Introduction: Dual chamber pacing for pressure gradient reduction in the left ventricular outflow tract (LVOT) is a minimal invasive therapy. Its results are still debatable, especially regarding clinical response. Because of that, even if it associates less possible complications, it is recommended only for patients with obstructive hypertrophic cardiomyopathy (OHCM) that are still symptomatic with maximal medical treatment and for which the other options for septal reduction therapy are not suitable.

Objective: Our purpose is to report a patient with OHCM treated by dual chamber pacing, describing his evolution during a period of more than 20 years. Data in the literature is scarce in this regard.

Methods: The 64 years-old patient was diagnosed 25 years ago with OHCM, manifested with signs and symptoms of heart failure (HF). Improvement of the obstruction and symptoms was tempted with maximal medical treatment, but without any success. After 2 years, dual chamber pacing with a short atrioventri-cular interval was implemented, achieving a significant decrease in the LVOT pressure gradient bellow the obstruction limit, with a progressive improvement of the symptomatology, corresponding to NYHA class I HF. The patient was asymptomatic for ~15 years, without any significant LVOT pressure gradient, a preserved ejection fraction (LVEF), diastolic dysfunction with progressive left atrium (LA) dilation, mild degenerative mitral regurgitation (MR), moderate functional tricuspid regurgitation (TR). After that period, the patient presented with NYHA class III HF signs and symptoms, with the ECG showing permanent atrial fibrillation, given the severely dilated LA. Echocardiography revealed hypertrophic, hyperechogenic and hypokinetic interventricular sep-tum (IVS), suggestive for intramyocardial fibrosis, with preserved LVEF, small amount of pericardial fluid secondary to stasis and moderate pulmonary hypertension (PHT). At the beginning, symptoms were improved by medical treatment adjustment. Now, a LVEF of 40-45%, global hypokinesia with akinetic IVS, moderate MR, severe TR with severe PHT were detected. Pace-maker up-grade to a biventricular one was tempted without any success. The patient refused at the time epicardial leads’ placement.

Conclusions: The presented case describes a clearly favorable evolution with contraction dyssynchrony after dual chamber pacing with a short atrioventricular interval in OHCM, regarding LVOT obstruction but also the clinical response. On the other hand, it confirms the fact that in the evolution of OHCM, intramyocardial fibrosis progresses, especially in the most hypertrophied areas, leading to LVEF decrease by affecting the contractility. Diastolic dysfunction is also progres-sive, with significant LA dilation, increased pulmonary pressures, significant functional tricuspid regurgitation associated with progressive heart failure signs and symptoms.