Recovery of pulmonary function in patients undergoing extended left ventricular assistance

LVAD-Induced Reverse Remodeling: Basic and Clinical Implications for Myocardial Recovery

BACKGROUND

With improved technology, increasing clinical experience, and expanding indications for use, left ventricular assist devices (LVADs) are assuming a greater role in the care of patients with end-stage heart failure. Early in the course of LVAD use as a bridge to transplant, it became evident that some patients exhibit substantial recovery of ventricular function, which led to the concept of reverse remodeling.

METHODS AND RESULTS

Herein we summarize and integrate insights derived from a multitude of studies that have investigated how LVAD support influences ventricular structural, cellular, extracellular matrix, molecular, biochemical, and metabolic characteristics of the end-stage failing heart. The focus includes a review of the extent and sustainability of reverse remodeling, the important advances in understanding of the pathophysiology of heart failure derived from these studies and the implications of these findings for development of new therapeutic strategies.

CONCLUSION

In brief, studies of LVAD-heart interactions have led to the understanding that although we once considered the end-stage failing heart of patients near death to be irreversibly diseased, when given sufficient mechanical unloading and restoration of more normal neurohormonal milieu, a relatively large degree of myocardial recovery is possible. Comparison of effects on right and left ventricles have provided mechanistic insights by implicating hemodynamic unloading as primarily regulating certain aspects of reverse remodeling, neurohormonal factors as regulating other aspects, and joint regulation of still other aspects. As such these observations have driven a shift of thinking of chronic heart failure as a progressive irreversible disease process to a potentially treatable entity.

[Perioperative management of ventricular assist devices]

OBJECTIVE

To review the perioperative anaesthetic management of ventricular assist devices.

DATA SOURCES

Extraction from Pubmed database of french and english articles on the perioperative anaesthetic management of ventricular assist devices for 15 years.

DATA SELECTION

The collected articles were reviewed and selected according to their quality and originality. The more recent data were selected.

DATA SYNTHESIS

Cardiac transplantation is an effective treatment for patients in end stage cardiac failure, but the average waiting time of 17 months, associated with the lack of organs (357 out of 832 candidates were transplanted in 1996) results in a high number of deaths in patients awaiting transplantation. The appearance in the 1980's, of the first ventricular assist device (VAD) provided a new possibility for the management of patients with end-stage cardiac failure awaiting transplantation ("bridge to transplant"). The perioperative anaesthetic management of these patients is complex. End stage cardiac failure, poorly responsive to pharmacological interventions, results rapidly in secondary organ dysfunctions. VADs produce a rapid improvement in haemodynamic, renal, hepatic and neuro-endocrine functions over a 2 months period, allowing transplantation to take place under optimal conditions. However VADs are not without complications (1 year mortality of 20%), of which the major are: infections (40%), perioperative haemorrhage (30%) and thrombo-embolic sequelae (30%). A best knowledge of pathophysiology of these complications is necessary to an optimal management of patients with ventricular assist devices.

Left ventricular assist devices: an alternative to medical therapy for end-stage heart failure

Although aggressive medical therapy and ultimately cardiac transplantation have long been the therapeutic mainstays for patients with end-stage heart failure, the left ventricular assist device (LVAD), which was originally used clinically as a bridge to transplantation, may also be used as destination therapy. LVAD therapy for selected patients has been shown in the REMATCH trial to be superior to medical therapy in ameliorating symptoms and improving outcome in patients with terminal heart failure. LVAD therapy has also proved useful in improving native heart function by neuroendocrine modulation and reverse remodeling. Furthermore, current evidence suggests that when LVAD therapy is utilized to improve ventricular function, it may be further enhanced when combined with aggressive medical therapy.

Permanent ventricular assist device support versus cardiac transplantation

BACKGROUND

Although cardiac transplantation provides excellent therapy for some patients with terminal heart failure, the results are limited by the scarcity of donor organs, reduced long-term survival, and comorbid conditions. Current experience with temporary left ventricular assist devices suggest that a permanent, totally, or near totally implantable device may be a viable alternative.

METHODS

We analyzed data from the 1997 International Society for Heart and Lung Transplantation (ISHLT) Registry and other literature on heart transplantation and compared survival and complication rates with our experience and that of others with temporary ventricular assist devices. From these data, we attempted to identify those patients who would benefit most from permanent left ventricular assist systems (LVASs).

RESULTS

Among heart transplant candidates, United Network for Organ Sharing (UNOS) status II, O blood type, weight >180 lb, older age, and preformed antibodies are negative factors for receipt of donor hearts. Of patients transplanted, women and nonwhites have poorer outcomes. Success with wearable LVAS's suggest some of these patients might be better served with an LVAS than with cardiac transplantation.

CONCLUSIONS

Because LVAS's could be made readily available without the need for a waiting list, they might compete well with the strategy of cardiac transplantation.

The continuing evolution of mechanical ventricular assistance

A great number of patients suffer and die of the sequelae of acute and chronic heart failure each year. Although advances in medical and surgical therapy have benefited many of these patients, most have disease that is refractory to any definitive therapy. For these patients cardiac transplantation is the only remaining hope. Unfortunately, because of the increasing demand for donor organs in the face of a fixed and limited supply, this option is available to only a small percentage of these patients. Even in patients accepted for transplantation, a significant waiting list mortality has been observed. A variety of VADs have been developed since the first successful case of mechanical cardiac assistance more than 30 years ago. These devices differ in basic mechanical function, method of insertion, and degree of implantability and thus have different indications and potential applications. Whereas the intraaortic balloon pump and centrifugal pumps are effective short-term support modalities, extracorporeal and implantable pulsatile devices have been used successfully for long-term support of patients with reversible and nonreversible cardiac failure. Although these pumps have most commonly been used as bridges to transplantation, increasing clinical experience has supported the notion of long-term mechanical assistance as a definitive therapy for patients with end-stage heart disease. Although complications, particularly infection and thromboembolism, pose significant challenges and long-term device reliability remains to be fully determined, available implantable devices appear to be capable of providing effective long-term support. As data are obtained from currently ongoing trials comparing VAD support with medical therapy for end-stage heart failure, ethical and economic issues will assume increasing importance.