Comprehensive Cardiothoracic Dual Source CT for the Early Triage of Patients With Acute Chest Pain

Undifferentiated chest pain is one of the most common complaints in the acute care setting, accounting for over five million emergency department (ED) visits in the U.S. each year. Moreover, early and accurate triage of these patients remains difficult as neither the chest pain history, a single set of biochemical markers for myocardial necrosis, or the initial 12-lead electrocardiogram (ECG), alone or in combination, identify a group of patients that can be safely discharged without further diagnostic testing. As a result, patients presenting to the ED with undifferentiated chest pain are often evaluated with multiple examinations to exclude the presence of myocardial infarction (MI),pulmonary embolism (PE), and/or aortic dissection (AD).

While contrast-enhanced spiral computed tomography angiography (CTA) has become a standard procedure in the evaluation of the presence of PE and AD, it was only within the past few years that noninvasive detection of coronary artery stenosis with CTA has become feasible. Coronary CTA has been proven to be an effective tool to rule out CAD with reported sensitivities of 93-99% and specificities of 95-97% as compared to invasive coronary angiography.

Recent data from our Rule Out Myocardial Infarction by Computer Assisted Tomography (ROMICAT) study indicates that coronary CTA accurately rules out acute coronary syndrome (ACS) in patients with acute chest pain and therefore may enhance the diagnostic work up of chest pain patients in the ED. Moreover, this study demonstrated the distribution of several CT-angiographic patterns of CAD which may change management of subjects with inconclusive initial ED evaluation admitted to the hospital. For example, CTA demonstrated the absence of any CAD in 50% of the patients. None of the subjects without any CAD on CTA developed unstable angina or had an MI during index hospitalization. Furthermore, none of these patients had any MACE over the next six months, confirming previous observations in ACS patients. These data suggest that 50% of hospital admissions could be saved. Another recent study our group has demonstrated that an individually tailored ECG-gated CT protocol with a single contrast injection permits simultaneous visualization of the coronary arteries, thoracic aorta, and pulmonary arteries with excellent image quality.

The very recent introduction of dual source CT (DSCT) technology offers a two-fold improvement in temporal resolution as compared to the standard 64-slice CTA that was used for these studies (83ms vs. 165ms, respectively). This significant improvement in temporal resolution allows for the acquisition of diagnostic images with higher and irregular heart rates, precluding the need for intravenous beta blockade. Given the improved temporal resolution and faster acquisition time, the amount of radiation exposure can be markedly reduced in many patients.

With the need to improve triage of patients with undifferentiated chest pain and the advantages offered by DSCT technology, several observational case series have suggested the feasibility of a comprehensive thoracic DSCT (CT-DSCT) to simultaneously evaluate the coronary arteries, thoracic aorta, and pulmonary arteries. Whether this will result in an improvement of patient management and test utilization remains unclear as compared to a standard ED evaluation protocol needs to be evaluated.

Thus, the purpose of this research is to determine the efficiency of a single CT-DSCT protocol to establish or exclude MI, PE, or AD as compared to the individual protocols. Endpoints aim to compare the rate of ED discharge, length of hospital stay, the diagnostic imaging test utilization, and the costs between the comprehensive and the standard protocol strategy in patients with undifferentiated chest discomfort or shortness of breath with a component of chest discomfort.

Inclusion criteria

• Males or females >30 years of age in sinus rhythm
• Willing and able to provide written informed consent
• Undifferentiated chest discomfort or shortness of breath with a component of chest discomfort within the last 24 hours
• Intermediate likelihood of MI, pulmonary embolism (PE), or aortic dissection (AD) as determined by ED providers after completion of standard initial clinical evaluation
• ED providers independently decide that the patient's care plan should include a coronary, PE, or AD CT.
• Female patients must be either of non-childbearing potential (i.e., surgically sterilized or post menopausal [≥ 12 consecutive months without menses]) or must have a negative pregnancy test

Exclusion criteria

• Positive cardiac biomarkers (elevated serum creatine phosphate (CK) with elevated CK-MB isoform and/or elevated troponin)
• Diagnostic ECG changes (e.g., >1 mm ST-segment elevation or depression in two anatomically contiguous leads)
• Known history of CAD (i.e., past myocardial infarction, prior coronary stent Placement, and/or coronary artery bypass graft surgery)
• Known history of thoracic aortic disease (i.e., thoracic aortic aneurysm > 5cm in diameter, history of aortic dissection, and/or history of thoracic aortic aneurysm repair (via open surgery or stent-graft placement))
• Known history of pulmonary embolism
• Heart rate > 100 beats per minute
• Systolic blood pressure <105 mmHg
• Oxygen saturation < 90%
• Any cardiac arrhythmia causing hemodynamic compromise
• Serum creatinine clearance <60 mL/min by Cockcroft-Gault
• Known allergy to iodinated contrast agents
• Subjects on metformin therapy that are unable or unwilling to discontinue therapy for 48 hours after CT procedure