Buoyed by highly promising preliminary results, radiologists and cardiologists are lining up to learn coronary artery CT. Interest is growing in new CCT fellowships and medical conferences offering CCT training. Record sales of cardiovascular 64-slice CT scanners, many installed in the first half of 2006, are fueling the demand.
Few physicians have accumulated enough experience to competently perform CCT. Fewer still are qualified to teach physicians how to conduct interpretations.
"There are just too many people [who want to learn]," said Dr. Arthur Stillman, director of cardiovascular and thoracic imaging at Emory University.
Professional competency standards for CCT require that physicians make a concerted effort to learn the technique. The American College of Cardiology Foundation/American Heart Association (ACCF/AHA) clinical competency statement requires 150 supervised cases. These include 50 cases in which a physician is directly involved in scanning to establish skill in interpreting a coronary artery CT scan. An interim statement published by the American College of Radiology requires board-certified radiologists perform 75 supervised scans to achieve competence. The difference recognizes the training in thoracic CT interpretation that radiologists receive during their residencies.
To help physicians meet these requirements, the American Roentgen Ray Society, the American College of Cardiology, the North American Society for Cardiac Imaging, the Society of Cardiovascular Computed Tomography, and the Society of Cardiovascular Angiography and Intervention have sponsored conferences, seminars, and Web-based initiatives in the first half of 2006. Many universities have launched full- and short-term fellowships to train Level III-competent physicians to teach CCT and Level II courses to help radiologists and cardiologists read enough supervised cases to competently perform coronary artery CT scans.
"Labs like my own are inundated with trainees and training requests," said Dr. Matthew Budoff, an associate professor of medicine at Harbor-UCLA Medical Center in Torrance, CA. Budoff, author of the ACCF/AHA competency statement, teaches three courses per month.
Initiatives to gain reimbursement for CCT have also stepped ahead. In January, the American Medical Association adopted eight CPT codes for cardiac CT applications. Last December, an intersociety task force published a model local coverage determination. It serves as a blueprint to help insurers justify coverage.
STAKING A CLAIM
The ACC has reinforced its claim to cardiovascular imaging and set up the possibility of renewed conflicts with radiologists over imaging privileges. At the organization's annual meeting, Dr. Pamela S. Douglas, outgoing ACC president, urged cardiologists to take the lead in improving cardiovascular imaging research and practice.
"If imaging were a drug, approval would be denied," she said speaking of alleged problems with cardiovascular imaging research.
Core Cardiology Training guidelines for cardiology fellowship education were revised in February to require CCT training. At least a month will now be devoted to CCT applications. Fellows will read at least 150 supervised cases including 35 where they observe the procedure.
Standards for fellowship in nuclear cardiology and cardiac MRI have also been recalibrated. Cardiology fellows receive at least two months training with 80 hours devoted to interpreting cardiac PET and SPECT. At least four months of training, including 300 supervised scans, must be performed to read cardiac SPECT and PET scans without supervision. Cardiology fellows will undergo at least one month of CMR training. Three months, including 150 supervised exams, are required for fellows to perform CMR.
CCT was added to the mandatory curricula because it is becoming integral to cardiology practice, according to Budoff.
"As CCT enters mainstream cardiology practice, we have to make sure our fellows are at least exposed to it, if not giving them enough training to allow them to interpret it. Introducing this in a form of a revision is actually a big deal," he said.
The ACC's quality initiative encompasses appropriateness criteria, laboratory accreditation, and possibly physician credentialing for CCT, cardiac MRI, nuclear cardiology, and echocardiography, said Dr. Stefan Achenbach, president of the Society of Cardiovascular Computed Tomography. The society announced in April that it would issue certificates to physicians who meet the ACCF/AHA Level II or III competency criteria for imaging interpretation and clinic supervision.
Impressive trial results have led some radiologists and cardiologists to recognize CCT as a new standard of care for patients with an intermediate risk for acute coronary syndrome, even without the reassurance of a randomized, multicenter trial. Researchers at the Erasmus Medical Center in Rotterdam, the Netherlands have confirmed that 64-slice CT rarely fails to diagnose significant coronary artery stenoses. On a per-segment basis among 35 patients with stable angina, its sensitivity and specificity for detecting 50% or greater stenosis were 99% and 96% respectively. On a per-patient basis, the sensitivity and specificity were 100% and 90% (European Journal Radiology 2006;16(3):575-582).
ACC abstracts demonstrating CCT's potential value in screening chest pain patients in the ER are encouraging, Achenbach said. But it is too early to draw conclusions from these pilot studies, although they did show that CCT speeds diagnosis and allows for earlier discharge of patients who have intermediate or low risk of myocardial infarction.
"This could be a tremendous application because about three million patients report to emergency rooms with chest pain every year," Achenbach said.
CARDIAC MR PROGRESS
With the spotlight focused on CCT, important cardiac MR findings have not attracted as much attention as in previous years. But the field is moving forward with discoveries that promise to expand MR's role for evaluation of dilated cardiomyopathy and myocarditis.
Researchers at Royal Brompton Hospital in London established a relationship between widespread patchy fibrosis in the myocardium detected with delayed-enhancement CMR and the risk of sudden cardiac death among patients with dilated cardiomyopathy. The delayed enhancement strategy revealed a midwall pattern of circumferential fiber, and follow-up outcome analysis showed fibrotic patients were significantly more likely to die or be hospitalized than patients without fibrosis, according to principal investigator Dr. Ravi Assomull. The work was presented at the 2006 Society of Cardiovascular Magnetic Resonance meeting.
Another research team, headquartered at the Robert Bosch Medical Center in Stuttgart, Germany, discovered that delayed-enhancement MR patterns are associated with viral causes of myocarditis. Imaging studies compared to histology showed that herpes virus tended to affect the septum and was more aggressive than parvovirus, which concentrated in the lateral wall.
Others have documented that T2-weighted CMR can delineate reversible and irreversibly infarcted myocardial tissue following coronary occlusion (Circulation 2006; 114: 1865-1870). The protocol, performed on dogs, promises a convenient alternative to Tc-99m-sestamibi for identifying such salvageable regions.
Lastly, a joint National Institute on Aging/Icelandic Health Association study has found that unrecognized myocardial infarction among elderly people is more common than previously thought. Delayed-enhancement MR revealed previous infarction among 21.7% of 458 Icelandic subjects, ages 67 to 95. By comparing this finding against hospital and registry records, Dr. Andrew Arai, principal investigator of cardiovascular imaging at the National Heart, Lung, and Blood Institute's cardiac energetics lab, concluded that the prevalence of unrecognized infarction was 12.5%.
