Interplay Between RV Function and CRT, Which One Affects the Other?
Background: Cardiac resynchronization therapy (CRT) is an established treatment of heart failure with reduced EF (HFrEF) and wide QRS complex. Nearly 30% of candidates are non-responders. One of the suggested mechanisms of inadequate response is the reduced baseline RV function; also the effect of CRT on right ventricular systolic function has not been well studied. We examined the effect of CRT on right ventricular (RV) dimensions and overall systolic function and whether RV function prior to CRT could have an impact on CRT response.
Methods: 30 patients with a mean age of 51.9 ± 9.2 years including 9 (30%) females, with advanced HF (EF < 35%, LBBB > 120 ms, or non-LBBB > 150 ms, with NYHA class III or ambulatory class IV) were enrolled and underwent CRT implantation. Standard two dimensional (2D) echocardiography, tissue Doppler imaging, for assessment of Left ventricular (LV) end-diastolic (LVEDV), and end-systolic volumes (LVESV), ejection fraction, RV maximum basal (RVD1 basal), maximum mid (RVD2 mid) transverse, maximum longitudinal (RVD3 long) diameters, TAPSE, fractional area change (FAC), right ventricle index of myocardial performance(RIMP) and tricuspid lateral annular systolic velocity (S’), were done before CRT implantation and at the end of the follow up period (6 months). Patients presenting with reduction of LVESV of >15% were considered responders.
Results: 20 (67%) cases were responders. Both groups were similar regarding demographic, clinical, ECG, and echocardiographic criteria at baseline however, the RA volume and RV transverse diameters were smaller and systolic function parameters were significantly better in the responders group prior to CRT compared to non-responders (NR) group. At the end of the follow up, only the responders group had further significant reduction in RV basal, mid and longitudinal diameters together with significant improvement in RV systolic function, in contrast to non-responders group who showed more RV dilatation and more decline of RV systolic function, compared to baseline readings(with P value <0.0001 for all parameters), Correlation between RV parameters before CRT implantation and CRT response was performed and ROC curves were plotted to define cutoff values for each parameter with FAC of >40 % has 85% sensitivity and 90 % specificity (P value= 0.004). TAPSE of >20 mm has 85% sensitivity and 80 % specificity (P value=0.002), S' of >10 cm/s % has 85% sensitivity and 70 % specificity (P value=0.001) and RIMP of <0.52 has 85% sensitivity and 70 % specificity (P value=0.003) in predicting CRT response.
Conclusions: CRT induces RV reverse remodeling and improves RV systolic function particularly in cardiac volumetric responders. RV systolic dysfunction before CRT implantation could identify patients that might not benefit from CRT thus helping proper patient selection and optimizing CRT response.