The prevalence of long QT interval in post-operative intensive care unit patients.

Abstract

The severity of patient illnesses and medication complexity in post-operative critically ill patients increase the risk for a prolonged QT interval. We determined the prevalence of prolonged QTc in surgical intensive care unit (SICU) patients. We performed a prospective cross-sectional study over a 15-month period at a major academic center. SICU pre-admission and admission EKGs, patient demographics, and laboratory values were analyzed. QTc was evaluated as both a continuous and dichotomous outcome (prolonged QTc>440ms). 281 patients were included in the study: 92% (n=257) post-operative and 8% (n=24) non-operative. On pre-admission EKGs, 32% of the post-operative group and 42% of the non-operative group had prolonged QTc (p=0.25); on post-admission EKGs, 67% of the post-operative group but only 33% of the non-operative group had prolonged QTc (p<0.01). The average change in QTc in the post-operative group was +30.7ms, as compared to +2ms in the non-operative group (p<0.01). On multivariable adjustment for long QTc as a dichotomous outcome, pre-admission prolonged QTc (OR 3.93, CI 1.93-8.00) and having had an operative procedure (OR 4.04, CI 1.67-9.83) were associated with developing prolonged QTc. For QTc as a continuous outcome, intra-operative beta-blocker use was associated with a statistically-significant decrease in QTc duration. None of the patients developed a lethal arrhythmia in the ICU. Prolonged QTc is common among post-operative SICU patients (67%), however lethal arrhythmias are uncommon. The operative experience increases the risk for long QTc.