The relationship of QRS morphology and mechanical dyssynchrony to long-term outcome following cardiac resynchronization therapy.

AIMS: Because benefits of cardiac resynchronization therapy (CRT) appear to be less favourable in non-left bundle branch block (LBBB) patients, this prospective longitudinal study tested the hypothesis that QRS morphology and echocardiographic mechanical dyssynchrony were associated with long-term outcome after CRT. METHODS AND RESULTS: Two-hundred and seventy-eight consecutive New York Heart Association class III and IV CRT patients with QRS ≥120 ms and ejection fraction ≤35% were studied. The pre-specified primary endpoint was death, heart transplant, or left ventricular assist device over 4 years. Dyssynchrony assessed before CRT included interventricular mechanical delay (IVMD) and speckle-tracking radial strain using pre-specified cut-offs for each. Of 254 with baseline quantitative echocardiographic data available, 128 had LBBB, 81 had intraventricular conduction delay (IVCD), and 45 had right bundle branch block (RBBB). Radial dyssynchrony was observed in 85% of the patients with LBBB, 59% with IVCD*, and 40% with RBBB* (*P < 0.01 vs. LBBB). Of 248 (98%) with follow-up, LBBB patients had a significantly more favourable long-term survival than non-LBBB patients. However, non-LBBB patients with dyssynchrony had a more favourable event-free survival than those without dyssynchrony: radial dyssynchrony hazard ratio 2.6, 95% confidence interval (CI) 1.47-4.53 (P = 0.0008) and IVMD hazard ratio 4.9, 95% CI 2.60-9.16 (P = 0.0007). Right bundle branch block patients who lacked dyssynchrony had the least favourable outcome. CONCLUSION: Non-LBBB patients with dyssynchrony had a more favourable long-term survival than non-LBBB patients who lacked dyssynchrony. Mechanical dyssynchrony and QRS morphology are associated with outcome following CRT.

A practical approach to imaging dyssynchrony for cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) is believed to benefit patients by primarily correcting heterogeneity in regional ventricular mechanical contraction, known as dyssynchrony. Although many symptomatic heart failure patients with depressed left ventricular ejection fraction and widened electrocardiographic QRS complexes have clinical improvement from CRT, a significant subset of approximately one-third do not seem to respond. Because the degree of mechanical dyssynchrony may be widely variable, interest has remained high to attempt to improve patient selection for CRT using cardiac imaging as a means to quantify dyssynchrony. This article will review the principal echocardiographic methods of dyssynchrony analysis by tissue Doppler imaging, (opposing wall delay, 12-site standard deviation or Yu index, and longitudinal strain), routine pulsed-Doppler (interventricular mechanical delay, pre-ejection delay and filling time ratio), and speckle tracking (including radial, circumferential, and longitudinal strain). In addition, dyssynchrony analysis by cardiac magnetic resonance imaging is introduced as a potential alternative technique. The technical features, strengths and limitations, and clinical evidence for these methods are discussed, including a practical clinical approach.

Echocardiography-guided left ventricular lead placement for cardiac resynchronization therapy: results of the Speckle Tracking Assisted Resynchronization Therapy for Electrode Region trial.

BACKGROUND: Cardiac resynchronization therapy improves mortality and morbidity in patients with heart failure (HF) with wide QRS complex and diminished left ventricular (LV) function, but response is variable. METHODS AND RESULTS: The Speckle Tracking Assisted Resynchronization Therapy for Electrode Region (STARTER) was a prospective, double-blind, randomized controlled trial testing the hypothesis that an incremental benefit to cardiac resynchronization therapy would be gained by echo-guided (EG) transvenous LV lead placement versus a routine fluoroscopic approach. EG LV lead placement was attempted at the site of latest time to peak radial strain by speckle tracking echocardiography. The prespecified primary end point was first HF hospitalization or death. Of 187 New York Heart Association class II to IV patients with HF (62% ischemic; ejection fraction 26±6%; QRS 159±27 ms), 110 were randomized to EG and 77 to routine strategies. Primary events included 30 deaths and 37 HF hospitalizations over 1.8 years. Using intention-to-treat, patients randomized to an EG strategy had a significantly more favorable event-free survival (hazard ratio, 0.48; 95% confidence interval, 0.28-0.82; P=0.006). Exact or adjacent concordance of LV lead with latest site could be achieved in 85% of the EG group and occurred fortuitously in 66% of controls (P=0.010) and was associated with an improvement in event-free survival (hazard ratio, 0.40; 95% confidence interval, 0.22-0.71; P=0.002). CONCLUSIONS: A strategy of EG LV lead placement for cardiac resynchronization therapy improved patient outcomes by reducing the combined risk of death or HF hospitalizations and has implications for delivery of cardiac resynchronization therapy. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00156390.