Analysis of referral patterns, predictive accuracy, and impact on patient management of myocardial perfusion imaging in a new nuclear cardiology laboratory

Investigation Myocardial Perfusion Scan Parameters and Walls Motion in Patients undergoing Cardiac Surgery

Background

Coronary heart disease the most prevalent form of cardiovascular disease, results from the blockage of blood flow through arteries. The Myocardial Perfusion Scan (MPS) is considered a non-invasive method to assess the heart condition and provides valuable information, such as End Diastolic Volume (EDV), End Systolic Volume (ESV), Ejection Fraction (EF), Lung to Heart Ratio (LHR), and Transient Ischemic Dilatation (TID).

Objective

This study aimed to investigate changes in gated heart scan parameters to diagnose patients, who are candidates for heart surgery.

Material and Methods

In this descriptive cross-sectional study, 40 patients who are candidates for heart surgery were enrolled to evaluate the relation between the parameters of the gated heart scan and the amount of ischemic area of the heart. After scanning the patients, TID, ESV, LHR, and EF and also the movements of the heart walls are examined and analyzed in these patients.

Results

According to the results of the one-sample t-test showing a significant difference between the parameters, the results were within the normal range (P-value<0.0001). Additionally, all patients showed changes in cardiac output and wall movement issues.

Conclusion

The evaluation of Myocardial Perfusion Scan (MPS) and gated heart scan parameters can provide an effective method for diagnosing patients who may require heart surgery.

Non-traditional factors affecting referral for coronary angiography following SPECT myocardial perfusion imaging

BACKGROUND

The use of myocardial perfusion imaging (MPI) in the management of coronary artery disease (CAD) is well established. Although prior studies have shown disparities in the use of invasive angiography in patients with acute MI, data on factors affecting referral to angiography post-MPI are lacking. We sought to evaluate the primary determinants of referral to invasive angiography post-MPI and specifically assess the role of non-traditional non-clinical factors such as race/ethnicity, socioeconomic factors, insurance status, and marital status.

METHODS

All patients without known CAD who underwent stress SPECT MPI over 15 years were reviewed and the performance of coronary angiography within 90 days of their MPI was recorded. Multiple factors were analyzed for an association with referral to angiography, including exercise and MPI results, baseline demographics, traditional cardiac risk factors, and non-traditional factors such as ethnicity, insurance, marital and socioeconomic status. In a secondary analysis, these factors were assessed with regard to abnormal MPI results.

RESULTS

Out of 27,895 total patients, 2,150 (7.7%) underwent invasive coronary angiography. On multivariate analysis, inpatient location, positive ECG response, and abnormal MPI results were the strongest predictors of angiography. Non-traditional factors such as race/ethnicity and insurance status had a significant association with referral to angiography with Caucasians (OR 1.42, 95% CI 1.18-1.71, P < .0001) and those with private insurance (OR 1.35, 95% CI 1.13-1.62, P = .001) or Medicare (OR 1.30, 95% CI 1.08-1.56, P = .006) having higher rates of angiography despite controlling for traditional risk factors and test results.

CONCLUSION

Our study results indicate that non-traditional factors such as race/ethnicity and insurance status influence patient management decisions and impact the performance of downstream cardiac invasive testing after stress MPI. Higher rates of angiography in Caucasians, privately insured and Medicare patients were seen despite controlling for traditional risk factors and abnormal test results. Further research is needed to better understand these disparities, especially in the current healthcare environment.

Clinical implications of referral bias in the diagnostic performance of exercise testing for coronary artery disease

BACKGROUND

Exercise testing with echocardiography or myocardial perfusion imaging is widely used to risk-stratify patients with suspected coronary artery disease. However, reports of diagnostic performance rarely adjust for referral bias, and this practice may adversely influence patient care. Therefore, we evaluated the potential impact of referral bias on diagnostic effectiveness and clinical decision-making.

METHODS AND RESULTS

Searching PubMed and EMBASE (1990-2012), 2 investigators independently evaluated eligibility and abstracted data on study characteristics and referral patterns. Diagnostic performance reported in 4 previously published meta-analyses of exercise echocardiography and myocardial perfusion imaging was adjusted using pooled referral rates and Bayesian methods. Twenty-one studies reported referral patterns in 49 006 patients (mean age 60.7 years, 39.6% women, and 0.8% prior history of myocardial infarction). Catheterization referral rates after normal and abnormal exercise tests were 4.0% (95% CI, 2.9% to 5.0%) and 42.5% (36.2% to 48.9%), respectively, with odds ratio for referral after an abnormal test of 14.6 (10.7 to 19.9). After adjustment for referral, exercise echocardiography sensitivity fell from 84% (80% to 89%) to 34% (27% to 41%), and specificity rose from 77% (69% to 86%) to 99% (99% to 100%). Similarly, exercise myocardial perfusion imaging sensitivity fell from 85% (81% to 88%) to 38% (31% to 44%), and specificity rose from 69% (61% to 78%) to 99% (99% to 100%). Summary receiver operating curve analysis demonstrated only modest changes in overall discriminatory power but adjusting for referral increased positive-predictive value and reduced negative-predictive value.

CONCLUSIONS

Exercise echocardiography and myocardial perfusion imaging are considerably less sensitive and more specific for coronary artery disease after adjustment for referral. Given these findings, future work should assess the comparative ability of these and other tests to rule-in versus rule-out coronary artery disease.

Achieving an exercise workload of > or = 10 metabolic equivalents predicts a very low risk of inducible ischemia: does myocardial perfusion imaging have a role?

OBJECTIVES

We sought to identify prospectively the prevalence of significant ischemia (> or =10% of the left ventricle [LV]) on exercise single-photon emission computed tomography (SPECT) imaging relative to workload achieved in consecutive patients referred for myocardial perfusion imaging (MPI).

BACKGROUND

High exercise capacity is a strong predictor of a good prognosis, and the role of MPI in patients achieving high workloads is questionable.

METHODS

Prospective analysis was performed on 1,056 consecutive patients who underwent quantitative exercise gated (99m)Tc-SPECT MPI, of whom 974 attained > or =85% of their maximum age-predicted heart rate. These patients were further divided on the basis of attained exercise workload (<7, 7 to 9, or > or =10 metabolic equivalents [METs]) and were compared for exercise test and imaging outcomes, particularly the prevalence of > or =10% LV ischemia. Individuals reaching > or =10 METs but <85% maximum age-predicted heart rate were also assessed.

RESULTS

Of these 974 subjects, 473 (48.6%) achieved > or =10 METs. This subgroup had a very low prevalence of significant ischemia (2 of 473, 0.4%). Those attaining <7 METs had an 18-fold higher prevalence (7.1%, p < 0.001). Of the 430 patients reaching > or =10 METs without exercise ST-segment depression, none had > or =10% LV ischemia. In contrast, the prevalence of > or =10% LV ischemia was highest in the patients achieving <10 METs with ST-segment depression (14 of 70, 19.4%).

CONCLUSIONS

In this referral cohort of patients with an intermediate-to-high clinical risk of coronary artery disease, achieving > or =10 METs with no ischemic ST-segment depression was associated with a 0% prevalence of significant ischemia. Elimination of MPI in such patients, who represented 31% (430 of 1,396) of all patients undergoing exercise SPECT in this laboratory, could provide substantial cost-savings.

Marked differences between patients referred for stress echocardiography and myocardial perfusion imaging studies

BACKGROUND

Patients referred for stress echocardiography may differ significantly from those referred for stress myocardial perfusion imaging (MPI). Such differences, if present, should be considered when comparing the accuracy and discriminatory performance of these tests.

METHODS

We prospectively collected demographic and clinical information on all stress imaging studies performed at our institution between 1998 and 2001. The data were reviewed, summarized, and compared using the t test and chi2 test where appropriate.

RESULTS

Of 5320 stress imaging studies performed, 3383 were stress echocardiographies and 1937 were MPI studies. Patients referred for MPI were older (59 vs 54, P < .0001), and more likely to have diabetes (32% vs 20%, P < .0001), prior myocardial infarction (39% vs 15%, P < .0001), and prior revascularization (38% vs 12%, P < .0001). Pharmacologic stress testing was much more common in the MPI group (66% vs 17%, P < .0001). More patients referred for MPI had decreased left ventricular function (23% vs 7%, P < .0001) and abnormal stress test results (41% vs 18%, P < .0001).

CONCLUSIONS

Patients with a history of myocardial infarction, revascularization, or higher risk profiles are more likely to be referred for MPI compared to stress echocardiography at our institution. These differences in referral patterns are likely to exist in other centers, and it is reasonable to assume that systematic differences in test selection occur, resulting in patient populations with differing clinical risk profiles. Caution in interpreting analyses comparing the accuracy of stress imaging modalities is appropriate.

Imaging of myocardial perfusion with magnetic resonance

Coronary artery disease (CAD) is currently the leading cause of death in developed nations. Reflecting the complexity of cardiac function and morphology, noninvasive diagnosis of CAD represents a major challenge for medical imaging. Although coronary artery stenoses can be depicted with magnetic resonance (MR) and computed tomography (CT) techniques, its functional or hemodynamic impact frequently remains elusive. Therefore, there is growing interest in other, target organ-specific parameters such as myocardial function at stress and first-pass myocardial perfusion imaging to assess myocardial blood flow. This review explores the pathophysiologic background, recent technical developments, and current clinical status of first-pass MR imaging (MRI) of myocardial perfusion.