Aims: Identifying potential responders to cardiac resynchronization therapy (CRT) may be sometimes difficult and time consuming. Searching for a simple method, we chose vectorcardiography (VCG) for our study. The aim was to evaluate whether a VCG parameter can be used to predict invasively measured acute hemodynamic changes after CRT onset.
Methods and results: Baseline VCG data were prospectively recorded just before initiation of CRT in a series of 126 consecutive patients (♂74 %, DCMP 60 %, ICMP 40 %, NYHA class III 100 %, QRS width 161 ± 27 ms, LV-EF 25 ± 6.5 %) prior to implantation at our specialized center. The time interval (TI) between the maximum vector and the end of the vector loop (initial description by Koglek W.) was correlated with acute hemodynamic change after CRT onset. Positive response to CRT was defined as an increase in dp/dt max >10 % or pulse pressure >5 %. According to these invasive hemodynamic parameters, 25 patients (20 %) were defined as non-responders. Using ROC analysis, the threshold value of the TI for responders was found to be 64 ms. TI is a predictor of acute hemodynamic response with a sensitivity of 96 %, a specificity of 76 %, a positive predictive value of 94 %, and a negative predictive value of 79 %. More non-responders are identified by TI than by using conventional QRS width in the 12-lead surface ECG.
Conclusion: TI is a new method of evaluation based on baseline VCG analysis. It may be a useful diagnostic test for predicting acute hemodynamic response to CRT.