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Local injury current identified as marker of functional impairment in congestive HF following ICD shock
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The local injury current detected on a near-field bipolar right ventricular electrogram following induced ventricular fibrillation from an implantable cardioverter defibrillator shock may be an early marker for HF progression.
Researchers enrolled 310 patients with structural heart disease, NYHA Class I through III HF implanted with a single- or dual-chamber ICD. Near-field right ventricular electrograms taken during induced ventricular fibrillation and following a rescue defibrillator shock were analyzed, and the primary endpoint was a composite of either death or hospitalization due to congestive HF exacerbation. Patients were followed up for a mean of 29.3 months.
According to the study results, significant local injury currents following induced defibrillator shock were found in 34.2% of patients. The combined endpoint of death or hospitalization due to congestive HF exacerbation occurred in 12.9% of patients. Multivariate risk analysis suggested that patients with observed local injury currents following induced ventricular fibrillation from rescue defibrillator shock at ICD implantation had a greater risk for death or hospitalization from exacerbated congestive HF (HR=2.69; 95% CI, 1.41-5.14).
“The observed local injury current phenomenon predicts progression of congestive HF in ICD patients with appropriate ICD shocks and with otherwise stable NYHA functional Class I to III congestive HF,” the researchers concluded. “Early awareness of the high risk for congestive HF exacerbation and thoughtful medical management may improve congestive HF prognosis in ICD patients.”
In an accompanying editorial, Richard K. Shepard, MD, an assistant professor of medicine, and Kenneth A. Ellenbogen, MD, a professor of medicine, both of Virginia Commonwealth University’s Pauley Heart Center in Richmond, Va. incorporated the study results with those from other studies conducted to examine the effects of shocks from ICD therapy.
“This is an important and well-done study that is the first to demonstrate a clear and simple intracardiac marker for patients who do poorly after appropriate ICD shocks,” they wrote. “These patients may benefit from increased follow-up and aggressive medical therapy. Only future prospective studies can answer some of these questions and should be on the mind of clinicians who are trying to improve the prognosis of patients who receive ICD shocks.”
Tereshchenko LG. J Am Coll Cardiol. 2009;54:822-828.