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Images in Cardiovascular Medicine Right Ventricular Pacing for Right Ventricular Outflow Tract Obstruction in a Man with Biventricular Hypertrophic Cardiomyopathy Sarah E. Nelson, MD Gautam R. Shroff, MBBS Ronald A. Johannsen, MD Rehan M. Karim, MBBS A 40-year-old man with known hypertrophic cardiomyopathy presented with syncope after coughing. Physical examination revealed a systolic murmur that was accentuated by the Valsalva maneuver. An electrocardiogram suggested biventricular hypertrophy and biatrial enlargement (Fig. 1). Echocardiograms revealed asymmetric septal hypertrophy with a diastolic septal thickness of 2.3 cm, and evidence of flow acceleration across the right ventricular outflow tract (RVOT) and left ventricular outflow tract (LVOT) (Figs. 2 and 3). Cardiac magnetic resonance images confirmed noncontiguous hypertrophy involving the basal septal, basal anterior, and apical walls of the left ventricle, as well as the inferior and free walls of the right ventricle (RV). A prominent muscle band in the RVOT contributed to dynamic obstruction across the RVOT (Figs. 4 and 5). Patchy hyperenhancement in the septum, visible in delayed-enhancement sequences after Fig. 1 Electrocardiogram shows evidence of biventricular hypertrophy and biatrial enlargement. Section Editor: Raymond F. Stainback, MD, Department of Adult Cardiology, Texas Heart Institute at St. Luke’s Episcopal Hospital, 6624 Fannin St., Suite 2480, Houston, TX 77030 From: Department of Internal Medicine (Dr. Nelson) and Division of Cardiology (Drs. Johannsen, Karim, and Shroff), Hennepin County Medical Center, Minneapolis, Minnesota 55415 Address for reprints: Sarah E. Nelson, MD, Department of Internal Medicine, Hennepin County Medical Center, 701 Park Ave., Minneapolis, MN 55415 E-mail: [email protected] Fig. 2 Transthoracic echocardiogram (parasternal long-axis view) shows systolic flow acceleration across the right (RVOT) and left ventricular outflow tracts (LVOT). Fig. 3 Transthoracic echocardiogram (parasternal long-axis view) shows systolic flow acceleration across the right ventricular outflow tract (RVOT). Click here for real-time motion image: Fig. 2. Click here for real-time motion image: Fig. 3. © 2013 by the Texas Heart ® Institute, Houston Texas Heart Institute Journal Right Ventricular Pacing in Biventricular Hypertrophic Cardiomyopathy 367 gadolinium administration, was consistent with myocardial fibrosis (Fig. 6). The subendocardium was not involved, suggesting a cause other than coronary disease. Angiography was performed to measure and characterize the gradient across the RVOT. There was a hemodynamically significant gradient of 54 mmHg (mean, 33 mmHg). When the patient coughed and then performed the Valsalva maneuver, the peak gradients increased to 94 mmHg and 106 mmHg, respectively. Potentiation of the peak gradient across the RVOT was observed after a premature ventricular contraction (Fig. 7). Because of the patient’s unexplained syncope, a carFig. 6 Cardiac magnetic resonance image shows delayed enhancement in the interventricular septum after gadolinium administration (arrow), consistent with myocardial fibrosis that spares the subendocardium. Fig. 4 Cardiac magnetic resonance image shows noncontiguous left ventricular hypertrophy involving the basal septum and apex (arrows). Fig. 7 Hemodynamic tracings from right-sided heart catheter ization show simultaneous right ventricular (RV) pressure (across the RV outflow tract) and pulmonary artery (PA) tracings. This figure shows potentiation of the peak RV gradient (bottom tracing) after a premature ventricular contraction. dioverter-defibrillator was implanted for the primary prevention of sudden cardiac death. An atrial lead was also implanted to accommodate any future need for atrioventricular synchronous pacing. Transthoracic echocardiography was performed to evaluate the effect of RV pacing on the RVOT gradient. The peak gradient across the RVOT was 17 mmHg with RV pacing and 37 mmHg without RV pacing (Fig. 8). Comment Fig. 5 Cardiac magnetic resonance image shows a hypertrophied muscle band in the right ventricular outflow tract contributing to dynamic obstruction indicated by flow acceleration (arrow). 368 Right ventricular involvement has been reported in hypertrophic cardiomyopathy; however, its prevalence is variably described.1 Dual-chamber pacing has produced favorable hemodynamic effects in patients with symp- Right Ventricular Pacing in Biventricular Hypertrophic Cardiomyopathy Volume 40, Number 3, 2013 A tomatic LVOT obstruction.2 In comparison, RV pacing reduced the gradient across our patient’s RVOT. B Acknowledgment We thank Dr. Richard Asinger for his help with hemodynamic evaluation and critical review of the manuscript. References Fig. 8 Transthoracic echocardiograms show gradients across the right ventricular outflow tract. A) With pacing, the peak gradient was 17 mmHg at 72 beats/min. B) Without pacing, the peak gradient was 37 mmHg at approximately 72 beats/min. AT = acceleration time; ET = ejection time; Grad = gradient; Pk = peak; RVOT = right ventricular outflow tract; Vmax = maximum velocity; Vmin = minimum velocity; VTI = velocity time integral Texas Heart Institute Journal 1. Maron MS, Hauser TH, Dubrow E, Horst TA, Kissinger KV, Udelson JE, Manning WJ. Right ventricular involvement in hypertrophic cardiomyopathy. Am J Cardiol 2007;100(8): 1293-8. 2. Fananapazir L, Epstein ND, Curiel RV, Panza JA, Tripodi D, McAreavey D. Long-term results of dual-chamber (DDD) pacing in obstructive hypertrophic cardiomyopathy. Evidence for progressive symptomatic and hemodynamic improvement and reduction of left ventricular hypertrophy. Circulation 1994;90(6):2731-42. Right Ventricular Pacing in Biventricular Hypertrophic Cardiomyopathy 369