Native stress imaging is insensitive for distinguishing patients with myocardial infarction with non-obstructive coronary arteries from healthy volunteers

Background: Myocardial infarction with non-obstructive coronary arteries (MINOCA) presents as evidence of a myocardial infarction in the absence of significant epicardial stenosis. Coronary microvascular dysfunction, which may cause MINOCA, is characterized by an impaired myocardial perfusion response to physiological stress and can be assessed using cardiac magnetic resonance imaging. Native T1 and T2 responses to adenosine stress reflect changes in myocardial perfusion in healthy subjects, however it is unknown whether native T1 and T2 are affected in patients with MINOCA and a previously normal cardiac MRI examination.

Methods: A total of 463 segments at rest and 173 segments during adenosine stress measured using native T1- and T2-mapping sequences were compared between patients with MINOCA and a normal cardiac MRI at index event (n=15, 59±7 years, 60% female) and age- and sex matched volunteers (n=15) without previous or current symptoms of coronary artery disease. Participants with previous MINOCA underwent a 1.5T cardiac MRI follow-up a median 5 years after initial presentation. Native T1 (MOLLI 5s(3s)3s), Siemens Healthcare, Erlangen Germany) and T2 short-axis maps (T2prep SSFP, MyoMaps, Siemens) were acquired at rest and during adenosine stress. Quantitative perfusion maps using first pass perfusion after Gadobutrol administration were also acquired during rest and stress. All maps were acquired in basal, midventricular and apical slices, and outlined by two independent observers.

Results: There were no differences in native T1 at rest (975.4±53.2 vs 989.3±30.3 ms, p = 0.38), native T1 at stress (1036.7±44.1 vs 1033.2±32.7 ms, p = 0.81), native T2 at rest (49.9±3.1 vs 49.8±2.3 ms, p = 0.19) or native T2 at stress (54.9±3.8 vs 56.1±4.7 ms, p = 0.48) between patients with MINOCA and a previous normal cardiac MRI and volunteers.

The relative changes in T1 and T2 from rest to stress, ΔT1 (6.5±5.4 vs 4.5±2.2 %, p=0.19) and ΔT2 (10.4±8.4 vs 12.5±7.9 %, p=0.46) respectively, did not differ between patients with MINOCA and volunteers.

Overall, the T1 (R2=0.27, p< 0.001) and T2 (R2=0.48, p< 0.001) each correlated with myocardial perfusion. The ΔT1 correlated with the MPR in pooled patient and volunteer data (R2 = 0.39, p=0.03).

Conclusion: Quantitative native T1 and T2 mapping at rest and during adenosine stress correlated with myocardial perfusion, but there were no differences between native deltas or absolute native stress values between MINOCA patients with a normal cardiac MRI scan and healthy volunteers.

Native T1 in patients with MINOCA and volunteers. Absolute native T1 values in rest and stress, as well as ΔT1, in patients and volunteers. Points denote outlier values.

Native T2 in patients with MINOCA and volunteers. Absolute native T2 values in rest and stress, as well as ΔT2, in patients and volunteers. Points denote outlier values.

Correlation between native T2 and perfusion Native T2 values plotted against perfusion. The trendline and R2-value denote the correlation for all data points- both rest and stress in pooled patients and volunteers (R2=0.48, p<0.001). There was no significant correlation for rest and stress values separately.