Efficacy of myocardial contrast echocardiography in the diagnosis and risk stratification of acute coronary syndrome

The diagnostic accuracy of cardiac ultrasound for acute myocardial ischemia in the emergency department: a systematic review and meta-analysis

BACKGROUND

Chest pain is responsible for millions of visits to the emergency department (ED) annually. Cardiac ultrasound can detect ischemic changes, but varying accuracy estimates have been reported in previous studies. We synthetized the available evidence to yield more precise estimates of the accuracy of cardiac ultrasound for acute myocardial ischemia in patients with chest pain in the ED and to assess the effect of different clinical characteristics on test accuracy.

METHODS

A systematic search for studies assessing the diagnostic accuracy of cardiac ultrasound for myocardial ischemia in the ED was conducted in MEDLINE, EMBASE, CENTRAL, CINAHL, LILACS, Web of Science, two trial registries and supplementary methods, from inception to December 6th, 2022. Prospective cohort, cross-sectional, case-control studies and randomized controlled trials (RCTs) that included data on diagnostic accuracy were included. Risk of bias was assessed with the QUADAS-2 tool and a bivariate hierarchical model was used for meta-analysis with paired Forest and SROC plots used to present the results. Subgroup analyses was conducted on clinically relevant factors.

RESULTS

Twenty-nine studies were included, with 5043 patients. The overall summary sensitivity was 79.3% (95%CI 69.0-86.8%) and specificity was 87.3% (95%CI 79.9-92.2%), with substantial heterogeneity. Subgroup analyses showed increased sensitivity in studies where ultrasound was conducted at ED admission and increased specificity in studies that excluded patients with previous heart disease, when the target condition was acute coronary syndrome, or when final chart review was used as the reference standard. There was very low certainty in the results based on serious risk of bias and indirectness in most studies.

CONCLUSIONS

Cardiac ultrasound may have a potential role in the diagnostic pathway of myocardial ischemia in the ED; however, a pooled accuracy must be interpreted cautiously given substantial heterogeneity and that important patient and test characteristics affect its diagnostic performance.

PROTOCOL REGISTRATION

PROSPERO (CRD42023392058).

Feasibility of fast cardiovascular magnetic resonance strain imaging in patients presenting with acute chest pain

Background

Cardiovascular magnetic resonance (CMR) is the current reference standard for the quantitative assessment of ventricular function. Fast Strain-ENCoded (fSENC)-CMR imaging allows for the assessment of myocardial deformation within a single heartbeat. The aim of this pilot study was to identify obstructive coronary artery disease (oCAD) with fSENC-CMR in patients presenting with new onset of chest pain.

Methods and results

In 108 patients presenting with acute chest pain, we performed fSENC-CMR after initial clinical assessment in the emergency department. The final clinical diagnosis, for which cardiology-trained physicians used clinical information, serial high-sensitive Troponin T (hscTnT) values and—if necessary—further diagnostic tests, served as the standard of truth. oCAD was defined as flow-limiting CAD as confirmed by coronary angiography with typical angina or hscTnT dynamics. Diagnoses were divided into three groups: 0: non-cardiac, 1: oCAD, 2: cardiac, non-oCAD. The visual analysis of fSENC bull´s eye maps (blinded to final diagnosis) resulted in a sensitivity of 82% and specificity of 87%, as well as a negative predictive value of 96% for identification of oCAD. Both, global circumferential strain (GCS) and global longitudinal strain (GLS) accurately identified oCAD (area under the curve/AUC: GCS 0.867; GLS 0.874; p<0.0001 for both), outperforming ECG, hscTnT dynamics and EF. Furthermore, the fSENC analysis on a segmental basis revealed that the number of segments with impaired strain was significantly associated with the patient´s final diagnosis (p<0.05 for all comparisons).

Conclusion

In patients with acute chest pain, myocardial strain imaging with fSENC-CMR may serve as a fast and accurate diagnostic tool for ruling out obstructive coronary artery disease.

Prognostic value of resting myocardial contrast echocardiography: a meta-analysis

BACKGROUND

Resting myocardial perfusion (MP) and wall motion (WM) imaging during real time myocardial contrast echocardiography (MCE) improves the detection of coronary artery disease (CAD). However, its prognostic role in different clinical settings (emergency department and outpatient setting) remains unclear.

METHODS

A systematic search in PubMed and Embase databases, and the Cochrane library, was conducted to evaluate the role of resting MP and WM in predicting major adverse cardiac events (MACE), including death, nonfatal myocardial infarction (NFMI) and urgent revascularization in patients presenting to either outpatient clinics or emergency departments with suspected symptomatic CAD. Summary receiver operating characteristic (SROC) curves, sensitivity and specificity plots were applied to assess diagnostic performance using RevMan 5.3.

RESULTS

Seven studies met criteria, including 3668 patients (six with follow up ranging from two days to 2.6 years). The relative risk (RR) for predicting MACE in patients with both abnormal resting MP and WM was 6.1 (95% CI, 5.1-7.2) and 14.3 (95% CI, 10.3-19.8) for death/NFMI, when compared to normal resting MP and WM patients. Having both abnormal resting MP and WM was also more predictive of MACE (RR 1.7; 95% CI 1.5-1.9) and death/NFMI (RR, 2.2; 95% CI, 1.8-2.7) when compared to abnormal WM with normal resting MP.

CONCLUSION

In this meta-analysis of both ED and outpatient clinic presentations for suspected CAD, having both a resting regional MP and WM abnormality identifies the highest risk patient for adverse events.

Myocardial perfusion imaging using contrast echocardiography

Microbubbles are an excellent intravascular tracer, and both the rate of myocardial opacification (analogous to coronary microvascular perfusion) and contrast intensity (analogous to myocardial blood volume) provide unique insights into myocardial perfusion. A strong evidence base has been accumulated to show comparability with nuclear perfusion imaging and incremental diagnostic and prognostic value relative to wall motion analysis. This technique also provides the possibility to measure myocardial perfusion at the bedside. Despite all of these advantages, the technique is complicated, technically challenging, and has failed to scale legislative and financial hurdles. The development of targeted imaging and therapeutic interventions will hopefully rekindle interest in this interesting modality.

Imaging strategies for acute chest pain in the emergency department

OBJECTIVE

Echocardiography, radionuclide myocardial perfusion imaging (MPI), and coronary CT angiography (CTA) are the three main imaging techniques used in the emergency department for the diagnosis of acute coronary syndrome (ACS). The purpose of this article is to quantitatively examine existing evidence about the diagnostic performance of these imaging tests in this setting.

CONCLUSION

Our systematic search of the medical literature showed no significant difference between the modalities for the detection of ACS in the emergency department. There was a slight, positive trend favoring coronary CTA. Given the absence of large differences in diagnostic performance, practical aspects such as local practice, expertise, medical facilities, and individual patient characteristics may be more important.

Future applications of contrast ultrasound

Contrast agents are currently used during echocardiography for enhancement of structure and function, as well as for perfusion imaging. The next frontiers in contrast ultrasonography are targeted imaging, and using microbubbles for therapeutic purposes. Targeted imaging is the detection of specific components of cardiovascular disease in vivo, with microbubbles which may non-specifically attach to diseased endothelial cells, or with microbubbles which have been specifically designed to detect a pathologic process. Therapeutic applications of contrast ultrasonography include the use of microbubbles to enhance delivery of agents (like drugs, genes, growth factors, etc.) to the endothelium or perivascular cells. This review will discuss differences in contrast agents used for current applications versus targeted imaging, technical considerations required to achieve site-specific imaging, and potential applications of this technology. The potential for contrast ultrasonography to enhance drug and gene delivery to tissue will also be discussed.

Usefulness of contrast echocardiography for predicting the severity of angiographic coronary disease in non-ST-elevation myocardial infarction

Guidelines recommend coronary angiography in patients with non-ST-elevation myocardial infarction (NSTEMI) within 24 to 72 hours, a requirement that cannot always be met. The aim of this study was to evaluate the potential use of contrast echocardiography in prioritizing these patients by identifying those with NSTEMI and angiographically severe coronary artery disease (CAD). Echocardiography was performed before coronary angiography in 110 patients with NSTEMI (67 ± 12 years old, 31% women). Segmental myocardial perfusion and wall motion was scored using a 17-segment left ventricular model. CAD was assessed by quantitative coronary angiography. In the total study population, median troponin T level was 0.27 μg/L (0.13 to 0.86) and Thrombolysis In Myocardial Infarction risk score 3.1 ± 1.5. By quantitative coronary angiography 15% had normal coronary angiographic findings, whereas 1-, 2-, and 3-vessel disease were present in 35%, 27%, and 23%, respectively. Severe CAD (left main stem stenosis, 3-vessel disease, or multivessel disease including proximal stenosis in left anterior descending artery) was found in 42%. Number of segments with hypoperfusion increased with CAD severity from 4.1 ± 2.0 in patients with normal coronary arteries to 5.9 ± 2.4, 7.8 ± 3.5, and 10.4 ± 2.8 in patients with 1-, 2-, and 3-vessel disease, respectively (p<0.01). In multiple logistic regression analysis risk of severe CAD increased by 39% for every additional hypoperfused segment by echocardiography independent of wall motion abnormalities and Thrombolysis In Myocardial Infarction risk score. In conclusion, contrast echocardiography may be used for prediction of angiographic CAD severity in patients with NSTEMI awaiting coronary angiography.

Comparison of myocardial contrast echocardiography versus rest sestamibi myocardial perfusion imaging in the early diagnosis of acute coronary syndrome

BACKGROUND

It remains unclear whether myocardial contrast echocardiography (MCE) is as accurate as myocardial perfusion imaging with technetium-99m sestamibi (MPI) for the diagnosis of acute coronary syndrome (ACS). We sought to directly compare the diagnostic accuracy of MCE with resting MPI in a head-to-head fashion.

METHODS

We prospectively enrolled 98 consecutive patients (mean age; 59+/-9 years, 68 males) who presented to the emergency department with chest pain suggestive of acute myocardial ischemia. Early MCE was performed by using continuous infusion of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) during intermittent power Doppler harmonic imaging. Myocardial perfusion defects observed in at least one coronary territory were considered positive. Sestamibi was injected immediately after MCE and MPI was obtained within 6 hours of tracer injection.

RESULTS

ACS was confirmed in 67 patients. There were 32 patients with acute myocardial infarction (AMI) and 35 patients with unstable angina requiring urgent revascularization. The sensitivities of MCE and MPI for the diagnosis of ACS were 72% and 61%, respectively, which were significantly higher than those of ST segment change (24%, p<0.001 vs. MCE and vs. MPI) and troponin I (27%, p<0.001 vs. MCE and vs. MPI), with similar specificities of 90% to 100%. On a receiveroperating characteristics curve demonstrating diagnostic accuracy for ACS, the area under the curve of MCE was significantly larger than that of MPI (0.86 vs. 0.77, respectively; p=0.019).

CONCLUSION

MCE and MPI overcome the low sensitivity of routine triage tests for detecting ACS, and MCE is more accurate than MPI for the diagnosis of ACS in the emergency department.

Contrast ultrasound in the assessment of patients presenting with suspected cardiac ischemia

Echocardiography is a portable technology that can be used to assess myocardial, pericardial, and valvular structure and function. Doppler echocardiography provides the ability to evaluate blood flow in large vessels and within cardiac chambers. Recently, the advent of microbubble contrast agents, which can opacify the systemic circulation, has improved the ability of echocardiography to evaluate left-ventricular function by improving delineation of the left-ventricular endocardial border. Furthermore, these microbubbles can be used to assess myocardial perfusion and quantify myocardial blood flow. Myocardial contrast echocardiography has been studied in multiple clinical situations, including the acute evaluation of patients presenting with suspected cardiac ischemia. Ongoing research is focused on the development of microbubbles that are capable of detecting molecular and cellular events within the circulation, which may allow distinction of acute vs. remote ischemic insults to the myocardium. This multifaceted technology promises to be of increasing clinical utility--not only for the heart, but for any organ accessible to ultrasound.