Hospitalized cancer patients with acquired long QT syndrome-a matched case-control study

BACKGROUND: Our recent study has revealed that many hospitalized patients with acquired long QT syndrome (ALQTS) are cancer patients. This study aims to determine the risk factors and outcomes of hospitalized cancer patients with ALQTS. METHODS: We performed a matched case-control study within a cohort of 10,180 cancer patients hospitalized between September 2013 and April 2016. Among them, 150 patients defined as having severe ALQTS with a markedly prolonged QT interval (QTc ≥ 500 ms) were compared with 293 age-, sex- and cancer-type-matched controls (non-ALQTS). Death as the endpoint was followed for up to 2 years. Cox regression and Kaplan-Meier survival analyses were performed to assess the effects of particular clinical variables on all-cause mortality. Multivariate logistic regression was performed to calculate odds ratios (OR) for various predictors of QT prolongation. RESULTS: The mortality was significantly higher in ALQTS group (63.3% vs. 33.4%). Hypertension, hypokalemia, hypocalcemia, QT-prolonging drugs, infection, anemia, anti-microtubule agents were contributing factors to ALQTS. Renal insufficiency, male gender and hypokalemia were found to be independent risk factors for all-cause mortality in ALQTS group. CONCLUSION: Markedly prolonged QT interval was seen in 1.5% of hospitalized cancer patients. The all-cause mortality was high in cancer patients with severe ALQTS.