ECG

What is MI?

A myocardial Infarction is death of myocardial (muscle) tissue most likely due to lack of oxygen and nutrients. During physical exercision the heart beats harder and faster to pump blood around the body. The muscles of the heart will contract at a faster rate and more muscles will be involved in the contraction of heart muscle for a stronger heart beat. You will notice yourself after physical activity that your heart isn't just beating faster but also alot harder than when relaxing. This is because more muscles are involved. Because of the increase in muscular activity the muscles require an increase supply of oxygen and nutrients. People with coronary artery disease have partially blocked coronary arteries so blood can only flow to the muscle at a reduced rate. The increased demand for oxygen and nutrients by heart muscle during exercise can not be met because the blood can't get to the muscles quick enough through the partially blocked arteries. The result is that the active heart muscle will die. This death of heart muscle is a myocardial infarction or MI.

Myocardial infarcts are caused by lack of oxygen delivered to the tissue, and during vigorous exercise:

1. the heart muscle contracts faster and the amount of time it spends in diastole is shortened, therefore the coronary arteries have less time to oxygenize the myocardium.

2. during vigorous exercise the myocardium requires more oxygen, at a time when blood flow is impeded by the shortened diastole.

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