New Strategy Distinguishes Inferior STEMI from Pericarditis



DENVER – The presence of any ST depression in the ECG lead aVL in a patient with significant ST segment elevation in inferior leads is highly sensitive and specific for inferior ST-elevation MI as opposed to pericarditis or early repolarization, Dr. Johanna E. Bischof reported at the annual meeting of the American College of Emergency Physicians.

In her retrospective study of three different patient populations with ST elevation in leads II, III, and/or aVF, the finding of at least 0.25 mm of ST depression in lead aVL had 99% sensitivity and 100% specificity for inferior STEMI.

Dr. Johanna E. Bischof

"It’s more sensitive than traditional ST elevation intervention criteria, and more sensitive and specific than comparing the difference in ST elevation between leads III and II," said Dr. Bischof of Hennepin County Medical Center, Minneapolis.

Numerous non–life-threatening cardiac conditions can provoke ST elevation in the inferior leads in the presence of normal conduction with no left bundle branch block, Wolff-Parkinson-White syndrome, paced rhythm, or left ventricular hypertrophy. She and her coworkers evaluated the significance of any ST depression in aVL in two of these conditions that are often confused with inferior STEMI based upon the ECG: pericarditis and early repolarization.

Her retrospective study included 156 Hennepin County Medical Center patients with confirmed inferior STEMI, 39 patients with pericarditis and 1 mm or more of ST elevation in two or more inferior leads, and 66 Finns with early repolarization and ST elevation in inferior leads. The subjects with early repolarization came from the Finnish Health 2000 Survey, in which ECGs were recorded for nearly 11,000 asymptomatic adults.

Of the 156 patients with confirmed inferior STEMI, 155 had ST depression in aVL. Not one of the patients with ST elevation in inferior leads and pericarditis or early repolarization did.

Only 86% of patients with a true inferior STEMI met traditional intervention criteria for STEMI. That means 14% of them might not have gotten to the cardiac catheterization promptly. Using the novel ECG criterion of ST depression in aVL, everyone with an inferior STEMI would have been sent to the cath lab straight away.

Moreover, based upon the finding of ST elevation in inferior leads, 49% of patients in the pericarditis group would have been sent to the cath lab for what would have turned out to be a negative angiogram. With application of the new finding regarding the clinical significance of any ST depression in aVL, none of the patients with pericarditis would have gone to the cath lab, Dr. Bischof continued.

When the degree of ST elevation in lead III exceeds that in lead II, it has traditionally been thought to be more suggestive of inferior STEMI, whereas ST elevation in lead II that’s greater than in lead III is more often thought of as pericarditis. But in Dr. Bischof’s study, only 87% of patients with confirmed inferior STEMI had greater ST elevation in lead III than II. In the pericarditis group, 98% of patients had more ST elevation in II than III. And in subjects with early repolarization, it was roughly 50/50 as to which lead had greater ST elevation.

Senior emergency medicine physicians in the audience called Dr. Bischof’s study "fabulous," adding that they’d like to see the study expanded to include larger numbers of pericarditis patients just to be sure of those excellent sensitivity and specificity figures.

"Truly, if we could take this finding out and utilize it in the ED it would make things very easy for us," one physician commented.

Dr. Bischof reported having no financial conflicts.

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