Author(s): GARBSCH, R., DMITRIEVA, A., TESCHLER, M., MOOREN, F.C., SCHMITZ, B., Institution: UNIVERSITY WITTEN/HERDECKE, Country: GERMANY, Abstract-ID: 746

INTRODUCTION:
Cardiac rehabilitation (CR) represents a comprehensive intervention to address reduced exercise capacity and early vascular aging (VA) in coronary artery disease (CAD) patients. Intermittent hypoxic-hyperoxic training (IHHT) may improve mitochondrial function and promote vascular regeneration through adaptive cellular mechanisms. The aim of this randomized controlled trial was to investigate the effects of IHHT on exercise capacity and markers of VA in CAD patients during CR.
METHODS:
36 CAD patients following myocardial infarction and/or percutaneous coronary intervention referred to 3-4 weeks of inpatient CR were randomized into an IHHT (N=18; 31% female; 53.9±9.2 years) or control group (CG, N=18; 37% female; 58.4±8.0 years). Full-clinical assessment included cardiopulmonary exercise testing, functional tests (6-MWT and Chair Rise Test) and pulse wave analysis (PWA) as well as disease perception questionnaires at admission and before discharge. In addition to standard CR, IHHT patients were prescribed three weekly sessions (30-40 min/session) consisting of six to eight individually adjusted cycles alternating between hypoxic (10-12% O2, 3-5 min) and hyperoxic breathing (30-35% O2). CG patients received standard care with additional relaxation and breathing exercises (3 sessions/week, 30 min).
RESULTS:
Patients completed 24.8±3.6 days of CR, with IHHT patients receiving 6.9±1.2 sessions corresponding to 26±6 min of hypoxic breathing per patient. No adverse events were reported. Improvement in submaximal and peak exercise capacity (workload and oxygen uptake) and functional tests were not different between IHHT and CG (p>0.05). However, improvement in peak oxygen uptake (VO2peak) was larger in IHHT (+1.9±1.7 ml/min/kg) compared to CG (+0.8±2.3 ml/min/kg) but missed statistical significance (p=0.098). In addition, IHHT demonstrated significantly greater improvements in respiratory minute volume (IHHT, +9.3±10.6 l/min; CG, +2.4±9.8 l/min; p=0.049), with changes correlating with those observed for VO2peak (p<0.001; r=0.83). PWA revealed significant differences in Pulse Pressure Amplification (PPA), reducing the cardiac load on the heart (decreased PPA is a key indicator of VA) (IHHT, +0.05±0.11; CG, -0.06±0.06; p=0.002). Also, Total Vascular Resistance (IHHT, -0.11±0.22 s/mmHg/ml; CG, +0.06±0.21 s/mmHg/ml; p=0.031), Augmentation Pressure (IHHT, -5.27±8.88 mmHg; CG: +1.38±3.86 mmHg; p=0.038) and Augmentation Index (IHHT, -9.6±14.4%; CG, +4.1±11.6%; p=0.004), were improved in IHHT.
CONCLUSION:
IHHT demonstrated beneficial effects on ventilatory efficiency at peak exercise and markers of VA, particularly pulse pressure amplification and arterial stiffness indices. A tendency for greater improvement of VO2peak in the IHHT group was also observed. These findings suggest that IHHT may serve as a valuable adjunct to CR by targeting vascular function and hemodynamic parameters in CAD patients, potentially improving mitochondrial function.