Relationship between the QTc interval at hospital admission and the severity of the underlying ischaemia in low and intermediate risk people studied for acute chest pain.
BACKGROUND
The corrected QT interval (QTc) is prolonged in the setting of acute coronary artery disease. However, very little data are available concerning the relationship between the QTc obtained soon after an episode of acute chest pain (ACHP) and the magnitude and severity of the myocardial ischaemia objectified in subsequent stress tests (STS).


METHODS
This was a prospective and observational study in which we investigated the relationship between the QTc determined on the hospital admission electrocardiogram (AQTc) using Bazett's formula and the results of the STS performed subsequently in 206 patients consecutively admitted to the Emergency Department for ACHP without persistent ST-elevation.


RESULTS
The mean AQTc was 456+/-60 ms. There were 88 (42%) individuals with a moderately or severely abnormal STS. The AQTc was longer in the patients with a moderately or severely abnormal STS: 490+/-52 versus 430+/-56 (p<0.001) and was correlated with the probability of the patient having a moderately or severely abnormal STS (c=0.84; p<0.001). The best cut-off point was 450 ms (sensitivity, specificity and negative predictive value: 81, 77 and 84 %). Patients with AQTc>or=450 had a higher frequency of moderately or severely abnormal STS (73 versus 16%; OR: 2.9; 95% CI: 2.1-4.1; p<0.001). After adjusting for age, sex, cardiac risk factors, cardiac history, QRS duration, ST-depression, troponin I release and pre-STS medical treatment, AQTc>or=450 remained as an independent predictor (OR: 12; 95% CI: 6-24; p<0.001).


CONCLUSIONS
In patients studied for ACHP, the QTc on the hospital admission electrocardiogram correlates with the underlying myocardial ischaemia. AQTc>or=450 ms selects a group of people at risk of presenting a moderately or severely abnormal STS, regardless of ST abnormalities and troponin release.
Jiménez-Candil
Javier
J
Department of Cardiology, University Hospital, Paseo de San Vicente, 58-182, 37007 Salamanca, Spain. jimenezcandil@secardiologia.es
Diego
Maximiliano
M
Cruz González
Ignacio
I
González Matas
José M
JM
Martín
Francisco
F
Pabón
Pedro
P
Ramírez
Víctor
V
León
Víctor
V
Martín-Luengo
Cándido
C
D000208:Acute Disease; D000368:Aged; D002637:Chest Pain / Q000175:diagnosis* / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000503:physiopathology; D010343:Patient Admission / Q000592:standards; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index