Coronary Plaque Burden, as Determined by Cardiac Computed Tomography, in Patients with Myocardial Infarction and Angiographically Normal Coronary Arteries Compared to Healthy Volunteers: A Prospective Multicenter Observational Study

<div><p>Objectives</p><p>Patients presenting with acute myocardial infarction and angiographically normal coronary arteries (MINCA) represent a diagnostic and a therapeutic challenge. Cardiac computed tomography (CT) allows detection of coronary artery disease (CAD) even in the absence of significant stenosis. We aimed to investigate whether patients suffering from MINCA had a greater coronary plaque burden, as determined by cardiac CT, than a matched group of healthy volunteers.</p><p>Methods</p><p>Consecutive patients, aged 45 to 70, with MINCA were enrolled in the Stockholm metropolitan area. Patients with myocarditis were excluded using cardiovascular magnetic resonance imaging. Remaining patients underwent cardiac CT, as did a reference group of healthy volunteers matched by age and gender, with no known cardiovascular disease. Plaque burden was evaluated semi-quantitatively on a per patient and a per segment level.</p><p>Results</p><p>Despite a higher prevalence of smoking and hypertension, patients with MINCA did not have more CAD than healthy volunteers. Among 57 MINCA patients and 58 volunteers no signs of CAD were found in 24 (42%) and 25 (43%) respectively. On a <i>per segment</i> level, MINCA patients had less segments with stenosis ≥20% (2% vs. 5%, p<0.01), as well as a smaller proportion of large (2% vs. 4%, p<0.05) and mixed type plaques (1% vs. 4%, p<0.01). The median coronary calcium score did not differ between MINCA patients and healthy volunteers (6 vs. 8, <i>ns</i>).</p><p>Conclusions</p><p>MINCA patients with no or minimal angiographic stenosis do not have more coronary atherosclerosis than healthy volunteers, and a large proportion of these patients do not have any signs of CAD, as determined by cardiac CT. The MINCA patient group is probably heterogeneous, with a variety of different underlying mechanisms. Non-obstructive CAD is most likely not the most prevalent cause of myocardial infarction in this patient group.</p></div

Different plaque types, as seen by cardiac computed tomography.

<p>A non-calcified plaque is shown in longitudinal and cross section (A and B). The degree of stenosis was 20–50%. A large mixed plaque is shown in longitudinal section (C) and in cross section at the level of non calcified (D) and calcified (E) components. A large calcified plaque is shown to the right. (F and G). The mixed and calcified plaques (C to G) were both eccentric in location and the degree of stenosis was <20%.</p

Cardiac CT plaque burden per segment.

<p>Abbreviations: Cardiac CT, cardiac computed tomography; MINCA, myocardial infarction with angiographically normal coronary arteries; CAD, coronary artery disease; Values are presented as absolute value (percentage).</p><p>*P-values apply to the comparison of the four categories in the two columns to the left of the value, using the chi-square test.</p

Baseline characteristics.

<p>Abbreviations: MINCA, myocardial infarction with angiographically normal coronary arteries; CAD, coronary artery disease; BMI, body mass index; SD, standard deviation. Data are presented as mean ± SD or absolute value (percentage).</p><p>*P<0.05,</p>†<p>P<0.01, using Fisher’s exact test.</p

Cardiac CT plaque burden per patient.

<p>Abbreviations: Cardiac CT, cardiac computed tomography; MINCA, myocardial infarction with angiographically normal coronary arteries; CAD, coronary artery disease; <i>ns</i>, non significant. Values are presented as absolute value (percentage) or median (range).</p><p>*refers to the maximum diameter stenosis;</p>†<p>refers to obstructive and non-obstructive CAD.</p

The right coronary artery in a patient presenting with acute myocardial infarction.

<p>Cardiac computed tomography (A) shows a large atherosclerotic plaque and more distally a small plaque, both with <20% stenosis. Coronary angiography (B) shows only minimal signs of atherosclerosis.</p