X-ray angiography misses anomalous coronary artery detail

Electron-beam CT angiography topped catheter angiography in determining the most at-risk adult patients with congenital coronary artery defects. Although both techniques showed the anomalies, EBCT better depicted the proximal course of anomalous vessels, according to a small study from Turkey reported in the September issue of Catheterization and Cardiovascular Interventions.

While most congenital coronary anomalies in adults are harmless, some carry significant morbidity and mortality risk. Discriminating the potentially catastrophic interarterial course of ectopic coronary arteries from other variants is especially important, according to the study.

For the most part, information obtained from catheter angiography is sufficient to diagnose coronary abnormalities. But in cases of complex anomalous courses around the great vessels, conventional angiography's diagnostic ability is limited by its lack of 3D capability and its inability to depict adjacent soft-tissue structures.

In these situations, 3D data provided by EBCT, multislice CT, or MRI can provide useful complementary information. The use of transesophageal echocardiography in this patient population remains understudied, but its cost and semi-invasive nature limit utilization.

MR angiography can be time-consuming and difficult to reproduce, and it suffers from motion artifacts and contraindication issues regarding stents and pacemakers. The data from this EBCT study are transferable to MSCT, but MSCT requires the use of beta blockers and provides three times the radiation exposure, according to lead author Dr. Esat Memisoglu, now an assistant professor of radiology at St. Louis University Hospital.

The radiation exposure for EBCT angiography is 1.3 mSv. For catheter angiography, it's 2.5 mSv, provided the exam is done quickly and in good hands. For MSCT with newer modulation protocols, it is about 4.5 mSv. Without modulation, it is between 10 and 12 mSv, according to Memisoglu.

Memisoglu and colleagues at Test Cardiovascular Imaging and the Siyami Ersek Heart Surgery Center in Istanbul enrolled 28 adult patients who previously had undergone conventional angiography: three for stable angina, three for atypical angina, six for chest pain, and two for shortness of breath.

Angiography incidentally picked up coronary anomalies in 14 patients. The other 14 served as a control group.

Cardiologists sent the patients to be imaged by EBCT angiography (C-150 XP, GE Healthcare), where radiologists were blinded to the catheter angiographic results. Radiologists reading EBCT exams also detected all abnormalities. In more than one-third of EBCT exams, however, radiologists were able to determine whether the abnormal arteries were safely coursing around the great vessels or passed perilously close between them.

EBCT protocol included injection of 140 cc of contrast and no use of beta blockers. Forty to 50 overlapping axial 3-mm sections with 2-mm table movement were obtained in a single breath-hold, which lasted 30 to 40 seconds.

Initially, technologists removed from the axial images all extracardiac structures and parts of the atria and veins. Although not necessary, the editing, which takes only 10 minutes, was done to provide clinicians with crisp volumetric images, Memisoglu said.

Radiologists reviewed both the source images and the 3D volume-rendered reconstructions and, occasionally, maximum intensity projections before reaching a clinical diagnosis.

Memisoglu said that the radiologists favored the 3D VR technique over 2D multiplanar reconstruction, 2D MIPs, and 3D surface-shaded display. The 3D VR technique better depicted the heart as a whole due to the preservation of soft-tissue densities within the reconstructed volume.

Identified anomalies were:

• three cases of a single coronary artery originating from the right sinus of Valsalva

• three cases of an anomalous left-sided right coronary artery with an acute angle takeoff from the left coronary sinus of Valsalva - in each case, the anomalous artery ran interarterially between the aortic root and the pulmonary artery

• three cases of a right-sided left main coronary artery and two cases of left anterior descending coronary artery showing contralateral ectopic origin

• two cases of a right-sided anomalous origin of left circumflex artery, one arising directly from the right sinus of Valsalva and the other from the proximal right coronary artery, with the left circumflex following a retroaortic path reaching the left atrioventricular sulcus in both

• one case of absent left main coronary artery with a separate left-sided ostia for the left anterior descending and left circumflex coronary arteries

Disagreement between the two modalities occurred in five cases: identification of septal (EBCT) versus interarterial course in three patients, septal (EBCT) versus prepulmonic in one, and interarterial (EBCT) versus prepulmonic in another.

In these cases, unblinded consensus reading among cardiologists and the radiologists favored the interpretation of EBCT over catheter angiography.

"Although our study involved a small number of patients, the spectrum of coronary anomalies is well represented, which demonstrates the added value of EBCT in depicting the true course of the anomalous coronary arteries," Memisoglu said.

For more information from the Diagnostic Imaging archives:

Heart docs embrace new cardiac CT, MR guidelines

Use multislice CT for coronary imaging only when EBCT is not available

MDCT challenges EBCT in coronary imaging

Cooperation over coronary CTA may doom EBCT

CT angiography safely visualizes pediatric vascular anomalies