Early planned institution of biventricular mechanical circulatory support results in improved outcomes compared with delayed conversion of a left ventricular assist device to a biventricular assist device

A novel approach to percutaneous right-ventricular mechanical support

OBJECTIVE

We report our initial experience with our newly developed percutaneous right-ventricular assist device (VAD) with CentriMag (perc CM-RVAD).

METHODS

A flexible outflow cannula placed from the right internal jugular vein to the pulmonary artery and an inflow cannula placed from the femoral vein to the right atrium constituted the perc CM-RVAD. When needed, biventricular support was provided with left VAD (LVAD), either with a percutaneous LVAD placed through axillary or femoral artery access or with a fully implantable LVAD.

RESULTS

Between January 2009 and June 2010, all of the attempted patients successfully received perc CM-RVAD (n = 8). Mean blood pressure, heart rate, and central venous pressure showed a trend toward improvement after the perc CM-RVAD, with less inotrope/vasopressor requirement. Mixed venous oxygen saturation (SvO(2)) increased significantly from 64 ± 20 Torr to 78 ± 6 Torr (P < 0.01). The percutaneous VADs were explanted after myocardial recovery in seven patients; however, in three of these, perc CM-RVAD was used as a temporary bridge to other devices. One patient was bridged to a surgical biventricular assist device (BiVAD) and transferred back to the referring hospital on support. One death occurred due to multiple-organ failure 8 days after explantation of the RVAD with recovery.

CONCLUSIONS

Perc CM-RVAD was feasible and provided hemodynamic improvement.

Who needs an RVAD in addition to an LVAD?

Mechanical circulatory support using left ventricular assist devices (LVAD) has become an accepted mode of therapy for both bridging patients with end-stage heart failure to transplant and as a destination therapy. Right ventricular (RV) dysfunction is common after LVAD insertion and is a significant source of morbidity and mortality in patients undergoing LVAD placement. Several studies have identified clinical, laboratory, hemodynamic, and echocardiographic parameters that may serve as risk factors for RV dysfunction after LVAD placement. Furthermore, scoring systems have been established to help quantitatively predict the potential need for RV support after LVAD placement.

Prolonged biventricular assist device support as a bridge to heart transplantation

We report a case in which long-term biventricular assist device (BiVAD) support enabled successful heart transplantation. The patient was diagnosed with dilated cardiomyopathy at age 11. She underwent implantation of a Toyobo LVAD, tricuspid valvuloplasty and annuloplasty at age 15. Right heart bypass (RHB) was established using a centrifugal pump. Right ventricular function showed no improvement during a ten-day period, and RHB was switched to a Toyobo RVAD on postoperative day (POD) 11. Because of poor oxygenation, veno-venous extracorporeal membrane oxygenation (V-V ECMO) was instituted. She was weaned from V-V ECMO on POD 14. She was brought to the United States on POD 189 under BiVAD support, and underwent heart transplantation on POD 199. She was discharged 4 months later. Two years after heart transplantation, she remained in New York Heart Association class one without rejection.

Assessment of right pump outflow banding and speed changes on pulmonary hemodynamics during biventricular support with two rotary left ventricular assist devices

The absence of an effective, easily implantable right ventricular assist device (RVAD) significantly diminishes long-term treatment options for patients with biventricular heart failure. The implantation of a second rotary left ventricular assist device (LVAD) for right heart support is therefore being considered; however, this approach exhibits technical challenges when adapting current devices to produce the lower pressures required of the pulmonary circulation. Hemodynamic adaptation may be achieved by either reducing the rotational speed of the right pump impeller or reducing the diameter of the right outflow cannula by the placement of a restricting band; however, the optimal value and influence of changes to each parameter are not well understood. Hemodynamics were therefore investigated using different banding diameters of the right outflow cannula (3-6.5 mm) and pump speeds (500-4500 rpm), using two identical rotary blood pumps coupled to a pulsatile mock circulation loop. Reducing the speed of the right pump from 4900 rpm (for left ventricle support) to 3500 rpm, or banding the Ø10 mm (area 78.5 mm²) right outflow graft to Ø5.4 mm (22.9 mm²) produced suitable hemodynamics. Pulmonary pressures were most sensitive to banding diameters, especially when RVAD flow exceeded LVAD flow. This occurred between Ø5.3 and Ø6.5 mm (22.05-38.5 mm²) and speeds between 3200 and 4400 rpm, with the flow imbalance potentially leading to pulmonary congestion. Total flow was not affected by banding diameters and speeds below this range, and only increased slightly at higher values. Both right outflow banding or right pump speed reduction were found to be effective techniques to allow a rotary LVAD to be used directly for right heart support. However, the observed sensitivity to diameter and speed indicate that challenges may be presented when setting appropriate values for each patient, and control over these parameters is desirable.

Survival after biventricular assist device implantation: an analysis of the Interagency Registry for Mechanically Assisted Circulatory Support database

BACKGROUND

Patients requiring biventricular assist device (BiVAD) for mechanical circulatory support (MCS) have substantially worse outcomes than patients requiring left VAD (LVAD) support only. Patient-specific risk factors have yet to be consistently identified in a large, multicenter registry, which may underlie the poorer outcomes for BiVAD patients. The Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) is a registry of U.S. Food and Drug Administration-approved durable MCS devices used for bridge-to-transplantation, destination therapy, or recovery. The purposes of this study were to 1) identify the underlying pre-implant characteristics of the population requiring BiVAD support that contribute to reduced survival, and 2) identify differences in postoperative outcomes with respect to adverse events compared with patients supported with LVAD alone.

METHODS

From June 2006 to September 2009, 1,646 patients were entered into the INTERMACS database in which adverse events and outcomes were recorded for primary implants with LVAD or BiVAD. Competing outcomes methodology was used to estimate the time-related probability of death, transplant, or recovery. Overall survival for all groups was analyzed with Kaplan-Meier methods and Cox proportional regression analysis.

RESULTS

The distribution of primary device implants included 1,440 LVADs and 206 BiVADs. BiVAD patients presented with a lower INTERMACS profile 93% in INTERMACS 1 or 2, compared with 73% for LVAD patients (p < 0.001). Survival at 6 months was 86% for LVADs and 56% for BiVADs (p < .0001). Adverse event rates, expressed as episodes/100 patient-months for the BiVAD group compared with LVAD, were significantly higher for infection (33.2 vs 14.3), bleeding (71.6 vs 15.5), neurologic events (7.9 vs 2.6), and for device failure (4.9 vs 2.0).

CONCLUSIONS

Patients requiring BiVAD support at the time of durable MCS implant are more critically ill at the time of MCS implant. BiVAD patients experience worse survival than patients supported with LVAD alone and higher rates of serious adverse events. Characteristics of the population present at the time of BiVAD implant likely influence post-implant MCS outcomes.

Management of right ventricular failure in the era of ventricular assist device therapy

The increasing incidence of patients with advanced heart failure, limited donor availability, and continued advancements in the field of mechanical circulatory support have made implantation of left ventricular assist device therapy (LVAD) an attractive option for patients with end-stage heart failure. Perioperative right ventricular failure (RVF) occurs frequently in patients undergoing LVAD implantation and is associated with significant morbidity and mortality. This review will discuss the pathophysiology of RVF, recent efforts to risk-stratify patients preoperatively, and current preoperative, perioperative, and postoperative management strategies.

Mechanical circulatory assistance

Although heart transplantation is the gold standard for the treatment of advanced stage heart failure, the implantation of mechanical circulatory support devices (MCSDs) has become a well-established therapy for this disease. As the population of patients with severe heart failure has grown, the utilization of MCSDs has increased considerably. That trend is expected to continue, especially in light of dramatic advances in MCSD technology. This review outlines the current status and future directions of mechanical circulatory support therapy in the setting of a constantly evolving field of supportive devices and adjuvant therapies.

Risk factors predictive of right ventricular failure after left ventricular assist device implantation

Right ventricular failure (RVF) after left ventricular assist device (LVAD) implantation appears to be associated with increased mortality. However, the determination of which patients are at greater risk of developing postoperative RVF remains controversial and relatively unknown. We sought to determine the preoperative risk factors for the development of RVF after LVAD implantation. The data were obtained for 175 consecutive patients who had received an LVAD. RVF was defined by the need for inhaled nitric oxide for >/=48 hours or intravenous inotropes for >14 days and/or right ventricular assist device implantation. An RVF risk score was developed from the beta coefficients of the independent variables from a multivariate logistic regression model predicting RVF. Destination therapy (DT) was identified as the indication for LVAD implantation in 42% of our patients. RVF after LVAD occurred in 44% of patients (n = 77). The mortality rates for patients with RVF were significantly greater at 30, 180, and 365 days after implantation compared to patients with no RVF. By multivariate logistic regression analysis, 3 preoperative factors were significantly associated with RVF after LVAD implantation: (1) a preoperative need for intra-aortic balloon counterpulsation, (2) increased pulmonary vascular resistance, and (3) DT. The developed RVF risk score effectively stratified the risk of RV failure and death after LVAD implantation. In conclusion, given the progressively growing need for DT, the developed RVF risk score, derived from a population with a large percentage of DT patients, might lead to improved patient selection and help stratify patients who could potentially benefit from early right ventricular assist device implantation.

Simultaneous temporary CentriMag right ventricular assist device placement in HeartMate II left ventricular assist system recipients at high risk of right ventricular failure

An approach is reported for right ventricle temporary mechanical support in long-term axial left ventricular assist device (LVAD) patients preoperatively judged at high risk of right ventricular (RV) failure. The timing for RV assist device (RVAD) weaning and the technique for its removal through a right mini-thoracotomy are described. This strategy provides a good outcome in LVAD recipients avoiding the risk of immediate postoperative RV failure.

Clinical management of continuous-flow left ventricular assist devices in advanced heart failure

Continuous-flow left ventricular assist devices (LVAD) have emerged as the standard of care for advanced heart failure patients requiring long-term mechanical circulatory support. Evidence-based clinical management of LVAD-supported patients is becoming increasingly important for optimizing outcomes. In this state-of-art review, we propose key elements in managing patients supported with the new continuous-flow LVADs. Although most of the presented information is largely based on investigator experience during the 1,300-patient HeartMate II clinical trial, many of the discussed principles can be applied to other emerging devices as well. Patient selection, pre-operative preparation, and the timing of LVAD implant are some of the most important elements critical to successful circulatory support and are principles universal to all devices. In addition, proper nutrition management and avoidance of infectious complications can significantly affect morbidity and mortality during LVAD support. Optimizing intraoperative and peri-operative care, and the monitoring and treatment of other organ system dysfunction as it relates to LVAD support, are discussed. A multidisciplinary heart failure team must be organized and charged with providing comprehensive care from initial referral until support is terminated. Preparing for hospital discharge requires detailed education for the patient and family or friends, with provisions for emergencies and routine care. Implantation techniques, troubleshooting device problems, and algorithms for outpatient management, including the diagnosis and treatment of related problems associated with the HeartMate II, are discussed as an example of a specific continuous-flow LVAD. Ongoing trials with other continuous-flow devices may produce additional information in the future for improving clinical management of patients with these devices.

Right ventricular function and left ventricular assist device placement: clinical considerations and outcomes

The HeartMate II is an axial-flow left ventricular assist device that is approved for the treatment of advanced heart failure as a bridge to transplant or destination therapy. Despite the success of this device, right ventricular failure remains a persistent problem in most studies. Right ventricular dysfunction is usually defined as the need for right heart mechanical support or the persistent requirement for inotropes to support right heart function beyond 14 days. Over 21 months, 45 patients with end-stage heart disease underwent placement of the HeartMate II at our institution. This continuous cohort of patients underwent a retrospective review to evaluate the incidence of right heart failure. The perioperative survival was 91% with no incidents of mechanical support for the right ventricle and no requirements for inotropes beyond 14 days. This survival was consistent to beyond 1 year at the time of the study, and 18% of patients underwent heart transplant with 100% survival.

Recent progress in heart failure treatment and heart transplantation

There has been significant progress in heart failure treatment; its stages are defined as a management platform for cardiovascular specialists. Surgical ventricular restoration adds no outcome advantage in ischemic heart failure over coronary artery bypass surgery alone. Novel medical therapies may include cytokine blockade and the vasodilator, relaxin. Although diastolic failure is prevalent, its clinical significance is unclear. Cardiac resynchronization reduces mortality and hospitalization. Perioperative enoximone facilitates beta-blockade for prophylaxis against myocardial ischemia. Heart failure still determines outcome in pulmonary embolism and cardiac surgery. The practice of ventricular assist devices continues to progress. A profile system based on urgency of mechanical support will guide future outcome assessment. Clinical scoring systems will guide the management of right heart failure. Device flow determines the risk of cerebral hyperperfusion and neurologic dysfunction. Regardless of device type, renal dysfunction remains an important outcome determinant. Postoperative heparinization is increasingly challenged because of the risks of bleeding and heparin-induced thrombocytopenia. The practice of heart transplantation continues to mature. The bicaval rather than the biatrial technique improves short-term outcome. Oral sildenafil is effective for pulmonary hypertension and right ventricular support. Although immunosuppression with tacrolimus is beneficial, sirolimus is less nephrotoxic and preserves coronary vasomotor function. The induction of immunosuppression may be modified as it has a weak evidence base. Psychosocial factors also continue to influence clinical outcome significantly. The future of heart failure treatment is bright with signs of active growth and progress in this vibrant subspecialty.