MINOCA - A New Type of Myocardial Infarction?
A new syndrome of myocardial infarction (MI) has been defined in the clinical context over the past few years - myocardial infarction with non-obstructive coronary arteries (MINOCA).
Several large, international acute myocardial infarction (AMI) studies confirmed that 5%-15% of AMIs occur in the absence of an obstructive coronary artery disease (AMI-CAD), or at least atherosclerosis is not considered sufficiently severe to compromise myocardial blood flow.
Clinically, this infarction type is bringing up questions about the underlying mechanism of the myocardial damage and the need for different treatment methods according to the underlying cause. The question in the context of insurance is whether or not patients with non-obstructive myocardial infarction differ in severity and outcome from the classical artery blockage and whether they are covered by the current heart attack policy definitions.
Clinical Definition of Myocardial Infarction
The current universal definition of myocardial infarction - used by the European Society of Cardiology, the American College of Cardiology, the American Heart Association and the World Heart Federation Force - was published in August 2018 (4th edition).
In this expert consensus for clinical purposes, MI is defined as an acute myocardial injury with clinical evidence of acute myocardial ischaemia including the rise of cardiac troponin beyond the 99th percentile of its upper reference level and with at least one of the following conditions:
- Symptoms of myocardial ischaemia
- New significant ST-T changes or new left bundle branch block in ECG
- Development of pathological Q-waves in ECG
- Imaging evidence of new loss of viable myocardium or regional wall motion abnormality
- Identification of a coronary thrombus
Clinical Definition of MINOCA
The diagnosis of MINOCA identically requires the presence of the exact conditions mentioned above, but in contrast to AMI-CAD patients no diagnosis of coronary stenosis of more than 49% in any potential infarct-related artery is to be made upon coronary angiography. At the same time, no specific alternate diagnoses, e.g., sepsis, pulmonary embolism or myocarditis, can be made to explain the clinical picture. The diagnosis of MINOCA is inherently descriptive and clinicians should always be prompted to continue seeking for an underlying cause before committing themselves to the diagnosis of MINOCA.
Causes for MINOCA can be plaque rupture, erosion and calcific nodules. Other common causes are vasospasm, coronary thrombosis or embolism, or spontaneous coronary artery dissection.
Myocardial Infarction in Critical Illness Insurance
The definition for MI in the context of Critical Illness (CI) insurance products differs from the clinical approach. The contrasting insurance industry aim is to focus on heart attacks with serious and permanent health consequences.
Most heart attack definitions define MI as death of heart muscle in a limited area due to inadequate blood supply following an occlusion or partial blockage or narrowing of coronary arteries. Additional criteria are mostly typical clinical symptoms of MI; new characteristic ECG changes and the transient increase of cardiac biomarker blood levels. Newer definitions furthermore demand a permanent reduction of the heart function, such as reduced left ventricular ejection fraction or significant and persistent wall motion abnormalities.
In comparison with AMI-CAD patients, MINOCA patients can present ST-segment elevation in an ECG, but they are less likely to have deviations. They can also show an increase of troponin blood levels. Usually the increase is less pronounced than with obstructive CAD patients.
Studies have shown that MINOCA patients differ from AMI-CAD patients in terms of age and risk factors. The average age of MINOCA patients is 58 years compared to AMI-CAD patients with 61 years in average. Fifty percent of MINOCA patients are woman, compared to only 25% in AMI-CAD events. MINOCA patients also show lower prevalence of typical CAD risk factors, such as dyslipidemia, hypertension, diabetes, smoking and family history of MI.
In general patients with MINOCA show better clinical courses compared to AMI patients, but severe courses with longstanding health consequences are possible.
MINOCA Impact on CI Insurance
The main target of CI insurance cover in terms of heart attacks is mostly covering heart attacks with severe and longstanding health consequences. MINOCA claims should be assessed as any MI with obstructive CAD. If they fulfill all required criteria of MI, and if they fulfill the permanent reduction of cardiac output as a main measuring tool for the definition of load limits, they are likely to be covered.
With the widespread use of modern diagnostics and intervention methods, a more precise differentiation and classification of myocardial infarction has become possible within the last few years. Establishing the diagnosis of MINOCA simply represents a newly defined, more precise myocardial infarction syndrome. However, this concerns only a reclassification of myocardial injury cases; adding the classification of MINOCA doesn’t trigger any additional heart attack cases. Therefore, no impact on the pricing of CI products is to be assumed.
- Tamis-Holland, J et al. Contemporary Diagnosis and Management of Patients With Myocardial Infarction in the Absence of Obstructive Coronary Artery Disease: A Scientific Statement From the American Heart AssociationCirculation, Volume 139, Issue 18, 30 April 2019, Pages e891-e908. https://doi.org/10.1161/CIR.0000000000000670
- Agewall, S et al. ESC working group position paper on myocardial infarction with non-obstructive coronary arteries, European Heart Journal (2017) 38, 143-153. https://doi.org/10.1093/eurheartj/ehw149