Predicting severe ischemic events after uncomplicated myocardial infarction by exercise testing and rest and exercise radionuclide ventriculography

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

STUDY OBJECTIVE

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

PATIENTS AND SETTING

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

MEASUREMENT AND RESULTS

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

CONCLUSIONS

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

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.