Mechanisms of Myocardial Infarction in Women Without Angiographically Obstructive Coronary Artery Disease

Study Questions:

Do women with nonobstructive coronary artery disease by angiography have specific mechanisms for their myocardial infarction (MI)?

Methods:

Women were eligible for the study if they were 18 years or older, had presented with an MI, and had no coronary lesions ≥50% in diameter. Patients underwent intravascular ultrasound (IVUS) at the time of angiography. Women suspected to have takotsubo cardiomyopathy, or who used vasospastic agents were excluded. Cardiac magnetic resonance (CMR) imaging was performed within 1 week of the angiographic study.

Results:

A total of 121 women who met the clinical inclusion criteria between June 2007 and August 2010 were included in this analysis: 71 were ineligible because of ≥50% stenosis (n = 69), coronary dissection (n = 1), or excessive tortuosity (n = 1). Fifty women were fully eligible with <50% angiographic stenosis of all major vessels, of which eight patients did not undergo IVUS for logistical reasons. Forty-four patients underwent CMR, including 36 of the 42 patients who underwent IVUS; the remaining six patients declined CMR after initial consent. Mean age of the study population was 57 years; 46/50 (92%) presented with chest pain. Six (12%) had a history of prior MI. Median peak troponin was 1.60 ng/ml (interquartile range, 0.44–4.31); 88% of patients had peak troponin >5 times the upper limit of normal (0.04 ng/ml). Thirty-four patients (68%) had an abnormal electrocardiogram, including ST-segment elevation in 11 patients (22%), ST-segment depression in 7 (14%), left bundle branch block in 1 (2%), and T-wave inversion (≥2 contiguous leads) in 22 (44%). Median diameter stenosis of the worst lesion was 20% by angiography; 15 patients (30%) had normal angiograms. Plaque disruption was observed in 16/42 patients (38%) undergoing IVUS. There were abnormal myocardial CMR findings in 26/44 patients (59%) including late gadolinium enhancement (LGE) in 17 patients, and T2 signal hyperintensity indicating edema in nine additional patients. The most common LGE pattern was ischemic (transmural/subendocardial). Nonischemic LGE patterns (midmyocardial/subepicardial) were also observed. Although LGE was infrequent with plaque disruption, T2 signal hyperintensity was common with plaque disruption.

Conclusions:

The investigators concluded that plaque rupture and ulceration are common among women with nonobstructive CAD who have experienced an MI. IVUS and CMR imaging may provide further insights into mechanisms of injury among such women.

Perspective:

These findings provide an insight into an aspect of women’s cardiovascular disease that is not well studied. Women comprise the majority of patients who have cardiac events with nonobstructive coronary artery disease. Studies such as this one, will assist in better understanding how to manage such patients, and will likely inform on mechanisms of acute coronary events among women with obstructive coronary artery disease as well.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Atherosclerotic Disease (CAD/PAD), EP Basic Science

Keywords: Depression, Myocardial Infarction, Coronary Artery Disease, Plaque, Atherosclerotic, Takotsubo Cardiomyopathy, Coronary Disease, Edema, Chest Pain, Bundle-Branch Block, Cardiovascular Diseases, Pregnancy, Troponin


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