Oral Abstract Session
SCMR 22nd Annual Scientific Sessions
Four million elective invasive coronary angiograms (ICA) are performed in Europe and the USA annually for the investigation of angina. Approximately half of these do not disclose obstructive CAD. The diagnosis and onward management of symptomatic patients with a ‘negative’ ICA is uncertain and heterogeneous. The prevalence of microvascular angina (MVA) in this population is unknown. We hypothesized that multiparametric CMR imaging would be clinically useful in patients with angina and non-obstructive CAD (ANOCA).
We performed a prospective, observational study at a regional referral center. Patients undergoing ICA for the investigation of angina were eligible if the ICA revealed no obstructive CAD and anginal symptoms were confirmed using the Rose and Seattle Angina Questionnaires. Patients underwent standardized adenosine stress perfusion CMR study (1.5T) (Figure 1).
The protocol consisted of LV function (SSFP cine), myocardial blood flow (MBF) (novel pixel-wise fully quantitative method), tissue characterization (T1 and extracellular volume (ECV) mapping, and late gadolinium enhancement (LGE) imaging). Coronary microvascular dysfunction was defined as a global myocardial perfusion reserve (MPR) <2.0 using quantitative methods. Myocardial perfusion was also assessed qualitatively by two blinded observers (Level 3 EACVI accredited).
A total of 162 patients were enrolled (Aug 2017-Jan 2018) and 19 (12%) had an incomplete CMR (all due to claustrophobia) leaving 143 (88%) in the analysis set (mean age 60±10 years; 41 (29%) male, 25 (17%) diabetes, 25 (17%) current cigarette smokers).
A diagnosis of MVA (MPR<2.0) was established in 101 (71%) patients. Fewer patients had abnormal perfusion when assessed qualitatively vs. quantitatively (68 (48%) vs. 101 (71%) respectively). There was a significant difference between the endocardial:epicardial MBF ratio from rest to stress (p<0.0001). Further, MPR in the endocardial sector was significantly lower than in the epicardial sector (p<0.0001) (Table 1).
In binary logistic regression analysis of variables associated with CAD, current cigarette smoking was the only predictor of reduced MPR (<2.0), (OR 4.09 95% CI 1.13-14.8, p=0.03).
Mean mid-septal native myocardial T1 and ECV values were 951±32 ms and 27±4%, respectively. Considering reference values in our center, increased native T1 and ECV values occurred in 1 (0.7%) and 15 (11%) patients, respectively. Abnormal LGE imaging was present in 14 patients (10%) (8 (6%) with occult myocardial infarction) (Figure 2). There were 22 (15%) patients with an incidental clinically-significant finding.
Conclusion: MVA is common and routinely under-diagnosed using ICA alone. Multiparametric CMR provides diagnostic and clinical utility in ANOCA. Quantitative pixel-mapping has a higher detection rate than qualitative methods. Further research is warranted to establish the external validity and clinical significance of our findings.