What are causes of a heart flutter?

Any arrhythimia: The heart can flutter with premature ventricular contractions ( pvc), premature atrial contractions (pac ), atrial fibrillatrion etc. Fluttering also known as palpitations is basically a symptom and further work up is needed.

Here are few: Hypertension, heart attacks, cardiomyopathy with chf, mitral valve disease, hypertrophic cardiac disease, hyperthyroidism, pulmonary embolus, severe copd/emphysema with pulmonary hypertension, Cocaine and amphetamine addiction, alcoholism, anorexia, congenital heart disease like wpw.