Follow up
Long-term follow up is vital in order to ascertain the effects of ASA in patients with drug refractory HOCM. Usual methods include yearly echocardiograms looking into LVEF, septal wall thickness, valvular function, LV systolic and diastolic function. Akita et al. propose the use of brain natriuretic peptide (BNP) as a prognostic indicator in patients who have had ASA. BNP is expressed in the ventricular myocytes during stress and can appear elevated in patients with LVOTO and diastolic dysfunction. They found reduction in BNP post ASA; with greater reduction up till the 3-month period and plateaus until the 12th month, greater declines were seen in the good responder group (Drop in NYHA class >1) [26]
Exercise tolerance along with symptomology is a useful indicator of the therapeutic effects of ASA. Fernandes et al. used monitored the exercise tolerance of their ASA during follow up using the treadmill test. The patients chosen for the study had NYHA class III-IV dyspnoea; they found significant improvement in NYHA class as well as LVOT gradient at the 3 month and 1 year phase. The treadmill time significantly improved 3 months post ASA and remained elevated though fewer patients were subjected to the treadmill test in the latter stages of follow up. [6]
Cardiac MRI was used by Sohns et al. compare the short-term results of ASA when compared to conventional echocardiography and cardiac catheterization. CMR was able to assess the scar tissue formed as a result of ASA; it showed a correlation between scar size and post extrasystolic gradient reduction, whereas echocardiogram did not record similar findings. CMR also identified that greater areas of scar tissue were associated with higher doses of ethanol. CMR may be able to perform a functional assessment on tissue by measuring flow velocity and flow volume, it can also assess myocardial viability and be used to follow ventricular remodelling. CMR may be useful as a non-invasive tool in conjunction with other imaging techniques to assess the effectiveness of ASA in the short and long term. [33]