Abstract 11041: Relationship Between the Morphology of Far-Field Electrograms and Antitachycardia Pacing effectiveness Among Ventricular Tachycardias occurring in ICD Patients.
Among ICD patients, antitachycardia pacing (ATP) is very effective in terminating ventricular tachycardias (VT); however in 10–30% of VT, depending on their cycle length (CL), shocks (SH) are needed to terminate the arrhythmia. Unsuccessful ATP therapies have negative clinical implications, because delaying the definitive therapy prolongs the duration of the episode. In addition, SH are associated with an increase in mortality in patients with left ventricular dysfunction (LVD). In VT occurring in ICD patients, no information is available regarding the ability of the morphology of far-field electrograms (Ff-M) to predict the result of the subsequent ATP. We hypothesized that the Ff-M, as a pseudo-unipolar signal and as hence an indicator of the direction of propagation front, could be related to ATP effectiveness.
Methods: We prospectively studied 466 VT (CL: 335±32 ms) occurring consecutively in 44 ICD patients with Medtronic devices and LVD (LVEF: 31±11; pacing site: right ventricular apex). ICD programming was standardized, including ATP for slow and fast VT (CL: 250–320 ms). The configuration of Ff-M was ICD can vs. right ventricular coil. VTs were classified as Q-VT or non-Q-VT, depending on the presence or absence of a negative initial deflection in the Ff-M.
Results: The effectiveness of ATP was 83%. Q-VT (n=307, 66%) had a lower CL (326±31 vs. 334±41; p=0.01), were associated with a higher left ventricular ejection fraction (LVEF) (36±7 vs. 32±7; p<0.001), and with a lower frequency of ischemic etiology (46 vs. 75% p<0.001). The frequency of successful ATP was higher in Q-VT: 88 vs. 72% (p<0.001) because the first attempt was more effective: 83 vs. 65% (p<0.001). By logistic regression analysis -which included LVEF, CL, etiology, functional class, beta-blocker therapy, and indication- the Q-VT pattern was found to be an independent predictor of effective ATP: OR: 2.4 (95% CI: 1.3–4.3); p=0.005. As a result, non Q-VTs need SH to be terminated more frequently: 23 vs. 12% p=0.001.
Conclusions: Q-VTs are more suitable for termination by ATP, independently of CL. On the other hand, non-Q-VT -which are usually ischemic- are more frequently terminated by SH. In order to avoid SH, the substrate of non-Q-VTs may need a more intensive treatment.
- © 2010 by American Heart Association, Inc.