Abstract
A 66-year-old woman with atrial fibrillation and hypertension developed tako-tsubo cardiomyopathy following acutely uneventful radiofrequency catheter ablation of the atrioventricular (AV) node. We speculate that the increase in sympathetic activity that accompanies AV node ablation contributed to the pathophysiological process, which involves increased catecholamines and/or apical adrenoreceptor density and responsiveness.
A 66-year-old woman with labile hypertension, concentric left ventricular hypertrophy, and normal left ventricular ejection fraction was hospitalized with recalcitrant rapid permanent atrial fibrillation. Rate control remained inadequate despite the implantation of a permanent pacemaker and high-dose combination therapy. A high level of anxiety preceded atrioventricular (AV) node ablation, performed under conscious sedation with a 4 mm electrode tip 7F quadripolar radiofrequency catheter (EP Technologies Inc., San Jose, CA, USA). Complete AV block was achieved on the first 60 s application, using temperature-controlled settings (50 W; maximum 70°C). A junctional escape rate emerged at 45 bpm. A second 1 min application was administered at the site of success. The procedure was acutely uneventful and the pacemaker was programmed to 80 bpm in the VVIR mode.
The following day, the patient complained of retrosternal chest pain. The 12-lead ECG was unrevealing, with a ventricular paced rhythm of left bundle branch block morphology. Emergent coronary angiography was normal. Contrast ventriculography (Figure 1) and echocardiography exposed apical akinesia, hyperkinetic anterior and posterobasal segments, and a left ventricular ejection fraction of 38%. Troponin-T levels rose to 0.11 µg/L, and CK-MB mass to 2.3 µg/L. A diagnosis of tako-tsubo cardiomyopathy was entertained. The patient responded favourably to intravenous diuretics and nitrates. On echocardiography 1 month later, left ventricular function had entirely normalized.
Contrast ventriculography of the left ventricle in a right anterior oblique view in diastole (A) and systole (B). There is apical ballooning during systole with a narrower neck, resembling a tako-tsubo or octopus pot.
To our knowledge, this is the first report of tako-tsubo cardiomyopathy following radiofrequency catheter ablation of the AV node. This unusual cardiomyopathy is characterized by transient apical ballooning with a left ventricular shape that resembles a tako-tsubo, a Japanese pot used to capture octopus. A higher prevalence is noted in women (7:1), typically in the seventh decade of life. Hypertension is noted in up to 76%, and atrial fibrillation is an associated factor.
The exact pathophysiology remains debated, but the prevailing theory relates mental or physical stress to increased catecholamine levels and/or increased apical adrenoreceptor density and responsiveneness. High catecholamine levels may induce myocardial stunning through the stimulation of myocardial adrenoreceptors. Interestingly, AV node ablation is associated with a 34% increase in sympathetic nerve activity that persists throughout the post-ablation period, as recorded from right peroneal nerves in efferent post-ganglionic muscles. Increased sympathetic nerve activation may reflect a disruption in cardioinhibitory afferent signals, acute haemodynamic effects, and/or stabilization of arterial pressure fluctuations allowing uninhibited high basal sympathetic activity. Moreover, increased sympathetic activation is implicated in the pathogenesis of post-AV node ablation sudden death, reported in 2.1% of patients. This provocative observation raises the question of whether some fatal events following AV node ablation may be due to unrecognized tako-tsubo cardiomyopathy. These deaths typically occur within 4 days, and risk factors common to both entities include cardiac hypertrophy and diabetes.
In conclusion, we report a case of tako-tsubo cardiomyopathy following transcatheter radiofrequency ablation of the AV node. We speculate that the increase in sympathetic nerve activity that accompanies AV node ablation may have contributed to the pathophysiological process, which includes a stress-related increase in catecholamines and/or apical adrenoreceptor density and responsiveness.
Acknowledgements
This work was supported in part by the Canada Research Chair in Electrophysiology and Adult Congenital Heart Disease (P.K.).
Conflict of interest: none declared.
