Despite cutting edge technologies and preventive medical therapies, myocardial infarction (MI)-associated mortality remains a major concern. Overlooked among the management of MI patients are the 5%to 10% who do not have obstructive coronary artery disease (CAD). This subtype of MI has recently been dubbed “myocardial infarction with non-obstructive coronary arteries” (MINOCA). The lack of obstructive disease in this population has historically led clinicians to disregard them as false positive presentations. Despite the myocardial infarct presentation, many patients are discharged home with minimal or no cardioprotective therapies and no explanation for their presentation. With the widespread use of coronary angiography and more sensitive cardiac biomarkers, MINOCA presentations have started to gain attention among cardiologists and researchers in recent years.
In contemporary cardiac registries, approximately 10% of myocardial infarct presentations are identified as MINOCA. Available data suggest that these patients are likely be younger, females, and have fewer cardiovascular risk factors. However, delineating MINOCA presentations from those with obstructive coronary arteries are not feasible with clinical characteristics.
The 2017 European Society of Cardiology (ESC) guideline defines MINOCA with three core criteria:
- Myocardial infarction criteria as per the universal definition: positive cardiac biomarker with clinical evidence such as ischemic symptoms (chest pain and/or dyspnea) and ischemic ECG changes.
- Absence of obstructive CAD on angiography (defined as no lesions ≥50%).
- No clinically apparent cause for the acute presentation.
The diagnosis of MINOCA is only made when the underlying cause for the presentation following coronary angiography is not clear. The MINOCA diagnosis is not applied to patients with overt clinical evidence for a non-ischemic cause of the elevated troponin, such as pulmonary embolism or myocarditis. The ESC criteria stresses that MINOCA presentations should be further evaluated with additional tests for the underlying cause so patients may receive appropriate management.
Patients identified with MINOCA following coronary angiography should be clinically re-evaluated, with multiple potential causes in mind. Key underlying causes and corresponding diagnostic investigations are highlighted in the Table.
Although prognosis associated with MINOCA is influenced by the underlying cause, no studies have specifically addressed etiology-associated prognosis. However, available literature suggests that MINOCA patients as a whole have a favorable prognosis compared with those with obstructive coronary artery disease. Further examination of literature demonstrates that MINOCA patients had the equivalent 12-month all-cause mortality as those with myocardial infarction associated with single- or double-vessel CAD. The most recent publication using MINOCA data showed that 2-year mortality for non-fatal myocardial infarction was 14% for myocardial infarct with obstructive coronaries and 5% for MINOCA. Given the limited attention and medical management in the MINOCA cohort, one may speculate that closer clinical attention would reduce the observed event rates.
Treatment & Beyond
There are no randomized trials specifically addressing treatment for MINOCA. However, a recent publication provides the first insight into potential long-term medical therapy in the management of MINOCA. The study indicates the potential benefits of statins, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, and possibly beta-blocker therapy in MINOCA patients. These observational studies require confirmation with randomized clinical trials.
The key advance made in recent years is the recognition that MINOCA is an important clinical entity that needs to be diagnosed and appropriate investigations undertaken to identify the underlying cause. Ongoing studies should provide an evidence base for the optimal management of these patients.