Long-Term Mechanical Support With the HeartMate II LVAS

Contemporary outcomes of continuous-flow left ventricular assist devices-a systematic review

Background

End stage heart failure is a major cause of morbidity and mortality, and its prevalence is expected to rise with the ageing population. For suitable patients, orthotopic heart transplantation remains the gold standard therapy, however, a paucity of donor organs has led to the development of left ventricular assist devices (LVAD). These devices can be utilized as either a bridge-to-transplant (BTT) or as an alternative to heart transplantation. While these devices can prolong life and improve quality of life, they are associated with a significant number of adverse events. We aim to systematically review the literature to quantify survival and the incidence of adverse events following implantation of continuous-flow LVADs (cf-LVAD).

Methods

A systematic review was performed to determine outcomes following implantation of a cf-LVAD. Primary outcomes were survival and frequency of adverse events (such as bleeding, infection, thrombosis, stroke and right ventricular failure). Secondary outcomes included quality of life and assessment of functional status.

Results

Sixty-three studies reported clinical outcomes of 9,280 patients. Survival after cf-LVAD varied between studies. Industry-funded trials generally reported better overall survival than the single- and multi-center case series, which showed significant variation. The largest registry report documented twelve, twenty-four and forty-eight-month survival rates of 82%, 72% and 57% respectively. The most commonly reported adverse events were gastrointestinal bleeding (GIB), device-related infection, neurological events and right heart failure (RHF). Bleeding, RHF and infection were the most frequent complications experienced by those supported with cf-LVAD, occurring in up to 35%, 40% and 55% of patients, respectively. Quality of life as measured using the Kansas City Cardiomyopathy Questionnaire (KCCQ) and functional status as measured with the 6-minute walk test (6MWT) improved after cf-LVAD implantation with no decline evident two years after implantation.

Conclusions

The paucity of donor hearts has led to the development of left-ventricular assist devices as a BTT or as a destination therapy (DT). Outcomes after cf-LVAD implantation are excellent, with short-term survival comparable to heart transplantation, but long-term survival remains limited due to the incidence of post-implantation adverse events. Despite these complications, quality of life and functional status improve significantly post-implantation and remain improved over the long-term. This study demonstrates the potential benefits of cf-LVAD therapy whilst also identifying adverse events as an area of increased morbidity and mortality.

Survival in elderly patients supported with continuous flow left ventricular assist device as bridge to transplantation or destination therapy

BACKGROUND

Published data on mechanical circulatory support for elderly patients in continuous flow devices are sparse and suggest relatively poor survival. This study investigated whether LVADs can be implanted in selected patients over the age of 65 years with acceptable survival compared with published outcomes.

METHODS AND RESULTS

A single-center retrospective analysis was conducted in 64 consecutive patients ≥65 years of age implanted with a continuous-flow left ventricular assist device (CF-LVAD) as either bridge to transplantation or destination therapy from August 2005 to January 2012. Baseline laboratory and hemodynamic characteristics and follow-up data were obtained. Median survival was 1,090 days. Survival was 85%, 74%, 55%, and 45% at 6 months and 1, 2, and 3 years, respectively. Our cohort had a baseline mean Seattle Heart Failure Model (SHFM) score of 2.6 ± 0.9. Observed survival was significantly better than SHFM-predicted medical survival. Stratification by age subsets, renal function, SHFM, implantation intention, or etiology did not reveal significant differences in survival. The most common cause of death was sepsis and nonlethalcomplication was bleeding.

CONCLUSIONS

Our experience with patients over the age of 65 receiving CF-LVADs suggests that this group demonstrates excellent survival. Further research is needed to discern the specific criteria for risk stratification for LVAD support in the elderly.

Ventricular assistance devices as bridge to transplantation

The authors herein review the rationale and indications for the use of ventricular assistance devices as a bridge to heart transplantation and discuss the current evidence on the subject. The potential effects of device implantation on posttransplant outcomes and the therapeutic strategies in acute and elective cases are revised and illustrated.

Cerebrovascular complications of left ventricular assist devices

Left ventricular assist devices (LVADs) are increasingly being used as a bridge to heart transplantation or destination therapy. It is unclear which antithrombotic regimen should be used to reduce the risk of stroke. We systematically reviewed the literature on all types of antithrombotic regimens and stroke in patients with any type of LVADs. Our primary outcome measure was the mean incidence of any type of stroke. Twenty-six articles were selected as relevant, comprehending 1989 patients with a mean LVAD support of 200 days (range 30-621). The mean proportion of patients affected with stroke was 20% (range 0-55%), with a mean incidence of 0.74 (range 0-6.91) events/patient-year. Support with HeartMate II and a regimen of postoperative heparin converted to coumarins, acetylsalicylic acid (ASA) and dipyridamole resulted in 0.17 (mean; range 0.06-0.29) strokes/patient-year. HeartMate II support and the same regime without heparin was associated with 0.07 (mean; range 0.03-0.11) strokes/patient-year. A Novacor device with heparin, converted to coumarins, was associated with 3.82 (mean; range 1.03-6.91) strokes/patient-year, while ASA added to this regime resulted in 0.97 ischaemic strokes/patient-year (mean; range 0.53-1.48). Other combinations of assist devices and antithrombotic regimes were investigated in one or two studies only. This systematic review provides risk estimates for stroke for various LVADs and antithrombotic regimes. Our findings indicate that the postoperative use of heparin in HeartMate II patients is doubtful, and suggest an important role for antiplatelet drugs to prevent stroke in patients supported with a Novacor device.

Changing outcomes in patients bridged to heart transplantation with continuous- versus pulsatile-flow ventricular assist devices: an analysis of the registry of the International Society for Heart and Lung Transplantation. J Heart Lung Transplant. 2011;30:854-861. [PMID: 21571550 DOI: 10.1016/j.healun.2011.03.019]

BACKGROUND

Patients bridged to heart transplantation with left ventricular assist devices (LVADs) have been reported to have higher post-transplant mortality compared with those without LVADs. Our aim was to determine the impact of the type of LVAD and implant era on post-transplant survival.

METHODS

In this study we included 8,557 patients from the registry of the International Society for Heart and Lung Transplantation. We examined post-transplant outcomes in 1,100 patients bridged to transplant with pulsatile-flow LVADs between January 2000 and June 2004 (first era), 880 patients bridged with pulsatile-flow LVADs between July 2004 and May 2008 (second era), and 417 patients bridged with continuous-flow LVADs in the second era. Patients who required intravenous inotropes but not LVAD support (n = 2,728) and patients who did not require either LVAD or inotropes (n = 3,432) served as controls.

RESULTS

Post-transplant survival of patients bridged with pulsatile LVADs improved significantly between the first and the second era (p = 0.03). In the second era, there was no significant difference in post-transplant survival of patients bridged with pulsatile- vs continuous-flow LVADs (p = 0.26), and survival rates in the 2 groups were not statistically different from that of the non-LVAD group. Graft rejection was similar in patients bridged with LVADs compared to those without LVADs.

CONCLUSIONS

In the most recent era, the use of either pulsatile- or continuous-flow LVADs did not result in increased post-transplant mortality. This finding is important as the proportion of patients with LVADs at the time of transplant has been rising.

Miniaturization of a magnetically levitated axial flow blood pump

This article introduces a unique miniaturization process of a magnetically levitated axial flow blood pump from a functional prototype to a pump suitable for animal trials. Through COMSOL three-dimensional finite element analysis and experimental verification, the hybrid magnetic bearings of the pump have been miniaturized, the axial spacing between magnetic components has been reduced, and excess material in mechanical components of the pump was reduced. Experimental results show that the pump performance was virtually unchanged and the smaller size resulted in the successful acute pump implantation in calves.