Abstract 18437: Transient Deterioration of Left Ventricular Diastolic Function Caused by Defibrillation Threshold Testing During Implantable-Cardioverter Defibrillator Implantation: Its Impact on Ca2+ Transient and Clinical Evidence
Background: Defibrillation threshold (DFT) testing during implantable-cardioverter defibrillator (ICD) implantation sometimes causes serious complications. However, there has been limited data on the impact of DFT testing on cardiac function and its underlying mechanism. Recently, global strain rate during the isovolumetric relaxation period (SRIVR) by 2-dimensional speckle tracking has been shown to correlate well with left ventricular (LV) relaxation, which is known to be impaired by intracellular Ca2+ overload. In this study, we examined the impact of DFT testing on myocardial injury and LV function in patients, and we also investigated the impact of high energy stimulation on Ca2+ transients of myocytes in vitro.
Methods: In a clinical study, we studied 25 patients with preserved LV ejection fraction (EF) who underwent ICD implantation and DFT testing. We measured serum creatine kinase (CK), CK-MB, cardiac troponin T and I, myoglobin, and BNP. We also measured LVEF and global SRIVR with EchoPAC PC (GE). All measurements were performed before, immediately after, and 5 min and 4 h after two consecutive 20 joule DFT testing. In an in vitro study, isolated rat ventricular myocytes were exposed to field stimulation for inducing Ca2+ transients. Intracellular Ca2+ concentration ([Ca2+]i) and time constant of Ca2+ decay were assessed by fura-2 ratio before and after high energy stimulation.
Results: In the clinical study, there were no significant changes in any of the biomarkers and LVEF at any measured time point. Global SRIVR was decreased immediately after and at 5 min after DFT testing and had recovered to the baseline level at 4 h (0.38 ± 0.14 vs. 0.23 ± 0.13* vs. 0.23 ± 0.13* vs. 0.39 ± 0.13 s−1, *p < 0.05 vs. baseline). In the in vitro study, high energy stimulation increased [Ca2+]i during the diastolic period (1.017 ± 0.008 vs. 1.055 vs. 0.018, p<0.05) and attenuated Ca2+ transient decay.
Conclusions: DFT testing during ICD implantation impaired LV relaxation, although neither myocardium necrosis nor systolic dysfunction was provoked. Ca2+ overload induced by excessive electrical stimulation may contribute to impairment of LV relaxation.
- Implantable cardioconvert defibrillator
- Ventricular defibrillation
- Diastolic function
- © 2010 by American Heart Association, Inc.