Outcomes in Tachycardia-Induced Cardiomyopathy
Outcomes in Tachycardia-Induced Cardiomyopathy
Abstract & Commentary
By Michael H. Crawford, MD
Source: Medi C, et al. Tachycardia-mediated cardiomyopathy secondary to focal atrial tachycardia. J Am Coll Cardiol. 2009;53:1791-1797.
Although it is well known that incessant atrial tachyarrhythmias can cause left ventricular (LV) dysfunction, little is known about focal atrial tachycardia and LV dysfunction. Thus, Medi et al from Australia studied 345 consecutive patients with focal atrial tachycardia referred for radiofrequency ablation. LV function was measured before ablation by echo. Patients with structural heart disease were excluded (n = 14). Of the remaining 331 patients, 30 had LV dysfunction (EF < 50%). Mean EF was 35% among these 30 patients, 27 of whom had had the echo done while in the tachycardia. Among 11 patients with LV dysfunction who had a post ablation echo within 48 hours and were in sinus rhythm, EF was similar post ablation (39%). Those with LV dysfunction tended to be younger and male. Also, all had incessant tachycardia versus only 20% of those without LV dysfunction, and their heart rate in tachycardia was slower (117 vs. 141, beats/min. p < .001). Atrial appendage tachycardia origin sites had the highest incidence of incessant tachycardia (84%) and LV dysfunction (42%). After successful ablation, 97% of the LV dysfunction patients had normal LV function at three months. Medi et al concluded that cardiomyopathy occurs in 10% of patients with focal atrial tachycardia, and is more common with a slower and incessant tachycardia. Restoration of normal LV function almost always occurs after successful ablation therapy.
Commentary
Rapid atrial pacing in dogs leads to heart failure due to LV systolic dysfunction in about two weeks in almost all the animals. Thus, it makes sense that LV dysfunction caused by focal atrial tachycardia in humans would be more common with incessant tachycardia, but why at a slower rate? One possibility is that slower tachycardias may be less symptomatic than faster ones, allowing more time without medical attention for LV dysfunction to develop. Why is it more common in men? It could be genetic, as there are certain angiotensin receptor polymorphisms that increase the incidence of tachycardia-induced cardiomyopathy. Or it could be that men ignore mild symptoms and women do not. Also, why was LV dysfunction due to atrial tachycardia more common in younger individuals? This seems counterintuitive. Again, it may relate to symptom tolerance, allowing more time for cardiomyopathy to develop.
Tachycardia-induced LV dysfunction has also been described with atrial fibrillation and permanent junctional reciprocating tachycardia in children. It is rare in AV nodal re-entrant or AV re-entrant tachycardia. Focal atrial tachycardia is frequently missed because it is mistaken for sinus tachycardia, especially if the rate is not particularly fast. Often it is believed to be a compensation response to heart failure. Careful inspection of the P waves in sinus rhythm and the tachyarrhythmia is necessary to establish diagnosis. According to this study, about 25% of focal atrial tachyarrhymias are incessant and, of those, one-third develops cardiomyopathy.
One limitation of this study is the lack of echoes in sinus rhythm before the tachycardia developed in these patients. In some cases, the reduced LV filling associated with tachycardia can result in a reduced LVEF, which is immediately reversible with increased filling due to heart rate reduction. This phenomenon is frequently seen in patients with acute atrial fibrillation with a rapid ventricular response who are in heart failure. When they are given LV depressant drugs such as beta blockers and diltiazem acutely, heart failure resolves and LV function improves as their heart rate slows. Sometimes it is difficult to distinguish the chicken from the egg, but awareness of the potential for focal atrial tachycardia to mimic sinus tachycardia and cause heart failure is an important reversible cause of LV dysfunction.
Although it is well known that incessant atrial tachyarrhythmias can cause left ventricular (LV) dysfunction, little is known about focal atrial tachycardia and LV dysfunction.Subscribe Now for Access
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