The safety of carotid stenosis during vasodilator pharmacologic stress testing

BACKGROUND

While thousands of patients undergo stress testing annually, the risk of exercise and pharmacologic stress in patients with carotid artery disease has not been fully defined but is of concern as patients are at risk for cerebrovascular accidents and transient ischemic attacks.

METHODS

All patients with either ultrasound or CTA evaluation of their carotid arteries from over a 10 year period who underwent stress testing within 180 days without intervening carotid intervention were reviewed for any adverse events within 24 hours of their stress test. The primary end point was any cerebrovascular event or syncope while the secondary endpoints included death, myocardial infarction, urgent angiography, urgent revascularization, or exaggerated hemodynamic response (systolic BP drop > 20 mmHg or systolic BP > 180 mmHg at peak stress). Patients were stratified into categories based on their level of carotid disease. Patients with severe carotid stenosis were propensity matched to those with mild or no stenosis.

RESULTS

A total of 4457 patients underwent carotid ultrasound, 10,644 CTA, and 16,011 had stress testing during this time period with 514 having both a carotid evaluation and a stress test within 6 months. After propensity matching, 62 patients with severe carotid stenosis were matched to 170 patients with mild or no carotid stenosis. Incidentally, all patients with severe carotid stenosis underwent pharmacologic stress. There were no primary endpoints and only three secondary endpoints in two patients in the mild or no carotid stenosis group. The proportion of exaggerated hemodynamic response to stress was similar in both groups-21.0% in the carotid stenosis group vs 31.2% without (P = .17) having a significant drop in systolic BP, and 3.2% vs 4.7% (P = 1.0) having a significantly elevated systolic BP.

CONCLUSION

In this study cohort there were few primary and secondary outcome events with no events occurring in patients with significant carotid stenosis. Additionally, there was no difference in exaggerated hemodynamic responses. While these results suggest that stress testing entails no demonstrable increased risk in patients with significant carotid stenosis, continued care should be taken given the limitations of the small size of this study.

Buccal caffeine strips for reversal of adverse symptoms of vasodilator stress

BACKGROUND

Due to recurrent shortages of aminophylline, intravenous caffeine has emerged as a commonly used, safe and reliable method to treat adverse effects of vasodilator stress agents. We sought to evaluate the safety and effectiveness of buccal caffeine strips which are rapidly absorbed, inexpensive, readily available, and simplify caffeine administration.

METHODS

Consecutive patients undergoing regadenoson stress SPECT MPI were assessed for the occurrence of symptoms during testing over an 11-week period at a single metropolitan hospital. Adverse symptoms, including their severity and duration, were recorded at the time of testing. Patient satisfaction was rated on a scale of 1 to 5 (5 being the most satisfied). Patients received reversal with caffeine if symptoms were felt to be significant enough by the patient and physician performing the test. The treatment received alternated week to week between IV caffeine (60 mg) or 100 mg buccal caffeine strips. Caffeine was given at least 3 minutes after tracer injection. A rescue dose of IV caffeine was offered 10 minutes later if indicated.

RESULTS

Of the 122 patients enrolled in the study, 70 (57%) were included during buccal caffeine weeks and 52 (43%) during IV caffeine weeks, and only 28 (24%) received reversal with a caffeine agent. Seven (6%) received IV caffeine and 21 (17%) received buccal caffeine. There was no significant difference in symptom duration between IV and buccal caffeine after treatment (152.8 vs 163.4 seconds, P = 0.87). There was no significant difference in initial and final symptom severity between groups. Only 2 patients in the buccal group required rescue IV caffeine for ongoing symptoms and emesis. None of the IV group required a rescue dose. There was no significant difference in patient satisfaction between the groups (2.8 vs 3.2, P = 0.38).

CONCLUSION

Buccal caffeine strips are a safe, well tolerated, and effective initial strategy to reverse adverse effects of vasodilator stress in the minority of patients who request it. Buccal caffeine alone or with IV rescue caffeine was highly effective in reversing adverse effects and was free of major adverse clinical events.

Stress-First Myocardial Perfusion Imaging

Stress-first approaches to myocardial perfusion imaging provide diagnostically and prognostically accurate perfusion data equivalent to a full rest-stress study while saving time in the imaging laboratory and reducing the radiation exposure to patients and laboratory staff. Unfortunately, implementing a stress-first approach in a nuclear cardiology laboratory involves significant challenges such as the need for attenuation correction, triage of patients to an appropriate protocol, real-time review of stress images, and consideration of differential reimbursement. Despite it being best practice for both the patient and the laboratory, these impediments have kept the proportions of studies performed stress-first relatively unchanged in North America and world-wide in the last 10 years.

Hemiplegic migraine episode triggered by regadenoson

SPECT and PET myocardial perfusion imaging (MPI) are widely used to evaluate patients for coronary artery disease. Regadenoson (a selective A2A adenosine receptor agonist) is a commonly used vasodilator agent for stress MPI because of its safety profile and ease of use. Common adverse reactions such as headache, shortness of breath, flushing, and chest and abdominal discomfort are typically mild and can be effectively reversed using methylxanthines such as aminophylline and caffeine. Neurological adverse reactions such as seizure and stroke have rarely been reported with the use of regadenoson. The hemodynamic changes associated with regadenoson administration, such as an exaggerated hypotensive or hypertensive response, may be the cause for the reported cerebrovascular accidents. Activation of central nervous system A2A adenosine receptors is thought to be responsible for seizure episodes in patients with or without known histories of seizure. A2A adenosine receptors activation is also believed to play a role in headaches and migraine. This patient reported who has a history of hemiplegic migraine developed left side weakness and headache following the administration of regadenoson during a PET MPI study. Imaging work-up to rule out cerebrovascular accident was normal. After 1 hour from the onset of his symptoms, his weakness and headache significantly improved with complete resolution within 24 hours. We concluded that regadenoson triggered a hemiplegic migraine episode in this patient, which has not been previously reported in the literature. It may be prudent to avoid regadenoson and adenosine use in patients with a history of hemiplegic migraine.

Impact of Gd-153 scanning line source attenuation correction on downstream invasive testing

BACKGROUND

Attenuation correction (AC) using hardware and software solutions has been shown to increase the specificity of SPECT MPI by decreasing false positive results and improving prognostic ability. Theoretically this should reduce downstream testing and unnecessary costs. We sought to assess the consequences of the use of Gd-153 scanning line source attenuation correction during SPECT myocardial perfusion imaging (MPI) on downstream invasive testing.

METHODS

All patients who underwent a clinically indicated Tc-99m stress SPECT MPI study from 2013 to 2015 at five hospitals (2 with AC and 3 without) were retrospectively reviewed. Patient demographics, results of testing, subsequent coronary angiography within 3 months, and revascularization were recorded. The results of the MPI studies, downstream angiogram utilization, and results of angiography were compared and a propensity matched subgroup analysis was performed.

RESULTS

A total of 9968 patients underwent SPECT MPI during the study time period (6106 performed with AC and 3862 without). Out of 3928 patients included in the propensity matched cohort, there was no difference in the proportion of abnormal MPI results between the two groups (31.5% vs 30.4%, P = 0.47), however, more patients underwent coronary angiography within 90 days in the AC group (10.6% vs 8.7%, P = 0.05). There was no significant difference in the proportion of patients with angiographically significant obstructive disease (53.4% vs 56.1%, P = 0.19), however, fewer patients in the AC group with obstructive coronary disease were revascularized (36.1% vs 46.8%, P = 0.04). The findings remained consistent after sub-group analysis in patients without known coronary disease.

CONCLUSION

The use of scanning line source AC did not meaningfully influence the rate of abnormal MPI results or downstream invasive testing in this cohort. The clinical utility of scanning line source AC may be limited to facilitating stress-first imaging protocols.

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.

Efficiency of tetrofosmin versus sestamibi achieved through shorter injection-to-imaging times: A systematic review of the literature

Based on superior image quality, more accurate gated images, and lower radiation exposure to patients, Technetium-99m (Tc-99m) based tracers are preferred over Thallium-201 for SPECT myocardial perfusion imaging. The two Tc-99m tracers, sestamibi and tetrofosmin, have many similar characteristics but there are differences in blood and liver clearance rates, as well as the recommended time after injection for imaging to achieve optimal image quality. Because published peer-reviewed studies examining optimal times between injection and imaging are limited, it can be difficult to identify evidence-based opportunities to optimize imaging protocols. Using systematic literature review methods, this study was designed to identify and consolidate the available evidence on the use of sestamibi compared to tetrofosmin for variable injection to imaging times in regard to test efficiency, including test length and re-scan rates, and image quality, including overall quality and cardiac to extra-cardiac ratios. The composite of this data shows that earlier imaging with tetrofosmin is equivalent to later imaging with sestamibi when assessing subjective image quality or when quantifying heart-to-extra-cardiac ratios. Image quality and heart-to-extra-cardiac ratios comparing early versus later imaging with tetrofosmin were comparable if not equivalent to each other. The equivalency of the imaging quality occurs with 15 minutes (on average) earlier imaging compared to sestamibi and 30 minutes compared to standard time tetrofosmin. The subjective findings of equivalent image quality are also shown with objective measurements of heart-to-extra-cardiac ratios. In this review, the significantly shorter injection-to-acquisition times with tetrofosmin compared to sestamibi resulted in better efficiency and less waiting times for patients; in addition, significantly higher re-scan rates with sestamibi compared to tetrofosmin due to hepatic activity contributed to better throughput with tetrofosmin.

Comparison of intravenous and buccal caffeine for reversal of adverse effects of regadenason

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction

Regadenason is a common coronary vasodilator for myocardial perfusion imaging (MPI). Use has been associated with side effects including dyspnea, gastrointestinal upset and chest discomfort. Aminophylline is a common reversal agent. Due to frequent shortages caffeine has emerged as an alternative treatment.

Purpose

Our study aimed to compare the efficacy of intravenous (IV) caffeine and buccal caffeine strips for reversal of regadenason adverse effects.

Methods

Consecutive patients undergoing regadenoson stress SPECT MPI were assessed for the occurrence of symptoms during testing over an 11 week period at a single metropolitan hospital. Adverse symptoms, including their severity and duration, were recorded at the time of testing. Patient satisfaction was rated on a scale of 1 to 5 (5 being the most satisfied). Patients received reversal with caffeine if symptoms were felt to be significant enough by the patient and physician performing the test. The treatment received alternated week to week between IV caffeine (60mg) or 100 mg buccal caffeine strips. Caffeine was given at least 3 minutes after tracer injection. A rescue dose of IV caffeine was offered 10 minutes later if indicated.

Results

Of the 122 patients enrolled in the study, 70 (57%) were included during buccal caffeine weeks and 52 (43%) during IV caffeine weeks, and only 28 (23.9%) received reversal with a caffeine agent. Seven (5.7%) received IV caffeine and 21 (17.2%) received buccal caffeine. The most common adverse symptom reported was dyspnea, which occurred in 54 patients (44.3%). There was no significant difference in symptom duration between IV and buccal caffeine after treatment (152.8 vs 163.4 sec, p = 0.87). There was no significant difference in initial and final symptom severity between groups. Only 2 patients in the buccal group required rescue IV caffeine for ongoing symptoms and emesis. None of the IV group required rescue dose. There was no significant difference in patient satisfaction between the groups (2.8 vs 3.2, p = 0.38). Interestingly, patients were more likely to receive treatment on buccal caffeine weeks compared to IV weeks (30.0% vs 13.5%, p = 0.049)

Conclusion(s)

Buccal caffeine is an effective alternative to IV caffeine for the management of adverse effects from regadenason and may be a more cost effective option. Buccal caffeine is easier to store and prepare than IV caffeine, and compared to other oral caffeine alternatives provides consistent dosing and easier consumption.

The use of a novel method for SPECT/CT quantification of 99m-Tc-PYP uptake in the evaluation of ATTR cardiac amyloidosis

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction:  Bone scintigraphy with 99m-Technecium-Pyrophosphate (99m-Tc-PYP) with planar and SPECT imaging is now commonplace for the non-invasive diagnosis of ATTR cardiac amyloidosis. However, the quantification of 99m-Tc-PYP uptake is based on a semi-quantitative visual score and a heart to contralateral lung ratio which suffer from poor reproducibility. A more robust method of quantifying uptake and reporting results would be beneficial and may be possible using volumetric assessment with fused SPECT/CT acquisition.

Purpose

  The aim of this study was to evaluate the performance of a novel semi-automated quantitative software to diagnose ATTR cardiac amyloidosis in patients with a clinical suspicion of cardiac amyloidosis who underwent 99m-Tc-PYP SPECT/CT imaging.

Methods

This was a retrospective, single-center study of consecutive patients who underwent 99m-Tc-PYP SPECT/CT imaging from September to December 2020. Quantification software was used to obtain standardized uptake values (SUVs) of 99m-Tc-PYP activity in the whole heart using SPECT/CT data. The total SUVs, mean SUVs, and percentage of injected tracer dose in the heart, as well as two other sets of these measurements adjusted for residual blood pool activity were obtained. Activity in the lung and bone was used to calculate heart to bone and heart to right lung ratios. The results from the software quantification were compared to the results from planar imaging as well as to the final clinical diagnosis of amyloidosis.

Results

  A total of 59 patients were imaged during this time with an average age of 74.1 ± 11.8, and 32 (54.2%) were male. After excluding 8 patients for technical issues, 12 patients were found to be positive for amyloid, 39 were negative, and the average imaging delay time was 75.0 ± 15.2 minutes. 13 methods of assessment were evaluated with the metric of the percentage of injected tracer dose found in the heart that was adjusted for the mean residual blood pool activity having the best discrimination between abnormal and normal studies. The mean percentage of injected dose in positive patients was 2.87% vs 0.98% in the patients without amyloidosis (p &lt; 0.0001). Using a cutoff of 2% to ensure that no patients with amyloid would be missed by screening, there was 100% sensitivity, 94.9% specificity, and 96.1% accuracy. There was a significant difference in the percentage injected dose based on gradations of planar heart to contralateral lung ratio and planar visual score.

Conclusion

Volumetric software quantification may be a superior method of evaluating 99m-Tc-PYP cardiac amyloidosis studies. This methodology may allow for a quantitative definition of a normal or abnormal 99m-Tc-PYP cardiac amyloid study and provide for the potential of following response to therapy.

The use of SPECT/CT quantification of 99mTc-PYP uptake to assess tafamidis treatment response in ATTR cardiac amyloidosis

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction

Nuclear scintigraphy with bone-avid radiotracers such as Tc-99m-PYP, Tc99m-DPC and Tc-99m-HMDP are used to diagnose transthyretin (ATTR) cardiac amyloidosis with limited quantification employing a semi-quantitative visual score and a heart to contralateral lung ratio. Therapy for ATTR cardiac amyloid currently is limited to a single FDA approved agent, tafamidis, however, there is no data regarding the longitudinal assessment of imaging findings in patients undergoing therapy. SPECT/CT acquisition and analysis with dedicated software can provide volumetric assessment and quantification of cardiac tracer uptake.

Purpose

The purpose of this study was to perform longitudinal assessment of cardiac ATTR amyloid 99mTc-PYP imaging findings to determine if treatment with tafamidis results in any change in quantitative measures of tracer uptake. There is no data on if treatment results in a decrease in cardiac amyloid burden as assessed by 99mTc-PYP imaging.

Methods

A prospective, single center, study of patients with ATTR cardiac amyloid being treated with tafamidis (either 80mg or 61mg dose) who have baseline and follow-up 99mTc-PYP studies. SPECT/CT quantification software was used to quantify heart, lung, and bone tracer uptake and generate standardized uptake values (SUVs). Comparison of baseline (before treatment) total SUVs, mean SUV value, percentage of the injected dose, mean SUV of heart to mean SUV of bone ratio and to mean SUV of right lung ratio was made to the values obtained at follow-up after tafamidis treatment. Measurements were obtained from the whole heart and the isolated left ventricle. Data was obtained by two physicians and the results averaged.

Results

5 patients were analyzed with a mean age 73.8 ± 7.7, 80% were males, and a mean length of tafamidis therapy at repeat imaging of 12.5 ± 3.8 months. At follow-up there was an average decrease in whole heart total SUV counts by -25.9 ± 10.3%, in the mean SUV value by -18.2 ± 18.2% and in the percentage of injected dose by -23.7 ± 14.0%. Similar decreases were seen in the isolated left ventricle measures. Heart to bone and heart to lung ratios showed a mixed response to therapy. Detailed results are provided in the table.

Conclusion

The measurements of total SUV counts, mean SUV value, and percentage of the injected dose showed improvement with tafamidis treatment. The ratios did not uniformly show improvement and the reason for this finding is unclear. This new technique offers a potential method for following tafamidis therapy and assessing the cardiac amyloid burden.

Risk stratification with vasodilator stress SPECT myocardial perfusion imaging in patients with elevated cardiac biomarkers

BACKGROUND

Although the diagnostic accuracy and prognostic utility of vasodilator stress MPI have been well established in the non-acute setting, the efficacy of all of the vasodilator stressors in risk stratifying post-MI patients as well as the evaluation of cardiac troponin elevation of unclear etiology is not established. Accordingly, the aim of the present study was to investigate the prognostic efficacy of vasodilator stress MPI in the setting of elevated cardiac troponin to accurately risk stratify these higher-risk patients.

METHODS

All patients from two tertiary centers, from 1/1/2010 through 12/31/2012, with elevated cardiac biomarkers within < 7 days and undergoing stress SPECT MPI testing were studied. Results of stress MPI were scored using a 17-segment model based on semiquantitative scoring as normal or abnormal (mild, moderate, or severe) using a total perfusion defect (TPD) of 0%, 1-10%, 10-20%, and > 20%. Mortality data through the year 2014 were obtained from the National Death Index, and survival analyses were performed. The primary endpoint was all-cause mortality with the secondary endpoint being cardiac mortality.

RESULTS

A total of 503 patients were followed for an average of 33.6 ± 16.2 months, with a mean age of 69.3 years; 53.7% male; and a majority (88.7%) of them undergoing vasodilator stress. A significant increase in all-cause mortality was seen based on the severity of TPD results for all vasodilators (P < .0001) and regadenoson (P < .0001). Similar prognostic ability was seen for all-cause mortality. This association was maintained even after adjustment for cardiac risk factors, previous coronary disease, and troponin quartiles. MPI results (stress TPD and LVEF) added to traditional cardiac risk factors, and troponin values resulted in a significant incremental increase in the ability to predict all-cause and cardiac mortality, and stress TPD remained independently predictive for both all-cause and cardiac mortality in a multivariate model.

CONCLUSION

Vasodilator stress (including regadenoson) MPI effectively risk stratifies patients with recently elevated cardiac biomarkers, with the increasing risk of mortality with the increasing severity of perfusion defects. It provides incremental prognostic value, in addition to clinical factors and degree of troponin elevation.

Clinical effectiveness of an outpatient pathway for low-risk chest pain emergency department visits

BACKGROUND

Studies suggest that patients who present with atypical chest pain and are low or low-intermediate risk can safely undergo a rapid rule-out for cardiac ischemia with serial ECGs and cardiac biomarkers followed by additional testing as needed. We sought to evaluate a novel Emergency Department (ED) protocol for patients to undergo their additional functional testing as an outpatient.

METHODS

Patients presenting to the ED with atypical chest pain, normal ECG, and negative cardiac troponin felt to be low risk were referred for outpatient stress testing within 72 hours of presentation as part of a pilot program. We analyzed test characteristics, length of stay, and 30-day return visits to ED in the pilot group and compared results to a similar cohort assessed in the ED by a traditional chest pain observation protocol.

RESULTS

A total of 156 patients were included over a 5-month period with 29.5% not returning for testing. There was a 70% reduction in length of stay for outpatient stress test protocol patients. All-cause and cardiac return visits to the ED were not significantly different between the outpatient cohort and the traditional chest pain unit group and were reduced by 47 and 75%, respectively, in patients who completed their outpatient testing. The provisional injection protocol resulted in a 81% reduction in radiation exposure when compared to traditional MPI stress protocols due to a greater utilization of exercise treadmill tests without imaging.

CONCLUSION

Outpatient stress testing is a reliable alternative to traditional chest pain observation with a significantly shorter length of stay, reduced healthcare costs, and improved radiation safety profile for patients when compared to traditional inpatient observation.

Correction to: Risk stratification with vasodilator stress SPECT myocardial perfusion imaging in patients with elevated cardiac biomarkers

The following error (highlighted in bold below) appears in the Results section of the Abstract: A total of 503 patients were followed for an average of 33.6 ± 16.2 months, with a mean age of 69.3 years; 53.7% male; and a majority (88.7%) of them undergoing vasodilator stress. A significant increase in all-cause mortality was seen based on the severity of TPD results for all vasodilators (P < .0001) and regadenoson (P < .0001). Similar prognostic ability was seen for all-cause (this should actually be cardiac) mortality. This association was maintained even after adjustment for cardiac risk factors, previous coronary disease, and troponin quartiles. MPI results (stress TPD and LVEF) added to traditional cardiac risk factors, and troponin values resulted in a significant incremental increase in the ability to predict all-cause and cardiac mortality, and stress TPD remained independently predictive for both all-cause and cardiac mortality in a multivariate model.

Comparison of Benefit of Transcatheter Aortic Valve Implantation in Patients With Low Gradient Versus High Gradient Aortic Stenosis and Left Ventricular Dysfunction

Patients with low gradient severe aortic stenosis (LG-AS) often exhibit significant limitations in functional status and quality of life. We aimed to evaluate the clinical effect of transcatheter aortic valve implantation (TAVI) on LG-AS patients compared to those with high transvalvular gradients and similar left ventricular dysfunction. Retrospective analysis of records for all patients with a left ventricular ejection fraction <50% who underwent TAVI at our institution was performed. Patients were grouped according to their transvalvular gradient. Data were collected from The Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy Registry. Clinical benefit endpoints included improvements in left ventricular ejection fraction and changes in the Kansas City Cardiomyopathy Questionnaire. Additional outcomes analyzed included 1-year all-cause mortality, stroke rates, rates of rehospitalization, need for a permanent pacemaker, and hospital length of stay. Two hundred three patients met our inclusion criteria. one hundred one LG-AS patients (mean transvalvular gradient <40 mm Hg) were compared to 102 patients with high transvalvular gradients (mean transvalvular gradient >40 mm Hg). LG-AS patients yielded similar improvements in left ventricular ejection fraction (43.5% ± 63.7 vs 37.7% ± 58.7; p = 0.525) and Kansas City Cardiomyopathy Questionnaire scores (423.51% ± 1257.02 vs 266.56% ± 822.81; p = 0.352). There were no differences between the groups with respect to 1-year mortality (16.8% vs 12.7%; p = 0.412), stroke rates, hospital length of stay, need for permanent pacemaker implantation or hospital readmissions. In conclusion, we found that TAVI is associated with comparable improvement in clinical and echocardiographic outcomes in LG-AS patients as compared to those with high gradient severe aortic stenosis.

SPECT myocardial perfusion imaging in liver transplantation candidates

BACKGROUND

The optimal cardiovascular evaluation prior to liver transplantation remains controversial and includes stress echocardiography, stress MPI, cardiac CTA, and coronary angiography. This study summarizes our experience of the past decade using SPECT MPI in patients with end-stage liver disease, including patient characteristics, stress testing protocols, test results, the need for repeat testing, and downstream testing.

METHODS

All patients who underwent a clinically indicated stress SPECT MPI study as part of their pre-liver transplant evaluation from 2004 to 2014 were reviewed from the Nuclear Cardiology database. Results of perfusion imaging, repeat testing, subsequent angiography, and need for revascularization were reviewed.

RESULTS

A total of 2500 patients were referred for SPECT MPI, of those 111 had known CAD and 271 underwent more than one MPI study. Compared to other patients undergoing stress MPI, pre-liver transplant patients were younger, had fewer cardiac risk factors and lower prevalence of prior cardiac history, and used pharmacologic stress more often. During the study decade, patient age increased, prevalence of hypertension increased and smoking decreased, prevalence of known CAD increased, and the number of abnormal studies decreased. Abnormal perfusion results were present in 7.8% of pre-liver transplant patients compared to 34.3% of all other patients. In a multivariate model, age and lower ejection fraction were associated with an abnormal MPI result. Of the 64 patients who underwent subsequent invasive or non-invasive coronary angiography after an abnormal MPI, obstructive CAD was diagnosed in 25 patients (1.0%), non-obstructive CAD was diagnosed in 23 patients (0.9%), and normal coronaries found in 16 patients (0.6%); a total of 18 (0.7%) of these underwent coronary revascularization. The average time to repeat testing was 27.2 ± 17.9 months. In a multivariate model, younger age and exercise stress were associated with repeat testing. In only 17 patients out of 271 with a normal initial perfusion, the repeat study became abnormal. The use of stress-first imaging was successful in 80% of patients with a reduction in Tc-99m dose from 39.1 to 18.3 mCi.

CONCLUSION

Abnormal SPECT MPI results in candidates for liver transplantation are infrequent compared to non-liver transplant patients and the incidence of obstructive CAD on subsequent angiography even less. Repeat testing in those on the transplant waiting list after initial normal test results appears to be of limited value. Stress-first protocols may be considered for the majority of these patients to reduce testing time and radiation exposure.

Clinical predictors of antitachycardia pacing response in implantable cardioverter defibrillator patients

BACKGROUND

Antitachycardia pacing (ATP) provides safe and painless termination of reentrant ventricular arrhythmias in patients with implantable cardioverter defibrillator (ICDs), improving their quality of life. Established predictors of ATP responsiveness are not well known; only longer ventricular tachycardia (VT) cycle length and higher ejection fraction have been found to predict ATP success.

OBJECTIVE

To investigate clinical and ECG predictors of ATP response in ICD patients with monomorphic VT.

METHODS

The ICD clinic database was searched for monomorphic VT events requiring ICD therapy in patients with ischemic or non-ischemic cardiomyopathy. Each patient's first ICD encounter for VT was assessed. Patient demographics, clinical characteristics, VT rate, and ATP responsiveness (always, sometimes, and never successful) were recorded. An ECG was analyzed for QRS morphology and duration. Data was assessed for predictors of ATP responsiveness.

RESULTS

In 527 patients, characteristics associated with always successful ATP included ACE-I/ARB therapy and slower VT rate (never successful ATP 197 ± 28 bpm, sometimes successful ATP 190 ± 27 bpm, always successful ATP 183 ± 22 bpm, P < .0001). Secondary prevention indication, amiodarone therapy, and longer QRS duration were associated with ATP failure. After multivariate analysis, only faster VT rate and amiodarone therapy were predictive of ATP failure.

CONCLUSIONS

Neither QRS morphology nor duration was predictive of ATP success. Slower VT rate was predictive of repeated ATP responsiveness. Amiodarone therapy, which is known to increase VT cycle length, interestingly was associated with ATP failure for unclear reasons. More individualized and possibly more aggressive ATP programming may be warranted in patients on amiodarone.

Aminophylline shortage and current recommendations for reversal of vasodilator stress: An ASNC information statement endorsed by SCMR

Pharmacologic reversal of serious or intolerable side effects (SISEs) from vasodilator stress is an important safety and comfort measure for patients experiencing such effects. While typically performed using intravenous aminophylline, recurrent shortages of this agent have led to a greater need to limit its use and consider alternative agents. This information statement provides background and recommendations addressing indications for vasodilator reversal, timing of a reversal agent, incidence of observed SISE with vasodilator stress, clinical and logistical considerations for aminophylline-based reversal, and alternative non-aminophylline based reversal protocols.

Aminophylline shortage and current recommendations for reversal of vasodilator stress: an ASNC information statement endorsed by SCMR

Pharmacologic reversal of serious or intolerable side effects (SISE) from vasodilator stress is an important safety and comfort measure for patients experiencing such effects. While typically performed using intravenous aminophylline, recurrent shortages of this agent have led to a greater need to limit its use and consider alternative agents. This information statement provides background and recommendations addressing indications for vasodilator reversal, timing of a reversal agent, incidence of observed SISE with vasodilator stress, clinical and logistical considerations for aminophylline-based reversal, and alternative non-aminophylline based reversal protocols.

Triage of patients for attenuation-corrected stress-first Tc-99m SPECT MPI using a simplified clinical pre-test scoring model

BACKGROUND

Stress-only Tc-99m SPECT MPI saves time and reduces radiation exposure while a normal study has a benign prognosis. However, no guidelines exist as to which patients should undergo stress-first MPI. The purpose of this study was to validate a previously published pre-test prediction scoring model and refine the stress-first triage process further if possible.

METHODS

We retrospectively reviewed all patients who underwent an attenuation-corrected Tc-99m SPECT MPI over a 39-month period. Based on 17-segment model semi-quantitative scoring, a successful stress-first MPI was defined as a summed stress attenuation-corrected score ≤ 1. Based on results from multivariate analysis, the previously published prediction score (comprised eight clinical and demographic variables) was compared to triage based on coronary artery disease (CAD) status alone and with the addition of other highly associated variables. Logistic regression and Chi-squared analyses were used to determine the magnitude of variable effect and to compare model results.

RESULTS

A total of 2,277 patients were included, and the prediction score successfully stratified patients into low-risk (91.1% successful stress-first), intermediate-risk (79.4%), and high-risk (50.7%) groups. Comparing the use of the prediction score to the use of a history of CAD as the only triage factor, 69.0% of patients would be accurately triaged using the prediction score with a cutoff of 7 (maximized sensitivity and specificity), while 78.6% were correctly triaged with CAD status alone (P < .0001). The addition of variables highly associated with a successful stress-first protocol (congestive heart failure [OR 3.4] and an abnormal resting ECG [OR 2.1]) to CAD status further enhanced triage accuracy to 81% (P < .0001).

CONCLUSIONS

While the previously described prediction score effectively identifies patients who can successfully undergo stress-first MPI, it is cumbersome. Triaging based solely on CAD status and with the addition of other key variables is practical and provides improved predictive accuracy for successful stress-first MPI. Utilizing this simplified pre-test scoring model may allow for wider adoption of stress-first imaging protocols which have clear advantages over traditional rest-stress protocols.

Multicenter evaluation of stress-first myocardial perfusion image triage by nuclear technologists and automated quantification

BACKGROUND

A stress-first myocardial perfusion imaging (MPI) protocol saves time, is cost effective, and decreases radiation exposure. A limitation of this protocol is the requirement for physician review of the stress images to determine the need for rest images. This hurdle could be eliminated if an experienced technologist and/or automated computer quantification could make this determination.

METHODS

Images from consecutive patients who were undergoing a stress-first MPI with attenuation correction at two tertiary care medical centers were prospectively reviewed independently by a technologist and cardiologist blinded to clinical and stress test data. Their decision on the need for rest imaging along with automated computer quantification of perfusion results was compared with the clinical reference standard of an assessment of perfusion images by a board-certified nuclear cardiologist that included clinical and stress test data.

RESULTS

A total of 250 patients (mean age 61 years and 55% female) who underwent a stress-first MPI were studied. According to the clinical reference standard, 42 (16.8%) and 208 (83.2%) stress-first images were interpreted as "needing" and "not needing" rest images, respectively. The technologists correctly classified 229 (91.6%) stress-first images as either "needing" (n = 28) or "not needing" (n = 201) rest images. Their sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 66.7%, 96.6%, 80.0%, and 93.5%, respectively. An automated stress TPD score ≥1.2 was associated with optimal sensitivity and specificity and correctly classified 179 (71.6%) stress-first images as either "needing" (n = 31) or "not needing" (n = 148) rest images. Its sensitivity, specificity, PPV, and NPV were 73.8%, 71.2%, 34.1%, and 93.1%, respectively. In a model whereby the computer or technologist could correct for the other's incorrect classification, 242 (96.8%) stress-first images were correctly classified. The composite sensitivity, specificity, PPV, and NPV were 83.3%, 99.5%, 97.2%, and 96.7%, respectively.

CONCLUSION

Technologists and automated quantification software had a high degree of agreement with the clinical reference standard for determining the need for rest images in a stress-first imaging protocol. Utilizing an experienced technologist and automated systems to screen stress-first images could expand the use of stress-first MPI to sites where the cardiologist is not immediately available for interpretation.

Safety of vasodilator stress myocardial perfusion imaging in patients with elevated cardiac biomarkers

BACKGROUND

While adenosine and dipyridamole as myocardial perfusion imaging (MPI) stress agents have literature supporting their safety in the setting of myocardial infarction (MI), regadenoson does not. Studying a high risk cohort of patients with elevated cardiac biomarkers may shed light on potential safety issues of these agents which might also affect lower risk cohorts.

METHODS

All patients who had undergone a clinically indicated stress MPI study at two academic centers from 1/1/2010 through 12/31/2012 with elevated troponin ≤7 days prior to testing were included. The primary endpoint was a composite of death, non-fatal MI, congestive heart failure (CHF), stroke, ventricular arrhythmias, atrial fibrillation/flutter, or atrioventricular block requiring intervention within 24 h of testing.

RESULTS

Of the 703 stress MPI studies that met inclusion criteria, 360 (51.2%), 199 (28.3%), 74 (10.5%), 9 (1.3%), and 61 (8.7%) underwent regadenoson, dipyridamole, adenosine, dobutamine, and exercise stress, respectively. The primary endpoint occurred in 11 (1.6%) patients with an incidence of 1.4% (n = 5), 1.0% (n = 2), 1.4% (n = 1), 11.1% (n = 1), and 3.3% (n = 2) following regadenoson, dipyridamole, adenosine, dobutamine, and exercise stress, respectively (P = 0.137). The adverse events included non-fatal MI in 7 (1.0%) patients, death in 1 (0.1%) patient, CHF in 1 (0.1%) patient, ventricular arrhythmia in 1 (0.1%) patient, and atrial arrhythmia in 1 (0.1%) patient.

CONCLUSION

In the setting of elevated troponin, serious complications associated with either exercise or vasodilator stress testing appear to be relatively rare with no increased risk attributable to a particular vasodilator agent.

Radiation reduction and faster acquisition times with SPECT gated blood pool scans using a high-efficiency cardiac SPECT camera

BACKGROUND

Planar gated blood pool scans are an established method for the evaluation of left ventricular ejection fraction (LVEF) but the camera technology used for these studies has not significantly changed in decades. The purpose of this study was to determine the diagnostic accuracy of new high-efficiency SPECT gated blood pool scans compared to traditional scans and determine if they can be performed with lower radiation doses or faster acquisition times.

METHODS

Patients undergoing a planar gated blood pool scan on a Na-I SPECT camera who consented to participate were subsequently imaged for 5 minutes in "List Mode" using a high-efficiency SPECT camera. LVEF was calculated for both the planar study and at 1, 2, 3, 4, and 5 minutes of acquisition on the high-efficiency camera. Counts acquired in the field of view, counts in the cardiac blood pool and LVEF were compared.

RESULTS

A total of 46 patients were analyzed (48% male, mean age 55 years, and BMI 27.6 kg/m(2)) who received an average Tc-99m dose of 20.3 mCi (5.3 mSv), 17 (37%) with abnormal LVEF's. The Na-I camera averaged 24,514 counts/min/mCi in the field of view and 8662 counts/min/mCi in the cardiac blood pool while the high-efficiency camera averaged 65,219 counts/min/mCi and 41,427 counts/min/mCi, respectively. Compared to the planar calculation of LVEF, 1-minute SPECT LVEF was on average 8.6 ± 10.7 higher, 2 minutes 3.5 ± 7.6 higher, 3 minutes 2.9 ± 8.5 higher, 4 minutes 2.5 ± 7.0 higher, and 5 minutes 1.1 ± 6.2 higher. Good correlation was seen between the SPECT LVEF's and the planar LVEF's across all acquisition times with correlation coefficients of 0.74-0.93.

CONCLUSIONS

High-efficiency SPECT technology can reduce radiation exposure to patients during gated blood pool imaging or decrease acquisition time while maintaining diagnostic accuracy. Based on the improved count sensitivity with high-efficiency SPECT, a 50% reduction in injected activity may be achievable while maintaining short imaging times of 5 minutes, with further reduction possible at longer imaging times.

Temporal trends of stress myocardial perfusion imaging: Influence of diabetes, gender and coronary artery disease status

INTRODUCTION

Temporal trends of myocardial perfusion imaging (MPI) among diabetics and non-diabetics and the influence of gender and prior coronary artery disease (CAD) status has not been previously investigated.

MATERIALS AND METHODS

Consecutive patients who underwent clinically indicated stress-MPI over a 17-year period (1996 through 2012) were studied. Data were collected prospectively as a part of the ongoing clinical databases. Study patients were divided into 4 temporal subgroups (1996 to 2000, 2001 to 2004, 2005 to 2008 and 2009 to 2012) to compare the trends of cardiac risk factors and the frequency of abnormal and ischemic MPI.

RESULTS

Of 78,344 total stress MPI studies, 30.2% were in diabetics. The frequency of abnormal MPI studies, while substantially higher in diabetics, significantly declined over time both in diabetics (53.6% in 1996 to 39.8% in 2012) and non-diabetics (37% in 1996 to 27.4% in 2012), despite an increase in the cardiac risk factor profile. Furthermore, among patients with no known CAD, the temporal prevalence of abnormal MPI was highest in diabetic men (57.5% in 1996 to 31.9% in 2012), lowest in non-diabetic women (18.8% in 1996 to 11% in 2012), and both intermediate and comparable in non-diabetic men and diabetic women (36.4% and 35.7% in 1996 and 20.7% and 17.5% in 2012, respectively).

CONCLUSIONS

Despite a temporal reduction in the prevalence of abnormal studies from 1996 through 2012, stress MPI continues to play an important clinical role, particularly in diabetics, men and patients with known-CAD.

A multi-center assessment of the temporal trends in myocardial perfusion imaging

BACKGROUND

Recent literature suggests that the frequency of abnormal SPECT myocardial perfusion imaging (MPI) has decreased over the past two decades despite an increase in the prevalence of many cardiac risk factors. This study examined the trends in the prevalence of obstructive coronary artery disease (CAD) by abnormal and ischemic MPI and invasive angiography.

METHODS

We analyzed all patients who underwent stress MPI or invasive angiography at two academic centers between January 1996 and December 2012, for their demographic data and study results.

RESULTS

A total of 108,654 MPI studies were performed. Over time, the percentage of patients with hypertension, hyperlipidemia, diabetes, and a history of smoking increased. There was a decline in the prevalence of abnormal MPI studies in all patients as well as in those with and without known CAD (from 47.2%, 71.8%, and 31.4% in 1996 to 33.9%, 64.8%, and 18.8% in 2012, respectively, all P < .0001). Similarly, there was a decline in the prevalence of ischemic MPI studies in all patients as well as in those with and without known CAD. A total of 142,924 invasive angiograms were performed. There was a decline in the prevalence of one-vessel and multi-vessel coronary disease (from 29.1% and 53.6% in 1996 to 22.4% and 35.9% in 2012, respectively, all P < .0001).

CONCLUSIONS

There has been a temporal decline in the prevalence of abnormal and ischemic MPI studies as well as the frequency and extent of obstructive CAD on angiography. However, this decline was not to the same extent as previously reported, and the overall 34% abnormal MPI rate, with 19% in patients with no known CAD and 65% in patients with known CAD, remains a clinically relevant percentage of patients tested.

Prospective evaluation of a new protocol for the provisional use of perfusion imaging with exercise stress testing

PURPOSE

Previous literature suggests that myocardial perfusion imaging (MPI) adds little to the prognosis of patients who exercise >10 metabolic equivalents (METs) during stress testing. With this in mind, we prospectively tested a provisional injection protocol in emergency department (ED) patients presenting for the evaluation of chest pain in which a patient would not receive an injection of radioisotope if adequate exercise was achieved without symptoms and a negative ECG response.

METHODS

All patients who presented to the ED over a 5-year period who were referred for stress testing as part of their ED evaluation were included. Patients considered for a provisional protocol were: exercise stress, age <65 years, no known coronary artery disease, and an interpretable rest ECG. Criteria for not injecting included a maximal predicted heart rate ≥85%, ≥10 METs of exercise, no anginal symptoms during stress, and no ECG changes. Groups were compared based on stress test results, all-cause and cardiac mortality, follow-up cardiac testing, subsequent revascularization, and cost.

RESULTS

A total of 965 patients were eligible with 192 undergoing exercise-only and 773 having perfusion imaging. After 41.6 ± 19.6 months of follow-up, all-cause mortality was similar in the exercise-only versus the exercise plus imaging group (2.6% vs. 2.1%, p = 0.59). There were no cardiac deaths in the exercise-only group. At 1 year there was no difference in the number of repeat functional stress tests (1.6% vs. 2.1%, p = 0.43), fewer angiograms (0% vs. 4.0%, p = 0.002), and a significantly lower cost ($65 ± $332 vs $506 ± $1,991, p = 0.002; values are in US dollars) in the exercise-only group. The radiation exposure in the exercise plus imaging group was 8.4 ± 2.1 mSv.

CONCLUSIONS

A provisional injection protocol has a very low mortality, few follow-up diagnostic tests, and lower cost compared to standard imaging protocols. If adopted it would decrease radiation exposure, save time and decrease health-care costs without jeopardizing prognosis.

A simple scoring tool for the evaluation of patients in an emergency department chest pain unit

BACKGROUND

There are multiple risk scores to determine the prognosis of high-risk patients presenting with acute coronary syndromes (ACS) to emergency departments (ED) and chest pain units (CPU), however, there are few options for patients without ACS (no diagnostic ST-segment deviation or positive biomarkers).

OBJECTIVES

To derive a clinical risk score for the management of lower-risk patients seen in ED CPUs.

METHODS

We evaluated all patients triaged through the Mount Sinai ED CPU over a 76-month period who underwent stress testing after negative serial biomarkers and ECGs. Primary and secondary endpoints of hospital admission and coronary revascularization were retrospectively obtained. Variables associated with admission at P < 0.1 level were entered into a multivariable model. Each variable was assigned an integer score based on the beta coefficients in the final model.

RESULTS

A total of 4,666 patients were evaluated and 738 (15.8%) had an abnormal stress test, 575 (12.3%) were admitted to the hospital, and 133 (2.9%) underwent coronary revascularization. A score consisting of age > 55 years, gender, chest pain quality (typical vs atypical), known coronary artery disease, shortness of breath, diabetes, smoking, and abnormal ECG demonstrated strong correlation between observed vs predicted hospital admission. The clinical score showed good ability to predict admission with a receiver operating characteristic (ROC) area of 0.72, which improved to 0.81 when the results of stress testing were added.

CONCLUSIONS

This new clinical risk score is simple to use, predicts a clinically relevant outcome to ED physicians, and the results of noninvasive testing are additive.

A comparison of coronary CTA and stress testing using high-efficiency SPECT MPI for the evaluation of chest pain in the emergency department

BACKGROUND

Recent studies have compared CTA to stress testing and MPI using older Na-I SPECT cameras and traditional rest-stress protocols, but are limited by often using optimized CTA protocols but suboptimal MPI methodology. We compared CTA to stress testing with modern SPECT MPI using high-efficiency CZT cameras and stress-first protocols in an ED population.

METHODS

In a retrospective, non-randomized study, all patients who underwent CTA or stress testing (ETT or Tc-99m sestamibi SPECT MPI) as part of their ED assessment in 2010-2011 driven by ED attending preference and equipment availability were evaluated for their disposition from the ED (admission vs discharge, length of time to disposition), subsequent visits to the ED and diagnostic testing (within 3 months), and radiation exposure. CTA was performed using a 64-slice scanner (GE Lightspeed VCT) and MPI was performed using a CZT SPECT camera (GE Discovery 530c). Data were obtained from prospectively acquired electronic medical records and effective doses were calculated from published conversion factors. A propensity-matched analysis was also used to compare outcomes in the two groups.

RESULTS

A total of 1,458 patients underwent testing in the ED with 192 CTAs and 1,266 stress tests (327 ETTs and 939 MPIs). The CTA patients were a lower-risk cohort based on age, risk factors, and known heart disease. A statistically similar proportion of patients was discharged directly from the ED in the stress testing group (82% vs 73%, P = .27), but their time to disposition was longer (11.0 ± 5 vs 20.5 ± 7 hours, P < .0001). There was no significant difference in cardiac return visits to the ED (5.7% CTA vs 4.3% stress testing, P = .50), but more patients had follow-up studies in the CTA cohort compared to stress testing (14% vs 7%, P = .001). The mean effective dose of 12.6 ± 8.6 mSv for the CTA group was higher (P < .0001) than 5.0 ± 4.1 mSv for the stress testing group (ETT and MPI). A propensity score-matched cohort showed similar results to the entire cohort.

CONCLUSIONS

Stress testing with ETT, high-efficiency SPECT MPI, and stress-only protocols had a significantly lower patient radiation dose and less follow-up diagnostic testing than CTA with similar cardiac return visits. CTA had a shorter time to disposition, but there was a trend toward more revascularization than with stress testing.

A hypothetical protocol for the provisional use of perfusion imaging with exercise stress testing

BACKGROUND

Previous literature suggests that the results of myocardial perfusion imaging (MPI) add little to the prognosis of patients who exercise >10 metabolic equivalents (METS) during stress testing. With this in mind, we attempted to determine if a provisional injection protocol could be developed in which a patient would not receive an injection of radioisotope if adequate exercise was achieved without symptoms and a negative ECG response. This protocol would save a substantial amount of time, radiation exposure, and cost.

METHODS

All patients who underwent a stress SPECT MPI over a 6.5-year period from 2004 to 2010 were included. Patients who would have been considered for a standby injection protocol were: exercise stress, age < 65, no known coronary artery disease (CAD), and an interpretable ECG. Patients were retrospectively divided into two groups based on whether they would have received radioisotope or not. Criteria for not injecting included a maximal predicted heart rate ≥ 85%, ≥10 METS of exercise, no symptoms of chest pain or shortness of breath, and no ECG changes (ST depression or arrhythmia). The two groups were then compared based on MPI results and all-cause mortality derived from the Social Security Death Index.

RESULTS

A total of 24,689 patients underwent SPECT MPI during this period, and 5,352 would have been eligible for a provisional injection protocol. There were 3,791 (70.8%), who would have been injected and 1,561 (29.2%), who would not have been. Perfusion results were abnormal in 5.9% of non-injected group compared to 14.4% in those who would have been injected. After a mean follow-up of 60.6 ± 21.4 months, 1.1% had died in the non-injected cohort compared to 2.2% in the injected group.

CONCLUSION

A provisional injection protocol defined as age < 65, normal rest ECG, no history of CAD, and high level exercise with a negative ECG response and no symptoms has a very low 5-year all-cause mortality and low yield of MPI. If adopted it would decrease radiation exposure and save time and health care costs without jeopardizing prognosis.

High-efficiency SPECT MPI: comparison of automated quantification, visual interpretation, and coronary angiography

BACKGROUND

Recently introduced high-efficiency (HE) SPECT cameras with solid-state CZT detectors have been shown to decrease imaging time and reduce radiation exposure to patients. An automated, computer-derived quantification of HE MPI has been shown to correlate well with coronary angiography on one HE SPECT camera system (D-SPECT), but has not been compared to visual interpretation on any of the HE SPECT platforms.

METHODS

Patients undergoing a clinically indicated Tc-99m sestamibi HE SPECT (GE Discovery 530c with supine and prone imaging) study over a 1-year period followed by a coronary angiogram within 2 months were included. Only patients with a history of CABG surgery were excluded. Both MPI studies and coronary angiograms were reinterpreted by blinded readers. One hundred and twenty two very low (risk of CAD < 5%) or low (risk of CAD < 10%) likelihood subjects with normal myocardial perfusion were used to create normal reference limits. Computer-derived quantification of the total perfusion deficit at stress and rest was obtained with QPS software. The visual and automated MPI quantification were compared to coronary angiography (≥70% luminal stenosis) by receiver operating curve (ROC) analysis.

RESULTS

Of the 3,111 patients who underwent HE SPECT over a 1-year period, 160 patients qualified for the correlation study (66% male, 52% with a history of CAD). The ROC area under the curve (AUC) was similar for both the automated and the visual interpretations using both supine only and combined supine and prone images (0.69-0.74). Using thresholds determined from sensitivity and specificity curves, the automated reads showed higher specificity (59%-67% vs 27%-60%) and lower sensitivity (71%-72% vs 79%-93%) than the visual reads. By including prone images sensitivity decreased slightly but specificity increased for both. By excluding patients with known CAD and cardiomyopathies, AUC and specificity increased for both techniques (0.72-0.82). The use of a difference score to evaluate ischemic burden resulted in lower sensitivities but higher specificities for both automated and visual quantification. There was good agreement between the visual interpretation and automated quantification in the entire cohort of 160 unselected consecutive patients (r = 0.70-0.81, P < .0001).

CONCLUSIONS

Automated and visual quantification of high-efficiency SPECT MPI with the GE Discovery camera provides similar overall diagnostic accuracy when compared to coronary angiography. There was good correlation between the two methods of assessment. Combined supine and prone stress imaging provided the best diagnostic accuracy.

Yield of routine provocative cardiac testing among patients in an emergency department-based chest pain unit

IMPORTANCE

The American Heart Association recommends routine provocative cardiac testing in accelerated diagnostic protocols for coronary ischemia. The diagnostic and therapeutic yield of this approach are unknown.

OBJECTIVE

To assess the yield of routine provocative cardiac testing in an emergency department-based chest pain unit.

DESIGN AND SETTING

We examined a prospectively collected database of patients evaluated for possible acute coronary syndrome between March 4, 2004, and May 15, 2010, in the emergency department-based chest pain unit of an urban academic tertiary care center.

PARTICIPANTS

Patients with signs or symptoms of possible acute coronary syndrome and without an ischemic electrocardiography result or a positive biomarker were enrolled in the database.

EXPOSURES

All patients were evaluated by exercise stress testing or myocardial perfusion imaging.

MAIN OUTCOMES AND MEASURES

Demographic and clinical features, results of routine provocative cardiac testing and angiography, and therapeutic interventions were recorded. Diagnostic yield (true-positive rate) was calculated, and the potential therapeutic yield of invasive therapy was assessed through blinded, structured medical record review using American Heart Association designations (class I, IIa, IIb, or lower) for the potential benefit from percutaneous intervention.

RESULTS

In total, 4181 patients were enrolled in the study. Chest pain was initially reported in 93.5%, most (73.2%) were at intermediate risk for coronary artery disease, and 37.6% were male. Routine provocative cardiac testing was positive for coronary ischemia in 470 (11.2%), of whom 123 underwent coronary angiography. Obstructive disease was confirmed in 63 of 123 (51.2% true positive), and 28 (0.7% overall) had findings consistent with the potential benefit from revascularization (American Heart Association class I or IIa).

CONCLUSIONS AND RELEVANCE

In an emergency department-based chest pain unit, routine provocative cardiac testing generated a small therapeutic yield, new diagnoses of coronary artery disease were uncommon, and false-positive results were common.