Myocardial Blood Flow Determination From Contrast-Free Magnetic Resonance Imaging Quantification of Coronary Sinus Flow

BACKGROUND

Determination of myocardial blood flow (MBF) with MRI is usually performed with dynamic contrast enhanced imaging (MBFDCE ). MBF can also be determined from coronary sinus blood flow (MBFCS ), which has the advantage of being a noncontrast technique. However, comparative studies of MBFDCE and MBFCS in large cohorts are lacking.

PURPOSE

To compare MBFCS and MBFDCE in a large cohort.

STUDY TYPE

Prospective, sequence-comparison study.

POPULATION

147 patients with type 2 diabetes mellitus (age: 56+/-12 years; 106 male; diabetes duration: 12.9+/-8.1 years), and 25 age-matched controls.

FIELD STRENGTH/SEQUENCES

1.5 Tesla scanner. Saturation recovery sequence for MBFDCE vs. phase-contrast gradient-echo pulse sequence (free-breathing) for MBFCS .

ASSESSMENT

MBFDCE and MBFCS were determined at rest and during coronary dilatation achieved by administration of adenosine at 140 μg/kg/min. Myocardial perfusion reserve (MPR) was calculated as the stress/rest ratio of MBF values. Coronary sinus flow was determined twice in the same imaging session for repeatability assessment.

STATISTICAL TESTS

Agreement between MBFDCE and MBFCS was assessed with Bland and Altman's technique. Repeatability was determined from single-rater random intraclass and repeatability coefficients.

RESULTS

Rest and stress flows, including both MBFDCE and MBFCS values, ranged from 33 to 146 mL/min/100 g and 92 to 501 mL/min/100 g, respectively. Intraclass and repeatability coefficients for MBFCS were 0.95 (CI 0.90; 0.95) and 5 mL/min/100 g. In Bland-Altman analysis, mean bias at rest was -1.1 mL/min/100 g (CI -3.1; 0.9) with limits of agreement of -27 and 24.8 mL/min/100 g. Mean bias at stress was 6.3 mL/min/100 g (CI -1.1; 14.1) with limits of agreement of -86.9 and 99.9. Mean bias of MPR was 0.11 (CI: -0.02; 0.23) with limits of agreement of -1.43 and 1.64.

CONCLUSION

MBF may be determined from coronary sinus blood flow, with acceptable bias, but relatively large limits of agreement, against the reference of MBFDCE .

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 2.

Transesophageal Echocardiographic Estimation of Coronary Sinus Blood Flow for Predicting Favorable Postoperative Transit Time Coronary Graft Flow Measurements: A Pilot Study

BACKGROUND

Augmentation of coronary artery flow by surgical grafting increases coronary sinus blood flow (CSBF), which can be quantified on transesophageal echocardiography (TEE). However, transit time flowmetry (TTF) technology remains the most used intraoperative technique for coronary artery graft assessment. The purpose of the present pilot study was to evaluate the predictive value of TEE-based CSBF estimation for identifying favorable TTF graft measurements.

DESIGN

Prospective observational study.

SETTING

Single university hospital.

PATIENTS

Forty patients undergoing triple vessel coronary artery bypass grafting.

MEASUREMENTS AND MAIN RESULTS

CSBF was assessed on TEE examination before and after revascularization, estimating the percentage increase in CSBF (∆CSBF). Postoperative TTF graft measurements were averaged to compute mean diastolic filling (DF) and pulsatility index (PI). Subjects were grouped based on favorable (PI ≤ 3, DF ≥ 50%) and unfavorable (PI > 3, DF < 50%) parameters. The group with PI ≤ 3 (n = 32) had significantly higher ∆CSBF compared with the group with PI > 3 (n = 8) (38.22% ± 12.05%, 13.75% ± 3.37%, p < 0.001). ∆CSBF was higher in the DF ≥ 50% group (n = 35) (36.40 ± 12.99) in contrast to DF < 50% group (n = 5) (11.80 ± 2.59%). A strong negative and significantly positive correlation was observed between ∆CSBF with PI, DF (r = -0.903, 0.571, respectively, p < 0.001). A ∆CSBF ≥15.5% was found to predict a mean PI ≤ 3 and DF ≥ 50% with sensitivity and specificity of 100% and 62.5% for PI and 100% and 100% for DF. A ∆CSBF ≥19% demonstrated a sensitivity and specificity of 100% and 100%, 100% and 91.4% for prediction of PI ≤ 3 and DF ≥ 50%, respectively.

CONCLUSION

TEE-based demonstration of an augmented CSBF can ensure favorable TTF graft parameters, guiding the adequacy of surgical revascularization.

Combined Assessment of Stress Myocardial Perfusion Cardiovascular Magnetic Resonance and Flow Measurement in the Coronary Sinus Improves Prediction of Functionally Significant Coronary Stenosis Determined by Fractional Flow Reserve in Multivessel Disease

Background

Recent studies using stress‐rest perfusion cardiovascular magnetic resonance (CMR) demonstrated a close correlation between myocardial ischemia and reduced fractional flow reserve (FFR). However, its diagnostic concordance may be reduced in patients with multivessel disease. We sought to evaluate the concordance of adenosine stress‐rest perfusion CMR for predicting reduced FFR, and to determine the additive value of measuring global coronary flow reserve (CFR) in the coronary sinus in multivessel disease.

Methods and Results

Ninety‐six patients with angiographic luminal narrowing >50% underwent comprehensive CMR study and FFR measurements in 139 coronary vessels. FFR <0.80 was considered hemodynamically significant. Global CFR was quantified as the ratio of stress‐rest coronary sinus flow measured by phase‐contrast cine CMR. In 25 patients with single‐vessel disease, visual assessment of perfusion CMR yielded high diagnostic concordance for predicting flow‐limiting stenosis, with the area under receiver operating characteristic curve of 0.93 on a per‐patient basis. However, in 71 patients with multivessel disease, perfusion CMR underestimated flow‐limiting stenosis, resulting in the reduced area under receiver operating characteristic curve of 0.74. When CFR of <2.0 measured in the coronary sinus was considered as global myocardial ischemia, combined assessment provided correct reclassifications in 7 patients with false‐negative myocardial ischemia, and improved the diagnostic concordance to 92% sensitivity and 73% specificity with the area under receiver operating characteristic curve of 0.88 (95% confidence interval, 0.80%–0.97%, P=0.002).

Conclusions

Visual analysis of stress‐rest perfusion CMR has limited concordance with FFR in patients with multivessel disease. Multiparametric CMR integrating stress‐rest perfusion CMR and flow measurement in the coronary sinus is useful for detecting reduced FFR in multivessel disease.