Continuous flow left ventricular assist device implant significantly improves pulmonary hypertension, right ventricular contractility, and tricuspid valve competence

Physiologic effects of continuous-flow left ventricular assist devices

BACKGROUND

Within the past 10 years, continuous-flow left ventricular assist devices (LVADs) have replaced pulsatile-flow LVADs as the standard of care for both destination therapy and bridging patients to heart transplantation. Despite the rapid clinical adoption of continuous-flow LVADs, an understanding of the effects of continuous-flow physiology, as opposed to more natural pulsatile-flow physiology, is still evolving.

MATERIALS AND METHODS

A thorough review of the relevant scientific literature regarding the physiological and clinical effects of continuous-flow physiology was performed. These effects were analyzed on an organ system basis and include an evaluation of the cardiovascular, respiratory, hematologic, gastrointestinal, renal, hepatic, neurologic, immunologic, and endocrine systems.

RESULTS

Continuous-flow physiology is, generally speaking, well tolerated over the long term. However, several changes are manifest at the organ system level. Although many of these changes are without appreciable clinical significance, other changes, such as an increased rate of gastrointestinal bleeding, appear to be associated with continuous-flow physiology.

CONCLUSIONS

Continuous-flow LVADs confer a significant advantage over their pulsatile-flow counterparts with regard to size and durability. From a physiological standpoint, continuous-flow physiology has limited clinical effects at the organ system level. Although improved over previous generations, challenges with this technology remain. Approaching these problems with a combination of clinical and engineering solutions may be needed to achieve continued progression in the field of durable mechanical circulatory support.

Use of Heart Failure Medical Therapies Among Patients With Left Ventricular Assist Devices: Insights From INTERMACS

BACKGROUND

Use of left ventricular assist devices (LVADs) for treatment of advanced heart failure has expanded significantly over the past decade. However, concomitant use of heart failure medical therapies after implant is poorly characterized.

METHODS AND RESULTS

We examined the use of heart failure medications before and after LVAD implant in adult patients enrolled in the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) between 2008 and 2013 (N = 9359). Using logistic regression, we examined relationships between patient characteristics and medication use at 3 months after implant. Baseline rates of heart failure therapies before implant were 38% for angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs), 55% for β-blockers, 40% for mineralocorticoid receptor antagonists (MRAs), 87% for loop diuretics, 54% for amiodarone, 11% for phosphodiesterase inhibitors, 22% for warfarin, and 54% for antiplatelet agents. By 3 months after implant, the rates were 50% for ACE inhibitors or ARBs, 68% for β-blockers, 33% for MRAs, 68% for loop diuretics, 42% for amiodarone, 21% for phosphodiesterase inhibitors, 92% for warfarin, and 84% for antiplatelet agents. In general, age, preimplant INTERMACS profile, and prior medication use were associated with medication use at 3 months.

CONCLUSIONS

Overall use of neurohormonal antagonists was low after LVAD implant, whereas use of loop diuretics and amiodarone remained high. Heart failure medication use is highly variable, but appears to generally increase after LVAD implantation. Low neurohormonal antagonist use may reflect practice uncertainty in the clinical utility of these medications post-LVAD.

Tricuspid Valve Annular Dilation as a Predictor of Right Ventricular Failure After Implantation of a Left Ventricular Assist Device

BACKGROUND

Tricuspid annular (TA) dilation has been suggested as a more reliable marker of concomitant advanced right ventricular failure (RVF) than severity of tricuspid regurgitation (TR). Our objective was to examine the impact of TA dilation on occurrence of RVF and in-hospital mortality following left ventricular assist device (LVAD) implant.

METHODS

Consecutive patients undergoing implantation of a continuous-flow LVAD implant were grouped according to the presence or absence of preoperative dilated TA. Clinical characteristics, hemodynamics, and short-term postoperative outcomes were compared between groups. RVF was defined as unplanned right ventricular assist device (RVAD) or postoperative use of inotropes for >14 days. Linear and logistic regressions were used to explore associations of TA with occurrence of RVF and duration of inotrope use.

RESULTS

We included 69 patients who had continuous-flow LVAD implanted between 2006 and 2013 (50 ± 13 years old; 69% males; 37% ischemic etiology; 69% bridge-to-transplant LVAD; 18% INTERMACS 1-2; 48% with significant TR). RVF occurred in nine cases, and overall in-hospital mortality rate was 14%. Tricuspid valve repair was performed in ten cases. Dilated TA (OR 4.86; 95% CI 1.05-22.33; p = 0.04) was associated with RVF. In an adjusted multivariable analysis, indexed TA was an independent predictor of increased days of inotrope use (0.8-day increase in inotrope use for every 1 mm/m2 increase; p = 0.04).

CONCLUSION

In this cohort, TA dilation was a predictor of RVF after LVAD implant. The potential benefit of concomitant TVR in selected patients with a dilated TA undergoing LVAD implantation remains to be determined.

Durability and clinical impact of tricuspid valve procedures in patients receiving a continuous-flow left ventricular assist device

OBJECTIVE

Patients evaluated for a continuous-flow left ventricular assist device frequently present with severe right ventricular dysfunction with tricuspid regurgitation. Long-term outcomes of concurrent tricuspid valve procedures in continuous-flow left ventricular assist device implantation are unclear.

METHODS

From May 2004 to December 2013, 336 patients received continuous-flow left ventricular assist devices. Among these, 8 patients with prior tricuspid valve procedures were excluded. At continuous-flow left ventricular assist device implantation, 76 patients underwent tricuspid valve procedures (group A), including 68 repairs and 8 replacements. The remaining 252 patients did not receive concurrent tricuspid valve procedures (group B).

RESULTS

Preoperatively, group A had higher central venous pressure/pulmonary capillary wedge pressure (P = .032), total bilirubin (P = .009), and percentage of moderate or greater tricuspid regurgitation (98.7% vs 18.8%; P < .001). In group A, cardiopulmonary bypass time (136 ± 52.0 minutes vs 83.9 ± 38.8 minutes; P < .001), intraoperative platelet use (13.6 ± 6.70 units vs 11.7 ± 5.92 units; P = .042), and bleeding requiring reoperation (27.5% vs 16.7%; P = .046) were significantly increased. In-hospital mortality was similar (10.5% vs 6.4%; P = .22). On-device 2-year survival was 73.9% in group A and 74.2% in group B (P = .24). At 2 years, mean cumulative readmissions for right heart failure was 0.21 in group A and 0.27 in group B (P = .95). A generalized linear mixed-effects model showed that tricuspid valve procedures are protective for developing future significant tricuspid regurgitation (odds ratio, 0.38; 95% confidence interval, 0.19-0.76; P = .006).

CONCLUSIONS

Concomitant tricuspid valve procedures at continuous-flow left ventricular assist device implantation can be performed safely and are protective against worsening tricuspid regurgitation during the first 2 years of support.

Pulmonary Hypertension in the Intensive Care Unit

Pulmonary hypertension occurs as the result of disease processes increasing pressure within the pulmonary circulation, eventually leading to right ventricular failure. Patients may become critically ill from complications of pulmonary hypertension and right ventricular failure or may develop pulmonary hypertension as the result of critical illness. Diagnostic testing should evaluate for common causes such as left heart failure, hypoxemic lung disease and pulmonary embolism. Relatively few patients with pulmonary hypertension encountered in clinical practice require specific pharmacologic treatment of pulmonary hypertension targeting the pulmonary vasculature. Management of right ventricular failure involves optimization of preload, maintenance of systemic blood pressure and augmentation of inotropy to restore systemic perfusion. Selected patients may require pharmacologic therapy to reduce right ventricular afterload by directly targeting the pulmonary vasculature, but only after excluding elevated left heart filling pressures and confirming increased pulmonary vascular resistance. Critically-ill patients with pulmonary hypertension remain at high risk of adverse outcomes, requiring a diligent and thoughtful approach to diagnosis and treatment.

Left Ventricular Assist Devices in the Management of Heart Failure

Mechanical circulatory support has emerged as an important therapy for advanced heart failure, with more than 18,000 continuous flow devices implanted worldwide to date. These devices significantly improve survival and quality of life and should be considered in every patient with end-stage heart failure with reduced ejection fraction who has no other life-limiting diseases. All candidates for device implantation should undergo a thorough evaluation in order to identify those who could benefit from device implantation. Long-term management of ventricular assist device patients is challenging and requires knowledge of the characteristic complications with their unique clinical presentations.