supraventricular tachycardia
"My tachycardia started in my middle 30s, and though they were rare, became more severe as i entered my middle 40's and had to ER visits requiring the injection that stops the heart-no fun and scary. After this I went to a cardiologist who gave me 50 mg Metoprolol to take as needed. I am happy that i don't have to take it daily because it does make me sluggish on the very rare times that I do-I am pleased to have a solution when these events happen and my fears of dying suddenly from a heart episode have been drastically reduced."