Characterization and long-term prognosis of patients with effort-induced silent myocardial ischaemia

Cost-effectiveness of screening for coronary artery disease in asymptomatic patients with Type 2 diabetes and additional atherogenic risk factors

OBJECTIVE

Screening for coronary artery disease (CAD) in asymptomatic diabetic patients with two additional atherogenic risk factors has been recommended by the American College of Cardiology/American Diabetes Association, but its cost-effectiveness is yet to be determined. The present study aims to evaluate the cost-effectiveness of screening and determine acceptable strategies.

DESIGN

Cost-effectiveness analysis using a Markov model was performed from a societal perspective to measure the clinical benefit and economic consequences of CAD screening in asymptomatic men with diabetes and two additional atherogenic risk factors. We evaluated cohorts of patients stratified by different age groups, and 10 possible combination pairs of atherogenic risks. Incremental cost-effectiveness of no screening, exercise electrocardiography, exercise echocardiography, or exercise single-photon emission-tomography (SPECT) was calculated. Input data were obtained from the published literature. Outcomes were expressed as U.S. dollars per quality-adjusted life-year (QALY).

MEASUREMENTS AND MAIN RESULTS

Compared with no screening, incremental cost-effectiveness ratio of exercise electrocardiography was $41,600/QALY in 60-year-old asymptomatic diabetic men with hypertension and smoking, but was weakly dominated by exercise echocardiography. Exercise echocardiography was most cost-effective, with an incremental cost-effectiveness ratio of $40,800/QALY. Exercise SPECT was dominated by other strategies. Sensitivity analyses found that results varied depending on age, combination of additional atherogenic risk factors, and diagnostic test performance.

CONCLUSIONS

Incremental cost-effectiveness ratio of CAD screening in asymptomatic patients with diabetes and two or more additional atherogenic risk factors is shown to be acceptable from a societal perspective. Exercise echocardiography was the most cost-effective strategy, followed by exercise electrocardiography.

Medical treatment to reduce total ischemic burden: total ischemic burden bisoprolol study (TIBBS), a multicenter trial comparing bisoprolol and nifedipine. The TIBBS Investigators

OBJECTIVES

We compared the effects of bisoprolol on transient myocardial ischemia with those of nifedipine in patients with chronic stable angina.

BACKGROUND

Both beta-adrenergic blocking agents and calcium antagonists reduce transient ischemic episodes, but comparisons of these agents have been made in only a few larger studies.

METHODS

The Total Ischemic Burden Bisoprolol Study (TIBBS) was a randomized double-blind controlled study with two parallel groups; 330 patients from 30 centers in seven European countries with stable angina pectoris, a positive exercise test and more than two transient ischemic episodes during 48 h of Holter monitoring (central evaluation) were included. Of these patients 161 were randomized to receive bisoprolol and 169 to receive nifedipine slow release. There were two treatment phases of 4 weeks each, with 48-h Holter monitoring after each phase. During phase 1, patients received either 10 mg of bisoprolol daily or 2 x 20 mg of nifedipine slow release. During phase 2, they received either 20 mg of bisoprolol daily or 2 x 40 mg of nifedipine slow release.

RESULTS

In phase 1 of the trial, 4 weeks of bisoprolol therapy (10 mg daily) reduced the mean [+/- SD] number of transient ischemic episodes from 8.1 +/- 0.6 to 3.2 +/- 0.4/48 h. Nifedipine (2 x 20 mg) reduced transient ischemic episodes from 8.3 +/- 0.5 to 5.9 +/- 0.4/48 h. Total duration of ischemia was reduced from 99.3 +/- 10.1 to 31.9 +/- 5.5 min/48 h with bisoprolol and from 101 +/- 9.1 to 72.6 +/- 8.1 min/48 h with nifedipine. Reductions were statistically significant for both drugs; the difference between bisoprolol and nifedipine was also significant (p < 0.0001). Bisoprolol reduced the heart rate at onset of episodes by 13.7 +/- 1.4 beats/min from a baseline value of 99.5 +/- 1.2 beats/min (p < 0.001). Heart rate was unchanged with nifedipine. Bisoprolol had significantly higher responder rates than nifedipine. Doubling of the dose in phase 2 of the trial had small additive effects. Only bisoprolol showed a marked circadian effect by reducing the morning peak of transient ischemic episodes (by 68% at peak time, 8:00 to 8:59 AM).

CONCLUSIONS

Both bisoprolol and nifedipine reduced the number and duration of transient ischemic episodes in patients with chronic stable angina. Bisoprolol was significantly more effective than nifedipine in both doses tested and reduced the morning peak of ischemic activity.

Digital dipyridamole stress echocardiography in silent ischemia after coronary artery bypass grafting and/or after healing of acute myocardial infarction

This study evaluates dipyridamole stress echocardiography in silent ischemia. Fourteen patients with previous coronary artery bypass grafting (group A) and 16 patients with healed myocardial infarction (group B) were studied. All had > or = 1 mm ST depression without chest pain during bicycle exercise testing. Left ventricular wall motion was analyzed using a computerized display of digital systolic cineloops with a high frame rate. Test results were compared with coronary angiography. Dipyridamole echocardiography accurately identified patients with significant coronary artery stenosis in both groups (3 of 4 in group A, 11 of 14 in group B). Retrograde flow to the occluded native artery was associated with positive results on dipyridamole testing in 6 of 7 patients in group A and all 3 in group B. Sensitivity, specificity and diagnostic accuracy for detecting significant coronary stenosis or occlusions with retrograde flow was 78, 100 and 83%, respectively. Patients with angiographic multivessel disease had a significantly larger increase in wall motion score index during dipyridamole stress than patients with 0- or 1-vessel disease, 0.18 +/- 0.11 versus 0.05 +/- 0.18 (p < 0.05). Two patients developed symptomatic bradycardia and hypotension during dipyridamole infusion. It is concluded that dipyridamole echocardiography accurately identifies myocardial regions with restricted coronary flow. Stress echocardiography is a valuable tool for assessing coronary flow in silent ischemia.