Prognostic value of dipyridamole thallium-201 scintigraphy in patients with stable chest pain

The use of nuclear cardiology in clinical decision making

Extensive data exist to support the role of myocardial perfusion single-photon emission computed tomography (MPS) in risk stratification. Normal MPS studies usually are associated with very low risk, and patient risk increase significantly as a function of MPS results. Ventricular function measurements from gated single-photon emission computed tomography further augment risk stratification, particularly with respect to identifying patients at risk of cardiac death. Ancillary findings are prognostically important, particularly in the setting of normal or near-normal MPS results. Recent data suggest that MPS results can identify which patients will benefit from revascularization versus medical therapy and have expanded the understanding of how stress MPS is helpful in the identification of risk, enhanced the means of identifying risk, and improved its use as a means to identify optimal posttest treatment.

Comparison of risk stratification with pharmacologic and exercise stress myocardial perfusion imaging: a meta-analysis

BACKGROUND

Although pharmacologic stress myocardial perfusion imaging (MPI) and exercise stress MPI have comparable diagnostic accuracy, their comparative value for risk stratification of patients with known or suspected coronary disease is not known.

METHODS AND RESULTS

The data of 14,918 patients were combined from 24 studies evaluating prognosis in patients undergoing either pharmacologic stress or exercise stress MPI. Studies were included if a 2 x 2 table for hard cardiac events (cardiac death and myocardial infarction [MI]) could be constructed from the data available. Excluded were studies performed for post-MI, post-revascularization, or preoperative risk stratification. A weighted t test was used to compare the cardiac events, and a random effects model was used to calculate summary odds ratios. Summary odds ratios for hard cardiac events were similar for pharmacologic stress and exercise stress MPI. Summary receiver operating characteristic curves also showed no difference in discriminatory power between the stressors. The cardiac event rates were significantly higher with normal and abnormal test results with pharmacologic stress MPI than with exercise stress MPI (1.78% vs 0.65% [P < .001] for normal results and 9.98% vs 4.3% [P < .001] for abnormal results). Subgroup analysis revealed that both cardiac death and nonfatal MI were significantly higher with pharmacologic stress MPI. Patients undergoing pharmacologic stress MPI had a significantly higher prevalence of poor prognostic factors, and meta-regression revealed that exercise capacity was the single most important predictor of cardiac events.

CONCLUSIONS

This meta-analysis shows that exercise stress MPI and pharmacologic stress MPI are comparable in their ability to risk-stratify patients. However, patients undergoing pharmacologic stress studies are at a higher risk for subsequent cardiac events. This is true even for those with normal perfusion imaging results.

Medium- to long-term prognostic impact of dipyridamole thallum-201 myocardial single-photon emission computed tomography in elderly patients

Dipyridamole thallium-201 single-photon emission computed tomography (SPECT) has not been extensively evaluated for risk stratification and the medium- to long-term prognostic value in elderly cardiac patients who are unable to exercise. The present study group comprised 210 consecutive patients aged at least 70 years with known or suspected coronary artery disease (CAD). The SPECT findings were classified as a reversible, fixed, or combined (reversible and fixed) defect. Of the 210 patients, 201 (77+/-5 years, 85 male) were successfully followed for 49+/-26 months. Thirteen (7%) patients had cardiac events: cardiac death (n=10), non-fatal myocardial infarction (n=1), or coronary artery bypass grafting (n=2). Cardiac events occurred in 3 of 112 patients with normal SPECT and in 10 of 89 patients with an abnormal scan (0.7% /year vs 2.8% /year, p=0.01). Stepwise Cox regression analysis revealed that the significant predictors of cardiac events were combined defects (relative risk 7.3) and the number of defect areas (relative risk 4.4). The predictive value of dipyridamole thallium-201 SPECT is maintained over 4 years in mixed populations of elderly CAD patients who are unable to exercise.

Pharmacologic radionuclide myocardial perfusion imaging

Pharmacologic stress testing with myocardial perfusion imaging has enabled patients who cannot complete adequate exercise to undergo diagnostic and prognostic evaluation for coronary artery disease. Pharmacologic stress agents belong to two groups: vasodilators (such as adenosine and dipyridamole), and inotropes (such as dobutamine). All have similar sensitivity (89%-91%) and specificity (78%-86%) for the diagnosis of coronary disease. For risk stratification, the risk of future cardiac events is related to the extent and severity of perfusion abnormalities. Pharmacologic stress testing permits risk stratification as early as 1 to 4 days following an acute myocardial infarction, and is superior to exercise stress testing in this regard. Similarly, it identifies patients at high risk for perioperative cardiac events prior to noncardiac surgery. This review summarizes the current evidence available regarding the diagnostic and prognostic use of pharmacologic stress testing.

Long-term prognostic value of stress-redistribution-reinjection Tl-201 imaging in patients with severe left ventricular dysfunction and coronary artery bypass surgery

OBJECTIVES

This study sought to evaluate the long-term prognostic significance of stress-redistribution-reinjection Tl-201 imaging in patients with severe left ventricular (LV) dysfunction and coronary artery bypass surgery.

BACKGROUND

Preoperative stress-redistribution-reinjection Tl-201 imaging detects viable but asynergic segments which show functional improvement postoperatively and is considered as a valuable noninvasive method in selection of patients with severe LV dysfunction for revascularization. The long-term prognostic value of the reinjection technique remains unclear.

METHODS

Fifty-two patients with severe LV dysfunction (mean ejection fraction (EF) 0.32+/-0.03) who underwent coronary artery bypass surgery in 1993-1994 were included in the study. Patients had follow-up 49+/-12 months. LV function was assessed by two-dimensional echocardiography. Perfusion was assessed by Tl-201 SPECT imaging and was graded on a four-point scale (0 = normal, 3 = absent uptake) using the 20 segment model. Perfusion index was derived by adding the score of all segments and dividing these by 20. Patients were divided into two groups. Group A comprised patients with seven and more dysfunctional viable myocardial segments. Group B included patients with less than seven dysfunctional but viable segments.

RESULTS

Mean EF increased from 0.32+/-0.03 to 0.46+/-0.04. Mean perfusion index did not show a significant difference as a whole during follow-up compared to the early postoperative values (0.9+/-0.4 and 1.1+/-0.4, p = NS). When adequacy of revascularization was considered, the predictive value of a positive preoperative viability test for functional improvement was 82%. Nineteen cardiac events occurred in group B patients and six in group A patients: six deaths (four from cardiac and two from noncardiac causes), 13 myocardial infarctions (MI). Multivariate Cox survival analysis identified the number of viable segments detected preoperatively (chi2 = 7.2, p = 0.002), postoperative improvement in Tl-uptake (chi2 = 6.6, p = 0.01) and functional improvement (chi2 = 5.3, p = 0.03) postoperatively as independent predictors of cardiac events. Preoperative EF and functional capacity were not associated with cardiac events in long-term prognosis.

CONCLUSION

These data suggest that preoperative stress-redistribution-reinjection Tl-201 imaging, specifically the number of viable segments detected preoperatively and postoperative improvement in Tl-201 uptake provide important long-term prognostic information in patients with severe LV dysfunction who had coronary artery bypass surgery.

Thallium reinjection versus standard stress/delay redistribution imaging for prediction of cardiac events

OBJECTIVES

The purpose of this study was to compare thallium reinjection with standard stress/delay redistribution for the prediction of cardiac events.

BACKGROUND

Although thallium reinjection enhances the detection of viable myocardium, its contribution to prognosis over stress/delay redistribution in a general referral population has not been clearly evaluated.

METHODS

This retrospective analysis included 366 consecutive patients with coronary artery disease who underwent stress/delay redistribution imaging and thallium reinjection scintigraphy, with a mean follow-up of 33+/-12 months.

RESULTS

Cardiac events occurred in 48 patients (40 deaths, 8 myocardial infarctions). Of the 366 original patients, 159 demonstrated ischemia by stress/delay redistribution, 107 showed ischemia by reinjection only, and 100 showed infarction only. Cardiac events occurred in 20 patients (12.6%) with stress/delay redistribution, 13 patients (12%) with ischemia detected by thallium reinjection only and 15 patients (15%) with infarction only. The size of the reversible thallium defect by either stress/delay redistribution imaging or reinjection scintigraphy did not predict cardiac events. Independent predictors of cardiac events included left ventricular cavity size, the size of the abnormal perfusion defect and patient age.

CONCLUSIONS

Thallium reinjection does not contribute independent prognostic utility for cardiac events when compared with stress/delay redistribution. Left ventricular dilation and the size of the post-stress defect were predictors of cardiac events.

Incremental prognostic value of adenosine stress myocardial perfusion single-photon emission computed tomography and impact on subsequent management in patients with or suspected of having myocardial ischemia

We examined 1,159 consecutive patients who underwent adenosine stress dual isotope single-photon emission computed tomography (SPECT) and had follow-up performed at a mean of 27.5 +/- 9.1 months (94% complete) for hard events (cardiac death and myocardial infarction) and referral to cardiac catheterization after nuclear testing. During follow-up, 120 hard events occurred (11.0% hard event rate; 72 cardiac deaths [6.7% cardiac death rate] and 57 myocardial infarctions [5.3% myocardial infarction rate]). Cox proportional hazards analysis revealed that nuclear testing added incremental value after adjusting for clinical and historical variables (global chi-square increased 13 to 98 for cardiac death as the end point, global chi-square increased 19 to 105 for hard events as the end point; p <0.0001 for both). Kaplan-Meier analysis demonstrated that after clinical risk stratification of the patient population, the results of nuclear testing were further able to significantly stratify both low- and intermediate- to high-risk patients. Patients with both normal and mildly abnormal scans were at low risk of cardiac death (<1% cardiac death per year of follow-up) and the risk of events increased significantly with worsening scan result. Multivariable analysis revealed that the only predictor of referral to catheterization was the extent and severity of reversible defect present on the scan. Referral rates to early catheterization were very low in patients with normal scans and increased significantly as a function of worsening scan results. In patients who underwent myocardial perfusion SPECT using adenosine stress, the results of nuclear testing yielded incremental prognostic information and clinically relevant risk stratification. Referring physicians predominantly utilized nuclear information when referring patients to catheterization after nuclear testing and do so at rates comparable with those after exercise SPECT despite the higher risk of events in patients undergoing pharmacologic stress.

Prognostic importance of scintigraphic left ventricular cavity dilation during intravenous dipyridamole technetium-99m sestamibi myocardial tomographic imaging in predicting coronary events

Left ventricular (LV) cavity dilation during stress myocardial perfusion imaging has been associated with multivessel disease, and may be an independent prognostic marker in addition to perfusion defects. The present study examines the predictive value for future cardiac events of transient or fixed LV dilation during dipyridamole technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) imaging. The study included 512 consecutive patients who underwent SPECT imaging with Tc-99m sestamibi after dipyridamole infusion. Transient LV dilation was seen in 70 patients (14%) and 74 had fixed cavity dilation (14%); cavity size was normal in 368 patients (72%). Each perfusion scan was classified as normal or abnormal, and if abnormal, defects were categorized as transient or fixed, and as small, medium, or large (depending upon the number of abnormal vascular territories). Events during a mean follow-up of 12.8 +/- 6.8 months were tabulated by direct review of hospital charts and death certificates. The cardiac event rate (cardiac death or nonfatal infarction) was 1.9% in patients with normal cavity size, 11.4% with transient LV dilation, and 13.5% with fixed LV dilation (p < 0.01). Compared with patients with normal cavity size, those with transient LV dilation were more likely to sustain a myocardial infarction (p < 0.01) and those with fixed dilation more frequently suffered cardiac death (p < 0.01) and hospitalization for heart failure (p < 0.01). The group with the highest risk had both a large perfusion defect and cavity dilation. By Cox proportional hazard regression analysis, both transient and fixed LV dilation were strong independent predictors of cardiac events. Transient or fixed LV dilation are commonly seen during dipyridamole Tc-99m sestamibi SPECT imaging (14% incidence for each) and are useful predictors of cardiac events.

Independent prognostic value of intravenous dipyridamole with technetium-99m sestamibi tomographic imaging in predicting cardiac events and cardiac-related hospital admissions

OBJECTIVES

This study sought to establish the prognostic value of intravenous dipyridamole technetium-99m (Tc-99m) sestamibi single-photon emission computed tomographic (SPECT) myocardial perfusion imaging.

BACKGROUND

Optimal management of patients with coronary artery disease involves strategies designed to reduce the risk of myocardial infarction and cardiac death. The role of myocardial perfusion imaging using newer clinical techniques to determine risk and possible benefit from therapy has not been evaluated.

METHODS

Myocardial imaging results were classified as normal or abnormal (fixed or reversible defects; small, moderate or large). Follow-up evaluation of all patients included the occurrence of cardiac death or nonfatal myocardial infarction and other cardiac-related hospital admissions.

RESULTS

During a mean (+/- SD) follow-up period of 12.8 +/- 6.8 months in 512 patients, 25 had a cardiac event. Patients with abnormal perfusion had significantly more cardiac events than those with normal perfusion (22 vs. 3, p < 0.01). Patients with reversible defects had the highest event rates (8.6%), and those with normal study results had a very low event rate (1.4%). Large defects were strongly associated with more cardiac events and hospital admissions than either normal scan results or abnormal results showing small defects.

CONCLUSIONS

Patients with normal study results or a small defect after intravenous dipyridamole Tc-99m sestamibi SPECT imaging had an excellent short-term prognosis. Those with abnormal results (reversible or large defect) had an increased risk of subsequent cardiac death, nonfatal myocardial infarction and other cardiac-related hospital admissions.

Prognostic value of predischarge dipyridamole technetium 99m sestamibi myocardial tomography in medically treated patients with unstable angina

Recently developed unstable angina clinical practice guidelines have recommended risk stratification with dipyridamole thallium-201 myocardial imaging in patients at "intermediate" pretest clinical risk who cannot exercise maximally. The prognostic value of predischarge dipyridamole technetium 99m sestamibi (MIBI) tomography has not been assessed in this clinical setting. To this end, 128 medically treated patients with unstable angina at intermediate pretest clinical risk underwent follow-up for 16 +/- 11 (mean +/- SD) months after predischarge intravenous dipyridamole MIBI tomography. An abnormal MIBI scan result was present in 99 patients (77%), of whom 47 had one or more reversible and 76 had one or more fixed perfusion defects. Cardiac events occurred in 68 (53%) patients after dipyridamole testing: recurrent unstable angina (n = 36), nonfatal acute myocardial infarction (n = 6), or death (n = 26). A cardiac event occurred in 10% of patients with normal MIBI tomography results compared with 69% of those with abnormal results (p < 0.01). Event rates associated with specific perfusion defects were similar (reversible = 68%; fixed = 71%) and were greater than rates in patients without defects (both p < 0.05). Clinical variables associated with increased risk of cardiac events by univariate analysis included a history of congestive heart failure, prior myocardial infarction, and diabetes mellitus (all p < 0.05). Independent multivariable predictors (Cox proportional hazards model) of any cardiac event were an abnormal result of MIBI scan (relative risk [RR] = 4.3, 95% confidence interval [CI] 1.5 to 12.0) and a reversible (RR = 1.8, 95% CI 1.1 to 2.9) or a fixed perfusion defect (RR = 2.9, 95% CI 1.6 to 5.4).(ABSTRACT TRUNCATED AT 250 WORDS)

Stress imaging. Current clinical options for the diagnosis, localization, and evaluation of coronary artery disease

As technology advances, new methods evolve. In this article, the methods of stress testing and related imaging in coronary disease are addressed, and dynamic and pharmacologic stress, direct and indirect methods, are defined and evaluated. The stress imaging methods related to the modalities of scintigraphy and ultrasound are reviewed and their advantages and disadvantages assessed in view of scientific and economic factors.

Preoperative clinical assessment and dipyridamole thallium-201 scintigraphy for prediction and prevention of cardiac events in patients having major noncardiovascular surgery and known or suspected coronary artery disease

The aim of this study was to assess the relative prognostic use of clinical risk stratification and intravenous dipyridamole thallium-201 scintigraphy in patients with an intermediate to high prevalence of coronary artery disease (CAD) who have undergone major noncardiovascular surgery, and to assess the effects of medical therapy or coronary revascularization based on the result of this clinical scintigraphic screening on perioperative cardiac morbidity and mortality. Patients (n = 161) with an intermediate to high likelihood of CAD had clinical assessment and intravenous dipyridamole planar thallium-201 testing which was analyzed semiquantitatively. Cardiac events were cardiac death (n = 9), nonfatal myocardial infarction (n = 6), acute pulmonary edema (n = 6), and unstable angina (n = 4). Multiple (> or = 2) clinical risk variables predicted any cardiac event (p = 0.04). Presence of multiple (> or = 2) abnormal thallium-201 segments was the only independent predictor of cardiac death or nonfatal myocardial infarction (p < 0.001), and was the most powerful multivariate predictor of any cardiac event (p < 0.002). Patients with an abnormal dipyridamole thallium-201 scan had a higher risk of perioperative cardiac death, myocardial infarction (18% vs 2%; p < 0.001), or any perioperative cardiac event (27% vs 6%; p < 0.001) when compared with those with a normal scan. Preoperative changes in anti-ischemic therapy or coronary revascularization in 36 of 72 patients with abnormal dipyridamole thallium-201 studies reduced perioperative death or myocardial infarction from 31% to 6% (p < 0.01), and all cardiac events from 47% to 8% (p < 0.001) compared with those in patients without intervention.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic value of dipyridamole technetium-99m sestamibi myocardial tomography in patients with stable chest pain who are unable to exercise

Unlike dipyridamole testing with thallium-201, the ability of technetium-99m sestamibi (MIBI) myocardial imaging to evaluate risk of later cardiac events has not been established. In this study, the prognostic value of dipyridamole MIBI myocardial tomography (same-day, rest-stress protocol) was assessed in 534 patients with stable chest pain consistent with angina pectoris. During follow-up (mean 13 +/- 5 months), 58 patients (11%) had a major cardiac event--nonfatal myocardial infarction (n = 14) or cardiac death (n = 44). A history of congestive heart failure, prior myocardial infarction or diabetes mellitus, and either a reversible or fixed myocardial perfusion defect on MIBI scans were univariate and multivariate predictors of increased cardiac risk. Cardiac events occurred in 2% of patients with normal MIBI scans, compared with 15% with abnormal scans, 17% with reversible perfusion defects and 16% with fixed defects (all p < 0.01). Relative risks (univariate Cox analysis) associated with an abnormal MIBI scan, a reversible perfusion defect and a fixed defect were 8.4 (95% confidence interval [CI] 2.6 to 26.8), 1.9 (95% CI 1.1 to 3.2) and 2.4 (95% CI 1.4 to 4.3), respectively. Patients with any kind of perfusion abnormality (reversible or fixed) had a significantly lower cardiac event-free survival than those with normal scans (all p < 0.0001). It is concluded that, as with thallium-201 myocardial scintigraphy, a normal MIBI scan is associated with low cardiac risk, whereas dipyridamole-induced myocardial perfusion defects identify patients with significantly increased risk.

Exercise technetium-99m sestamibi tomography for cardiac risk stratification of patients with stable chest pain

BACKGROUND

This study was designed to evaluate the prognostic value of symptom-limited maximal exercise treadmill testing with tomographic technetium-99m sestamibi (MIBI) myocardial imaging in patients referred for evaluation of stable angina. Exercise stress thallium-201 myocardial imaging provides prognostic information in coronary artery disease subsets including patients with stable chest pain. The prognostic value of exercise technetium-99m MIBI myocardial tomography has not been established.

METHODS AND RESULTS

Of 548 consecutive patients with stable angina pectoris who underwent maximal exercise treadmill stress testing in combination with a same-day "rest-stress" tomographic technetium-99m MIBI myocardial imaging protocol, 521 patients were followed for 13 +/- 5 months to determine the univariate and multivariate variables associated with cardiac events and to define their cardiac event-free survival. Ten patients were lost to follow-up (98% complete), and 17 who had coronary revascularization within 6 months of testing were excluded. Major cardiac events occurred in 24 patients (9%)--nonfatal myocardial infarction in 11 and cardiac death in 13. Univariate Cox survival analysis demonstrated significant relative risk (RR) and 95% confidence intervals (CI) for exercise ST segment depression (RR = 2.3; 95% CI, 1.0 to 5.3), an abnormal MIBI scan (RR = 13.8; 95% CI, 1.9 to 102.3), and a reversible MIBI perfusion defect (RR = 3.2; 95% CI, 1.4 to 7.5). Multivariate models demonstrated that both exercise MIBI perfusion abnormalities (RR = 11.9; 95% CI, 1.6 to 89.4) and reversible MIBI perfusion defects (RR = 2.9; 95% CI, 1.2 to 7.0) had independent predictive value. During 1 year of follow-up, cardiac events occurred in only 0.5% of patients with normal MIBI scans compared with 7% of those with abnormal MIBI scans (P < .001). One-year, cardiac event-free survival was 92% in patients with reversible MIBI perfusion defects (P < .01 versus normal), 96% in patients with fixed defects (P < .01), and 93% in patients with combined reversible and fixed MIBI myocardial perfusion abnormalities (P < .02).

CONCLUSIONS

As with exercise thallium-201 myocardial imaging, exercise stress technetium-99m MIBI myocardial tomography provides significant independent information concerning the subsequent risk of serious cardiac events (death, myocardial infarction) in patients with stable angina pectoris. The identification of MIBI perfusion abnormalities, in particular, the presence of reversible MIBI defects, was associated with reduced 1-year, event-free survival. The recognized imaging and radiotracer biokinetic differences between thallium-201 and MIBI do not appear to modulate the prognostic value associated with scintigraphic evidence of ischemic myocardial jeopardy in the stable angina population.

Dipyridamole technetium 99m sestamibi myocardial tomography as an independent predictor of cardiac event-free survival after acute ischemic events

BACKGROUND

A total of 137 consecutive patients with recent uncomplicated myocardial infarction (n = 31) or unstable angina (n = 106) were studied to determine the relative prognostic value of predischarge clinical risk stratification and intravenous dipyridamole stress sestamibi (MIBI) myocardial tomography in patients unable to exercise maximally after an acute ischemic coronary event.

METHODS AND RESULTS

Patients were followed up after the index study for 10 +/- 5 months (range 1 to 23 months) to ascertain cardiac events that occurred in 20 patients (15%): nonfatal myocardial infarction (n = 5) or cardiac death (n = 15). Cardiac event rates were 35% in patients with a recent myocardial infarction and 8% in the group with unstable angina (p < 0.001). Patients with these cardiac events had more frequent abnormal MIBI study results, fixed defects, and reversible plus fixed (combined) defects (all p < 0.05). The univariate relative risk of death or myocardial infarction associated with an abnormal MIBI study was 6.0 (95% confidence limits 0.8 to 44.7). Multivariate stepwise logistic regression models identified an abnormal MIBI study and either fixed or reversible MIBI defects as being predictive of death or myocardial infarction (all p < 0.05). The Mantel-Haentzel 1-year cardiac event-free survival rate was excellent in 27 patients with a normal MIBI single-photon computed emission tomographic scan (100%) but significantly reduced in the 110 patients with an abnormal MIBI study (80%; p < 0.05 vs normal subjects). The presence of combined MIBI defects was associated with the poorest event-free survival rate (66%; difference not significant vs fixed or reversible defects only).

CONCLUSION

We conclude that predischarge dipyridamole MIBI tomography provided independent prognostic information in this population of patients who were unable to exercise after a recent acute ischemic coronary event.