To analyze the relation between prolonged QT interval and mortality in patients with ST-elevation myocardial infarction and complementarity with Killip, Thrombolysis in Myocardial Infarction (TIMI) and Acute Physiology and Chronic Health Evaluation-II (APACHE-II) scales.
A nested cohort case–control study was conducted in a Spanish hospital. The cohort consisted of patients with ST-elevation myocardial infarction admitted between 2008 and 2010 (n = 524). The cases were the patients who died (n = 38) and the controls (n = 81) were a random sample of those who survived (one of every six).
The corrected QT (QTc) interval of first ECG (prehospital-or-hospital admission) was prolonged in 18 of the 35 patients who died (51.4%) and in 12 of the controls (16.7%; P < 0.001). APACHE-II, TIMI and Killip scores were higher in the patients who had died (P < 0.001). Mortality with prolonged QTc (19.3%) was 20%, and 4.5% were with normal QTc (80.7%; P < 0.001).
Logistic regression showed a relation between mortality with prolonged QTc and TIMI [odds ratio (OR) 3.57(1.16–10.97)]. A second model was constructed with APACHE-II and prolonged QTc [OR 6.47(1.77–23.59)]; receiver operating characteristic (ROC) curve area [0.92(0.87–0.97)], and individually, for APACHE-II was 0.88 (0.81–0.95). A new score was constructed: QTc (not prolonged: 0 points, prolonged: 7 points), age (<65 years: 0 points, 65–74 years: 6 points, ≥75 years: 9 points), Killip (I: 0 points, II–III: 4 points, IV: 17 points). ROC area: 0.88.
Hospital mortality was higher with prolonged QTc at prehospital-or-hospital admission, given equal Killip, TIMI and APACHE values. Discrimination of Killip, TIMI and APACHE values can be improved with prolonged QTc. Discrimination of a model including Killip, age and prolonged QTc is quite good. We have made a new simple prognostic scale with these variables.
aIntensive Care Unit
bCoronary Care Unit, Hospital Carlos Haya, Malaga
cCIBERESP, Preventive Medicine and Public Health, University of Jaen
dIntensive Care Unit, Hospital Infanta Margarita, Cabra (Cordoba), Spain
Correspondence to Eduardo Aguilar-Alonso, MD, Intensive Care Unit, Hospital Infanta Margarita, Avenida Gongora s/n, 14940 Cabra, Cordoba, SpainTel: +34 957 021300; fax: +34 957 021 322; e-mail: firstname.lastname@example.org
Received 25 March, 2013
Revised 24 January, 2014
Accepted 24 January, 2014