Supported in part by the NIH/NHLBI Grants P01 HL78931, R01 HL78932, R01 HL71140 and a Pauline and Harold Price Endowment.
Using the Upper Limit of Vulnerability to Assess Defibrillation Efficacy at Implantation of ICDs
Article first published online: 28 FEB 2007
Pacing and Clinical Electrophysiology
Volume 30, Issue 2, pages 258–270, February 2007
How to Cite
SWERDLOW, C. D., SHEHATA, M. and CHEN, P.-S. (2007), Using the Upper Limit of Vulnerability to Assess Defibrillation Efficacy at Implantation of ICDs. Pacing and Clinical Electrophysiology, 30: 258–270. doi: 10.1111/j.1540-8159.2007.00659.x
- Issue published online: 28 FEB 2007
- Article first published online: 28 FEB 2007
- Received July 20, 2006; revised August 25, 2006; accepted August 28, 2006.
- upper limit of vulnerability;
- T-wave shock;
- defibrillation threshold;
- implantable cardioverter defibrillator;
- defibrillation testing
The upper limit of vulnerability (ULV) is the weakest shock strength at or above which ventricular fibrillation (VF) is not induced when the shock is delivered during the vulnerable period. The ULV, a measurement made in regular rhythm, provides an estimate of the minimum shock strength required for reliable defibrillation that is as accurate or more accurate than the defibrillation threshold (DFT). The ULV hypothesis of defibrillation postulates a mechanistic relationship between the ULV—measured during regular rhythm—and the minimum shock strength that defibrillates reliably. Vulnerability testing can be applied at implantable cardioverter defibrillator (ICD) implant to confirm a clinically adequate defibrillation safety margin without inducing VF in 75%–95% of ICD recipients. Alternatively, the ULV provides an accurate patient-specific safety margin with a single fibrillation–defibrillation episode. Programming first ICD shocks based on patient-specific measurements of ULV rather than programming routinely to maximum output shortens charge time and may reduce the probability of syncope as ICDs age and charge times increase. Because the ULV is more reproducible than the DFT, it provides greater statistical power for clinical research with fewer episodes of VF. Limited evidence suggests that vulnerability testing is safer than conventional defibrillation testing.