Arrhythmias are usually caused by heart disease such as coronary artery disease, hypertension, electrolyte abnormalities, valvular heart disease, congestive heart failure, as well as thyroid disease, kidney disease, and lung diseases. Therefore the question you re asking is very difficult because it is based on the disease that is causing the arrhythmia. Generally speaking, beta blockers are the first line treatment for arryhtmias. However, if the heart rate becomes too slow then that is a contraindication to beta blockers. Additionally, some people can have side effects such as difficulty breathing would be up blockers. And therefore they should be to a calcium channel blocker. Some people can also convert back to a normal sinus rhythm which means they would no longer need a beta blocker.