Thallium Imaging Research Articles

Benefício da revascularização do miocárdio em pacientes com disfunção ventricular e músculo viável: remodelamento ventricular reverso e prognóstico

OBJECTIVES: To evaluate the integration of both viability and clinical parameters on the improvement in systolic performance, symptoms and prognosis, with post-revascularization reverse remodeling. METHOD: One hundred and fifteen patients underwent thallium-201 imaging before myocardial revascularization. Left ventricular ejection fraction, left ventricular end-systolic volume index and left ventricular end-diastolic volume index were determined before and at each 6 months post-revascularization for 3 years. RESULTS: Patients with > 4 viable segments on thallium-201 imaging demonstrated an improvement in left ventricular ejection fraction from 34±6 to 44±4%, p<0.001), left ventricular end-systolic volume decreased from 78.3±11 to 57±17 mL/m2, p<0.001; left end-diastolic volume decreased from 113±31 to 91±22 ml/m2, p<0.001). Patients with < 4 viable segments failed to demonstrate an improvement of the left ventricle ejection fraction, 33.4±4 vs. 35.1±5% (p=0.19), and exhibited ongoing left ventricle end-systolic remodeling, 72±23 vs. 73±12 mL/m2 (p= 0.81), and the left ventricle end-diastolic volume increased from 112±24 to 118±16 mL/m2 (p=0.34), without improvement in NYHA class, and worse long-term prognosis (event; log rank test, p=0.0053). The multivariable analysis demonstrated clinical variables related to the unfavorable evolution showed diabetes, more than one myocardial infarction, and time interval between myocardial infarction and surgery were associated with worse prognosis. CONCLUSION: The benefits of myocardium revascularization in patients with viable muscle, as well as an improvement in the left ventricular ejection fraction, provide reverse remodeling, improvement in functional class and favorable long-term prognosis.

Prognostic value of rest-redistribution 201-Thallium imaging in patients with chronic coronary artery disease and left ventricular dysfunction

Prognostic value of rest-redistribution 201-Thallium imaging in patients with chronic coronary artery disease and left ventricular dysfunction

Incremental prognostic value of exercise single-photon emission computed tomographic (SPECT) thallium 201 imaging in patients with ST-T abnormalities on their resting electrocardiograms

The incremental prognostic value of thallium 201 imaging in patients with nonspecific ST-T abnormalities on the resting electrocardiogram (ECG) may be different from those with a normal resting ECG. Nine hundred thirty-nine consecutive patients with nonspecific ST-T abnormalities on their resting ECG who had undergone exercise 201 Tl imaging were followed for a median duration of 7.0 y (94% complete). The Cox proportional hazards regression model was used in a stepwise fashion to generate (1) a clinical (Cl) model, (2) a clinical and exercise (Cl + Ex) model, (3) and a clinical, exercise, and thallium (Cl + Ex + Tl) model, for the prediction of cardiac death. Age, sex, and diabetes composed the Cl model (chi2 = 63, P < .0001). The Duke treadmill score added to the Cl + Ex model (chi2 = 71, P < .0001). Increased lung uptake (P < .0001) added significantly and summed reversibility score ( P = .03) added modestly to the Cl + Ex + Tl model (chi2 = 96, P < .0001). On the basis of the Cl + Ex + Tl model, the low-, intermediate-, and high-risk groups had a 7-y survival free of cardiac death of 99%, 88%, and 58%, respectively (P < .0001). Using the Cl + Ex + Tl model, only a small number of low-risk and high-risk patients by the Cl + Ex model were reclassified. However, 48% of the 230 patients in the intermediate-risk group by the Cl + Ex model were reclassified as low risk or high risk. 201 Tl imaging has incremental prognostic value in patients with nonspecific abnormalities on their resting ECG. However, patients classified as low risk or high risk by exercise testing using the Cl + Ex model do not require 201 Tl imaging. Intermediate-risk patients should be further risk-stratified by 201 Tl imaging.

Prognostic Value of I-123 Metaiodobenzylguanidine Imaging in Vasospastic Angina Without Significant Coronary Stenosis

Myocardial imaging is widely used to detect coronary artery disease and to assess its prognosis. In vasospastic angina (VA), cardiac imaging can provide information on disease activity, which is related to cardiac events. The aim of this study was to clarify whether exercise thallium-201 imaging (Tl-SPECT) and 123I-metaiodobenzylguanidine imaging (MIBG) have prognostic value for patients with VA, but without significant coronary artery stenosis. One hundred and 5 patients who showed acetylcholine-induced coronary spasm, normal left ventricular function and no significant stenosis (<50%) underwent both symptom-limited Tl-SPECT and MIBG within 1 month. All patients were prescribed calcium antagonist during the follow-up period (mean 4.7 years). Exercise-induced ischemia was detected by Tl-SPECT in 53 patients and multivessel coronary spasm by coronary angiography in 33 patients. During the follow-up period, 1 patient died suddenly and another died of acute myocardial infarction (MI). Two patients developed nonfatal acute MI and 7 patients underwent emergency coronary angiography because of unstable angina. According to the baseline characteristics, VA with cardiac events showed a significantly higher heart-to-mediastinum ratio (H/M ratio) and a significantly lower MIBG washout rate than those without cardiac events (p<0.03 and p<0.02, respectively). Among 8 clinical variables, including coronary risk factors, exercise parameters and exercise-induced ischemia on Tl-SPECT and the MIBG delayed H/M ratio and washout rate, univariate Cox proportional hazard regression analysis showed that the high H/M ratio and reduced washout rate of MIBG were significant predictors of future cardiac events (relative risk (RR) =4, confidence interval (CI) =1.21-13.29, p<0.02 for H/M ratio and RR 0.92, CI 0.85-0.99, p<0.02 for washout rate). However, exercise-induced ischemia did not show any statistical significance. By multivariate Cox proportional hazard regression analysis, a reduced MIBG washout rate was the only significant predictor of future cardiac events (odds ratio =0.90, CI =0.82-1.00, p<0.04). MIBG imaging can identify high-risk patients, even among those with VA who were previously regarded as low risk. This result strongly supports the idea that cardiac sympathetic dysfunction contributes to coronary artery spasm leading to cardiac events.

Cardiac Sarcoidosis

This retrospective study concerned 18 female and 23 male patients with cardiac sarcoidosis (CS). The average age at CS diagnosis was 38 years. CS was observed in white (73% of cases) and in black or Caribbean patients (27% of cases). All patients had extracardiac histologic proof of sarcoid tissue. In 63% of cases, the CS arose during the follow-up of systemic sarcoidosis. Systemic sarcoidosis was not specific except for a high frequency of neurosarcoidosis. Revealing cardiac signs were clinical in 63% of cases and electrical in 22%. In most patients these signs were associated with an abnormal echocardiography (77%) and/or a defect on thallium-201 or sestamibi imaging (75%). Thirty-nine patients received steroid therapy (initial dose mostly equal to 1 mg/kg per day), associated in 13 cases with another immunosuppressive treatment. In 26% of cases the immunosuppressive treatment was associated with a specific cardiac treatment. In the long-term follow-up (average follow-up, 58 mo), 87% of the cases showed an improvement, and 54% were cured from a clinical and laboratory point of view (electrocardiogram, 24-hour monitoring, echocardiography, radionuclide imaging). There was no sudden death. Two patients worsened, which can be explained in 1 case by very late treatment and in the other case by lack of treatment, except for a pacemaker. Our experience leads us to treat CS with corticosteroids as soon as possible and to use another immunosuppressive treatment where there is an insufficient therapeutic response or where there are contraindications to corticosteroids.

Prognostic value of fatty acid imaging in patients with angina pectoris without prior myocardial infarction: comparison with stress thallium imaging

A fatty acid analogue, 123I-labelled beta-methyl iodophenyl pentadecanoic acid (BMIPP), has been used to identify ischaemic and metabolically impaired myocardium. However, the prognostic value of BMIPP imaging, particularly in relation to stress myocardial perfusion imaging, remains unclear. Data from 167 consecutive patients with angina pectoris but without prior myocardial infarction (MI) who had undergone both BMIPP and stress 201Tl (sTL) imaging were analysed. Tracer uptake was graded using a 13-segment, 4-point scoring model. Patients were followed up for 48 months with primary end points (cardiac death, non-fatal MI) as hard cardiac events and with secondary end points (late revascularisation, recurrent angina and heart failure) as soft events. For overall cardiac events (5 hard and 29 soft events), Kaplan-Meier analysis revealed significantly lower event rates in subgroups with normal BMIPP uptake, a summed difference score of sTL (SDS) of <3 or absence of diabetes mellitus when compared to each counterpart. Multivariate Cox's analysis revealed reduced BMIPP uptake, SDS > or =3, diabetes and reduced ejection fraction to be significant predictors. Negative predictive values of normal BMIPP and SDS <3 for all events were 91% and 84%, respectively. No hard event occurred in 66 patients with normal BMIPP uptake, whereas two patients with SDS <3 but impaired BMIPP uptake had hard events. In conclusion, normal BMIPP imaging is an excellent prognostic sign, independently of stress myocardial perfusion imaging, in patients with angina pectoris without prior MI.

A quantitative analysis of I-123 BMIPP uptake in the heart and surrounding tissues

Background: After an exercise-induced ischemia, recent studies have shown prolonged disturbances in myocardial fatty acid metabolism, termed “ischemic memory”, which can be successfully imaged by [ 123I] BMIPP at rest. A potential advantage of BMIPP is that it permits uncoupling of the treadmill stress from tracer injection. In this study, we determined the cardiac image quality of BMIPP by quantifying regional tracer uptake in the heart and surrounding tissues in coronal slices. The results were compared with thallium images obtained in the same patients. Methods: 13 pts with documented reversible thallium defects during exercise underwent subsequent rest BMIPP SPECT imaging within 30 hours of the thallium study. The mean thallium dose injected was 5.2 ± 0.4 mCi while the mean BMIPP dose injected was 3.6 ± 0.4 mCi. After BMIPP injection, two sets of SPECT images were acquired; a 10-minute acquisition obtained 10 minutes after BMIPP injection and a 20-minute acquisition obtained 35–60 minutes after injection. A circular region of interest (ROI) was drawn around the heart, which was then duplicated and repositioned over the lung, liver, and left upper quadrant bowel in coronal slices. Mean counts in each ROI were expressed as lung/heart, liver/heart, and bowel/heart region ratios for thallium, 10-minute BMIPP and 35–60 minute BMIPP images (table). Results: BMIPP images showed excellent cardiac tracer uptake by quantitative SPECT analysis without lung or abdominal visceral interference. The lung/heart and bowel/heart ratios were similar for thallium and BMIPP images. However, the liver/heart ratio was higher for BMIPP images than thallium. Conclusion: The cardiac imaging characteristics of BMIPP are excellent with greater tracer uptake in the heart than the surrounding tissues of lung, liver and bowel. Compared to thallium, BMIPP shows higher liver/heart but similar lung/heart and bowel/heart ratios. However, when the more favorable physical properties of I-123 are taken into consideration, [ 123I] BMIPP becomes an excellent “ischemic memory” cardiac agent. * lung/heart liver/heart bowel/heart BMIPP 10 minute .30 ± .03 .65 ± .18 .25 ± .09 BMIPP 35–60 minute .33 ± .06 .61 ± .15 .30 ± .10 thallium .23 ± .14 .22 ± .07 * .21 ± .06 * different from BMIPP (10 and 35–60 minute) p < 0.03.

The spillover fraction of thallium photons in the I-123 energy window: Implications for post-exercise dual isotope simultaneous [ 123i] BMIPP and thallium imaging

Background: β-Methyl-ω-[p- 123I-phenyl]pentadecanoic acid (BMIPP) is a radiolabeled branched-chain fatty acid analog under clinical investigation in the United States for the detection of myocardial “ischemic memory”. In a recent Phase II clinical trial, BMIPP images acquired within 30 hours of an exercise-induced ischemia by Tl-201 SPECT, showed fatty acid disturbances at rest that were similar in extent and severity to the thallium perfusion defects on stress. The clinical relevance of these data is in the potential for uncoupling the treadmill portion of cardiac SPECT from BMIPP injection and imaging. This sets the stage for post-treadmill dual isotope simultaneous imaging of the ischemic metabolic signal (BMIPP) with rest perfusion signal (Tl-201). The current study, therefore, was undertaken to determine the spillover fraction of Tl-201 photons in the I-123 energy window of BMIPP. Methods: Spillover was calculated by acquiring SPECT data in both Tl-201 and I-123 energy windows for a phantom filled only with Tl-201. The phantom arrangement consisted of a water filled thorax phantom (300 × 230 mm) with a central cylindrical compartment (50 mm diameter) to simulate the heart. The background and heart regions had activity concentrations of 5.3 kBq/ml and 104.9 kBq/ml respectively. All image data were acquired on a dual-head DST gamma camera (SMV, Twinsburg, OH) with low-energy high-resolution collimators. Two separate SPECT acquisitions were performed immediately after one another using the Tl-201 (73 keV 30% + 167 keV 20%) and the I-123 (159 keV 20%) energy windows. The resulting pair of images were analyzed by placing regions-of-interest (ROIs) over corresponding parts of the heart compartment. The spillover fraction was defined as the ROI counts in the I-123 window divided by the ROI counts in the Tl-201 window. Results: The spillover fraction was 0.14 +- 0.01. Conclusion: The spillover fraction of Tl-201 photons in the I-123 energy window is only 14%. If confirmed in the clinical setting, post-treadmill dual isotope simultaneous imaging of BMIPP and thallium may become an attractive alternative to exercise myocardial perfusion SPECT.

Identification of proximal left anterior descending artery stenosis with thallium-201 defect patterns in patients with angina pectoris

We determined the accuracy of perfusion defect patterns in predicting the presence of proximal left anterior descending (LAD) artery stenosis in patients with angina pectoris. The development population consisted of 80 patients with single-vessel LAD stenosis and reversible LAD territory defects on thallium-201 tomography. The types of defect patterns associated with angiographic proximal LAD stenosis in this population were categorized as “proximal LAD patterns.” The accuracy of these patterns for identifying proximal LAD stenosis was evaluated in a separate validation population of 152 patients with angina pectoris. The development population demonstrated LAD territory defects of type I (most of the LAD territory; n = 12); type II (apex, apicoanterior, and most of the septum; n = 26), type III (septum; n = 19); type IV (anteroseptum; n = 6); type V (apex; n = 10); and type VI patterns (anterolateral wall; n = 7). Patients with type I, II, and IV patterns were highly associated with proximal LAD stenosis (38 of 44 segments), whereas those with type III, V, and VI patterns were mostly related to distal LAD disease (29 of 36 segments). In the validation population, proximal LAD patterns had a sensitivity, specificity, and accuracy of 72%, 95%, and 91%, respectively, for identifying patients with proximal LAD stenosis. Test sensitivity was 86% when patients without LAD territory defects were excluded from analysis. Results were virtually identical in the subgroup of 84 patients with stable angina. Thus, recognition of LAD territory thallium defect patterns is useful for identifying patients with angina who are likely to have proximal LAD stenosis.

Stress Imaging in Renal Transplant Candidates

To the Editor: I read with interest the recent paper published by De Lima et al.1 A recent meta-analysis by Rabbat et al2 casts doubt on one conclusion of De Lima et al, as Rabbat et al found that noninvasive stress imaging was predictive of acute myocardial infarction and cardiac death in renal transplant candidates. De Lima et al’s findings regarding the accuracy of dipyridamole single-photon emission computed tomography (SPECT) thallium for prediction of coronary anatomy are generally concordant with previous publications (with the notable exception of Dahan et al,3 who employed a novel stress protocol utilizing combined dipyridamole and exercise thallium imaging in hemodialysis patients). The findings of De Lima et al regarding dobutamine stress echocardiography are difficult to accept in the context of conventional clinical practice. Specifically, the authors in the present study did not administer atropine to augment the heart rate response during the administration of dobutamine. It would be helpful for …

Value of low-dose dobutamine addition to routine dual isotope gated SPECT myocardial imaging in patients with healed myocardial infarction or abnormal wall thickening by echocardiogram

There is overlap in myocardial viability detection by thallium-201 uptake and contractile reserve (CR) using low-dose dobutamine (LDD). The dual isotope protocol was modified in this study by acquiring thallium-201 images using LDD to enhance viability detection in addition to coronary flow reserve assessment. One hundred twenty-four patients with coronary disease underwent gated single-photon emission computed tomographic thallium-201 imaging at rest with LDD (10 μg/kg/min) during acquisition followed by stress technetium-99m sestamibi myocardial perfusion (MP) imaging with dobutamine, adenosine, or treadmill exercise. F-18-fluorodeoxyglucose (FDG) positron emission tomography was obtained in 41 patients. Myocardial perfusion (MP) imaging was divided into normal, fixed, and ischemic segments, and subclassified by wall motion and/or thickening changes between 1-hour poststress and LDD into normal, fixed, or improved dysfunctional segments (CR present). Mean left ventricular ejection fraction was 39% at 1 hour after stress and 47% with LDD (p <0.001). In dysfunctional myocardium, CR was significantly higher (p <0.001) in ischemic (233 of 368) and fixed segments (150 of 335) than in normal MP segments (43 of 220). Combined MP and CR analysis showed higher accuracy and negative predictive value in identifying FDG-viable myocardium than either method alone, whereas a high positive predictive value was maintained, similar to both markers. Quantitative analysis showed significant increased wall motion and thickening with LDD compared with 1 hour after stress, which was highest in ischemic segments and lowest in fixed segments. Thus, LDD dual isotope is a practical protocol that improves viability detection by simultaneous MP and CR analysis in addition to coronary flow reserve assessment in 1 study. Moreover, it requires no extra imaging time or radioactivity than the routine protocol.

Galα(1,3)-galactose on xenogeneic endothelium is a putative ligand for human monocytes

cell transplantation (CD34 /CD45-) was performed in patients with coronary artery disease, an ejection fraction of 35% who are going to have OBCAB. Preoperatively, the patients have an echocardiogram, stress thallium imaging – SPECT, and a cardiac catheterization. These imaging modalities were used in identifying ischemic regions of heart and guide in mapping for injection of the stem cells. Patient follow-up was one, three, and six month echocardiogram, SPECT, and angiography. Results: There were six patients enrolled in the study. All six patients had successful transplantation of autologous stem cells into ischemic myocardium. The median number of grafts peformed was 1. All grafts were patent at 6 months. At 3 and 6 months, there was improvement in perfusion on SPECT imaging in areas injected with stem cells. There were no perioperative arrhythmias, neurological or ischemic myocardial events.

Correlation of plasma concentrations of B-type natriuretic peptide with infarct size quantified by tomographic thallium-201 myocardial scintigraphy in asymptomatic patients with previous myocardial infarction.

Secretion of A-type (atrial) and B-type (brain) natriuretic peptides (ANP and BNP) increases in relation to left ventricular (LV) dysfunction in patients with myocardial infarction (MI). However, it is unknown what determines the concentrations of ANP and BNP in asymptomatic MI patients with preserved LV function, so the aim of the present study was to examine if they are associated with MI size. Plasma concentrations of ANP and BNP in the peripheral blood were measured in 88 asymptomatic (New York Heart Association class I) patients with previous MI. The infarct size was quantitatively calculated from rest thallium-201 myocardial single photon emission computed tomography. In multivariate linear regression analysis that included MI size, hemodynamic parameters, and age as covariables, only BNP concentrations had a significant association with MI size (p=0.0001). In contrast, ANP concentrations were not significantly correlated with MI size in either the univariate or multivariate analysis. BNP but not ANP concentrations increased in proportion to the scintigraphic MI size despite the lack of heart failure in asymptomatic patients with previous MI. Thus, the increase in plasma BNP concentrations reflects the MI size, an important determinant of prognosis, in asymptomatic patients with MI.

ACC/AHA/ASE 2003 Guideline Update for the Clinical Application of Echocardiography: Summary Article: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASE Committee to update the 1997 guidelines for the clinical application of echocardiography)

ACC/AHA/ASE 2003 Guideline Update for the Clinical Application of Echocardiography: Summary Article: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASE Committee to update the 1997 guidelines for the clinical application of echocardiography)

Preoperative comparison of different noninvasive strategies for predicting improvement in left ventricular function after coronary artery bypass grafting

Thallium-201 (Tl-201) imaging and dobutamine stress echocardiography (DSE) are the most frequently used tests in the clinical setting for assessing viability. However, Tl-201 has a suboptimal specificity and DSE a suboptimal sensitivity to predict functional improvement after revascularization. F18-fluorodeoxyglucose (FDG) imaging is considered highly accurate, but availability is limited. Sequential imaging of Tl-201 and DSE may improve accuracy for assessing viability and may be comparable to FDG. Forty-seven patients with ischemic cardiomyopathy underwent Tl-201 single-photon emission computed tomography (SPECT) at rest (4-hour delayed imaging), DSE, and FDG SPECT before bypass surgery. Sensitivity, specificity, and accuracy of 2 sequential strategies were compared with those of FDG SPECT. Strategy 1 considered Tl-201 imaging as the first step, followed by DSE in patients with an intermediate likelihood of viability on Tl-201. Strategy 2 considered DSE as the first step, followed by Tl-201 imaging. Left ventricular ejection fraction was assessed before and 6 months after revascularization, and improvement of ≥5% was considered significant. Tl-201 had a high sensitivity (95%, p <0.05 vs DSE) with a low specificity (57%, p <0.05 vs DSE). DSE had a low sensitivity (63%, p <0.05 vs Tl-201) with a high specificity (89%, p <0.05 vs Tl-201). Both strategies 1 and 2 resulted in high sensitivities (89% and 89%, respectively) and high specificities (89% and 86%, respectively), compared with FDG SPECT (sensitivity 89%, specificity 86%). Sequential testing by Tl-201 SPECT and DSE has a comparable accuracy to FDG SPECT to predict improvement in left ventricular ejection fraction after revascularization. In centers without access to FDG, sequential imaging with Tl-201 and DSE offers an accurate alternative for assessing myocardial viability.

Comparison of the predischarge exercise thallium-201 perfusion defect after myocardial infarction with myocardium at risk measured during acute infarction with technetium-99m sestamibi imaging

Background Exercise thallium-201 imaging provides a noninvasive estimate of the amount of myocardium presumed to be at risk of infarcting should a complete occlusion of the coronary stenosis occur. The relationship between the size of the exercise thallium perfusion defect and the extent of myocardium supplied by a diseased coronary artery has not been established. This study evaluates that presumed correlation. Methods Patients were injected intravenously with technetium-99m sestamibi during acute myocardial infarction before thrombolysis or conventional therapy to quantify the myocardium at risk. Twenty-six patients who underwent risk-area assessment subsequently underwent clinically driven, predischarge, submaximal exercise imaging with thallium-201. The exercise testing was performed on day 7 ± 2 days. A conventional polar map display was used to quantify the perfusion defect. Results The myocardium at risk determined by technetium-99m sestamibi at the time of infarction was 30% ± 20% of the left ventricle. The mean exercise thallium-201 defect was 34% ± 22% of the left ventricle. The exercise defect tended to be slightly larger than the myocardium at risk (4% ± 10% of the left ventricle, P =.05). There was a close correlation between the 2 measurements (r = 0.89, SE = 9.4, P <.0001). Conclusions This study shows a close correlation between the myocardium “at risk” assessed acutely by technetium-99m sestamibi and the “presumed at-risk area” determined by thallium-201 imaging on predischarge exercise testing. This finding supports the concept that the size of the exercise thallium defect caused by coronary stenosis indicates the likely size of a myocardial infarction resulting from occlusion of that stenosis. (Am Heart J 2003;145:357-63.)

Single photon emission computed tomography perfusion imaging for assessment of myocardial viability and management of heart failure.

In the setting of coronary artery disease, some areas of dysfunctional myocardium may realize significant improvement in function as a consequence of revascularization. These areas represent viable myocardium, encompassing a spectrum of pathophysiology ranging from chronic stunning, in which resting blood flow is preserved, to hibernating myocardium, in which resting blood flow is decreased. The accurate preoperative evaluation of viable myocardium helps identify those patients with left ventricular dysfunction who will most benefit from coronary revascularization. Of the various modalities available for viability assessment, the nuclear medicine techniques (201)Thallium and (18)Fluorodeoxyglucose positron emission tomography have emerged as the most sensitive. It has been consistently shown that in patients with a significant amount of viable myocardium, there is a substantial survival benefit in revascularization versus medical therapy. The likelihood of affecting a significant improvement decreases with time to revascularization, however, particularly in the setting of an enlarged left ventricle secondary to ventricular remodeling.

Myocardial perfusion imaging by magnetic resonance imaging.

In the diagnosis and treatment of patients with suspected or known coronary artery disease, noninvasive methodologies for assessing myocardial perfusion have been invaluable. Clinically, nuclear techniques such as single photon emission tomography thallium and sestamibi have predominated. They are limited, however, by the radiation burden, relatively poor spatial resolution, and attenuation artifact caused by soft tissue. In contrast, magnetic resonance imaging (MRI) is notable for its anatomic detail, sharp tissue contrast, excellent spatial and temporal resolution, versatility, and lack of ionizing radiation. It is therefore a potentially attractive alternative to nuclear imaging for the assessment of myocardial perfusion. This review summarizes the principles of MRI myocardial perfusion measurement, discusses recent clinical applications, and highlights future developments in the field.

Transthoracic Doppler assessment of coronary flow velocity reserve in children with Kawasaki disease: Comparison with coronary angiography and thallium-201 imaging

ObjectivesThe purpose of this study was to determine the feasibility of coronary flow velocity reserve (CFVR) measurement by transthoracic Doppler echocardiography (TTDE) in children with Kawasaki disease (KD). BackgroundDoppler-derived CFVR is a reliable marker predicting the presence of myocardial ischemia. MethodsWe studied 49 patients (median age 11 years) with KD. The CFVR was calculated as the ratio of hyperemic to basal peak (peak CFVR) and mean (mean CFVR) diastolic flow velocities in the posterior descending coronary artery (PD) and left anterior descending coronary artery (LAD). The CFVR measurements by TTDE were compared with the results of coronary angiography, thallium-201 (Tl-201) single-photon emission computed tomography (SPECT), and intracoronary Doppler study. ResultsThe CFVR measurements by TTDE were obtained in 92 (94%) of 98 vessels of the PD and LAD in 49 study patients. Both peak and mean CFVRs for 21 stenotic vessels were significantly smaller than those for 35 normal vessels and for 20 vessels with aneurysmal lesions (p < 0.0001). Peak and mean CFVR <2.0 predicted significant coronary stenosis, as determined by coronary angiography, with sensitivities and specificities of 89% and 96% and 89% and 97%, respectively. Also, both peak and mean CFVRs were correlated with reversible perfusion defects on Tl-201 SPECT (agreement 80%; kappa 0.4). The correlation between peak and mean CFVRs determined by the TTDE and intracoronary Doppler studies in 36 vessels of 23 patients were 0.76 and 0.80, respectively. ConclusionsThe CFVR measured by TTDE predicts the presence of significant coronary stenosis of either the right coronary artery or LAD, as well as myocardial ischemia of these territories in children with KD.

The beneficial effect of revascularization on jeopardized myocardium: reverse remodeling and improved long-term prognosis.

To evaluate the impact of viability/ischemia before revascularization on improvement in systolic performance, reverse remodeling, symptoms and long-term prognosis post-revascularization. Fifty patients underwent thallium-201 imaging before revascularization to assess stress-induced ischemia and viability ('jeopardized myocardium'). Left ventricular (LV) ejection fraction (EF), LV end-systolic volume index (LVESVI) and LV end-diastolic volume index (LVEDVI) were determined before and 3 months post-revascularization. Graft/vessel patency was controlled by repeat angiography. Long-term follow-up data (New York Heart Association (NYHA) class, hard events) were acquired up to 3 years. Patients with > or = 5 jeopardized segments on thallium-201 imaging demonstrated improvement of LVEF at 3 months (from 35+/-6 to 43+/-6%, P<0.001), with reverse remodeling (LVESVI decreased from 68+/-16 to 52+/-14 ml/m(2), P<0.001; LVEDVI decreased from 103+/-21 to 91+/-18 ml/m(2), P<0.001), and improved in NYHA class with excellent long-term prognosis (0% event rate). Conversely, patients with <5 jeopardized segments failed to improve in LVEF (34+/-4 vs. 33+/-7%, NS), and exhibited ongoing remodeling (LVESVI increased from 70+/-14 to 78+/-23 ml/m(2), P<0.001; LVEDVI increased from 106+/-19 to 116+/-25 ml/m(2), P<0.001), without improvement in NYHA class, and worse long-term prognosis (29% event rate). Patients with jeopardized myocardium benefit from revascularization with improvement in LVEF, reverse remodeling, improvement in NYHA class and favorable long-term prognosis.