Clinical and echocardiographic variables fail to predict response to dual-chamber pacing for hypertrophic cardiomyopathy

Background: Although dual-chamber pacing therapy for obstructive hypertrophic cardiomyopathy has been relegated to a limited role, there remains a subset of patients who are not good candidates for more definitive therapies. Objective: The goal of this investigation was to determine whether preprocedural variables could help identify patients most likely to respond. Methods: Retrospective review of 84 patients with hypertrophic cardiomyopathy who underwent dual-chamber pacing for obstructive physiology at Mayo Clinic, Rochester, MN, included baseline demographics and echocardiographic features known to favor left ventricular outflow tract obstruction. Results of therapy, based on clinical visit, were obtained at two time points: within 2 years after pacemaker placement and at final follow-up (mean 3.7 years). Successful response to therapy was defined by improvement in New York Heart Association of at least 1 class without the need for surgical myectomy. Results: Overall, 66 (79%) patients had a follow-up visit within 2 years after the pacemaker placement, and 78 (93%) had at least one follow-up visit. There were 18 myectomies performed for persistent symptoms. A total of 33 (50%) patients had positive response to pacing therapy at the short-term analysis, whereas 34 (44%) had improvement sustained to the final visit. No preprocedural demographic or echocardiographic variables readily distinguished between responders and nonresponders. Conclusion: Dual-chamber pacing therapy for the relief of symptoms caused by dynamic left ventricular outflow tract obstruction has a limited role because of the availability of more definitive therapies; less than 50% long-term symptom relief; less than 20% long-term relief from a combined end point of death, symptoms, surgery, residual gradient, or a combination of these; and the inability to appropriately identify those patients most likely to derive benefit.