Patients with serious mental illness (SMI) have an increased risk of sudden death. Higher rates of signal-averaged electrocardiogram (SAECG) abnormal late potentials (LP), which may be a predictor of sudden death risk, have been shown in patients with schizophrenia. We aimed to assess the prevalence and predictors of electrocardiograph (ECG) and SAECG abnormalities in a mixed SMI population.

Consecutive consenting inpatients with SMI had 12-lead ECG and SAECG recorded in addition to demographics, diagnoses and medications. Standard criteria for abnormal SAECG were applied. Multivariate regression analysis was performed to determine predictors of SAECG abnormalities including diagnoses, body mass index, ECG parameters, psychotropic medication use, and medications associated with Long QT or Brugada syndromes.

Eighty (80) patients, 49% male, mean age 39±17 years were included. SAECG criteria abnormality for 1, 2 or 3 criteria were seen in 19, 3 and 5 cases (34% in total) respectively. Early repolarisation pattern was seen in 19% of patients. SAECG abnormality was associated with male gender (OR 7.3; 95% CI 2.3–23.4), and schizophrenia/schizoaffective disorder diagnosis (OR 7.4; 95% CI 1.9–29.0), but not with medication type or dose.

In the mixed SMI population studied, there was a high rate of SAECG-detected late potentials (34%) and early repolarisation pattern (19%). Schizophrenia/schizoaffective disorder diagnosis was the strongest multivariate predictor identified. Further studies are needed to define the mechanism and significance of these cardiac abnormalities in SMI patients.