Diagnostic accuracy of myocardial perfusion imaging in a study population without post-test referral bias

Myocardial perfusion imaging and appropriateness of the test for preoperative cardiac risk evaluation in an Iranian population: clinical role of Duke Activity Status Index

OBJECTIVE

For preoperative radionuclide myocardial perfusion imaging, metabolic equivalent is one of the key factors to evaluate the appropriateness. Duke Activity Status Index is a practical method to calculate metabolic equivalents. We intended to validate Duke Activity Status Index in our population for the assessment of preoperative myocardial perfusion imaging appropriateness.

METHODS

A total of 542 patients referred for myocardial perfusion imaging were recruited. A questionary compiled from Duke Activity Status Index was filled out based on which metabolic equivalents were calculated. Demographic data and history of cardiac risk factors were also collected. Myocardial perfusion imaging was performed using a 2-day stress-rest protocol either by exercise tolerance test or by pharmacologic stress through injection of Tc-MIBI and imaging by a dual-head gamma camera.

RESULTS

Out of 542 patients, 369 (68.1%) were evaluated for preoperative risk assessment. Metabolic equivalents (oxygen consumption/min/kg) were calculated at 9.3 ± 5.1, 10.8 ± 4.8, and 8.7 ± 5.1 in total, preoperative patients and patients evaluated for ischemia due to nonsurgical purposes, respectively (p = 0.001). The myocardial perfusion imaging was rarely appropriate in 291 (79.5%), maybe appropriate in 67 (18.3%), and appropriate in 8 (2.2%) patients. The prevalence of abnormal myocardial perfusion imaging was 22.5%, 28.4%, and 12.5% in "rarely appropriate," "maybe appropriate," and "appropriate" scenarios, respectively. Metabolic equivalents were similar between patients with normal and abnormal myocardial perfusion imaging (8.7 ± 5.0 vs. 8.5 ± 5.4).

CONCLUSION

Either Duke Activity Status Index is not a proper tool for calculation of metabolic equivalents or the appropriate use criteria is not operational in the population of Iranian preoperative patients in which cultural factors may contribute.

Noninvasive Testing in Emergency Department Patients with Low-Risk Chest Pain: Does the Evidence Support Current Guidelines?

Patients who present to the emergency department with chest pain but no evidence of ischemia on the electrocardiogram and negative cardiac markers are at very low risk. The newest American Heart Association/American College of Cardiology guidelines give noninvasive cardiac testing a IIa recommendation in this patient population. Here, we will review the existing literature that was cited in the American Heart Association/American College of Cardiology document, as well as several large, contemporary, comparative observational studies which were not included to address the following question: Do the benefits of noninvasive cardiac testing in this patient population outweigh the risks?

Rationale and design of the Randomized Evaluation of patients with Stable angina Comparing Utilization of noninvasive Examinations (RESCUE) trial

RESCUE is a phase III, randomized, controlled, multicenter, comparative efficacy study, designed to compare two diagnostic imaging/treatment paradigms that use coronary computed tomography angiography (CCTA) or single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) for assisting in the diagnosis of ischemic heart disease in patients with stable angina symptoms, and guiding subsequent treatment. The study is based on the hypothesis that CCTA as a diagnostic tool is associated with no increase in cardiac risk, decreased cost, and reduced radiation exposure compared with SPECT MPI. The RESCUE trial was funded by the Agency for Healthcare Research and Quality (AHRQ) and the American College of Radiology Imaging Network (ACRIN) Fund for Imaging Innovation, began in 2011, and completed in 2014.

Comparison of the diagnostic accuracies of very low stress-dose with standard-dose myocardial perfusion imaging: Automated quantification of one-day, stress-first SPECT using a CZT camera

BACKGROUND

Previous studies have demonstrated accurate diagnosis of reduced dose myocardial perfusion imaging (MPI) using Cadmium-Zinc-Telluride (CZT) technology. We compared the diagnostic performances of very low stress-dose (<2 mSv) with standard-dose stress-first, quantitative MPI using a CZT camera.

METHODS

Patients without known coronary artery- disease who underwent a stress-first Tc-99 m sestamibi CZT-MPI and invasive coronary angiography (ICA), and low-risk patients without ICA were included. A stress-rest standard-dose (10/30 mCi) MPI and a low-dose (5/15 mCi) MPI were compared. Normal limits for quantification were developed from 40 (20 males) low-risk patients, and total perfusion deficit (TPD) was derived.

RESULTS

208 patients who underwent MPI and ICA, and 76 low-risk patients were included. Of these, 128 had a standard-dose MPI and 156 had a low-dose MPI. Stress-doses in low-dose and standard-dose groups were 5.9 ± 1.2 vs 10.2 ± 0.5 mCi (1.7 ± 0.3 vs 3.0 ± 0.1 mSv), respectively, P < 0.001, and stress-rest effective radiation was 6.9 ± 1.1 vs 11.7 ± 0.4 mSv, respectively, P < 0.001. Sensitivity, specificity, and accuracy values in the low-dose and standard-dose groups were 86.1%, 76.6%, and 81.4%; and 90.6%, 78.1%, and 84.4%, respectively, P = ns. Using TPD prone, specificity values were 84.9% and 80.3%, respectively, P = ns.

CONCLUSION

One-day stress-first MPI with 50% radiation reduction and a very low stress-dose (<2 mSv) using CZT technology and quantitative supine and prone analysis provided a high diagnostic value, similar to standard-dose MPI.

Quantitative myocardial perfusion by O-15-water PET: individualized vs. standardized vascular territories

AIMS

Reporting of quantitative myocardial blood flow (MBF) is typically performed in standard coronary territories. However, coronary anatomy and myocardial vascular territories vary among individuals, and a coronary artery may erroneously be deemed stenosed or not if territorial demarcation is incorrect. So far, the diagnostic consequences of calculating individually vs. standardly assessed MBF values have not been reported. We examined whether individual reassignment of vascular territories would improve the diagnostic accuracy of MBF with regard to the detection of significant coronary artery disease (CAD).

METHODS AND RESULTS

Forty-four patients with suspected CAD were included prospectively and underwent coronary CT-angiography and quantitative MBF assessment with O-15-water PET followed by invasive, quantitative coronary angiography, which served as reference. MBF was calculated in the vascular territories during adenosine stress according to a standardized 17-segment American Heart Association model and an individualized model, using CT-angiography to adjust the coronary territories to their feeding vessels. Individually defined territories deviated from standard territories in 52% of patients. However, MBF in the three coronary territories defined by standard and individualized models did not differ significantly, except in one patient, in whom the MBF of an individualized coronary territory deviated sufficiently as to change the test from a false positive to a true negative result in this particular territory.

CONCLUSION

Disparity between standardized and individualized vascular territories was present in half of the patients, but had little clinical impact. Still, caution should be taken not always to rely on standard territories, as this may at times cause misinterpretation.

Diagnostic performance of stress myocardial perfusion imaging for coronary artery disease: a systematic review and meta-analysis

Objectives

To determine and compare the diagnostic performance of stress myocardial perfusion imaging (MPI) for the diagnosis of obstructive coronary artery disease (CAD), using conventional coronary angiography (CCA) as the reference standard.

Methods

We searched Medline and Embase for literature that evaluated stress MPI for the diagnosis of obstructive CAD using magnetic resonance imaging (MRI), contrast-enhanced echocardiography (ECHO), single-photon emission computed tomography (SPECT) and positron emission tomography (PET).

Results

All pooled analyses were based on random effects models. Articles on MRI yielded a total of 2,970 patients from 28 studies, articles on ECHO yielded a sample size of 795 from 10 studies, articles on SPECT yielded 1,323 from 13 studies. For CAD defined as either at least 50 %, at least 70 % or at least 75 % lumen diameter reduction on CCA, the natural logarithms of the diagnostic odds ratio (lnDOR) for MRI (3.63; 95 % CI 3.26–4.00) was significantly higher compared to that of SPECT (2.76; 95 % CI 2.28–3.25; P = 0.006) and that of ECHO (2.83; 95 % CI 2.29–3.37; P = 0.02). There was no significant difference between the lnDOR of SPECT and ECHO (P = 0.52).

Conclusion

Our results suggest that MRI is superior for the diagnosis of obstructive CAD compared with ECHO and SPECT. ECHO and SPECT demonstrated similar diagnostic performance.

Key Points

• MRI can assess myocardial perfusion.

• MR perfusion diagnoses coronary artery disease better than echocardiography or SPECT.

• Echocardiography and SPECT have similar diagnostic performance.

• MRI can save coronary artery disease patients from more invasive tests.

• MRI and SPECT show evidence of publication bias, implying possible overestimation.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-012-2434-1) contains supplementary material, which is available to authorized users.

Use of electrocardiographic depolarization abnormalities for detection of stress-induced ischemia as defined by myocardial perfusion imaging

High-frequency mid-QRS (HFQRS) analysis was recently introduced as a tool for identification of stress-induced ischemia. The diagnostic performance of this electrocardiographic technique has not been determined in a large cohort of patients. This study compared the diagnostic performance of HFQRS analysis to conventional ST-segment analysis in detecting exercise-induced ischemia. The study included 996 patients (56 ± 10 years of age, 670 men) referred for exercise myocardial perfusion imaging (MPI), which served as the gold standard of ischemia. High-resolution electrocardiogram was used for computer analysis of HFQRS signals. Number of electrocardiographic leads with ≥50% decrease of HFQRS intensity (L(50%)) was used as an index of ischemia. Perfusion images were evaluated semiquantitatively. Receiver operating characteristic analysis demonstrated an L(50%) ≥3 as the criterion that yielded optimal sensitivity and specificity for diagnosing moderate/severe ischemia. Compared to ST-segment analysis HFQRS analysis was more sensitive (69% vs 39%, p <0.005) and more specific (86% vs 82%, p <0.05). L(50%) correlated with amount of MPI ischemia (R(2) = 0.75, p <0.0001). Multivariate logistic regression analysis demonstrated a significant incremental diagnostic value for the addition of HFQRS data to a model containing pretest and conventional exercise parameters. L(50%) was the best predictor of mild or moderate/severe MPI ischemia. In conclusion, computerized HFQRS analysis improved the diagnostic performance of conventional stress electrocardiogram in detecting exercise-induced ischemia. Thus, this technique might aid in the noninvasive evaluation of coronary artery disease.

Patients with adenosine-induced ST-segment depressions and normal myocardial perfusion imaging: cardiac outcomes at 24 months

BACKGROUND

The significance of ischemic ECG changes during adenosine infusion in patients with normal myocardial perfusion imaging (MPI) is controversial. We evaluated the prevalence of, and defined the predictors for, severe coronary artery disease (CAD) in patients with such discordant findings.

METHODS

The findings of 3700 adenosine MPI studies performed at our institution between June 2005 and March 2009 were reviewed.

RESULTS

Data for 76 patients who had not previously undergone coronary revascularization and who had sufficient follow-up were analyzed; 22 (29%) were referred for coronary angiography and 10 (13%) underwent revascularization. None had left main disease and only three (14%) had multivessel disease. Diabetes mellitus was more prevalent (70% vs. 23%; P = .010) and ischemic ST-segment depressions more often lasted >5 minutes (50% vs. 15%; P = 0.021) in patients undergoing revascularization. During a 24 ± 13 month follow-up period, there were no deaths or myocardial infarctions, while an eleventh patient underwent revascularization 19 months after MPI.

CONCLUSIONS

In the presence of normal MPI, the specificity of ischemic ECG changes during adenosine infusion for the detection of severe obstructive CAD is poor, although patients with multiple coronary risk factors, particularly diabetes mellitus, should undergo further investigation.

Diagnosis and treatment of musculoskeletal chest pain: design of a multi-purpose trial

Background

Acute chest pain is a major health problem all over the western world. Active approaches are directed towards diagnosis and treatment of potentially life threatening conditions, especially acute coronary syndrome/ischemic heart disease. However, according to the literature, chest pain may also be due to a variety of extra-cardiac disorders including dysfunction of muscles and joints of the chest wall or the cervical and thoracic part of the spine. The diagnostic approaches and treatment options for this group of patients are scarce and formal clinical studies addressing the effect of various treatments are lacking.

Methods/Design

We present an ongoing trial on the potential usefulness of chiropractic diagnosis and treatment in patients dismissed from an acute chest pain clinic without a diagnosis of acute coronary syndrome. The aims are to determine the proportion of patients in whom chest pain may be of musculoskeletal rather than cardiac origin and to investigate the decision process of a chiropractor in diagnosing these patients; further, to examine whether chiropractic treatment can reduce pain and improve physical function when compared to advice directed towards promoting self-management, and, finally, to estimate the cost-effectiveness of these procedures. This study will include 300 patients discharged from a university hospital acute chest pain clinic without a diagnosis of acute coronary syndrome or any other obvious cardiac or non-cardiac disease. After completion of the clinic's standard cardiovascular diagnostic procedures, trial patients will be examined according to a standardized protocol including a) a self-report questionnaire; b) a semi-structured interview; c) a general health examination; and d) a specific manual examination of the muscles and joints of the neck, thoracic spine, and thorax in order to determine whether the pain is likely to be of musculoskeletal origin. To describe the patients status with regards to ischemic heart disease, and to compare and indirectly validate the musculoskeletal diagnosis, myocardial perfusion scintigraphy is performed in all patients 2–4 weeks following discharge. Descriptive statistics including parametric and non-parametric methods will be applied in order to compare patients with and without musculoskeletal chest pain in relation to their scintigraphic findings. The decision making process of the chiropractor will be elucidated and reconstructed using the CART method. Out of the 300 patients 120 intended patients with suspected musculoskeletal chest pain will be randomized into one of two groups: a) a course of chiropractic treatment (therapy group) of up to ten treatment sessions focusing on high velocity, low amplitude manipulation of the cervical and thoracic spine, mobilisation, and soft tissue techniques. b) Advice promoting self-management and individual instructions focusing on posture and muscle stretch (advice group). Outcome measures are pain, physical function, overall health, self-perceived treatment effect, and cost-effectiveness.

Discussion

This study may potentially demonstrate that a chiropractor is able to identify a subset of patients suffering from chest pain predominantly of musculoskeletal origin among patients discharged from an acute chest pain clinic with no apparent cardiac condition. Furthermore knowledge about the benefits of manual treatment of patients with musculoskeletal chest pain will inform clinical decision and policy development in relation to clinical practice.

Trial registration

NCT00462241 and NCT00373828

High-frequency QRS electrocardiogram analysis during exercise stress testing for detecting ischemia

INTRODUCTION

ECG stress testing is an inexpensive and non-invasive detector of myocardial ischemia; addition of high-frequency QRS analysis (HFQRS) may improve accuracy. This study compared HFQRS during exercise in patients with and without ischemia as defined by multiple criteria.

MATERIAL AND METHODS

High-resolution ECGs were recorded for 139 patients undergoing T99-sestamibi/T201-thallium stress testing. Twenty-three were positive by at least two and 37 were negative for ischemia by all three of the following criteria: nuclear scan, ST-segment analysis and typical angina. Sixty-four not meeting criteria for positive or negative, six with adenosine test and nine patients with ECG recording artifacts were excluded. Mean age of the study group was 62+/-10 years, 83% were male. Ischemic patients had a higher incidence of previous myocardial infarction and coronary intervention than non-ischemic patients (74% vs. 46%; P=0.03 and 70% vs. 43%; P=0.05, respectively), but had a lower body mass index (28.7+/-5 vs. 33.0+/-8; P=0.015). HFQRS analysis consisting of signal averaging (150-250 Hz) and calculation of root mean squared values for each lead at different time points was performed and was similar between the groups. The relative change in HFQRS (RCQ) was calculated for each lead: {(maxHFQRS-minHFQRS)/maxHFQRS}. For each patient an RCQ index was calculated by averaging the two leads with the greatest RCQ value. The RCQ index was greater in ischemic vs. non-ischemic patients (45% vs. 34%; P=0.0069).

CONCLUSION

Maximum decrease in HFQRS, as quantified by RCQ index, was greater in ischemic vs. non-ischemic patients. Use of the RCQ index may improve the diagnosis of ischemia during exercise stress testing.

How well does standard clinician evaluation identify low likelihood of ischaemic or coronary heart disease?

Guidelines claim that patients with a low likelihood of coronary artery disease can be reliably identified clinically by a simple set of rules. Among 385 patients referred for coronary angiography because of suspected stable angina pectoris we found by myocardial perfusion scintigraphy in three selected low likelihood groups reversible perfusion defects in 23%-29% of male and 11%-17% of female patients. Rates of significant angiographic disease were similar. These data question the validity of current clinical practice for identifying low likelihood of disease in this category of patients.

Diagnostic impact of SPECT image display on assessment of obstructive coronary artery disease

BACKGROUND

Diagnostic assessment of myocardial perfusion impacts the management of patients with suspected coronary artery disease (CAD). Although various image displays are available for single photon emission computed tomography (SPECT) interpretation, the effects of display differences on SPECT interpretation remain undetermined.

METHODS AND RESULTS

We studied 183 patients undergoing SPECT, including 131 consecutive patients referred for angiography and 52 at low CAD risk. Studies were visually interpreted by use of color and gray images, with readers blinded to the results of the other display. In accordance with established criteria, a summed stress score (SSS) of 4 or greater was considered abnormal. The prevalence of abnormal SPECT findings was higher with gray images than with color images (54% vs 48%, P < .001) based on a uniform criterion (SSS > or =4). However, color images yielded equivalent sensitivity (79% vs 82%, P = .7) and improved specificity for global (50% vs 33%, P = .02) and vessel-specific CAD involving the right coronary artery (P < .01) and left anterior descending artery (P < .05). When the criterion for gray images was adjusted upward (SSS > or =5) to reflect increased mean defect severity (SSS of 5.1 vs 4.4, P = .01), gray and color images provided equivalent sensitivity and specificity for global and vessel-specific CAD.

CONCLUSIONS

SPECT interpretation can vary according to image display as a result of differences in perfusion defect severity. Adjustment of abnormality criteria for gray images to reflect minor increases in defect severity provides equivalent diagnostic performance of gray and color displays for CAD assessment.

High probability of disease in angina pectoris patients: is clinical estimation reliable?

BACKGROUND

According to most current guidelines, stable angina pectoris patients with a high probability of having coronary artery disease can be reliably identified clinically.

OBJECTIVES

To examine the reliability of clinical evaluation with or without an at-rest electrocardiogram (ECG) in patients with a high probability of coronary artery disease.

PATIENTS AND METHODS

A prospective series of 357 patients referred for coronary angiography (CA) for suspected stable angina pectoris were examined by a trained physician who judged their type of pain and Canadian Cardiovascular Society grade of pain. Pretest likelihood of disease was estimated, and all patients underwent myocardial perfusion scintigraphy (MPS) followed by CA an average of 78 days later. For analysis, the investigators focused on the approximate groups of patients with more severe disease, ie, typical angina (n=187), Canadian Cardiovascular Society grade 2 pain or higher (n=176) or high (higher than 85%) estimated pretest likelihood of disease (n=142).

RESULTS

In the three groups, 34% to 39% of male patients and 65% to 69% of female patients had normal MPS, while 37% to 38% and 60% to 71%, respectively, had insignificant findings on CA. Of the patients who had also an abnormal at-rest ECG, 14% to 21% of men and 42% to 57% of women had normal MPS. Sex-related differences were statistically significant.

CONCLUSIONS

Clinical prediction appears to be unreliable. Addition of at-rest ECG data results in some improvement, particularly in male patients, but it makes the high probability groups so small that the addition appears to be of limited clinical relevance.

Prognostic value of myocardial perfusion imaging in patients with known or suspected stable angina pectoris: Evaluation in a setting in which myocardial perfusion imaging did not influence the choice of treatment

OBJECTIVE

Previous investigations on the prognostic value of myocardial perfusion imaging (MPI) were performed under circumstances in which the test result was known to the patient's physician. We wanted to examine the prognostic value of MPI in patients with known or suspected stable angina in a setting in which MPI could not influence the diagnostic and therapeutic strategy.

DESIGN

A prospective series of 507 patients referred to coronary angiography for this condition were examined by MPI before angiography. Management was based on symptoms and angiographic findings, as the results of MPI were not communicated. Patients were followed for a mean of 45.3 +/- 7.7 months.

RESULTS

During follow-up, 20 patients (3.9%) suffered from myocardial infarction, 19 (3.8%) died and eight (1.6%) were revascularized >1 year after MPI resulting in a combined annual event rate of 2.5%. Patients with normal MPI had a low annual event rate of 1.6% (or 1.1% with regard to myocardial infarction or death only). In contrast, event rates in patients with reversible or mixed ischaemia were 4.0% per year. MPI added independent prognostic value to standard clinical data in a multivariate Cox model.

CONCLUSION

We could confirm that in patients with known or suspected stable angina, MPI is a valuable risk stratifying tool.

Electrocardiographic exercise stress testing: an update beyond the ST segment

Routine exercise testing is frequently ordered to evaluate a patient's cardiovascular performance. The test is more direct and less expensive than imaging technology, and derives valuable information. New variables such as dyspnea and heart rate recovery, as well as integrated scores, provide incremental value to conventional analysis of exercise-induced angina or electrocardiographic changes. Considerations relating to test accuracy in women need to be weighed. This paper seeks to make physicians aware of the current status of the test, and improve their understanding of and ability to integrate new variables and scores to more effectively manage their patients.

Redefinition of the Q wave -- is there a clinical problem?

This study evaluated the potential consequences of the redefined joint European/American electrocardiographic criteria for an established myocardial infarction (MI). New and previous diagnostic Q-wave criteria were used in patients with stable angina pectoris. Seventy-nine patients with and 77 patients without a documented previous MI were compared using the results of myocardial perfusion imaging at rest as a reference. With the new Q-wave criteria, 71% of the former group and 40% of the latter had evidence of established MI compared with 33% and 3% when using the previous criteria (p <0.0001). Sensitivity, specificity, and positive and negative predictive values were 71%, 60%, 64%, and 67% for the new criteria versus 33%, 97%, 93%, and 59% with the previous criteria. These data suggest that that the new Q-wave criteria may be too nonspecific, resulting in an inappropriately high number of false-positive results.

Potential impact of myocardial perfusion scintigraphy as gatekeeper for invasive examination and treatment in patients with stable angina pectoris: observational study without post-test referral bias

AIMS

To evaluate the impact of using myocardial perfusion scintigraphy (MPS) as gatekeeper for coronary angiography and revascularization in stable angina pectoris.

METHODS AND RESULTS

A prospective series of 507 out of 972 adult patients referred to coronary angiography for known or suspected stable angina pectoris underwent clinical examination followed immediately by MPS, the result of which was not communicated. MPS showed normal perfusion in 258/507 (51%) patients, reversible defects in 201/507 (40%), and fixed defects in 48/507 (9%). Of 168 revascularized patients, 27 (16%) had normal perfusion and 13 (8%) had fixed defects. Coronary angiography was undertaken in 476 patients of whom 252 (53%) had normal findings or insignificant stenoses. The same was the case in 361 (41%) out of the 883 of the 972 consecutive patients, who had this examination. Assuming that the true rate of normal perfusion in the entire series was correspondingly lower, 48% of catheterizations and 19% of revascularizations were superfluous.

CONCLUSION

The use of MPS as gatekeeper appears to make about half of catheterizations and almost one-fifth of revascularizations redundant. Even in high-risk groups, substantial savings are possible, and the risk of overlooking patients with severe disease seems negligible.