Optimization of cardiac resynchronization therapy in patients with heart failure secondary to ischemic or idiopathic dilated cardiomyopathy: Comparison of invasive, echocardiographic and electrocardiographic techniques

Cardiac resynchronization therapy (CRT) is an effective way of improving left ventricular (LV) dysfunction with atrioventricular and interventricular conduction delay. In recent years, various studies has demonstrated that CRT improves morbidity, functional status and survival in patients with symptoms of heart failure despite optimal medical treatment, reduced LV ejection fraction (EF <35%) and QRS duration wider than 120 milliseconds. Also, improvement in dyssynchrony, EF and LV remodeling with CRT has been shown. In order to get the best efficacy from CRT, it is important to make device optimization. In clinical practice, optimization of atrioventricular (AV) and interventricular (VV) delay time with invasive and noninvasive methods were compared after CRT and acute hemodynamic benefits were shown. However, there is not enough evidence about the long term effects of therapy and the ideal optimization strategy is yet to be determined. In our study, we aimed to investigate the correlation of AV and VV delay times assessed by echocardiographic (ECHO) and electrocardiographic (ECG) methods with AV delay times found while using invasive measurement of LV dP/dt as a reference value. Also we targeted to find the optimization method which provides better hemodynamic outcome. Twenty one patients (17 men, 4 women) having ischemic or nonischemic cardiomyopathy who met the inclusion criteria according to guidelines were included in the study. We randomized patients 1:1 into ECHO or invasively optimized groups in order to evaluate long term clinical outcomes. However, the study time was limited, long term clinical follow up couldn't be done. The optimization measurements were performed < 24 hours after pacemaker implantation. Invasively LV dP/dt was measured. The Doppler ECHO methods were the time velocity integral of left ventricular outflow tract (LVOT TVI), Iterative method and maximal diastolic filling time (DFT). After optimization of AV and VV delay time with invasive and ECHO methods there was a marked increase in hemodynamic parameters. The optimal AV delay time when LVOT TVI and Iterative methods used simultaneously was concordant with AV delay obtained from LV dP/dt measurement. Although invasive methods correlated with maximal DFT, LVOT TVI method was concordant with neither invasive methods nor maximal DFT. In AV delay time optimization, LVOT TVI and Iterative method used simultaneously and a correlation found in AV delays measured with the methods when LVOT TVI and DFT used alone. After optimization of AV delay, the VV delay time was also adjusted. Invasive LV dP/dt, QRS duration in ECG and LVOT TVI methods were compared and there were not any correlation between these methods despite improvement in hemodynamic parameters. In conclusion, to obtain the optimal acute hemodynamic benefit of CRT, usage of LVOT TVI and Iterative simultaneously is a reliable method to optimize the AV delay time compared with the invasive LV dP/dt. We need further investigation to find alternative VV delay time optimization techniques that can better correlate with invasive methods and make hemodynamic improvement. Key words: cardiac resynchronization therapy, three chamber pacemaker, heart failure, optimization of CRT