The Physiological Timely Effects of Aerobic Exercise After Myocardial Infarction

Background: Myocardial infarction (MI), caused by a blood vessel blockage leading to acute ischemia, is a common form of ischemic heart disease (IHD). Nowadays, MI`s initial treatment includes percutaneous coronary intervention to re-open the blockage and resume coronary flow, thus results with ischemia reperfusion (I/R) manifestation. Cardiac rehabilitation (exercise) is recommended "early", as a standard of care after I/R. Yet, the "early" definition is unclear. Clinicians are concerned about the appropriate timing (e.g., not "too early") to start exercising after I/R.

Aim: To find the optimal time to start exercising post-I/R, while considering both its pros and cons.

Methods: 50 rats` cardio-respiratory function, cardiac function and inflammatory profile were assessed by exercise stress test, echocardiography and blood tests, respectively. Then the rats were divided into six groups: 39 rats underwent I/R surgery followed by exercise at 60-75% of maximal O2 consumption for 8 weeks, 5 days/week. 30 of which started exercise at different time points (1, 3, 7 or 21 days) post-I/R. Sedentary and sham-operated rats were used as controls.

Results: Baseline parameters were comparable among the groups (p>0.05). All exercise groups showed superior results after 8 weeks of training in mortality rate, maximal speed, , heart function and inflammatory indices (p<0.01). Data indicate a reverse dose response, i.e. the earlier the exercise began; the better physiological results were achieved.

Conclusions: Until now, most pre-clinical research in cardiac rehabilitation was concentrated on the MI model (permanent occlusion), showing favorable results of exercise over sedentary life-style. Yet, we have found that early exercise after I/R improves general cardio-respiratory, cardiac function and reduces inflammation indices. Thus, it seems that starting exercise as soon as possible after MI is better and may attenuate cardiac muscle dysfunction.