Prognostic implications of normal exercise SPECT thallium images in patients with strongly positive exercise electrocardiograms

Higher event rate in patients with high-risk Duke Treadmill Score despite normal exercise-gated myocardial perfusion imaging

This prospective study was carried out to find the negative predictive value of various Duke Treadmill Scores (DTSs) in patients with normal myocardial perfusion imaging (MPI). This study was conducted from August 2012 to July 2015, and 603 patients having normal exercise MPIs were included. Patients were followed for 2 years for fatal myocardial infarction (FMI) and nonfatal myocardial infarction (NFMI). Follow-up was not available in 23 patients, leaving a cohort of 583 participants. DTS was low risk (≥5) in 286, intermediate risk (between 4 and − 10) in 211, and high risk (≤−11) in 86 patients. Patients with high- and intermediate-risk DTS were significantly elder than low-risk DTS cohort. Patients with high-risk DTS had significantly higher body mass index with male preponderance compared to other groups. No significant difference was found among three groups regarding modifiable or nonmodifiable risk factors and left ventricular ejection fraction. On follow-up, single FMI was observed in high-risk DTS group (log-rank test value = 5.779, P = 0.056). Five NFMI events were observed in high-risk DTS (94.2% survival; log-rank test value = 19.398, P = 0.0001; significant) as compared to two events each in low- and intermediate-risk DTS (nonsignificant). We conclude that patients with normal exercise MPI and low-to-intermediate risk DTS have significantly low NFMI. High-risk DTS despite normal exercise MPI had high NFMI. Further, validation studies to find the predictive value of symptomatic and asymptomatic ST deviation resulting in high-risk DTS in patients with normal exercise MPI are warranted.

Outcome of patients with high-risk Duke treadmill score and normal myocardial perfusion imaging on spect

BACKGROUND

Annual mortality rate can range from <1% for patients with normal myocardial perfusion by SPECT to >5% based on a high-risk Duke treadmill score (DTS). Information on the prognosis of patients with the combination of HRDTS and normal SPECT is limited and is the purpose of this study.

METHODS

Data from a large nuclear cardiology registry (n = 17,972 patients) were reviewed. A total of 340 had HRDTS (score ≤ -11) while undergoing SPECT. Combined cardiovascular mortality and non-fatal myocardial infarction (MI) and cardiovascular mortality alone were available in 310 patients at a mean follow-up of 4.01 ± 1.5 years.

RESULTS

The majority of the patients had abnormal SPECT (n = 270, 71%). The abnormal SPECT patients compared to the normal were older (65.6 vs 62.8 years of age; P = .025), more likely to have abnormal left ventricular ejection fraction (26.1% vs 0%; P < .0001), known coronary artery disease (CAD, 35.9% vs 7.8%; P < .0001) and lower DTS (-14.5 vs -13.2; P = .0006), Kaplan-Meier survival analysis demonstrated a significantly lower cardiovascular mortality (5.4% vs 0%, P = .02) and combined outcome of MI and cardiovascular mortality (15% vs 4.4%, P = .009) in patients with normal versus abnormal SPECT.

CONCLUSIONS

High-risk DTS is associated with abnormal perfusion SPECT in most patients, but nearly one-third of the patients had normal perfusion. Patients with a normal SPECT had a lower cardiovascular event rates.

Prognostic value of myocardial ischemic electrocardiographic response in patients with normal stress echocardiographic study

The prognostic value of ST-segment depression on exercise electrocardiogram (eECG) in the setting of a normal wall motion response in a stress echocardiographic study is not well defined. The aim of the study was to compare outcomes among patients with normal wall motion during stress echocardiography with and without ischemic exercise electrocardiographic changes. A total of 4,233 patients underwent stress echocardiography from 2007 to 2010. The primary outcomes were a composite of all-cause mortality and myocardial infarction. Coronary revascularization was a secondary outcome. A Cox regression model was used for the primary analysis. Ischemic exercise electrocardiographic changes were defined as ST-segment depression of at least 1 mm, on at least 3 consecutive beats, and in at least 2 contiguous leads. A normal stress echocardiogram was present in 2,975 patients; of them, 2,228 (74%) had a normal eECG and 747 (26%) had ischemic changes on eECG. Patients with and without ischemic changes during exercise electrocardiography were similar in age and gender. At 4-years follow-up, 36 patients (2.8%) with a normal eECG experienced a primary end point versus 12 patients (1.9%) in the group with an ischemic exercise electrocardiographic response (p = 0.56). The rate of coronary revascularization was similar between the groups (7.0% and 5.7%, respectively, p = 0.2). There were no differences in the primary outcomes of patients with and without exercise electrocardiographic changes and normal stress echocardiogram (hazard ratio 1.33, 95% confidence interval 0.69 to 2.58). In conclusion, a normal wall motion response even in the setting of an ischemic exercise electrocardiographic response portends a benign prognosis in patients undergoing stress echocardiography.

Electrocardiographic changes during vasodilator SPECT myocardial perfusion imaging: does it affect diagnosis or prognosis?

BACKGROUND

Significance of electrocardiographic (ECG) changes during vasodilator stress myocardial perfusion imaging (MPI) is controversial. We examined the diagnostic and prognostic significance of ECG changes during vasodilator single photon emission computerized tomography (SPECT) MPI.

METHODS

We studied consecutive patients who underwent vasodilator SPECT MPI from 1995 to 2009. Patients with baseline ECG abnormalities, previous history of coronary artery bypass graft surgery or myocardial infarction (MI) were excluded. Significant coronary artery disease (CAD) was defined as >70% stenosis of any vessel or ≥50% stenosis of left main. Mean follow-up was 2.4 ± 1.5 years for cardiac events (cardiac death and non-fatal MI).

RESULTS

Of patients in the diagnostic cohort, ST depression was associated with increased incidence of CAD with abnormal (P = .020 and P <.001) but not in those with normal perfusion (P = .342). Of 3,566 patients with follow-up in the prognostic cohort, including 130 (5.0%) with ST depression and normal perfusion, the presence of ST depression ≥1 mm did not affect the outcomes in any summed stress score category.

CONCLUSIONS

ST depression ≥1 mm during vasodilator SPECT MPI is associated with CAD in patients with abnormal perfusion, but provides no additional risk stratification beyond concomitant perfusion imaging, including those with normal studies.

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.

Prognostic value of stress myocardial perfusion imaging in patients with mildly impaired systolic left ventricular function or left ventricular asynergy without chest pain but with suspected coronary artery disease

BACKGROUND

The prognostic value of myocardial perfusion imaging (MPI) was investigated in patients with mildly impaired left ventricular (LV) function who had no chest pain but were suspected to have coronary artery disease (CAD).

METHODS AND RESULTS

Consecutive patients (n=72, mean age =67) who had no chest pain but with mildly impaired systolic LV function (mean LV ejection fraction =52%) or LV asynergy and suspected to have CAD were followed up for 4.9 years after stress MPI. The follow-up time was censored at the occurrence of cardiac death, hospitalization for congestive heart failure (CHF), acute coronary syndromes (ACS), or revascularization. Images were scored using a 20-segment model and a 0-4 scale, and then the summed stress, rest, and difference scores (SDS) were calculated. During follow-up, there were 2 cases of cardiac death, 8 of hospitalization for CHF, 4 of ACS and 2 of revascularization. Cox regression demonstrated that SDS >or=4 was an excellent predictor of cardiac events in all patients (hazard ratio =4.2, p=0.01), and especially in diabetic patients (hazard ratio =28.4, p=0.01).

CONCLUSION

Stress MPI is useful for predicting cardiac events and may be performed in patients without chest pain if they have mildly impaired systolic LV function or LV asynergy.

Overview of exercise stress testing

Exercise stress testing is a non-invasive, safe and affordable screening test for coronary artery disease (CAD), provided there is careful patient selection for better predictive value. Patients at moderate risk for CAD are best served with this kind of screening, with the exception of females during their reproductive period, when a high incidence of false positive results has been reported. Patients with a high pretest probability for CAD should undergo stress testing combined with cardiac imaging or cardiac catheterization directly. Data from the test, other than ECG changes, should be taken into consideration when interpreting the exercise stress test since it has a strong prognostic value, i.e. workload, heart rate rise and recovery and blood pressure changes. Only a low-level exercise stress test can be performed early post myocardial infarction (first week), and a full exercise test should be delayed 4 to 6 weeks post uncomplicated myocardial infarction. The ECG interpretation with myocardial perfusion imaging follows the same criteria, but the sensitivity is much lower and the specificity is high enough to overrule the imaging part.

Comparison of prognostic value of stress echocardiography versus stress electrocardiography in patients with suspected coronary artery disease

Stress electrocardiographic (ECG) ST-segment depression is a prognostic marker of adverse cardiac outcomes in coronary artery disease. However, use of concurrent stress echocardiography (ECHO) has lead to concordant and discordant findings on stress electrocardiogram during stress studies. The prognostic value of stress ECHO in the setting of these stress ECG findings has not been previously evaluated. Outcomes of 1,268 patients (60 +/- 12 years old, 48% women) who had normal electrocardiograms and underwent stress ECHO were analyzed. ST-segment depression > or =1.5 mm in 2 contiguous leads on stress electrocardiogram and a wall motion score index of >1 on peak stress echocardiogram were considered abnormal. Events of nonfatal myocardial infarction (n = 18) and cardiac death (n = 32) were analyzed during follow-up (2.8 +/- 0.9 years). In 91 patients (7%) who had abnormal findings on stress electrocardiogram, 38 (41%) had an abnormal finding on stress echocardiogram and 4 had cardiac events (0.6% per year), and all who had a normal finding on stress echocardiogram had no events (n = 53, 59%, p = 0.01). Among 46 events (92%) with a normal finding on stress electrocardiogram, 30 (60%) showed a discordantly abnormal finding on stress echocardiogram (3.2% per year, p <0.01). Overall, the cohort that had normal findings on stress echocardiogram showed a lower event rate (72%, 16 events, 1.1% per year) compared with the cohort that had abnormal findings on stress echocardiogram (28%, 34 events, 3.6% per year, p <0.001), independent of stress ECG response. Peak wall motion score index (hazard ratio 2.55, p <0.001) and left ventricular ejection fraction (hazard ratio 0.99, p <0.001) were independent and incremental (global chi-square, p <0.001) prognostic markers by stress ECHO. In conclusion, a normal finding on stress echocardiogram confers a benign prognosis independent of the type of stress ECG response during stress studies. In addition, peak wall motion score index and ejection fraction by ECHO are stronger prognostic markers over stress electrocardiography in patients who are evaluated for coronary artery disease.

[Myocardial perfusion scintigraphy in type 2 diabetic patients with atypical chest pain]

To verify the prevalence of ischemic myocardial abnormalities, 67 patients with type 2 diabetes mellitus (DM2) with normal basal electrocardiogram (EKG) or with ventricular repolarization abnormalities were evaluated by a perfusional myocardial scintigraphy. The average age was 63.5 +/- 9 years. Twenty-one (31.3%) were male and 46 (68.7%) female. A significant part of the sample (62.7%) had a normal myocardial scan, 37.3% were positive for ischemia. The majority of the sample (91%; n = 61) was submitted to an EKG during exercise which was positive for ischemia in 31.1%. The concordance between myocardial scintigraphy and the EKG during exercise demonstrated a low correlation between the two procedures (Kappa = 0.49; P = 0.0001). We conclude that perfusional myocardial scan is a highly valuable tool for evaluation and diagnosis of coronary artery disease in DM2 patients with atypical angina.

Risk assessment by myocardial perfusion imaging for coronary revascularization, medical therapy, and noncardiac surgery

Stress myocardial perfusion imaging (MPI) has become an important tool in risk stratification of patients with known coronary artery disease. A normal myocardial perfusion scan has a high negative predictive value and is associated with low annual mortality rate (< 1%). Patients with extensive ischemia (> 20% of the left ventricle), defects in more than 1 coronary vascular territory, transient or persistent left ventricular cavity dilation, and ejection fraction less than 45% have a high annual mortality rate (> 3%). Those patients should undergo coronary revascularization whenever feasible, as the cardiac event rate increases in proportion to the magnitude of the jeopardized myocardium. Stress MPI can be used to demonstrate ischemia in patients with symptoms early after coronary artery bypass surgery (< 5 years) or in those without symptoms late (>/= 5 years) after coronary artery bypass surgery. With respect to patients who underwent percutaneous interventions, stress MPI can help detect in-stent restenosis early after the intervention (3-6 months) or assess the progression of native coronary disease afterward. Since preliminary data suggest that a reduction in the perfusion defect size may translate to a reduction of coronary events, stress MPI can help assess the efficacy of medical management of coronary disease. Finally, stress MPI is indicated for perioperative cardiac risk stratification for noncardiac surgery in patients with intermediate risk predictors (mild angina, prior myocardial infarction or heart failure symptoms, diabetes mellitus, renal insufficiency) and poor functional capacity or in those who undergo high-risk surgery with significant implications in further preoperative management.

Exercise echocardiography for the prognostic stratification of patients with low pretest probability of coronary artery disease

PURPOSE

The aim of this study was to determine whether exercise echocardiography provides incremental data for risk stratification of patients with a low pretest probability of coronary artery disease.

PATIENTS AND METHODS

The study included patients referred for exercise echocardiography whose probability of coronary artery disease was 25% or less. We calculated an exercise wall motion score index (on a 1-5 scale), an indicator of the extent and severity of exercise-induced abnormalities. The primary outcomes of the study were subsequent cardiac events (cardiac death and nonfatal myocardial infarction).

RESULTS

We studied 571 men and 1047 women; their mean (+/- SD) age was 55 +/- 13 years. During a median follow-up of 3 years, there were 19 cardiac events (6 cardiac deaths and 13 nonfatal myocardial infarctions); an additional 37 patients underwent coronary revascularization. In a multivariate analysis of clinical, exercise electrocardiographic, and echocardiographic parameters, exercise wall motion score index (hazard ratio [HR] = 2.1 per 0.5 units; 95% confidence interval [CI]: 1.3 to 3.4), and age (HR = 2.0 per decade; 95% CI: 1.2-2.8) were independently associated with the risk of cardiac events. Although exercise echocardiographic variables contributed significantly (P = 0.01) to a model of the risk of adverse events, only 9 (47%) of the 19 patients with cardiac events were identified by an abnormal exercise echocardiogram.

CONCLUSION

Among patients with low pretest probability of coronary artery disease by clinical criteria, exercise echocardiography identifies some, but not all, patients at risk of future events. Because of the low event rate, routine application of exercise echocardiography in a patient with a low pretest probability does not appear to be cost-effective and therefore cannot be recommended.

Cardiac nuclear medicine in monitoring patients with coronary heart disease

Patient monitoring is a major indication for cardiac nuclear medicine procedures. Stress myocardial perfusion scintigraphy was initially used for diagnosis, but monitoring patients with coronary artery disease has become more common. Stress myocardial perfusion scintigraphy has been shown to provide a considerable amount of incremental prognostic information, which may be useful in selecting patients for therapy. In patients being considered for revascularization, fluorodeoxyglucose can be used to identify regions of dysfunctional but viable myocardium, even within regions that show fixed defects on stress perfusion imaging. It can be used to select a group of patients who will improve function with revascularization and who may have an improved outcome. Thus, cardiac nuclear medicine plays a pivotal role in monitoring patients with coronary artery disease.

Principal uses of myocardial perfusion scintigraphy in the management of patients with known or suspected coronary artery disease

The use of myocardial perfusion single photon emission computed tomography (SPECT) has undergone considerable expansion and evolution over the past 2 decades. Although myocardial perfusion imaging was first conceived as a noninvasive diagnostic tool for determining the presence or absence of coronary artery disease, its prognostic value is now well established. Thus, identification of patients at risk for future cardiac events has become a primary objective in the noninvasive evaluation of patients with chest pain syndromes and among patients with known coronary artery disease. In particular, the ability of myocardial perfusion SPECT to identify patients at low (< 1%), intermediate (1% to 5%) or high (> 5%) risk for future cardiac events is essential to patient management decisions. Moreover, previous studies have conclusively shown the incremental prognostic value of myocardial perfusion SPECT over clinical and treadmill exercise data in predicting future cardiac events. This report addresses the current role and new developments, with respect to the use of myocardial perfusion imaging, in determining patient risk for cardiac events and the cost-effective integration of such information into patient management decisions.

Stress nuclear myocardial perfusion imaging versus stress echocardiography: prognostic comparisons

The use of noninvasive stress cardiac imaging for stratifying risk in patients with known or suspected coronary artery disease is growing as a tool for identification of the subgroup most likely to benefit from the expense and risk of more invasive procedures, including cardiac catheterization and coronary revascularization. In this setting, it is especially important that a test be able to identify patients with sufficiently low risk that clinicians are comfortable in deferring such interventions, especially in those with other markers of increased risk. Previous data have shown that cardiac risk is most closely related to the presence and extent of jeopardized viable myocardium on noninvasive stress cardiac imaging. Although stress echocardiography may have comparable ability to detect coronary artery disease, current data suggest that stress echocardiography detects significantly less jeopardized viable myocardium than stress nuclear myocardial perfusion imaging and consequently fewer patients at risk for cardiac events. Stress nuclear myocardial perfusion imaging may therefore have important advantages for risk stratification and the direction of future care of patients with known or suspected coronary artery disease.

The prognostic value of a normal Tc-99m sestamibi SPECT study in suspected coronary artery disease

BACKGROUND

Myocardial perfusion is widely used for risk stratification of patients with suspected or known coronary artery disease (CAD). Recent years have seen an increasing demand for screening of such patients. The value of a normal stress thallium-201 scanning is well established. The advent of technetium 99m-sestamibi single photon emission computed tomography (SPECT) has enhanced the profile of nuclear cardiology even further as a reliable test for screening. However, in spite of previous reports, there is paucity of large-scale data regarding the prognostic value of a normal Tc 99m-sestamibi scanning result.

METHODS

The aim of our study was to assess the incidence of cardiac death and non-fatal myocardial infarction in patients with an intermediate probability of coronary artery disease (CAD). A total of 473 patients with normal stress Tc-99m-sestamibi SPECT were monitored for 30+/-16 (6 to 56) months to assess serious cardiac events. There were 272 men and 201 women, with a mean age of 56+/-2 years, of whom 89% had symptoms suggestive of CAD, 65% had an abnormal exercise electrocardiography, 6% had known CAD, and 5% had a high risk of CAD. The average workload was 9.14 metabolic equivalents, peak exercise heart rate was 93%+/-13% of the age predicted target.

RESULTS

The annualized mortality rate was 0.2% (95%CI 0.02% to 0.7%) and no infarctions occurred in this group.

CONCLUSIONS

A normal stress Tc-99m-sestamibi is highly predictive of a benign outcome, even in patients with intermediate probability of CAD.

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.

Prognostic value of stress echocardiography in the evaluation of atypical chest pain patients without known coronary artery disease

Patients with atypical chest pain frequently lack significant coronary artery disease (CAD) and are, therefore, at low risk for future adverse cardiovascular events. We hypothesized that in this group of patients, stress echocardiography could identify those at risk for cardiac events. We retrospectively reviewed (mean follow-up 23.0 +/- 7.2 months) the prognostic value of stress echocardiography for major (cardiac death, myocardial infarction, congestive heart failure, and unstable angina) and total (major events plus coronary revascularization) cardiac events in 661 patients with atypical chest pain, normal global left ventricular (LV) systolic function, and no history of CAD. A positive stress echocardiogram was defined as the development of new or worsening wall motion abnormalities with exercise stress (80%) or dobutamine (20%). A total of 41 cardiac and 16 major events were noted. The event-free survival for total cardiac events was 97% for a normal stress echocardiogram and 93% for a normal stress electrocardiogram (ECG) at 30 months. A positive stress ECG predicted an event-free rate of 86% compared with 74% for stress-induced wall motion abnormalities and 42% if stress-induced LV dysfunction accompanied the wall motion abnormalities. A strategy recommending invasive studies based on positive stress echocardiogram results increased the per-patient cost, but led to greater savings per cardiac event predicted and provided incremental prognostic value for future cardiac events beyond clinical and stress electrocardiographic data. Thus, stress echocardiography in low-risk patients for CAD appears to be more cost effective than a stress ECG.

Clinical and angiographic significance of a normal thallium-201 tomographic study in patients with a strongly positive exercise electrocardiogram

Among 23,059 patients who underwent exercise myocardial tomography between 1985 and 1994 at our institution, there were 817 (3.5%) with a strongly positive exercise electrocardiogram and normal myocardial tomograms. Among these, 52 patients had no conditions known to be associated with a false-positive exercise electrocardiogram and no previous coronary revascularization, and underwent coronary angiography. Of the 32 patients with significant coronary stenoses, 50% had 1-vessel disease and only 22% had 3-vessel disease (p < 0.05). Among 55 stenosed arteries, 56% were of moderate severity (50 to 74%), whereas only 9% had subtotal or total occlusion (95 to 100%) (p < 0.001). There was a significant gender difference in the prevalence of significant coronary stenoses (80% in male vs 24% in female patients, p < 0.0001). A strongly positive exercise electrocardiogram coupled with normal exercise myocardial tomograms is a rare clinical finding. In women, this finding is usually associated with normal coronary arteries, whereas in men it often denotes coronary artery disease, usually of mild to moderate degree.

Prognostic significance of silent ischemia

This study examined the prognostic predictors in 521 patients with angiographic evidence of coronary artery disease (CAD). All patients underwent exercise single-photon emission computed tomographic thallium imaging. The patients were divided into those with symptomatic ischemia defined as reversible thallium defects, S-T segment depression (or both) and angina during exercise (n = 210, group 1), and silent ischemia defined as thallium defects or ST segment depression (or both) but no angina during exercise (n = 311, group 2). During a mean follow-up of 24 +/- 21 months, there were 30 cardiac events (death or nonfatal myocardial infarction). The extent of CAD (2.0 +/- 0.8 diseased vessels in group 1 and 2.1 +/- 0.8 diseased vessels in group 2), the left ventricular ejection fraction, the extent of perfusion abnormality (21% +/- 11% in group 1 and 24% +/- 12% in group 2), and the peak heart rate and double product were similar in the two groups. Survival analysis showed no significant difference in the event-free survival in patients with symptomatic or silent ischemia. The 2-year event-free survival rate was 95% in group 1 and 94% in group 2 (difference not significant). The extent of perfusion abnormality and history of diabetes mellitus were the most important predictors of events. Thus the prognosis of medically treated patients with CAD is comparable in those patients with silent or symptomatic ischemia and is dependent on the extent of myocardium at risk rather than presence or absence of angina pectoris during exercise.

Comparison of the treadmill exercise score and single-photon emission computed tomographic thallium imaging in risk assessment

BACKGROUND

This study compared the prognostic value of exercise single-photon emission computed tomographic (SPECT) thallium imaging with that of treadmill exercise score in medically treated patients with coronary artery disease (CAD).

METHODS AND RESULTS

The treadmill exercise score was derived from exercise duration, degree of ST segment depression, and the treadmill anginal index. There were 121 patients with no CAD and 316 patients with angiographically defined CAD (> or = 50% diameter stenosis of one or more vessels). During a mean follow-up of 29 months, there were 35 cardiac deaths or nonfatal myocardial infarctions. Multivariate Cox survival analysis showed the extent of thallium imaging abnormality and CAD to be independent predictors of prognosis. On the other hand, the treadmill exercise score was not a significant predictor even on univariate analysis. The results of thallium uptake were the strongest independent predictors of prognosis and in addition provided incremental prognostic power to coronary angiography (chi 2 = 29 for SPECT, 27 for coronary angiography, and 37 for both).

CONCLUSIONS

Thus exercise SPECT thallium imaging is significantly better than the treadmill exercise score in risk assessment. The size of the perfusion abnormality is an important predicator of prognosis.