Factors associated with resistance to disopyramide in obstructive hypertrophic cardiomyopathy

Background: Disopyramide (DISO) lowers resting LV outflow gradients in symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM). Some of these patients are resistant to DISO and require surgical myectomy. Our objective was to identify factors associated with DISO resistance. Methods: From a cohort of 737 patients with HCM we analyzed 113 clinical and echo variables in 73 patients with resting gradients ≥30mmHg receiving DISO for symptoms and gradients resistant to beta-blocker and verapamil. Non-response was defined as resting gradient ≥30mmHg post-DISO. Results: There were 26% non-responders. Non-responders were younger (55±18 vs. 63±15 years, p=0.04); had longer anterior mitral leaflets (18±3 vs. 15±1.9 mm/m2, p 88mmHg were non-responders (p<0.00001, fig 1). At 5-years follow-up 40% of all patients required myectomy (31.5% of the responders vs. 63% of the non-responders, p=0.015). Patients requiring myectomy had longer anterior leaflets (16.6±3 vs. 15.2±2mm/m2, p=0.024) and were younger (56±15 vs. 65±16 years, p<0.02). Myectomy was more common in patients with anterior leaflets ≥35mm (75%) compared to ≤35mm (33%, p<0.01). ![Figure][1] Figure 1 Conclusions: Resistance to DISO is a strong predictor of need for septal myectomy. Symptomatic patients with both resting baseline gradients >88mmHg and anterior mitral leaflets ≥33mm could reasonably be referred for myectomy without a trial of DISO. [1]: pending:yes