Effect of resistance- and aerobic-based cardiac rehabilitation on resting heart rate and cardiac workload (rate-pressure product) after coronary artery bypass grafting: a randomized controlled trial

Background: Resting heart rate is a modifiable marker of autonomic balance and cardiovascular prognosis, and with systolic blood pressure it determines the rate-pressure product (RPP), an index of myocardial oxygen demand. How resistance- and aerobic-based rehabilitation compare on these markers after coronary artery bypass grafting (CABG), especially in South Asian patients, is unclear. This trial examined their effects on resting heart rate, with derived RPP as an index of cardiac workload. Methods: Forty-five clinically stable patients recovering from CABG (40 men, 5 women; mean age ? 57 years) took part in a single-centre, parallel-group randomized controlled trial in Karachi, Pakistan, and were assigned in equal proportions to resistance-based rehabilitation, aerobic-based rehabilitation, or conventional care. A computer-generated sequence governed assignment, concealment used serially numbered sealed opaque envelopes, and assessors were masked. The two exercise arms trained under supervision thrice weekly for ten weeks. Resting heart rate and systolic blood pressure were recorded at entry and at ten weeks; heart rate was analysed by two-way repeated-measures analysis of variance (Group × Time), and RPP was derived as the product of systolic pressure and heart rate. Results: The arms were balanced at entry for age, sex and resting heart rate. Heart rate fell in every arm but to differing degrees, yielding a significant Group × Time interaction (F(2, 42) = 19.67, p < 0.001, partial ?² = 0.484). Both exercise arms reached a lower post-intervention heart rate (resistance ? 72.9 bpm; aerobic ? 72.3 bpm) than conventional care (? 76.5 bpm), and the between-group difference at ten weeks was significant (p = 0.024). Derived RPP declined most after aerobic-based rehabilitation (?21.7%), followed by resistance-based rehabilitation (?18.5%) and conventional care (?10.5%). Conclusions: Both exercise-based rehabilitation modalities lowered resting heart rate after CABG more than conventional care, and the accompanying fall in derived cardiac workload was largest with aerobic-based training. Structured exercise, and an aerobic emphasis in particular, favourably modifies autonomic-related and workload markers after CABG, supporting its routine use in Pakistani and comparable settings.