DALLAS – The initial ECG is invaluable in predicting which emergency department patients with acute drug overdose will have a major cardiovascular event during hospitalization, a prospective study indicates.
"Based on our data, ECG evidence of ischemia or infarction really mandates sending for a troponin level in ED patients with overdose," Dr. Alex F. Manini said at the annual meeting of the Society for Academic Emergency Medicine.
Dr. Alex F. Manini
The findings are important as "we’re currently undergoing the worst epidemic of drug overdoses in our nation’s history," observed Dr. Manini of the department of emergency medicine at Mount Sinai School of Medicine in New York. Poisoning is now the No. 1 cause of injury-related fatalities in the United States, and many patient series indicate 10%-15% of ED patients with an acute drug overdose experience a major cardiac event during their hospitalization.
Dr. Manini and his colleagues performed a study that validated the prognostic value of four high-risk features of the ED admission ECG in an acute drug overdose cohort: ectopy, a QTc interval of 500 msec or longer, non–sinus rhythm, and any evidence of ischemia or infarction.
Emergency physicians can readily identify those features without need for input from a cardiologist, he said.
In their study performed at two university EDs, 16% of 589 adults with acute drug overdoses experienced an acute MI, cardiogenic shock, dysrhythmia, or cardiac arrest during their hospitalization. The most common drug exposures were benzodiazepines, opioids, and acetaminophen.
Ectopy was associated with an 8.9-fold increased odds ratio for a major cardiovascular event. A QTc of 500 msec or longer was associated with an odds ratio of 11.2; a non–sinus rhythm, 8.9; and ischemia, 5.0.
The presence of one or more of these four ECG predictors was associated with 68% sensitivity and 69% specificity for a subsequent in-hospital cardiac event, with a negative predictive value of 91.9%. Dr. Manini called those sensitivity and specificity figures "modest." Thus, the ECG findings alone are not sufficient to exclude the likelihood of a cardiac event, although they certainly are useful in risk stratification. Future studies will seek to boost the predictive power by combining the ECG findings with other clinical tools, he said.
A QT dispersion of 50 msec or more also proved useful for prognosis, with an associated 2.2-fold increased risk of an in-hospital cardiac event. However, measuring QT dispersion is a fairly cumbersome process, and for this reason it needs further study before being introduced into clinical practice in busy EDs, Dr. Manini added.
In this study, any ECG evidence of ischemia or infarction – including ST depression or elevation, T wave inversion, or Q waves – had specificities of 91%-98% for an elevated troponin assay. In addition, ST depression was associated with a 6.4-fold increased odds ratio for in-hospital cardiac arrest.
The study was funded by the National Institute on Drug Abuse. Dr. Manini reported having no financial conflicts.