LBBB and heart failure-Relationships among QRS amplitude, duration, height, LV mass, and sex

Left Ventricular Mass as a Modulator of Ventricular Arrhythmia Risk and Sex Differences Following CRT for Non-Ischemic Cardiomyopathy and LBBB

BACKGROUND

Risk for ventricular arrhythmias (VA) following cardiac resynchronization therapy (CRT) has been associated with ischemic disease/scar, sex, and possibly left ventricular mass (LVM).

OBJECTIVE

To evaluate sex differences and baseline/post-implant change [Δ] of LVM on VA risk after CRT implant among patients with non-ischemic cardiomyopathy (NICM) and left bundle branch block.

METHODS

Among patients meeting the criteria, baseline and follow-up echocardiographic images were obtained for LVM assessment. VA events were reported from device diagnostics and therapies. VA risk was stratified by ROC (Youden-index cut-point) for baseline LVM and ΔLVM, and baseline patient characteristics using a multivariable Cox regression model.

RESULTS

118 patients (71[60.2%] female, age 60.5 ±11.3 years, LVEF 19.2 ±7.0%, QRS 165.6 ±20 ms, LVM 313.9 ±108.8 g) were enrolled and followed for median 90 (IQR 44-158) months. Thirty-five (29.6%) patients received appropriate shocks or anti-tachycardia pacing at a median of 73.5 (IQR 25-130) months post-implant. Males had a higher VA incidence (male 18/47 [38.3%] vs. female 17/71 [23.9%], P=0.02). Baseline LVM >308.9g separated patients with higher VA risk (P=0.001). Less than a 20% decrease in LVM increased VA risk (P<0.001). Baseline LVM was the only baseline characteristic predicting VA events in the Cox regression model (Hazard ratio 1.01 [95%CI, 1.001-1.009], Log-rank P=0.003). Sex differences in VA risk were eliminated by the baseline LVM parameters.

CONCLUSION

VA risk after CRT in NICM was associated with baseline LV >308.9g and a decrease in LVM ≤ 20%, without sex differences.

Clinical utility of QRS duration normalized to left ventricular volume for predicting cardiac resynchronization therapy efficacy in patients with "mid-range" QRS duration

BACKGROUND

Cardiac resynchronization therapy (CRT) is effective for patients with heart failure with QRS duration (QRSd) ≥150 ms. However, its beneficial effect seems to be limited for those with "mid-range" QRSd (120-149 ms). Recent studies have demonstrated that modifying QRSd to left ventricular end-diastolic volume (LVEDV)-modified QRSd-improves the prediction of clinical outcomes of CRT.

OBJECTIVE

The purpose of this study was to investigate the clinical impact of the modified QRSd on the efficacy of CRT in patients with "mid-range" QRSd.

METHODS

We conducted a retrospective, multicenter, observational study, with heart failure hospitalization (HFH) after CRT as the primary endpoint. Modified QRSd is defined as QRSd divided by LVEDV, determined through the Teichholtz method of echocardiography.

RESULTS

Among the 506 consecutive patients considered, 119 (mean age 61 ± 15 years; 80% male, QRSd 135 ± 9 ms) with a "mid-range" QRSd who underwent de novo CRT device implantation were included for analysis. During median follow-up of 878 days [interquartile range 381-1663 days], HFH occurred in 45 patients (37%). Fine-Gray analysis revealed modified QRSd was an independent predictor of HFH (hazard ratio [HR] 0.97; 95% confidence interval [CI] 0.96-0.99; P <.01). Receiver operating characteristic curve analysis revealed a cutoff value of 0.65 ms/mL for the modified QRSd in predicting HFH. Patients above the threshold exhibited a significantly lower incidence of HFH than patients below the threshold (HR 0.46; 95% CI 0.25-0.86; P = .01).

CONCLUSION

Modified QRSd can effectively predict the efficacy of CRT in patients with a "mid-range" QRSd.