Relative role of coronary stenosis severity and morphology in determining pharmacologic stress echo positivity

Endothelial microparticles correlate with high-risk angiographic lesions in acute coronary syndromes

BACKGROUND

Endothelial Microparticles (EMP) are small fragments of endothelial cell membrane shed during apoptosis or activation. Our group has previously reported elevations of EMP in patients with coronary artery disease (CAD), thrombotic thrombocytopenic purpura (TTP), pre-eclampsia, multiple sclerosis (MS), and severe hypertension (HTN). In the present study, we evaluate the possible relationship between EMP levels and the angiographic severity and characteristics of coronary obstructive lesions.

METHODS

We studied a total of 43 patients undergoing coronary angiography. Fifteen had presented with acute myocardial infarction (MI), 20 with unstable anginas (UA), 5 with stable angina (SA) and 3 with congestive heart failure. Coronary angiography was reviewed and coronary lesions were classified using the Ambrose classification. Coronary stenoses were classified as high and low risk. High-risk included lesions with eccentric appearance (type II), presence of thrombi, or multiple irregularities. Low-risk lesions were defined as concentric or type I. Lesions were also analyzed by degree of stenosis and history of acute coronary syndrome (ACS). EMP in plasma was assayed by flow cytometry.

RESULTS

EMP in eccentric type II or multiple irregular lesions (high-risk) were 2.5-fold higher than in type I or concentric (low-risk) lesions, p<0.05. Lesions with thrombi had three-fold higher EMP than those without (p=0.05). Mild stenosis (>20%-<45%) had three-fold higher EMP than more severe (>45%), and five-fold higher than those without stenosis (p<0.01). Among patients with type II lesions, those with first ACS episode had four-fold higher EMP levels than those with recurrent ACS (p<0.01).

CONCLUSION

High EMP was associated with high-risk angiographic lesions including eccentric type II, multiple irregular, and lesions with thrombi. Mild to moderate stenosis was associated with higher EMP levels than severe stenosis. EMP may be a useful marker in detecting endothelial injury and risk of ACS as defined by angiography.

Independent contribution of plaque complexity to myocardial ischemia during dobutamine stress echocardiography

The influence of complex plaque morphology on the extent of demand-induced ischemia in unselected patients is not well defined. We sought to investigate the functional significance of lesion morphology in patients who underwent coronary angiography and dobutamine stress echocardiography (DSE). Angiography and DSE were performed within a 6-month period (mean 1 +/- 1 month) in 196 patients. Angiographic assessments involved quantification of stenosis severity, assessment of the extent of jeopardized myocardium, and categorization of plaque morphology according to the Ambrose classification. DSE was interpreted by separate investigators with respect to wall motion score index (WMSI) and number of coronary territories involved. A general linear model was constructed to assess the independent contribution of patient characteristics and angiographic and DSE results with respect to extent of ischemic myocardium. Complex lesion morphology was seen in 62 patients (32%). Patients with complex lesions were more likely to have had prior myocardial infarction (p <0.001) and be current smokers (p = 0.03). During angiography, they exhibited a trend toward a greater number of diseased vessels, had a greater coronary jeopardy score (p <0.001) and more frequent collateral flow (p = 0.03). During echocardiography, patients had a higher stress WMSI (p <0.001) and were more likely to show ischemia in all 3 arterial territories (p <0.01). On multivariate regression, the coronary artery jeopardy score and the presence of complex plaque morphology were independent predictors of the extent of ischemic myocardium (R(2) = 34%, p <0.001). Thus, patients with complex plaque morphology are older, more likely to smoke, and more likely to have had prior myocardial infarction. They exhibit more extensive disease with higher coronary jeopardy scores and a higher resting and peak stress WMSI. Despite these differences, complex plaque morphology remains an independent predictor of the extent of ischemia during stress.

Prognostic value of pharmacological stress echocardiography in patients with known or suspected coronary artery disease: a prospective, large-scale, multicenter, head-to-head comparison between dipyridamole and dobutamine test. Echo-Persantine International Cooperative (EPIC) and Echo-Dobutamine International Cooperative (EDIC) Study Groups

OBJECTIVES

The study compared the prognostic value of dipyridamole and dobutamine stress echocardiography in patients with known or suspected coronary artery disease.

BACKGROUND

Extensive information is available on the relative diagnostic accuracy of the two tests assessed in a head-to-head fashion, whereas comparative data on their prognostic yield are largely preliminary to date.

METHODS

Dipyridamole (up to 0.84 mg/kg over 10 min) atropine (up to 1 mg over 4 min) (DIP) and dobutamine (up to 40 microg/kg/min)-atropine (1 mg over 4 min) (DOB) stress tests were performed in 460 patients with known or suspected coronary artery disease. Patients were followed up for 38+/-21 months.

RESULTS

The DIP was negative in 253 and positive in 207 patients. The DOB was negative in 242 and positive in 218 patients. During the follow-up, there were 80 cardiac events. For all cardiac events, the negative and positive predictive value were 83% and 17% for DOB, 84% and 19% for DIP, respectively (p = NS). Considering only cardiac death, by univariate analysis Wall-Motion Score Index (WMSI) at DIP peak dose (chi-square 13.80, p<0.0002) was the strongest predictor, followed by WMSI DOB (chi2 = 8.02, p<0.004) and WMSI at rest (chi2 = 6.85, p<0.008). By stepwise analysis, WMSI at DIP peak dose was the most important predictor (RR [relative risk] 7.4, p<0.0001).

CONCLUSIONS

In patients at low-to-moderate risk of cardiac events, pharmacological stress echocardiography with either dobutamine or dipyridamole allows effective and grossly comparable, risk stratification on the basis of the presence, severity and extension of the induced ischemia.

Can dobutamine stress echocardiography predict cardiac events in nonrevascularized diabetic patients following acute myocardial infarction?

STUDY OBJECTIVE

To determine whether the prognostic value of dobutamine stress echocardiography (DSE) performed early after acute myocardial infarction (AMI) is as high in diabetic patients as in nondiabetic patients.

DESIGN

Inception cohort study.

SETTING

Tertiary cardiac referral center.

PATIENTS AND INTERVENTIONS

Three hundred thirty-eight patients (116 diabetic and 222 nondiabetic) who underwent DSE after AMI were followed up for cardiac events.

MEASUREMENTS AND RESULTS

Outcome events were as follows: "hard" events consisted of cardiac death and nonfatal reinfarction, while "all events" included hard events and unstable angina. The mean follow-up duration was 21 +/- 9 months. DSE results were positive in 69 diabetic patients (59.5%) and 129 nondiabetic patients (58.1%; p = 0.817). During the follow-up period, there were 25 cardiac deaths, 16 cases of nonfatal reinfarction, and 55 cases of unstable angina. The Kaplan-Meier life table showed that a positive DSE result was associated with a lower event-free survival rate in nondiabetic but not in diabetic patients in terms of hard and all events. By multivariate analysis, a positive DSE result was the strongest independent predictor of future cardiac events in nondiabetic patients. However, in diabetics, a shorter dobutamine time, rather than a positive DSE result, independently predicted cardiac events.

CONCLUSIONS

Our preliminary data suggest that different DSE variables should be considered when assessing the likelihood of future events in diabetic and nondiabetic patients after AMI. The observation of shorter dobutamine time, instead of DSE positivity, has a higher prognostic value in diabetics. In diabetic patients, the only significant role of DSE positivity is for predicting future unstable angina; however, its predictive value is not as good as in nondiabetic patients.

Pharmacologic stress echocardiography in the assessment of coronary artery disease

Pharmacologic stress echocardiography has gained widespread popularity in recent years because it is more feasible for the patient and less technically demanding for the echocardiographer than exercise stress testing. The two most popular pharmacologic stresses are dobutamine and dipyridamole. These agents provide similar prognostic value and diagnostic accuracy for angiographically assessed coronary artery disease; dobutamine has marginally higher sensitivity in single-vessel disease, and dipyridamole has marginally higher specificity in patients with normal coronary arteries. Both stresses are safe, but a physician should always be in attendance when they are administered: Life-threatening reactions can occur in one of 300 to 500 cases with dobutamine and in one of 700 to 1500 cases with dipyridamole. For dipyridamole and dobutamine echocardiography, outcome data are available from multicenter, international, observational, prospective studies, such as the EPIC (Echo Persantine International Cooperative) and EDIC (Echo Dobutamine International Cooperative).

Integrated evaluation of relation between coronary lesion features and stress echocardiography results: the importance of coronary lesion morphology

OBJECTIVES

The aim of this study was to analyze, in the same group of patients, the relationship between multiple variables of coronary lesion and results of exercise, dobutamine and dipyridamole stress echocardiography tests.

BACKGROUND

Integrated evaluation of the relation between stress echocardiography results and angiographic variables should include not only the assessment of stenosis severity but also evaluation of other quantitative and qualitative features of coronary stenosis.

METHODS

Study population consisted of 168 (138 male, 30 female, mean age 51+/-9 years) patients, on whom exercise (Bruce treadmill protocol), dobutamine (up to 40 mcg/kg/min) and dipyridamole (0.84 mg/kg over 10 min) stress echocardiography tests were performed. Stress echocardiography test was considered positive for myocardial ischemia when a new wall motion abnormality was observed. One-vessel coronary stenosis ranging from mild stenosis to complete obstruction of the vessel was present in 153 patients, and 15 patients had normal coronary arteries. The observed angiographic variables included particular coronary vessel, stenosis location, the presence of collaterals, plaque morphology according to Ambrose classification, percent diameter stenosis and obstruction diameter as assessed by quantitative coronary arteriography.

RESULTS

Covariates significantly associated with the results of physical and pharmacological stress tests included for all three stress modalities presence of collateral circulation, percent diameter stenosis and obstruction diameter, as well as lesion morphology (p < 0.05 for all, except collaterals for dobutamine stress test, p = 0.06). By stepwise multiple logistic regression analysis, the strongest predictor of the outcome of exercise echocardiography test was only percent diameter stenosis (p = 0.0002). However, both dobutamine and particularly dipyridamole stress echocardiography results were associated not only with stenosis severity - percent diameter stenosis (dobutamine, p = 0.04; dipyridamole, p = 0.003) - but also, and even more strongly, with lesion morphology (dobutamine, p = 0.006; dipyridamole, p = 0.0009). As all of stress echocardiography results were significantly associated with percent diameter stenosis, the best angiographic cutoff in relation to the results of stress echocardiography test was: exercise, 54%; dobutamine, 58% and dipyridamole, 60% (p < 0.05 vs. exercise).

CONCLUSIONS

Integrated evaluation of angiographic variables have shown that the results of dobutamine and dipyridamole stress echocardiography are not only influenced by stenosis severity but also, and even more importantly, by plaque morphology. The results of exercise stress echocardiography, although separately influenced by plaque morphology, are predominantly influenced by stenosis severity, due to a stronger exercise capacity in provoking myocardial ischemia in milder forms of coronary stenosis.