One in eight young women with acute Myocardial Infarction (MI) have a type of MI that falls in the “unclassified” category under a current classification system, researchers report; they propose a new taxonomy that better captures different presentations in young women.
The researchers used data from young men and women with acute MI who were enrolled in the Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients (VIRGO) study to develop a taxonomy that is especially good at classifying MI in young women. The study was published online September 8, 2015 in Circulation.
“This could serve as a framework for understanding biological disease mechanisms, therapeutic efficacy, and prognosis in this population,” Dr Erica S Spatz (Yale University School of Medicine, New Haven, CT) said.
“As clinicians involved in the management of adults with AMI, I think most of us are familiar with the young woman who presents with AMI but has none of its classic features,” Spatz said. “This is frustrating for the clinician and the patient, as the diagnosis remains uncertain, and we lack a common language for communicating meaningful aspects of the clinical presentation, which may influence treatment and prognosis.”
The third universal definition of MI issued in 2012 “has been incredibly helpful in distinguishing type I from type 2 acute MI,” she added. “However, for young women and others who do not fit into the universal definition, the VIRGO taxonomy affords a more comprehensive approach to classifying AMI.”
“We believe it is a breakthrough to think that AMI in younger women is, for many people, a different disease,” senior author Dr Harlan M Krumholz (Yale University School of Medicine) added. Important facets of heart disease in young women may be missed by studying heart attacks in this population as some uniform condition or using a taxonomy that was not developed with this group in mind. “We need more specific labels, more personalized and precise phenotyping of what is happening to these women if we are to be better at prevention and treatment,” according to Krumholz.
A More Nuanced Classification of MI
The current classification schemes for acute MI may not take into account the different types of clinical phenotypes in young women, Spatz and colleagues write.
They aimed to develop a more nuanced classification of acute MI, by drawing data from VIRGO, a prospective cohort that enrolled 2009 women and 976 men, aged 18 to 55, with acute MI.
They first reviewed the medical charts of 600 randomly selected patients in a subset of VIRGO, preserving the 2:1 ratio of women to men. Based on the third universal definition of MI, they classified 514 patients as type 1 (plaque rupture, ulceration, fissuring, erosion, dissection with resulting thrombus), 40 patients as type 2 (condition other than CAD contributes to imbalance between myocardial oxygen supply or demand), and two patients as type 4b (stent thrombosis).
Patients with other types of acute MI—type 3 (cardiac death with symptoms suggesting ischemia), type 4a (related to PCI), and type 5 (related to CABG) were excluded from VIRGO. This left 54 patients (9%, including 51 women) who were unclassified, who had no evidence of acute plaque disruption with thrombus or of myocardial oxygen supply-demand mismatch.
The researchers then used a constant comparative method to develop a new taxonomy. With the new VIRGO taxonomy, the MI types in 2802 patients (67% women) in the VIRGO population were classified as:
Class 1 (plaque-mediated culprit lesion): 2425 patients (82.5% of women, 94.9% of men).
- Class 2a (obstructive CAD with myocardial oxygen supply-demand mismatch): 35 patients (1.4% of women, 0.9% of men).
- Class 2b (obstructive CAD without myocardial oxygen supply-demand mismatch): 55 patients (2.4% of women, 1.1% of men).
- Class 3a (nonobstructive CAD with myocardial oxygen supply-demand mismatch): 88 patients (4.3% of women, 0.8% of men).
- Class 3b (nonobstructive CAD without myocardial oxygen supply/demand mismatch): 150 patients (7.0% of women, 1.9% of men).
- Class 4 (other identifiable mechanism: spontaneous dissection, vasospasm, embolism): 31 patients (1.5% of women, 0.2% of men).
Class 5 (undetermined classification): 18 patients (0.8% of women, 0.2% of men).
Young women with AMI who do not fit the traditional classification system for AMI remain an enigma and may warrant additional studies looking for microvascular disease (eg, coronary flow reserve with positron emission tomography) or signs of vasomotor instability or thrombophilia, according to Spatz. “I also think it is important for women to know that the efficacy of standard therapies for AMI, including antiplatelet therapy, statins, and beta-blockers, is uncertain,” she said.
The VIRGO taxonomy gives clinicians a tool for communicating with the patient and others on the care team, Spatz noted. “In medicine, we learn from each patient—but without a filing system, we may not see the commonalities that exist even among ‘nontraditional’ presentations, shorting us of new insights.
Spatz ES, Curry LA, Masoudi FA, et al. The VIRGO classification system: A taxonomy for young women with acute myocardial infarction.Circulation 2015; DOI: 10.1161/CIRCULATIONAHA.115.016502. Abstract
Thygesen K, Alpert JS, Jaffe AS, et al. Third universal definition of myocardial infarction. J Am Coll Cardiol 2012; 60:1581-1598. Article