Did cocain almost give me a heart attack?

Cocaine increases the heart rate, and at the same time causes some degree of constriction of the blood vessels that feed the heart.  These are effects that occur each time it is used.  Cocaine can also cause arrhythmia at times, but this doesn't occur each time it is used.  Cocaine has the potential to cause a heart attack even in a young person who does not have heart disease.  The arrhythmia can cause an even worse problem, a cardiac arrest in which the heart stops beating entirely.  There may even be some cardiovascular damage such as higher blood pressure or thicker heart walls which persist after regular use. You definitely stressed your heart, but it would be difficult to know exactly how close you actually came to having a heart attack.