Coronary flow capacity and survival prediction after revascularization: physiological basis and clinical implications.

BACKGROUND AND AIMS: Coronary flow capacity (CFC) is associated with an observed 10-year survival probability for individual patients before and after actual revascularization for comparison to virtual hypothetical ideal complete revascularization. METHODS: Stress myocardial perfusion (mL/min/g) and coronary flow reserve (CFR) per pixel were quantified in 6979 coronary artery disease (CAD) subjects using Rb-82 positron emission tomography (PET) for CFC maps of artery-specific size-severity abnormalities expressed as percent left ventricle with prospective follow-up to define survival probability per-decade as fraction of 1.0. RESULTS: Severely reduced CFC in 6979 subjects predicted low survival probability that improved by 42% after revascularization compared with no revascularization for comparable severity (P = .0015). For 283 pre-and-post-procedure PET pairs, severely reduced regional CFC-associated survival probability improved heterogeneously after revascularization (P < .001), more so after bypass surgery than percutaneous coronary interventions (P < .001) but normalized in only 5.7%; non-severe baseline CFC or survival probability did not improve compared with severe CFC (P = .00001). Observed CFC-associated survival probability after actual revascularization was lower than virtual ideal hypothetical complete post-revascularization survival probability due to residual CAD or failed revascularization (P < .001) unrelated to gender or microvascular dysfunction. Severely reduced CFC in 2552 post-revascularization subjects associated with low survival probability also improved after repeat revascularization compared with no repeat procedures (P = .025). CONCLUSIONS: Severely reduced CFC and associated observed survival probability improved after first and repeat revascularization compared with no revascularization for comparable CFC severity. Non-severe CFC showed no benefit. Discordance between observed actual and virtual hypothetical post-revascularization survival probability revealed residual CAD or failed revascularization.

Reduction of left ventricular diastolic pressure as a key regulator of infarct coronary flow under mechanical left ventricular support.

Restoring ischaemic myocardial tissue perfusion is crucial for minimizing infarct size. Acute mechanical left ventricular (LV) support has been suggested to improve infarct tissue perfusion. However, its regulatory mechanism remains unclear. We investigated the physiological mechanisms in six Yorkshire pigs, which were subjected to 90-min balloon occlusion of the left anterior descending artery. During the acute reperfusion phase, LV support using an Impella heart pump was initiated. LV pressure, coronary flow and pressure of the infarct artery were simultaneously recorded to evaluate the impact of LV support on coronary physiology. Coronary wave intensity was calculated to understand the forces regulating coronary flow. Significant increases in coronary flow velocity and its area under the curve were found after mechanical LV support. Among the coronary flow-regulating factors, coronary pressure was increased mainly during the late diastolic phase with less pulsatility. Meanwhile, LV pressure was reduced throughout diastole resulting in significant and consistent elevation of coronary driving pressure. Interestingly, the duration of diastole was prolonged with LV support. In the wave intensity analysis, the duration between backward suction and pushing waves was extended, indicating that earlier myocardial relaxation and delayed contraction contributed to the extension of diastole. In conclusion, mechanical LV support increases infarct coronary flow by extending diastole and augmenting coronary driving pressure. These changes were mainly driven by reduced LV diastolic pressure, indicating that the key regulator of coronary flow under mechanical LV support is downstream of the coronary artery, rather than upstream. Our study highlights the importance of LV diastolic pressure in infarct coronary flow regulation. KEY POINTS: Restoring ischaemic myocardial tissue perfusion is crucial for minimizing infarct size. Although mechanical left ventricular (LV) support has been suggested to improve infarct coronary flow, its specific mechanism remains to be clarified. LV support reduced LV pressure, and elevated coronary pressure during the late diastolic phase, resulting in high coronary driving pressure. This study demonstrated for the first time that mechanical LV support extends diastolic phase, leading to increased infarct coronary flow. Future studies should evaluate the correlation between improved infarct coronary flow and resulting infarct size.

Impact of vessel volume on thermodilution measurements in patients with coronary microvascular dysfunction.

BACKGROUND: Two invasive methods are available to estimate microvascular resistance: bolus and continuous thermodilution. Comparative studies have revealed a lack of concordance between measurements of microvascular resistance obtained through these techniques. AIMS: This study aimed to examine the influence of vessel volume on bolus thermodilution measurements. METHODS: We prospectively included patients with angina with non-obstructive coronary arteries (ANOCA) undergoing bolus and continuous thermodilution assessments. All patients underwent coronary CT angiography to extract vessel volume. Coronary microvascular dysfunction was defined as coronary flow reserve (CFR) < 2.0. Measurements of absolute microvascular resistance (in Woods units) and index of microvascular resistance (IMR) were compared before and after volumetric adjustment. RESULTS: Overall, 94 patients with ANOCA were included in this study. The mean age was 64.7 ± 10.8 years, 48% were female, and 19% had diabetes. The prevalence of CMD was 16% based on bolus thermodilution, while continuous thermodilution yielded a prevalence of 27% (Cohen's Kappa 0.44, 95% CI 0.23-0.65). There was no correlation in microvascular resistance between techniques (r = 0.17, 95% CI -0.04 to 0.36, p = 0.104). The adjustment of IMR by vessel volume significantly increased the agreement with absolute microvascular resistance derived from continuous thermodilution (r = 0.48, 95% CI 0.31-0.63, p < 0.001). CONCLUSIONS: In patients with ANOCA, invasive methods based on coronary thermodilution yielded conflicting results for the assessment of CMD. Adjusting IMR with vessel volume improved the agreement with continuous thermodilution for the assessment of microvascular resistance. These findings strongly suggest the importance of considering vessel volume when interpreting bolus thermodilution assessment.

Quantitative myocardial perfusion in liver transplantation candidates: Poorly metabolized caffeine inhibition of vasodilatory stress.

BACKGROUND: Data on cardiac positron emission tomography (PET) in liver transplantation (LT) candidates are limited with no prior study accounting for poorly metabolized caffeine reducing stress perfusion. METHOD: Consecutive LT candidates (n = 114) undergoing cardiac rest/stress PET were instructed to abstain from caffeine for 2 days extended to 5 and 7 days. Due to persistently high prevalence of measurable blood caffeine after 5-day caffeine abstinence, dipyridamole (n = 41) initially used was changed to dobutamine (n = 73). Associations of absolute flow, coronary flow reserve (CFR), detectable blood caffeine, and Modified End-Stage Liver Disease (MELD) score for liver failure severity were evaluated. Coronary flow data of LT candidates were compared to non-LT control group (n = 102 for dipyridamole, n = 29 for dobutamine). RESULTS: Prevalence of patients with detectable blood caffeine was 63.3%, 36.7% and 33.3% after 2-, 5- and 7-day of caffeine abstinence, respectively. MELD score was associated with detectable caffeine (odd ratio 1.18,P < 0.001). CFR was higher during dipyridamole stress without-caffeine versus with-caffeine (2.22 ± 0.80 vs 1.55 ± 0.37,P = 0.048) but lower than dobutamine stress (2.22 ± 0.80 vs 2.82 ± 1.02,P = 0.026). Mediation analysis suggested that the dominant association between CFR and MELD score in dipyridamole group derived from caffeine-impaired CFR and liver failure/caffeine interaction. CFR in LT candidates was lower than non-LT control population in both dipyridamole and dobutamine group. CONCLUSION: We demonstrate exceptionally high prevalence of detectable blood caffeine in LT candidates undergoing stress PET myocardial perfusion imaging resulting in reduced CFR with dipyridamole compared to dobutamine. The delayed caffeine clearance in LT candidates makes dobutamine a preferred stress agent in this population.

Basal Coronary Microvascular Resistance Predicting Death and Heart Failure in Patients Without Functional Coronary Stenosis.

BACKGROUND: Abnormal coronary microcirculation is linked to poor patient prognosis, so the aim of the present study was to assess the prognostic relevance of basal microvascular resistance (b-IMR) in patients without functional coronary stenosis.Methods and Results: Analyses of 226 patients who underwent intracoronary physiological assessment of the left anterior descending artery included primary endpoints of all-cause death and heart failure, as well as secondary endpoints of cardiovascular death and atherosclerotic vascular events. During a median follow-up of 2 years, there were 12 (5.3%) primary and 21 (9.3 %) secondary endpoints. The optimal b-IMR cutoff for the primary endpoints was 47.1 U. Kaplan-Meier curve analysis demonstrated worse event-free survival of the primary endpoints in patients with a b-IMR below the cutoff (χ2=21.178, P<0.001). b-IMR was not significantly associated with the secondary endpoints (P=0.35). A low coronary flow reserve (CFR; <2.5) had prognostic value for both endpoints (primary endpoints: χ2=11.401, P=0.001; secondary endpoints: (χ2=6.015; P=0.014), and high hyperemic microvascular resistance (≥25) was associated only with the secondary endpoints (χ2=4.420; P=0.036). Incorporating b-IMR into a clinical model that included CFR improved the Net Reclassification Index and Integrated Discrimination Improvement for predicting the primary endpoints (P<0.001 and P=0.034, respectively). CONCLUSIONS: b-IMR may be a specific marker of the risk of death and heart failure in patients without functional coronary stenosis.

Cut-off value for interleukin-34 as an additional potential inflammatory biomarker for estimation of slow coronary flow risk.

BACKGROUND: Inflammatory markers may provide insights into the underlying mechanisms of slow coronary flow (SCF), including subclinical atherosclerosis and endothelial dysfunction. Interleukin-34 (IL-34), known for its role in immuno-inflammatory diseases, might hold significance in SCF. We aimed to explore the potential association between IL-34 and SCF in patients undergoing diagnostic elective coronary angiography. METHODS: This observational, cross-sectional study enrolled 256 participants: 124 with SCF and 132 with normal coronary flow (NCF). All participants had undergone outpatient coronary angiography for suspected coronary artery disease. SCF assessment employed the TIMI frame count (TFC) for quantifying coronary flow rate. RESULTS: SCF patients exhibited significantly elevated TFC in all three major coronary arteries compared to controls (p < 0.05). IL-34 displayed a noteworthy positive correlation with average TFC [for all participants: r = 0.514, p < 0.001; for SCF patients: r = 0.526, p < 0.001; for normal controls: r = -0.288, p > 0.05]. Similarly, high-sensitivity C-reactive protein (hsCRP) showed a significant and positive relationship with average TFC [for all participants: r = 0.504, p < 0.001; for SCF patients: r = 0.558, p < 0.001; for normal controls: r = -0.148, p > 0.05]. SCF patients presented coronary arteries of larger size compared to controls. CONCLUSION: Mean coronary diameter and IL-34 emerged as independent predictors of SCF. Additionally, hsCRP, mean coronary diameter, and IL-34 exhibited a positive correlation with mean TFC values. IL-34 appears to be a more effective indicator than hsCRP in SCF patients.

Triglyceride glucose-body mass index as a novel predictor of slow coronary flow phenomenon in patients with ischemia and nonobstructive coronary arteries (INOCA).

BACKGROUND: The triglyceride glucose-body mass index (TyG-BMI index) has been suggested as a novel predictor of insulin resistance. However, its predictive value for slow coronary flow phenomenon (SCFP) in patients with ischemia and nonobstructive coronary arteries (INOCA) remains unclear. METHODS: We consecutively recruited 1625 patients with INOCA from February 2019 to February 2023 and divided them into two groups based on thrombolysis in myocardial infarction (TIMI) frame counts (TFCs): the SCFP group (n = 79) and the control group. A 1:2 age-matched case-control study was then performed. The TyG-BMI index was calculated as ln [plasma triglyceride (mg/dL) × fasting blood glucose (mg/dL)/2] × BMI. RESULTS: TyG-BMI index in the SCFP group (218.3 ± 25.2 vs 201.0 ± 26.5, P < .001) was significantly higher than in the normal controls. TyG-BMI index also increased with the number of coronary arteries involved in the SCFP. Multivariate logistic regression analysis showed that TyG-BMI, BMI, and TG were independent predictors for SCFP. Receiver operating characteristic (ROC) curve analysis showed that when the TyG-BMI index was above 206.7, the sensitivity and specificity were 88.6% and 68.5%, respectively, with an AUC of 0.809 (95% CI: 0.756-0.863, P = .027). Combined BMI with TG, the TyG-BMI index had a better predictive value for SCFP than BMI and TG (P < .001). CONCLUSION: The TyG-BMI index was an independent predictor for SCFP in INOCA patients, and it had a better predictive value than BMI and TG.

Effects of left bundle branch block on echocardiographic coronary flow assessment: A systematic review.

This systematic review investigates the diagnostic and prognostic utility of coronary flow reserve (CFR) assessment through echocardiography in patients with left bundle branch block (LBBB), a condition known to complicate the clinical evaluation of coronary artery disease (CAD). The literature search was performed on PubMed, EMBASE, Web of Science, Scopus, and Google Scholar, was guided by PRISMA standards up to March 2024, and yielded six observational studies that met inclusion criteria. These studies involved a diverse population of patients with LBBB, employing echocardiographic protocols to clarify the impact of LBBB on coronary flow dynamics. The findings emphasize the importance of CFR in stratifying cardiovascular risk and guiding clinical decision-making in patients with LBBB. Pooled results reveal that patients with LBBB and significant left anterior descending (LAD) artery stenosis exhibited a marked decrease in stress-peak diastolic velocity (MD = -19.03 [-23.58; -14.48] cm/s; p < .0001) and CFR (MD = -.60 [-.71; -.50]; p < .0001), compared to those without significant LAD lesions, suggesting the efficacy of stress echocardiography CFR assessment in the identification of clinically significant CAD among the LBBB population. This review highlights the clinical relevance of echocardiography CFR assessment as a noninvasive tool for evaluating CAD and stratifying risk in the presence of LBBB and underscores the need for standardized protocols in CFR measurement.

Acute Hyperglycemia-Induced Injury in Myocardial Infarction.

Acute hyperglycemia is a transient increase in plasma glucose level (PGL) frequently observed in patients with ST-elevation myocardial infarction (STEMI). The aim of this review is to clarify the molecular mechanisms whereby acute hyperglycemia impacts coronary flow and myocardial perfusion in patients with acute myocardial infarction (AMI) and to discuss the consequent clinical and prognostic implications. We conducted a comprehensive literature review on the molecular causes of myocardial damage driven by acute hyperglycemia in the context of AMI. The negative impact of high PGL on admission recognizes a multifactorial etiology involving endothelial function, oxidative stress, production of leukocyte adhesion molecules, platelet aggregation, and activation of the coagulation cascade. The current evidence suggests that all these pathophysiological mechanisms compromise myocardial perfusion as a whole and not only in the culprit coronary artery. Acute hyperglycemia on admission, regardless of whether or not in the context of a diabetes mellitus history, could be, thus, identified as a predictor of worse myocardial reperfusion and poorer prognosis in patients with AMI. In order to reduce hyperglycemia-related complications, it seems rational to pursue in these patients an adequate and quick control of PGL, despite the best pharmacological treatment for acute hyperglycemia still remaining a matter of debate.

Implementation of Microcirculation Examination in Clinical Practice-Insights from the Nationwide POL-MKW Registry.

Background and Objectives: The assessment of coronary microcirculation may facilitate risk stratification and treatment adjustment. The aim of this study was to evaluate patients' clinical presentation and treatment following coronary microcirculation assessment, as well as factors associated with an abnormal coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) values. Materials and Results: This retrospective analysis included 223 patients gathered from the national registry of invasive coronary microvascular testing collected between 2018 and 2023. Results: The frequency of coronary microcirculatory assessments in Poland has steadily increased since 2018. Patients with impaired IMR (≥25) were less burdened with comorbidities. Patients with normal IMR underwent revascularisation attempts more frequently (11.9% vs. 29.8%, p = 0.003). After microcirculation testing, calcium channel blockers (CCBs) and angiotensin-converting enzyme inhibitors were added more often for patients with IMR and CFR abnormalities, respectively, as compared to control groups. Moreover, patients with coronary microvascular dysfunction (CMD, defined as CFR and/or IMR abnormality), regardless of treatment choice following microcirculation assessment, were provided with trimetazidine (23.2%) and dihydropyridine CCBs (26.4%) more frequently than those without CMD who were treated conservatively (6.8%) and by revascularisation (4.2% with p = 0.002 and 0% with p < 0.001, respectively). Multivariable analysis revealed no association between angina symptoms and IMR or CFR impairment. Conclusions: The frequency of coronary microcirculatory assessments in Poland has steadily increased. Angina symptoms were not associated with either IMR or CFR impairment. After microcirculation assessment, patients with impaired microcirculation, expressed as either low CFR, high IMR or both, received additional pharmacotherapy treatment more often.

Anxiety is associated with coronary microvascular dysfunction: Results from the CAMADA study.

OBJECTIVE: Coronary microvascular dysfunction (CMD) is an important component of ischemic heart disease. Here, we assessed the associations between anxiety/depression and CMD using coronary microvascular function indicators. METHODS: The study included 81 patients (26 males and 55 females) with nonobstructive coronary artery disease. The symptoms of anxiety and depression were measured with Self-rating Anxiety Scale and Self-rating Depression Scale. Coronary microvascular function was assessed using coronary flow reserve (CFR) measured by transthoracic Doppler echocardiography. RESULTS: The anxiety group had significantly lower CFR than that in the no-anxiety group (2.97 ± 0.63 vs. 3.40 ± 0.61, p = .029). In bivariate correlation analysis, anxiety was negatively associated with CFR (r = -.333, p = .002). In the multiple linear regression model, after adjusting for age, sex, BMI, hypertension, dyslipidemia, smoking status, and family history of premature coronary heart disease, anxiety was negatively associated with CFR (ß = -.314, p = .008). When both anxiety and depression were included in the multiple linear regression model, anxiety was also negatively associated with CFR (ß = -.345, p = .012). CONCLUSION: Anxiety patients had lower CFR, anxiety was independently associated with CFR. Psychological disorders may play an important role in coronary microvascular dysfunction.

Association of hydroxytyrosol enriched olive oil with vascular function in chronic coronary disease.

BACKGROUND: Hydroxytyrosol reduces low-density lipoprotein oxidation, contributing to prevention of atherosclerosis progression. METHODS: In a prospective, crossover, double-blind, placebo-controlled trial, 30 chronic coronary artery syndrome (CCAS) patients were randomized to 4 capsules/day, containing 412.5 mg olive oil with 2.5 mg hydroxytyrosol (OOHT) each one or placebo for 1 month and then were crossed over to the alternate treatment (placebo or OOHT). We measured (a) perfused boundary region (PBR) of the sublingual arterial microvessels (increased PBR indicates reduced glycocalyx thickness), (b) flow-mediated dilation (FMD), (c) Coronary Flow Reserve (CFR) and markers of LV diastolic function by Doppler echocardiography, (d) pulse wave velocity (PWV), and (e) oxidative stress, inflammatory biomarkers and blood lipids at baseline and after treatment. RESULTS: Treatment with OOHT improved PBR, FMD, CFR and PWV compared to baseline (1.8 ± .3 vs. 1.7 ± .4 µm, p = .040, 3.7 ± 2.1 vs. 6.5% ± 2.3%, p < .001, 2.3 ± .4 vs. 2.5 ± .4, p = .030 and 11.1 ± 1.8 vs. 11.8 ± 2.3 m/s, p = .002) while there was no effect after placebo (p = NS). No effect of OOHT treatment was observed on blood pressure. There was a parallel improvement of E' of the mitral annulus and deceleration time of the E wave of mitral inflow after OOHT (p < .05) but not after placebo. Compared to baseline, treatment with OOHT reduced malondialdehyde, a marker of lipid peroxidation, oxidized LDL, triglycerides, PCSK9 and CRP blood levels (p < .05) in contrast to placebo. CONCLUSIONS: Hydroxytyrosol-enriched olive oil may have beneficial effects on endothelial, arterial and LV diastolic function likely by reducing oxidative and inflammatory burden in CCAS, though further studies are needed to confirm this mechanism.

The prognostic value of CZT SPECT myocardial blood flow (MBF) quantification in patients with ischemia and no obstructive coronary artery disease (INOCA): a pilot study.

BACKGROUND: Despite the demonstrated adverse outcome, it is difficult to early identify the risks for patients with ischemia and no obstructive coronary artery disease (INOCA). We aimed to explore the prognostic potential of CZT SPECT in INOCA patients. METHODS: The study population consisted of a retrospective cohort of 118 INOCA patients, all of whom underwent CZT SPECT imaging and invasive coronary angiography (ICA). Dynamic data were reconstructed, and MBF was quantified using net retention model. Major adverse cardiovascular events (MACEs) were defined as cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, heart failure, late coronary revascularization, or hospitalization for unstable angina. RESULTS: During a median follow-up of 15 months (interquartile range (IQR) 11-20), 19 (16.1%) MACEs occurred; both stress myocardial blood flow (sMBF) ([Formula: see text]) and coronary flow reserve (CFR) ([Formula: see text]) were significantly lower in the MACE group. Optimal thresholds of sMBF<3.16 and CFR<2.52 were extracted from the ROC curves, and both impaired sMBF (HR: 15.08; 95% CI 2.95-77.07; [Formula: see text]) and CFR (HR: 6.51; 95% CI 1.43-29.65; [Formula: see text]) were identified as prognostic factors for MACEs. Only sMBF<3.16 (HR: 11.20; 95% CI 2.04-61.41; [Formula: see text]) remained a robust predictor when sMBF and CFR were integrated considered. Compared with CFR, sMBF provides better prognostic model discrimination and reclassification ability (C-index improvement = 0.06, [Formula: see text]; net reclassification improvement (NRI) = 0.19; integrated discrimination improvement (IDI) = 0.10). CONCLUSION: The preliminary results demonstrated that quantitative analysis on CZT SPECT provides prognostic value for INOCA patients, which may allow the stratification for early prevention and intervention.

Coronary Microvascular Dysfunction: What Clinicians and Investigators Should Know.

PURPOSE OF REVIEW: Abnormal structure and function of the coronary microvasculature have been implicated in the pathophysiology of multiple cardiovascular disease processes. This article reviews recent research progress related to coronary microvascular dysfunction (CMD) and salient clinical takeaways. RECENT FINDINGS: CMD is prevalent in patients with signs and symptoms of ischemia and no obstructive epicardial coronary artery disease (INOCA), particularly in women. CMD is associated with adverse outcomes, including most frequently the development of heart failure with preserved ejection fraction. It is also associated with adverse outcomes in patient populations including hypertrophic cardiomyopathy, dilated cardiomyopathy, and acute coronary syndromes. In patients with INOCA, stratified medical therapy guided by invasive coronary function testing to define the subtype of CMD leads to improved symptoms. There are invasive and non-invasive methodologies to diagnose CMD that provide prognostic information and mechanistic information to direct treatment. Available treatments improve symptoms and myocardial blood flow; ongoing investigations aim to develop therapy to improve adverse outcomes related to CMD.

Potential of non-contrast stress T1 mapping for the assessment of myocardial injury in hypertrophic cardiomyopathy.

BACKGROUND: Ischemia of the hypertrophied myocardium due to microvascular dysfunction is related to a worse prognosis in hypertrophic cardiomyopathy (HCM). Stress and rest T1 mapping without contrast agents can be used to assess myocardial blood flow. Herein, we evaluated the potential of non-contrast stress T1 mapping in assessing myocardial injury in patients with HCM. METHODS: Forty-five consecutive subjects (31 HCM patients and 14 control subjects) underwent cardiac magnetic resonance (CMR) at 3T, including cine imaging, T1 mapping at rest and during adenosine triphosphate (ATP) stress, late gadolinium enhancement (LGE), and phase-contrast (PC) cine imaging of coronary sinus flow at rest and during stress to assess coronary flow reserve (CFR). PC cine imaging was performed on 25 subjects (17 patients with HCM and 8 control subjects). Native T1 values at rest and during stress were measured using the 16-segment model, and T1 reactivity was defined as the change in T1 values from rest to stress. RESULTS: ATP stress induced a significant increase in native T1 values in both the HCM and control groups (HCM: p < 0.001, control: p = 0.002). T1 reactivity in the HCM group was significantly lower than that in the control group (4.2 ± 0.3% vs. 5.6 ± 0.5%, p = 0.044). On univariate analysis, T1 reactivity correlated with native T1 values at rest, left ventricular mass index, and CFR. Multiple linear regression analysis demonstrated that only CFR was independently correlated with T1 reactivity (ß = 0.449; 95% confidence interval, 0.048-0.932; p = 0.032). Furthermore, segmental analysis showed decreased T1 reactivity in the hypertrophied myocardium and the non-hypertrophied myocardium with LGE in the HCM group. CONCLUSIONS: T1 reactivity was lower in the hypertrophied myocardium and LGE-positive myocardium compared to non-injured myocardium. Non-contrast stress T1 mapping is a promising CMR method for assessing myocardial injury in patients with HCM. Trial registration Retrospectively registered.

Coronary flow reserve evaluated by phase-contrast cine cardiovascular magnetic resonance imaging of coronary sinus: a meta-analysis.

BACKGROUND: Phase-contrast cine cardiovascular magnetic resonance (CMR) of the coronary sinus has emerged as a non-invasive method for measuring coronary sinus blood flow and coronary flow reserve (CFR). However, its clinical utility has not yet been established. Here we performed a meta-analysis to clarify the clinical value of CMR-derived CFR in various cardiovascular diseases. METHODS: An electronic database search was performed of PubMed, Web of Science Core Collection, Cochrane Advanced Search, and EMBASE. We compared the CMR-derived CFR of various cardiovascular diseases (stable coronary artery disease [CAD], hypertrophic cardiomyopathy [HCM], dilated cardiomyopathy [DCM]) and control subjects. We assessed the prognostic value of CMR-derived CFR for predicting major adverse cardiac events (MACE) in patients with stable CAD. RESULTS: A total of 47 eligible studies were identified. The pooled CFR from our meta-analysis was 3.48 (95% confidence interval [CI], 2.98-3.98) in control subjects, 2.50 (95% CI, 2.38-2.61) in stable CAD, 2.01 (95% CI, 1.70-2.32) in cardiomyopathies (HCM and DCM). The meta-analysis showed that CFR was significantly reduced in stable CAD (mean difference [MD] = -1.48; 95% CI, -1.78 to -1.17; p < 0.001; I2 = 0%; p for heterogeneity = 0.33), HCM (MD = -1.20; 95% CI, -1.63 to -0.77; p < 0.001; I2 = 0%; p for heterogeneity = 0.49), and DCM (MD = -1.53; 95% CI, -1.93 to -1.13; p < 0.001; I2 = 0%; p for heterogeneity = 0.45). CMR-derived CFR was an independent predictor of MACE for patients with stable CAD (hazard ratio = 0.52 per unit increase; 95% CI, 0.37-0.73; p < 0.001; I2 = 84%, p for heterogeneity < 0.001). CONCLUSIONS: CMR-derived CFR was significantly decreased in cardiovascular diseases, and a decreased CFR was associated with a higher occurrence of MACE in patients with stable CAD. These results suggest that CMR-derived CFR has potential for the pathological evaluation of stable CAD, cardiomyopathy, and risk stratification in CAD.

Complementary prognostic value of stress perfusion imaging and global coronary flow reserve derived from cardiovascular magnetic resonance: a long-term cohort study.

BACKGROUND: Phase-contrast cine cardiovascular magnetic resonance (CMR) quantifies global coronary flow reserve (CFR) by measuring blood flow in the coronary sinus (CS), allowing assessment of the entire coronary circulation. However, the complementary prognostic value of stress perfusion CMR and global CFR in long-term follow-up has yet to be investigated. This study aimed to investigate the complementary prognostic value of stress myocardial perfusion imaging and global CFR derived from CMR in patients with suspected or known coronary artery disease (CAD) during long-term follow-up. METHODS: Participants comprised 933 patients with suspected or known CAD who underwent comprehensive CMR. Major adverse cardiac events (MACE) comprised cardiac death, non-fatal myocardial infarction, unstable angina, hospitalization for heart failure, stroke, ventricular arrhythmia, and late revascularization. RESULTS: During follow-up (median, 5.3 years), there were 223 MACE. Kaplan-Meier curve analysis revealed a significant difference in event-free survival among tertile groups for global CFR (log-rank, p < 0.001) and between patients with and without ischemia (p < 0.001). The combination of stress perfusion CMR and global CFR enhanced risk stratification (p < 0.001 for overall), and prognoses were comparable between the subgroup with ischemia and no impaired CFR and the subgroup with no ischemia and impaired CFR (p = 0.731). Multivariate Cox proportional hazard regression analysis showed that impaired CFR remained a significant predictor for MACE (hazard ratio, 1.6; p = 0.002) when adjusted for coronary risk factors and CMR predictors, including ischemia. The addition of impaired CFR to coronary risk factors and ischemia significantly increased the global chi-square value from 88 to 109 (p < 0.001). Continuous net reclassification improvement and integrated discrimination with the addition of global CFR to coronary risk factors plus ischemia improved to 0.352 (p < 0.001) and 0.017 (p < 0.001), respectively. CONCLUSIONS: During long-term follow-up, stress perfusion CMR and global CFR derived from CS flow measurement provided complementary prognostic value for prediction of cardiovascular events. Microvascular dysfunction or diffuse atherosclerosis as shown by impaired global CFR may play a role as important as that of ischemia due to epicardial coronary stenosis in the risk stratification of CAD patients.

Dose-consistent dynamic SPECT.

BACKGROUND: Coronary flow reserve (CFR) values measured by dynamic SPECT systems are typically consistent with other modalities (e.g., PET). However, large discrepancies are often observed for individual patients. Positioning of the region-of-interest (ROI), representing the arterial input function (AIF) could explain some of these discrepancies. We explored the possibility of positioning the ROI in a manner that evaluates its consistency with patient-based injected radiotracer doses. METHODS: Dose-consistent dynamic SPECT methodology was introduced, and its application was demonstrated in a twenty-patient clinical study. The effect of various ROI positions was investigated and comparison to myocardial perfusion imaging was performed. RESULTS: Mean AIF ratios were consistent with the injected dose ratios for all examined ROI positions. Good agreement (> 80%) between total perfusion deficit and CFR was found in the detection of obstructive CAD patients for all ROIs considered. However, for individual patients, significant dependence on ROI position was observed (altering CFR by typically 30%). The proposed methodology's uncertainty was evaluated (~ 7%) and found to be smaller than the variability due to choice of ROI position. CONCLUSION: Dose-consistent dynamic SPECT may contribute to evaluating uncertainty of CFR measurements and may potentially decrease uncertainty by allowing improved ROI positioning for individual patients.

Coronary microvascular disease in hypertrophic and infiltrative cardiomyopathies.

Pathologic hypertrophy of the cardiac muscle is a commonly encountered phenotype in clinical practice, associated with a variety of structural and non-structural diseases. Coronary microvascular disease is considered to play an important role in the natural history of this pathological phenotype. Non-invasive imaging modalities, most prominently positron emission tomography and cardiac magnetic resonance, have provided insights into the pathophysiological mechanisms of the interplay between hypertrophy and the coronary microvasculature. This article summarizes the current knowledge on coronary microvascular dysfunction in the most frequently encountered forms of pathologic hypertrophy.

Prognostic Implications of Fractional Flow Reserve and Coronary Flow Reserve After Drug-Eluting Stent Implantation.

BACKGROUND: Fractional flow reserve (FFR) after percutaneous coronary intervention (PCI) provides prognostic information, but limited data are available regarding prognostication using post-PCI coronary flow reserve (CFR). In this study we aimed to assess the prognostic value of post-procedural FFR and CFR for target vessel failure (TVF) after PCI.Methods and Results: This lesion-based post-hoc pooled analysis of previously published registry data involved 466 patients with chronic coronary syndrome with single-vessel disease who underwent pre- and post-PCI FFR and CFR measurements, and were followed-up to determine the predictors of TVF. The prognostic value of post-PCI CFR and FFR was compared with that of FFR or CFR alone. Post-PCI FFR/CFR discordant results were observed in 42.5%, and 10.3% of patients had documented TVF. Receiver-operating characteristic curve analysis revealed that the optimal cutoff values of post-PCI FFR and CFR to predict the occurrence of TVF were 0.85 and 2.26, respectively. Significant differences in TVF were detected according to post-PCI FFR (≤0.85 vs. >0.85, P=0.007) and post-PCI CFR (<2.26 vs. ≥2.26, P<0.001). Post-PCI FFR ≤0.85 and post-PCI CFR <2.26 were independent prognostic predictors. CONCLUSIONS: After PCI completion, discordant results between FFR and CFR were not uncommon. Post-PCI CFR categorization showed incremental prognostic value for predicting TVF independent of post-PCI FFR risk stratification.