Comparison of thallium-201 single-photon emission computed tomography and electrocardiographic response during exercise in patients with normal rest electrocardiographic results

Typical angina during exercise stress testing improves the prediction of future acute coronary syndrome

INTRODUCTION

The prognostic value of angina during exercise stress testing is controversial, possibly due to previous studies not differentiating typical from non-typical angina. We aimed to assess the prognostic value of typical angina alone, or in combination with ST depression, during exercise stress testing for predicting cardiovascular events.

METHODS

We conducted a prospective observational cohort study including all patients who performed a clinical exercise stress test at the department of Clinical Physiology, Kalmar County Hospital between 2005 and 2012. The association between typical angina/ST depression and incident acute coronary syndrome (ACS) and cardiovascular mortality were analysed using Cox regression for long-term and 1-year follow-up.

RESULTS

Out of 11605 patients (median follow-up 6.7 years), 623 (5.4%) developed ACS and 319 (2.7%) died from cardiovascular causes. Compared to patients with no angina and no ST depression, typical angina and ST depression were associated with increased risk of future ACS; hazard ratio (HR) 3.5 ([95%CI] 2.6-4.7). This association was even stronger for ACS within one year (typical angina with and without concomitant ST depression; HR 20.8 (13.9-31.3) and 9.7 (6.1-15.4), respectively). Concordance statistics for ST depression in predicting ACS during long-term follow-up was 0.58 (0.56-0.60) and 0.69 (0.65-0.73) for ACS within one year, and 0.64 (0.62-0.66) and 0.77 (0.73-0.81), respectively, when typical angina was added to the model.

CONCLUSIONS

Typical angina during exercise stress testing is predictive of future ACS, especially in combination with ST depression, and during the first year after the test.

Myocardial perfusion imaging in patients with a recent, normal exercise test

AIM: To investigate the added value of myocardial perfusion scintigraphy imaging (MPI) in consecutive patients with suspected coronary artery disease (CAD) and a recent, normal exercise electrocardiography (ECG).

METHODS: This study was a retrospective analysis of consecutive patients referred for MPI during a 2-year period from 2006-2007 at one clinic. All eligible patients were suspected of suffering from CAD, and had performed a satisfactory bicycle exercise test (i.e., peak heart rate > 85% of the expected, age-predicted maximum) within 6 mo of referral, their exercise ECG was had no signs of ischemia, there was no exercise-limiting angina, and no cardiac events occurred between the exercise test and referral. The patients subsequently underwent a standard 2-d, stress-rest exercise MPI. Ischemia was defined based on visual scoring supported by quantitative segmental analysis (i.e., sum of stress score > 3). The results of cardiac catheterization were analyzed, and clinical follow up was performed by review of electronic medical files.

RESULTS: A total of 56 patients fulfilled the eligibility criteria. Most patients had a low or intermediate ATPIII pre-test risk of CAD (6 patients had a high pre-test risk). The referral exercise test showed a mean Duke score of 5 (range: 2 to 11), which translated to a low post-exercise risk in 66% and intermediate risk in 34%. A total of seven patients were reported with ischemia by MPI. Three of these patients had high ATPIII pre-test risk scores. Six of these seven patients underwent cardiac catheterization, which showed significant stenosis in one patient with a high pre-test risk of CAD, and indeterminate lesions in three patients (two of whom had high pre-test risk scores). With MPI as a gate keeper for catheterization, no significant, epicardial stenosis was observed in any of the 50 patients (0%, 95% confidence interval 0.0 to 7.1) with low to intermediate pre-test risk of CAD and a negative exercise test. No cardiac events occurred in any patients within a median follow up period of > 1200 d.

CONCLUSION: The added diagnostic value of MPI in patients with low or intermediate risk of CAD and a recent, normal exercise test is marginal.

Acoustic cardiography to improve detection of coronary artery disease with stress testing

AIM

To assess if performance of 12-lead exercise tolerance testing (ETT) can be improved by simultaneous acoustic cardiography and to compare the diagnostic performances of electrocardiography (ECG) during ETT and acoustic cardiography for detection or exclusion of angiographically proven coronary artery disease (CAD).

METHODS

We conducted an explorative study with retrospective data analysis using a convenience sample of consecutive patients (n = 59, mean age: 62 years) from an outpatient clinic in Switzerland, who were referred for ETT by their general practitioner on suspicion of CAD, and in whom, coronary angiography was carried out. Measurements included sensitivity, specificity, likelihood ratios and receiver operating characteristic curves. A standard, symptom-limited, 12-lead ECG exercise tolerance test was performed by independent persons with simultaneous acoustic cardiography and subsequent cardiac angiography for determination of significant CAD.

RESULTS

Thirty-four of the 59 adult subjects (58%) had a final diagnosis of CAD by angiography, and in 25 subjects, CAD was excluded by angiography. Sensitivity/specificity of ST segment depression in the group was 29%/92%, whereas the most powerful acoustic cardiographic parameter was the strength of the fourth heart sound (S4), with corresponding sensitivity/specificity of 53%/92%. The disjunctive combination of the S4 and ST depression had sensitivity/specificity of 68%/84%.

CONCLUSION

In this preliminary pilot study, the use of acoustic cardiography alone during ETT or disjunctively with ST depression has been shown to be a simple and convenient method for the detection of CAD, which was superior to ST depression on the standardized ECG.

Evaluation of myocardial perfusion and function by gated SPECT in patients with Behçet's disease

BACKGROUND

Behçet's disease (BD) is a systemic multi-system vasculitis that can have a wide range of effects on the cardiovascular system.

OBJECTIVE

To determine the existence of myocardial perfusion defects caused by coronary microvascular dysfunction in BD and to evaluate coronary arterial distribution and left ventricular systolic function by gated single-photon emission computed tomography (SPECT).

METHODS

The study population consisted of 23 (15 men and 8 women) patients with BD and 20 healthy controls (12 men and 8 women). Technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) gated SPECT studies were performed at stress and rest in a 2-day protocol. Stress and rest left ventricular ejection fraction (LVEF) were calculated. Using non-gated SPECT images myocardial perfusion scores [summed stress score (SSS), summed rest score (SRS), summed difference score (SDS), and fix defect score (FDS)] and perfusion defect extent as percentage (stress, rest ischemic, and fix %LV) were determined. Using gated SPECT images, wall motion score indices (stress wall motion score indices and rest wall motion score indices) were calculated. Coronary angiography (CAG) was applied to patients with abnormal myocardial perfusion scintigraphy (MPS).

RESULTS

The mean ages of the BD and control groups were 39.3 +/- 10.6 years and 36.2 +/- 8.3 years, respectively. No statistically significant differences were observed between the two groups regarding clinical features and cardiologic findings. Abnormal MPS was found in 13 (56.5%) of the BD patients; 3 patients had non-transmural infarcts and 10 patients reversible perfusion defects. Reversible perfusion defects were also found in two controls (10.0%). When the two groups were compared regarding the gated SPECT findings, differences were determined in the following parameters; SSS, SRS, SDS, FDS, stress and rest LVEF, stress and rest %LV, and stress and rest WMSI. In the BD group, when gated SPECT results were compared between those with and without abnormal MPS, differences were determined in SSS, SRS, SDS, FDS, stress and rest %LV, and stress and rest WMSI. Epicardial coronary arteries were normal in CAG.

CONCLUSIONS

Myocardial perfusion and function are disturbed owing to influenced coronary microvascularity in BD, and CAG is frequently observed to be normal. Gated SPECT is a non-invasive reliable method that simultaneously evaluates the existence, extent and severity of myocardial ischemia or infarction and the wall movements in cardio-Behçet.

Computed tomographic coronary angiographic assessment of high-risk coronary anatomy in patients with suspected coronary artery disease and intermediate pretest probability

BACKGROUND

It is unclear if computed tomographic coronary angiography (CTA), an evolving technique for the evaluation of coronary artery disease (CAD), can identify patients with high-risk coronary anatomy.

METHODS

Among patients referred for invasive angiography at Hamilton Health Sciences (Hamilton, Ontario, Canada), those with an intermediate pretest probability (25%-60% likelihood of a significant stenosis) were prospectively identified using a multivariate risk score and were studied on a 64-detector Toshiba Aquilion scanner (Toshiba Medical Systems, Tokyo, Japan) before invasive angiography. Patients with high-risk anatomy (left main, 3-vessel CAD, or 2-vessel CAD involving the proximal left anterior descending artery) or at least 1 significant stenosis were identified on CTA and invasive angiography, and the results of these modalities were compared on a per patient basis.

RESULTS

Eighty patients were enrolled in the study (mean age 56 +/- 9 years, male-female ratio 43:37). Nondiagnostic scan results were obtained in 5 patients (6%). By CTA, 13 patients had high-risk anatomy and 31 patients had at least 1 significant stenosis. For the per patient detection of high-risk anatomy, CTA had 100% sensitivity (95% CI 69%-100%), 95% specificity (95% CI 86%-95%), a positive likelihood ratio of 18.0 (95% CI 6.4-50.3), and a negative likelihood ratio of 0.05 (95% CI 0-0.072). Revascularization was performed in 100% of patients with high-risk anatomy on CTA, 83% with at least 1 significant stenosis on CTA, and 0% without a significant stenosis on CTA.

CONCLUSION

In appropriately selected patients, CTA is a highly sensitive and specific technique for the detection of high-risk anatomy and maybe a valuable method for noninvasive risk stratification.

Receiver operating characteristic (ROC) curves and the definition of threshold levels to diagnose coronary artery disease on electrocardiographic stress testing. Part I: The use of ROC curves in diagnostic medicine and electrocardiographic markers of ischaemia

A common problem in diagnostic medicine, when performing a diagnostic test, is to obtain an accurate discrimination between 'normal' cases and cases with disease, owing to the overlapping distributions of these populations. In clinical practice, it is exceedingly rare that a chosen cut point will achieve perfect discrimination between normal cases and those with disease, and one has to select the best compromise between sensitivity and specificity by comparing the diagnostic performance of different tests or diagnostic criteria available. Receiver operating characteristic (or receiver operator characteristic, ROC) curves allow systematic and intuitively appealing descriptions of the diagnostic performance of a test and a comparison of the performance of different tests or diagnostic criteria. This review will analyse the basic principles underlying ROC curves and their specific application to the choice of optimal parameters on exercise electrocardiographic (ECG) stress testing. Part I will focus on theoretical description and analysis along with reviewing the common problems related to the diagnosis of myocardial ischaemia by means of exercise ECG stress testing. Part II will be devoted to applying ROC curves to available diagnostic criteria through the analysis of ECG stress test parameters.

Can Exercise-Induced Changes in B-Type Natriuretic Peptides Be Used to Detect Cardiac Ischemia?

BACKGROUND

We reviewed the current medical literature that pertained to the question of whether myocardial ischemia triggers the release of B-type natriuretic peptides (BNPs) and, in particular, whether transient exercise-induced ischemia can be detected by the measurement of changes in these biomarkers. BNPs are well-established as markers of left ventricular dysfunction, particularly heart failure. There is accumulating evidence that various conditions with the common denominator of myocardial ischemia are also associated with increased circulating levels of these peptides.

METHODS AND RESULTS

Recently published methods and results, which includes our published and unpublished data, were reviewed.

CONCLUSION

The results show that exercise-induced ischemia or its associated regional wall-motion abnormalities trigger the release of BNPs and that the measurement of plasma levels of N-terminal pro brain natriuretic peptide and BNP before and immediately after symptom-limited exercise can distinguish patients with and without ischemia with a high degree of accuracy.

Detection of exercise-induced ischemia by changes in B-type natriuretic peptides

OBJECTIVES

The purpose of this study was to examine the effect of exercise-induced ischemia on levels of B-type natriuretic peptide (BNP) and its inactive N-terminal fragment (NT-pro-BNP)and to determine whether measurement of these peptides can improve the diagnostic accuracy of exercise testing.

BACKGROUND

The ability of exercise testing to detect coronary artery disease (CAD) is limited by modest sensitivity and specificity. B-type natriuretic peptides (NT-pro-BNP and BNP) are released by ventricular myocytes in response to wall stress. We hypothesized that exercise-induced ischemia results in increased wall stress and triggers release of NT-pro-BNP and BNP.

METHODS

A total of 74 patients with known CAD, normal left ventricular function, and normal resting levels of NT-pro-BNP and BNP who were referred for exercise testing with radionuclide imaging, and 21 healthy volunteers, were enrolled. Blood was drawn before and after maximal exercise and analyzed for NT-pro-BNP and BNP.

RESULTS

Of the patients with CAD, 40 had ischemia on perfusion images and 34 did not. Median post-exercise increases in NT-pro-BNP and BNP (DeltaNT-pro-BNP and DeltaBNP) were approximately four-fold higher in the ischemic group than in the nonischemic group (DeltaNT-pro-BNP 14.5 vs. 4 pg/ml, p < 0.0001; DeltaBNP 36.5 vs. 7.5 pg/ml, p < 0.0001). In volunteers, median DeltaNT-pro-BNP was almost identical to that of the nonischemic patient group. At equal specificity to the electrocardiogram (ECG) (58.8%), the sensitivities of DeltaNT-pro-BNP and DeltaBNP for detecting ischemia were 90% and 80%, respectively; in contrast, the sensitivity of the exercise ECG was 37.5%.

CONCLUSIONS

Measurement of exercise-induced increases in BNPs more than doubles the sensitivity of the exercise test for detecting ischemia with no loss of specificity.

Failure of right precordial electrocardiography during stress testing to identify coronary artery disease

BACKGROUND

It has been reported that the use of right precordial leads results in the same diagnostic accuracy as thallium-201 exercise scintigraphy for the detection of coronary artery disease (CAD). The aim of this study was to evaluate the utility of right precordial leads in the detection of CAD.

METHODS AND RESULTS

We evaluated 900 consecutive patients (514 men, 386 women) ranging in age from 39 to 84 years (mean +/- SD, 64 +/- 11 years). Seven hundred forty patients underwent treadmill exercise testing, and 160 underwent pharmacologic stress testing for the diagnosis of chest pain or dyspnea. All received either Tl-201 or technetium-99m sestamibi during stress. During stress testing, the ECG was recorded every minute with 12 limb and left precordial leads and 3 right precordial leads (V(3)R, V(4)R, and V(5)R). The electrocardiogram was considered positive when the ST segment was either elevated or depressed by at least 0.1 mV at 80 ms after the J point, and results were also compared with single photon emission computed tomography myocardial perfusion imaging results. Of the 900 patients, 158 had significant positive changes in the limb or left precordial leads. Only 4 patients had positive changes in the right precordial leads (Fisher exact test, P <.001). Of the patients who had positive electrocardiographic changes, 95 (60%) had abnormal myocardial perfusion scans, with 91 in patients with normal right precordial leads. All 4 patients with ischemic changes in the right precordial leads had abnormal scans, but the left leads were also positive. Three hundred seventy-three of 900 patients (41%) had abnormal scans with no electrocardiographic evidence of ischemia.

CONCLUSIONS

Our experience is far different than that published and suggests that the use of right precordial leads during stress testing fails to provide the same diagnostic accuracy as either the standard left-sided electrocardiography or myocardial perfusion imaging for the detection of CAD.

Heart-rate recovery immediately after exercise as a predictor of mortality

BACKGROUND

The increase in heart rate that accompanies exercise is due in part to a reduction in vagal tone. Recovery of the heart rate immediately after exercise is a function of vagal reactivation. Because a generalized decrease in vagal activity is known to be a risk factor for death, we hypothesized that a delayed fall in the heart rate after exercise might be an important prognostic marker.

METHODS

For six years we followed 2428 consecutive adults (mean [+/-SD] age, 57+/-12 years; 63 percent men) without a history of heart failure or coronary revascularization and without pacemakers. The patients were undergoing symptom-limited exercise testing and single-photon-emission computed tomography with thallium scintigraphy for diagnostic purposes. The value for the recovery of heart rate was defined as the decrease in the heart rate from peak exercise to one minute after the cessation of exercise. An abnormal value for the recovery of heart rate was defined as a reduction of 12 beats per minute or less from the heart rate at peak exercise.

RESULTS

There were 213 deaths from all causes. A total of 639 patients (26 percent) had abnormal values for heart-rate recovery. In univariate analyses, a low value for the recovery of heart rate was strongly predictive of death (relative risk, 4.0; 95 percent confidence interval, 3.0 to 5.2; P<0.001). After adjustments were made for age, sex, the use or nonuse of medications, the presence or absence of myocardial perfusion defects on thallium scintigraphy, standard cardiac risk factors, the resting heart rate, the change in heart rate during exercise, and workload achieved, a low value for heart-rate recovery remained predictive of death (adjusted relative risk, 2.0; 95 percent confidence interval, 1.5 to 2.7; P<0.001).

CONCLUSIONS

A delayed decrease in the heart rate during the first minute after graded exercise, which may be a reflection of decreased vagal activity, is a powerful predictor of overall mortality, independent of workload, the presence or absence of myocardial perfusion defects, and changes in heart rate during exercise.

Long-term additive prognostic value of thallium-201 myocardial perfusion imaging over clinical and exercise stress test in low to intermediate risk patients : study in 1137 patients with 6-year follow-up

BACKGROUND

The exercise treadmill test (ETT) and Tl201 single proton emission computed tomography (SPECT) are of short- to medium-term prognostic value in coronary heart disease. We assessed the long-term prognostic value of these tests in a large population of patients with low- to intermediate risk of cardiac events.

METHODS AND RESULTS

One thousand one hundred thirty-seven patients (857 men, age 55+/-9 years) referred for typical (62.1%) or atypical (22.4%) chest pain, or suspected silent ischemia (15.5%), were followed up for 72+/-18 months. Overall mortality was higher after strongly positive (ST depression >2 mm, or >1 mm for a workload </=75 W) (2. 36%/y) or nondiagnostic ETT (1.63%/y) than after normal (0.85%/y) or positive ETT (1.37%/y) (P=0.002), and after abnormal SPECT than after normal SPECT (1.60%/y versus 0.68%/y, P=0.001). The major cardiac event rate (cardiac death or myocardial infarction [MI]) was 0.88%, 1.59%, 2.10%, and 2.13%/y after negative, positive, strongly positive, and nondiagnostic ETT, respectively (P=0.003), and 0.56%, 1.43%, and 2.05%/y in patients with 0, 1 to 2, and >/=3 abnormal segments on SPECT, respectively (P<0.002). An abnormal SPECT was predictive of MI (P<0.001), whereas ETT was not. In multivariate analysis, SPECT was of incremental prognostic value over clinical and ETT data for predicting overall mortality and major cardiac events.

CONCLUSIONS

The incremental predictive value of SPECT is maintained over 6 years and is particularly relevant after positive, strongly positive, and nondiagnostic ETT.

Relation between the electrocardiographic stress test and degree and location of myocardial ischemia

Factors that influence frequency and location of stress-induced electrocardiographic (ECG) ST depression and the development of chest pain are incompletely understood. We studied 331 patients with ischemic myocardial nuclear defects in response to routine clinical treadmill testing with simultaneous ECG recording. Nuclear defects were analyzed for location and extent of myocardium involved. Exercise-induced ischemic ST changes were demonstrated in 59% of patients (196 of 331). Subjects with stress-induced ECG changes and/or chest pain had more extensive nuclear perfusion defects. Diabetic patients were significantly less likely to experience chest pain (24%) versus nondiabetics (41%) during testing (p = 0.04). Larger perfusion defects were associated with greater magnitude, lead distribution, and incidence of ECG changes. The number of ECG lead zones (anterior, lateral, and inferior) responding positively were related to both magnitude of ST depression and severity of ischemia, but not to location of ischemic defects. Regardless of location of ischemia, ST depression occurred with similar frequency. Thus, exercise-induced ECG ST depression remains a valuable indicator of the severity of myocardial ischemia. Greater ST depression involving multiple leads usually signified extensive myocardial ischemia, but provided no information regarding its location. Anginal-type chest pain induced by exercise testing also denoted more extensive ischemia.

Assessment of the severity of coronary artery stenosis by the ratio of the regional washout rate determined by adenosine triphosphate stress Tl-201 SPECT

BACKGROUND

Adenosine triphosphate stress thallium-201 single-photon emission computed tomography (ATP SPECT) is useful for diagnosis of coronary artery disease, but its usefulness for evaluating the severity of coronary artery stenosis has not been established.

METHODS AND RESULTS

We performed region-of-interest analysis of short-axis images obtained by ATP SPECT in 31 patients with single-vessel disease (>50% stenosis of the luminal diameter). We selected the lowest and highest washout rates (WR) among the anterior, lateral, and inferior WRs and calculated the ratio of the lowest WR to the highest WR (WR ratio = 0.925+/-0.027 in 14 control subjects). ATP SPECT showed positive results in 29 (94%) of 31 patients. The severity of coronary artery stenosis was inversely correlated with the WR ratio (r = -0.703, P < .0001). The sensitivity and specificity of a WR ratio < or = 0.660 for the diagnosis of severe coronary stenosis (> or =80% stenosis) were 83% and 80%, respectively.

CONCLUSIONS

Results suggest that ATP SPECT may be useful for assessment of the severity of coronary artery stenosis in patients with single-vessel disease.