Right Ventricular Function Does Not Significantly Influence 6-Minute Walk Distance in Patients with LVAD

Abstract

6-minute walk distance (6MWD) is a predictor of outcome in patients with left ventricular assist device (LVAD). The aim of this study was to evaluate the exercise capacity and LVAD-flow parameters in relation to right ventricular function. All patients that presented at our center 6 months after LVAD-Implantation underwent clinical assessment, 6 minutes-walk test (6MWT) and echocardiography (6mEcho). Patients were divided into two groups regarding 6MWD. Patients with a 6MWD <300 m were considered to have impaired exercise tolerance (i6MWD). 121 adult patients underwent LVAD-Implantation between 3/2018 and 2/2019. 31 patients died and 4 were lost to follow up. Patients with congenital heart disease (n=2) and patients who did not perform 6MWT or were limited in mobility by non cardiac problems (n=13) were excluded. 71 patients presented after a median of 6.25 months (IQR: [5.88, 702]) and were included. All received optimal medical heart failure therapy (23 ACE-Inhibitor or angiotensin II receptor blocker, 46 sacubitril/valsartan, 61 aldosterone antagonist, 59 beta blocker). 16 patients had i6MWD (223±66,8 m) while 55 patients showed good exercise tolerance (g6MWD) (6MWD 441±85m). There was no difference between groups regarding age (56.75 ± 11.14 vs. 55.42±11.13; p= 0.675), cause of heart failure, atrial fibrillation (31.2 vs. 39.6%; p= 0.756) or INTERMACS level. There was no significant difference in 6mEcho regarding right ventricular function (diameter of the right ventricular outflow tract (34.5±6.2 vs. 34.4±6.2 mm; p=0.969), right ventricular ejection fraction (47.5, IQR 40 to 55 vs. 45.0, IQR 45 to 55 %; p= 0.46), TAPSE (15.2±3.6 vs. 14.9±3.6 mm; p=0.314), grade of tricuspid regurgitation) between patients with i6MWD and g6MWD. It is notable that in patients with a HeartWare HVAD (n=59) LVAD-Flow increased from 4.8±0,6 to 5.6±0.75 l/min (p<0.001) and delta-pulsatility from 4.3±1.5 to 5.0±1.5 l/min (p<0.001). In patients with HeartMate 3 (n=12) LVAD-Flow increased from 4.8±0.5 to 5.0±0,5 l/min (p=0.006). Pulsatility Index (PI) of HeartMate 3 did not change significantly (from 3.8±1.4 to 3.9±1.2 (p=0.612)). LVAD-flow increases slightly under exercise. Echocardiographic measures of RV-Function did not correlate with 6MWD and are therefore no predictor for exercise capacity.