrent tricuspid valve procedure or isolated anterior leaflet repair were more likely to develop progression of mitral regurgitation (all P < .05), and posterior leaflet repair was protective (P = .038). On multivariate analysis diabetes, previous coronary artery bypass grafting and concurrent tricuspid valve intervention predicted MR progression.

Conclusions: Mitral valve repair has excellent outcomes. Our results demonstrate failures appear to occur less in those who undergo posterior leaflet repair.
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September 2017

The Utility of Nurse-Managed Extracorporeal Life Support in an Adult Cardiac Intensive Care Unit.

Ann Thorac Surg 2017 Aug 10;104(2):510-514. Epub 2017 Feb 10.

Division of Cardiothoracic Surgery, Department of Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, California.

Background: The use of extracorporeal life support (ECLS) worldwide has increased exponentially since 2009. The patient requiring ECLS demands an investment of hospital resources, including personnel. Educating bedside nurses to manage ECLS circuits broadens the availability of trained providers.

Methods: Experienced cardiothoracic intensive care unit (CTICU) nurses underwent training to manage ECLS circuits, including volume assessment, treatment of arterial blood gas values, the physiology of ECLS, and recognition of common emergencies. In addition to lectures and a written examination, simulation using water circuits and an ICU model allowed assessment of skills and understanding of concepts. Performance assessments were completed regularly at the bedside, and skills revalidation occurred every 6 months. A sequential cohort of 40 patients was tracked over 1 year.

Results: Despite doubling the census of ECLS patients in 1 year, management by specially trained CTICU nurses has positively affected patient care and outcomes. At a single institution, 40 patients had a median of 6 days (interquartile range, 2 to 226 days) of support in 2014, leading to 767 patient-days of support. Survival to hospital discharge increased to 45% in 2014. Most survivors were weaned from support. Neurologic injury was the most common cause of death, followed by failure to qualify for advanced therapies.

Conclusions: With on-going education and assessment, including crisis training, physiology, and cannulation strategies, CTICU nurses can safely operate ECLS circuits and can increase the availability of appropriately trained providers to accommodate the exponential increase in ECLS occurrences without negatively affecting outcomes and generally at a lower cost.
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August 2017

Evaluation of Hemodynamic Performance of Aortic Valve Bioprostheses in a Model of Oversizing.

Ann Thorac Surg 2017 Jun 26;103(6):1866-1876. Epub 2017 Jan 26.

Department of Surgery, Keck School of Medicine of USC, University of Southern California, Los Angeles, California. Electronic address:

Background: The risk of patient-prosthesis mismatch drives most surgeons to select the largest bioprosthesis possible during aortic valve replacement, but interactions between the native aortic annulus and valve prosthesis remain poorly defined. We examined the hemodynamic and functional consequences of oversizing contemporary bioprostheses in an in vitro model.

Methods: Three sizes each (21, 23, and 25 mm) of 5 aortic bioprostheses (Magna, Edwards Lifesciences, Irvine, CA; Trifecta and Epic, St. Jude, St. Paul, MN; and Mosaic and Hancock II, Medtronic, Minneapolis, MN) were tested on a mock annulus in a pulsatile aortic simulator. After the annulus was sized to match each valve, the annulus was decreased by 3 mm and then by 6 mm to simulate oversizing. We measured the effective orifice area and the mean pressure gradient. Changes in prosthetic leaflet behavior and geometric orifice area were assessed with slow-motion video. Statistical analysis used mixed-effects models for repeated-measures data, allowing comparison within and between groups.

Results: For each valve model and size, oversizing resulted in decreased effective orifice areas and geometric orifice areas and increased pressure gradients. This was more pronounced with smaller valve sizes and higher flow rates but varied between valve types. Slow-motion imaging revealed this change in geometric orifice area was a result of an inward shift of the valve leaflet hinge point.

Conclusions: Bioprosthetic oversizing impairs hemodynamic performance of aortic valve bioprostheses. The magnitude of this effect varies by valve model and size. Clinically, these data suggest that during aortic valve replacement, placing a valve whose internal orifice closely matches the aortic annulus will provide the optimal hemodynamic performance.
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June 2017

Type A Aortic Dissection Repair: How I Teach It.

Ann Thorac Surg 2017 Jan;103(1):14-17

Department of Surgery, Keck School of Medicine of University of Southern California, Los Angeles, California.

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January 2017

Rate Control versus Rhythm Control for Atrial Fibrillation after Cardiac Surgery.

N Engl J Med 2016 May 4;374(20):1911-21. Epub 2016 Apr 4.

From the Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic Foundation, Cleveland (A.M.G.); the International Center for Health Outcomes and Innovation Research, Department of Population Health Science and Policy, Icahn School of Medicine at Mount Sinai (E.B., A.J.M., K.A.K., M.K.P., D.L.W., E.G.M., K.L.O., K.J.S., A.C.G.), Department of Cardiac Surgery, Mount Sinai Health System (E.A.R.), and Division of Cardiothoracic Surgery, Department of Surgery, College of Physicians and Surgeons, Columbia University (M.A.) - all in New York; Department of Anesthesiology and Critical Care, University of Pennsylvania (J.M.R.), and Department of Surgery, Division of Cardiovascular Surgery, University of Pennsylvania School of Medicine (M.L.M.) - both in Philadelphia; Cardiovascular and Thoracic Surgery, Mission Health and Hospitals, Asheville, NC (M.A.G., R.F.M.); Department of Surgery, Keck School of Medicine of USC, University of Southern California, Los Angeles (M.E.B., A.E.H.); Division of Thoracic and Cardiovascular Surgery, University of Virginia School of Medicine, Charlottesville (G.A., J.A.K.); Montreal Heart Institute, Université de Montréal, Montreal (L.P.P., M.P.), Institut Universitaire de Cardiologie et de Pneumologie de Québec, Hôpital Laval, Quebec, QC (G.D., P.V.), and Peter Munk Cardiac Centre and Division of Cardiovascular Surgery, Toronto General Hospital, University Health Network and the Division of Cardiac Surgery, University of Toronto, Toronto (R.D.W.) - all in Canada; Department of Cardiovascular Surgery, Heart Hospital Baylor Plano, Baylor Health Care System, Plano, TX (R.L.S., M.J.M.); Office of Biostatistics Research (N.O.J.) and Division of Cardiovascular Sciences (M.A.M., W.C.T.-P.), National Heart, Lung, and Blood Institute, Bethesda, and Department of Surgery, University of Maryland Medical Center, Baltimore (J.S.G.) - both in Maryland; and the Cardiovascular Division, Brigham and Women's Hospital, Boston (P.T.O.).

Background: Atrial fibrillation after cardiac surgery is associated with increased rates of death, complications, and hospitalizations. In patients with postoperative atrial fibrillation who are in stable condition, the best initial treatment strategy--heart-rate control or rhythm control--remains controversial.

Methods: Patients with new-onset postoperative atrial fibrillation were randomly assigned to undergo either rate control or rhythm control. The primary end point was the total number of days of hospitalization within 60 days after randomization, as assessed by the Wilcoxon rank-sum test.

Results: Postoperative atrial fibrillation occurred in 695 of the 2109 patients (33.0%) who were enrolled preoperatively; of these patients, 523 underwent randomization. The total numbers of hospital days in the rate-control group and the rhythm-control group were similar (median, 5.1 days and 5.0 days, respectively; P=0.76). There were no significant between-group differences in the rates of death (P=0.64) or overall serious adverse events (24.8 per 100 patient-months in the rate-control group and 26.4 per 100 patient-months in the rhythm-control group, P=0.61), including thromboembolic and bleeding events. About 25% of the patients in each group deviated from the assigned therapy, mainly because of drug ineffectiveness (in the rate-control group) or amiodarone side effects or adverse drug reactions (in the rhythm-control group). At 60 days, 93.8% of the patients in the rate-control group and 97.9% of those in the rhythm-control group had had a stable heart rhythm without atrial fibrillation for the previous 30 days (P=0.02), and 84.2% and 86.9%, respectively, had been free from atrial fibrillation from discharge to 60 days (P=0.41).

Conclusions: Strategies for rate control and rhythm control to treat postoperative atrial fibrillation were associated with equal numbers of days of hospitalization, similar complication rates, and similarly low rates of persistent atrial fibrillation 60 days after onset. Neither treatment strategy showed a net clinical advantage over the other. (Funded by the National Institutes of Health and the Canadian Institutes of Health Research; number, NCT02132767.).
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May 2016

A randomized, placebo-controlled trial of doxycycline after endoluminal aneurysm repair.

J Vasc Surg 2008 Sep 15;48(3):519-26; discussion 526. Epub 2008 Jul 15.

Department of Surgery (Section of Vascular Surgery), Washington University School of Medicine, St. Louis, Mo.

Background: The late durability of endovascular aneurysm repair (EVAR) has been limited by progressive aortic degeneration believed to be mediated by matrix metalloproteases (MMP). The goal of this study was to evaluate the effect of a MMP inhibitor, doxycycline, on EVAR.

Methods: Patients undergoing EVAR were randomized to doxycycline (100 mg twice daily) or placebo for 6 months following the procedure. Clinical data, blood samples, and computed tomography (CT) scans were obtained preoperatively, postoperatively (blood only), and at 1- and 6-month follow-up. Forty-four subjects were analyzed based on intention-to-treat.

Results: Plasma MMP-9 decreased significantly below baseline in the doxycycline (N = 20) treated patients at 6 months (-16.4% +/- 20.7%, P < .05) while there was a nonsignificant increase in the placebo (N = 24) group (128.1% +/- 73.5%). This was primarily related to changes between 1 and 6 months. In patients with endoleaks at 6 months, plasma MMP-9 increased in 83% of the placebo treated patients, but in only 14% of the doxycycline treated group (P < .03). Among endoleak-free patients with AneuRx or Excluder endografts, doxycycline treatment resulted in greater decreases in maximum aortic diameter than placebo treatment (-13.3% +/- 3.3% vs -3.8% +/- 3.0%, P < .05). Furthermore, doxycycline treatment significantly reduced the aortic neck dilatation at 6 months in Excluder treated patients.

Conclusion: There is evidence of persistent MMP release representing ongoing aortic degradation after endografting which can be inhibited by doxycycline therapy. In analyses based on the endograft used, treatment with doxycycline also demonstrated evidence of increased aortic dimensional stability, a surrogate marker for long-term success of EVAR. Although encouraging, these results require confirmation in larger patient populations. Doxycycline should undergo more thorough evaluation as a potential adjuvant treatment to improve the results of EVAR, particularly in certain subgroups.
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September 2008

MF-tricyclic inhibits growth of experimental abdominal aortic aneurysms.

J Surg Res 2007 Aug 14;141(2):192-5. Epub 2007 Jun 14.

University of South Florida Division of Vascular and Endovascular Surgery, Tampa, Florida 33606, USA.

Background: Experimental abdominal aortic aneurysm (AAA) development can be pharmacologically suppressed by inhibiting matrix metalloproteinase-9 (MMP-9). Cyclooxygenase-2 (COX-2) inhibitors are potent anti-inflammatory agents that have been demonstrated to inhibit experimental aneurysm development. We hypothesized that treatment with MF-tricyclic, a selective COX-2 inhibitor, incorporated into rodent chow would inhibit aneurysm development in a rat AAA model.

Methods: Twelve male Sprague Dawley rats underwent induction of experimental AAA using intra-aortic porcine elastase infusion. Six rats received control feed, and six received MF-tricyclic rodent chow for a period of 14 days. Aortic diameters were measured pre- and postinfusion as well as at harvest. Aortic tissue samples were evaluated by real-time polymerase chain reaction (RT-PCR) for MMP-9, by immunohistochemistry for elastin.

Results: Elastase infusion produced AAA in all untreated rats. At 14 days MF-tricyclic-treated rats had significantly reduced aortic diameter (1.9 +/- 0.1 mm versus 2.4 +/- 0.0 mm, P = 0.00001). Percent increase in aortic diameter was also significantly less in animals receiving MF-tricyclic (65.7 +/- 8.5% versus 132.3 +/- 7.3%, P = 0.0001). RT-PCR demonstrated a decrease in the mean expression of MMP-9 in the treated animals (0.414 ng of RNA versus 1.114 ng of RNA) (P = 0.07). Sections stained for elastin demonstrated preserved elastin integrity in MF-tricyclic treated aortas.

Conclusions: COX-2 inhibition helps to retard the growth of experimental AAAs possibly through inhibition of MMP-9. Experimentally treated animals demonstrated smaller aortic diameters and lower levels of tissue MMP-9 when compared to untreated animals. Selective COX-2 inhibition may offer an additional method to pharmacologically inhibit AAAs.
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August 2007

Cigarette smoking increases aortic dilatation without affecting matrix metalloproteinase-9 and -12 expression in a modified mouse model of aneurysm formation.

J Vasc Surg 2007 Jun 29;45(6):1217-1227. Epub 2007 Mar 29.

Department of Surgery (Section of Vascular Surgery), Washington University School of Medicine, St. Louis, MO 63110, USA.

Objective: The development of abdominal aortic aneurysms (AAA) is presumed to result from multiple genetic and environmental factors, with exposure to tobacco smoke the single largest known factor predisposing to aneurysm growth. We have attempted to adapt the elastase-perfused animal model to determine whether tobacco exposure can lower the threshold of aortic injury necessary for AAA development.

Methods: Adult C57BL/6 mice underwent transient perfusion of the infrarenal aorta with an active solution of elastase: high-dose (HDE, 0.19 U/mL, n=9), standard-dose (SDE, 0.16 U/mL, n=21) or low-dose (LDE, 0.07 U/mL, n=24). Control animals (n=24) were treated with heat inactivated elastase (HIE). Twenty LDE perfused mice were exposed to cigarette smoke (LDE-S) beginning 2 weeks before perfusion and continuing until aortic harvest. Aortic diameter (AD) was measured preperfusion, postperfusion, and at harvest on day 14. AAA was defined as %DeltaAD>or=100% between preperfusion and harvest. Aortas from each group (except HDE) were analyzed for matrix metalloproteinase-9 (MMP-9) and MMP-12 expression by real-time polymerase chain reaction normalized to glyceraldehyde-3-phosphate dehydrogenase.

Results: All SDE mice developed large AAA by %DeltaAD (189.3%+/-16.9%, mean+/-standard error of the mean), but control mice had only a small dilatation (69.7%+/-3.7%, P<.01). Higher doses of elastase did not produce larger aneurysms in HDE mice. In contrast, only 63% of LDE mice showed aneurysmal dilatation, and these were significantly smaller (104.3%+/-4.2%, P<.01). When exposed to cigarette smoke, LDE animals developed significantly larger aneurysms (%DeltaAD, 134.5%+/-7.9%, P=.0021). There was no difference in normalized aortic MMP-9 and MMP-12 expression between elastase doses or between smoke-exposed and unexposed animals. Histologic analysis revealed that smoking increased the extent of aortic elastin degradation when compared with LDE-S animals.

Conclusion: Aneurysm development in the elastase model is dependent on the quantity of active elastase infused. Exposure of animals to tobacco smoke after a relatively minor aortic elastase injury produces increases in elastin degradation and aneurysm size without affecting MMP-9 or MMP-12 expression. To our knowledge, this is the first demonstration in an animal model that smoking can act as a synergistic factor in AAA development. Further understanding of the relationship between smoking and AAA in this model may help unveil the pathophysiologic pathways involved between cigarette smoke and AAAs.
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June 2007