How late is too late? Influence of scan timing on CMR’s diagnostic yield in suspected MINOCA

Background: Cardiovascular magnetic resonance imaging (CMR) is a Class 1 diagnostic tool for suspected myocardial infarction with no obstructive coronary artery disease (MINOCA). However, time-sensitive conditions like myocarditis or Takotsubo syndrome, may become undetectable if imaging is delayed. Thus, scan timimg is crucial for optimizing diagnostic yield and clinical value. We evaluated the impact of scan timing on the diagnostic performance of cardiac magnetic resonance (CMR) in patients presenting with acute coronary syndrome (ACS) and nonobstructed coronary arteries.

Methods: Patients enrolled in the Bristol MINOCA CMR Registry were identified and included. All participants underwent a 1.5-T CMR examination using a comprehensive protocol incorporating cine imaging, T2-weighted, and late gadolinium enhancement sequences. Based on CMR findings, patients were categorized into five diagnostic groups: MINOCA (embolic/spontaneous recanalization, coronary artery dissection), myocarditis, Takotsubo syndrome, cardiomyopathy, and unremarkable or normal CMR. The diagnostic rate was calculated as the proportion of non-normal CMR studies out of all CMR studies performed. Logistic regression analysis was conducted to assess the relationship between the probability of diagnosis and time to CMR. To account for potential non-linearity in the effect of scan timing, restricted cubic splines with four knots were employed.

Results: A total of 888 consecutive patients presenting with ACS and nonobstructed coronary arteries were included in the study (51% females). CMR identified an underlying cause in 672 (75.68%). The diagnostic yield was highest when CMR was performed within 7 days following acute presentation, subsequently declining at an average rate of 1% per day up to 15 days. Notably, while the detection rate of myocardial infarction remained relatively stable over time, the diagnosis of Takotsubo syndrome decreased from 24% within the first week to only 6% beyond 3 months post presentation.

Conclusion: CMR should be performed within 15 days of acute presentation to optimize diagnostic yield, as delayed imaging may miss up to 20% of cases. Takotsubo syndrome is particularly time-sensitive, and CMR availability must be considered when interpreting results in suspected MINOCA.

Rate of diagnostic CMR by time to scan