Abstract
Aims
Cardiac resynchronization therapy (CRT) is an established treatment for patients with heart failure (HF), reduced left ventricular ejection fraction (EF ≤ 35%) and high-grade intraventricular conduction delays. CRT improves cardiac function, symptoms and well-being, and reduces morbidity and mortality in this setting. However, there are patients unresponsive to CRT. Responders show reverse ventricular remodelling, volumes and diameters reduction, and EF improvement. Noninvasive cardiovascular imaging for visualization and quantitation of intracardiac flows and turbulences has not been assessed thoroughly in CRT. This study seeks to evaluate if the quantitative analysis of intracardiac flow dynamics in HF patients treated by CRT might provide additional information for device optimization and clinical response.
Methods and results
Fifteen HF patients (five females, age 69.6 ± 9.4 years, NYHA class II/III, EF 29.3 ± 4.6%) were enrolled in the study. Eleven had primitive dilated cardiomyopathy and four had post-ischaemic etiology with completed revascularization. Pacemaker-dependent cases were excluded. MyLab™ X8 platform was used for echocardiographic assessment of intracardiac flow dynamics performed on apical three chamber views. All examinations were realized in baseline (active CRT) and after 5 min of biventricular pacing switch off. The hyperDoppler software was used to assess intracardiac vortexes properties. The analyzed parameters were: vortex area, vortex length, vortex depth, and kinetic of energy dissipation (ΔKE). Categorical variables are expressed as numbers and percentages. Quantitative variables are expressed as mean and standard deviation (SD). Shapiro–Wilk test, D’Agostino Pearson test, and visual inspection of Q–Q-plots were executed to evaluate if variables were normally distributed. Quantitative variables were evaluated with paired sample T-test or Wilcoxon test when appropriate. Clinical features, biochemical parameters, electrocardiograms with and without cardiac pacing, and EF before and after CRT implantation were collected. Although no difference was observed in vortex area/depth/length, a significant increase in KE dissipation after switching OFF the CRT devices (from 1.2 ± 0.9 to 3.5 ± 2.3 J, P < 0.03) was remarkably observed. According to EF improvement after CRT, the patients were divided in responders (5% increase in EF, N = 10) and non-responders (N = 5). Moreover, by analysing the extent of QRS dispersion and the variation of KE dissipation in spontaneous rhythm and after silencing the biventricular pacing, a positive ventricular remodelling (QRS 141.3 ± 29.3 vs. 154.4 ± 24.4ms, P = 0.02; KE dissipation 0.92 ± 0.87 J in responders and 1.53 ± 1.76 J in non-responders, P = 0.006) was detected in responders.
Conclusions
Noninvasive intracardiac flow dynamics in HF patients represents a complementary tool to standard echocardiography, and provides additional parameters for assessing prognosis and outcomes in CRT recipients. The impact of maladaptation in intracardiac flow dynamic on progressive LV remodelling could be useful to evaluate the prognostic meaning of implanted CRT device and to predict the response to device implantation, based on cardiac flow analysis.
Septal contraction predicts acute haemodynamic improvement and paced QRS width reduction in cardiac resynchronization therapy
