It remains unclear whether flecainide, a Class I antiarrhythmic drug, improves 
left ventricular pressure gradient (LVPG) or symptoms in patients with 
obstructive hypertrophic cardiomyopathy (HCM). Our study evaluated the long-term 
efficacy of flecainide, compared to disopyramide, when administered orally, on 
LVPG and symptoms in obstructive HCM patients. Among 164 obstructive HCM 
patients, 15 were administered oral flecainide therapy and 33 administered oral 
disopyramide therapy. LVPG declined from 79.8 ± 36.6 to 39.2 ± 36.7 mmHg 
(p = 0.003) after flecainide therapy and from 74.5 ± 26.4 to 31.4 ± 24.8 mmHg 
(p < 0.001) after disopyramide therapy. The percent reduction in LVPG was 
-47.9 ± 43.2 % in patients treated with flecainide, comparable to the results 
for those treated with disopyramide (-57.1 ± 33.0 %; p = 0.425). We found no 
significant differences in improvement in NYHA functional class between patients 
treated with flecainide and those treated with disopyramide (p = 0.331). 
Patients treated with flecainide exhibited no significant adverse side effects, 
and there was no need for myectomy or alcohol septal ablation to reduce LVPG and 
symptoms. Improvements in LVPG and symptoms were similar in patients treated 
with flecainide and patients treated with disopyramide, suggesting that 
flecainide is a potentially useful alternative for symptomatic obstructive HCM 
patients, particularly those with disopyramide-induced vagolytic side effects, 
narrow angle glaucoma, or prostatic hyperplasia and pre-existing urination 
difficulties. Our data must be viewed with caution, however, in view of the 
small number of study patients. Flecainide therapy will require further proof of 
safety before it can be routinely recommended in patients with symptomatic 
obstructive HCM.