Patients with myocardial infarction (MI) and non-obstructive coronary arteries (MINOCA) may have a better prognosis than their obstructive counterparts, but it’s not benign, a new Australian-led review suggests.
The 23-study meta-analysis assessing clinical outcomes for MINOCA, MI with obstructive coronary disease (CAD) and non-MI patients found those with MINOCA had unadjusted 12-month all-cause mortality and reinfarction rates of 3.4% and 2.6%, respectively.
Compared with MI-CAD patients, MINOCA patients had lower 12-month all-cause mortality, cardiac and reinfarction rates at 3.3%, 1.5% and 2.9% versus 5.6% (odds ratio [OR]: 0.60, P < 0.001), 4.1% (OR: 0.40, P = 0.006) and 6.4% (OR: 6.4, P = 0.02), though the groups had a similar incidence of heart failure (4.7% versus 6.1%, OR: 0.71, P = 0.17).
Contrary to other studies, all-cause mortality rates were slightly, but not significantly, higher in MINOCA versus non-MI patients, (2.6% [95% CI: 0%–5.9%] versus 0.7% [95% CI: 0.1%–1.3%], OR: 3.71 [95% CI: 0.58–23.61], P = 0.09), the authors found, adding that their study may have been underpowered to properly address this comparison.
The “largest contemporary meta-analysis to date” showed MINOCA patients had “significant cardiovascular events at 12 months” and worse outcomes than non-MI patients but still had a more favourable prognosis than those with MI-CAD, the authors including Professor John Beltrame from Adelaide University said.
While they proposed a number of risk factors for MINOCA, they suggested plaque burden isn’t one of them.
“The all-cause mortality and reinfarction in suspected MINOCA do not appear to relate to atherosclerotic burden because there was no difference in these outcomes between patients with suspected MINOCA with nonobstructive CAD (1%–49% stenosis) or angiographically normal coronaries,” they wrote.
Instead, the condition may be influenced by certain cardiovascular risk factors that are less prevalent in MINOCA versus MI-CAD patients but similar to those with no-MI, pathophysiological factors — such as plaque disruption, epicardial coronary spasm, microvascular dysfunction or thromboembolism, and post-MI medical management.
Previous studies have identified long-term benefits with statins and renin-angiotensin modulating agents, but the role of beta-blockers “is less clear”, with one analysis suggesting they may improve MACE outcomes and another suggesting they may be detrimental. Meanwhile, dual antiplatelet therapy had a “neutral” effect on MINOCA.
“The impact of these cardioprotective therapies (beta-blockers and renin-angiotensin system modulating agents) on MACE in patients with suspected MINOCA is currently being prospectively assessed in a registry-based, randomized, parallel, open-label, multicenter trial with 2:2 factorial design—the MINOCA-BAT (Randomized evaluation of beta blocker and Angiotensin converting enzyme-inhibitor/angiotensin receptor blocker treatment in patients with myocardial infarction with nonobstructive coronary arteries) Trial,” the authors noted.
Although their analysis “has not identified extent of angiographic atherosclerotic disease as an important determinant of 12-month outcomes in patients with MI with <50% stenoses (ie, MINOCA)”, clinicians should still be wary about the condition, with “several studies [showing] its prognostic importance in patients with >50% lesions (ie, MI-CAD)”.
“Moreover, these studies have shown that patients with suspected MINOCA have a similar prognosis to patients with 1 or 2-vessel disease. This may be a useful clinical corollary when considering the relative prognosis of patients with suspected MINOCA.”
Along with risk factors, diagnosis and prognosis should be supported by MRI, which is “pivotal” in excluding MI-mimicking disorders such as myocarditis and Takotsubo syndrome, the authors wrote.
Where MRI availability is limited, “patients with (1) clinical criteria for MI (myocardial injury+evidence of ischaemia), (2) nonobstructive coronary arteries (ie, no lesions ≥50%), and (3) no overt clinical cause for the MI presentation (ie, myocarditis or Takotsubo syndrome), at the time of angiography, should be considered as Suspected MINOCA,” they suggested.
The full study is available in Circulation: Cardiovascular Quality and Outcomes.