Prolonged Mechanical Support Research Articles

Off-pump versus on-pump myocardial revascularization in patients with ST-segment elevation myocardial infarction: A randomized trial

Conventional cardioplegic arrest coronary artery bypass grafting after ST-segment elevation myocardial infarction is associated with high mortality and morbidity. The benefits of off-pump surgery have been suggested. This study randomly evaluated the impact of the off-pump technique on clinical results. Between February 2002 and October 2007, 128 patients with ST-segment elevation myocardial infarction who underwent myocardial revascularization within 48 hours from the onset of symptoms were randomly assigned to 2 groups: on-pump group (66 patients/51.5%) and off-pump group (63 patients/48.5%). The primary end point was the incidence of in-hospital death and outcomes (low cardiac output syndrome, prolonged mechanical and pharmacologic cardiac support, prolonged mechanical ventilation support, and postoperative length of stay in intensive care unit and hospital). The secondary end point was the evaluation of myocardial infarct size measured by the perioperative serum release of cardiac troponin I and the improvement of contractile cardiac function evaluated by the wall motion score index. Overall in-hospital mortality was 4.6%. In-hospital mortality was 7.7% (5 patients) in the on-pump group and 1.6% (1 patient) in the off-pump group (P = .04). Statistically significant differences were found between the 2 groups concerning the incidence of low cardiac output syndrome (P = .001), time of inotrope drugs support (P = .001), time of mechanical ventilation (P = .006), reoperation for bleeding (P = .04), intensive care unit stay (P = .01), and in-hospital stay (P = .02). Statistically significant differences also were found between the 2 groups concerning the incidence of in-hospital death in patients who were admitted to surgery in cardiac shock (P = .0018) and patients who underwent surgery within 6 hours from the onset of symptoms (P = .0026). The procedure in 1 patient (1.6%) in the off-pump group was converted to the on-pump beating heart technique. The serum levels of cardiac troponin I were high in the on-pump group during the first 48 hours after surgery. Myocardial function was better in the off-pump group. There were no cardiac-related late deaths, and patients had no recurrent cardiac events. Off-pump surgery reduced early mortality and morbidity in patients with ST-segment elevation myocardial infarction in respect to the conventional procedure. Off-pump surgery showed better results than on-pump surgery in patients who underwent surgery within 6 hours from the onset of symptoms and in patients with cardiogenic shock.

Mechanical circulatory support: registering a therapy in evolution.

Received March 26, 2008; accepted June 5, 2008. The development of durable mechanical circulatory support systems paralleled the expansion of cardiac transplantation. The National Institutes of Health sponsored grants in the 1980s to develop implantable left heart assist systems; 20 years later, they contracted for a national registry, the Interagency Registry for Mechanical Assisted Circulatory Support, to track the clinical evolution of this new technology. The Interagency Registry for Mechanical Assisted Circulatory Support has refined the classification of New York Heart Association class IV heart failure, standardized adverse event definitions, and explored outcomes of device type, location, and strategy. The majority of mechanical circulatory support patients are between the ages of 50 and 70 years, and ≈90% of patients are in the highest levels of clinical instability before implantation. Six-month survival after device implant is 75%, but it increases to 80% among those not in shock at implantation. Patients who require biventricular support have decreased survival. As longer-term outcomes are analyzed, improved outcomes may justify triage of high-risk patients awaiting heart transplantation to chronic mechanical circulatory support. The application of mechanical circulatory support in animal experiments can be traced back to the work of Carrel and Lindberg in the 1930s.1,2 With the initial foray into open-heart surgery in the 1950s,3,4 the stage was set for application of more prolonged mechanical support for myocardial recovery in situations of failure to wean from cardiopulmonary bypass. Although initial reports of successful recovery used roller-pump technology,5 their applicability was limited by issues of blood trauma and difficulties in modulation of pump speed in response to changes in left atrial and left ventricular pressure. The first clinical application of a pneumatically driven ventricular assist device (VAD) is attributed to DeBakey in 1966, in which a 37-year-old woman was successfully supported for 10 …

Recovery of Heart Function in Children With Acute Severe Heart Failure

The prognosis of acute heart failure is such that many children are considered for transplantation. Recovery of severe heart failure in a proportion of patients diagnosed with either dilated cardiomyopathy or myocarditis is well recognized, and this complicates the assessment for transplantation. There is little data on the time scale of recovery of heart function in children. To describe the time course over which echocardiographic improvement of systolic function occurred in a cohort of children who presented in acute heart failure, without structural or metabolic abnormality. Children with a first presentation of acute severe heart failure between 1990 and 2005. Time from presentation to the echocardiogram before left ventricular fractional shortening (FS) improved to 20% and 30% (complete recovery) was recorded. Twenty-seven children (11 male) were identified, and all had an initial FS <15%. Twenty-one patients required intravenous inotropes and three patients required extracorporeal membrane oxygenation. Seven patients had been on the active transplant list for a mean duration of 155 days. Four patients had probable viral myocarditis. Mean age at presentation was 15.7 (range, 0.1-72) months. Mean time to an FS of 20% was 3.6 (0.2-18) months and to 30% was 8.9 (0.7-24) months. Complete recovery occurred within 6, 9, 12, 18, and 24 months of presentation in 44%, 55%, 66%, and 96%, respectively. There was no correlation between age of presentation and length of time to recovery. Complete recovery of left ventricular systolic function is often delayed to more than 1 year from presentation. This may have major implications for timing of transplantation in an era where prolonged mechanical cardiac support is feasible even in infants.

Pronóstico de los enfermos con enfermedad pulmonar obstructiva crónica reagudizada que precisan ventilación mecánica

To determine the variables associated with prognosis for acute exacerbation of chronic obstructive pulmonary disease (AECOPD) in mechanically ventilated patients. Prospective cohort study with retrospective analysis. 361 Intensive Care Units (ICU) in 20 countries. There were included in the study 522 patients who required mechanical ventilation for more than 12 hours due to an acute exacerbation of chronic obstructive pulmonary disease (AECOPD). In order to determine those variables associated with mortality, there was performed a recursive partition analysis in which the following variables were included: demographics, arterial blood gas prior to intubation, complications arising during mechanical ventilation (barotrauma, acute respiratory distress syndrome, ventilator-associated pneumonia, sepsis), organ dysfunction (cardiovascular, renal, liver, coagulation) and duration of ventilatory support. None. VARIABLES OF PRIME IMPORTANCE: ICU mortality. ICU and hospital mortality rates were 22% and 30%, respectively. Variables associated with mortality were cardiovascular dysfunction, renal dysfunction and duration of ventilatory support > 18 days. Median durations were as follows: mechanical ventilatory support, 4 days (P25: 2, P75: 6); weaning from ventilatory support, 2 days (P25: 1, P75: 5); stay in intensive care unit, 8 days (P25: 5, P75: 13); stay in hospital, 17 days (P25: 10, P75: 27). Mortality in the studied cohort of patients with AECOPD was associated with cardiovascular dysfunction, renal dysfunction and prolonged mechanical support.

Improvement of sympathetic nerve activity rather than myocardial fibrosis may contribute to functional recovery of idiopathic cardiomyopathy during prolonged mechanical ventricular support

Improvement of sympathetic nerve activity rather than myocardial fibrosis may contribute to functional recovery of idiopathic cardiomyopathy during prolonged mechanical ventricular support

Air-mattress motion therapy for respiratory failure after cardiothoracic surgery.

The standard management of respiratory failure after cardiothoracic surgery involves prolonged mechanical ventilation, drug support, and chest physiotherapy. We report the effectiveness of a novel type of respiratory physiotherapy, the air mattress V-CUE unit, which utilizes a computerized automatic combination of three movements: rotation, percussion, and vibration. Among 189 patients who underwent various cardiothoracic operations, 6 were eligible for V-CUE application, after the development of respiratory failure caused by early adult respiratory distress syndrome, massive atelectasis, or pulmonary infection. The V-CUE unit was used to treat six postsurgical patients, aged 58-73 years (mean, 65.8 years); four who had undergone coronary artery bypass grafting, one who had undergone mitral valve replacement, and one who had undergone a bilobectomy. The mean duration of supportive V-CUE was 3.9 days (range 2-6 days), and the mean duration of mechanical ventilation was 2.9 days. There was no need for reintubation or tracheotomy, and all six patients recovered uneventfully. Our preliminary results indicate that V-CUE dynamic air therapy is effective for managing postoperative respiratory failure, adjuvant to or complementary to standard therapy.

Platelet activation and aggregation profile in prolonged external ventricular support

Background Platelet function plays a major role in the understanding of thromboembolic events in prolonged mechanical support. We studied the platelet activation, platelet aggregation profile, and efficacy of aspirin in patients in whom an external ventricular assist device had been implanted. Patients and methods Fifteen patients were studied prospectively up to 6 weeks after implantation of the same type of ventricular assist device. Platelet function was studied weekly before daily aspirin administration. Aspirin efficacy was tested ex vivo by measuring platelet aggregation triggered by arachidonic acid. Flow cytometry was used to quantify the spontaneous and induced (adenosine diphosphate stimulation) expression of glycoproteins αIIbβ3, Ibα, and CD62P on platelet membranes. The plasma levels of von Willebrand factor (von Willebrand factor activity and von Willebrand factor antigen) and fibrinogen were also determined. Results Six of the 15 patients (26%) maintained an arachidonic acid-induced platelet aggregation despite daily aspirin treatment (250 mg). CD62P values remained increased during a 5-week postoperative period. Spontaneous levels of glycoproteins αIIbβ3 and Ibα on platelet membranes remained within a normal range with a preserved reactivity. The plasma levels of fibrinogen and von Willebrand factor remained increased during the entire study period. Conclusion In patients with an implanted external ventricular assist device, the platelet activation profile displays a persistent activation with a preserved reactivity associated with a persistent high inflammatory state and endothelial activation.

Effect of left ventricular assist device on circulatory autonomic nervous activity.

For evaluation of the autonomic nervous system (ANS) activity of patients with mechanical circulatory support including LVAD, IABP and PCPS, arterial pressure variability (APV) was examined. APV is the power density values of pressure signals. High frequency (0.15 to 0.4 Hz) and low frequency (0.04 to 0.15 Hz) components of APV are regarded as a function of the autonomic nervous system. Arterial pressure signals were acquired every 2 hours at 100 Hz for 6 minutes. Power spectral analysis was carried out, and APV was observed in 18 patients with IABP and/or PCPS. APV was also observed in 3 patients with LVADs (Xemex, Zeon Medical, Japan) before their discharge from ICU for transfer to another hospital for cardiac transplantation. Although the value gradually increased in 18 patients with IABP and/or PCPS, sustained low values of LFAnorm of APV in 6 patients were related to prolonged mechanical support, and 4 patients among them died consequently. The normalized power spectral component with low frequency (LFAnorm) was maintained at relatively high values in 3 patients with LVADs. The study results suggest that power spectral analysis of systemic arterial pressure offers a reasonable means for the evaluation of the severity of patient cardiovascular condition and for the prediction of clinical outcome. It also suggested that LVAD support exerts a favorable effect on ANS in patients with severe heart failure before cardiac transplantation.

Left ventricular assist devices: bridges to transplantation, recovery, and destination for whom?

Application of mechanical cardiac support now requires consideration of a wider range of goals beyond bridging to transplantation to include destination therapy and perhaps bridging to recovery.1,2 Responsible dissemination of the technology requires identification of patient populations from which to select candidates most likely to benefit. At this early stage, benefit is most apparent against a high background mortality from end-stage heart failure. Heart failure affects an estimated 5 million patients in the United States. Of those, ≈60% have heart failure with left ventricular dilation and reduced ejection fraction. Trials demonstrating benefit of therapies for heart failure have focused primarily on mild–moderate heart failure with reduced ejection fraction, generally with annual mortality in the range of 8% to 18%.3 Advanced heart failure has been defined as symptoms limiting daily activity (New York Heart Association class III and IV) despite attempted therapy with angiotensin-converting enzyme inhibitors, β-blockers, digoxin, and diuretics,4 a description that applies to ≈300 000 to 800 000 patients in the United States. Although often labeled as “refractory,” many patients enjoy improved quality of life and decreased hospitalizations after referral to experienced heart failure centers, where aggressive medical strategies focus on relief of congestion. Surgical approaches include complex revascularization, valvular repair/replacement, or ventricular reconstruction. When technically successful, biventricular pacing can improve functional status for many of the 25% to 40% of patients with marked ventricular asynchrony.5 If early stabilization allows institution of β-adrenergic–blocking agents, prognosis is further improved.6 Dedicated heart failure management programs that facilitate patient education, compliance, and fluid balance have been integral to benefits observed with these therapies. The highest-risk heart failure populations are best identified after optimization of current therapies. Low left ventricular ejection fraction is not sufficient description of either function or prognosis once heart failure has become advanced. Neither …

Cellular regression of fibrosis and hypertrophy following chronic LVAD support does not translate into sustained improvements in contractile function: results from the LVAD working group

Single case series from a small number of centers have documented that LVAD removal following prolonged mechanical support for patients with end-stage chronic heart failure is possible. Also, it has become clear that chronic mechanical unloading induces the regression of hypertrophy in failing myocardium. However, whether normalization of myocardial structure is essential or sufficient for the phenomenon of recovery is not clearly known. The LVAD Working Group (LVWG) is a multi-center prospective study of cardiac function during LVAD support that will define the rate, time course and durability of recovery of cardiac function.

ARTERIAL PRESSURE VARIABILITY FOR EVALUATION OF AUTONOMIC NERVOUS ACTIVITY OF PATIENTS WITH LEFT VENTRICULAR ASSIST DEVICE

Purpose: Arterial pressure variability (APV) is the power density values of pressure signals and high frequency (0.15 to 0.4 Hz) and low frequency (0.04 to 0.15 Hz) components of APV are regarded as the function of autonomic nervous system (ANS). APV was examined for evaluation of the ANS activity of patients with left ventrienlar assist device (LVAD). Methods: Arterial pressure signals were acquired every 2 hours at 100 Hz for 6 minitutes in patients in ICU. Power spectral analysis was carried out, and APV was observed in 3 patients with Zeon LVADs before their transfer for cardiac transplantation. For comparison, APV was also obsereved in 17 patients with IABP and/or PCPS. Results: The observation periods of 3 patients with LVADs were 15, 33 and 58 days respectively. The normalized power spectral component with low frequency (LFAnorm) was depressed initially and was gradually increased before their transfer. Although the value also gradually increased in 13 patients with LABP and/or PCPS, sustained low values of LFAnorm of APV in 4 patients were related to prolonged mechanical support, and 3 patients among them were expired consequently. Conclusion: Depressed LFAnorm of APV represented marked stress on ANS. The study results suggest that LVAD support exert a favorable effect on ANS in patients with severe heart failure before cardiac transplantation.

Predictors of poor RV function following LVAD implantation

Introduction: LVAD implantation is used as a bridge to cardiac transplantation in patients with decompensated end-stage CHF despite maximal medical therapy. Mechanical RV support may also be required in some patients but currently increases morbidity and requires continued hospitalization until transplantation. The etiology of the underlying disease process leading to CHF may impact on the likelihood of needing prolonged inotropic or mechanical RV support following LVAD implantation.

Enhanced immunoglobulin expression after prolonged mechanical support with left ventricular assist devices in myocardial samples from patients with severe congestive heart failure: a possible indicator of augmented humoral responsiveness

Prolonged mechanical support with left ventricular assist devices (LVADs) has become commonplace as a bridge to cardiac transplantation in patients with severe congestive heart failure (CHF). Patients with LVAD support have immune sensitization characterized by increased levels of panel reactive antibodies (PRAs). Prior work by others implicates B cell activation in patients with LVADs. LVAD support also decreases the expression of proteins whose expression is abnormally enhanced by CHF. To evaluate the effect of LVAD support on immunoglobulin (Ig) expression, we examined left ventricular (LV) tissue obtained from 8 patients at the time of LVAD implantation and subsequently at the time of cardiectomy and LVAD removal for cardiac transplantation after prolonged LVAD support. The abundance of mRNA for genes of interest was determined in matched LV tissues from these 8 patients by performing a broad analysis of gene expression using an Affymetrix chip platform examining 60,000 defined gene sequences. The mRNA was compared between LV samples from LVAD implantation and from cardiectomy. 54 genes were noted to have significant up-regulation at cardiectomy compared to LVAD implantation. In particular, the genes for the Ig heavy constant γ and μ regions and Igκ and λ regions showed significantly enhanced LV expression at cardiectomy compared to LV from LVAD insertion, indicating enhanced expression in the LV as a result of LVAD support. This enhanced expression ranged from a 3.6 fold increase for Igκ constant region to a 16.02 fold increase in the Ig heavy constant gamma 3(G3m) gene. In contrast, natiuretic peptide (NP) expression declined 5.88 fold from LVAD insertion to cardiectomy. This latter finding is consistent with previous observations from our group and others that LVAD support results in decreased NP expression. We conclude that LVAD support results in enhanced expression of Ig genes, most likely reflecting activation of immune cells in the LV which subsequently produce these Ig and may play a role in the elevated PRAs after LVAD support.

Reversal of metallothionein expression is different throughout the human myocardium after prolonged left-ventricular mechanical support

Objectives We examined the distribution of metallothionein (MT), a stress-inducible protein, and the cardiomyocyte diameter in human hearts after left-ventricular assist device (LVAD) support. Background Remodeling in end-stage heart failure is characterized by myocyte hypertrophy and alterations of several inducible proteins. LVADs used as a bridge to cardiac transplantation unload the left ventricle and may lead to a reversal of the remodeling, but little is known about the pathophysiology of this process. Methods The immunoreactivity for MT and the cardiomyocyte diameter was analyzed in left-ventricular tissue specimens of 17 patients with end-stage heart failure before and after LVAD support. Results MT positive cells were mainly located sub-endocardially in vacuolized cardiomyocytes and in small vessels throughout the myocardium. During LVAD support, MT-positive myocytes decreased in the sub-endocardial ( p < 0.008) and sub-epicardial region ( p < 0.003), MT-positive vessels decreased similarly ( p < 0.003). Cardiomyocyte diameter decreased significantly only in the sub-endocardium ( p < 0.03). Hearts of patients supported longer than 88 days (= median) showed substantially lower MT reactivity at the time of LVAD explantation as compared to patients supported less than 88 days. Conclusion Our results suggest that unloading of the left ventricle during prolonged LVAD support leads to regression of cellular hypertrophy and a decrease of MT expression. The preferential reduction of MT-positive vacuolized cardiomyocytes in the sub-endocardium is comparable with the concept of greatest reduction of wall stress in this area of the myocardium and may be due to the improvement of myocardial blood flow and the energy balance.

Mechanical circulatory support devices in the treatment of heart failure.

With an increasingly aging population, heart failure is a major health issue, affecting more than 10% of the population over 65 years of age, and costing hundreds of millions of dollars per year for ongoing care. Even with maximal medical therapy, annual mortality rates of in excess of 25% are commonly reported. Over the last three decades, various surgical approaches have been examined in the hope of improving the outcome of congestive cardiac failure. These procedures range from simple coronary revascularisation to left ventricular reduction surgery and cardiac transplantation. Although of value in selected situations, no surgical approach, beyond transplantation, has had significant impact on the outcome of heart failure. In the last decade, development in the area of mechanical support for the failing heart has continued to expand at a rapid rate. Strong evidence now exists to show that in many patients with advanced heart failure, prolonged mechanical support results in significant myocardial recovery. There are currently several mechanical support devices available for clinical use, although most are considered experimental in this country. These devices are expensive and are not without significant complications, but early results of their use as either a bridge to transplantation or as a stand alone treatment, have been very encouraging. Currently available mechanical assist devices are described, with discussion of indications for implantation, complications and results of their use.

ALTERED MYOCARDIAL AND ENDOTHELIAL EXPRESSION OF CYCLOOXYGENASE-2 AFTER PROLONGED MECHANICAL SUPPORT IN PATIENTS WITH SEVERE IDIOPATHIC DILATED CARDIOMYOPATHY

1044 Cyclooxygenase-2 (COX-2) expression is induced by inflammatory cytokines in cardiac myocytes and endothelial cells of patients with severe congestive heart failure (CHF). COX-2 in turn produces prostanoids which are inflammatory mediators involved in the pathogenesis of CHF. Prolonged mechanical support of the cardiovascular system with left ventricular assist devices (LVAD), which are used to bridge patients with severe CHF to cardiac transplantation, have been shown to reduce myocardial TNF-α expression as a result of sustained mechanical unloading of the failing myocardium. The effect of this sustained unloading on myocardial expression of COX-2. We hypothesized that myocardial expression of COX-2 would be enhanced in patients with severe congestive heart failure and that sustained unloading of the myocardium by LVAD would significantly reduce cardiac myocyte and endothelial COX-2 expression. As sepsis also induces COX-2 expression, the role of infection in patients with LVAD was also investigated. To explore this, we obtained myocardial samples from eight patients awaiting transplant at the time of LVAD placement and subsequently at the time of transplantation. Three of these patients had no infection at the time of transplant; five were infected at the time of transplant. The paired myocardial samples obtained at LVAD implantation and after transplant were stained immunohistochemically for COX-2. Myocyte and endothelial COX-2 expression was defined as the percentage of myocardium expressing COX-2. Three patients without infection showed reduced COX-2 expression (mean±SD) after LVAD support (50±35% vs 13±6%,p<0.05). In contrast, the five infected patients showed no significant change in COX-2 expression after LVAD support (43±28% vs 54±28%;p=NS). We conclude that: 1) COX-2 expression by the myocardium and endothelium is reduced as a result of LVAD support in the absence of infection but; 2) the presence of concomitant infection maintains myocardial COX-2 expression likely due to the continued presence of inflammatory cytokines.

Altered myocardial and endothelial expression of cyclooxygenase-2 after prolonged mechanical support in patients with severe idiopathic dilated cardiomyopathy: S. E. Belland, R. Sangrigoli, V. Jeevanandam, H. J. Eisen, Temple University School of Medicine, Philadelphia, PA

Altered myocardial and endothelial expression of cyclooxygenase-2 after prolonged mechanical support in patients with severe idiopathic dilated cardiomyopathy: S. E. Belland, R. Sangrigoli, V. Jeevanandam, H. J. Eisen, Temple University School of Medicine, Philadelphia, PA

Inflow Valve Regurgitation During Left Ventricular Assist Device Support May Interfere With Reverse Ventricular Remodeling

Background. Left ventricular assist devices have been reported previously to reverse ventricular remodeling in patients with dilated cardiomyopathy. In patients with prolonged mechanical support, structural failure of the left ventricular assist device inflow valve can cause regurgitation into the left ventricle, which may affect adversely this process.Methods. Left ventricular end-diastolic pressure–volume relation of hearts explanted from 8 patients with left ventricular assist device and 8 control subjects with idiopathic cardiomyopathy was determined ex vivo at the time of transplantation.Results. Duration of mechanical support ranged from 210 to 276 days (mean ± standard deviation = 283 ± 76 days) in 3 patients with inflow valve regurgitation versus 100 to 155 days (132 ± 22 days) in 5 patients without (p = 0.005). The end-diastolic pressure–volume relation of all hearts supported mechanically was shifted to the left toward normal controls. This effect was markedly attenuated in patients with inflow valve regurgitation.Conclusions. Mechanical assistance can cause reverse remodeling in patients with dilated cardiomyopathy as evidenced by the shift in the end-diastolic pressure–volume relation curve to the left. Inflow valve failure, associated with prolonged support, can attenuate changes in left ventricular structure and dimension. Ineffective pressure and volume unloading may explain these observations.

Weaning from Cardiopulmonary Bypass: A Practical and Simplified Overview

Weaning off cardiopulmonary bypass is a simple process that may occasionally prove very difficult or virtually impossible. Preparation for weaning includes the adjustment of temperatures, tissue oxygenation, hematocrit, pH, electrolytes, and cardiac rhythm and rate. Cardiac action as routinely assessed will allow patients to be classified into 3 groups. Group A includes patients which will obviously offer no difficulties to remove from CPB. Group B comprises patients with mild to moderate dysfunction; they will require some physiological (Starling law) or pharmacological (inotropes, vasoactive drugs) support to be disconnected from pump. Group C are the patients with poor or no cardiac action, which will require either an aggressive pharmacological support or prolonged mechanical support as alternatives to sustain life. Resources for prolonged supportive bypass and mechanical devices shall be available and their application to difficult situations should be part of CPB protocols.

Evolution of human cardiac myocyte dimension during prolonged mechanical support

In animal models using left ventricular assist systems over long time periods, myocardial cellular atrophy has been reported, raising concern that prolonged clinical use of such systems might lead to deterioration in left ventricular function. At the University of Pittsburgh, long-term clinical use of the Novacor (Baxter Healthcare Corp., Novacor Div., Oakland, Calif.) left ventricular support system for patients awaiting heart transplants has allowed study of the effects of long-term mechanical support on human subjects. This study determined that cardiac myocyte dimension is initially greater in patients with end-stage cardiac disease who require support rather than in patients with the same disease who do not require such support. Although myocyte dimension does decrease within a few days of the inception of support, this decrease merely brings cell size closer to the values usual in patients with chronic end-stage cardiac disease, and no further shrinkage is observed. Thus the Novacor left ventricular assist system does not appear associated with left ventricular atrophy, and its long-term use may not be detrimental to left ventricular function.