Question

in the past, an irregular heart rhythm was treated by using a drug to help regulate the beat. there is a treatment that can also regulate heart rhythms that has replaced drugs in some cases. what is that treatment?
pacemaker
angioplasty
clot - dissolving drugs
myocardial infarction

Explanation:

A pacemaker is a device that can regulate heart rhythms and has replaced drug - based treatments in some cases. Angioplasty is for opening blocked blood vessels, clot - dissolving drugs are for treating blood clots, and myocardial infarction is a heart attack, not a treatment for heart rhythm regulation.

Answer:

A. pacemaker