Can we predict which patients with implantable cardioverter defibrillators receive appropriate shock therapy? A study...

Appropriate shock therapy (AST) occurs in the minority of patients with implantable cardioverter defibrillators (ICDs). We assessed which patients received AST and whether there were any predictive factors.

We retrospectively analysed data from 155 patients implanted with ICDs at our institution from a period from February 1984 to February 2001. Stored electrogram data were analysed. We sub-divided patients on the basis of underlying cardiac disease. Various clinical echocardiographic and electrophysiological variables were studied.

AST occurred in 53 (34%) of patients (Group 1) and no AST in 102 (64%) of patients (Group 2). Impaired LV function was significantly associated with AST. Group 1 patients had a lower ejection fraction (EF) compared to Group 2 (37.5+/-13% vs. 47.8+/-14%, P<0.0001). Seventy-two percent of patients with AST had an EF <40% vs. 35% of patients in Group 2 (P<0.0001). NYHA Class was also associated with AST, 42% of Group 1 were in NYHA Class III/IV vs. 12% in Group 2 (P<0.001). Programmed electrical stimulation (PES) was a predictor of AST. PES was positive in a greater proportion of patients in Group 1 vs. 2 (88% vs. 64%, P<0.0006). Sub-group analysis showed that patients with dilated cardiomyopathy (DCM) had a high incidence of AST (80%). In these patients PES was a poor predictor of AST being positive in only 25%.

AST occurs in the minority of our patients. Certain pre-procedural variables predict AST. PES does not appear useful in predicting shock therapy in DCM patients and a negative PES should not preclude ICD implantation in this group.