Todd D. Miller

Prognostic value of the Duke treadmill score in the elderly

OBJECTIVES The purpose of this study was to test the hypothesis that the Duke treadmill score works less well for risk stratification in patients age 75 years or above. BACKGROUND Although the Duke treadmill score is generally effective for risk stratification, its prognostic value in the elderly may be limited because they have a higher prevalence of coronary artery disease (CAD), more severe CAD and a lower exercise tolerance. METHODS The study population consisted of 247 patients age 75 years or above, and the control population consisted of 2,304 patients below 75 years of age. All patients were symptomatic, had undergone exercise thallium testing between 1989 and 1991 and were followed for a median of >6.5 years. The Cox regression model was used to test the association of the Duke score (utilized both as a continuous variable and using previously published risk group cutoffs) with outcomes (cardiac death, nonfatal myocardial infarction [MI], late revascularization). RESULTS Using the Duke score to risk-stratify the elderly, 26% were in the low risk group, 68% were in the intermediate risk group and 6% were in the high risk groups; seven-year cardiac survival was 86%, 85% and 69%, respectively (p = 0.45). There was also no significant association between these Duke score risk groups and all other outcome end points in the elderly. The Duke score as a continuous variable did not predict cardiac death (p = 0.43) or cardiac death or MI (p = 0.42), but did predict total cardiac events (which included late revascularization) (p = 0.0027). For the control population, more patients (55%) were in the low risk group, and the Duke score (as a continuous variable or in risk groups) was highly predictive of all end points (p = 0.0001). CONCLUSIONS The Duke score predicted cardiac survival in younger patients but not in patients age 75 years or above. The majority of the elderly were classified as intermediate risk by the Duke score. Only a minority of the elderly were classified as low risk, but this group still had an annual cardiac mortality of 2%/year.

Appropriate Use Criteria For Stress Single-Photon Emission Computed Tomography Sestamibi Studies A Quality Improvement Project

Background— We previously reported the application of the 2005 American College of Cardiology Foundation appropriate use criteria for stress single-photon emission computed tomography (SPECT) imaging to patients at Mayo Clinic (Rochester, MN) in 2005 and 2006. A subsequent internal quality improvement project focused on physician education in an attempt to reduce the rate of inappropriate SPECT studies. Methods and Results— Our 2008 physician education effort, focused on 4 specific indications that accounted for 88% of the inappropriate SPECT studies, included a presentation at medical grand rounds, a publication in the staff newsletter, meetings with physician administrators, and focused presentations to departments/divisions with many ordering physicians. We then remeasured the appropriateness of SPECT studies using previously published methods. The general categories of study indications, eg, after revascularization, were similar in 273 SPECT patients in 2008 and in our 2005 (n=284) and 2006 (n=284) cohorts. There was a trend suggesting a change in the overall classification of appropriateness over time (P=0.08) and a significant change in the rate of inappropriate studies over time (P=0.018). Inappropriate studies decreased from 14.4% in 2005 to 7.0% in 2006 before initiation of the quality improvement project. After completion of the quality improvement project, inappropriate studies increased to 11.7% (P=0.06). The 95% confidence limits for the 4.7% increase in inappropriate studies after the quality improvement project included a decrease of 0.2% and an increase of 9.6%. Conclusions— This quality improvement project, focused on feedback, physician education, and remeasurement, did not reduce the rate of inappropriate stress SPECT studies in a single academic medical center. Similar limited interventions focused on physician education alone may have limited benefit. More extensive intervention may be necessary to improve the quality of care with appropriateness criteria.

Gender differences in use of stress testing and coronary heart disease mortality: a population-based study in Olmsted County, Minnesota

OBJECTIVES We sought to examine the utilization of exercise stress testing in relation to age and gender in a population-based setting. BACKGROUND The utilization of noninvasive procedures has been shown to be associated with the subsequent use of invasive procedures. Yet, there are no population-based data on the utilization of stress testing; in particular, although gender differences in the use of invasive procedures have been reported, the use of noninvasive procedures has not been examined in relation to gender. METHODS In Olmsted County, Minnesota, passive surveillance of the medical care of the community is provided through the Rochester Epidemiology Project. A population-based cohort of Olmsted County residents undergoing exercise tests was identified. The medical records of residents with prevalent and incident exercise tests in 1987 and 1988 were reviewed. For persons with an initial test (incidence cohort), data on clinical presentation, test indications and results were abstracted. Stress test utilization rates were calculated, and crude rates were directly adjusted to the age distribution of the 1980 U.S. population. To help interpret patterns of use at the population level, coronary heart disease mortality rates (International Classification of Diseases, 9th revision, codes 410 to 414) were calculated (crude and directly adjusted to the overall age distribution of the 1980 U.S. population) and used as an indicator of coronary disease burden. RESULTS A total of 2,624 tests were performed. The crude utilization rate (per 100,000) was 1,888 for men and 703 for women (rate ratio for men over women 2.7, 95% confidence interval [CI] 2.5 to 2.9); it remained significantly higher in men across all age strata. The crude incidence rate (per 100,000) of initial stress tests was 1,112 for men and 517 for women (rate ratio 2.2, 95% CI 1.9 to 2.4). For both men and women, the incidence increased with age; however, incidence remained lower in women in all age strata. At the time that they underwent an initial test, women were more symptomatic and had poorer exercise performance than men. The rate ratio of men over women for coronary heart disease mortality was 1.1 (95% CI 0.9 to 1.2). The age-adjusted rate ratios for stress test utilization were 2.8 (95% CI 2.5 to 3.0), and that for coronary heart disease mortality was 1.9 (95% CI 1.7 to 2.2). CONCLUSIONS These population-based data show that during the study period, the utilization of stress testing in Olmsted County was lower in women than in men. Women in the incidence cohort were older and more symptomatic and had poorer exercise performance than men. Such differences should be considered when examining the utilization of subsequent invasive procedures according to gender.

Prevalence of spontaneous reperfusion and associated myocardial salvage in patients with acute myocardial infarction

This study sought to determine the prevalence of spontaneous reperfusion of an infarct-related artery (IRA) and associated myocardial salvage in the absence of thrombolysis or angioplasty. Twenty-one patients with acute myocardial infarction received only heparin and aspirin. At a median of 18 hours after presentation, 12 patients (57%) had angiographic patency of the IRA. Technetium-99m sestamibi was injected acutely on presentation and again at hospital discharge. Acute and final perfusion defect sizes were measured. Their difference, myocardial salvage, was calculated along with salvage index (myocardial salvage/acute defect). Comparing patients with a patent versus occluded IRA, myocardium at risk was similar (16% +/- 12% vs 12% +/- 9% left ventricle, p = NS); however, myocardial salvage (9% +/- 9% vs -2% +/- 7% left ventricle, p = 0.01), and salvage index (0.62 +/- 0.37 vs 0.19 +/- 0.33, p = 0.01) were greater in patients with spontaneous reperfusion. Resolution of chest pain was greater in patients with a patent IRA (100% vs 55%, p = 0.003). Spontaneous reperfusion of the IRA occurs frequently in patients with acute myocardial infarction and is associated with significant myocardial salvage.

The Timing and Impact of Follow-Up Studies After Normal Stress Single-Photon Emission Computed Tomography Sestamibi Studies

Background—The purpose of this study was to determine the prevalence and timing of routine follow-up single-photon emission computed tomography (SPECT) studies after a normal stress SPECT scan compared with the patients warranty period (ie, time to 1% risk of death or myocardial infarction). Methods and Results—We identified patients at Mayo Clinic Rochester who had normal stress SPECT scans in 2002. Of 2354 patients without prior coronary artery disease, 309 (13%) had routine follow-up scans. The time to routine follow-up was a median of 2.1 years (25th percentile, 1.2 years; 75th percentile, 3.6 years). This interval was a median of 45% of the warranty period. Of the 309 patients, only 9 (3%) underwent subsequent coronary angiography, without revascularization. Of 656 patients with prior coronary artery disease, 171 (26%) had routine follow-up scans. The time to routine follow-up was a median of 1.6 years (25th percentile, 1.0 years; 75th percentile, 2.7 years). This interval was a median of 164% of the warranty period. Of the 171 patients, only 7 (4%) underwent coronary angiography, without revascularization. Conclusions—In patients without prior coronary artery disease, routine follow-up SPECT scans are performed infrequently but well before the end of the patients warranty period. Routine follow-up scans are performed more commonly in patients with prior coronary artery disease but generally after the end of the warranty period. Routine follow-up SPECT scans have minimal impact on referral to catheterization or revascularization.

Prognostic value of exercise thallium-201 imaging in a community population

BACKGROUND The prognostic value of exercise thallium-201 imaging has been well established in referral patient populations at tertiary care centers, but these results may be influenced by referral bias. METHODS This study was performed to evaluate the prognostic value of thallium imaging in a community-based population of 446 residents of Olmsted County, Minn. Eleven variables were prospectively selected and tested for their associations with outcome end points. RESULTS Four variables (age, history of myocardial infarction, number of abnormal thallium segments on the postexercise images, and increased thallium lung uptake) contained the most independent prognostic information. For the end point overall mortality rate, the multivariate chi-square values were 17.2 (p < 0.0001) for age and 20.9 (p < 0.0001) for the number of abnormal thallium segments on the postexercise images. Five-year survival rate for patients older than the median age of 59 years with an abnormal scan was 84% versus 97% for patients < or = 59 years of age with a normal scan. CONCLUSION Exercise thallium imaging was useful for prognostic purposes in this relatively low-risk community population, confirming the findings of referral population studies.

Prognosis in patients with an abnormal exercise radionuclide angiogram in the absence of significant coronary artery disease

To investigate the prognostic importance of abnormal exercise left ventricular function on radionuclide angiography in the absence of significant angiographic coronary artery disease, 79 consecutive patients with these findings were followed up for a mean of 25 months (range 12 to 55). All patients had 1) an ejection fraction at rest greater than or equal to 0.40, 2) an ejection fraction that decreased with exercise or peak exercise ejection fraction less than 0.60, and 3) no significant coronary artery disease. The mean change in ejection fraction was a decrease of 0.07. In 63 patients (80%), the ejection fraction decreased during exercise; in 45 patients, it decreased by greater than or equal to 0.05. Twenty patients (25%) had a peak exercise ejection fraction less than 0.50. All patients were alive at follow-up study. One patient had a nonfatal myocardial infarction, and three patients were hospitalized for recurrent chest pain. No patient underwent coronary angioplasty or bypass surgery. The calculated infarction-free survival rate at 4 years by life table analysis was 97%. Patients with an abnormal exercise radionuclide angiogram in the absence of significant angiographic coronary artery disease have an excellent short-term prognosis.