Palpography Detects Mechanical Dyssynchrony and Worsens with Right Ventricular Pacing and Reduced Left Ventricular Ejection Fraction

Abstract

QRS width and echocardiography-derived indices are limited predictors of response to resynchronization therapy. We applied digital palpography, using vibration resonance imaging, to investigate the effects of right ventricular pacing and left ventricular ejection fraction (LVEF) on mechanical and electrical dyssynchrony. Forty-nine subjects were examined: 24 normal controls, 18 subjects with right ventricular apical pacing (12 with reduced LVEF), and seven subjects with reduced LVEF and narrow QRS. Digital measurement of QRS width was performed. Electric dyssynchrony index (EDI) was measured as the time interval between peak R-waves of the same QRS complex of simultaneously recorded standard limb electrocardiograms, L1 and L2. A matrix of 6 × 6 vibration recording transducers was applied to chest. The interval between the onset of Q-wave and the peak of amplitude vibration for each transducer was measured, and a three-dimensional map for the whole matrix of transducers was generated. Median values (QE1) were measured. Mechanical vibration systolic dyssynchrony index (VSDI) for each subject was determined as the standard deviation of the difference between the median value and each transducer interval. EDI was larger in subjects with right ventricular pacing. Mechanical dyssynchrony indices were larger with pacing and reduced LVEF. EDI correlated with QRS width (r(2) = 0.7), with VSDI (r(2) = 0.42), and with QE1 (r(2) = 0.74). QRS width correlated with QE1 (r(2) = 0.75). Digital chest palpography can determine dyssynchrony indices that are larger in subjects with right ventricular pacing and reduced LVEF and correlate with parameters of electrical dyssynchrony.