technetium-tc-99m-tetrofosmin and Coronary-Occlusion

Computed tomographic coronary angiography (CTA) appears to be a useful modality for the detection of obstructive coronary artery disease (CAD). Recent data suggest that CTA may reduce the frequency of normal invasive coronary angiograms. However, there remains concern that the implementation of CTA could increase referrals to invasive coronary angiography (ICA). To further support the clinical acceptance of CTA, it is important to compare CTA to another accepted modality such as single photon emission computed tomography (SPECT). We followed a cohort of 64-slice CTA patients and a matched cohort of Tc-99m SPECT patients to determine downstream referrals for ICA and revascularization.. Consecutive CTA patients (without history of revascularization or cardiac transplantation) were prospectively enrolled and compared with a Tc-99m SPECT cohort (matched for age, gender, and Morise score). Each CTA and SPECT was evaluated for obstructive CAD and patients were followed for downstream ICA and revascularization. Of the 1221 patients in each cohort, 129 (10.6%) CTA patients and 125 (10.2%) SPECT patients were referred to ICA. Of those referred to ICA, obstructive CAD was confirmed in 105 (81.4%) CTA patients and in 88 (70.4%) SPECT patients. Differences in false positive rates were significantly lower in the CTA than the SPECT cohort (9.7 and 25.8%, respectively, P = 0.009). Rates of revascularization were similar in the CTA and SPECT cohorts (6.2 vs. 5.9%, respectively).. Compared with SPECT, CTA had similar referrals for ICA and revascularization rates but lower false positive rates. Computed tomographic coronary angiography appears to be a viable non-invasive diagnostic modality and does not appear to negatively impact upon ICA resources.

Topics: Aged; Coronary Angiography; Coronary Occlusion; False Positive Reactions; Female; Humans; Male; Middle Aged; Myocardial Revascularization; Organophosphorus Compounds; Organotechnetium Compounds; Prospective Studies; Radiopharmaceuticals; Referral and Consultation; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed

Absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR) provide incremental diagnostic and prognostic information over relative perfusion alone. Recent development of dedicated cardiac SPECT cameras with better sensitivity and temporal resolution make dynamic SPECT imaging more practical. In this study, we evaluate the measurement of MBF using a multipinhole dedicated cardiac SPECT camera in a pig model of rest and transient occlusion at stress using 3 common tracers: (201)Tl, (99m)Tc-tetrofosmin, and (99m)Tc-sestamibi.. Animals (n = 19) were injected at rest/stress with (99m)Tc radiotracers (370/1,100 MBq) or (201)Tl (37/110 MBq) with a 1-h delay between rest and dipyridamole stress. With each tracer, microspheres were injected simultaneously as the gold standard measurement for MBF. Dynamic images were obtained for 11 min starting with each injection. Residual resting activity was subtracted from stress data and images reconstructed with CT-based attenuation correction and energy window-based scatter correction. Dynamic images were processed with kinetic analysis software using a 1-tissue-compartment model to obtain the uptake rate constant K(1) as a function of microsphere MBF.. Measured extraction fractions agree with those obtained previously using ex vivo techniques. Converting K(1) back to MBF using the measured extraction fractions produced accurate values and good correlations with microsphere MBF: r = 0.75-0.90 (P < 0.01 for all). The correlation in the MFR was between r = 0.57 and 0.94 (P < 0.01).. Noninvasive measurement of absolute MBF with stationary dedicated cardiac SPECT is feasible using common perfusion tracers.

Topics: Animals; Blood Flow Velocity; Coronary Occlusion; Coronary Vessels; Disease Models, Animal; Humans; Image Processing, Computer-Assisted; Kinetics; Models, Statistical; Myocardium; Organophosphorus Compounds; Organotechnetium Compounds; Swine; Technetium Tc 99m Sestamibi; Thallium; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed

Myocardial perfusion single-photon emission computed tomography (MPS) can be used to assess myocardium at risk in occlusive coronary ischaemia. The aim was to develop a method to quantify myocardium at risk as perfusion defect size on ex vivo MPS using co-registration and fusion with ex vivo magnetic resonance imaging (MRI).. Pigs (n = 19) were injected 99mTc-tetrofosmin prior to concluding 40 min of coronary artery occlusion, followed by reperfusion and MRI contrast injection. The excised heart was imaged with T1-weighted MRI and MPS, and images were co-registered using freely available software (Segment v1.8, http://segment.heiberg.se). The left ventricle was semi-automatically delineated in MRI and copied to MPS. The threshold for a MPS perfusion defect was defined as the mean counts in the MPS image at the MRI-determined border between remote myocardium and air. The threshold was measured using count maxima set to the 100th-95th percentile of counts within the myocardium. The count maximum that gave the lowest threshold variability (SD) was considered the most robust.. A count maximum using the 100th percentile yielded a threshold of (mean ± SD) 55 ± 6·2%. This method showed the lowest SD compared to 99th-95th percentile count maxima (6·6-7·2%).. We describe a method for objective quantification of myocardium at risk as perfusion defect size on MPS using knowledge of the anatomy of the myocardium from co-registered MRI. This enables simultaneous quantification of myocardium at risk by MPS and infarct size by MRI for the evaluation of treatments for myocardial infarction.

Topics: Animals; Contrast Media; Coronary Circulation; Coronary Occlusion; Disease Models, Animal; Female; Magnetic Resonance Imaging; Male; Myocardial Infarction; Myocardium; Organophosphorus Compounds; Organotechnetium Compounds; Predictive Value of Tests; Radiopharmaceuticals; Swine; Tomography, Emission-Computed, Single-Photon

To evaluate the prognostic value of exercise myocardial scintigraphy in patients undergoing incomplete revascularization by means of percutaneous coronary intervention (PCI) with at least a residual chronic total occlusion (CTO) left untreated.. Of 569 consecutive patients with multivessel disease undergoing myocardial scintigraphy after incomplete revascularization by PCI between March 1997 and December 2004, 126 (79% male, 64+/-10 years) with >or= 1 residual CTO fulfilled the eligibility criteria and entered in the study. Hard events defined as cardiac death and myocardial infarction, soft events defined as incidence of unstable angina and PCI procedures, and their composite were assessed at a median follow-up period of 44 months.. Hard events were observed in six patients (4.8%). All of them had severely abnormal perfusion defects detected by myocardial scintigraphy. Soft events occurred in 0 (0%), 10 (7.9%), and 15 (11.9%) patients with normal, mildly abnormal, and severely abnormal perfusion, respectively. In the Kaplan-Meier analysis, the log-rank test was statistically significant across patients stratified by summed stress score either in terms of hard, soft and hard, or soft events. Univariate and multivariate Cox proportional-hazards showed an incremental significant information when the scintigraphic variables were added to clinical, angiographic, left ventricular ejection fraction, and Duke treadmill score, for prediction of the composite of hard and soft cardiac events (P < 0.006).. Among patients with a residual CTO left untreated after PCI, myocardial perfusion imaging provides significant independent information concerning the subsequent risk of cardiac events.

Topics: Aged; Angioplasty, Balloon, Coronary; Chronic Disease; Coronary Angiography; Coronary Circulation; Coronary Occlusion; Exercise Test; Female; Follow-Up Studies; Heart Diseases; Humans; Male; Middle Aged; Myocardial Perfusion Imaging; Organophosphorus Compounds; Organotechnetium Compounds; Predictive Value of Tests; Prognosis; Proportional Hazards Models; Radiopharmaceuticals; Risk Assessment; Tomography, Emission-Computed, Single-Photon

Topics: Coronary Artery Disease; Coronary Occlusion; Diabetes Complications; Fistula; Heart Diseases; Heart Ventricles; Humans; Male; Middle Aged; Organophosphorus Compounds; Organotechnetium Compounds; Radiopharmaceuticals; Tomography, Emission-Computed, Single-Photon