MI ‘mechanism’ identified in women without angiographically obstructive CAD
MedWire News: Study results show that plaque rupture and ulceration are the mechanisms behind myocardial infarction (MI) in some women with no angiographically obstructive coronary artery disease (CAD).
"A substantial proportion of patients with MI have no angiographically obstructive (≥50% diameter stenosis) CAD," explain the researchers; referring to approximately 7%-32% of women and 6%-12% of men.
"Several pathogenetic mechanisms of MI in the absence of obstructive CAD have been postulated, including, among others, atherosclerosis with plaque disruption that does not lead to luminal occlusion, endothelial dysfunction with the inability to augment coronary flow in response to stress, and vasospasm." However, "the data are extremely limited," they continue.
In addition, the researchers say that women are less likely to display obstructive coronary lesions when presenting with all forms of ischemic heart disease, and that there are significant gender differences in morphologic characteristics of the vasculature.
Harmony Reynolds (New York University School of Medicine, USA) and co-authors therefore investigated the mechanisms of MI in 50 women (mean age 56.9 years) presenting with acute MI. None of the women had angiographically obstructive CAD. Intravascular ultrasound (IVUS) was performed during their index admission and cardiac magnetic resonance imaging (CMR) was performed within 1 week of angiography.
As reported in Circulation, 16 (38%) of the 42 patients who underwent IVUS had plaque disruption; 12 had plaque rupture (29%), including two with multiple ruptures and one with plaque rupture and a distinct plaque ulceration, and four had plaque ulceration only (10%).
"The finding of plaque disruption in a patient with MI and nonobstructive CAD has implications for treatment," remark Reynolds et al. "Such patients would presumably benefit from treatment with antiplatelet agents and statins. However, patients without obstructive CAD are less likely to be prescribed medical therapies for secondary prevention of MI, including aspirin, clopidogrel, and statins."
The researchers conclude: "Intravascular ultrasound and CMR provide distinct, complementary information in patients with MI and no obstructive CAD and could be considered for use in series to permit categorization of potential mechanisms in these patients.
"Such classification will facilitate future research into the mechanisms and treatment of MI with nonobstructive CAD," they add.
Commenting on these findings, editorialists Domenico Rocca and Carl Pepine, from the University of Florida in Gainesville, USA, said: "It would not be appropriate to simply assume that such patients with so-called normal coronary angiograms have no coronary atherosclerosis, because such an assumption has the potential to result in a lost opportunity for appropriate prevention therapies."
They added: "The possibility of microvascular abnormalities should be considered among those women with late gadolinium enhancement on CMR… because coronary microvascular dysfunction has been linked with adverse outcomes among women with stable ischemic heart disease and nonobstructive CAD."
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By Nikki Withers