Abstract 16664: Intrapatient Variability in the Brockenbrough-Braunwald-Morrow Sign and Peak Instantaneous Left Ventricular Outflow Gradients in Obstructive Hypertrophic Cardiomyopathy

Abstract

Introduction: Although the variability in left ventricular outflow tract (LVOT) gradients in patients with hypertrophic cardiomyopathy (HCM) is well known, the value of pulse pressure (PP) changes with ectopy for predicting changes in LVOT gradient remains unreported. Hypothesis: This study examines the intrapatient variability in peak instantaneous LVOT gradients and aortic pulse pressure (PP) associated with the Brockenbrough-Braunwald-Morrow sign (BBM sign) compared with beat-to-beat variability. Methods: Variability in continuously recorded, high-fidelity left ventricular and aortic pressure waveforms were evaluated by computer-aided analysis in the resting state (N = 659 beats) and during supine exercise (N = 379 beats) in a symptomatic patient with a resting LVOT gradient >30 mmHg. Results: BBM sign was observed in 92.9% (26/28) of post-PVC beats at rest and the post PVC PP decreased 11.8±8.2% (P<0.001) compared with a 148.3±49.5% (P<0.001) increase in the LVOT gradient. During exercise, BBM sign was noted in 84.2% (32/38) of post-PVCs beats and PP decreased 4.0±6.3% (P<0.001) compared with a 74.2±37.5% (P<0.001) increase in LVOT gradient. PP decreases were also noted in 89.5% (17/19) beats during sinus arrhythmia following prolonged RR intervals. Changes in pulse pressure with ectopy poorly predicted quantitative changes in the LVOT gradient (R 2 ≤ 0.198). However, component analysis of the LVOT gradient suggests that beat-to-beat variability provides information similar to ectopic provocation in characterizing gradients in HCM and that rest and exercise changes converge to a common reference value. Conclusions: Although caution is suggested when interpreting pulse pressure changes with the BBM sign as surrogate for measuring LVOT gradients, this study suggests that analysis of hemodynamic variability in HCM may prove useful in characterizing the severity of obstruction.