Selective use of single-photon emission computed tomography myocardial perfusion imaging in a chest pain center

The chest pain guidelines revisited: cherry picking from the frequentist tree

The new chest pain guideline document was recently released. The biggest changes are in the recommendations for intermediate and high-risk patients with known and unknown CAD. Coronary CT angiography has been recommended as the preferred imaging test for patients < 65 years old with chest pain. This paper will review the major evidence and omissions in the document that prompted that recommendation and provide thoughts on potential actions going forward.

Combined stress myocardial CT perfusion and coronary CT angiography as a feasible strategy among patients presenting with acute chest pain to the emergency department

BACKGROUND

A combined approach of myocardial CT perfusion (CTP) with coronary CT angiography (CTA) was shown to have better diagnostic accuracy than coronary CTA alone. However, data on cost benefits and length of stay when compared to other perfusion imaging modalities has not been evaluated. Therefore, we aim to perform a feasibility study to assess direct costs and length of stay of a combined stress CTP/CTA and use SPECT myocardial perfusion imaging (SPECT-MPI) as a benchmark, among chest pain patients at intermediate-risk for acute coronary syndrome (ACS) presenting to the emergency department (ED).

METHODS

This is a prospective two-arm clinical trial (NCT02538861) with 43 patients enrolled in stress CTP/CTA arm (General Electric Revolution CT) and 102 in SPECT-MPI arm. Mean age of the study population was 65 ​± ​12 years; 56% were men. We used multivariable linear regression analysis to compare length of stay and direct costs between the two modalities.

RESULTS

Overall, 9 out of the 43 patients (21%) with CTP/CTA testing had an abnormal test. Of these 9 patients, 7 patients underwent invasive coronary angiography and 6 patients were found to have obstructive coronary artery disease. Normal CTP/CTA test was found in 34 patients (79%), who were discharged home and all patients were free of major adverse cardiac events at 30 days. The mean length of stay was significantly shorter by 28% (mean difference: 14.7 ​h; 95% CI: 0.7, 21) among stress CTP/CTA (20 ​h [IQR: 16, 37]) compared to SPECT-MPI (30 ​h [IQR: 19, 44.5]). Mean direct costs were significantly lower by 44% (mean difference: $1535; 95% CI: 987, 2082) among stress CTA/CTP ($1750 [IQR: 1474, 2114] compared to SPECT-MPI ($2837 [IQR: 2491, 3554]).

CONCLUSION

Combined stress CTP/CTA is a feasible strategy for evaluation of chest pain patients presenting to ED at intermediate-risk for ACS and has the potential to lead to shorter length of stay and lower direct costs.

Electromechanical wave imaging and electromechanical wave velocity estimation in a large animal model of myocardial infarction

Echocardiography is often used in the clinic for detection and characterization of myocardial infarction. Electromechanical wave imaging (EWI) is a non-invasive ultrasound-based imaging technique based on time-domain incremental motion and strain estimation that can evaluate changes in contractility in the heart. In this study, electromechanical activation is assessed in infarcted heart to determine whether EWI is capable of detecting and monitoring infarct formation. Additionally, methods for estimating electromechanical wave (EW) velocity are presented, and changes in the EW propagation velocity after infarct formation are studied. Five (n  =  5) adult mongrels were used in this study. Successful infarct formation was achieved in three animals by ligation of the left anterior descending (LAD) coronary artery. Dogs were survived for a few days after LAD ligation and monitored daily with EWI. At the end of the survival period, dogs were sacrificed and TTC (tetrazolium chloride) staining confirmed the formation and location of the infarct. In all three dogs, as soon as day 1 EWI was capable of detecting late-activated and non-activated regions, which grew over the next few days. On final day images, the extent of these regions corresponded to the location of infarct as confirmed by staining. EW velocities in border zones of infarct were significantly lower post-infarct formation when compared to baseline, whereas velocities in healthy tissues were not. These results indicate that EWI and EW velocity might help with the detection of infarcts and their border zones, which may be useful for characterizing arrhythmogenic substrate.

Stress myocardial perfusion imaging for the evaluation and triage of chest pain in the emergency department: a randomized controlled trial

BACKGROUND

Patients with acute coronary syndrome (ACS) often present atypically. In a randomized controlled trial, we studied whether adding stress myocardial perfusion imaging (SMPI) to an evaluation strategy for emergency department (ED) patients presenting with chest pain more effectively identifies patients with ACS.

METHODS

Participants were randomized to standard ED chest pain protocol (clinical assessment) or standard protocol supplemented with SMPI results. During 6 hours of electrocardiogram (ECG) monitoring and serial cardiac markers (creatine kinase-MB isoenzyme, troponin), participants developing ST segment changes or elevated cardiac markers were admitted. Those with a negative observation period underwent SMPI (N = 1,004) or clinical assessment (N = 504) based on randomization, and admitted if their SMPI scan was abnormal or senior clinicians found a high or intermediate risk for ACS.

RESULTS

SMPI participants had a significantly lower admission rate than clinical assessment participants (10.16% vs 18.45%), with no significant between-group differences in risk of cardiac events (CEs) after 30 days (0.40% vs 0.79%) or 1 year (0.70% vs 0.99%).

CONCLUSIONS

When added to a standard triage strategy incorporating clinical evaluation, serial ECGs, and cardiac markers, SMPI improved clinical decision making for chest pain patients, significantly reducing the need for hospitalization without an increase in adverse CE rates at 30 days or 1 year.

The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) trial

OBJECTIVES

The purpose of this study was to compare the efficiency, cost, and safety of a diagnostic strategy employing early coronary computed tomographic angiography (CCTA) to a strategy employing rest-stress myocardial perfusion imaging (MPI) in the evaluation of acute low-risk chest pain.

BACKGROUND

In the United States, >8 million patients require emergency department evaluation for acute chest pain annually at an estimated diagnostic cost of >$10 billion.

METHODS

This multicenter, randomized clinical trial in 16 emergency departments ran between June 2007 and November 2008. Patients were randomly allocated to CCTA (n = 361) or MPI (n = 338) as the index noninvasive test. The primary outcome was time to diagnosis; the secondary outcomes were emergency department costs of care and safety, defined as freedom from major adverse cardiac events in patients with normal index tests, including 6-month follow-up.

RESULTS

The CCTA resulted in a 54% reduction in time to diagnosis compared with MPI (median 2.9 h [25th to 75th percentile: 2.1 to 4.0 h] vs. 6.3 h [25th to 75th percentile: 4.2 to 19.0 h], p < 0.0001). Costs of care were 38% lower compared with standard (median $2,137 [25th to 75th percentile: $1,660 to $3,077] vs. $3,458 [25th to 75th percentile: $2,900 to $4,297], p < 0.0001). The diagnostic strategies had no difference in major adverse cardiac events after normal index testing (0.8% in the CCTA arm vs. 0.4% in the MPI arm, p = 0.29).

CONCLUSIONS

In emergency department acute, low-risk chest pain patients, the use of CCTA results in more rapid and cost-efficient safe diagnosis than rest-stress MPI. Further studies comparing CCTA to other diagnostic strategies are needed to optimize evaluation of specific patient subsets. (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment [CT-STAT]; NCT00468325).

Negative predictive value and potential cost savings of acute nuclear myocardial perfusion imaging in low risk patients with suspected acute coronary syndrome: a prospective single blinded study

BACKGROUND

Previous studies from the USA have shown that acute nuclear myocardial perfusion imaging (MPI) in low risk emergency department (ED) patients with suspected acute coronary syndrome (ACS) can be of clinical value. The aim of this study was to evaluate the utility and hospital economics of acute MPI in Swedish ED patients with suspected ACS.

METHODS

We included 40 patients (mean age 55 +/- 2 years, 50% women) who were admitted from the ED at Lund University Hospital for chest pain suspicious of ACS, and who had a normal or non-ischemic ECG and no previous myocardial infarction. All patients underwent MPI from the ED, and the results were analyzed only after patient discharge. The current diagnostic practice of admitting the included patients for observation and further evaluation was compared to a theoretical "MPI strategy", where patients with a normal MPI test would have been discharged home from the ED.

RESULTS

Twenty-seven patients had normal MPI results, and none of them had ACS. MPI thus had a negative predictive value for ACS of 100%. With the MPI strategy, 2/3 of the patients would thus have been discharged from the ED, resulting in a reduction of total hospital cost by some 270 EUR and of bed occupancy by 0.8 days per investigated patient.

CONCLUSION

Our findings in a Swedish ED support the results of larger American trials that acute MPI has the potential to safely reduce the number of admissions and decrease overall costs for low-risk ED patients with suspected ACS.

Effectiveness and safety of chest pain assessment to prevent emergency admissions: ESCAPE cluster randomised trial

OBJECTIVE

To determine whether introducing chest pain unit care reduces emergency admissions without increasing reattendances and admissions over the next 30 days.

DESIGN

Cluster randomised before and after intervention trial.

SETTING

14 diverse acute hospitals in the United Kingdom.

PARTICIPANTS

Patients attending the emergency department with acute chest pain during the year before and the year after the intervention started.

INTERVENTION

Establishment of chest pain unit care compared with continuation of routine care.

MAIN OUTCOME MEASURES

Proportion of chest pain attendances resulting in admission; reattendances and admissions over the next 30 days; daily emergency medical admissions (all causes); and proportion of emergency department attendances with chest pain.

RESULTS

The introduction of chest pain unit care was associated with weak evidence of an increase in emergency department attendances with chest pain (16% v 3.5%; P=0.08); no change in the proportion of chest pain attendances resulting in admission (odds ratio 0.998, 95% confidence interval 0.940 to 1.059; P=0.945); small increases in the proportion reattending (odds ratio 1.10, 1.00 to 1.21; P=0.036) or being admitted (1.30, 0.97 to 1.74; P=0.083) over the next 30 days; and evidence of increased daily medical admissions (1.7 per day, 95% confidence interval 0.8 to 2.5; P<0.001). However, this last finding was highly sensitive to changes in the method used to handle missing data.

CONCLUSION

The introduction of chest pain unit care did not reduce the proportion of patients with chest pain admitted and may have been associated with increased emergency department attendances with chest pain.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN55318418.

Myocardial perfusion imaging after transient balloon occlusion during percutaneous coronary interventions

BACKGROUND

Myocardial perfusion imaging (MPI) is highly sensitive in detecting rest ischemia when the radiotracer is injected during the episode of ischemia. The frequency of abnormal MPI results after resolution of ischemia is not well defined. The aim of this study was to determine how long MPI results remain abnormal after transient coronary artery occlusion.

METHODS AND RESULTS

Patients undergoing single-vessel percutaneous coronary intervention were injected with technetium 99m sestamibi at 30 to 60 minutes (group 1) (n = 20) or 90 to 120 minutes (group 2) (n = 10) after the last balloon inflation and 24 hours later. There were 30 men aged 59 +/- 8 years. The culprit vessel was the left anterior descending artery in 14 patients and the right coronary artery in 13. The diameter stenosis was reduced from 76.1% +/- 8.7% to 3.0% +/- 6.4% (P < .001). The duration of balloon inflation was 40.3 +/- 12.5 seconds. Chest pain or ST shifts occurred in 66% of patients. A perfusion defect in the territory of the culprit artery was detected in 3 of 20 patients (15%) in group 1 and in 0 of 10 patients (0%) in group 2 (P = .3). One of those three patients had a perfusion defect on MPI done 24 hours later, along with a regional wall motion abnormality on the 2 sets of images.

CONCLUSIONS

Abnormal perfusion is seen in a small percentage of patients at 30 to 60 minutes and in none at 90 to 120 minutes after a brief transient balloon occlusion. These results might have important implications in patient care.

Noninvasive cardiac imaging in the evaluation of suspected acute coronary syndromes

Optimal management of patients presenting with chest pain to the emergency department is a major challenge, both in terms of a diagnostic dilemma and consumption of resources. The triage of such patients can be aided vastly by the appropriate use of noninvasive imaging. Noninvasive imaging modalities such as echocardiogram, radionuclide perfusion studies, positron emission tomography, cardiac magnetic resonance imaging and computed tomography have all been demonstrated to have favorable diagnostic and prognostic value, with an enhanced sensitivity to detect acute ischemia. A normal noninvasive evaluation in the appropriate clinical setting presents a strong argument against acute ischemia as an etiology of the chest pain. Randomized trials of both rest and stress imaging in the emergency department have confirmed a reduction in unnecessary hospitalizations and cost savings without compromising the safety of the patient. Cardiac magnetic resonance and computed tomography would provide an insight into subendocardial ischemia, the detection of which has previously been difficult, using single-photon emission tomography and echocardiography. In this review, novel hot-spot imaging modalities are discussed including infarct-avid imaging agents and ischemia-avid imaging agents, thus elucidating the pathophysiology of reperfusion-induced cell death. These agents represent work in evolution and are likely to be used routinely in the future as understanding of coronary syndromes and coronary artery disease becomes clearer.

Efficacy of Multislice Computed Tomography for the Detection of Acute Coronary Syndrome in the Emergency Department

BACKGROUND

The diagnosis of acute coronary syndrome (ACS), especially non-ST-elevation myocardial infarction and unstable angina in the emergency department (ED) still remains a challenge. Multislice computed tomography (MSCT) allows assessment of not only coronary artery stenoses and occlusions, but also assessment of coronary artery plaques and myocardial perfusion status.

METHODS AND RESULTS

MSCT was performed in 31 patients who were admitted to the ED because of chest pain persisting at least 30 min and non-diagnostic ECG changes and normal serum enzyme concentrations. Using MSCT, ACS was defined by coronary artery stenosis > or = 75% accompanied by computed tomography (CT)-low-density plaques, and/or by the presence of myocardial perfusion defects. ACS was confirmed by coronary stenosis > or = 75% by coronary angiography and/or subsequent elevation of troponin I concentration. In total, 22 patients were diagnosed as having ACS. MSCT detected stenoses with CT-low-density plaques in 21 and non-transmural myocardial perfusion defect in 3 patients. There was 1 false-positive and 1 false-negative result. The sensitivity and specificity of MSCT to identify ACS was 95.5% and 88.9%, respectively.

CONCLUSION

MSCT provides diagnostic operating characteristics suitable for triage of patients with ACS in the ED.

Acute resting myocardial perfusion imaging in patients with diabetes mellitus: results from the Emergency Room Assessment of Sestamibi for Evaluation of Chest Pain (ERASE Chest Pain) trial

BACKGROUND

Resting myocardial perfusion imaging (MPI) improves the triage of patients presenting to the emergency department (ED) with symptoms suggestive of acute cardiac ischemia (ACI). In the ED setting the presence of diabetes mellitus (DM) is a predictor of ACI and hospitalization, but the role of resting MPI in patients with DM is unknown.

METHODS AND RESULTS

A secondary data analysis of a prospective, multicenter, randomized, controlled trial of ED evaluation strategies in patients with symptoms suggestive of ACI and normal or nondiagnostic electrocardiograms was performed. In the main trial 2475 patients were randomized to receive either the usual ED evaluation strategy (n = 1260) or the usual strategy supplemented by results from resting MPI by use of single photon emission computed tomography (SPECT) technetium 99m sestamibi (n = 1215). Patients with diabetes (n = 341) were evaluated separately. Imaging results, final diagnoses, effect on triage, and prognostic value of the SPECT imaging were compared between diabetic and nondiabetic patients. Of the 341 patients with diabetes, 153 (45%) were randomized to the imaging strategy. Patients with DM had higher rates of hospitalization (66% vs 49.6%, P = .0001) and ACI (21.1% vs 12.0%, P < .001) than patients without DM. Among diabetic patients without ACI, the admission rate was 63% in the usual strategy group versus 54% in the imaging strategy group (relative risk [RR] = 0.91 [95% CI, 0.76-1.06]; P = .24). There was no difference in the magnitude of this reduced risk of admission compared with patients without DM (RR = 0.84 [95% CI, 0.77-0.92]; P = .0002 for patients without DM and P = .35 for interaction of diabetes and RR reduction).

CONCLUSIONS

Acute resting MPI with Tc-99m sestamibi is associated with improved triage decision making in symptomatic ED patients with diabetes.

Incremental value of cardiac imaging in patients presenting to the emergency department with chest pain and without ST-segment elevation: a multicenter study

BACKGROUND

We hypothesized that imaging of regional myocardial function (RF) and perfusion (PER) will add incremental value for both diagnosis and short-term prognosis to routine demographic, clinical, and electrocardiographic findings in patients presenting to the emergency department (ED) with chest pain and without ST-segment elevation on the electrocardiogram.

METHODS

We compared contrast echocardiography (CE) with gated single-photon emission computed tomography (SPECT) for this purpose. Both CE and SPECT readings included separate and composite assessments of both RF and PER. Adverse events in the first 48 hours after ED presentation included acute myocardial infarction, emergent revascularization, and cardiac-related death.

RESULTS

Concordance between CE and SPECT was 77% (73% to 82%) for all territories, with a higher concordance for the anterior wall of 84% (78% to 89%). Of the 203 patients recruited for the study, 38 (19%) had a cardiac event within 48 hours of ED presentation: 21 had acute myocardial infarction, 16 underwent an urgent revascularization procedure, and 1 died. In multivariate logistic regression models, the number of abnormal segments on CE and SPECT were significant predictors (P <.05) of cardiac events. The composite scores on CE provided 17% incremental information (P =.009, n = 203) and gated SPECT provided 23.5% additional information (P =.020, n = 163) for predicting cardiac events compared with routine demographic, clinical, and electrocardiographic variables. RF and composite evaluation was superior on SPECT compared with CE, whereas PER alone was not.

CONCLUSIONS

Cardiac imaging of RF and PER at the time of ED presentation offers substantially greater diagnostic and prognostic information for early cardiac events in patients presenting to the ED with chest pain and no ST elevation than does the routine demographic, clinical, and electrocardiographic assessment.

Impact of myocardial perfusion imaging on clinical management and the utilization of hospital resources in suspected acute coronary syndromes

Recent advances in the treatment of acute coronary syndromes has raised awareness in the community that prompt presentation for chest pain may be life saving. Each year in the United States, more than 6 million people present to the hospital with an acute chest pain, making this the most common presenting chief complaint second only to abdominal pain. Most patients presenting with chest discomfort have a non-ischaemic electrocardiogram on presentation. However, these patients are routinely admitted to hospital due to diagnostic uncertainty for occult myocardial infarction or ischaemia. As an approach to this dilemma, many hospitals have created protocols as a means of facilitating the identification of infarction and ischaemia and the safe and effective triage of patients with a chief complaint of chest pain. Myocardial perfusion imaging at rest has been shown to be highly sensitive for the detection of acute myocardial infarction, and can be supplemented with provocative testing after infarction has been excluded. Diagnostic strategies that utilize myocardial perfusion imaging for the evaluation of acute chest pain have successfully improved the triage of these patients by avoiding inadvertent discharge of patients with myocardial infarctions, and reducing unnecessary hospital admissions and overall cost and expenditure.

Value of definitive diagnostic testing in the evaluation of patients presenting to the emergency department with chest pain

The optimal diagnostic evaluation of patients presenting to the emergency department (ED) with chest pain but without myocardial infarction or unstable angina is controversial. We performed a prospective, nonrandomized, observational study of 1,195 consecutive patients presenting to the ED with chest pain but who had normal or nondiagnostic electrocardiograms and negative cardiac biomarkers. Patients (mean +/- SD age 61 +/- 15 years; 55% women) were admitted to the hospital and a standard protocol for evaluation and treatment was suggested. The use of stress myocardial perfusion imaging (MPI) or cardiac catheterization during their index hospitalization, and the 3-month incidence of coronary angiography, percutaneous cardiac intervention, coronary artery bypass surgery, re-presentation to our institution's ED for chest pain, myocardial infarction, or death were followed. Five hundred nine of 1,195 patients (43%) underwent provocative stress MPI during their index hospitalization; 37% had perfusion defects (predominantly ischemia). Fifty-six of 1,195 patients (4%) underwent cardiac catheterization without stress MPI for their primary diagnostic evaluation. Six hundred thirty of 1,195 patients (53%) had neither MPI or cardiac catheterization during their index hospitalization. During the 3-month follow-up period, patients with a normal stress perfusion study during their index hospitalization had fewer return visits (4%) compared with patients with abnormal perfusion studies (19%), those who underwent catheterization directly (16%), or patients with no initial diagnostic evaluation (15%) (p <0.001). In addition, patients who had a diagnostic evaluation during their index hospitalization had a lower incidence of either acute myocardial infarction (0.9% vs 2.1%) or death (0.4% vs 3.0%, p <0.001) in the 3-month follow-up period. Accordingly, we strongly advocate provocative stress MPI early after presentation for chest pain in all patients with risk factors for coronary artery disease.

Use of radionuclide imaging in acute coronary syndromes

The triage of patients presenting to the emergency department (ED) with acute chest pain is a diagnostic challenge. Radionuclide myocardial perfusion imaging has been shown to have favorable diagnostic and prognostic value in this setting, with an excellent early sensitivity to detect acute myocardial infarction (MI) not achieved by other testing modalities. A normal resting perfusion imaging study has been shown to have a negative predictive value of over 99% to exclude MI. Observational and randomized trials of both rest and stress imaging in the ED evaluation of patients with chest pain have demonstrated reductions in unnecessary hospitalizations and cost savings compared with routine care. Perfusion imaging has also been used in risk stratification after MI, and for measurement of infarct size to evaluate reperfusion therapies. Novel "hot spot" imaging radiopharmaceuticals that visualize infarction or ischemia are currently undergoing evaluation and hold promise for future imaging of acute coronary syndromes.