10/07/2019 | Press release | Distributed by Public on 10/07/2019 15:51
What is the prognostic impact of cardiac magnetic resonance (CMR) and other risk factors in patients with myocardial infarction with nonobstructed coronary arteries (MINOCA)?
A registry database was used to identify 388 patients with CMR imaging for a suspected diagnosis of MINOCA. The primary clinical outcome was all-cause mortality. The CMR used standard protocols and the findings were used to categorize patients into four groups: myocardial infarction (MI) (embolic/spontaneous recanalization), myocarditis, cardiomyopathy, and normal CMR.
CMR (performed at median 37 days from presentation) diagnosed myocarditis (25%), MI (25%), and cardiomyopathy (including Takotsubo, hypertrophic, dilated cardiomyopathies) (25%). CMR was normal in 26% and thus not able to determine the cause of the MINOCA. The overall mortality rate was 5.7% over median follow-up of 1,262 days: 15% in the cardiomyopathy group, 4% in the MI group, 2% in the myocarditis group, and 2% in the normal CMR group. In multivariable Cox regression, the only two significant predictors of mortality were CMR diagnosis of cardiomyopathy and ST-segment elevation on electrocardiogram (ECG) at diagnosis.
CMR (median 37 days from presentation) identified a diagnosis in patients with suspected MINOCA in 74% of patients. Patients with CMR diagnosis of cardiomyopathy had the highest mortality. Cardiomyopathy and ST-elevation on ECG were the strongest predictors of mortality.
In this study, only 25% of patients with suspected MINOCA had evidence of infarction on CMR. The authors reported that the highest mortality was among patients with cardiomyopathy and suggested that CMR is useful for prognostic purposes in patients with MINOCA. After CMR imaging, one half of the patients with suspected MINOCA were diagnosed with cardiomyopathy (including a large proportion of Takotsubo cardiomyopathy) or myocarditis.
The recent expert consensus from the American Heart Association emphasizes that the diagnosis of MINOCA should only be made when there is evidence for MI, and not an alternative cause for troponin elevation such as myocarditis or Takotsubo syndrome.1 Specifically, 'the term MINOCA should be reserved for patients in whom there is an ischemic basis for their clinical presentation.'1 Additionally, CMR was performed at a median of 37 days from presentation, and therefore, many of the studies may have appeared normal due to the delay in imaging from the time of diagnosis. Therefore, the results of this study support the recommendation that CMR may be useful in establishing a diagnosis in certain patients with suspected MINOCA. Accurate diagnosis is essential since there is considerable variation in treatment and prognosis.
Keywords:Acute Coronary Syndrome, Cardiomyopathies, Cardiomyopathy, Dilated, Cardiomyopathy, Hypertrophic, Diagnostic Imaging, Electrocardiography, Heart Failure, Magnetic Resonance Imaging, Myocardial Infarction, Myocarditis, Risk Factors, Takotsubo Cardiomyopathy, Troponin