Chest radiologists take closer look at heart

The advent of 64-slice and dual-source CT has undoubtedly been welcomed by cardiovascular imaging experts. The systems' rapid rotation speeds and high-volume coverage have made it far easier to attain quality images of the beating heart and coronary arteries.

These improvements to cardiac imaging quality could also benefit chest radiologists, according to Prof. Martine Remy-Jardin, head of radiology and chair of thoracic imaging at the Calmette Hospital, University Center in Lille, France. But the move from thoracic imaging to cardiothoracic imaging should not trigger a new turf war, she said during an honorary lecture at the European Congress of Radiology held in Vienna in March.

The low temporal resolution of early-generation CT systems previously prevented data on patients' cardiovascular and/or cardiac health from being extracted from standard chest CT scans. This no longer needs to be the case. Advances in technology mean that radiologists reporting a chest CT examination can look at the morphology of the heart and coronary arteries as well as that of the thoracic organs. Information on cardiac function can also be obtained from the same multislice CT data set. This added knowledge can improve diagnostic decision making and affect treatment for numerous acute and chronic respiratory diseases.

The emergence of CT as a valid noninvasive tool for cardiac and cardiovascular imaging has already caused some tension between cardiologists and radiologists. Remy-Jardin is confident that chest radiologists can avoid being drawn into these disputes. The two communities will see quite different patient populations, so there need be no poaching from referral lists. Patients whose asymptomatic coronary disease is picked up from a thoracic CT scan may then require additional diagnostic workup or endovascular procedures in cardiovascular clinics. So, in a sense, the development of cardiothoracic imaging will actually benefit the cardiology community.

Turf battles within the radiology community should also be unnecessary. Chest radiologists have no desire to become cardiovascular radiologists, and they will continue to see a very different group of patients, she said.

"We need collaboration between cardiovascular and thoracic radiologists. The perspective is radiology's participation in cardiac imaging, and we should concentrate our forces in that direction," she said. "Imaging tools are in radiologists' hands, and it is up to us to keep them."

While the evolution of CT technology brought steady improvements to thoracic imaging, chest radiologists had to wait for 64-slice CT before they could introduce ECG-gated acquisitions over the entire thorax into daily practice. The 64-slice systems cut the breath-hold time, removed the need for beta blockers, and ensured that radiation dose could be kept to a reasonable level.

"Using a low-dose ECG-gated CT angiography protocol, we can get diagnostic-quality images in patients with a normal body mass index and also in obese patients. The images are a bit fuzzy in the latter group, but parameters can be modified to get a good compromise between image quality and dose," Remy-Jardin said.

Images acquired with ECG gating are less likely to contain artifacts that can mimic actual disease, such as endovascular clots. Extraction of functional parameters from these image data, especially at the level of the pulmonary vessels and right ventricle, may reveal associated cardiac dysfunction. High-resolution CTA could also show that the patient's respiratory symptoms are linked to an underlying cardiovascular disorder.

Coronary arteries should be of interest to chest radiologists in two key situations. The first involves patients scheduled for pulmonary resection. The greatest cardiac risk factor in this patient population is linked to coronary artery disease. Asymptomatic patients with minimal cardiovascular risk factors could now be screened for CAD with a presurgical CT scan.

Chest radiologists should also seek out signs of CAD in patients with chronic obstructive pulmonary disease. A high proportion of COPD patients with no history of systemic coronary disease will be found to have coronary artery abnormalities on imaging. Researchers now believe that these lesions are caused by the same systemic inflammation that produces respiratory symptoms in COPD patients.

The evolution of thoracic imaging toward cardiothoracic imaging should be supported by appropriate modifications to radiology teaching and training programs, Remy-Jardin said. She advised chest radiologists to boost their credibility in cardiothoracic imaging by participating in relevant research programs.