Assessment Of Coronary Blood Flow Research Articles

Thrombolysis in Myocardial Infarction Frame Count for Coronary Blood Flow Evaluation during Interventional Diagnostic Procedures.

Background and Objectives: An interventional diagnostic procedure (IDP), including intracoronary acetylcholine (ACh) provocation and coronary physiological testing, is recommended as an invasive diagnostic standard for patients suspected of ischemia with no obstructive coronary arteries (INOCA). Recent guidelines suggest Thrombolysis In Myocardial Infarction frame count (TFC) as an alternative to wire-based coronary physiological indices for diagnosing coronary microvascular dysfunction. We evaluated trajectories of TFC during IDP and the impact of ACh provocation on TFC. Materials and Methods: This was a single-center, retrospective study. Patients who underwent IDP to diagnose INOCA were included and divided into two groups according to the positive or negative ACh provocation test. Wire-based invasive physiological assessment was preceded by ACh provocation tests and intracoronary isosorbide dinitrate (ISDN). We evaluated TFC at three different time points during IDP; pre-ACh, post-ISDN, and post-hyperemia. Results: Of 104 patients, 58 (55.8%) had positive ACh provocation test. In the positive ACh group, resting mean transit time (Tmn) and baseline resistance index were significantly higher than in the negative ACh group. Post-ISDN TFC was significantly correlated with resting Tmn (r = 0.31, p = 0.002). Absolute TFC values were highest at pre-ACh, followed by post-ISDN and post-hyperemia in both groups. All between-time point differences in TFC were statistically significant in both groups, except for the change from pre-ACh to post-ISDN in the positive ACh group. Conclusions: In patients suspected of INOCA, TFC was modestly correlated with Tmn, a surrogate of coronary blood flow. The positive ACh provocation test influenced coronary blood flow assessment during IDP.

Lumped-parameter model as a non-invasive tool to assess coronary blood flow in AAOCA patients

Anomalous aortic origin of the coronary artery (AAOCA) is a rare disease associated with sudden cardiac death, usually related to physical effort in young people. Clinical routine tests fail to assess the ischemic risk, calling for novel diagnostic approaches. To this aim, some recent studies propose to assess the coronary blood flow (CBF) in AAOCA by computational simulations but they are limited by the use of data from literature retrieved from normal subjects. To overcome this limitation and obtain a reliable assessment of CBF, we developed a fully patient-specific lumped parameter model based on clinical imaging and in-vivo data retrieved during invasive coronary functional assessment of subjects with AAOCA. In such a way, we can estimate the CBF replicating the two hemodynamic conditions in-vivo analyzed. The model can mimic the effective coronary behavior with high accuracy and could be a valuable tool to quantify CBF in AAOCA. It represents the first step required to move toward a future clinical application with the aim of improving patient care. The study was registered at Clinicaltrial.gov with (ID: NCT05159791, date 2021-12-16).

Characterization and implications of intracoronary hemodynamic assessment during coronary spasm provocation testing.

Current diagnostic criteria for coronary spasm are based on patient's symptoms, ECG shifts and epicardial vasoconstriction during acetylcholine (ACh) spasm testing. To assess the feasibility and diagnostic value of coronary blood flow (CBF) and resistance (CR) assessment as objective parameters during ACh testing. Eighty-nine patients who underwent intracoronary reactivity testing including ACh testing with synchronous Doppler wire-based measurements of CBF and CR were included. Coronary microvascular and epicardial spasm, respectively, were diagnosed based on COVADIS criteria. Patients were 63 ± 13years old, predominantly female (69%) and had preserved LV ejection fraction (64 ± 8%). Overall, assessment of CBF and CR during ACh testing revealed a decrease in CBF of 0.62 (0.17-1.53)-fold and an increase of CR of 1.45 [0.67-4.02]-fold in spasm patients compared to 2.08 (1.73-4.76) for CBF and 0.45 (0.44-0.63) for CR in patients without coronary spasm (both p < 0.01). Receiver operating characteristic revealed a high diagnostic ability of CBF and CR (AUC 0.86, p < 0.001, respectively) in identifying patients with coronary spasm. However, in 21% of patients with epicardial spasm and 42% of patients with microvascular spasm a paradoxical response was observed. This study demonstrates feasibility and potential diagnostic value of intracoronary physiology assessments during ACh testing. We observed opposite responses of CBF and CR to ACh in patients with positive vs. negative spasm test. While a decrease in CBF and an increase in CR during ACh seem pathognomonic for spasm, some patients with coronary spasm demonstrate paradoxical ACh response demanding further scientific investigations.

Transesophageal echocardiography: a tool for intraoperative assessment of coronary blood flow

Transesophageal echocardiography (TEE) has become an indispensable part of cardiac surgery, but its potential for assessing coronary anatomy and blood flow remains underutilised. This case report presents a case of acute iatrogenic left main coronary artery obstruction following re-operative aortic valve replacement that was promptly diagnosed by intraoperative TEE and managed successfully by Bentall operation. We also emphasise the technique of TEE for coronary evaluation, its caveats and its clinical application during cardiac surgery.

Coronary Microvascular Disease.

Coronary microvascular disease or dysfunction (CMVD) has been associated with adverse cardiovascular outcomes. Despite a growing prevalence, guidelines on definitive treatment are lacking. Proposed mechanisms of endothelial dysfunction and resultant inflammation have been demonstrated as the underlying cause. Imaging modalities such as echocardiography, cardiac MRI, PET, and in some instances CT, have been shown to be useful in diagnosing CMVD mainly through assessment of coronary blood flow. Invasive measurements through thermodilution and pressure sensor-guided Doppler microcatheters have also been utilized. Treatment options are directed at targeting inflammatory pathways and angina. In our review, we highlight the current literature on the background of CMVD, diagnostic modalities, and management of this disease.

Functional assessment of coronary blood flow as contemporary method for optimizing results of percutaneous coronary interventions in patients with ischemic heart disease

Coronary angiography is still the ‘gold standard’ in assessing the severity of stenotic lesions of the coronary arteries in the catheter laboratory. However, it is often difficult to identify the hemodynamic significance of one or another coronary artery stenosis, which is especially difficult in the case of borderline lesions with a coronary artery stenosis of 40–70 % according to angiography. It is important to note that the results of performed PCI are still largely assessed only on the basis of control angiographic data. This is due to the fact that the largest difference between angiography and FFR is in the intermediate range, and in general there is much less variation between angiography and fractional blood flow reserve (FFR) in the severe and mild lesions. However, the results of studies evaluating FFR after PCI showed a wide range of FFR values after satisfactory results of stenting according to angiography data. This additionally confirms the thesis that only one angiography is limited in determining the ischemic boundaries after PCI, and the level of FFR values after PCI is directly related to the results in the long-term period. Percutaneous coronary interventions under the control of FFR allows the operator to improve the results of endovascular treatment of coronary lesions in patients with coronary heart disease. The use of FFR in a catheter laboratory contributes to an increase in the clinical and economic efficiency of procedures, which is achieved due to the fact that the determination of FFR before PCI can significantly reduce the number of stents implanted during PCI, as well as to avoid unnecessary PCI stages in the treatment of patients with lesions of the LMCA. In addition, FFR allows to timely optimize the results of suboptimal PCI, as well as to reduce the frequency of main adverse cardiovascular events in the long-term period.

Accurate assessment of coronary blood flow by continuous thermodilution technique: Validation in a swine model.

To assess the accuracy of coronary thermodilution measurements made with the RayFlow® infusion catheter. Measurements of absolute coronary blood flow (ABF) and absolute microvascular resistance (Rμ ) by continuous coronary thermodilution can be obtained in humans but their accuracy using a novel dedicated infusion catheter has not yet been validated. We compared ABF values obtained at different infusion rates to coronary blood flow (CBF) values obtained using flow probes, in swine. Twelve domestic swine were instrumented with coronary flow probes placed around the left anterior descending and circumflex coronary arteries. ABF was assessed with the RayFlow® infusion catheter during continuous saline infusion at fixed rates of 5 (n=14), 10 (n=15), 15 (n=19), and 20 (n=12) ml/min. In the 60 measurements, ABF measured using thermodilution averaged 41 ± 17 ml/min (range from 17 to 90) and CBF values obtained with the coronary flow probes averaged 37 ± 18 ml/min (range from 8 to 87). The corresponding Rμ values were 1532 ± 791 (range from 323 to 5103) and 1903 ± 1162 (range from 287 to 6000) Woods units using thermodilution and coronary flow probe assessments, respectively. ABF and Rμ values measured using thermodilution were significantly correlated with the corresponding measurements obtained using coronary flow probes (R=0.84 [0.73-0.95] and R=0.80 [0.69-0.88], respectively). ABF and Rμ assessed by continuous saline infusion through a RayFlow® catheter closely correlate with measurements obtained with the gold standard coronary flow probes in a swine model.

The role of invasive coronary physiology in Takotsubo Syndrome.

The pathophysiology of Takotsubo Syndrome has not yet been precisely defined. Different hypotheses have been proposed, including cardiotoxicity due to catecholaminergic hormone release, metabolic disorders, coronary microvascular dysfunction and epicardial coronary artery spasm. Invasive coronary physiology is considered the cornerstone to understand physiological assessment of coronary blood flow in this setting. We have reviewed most important studies in coronary invasive physiology in this field to update the state of the art in TakoTsubo Syndrome.

High-Resolution Cardiac Magnetic Resonance Imaging Techniques for the Identification of Coronary Microvascular Dysfunction

ObjectivesThis study assessed the ability to identify coronary microvascular dysfunction (CMD) in patients with angina and nonobstructive coronary artery disease (NOCAD) using high-resolution cardiac magnetic resonance (CMR) and hypothesized that quantitative perfusion techniques would have greater accuracy than visual analysis. BackgroundHalf of all patients with angina are found to have NOCAD, while the presence of CMD portends greater morbidity and mortality, it now represents a modifiable therapeutic target. Diagnosis currently requires invasive assessment of coronary blood flow during angiography. With greater reliance on computed tomography coronary angiography as a first-line tool to investigate angina, noninvasive tests for diagnosing CMD warrant validation. MethodsConsecutive patients with angina and NOCAD were enrolled. Intracoronary pressure and flow measurements were acquired during rest and vasodilator-mediated hyperemia. CMR (3-T) was performed and analyzed by visual and quantitative techniques, including calculation of myocardial blood flow (MBF) during hyperemia (stress MBF), transmural myocardial perfusion reserve (MPR: MBFHYPEREMIA / MBFREST), and subendocardial MPR (MPRENDO). CMD was defined dichotomously as an invasive coronary flow reserve <2.5, with CMR readers blinded to this classification. ResultsA total of 75 patients were enrolled (57 ± 10 years of age, 81% women). Among the quantitative perfusion indices, MPRENDO and MPR had the highest accuracy (area under the curve [AUC]: 0.90 and 0.88) with high sensitivity and specificity, respectively, both superior to visual assessment (both p < 0.001). Visual assessment identified CMD with 58% accuracy (41% sensitivity and 83% specificity). Quantitative stress MBF performed similarly to visual analysis (AUC: 0.64 vs. 0.60; p = 0.69). ConclusionsHigh-resolution CMR has good accuracy at detecting CMD but only when analyzed quantitatively. Although omission of rest imaging and stress-only protocols make for quicker scans, this is at the cost of accuracy compared with integrating rest and stress perfusion. Quantitative perfusion CMR has an increasingly important role in the management of patients frequently encountered with angina and NOCAD.

Coronary Blood Flow Measurement in Conventional Coronary Angiograms by a New Method Based on Contrast Density Detection. A Physiological Insight.

ResumoFundamento O grau de fluxo TIMI e a contagem quadro a quadro TIMI corrigida (CTFC) são métodos amplamente utilizados para avaliar o fluxo sanguíneo coronariano angiográfico. A medição do fluxo sanguíneo coronariano (FSC) na coronariografia (CAG) padrão despertou grande interesse recentemente, tentando combinar o conceito de CTFC com novos métodos para pós-angioplastia e avaliação da síndrome cardíaca X. Além disso, o fluxo coronariano lento é considerado um critério importante para a angina microvascular.Objetivo Explorar uma nova abordagem de medição angiográfica quantitativa do FSC com base na detecção densitométrica de contraste na CAG offline, usando um software acessível para obter uma avaliação mais precisa e confiável do FSC.Métodos Trinta pacientes foram estudados e divididos em 2 grupos: fluxo sanguíneo coronariano normal (FN) e fluxo sanguíneo coronariano lento (FL), de acordo com a definição da CTFC. O MD foi aplicado à amostra do estudo para diferenciar entre FN e FL. A estatística não paramétrica foi usada para avaliar diferenças entre os grupos com p<0,05.Resultados O valor de referência normal do MD obtido para o fluxo sanguíneo coronariano foi de 9 [5–10] quadros. Os grupos FN vs. FL foi comparado e expresso como mediana [intervalo interquartil], para a artéria descendente anterior esquerda: 10 [7–11] vs. 21 [8–33]; p=0,016; artéria circunflexa: 9 [4–13] vs. 14 [11–30]; p=0,012 e artéria coronária direita: 5 [3–11] vs. 13 [8–26]; p=0,009.Conclusão O MD mostrou a viabilidade de medir o fluxo sanguíneo coronariano com precisão, consistência e reprodutibilidade em um angiograma coronariano padrão, mostrando a capacidade adicional de diferenciar FN de FL em pacientes com dor precordial e artérias coronárias normais. (Arq Bras Cardiol. 2020; 115(3):503-512)

Imaging to Assess Ischemic Heart Disease in Women.

Ischemic heart disease is a leading cause of morbidity and mortality for women and men around the world. However, traditional cardiovascular risk factors do not fully capture cardiac risk in women. This review summarizes sex-based differences in the clinical presentation, pathophysiology, and risk assessment of ischemic heart disease. We also examine the use of anatomic and functional imaging modalities in the diagnosis of ischemic heart disease in women. Recent studies with women subjects have bolstered the predictive value of the coronary artery calcium (CAC) score in predicting atherosclerotic cardiovascular disease risk and major adverse cardiac events in a graded fashion. In addition, combined CAC scoring and coronary computed tomography (CCTA) has shown promise in excluding coronary artery disease (CAD). Using CCTA, data have suggested that increasing cardiovascular risk factors are associated with an increase in noncalcified coronary plaque in women compared with an increase in both calcified and noncalcified plaque in men with cardiac risk factors. Some data have suggested that women obtain greater prognostic benefit from CCTA than from other noninvasive tests. Fractional flow reserve obtained from a CCTA (FFRCT) is a new mathematical assessment of coronary blood flow that determines the presence of lesion-specific myocardial ischemia. Prevention and identification of ischemic heart disease remains a foundation of cardiology and public health. In women, atypical symptoms and limitations in traditional risk factor assessment lead to challenges in the identification of ischemic heart disease. With improvements in technologies such as CAC scoring, CCTA, instantaneous flow reserve (iFR), optical coherence tomography (OCT), and FFRCT, there is great promise for identification of ischemic heart disease, and the future of prevention in women. Future studies with strong female representation should investigate the role of novel imaging techniques in women.

Показатели глобальной продольной деформации миокарда левого желудочка и коронарного кровотока у пациентов с первичным гипотиреозом

Assessment of global longitudinal strain of left ventricle and coronary bloodflow in patients with primary subclinical hypothyroidism. The study involved 23 women with primary subclinical hypothyroidism of age from 55 to 75 years. Physical examination, transthoracic EchoCG, coronary bloodflow assessment and global LV longitudinal strain by speckle tracking method were performed to all patients. The data obtained were compared to the results of 20 women without any thyroid diseases comparable to the main group by age and concomitant diseases. Patients with primary subclinical hypothyroidism have signs of diastolic dysfunction significantly more frequently than in control group, and increased values of posterior left ventricle wall and interventricular septum thickness. Global longitudinal strain of left ventricle in patients with hypothyroidism was lower than in control group and patients with hypothyroidism had higher FVI values in perforant coronary arteries. Patients with subclinical hypothyroidism demonstrated decrease of global longitudinal strain and increase of volume bloddflow rate in performant coronary arteries.

The Role of Radionuclide Imaging in Congenital Heart Disease

Congenital heart disease is a growing healthcare issue since the majority of children who underwent surgical repair are now surviving into adult life. However, these patients are generally fixed but not cured and many will go on to develop significant morbidity as adults. The purpose of this review is to discuss the utility of radionuclide imaging in the management of these patients with a focus on the longer-term follow-up into adult life. Radionuclide imaging is a relatively niche tool in the management of congenital heart disease patients and many of the techniques have been around for decades. What is new is the application of techniques such as fluorodeoxyglucose (FDG) imaging for endocarditis and device infection using anatomic colocalization by MR-PET or PET-CT. There is also growing interest in the quantitative assessment of coronary blood flow with tracers such as rubidium that are available without the need for a cyclotron on site. This is likely to be very useful in the management of patients with coronary anomalies or surgically re-implanted coronary arteries. Radionuclide imaging has specific but rather limited application to congenital heart disease at the current time. With the development of new molecular imaging agents, low-dose protocols, and the wider availability of hybrid imaging modalities, we suggest that the ground is prepared for a resurgence of interest in the application of these techniques to the population of patients living with congenital heart disease.

Noninvasive assessment of coronary blood flow by transthoracic Doppler echocardiography: basic to practical use in the emergency room.

Echo Doppler is widely available in the clinical setting, and the feasibility of coronary flow detection in the left anterior descending coronary artery has been reported as >90% with the use of a high-frequency transducer. Coronary flow detection takes only a few minutes by skilled echocardiologists, and this noninvasive technique can provide useful physiological information in patients with various types of coronary artery disease. Coronary flow velocity reserve measurement by echo Doppler is a simple and easy technique. It is available in the echo laboratory as well as in the outpatient clinic, and can be used as an alternative examination to screen for significant coronary stenosis in patients with stable angina. Moreover, physiological information provided by coronary flow velocity reserve can be used in combination with other imaging modalities that can provide anatomical information of the coronary arteries such as coronary computed tomography or coronary angiography. Coronary flow velocity in patients with acute coronary syndrome (ACS) enables rapid noninvasive differentiation of TIMI-III from TIMI-II coronary reperfusion before emergency coronary intervention. Transthoracic coronary flow detection by echo Doppler contributes to the assessment of the coronary reperfusion status in the emergency room for patients with ACS, prior to invasive coronary angiography.

Fluoroscopy Assisted Scoring of Myocardial Hypoperfusion (FLASH) ratio as a novel predictor of mortality after primary PCI in STEMI patients

BackgroundThe aim of this study was to investigate whether Fluoroscopy Assisted Scoring of Myocardial Hypoperfusion (FLASH) enabled a more accurate assessment of coronary blood flow and prediction of cardiac mortality after primary PCI (pPCI), than the presently used angiographic scores of reperfusion. MethodsWe included 453 STEMI patients who received pPCI at our hospital. Using the novel FLASH algorithm, based on contrast passage time and quantitative coronary analysis, FLASH flow was measured after pPCI and was used to calculate FLASH ratio of culprit and reference artery. In 28 of the 453 patients, FLASH flow was compared to Doppler-derived-flow. ResultsFLASH flow had a good correlation with Doppler derived flow (Pearson's R=0.65, p<0.001) and had a high inter-observer agreement (ICC=0.83). FLASH flow was significantly lower in patients that died of cardiac death within six months (25.9±17.7ml/min vs. 38.2±18.8ml/min, p=0.004). FLASH ratio had a high accuracy of predicting cardiac mortality with a significant higher area under the curve as compared with CTFC and QuBe (p=0.041 and p=0.008). FLASH ratio was an independent predictor of mortality at 6months (HR=0.98 per 1% increase, p=0.014). ConclusionFLASH is a simple non-invasive method to estimate coronary blood flow and predict mortality directly following pPCI in STEMI patients, with a higher accuracy compared to the presently used angiographic scores.

Assessment of Coronary Blood Flow in the Cardiac Catheterization Laboratory

Coronary blood flow is tightly autoregulated but is subject to epicardial and microvascular obstruction, primarily owing to coronary atherosclerosis. Because coronary flow limitation underlies ischemic heart disease, an understanding of coronary physiology is paramount. Measurement of coronary blood flow, once relegated to the research laboratory is now easily performed in the cardiac catheterization laboratory. In particular, the measurement of fractional flow reserve has been extensively studied and is an important adjunct to clinical decision making. Measurement of coronary flow informs clinicians of prognosis, guides revascularization therapy, and forms the basis of ongoing research in treatment of complex myocardial disease processes. Newer methods of assessing coronary flow measurements are undergoing validation for clinical use and should further enhance our ability to assess the importance of coronary flow in clinical disease.

Recurrent angina after coronary angioplasty: mechanisms, diagnostic and therapeutic options

Recurrent angina in patients who underwent percutaneous coronary intervention is defined as recurrence of chest pain or chest discomfort. Careful assessment is recommended to differentiate between non-cardiac and cardiac causes. In the case of the latter, recurrent angina occurrence can be related to structural ('stretch pain', in-stent restenosis, in-stent thrombosis, incomplete revascularization, progression of coronary atherosclerosis) or functional (coronary micro-vascular dysfunction, epicardial coronary spasm) causes. Even though a complete diagnostic algorithm has not been validated, ECG exercise testing, stress imaging and invasive assessment of coronary blood flow and coronary vaso-motion (i.e. coronary flow reserve, provocation testing for coronary spasm) may be required. When repeated coronary revascularization is not indicated, therapeutic approaches should aim at targeting the underlying mechanism for the patient's symptoms using a variety of drugs currently available such as beta-blockers, calcium-channel blockers, ivabradine or ranolazine.

Assessment of Coronary Blood Flow in Children with Chronic Renal Failure on Regular Hemodialysis

Background: Coronary flow reserve (CFR) reflects the functional capacity of the microcirculation to adapt to blood demand during increased cardiac work. Diminished CFR may account for several symptoms that are often encountered in haemodialysis patients such as chest pain, arrhythmia and hypotension. lschemic heart disease is by far the leading cause of morbidity and mortality in haemodialysis (HD) patients. Sіnce prevention is not easy, early detection of the disease is the key issue.Objectives: Assessment of coronary flow reserve in children with chronic renal failure on regular hemodialy-sis with transthoracic Doppler echocardiography using dipyridamole as and inducer of coronary hyperemia. Methods: Sixty children of matching age and sex were included in this study, 20 healthy children as a control group and 40 children with chronic renal failure on regular haemodialysis. All studied children were subjected complete history taking, thorough clinical examination, laboratory investigations and assessment of coronary flow reserve with transthoracic Doppler echocardiography using dipyridamole as inducer of coronary hyperemia.Results: There was a significant negative correlation between CFR and LVMI, duration of dialysis, serum cholesterol, triglycerides, LDL levels and blood pressure in hemodialysis patients. A significant positive correlation between CFR and serum IIDI. level was found. There was no significant correlation between CFR and different laboratory parameters.Conclusion: CFR is significantly reduced in children with CAF on regular hemodialysis. Control of blood pressure, correction of anemia and hypervolemia, diet management and physical activity are important in the prevention of / decrease in or improving the coronary flow reserve (CFR).

Influence of polymeric microspheres on the myocardial oxygen partial pressure in the beating heart of pigs

Injection of labeled microspheres is an established method in animal models to analyze the capillary organ blood flow at different time points. However, the microspheres can lead to stenoses of the capillary lumen, which might affect tissue oxygen supply. Our study aimed to investigate the influence of repeated injections of microspheres into the left coronary artery on the tissue oxygen partial pressure (pO 2) in the downstream supplied myocardium of Göttingen minipigs. Tests ( n = 6 pigs each) were performed with two differently sized microspheres ( ø = 10 ± 0.1 μm (M10) or ø = 15 ± 0.15 μm (M15)) from polystyrene. The pO 2 was measured in the midmyocardium of the left and right ventricle for 6 min continuously after each of five injections (1 × 10 6 microspheres each). There was a time laps of 12 min between each injection. In addition, the influence of the carrier solution was analyzed solely in the identical time frame. pO 2 decreased significantly in the myocardial area supplied by the ramus interventricularis paraconalis after injection of M15 microspheres. In contrast, the application of the M10 microspheres did not change the myocardial pO 2. This finding suggests to use microspheres with diameters not exceeding 10 μm for the coronary blood flow assessment.

Microvascular Angina: Assessment of Coronary Blood Flow, Flow Reserve, and Metabolism

Microvascular angina (MVA) is an often overlooked cause of significant chest pain. Decreased myocardial perfusion secondary to dysregulated blood flow in the microvasculature can occur in the presence or absence of obstructive epicardial coronary artery disease. The corresponding myocardial ischemia and angina is now a well-established diagnosis, made by detection of decreased coronary flow reserve (CFR). Although low CFR and MVA are associated with poor prognosis, there is initial evidence for reversibility of this abnormal vascular regulation with aggressive medical therapy and control of associated risk factors. Current assessment of MVA is carried out predominantly during cardiac catheterization; however, noninvasive techniques to assess CFR are being developed, including PET, MRI, and CT modalities. Quantitative tracer techniques or imaging of metabolic disturbances reflecting ischemia will likely enhance diagnostic approaches for such patients as well as allow more frequent monitoring of response to therapy.