We all know how devastating a heart attack (known to science as a myocardial infarction or MI) can be. Luckily, science has made great strides, and many people now survive heart attacks and live for many years (though the death rate is still very high). But now that people are SURVIVING heart attacks, the quality of life and ability to prevent another MI is of more concern. Scientists are looking at pharmacological interventions, dietary interventions, etc, etc. And of course, they are looking in to EXERCISE.
Exercise is usually thought to be beneficial to just about everything. But in the case of heart attack, how beneficial is it, what can it help and when should people start?
Guizoni et al. “Cardiac effects of late exercise training in rats with different sizes of myocardial infarction”. Internal Medicine, Botucatu Medical School – UNESP, Botucatu, Brazil, presented at Experimental Biology, 2011.
The goal of this particular study was to look at the effects of LATE exercise on recovery from MI. After all, it’s often not feasible for people who have just had heart attacks to start a new workout regimen. You usually have to wait until the person is up and about again, at least.
In this case, the authors took groups of rats, and created an MI by blocking the left coronary artery. The rats had heart attacks, and were given three months to recover. At the three month mark, the animals were assessed with an echocardiogram (they had an ADORABLE picture of a rat on a patient bed, being given an electrocardiogram with equipment used in human patients. He had his own bed!), and divided into groups who had large MIs and small MIs (while you can try to induce the same heart attack, you will always get variation like this in the effects).
They then took the large MI and small MI groups and gave half of them exercise and allowed half of them to be sedentary. For exercise, the rats were allowed to run on treadmills (you’d be amazed at how fast they learn this), for 40 min/day, 5 days a week, for 5 weeks. The running pace was about 16m/min, a comfortable rat jog.
After 5 weeks of exercise (or no exercise as in the sedentary group), the rats got another electrocardiogram to look at their heart function. Guizoni et al found that rats with SMALL MIs showed very little improvement following exercise. Their hearts didn’t really improve in infarct size or in contractile ability. But the rats with LARGE MIs showed improvements in systolic area and decreases in the size of the infarct, making the extent of the injury look more like the rats with smaller MIs.
This means that while late stage (more than three months after injury) exercise after a heart attack in rats may help with large MIs, small MIs appear to be less sensitive to improvements. The lab hopes to study this effect more, to find out how exactly the large MI rats are improving, and why the small MI rats are not. Eventually, they hope to be able to apply the results of their study to human health, to help people recover from heart attacks.
