supraventricular tachycardia
"I used Verapamil for 5 years to treat supraventricular tachycardia (SVT). With each visit to the doctor, they increased my dosage. I started out taking 30mg once a day, and ended with 180mg once a day.  For the most part, my symptoms were never controlled. The drug caused extreme fatigue and tiredness. I often had severe headaches and was constipated.  I have been switched to Atenolol 50mg once a day now. Hopefully I won't have as many unwanted side effects."