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]