Stress single photon emission computed tomography for detection of coronary artery disease and risk stratification of asymptomatic patients at moderate risk

BACKGROUND

The American College of Cardiology Foundation/American Society of Nuclear Cardiology appropriateness criteria document assigns single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) a rating of uncertain for detection and risk assessment of coronary artery disease (CAD) in asymptomatic patients at moderate risk.

METHODS AND RESULTS

The nuclear cardiology database was used to identify 260 asymptomatic patients (67 +/- 8 years, 72% men) without known CAD who were at moderate CAD risk according to the Framingham risk score. SPECT MPI images were categorized using the summed stress score (SSS). Mean follow-up 9.9 +/- 3.0 years. Abnormal SPECT MPI scans were present in 142 patients (55%). By SSS categories, SPECT scans were low-risk in 67%, intermediate-risk in 20%, and high-risk in 13% of patients. Overall survival at 10 years was 79%, significantly better than the age- and gender-matched Minnesota general population (P < 0.001). Survival was 60% for patients with high-risk scans (95% CI 45-80%), 79% with intermediate-risk scans (95% CI 69-91%), and 83% with low-risk scans (95% CI 77-88%) (P = 0.03), including 84% (95% CI 77-91%) with normal scans.

CONCLUSIONS

In this retrospectively identified group of asymptomatic patients at moderate CAD risk, stress SPECT MPI was effective for the detection and risk stratification of CAD. Average annual mortality was 4.0% in patients with high-risk scans vs 1.6% in patients with normal scans.

Low-dose nesiritide in human anterior myocardial infarction suppresses aldosterone and preserves ventricular function and structure: a proof of concept study

BACKGROUND

B-type natriuretic peptide (BNP, nesiritide) has anti-fibrotic, anti-hypertrophic, anti-inflammatory, vasodilating, lusitropic and aldosterone-inhibiting properties but conventional doses of BNP cause hypotension, limiting its use in heart failure.

OBJECTIVE

To determine whether infusion of low-dose BNP within 24 h of successful reperfusion for anterior acute myocardial infarction (AMI) would prevent adverse left ventricular (LV) remodelling and suppress aldosterone.

METHODS

A translational proof-of-concept study was carried out to determine tolerability and biological activity of intravenous BNP at 0.003 and 0.006 microg/kg/min, without bolus started within 24 h of successful reperfusion for anterior AMI. 24 patients with first anterior wall ST elevation AMI and successful revascularisation were randomly assigned to receive 0.003 (n = 12) or 0.006 (n = 12) microg/kg/min of IV BNP for 72 h in addition to standard care during hospitalisation for anterior AMI.

RESULTS

Baseline characteristics, drugs and peak cardiac biomarkers for myocardial damage were similar between both groups. Infusion of BNP at 0.006 microg/kg/min resulted in greater biological activity than infusion at 0.003 microg/kg/min as measured by higher mean (SEM) plasma cGMP levels (8.6 (1) vs 5.5 (1) pmol/ml, p<0.05) and suppression of plasma aldosterone (8.0 (2) to 4.6 (1) ng/dl, p<0.05), which was not seen in the 0.003 microg/kg/min group. LV ejection fraction (LVEF) improved significantly from baseline to 1 month (40 (4)% to 54 (5)%, p<0.05) in the 0.006 group but not in the 0.003 group. Infusion of BNP at 0.006 microg/kg/min was associated with a decrease of LV end-systolic volume index (61 (9) to 43 (8) ml/m(2), p<0.05) at 1 month, which was not seen in the 0.003 group. No drug-related serious adverse events occurred in either group.

CONCLUSIONS

72 h infusion of low BNP at the time of anterior AMI is well tolerated and biologically active. Patients treated with low-dose BNP had improved LVEF and smaller LV end-systolic volume at 1 month.

Applicability of Appropriateness Criteria for Stress Imaging

Background— Appropriateness criteria for stress imaging have been published to promote the effective use of stress nuclear scintigraphy and stress echocardiography. We sought to evaluate the application of the stress echocardiography appropriateness criteria to patients undergoing stress echocardiography in an academic medical center.

Methods and Results— The stress echocardiography criteria were applied to 298 consecutive patients who underwent stress echocardiography. Patients were rated as appropriate, uncertain, inappropriate, or not classifiable. Results were compared with those of a previous analysis in the same patients using the single-photon computed tomography myocardial perfusion imaging (SPECT MPI) criteria. The level of agreement between 2 cardiac nurse abstractors for categorizing appropriateness by the stress echocardiography criteria was good (κ=0.72). Overall, 54% of patients were classified as appropriate, 8% as uncertain, and 19% as inappropriate; 19% were not classifiable. By the SPECT MPI criteria, 64% of patients were classified as appropriate, 9% as uncertain, and 18% as inappropriate; 9% were not classifiable ( P <0.001 compared with stress echocardiography criteria). By the stress echocardiography criteria, 6 clinical situations or indications accounted for more than 90% of the inappropriate tests; most of these involved asymptomatic patients.

Conclusions— Applying stress echocardiography appropriateness criteria to a patient population is feasible, although 1 in 5 of our patients was not classifiable. Overall, the stress echocardiography criteria classified patients differently compared with the SPECT MPI criteria. Future refinements of the appropriateness criteria for stress imaging should address gaps in the criteria and disparities between the stress echocardiography and SPECT MPI criteria.

Perioperative cardiovascular assessment of patients undergoing noncardiac surgery

Preoperative assessment of the cardiac patient before noncardiac surgery is common in the clinical practice of the medical consultant, anesthesiologist, and surgeon. Currently, most noncardiac surgical procedures are performed for patients of advanced age, and the number of such surgeries is likely to increase with the aging of the population. These same patients have an increased prevalence of cardiovascular disease, especially ischemic heart disease, which is the primary cause of perioperative morbidity and mortality associated with noncardiac surgery. Since 1996, 3 American College of Cardiology/American Heart Association guideline documents have been published, each reflecting the available literature, with recommendations for the preoperative cardiovascular evaluation and treatment of the patient undergoing noncardiac surgery. Our review describes the 2007 American College of Cardiology/American Heart Association guidelines, the most recent revision, focusing on a newly recommended 5-step algorithmic approach to managing this clinical problem, particularly for the patient with known or suspected coronary heart disease. Continued emphasis should be given to preoperative clinical risk stratification, with noninvasive testing reserved for those patients in whom a substantial change in medical management would be anticipated based on results of testing. Pharmacologic therapy holds more promise than coronary revascularization for the reduction of major adverse perioperative cardiac events that might complicate noncardiac surgery.

Perioperative cardiovascular assessment of patients undergoing noncardiac surgery

Preoperative assessment of the cardiac patient before noncardiac surgery is common in the clinical practice of the medical consultant, anesthesiologist, and surgeon. Currently, most noncardiac surgical procedures are performed for patients of advanced age, and the number of such surgeries is likely to increase with the aging of the population. These same patients have an increased prevalence of cardiovascular disease, especially ischemic heart disease, which is the primary cause of perioperative morbidity and mortality associated with noncardiac surgery. Since 1996, 3 American College of Cardiology/American Heart Association guideline documents have been published, each reflecting the available literature, with recommendations for the preoperative cardiovascular evaluation and treatment of the patient undergoing noncardiac surgery. Our review describes the 2007 American College of Cardiology/American Heart Association guidelines, the most recent revision, focusing on a newly recommended 5-step algorithmic approach to managing this clinical problem, particularly for the patient with known or suspected coronary heart disease. Continued emphasis should be given to preoperative clinical risk stratification, with noninvasive testing reserved for those patients in whom a substantial change in medical management would be anticipated based on results of testing. Pharmacologic therapy holds more promise than coronary revascularization for the reduction of major adverse perioperative cardiac events that might complicate noncardiac surgery.

Heart rate control in patients with atrial fibrillation referred for exercise testing

Clinical practice guidelines for patients with atrial fibrillation (AF) recommended a heart rate (HR) of 60 to 80 beats/min at rest and 90 to 115 at moderate exercise. The degree to which HR control at rest and with exercise in patients with AF complies with these recommendations is unknown. HR at rest and at peak exercise was retrospectively examined in 1,097 consecutive patients with AF referred for exercise myocardial perfusion imaging. In a subgroup of 195 patients, HR was also measured at an intermediate "moderate" level. Median HR at rest was 80 beats/min, at the upper end of the recommended range of 60 to 80. Only patients administered a beta blocker (BB; 31%) had lower (p <0.001) median HRs at rest. Median HR at moderate exercise was 128 beats/min, higher than the range of 90 to 115 recommended by the guidelines. Only patients administered a BB had significantly reduced HRs (p <0.003) at moderate exercise. Median peak exercise HR was 147 beats/min. Forty-five percent of patients exceeded their age-predicted maximal HR. Patients administered BBs were significantly less likely (p <0.01) to exceed their age-predicted maximal HR. In conclusion, in patients with AF, HR control at rest and during exercise often did not comply with guideline recommendations. Regimens including a BB were more effective in achieving HR control.

Translating Research Into Practice for Healthcare Providers

The American Heart Association’s (AHA’s) mission is “to build healthier lives, free of cardiovascular diseases and stroke.” This first article in a 2-part series will serve to present an overview of the work the AHA has undertaken to translate evidence into practice for healthcare professionals. It describes the extensive work of the AHA to support and further the delivery of evidence-based medicine, which includes the following: (1) supporting scientific discovery and the next generation of healthcare professionals and researchers; (2) disseminating scientific information; (3) developing evidence-based guidelines and statements; (4) creating and advocating for the implementation of performance indicators/measures; (5) developing clinical decision support and quality improvement tools; and (6) developing directed-cause campaigns, all of which can lead to improved patient care. This article also discusses the need for novel approaches and some of the AHA’s evolving strategies to help address gaps in care. The second article, which will be published shortly after this one, will examine the AHA’s efforts to engage and empower healthcare consumers to become more involved with their own health and health care.

Contemporary outcomes of rescue percutaneous coronary intervention for acute myocardial infarction: comparison with primary angioplasty and the role of distal protection devices (EMERALD trial)

BACKGROUND

The value of distal protection devices during rescue PCI has not been studied.

METHODS

The population enrolled in a prospective, randomized multicenter trial of distal microcirculatory protection in ST-elevation MI, was stratified for those undergoing rescue (n = 93) or primary (n = 408) PCI; we performed the prespecified comparisons of distal protection in rescue and primary PCI.

RESULTS

Compared to primary PCI, rescue patients had higher baseline rates of TIMI-3 flow, but lower rates of post PCI TIMI-3 flow. However, no differences in the primary endpoints of complete ST-segment resolution (STR) at 30 minutes or infarct size, or 6 month mortality were present. In rescue PCI patients, randomization to distal protection did not significantly affect infarct size, STR, mortality or other clinical events.

CONCLUSION

Despite reduced rates of post-procedural TIMI-3 flow, patients undergoing rescue PCI compared to primary PCI have similar myocardial perfusion, infarct size and clinical outcomes. Distal protection did not offer any detectable benefit in this patient population.

Hypertensive response with exercise does not increase the prevalence of abnormal Tc-99m SPECT stress perfusion images

BACKGROUND

Systemic hypertension and an exaggerated blood pressure (BP) response with exercise have been associated with 'false-positive' findings on stress electrocardiography and echocardiography; however, limited data is available for stress myocardial perfusion imaging (MPI). The purpose of this study was to investigate whether an exaggerated elevation in BP with exercise is associated with an increased prevalence of abnormal MPI.

METHODS

BP responses to exercise were assessed in a cohort of 7,205 patients who underwent stress testing with technetium 99m-SPECT MPI (7/1999-6/2005) for the evaluation of chest pain or dyspnea.

RESULTS

A hypertensive response, defined as a peak systolic BP > or = 220 mmHg, occurred in 355 (4.9%) and was not associated with higher rates of ischemic ECG changes (16.1 versus 16.6%; P = .7), differences in Duke treadmill scores (4.7 +/- 4 versus 5.1 +/- 5; P = .3) or an increased prevalence of abnormal perfusion images (30.1% versus 32.9%; P = .3) to those without a hypertensive exercise response. Patients with a hypertensive response and either intermediate or high-risk MPI (on the basis of summed-difference-scores) referred for coronary angiography, had a high prevalence of coronary artery disease which was similar to those without a hypertensive response (88% versus 83%; P = .5). In an analysis of a community-based patient subset, a hypertensive response was not associated with a difference in either all-cause mortality or subsequent myocardial infarction, coronary revascularization or cardiac death (8% versus 9%; P = .7).

CONCLUSION

A hypertensive BP response to exercise is not associated with increased rates of ischemic ECG changes, higher-risk Duke treadmill scores, greater degrees of abnormal MPI or worse clinical outcome.

Abnormal electron beam computed tomography results: the value of repeating myocardial perfusion single-photon emission computed tomography in the ongoing assessment of coronary artery disease

OBJECTIVE

To determine whether asymptomatic patients with atherosclerosis, indicated by the presence of coronary artery calcium on electron beam computed tomography, are at enough risk for progression of disease to justify a repeated stress single-photon emission computed tomography (SPECT) examination after an initial normal to low-risk perfusion study.

PATIENTS AND METHODS

We retrospectively identified patients who had abnormal results on electron beam computed tomography (coronary artery calcium score > 0) and normal to low-risk results on SPECT (defined as a summed stress score of 0-3) within a 3-month period from January 1, 1995, to October 31, 2002. Of the 504 identified patients, 285 remained after exclusion criteria were applied. Of the 285 patients, 69 (mean +/- SD age, 58.2 +/- 7.6 years; 91% male) underwent at least 1 repeated myocardial perfusion SPECT imaging study within 4 years of their initial assessment as normal or at low risk without recurrence of symptoms. The value of repeated SPECT imaging was assessed by detection of a substantial change in the repeated SPECT study and by documentation of a clinical event (death, nonfatal myocardial infarction, or revascularization). Follow-up was 100% complete at a mean of 4.3 +/- 1.6 years.

RESULTS

Only 4 patients (6%) had a substantial progression in their SPECT risk category; substantial changes on the SPECT scans occurred only in patients with a coronary artery calcium score greater than 100. Three patients underwent revascularization, yielding a 5-year rate for survival free of revascularization of 94% (95% confidence interval, 88%-100%). No deaths or nonfatal myocardial infarctions were reported.

CONCLUSION

The principal findings of this study indicate that asymptomatic patients with initial normal or low-risk results from stress SPECT performed because of abnormal coronary artery calcium scores who remain asymptomatic are at low risk of death, myocardial infarction, or coronary revascularization. Three patients underwent revascularization by percutaneous coronary intervention despite the absence of symptoms. A substantial change in SPECT results (defined as progression from normal or low-risk summed stress score to intermediate- or high-risk summed stress score) affected 6% of patients and was not associated with any adverse hard events (nonfatal myocardial infarction or death).

Predictors of infarct size after primary coronary angioplasty in acute myocardial infarction from pooled analysis from four contemporary trials

Determinates of infarct size in patients with acute myocardial infarction (AMI) undergoing percutaneous coronary intervention (PCI) have been incompletely characterized, in part because of the limited sample size of previous studies. Databases therefore were pooled from 4 contemporary trials of primary or rescue PCI (EMERALD, COOL-MI, AMIHOT, and ICE-IT), in which the primary end point was infarct size assessed using technetium-99m sestamibi single-photon emission computed tomographic imaging, measured at the same core laboratory. Of 1,355 patients, infarct size was determined using technetium-99m sestamibi imaging in 1,199 patients (88.5%), at a mean time of 23 +/- 15 days. Median infarct size of the study population was 10% (interquartile range 0% to 23%; mean 14.9 +/- 16.1%). Using multiple linear regression analysis of 18 variables, left anterior descending infarct artery, baseline Thrombolysis In Myocardial Infarction grade 0/1 flow, male gender, and prolonged door-to-balloon time were powerful independent predictors of infarct size (all p <0.0001). Other independent correlates of infarct size were final Thrombolysis In Myocardial Infarction grade <3 flow (p = 0.0001), previous AMI (p = 0.005), symptom-onset-to-door time (p = 0.021), and rescue angioplasty (p = 0.026). In conclusion, anterior infarction, time to reperfusion, epicardial infarct artery patency before and after reperfusion, male gender, previous AMI, and failed thrombolytic therapy were important predictors of infarct size after angioplasty in patients with AMI assessed using technetium-99m sestamibi imaging and should be considered when planning future trials of investigational drugs or devices designed to enhance myocardial recovery.

Infarct size, ejection fraction, and mortality in diabetic patients with acute myocardial infarction treated with thrombolytic therapy

BACKGROUND

Diabetic patients with acute myocardial infarction (MI) have higher mortality than nondiabetic patients. The purpose of this study was to examine if larger infarct size explains the higher mortality in diabetic patients with acute ST-segment-elevation MI.

METHODS

In the CORE trial (n = 2948), subsets of patients underwent quantitative radionuclide measurement of technetium Tc 99m sestamibi infarct size (n = 1164) or gated equilibrium left ventricular ejection fraction (LVEF) (n = 1137) at days 6 to 16 after thrombolytic therapy. Clinical follow-up was 96.7% complete at 6 months.

RESULTS

The prevalence of diabetes in these patient imaging subsets was 16% to 17%. Higher risk clinical characteristics including older age and a greater prevalence of prior MI were more common in diabetic patients. Median infarct size was larger in diabetic patients (22% vs 17% of the left ventricle, P = .04), a difference that remained significant after adjustment for clinical variables (P = .048). Patients with diabetes also had lower median LVEF (48% vs 51%, unadjusted P = .002, adjusted P = .007). Six-month mortality was higher in diabetic patients: infarct size subset, 5.9% vs 1.6% (P = .0016); LVEF subset, 6.1% vs 1.0% (P < .0001). Multivariable models demonstrated that diabetes and each imaging variable were independent predictors of mortality.

CONCLUSIONS

Infarct size is modestly larger and LVEF modestly lower in diabetic patients with ST-segment-elevation MI. The substantially higher (4- to 6-fold) mortality rate in diabetic vs nondiabetic patients is only partially explained by relatively small differences in infarct size and LVEF.

The Value of Myocardial Perfusion Single-Photon Emission Computed Tomography in Screening Asymptomatic Patients With Atrial Fibrillation for Coronary Artery Disease

OBJECTIVES

We sought to determine if screening for coronary artery disease (CAD) with stress single-photon emission computed tomography (SPECT) is of value in patients with atrial fibrillation (AF) who do not have symptoms of chest pain or dyspnea.

BACKGROUND

Although noninvasive stress testing is often done to screen for CAD in asymptomatic patients with AF and is considered to be appropriate in selected patients, its potential utility has not been demonstrated.

METHODS

A retrospective study was conducted of 374 asymptomatic patients with AF referred for the detection of CAD. Mean follow-up was 5.7 +/- 3.8 years. The study group was compared with a control group of 374 asymptomatic age and gender-matched patients without AF.

RESULTS

The mean summed stress score (SSS) was not significantly different between AF patients and control subjects (3.6 +/- 5.3 vs. 3.5 +/- 5.9; p = 0.35). Compared with controls, asymptomatic AF patients had similar rates of abnormal SPECT studies (51.6% vs. 48.4%; p = 0.38) and high-risk studies (14.4% vs. 14.4%; p = 1.0). The SSS was a significant predictor of outcome in both AF patients and control subjects. However, total mortality was significantly greater in AF patients (5-year overall mortality 27% vs. 18%, 10-year overall mortality 47% vs. 40%; p < 0.001), and this difference persisted (p = 0.01) after adjusting for multiple clinical variables and the SSS.

CONCLUSIONS

Screening for CAD using stress SPECT in asymptomatic AF patients has a yield similar to age- and gender-matched control patients without AF. Although SSS predicts mortality in patients with and without AF, patients with AF have increased total mortality independent of the findings on stress SPECT. These results suggest that factors other than obstructive CAD are responsible for the increased mortality in AF.

Prevalence and prognosis of left ventricular systolic dysfunction in asymptomatic diabetic patients without known coronary artery disease referred for stress single-photon emission computed tomography and assessment of left ventricular function

BACKGROUND

The prevalence and prognosis of reduced left ventricular ejection fraction (LVEF) in asymptomatic diabetic patients without known coronary artery disease (CAD) are not known.

METHODS

We examined 1046 asymptomatic diabetic patients (age 60 +/- 13 years, 69% male) without known CAD referred to a tertiary referral center for stress single-photon emission computed tomography (SPECT) and assessment of LVEF. Patients were stratified according to the presence of normal LVEF (> or = 50%), mildly reduced LVEF (35%-49%), or moderately/severely reduced LVEF (< 35%). Single-photon emission computed tomographic images were classified as low, intermediate, or high risk based on the summed stress score (normal = 56). The mean follow-up was 5.3 +/- 3.3 years.

RESULTS

The prevalence of reduced LVEF was 16.7% (n = 175, mean LVEF 40.0% +/- 7.7%). This group was older (63 +/- 11 vs 59 +/- 14 years, P = .005), had more peripheral arterial disease (45% vs 29%, P < .001), and had a higher prevalence of electrocardiographic Q waves (21% vs 9%, P < .001) than the group without reduced LVEF. Mean summed stress (44.8 +/- 9.8 vs 51.7 +/- 6.3, P < .001), summed reversibility (4.7 +/- 5.0 vs 2.9 +/- 4.5, P < .001), and summed rest scores (49.4 +/- 7.2 vs 54.6 +/- 3.1, P < .001) were significantly more abnormal in the reduced LVEF group. High-risk summed stress score was significantly more common in the reduced LVEF group (46% vs 16%, P < .001). Survival was significantly lower in patients with any reduction in LVEF compared with those without reduced LVEF (10-year survival, 29% vs 57%, P < .0001). By multivariate analysis, reduced LVEF was independently associated with increased mortality (adjusted chi2 = 6.26, P = .01).

CONCLUSIONS

In this population of asymptomatic diabetic patients without known CAD referred for stress SPECT, 1 in 6 patients had reduced LVEF. Most of these patients have intermediate-/high-risk SPECT scans. The annual mortality rates of the groups with and without reduced LVEF were 7% and 4%, respectively.