EFFECTS OF THE HEARTMATE II LEFT VENTRICULAR ASSIST DEVICE AS OBSERVED BY SERIAL ECHOCARDIOGRAPHY

Second generation continuous-flow left ventricular assist devices (LVADs) are now considered standard of care for patients with end-stage heart failure. Although heart transplantation is typically the goal, organs are often not readily available. Additionally, some patients may fail to meet the requirements necessary to receive this scarce commodity. The HeartMate II (Thoratec Corporation, Pleasanton, CA) is currently the only surgical device which is approved by the United States Food and Drug Administration to be used as a bridge to transplantation or for destination therapy. Increasing usage of these devices has lead not only to improved survival but also improvement in heart failure symptoms and quality of life.1,2 The serial evaluation of the effects on cardiac function, specifically of the HeartMate II, has recently been under review. Echocardiography is the imaging modality most often used as it is non-invasive, widely available and generally produces adequate image quality. Expected changes in ventricular geometry, systolic and diastolic function, hemodynamics and valvular function are critically important to understand, not only to maximize potential benefits of this therapy but also to avoid complications. It is generally agreed upon that the HeartMate II is a ventricular unloading device. Left ventricular (LV) dimensions have been reported to decrease and both mitral regurgitation and measures of ventricular filling are noted to improve.3-5 Reverse remodeling to the point of systolic or diastolic LV recovery is more controversial and likely depends on the cohort of patients being evaluated. Recovery to the point of explant of an LVAD remains rare although it has been documented that there are notable shifts at the myocyte and gene level towards more normal ventricular function.6 In general, those with ischemic cardiomyopathy that is end-stage and non-ischemic cardiomyopathy that is significantly dilated have shown little in the way of improvements in left ventricular ejection fraction (LVEF) with continuous-flow LVADs.4 Improvements in right ventricular (RV) size and function also remains controversial and depends on the echocardiographic parameter used. Right sided hemodynamics, however, have shown to improve.4,7 Finally, evaluation of the aortic valve and its notable structural and functional changes over time has been of increasing interest. Several published case series, reviews and mock circulatory systems have demonstrated a worsening of aortic insufficiency (AI), enlargement in aortic root dimensions, commissural aortic valve fusion and aortic stenosis. A better understanding of the pathophysiology behind these aortic valve changes is still desired in efforts to prevent potential clinical adverse effects.8-11 Several more recent publications have focused on the utility of transthoraic echocardiography to provide a comprehensive assessment of LVAD function.3,12 The primary aim of this study was to use echocardiography to serially evaluate all patients with a HeartMate II implanted at our institution out to 12 months to help establish the expected cardiac changes in this cohort. Some data has now been published establishing normal values for different echocardiographic measurements in stable outpatients out to 6 months but the total number of patients assessed with a HeartMate II remains small.4 Our goal is to not only further enrich the data available describing these effects but to also help draw conclusions about how best to monitor these patients and manage their devices. An additional goal is to supplement what is known regarding the effects of the HeartMate II on diastolic function, as little has been previously published.