Abstract Body (Do not enter title and authors here): Background: During exercise, the right ventricle (RV) is subjected to proportionally greater increases in wall stress given its larger size, lower resting pressure and thinner walls compared to the left ventricle (LV). There is limited understanding in how the RV remodels to habitual, long term aerobic exercise. Based on previous studies, the LV remodels proportionally to exercise intensity while the left atrium (LA) remodels in proportion to exercise duration. In a prospective study, we evaluated the effects of 2 years of high intensity aerobic exercise training on RV remodeling in sedentary, healthy middle-aged adults.

Methods: Sixty-one (48% male) healthy sedentary middle-aged participants (53±5 years) were randomized to either high-intensity aerobic exercise (n=33) or yoga (n=28). RV size was measured using 2D echocardiographic assessment at 0, 10, and 24 months, using the maximal transversal dimension in the basal one third of the RV inflow at end diastole. At 0 and 24 months, central venous pressure (CVP) was obtained under preload manipulation using normal saline (NS) rapid infusion across 3 conditions: baseline, NS15 mg/kg, and NS 30ml/kg. RV compliance was calculated as the slope of RV size/CVP across conditions.

Results: Twenty-eight participants (46% male) completed the study in the high intensity aerobic exercise group. In these subjects, RV size increased 9.6% between 0 months and 24 months (Pre: 3.1±0.3 cm, 10 months: 3.4±0.2 cm, Post: 3.4±0.2 cm, p-value 4.40 x 10^-7). RV compliance did not change between 0 and 24 months (Pre: 0.046±0.02 cm/mmHg, Post: 0.042±0.03 cm/mmHg, p-value 0.514). Twenty-five participants (44% male) completed the study in the yoga group. Two subjects had unanalyzable images. RV size increased 9.3% between 0 months and 24 months (Pre: 2.9±0.3 cm, 10 months: 3.1±0.3 cm, Post: 3.2±0.3 cm, p-value 1.41 x 10^-7). RV compliance did not change between 0 and 24 months (Pre: 0.052±0.03 cm/mmHg, Post: 0.061±0.04 cm/mmHg, p-value 0.329). There were no differences in change in RV compliance between groups (p-value 0.258).

Conclusions: In previously healthy sedentary adults, 2 years of high intensity aerobic exercise training increased RV size while having no effect on RV compliance. This data suggests that although RV remodeling occurs, there is no change in material stiffness properties, unlike what occurs in LV remodeling with long duration aerobic exercise.