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Left ventricular ejection fraction (LVEF) is a measure of heart’s pumping function and normally ranges from 55-65%. When the LVEF decreases due to conditions affecting the heart muscle (Cardiomyopathy), patients develop heart failure or LV dysfunction. People can develop heart failure from several causes. Myocardial infarctions from coronary artery disease, myocardidtis (inflammation of the heart muscle), chemotherapy drugs (adriamycin, doxorubicin, daunorubicin etc) and prolonged rapid heartbeat (sustained tachycardia). Tachycardia mediated cardiomyopathy (TCM) is a common reversible causes of LV dysfunction in patients with heart rhythm disorders. It is very important to identify and treat it in its early phase to reverse the LV dysfunction completely. Arrhythmias both from atria and ventricles are capable of causing tachycardia mediated cardiomyopathy. Appropriate control of ventricular rate with drugs or elimination of the tachycardia focus using catheter ablation can prevent this disorder. Catheter ablation is a very minimally invasive and highly successful procedure in treating rapid heart beats.
Atrial tachycardias are rapid arrhythmias from the upper cardiac chambers and are often due to triggered electrical activity from the atrial muscle or reentry within the chamber. A recent study by Caroline Medi etal published in the Journal of American College of Cardiology (Tachycardia – mediated Cardiomyopathy Secondary to Focal atrial tachycardia, JACC2009,vol.53,no.19 _1791-7), focused on focal atrial tachycardia (AT) and the usefulness of catheter ablation to reverse LV dysfunction due to cardiomyopathy. A total of 345 patients who underwent ablation for Focal AT between January 1997 and July 2008 were studied. All patients had either intermittent or incessant AT. Electrocardiogaphic features were used to identify ectopic AT. Incessant tachycardia is defined as continuous tachycardia or continuous paroxysm of tachycardia separated by < 2 sinus beats.
Tachycardia mediated cardiomyopathy is usually underestimated among patients with atrial fibrillation and dilated cardiomyopathy in whom uncontrolled tachycardia can cause or worsen heart failure. The cycle length and ventricular response to tachycardia are the major determinants for developing tachycardia while age at presentation, symptom duration and sex not much influential. In the above study, foci arising from atrial appendage and pulmonary veins were frequently incessant; however there was no significant difference in the likelihood of TCM developing according to site of origin, if tachycardia was incessant. Angiotensin converting enzyme gene polymorphism was also found to be another important predictor of TCM.
TCM occurs in 10% patients with focal AT. Incessant tachycardia is necessary for the development of TCM, and it is seen in one third of the total population of patients with focal AT. Long term restoration of LV function can be achieved with successful control or elimination of tachycardia in the majority of patients by using catheter ablation. Hence it is important to agnize this relation and preclude from the harmful effects of TCM.
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