Impact of S-Wave Amplitude in Right Precordial Leads on Improvement in Mitral Regurgitation following Cardiac Resynchronization Therapy

Abstract

Background: The therapeutic strategy for mitral regurgitation (MR) in patients with advanced heart failure and wide QRS complex who are indicated for both intervention to MR and cardiac resynchronization therapy (CRT), remains unclear.

Objective: We aimed to determine electrocardiogram parameters that associate with MR reduction following CRT implantation.

Methods: Among the patients with advanced heart failure and functional MR who intended to receive CRT implantation, baseline QRS morphology, electrical axis, PR interval, QRS duration, and averaged S-wave in right precordial leads (V1 to V3) in surface electrocardiogram were measured. The impact of these parameters on MR reduction following CRT implantation, which was defined as a reduction in MR ≥1 grade six months later, was investigated.

Results: In 35 patients (median 71 years old, 18 men), 17 (49%) achieved an MR reduction following CRT implantation. Among baseline characteristics, only the higher S-wave amplitude in right precordial leads was an independent predictor of MR reduction (odds ratio 14.00, 95% confidence interval 1.65-119.00, p = 0.016) with a cutoff of 1.3 mV calculated through the area under the curve. The cutoff significantly stratified the cumulative incidences of heart failure re-admission and percutaneous mitral valve repair following CRT implantation (p = 0.032 and p = 0.011, respectively).

Conclusions: In patients with advanced heart failure and functional MR, the baseline higher amplitude of S-wave in the right precordial leads might be a good indicator of MR improvement following CRT.

Keywords: QRS amplitude; cardiac resynchronization therapy; heart failure.

Figure 1

Receiver operating characteristic curve of averaged S-wave amplitude in right precordial leads for predicting mitral regurgitation reduction following cardiac resynchronization therapy.

Figure 2

Representative baseline electrocardiograms (left bundle branch block (A,B), right ventricular apical pacing (C,D)). Arrows indicate S-waves in right precordial leads. (A). Left bundle branch block and averaged S-wave amplitude >1.3 mV: the patient with MR reduction (B). Left bundle branch block and the averaged S-wave amplitude <1.3 mV: the patient without MR reduction (C). Right ventricular apical pacing and the averaged S-wave amplitude >1.3 mV: the patient with MR reduction (D). Right ventricular apical pacing and the averaged S-wave amplitude <1.3 mV: the patient without MR reduction.

Figure 3

Cumulative incidence of clinical events stratified by the cutoff of S-wave amplitude ((A) heart failure readmission; (B) percutaneous mitral valve repair; (C) cardiovascular death). Odds ratio of S > 1.3 mV for heart failure readmission was 0.31 [0.10–0.95], p = 0.040, and for cardiovascular death was 0.11 [0.01–0.95], p = 0.045.

Figure 4

The proposed management strategy of functional mitral regurgitation in patients with advanced heart failure. CRT = cardiac resynchronization therapy and MR = mitral regurgitation.