Right heart assessment is important for monitoring RV function and identifying possible causes of RV dysfunction. Assessment of the RV is sometimes challenging because of its anterior retrosternal position, complex geometry, and hemodynamic load dependence.

Echocardiography has been the most common method for RV evaluation. Three-dimensional echocardiography is a promising modality that can provide more accurate evaluation, although cardiac magnetic resonance imaging (MRI) has become a standard. Assessment of RV structure should include observations of the RV size, shape, volume, and wall thickness [25], and MRI is now considered the most reliable method for measuring RV volume [26, 27]. RVEF and RV fractional area change (RVFAC) are calculated on the basis of size and volume measurements determined by the imaging studies.

Tricuspid valve (TV) annular plane systolic excursion (TAPSE), which is an echocardiographic measurement of the longitudinal displacement of the TV annulus during systole, is used for evaluation of RV function. Displacement >15 mm in TAPSE is a quantitative measure of normal RV systolic function. However, TAPSE is less reliable in patients with focal RV dysfunction because it only measures the longitudinal movement of the lateral free wall. Evaluation of the TV annulus size, the presence and severity of TR, the inferior vena cava size, and the hepatic venous blood flow pattern are also important parts of the evaluation of RV function. Although there is good correlation among TAPSE, RVFAC, and RVEF, many cardiographers use a subjective assessment that classifies global RV function as good or as mildly, moderately, or severely reduced.

Echocardiography is the primary imaging modality for evaluating cardiac function after LVAD implantation because MRI is not an option for patients with these devices [27]. Changes in RV size and the degree of TR are followed serially. When RV function is worsening, RV size and the extent of TR increase correspondingly.

In patients with LVAD, a decrease in the TAPSE is seen because RV afterload and RV contractile work to maintain cardiac output (CO) are reduced [17]. However, low TAPSE in the presence of increasing RV size and TR suggests worsening RV function [28].

An important structural feature in evaluation of heart function is the position the IVS, as it reflects various factors. A shift of the IVS may indicate RV dysfunction, inappropriate volume loading, incorrect LVAD setting, and LVAD device failure. Because of the space limitations imposed by the pericardium, potential right heart compression by fluid collection or thrombus should also be considered.

With continuous-flow LVAD support, preexisting RV dysfunction was not exacerbated during a median follow-up of 4.5 months [29]. Moreover, the size of RV chamber is reduced in parallel with that of the LV chamber, although the degree of the change in the RV is variable. In contrast, the pulsatile LVADs consistently decompressed the LV to a greater degree, thus impairing RV function by leftward shifting of the IVS.

Many studies have attempted to identify preoperative risk factors and develop risk scores in order to identify patients at the greatest risk for postoperative RV failure after LVAD implantation and to formulate the appropriate treatment strategies for them. Patients at high risk for postoperative RV failure would receive benefits from preoperative optimization of RV function and possibly even planned biventricular assist device (BiVAD) support. However, it is still difficult to predict the incidence of postoperative RV failure in the LVAD patients because RV failure includes multiple factors throughout the treatment.

Some studies have identified particular patient characteristics and hemodynamic parameters as risk factors for postoperative RV failure, but the significance of the findings is limited by small cohorts, single institution, retrospective nature, and inconsistent use of an LVAD type.

According to published studies, preoperative risk factors for postoperative RV failure in patients with LVAD are female gender; non-ischemic cardiomyopathy [30]; preoperative support, including mechanical ventilation, mechanical circulatory support [4, 8, 23], or intra-aortic balloon pumping (IABP) [6]; hemodynamic parameters; biochemical markers; and echocardiographic measurements.

The hemodynamic parameters that can indicate RV failure after LVAD implantation include elevated preoperative and intraoperative central venous pressure (CVP) and reduced RV stroke work index (RVSWI < 300 mmHg mL⁻¹ m⁻²) [4, 8, 21, 31]. Although high PAP is an easily measured parameter, RV function, which may not always be related to high PAP, remains the most critical determinant of survival. In fact, patients without pulmonary hypertension are more likely to develop RV failure and have more serious morbidity after LVAD implantation. This situation indicates that decreased RV contractility is unable to overcome increased PVR. RVAD or BiVAD support should be considered for patients with poor RV function indicated by low PAP or RVSWI. Preoperative treatment, including a pulmonary vasodilator, is required for patients with chronic pulmonary hypertension associated with pulmonary disease.

Findings consistent with organ failure and hepatic congestion secondary to impaired preoperative RV function are also important risk factors for postoperative RV failure and BiVAD requirement. These signs include elevated serum creatinine (Cr) [4, 31], blood urea nitrogen [8], aspartate aminotransferase (AST), and bilirubin levels [4]. Increased nonspecific neurohumoral markers of heart failure, such as N-terminal pro-brain natriuretic peptide and neopterin, and inflammatory markers such as procalcitonin and big endothelin-1 are also counted as risk factors for RV failure after LVAD implantation [24].

Severe preoperative TR and a short/long axis ratio of >0.6 for RV have high specificity (87 % and 97 %, respectively) and good sensitivity (66 % and 37 %) to identify patients with high risk of postoperative RV failure [9]. Increasing severity of TR is also associated with the occurrence of postoperative RV failure. Puwanant et al. found that preoperative TAPSE <7.5 mm was better related to post-LVAD RV failure than RVFAC, with a specificity of 91 % and a sensitivity of 46 % [28].

Other risk scoring systems have been developed to quantify the risk of RV failure after LVAD implantation. Rao et al. revised a previous screening scale to more accurately predict survival after LVAD implantation and to determine emerging risk factors for mortality (Table 7.1). In their study, mechanical ventilation and a previous LVAD were independent predictors of mortality after device insertion. The correlation between observed and predicted values was better in the revised score than in the old score, which overpredicted mortality in patients at low risk and underpredicted mortality in patients at high risk [32].

Through multivariable regression analysis, Drakos et al. found seven preoperative variables that were correlated with postoperative RV failure, including destination therapy, IABP, and increased PVR [22] (Table 7.2). They reported that the incidence of postoperative RV failure was 44 %, although their study included various pulsatile and non-pulsatile LVAD systems. The authors defined RV failure as requirement for inotropic support for >14 days, iNO for >48 h, or RVAD implantation. Patients were stratified into four risk groups from a sum of all points assigned to each variable. The incidence of RV failure was 11 % in the lowest risk group, while in the highest group, it was 83 %. Destination therapy, elevated PVR, and preoperative IABP support were significant independent predictors for postoperative RV failure.

In a study with 197 patients undergoing LVAD, Matthews et al. reported that 35 % of the patients developed RV failure and that the independent predictors were the use of vasopressors and increased AST, bilirubin, and Cr levels; using these predictors, they developed a risk score system [4] (Table 7.2).

Fitzpatrick et al. proposed a similar risk score from a cohort of 266 patients after implantation of various types of LVAD [31]. In their study, they defined RV failure as the need for RVAD, which was found in 34 % of the patients. Using preoperative risk factors associated with postoperative RV failure, they proposed a risk score for RV failure based on multivariate logistic regression analysis. According to the scoring system, a score >50 is an indication for a BiVAD and has good sensitivity (83 %) and specificity (80 %).

The National Institutes of Health-sponsored Interagency Registry for Mechanical Assisted Circulatory Support (INTERMACS) developed a systematic scoring system through the largest LVAD database in the USA [33]. Alba et al. compared INTERMACS level I and II (sicker and decompensating) to level III and IV patients, showing that the system is a good predictor of postoperative complications and mortality, but not sensitive for postoperative RV failure [34].