Simon Maybaum

Cardiac Improvement During Mechanical Circulatory Support A Prospective Multicenter Study of the LVAD Working Group

Background— Myocardial recovery after left ventricular assist device (LVAD) support has been reported. The LVAD Working Group Recovery Study was a prospective multicenter trial to assess the incidence of myocardial recovery in patients bridged to cardiac transplantation. Methods and Results— After LVAD implantation, patients were evaluated with the use of rest echocardiograms with partial LVAD support and cardiopulmonary exercise testing. Dobutamine echocardiography with hemodynamic measurements was performed in those patients with left ventricular ejection fraction >40% during resting studies. Histological analysis was performed on myocardial samples taken at LVAD implantation and explantation. Sixty-seven LVAD patients with heart failure participated in the study. After 30 days, significant improvement occurred in left ventricular ejection fraction (17±7% versus 34±12%; P<0.001) and reductions in left ventricular end-diastolic diameter (7.1±1.2 versus 5.1±1.1 cm; P<0.001) and left ventricular mass (320±113 versus 194±79 g; P<0.001) compared with before LVAD. Thirty-four percent of patients had left ventricular ejection fraction >40% with partial device support. Left ventricular ejection fraction decreased over time to pre-LVAD measurement by 120 days. Peak &OV0312;o2 improved with mechanical support (13.7±4.2 versus 18.9±5.5 mL/kg per minute, 30 versus 120 days; P<0.001). Tissue analysis revealed significant reductions in myocyte size, collagen content, and cardiac tumor necrosis factor-&agr;. Six subjects (9%) underwent LVAD explantation for recovery. Conclusions— Cardiac function improves significantly after device implantation. Although cellular recovery and improvement in ventricular function are observed, the degree of clinical recovery is insufficient for device explantation in most patients with chronic heart failure.

Acute type 5 phosphodiesterase inhibition with sildenafil enhances flow-mediated vasodilation in patients with chronic heart failure

OBJECTIVES To determine the acute effects of type 5 phosphodiesterase inhibition with sildenafil on flow-mediated vasodilation in the brachial artery of patients with chronic heart failure. BACKGROUND Impaired endothelium-dependent, flow-mediated vasodilation in patients with heart failure is partly attributable to hyporesponsiveness of cyclic guanosine monophosphate (cGMP) mediated vasorelaxation effector mechanisms in vascular smooth muscle. The effect of inhibition of cGMP degradation with sildenafil, a specific type 5 cGMP phosphodiesterase inhibitor, on flow-mediated dilation in heart failure is unknown. METHODS Flow-mediated vasodilation after release of 1, 3 and 5 min of transient arterial occlusion was measured in the brachial artery with high resolution two-dimensional ultrasound imaging in 48 patients with chronic heart failure before and 1 h after randomized, double-blind assignment to a single oral dose of sildenafil 12.5, 25 or 50 mg or matching placebo. RESULTS In response to oral administration of a single dose of study drug, the change in flow-mediated vasodilation after release of 1, 3 and 5 min of arterial occlusion was significantly greater in patients receiving sildenafil 25 mg (3.3 +/- 1.9, 3.8 +/- 1.8 and 4.0 +/- 1.8%, respectively, p < 0.05) and patients receiving sildenafil 50 mg (3.7 +/- 1.3, 4.1 +/- 1.1, 3.9 +/- 1.3%, respectively, p < 0.05) than that of patients receiving placebo (0.7 +/- 1.1, 0.2 +/- 1.2, 0.6 +/- 0.8%, respectively). CONCLUSIONS Acute type 5 phosphodiesterase inhibition with sildenafil 25 and 50 mg increases endothelium-dependent, flow-mediated vasodilation in patients with chronic heart failure when compared with placebo.

Increased Incidence of Gastrointestinal Bleeding Following Implantation of the HeartMate II LVAD

Abstract  Background: The HeartMate II (HMII) Left Ventricular Assist System (Thoratec Corporation, Pleasanton, CA, USA), an axial continuous‐flow left ventricular assist device (LVAD), has been approved for use in bridge‐to‐transplant patients and is under investigation for destination therapy. To avoid device‐related thromboembolic complications, antiplatelet, and anticoagulation therapy are routinely administered. A worrisome frequency of gastrointestinal (GI) bleeding events has been observed. Methods: A retrospective review of all 33 patients undergoing long‐term LVAD implantation between June 1, 2006 and July 31, 2008 at our institution for any indication was conducted. Anticoagulation consisted of heparin (intravenous or subcutaneous) followed by transition to Coumadin therapy to a target INR of two to three. Antiplatelet therapy consisted of low‐dose aspirin and dipyridamole. Results: Twenty patients received the HMII and 13 patients received other devices. Eight (40%) HMII recipients suffered at least one episode of GI bleeding while no GI bleeding occurred in recipients of other devices (p = 0.012). Of 17 total bleeding episodes, no definitive source could be identified in 11 instances (65%). Conclusions: Although definitive source identification remains elusive, we believe that the majority of bleeding arises in the small bowel, possibly due to angiodysplasias, similar to the pathophysiology encountered in patients with aortic stenosis and GI bleeding. As we move toward wider use of the HMII and other axial continuous‐flow devices in both bridge‐to‐transplant patients and for destination therapy, more studies will be necessary to understand the mechanisms of this obscure GI bleeding and develop treatment strategies to minimize its development. (J Card Surg 2010;25:352‐356)

Myostatin activation in patients with advanced heart failure and after mechanical unloading

Myostatin inhibits myoblast differentiation/proliferation and may play a role in heart failure (HF) and reverse remodelling after left ventricular assist device (LVAD) support. This study sought to characterize myostatin expression and activation in advanced HF before and after LVAD support.

Recurrent remodeling after ventricular assistance: is long-term myocardial recovery attainable?

BACKGROUND Long-term left ventricular assist devices (LVAD) have been used both as a bridge to heart transplantation and to recovery of native myocardial function. Despite much evidence for reversal of some of the structural and functional changes present in the failing heart during LVAD support, clinical evidence for sustained myocardial recovery is scant. We describe 2 patients in whom myocardial recovery during LVAD support led to device explanation only to have heart failure recur. This necessitated a second LVAD implantation, a process that we have termed recurrent remodeling. METHODS The medical records of 2 patients with cardiomyopathy supported with HeartMate LVADs (Thermo Cardiosystems, Inc, Woburn, MA) were retrospectively reviewed. RESULTS One patient was supported with an LVAD for 2 months, at which time the LVAD was explanted. Progressive deterioration of cardiac function followed, requiring a second LVAD 19 months after LVAD explanation. After 2 months of further LVAD support, a second episode of apparent myocardial recovery was observed during a period of device malfunction. The other patient was supported with an LVAD for 12 months, at which time the LVAD was explanted. The patient experienced progressive hemodynamic deterioration and required a second LVAD 6 months after LVAD explantation. Heart transplantations of both patients were successful. CONCLUSIONS Our understanding of myocardial recovery in the setting of hemodynamic unloading with LVAD support has not yet progressed to the point where we are able to accurately predict successful long-term LVAD explantation. The evolution of reliable predictors of sustainable myocardial recovery will help to avoid further cases of recurrent remodeling requiring repeat LVAD implantation.

Cardiac Recovery During Mechanical Assist Device Support

It is estimated that approximately 100,000 patients in the United States with advanced heart failure might benefit from cardiac transplantation, while donors are available for only 2000 recipients each year. Left ventricular assist devices (LVADs) are used both for bridge to transplantation and for long term support in patients ineligible for transplant. Both cardiac transplantation and long term LVAD therapy are limited by the complications of immunosuppression and device malfunction. Currently, a major focus of investigation in advanced heart failure is the temporary use of LVADs as a bridge to recovery of the native heart. While end-stage heart failure was once thought to be irreversible, research now suggests that LVAD support may lead to both cellular and functional recovery. Ultimately, patients with advanced cardiac disease might be managed with temporary mechanical support combined with pharmacological and cellular therapies, in place of cardiac transplantation or long term LVAD support. In this paper we review the evidence demonstrating the impact of LVAD support on the pathophysiology of end stage heart failure. Furthermore, we outline the clinical evidence for cardiac recovery seen in LVAD patients. Finally, we describe techniques to measure cardiac function during LVAD support and the criteria that have been suggested to select patients for device explantation for recovery.

Young Patients With Nonischemic Cardiomyopathy Have Higher Likelihood of Left Ventricular Recovery During Left Ventricular Assist Device Support

BACKGROUND Recovery of ventricular function during left ventricular assist device (LVAD) support allowing device explantation occurs infrequently. We explored the hypothesis that certain patient profiles are more likely to exhibit LV recovery during LVAD support. METHODS AND RESULTS A retrospective analysis of data from the HeartMate II bridge to transplant (BTT) and destination therapy (DT) trials was conducted, including 490 BTT, 600 DT, and 18 compassionate-use patients. Of the 1,108 patients, 20 (1.8%; 10 BTT, 10 DT) were explanted owing to LV recovery. The median age was 33 years, and 12 patients (60%) were <40 years of age. History of heart failure was <1 year for 11 patients (61%), and the primary etiology was nonischemic (90%). Of the patients with nonischemic etiologies and <1-year history of heart failure, 13% were explanted. Three patients required LVAD reimplantation; of the remaining 17, 16 remain alive. At follow-up (median 510 days), the mean ejection fraction was 42% (20%-67%) and the mean left ventricular end-diastolic diameter was 55 ± 8 mm. At the 2-year follow-up (n = 13), patients were New York Heart Association functional class I or II and overall survival rate was 85 ± 11%. CONCLUSIONS The results of this study suggest that LV recovery is most likely to occur in young patients (<40 years) with nonischemic cardiomyopathy of <1 year duration. Two-year postexplant survival was excellent.

Combining neurohormonal blockade with continuous-flow left ventricular assist device support for myocardial recovery: A single-arm prospective study

BACKGROUND Combining mechanical unloading by a continuous-flow left ventricular assist device (CF-LVAD) and neurohormonal blockade with heart failure medications (HFMED) is an underexplored clinical strategy to promote recovery of cardiac function in patients with advanced heart failure (HF). METHODS We implemented a clinical protocol to achieve maximal neurohormonal blockade after placement of a CF-LVAD and assessed its utility in an LVAD weaning (6,200 rpm) study. Thirty-four subjects were enrolled after CF-LVAD and were managed with aggressive, bi-weekly up-titration of HFMED. RESULTS Twenty-one subjects (8 with coronary artery disease, 13 with idiopathic dilated cardiomyopathy) were included in this LVAD weaning investigation. Overall, combined CF-LVAD and HFMED resulted in significant reverse remodeling with a decrease in left atrial volume index (44.7±16.0 to 31.6±12.1 ml/m(2), p < 0.001) and LV internal diastolic diameter (6.7±1.5 to 6.0±1.6 cm, p = 0.003) and an increase in LV ejection fraction (17.4±6.5 to 33.1±16.2%, p < 0.001) during LVAD weaning (6,200 rpm). Five of 21 (24%) subjects demonstrated recovery of biventricular function. Exploratory analysis showed that recovered subjects had shorter duration HF, less myocardial fibrosis and less myocyte hypertrophy, and were supported at higher LVAD speeds. CONCLUSIONS CF-LVAD support in combination with HFMED leads to significant reverse remodeling in patients with advanced HF. Using this approach, one quarter of patients demonstrated complete recovery of cardiac function. Our results suggest that bridge to recovery in the current device era is a clinically meaningful phenomenon and merits further investigation.

A Multicenter Study of Noninvasive Cardiac Output by Bioreactance During Symptom-limited Exercise

BACKGROUND Hemodynamic responses to exercise were assessed in patients with varying degrees of chronic heart failure (CHF) to determine the feasibility of using bioreactance during exercise testing in multicenter studies of CHF. METHODS AND RESULTS A total of 210 symptomatic CHF patients and 22 subjects without heart failure were subjected to symptom-limited exercise testing on a bicycle (105) or treadmill (127) while measuring gas exchange for VO(2), cardiac output (CO) noninvasively by a bioreactance technique, heart rate, and blood pressure. Peak CO (pCO) and VO(2) (pVO(2)) during exercise were lower in patients with higher New York Heart Association (NYHA) class, in females and in older patients. Multiple linear regression analysis showed that pCO (L/min)=19.6+4.M -2.1.NYHA+1.9.G -0.09.Age, where M=1 for treadmill and 0 for bicycle and G=1 for males and 0 for females. Similarly, pVO(2) (mL/kg/min)=24+2.1.M -2.9.NYHA+1.26.G -0.08.Age. VO(2) and CO were also highly correlated to each other: pCO (mL/kg/min)=0.059+0.007.pVO(2)+0.036.M -0.025.G. Similar correlations were determined for other parameters of exercise, including left ventricular power, and the ratio of peak/resting VO(2) (cardiovascular reserve), the ratio of peak/resting CO (cardiac reserve), and total peripheral vascular resistance. CONCLUSION Bioreactance-based noninvasive measurements of CO at rest and during exertion identified abnormalities of cardiovascular function consistent with those identified by pVO(2) and in prior studies using invasive CO measurements. This technique might therefore be useful for indexing disease severity, prognostication, and for tracking responses to treatment in clinical practice and in clinical trials.

Clenbuterol Increases Lean Muscle Mass but Not Endurance in Patients With Chronic Heart Failure

Clenbuterol, a beta(2)-agonist with potent anabolic properties, has been shown to improve skeletal muscle function in healthy subjects, and in high doses, promotes cardiac recovery in patients with left ventricular assist devices. In a small, randomized controlled study, we investigated the effect of clenbuterol on skeletal muscle function, cardiac function, and exercise capacity in patients with chronic heart failure. Clenbuterol was well tolerated and led to a significant increase in both lean mass and the lean/fat ratio. Maximal strength increased significantly with both clenbuterol (27%) and placebo (14%); however, endurance and exercise duration decreased after clenbuterol. Prior data support combining exercise training with clenbuterol to maximize performance, and on-going studies will evaluate this approach.