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.