acute MI

Pathophysiology of a classic acute MI is attributed to the concept of coronary atherothrombosis leading to myocardial ischaemia and ultimately infarction. The overall prognostic benefit with coronary revascularization has been established in these patients. Recently, there is a significant research and clinical interest in acute MI presentations without evidence of significant atherothromotic lesions, so that revascularization therapies are considered inappropriate. These presentations are referred as Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA) and is now an established clinical entity. The AHA just released the first scientific statement on diagnosis and management of MINOCA and is an important read¹. The document provides the first formal updated definition of MINOCA and clinically useful framework and algorithms for the diagnostic evaluation and management of these patients.

The key points from the statement are:

The diagnosis of MINOCA is made in patients with acute MI due to myocardial ischemia.

1. Acute myocardial infarction as per the “Fourth Universal definition of MI” Criteria
2. Nonobstructive coronary arteries on angiography: the absence of obstructive disease on angiography (ie, no coronary artery stenosis ≥50%) in any major epicardial vessel
3. No specific alternate diagnosis for the clinical presentation: Alternate diagnoses include but are not limited to non-ischemic causes such as sepsis, pulmonary embolism, and myocarditis

The “Traffic Light” Sequence for the Diagnosis of MINOCA.

Involving a clever adaptation of traffic light sequence, a very detailed diagnostic algorithm was provided for the diagnosis of MINOCA.

Red:  to exclude myocardial injury causes without ischemic context (Eg: Sepsis, Pulmonary Embolism)

Yellow: to exclude clinically subtle non-ischemic mechanisms of myocardial injury (Eg: Clinically overlooked CAD, Takotsubo, Myocardits)

Green: the final diagnosis of MINOCA is made upon a clear evidence of an ischemic context.

Specific causes of MINOCA Presentations: Atherosclerotic vs Nonatherosclerotic Causes of Myocardial Necrosis

Plaque disruption:

• Reported in approximately 1/3 of MINOCA undergoing IVUS.
• Authors recommend invasive imaging studies (IVUS or OCT) if available

Coronary Spasm:

• Reported in approximately 50% of MINOCA undergoing provocative spasm testing.
• Predilection for spasm in Asians compared with Caucasians.
• Spasm testing appears to be safe in MINOCA cohort.

Microvascular Dysfunction:

• Need to be studied in MINOCA population

Coronary embolism/Thrombosis:

• Consider the inherited hypercoagulable states in patients with MINOCA, especially in younger women

Spontaneous Coronary Artery Dissection

• Rare
• Should be suspected mainly in young women

Management strategies for MINOCA

Given that there is currently no randomized clinical trials or guidelines on treating MINOCA, the statement suggests careful considerations in managing patients. Overall, a ‘working diagnosis’ approach should be adopted, with cardioprotective therapies and treatments targeting the underlying cause considered.

The full AHA statement on MINOCA can be found here.

Reference:

1. Tamis-Holland Jacqueline E, Jneid H, Reynolds Harmony R, Agewall S, Brilakis Emmanouil S, Brown Todd M, Lerman A, Cushman M, Kumbhani Dharam J, Arslanian-Engoren C, Bolger Ann F, Beltrame John F and null n. Contemporary Diagnosis and Management of Patients With Myocardial Infarction in the Absence of Obstructive Coronary Artery Disease: A Scientific Statement From the American Heart Association. Circulation. 0:CIR.0000000000000670.