Evidence-based risk assessment in noninvasive imaging.

UNLABELLED: Assessment of important clinical and economic outcomes has become central to the evaluation of patient care. Outcome research is deeply rooted in epidemiology, including the use of multivariable, risk-adjusted regression analysis. In our current health care environment, these methods are increasingly being used to assess the quality of care and to profile physicians and laboratories. Nuclear medicine physicians therefore need to better understand outcome methodologies in order to evaluate patient outcomes, develop guidelines, and decide on patient management. METHODS: This review describes the methods of assessing the diagnostic and prognostic value of nuclear medicine techniques and, briefly, the methodologic limitations of sample size, frequency and type of events, and follow-up periods and the incremental value of imaging. Also described are logistic regression and Cox proportional hazards modeling. Models for risk assessment are designed to identify whether patients require conservative (i.e., low-risk) or aggressive (i.e., high-risk) treatment. Treatment selection is currently based on risk assessment and the formation of an integrated, empiric risk stratification algorithm of care. This review also includes the methods of assessing economic effectiveness and quality-of-life issues for patients examined with nuclear medicine techniques. CONCLUSION: In this era of constrained resources, low-cost outpatient-based care may be of increasing importance. High-quality evidence of the clinical and economic outcome of nuclear imaging is essential for helping health care providers and payers assess its value.

Predictors of improvement in left ventricular ejection fraction with carvedilol for congestive heart failure.

BACKGROUND: Beta-blocker therapy has been reported to improve survival and left ventricular ejection fraction (LVEF) in the setting of congestive heart failure (CHF). The magnitude and predictors of improved LVEF are unclear. METHODS: A total of 295 patients were enrolled in the study. Inclusion criteria were LVEF <35% at baseline and symptomatic (New York Heart Association class II to IV) CHF despite treatment with at minimum an angiotensin-converting enzyme inhibitor. Carvedilol was initiated at 3.125 mg twice daily and titrated to a target dose of 25 or 50 mg twice daily, depending on the patient's weight. Paired pretreatment baseline and 9 months with treatment follow-up quantitative LVEFs (assessed by resting radionuclide ventriculograms) were obtained in 161 (55 %) of the patients. RESULTS: LVEF improved from 25% +/- 6% at baseline to 36%+/-12% at follow-up (P<.001). Mean change in LVEF (deltaLVEF) was greater for nonischemic cardiomyopathy (NICM) (+14.5+/-2 LVEF points) than ischemic cardiomyopathy (deltaLVEF +/- 7.6+/-10 EF points, P = .001). The deltaLVEF was > or =21 LVEF points in 30% of the NICM group versus 10% of the ischemic cardiomyopathy group. Conversely, the deltaLVEF was unchanged to minimally improved (< or =5 LVEF points) in 21% of the NICM group versus 52% of the ischemic cardiomyopathy group. Multivariable analysis identified NICM and recent onset of congestive heart failure as correlates of improved LVEF. CONCLUSIONS: Carvedilol significantly improved LVEF, especially in patients with NICM and those with recent onset of CHF.

Cost-effectiveness of stress echocardiography and nuclear perfusion imaging.

Cost-effectiveness analysis is a method of comparing societal economic value of 2 different strategies. Ideally, it defines accurate test-related (direct and downstream) costs and appropriately converts differential patient outcomes into a dollar value. The likelihood that cost-effectiveness analysis translated into a policy-making tool will enhance health care and/or control costs is dependent on the validity of numerous assumptions about relative costs, patient outcomes, and generalizability of the literature to regional capabilities. The purpose of this report is to review the concept of cost-effectiveness analysis as it applies to stress echocardiography and stress myocardial perfusion imaging for selected patient subsets.

Lipid risk factor correlates of ischemic heart disease as diagnosed by myocardial perfusion scintigraphy.

Patients with known coronary artery disease frequently change their lifestyles (e.g., diet, exercise, and smoking habit) after the diagnosis is made. Such changes can alter lipid risk factor levels and obscure etiologic risk factor associations with the presence of coronary artery disease. It is therefore preferable to determine the contribution of potential risk factors before the diagnosis of coronary artery disease has been established. In this trial, we used stress nuclear myocardial perfusion imaging to diagnose coronary artery disease in patients presenting for evaluation of chest pain. Two groups of age- and sex-matched patients were identified: a normal group (patients with no evidence of coronary artery disease), and an abnormal group (patients whose scans indicated the presence of significant coronary artery disease due to either fixed or reversible perfusion defects). Blood samples were drawn before scanning and analyzed for lipid risk factors. Compared to the normal group, the abnormal group had higher levels of triglycerides (189±91 vs. 135±51 mg/dL, p=0.003), lower levels of high-density lipoprotein cholesterol (39±9 vs. 45±14 mg/dL, p=0.037), and higher levels of small, dense low-density lipoprotein (LDL(3)) (42±18 vs. 32±13 mg/dL, p=0.007). Total cholesterol, low-density lipoprotein, and lipoprotein(a) levels were similar between groups. These findings suggest that ischemic heart disease, as assessed by myocardial perfusion scintigraphy, is more closely associated with the low high-density lipoprotein/high triglyceride syndrome than with increased low-density lipoprotein or total cholesterol levels. (c) 2000 by CHF, Inc.

Outcome of medical versus invasive treatment strategies for non-high-risk ischemic heart disease.

The purpose of this study was to evaluate the outcomes of medical management compared with invasive management for patients with mild or moderate ischemia (non-high-risk) on stress tomographic myocardial perfusion scintigraphy. Of the 1,352 non-high-risk patients, 116 (9%) subsequently were referred for coronary angiography within the first 30 days after the scan; 99 (85%) of this group also underwent early revascularization procedures. The remaining 1,236 patients (91%) with non-high-risk ischemia did not undergo early invasive management. Unadjusted actuarial 3-year rate of cardiac death or nonfatal infarction was significantly better estimated survival in the medically managed group (2%) compared with the invasively managed group (22%), p = 0.0001. Subsequent coronary revascularization procedures during 3-year follow-up were less frequent in the medically managed group (4%) than in the invasively managed group (42%), p = 0.0001. A multivariable analysis identified invasive management strategy (p = 0.0001) as the only correlate of cardiac events during follow-up. In summary, this study showed that patients with non-high-risk ischemia on stress perfusion imaging can be treated safely with a conservative medical management strategy.

Bypass surgery versus coronary angioplasty for revascularization of treated diabetic patients.

BACKGROUND: The purpose of this study was to evaluate outcomes after coronary bypass surgery versus coronary angioplasty in 525 patients with pharmacologically treated diabetes. Diabetic patients constitute a significant portion of patients considered for coronary revascularization. Some studies have shown no difference in long-term outcome when comparing revascularization mode. Recently, the Bypass Angioplasty Revascularization Investigation reported better survival with bypass surgery over angioplasty in treated diabetic patients. However, the above studies have been limited by small cohorts of diabetic patients. METHODS AND RESULTS: By using a single-institution comprehensive database, a retrospective cohort design was used to study 525 consecutive pharmacologically treated diabetic patients who underwent coronary revascularization. Patients treated with surgery (n=246) were statistically similar when comparing age, gender, angina class, and ejection fraction to patients (n=279) treated with angioplasty. Follow-up was complete in 95% of bypass patients and 99% of angioplasty patients. Mean follow-up was 55.5 months. Complete revascularization was accomplished more often in the surgery group (79%) than in the angioplasty group (42%; P<.001). During a 6-year follow-up, repeat revascularization (8% versus 64%; P=.001), cardiac events (32% versus 41%; P=.04), and death (30% versus 37%; P=.08) occurred less in the bypass patients than the angioplasty patients. Multivariable analysis identified age >70 years, ejection fraction <40%, class IV angina, and incomplete revascularization, but not mode of revascularization, as correlates of late mortality. CONCLUSIONS: For most pharmacologically treated diabetic patients, freedom from death, myocardial infarction, and subsequent revascularization during long-term follow-up is superior with bypass surgery compared with angioplasty. This worse outcome was mediated in part by the frequent occurrence of incomplete revascularization with angioplasty.

Design and implementation of a nuclear cardiology testing facility in a private-practice cardiology office setting.

Nuclear cardiology services increasingly are being provided in private-practice cardiology office settings. Because training programs are hospital based, trainees in nuclear cardiology may find only limited guidance on how to set up a private-practice nuclear laboratory. Furthermore, there is no literature to date advancing "models" for such facilities that might be useful for practice managers. The purpose of this review is to address common issues related to setting up and administering a nuclear cardiology laboratory in a private-practice cardiology office.