Contrast-free whole heart myocardial blood flow quantification from magnetic resonance imaging-determination of coronary sinus flow

Background Non-invasive reference quantification of whole heart myocardial blood flow (MBF) requires radioisotopes for PET and gadolinium contrast for cardiovascular magnetic resonance imaging (CMR) which in some cases is contraindicated. MBF may be determined from CMR quantification of flow in the coronary sinus (CSBF), the large vein draining the majority of the myocardium. Comparative studies of CSBF from CMR and MBF as determined from a reference technique have not yet been published in any larger cohorts. Purpose Our objective was to evaluate to what extent CMR CSBF measurements can be used to determine MBF as determined from gadolinium-contrast CMR in a cohort of normal subjects and patients with type 2 diabetes mellitus (T2DM) already demonstrated to display a wide range of MBFs. Methods 147 patients with T2DM and 25 age-matched controls were recruited to a cohort study on cardiovascular changes in DM. MBF was quantified from gadolinium-contrast perfusion sequences based on Fermi-constrained deconvolution. Myocardial segments with late gadolinium hyperenhancement or visually significant perfusion defects were included. CSBF was determined with CMR flow-sequences applied across the coronary sinus (VENC 0.5–1.0 m/s). Patients were studied during rest and maximal coronary artery dilatation by adenosine infusion (140 mg/kg/min). Blood flow stress-reserves were the ratio of stress to rest values. Co-variation of MBF and CSBF were determined from Bland-Altman plots with lines of agreement. Repeatability of CSBF was determined during the same experiment and calculated from single rater random intra class and repeatability coefficients. Results In normal subjects and patients with T2DM, MBF and CSBF increased during adenosine-stress (Fig. 1) with mean absolute increments of 172 and 163 mL/min/100g, and with mean stress-reserves of 3.35 and 3.24, respectively. Bland-Altman plots showed that MBF and CSBF covaried with a small bias, but in some cases with relatively large limits of agreement (Fig. 2). Overall, the mean bias of increase from rest-to-stress was 6 (CI: −1; 14) mL/min/100g with corresponding limits of agreement of 93 (CI 81; 105) and −80.2 (CI −92.6; 67.8) mL/min/100g. The mean bias of stress-reserve was 0.106 (CI: −0.0209; 0.234) with corresponding limits of agreement of −1.43 (CI: −1.65; −1.21) and 1.64 (CI: 1.42; 1.86). Intra-class and repeatability coefficients for coronary sinus flow were 0.95 (CI: 0.90; 0.95) and 5 mL/min/100g, respectively. Conclusion Myocardial blood flow can reproducibly and with a small bias be determined from the non-contrast technique of applying magnetic resonance imaging flow-sequences across the coronary sinus. Determination of MBF from coronary sinus blood flow may be useful in patient-groups where contrast is contraindicated, but limits of agreement with MBF must be taken into account. FUNDunding Acknowledgement Type of funding sources: None. Figure 1 Figure 2

Prognostic value of unrecognized myocardial infarction and hyperemic coronary sinus flow in patients undergoing elective percutaneous coronary intervention

Background Cardiac magnetic resonance (CMR) imaging is a useful instrument for the assessment of pathological and functional conditions without the need for ionizing radiation, radioactive tracers, or intravascular catheterization. Both unrecognized myocardial infarction (UMI) and impaired global myocardial blood flow (g-MBF) have been reported to be strongly associated with worse outcome in patients with cardiovascular disease. However, their combined efficacy remains undetermined. Purpose We sought to assess the prognostic value of the presence of UMI and pre-procedural hyperemic g-MBF evaluated by phase-contrast cine magnetic resonance imaging (PC-CMR) in patients with chronic coronary syndrome who underwent elective percutaneous coronary intervention (PCI). Methods A total of 177 patients with de novo functionally significant stenosis who underwent pre-PCI CMR and PCI between September, 2016 and March, 2019 were retrospectively studied. UMI was defined as a scar detected by late gadolinium enhancement (LGE) without previously diagnosed MI. g-MBF was assessed by quantifying coronary sinus flow using PC-CMR at rest and hyperemic state. The predictors of major adverse cardiac events (MACE; cardiac death, nonfatal myocardial infarction, clinically driven unplanned revascularization, or hospitalization for congestive heart failure) during follow-up were investigated. Results UMI was detected in 40 (27.7%) patients and rest and maximal hyperemic g-MBF evaluated by the coronary sinus flow obtained by PC-CMR were 0.95 ml/min/g and 2.26 ml/min/g, respectively. During the median follow-up of 26 months, cardiovascular death occurred in 1 patient (0.6%), nonfatal myocardial infarction occurred in 4 patients (2.3%), and clinically driven revascularization and hospitalization due to congestive heart failure occurred in 25 patients (14.1%) and 3 patients (1.7%) patients, respectively. In patients with MACE, hyperemic g-MBF was significantly lower and the prevalence of UMI were significantly higher compared with those without MACE (1.94 ml/min/g vs 2.36 ml/min/g P=0.014; 48.3% vs 23.6%, P=0.011). Cox proportional hazards model indicated that impaired hyperemic g-MBF (<2.00 ml/min/g) and the presence of UMI were significant predictors of MACE (HR 2.22, 95% CI 1.060–4.640, P=0.034; HR 2.660, 95% CI 1.290–5.470, P=0.008). During follow-up, cardiac event-free survival was significantly worse in patients with impaired hyperemic g-MBF (<2.00 ml/min/g) and UMI (log-rank χ2=11.0, P=0.010). Conclusion In patients with chronic coronary syndrome undergoing elective PCI, the combined assessment of UMI and hyperemic g-MBF obtained by preprocedural noninvasive CMR may provide significant prognostic information. Funding Acknowledgement Type of funding source: None

Prognostic value of coronary flow capacity assessed by coronary sinus flow obtained by phase contrast cine-magnetic resonance imaging in patients with acute coronary syndrome

Background The concept of coronary flow capacity (CFC) originated from positron emission tomography has been reported to provide prognostic information. Phase contrast cine-magnetic resonance imaging (PC-CMR) of the coronary sinus (CS) is a promising approach for quantifying global coronary sinus flow (CSF) and global coronary flow reserve (g-CFR) without the need for ionizing radiation, radioactive tracers, or intravascular catheterization. Purpose We evaluated the prognostic value of postprocedural CFC by quantifying CSF using PC-CMR in patients with acute coronary syndrome (ACS) treated with primary or urgent percutaneous coronary intervention (PCI). Methods This study prospectively but nonconsecutively enrolled 569 ACS patients who underwent uncomplicated primary (for ST-segment elevation myocardial infarction (STEMI)) or urgent PCI within 48 hours of symptom onset (for non-ST elevation acute coronary syndrome (NSTE-ACS)). Breath-hold PC-CMR images of CS were acquired to assess absolute CSF at rest and during maximum hyperemia within 30 days after culprit lesion PCI and revascularization of functionally significant non-culprit lesions. The entire cohort was stratified by the CFC according to the thresholds of hyperemic CSF and g-CFR. Impaired CFC was defined as a severely-reduced CFC in the present study. The association of CFC and baseline clinical characteristics with major adverse cardiac events (all-cause death, nonfatal myocardial infarction, hospitalization for congestive heart failure or stroke) was investigated. Results In the final analysis of 502 patients (Male 417 (83.1%), mean age was 67 [58, 73]) and 310 patients (82.3%) with STEMI and 192 patients (38.2%) with NSTE-ACS were studied. In a total cohort, rest and maximal hyperemic CSF and corrected G-CFR were 0.93 [0.68, 1.24] ml/min/g, 2.08 [1.44, 2.77] ml/min/g, and 2.21 [1.58, 3.05], respectively. During a median follow-up of 28 months, MACE occurred in 53 patients (all-cause death: 19, nonfatal myocardial infarction: 16, late revascularization: 59, hospitalization for congestive heart failure: 9, stroke: 9). Cox proportional hazards analysis showed that corrected G-CFR and impaired CFC were both independent predictors of MACE. (hazard ratio (HR), 0.61, 95% confidence interval (CI): 0.45–0.82, p=0.001; HR, 3.51, 95% CI: 1.79–6.86, p≤0.001, respectively). Cardiac event-free survival was significantly worse in patients with impaired CFC (log-rank χ2=22.9, P<0.001). Net reclassification index (NRI) and integrated discrimination improvement (IDI) were both significantly improved when impaired CFC was added to the clinical risk model for predicting MACE. Conclusions In ACS patients successfully revascularized with primary or urgent PCI, CFC categorization stratified by noninvasive PC-CMR provided significant prognostic information independent of infarction size, conventional risk factors and g-CFR. Funding Acknowledgement Type of funding source: None

P3585Prognostic value of the assessment of coronary sinus flow by phase contrast cine-magnetic resonance imaging in patients with acute coronary syndrome

Background Phase contrast cine-magnetic resonance imaging (PC-CMR) of the coronary sinus (CS) is a promising approach for quantifying global coronary sinus flow (CSF) and global coronary flow reserve (G-CFR) without the need for ionizing radiation, radioactive tracers, or intravascular catheterization. Purpose We evaluated the prognostic value of G-CFR by quantifying CSF using PC-CMR in patients with ACS treated with primary or emergent percutaneous coronary intervention (PCI). Methods The study prospectively enrolled 387 ACS patients who underwent uncomplicated primary or emergent PCI within 48 hours of symptom onset. Breath-hold PC-CMR images of CS were acquired to assess absolute CSF at rest and during maximum hyperemia within 30 days after primary PCI and revascularization of functionally significant non-culprit lesions of ACS. The association of G-CFR and baseline clinical characteristics with major adverse cardiac events (cardiac death, nonfatal myocardial infarction, late revascularization, or hospitalization for congestive heart failure) was investigated. Results In the final analysis of 366 patients (Male 294 (80.3%), mean age 65) including 233 patients (63.7%) with ST-segment elevation myocardial infarction (STEMI) and 133 patients (36.3%) with non-ST-segment elevation acute coronary syndrome (NSTE-ACS), rest and maximal hyperemic CSF and corrected G-CFR were 1.24 [0.83, 1.71] ml/min/g, 2.56 [1.87, 3.66] ml/min/g, and 2.20 [1.53, 3.17], respectively. During a median follow-up of 16 months, MACE occurred in 84 patients (cardiac death: 9, nonfatal myocardial infarction: 11, late revascularization: 59, hospitalization for congestive heart failure: 5). Cardiac event-free survival was significantly worse in patients with a corrected G-CFR <2.00 (log-rank χ2=20.2, P<0.001). Cox proportional hazards analysis showed that corrected G-CFR were independent predictors of adverse cardiac events during follow-up in patients with STEMI (hazard ratio, 0.66, 95% confidence interval, 0.51–0.85, p=0.001) and NSTE-ACS (hazard ratio, 0.64, 95% confidence interval, 0.43–0.95, p=0.026), respectively. Conclusions In ACS patients successfully revascularized within 48 hours of onset, G-CFR obtained by noninvasive PC-CMR provided significant prognostic information independent of infarction size and conventional risk scores.