Does the tachycardia affect cardiac muscles?

Possibly: Prolonged periods of excessive heart rates can lead to weakening of the heart muscle (cardiomyopathy). It is important to identify causes of tachycardia and initiate treatment.

Yes: Tachycardia mediated cardiomyopathy is a wakening of the muscle of the heart from fast heart rates.

This is variable : But a real & reversible cause for chf.

Yes: Prolonged tachycardia causes tachycardia mediated cardiomyopathy... This is reversible with the appropriate treated of the tachycardia... Please follow up with a cardiologist or a cardiac electrophysiologist.

Sometimes: Fast heart rates that occur through a normal mechanism will not generally harm the heart (exercise, pain, anxiety, fever, etc.). Tachycardia from an abnormal mechanism (supraventricular tachycardia, ventricular tachycardia) can harm the heart muscle when it is sustained for many hours or days.