Abstract
Background
Patients with signs and symptoms of myocardial ischemia yet unobstructed coronary arteries represent a diagnostic and therapeutic challenge. Coronary vasomotor disorders such as coronary epicardial or microvascular spasm are frequently found among these patients. They can be diagnosed using intracoronary acetylcholine testing (ACH-test). It has been shown that patients with epicardial spasm have a worse prognosis compared to patients with microvascular spasm. The reasons for this finding are however not apparent. We speculated in this study that patients with epicardial spasm have a worse vasomotor dysfunction compared to patients with microvascular spasm or normal ACH-test. To assess this hypothesis all patients in this study not only underwent ACH-testing but in addition also adenosine stress perfusion cardiac MRI (CMR) with calculation of the myocardial perfusion reserve index (MPRI). The latter method allows for assessment of vasodilatory function compared to the vasoconstrictor assessment using acetylcholine.
Methods
Between 2012 and 2016, 129 consecutive patients (mean age 64±13 years, 46% female) with signs and symptoms of myocardial ischemia yet unobstructed coronary arteries were enrolled in this study. All patients underwent ACH-testing as well as adenosine stress perfusion CMR. According to the results of the acetylcholine test, patients were allocated to 3 groups: a) epicardial spasm (angina, ischemic ECG changes and >75% coronary diameter reduction), b) microvascular spasm (angina, ischemic ECG changes and <75% coronary diameter reduction) and c) no evidence of coronary artery spasm. CMR-derived MPRI was calculated semiquantitatively from myocardial signal intensity-over-time curves of adenosine stress and rest perfusion.
Results
Epicardial and microvascular spasm was found in 31 (24%) and 69 (53%) patients, respectively, while 29 (22%) patients had no evidence of coronary spasm on ACH-testing. Women were more likely to have microvascular spasm than men (68% vs. 36%, p<0.001). The prevalence of epicardial spasm did not significantly differ between female and male patients (18% vs. 31%, p=0.08). MPRI was similar in patients with microvascular spasm compared to patients without spasm (1.30 vs. 1.27, p=0.43). However, patients with epicardial spasm had significantly lower MPRI than patients without spasm (1.16 vs. 1.30, p<0.05) or those with microvascular spasm (1.16 vs. 1.27, p<0.05).
Conclusion
MPRI determined by stress perfusion CMR was significantly reduced in patients with epicardial spasm compared to those with microvascular spasm or normal ACH-test. This could indicate that patients with epicardial spasm have a more generalized coronary vasomotor disorder compared to other patients. This may be the reason for the worse outcome observed and could lead to more aggressive medical therapy and closer follow-up.
Acknowledgement/Funding
This work was funded by the Robert-Bosch-Stiftung, Stuttgart, Germany and the Berthold-Leibinger-Stiftung, Ditzingen, Germany.
Adenosine Stress Perfusion CMR Reliably Risk Stratifies Patients with Prior Indeterminate Exercise Treadmill Testing
