Myocardial technetium-99m sestamibi single-photon emission tomography as a prognostic tool in coronary artery disease: multivariate analysis in a long-term prospective study

Risk stratification using line source attenuation correction with rest/stress Tc-99m sestamibi SPECT myocardial perfusion imaging

BACKGROUND

Although line source attenuation correction (AC) in SPECT MPI studies improves diagnostic accuracy, its prognostic value is less understood.

METHODS

Consecutive patients (n = 6,513) who underwent rest/stress AC ECG-gated SPECT MPI were followed for cardiac death or non-fatal myocardial infarction (MI). A 17-segment model and AC summed stress score (SSS) were used to classify images.

RESULTS

Of the 6,513 patients, cardiac death or non-fatal MI occurred in 267 (4.1%), over 2.0 ± 1.4 years. The AC-SSS in patients with a cardiac event (5.6 ± 7.8) was significantly higher than in those without (1.9 ± 4.6, P < .001). The annualized cardiac event rate in patients with an AC-SSS 1-3 (3.6%) was significantly higher than in those with an AC-SSS = 0 (1.1%, P < .001) but similar to that in those with an AC-SSS 4-8 (2.9%, P = .4). Accordingly, patients were classified to AC-SSS = 0, 1-8, and >8 with annualized cardiac event rates of 1.1%, 3.2%, and 8.5%, respectively (P < .0001). In multivariate analysis, an AC-SSS 1-8 and >8 emerged as independent predictors of cardiac events (P < .02 and P < .0001, respectively).

CONCLUSION

Rest/stress ECG-gated SPECT MPI with line source AC provides highly effective and incremental risk stratification for future cardiac events.

Risk stratification with attenuation corrected stress Tc-99m sestamibi SPECT myocardial perfusion imaging in the absence of ECG-gating due to arrhythmias

BACKGROUND

Despite growing recognition of attenuation correction (AC) utilizing an external radiation source, prognostic studies using AC are lacking.

METHODS

Consecutive patients (n = 419) who underwent stress Tc-99m sestamibi SPECT imaging with AC but without ECG-gating, due to arrhythmia, were followed for cardiac death or non-fatal myocardial infarction (MI). A 17-segment model and the summed stress score (SSS) were used to classify both the non-AC and AC images.

RESULTS

The 419 patients had a mean age of 71.5 +/- 11.7 years and most (70.6%) underwent pharmacologic stress. In follow-up, 35 (8.4%) patients suffered an adverse cardiac event. Patients with AC-SSS 1-3 and AC-SSS 4-8 had similar cardiac event rates (11.4% vs 10.5%, P = NS). Accordingly, AC-SSS cutoffs of 0, 1-8, and >8 were selected to classify perfusion as normal, mildly abnormal, and moderately to severely abnormal with annualized event rates of 2.1%, 10.8%, and 18.7%, respectively (P < .001). In multivariable analysis, AC-SSS >8 was the most powerful predictor of cardiac events followed by AC-SSS 1-8, history of CAD, age >75 and pharmacologic stress.

CONCLUSIONS

AC provides powerful risk stratification when added to clinical variables in patients undergoing stress Tc-99m sestamibi SPECT imaging without ECG-gating. Moreover, smaller/less severe defects on AC data are more significant than if the same defects were seen on non-AC data.

The Prognostic Value of Normal Exercise Myocardial Perfusion Imaging and Exercise Echocardiography

OBJECTIVES

The purpose of this work was to determine the prognostic value of normal exercise myocardial perfusion imaging (MPI) tests and exercise echocardiography tests, and to determine the prognostic value of these imaging modalities in women and men.

BACKGROUND

Exercise MPI and exercise echocardiography provide prognostic information that is useful in the risk stratification of patients with suspected coronary artery disease (CAD).

METHODS

We searched the PubMed, Cochrane, and DARE databases between January 1990 and May 2005, and reviewed bibliographies of articles obtained. We included prospective cohort studies of subjects who underwent exercise MPI or exercise echocardiography for known or suspected CAD, and provided data on primary outcomes of myocardial infarction (MI) and cardiac death with at least 3 months of follow-up. Secondary outcomes (unstable angina, revascularization procedures) were abstracted if provided. Studies performed exclusively in patients with CAD were excluded.

RESULTS

The negative predictive value (NPV) for MI and cardiac death was 98.8% (95% confidence interval [CI] 98.5 to 99.0) over 36 months of follow-up for MPI, and 98.4% (95% CI 97.9 to 98.9) over 33 months for echocardiography. The corresponding annualized event rates were 0.45% per year for MPI and 0.54% per year for echocardiography. In subgroup analyses, annualized event rates were <1% for each MPI isotope, and were similar for women and men. For secondary events, MPI and echocardiography had annualized event rates of 1.25% and 0.95%, respectively.

CONCLUSIONS

Both exercise MPI and exercise echocardiography have high NPVs for primary and secondary cardiac events. The prognostic utility of both modalities is similar for both men and women.

Systematic review of the prognostic effectiveness of SPECT myocardial perfusion scintigraphy in patients with suspected or known coronary artery disease and following myocardial infarction

OBJECTIVES

In patients with suspected or known coronary artery disease (CAD), or following myocardial infarction (MI), assessing the degree of ischaemia is important from a prognostic and therapeutic point of view. Single photon emission computed tomography (SPECT) myocardial perfusion scintigraphy (MPS) is a non-invasive technique that allows the presence, location and extent of ischaemia to be determined. The aim of this systematic review was to assess the prognostic effectiveness of SPECT MPS.

METHODS

We sought prognostic studies involving SPECT, exercise tolerance testing (ETT) and/or coronary angiography (CA) in people with suspected or known CAD, or following MI. Outcomes included cardiac death, non-fatal MI and revascularization. We searched the following databases: MEDLINE, PREMEDLINE, EMBASE, BIOSIS, Science Citation Index, the Cochrane Library, the Health Management Information Consortium and the Health Technology Assessment Database.

RESULTS

Twenty-one observational studies enrolling 53,762 people reported the general prognostic value of SPECT MPS. In multivariate analysis, SPECT MPS variables yielded both independent and incremental value to combinations of clinical, ETT and angiographic variables in predicting cardiac death or non-fatal MI. Three comparative studies reported lower revascularization rates following a SPECT MPS-CA strategy (6-21%) compared with direct CA (16-44%). Four observational studies enrolling 2106 people reported the prognostic value of SPECT for patients following MI. In multivariate analysis including clinical history, ETT, SPECT MPS and angiographic variables, strategies involving SPECT MPS provided independent and incremental prognostic performance in predicting future cardiac events.

CONCLUSIONS

SPECT MPS provides important additional information to that from ETT and/or CA that helps to risk-stratify patients with suspected or known CAD or following MI, enabling them to be managed more appropriately. Increasing the use of strategies involving SPECT MPS may identify lower risk patients for whom invasive CA might be avoided.

Long-term prognosis after a normal exercise stress Tc-99m sestamibi SPECT study

BACKGROUND

Patients with a normal stress technetium 99m sestamibi study were shown to have a favorable outcome at intermediate-term follow-up. However, long-term survival has not been studied. The aim of this study was to evaluate the incidence and predictors of mortality and cardiac events at long-term follow-up after a normal exercise stress sestamibi study. Methods and results We studied 218 patients (mean age, 53 +/- 10 years, 108 men) who had normal myocardial perfusion assessed by Tc-99m sestamibi single photon emission computed tomography at rest and during symptom-limited bicycle exercise stress test. Endpoints during a follow-up period of 7.4 +/- 1.8 years were hard cardiac events (cardiac death and nonfatal myocardial infarction) and all-cause mortality. During follow-up, 13 patients died of various causes (cardiac death in 1 patient). Ten patients had nonfatal myocardial infarction (a total of 11 hard cardiac events). By multivariate analysis, independent predictors of cardiac events were history of coronary artery disease (chi(2) = 5, P =.03) and lower exercise heart rate (chi(2) = 12, P =.001). Independent predictors of all-cause mortality were age (chi(2) = 4, P =.05) and exercise heart rate (chi(2) = 5, P =.03). The annual mortality rate was 0.6% in the first 5 years and 1.8% between the sixth and eighth years. The annual hard cardiac event rate was 0.7% in the first 5 years and 1.5% between the sixth and eighth years. Receiver operating characteristic curves identified an exercise heart rate lower than 130 beats/min as the cutoff value that separated patients with regard to their risk for mortality and hard cardiac events.

CONCLUSIONS

It is concluded that the annual mortality and cardiac event rate is less than 1% during 5-year follow-up after a normal exercise sestamibi study. Therefore repeated testing would not be required unless there is a change in symptoms. Follow-up should be closer in patients with a history of coronary artery disease and in those who fail to achieve an exercise heart rate of 130 beats/min or greater.

[Clinical predictors of the presence of perfusion defects in more than than one territory in myocardial scintigraphy with GATED-SPECT]

BACKGROUND AND OBJECTIVE

Extension of perfusion defects is associated with outcome in patients undergoing myocardial scintigraphy. The study aimed to identify the clinical characteristics that can predict the existence of perfusion defects in more than one territory in patients referred for myocardial scintigraphy with GATED-SPECT.

PATIENTS AND METHODS

A total of 193 patients undergoing myocardial scintigraphy with GATED-SPECT (99mTc-tetrofosmine) were studied. Clinical variables and scintigraphy results were studied to determine what clinical variables are associated with perfusion defects in more than one territory.

RESULTS

The number of territories with perfusion defects per patient was 1.1 0.8 and 29% had perfusion defects in > 1 territory. Patients with greater probability of having perfusion defects in > 1 territory were those with previous myocardial infarction (44% vs 21%, p = 0.030) and males (33% vs 10%, p = 0.006). In addition, patients with > 2 coronary risk factors had a statistical tendency to have defects in > 1 territory (47% vs 20%, p = 0.057). Only 15% of the patients with one of these three characteristics had perfusion defects in > 1 territory in comparison with 45% and 83% in those with 2 or 3 factors, respectively.

CONCLUSION

Considering 3 simple clinical characteristics (male gender, previous infarction and existence of > 2 coronary risk factors), it is possible to predict which patients are more likely to show perfusion defects in > 1 territory during GATED-SPECT myocardial scintigraphy.

Prognostic value of dobutamine stress technetium-99m-sestamibi single-photon emission computed tomography myocardial perfusion imaging: stratification of a high-risk population

OBJECTIVES

This work was undertaken to define the intrinsic cardiac risk of the patient population referred for dobutamine stress perfusion imaging and to determine whether dobutamine technetium-99m ((99m)Tc)-sestamibi single-photon emission computed tomography (SPECT) imaging is capable of risk stratification in this population.

BACKGROUND

In animal models, dobutamine attenuates the myocardial uptake of (99m)Tc-sestamibi resulting in underestimation of coronary stenoses. Therefore, we hypothesized that the prognostic value of dobutamine stress (99m)Tc-sestamibi SPECT myocardial perfusion imaging might be impaired, owing to reduced detection of coronary stenoses.

METHODS

We reviewed the clinical outcome of 308 patients (166 women, 142 men) who underwent dobutamine stress SPECT (99m)Tc-sestamibi imaging at our institution from September 1992 through December 1996.

RESULTS

During an average follow-up of 1.9 +/- 1.1 years, there were 33 hard cardiac events (18 myocardial infarctions [MI] and 15 cardiac deaths) corresponding to an annual cardiac event rate of 5.8%/year, which is significantly higher than the event rate for patients referred for exercise SPECT imaging at our institution (2.2%/year). Event rates were higher after an abnormal dobutamine (99m)Tc-sestamibi SPECT study (10.0%/year) than after a normal study (2.3%/year) (p < 0.01), even after adjusting for clinical variables. In the subgroup (n = 29) with dobutamine-induced ST-segment depression and abnormal SPECT imaging, the prognosis was poor, with annual cardiac death and nonfatal MI rates of 7.9% and 13.2%, respectively.

CONCLUSIONS

Patients referred for dobutamine perfusion imaging are a high-risk population, and dobutamine stress (99m)Tc-sestamibi SPECT imaging is capable of risk stratification in these patients.

Increased prognostic value of combined myocardial perfusion imaging and exercise electrocardiography in patients with coronary artery disease

BACKGROUND

Myocardial perfusion imaging (MPI) with technetium-99m-labeled sestamibi and exercise electrocardiography (EECG) are widely used for risk stratification of patients with known or suspected coronary artery disease (CAD). However, no large-scale studies have addressed the prognostic power of the combined information from these diagnostic tools.

METHODS AND RESULTS

We studied 697 consecutive patients who underwent a 2-day Tc-99m sestamibi cardiac perfusion imaging protocol. The EECG was performed on a bicycle ergometer by symptom-limited exercise. Causes of death were obtained from death certificates. Univariate survival analyses were performed with a Kaplan-Meier estimate and a corresponding log-rank test. A multivariate Cox proportional hazards model was applied to test for potential predictor covariates obtained from hospital records. The predominant risk factors of cardiac death were fixed perfusion defects (relative risk, 2.55; range, 1.43 to 4.55) and an impaired circulatory exercise response (relative risk, 3.26; range, 1.74 to 6.08). The major prognostic information of MPI was the ability to detect patients with a definitively low risk. Patients with impaired circulatory response to exercise test and fixed perfusion defects were at a very high risk.

CONCLUSION

The combined results of MPI and EECG provide substantial information on the long-term risk of cardiac death in patients with suspected CAD.

Technetium Tc 99m sestamibi myocardial perfusion imaging: current role for evaluation of prognosis

Like 201Tl imaging, technetium Tc 99m sestamibi (MIBI) myocardial imaging can be used with exercise and pharmacologic testing to assess the presence of coronary artery disease. An increasing body of literature indicates that MIBI can also be used to assess risk of future cardiac events such as myocardial infarction or death. This article summarizes the current status of MIBI imaging for evaluating prognosis in patients with known or suspected coronary artery disease.

Risk assessment using single-photon emission computed tomographic technetium-99m sestamibi imaging

OBJECTIVES

This review summarizes the results of single-photon emission computed tomographic (SPECT) technetium-99m (Tc-99m) tracer imaging in patients with stable symptoms, patients with acute coronary syndromes, patients undergoing major non-cardiac surgery and patients with chest pain in the emergency department.

BACKGROUND

Previous studies have examined the prognostic value of stress thallium imaging in several subsets of patients with ischemic heart disease. At present, >50% of myocardial perfusion studies are performed with technetium-labeled tracers in the United States. Furthermore, there is a shift from diagnostic to the prognostic utility of stress testing. There are important differences between technetium-labeled tracers and thallium-201. It is therefore important to review the prognostic value of technetium-labeled tracers.

METHODS

We analyzed published reports in English on risk assessment using Tc-99m perfusion tracers. Results. The largest experience is in patients with stable symptoms, comprising >12,000 patients in 14 studies. In these patients, normal stress SPECT sestamibi images were associated with an average annual hard event rate of 0.6% (death or nonfatal myocardial infarction [MI]). In contrast, patients with abnormal images had a 12-fold higher event rate (7.4% annually). Both fixed and reversible defects are prognostically important, and quantitative analysis shows increased risk in relation to the severity of the abnormality. These results are similar to those obtained with thallium-201.

CONCLUSIONS

Patients with stable chest pain syndromes and normal stress SPECT sestamibi images have a very low risk of death or nonfatal MI. It is highly unlikely that coronary revascularization can improve survival in such patients. Patients with abnormal images have an intermediate to high risk for future cardiac events, depending on the degree of the abnormality. Further prospective studies comparing aggressive medical therapy with coronary revascularization in these patients are warranted.

Evaluation of exercise thallium scintigraphy versus exercise electrocardiography in predicting survival outcomes and morbid cardiac events in patients with single- and double-vessel disease. Findings from the Angioplasty Compared to Medicine (ACME) Study

OBJECTIVES

We sought to evaluate the prognostic ability of cardiac exercise stress tests in predicting cardiac mortality and morbidity in a low risk group of patients with established coronary artery disease (CAD).

BACKGROUND

Although previous studies have demonstrated the superior value of stress nuclear cardiac scintigraphy in the prognosis of patients with CAD, none of these studies have focused on patients with a proven angiographic low risk profile (i.e., single- and double-vessel CAD).

METHODS

Three hundred twenty-eight patients with documented single- and double-vessel disease were treated by random assignment to percutaneous transluminal coronary angioplasty or medical therapy in the Angioplasty Compared to Medicine (ACME) trial. Six months after randomization, maximal symptom-limited exercise tests were performed with electrocardiography (n = 300) and thallium scintigraphy (n = 270). Patients were followed up for a minimum of 5 years thereafter.

RESULTS

A reversible thallium perfusion deficit documented after 6 months of either therapy was associated with an adverse mortality outcome (18% mortality rate with a reversible thallium perfusion defect and 8% mortality rate with no reversible thallium perfusion deficit, p = 0.02). Moreover, an important mortality gradient was demonstrated in relation to the number of reperfusing defects (0 = 7%, 1 to 2 = 15%, >3 = 20%, p = 0.04). Exercise electrocardiography did not predict this mortality outcome.

CONCLUSIONS

A reversible thallium perfusion deficit demonstrated 6 months after medical therapy or coronary angioplasty is a valuable prognostic marker in patients with angiographically documented single- and double-vessel disease and is superior to exercise electrocardiography in this regard.

Prognostic evaluation of patients after myocardial infarction: incremental value of sestamibi single-photon emission computed tomography and echocardiography

BACKGROUND

This study compares the prognostic value of 99mTc-labeled methoxyisobutyl isonitrile (MIBI) single-photon emission computed tomographic (SPECT) imaging, echocardiography, and other clinical and laboratory prognostic factors in the long-term risk stratification of patients with stable uncomplicated infarcts.

METHODS AND RESULTS

Ninety-one consecutive patients affected by a first myocardial infarction without serious complications were enrolled. After at least 3 months from the infarction, they were submitted to stress-rest MIBI SPECT and rest echocardiography. Eighty-six patients completed a follow-up of at least 4 years (range 48 to 72 months; mean 55 months). By univariate (log-rank test) and multivariate analysis (Cox proportional hazards model), the main clinical, electrocardiographic, scintigraphic, and echocardiographic findings were evaluated and correlated statistically with the incidence of ensuing cardiac events. Twenty-five patients had cardiac events during the follow-up (four cardiac deaths, four myocardial infarctions, and 17 cases of unstable angina). At the multivariate analysis, the presence of reversible defects on MIBI SPECT (p = 0.008 and relative risk [RR] = 7.09), the wall motion score index, and the ejection fraction at echocardiography (respectively, p = 0.010, RR = 3.67, p = 0.036, and RR = 3.12), and stress angina (p = 0.007 and RR = 3.40) were significant and independent prognostic factors.

CONCLUSIONS

In our long-term follow-up, MIBI SPECT and echocardiography appeared to be significant and independent prognostic tools in the risk stratification of patients with stable, uncomplicated infarcts, furnishing complementary information. The reversibility of MIBI defects appeared the best indicator for a bad prognosis.