Indication for alcohol septal ablation
Criteria for patients who are deemed suitable for ASA include; New York Heart Association (NYHA) class III-IV, LVOT resting gradient >30mmHG or >50mmHG on provocation, evidence of systolic anterior motion (SAM) of the mitral valve leaflet, septal wall thickness >16mm. [6] Various centres will have their own criteria for patient selection for ASA, on the whole these tend to be based on symptomology, LVOT gradients and existing o-morbidities. Concomitant significant coronary artery disease or valvular pathologies need to be ruled out as these patients will benefit from cardiac surgery rather than ASA. Favourable coronary anatomy is also crucial to outcomes as easily accessible septal branches allow for uncomplicated procedures. [7] The 2011 ACCF/AHA guidelines state that surgical myectomy should be gold standard for drug refractory HOCM and advise against the use of ASA in those with marked septal hypertrophy (>30 mm), in younger patients, in mid ventricular obstruction, and in those with concomitant disease that requires surgical intervention. They particularly advised against both surgical and percutaneous intervention in those who are asymptomatic or have normal exercise tolerance. [2,8]. Indications have been summarised in Table 1
NYHA and CCS are useful indicators of symptoms, however they remain highly subjective. Jones et al. suggest the use of other tests in order to identify patients suitable for ASA. One such test is cardiopulmonary exercise testing which can be used in HOCM patients with mild symptoms, where peak VO2 is associated with NYHA class. 6-minute walk test can also provide an objective measure of exercise tolerance. Kansas City cardiomyopathy questionnaire involves clinical and non-clinical aspects as part of its scoring system and emphasises the importance of quality of life in choosing candidates for ASA. [9] Table 2 shows the calculation of the risk of sudden cardiac death in HOCM and how it can be used to predict mortality in those with severe HOCM who remain untreated.