Discussion
Coronary spasm is one rare yet still-existing complication of catheter ablation, which could
sometimes lead to catastrophic events 1,2. Tachycardia-induced heart failure has emerged in recent years as one common cause of acute decompensated heart failure, and patients also run a higher risk of sudden cardiac death3. In the case presented, the heart function had deteriorated
significantly with the incessant atrioventricular reentry tachycardia. The low ejection fraction with an acutely dilated heart renders it more vulnerable to severe arrhythmia. Catheter ablation has been proven to be an effective method for treating tachycardia-induced cardiomyopathy4,5. However, ablation in the acute decompensated heart also carries an increasing risk and has been reported with little evidence. During the initial ablation, a fast heart rate reduces the diastolic phase and blood flow to the coronaries. Emergency ablation of the accessory pathway in a failing heart with the adjacent left circumflex coronary had resulted in acute spasm and ventricular fibrillation. Coronary spasm is a rare complication that has also been reported to associate with catheter ablation. However, while the common culprit vessels would be the right coronary artery with its close course to the AV groove on the right side which made itself more vulnerable for ablation, left side coronary arteries are less likely to be affected by radiofrequency energy. The tricuspid annulus would protrude inside into the heart cavity more than the mitral annulus making the AV groove deeper compared with the left side. In addition to that, the myocardium around the mitral valve would be thicker but the ventricular insertion site of the accessory pathway in this area would be close to the valve. For these reasons, ablation of the APs in the mitral annulus would achieve higher acute success rate and lower complication, especially coronary injuries. For the case presented, this unfortunate circumstance still occurred. The ST interval elevation was documented to be elevated before the onset of VT/VF, providing more evidence for the coronary artery to be the culprit underlying the fatal arrhythmias. As for the cause of coronary injury, direct thermal assault would be most likely and has been reported to cause adjacent vessels spasm. In our case, we utilized the non-irrigated catheter for ablation which ruled out the possibility of air emboli. This complication has been reported in some previous studies in the pediatric patients with relatively thin myocardium as the predisposing factor6. For the group of older patients, the incidence seems to be significantly lower and ablation of the left AP is relatively safe and never before had there been a report discussing the acute dilation of the heart in adult patients as the predisposing factor for coronary injury during ablation. In the case, the patient’s risk factor would be different but also at the same time seem to be similar with the acutely dilated ventricle resulting in the thinning of the myocardium wall, energy might have more close proximity with the coronary. However, with the on-time intervention of extracorporeal support and the partial success management of the initial tachycardia, we managed to subdue the cause of heart failure and put the patient in a more stable condition.