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Can Coronary Artery Anomalies Be Detected on CT Calcium Scoring Studies?

Academic Radiology, 04/11/2013  Review Article

Maddux PT et al. – The purpose of this study is to determine whether coronary artery anomalies can be detected on noncontrast computed tomography (CT) coronary artery calcium scoring (CCS) studies. Benign and malignant coronary artery anomalies can be detected with relatively high accuracy on noncontrast–enhanced CCS studies. CCS studies should be reviewed for signs of coronary artery anomalies in order to identify malignant variants with possible impact on patient management.

Methods

• A total of 126 patients (mean age 62 years; 35 women) underwent noncontrast CCS and contrast enhanced coronary CT angiography (cCTA).
• Thirty–three patients were diagnosed with a coronary anomaly on cCTA, whereas coronary anomalies were excluded in 93.
• Two observers (reader 1 [R1] and reader 2 [R2]), blinded to patient information independently evaluated each CCS study for: 1) visibility of coronary artery origins, 2) detection of coronary anomalies, and 3) benign or malignant (ie, interarterial) course.
• Using cCTA as the reference standard, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CCS studies for detecting coronary anomalies were calculated.

Results

• Of the 33 coronary anomalies, 16 were benign and 17 malignant.
• Based on noncontrast CCS studies, R1 and R2 correctly identified the left main origin in 123/126 (97.6%) and 121/126 (96%) patients; the left anterior descending origin in 125/126 (99.2%) and 122/126 (96.8%); the circumflex origin in 120/126 (95.2%) and 105/126 (83.3%); and the right coronary artery origin in 117/126 (92.9%) and 103/126 (81.7%), respectively.
• R1 and R2 identified 34 and 27 coronary anomalies and classified 19 and 15 as malignant, respectively.
• Interobserver reproducibility for detection of coronary anomalies was good (k = 0.76).
• Interobserver agreement for detection of malignant variants was even stronger (k = 0.80).
• On average, coronary artery anomalies were diagnosed with 85.2% sensitivity, 96.4% specificity, 90.5% PPV, and 94.1% NPV on noncontrast CCS studies.

Acute Chest Pain/ER Admission: Three Emerging Alternatives to Angiography and PCI – Corus CAD, hs cTn, CCTA, Curator: Aviva Lev-Ari, PhD, RN, 3/10/2013

•  Non-inferiority study
• 5 Pennsylvania EDs
• 1,370 patients, Age > 30 years
• Inclusion criteria: TIMI score of 0–2, EKG without ischemic changes, and negative first set of Cardiac Biomarkers
• Randomized 2 patients to CCTA arm (908 patients) for every 1 patient to Standard Stress arm (462 patients)

Primary Outcome:

• MI or Death from CAD at 30 days

Secondary Outcomes:

• Rate of discharge from ED
• Length of stay (LOS) in ED
• Rate of detection of CAD
• Resource utilization

What they found:

• 640/908 pts (70.5%) who underwent CCTA had coronary stenosis of <50% and none had MI or death due to CAD at 30 days
• Discharge from ED 49.6% with CCTA vs 22.7% with standard stress arm
• ED LOS 18 hr in CCTA arm vs 24.8 hr in standard stress arm

Conclusion: CCTA allows early discharge of low to intermediate risk patients presenting to the ED with possible ACS.

• Randomized controlled trial
• 9 EDs in the US
• 1,000 patients with acute chest pain with ages 40–74 years
• CCTA (501 patients) versus Standard Evaluation (499 patients)

Primary Outcome:

• Hospital length of stay

Secondary Outcomes:

• Cardiovascular events at 28 days
• Rate of discharge from ED
• Time to diagnosis
• Cost
• Utilization of resources

What they found:

• Hospital LOS decreased by 7.6 hr in CCTA group
• Rate of discharge from ED 47% in CCTA arm vs 12% in Standard Evaluation Arm
• No difference in cardiovascular events at 28 days
• Cost was similar between two groups $4,289 CCTA vs $4,060 in Standard arm

Conclusion: CCTA decreases length of stay without an increase in rate of cardiovascular events.

• CCTA with 0 lesions is NEGATIVE: These patients can certainly be discharged home with primary care follow up with a nearly 100% NPV for ACS/AMI.
• CCTA with <50% lesion is NOT NEGATIVE: This patient has CAD. It may not be clinically significant, but we can see plaques. 2/3 of AMIs occur from plaques that have <50% stenosis. Certainly we can start risk factor modification with beta blockers, ASA, and statins, but there are no studies looking at how this group of patients will do long term.
• CCTAs are anatomic studies and not functional studies. Identified lesions will lead to more diagnostic tests, which is one of the big arguments against CCTA. CCTA identifies CAD more often than standard stress modalities, which leads to more heart catheterizations and PCIs.
• As the number of CT slice increases, radiation dose decreases:

1. A 64 slice CT = 10 – 15 mSv of radiation
2. A 128 slice CT = 5 – 10 mSv of radiation
3. A 256 slice CT = 1 – 5 mSv of radiation
4. In contrast, a single-view CXR = 0.02 mSV of radiation

• There is currently an ongoing National Heart, Lung, and Blood Institute-funded trial called the PROMISE (Prospective Multi-center Imaging Study for Evaluation of Chest Pain) Study with 10,000 patients. Patients with symptoms suggestive of CAD will be randomized to a CCTA vs usual care with a functional test.  What’s interesting about this study is it is being performed in the offices of primary care physicians and cardiologists rather than EDs. The study authors hypothesize that medically optimizing patients identified, as having non-obstructive CAD will yield improved long-term outcomes.