The use of real-time three-dimensional echocardiography for assessing mechanical synchronicity

Biventricular pacing (BIV) has been established as a credible adjuvant treatment for patients with moderate-to-severe systolic heart failure (class III-IV of the New York Heart Association (NYHA) classification) and left bundle branch block (LBBB), which results in acute haemodynamic, neurohormonal and functional improvements, ventricular remodelling and has significant impact on survival and symptomatic improvement. Based on the current guidelines (ESC/AHA/ACC), several studies have demonstrated a failure to respond to cardiac resynchronisation therapy (CRT) both with clinical criteria and using reverse remodelling (20-30% and 30-40%, respectively, of the implanted patients). Consequently, imaging-based measures of dyssynchronous myocardial contraction have been intensively investigated with the aim of improving the prediction of response to therapy. In this study, we hypothesised that real-time three-dimensional echocardiography (RT3DE) may be a robust technique in assessing mechanical synchronicity in heart failure patients and may be effective in identifying patients who might benefit from BIV.

48 consecutive heart failure patients were screened with routine echocardiography, 35 (72%) of whom were eventually included in the study. An additional 35 age-matched and sex-matched healthy subjects were recruited as a control group. 20 patients from the heart failure group received biventricular pacemakers and were followed up to six months. The response to CRT was defined as either improvement in the NYHA class or reduction of the end-systolic volume >15%. Tissue Doppler imaging and real-time 3D data were obtained for all subjects and evaluation of volumes, ejection fraction and systolic dyssynchrony index was performed.

Of 35 heart failure patients, five (14%) had mild, seven (20%) moderate and 23 (66%) severe systolic dysfunction based on the EF calculation (45-50%, 45-35% and <35% respectively). The systolic dyssynchrony index (SDI) was 11.2% (2.2%), 13.7% (3.2%) and 17.3% (4%), respectively, while in the control group it was 9.8% (2.1%). The QRS length was <120 ms in 29%, 120-140 ms in 26% and >140 ms in 45% of the patients.

Real-time three-dimensional echocardiography is a robust technique, which can be used to accurately and effectively assess global and regional mechanical dyssynchrony in heart failure patients.