What is cause of slow heart rate? what is side effect of slow heart rate?

Low heart rate: Low heart rate can be normal especially in very fit individuals. In normal patients, it does not cause any symptoms. If it is abnormally slow, patients may experience weakness, fatigue, syncope, dizziness upon standing, and other issues.

Slow heart rate: Slow heart rate can have a number of causes. Some people who are highly athletic and in peak physical condition have a low heart rate, and other healthy people just tend to have a low resting heart rate. Low heart rate can occur with certain medications and disease states, including hypothyroidism, cardiac diseases, autoimmune and infectious diseases, and central nervous system disorders.