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Cardiac Care 2020: Do actual medical literature depict a satisfactory view of Left ventricular assistant device and Right ventricular failure? - Issues with Management - Elio Aloia -University of Siena Viale M. Bracci 16 53100 Siena, Italy

Elio Aloia

Abstract:

Advanced Heart Failure, LVAD and RVF: What’s the Problem?

Here and now incidence and prevalence of heart failure are rising up. In addition disabling symptoms, improving quality of life and prognosis are fundamental clues to all successful therapies for the treatment of advanced heart failure. Left ventricular (LV) assist devices (LVADs) are an increasingly common therapy for advanced heart failure.

The REMATCH clinical trial was the first clinical study to randomly assign patients ineligible for transplantation (destination therapy) to either continued optimal medical therapy or electronically driven LVAD therapy. The trial revealed a significant survival benefit of LVAD therapy at 12 months compared with medical therapy alone (52% vs. 25%, respectively). Subsequent studies have demonstrated further improvements in survival, device durability and patient satisfaction parameters for both destination therapy and bridge-to- transplantation indications.

The most common indications include

1. Bridge to transplant (BTT).

2. Bridge to candidacy (BTC).

3. Destination therapy (DT):. The average length of LVAD support for BTT indication ranges from weeks to years and generally months to years for DT indication.

4. Bridge to recovery (BTR).

Influence of LVAD on RV Function

Intrinsic RV dysfunction, ischemia, intraoperative events  and LVAD management strategies  have all been implicated in RVF. Biventricular dysfunction is a common end point for stage D heart failure where chronically elevated left-sided filling pressures have induced high pulmonary vascular resistance (PVR), resulting in secondary pulmonary hypertension and subsequently RVF. Acute unloading of the left ventricle, seen after successful LVAD implantation, drops the PCWP, thereby relieving congestion and cardiac output recovery.

Two considerations can clearly be inferred:

1. RV afterload declines early after LVAD and continues to decline with prolonged support;

2. RV adaptation to load worsens after implantation and this relationship remains constant over time.

In Addition, the effect of ventricular interdependence is most prominent in a setting of loading changes such as after LVAD. Of note, excessive left-ward shift of the IVS, particularly with overly aggressive LV decompression with continuous-flow (CF) LVADs, may also decrease septal contribution to RV contraction, leading to RVF.

Predicting RVF and Patients Selection: Clinical Variables, Echocardiography, Hemodynamic Variables

In the current era, right ventricular mechanical support is mainly available to those patients who are listed for cardiac transplantation, thereby placing profound importance in identifying those at risk for postoperative right ventricular failure. In addition, prognosis of patients treated with biventricular assist devices (BiVAD) is worse than prognosis of those treated with LVAD. Analysis of international registry data has identified RV dysfunction requiring biventricular support as the most prominent risk factor for early mortality after VAD implantation.

Either way, the process of Identifying patients at high risk of RVF improves patient selection and allows for implementing strategies to avoid post-operative RVF: assessment of right ventricular function should incorporate a combination of imaging findings with hemodynamic and biochemical data.

Numerous pre-operative risk scores have been developed to quantify the risk of RVF in LVAD candidates. Female gender, nonischemic etiology, prior cardiac surgery, need for an intra-aortic balloon pump, inotrope dependency, vasopressor use and need for mechanical ventilation are all recognized as risk factors for RVF. Biochemical parameters (including elevated serum creatinine, blood urea nitrogen (BUN), bilirubin, aspartate aminotransferase) suggest increased risk of RVF. Special attention should be directed toward the arrhythmia burden, because significant ventricular arrhythmias may result in hemodynamic alterations: strong consideration should be given to biventricular MCS in patients with very frequent or refractory ventricular arrhythmia. The presence of peripheral arterial disease at the time of LVAD implantation may increase the risk of 1) stroke, 2) limb and mesenteric ischemia.

Of note, renal and hepatic dysfunction typically predict underlying chronicity of the disease and a worse right heart function.This predisposes to a greater propensity for bleeding and infection-related complications. However, on average, both renal and hepatic function improves by six months following LVAD implantation. Poor nutritional status and frailty increase the risk of death following LVAD implantation.

Considering echocardiography, we can find predictive of RVF: LA dimension; TAPSE; Em/SLAT (pulsed Doppler trans-mitral E Wave/tissue Doppler lateral systolic velocity ratio); Basal RVEDD (RV end-diastolic diameter; Pre-operative S<4.4 cm/s, RV-E/E >10 (45); Absolute RV longitudinal strain <14%; Longitudinal strain of RV free wall; RV end diastolic volume index; RV ejection fraction; RV end diastolic diameter; TR regurgitation; R/L ratio. Each of these variables was found to be significant or less significant, depending on the study

Results Postoperative:

Different authors state

The need for an RVAD is associated with worse outcomes, but elective RVAD correlates with better long-term survival than an emergency implantation. Risk assessment for RHF should be performed preoperatively to assess the need for initial BiVAD implantation or total artificial heart; Elective BiVAD implantation has better outcomes than unplanned urgent institution of mechanical RV support. The ability to wean from RVAD support varies widely in clinical trials, from 20% to 70%

The current evidence: there is not strong current evidence

Multiple risk scores using clinical, echocardiographic, and hemodynamic factors exist to predict RVF. However, no single variable adequately discriminates or is reliable for patient selection. Considering the great heterogeneity of the literature in terms of:

1. The lack of stratification, in almost all of the work, for Intermacs classes;

2. The lack of stratification, in some work, for the etiology of heart failure;

3. The presence of devices belonging to different generations;

4. The inhomogeneity of the definition of RVF, combined with the inhomogeneity of the severity of the clinical condition of the patients enrolled;

5. The presence of large standard deviations considering the cut-off values of RVSWI used to predict the RVF next to the implantation;

6. The lack of data, resulting from careful and precise selection criteria, which can guide the choice where it is convenient to schedule the Bi-VAD implantation rather than a use the support of the right ventricle only in terms of rescue therapy;

7. The presence of surveys with determined arbitrarily cut-off value of clinical conditions or echocardiography, that directly addressed the patients to Bi-VAD rather than being randomized.

Conclusions:

It’s time to develop a well-crafted informed consent process for patients and their caregivers to help them understand the expectations post implantation.