Real-time radionuclide cineangiography in the noninvasive evaluation of global and regional left ventricular function at rest and during exercise in patients with coronary-artery disease

Survival after Aortic Valve Replacement for Aortic Regurgitation: Prediction from Preoperative Contractility Measurement

BACKGROUND

Noninvasive measurement of myocardial contractility (end-systolic wall stress-adjusted change in left ventricular ejection fraction from rest to exercise [ΔLVEF - ΔESS]) predicts heart failure, subnormal LVEFrest, and sudden death in asymptomatic patients with chronic severe aortic regurgitation (AR). Here we assess the relation of preoperative ΔLVEF - ΔESS to survival after aortic valve replacement (AVR).

METHODS

Patients who underwent AVR for chronic, isolated, pure severe AR (n = 66) were followed for 13.0 ± 6.4 event-free years. Preoperative ΔLVEF - ΔESS (from combined echocardiographic and radionuclide cineangiographic data) enabled cohort stratification into 3 terciles (-1 to -11% [normal or mild] contractility deficit, -12 to -16% [moderate], and ≤-17% [severe], identical with segregation in our earlier study) to relate preoperative contractility to postoperative survival and to age- and gender-matched US census data.

RESULTS

Since AVR, 22 patients died (average annual risk [AAR] for all-cause mortality for the entire co hort = 3.15%). Preoperative ΔLVEF - ΔESS predicted postoperative survival (p = 0.009, log rank test). By contractility terciles, all-cause AARs were 1.44, 2.58, and 6.40%. Survival was lower than among US census comparators (p < 0.02), but the "mild" tercile was indistinguishable from census data (p = ns). By multivariable Cox regression, survival prediction by pre-AVR ΔLVEF - ΔESS was independent of, and superior to, prediction by age at surgery, gender, preoperative functional class, LVEFrest, LVEFexercise, change in LVEFrest to exercise, and LV diastolic or systolic dimensions (p ≤ 0.01, pre-AVR ΔLVEF - ΔESS vs. other covariates).

CONCLUSION

In severe AR, preoperative contractility predicts post-AVR survival and may be prognostically superior to clinical, geometric and performance descriptors, potentially impacting on patient selection for surgery.

Clinical value of hyperemic left ventricular systolic function in vasodilator stress testing

Exercise results in increased left ventricular contractility in normal individuals. Similar changes can also be seen with vasodilator stress. This article discusses the physiologic basis of these changes as well as reviews the clinical data supporting the use of these parameters for diagnostic and prognostic evaluation. Methodologic limitations as well as other concomitant pathologic processes which may confound interpretation of stress-induced changes in LVEF are also reviewed.

Nonischemic mitral regurgitation: prognostic value of nonsustained ventricular tachycardia after mitral valve surgery

BACKGROUND

Nonsustained ventricular tachycardia (VT), frequent in unoperated severe mitral regurgitation (MR), confers mortality risk [sudden death (SD) and cardiac death (CD)]. The prognostic value of VT after mitral valve surgery (MVS) is unknown; we aimed to define this prognostic value and to assess its modulation by left (LV) and/or right (RV) ventricular ejection fraction (EF) for mortality after MVS.

METHODS

In 57 patients (53% females, aged 58 ± 12 years) with severe MR prospectively followed before and after MVS, we performed 24-hour ambulatory electrocardiograms approximately annually. LVEF and RVEF were determined within 1 year after MVS by radionuclide cineangiography.

RESULTS

During 9.52 ± 3.49 endpoint-free follow-up years, late postoperative CD occurred in 11 patients (7 SD, 4 heart failures). In univariable analysis, >1 VT episode after MVS predicted SD (p < 0.01) and CD (SD or heart failure; p < 0.04). Subnormal postoperative RVEF predicted CD (p < 0.04). When adjusted for preoperative age, gender, etiology or antiarrhythmics, both postoperative VT and RVEF predicted CD (p ≤ 0.05). When postoperative VT and RVEF were both in the multivariable model, only subnormal RVEF predicted CD (p < 0.04). Among those with normal RVEF, VT >1 episode predicted SD (p = 0.03).

CONCLUSION

Postoperative VT and subnormal RVEF predict late postoperative deaths in nonischemic MR. Their assessment may aid patient management.

ST depression and left ventricular haemodynamics during exercise in patients with angina pectoris

The mechanism of ischaemic ST depression and the cause of its low sensitivity to coronary artery stenosis are not well understood. Of 30 patients with severe stable effort angina, 19 (63%) showed ischaemic ST depressions after exercise (the STAE group) and 11 did not. The highest load during the symptom-limited exercise test and the heart rate on that load did not differ between the two groups. The clinical characteristics and angiographic findings were also similar, but the findings at heart catheterization differed during exercise (in supine). Although the load was similar, the stroke index was significantly lower (38 vs. 53 ml/m2 BSA) and the left ventricular end-diastolic pressure rose to a significantly higher value in the STAE group (40 vs. 32 mmHg). When STAE occurred, they were exclusively or concomitantly present in chest lead 5. These findings suggest that ischaemic STAE may not reflect regional ischaemia but the consequent left ventricular dysfunction. The mechanism may, for example, be that a sufficiently elevated left ventricular diastolic pressure causes a global subendocardial ischaemia.

The effect of atenolol on the left ventricular performance in patients with angina pectoris measured with isotope technique

Working capacity, left ventricular ejection fraction (EF), stroke volume and the phase of the left ventricular contraction were tested before and after 3 weeks of atenolol treatment in 14 patients with angina pectoris and coronary insufficiency diagnosed by thallium tomography. Eight patients (group A) increased their EF during exercise and six patients (group B) showed a decrease in EF when tested with placebo. When treated with atenolol the changes in EF during exercise were reversed in the two groups. Group B increased and group A decreased their EF. Atenolol caused an increase in working capacity in group B, but not in group A. In both groups atenolol caused an increased stroke volume and a decreased phase deviation at rest, while no significant volume changes or phase changes occurred during exercise. These results indicate that atenolol treatment had the most marked effect in patients with the most pronounced disease.

M-mode echocardiographic mapping in differentiation of normal from dysfunctioning left ventricular myocardium. A study of patients with severe myocardial infarction and healthy controls

Seventeen severely ill patients with acute myocardial infarction (AMI) (12 men and 5 women; mean age 65) and 37 healthy persons with similar age and sex distribution were investigated. Regional left ventricular wall motion was studied in terms of mean wall velocity, in 16 segments, 8 basal and 8 apical, by M-mode echocardiographic (Echo) mapping from 6 probe positions. Adequate Echo registrations were obtained from 88% of the total of 864 segments. The best classification (88.5%) of normal and infarcted segments was obtained with a -30% deviation of mean systolic wall velocity (Vmean) values from the mean values of the control segments (CS). Non-infarcted segments (NIS) in the AMI group had significantly lower Vmean values than the CS (p less than 0.001). Subendocardially (SIS) and transmurally (TIS) infarcted segments could be clearly separated from both CS and NIS (p less than 0.001). Per cent deviation of Vmean from the mean value of the control segments (PD-V) for SIS varied considerably overlapping CS, NIS and TIS. With a PD-V between 0 and -30% the probability of NIS is 94%, SIS 6% and TIS less than 1%. A PD-V more than -66% was rarely seen among NIS (2%) but was the normal finding in TIS (94%).

Prognostic value of predischarge radionuclide ventriculography at rest and exercise after acute myocardial infarction treated with thrombolytic therapy or primary coronary angioplasty. The Zwolle Myocardial Infarction Study Group

BACKGROUND

Previous studies have demonstrated the prognostic value of radionuclide ventriculography at rest and exercise in patients post myocardial infarction (MI). The number of studies in patients treated with modern reperfusion techniques, including thrombolysis or primary angioplasty, however, is limited.

HYPOTHESIS

The aim of this study was to evaluate the prognostic significance of predischarge radionuclide ventriculography at rest and exercise in patients with acute MI treated with thrombolysis or primary angioplasty.

METHODS

A total of 272 consecutive patients with acute MI who were randomized to thrombolysis or primary coronary angioplasty underwent predischarge resting and exercise radionuclide ventriculography. Left ventricular ejection fraction at rest, decrease in ejection fraction during exercise > 5 units below the resting value, angina pectoris, ST-segment depression, and exercise test ineligibility were related to subsequent cardiac events (cardiac death, nonfatal reinfarction) during follow-up.

RESULTS

During a mean follow-up of 30 +/- 10 months, cardiac death occurred in 11 (4%) patients and nonfatal reinfarction in 14 (5%) patients. Resting left ventricular ejection fraction was the major risk factor for cardiac death. In patients with an ejection fraction < 40%, cardiac death occurred in 16% compared with 2% in those with an ejection fraction > or = 40% (p = 0.0004). In addition, cardiac death tended to be higher in patients ineligible than in those eligible for exercise testing (11 vs. 3%, p = 0.08). None of the other exercise variables (decrease in ejection fraction during exercise > 5 units below the resting value, angina pectoris or ST-segment depression) were predictive for cardiac death. When all exercise test variables in each patient were combined and expressed as a risk score, a low risk (n = 185) and a higher risk (n = 87) group of patients could be identified, with cardiac death occurring in 1 and 10%, respectively. As the predictive accuracy of a negative test was high, radionuclide ventriculography was of particular value in identifying patients at low risk for cardiac death. Radionuclide ventriculography was not able to predict recurrent nonfatal MI.

CONCLUSION

In patients with MI treated with thrombolysis or primary angioplasty, radionuclide ventriculography may be helpful in identifying patients at low risk for subsequent cardiac death. In this respect, left ventricular ejection fraction at rest was the major determinant. Variables reflecting residual myocardial ischemia were of limited prognostic value. Identification of a large number of patients at low risk allows selective use of medical resources during follow-up in this subgroup and has significant implications for the cost effectiveness of reperfusion therapies.

Prognostic value of exercise tolerance testing in asymptomatic chronic nonischemic mitral regurgitation

In many heart diseases, exercise tolerance testing (ETT) has useful functional correlates and/or prognostic value. However, its predictive value in mitral regurgitation (MR) is undefined. To determine whether ETT descriptors predict death or indications for mitral valve surgery in patients with MR, we prospectively followed, for 7 +/- 3 end-point-free years, a cohort of 38 patients with chronic severe nonischemic MR who underwent modified Bruce ETT; all lacked surgical indications at study entry. Their baseline exercise descriptors were also compared with those from 46 patients with severe MR who, at entry, already had reached surgical indications. End points during follow-up in the cohort included sudden death (n = 1), heart failure symptoms (n = 2), atrial fibrillation (n = 4), left ventricular (LV) ejection fraction <60% (n = 2), LV systolic dimensions > or =45 mm (n = 12) and >40 mm (n = 11), LV ejection fraction <60% plus LV systolic dimensions > or =45 mm (n = 3), and heart failure plus LV systolic dimensions > or =45 mm plus LV ejection fraction <60% (n = 1). In univariate analysis, exercise duration (p = 0.004), chronotropic response (p = 0.007), percent predicted peak heart rate (p = 0.01), and heart rate recovery (p <0.02) predicted events; in multivariate analysis, only exercise duration was predictive (p <0.02). Average annual event risk was fivefold lower (4.62%) with an exercise duration > or =15 versus <15 minutes (average annual risk 23.48%, p = 0.004). Relative risks in patients with and without exercise-inducible ST-segment depression were comparable (< or =1.3, p = NS) whether defined at entry and/or during follow-up. Exercise duration, but not prevalence of exercise-inducible ST-segment depression, was lower (p <0.001) in patients with surgical indications at entry versus initially end-point-free patients. In conclusion, in asymptomatic patients with chronic severe nonischemic MR and no objective criteria for operation, progression to surgical indications generally is rapid. However, those with excellent exercise tolerance have a relatively benign course. Exercise-inducible ST-segment depression has no prognostic value in this population.

Prevalence and prognosis of left ventricular systolic dysfunction in asymptomatic diabetic patients without known coronary artery disease referred for stress single-photon emission computed tomography and assessment of left ventricular function

BACKGROUND

The prevalence and prognosis of reduced left ventricular ejection fraction (LVEF) in asymptomatic diabetic patients without known coronary artery disease (CAD) are not known.

METHODS

We examined 1046 asymptomatic diabetic patients (age 60 +/- 13 years, 69% male) without known CAD referred to a tertiary referral center for stress single-photon emission computed tomography (SPECT) and assessment of LVEF. Patients were stratified according to the presence of normal LVEF (> or = 50%), mildly reduced LVEF (35%-49%), or moderately/severely reduced LVEF (< 35%). Single-photon emission computed tomographic images were classified as low, intermediate, or high risk based on the summed stress score (normal = 56). The mean follow-up was 5.3 +/- 3.3 years.

RESULTS

The prevalence of reduced LVEF was 16.7% (n = 175, mean LVEF 40.0% +/- 7.7%). This group was older (63 +/- 11 vs 59 +/- 14 years, P = .005), had more peripheral arterial disease (45% vs 29%, P < .001), and had a higher prevalence of electrocardiographic Q waves (21% vs 9%, P < .001) than the group without reduced LVEF. Mean summed stress (44.8 +/- 9.8 vs 51.7 +/- 6.3, P < .001), summed reversibility (4.7 +/- 5.0 vs 2.9 +/- 4.5, P < .001), and summed rest scores (49.4 +/- 7.2 vs 54.6 +/- 3.1, P < .001) were significantly more abnormal in the reduced LVEF group. High-risk summed stress score was significantly more common in the reduced LVEF group (46% vs 16%, P < .001). Survival was significantly lower in patients with any reduction in LVEF compared with those without reduced LVEF (10-year survival, 29% vs 57%, P < .0001). By multivariate analysis, reduced LVEF was independently associated with increased mortality (adjusted chi2 = 6.26, P = .01).

CONCLUSIONS

In this population of asymptomatic diabetic patients without known CAD referred for stress SPECT, 1 in 6 patients had reduced LVEF. Most of these patients have intermediate-/high-risk SPECT scans. The annual mortality rates of the groups with and without reduced LVEF were 7% and 4%, respectively.

Cardiac studies in patients treated with depsipeptide, FK228, in a phase II trial for T-cell lymphoma

PURPOSE

The histone deacetylase inhibitor depsipeptide (FK228) has activity in patients with cutaneous or peripheral T-cell lymphoma. Electrocardiogram abnormalities, thought to be a class effect, were observed in preclinical animal studies and phase I testing and led to the incorporation of intensive cardiac monitoring in an ongoing efficacy trial.

PATIENTS AND METHODS

This report summarizes the cardiac monitoring of 42 patients enrolled and treated on a phase II trial with depsipeptide. Cardiac evaluations included serial electrocardiograms to evaluate T-wave, ST segment, and QT interval effects and serial serum cardiac troponin I levels and left ventricular ejection fraction (LVEF) evaluations to exclude myocardial damage.

RESULTS

Cardiac studies from 282 cycles and 736 doses of depsipeptide included 2,051 electrocardiograms and 161 LVEF evaluations. Although T-wave flattening (grade 1) or ST segment depression (grade 2) was observed in more than half of the electrocardiograms obtained posttreatment, these electrocardiogram abnormalities were not associated with elevation of cardiac troponin I or with altered left ventricular function. No significant changes in LVEF were observed, even in 16 patients treated for >or=6 months and regardless of prior anthracycline exposure. Posttreatment electrocardiograms had a mean heart rate-corrected QT interval prolongation of 14.4 milliseconds compared with baseline. Electrolyte replacement has been instituted to mitigate potential untoward effects.

CONCLUSION

The data obtained in this study show that the administration of depsipeptide is not associated with myocardial damage or impaired cardiac function. The potential effect of heart rate-corrected QT interval prolongation remains under study.

The influence of post-exercise cardiac changes on thallium-gated myocardial perfusion scintigraphy findings in normal subjects

BACKGROUND AND AIM

During recovery after exercise, the heart rate and blood pressure return to a resting state more rapidly than the end-systolic left ventricular dimensions and fractional shortening. The aim of this study was to assess how exercise-related cardiac changes affect the interpretation of myocardial perfusion images in normal subjects. Systolic cardiac parameters on gated stress and rest images were evaluated in healthy young and elderly subjects.

METHODS

Twenty-six healthy young and 20 healthy elderly subjects participated in the study. An injection of 111-130 MBq of thallium-201 (201Tl) was given at peak exercise. Rest images were acquired 2.5 h after stress acquisition, 15 min after a second injection of 18.5-37 MBq of 201Tl. Data were analysed using automatic-processing software for quantitative gated single photon emission computed tomography (SPECT) (QGS). The parameters derived from QGS were the end-systolic volume (ESV), end-diastolic volume (EDV), left ventricular ejection fraction (LVEF), end-systolic surface area (ESSA) and end-diastolic surface area (EDSA). The difference between wall thickening in the basal and apical segments (Delta WT) was also calculated. Perfusion images were visually assessed for differences in cardiac size, evidence of reversible hypoperfusion and hot spots.

RESULTS

In the young group, LVEF was approximately 6% higher at stress than at rest. EDV, ESV, ESSA and EDSA were all significantly lower, and Delta WT was significantly higher, at stress than at rest. In the elderly group, the mean LVEF at stress was slightly higher than the finding at rest (P<0.05). Visual evaluation of perfusion images revealed mild reversible stress hypoperfusion in the inferoseptal region in eight young male subjects.

CONCLUSIONS

In healthy young subjects, post-exercise cardiac changes affect systolic functions detected on gated thallium myocardial perfusion scintigraphy, resulting in a smaller heart size during stress. This finding, accompanied by a significant difference in apex to base counts during stress, may cause basal portions of the heart to appear ischaemic. The absence of these findings in the elderly suggests a decrease in contractility with age.

Value of sequential monitoring of left ventricular ejection fraction in the management of thalassemia major

Regular monitoring of left ventricular ejection fraction (LVEF) for thalassemia major is widely practiced, but its informativeness for iron chelation treatment is unclear. Eighty-one patients with thalassemia major but no history of cardiac disease underwent quantitative annual LVEF monitoring by radionuclide ventriculography for a median of 6.0 years (interquartile range, 2-12 years). Intraobserver and interobserver reproducibility for LVEF determination were both less than 3%. LVEF values before and after transfusion did not differ, and exercise stress testing did not reliably expose underlying cardiomyopathy. An absolute LVEF of less than 45% or a decrease of more than 10 percentage units was significantly associated with subsequent development of symptomatic cardiac disease (P &lt; .001) and death (P = .001), with a median interval between the first abnormal LVEF findings and the development of symptomatic heart disease of 3.5 years, allowing time for intervention. In 34 patients in whom LVEF was less than 45% or decreased by more than 10 percentage units, intensified chelation therapy was recommended (21 with subcutaneous and 13 with intravenous deferoxamine). All 27 patients who complied with intensification survived, whereas the 7 who did not comply died (P &lt; .0001). The Kaplan-Meier estimate of survival beyond 40 years of age for all 81 patients is 83%. Sequential quantitative monitoring of LVEF is valuable for assessing cardiac risk and for identifying patients with thalassemia major who require intensified chelation therapy.

Left Ventricular Ejection Fraction Change with Exercise Versus Ejection Fraction at Rest in Coronary Artery Disease: Implications for Using Ejection Fraction Variations in Making Therapeutic Decisions

Previous studies have differed regarding the prognostic importance of the change (Delta) in left ventricular ejection fraction (LVEF) with exercise among patients with known or suspected coronary artery disease (CAD). Data suggest that these discrepancies may be owing to patient selection, including wide interstudy variations in the range of LVEFrest at study entry; however, the impact of LVEFrest on LVEF exercise response has not been adequately addressed. To test the hypothesis that magnitude and variability in DeltaLVEF are systematically related to LVEFrest, we analyzed data from 2655 patients who underwent rest/exercise radionuclide cineangiography for evaluation of clinically evident CAD, stratified into 5 successive LVEFrest subgroups: <30% (n = 205), 30%-44% (n = 563), 45%-59% (n = 1529), 60%-75% (n = 324), and >75% (n = 34). The standard deviation of DeltaLVEF among patients with LVEFrest <30% was found to be half that among patients in the higher LVEFrest subgroups (P < 0.00001, global). The average magnitude of the rise and fall in LVEF with exercise also varied markedly among LVEFrest subgroups (P < 0.0001, global), being smallest among patients with LVEFrest <30%. These findings may explain differences in predictive accuracy of DeltaLVEF noted among various study populations. Further study is needed to determine whether LVEFrest should be used in selecting exercise-based prognostic descriptors in individual patients.

Cardiac abnormalities in diabetic patients with neuropathy: effects of aldose reductase inhibitor administration

OBJECTIVE

The goal of this study was to determine whether treatment with an aldose reductase inhibitor (ARI) has beneficial effects on asymptomatic cardiac abnormalities in diabetic patients with neuropathy.

RESEARCH DESIGN AND METHODS

Diabetic subjects with neuropathy (n = 81) with either a low diastolic peak filling rate or impaired augmentation of left ventricular (LV) ejection fraction (LVEF) during maximal bicycle exercise were identified by gated radionuclide ventriculography. Coronary artery disease, left ventricular hypertrophy, and valvular heart disease were excluded by clinical evaluation, myocardial perfusion imaging, and echocardiography. Subjects were randomized to receive blinded treatment with either the placebo or the ARI zopolrestat 500 or 1,000 mg daily for 1 year.

RESULTS

After 1 year of ARI treatment, there were increases in resting LVEF (P < 0.02), cardiac output (P < 0.03), LV stroke volume (P < 0.004), and exercise LVEF (P < 0.001). In placebo-treated subjects, there were decreases in exercise cardiac output (P < 0.03), stroke volume (P < 0.02), and end diastolic volume (P < 0.04). Exercise LVEF increased with ARI treatment independent of blood pressure, insulin use, or the presence of baseline abnormal heart rate variability. There was no change in resting diastolic filling rates in either group.

CONCLUSIONS

Diabetic patients with neuropathy have LV abnormalities that can be stabilized and partially reversed by ARI treatment.

Molecular imaging in nuclear cardiology

State-of-the-art techniques have been used to measure key aspects of cardiovascular pathophysiology from the birth of radionuclide cardiovascular imaging. However, during the last 30 years, there have been few innovative imaging advances to further our understanding of the complex physiologic processes. Molecular imaging now offers an array of tools to develop advanced diagnostic approaches and therapies for patients with coronary artery disease and heart failure. For example, the enhanced understanding of the pathophysiology of atheroma makes it possible to identify vulnerable plaque based on its metabolic signature or the presence of excessive apoptosis. Because the metabolic and apoptotic signals are large, it is likely that even small lesions will be visible. Of the many approaches that are being developed, 2 tracers appear most likely to be tested in the near future: (1) [18F]-fluorodeoxyglucose, to determine macrophage metabolism; and (2) radiolabeled annexin, to measure apoptosis of the inflammatory cells. Using existing techniques such as perfusion imaging, appropriate patients can be selected for treatment with novel therapies, such as stem cell transplantation or vascular gene therapy. Using positron tomography in place of single photon imaging adds the capability for the measurement of absolute perfusion and perfusion reserve to the information on regional perfusion. Flow reserve detects global decreases in perfusion and refines the determination of lesion severity available from perfusion imaging.

Improvement of left ventricular dysfunction during exercise by walking in patients with successful percutaneous coronary intervention for acute myocardial infarction

A growing body of evidence suggests that walking reduces the incidence of coronary events, so the present study investigated whether walking influences left ventricular function in 30 patients with acute myocardial infarction (AMI) who had undergone successful percutaneous coronary intervention (PCI). The patients were randomly assigned to either a 3-month exercise training program of walking (group W, n=15) or a control group (group C, n=15). At both the beginning and end of the study, patients underwent exercise stress echocardiography to determine left ventricular ejection fraction (LVEF) at rest and during exercise. At baseline, there was no difference in LVEF at rest or during exercise between the two groups. After 3 months, LVEF during exercise was significantly improved compared with at rest in group W (61+/-3% during exercise vs 57+/-5% at rest, p<0.01), whereas no difference was observed between the LVEF at rest and that during exercise in group C (54+/-5% at rest vs 52+/-7% during exercise, NS). Walking may be beneficial for improving left ventricular function during exercise in patients with AMI.

Angiographic and prognostic correlates of cardiac output by cardiopulmonary exercise testing in patients with anterior myocardial infarction

STUDY OBJECTIVE

To assess the diagnostic and prognostic value of cardiac output assessed by cardiopulmonary exercise testing in patients with anterior acute myocardial infarction (AMI) and left ventricular dysfunction.

PATIENTS AND SETTING

Forty-six patients with AMI (7 female patients; mean +/- SD age, 55 +/- 8 years; ejection fraction, 39 +/- 7%) underwent cardiopulmonary exercise testing and coronary angiography following hospital discharge.

MEASUREMENT AND RESULTS

Cardiac output was estimated from oxygen uptake (VO(2)) during exercise according to a method based on the linear regression between arteriovenous oxygen content difference and percent maximum VO(2). Angiograms were scored using Gensini and Duke "jeopardy" scores. Cardiac output at anaerobic threshold (COAT) < or = 7.3 L/min was the best cutoff value for identifying multivessel coronary artery disease (relative risk, 3.1). Angiographic scores were significantly higher in patients with COAT < 7.3 L/min as compared to those with COAT > 7.3 L/min (82 +/- 8 vs 53 +/- 7 and 6 +/- 2 vs 4 +/- 3, respectively; p < 0.05) and were inversely and significantly correlated to COAT. Conversely, no correlation was found with ECG changes. COAT, VO(2) at anaerobic threshold, and peak VO(2) were univariate prognostic indicators. However, using Cox's model, COAT was the only multivariate predictor of outcome (odds ratio, 0.28; 95% confidence interval [CI], 0.09 to 0.9). Moreover, COAT < 7.3 L/min was associated to an increased risk of further cardiac events (odds ratio, 5; 95% CI, 1.4 to 17) and provided a significant discrimination of survival for the combined end point of cardiac death, reinfarction, and clinically driven revascularization.

CONCLUSIONS

COAT is a safe and feasible tool providing additional diagnostic and prognostic information in patients with AMI.

Relation of thallium uptake to morphologic features of chronic ischemic heart disease: evidence for myocardial remodeling in noninfarcted myocardium

OBJECTIVES

The aim of this study was to investigate the disparity between the extent of myocardial injury as assessed by thallium and the severity of left ventricular (LV) dysfunction in chronic ischemic heart disease.

BACKGROUND

Although it is believed that thallium differentiates between viable and nonviable myocardium, in some patients with chronic ischemic heart disease, viable regions by thallium may fail to improve function after revascularization.

METHODS

Thirteen transplant candidates with chronic ischemic heart disease (LV ejection fraction = 14 +/- 6% at rest) were studied prospectively with stress-redistribution-reinjection thallium single-photon emission computed tomography. We examined pretransplantation quantitative thallium uptake and post-transplantation extent and the histological distribution of collagen replacement in infarcted and noninfarcted myocardium and in 13 age-matched control hearts.

RESULTS

The volume fraction of collagen varied inversely with wall thickness (r = -0.70, p < 0.001) and was higher in irreversible (30.9 +/- 15.8%) compared with reversible (20.2 +/- 12.6%, p < 0.001) or normal thallium segments (15.0 +/- 8.7%, p < 0.001). The irreversible thallium segments had lower wall thickness and more severe coronary artery narrowing (9.7 +/- 2.8 mm and 95 +/- 8%) compared with reversible (11.7 +/- 2.7 mm and 87 +/- 13%, p < 0.001) and normal thallium segments (12.8 +/- 2.6 mm and 80 +/- 14%, p < 0.001). Mean volume fraction of collagen was significantly lower in noninfarcted than it was in infarcted segments (13 +/- 6% vs. 36 +/- 13%, p < 0.001) but exceeded that in the control hearts (4 +/- 2%, p < 0.001). Noninfarcted segments had predominantly interstitial fibrosis with either microscopic or patchy areas of replacement fibrosis.

CONCLUSIONS

In chronic ischemic heart disease with severe LV dysfunction, patterns of normal, reversible and irreversible thallium uptake correlated with the magnitude of collagen replacement, segmental wall thickness and severity of coronary artery narrowing. The finding of scattered areas of replacement fibrosis in noninfarcted myocardium may explain the observed disparity between LV contractile dysfunction and the extent of myocardial injury assessed by thallium.

Thallium gated SPECT: relation between immediate post-stress evolution of ejection fraction and severity of perfusion pattern

BACKGROUND AND AIMS

A significant decrease of left ventricular ejection fraction (LVEF) at stress has been reported with 99Tc(m) gated single-photon emission computed tomography (gSPECT) in severe myocardial stunning up to 1 h after exercise. This study was designed to show whether 201Tl gSPECT can measure LVEF evolution from rest to stress in routine examination and give additional information to perfusion interpretation since acquisition starts immediately after stress test.

METHODS

Post-exercise and rest 201Tl gSPECT were performed in 187 patients with suspected coronary artery disease. Myocardial perfusion was quantified by 20-segment analysis. Patients were divided into four groups according to their summed perfusion score, reversibility rate and electrocardiographic findings, i.e. in order of severity: I = normal perfusion, II = fixed defect owing to a myocardial infarction, III = full reversible ischaemia, and IV = partial reversible ischaemia. LVEF was calculated by Germano's automatic algorithm.

RESULTS

Normal subjects (n = 29) and infarcted patients (n = 34) showed a significant LVEF increase between rest and stress, +7 +/- 9% and +5 +/- 7% respectively. In full reversible ischaemic patients (n = 46), stress LVEF showed no increase (+1 +/- 8%) and this group was statistically different from both group I and group II. Furthermore, when ischaemia was partially reversible (n = 31), LVEF decreased significantly (-3 +/- 8%), particularly when exercise tests were abnormal (-4 +/- 8%). Group IV was statistically different from groups I and II.

CONCLUSIONS

Good agreement exists between the severity of ischaemic perfusion pattern and LVEF degradation at stress, which is consistent with previously published data using 99Tc(m) gSPECT. Additionally, the use of 201Tl for immediate post-exercise imaging allows the observation of a physiological LVEF increase in normal and infarcted patients.

Plasma renin activity in the emergency department and its independent association with acute myocardial infarction

Elevated plasma renin activity (PRA) is associated with increased risk of future myocardial infarction (MI) in ambulatory hypertensive patients. The present study evaluated the relationship of PRA to the diagnosis of acute MI in patients presenting to an emergency department with suspected acute MI. PRA was measured upon entry to the emergency department, before any acute treatment, as part of the standard evaluation of 349 consecutive patients who were hospitalized for suspected MI. Diagnosis of acute MI was confirmed in 73 patients, and ruled out in 276. They did not differ in age (65.9 +/- 2 v 66.1 +/- 1 years), systolic (143 +/- 4 v 140 +/- 2 mm Hg), or diastolic (81 +/- 2 v 81 +/- 1 mm Hg) pressures. Median PRA was 2.7-fold higher in acute MI (0.89 v 0.33 ng/L/s; P < .001). In a multivariate analysis controlling for other cardiac risk factors and prior drug therapy, PRA as a continuous variable was the predominant independent factor associated with acute MI (P < .0001), followed by white race (P = .002) and history of hypertension (P = .047). The height of the PRA level upon entry to the emergency department was directly and independently associated with the diagnosis of acute MI. These new findings extend earlier reports because they encompass acute MI patients, include both hypertensive and normotensive patients, and control for potentially confounding variables. Based on these observations, a randomized clinical trial is warranted to determine whether measurement of PRA in acute MI could refine the process by which treatments are applied.

Retrograde crystalloid cardioplegia preserves left ventricular systolic function better than antegrade cardioplegia in patients with occluded coronary arteries

OBJECTIVE

To investigate retrograde and antegrade crystalloid cardioplegia in terms of cardiac cooling and postoperative cardiac function.

DESIGN

Prospective, randomized, and blinded.

SETTING

University hospital.

PARTICIPANTS

Twenty male patients with triple-vessel disease and proximal occlusion of the circumflex or the left anterior descending coronary artery.

INTERVENTIONS

Left ventricular ejection fraction at rest and during exercise was evaluated by nuclear ventriculography the day before and 3 months after surgery. After induction of anesthesia and hourly for the first 5 postoperative hours, hemodynamic, echocardiographic, and electrocardiographic data were acquired. Myocardial temperature was measured with needle thermistors in 3 myocardial regions.

MEASUREMENTS AND MAIN RESULTS

Demographic and temperature data were analyzed by t-test. Hemodynamic and echocardiographic data were analyzed by analysis of variance. The groups were similar in baseline characteristics. Retrograde cardioplegia cooled the region distal to an occlusion better than antegrade cardioplegia (9.6 degrees C +/- 4.8 degrees C v 21.8 degrees C +/- 5.9 degrees C; p < 0.01). Hemodynamic, echocardiographic, and electrocardiographic data did not differ between the groups. Three months after surgery, the retrograde cardioplegia group showed a higher left ventricular ejection fraction at rest (58% +/- 10% v 47% +/- 10%; p < 0.02) and during exercise (58% +/- 13% v 47% +/- 10%; p < 0.05) compared with the antegrade cardioplegia group.

CONCLUSIONS

Retrograde cardioplegia provides more homogenous myocardial cooling than antegrade cardioplegia in hearts with coronary artery occlusions. The use of retrograde cardioplegia seems to benefit long-term left ventricular function.

Short- and long-term follow-up after coronary bypass grafting for single-vessel coronary artery disease

Short-term outcome and 10-year clinical outcome were reviewed in 114 consecutive patients after coronary artery bypass grafting (CABG) for single-vessel coronary artery disease (CAD). Gated equilibrium radionuclide cineangiography was performed soon after CABG in all cases, and revealed very good early graft patency rates. There was no perioperative mortality, and very low morbidity. During follow-up there were seven late deaths, two from cardiac disease and five from non-cardiac causes. Cumulative survival at 10 years was 93%. Cumulative freedom from additional cardiac invasive procedures was 96%, 93% and 80% at 1, 5, and 10 years, respectively, and cumulative freedom from angina was 93%, 80% and 73%. Conventional single-vessel CABG thus can be safely performed, with minimal postoperative morbidity and no mortality, providing good long-term relief of angina and circumventing need for additional invasive procedures.

Persistent preload defect in severe sepsis despite fluid loading: A longitudinal echocardiographic study in patients with septic shock

STUDY OBJECTIVE

To investigate the rate of recovery from septic shock in patients with suspected left ventricular (LV) preload deficiency and LV systolic dysfunction.

DESIGN

A monitoring period was defined by the need for inotropic/vasopressor support, and LV function was assessed daily during this period by bedside two-dimensional echocardiography (2D-ECHO).

SETTING

University hospital ICU.

PATIENTS

During a 5-year period, 90 patients with an episode of septic shock (60% with gram-positive bacteria as the causative agent) were consecutively enrolled in the study (mean age, 55 +/- 18 years). Standard volume resuscitation combined with inotropic/vasopressor support was used to maintain systolic arterial pressure > 90 mm Hg. All patients received mechanical ventilation because of associated respiratory failure. The average duration of hemodynamic support was 4.4 +/- 1.6 days. Thirty-four patients were weaned from hemodynamic support during the monitoring period and ultimately recovered (group I). Twenty-eight patients died from refractory circulatory failure during the monitoring period, and 28 died later from ARDS or multiple organ dysfunction syndrome, leading to a 62% overall mortality rate (group II).

METHODS

Daily bedside LV volumes and ejection fraction (LVEF) were recorded using 2D-ECHO. Data obtained at the start (day 1 and day 2) and end of the monitoring period (day n) were compared.

RESULTS

LV end-diastolic volume was within the normal range of our laboratory values in all patients, but was initially smaller in group II than in group I, and remained so despite fluid loading. LVEF was significantly depressed in all patients, resulting in severe reduction in LV stroke volume (LVSV), which was initially more marked in group I. In group I patients, LVEF significantly improved during the monitoring period, resulting in an increase in LVSV.

CONCLUSION

2D-ECHO changes during hemodynamic support in 90 septic patients confirmed defective LV preload with a propensity to worsen despite fluid loading in nonsurvivors (62% in the present study). Our results are also in agreement with previous studies reporting depressed LV systolic function at the initial phase of septic shock. Since LV dysfunction was more marked in patients who recovered, we suggest that the exact significance of this finding should be reevaluated.

Automatic quantification of left ventricular ejection fraction from gated blood pool SPECT

BACKGROUND

Cardiac gated blood pool single photon emission computed tomography (GBPS) better separates cardiac chambers compared with planar radionuclide ventriculography (PRNV). We have developed a completely automatic algorithm to measure quantitatively the left ventricular ejection fraction (LVEF) from gated technetium 99m-red blood cells (RBC) GBPS short-axis 3-dimensional image volumes.

METHODS AND RESULTS

The algorithm determines an ellipsoidal coordinate system for the left ventricle and then computes a static estimate of the endocardial surface by use of counts and count gradients. A dynamic surface representing the endocardium is computed for each interval of the cardiac cycle by use of additional information from the temporal Fourier transform of the image data sets. The algorithm then calculates the left ventricular volume for each interval and computes LVEF from the end-diastolic and end-systolic volumes. The algorithm was developed in a pilot group (N = 45) and validated in a second group (N = 89) of patients who underwent PRNV and 8-interval GBPS. Technically inadequate studies (N = 38) were rejected before grouping and processing. Automatic identification and contouring of the left ventricle was successful in 121/172 patients (70%) globally and in 76/89 patients (85 %) in the validation group. Correlation between LVEFs measured from GBPS and PRNV was high (y = 2.00 + 1.01x, r = 0.89), with GBPS LVEF significantly higher than PRNV LVEF (average difference = 2.8%, P < .004).

CONCLUSIONS

Our automatic algorithm agrees with conventional radionuclide measurements of LVEF and provides the basis for 3-dimensional analysis of wall motion.

Prognostication in 3-vessel coronary artery disease based on left ventricular ejection fraction during exercise : influence of coronary artery bypass grafting

BACKGROUND

Previous data indicate that left ventricular ejection fraction (LVEF) provides prognostic information among patients with coronary artery disease (CAD), but the value of such testing specifically for defining benefits of coronary artery bypass grafting (CABG) may relate to severity of exercise-inducible ischemia measured noninvasively before surgery.

METHODS AND RESULTS

To determine the independent prognostic importance of preoperative ischemia severity for predicting outcomes of CABG among patients with extensive CAD, we monitored 167 stable patients with angiographically documented 3-vessel CAD (average follow-up of 9 years in event-free patients) who previously had undergone rest and exercise radionuclide cineangiography. Their course was correlated with data obtained during initial radionuclide testing, coronary arteriography, and clinical evaluation at study entry. Fifty-two patients received medical treatment only, and 115 underwent CABG (44 early [</=1 month after initial study]). Multivariate Cox model analysis indicated that change (Delta) in LVEF from rest to exercise during radionuclide study was the strongest independent predictor of major cardiac events (P=0.003) before surgery and also predicted magnitude of CABG benefit (P=0.04). Patients with DeltaLVEF -8% or less derived significant survival-prolonging and event-reducing benefit from CABG performed </=1 month after initial testing (P<0.02 for cardiac death and P=0.008 for cardiac events], early CABG versus medical-treatment-only patients); similar benefits were absent among patients with DeltaLVEF more than -8%, and among those in whom CABG was deferred.

CONCLUSIONS

Assessment of ischemia severity based on LVEF response to exercise enables effective prognostication among patients with 3-vessel CAD and defines the likelihood of life-prolonging and event-reducing benefits from CABG.

Effect of myocardial ischaemia on left ventricular function and adaptability to exercise training

PURPOSE

We evaluated the possible interaction between exercise-induced myocardial ischemia and abnormalities in left ventricular function in 72 patients with coronary artery disease at entry and upon discharge from a 6-month exercise training program.

METHODS

Twenty-two patients with myocardial ischemia (MIS) defined by electrocardiographic and radionuclide imaging criteria constituted our experimental group (EG). Fifty patients without MIS were assigned to the control group for exercise training (CG-ET) and 31 healthy subjects to the control group for measures of left ventricular function (CG-LV).

RESULTS

Both groups EG and CG-ET showed significant and comparable increases in peak oxygen uptake (EG: 25.2 +/- 5.1 to 26.9 +/- 5.4 mL x kg(-1) x min(-1), P < 0.02; CG-ET: 25.1 +/- 0.6 to 27.4 +/- 0.7 mL x kg(-1) x min(-1), P < 0.001) after exercise training, but only CG-ET showed significant reductions in heart rate, systolic blood pressure, and rate-pressure product during submaximal exercise. A significant increase in end-diastolic volume contributed to the increase in cardiac output during exercise in patients with MIS. Heart rate or treadmill time at onset of ST segment depression failed to increase as a result of training, and stroke counts and the product of stroke counts and heart rate showed a trend toward a decrease in response to exercise, suggesting progression of disease.

CONCLUSIONS

Patients with myocardial ischemia showed improvements in maximal exercise capacity but failed to elicit physiologic adaptations during submaximal exercise or to increase the threshold for ischemia after exercise training. It is possible that the main emphasis in the management of this type of patient in a cardiac rehabilitation setting should be placed more on coronary risk factor modification to slow progression of disease than on improving cardiovascular efficiency.

Independent and incremental prognostic value of heart rate variability in patients with chronic heart failure

BACKGROUND

Decreased heart rate variability (HRV), indicating derangement in cardiac autonomic control, has been reported in patients with chronic heart failure. However, the independent and incremental prognostic value of HRV over clinical data and measures of left ventricular dysfunction has been less thoroughly investigated. This study was designed to evaluate the predictive value of HRV and Poincaré plots as assessed by 24-hour Holter recording in patients with chronic heart failure.

METHODS

Ninety-seven patients, mean age 55 +/- 13 years, with radionuclide left ventricular ejection fraction </=40% underwent echocardiographic examination and 24-hour Holter recording. Heart failure was caused by coronary artery disease in 57 patients (59%) and idiopathic dilated cardiomyopathy in 40 (41%).

RESULTS

During follow-up (39 +/- 18 months), 32 cardiac deaths occurred. By Cox multivariate analysis, significant predictors of death were left ventricular end-systolic volume (hazard ratio 1.04), low- to high-frequency ratio (hazard ratio 0.09), percentage of differences between successive normal R-R intervals >50 ms (hazard ratio 0.93), and age (hazard ratio 1.06). Furthermore, HRV analysis improved (P <. 001) the prognostic power of a model including clinical and echocardiographic data, left ventricular ejection fraction, and ventricular arrhythmias at Holter recording, whereas the inclusion of Poincaré plots did not add further predictive value.

CONCLUSIONS

Our investigation demonstrated that HRV has independent and incremental prognostic value in patients with chronic heart failure and seems useful to stratify patients at high risk of cardiac death.

Ventilatory responses to exercise in patients with asymptomatic left ventricular dysfunction

PURPOSE

Based on reports that patients with severe left ventricular (LV) dysfunction have a greater ventilatory response to effort than healthy people, we evaluated the ventilatory responses to effort of patients with coronary artery disease and various degrees of LV impairment before and after 6 months of exercise training in a community-based cardiac rehabilitation program.

METHODS

Out of 171 patients consecutively referred for cardiac rehabilitation, 102 were enrolled in the study. Fifteen patients were excluded because of lung disease and 54 because of poor adherence to the exercise program. Patients were divided into three groups according to their ejection fraction (EF): Group 1 (G1) included 63 patients with EF > or = 50%, Group 2 (G2) included 21 patients with EF > or = 35 and < 50% and group 3 (G3) included 18 patients with EF < 35%. Peak oxygen uptake, minute ventilation (V(E)), and minute carbon dioxide production (VCO2) were measured before and after training in all participants.

RESULTS

All groups showed a significant increase in peak oxygen uptake and treadmill time after training (G1: P = 0.0001 and P = 0.0001; G2: P = 0.0001 and P = 0.001; G3: P = 0.01 and P = 0.01; respectively). Patients in G3 had a significantly higher V(E)/VCO2 ratio than patients in G2 and G1 at 9 min and peak exercise, before (9 min: P = 0.046 and P = 0.025, peak: P = 0.024 and P = 0.002, respectively) and after training (9 min: P = 0.011 and P = 0.005, peak: P = 0.001 and P = 0.0001, respectively). The slope of the relation V(E) to VCO2 was significantly higher in G3 patients than in those in G2 and G1 (P = 0.0001, respectively) and was not reduced by exercise training in any group.

CONCLUSIONS

Patients with severe LV dysfunction had a greater ventilatory response to exercise than those with moderately impaired or normal LV function. Exercise training increased the effort tolerance of all patients irrespective of their degree of LV dysfunction but failed to reduce the higher ventilatory responses to effort of patients with EF below 35%.

A new method to evaluate ischemic heart disease: combined use of rest thallium-201 myocardial SPECT and Tc-99m exercise tetrofosmin first pass and myocardial SPECT

We developed a new diagnostic method for simultaneously evaluating myocardial ischemia, myocardial viability and ventricular function in less than 90 minutes by combined use of rest thallium-201 (Tl) SPECT and exercise Tc-99m tetrofosmin (TF) first pass and SPECT. The subjects were 9 healthy controls, 19 angina pectoris patients, and 19 old myocardial infarction patients, in all of whom coronary angiography had been performed. Rest Tl myocardial SPECT was performed first, and was followed by exercise TF myocardial SPECT. We also performed first pass radionuclide angiography by TF during maximum exercise on a bicycle ergometer to assess the left ventricular ejection fraction (LVEF). The total examination time was less than 90 minutes. SPECT diagnosis was performed by semi-quantitative analysis. LVEF below 55% was regarded as abnormal. In the patients with angina pectoris, analysis according to the coronary artery showed that the diagnostic accuracy of SPECT was 85.0% for ischemia in the region of the left anterior descending branch (LAD), 87.5% for the left circumflex branch (LCX) and 77.8% for the right coronary artery (RCA). The accuracy of diagnosis for angina pectoris was 82.1%, as determined by SPECT alone, and rose to 89.3% when the LVEF levels were also taken into consideration. In the patients with old myocardial infarction, the diagnostic accuracy of SPECT was 84.2% for the LAD, 92.3% for the LCX and 85.0% for the RCA. Analysis by patients showed that the accuracy of diagnosis for myocardial infarction was 85.7%, as determined by SPECT alone. The diagnostic accuracy, however, rose to 89.3% when the LVEF levels also were taken into consideration. In conclusion, it was demonstrated that this combined diagnostic method was highly reliable for evaluating ischemic heart disease within a short time.

Segmentation of gated Tl-SPECT images and computation of ejection fraction: a different approach

BACKGROUND

We describe a set of image processing algorithms and mathematical models that can be advantageously used in schemes for the segmentation of thallium-201-single photon emission computed tomography (SPECT) images and for computation of left ventricular ejection fraction (EF).

METHODS

The system consists of two independent blocs for image segmentation and computation of function. The former is based on a multiresolution elliptical coordinate transformation and dynamic contour tracking. Computation of EF is formulated on the basis of both the endocardial and epicardial contours, and we compare this formulation with that using only the endocardial border for images with low signal-to-noise ratios. The accuracy of border detection was validated against manual border tracing on FDG-PET images, simulated Tl-201-SPECT images where the true underlying borders were known, and actual Tl-201-SPECT images. Finally, we compared EFs computed for FDG-PET, technetium-99m-SPECT and Tl-201-SPECT with those obtained from planar gated blood pool imaging.

RESULTS

The automatically obtained results always were within the manual uncertainty range. Agreement between myocardial volumes from positron emission tomography and automatically obtained values from the simulated Tl-201-SPECT images was excellent (r = 0.95, n = 32). Agreement between EFs from planar gated blood pool imaging and the other image modalities was good (FDG-PET: y = 5.89 + 1.21x, r = 0.92, see = 6.24, n = 19, Tc-99m-SPECT: y = -3.86 + 1.06x, r = 0.88, see = 7.78, n = 9, Tl-201-SPECT: y = 17.8 + 0.81x, r = 0.77, see = 7.44, n = 26). For noisy input data the combined use of information from epicardial and endocardial contours gives more accurate EF values than the traditional formula on the basis of the endocardial contour only.

CONCLUSIONS

Alternate approaches for segmentation and computation of function have been presented and validated. They might also be advantageously incorporated into other existing techniques.

13N-ammonia myocardial blood flow and uptake: relation to functional outcome of asynergic regions after revascularization

OBJECTIVES

In this study we determined whether 13N-ammonia uptake measured late after injection provides additional insight into myocardial viability beyond its value as a myocardial blood flow tracer.

BACKGROUND

Myocardial accumulation of 13N-ammonia is dependent on both regional blood flow and metabolic trapping.

METHODS

Twenty-six patients with chronic coronary artery disease and left ventricular dysfunction underwent prerevascularization 13N-ammonia and 18F-deoxyglucose (FDG) positron emission tomography, and thallium single-photon emission computed tomography. Pre- and postrevascularization wall-motion abnormalities were assessed using gated cardiac magnetic resonance imaging or gated radionuclide angiography.

RESULTS

Wall motion improved in 61 of 107 (57%) initially asynergic regions and remained abnormal in 46 after revascularization. Mean absolute myocardial blood flow was significantly higher in regions that improved compared to regions that did not improve after revascularization (0.63+/-0.27 vs. 0.52+/-0.25 ml/min/g, p < 0.04). Similarly, the magnitude of late 13N-ammonia uptake and FDG uptake was significantly higher in regions that improved (90+/-20% and 94+/-25%, respectively) compared to regions that did not improve after revascularization (67+/-24% and 71+/-25%, p < 0.001 for both, respectively). However, late 13N-ammonia uptake was a significantly better predictor of functional improvement after revascularization (area under the receiver operating characteristic [ROC] curve = 0.79) when compared to absolute blood flow (area under the ROC curve = 0.63, p < 0.05). In addition, there was a linear relationship between late 13N-ammonia uptake and FDG uptake (r = 0.68, p < 0.001) as well as thallium uptake (r = 0.76, p < 0.001) in all asynergic regions.

CONCLUSIONS

These data suggest that beyond its value as a perfusion tracer, late 13N-ammonia uptake provides useful information regarding functional recovery after revascularization. The parallel relationship among 13N-ammonia, FDG, and thallium uptake supports the concept that uptake of 13N-ammonia as measured from the late images may provide important insight regarding cell membrane integrity and myocardial viability.