Discussion
In patients with CS, a higher RAVI/LAVI was significantly associated with adverse clinical outcomes. When stratified into quartiles, there was nearly a 2-fold and 3-fold increase in death and LVAD implantation in the third and fourth quartiles respectively when comparted to the first and second quartiles.
CS is a grave complication of HF with very high mortality [9]. Determinants of outcomes among patients with CS are poorly understood because of paucity of studies as well as a heterogeneity in patient characteristics [10]. Even less understood are the determinants of outcomes among patients with CS in the setting of “acute on chronic” decompensated HF [11]. Chronic HF is a progressive disease that is associated with structural remodeling due to neurohormonal and hemodynamic changes. Among these patients, the integrity of the right ventricular function determines clinical outcomes [12,13,14]. A compromised RV is associated with worse outcomes [15,16].
Unfortunately, the routine evaluation of the RV function on transthoracic echocardiogram had been neglected until recently. It has been shown that RAVI/LAVI, a novel index that reflects important inter-atrial interactions and RV dysfunction is associated with poor outcomes in patients with pulmonary hypertension [6]. In present study, we have also shown that RAVI/LAVI is also associated with adverse outcomes in CS. Prior studies have established that RA dilatation is a key indicator of the integrity of the RV functional status [17].
The RA is a thin walled chamber with a limited capacitance for the increased pressure load. Sustained pressure load on the RA leads to chamber dilatation rather than hypertrophy based on the law of Laplace. A dilated RA leads to leftward bowing of the interatrial septum thereby constraining the left atrium (LA).
In advanced stages of HFrEF with adverse remodeling, concurrent RV dysfunction occurs in up to 65% of patients with HFrEF [14,18]. As noted in this study, CS patients with higher RAVI/LAVI had significantly higher levels of BNP reflecting a structural milieu of adverse remodeling due to persistently elevated filling pressures. Thus, RAVI/LAVI is an index that constitutively integrates multiple hemodynamic variables between the left and right sides of the heart, and more specifically the pressure-volume interactions with inter-atrial structural remodeling. These results not only highlight the important interactions between left and right heart systems but also underscore the importance of identifying RA/LA structural remodeling in patients with HFrEF presenting with CS. CS is a lethal condition which requires timely initiation of advanced HF therapies in order to mitigate the downward trajectory of end organ function that ultimately leads to death. As we demonstrate, there were no differences in baseline patient characteristics between the RAVI/LAVI groups suggesting that patient co-morbidities, alone, are insufficient in prognostication in CS patients. Thus the utility of a non-invasive parameter such as RAVI/LAVI is a clinically readily available tool that can help risk stratify CS patients and guide management in a time sensitive manner. Indeed the identification of patients likely to suffer imminent adverse outcomes in HFrEF with CS is critical to the timely adjudication of the need for advanced HF therapies.