A new prospective observational study of 38 patients suffering from myocardial infarction with non-obstructive coronary artery disease (MINOCA) with the use of optical coherence tomography (OCT) and complementary cardiac magnetic resonance imaging (CMR) shows plaque disruption and thrombus account for one-fourth and one-fifth of MINOCA, respectively. Both plaque disruption and thrombosis were repeatedly found in coronary vessels supplying the infarct-related territory as confirmed by CMR. This is the first prospective study that successfully employed the use of OCT along with complementary CMR for studying the basic mechanisms leading to MINOCA suggesting that OCT may aid in deciphering the basic underpinnings of this not so rare type of myocardial infarction (MI).
MINOCA is increasingly being seen in clinical practice. Prior studies have served as a major effort to understand the pathophysiology of this presentation, which may aid in effective secondary prevention in this patient population. Several questions exist due to the heterogeneous nature of patients who suffer from MINOCA. Given this background, Opolski (Department of Interventional Cardiology and Angiology, Institute of Cardiology, Warsaw, Poland) and colleagues prospectively enrolled 38 patients (mean age 62 years; 55% women) with MI but <50 % stenosis on angiography (maximal diameter stenosis of 35%) in order to identify the mechanisms that lead to MINOCA. On OCT, nine patients (24%) showed signs of plaque disruption and seven (18%) had evidence of coronary thrombus. A per-lesion analysis of CMR results further demonstrated that, compared with non-infarct-related arteries, infarct-related arteries displayed more plaque disruption (40% vs 6%; P = 0.02), thrombus (50% vs 4%; P = 0.014), and thin-cap fibroatheroma (70% vs 30%; P = 0.03). Moreover, the investigators found that subjects with plaque disruption albeit non-significant tended to have numerically higher rates of ischemic late gadolinium contrast enhancement (LGE) on CMR than subjects without plaque disruption (50% vs. 13%, respectively; p = 0.053).
Utilization of OCT
Optical coherence tomography (OCT) is a high-resolution (10 to 15 mm) intracoronary imaging modality that employs the use of coherent light waves for precise assessment of the integrity of the atheromatous fibrous cap. This allows for visualizing plaques and thrombosis that may be otherwise missed on conventional angiography. In this study, the investigators aimed to perform OCT imaging in at least the coronary vessel that was suspected to be the culprit vessel (based on electrocardiography [EKG], echocardiography, and angiography).
Evaluation of Myocardial Injury on CMR
In this study, myocardial edema was evaluated as an area of high T2 signal intensity on a segmental basis (Left ventricle segments were defined by American Heart Association 17-segment model). The presence and pattern of late gadolinium enhancement (LGE) were determined for each segment and divided into subendocardial, subepicardial, midwall, or transmural. LGE in the subendocardial and transmural distributions were considered ischemic. Correlation between the coronary artery distribution and myocardial segments with LGE of ischemic origin served as a source of identification of infarct-related artery.
Limitations
The study has its limitations since it was a small, single-center, and observational study. In addition, loss of eligible patients due to logistical problems and withdrawals of informed consent gives rise to selection bias. Furthermore, the investigators failed to perform 3-vessel OCT imaging in all patients, which could have resulted in a lower proportion of patients with plaque disruption and/or thrombus (specifically owing to a lower rate of OCT in the right coronary artery).
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