The roles of the Q (q) wave in lead I and QRS frontal axis for diagnosing loss of left ventricular capture during cardiac resynchronization therapy.
INTRODUCTION
Loss of left ventricular (LV) capture may lead to deterioration of heart failure in patients with cardiac resynchronization therapy (CRT). Recognition of loss of LV capture in time is important in clinical practice.


METHODS AND RESULTS
A total of 422 electrocardiograms were acquired and analyzed from 53 CRT patients at 8 different pacing settings (LV only, right ventricle [RV] only, biventricular [BV] pacing with LV preactivation of 60, 40, 20, and 0 milliseconds and RV preactivation of 20 and 40 milliseconds). A modified Ammann algorithm by adding a third step-presence of Q (q, or QS) wave-to the original 2-step Ammann algorithm and a QRS axis shift method were devised to identify the loss of LV capture. The accuracy of modified Ammann algorithm was significantly higher than that of Ammann algorithm (78.9% vs. 69.1%, P < 0.001). The accuracy of the axis shift method was 66.4%, which was significantly lower than the modified Ammann algorithm (P < 0.001) and similar to the original one (P = 0.412). However, in the ECGs with QRS axis shift, 96.8% were correctly classified. LV preactivation or simultaneous BV activation and LV lead positioned in nonposterior or noninferior wall could elevate the accuracies of the modified Ammann algorithm and the QRS axis shift method.


CONCLUSIONS
The accuracy of the modified Ammann algorithm is greatly improved. The QRS axis shift method can help diagnose LV capture. The LV preactivation, or simultaneous BV activation and LV lead positioned in nonposterior or noninferior wall can increase the diagnostic power of the modified Ammann algorithm and QRS axis shift method.
['Cao|Yuan-Yuan|YY|', 'Su|Yan-Gang|YG|', 'Bai|Jin|J|', 'Wang|Wei|W|', 'Wang|Jing-Feng|JF|', 'Qin|Sheng-Mei|SM|', 'Ge|Jun-Bo|JB|']
D000368:Aged D000465:Algorithms D058406:Cardiac Resynchronization Therapy D058409:Cardiac Resynchronization Therapy Devices D002681:China D004562:Electrocardiography D005260:Female D006333:Heart Failure D006801:Humans D008297:Male D008875:Middle Aged D011237:Predictive Value of Tests D012815:Signal Processing, Computer-Assisted D013997:Time Factors D016896:Treatment Outcome D016277:Ventricular Function, Left D016278:Ventricular Function, Right
cardiac resynchronization therapy LV lead LV pacing congestive heart failure pacing electrocardiogram