Pvcs associated with exercise or tachycardia dangerous? if so what is the rationale?

PVC's: PVC's are fairly common and unless associated with passing out or weakness should not be a problem. Common causes for them though are stimulants, either medications or caffeinated beverages, diuretic (alcohol can be common one), low electorlytes. Magnesium supplementation often helps this.

PVC's: It is felt that benign ventricular irritability and tachycardias other than sinus tachycardia, tend to be suppressed by exercise and resulting sinus tachycardia and that potentially dangerous cardiac arrythmias can and do occur when ventricular irritability occurs during exercise or fast heart rates from an irritable focus. In these cases a cardiologist or electrophysiologist should be involved