Myocardial Blood Volume Research Articles

Abstract 16902: Quantification of Coronary Flow Reserve in Normal Subjects Using Regadenoson Vasodilator Stress Real-Time Contrast Echocardiography: A Feasibility Study

Background: Regadenoson is a selective A2A receptor agonist that is administered as a fixed dose bolus with rapid onset (∼30 sec), and short duration (∼2-4 min) of action. The aim of this study was to evaluate the feasibility of real-time myocardial contrast echocardiography (MCE) for quantification of coronary flow reserve (CFR) in healthy humans during regadenoson vasodilator stress. Methods: Fifteen subjects [3 males, age: 45.8±5.2 years, BMI 23.8±2.3 kg/m2] with normal LV wall motion and no CAD underwent real-time MCE. Three standard apical LV views were acquired during a continuous intravenous (IV) infusion of Definity (1.3 ml in 60 cc 0.9% saline at 200 ml/hr) at rest and during vasodilator stress (regadenoson 400 ug IV bolus). Following transient microbubble destruction, microbubble velocity (β, sec -1 ), myocardial blood volume (A, dB) and myocardial blood flow (MBF, dB/sec) were determined. Videodensitometric quantification using a 16-segment model at end-systole was performed off-line. Results: Quantification of reserve parameters was feasible in all (15/15) patients, 188/240 segments (78%)[82%, 80% and 70% of 4-, 2-, 3-chambers apical views] and 43/45 (95%) coronary territories [one each of Cx and RCA territories were not feasible]. Augmentation from baseline to vasodilator stress was observed for both ß (s -1 ) [0.65± 0.25 vs 0.79± 0.21, P=0.031] and MBF (dB/sec) [2.85± 1.43 vs 4.65± 2.06, P= 0.002], however A (dB) did not change [06.62± 2.57 vs 6.79±2.1, P=0.463]. CFR measurements from all views were similar (Fig 1). There was no significant difference between CFR measured in the 3 coronary territories, although some heterogeneity was noted in the posterior circulation CFR (Fig 2). Conclusion: Real-time MCE during Regadenoson vasodilator stress is feasible, and is a useful technique for the rapid noninvasive quantification of CFR in healthy humans.

Detection of coronary stenosis with myocardial contrast echocardiography using regadenoson, a selective adenosine A2A receptor agonist

Regadenoson is comparable to adenosine in pharmacologic radionuclide stress tests but has not been studied with stress myocardial contrast echocardiography. This study assessed the haemodynamic profile and ability of regadenoson, a novel selective A(2A) receptor agonist, to detect coronary artery stenosis during myocardial contrast echocardiography. Myocardial contrast echocardiography was performed to measure myocardial blood volume, myocardial blood flow velocity, and total regional myocardial blood flow before and after administration of regadenoson (5 µg kg(-1), 10 s bolus) in 10 open-chest dogs with mild-to-moderate coronary stenosis that was not flow limiting at rest. Regadenoson decreased blood pressure but did not change heart rate. It increased coronary blood flow significantly (P < 0.05) for 30 min, which was attenuated in proportion to coronary stenosis severity. Whereas myocardial blood volume maximally increased by 0.5-0.75-fold in the control region, it did not change in the region supplied by the non-flow limiting stenosis. Perfusion defects were visually and quantitatively detectable for as long as 10 min after administration of regadenoson. No arrhythmias were noted with regadenoson either prior to or during myocardial contrast echocardiography. Regadenoson can be used as a vasodilator stress agent with myocardial contrast echocardiography to detect the presence of physiologically significant coronary stenosis. The optimum time for image acquisition was 3-10 min after drug administration.

CT detection of myocardial blood volume deficits: Dual-energy CT compared with single-energy CT spectra

The performance of dual-energy CT (DECT) for the detection of myocardial blood volume deficits has not systematically been compared with single-energy CT (SCT) spectra. We evaluated the accuracy for detection of myocardial blood volume deficits in DECT and SCT compared with 99m-Tc-Sestamibi-SPECT (single-photon emission CT) during rest and stress. 47 patients underwent rest/stress SPECT myocardial perfusion imaging and cardiac DECT on a dual-source CT scanner. The A- and B-tubes were operated with 140 kV and 80 kV/100 kV, respectively. DECT raw data were reconstructed by (1) only using high-energy (140 kV) CT spectra, (2) only using low-energy (80 kV/100 kV) CT spectra, (3) merging data (30% low- and 70% high-energy CT spectra), and (4) DECT-based iodine maps. Two independent, blinded observers analyzed all CT data according to each of the 4 reconstruction strategies for myocardial blood volume deficits. Specificity and positive predictive values were relatively similar between the 4 reconstruction strategies, with highest specificity (98%) of SCT datasets based on 140 kV for mixed perfusion deficits seen on SPECT. DECT iodine maps showed highest sensitivity, negative predictive value, and accuracy of 91%, 97%, and 93%, respectively, for mixed perfusion deficits. Analysis with receiver operating characteristics showed highest area under the curve values (0.84-0.93) with the use of DECT iodine maps in the detection of purely fixed and mixed perfusion deficits. DECT iodine maps show superior performance for the detection of fixed and mixed perfusion deficits compared with SCT spectra.

Corrigendum

CorrigendaCorrigendumPublished Online:01 Jun 2011https://doi.org/10.1152/ajpheart.zh4-9901-corr.2011Original articleMoreSectionsPDF (53 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations Volume 300, March 2011Volume 69, March 2011Pages H1119–H1124: Indermühle A, Vogel R, Meier P, Zbinden R, Seiler C. Myocardial blood volume and coronary resistance during and after coronary angioplasty. Am J Physiol Heart Circ Physiol 300: H1119–H1124, 2011. First published January 7, 2011; doi:10.1152/ajpheart.01022.2010. (http://ajpheart.physiology.org/cgi/content/full/300/3/H1119).—An incorrect article was cited in Ref. 9. The correct reference is as follows:REFERENCE9. Kassab GS , Lin DH , Fung YC . Morphometry of pig coronary venous system. Am J Physiol Heart Circ Physiol 267: H2100–H2113, 1994.Link | ISI | Google Scholar Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Related ArticlesMyocardial blood volume and coronary resistance during and after coronary angioplasty 01 Mar 2011American Journal of Physiology-Heart and Circulatory Physiology More from this issue > Volume 300Issue 6June 2011Pages H2327-H2327 Copyright & PermissionsCopyright © 2011 the American Physiological Societyhttps://doi.org/10.1152/ajpheart.zh4-9901-corr.2011History Published online 1 June 2011 Published in print 1 June 2011 Metrics

A protocol for the measurement of myocardial blood volume and water exchange

Background Organ perfusion can be quantified by direct calibration of relative perfusion images using absolute blood volume (ml/100g) [1]. It is well known that for an intravascular gadolinium-based T1 shortening contrast agent, the parenchymal T1 change reflects tissue blood volume [2].However, to accurately quantify blood flow from blood volume, we must describe the compartmentalization effects of intrato extra-vascular water exchange [2,3].

Myocardial blood volume and coronary resistance during and after coronary angioplasty

Animal experiments have shown that the coronary circulation is pressure distensible, i.e., myocardial blood volume (MBV) increases with perfusion pressure. In humans, however, corresponding measurements are lacking so far. We sought to quantify parameters reflecting coronary distensibility such as MBV and coronary resistance (CR) during and after coronary angioplasty. Thirty patients with stable coronary artery disease underwent simultaneous coronary perfusion pressure assessment and myocardial contrast echocardiography (MCE) of 37 coronary arteries and their territories during and after angioplasty. MCE yielded MBV and myocardial blood flow (MBF; in ml · min(-1) · g(-1)). Complete data sets were obtained in 32 coronary arteries and their territories from 26 patients. During angioplasty, perfusion pressure, i.e., coronary occlusive pressure, and MBV varied between 9 and 57 mmHg (26.9 ± 11.9 mmHg) and between 1.2 and 14.5 ml/100 g (6.7 ± 3.7 ml/100 g), respectively. After successful angioplasty, perfusion pressure and MBV increased significantly (P < 0.001 for both) and varied between 64 and 118 mmHg (93.5 ± 12.8 mmHg) and between 3.7 and 17.3 ml/100 g (9.8 ± 3.4 ml/100 g), respectively. Mean MBF increased from 31 ± 20 ml · min(-1) · g(-1) during coronary occlusion, reflecting collateral flow, to 121 ± 33 ml · min(-1) · g(-1) (P < 0.01), whereas mean CR, i.e., the ratio of perfusion pressure and MBF, decreased by 20% (P < 0.001). In conclusion, the human coronary circulation is pressure distensible. MCE allows for the quantification of CR and MBV in humans.

Right ventricular absolute myocardial blood flow in complex congenital heart disease

ObjectiveA consequence in patients with d-transposition of the great arteries (d-TGA) and tetralogy of Fallot (TOF) is right ventricular hypertrophy (RVH) and right ventricular failure. Myocardial contrast echocardiography (MCE) permits...

Roles of myocardial blood volume and flow in coronary artery disease: an experimental MRI study at rest and during hyperemia

To validate fast perfusion mapping techniques in a setting of coronary artery stenosis, and to further assess the relationship of absolute myocardial blood volume (MBV) and blood flow (MBF) to global myocardial oxygen demand. A group of 27 mongrel dogs were divided into 10 controls and 17 with acute coronary stenosis. On 1.5-T MRI, first-pass perfusion imaging with a bolus injection of a blood-pool contrast agent was performed to determine myocardial perfusion both at rest and during either dipyridamole-induced vasodilation or dobutamine-induced stress. Regional values of MBF and MBV were quantified by using a fast mapping technique. Color microspheres and (99m)Tc-labeled red blood cells were injected to obtain respective gold standards. Microsphere-measured MBF and (99m)Tc-measured MBV reference values correlated well with the MR results. Given the same changes in MBF, changes in MBV are twofold greater with dobutamine than with dipyridamole. Under dobutamine stress, MBV shows better association with total myocardial oxygen demand than MBF. Coronary stenosis progressively reduced this association in the presence of increased stenosis severity. MR first-pass perfusion can rapidly estimate regional MBF and MBV. Absolute quantification of MBV may add additional information on stenosis severity and myocardial viability compared with standard qualitative clinical evaluations of myocardial perfusion.

Numerical Methods and Workstation for the Quantitative Analysis of Real-Time Myocardial Contrast Echocardiography

Using the quantitative analysis of real-time myocardial contrast echocardiography (RT MCE), clinicians can assess the myocardial perfusion of patients, noninvasively and accurately. We designed a workstation to assist clinicians to automatically implement the accurate analysis of RT MCE. The workstation can compute some hemodynamic parameters of myocardial microcirculation, e.g., myocardial blood flow, myocardial blood flow mean velocity, and myocardial blood volume. Our new methods involved in the quantitative analysis of RT MCE are summarized as follows. 1) A novel orthogonal array optimization (OAO) technique was proposed and used to estimate the unknown parameters of the nonlinear model to guarantee numerical stability. 2) Brox's coarse-to-fine warping optical flow technique was employed to automatically track the region of interest located inside the myocardial area to ensure the accuracy of the quantitative analysis. Finally, we illustrate some examples of clinical studies to indicate the effectiveness of the system and the reliability of the methods.

拡張型心筋症における心筋内血液量と左室収縮予備能の関係

目的：心筋コントラストエコー法（MCE）により計測される左室の心筋内血液量が，拡張型心筋症（DCM）患者の左室機能または左室収縮予備能と関連するか否かを検討すること．対象と方法：対象は，左室駆出率（LVEF）が45％未満のDCM患者21例．超音波造影剤Levovist®の持続静注下に，6心拍ごとの間歇送信法を行い心尖部二腔断面と四腔断面のハーモニック・パワードプラ画像を記録した．左室を6区域に分割し，心筋のコントラスト強度（CImyo）と心筋に隣接する左室内腔血液のコントラスト強度（CIblood）を計測した．相対的CI（RelCI）＝CImyo－CIblood ［dB］は，内腔血液に対する心筋の気泡密度の比率を対数で表し，心筋内血液量は10（RelCI/10）×100 ［％］と算出される．20μg/kg/minまでのドブタミン負荷心エコー法で負荷前と最大用量負荷時のLVEFを計測した．結果と考察：心筋内血液量はLVEFを含めた安静時の心機能指標とは相関せず，ドブタミン負荷によるLVEFの増加率と有意に相関した（r＝0.54，p＝0.01）．DCMによる心筋の組織形態学的変化に伴って，心筋内血管の相対的容積が減少し，そのことが収縮予備能の低下に関連していると考えられる．結論：MCEにより計測される心筋内血液量は，DCM患者の左室収縮予備能と関連した．

Quantification of Regional Myocardial Oxygenation by Magnetic Resonance Imaging

Background— A comprehensive evaluation of myocardial ischemia requires measures of both oxygen supply and demand. Positron emission tomography (PET) is currently the gold standard for such evaluations, but its use is limited because of its ionizing radiation, limited availability, and high cost. A cardiac MRI method was developed for assessing myocardial oxygenation. The purpose of this study was to evaluate and validate this technique compared with PET during pharmacological stress in a canine model of coronary artery stenosis. Methods and Results— Twenty-one beagles and small mongrel dogs without coronary artery stenosis (controls) or with moderate to severe acute coronary artery stenosis underwent MRI and PET imaging at rest and during dipyridamole vasodilation or dobutamine stress to induce a wide range of changes in cardiac perfusion and oxygenation. MRI first-pass perfusion imaging was performed to quantify myocardial blood flow and volume. The MRI blood oxygen level-dependent technique was used to determine the myocardial oxygen extraction fraction during pharmacological hyperemia. Myocardial oxygen consumption was determined by the Fick law. In the same dogs, 15 O-water and 11 C-acetate were used to measure myocardial blood flow and myocardial oxygen consumption, respectively, by PET. Regional assessments were performed for both MR and PET. MRI data correlated nicely with PET values for myocardial blood flow ( R 2 =0.79, P &lt;0.001), myocardial oxygen consumption ( R 2 =0.74, P &lt;0.001), and oxygen extraction fraction ( R 2 =0.66, P &lt;0.01). Conclusions— Cardiac MRI methods may provide an alternative to radionuclide imaging in settings of myocardial ischemia. Our newly developed quantitative MRI oxygenation imaging technique may be a valuable noninvasive tool to directly evaluate myocardial energetics and efficiency.

Quantitative analysis of myocaridal perfusion in rabbits by tansthoracic real-time myocardial contrast echocardiography

To evaluate the feasibility of real-time myocardial contrast echocardiography (RTMCE) by quantitative analysis of myocardial perfusion in rabbits, transthoracic RTMCE was performed in 10 healthy rabbits by using continuous infusion of SonoVue into the auricular vein. The short axis view at the papillary muscle level was obtained. The duration of the time that the contrast took to appear in right heart, left heart and myocardium was recorded. The regional myocardial signal intensity (SI) versus refilling time plots were fitted to an exponential function: y(t) =A(1-e(-beta(t-t0))) + C, where y is SI at any given time, A is the SI plateau that reflects myocardial blood volume, and beta is the slope of the refilling curve that reflects myocardial microbubble velocity. The A, beta and Axbeta values at different infusion rate of SonoVue were analyzed and the A, beta and Axbeta values in each segment in the short axis view at the papillary muscle level were compared. All the animal experiments were successful and high-quality images were obtained. The best intravenous infusion rate for SonoVue was 30 mL/h. The contrast appeared in right heart, left heart and myocardium at 7.5+/-2.2 s, 9.1+/-2.4 s and 12.2+/-1.6 s respectively. After 16.6+/-2.3s, myocardial opacification reached a steady state. The mean A, beta and Axbeta value in the short axis view at the papillary muscle level were 9.8+/-3.0 dB, 1.4+/-0.5 s(-1) and 13.5+/-3.6 dBxs(-1) respectively. A, beta and Axbeta values showed no significant differences among 6 segments. It was suggested that RTMCE was feasible for quantitative analysis of myocardial perfusion in rabbits. It provides a non-invasive method to evaluate the myocardial perfusion in rabbit disease models.

Prognostic Value of Dipyridamole Stress Myocardial Contrast Echocardiography: Comparison With Single Photon Emission Computed Tomography

Dipyridamole stress myocardial contrast echocardiography (MCE) can be used to detect coronary artery disease (CAD). Because it measures myocardial blood flow velocity in addition to measuring myocardial blood volume, it was hypothesized that it should have greater prognostic utility than single photon-emission computed tomography (SPECT), which measures only myocardial blood volume. Because blood flow mismatch precedes wall thickening (WT) abnormalities during demand ischemia, it was also postulated that perfusion on MCE would be superior to WT abnormalities on echocardiography for this purpose. The incidence of nonfatal myocardial infarction and cardiac death was determined in 261 patients with known or suspected CAD over a mean follow-up period of 14 months who underwent simultaneous dipyridamole stress MCE and 99mTc-sestamibi SPECT. Comparisons of survival curves were conducted with stratified (and unstratified) log-rank tests. Abnormal results on MCE were found to be the best predictor of an adverse outcome (odds ratio, 23; 95% confidence interval, 6-201; P<.0001) and provided incremental prognostic value over clinical variables (age>60 years, the presence of >or=3 cardiac risk factors, known peripheral vascular disease, prior myocardial infarction, and left ventricular systolic function), inducible WT abnormalities, and SPECT. Prognoses were worst in patients who had both abnormal results on MCE and inducible WT abnormalities and best in those who had neither. Patients with abnormal results on MCE but no inducible WT abnormalities had intermediate outcomes. In patients with known or suspected CAD undergoing dipyridamole stress, MCE provides powerful prognostic information that is superior to clinical variables, electrocardiography, left ventricular systolic function, WT analysis, and SPECT. MCE may therefore serve as a method of choice for myocardial perfusion assessment in patients with known or suspected CAD. Larger studies are needed to confirm these findings.

Angiotensin II Receptor Blocker, Valsartan, Increases Myocardial Blood Volume and Regresses Hypertrophy in Hypertensive Patients

Although a reduction in myocardial blood volume (MBV), an in vivo index of the myocardial microvasculature, measured by myocardial contrast echocardiography in patients with hypertension (HT), can be demonstrated, it is still unknown whether a decreased MBV can be improved by antihypertensive treatment. Eleven HT patients (mean age 58 years, 7 men) with left ventricular hypertrophy (LVH) and 10 age- and sex-matched normal controls were studied. Harmonic power Doppler images were acquired at end-diastole of every 6(th) beat and MBV was calculated as 10(X/10)x100%, where X (dB) is myocardial contrast intensity minus the contrast intensity of the adjacent intracavity blood pool. Baseline blood pressure (BP) and left ventricular mass index (LVMI) in the HT patients were higher and MBV was lower than in the controls (2.52 +/-0.37% vs 3.31 +/-0.61%, P<0.01). MBV did not correlate with mean BP, but was inversely correlated with LVMI (r=0.61, P<0.01). After treatment with valsartan for 6 months, LVMI significantly decreased and MBV increased (2.72 +/-0.26%, P<0.05 vs baseline) in the patients with HT. There was a significant inverse correlation between the changes in MBV and those of LVMI (r=0.62, P<0.05), but not between MBV and mean BP. Valsartan, an angiotensin II receptor blocker, corrected the decreased MBV in association with regression of LVH in patients with HT.

Microvascular damage prevention with thrombaspiration during primary percutaneous intervention in acute myocardial infarction

Despite rapid and complete recanalization of infarct-related artery with percutaneous coronary intervention, microvascular integrity is not often preserved. Several mechanical devices have been proposed to prevent distal embolization, but the impact of these devices on myocardial perfusion remains controversial. The aim of our study was to assess microvascular damage reduction with quantitative myocardial contrast perfusion echocardiography among patients with the first anterior acute myocardial infarction treated with thromboaspiration during percutaneous coronary intervention. Forty-two patients (57.4+/-10 years, 74% males) with first anterior acute myocardial infarction were randomized 1 : 1 to intracoronary thromboaspiration followed by stenting, or to a conventional strategy of stenting alone. Echocardiogram and quantitative myocardial contrast echocardiography were performed 7 days and 1 month later, respectively. Parameter A (reflecting myocardial blood volume), beta (reflecting velocity, myocardial blood flow), and product of A and beta as indicator of myocardial blood flow were analyzed. For each patient mean value of A, beta, and A x beta from all dysfunctional segments was calculated. The study population was divided into two groups: thromboaspiration (group I, 19 patients) and stenting alone (group II, 23 patients). No difference was observed between the both groups in demographic, clinical, echocardiographic, and angiographic data. Parameter A and A x beta were significantly higher in group I than in group II: 8.58+/-2.54 versus 5.29+/-3.18 dB (P<0.001) and 5.29+/-3.73 versus 2.78+/-3.03 dB/s (P<0.001). Multivariate step-down regression analysis revealed that only thromboaspiration before stenting and lower maximum troponin I have been associated with viability preservation in infarcted region. Thromboaspiration before stenting in patients with the first anterior myocardial infarction improves myocardial perfusion at the tissue level assessed by quantitative myocardial contrast echocardiography.

Myocardial perfusion defects in Bartter and Gitelman syndromes

Normotensive hypokalaemic tubulopathies (Bartter and Gitelman syndromes (BS/GS)) are genetic diseases that are considered benign. However, QT prolongation, left ventricular dysfunction and reduction of cardiac index upon exercise leading to arrhythmias and sudden cardiac death have been reported in these patients. Hence, we aimed to verifying whether an isometric exercise could represent a useful tool for the identification of patients at risk for future cardiac events. Myocardial function (MF) and perfusion, evaluated as myocardial blood flow (MBF) of 10 BS/GS patients and 10 healthy controls, were investigated at rest and during isometric exercise. MF and MBF were evaluated using quantitative two-dimensional and myocardial contrast echocardiography. BS/GS patients had normal baseline MF and MBF. During exercise in BS/GS patients, corrected QT (QTc) was prolonged to peak value of 494 +/- 9.1 ms (P < 0.001). In controls, MF increased from resting to peak exercise (left ventricular ejection fraction: 65 +/- 4% to 78 +/- 5%, P < 0.003) while in seven BS/GS patients (Group 1) it declined (64 +/- 5% to 43 +/- 9%, P < 0.001). Myocardial perfusion increased upon exercise in controls as shown by changes of its markers: beta (a measure of myocardial flow velocity; 0.89 +/- 0.12 vs. 0.99 +/- 0.12, P < 0.001) and myocardial blood volume (14.4 +/- 2 vs. 20.2 +/- 0.25, P < 0.001), while in Group 1 BS/GS it decreased (0.87 +/- 0.15 vs. 0.67 +/- 0.15, P < 0.001; and 14.5 +/- 1.9 vs. 8.3 +/- 0.22, P < 0.001, respectively). Our results document for the first time that exercise induce coronary microvascular and myocardial defects in BS/GS patients. Therefore, this may challenge the idea that BS/GS are benign diseases. In addition, the diagnostic approach to these syndromes should include an in-depth cardiac assessment in order to identify patients at higher risk.

Multimodality Cardiovascular Molecular Imaging, Part II

In Part I of this consensus article, the imaging methodology, evolving imaging technology, and development of novel targeted molecular probes relevant to the developing field of cardiovascular molecular imaging were reviewed. Novel reporter gene and reporter probe imaging approaches for tracking of cardiac transgene expression were also discussed and have important future implications for evaluation of gene- and cell-based therapies for the failing heart. The current role of metabolic and receptor imaging was also briefly reviewed, as these represent the beginning of our clinical application of molecular imaging within the cardiovascular system. Part II will summarize the available targeted imaging probes as well as specific future applications of molecular imaging for identification and evaluation of critical pathophysiological processes of the cardiovascular system.

Abstract 5731: An Increase of Intrinsic Endothelial Progenitor Cells after Acute Myocardial Infarction was Associated with Spontaneous Neovascularization but not with Improvement of Left Ventricula Remodeling

Endothelial progenitor cells (EPC) increase after acute myocardial infarction and may contribute to neovascularization in the infarct zone. The aim of this study was to elucidate the relation of EPC release to recovery of microvascualr and myocardial function. Eighteen patients with acute myocardial infarction (AMI) undergoing primary PCI within 12 hours after onset were enrolled. CD34 + cells were counted at days-1, 7 and 14 as an index of EPC. We performed triggered end-systolic myocardial contrast echocardiography (MCE) at every 6 cardiac cycles with continuous infusion of Levovist at days-2 and 14. We performed left ventriculography 6 months later to calculate left ventricular ejection fraction (LVEF) and end-diastolic volume index (LVEDVI). The number of EPC at day-7 was significantly higher than that at day-1 (1.29+/−0.75 vs. 2.10+/−1.25/micL, p&lt;0.001). It was correlated with myocardial blood volume (MBV), that implies microvascular integrity, at day-14 measured from MCE image (r 2 =0.652, p&lt;0.005) and with an increase in MBV from day-1 to day-7 (r 2 =0.533, p&lt;0.005). To evaluate the correlation between EPC and LV function, we divided patients into two groups according to the number of EPC at day-7. LVEF and LVEDVI were comparable between the higher number of EPC and the lower number of EPC groups (49.3+/−12.2 vs. 52.4+/−8.1%, 65.2+/−13.1 vs. 69.1+/−16.6ml/m 2 ). EPC spontaneously released after AMI and number of released EPC is correlated to the amount of neovascularization in the infarct zone. The number of EPC was not necessarily related to the functional improvement or attenuation of LV remodeling.

111 Detection of changes in myocardial blood flow and volume: a CMR study in a canine model of coronary artery stenosis

111 Detection of changes in myocardial blood flow and volume: a CMR study in a canine model of coronary artery stenosis

Identification of residual ischemia, infarction, and microvascular impairment in revascularized myocardial infarction using 64‐slice MDCT

This study aimed to assess the potential of 64-slice MDCT in characterizing revascularized infarcted myocardium at the cellular and microvascular levels. Pigs (n = 7) underwent 2 h left anterior descending coronary artery occlusion/reperfusion. In acute (2-4 h) and subacute (1 week) infarction, first-pass perfusion (FPP) (1 ml/kg of 300 mg/ml Omnipaque) was performed using a cine (rotation time 60 s/bpm) non-ECG gated sequence (mAS/kV = 100/120). Delayed contrast enhanced images (DE) (mAS/kV = 650/120) were acquired every 2 min for 10 min to determine the kinetics of Omnipaque and to define infarcted myocardium and microvascular impairment (representing microvascular obstruction and/or no- or low-reflow phenomenon). Maximum upslope, maximum attenuation and time to the peak were measured from FPP plots. 2,3,5-Triphenyltetrazolium-chloride (TTC) was used to define true infarction in the excised hearts. Hyperenhanced myocardium on DE was measured and compared with TTC. The contrast media caused minor beam hardening and X-ray scatter on FPP. The above-mentioned perfusion parameters significantly differed between remote and acute infarction. Infarcted myocardium showed two patterns of enhancement on DE, hyperenhanced rim representing the perfused infarction and hypoenhanced core representing a microvascular impaired region, with significantly different attenuation. The extent of infarction on DE-MDCT decreased over the course of 1 week and did not differ from TTC. Post-processed FPP semi-quantitative images showed a decline in myocardial blood volume and flow in acute revascularized infarction. In conclusion, modern MDCT has the potential to identify residual ischemia on FPP and microvascular impairment and infarction on DE images.