SCAD was common and frequently misdiagnosed, especially in women, which can be problematic for treatment decisions.
In patients who are 65 or younger when they have a first MI, the root cause is often nonatherosclerotic, a large analysis from the Rochester Epidemiology Project shows.
For women, in particular, more than half of MIs were attributable to things such as spontaneous coronary artery dissection (SCAD), embolism, and myocardial infarction with nonobstructed coronary arteries not meeting another category (MINOCA-U), according to findings published this week in JACC.
Senior author Rajiv Gulati, MD, PhD (Mayo Clinic, Rochester, MN), said while atherothrombosis remains the most common cause of MI in both sexes, the findings challenge common assumptions about how MI occurs in younger patients. Women had a much lower population incidence of MI compared with men—48 versus 137 per 100,000 person-years—but SCAD was more commonly a cause of their MI and also was frequently missed on initial presentation, causing problems for treatment planning.
“SCAD has a much higher risk of coronary complications when treated with PCI because the underlying mechanism is bleeding within the vessel wall media, and this intramural hematoma is predisposed to extend or disrupt when instrumented,” Gulati said. “There is also a theoretical risk that antithrombotics or antiplatelets can worsen intramural bleeding, but this remains to be proven.”
In an accompanying editorial, Harmony R. Reynolds, MD (NYU Grossman School of Medicine, New York, NY), says the analysis is “a major advance in our understanding of MI epidemiology in the young.”
She adds that conservative management is preferred in most cases of SCAD based on frequent early healing, making it important to implement initiatives aimed at improving the accuracy of SCAD diagnosis among cardiologists.
The analysis also provides some thought-provoking long-term prognoses.
“The noncardiovascular mortality among patients with Takotsubo syndrome was sobering, 26% at 5 years in a group with a median age of just 54 years,” Reynolds notes, adding that more research is needed to improve understanding of risk in this patient group.
To TCTMD, Gulati said most of the missed SCAD diagnoses in the study happened prior to 2012, the year that he and his colleagues published one of the largest series of confirmed SCAD. Since then, registries, a scientific statement from the American Heart Association, a review article, and other research efforts have helped raise awareness about SCAD, he added.
OCTOPUS Data
For the new analysis, Gulati and colleagues, led by Claire E. Raphael, MBBS, PhD (Mayo Clinic), analyzed data from 2,790 patients (36% women) who were 18 to 65 years old when they had a cardiac event associated with a cardiac troponin T (cTnT) concentration above the 99th percentile upper reference limit. All were citizens of Olmsted County, MN, and were enrolled in the OCTOPUS (Olmsted Cardiac Troponin in Persons Under Sixty-six) registry. The Rochester Epidemiology Project enrolls all patients who are residents of Olmsted County unless they opt out, and links to the medical records of the OCTOPUS patients.
Between 2003 to 2018, there were 4,116 events in 2,790 patients. After excluding some patients for periprocedural MI and withdrawal of others, 1,474 individuals with at least one MI were classified by index MI etiology at presentation. Atherothrombosis accounted for 67% of MIs, supply-demand mismatch for 23%, SCAD for 4%, MINOCA-U for 3%, embolism for 2%, and vasospasm for 1%.
After angiographic scrutiny, MI causes were reclassified in 61 patients (4%). A change from MINOCA-U to SCAD and from atherothrombosis to coronary embolism were the most common reclassifications.
On a population incidence level, MI caused by atherothrombosis occurred at a rate of 23 per 100 person-years for women compared with 105 per 100,000 person-years for men. When MI was caused by atherothrombosis, there was no difference in age between women and men (mean age 55 and 54 years, respectively). Angiography showed that in this patient group, men and women had similar disease extent, but women had a greater burden of risk factors, including hypertension and diabetes. The incidence of myocarditis was higher in men than in women, while Takotsubo syndrome was more common in women.
Although atherothrombosis was the most common cause of MI across all ages, analysis of women who were age 45 or younger at the time of the event showed that the most common cause of MI was supply-demand mismatch. As a group, SCAD, embolism, spasm, and MINOCA-U were as likely to be the cause of MI in these younger women as was atherothrombosis.
Patients with supply-demand mismatch as the cause of their MI had the highest rate of 5-year all-cause mortality at 33%, compared with 8% in those with atherothrombosis or embolism as the cause.
In her editorial, Reynolds says the high rate of supply-demand mismatch in these young patients is surprising.
“As the authors acknowledge, patients ultimately classified as supply-demand mismatch often (64%) did not undergo angiography, and it remains possible they would have been reclassified if angiography had been performed,” she writes.
Gulati said it can be challenging to identify supply-demand mismatch MI, and diagnoses are often made clinically based on presentation and concurrent illness.
“These patients are typically unwell from serious noncardiac or noncoronary illnesses, including acute bleeding, and may not be considered for angiography to exclude an acute coronary event,” he said. “The high mortality rate is largely driven by noncardiac deaths, consistent with the presence of serious noncardiac disease as the underlying cause of supply-demand mismatch.”
Gulati and colleagues add that the OCTOPUS data may be useful for “benchmarking” in future studies aimed at shedding more light on individualized management strategies based on the etiology of the MI.