Quantification Of Coronary Flow Reserve Research Articles

Abstract 10954: Quantification of Myocardial Perfusion Reserve Using a Cardiac-Centered Camera: First Comparison with Invasive Indexes of Coronary Microvascular Disease

Introduction: – The invasive quantification of coronary flow reserve (CFR), the index of microcirculatory resistance (IMR), and fractional flow reserve (FFR) allows to assess coronary physiology. Although semi-conductor (CZT) SPECT myocardial perfusion reserve (MPR) has been previously compared with FFR, there are no data documenting the relationships between CZT SPECT MPR on one hand and CFR and/or IMR on the other hand. We assessed the performances of noninvasive CZT SPECT MPR in comparison with invasively determined FFR, CFR, and IMR. Methods: – Rest and dipyridamole-induced stress myocardial blood flow and MPR were quantified using 99m Tc-SestaMIBI and a Discovery NM 530c camera in 26 patients with suspected or known coronary artery disease who underwent conventional invasive coronary angiography. Thermodilution-derived resting and adenosine-induced hyperemic mean transit times, distal intracoronary pressures, and mean aortic pressures were assessed for the quantification of FFR, CFR, and IMR values. Results: – Only 2/35 vessels presented with a pathological (<0.8) FFR. A moderate yet significant correlation was observed between regional CZT SPECT MPR and CFR (r=0.40, P =.02). The sensitivity, specificity, positive and negative predictive value, and accuracy of regional CZT SPECT MPR vs CFR were 69% [44-86%], 94% [74-100%], 91% [65-100%], 77% [56-90%], and 82% [65-93%], respectively. In territories without underlying CAD (n=32), CZT SPECT MPR values were significantly higher in those with CFR≥2 and IMR<25 (negative composite criterion, n=14) than in those with CFR<2 and IMR≥25 (positive composite criterion, n=8, CZT SPECT MPR, 2.6 [2.1-3.6] vs 1.6 [1.2-1.8]), P <.01). Regional CZT SPECT MPR displayed sensitivity, specificity, positive and negative predictive value, and accuracy of 87% [53-99%], 100% [78-100%], 100% [64-100%], 93% [70-99%], and 95% [77-99%] for the diagnosis of a positive composite criterion, respectively. Conclusions: – CZT SPECT MPR presented a moderate, significant correlation with thermodilution CFR and good diagnostic performances for the detection of patients at high risk of cardiovascular events (low CFR and high IMR) in the absence of obstructive CAD.

P27 Prevalencia de disfunción microvascular en pacientes con diabetes tipo 1 y 2 con GATED-SPECTnormal

Introducción: los pacientes con diabetes tienen un mayor riesgo de presentar eventos cardiovasculares. La disfunción microvascular es un marcador de daño precoz y su presencia se ha asociado con peor pronóstico en estos pacientes, incluso con pruebas funcionales evocadoras de isquemia, como GATED-SPECT, normales.Objetivos: evaluar la prevalencia de disfunción microvascular de acuerdo a tipo de diabetes a través de la cuantificación de reserva de flujo coronario (RFC) en pacientes con GATED-SPECT normal.Materiales y métodos: se incluyeron pacientes con diabetes tipo 1 (DM1) y tipo 2 (DM2) sin historia de enfermedad coronaria conocida que presentaron un estudio GATED-SPECT Tc99-MIBI con dipiridamol, sin defectos de perfusión y con función ventricular conservada. La RFC se calculó mediante la relación flujo pico post dipiridamol/flujo en reposo con el software 4DM® mediante SPECT con detectores Cadmio Zinc Telurio (CZT-SPECT). Se consideró presencia de disfunción microvascular una RFC <2 y disfunción severa cuando la RFC fue <1,6.

Quantification of Coronary Flow Reserve by <sup>15</sup>O-Water PET with ATP Stress; from a Practical Application Perspective

Quantification of Coronary Flow Reserve by <sup>15</sup>O-Water PET with ATP Stress; from a Practical Application Perspective

Quantification of Coronary Flow Reserve by <sup>15</sup>O-Water PET with ATP Stress; from a Practical Application Perspective

Quantification of Coronary Flow Reserve by <sup>15</sup>O-Water PET with ATP Stress; from a Practical Application Perspective

Quantification of coronary flow reserve in patients with ischaemic and non-ischaemic cardiomyopathy and its association with clinical outcomes.

Patients with left ventricular systolic dysfunction frequently show abnormal coronary vascular function, even in the absence of overt coronary artery disease. Moreover, the severity of vascular dysfunction might be related to the aetiology of cardiomyopathy.We sought to determine the incremental value of assessing coronary vascular dysfunction among patients with ischaemic (ICM) and non-ischaemic (NICM) cardiomyopathy at risk for adverse cardiovascular outcomes. Coronary flow reserve (CFR, stress/rest myocardial blood flow) was quantified in 510 consecutive patients with rest left ventricular ejection fraction (LVEF) ≤45% referred for rest/stress myocardial perfusion PET imaging. The primary end point was a composite of major adverse cardiovascular events (MACE) including cardiac death, heart failure hospitalization, late revascularization, and aborted sudden cardiac death.Median follow-up was 8.2 months. Cox proportional hazards model was used to adjust for clinical variables. The annualized MACE rate was 26.3%. Patients in the lowest two tertiles of CFR (CFR ≤ 1.65) experienced higher MACE rates than those in the highest tertile (32.6 vs. 15.5% per year, respectively, P = 0.004), irrespective of aetiology of cardiomyopathy. Impaired coronary vascular function, as assessed by reduced CFR by PET imaging, is common in patients with both ischaemic and non-ischaemic cardiomyopathy and is associated with MACE.

Association Between Coronary Vascular Dysfunction and Cardiac Mortality in Patients With and Without Diabetes Mellitus

Diabetes mellitus increases the risk of adverse cardiac outcomes and is considered a coronary artery disease (CAD) equivalent. We examined whether coronary vascular dysfunction, an early manifestation of CAD, accounts for increased risk among diabetics compared with nondiabetics. A total of 2783 consecutive patients (1172 diabetics and 1611 nondiabetics) underwent quantification of coronary flow reserve (CFR; CFR=stress divided by rest myocardial blood flow) by positron emission tomography and were followed up for a median of 1.4 years (quartile 1-3, 0.7-3.2 years). The primary end point was cardiac death. Impaired CFR (below the median) was associated with an adjusted 3.2- and 4.9-fold increase in the rate of cardiac death for diabetics and nondiabetics, respectively (P=0.0004). Addition of CFR to clinical and imaging risk models improved risk discrimination for both diabetics and nondiabetics (c index, 0.77-0.79, P=0.04; 0.82-0.85, P=0.03, respectively). Diabetic patients without known CAD with impaired CFR experienced a rate of cardiac death comparable to that for nondiabetic patients with known CAD (2.8%/y versus 2.0%/y; P=0.33). Conversely, diabetics without known CAD and preserved CFR had very low annualized cardiac mortality, which was similar to patients without known CAD or diabetes mellitus and normal stress perfusion and systolic function (0.3%/y versus 0.5%/y; P=0.65). Coronary vasodilator dysfunction is a powerful, independent correlate of cardiac mortality among both diabetics and nondiabetics and provides meaningful incremental risk stratification. Among diabetic patients without CAD, those with impaired CFR have event rates comparable to those of patients with prior CAD, whereas those with preserved CFR have event rates comparable to those of nondiabetics.

Quantification of absolute coronary flow reserve and relative fractional flow reserve in a swine animal model using angiographic image data

Coronary flow reserve (CFR) and fractional flow reserve (FFR) are important physiological indexes for coronary disease. The purpose of this study was to validate the CFR and FFR measurement techniques using only angiographic image data. Fifteen swine were instrumented with an ultrasound flow probe on the left anterior descending artery (LAD). Microspheres were gradually injected into the LAD to create microvascular disruption. An occluder was used to produce stenosis. Contrast material injections were made into the left coronary artery during image acquisition. Volumetric blood flow from the flow probe (Q(q)) was continuously recorded. Angiography-based blood flow (Q(a)) was calculated by using a time-density curve based on the first-pass analysis technique. Flow probe-based CFR (CFR(q)) and angiography-based CFR (CFR(a)) were calculated as the ratio of hyperemic to baseline flow using Q(q) and Q(a), respectively. Relative angiographic FFR (relative FFR(a)) was calculated as the ratio of the normalized Q(a) in LAD to the left circumflex artery (LC(X)) during hyperemia. Flow probe-based FFR (FFR(q)) was measured from the ratio of hyperemic flow with and without disease. CFR(a) showed a strong correlation with the gold standard CFR(q) (CFR(a) = 0.91 CFR(q) + 0.30; r = 0.90; P < 0.0001). Relative FFR(a) correlated linearly with FFR(q) (relative FFR(a) = 0.86 FFR(q) + 0.05; r = 0.90; P < 0.0001). The quantification of CFR and relative FFR(a) using angiographic image data was validated in a swine model. This angiographic technique can potentially be used for coronary physiological assessment during routine cardiac catheterization.

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.

Noninvasive Techniques to Assess Myocardial Ischemia in Hypertensive Patients

Hypertensive patients are more affected by coronary artery disease (CAD) than normotensive patients. Currently, established techniques are able to diagnose myocardial ischemia/CAD in hypertensive patients with suspected CAD. An irrevocable role remains for exercise electrocardiogram (ECG) owing to the many parameters evaluated under physiologic conditions. However, the suboptimal specificity of a positive exercise ECG demands further examination of hypertensive patients with either myocardial single-photon emission computed tomography (SPECT) or stress echocardiography, both more specific than exercise ECG in diagnosing CAD. The high specificity of imaging techniques also makes them highly predictive of cardiac events. Additional techniques to help diagnose CAD are available. Tissue Doppler imaging, strain and other echo-derived techniques may add quantitative elements to recognize CAD in hypertensive hearts. The accuracy of MRI is improving to study myocardial function and perfusion. Positron emission tomography and multislice computed tomography, also in-built with fusion scanners, are playing roles in combining coronary angiography and myocardial function/ischemia assessment. However, no significant application of these additional techniques is available for hypertensive patients. Epicardial CAD assessed by coronary angiography remains the gold standard to decide for revascularization procedures. The presence of microcirculatory dysfunction, a symptom typical of hypertensive hearts, is opening up new areas of noninvasive diagnostic techniques for the detection of coronary flow reserve (CFR) and related myocardial ischemia. The quantification of CFR may render this parameter pivotal to deciding the need for revascularization procedures of intermediate coronary stenosis and it may become an additional gold standard in evaluating coronary vessels. Moreover, even with normal epicardial coronary arteries, microcirculation dysfunction bears prognostic stratification capabilities for hypertensive patients and it may become a promising therapeutic target in the near future.

New Technology for Noninvasive Evaluation of Coronary Artery Disease

Cardiac computed tomography (CT) and positron emission tomography (PET) are emerging as powerful noninvasive imaging tools for the evaluation of atherosclerosis in patients with known or suspected coronary artery disease (CAD). Unlike invasive coronary angiography, CT coronary angiography (CTA) not only assesses disease within the coronary lumen but can also provide direct qualitative and quantitative information about nonobstructive atherosclerotic plaque burden within the vessel wall. Thus, it is possible that CTA-based patient evaluation may provide more clinically relevant information on which to base risk assessments compared with conventional “lumenography.” On the other hand, PET is rapidly growing as a powerful and efficient alternative to conventional single-photon emission CT (SPECT) imaging to evaluate regional myocardial perfusion and metabolism in patients with CAD. In addition, PET scanners are now being converted to hybrid PET/CT devices, which, in the setting of CAD, offer the potential for a comprehensive noninvasive cardiac evaluation of anatomy and function. This review will discuss current and potential future applications of cardiovascular CT, PET, and hybrid PET/CT, with a particular focus on ischemic heart disease. The information provided by noninvasive imaging generally falls into 1 of 3 categories: myocardial perfusion, left ventricular (LV) function, or coronary artery anatomy. The clinical utility, value, and role of a noninvasive modality are based on 2 test characteristics: What type of information is provided (eg, stress perfusion, stress and/or rest LV function, coronary anatomy), and what is the accuracy of the information provided. For example, SPECT and PET both provide stress and rest perfusion information, but the latter will be a superior clinical tool if the imaging data better represent the actual defect size and are subject to less artifact. The advantage of PET over SPECT will be further enhanced, as will be discussed later, if it provides additional clinically relevant information not …