Complications of alcohol septal ablation
The most common complications during or post ASA involve arrhythmias. AV block is common post ASA, some may be transient or permanent and may require PPM insertion. Conduction abnormalities are expected during ASA and so the patients will be paced during and after the procedure for an average of 48 hours. The volume of ethanol used may correlate with the occurrence of conduction abnormalities. The greater volumes of ethanol used result in larger areas of myocardial infarction and may result in conduction defects. Kazmierczak et al. monitored the Electrocardiogram (ECG) changes during and post ASA. Complete right bundle branch block (RBBB) was immediately seen (within 1 hour) in all 9 patients which is expected as these areas are supplied by the septal branches, though only 4 had RBBB at the 6 month follow up. Only one patient required PPM implantation and ventricular tachycardia was not observed in any of the patients. Anterior ST segment elevation was also seen in at least two consecutive leads immediately post procedure in 5 out of 9 patients. [24]
Ethanol dose may play a role in procedural complications and outcomes. Doses range between centres and can vary depending on the patient. Higher ethanol usage has been associated with greater risk of patients developing conduction abnormalities. Sathyamurthy et al. injected on average 2ml of alcohol into the target septal branch of their patients. They found satisfactory occlusion of the target septal branch, improvement of symptoms, and significant reduction of LVOT gradients which were found in the 6 months post procedure and remained the same 8 years after. Right bundle branch block (RBBB) was seen in 79% of patients post procedure however only 10% required PPM. [25] Akita et al observed that between the good (reduction in NYHA class >1) and poor (reduction in NYHA class <1) responder group; the good responder group required more ethanol during ablation, using 4ml as oppose to 3.1ml used by in the poor responder group. Greater incidences of arrhythmias were observed in the good responder group and may correlate with the amount of ethanol used during ASA. Those in the good responder group developed ventricular arrhythmias (6.9%), complete AV block (13.8%), and PPM implantation (11.1%), whereas the poor responder group which used less ethanol during ASA did not show any ventricular arrhythmias, PPM was not required and only 11.1% developed complete AV block. [26] Baggish et al. performed autopsies on patients post ASA. One autopsy performed soon after ASA found myocardial necrosis with marginating neutrophils at the periphery of the infraction; 3ml of ethanol was used during the procedure. Septal perforator artery and myocardium necrosis, as well as absence of nuclei from endothelial and smooth muscle cells. Another autopsy performed 14 months after ASA; only 1ml of ethanol was used and this patient required surgical myectomy as symptoms persisted as the LVOT gradient remained high. Autopsy revealed incomplete infarction showing viable myocytes surrounded by scar and thrombosed septal arteries with necrotic arterial walls. Indicating the vascular toxic role that ethanol plays, and the difference in pathology when lower and higher doses of ethanol are used. [27]
Steggerda et al. investigated the predictors of poor outcomes in ASA. They selected patients with NYHA class > III, and LVOT gradient >30mmHG and >50 mmHG on provocation. 37 out of 113 were deemed to have insufficient response to ASA; elevated resting gradient, and greater distances from the origin of the left anterior descending artery (LAD) to the first septal branch were shown to be associated with poorer outcomes. Suggesting that unfavourable coronary anatomy may result in either insufficient therapeutic effect, or increased chances of the procedure being abandoned. [28] Less common periprocedural complications include coronary artery dissection, cardiac tamponade, and arterial complications which are related to access such as femoral artery pseudoaneurysm or retroperitoneal haemorrhage. [29] Cuoco et al. studied the long-term risk of ventricular arrhythmias after ASA. They collected data from 123 patients and monitored the times a shock was delivered by an implantable cardioverter defibrillator (ICD). Only 9 patients out of 123 developed a rhythm that required an ICD shock. Suggesting that ventricular arrhythmias are uncommon after ASA however they are more likely to occur in the immediate post-operative phase. Studies have suggested that the scar tissue formed by ethanol injection could be pro-arrhythmogenic.[30] El-Sabawi et al. also report low instances of ventricular arrhythmia 1.2% following ASA, whereas complete AV block was more frequent at 24.3% especially in the initial 24 hours post procedure. [31] Atrial fibrillation (AF) can occur post ASA, Moss et al. studies 132 patient with no history of AF. During follow up 10 patients (7.6%) developed AF with only 2 having permanent AF, those affected tended to be older but the NYHA class was the same as the AF free group. Despite therapeutic anticoagulation, one patient developed stroke. [32]