No Difference In Heart Rate Recovery During Graded Treadmill Testing In Patients With And Without Nonalcoholic Fatty Liver Disease (NAFLD)

Abstract

Cardiac Mortality is the most common cause of death for nonalcoholic fatty liver disease (NAFLD), which is linked to physical inactivity and obesity. PURPOSE: To determine whether individuals with NAFLD show heart rate recovery impairment (iHRR is≤12 beats per minute at 1 minute post-exercise, an independent predictor of mortality) compared to non-NAFLD participants following graded treadmill testing (GTT) to volitional exhaustion. METHODS: Non-pharmacological clinical research participants with and without NAFLD were included. All performed symptom-limited, Modified Bruce GTT. Gas exchange captured cardiorespiratory variables and impedance cardiometry assessed heart rate, stroke volume, and cardiac output (CO) continuously during rest, testing, and recovery. Participants completed nutrition, activity, and fatigue questionnaires. Linear regression assessed effects of covariates on HRR. RESULTS: 86 participants (48.8% Male, 62.8% Caucasian, 65.8% NAFLD/NASH, Age 48 ± 13.6 years) were included for analysis. T-test comparisons showed individuals with NAFLD to be older (52 vs 41.4 years, p=.001), have higher body mass index (31.2 vs 28.4 kg/m 2 , p=.007), and increased body fat percentage, (34.1% vs 28.6%, p=.006) but showed no differences for resting pulse, blood pressure, gender, or ethnicity. Per GTT, individuals with NAFLD had reduced oxygen consumption at anaerobic threshold (AT) (12.3 vs 15.6 mL/kg/min) and peak exertion (23.1 vs 31.2 mL/kg/min, p<.001) compared to non-NAFLD. The NAFLD cohort also reported reduced maximal and average activity scores compared to the non-NAFLD group (MAS 89.8 vs 81.4, p=.001; AAS 88.1 vs 77.6, p<.001). No group differences were found for iHRR presence or continuous HRR measure. Stepwise linear regression showed peak CO (B=0.317, p=.041) and MAS (B=.348, p=.025) to be significant predictors of HRR for all participants (R 2 =.261). CONCLUSIONS: No HRR post exercise differences were found between NAFLD and non-NAFLD individuals. Increased CO and self-reported exercise capacity may indicate lower probability of impaired HRR. AAS and MAS were reduced in the NAFLD group, which may reflect reduced aerobic capacity at peak performance and AT. NAFLD individuals may benefit from exercise participation encouragement to improve tolerance of physical activity.