Abstract 339: Impact of Left Ventricular Dilatation on Characteristics of Ventricular Fibrillation and ICD Shock Success
Introduction ICD testing offers a unique setting to study VF characteristics under controlled conditions in humans. Recently, it was observed that myocardial substrate (infarction) affects VF characteristics and shock success in animals. To further study the effect of myocardial pathology on VF, we investigated the association between left ventricular (LV) dilatation and characteristics of induced VF and we determined the impact of dilatation on the success of the first ICD shock.
Methods Patients who underwent Medtronic ICD implantation with defibrillation testing between 2005-2011 were included. VF frequency characteristics were analyzed using intracardiac recordings of 4 seconds of induced VF before shock delivery (15 joule) and were compared between patients with normal-mildly and moderate-severely dilated LVs. Multivariate linear regression was performed to associate LV dilatation with the respective VF characteristics.
Results Patients with moderate-severely dilated LVs tended to have a lower first shock success during testing. In addition, the fundamental frequency of VF was lower and the organization index was higher (Table).
The fundamental frequency was independently associated with LV dilatation (β -0.28; p=0.007), amiodarone use (β -0.48; p<0.001) and history of myocardial infarction (MI) (β -0.20; p=0.048).
The organization index was independently associated with LV dilatation (β 0.04; p=0.030) and history of MI (β -0.05; p=0.003).
The median frequency was not associated with any of the tested variables.
Conclusions Characteristics of induced VF depend on LV dilatation: VF is slower and more regular in dilated LVs. Interestingly, ischemic etiology of cardiac disease and amiodarone also affect VF characteristics. ICD shock success was slightly lower in patients with dilated LVs. To improve future resuscitation strategies, further research is needed to evaluate the interaction between clinical characteristics, VF and shock success.
- Ventricular fibrillation
- Spectrum analysis
- Implantable cardioconvert defibrillator
- Ventricular defibrillation
- Heart disease
- © 2012 by American Heart Association, Inc.