Myocardial Blood Flow In Patients Research Articles

Quantitative Coronary Computed Tomography Angiography And Dynamic Czt Spect Derived Myocardial Blood Flow In Patients With Non-obstructive Coronary Artery Disease

Quantitative Coronary Computed Tomography Angiography And Dynamic Czt Spect Derived Myocardial Blood Flow In Patients With Non-obstructive Coronary Artery Disease

Changes in myocardial perfusion after coronary sinus reducer implantation for refractory angina - assessment using fully automated quantitative stress perfusion cardiac MRI

Abstract Introduction Previous reports show angina improvement after Coronary Sinus Reducer (CSR) implantation [1,2]. However, the mechanistic basis remains unconfirmed. Preliminary studies using semi-quantitative metrics derived from stress perfusion cardiac MRI (CMR), have suggested improved myocardial perfusion particularly in ischaemic segments [3]. To date, assessment by fully automated quantitative myocardial perfusion CMR has not been reported. Purpose To assess the effect of CSR implantation on quantitative regional myocardial blood flow in patients with refractory angina and advanced coronary artery disease (CAD). Methods Prospective cohort study of patients undergoing CSR implantation. CMR was performed at baseline and median 7 months follow-up. Automated segmentation into a 16-segment American Heart Association model was performed to quantify segmental rest and stress myocardial blood flow (MBF, ml/min/g) and myocardial perfusion reserve (MPR). Rest MBF was corrected for heart rate by dividing by the scan heart rate and multiplying by the mean resting heart rate among all subjects. Wilcoxon matched-pairs sign rank tests were used to compare paired global and segmental perfusion values. A linear mixed-effects model with random slopes and intercepts was used to assess the relationship between baseline segmental MPR and associated change in MPR (ΔMPR) after CSR implantation. Results 12 patients (10M:2F; mean age 67) were included. Median Canadian Cardiovascular Society class was 3. Globally, there was no change in rest (P=0.90), stress MBF (P=0.34) or MPR (P=0.72) from baseline to follow-up. However, ΔMPR was related to the degree of baseline ischaemia (panel A). Segments with baseline MPR<2.45 increased in MPR whereas segments with baseline MPR ≥2.45 experienced a decrease (P=0.003, conditional R2: 0.81). In segments with MPR<2.45 (n=138), median ΔMPR was +0.18 (15.4%; P<0.0001); whereas with MPR≥2.45 (n=52) it was -0.41 (-12.7%; P=0.03; panel B). When assessed by myocardial layer, significant increases in MPR were observed in both subendocardial (+0.19 [15.6%]; P<0.0001) and subepicardial (+0.19 [12.3%]; P<0.0002) segments with baseline MPR< 2.45 (panel C). Conversely, in segments with baseline MPR≥2.45, there was a significant reduction in MPR in the subendocardium (-0.43 [-15.9%]; P=0.04) but not in the subepicardium (-0.36 [-9.90%]; P=0.08; panel D). Conclusion To our knowledge, this is the first study showing changes in quantitative myocardial perfusion after CSR implantation by fully automated inline quantitative perfusion CMR. Our analysis shows a relationship between baseline MPR and change in MPR after CSR implantation, supporting redistribution of perfusion into both subendocardial and subepicardial layers as potential mechanisms of action of CSR. Further studies are needed to confirm these preliminary results.

Abstract 13848: Time to Coronary Angiography in Patients With NSTE-ACS is Longer in Women as Compared to Men

Introduction: Timely invasive coronary angiography (ICA) to restore myocardial blood flow in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS) improves prognosis and reduces morbidity and mortality. NSTE-ACS practice guidelines recommend ICA <2 hours [hrs] (very high-risk) or <24 hrs (high-risk). Troponin is useful for guiding timing of ICA. However, there is little evidence comparing time to troponin and ICA in women vs. men, which could uncover important treatment differences. Therefore, the purpose of this study was to examine time to ICA and first troponin in women vs. men in a cohort of hospitalized NTSE-ACS patients. Methods: Secondary data analysis in 121 patients with NSTE-ACS; women ( n =41, 34%) vs. men ( n =80, 66%), who underwent ICA and had a troponin test. Variables of interest were obtained from the electronic health record. Results: Compared to men, women were older (67±12 vs. 62±11 years, p =0.039), had a higher proportion of diabetes (44% vs. 19%, p =0.006), and were non-smokers (61% vs. 31%, p =0.013). Time, in minutes , to first troponin did not differ between women vs. men (81.53±261.04 vs . 33.49±107.20, p =0.167), when including one outlier (one woman). Excluding this outlier, it remained non-significant (44.43±127.66 vs. 33.49±107.20, p =0.167). Overall, the time to ICA, in hours , was longer in women than men (24.01±27.64 vs. 13.83±12.89, p= 0.007). The first troponin was positive in 26 women (67%) and 53 men (69%), p =0.98; however, time to ICA, in hours , was longer in women vs. men (21.55±20.26 vs. 12.56±11.41, p= 0.014). Conclusions: In patients with confirmed NSTE-ACS, time from admission to ICA was nearly twice as long in women as compared to men. One explanation could be symptoms differences and should be explored further. Time from admission to first troponin was not statistically different (with and without oulier [one women]). Despite an equivalent rate of the first troponin being positive, time to ICA was on average 9 hours longer in women vs. men. Future studies in a larger cohort(s) using contemporary data are needed to explore possible reasons for ICA delay (symptoms and clinical characteristics) to confirm if similar trends persists and whether short- and long-term outcomes are different by sex.

A retrospective evaluation of Bayesian-penalized likelihood reconstruction for [15O]H2O myocardial perfusion imaging

BackgroundNew Block-Sequential-Regularized-Expectation-Maximization (BSREM) image reconstruction technique has been introduced for clinical use mainly for oncologic use. Accurate and quantitative image reconstruction is essential in myocardial perfusion imaging with positron emission tomography (PET) as it utilizes absolute quantitation of myocardial blood flow (MBF). The aim of the study was to evaluate BSREM reconstruction for quantitation in patients with suspected coronary artery disease (CAD). Methods and ResultsWe analyzed cardiac [15O]H2O PET studies of 177 patients evaluated for CAD. Differences between BSREM and Ordered-Subset-Expectation-Maximization with Time-Of-Flight (TOF) and Point-Spread-Function (PSF) modeling (OSEM-TOF-PSF) in terms of MBF, perfusable tissue fraction, and vascular volume fraction were measured. Classification of ischemia was assessed between the algorithms. OSEM-TOF-PSF and BSREM provided similar global stress MBF in patients with ischemia (1.84 ± 0.21 g⋅ml−1⋅min−1 vs 1.86 ± 0.21 g⋅ml−1⋅min−1) and no ischemia (3.26 ± 0.34 g⋅ml−1⋅min−1 vs 3.28 ± 0.34 g⋅ml−1⋅min−1). Global resting MBF was also similar (0.97 ± 0.12 g⋅ml−1⋅min−1 and 1.12 ± 0.06 g⋅ml−1⋅min−1). The largest mean relative difference in MBF values was 7%. Presence of myocardial ischemia was classified concordantly in 99% of patients using OSEM-TOF-PSF and BSREM reconstructions ConclusionOSEM-TOF-PSF and BSREM image reconstructions produce similar MBF values and diagnosis of myocardial ischemia in patients undergoing [15O]H2O PET due to suspected obstructive coronary artery disease

Myocardial ischaemia in cardiac amyloidosis: a change of perspective

Abstract Introduction Cardiac involvement is the main driver of clinical outcomes in systemic amyloidosis; however many clinical observations are not explained by the concept of replacement of the interstitium by amyloid material. Preliminary studies support the hypothesis that myocardial ischaemia contributes to cellular damage. Purpose This study assesses the presence and mechanisms of myocardial ischaemia using cardiovascular magnetic resonance (CMR) with multiparametric mapping and histopathological assessment. Methods Ninety-two patients with cardiac amyloidosis (CA) (AL = 41, ATTR = 51) and 97 without CA (3-vessel coronary disease (3VD) = 47, unobstructed coronary arteries = 26, healthy volunteers (HV) = 24) underwent quantitative stress perfusion CMR with myocardial blood flow (MBF) mapping. Twenty-six myocardial biopsies and 3 explanted hearts with CA were analysed histopathologically. Results Stress MBF was severely reduced in patients with CA with lower values than patients with 3VD, unobstructed coronary arteries and HV (CA = 1.03±0.51 ml/min/g, 3VD = 1.35±0.50 ml/min/g, Unobstructed coronaries = 2.92±0.52 ml/min/g, HV = 3.14±0.69 ml/min/g; CA vs 3VD p=0.008, CA vs Unobstructed coronaries p<0.001, CA vs HV p<0.001). After adjustment for intracellular volume the MBF in patients with CA remained significantly lower than in HV (stress MBF/ICV: AL = 2.24±1.12, ATTR = 2.22±0.93, HV = 4.38±1.06; AL vs. ATTR p=1.000, AL vs HV p<0.001, ATTR vs. HV p<0.001). Myocardial perfusion reserve (MPR) was severely reduced in CA patients, compared to HV and patients with unobstructed coronary arteries, with the degree of reduction being comparable only to patients with 3VD (CA = 1.55±0.60, 3VD = 1.54±0.51, unobstructed coronaries = 2.78±0.70, HV = 4.08±0.86; CA vs 3VD p=1.000, CA vs unobstructed coronary arteries p<0.001, CA vs. HV p<0.001). Myocardial perfusion abnormalities correlated with amyloid burden, systolic and diastolic function, structural parameters and blood biomarkers (p<0.05). Biopsies demonstrated diffuse hypoxia with abnormal VEGF staining in cardiomyocytes and endothelial cells. Amyloid infiltration in intramural arteries was associated with severe lumen reduction in 20% of vessels, and severe reduction in capillary density. Conclusion CA is associated with severe myocardial ischaemia demonstrable by histology and CMR stress perfusion mapping. Histological evaluation indicates a complex pathophysiology, where systolic and diastolic dysfunction, amyloid infiltration of the epicardial arteries and disruption and rarefaction of the capillaries play a role in contributing to myocardial ischaemia. Funding Acknowledgement Type of funding sources: None.

Quantitative myocardial blood flow as a prognostic marker for cardiovascular outcomes in patients with Type 2 Diabetes Mellitus: a multicentre study

Abstract   Introduction: Patients with Type 2 Diabetes Mellitus (T2DM) are at increased risk of cardiovascular disease, including epicardial coronary heart disease, silent myocardial infarction (MI), and coronary microvascular dysfunction (CMD) [1]. All of these can be assessed and quantified using cardiac magnetic resonance (CMR), including most recently quantitative myocardial blood flow (MBF). We aimed to determine the prognostic relevance of MBF in patients with T2DM and test the hypothesis that impaired stress MBF and myocardial perfusion reserve (MPR) have independent prognostic value over standard clinical and imaging parameters. Methods A 4-centre study of patients with T2DM who underwent quantitative perfusion assessment using CMR. Diagnosis of T2DM was based on Hba1c >48mmol/l or a known diagnosis of T2DM. Image analysis was performed automatically using an artificial intelligence approach deriving global MBF and MPR [2]. Cox proportional hazard models adjusting for comorbidities and CMR parameters sought associations between stress MBF and MPR with death and major adverse cardiovascular events (MACE), including MI, non-fatal stroke, heart failure hospitalisation and death. Results A total of 630 patients with T2DM were included with a median follow-up of 722 days (interquartile range 493) days. There were 27 (4.3%) deaths and 76 MACE events in 62 (12.1%) patients. Patient data was represented into groups depending on threshold stress MBF values of 1.94ml/g/min and MPR thresholds of 1.96 using validated data from invasive coronary physiology [3]. Patient demographics and CMR data are seen in table 1. Kaplan-Meier curves are seen in figure 1. Stress MBF was associated with mortality and MACE after adjusting for age, LV ejection fraction and HbA1c. The stress MBF adjusted hazard ratios for all cause death and death and MACE were 0.35 (95% CI, 0.13–0.95, P=0.04) and 0.54 (95% CI, 0.30–0.96, P=0.04), respectively. MPR was not significantly associated with death and MACE after adjusting for age, LV ejection fraction and HbA1c; hazard ratio for all cause death and death and MACE was 0.83 (95% CI, 0.41–1.69, P=0.60) and 0.81 (95% CI, 0.53–1.23, p=0.32) respectively. Conclusion In patients with T2DM, reduced stress MBF measured automatically inline using artificial intelligence quantification of cardiovascular magnetic resonance perfusion mapping provides a strong, independent predictor of adverse cardiovascular outcome. Funding Acknowledgement Type of funding sources: Other. Main funding source(s): 1. REC ID 14/EE/0007 (Barts Heart Centre funding). 2. For PREDICT (Leicester data) ethical approval was provided by the UK Health Research Authority Research Ethics Committee (reference 17/WM/0192). 3. MATCH Study, Leeds - British Heart Foundation - 17/YH/0300. 4. LEAN-DM, Leeds - British Heart Foundation - 18/YH/01685. CEED, Leeds: British Heart Foundation - REC reference - 18/YH/0190

Coronary artery calcium burden, carotid atherosclerotic plaque burden, and myocardial blood flow in patients with end-stage renal disease: A non-invasive imaging study combining PET/CT and 3D ultrasound

BackgroundImaging-based measures of atherosclerosis such as coronary artery calcium score (CACS) and coronary flow reserve (CFR) as well as carotid atherosclerotic plaque burden (cPB) are predictors of cardiovascular events in the general population. The objective of this study was to correlate CACS, cPB, myocardial blood flow (MBF), and CFR in patients with end-stage renal disease (ESRD). Methods and results39 patients (mean age 53 ± 12 years) with ESRD prior to kidney transplantation were enrolled. MBF and CFR were quantified at baseline and under hyperemia by 13N-NH3-PET/CT. CACS was calculated from low-dose CT scans acquired for PET attenuation correction. cPB was assessed by 3D ultrasound. Uni- and multivariate regression analyses between these and clinical parameters were performed. Median follow-up time for clinical events was 4.4 years. Kaplan–Meier survival estimates with log-rank test were performed with regards to cardiovascular (CV) events and death of any cause. CACS and cPB were associated in ESRD patients (r = 0.48; p ≤ 0.01). While cPB correlated with age (r = 0.43; p < 0.01), CACS did not. MBFstress was negatively associated with age (r = 0.44; p < 0.01) and time on dialysis (r = 0.42; p < 0.01). There were negative correlations between MBFstress and CACS (r = − 0.62; p < 0.001) and between MBFstress and cPB (r = − 0.43; p < 0.01). Age and CACS were the strongest predictors for MBFstress. CFR was impaired (< 2.0) in eight patients who also presented with higher cPB and higher CACS compared to those with a CFR > 2.0 (p = 0.06 and p = 0.4). In contrast to MBFstress, there was neither a significant correlation between CFR and CACS (r = − 0.2; p = 0.91) nor between CFR and cPB (r = − 0.1; p = 0.55). CV event-free survival was associated with reduced CFR and MBFstress (p = 0.001 and p < 0.001) but not with cPB or CACS. ConclusionsCACS, cPB, and MBFstress are associated in patients with ESRD. Atherosclerosis is earlier detected by MBFstress than by CFR. CV event-free survival is associated with impaired CFR and MBFstress.

Hyperemic myocardial blood flow in patients with atrial fibrillation before and after catheter ablation: A dynamic stress CT perfusion study.

BackgroundAtrial fibrillation (AF) patients without coronary artery stenosis often show clinical evidence of ischemia. However myocardial perfusion in AF patients has been poorly studied. The purposes of this study were to investigate altered hyperemic myocardial blood flow (MBF) in patients with AF compared with risk‐matched controls in sinus rhythm (SR), and to evaluate hyperemic MBF before and after catheter ablation using dynamic CT perfusion.MethodsHyperemic MBF was quantified in 87 patients with AF (44 paroxysmal, 43 persistent) scheduled for catheter ablation using dynamic CT perfusion, and compared with hyperemic MBF in 87 risk‐matched controls in SR. Follow‐up CT after ablation was performed in 49 AF patients.ResultsPrior to ablation, hyperemic MBF of patients in AF during the CT (1.29 ± 0.34 ml/mg/min) was significantly lower than in patients in SR (1.49 ± 0.26 ml/g/min, p = 0.002) or matched controls (1.65 ± 0.32 ml/g/min, p < 0.001); no significant difference was seen between patients in SR during the CT and matched controls (vs. 1.50 ± 0.31 ml/g/min, p = 0.815). In patients in AF during the pre‐ablation CT (n = 24), hyperemic MBF significantly increased after ablation from 1.30 ± 0.35 to 1.53 ± 0.17 ml/g/min (p = 0.004); whereas in patients in SR during the pre‐ablation CT (n = 25), hyperemic MBF did not change significantly after ablation (from 1.46 ± 0.26 to 1.49 ± 0.27 ml/g/min, p = 0.499).ConclusionIn the current study using stress perfusion CT, hyperemic MBF in patients with AF during pre‐ablation CT was significantly lower than that in risk‐matched controls, and improved significantly after restoration of SR by catheter ablation, indicating that MBF abnormalities in AF patients are caused primarily by AF itself.

Amiodarone attenuates cardiac Rubidium-82 in consecutive PET/CT scans in a rodent model

BackgroundRisk stratification and diagnosis using Rubidium-82 (82Rb) positron emission tomography (PET) is a routine clinical approach in coronary artery disease (CAD). Various drugs are used to treat CAD; however, whether any of them change the uptake of 82Rb in the heart has not been investigated. The aim of this study is to determine whether drugs used in treatment of CAD affect the uptake of 82Rb in the heart in healthy rats. MethodsSeventy-seven Sprague-Dawley rats were included in the cross-sectional study. All rats underwent baseline 82Rb PET/CT and divided into eleven groups treated with different drugs. One group was control group (no treatment), eight groups were treated with monotherapy (amiodarone, acetylsalicylic acid (ASA), clopidogrel, ticagrelor, atorvastatin, enalapril, amlodipine, metoprolol succinate), and two groups were treated with polypharmacy (ASA, ticagrelor, atorvastatin, amlodipine or ASA, clopidogrel, atorvastatin, amlodipine). Once a day, they were administered pharmacological therapy through oral gavage, and on day seven, follow-up scanned with 82Rb PET/CT. ResultsIn the control group without pharmacological treatment, no difference in the standard uptake value (SUV) ratio between heart and muscle from baseline to follow-up (5.8 vs 7.0, P = .3) was found. The group treated with amiodarone had a significantly reduced SUV ratio from baseline to follow-up (5.8 vs 5.1, P = .008). All other drugs investigated had no difference in SUV ratio from baseline to follow-up. ConclusionIn this study, we showed that drugs normally used to treat CAD do not affect the uptake of 82Rb. However, amiodarone result in a significantly lowered 82Rb uptake, compared to control. This information about amiodarone would probably not change the size assessment of a myocardial perfusion defect in a clinical setting. However, it could change the kinetic parameters when assessing absolute myocardial blood flow in patients treated with amiodarone.

Extensive and balanced reduction of myocardial blood flow in patients with suspected obstructive coronary artery disease: 15O-water PET study

BackgroundDetection of obstructive coronary artery disease (CAD) by stress myocardial perfusion imaging (MPI) is conventionally based on relative differences in perfusion. This may lead to either underestimation of the extent of myocardial ischemia, or the ischemia might be completely missed in case of balanced perfusion reduction. Using absolute quantification of myocardial blood flow (MBF) by positron emission tomography (PET), we evaluated how common are extensive and balanced myocardial perfusion abnormalities in symptomatic patients with suspected obstructive CAD. Methods and resultsAmong 758 consecutive symptomatic patients undergone coronary computed tomography angiography (CTA), 286 patients subsequently underwent quantitative 15O-water adenosine-stress PET MPI to assess the hemodynamic significance of suspected obstructive stenosis. Out of these, 46 (16%) patients had reduced (≤2.3 ml/g/min) absolute stress MBF in all three standard coronary territories (LAD, LCX, RCA). Subsequently, relative stress MBF in each coronary territory was calculated, considering a territory with the highest absolute stress MBF as a reference region. Among the 46 patients, 72% had significant regional heterogeneity in myocardial perfusion (defined as having ≥1 territory with relative stress MBF <80%) while the remaining 28% (4.5% of the whole MPI cohort) showed balanced perfusion reduction (all relative MBF values ≥80%). ConclusionsAmong symptomatic patients with suspected obstructive stenosis on coronary CTA, quantitative PET revealed that 16% of patients had reduced stress MBF involving all three coronary artery territories, of whom approximately one third showed balanced reduction. Thus, in 4.5% of the patients the perfusion abnormalities could have been missed by conventional relative MPI analysis.

A comparison of standard and high dose adenosine protocols in routine vasodilator stress cardiovascular magnetic resonance: dosage affects hyperaemic myocardial blood flow in patients with severe left ventricular systolic impairment

BackgroundAdenosine stress perfusion cardiovascular magnetic resonance (CMR) is commonly used in the assessment of patients with suspected ischaemia. Accepted protocols recommend administration of adenosine at a dose of 140 µg/kg/min increased up to 210 µg/kg/min if required. Conventionally, adequate stress has been assessed using change in heart rate, however, recent studies have suggested that these peripheral measurements may not reflect hyperaemia and can be blunted, in particular, in patients with heart failure. This study looked to compare stress myocardial blood flow (MBF) and haemodynamic response with different dosing regimens of adenosine during stress perfusion CMR in patients and healthy controls.Methods20 healthy adult subjects were recruited as controls to compare 3 adenosine perfusion protocols: standard dose (140 µg/kg/min for 4 min), high dose (210 µg/kg/min for 4 min) and long dose (140 µg/kg/min for 8 min). 60 patients with either known or suspected coronary artery disease (CAD) or with heart failure and different degrees of left ventricular (LV) dysfunction underwent adenosine stress with standard and high dose adenosine within the same scan. All studies were carried out on a 3 T CMR scanner. Quantitative global myocardial perfusion and haemodynamic response were compared between doses.ResultsIn healthy controls, no significant difference was seen in stress MBF between the 3 protocols. In patients with known or suspected CAD, and those with heart failure and mild systolic impairment (LV ejection fraction (LVEF) ≥ 40%) no significant difference was seen in stress MBF between standard and high dose adenosine. In those with LVEF < 40%, there was a significantly higher stress MBF following high dose adenosine compared to standard dose (1.33 ± 0.46 vs 1.10 ± 0.47 ml/g/min, p = 0.004). Non-responders to standard dose adenosine (defined by an increase in heart rate (HR) < 10 bpm) had a significantly higher stress HR following high dose (75 ± 12 vs 70 ± 14 bpm, p = 0.034), but showed no significant difference in stress MBF.ConclusionsIncreasing adenosine dose from 140 to 210 µg/kg/min leads to increased stress MBF in patients with significantly impaired LV systolic function. Adenosine dose in clinical perfusion assessment may need to be increased in these patients.

Evaluation of effects of cardiac resynchronization on coronary blood flow by coronary flow reserve and in patients with İdiopathic dilated cardiomyopathy: Does it predict the response?

Background: The results of previous studies evaluating the effects of cardiac resynchronization therapy (CRT) on myocardial blood flow (MBF) and their relation with the response to CRT are conflicting. Materials and Methods: Sixty-one patients diagnosed with idiopathic dilated cardiomyopathy (IDC), a functional capacity (New York Heart Association [NYHA]) Class II or III, and left bundle branch block (LBBB) (QRS width >150 ms) were enrolled in the study. We aimed to evaluate the effects of CRT on MBF in patients with IDC and LBBB by coronary flow reserve (CFR) measurements and thereby tried to predict the responders. Results: Sixty-one patients with IDC were enrolled. CFR and hyperemic fractional flow reserve (FFR) increased after CRT. The only parameter affecting the increase in CFR was the change in FFR after CRT. Then, 44 patients who responded to the CRT treatment at 6 months were compared with 17 patients who did not. Left ventricle outflow tract time-velocity integral (LVOT-TVI), stroke volume (SV) and cardiac output index (COi) was detected significantly higher also left ventricular end-diastolic pressure (LVEDP) was lower in the CRT responders. However, there were no significant differences in coronary flow velocity measurements between the two groups. Moreover the regression analysis revealed that the baseline NYHA class, LVOT TVI, SV, COi, and LVEDP, which were changed due to increased blood flow after CRT implantation, is not associated with response to CRT. Conclusions: Our results suggest that MBF increased after CRT in patients with IDC probably by improving microvascular functions. However, the response to CRT treatment is not related to the changes in the coronary blood flow velocities after CRT.

Stimulation of the hepatic arterial buffer response using exogenous adenosine: hepatic rest/stress perfusion imaging.

The hepatic arterial buffer response is a mechanism mediated by adenosine whereby hepatic arterial perfusion (HAP) increases when portal flow decreases, and is implicated in liver disease. The first study aim was to measure HAP in patients undergoing myocardial perfusion imaging (MPI), thus developing hepatic arterial rest/stress perfusion imaging (HAPI). The second aim was to compare adenosine-induced changes in splenic perfusion (SP) and HAP with corresponding changes in myocardial blood flow (MBF). Patients had MPI with 82Rb PET/CT using adenosine (n = 45) or regadenoson (n = 33) for stressing. SP and HAP were measured using a first-pass technique that gives HAP rather than total hepatic perfusion. Renal perfusion (RP) was also measured. Mean MBF and HAP increased after both adenosine ([stress-rest]/rest 1.1 and 0.8) and regadenoson (1.4 and 0.6), but the respective changes did not correlate. After adenosine, SP (- 0.48) and RP (- 0.26) both decreased. The change in SP correlated positively with the change in MBF (r = 0.36; p = 0.015) but did not correlate with change in HAP. After regadenoson, SP (0.2) and RP (0.2) both increased. The changes in SP correlated with the changes in MBF (r = 0.39; p = 0.025) and HAP (r = 0.39; p = 0.02). Changes in RP correlated with changes in HAP (r = 0.51; p = 0.0008) but not MBF. Resting SP (r = 0.32; p = 0.004), but not resting HAP, correlated with hepatic fat burden. Adenosine-induced change in HAP also correlated with hepatic fat (r = 0.29; p = 0.05). HAPI could be a useful new hepatic function test. Neither splenic 'switch-off' nor hepatic arterial 'switch-on' identifies adequacy of stress in MPI. • This article describes a new method for assessing arterial perfusion of the liver and its capacity to respond to an infusion of adenosine, a substance that normally 'drives' hepatic arterial flow. • Hepatic arterial flow increased in response to adenosine, sometimes dramatically. Adenosine is already used clinically to stimulate myocardial blood flow in patients with suspected coronary disease, but the increase in flow did not correlate with the corresponding increase in hepatic arterial flow. • Analogous to the use of adenosine in the myocardium, the increase in hepatic arterial flow in response to adenosine has the potential to be a new clinically useful method for the evaluation of hepatic arterial haemodynamics in liver disease.

Comparison between ticagrelor and clopidogrel on myocardial blood flow in patients with acute coronary syndrome, using 13 N-ammonia positron emission tomography

The PLEIO (comParison of ticagreLor and clopidogrEl on mIcrocirculation in patients with acute cOronary syndrome) study showed that 6 months of ticagrelor therapy significantly improved microvascular dysfunction in acute coronary syndrome (ACS) patients with stent implantation compared to clopidogrel. Improved microvascular function may affect myocardial blood flow (MBF). We compared the effects of ticagrelor and clopidogrel on MBF over a 6-month follow-up period among patients diagnosed with ACS treated with percutaneous coronary intervention (PCI). In the PLEIO trial, 120 participants were randomized to receive ticagrelor 90 mg twice daily or clopidogrel 75 mg once daily after at least 6 months. 13 N-ammonia positron emission tomography (PET) imaging was performed in 94 patients to measure MBF at the 6-month follow-up visit. On a per-patient level, MBF (1.88 ± 0.52 versus 1.67 ± 0.64 mL/min per gram, P = .01) was significantly higher with ticagrelor compared with clopidogrel in the hyperemic state, but not under resting state (0.75 ± 0.24 versus 0.75 ± 0.19 mL/min per gram, P = .84). On a culprit-vessel analysis, the resting MBF was similar (0.69 ± 0.20 versus 0.70 ± 0.21, P = .89) between the two groups. However, the hyperemic MBF and myocardial flow reserve in the ticagrelor group were significantly higher compared with clopidogrel (1.75 ± 0.46 versus 1.52 ± 0.59, P = .03 and 2.71 ± 0.89 versus 2.20 ± 0.81, P = .02, respectively). These differences were not observed in non-culprit vessels. Maintenance treatment of ticagrelor increased the hyperemic MBF and myocardial flow reserve compared with clopidogrel. URL: http://www.clinicaltrials.gov. Unique identifier: NCT02618733.

P309Prognostic value of global stress myocardial blood flow in patients with suspected obstructive coronary artery disease

P309Prognostic value of global stress myocardial blood flow in patients with suspected obstructive coronary artery disease

Comparison of two software systems for quantification of myocardial blood flow in patients with hypertrophic cardiomyopathy

BackgorundQuantification of myocardial blood flow (MBF) by positron emission tomography (PET) is important for investigation of angina in hypertrophic cardiomyopathy (HCM). Several software programs exist for MBF quantification, but they have been mostly evaluated in patients (with normal cardiac geometry), referred for evaluation of coronary artery disease (CAD). Software performance has not been evaluated in HCM patients who frequently have hyperdynamic LV function, LV outflow tract (LVOT) obstruction, small LV cavity size, and variation in the degree/location of LV hypertrophy. AimWe compared results of MBF obtained using PMod, which permits manual segmentation, to those obtained by FDA-approved QPET software which has an automated segmentation algorithm. Methods13N-ammonia PET perfusion data were acquired in list mode at rest and during pharmacologic vasodilation, in 76 HCM patients and 10 non-HCM patients referred for evaluation of CAD (CAD group.) Data were resampled to create static, ECG-gated and 36-frame-dynamic images. Myocardial flow reserve (MFR) and MBF (in ml/min/g) were calculated using QPET and PMod softwares. ResultsAll HCM patients had asymmetric septal hypertrophy, and 50% had evidence of LVOT obstruction, whereas non-HCM patients (CAD group) had normal wall thickness and ejection fraction. PMod yielded significantly higher values for global and regional stress-MBF and MFR than for QPET in HCM. Reasonably fair correlation was observed for global rest-MBF, stress-MBF, and MFR using these two softwares (rest-MBF: r = 0.78; stress-MBF: r = 0.66.; MFR: r = 0.7) in HCM patients. Agreement between global MBF and MFR values improved when HCM patients with high spillover fractions (> 0.65) were excluded from the analysis (rest-MBF: r = 0.84; stress-MBF: r = 0.72; MFR: r = 0.8.) Regionally, the highest agreement between PMod and QPET was observed in the LAD territory (rest-MBF: r = 0.82, Stress-MBF: r = 0.68) where spillover fraction was the lowest. Unlike HCM patients, the non-HCM patients (CAD group) demonstrated excellent agreement in MBF/MFR values, obtained by the two softwares, when patients with high spillover fractions were excluded (rest-MBF: r = 0.95; stress-MBF: r = 0.92; MFR: r = 0.95). ConclusionsAnatomic characteristics specific to HCM hearts contribute to lower correlations between MBF/MFR values obtained by PMod and QPET, compared with non-HCM patients. These differences indicate that PMod and QPET cannot be used interchangeably for MBF/MFR analyses in HCM patients.

Cardiac PET/CT with Rb-82: optimization of image acquisition and reconstruction parameters

BackgroundOur aim was to characterize the influence of time-of-flight (TOF) and point spread function (PSF) recovery corrections, as well as ordered subset expectation maximization (OSEM) reconstruction parameters, in 82Rb PET/CT quantification of myocardial blood flow (MBF) and myocardial flow reserve (MFR).Rest and stress list-mode dynamic 82Rb PET acquisition data from 10 patients without myocardial flow defects and 10 patients with myocardial blood flow defects were reconstructed retrospectively. OSEM reconstructions were performed with Gaussian filters of 4, 6, and 8 mm, different iterations, and subset numbers (2 × 24; 2 × 16; 3 × 16; 4 × 16). Rest and stress global, regional, and segmental MBF and MFR were computed from time activity curves with FlowQuant© software. Left ventricular segmentation using the 17-segment American Heart Association model was obtained.ResultsWhole left ventricle (LV) MBF at rest and stress were 0.97 ± 0.30 and 2.30 ± 1.00 mL/min/g, respectively, and MFR was 2.40 ± 1.13. Concordance was excellent and all reconstruction parameters had no significant impact on MBF, except for the exclusion of TOF which led to significantly decreased concordance in rest and stress MBF in patients with or without perfusion defects on a coronary artery basis and in MFR in patients with perfusion defects.ConclusionsChanges in reconstruction parameters in perfusion 82Rb PET/CT studies influence quantitative MBF analysis. The inclusion of TOF information in the tomographic reconstructions had significant impact in MBF quantification.

Residual Activity Correction in Quantitative Myocardial Perfusion 13N-Ammonia PET Imaging: A Study in Post-MI Patients

Background/Introduction/AimPositron emission tomography (PET) is the gold standard for the quantification of myocardial blood flow (MBF). A standard PET scan is acquired in two phases (rest and pharmacological stress). 13N-ammonia is a perfusion radiotracer that may show residual activity, which may affect MBF estimation during the second phase of the scan. An algorithm for residual activity correction (RAC) is available when reconstruction is performed using Syngo MBF (by Siemens). The aim of this study was to evaluate differences in MBF estimation with and without RAC by Syngo MBF in patients with a previous MI using 13N-ammonia PET. MethodsMBF was evaluated by 13N-ammonia PET in a group of 25 patients with a history of MI. Dynamic MBF measurements were analyzed with Syngo Dynamic PET, with and without RAC, and the results were evaluated with statistical methods. ResultsSignificant differences in stress phase MBF after RAC were identified in the left anterior descending coronary artery (LAD) territory (p=0.0425) and the right coronary artery (RCA) territory (p=0.004). A trend towards significance was identified in the global polar plot (p=0.049). No statistically significant difference was found in the left circumflex artery (LCx) territory (p=0.333). ConclusionSyngo Dynamic PET, through its RAC function, can be a useful adjunct in assessing second-phase MBF of primarily the RCA territory and secondarily the global polar plot and LAD territory but not the LCx territory.

Semiautomated Global Quantification of Left Ventricular Myocardial Perfusion at Stress Dynamic CT:: Diagnostic Accuracy for Detection of Territorial Myocardial Perfusion Deficits Compared to Visual Assessment

To evaluate the diagnostic accuracy of semiautomated global quantification of left ventricular myocardial perfusion derived from stress dynamic computed tomography myocardial perfusion imaging (CTMPI) for detection of territorial perfusion deficits (PD). Dynamic CTMPI datasets of 71 patients were analyzed using semiautomated volume-based software to calculate global myocardial blood flow (MBF), myocardial blood volume, and volume transfer constant. Optimal cutoff values to assess the diagnostic accuracy of these parameters for detection of one- to three-vessel territories with PD in comparison to visual analysis were calculated. Nonsignificant differences (P = 0.694) were found for average global MBF in patients without PD and single-territorial PD. Significant differences were found for mean global MBF in patients with PD in two (P < 0.0058) and three territories (P < 0.0003). Calculated optimal thresholds for global MBF and myocardial blood volume resulted in a sensitivity, specificity, and negative predictive value of 100% for detection of three-vessel territory PD. For detection of ≥2 territories with PD, global MBF was superior to other parameters (sensitivity 81.3%, specificity 90.9%, and negative predictive value 94.3%). Semiautomated global quantification of left ventricular MBF during stress dynamic CTMPI shows high diagnostic accuracy for detection of ≥2 vessel territories with PD, facilitating identification of patients with multi-territorial myocardial PD.

Cardiovascular magnetic resonance profiling of coronary atherosclerosis: vessel wall remodelling and related myocardial blood flow alterations.

To determine the association between coronary vessel wall morphology and haemodynamic consequences to the myocardium using a combined cardiovascular magnetic resonance (CMR) imaging protocol. Non-invasive CMR profiling of coronary atherosclerotic wall changes and related myocardial blood flow impairment has not been established yet. Sixty-three patients (45 men, 61.5 ± 10.7 years) with suspected or known coronary artery disease underwent 3.0 Tesla CMR imaging. The combined CMR protocol consisted of the following imaging modules at rest: 3D vessel wall imaging and flow measurement of the proximal right coronary artery (RCA), myocardial T2*, and first-pass perfusion imaging. During adenosine stress coronary flow, T2* and first-pass perfusion imaging were repeated. Coronary X-ray angiography classified patient groups: (i) all-smooth (n = 19); (ii) luminal irregular (diameter reduction < 30%; n = 35); and (iii) stenosed RCA (diameter reduction ≥ 50%; n = 9). The ratio of CMR-derived vessel wall area-to-lumen area significantly increased stepwise for the comparison of all-smooth vs. luminal irregular vs. stenosed RCA (1.9 ± 0.6 vs. 2.6 ± 0.6 vs. 3.6 ± 0.9, P < 0.01). Epicardial coronary flow reserve exhibited a stepwise significant decrease (3.4 ± 0.5 vs. 2.9 ± 0.7 vs. 1.7 ± 0.3, P < 0.01). On the myocardial level, stress-induced percentage gain of T2* values (ΔT2*) was significantly decreased between groups (29.2 ± 10.6 vs. 9.0 ± 9.8 vs. 2.2 ± 11.8%, P < 0.01) while perfusion reserve index decreased in the presence of stenosed RCA only (2.2 ± 0.6 vs. 2.0 ± 0.4 vs. 1.3 ± 0.3, P = ns and P < 0.01, respectively). The proposed comprehensive CMR imaging protocol provided a non-invasive approach for direct assessment of coronary vessel wall remodelling and resultant pathophysiological consequences on the level of epicardial coronary and myocardial blood flow in patients.