Abstract 19716: A High Intensity Interval Training Protocol is Not Better Than Customary Continuous Exercise for a Rat Model of Chronic Thromboembolic Pulmonary Hypertension
High intensity interval training (HIIT) is superior to continuous exercise training (CExT) for reversing cardiac remodeling and dysfunction and improving exercise capacity in heart failure. Our group recently observed greater HIIT benefit in a pulmonary arterial hypertension (PAH) rat model as well. Here we investigated HIIT vs. CExT for chronic thromboembolic pulmonary hypertension (CTEPH).
Methods: Male SD rats (~375g) were injected with polystyrene microspheres (97/100g, 85μm, jugular vein) and SU 5416 (20mg/kg, sc.) to produce chronic pulmonary embolism (CPE, n=6), or vehicle (Sham, n=6). Subgroups of each (CPE+HIIT, Sham+HIIT, CPE+CExT, Sham+CExT, n=6 ea) underwent 6 wks (5x/wk) of treadmill running performed either as 30 min HIIT (5 x [2 min @ 85%VO2max + 3 min @ 30%VO2max) or 60 min mild CExT (50% VO2max). Sedentary counterparts were placed on a stationary treadmill (Sham+SED and CPE+SED, n=6 ea).
Results: CPE+SED had lower (p<0.05) final VO2max (in ml/kg/hr) (2656±73) post-CPE,vs. Sham+SED (3576±123). CExT, but not HIIT, attenuated CPE-induced decrement in VO2max (CPE+CExT 3115±70, p<0.05; CPE+HIIT 2771±101 p>0.05, vs. CPE+SED). RV systolic pressure (RVSP) was elevated as expected for CPE (85±10mmHg) and was not reduced (by <10%, p>0.05) by either training approach. RV hypertrophy
(RV to LV+S mass) was lower in both CPE-CExT (0.44±0.02) and CPE-HIIT (0.45±0.01) vs. CPE-SED (0.53±0.04, p<0.05). Reduced RV fractional shortening (echocardiography) following CPE (CPE+SED 0.2±0.02% vs. SHAM+SED 0.46±0.02%, p<0.05) was also improved (p<0.05) by both HIIT and CExT (CPE+HIIT 0.3±0.03%, CPE+CExT 0.3%±0.03). Additional hemodynamic recordings obtained during running via implantable telemetry revealed failure of HIIT’s high/low intensity intervals to elicit expected RVSP rise/fall once post-CPE, compared to pre-CPE.
Conclusion: In contrast to previous findings for a PAH rat, HIIT is not superior to CExT for CTEPH because while both approaches had mild salutary effects on the RV, HIIT failed to improve hemodynamics or exercise capacity. Diminished effectiveness of HIIT for CTEPH may be related to failure of HIIT intervals to stimulate heightened flow-mediated vascular endothelial shear in this model, which is believed to be key to HIIT benefit.
Author Disclosures: M. Brown: None. E. Neves: None. G. Long: None. J. Kline: None.
- © 2016 by American Heart Association, Inc.