Remember in the original Star Trek series when anyone was feeling under the weather, Dr. McCoy would use a handheld machine to instantly diagnose the patient's medical woes? The latest example of how advanced medical applications have merged with the realm of futuristic science fiction is the use of faster, more robust computed tomography (CT) scanners that allow snapshots to be taken of rapidly moving structures and diagnose disorders which heretofore were best evaluated through invasive techniques and/or indirect means. This new CT technology will have the biggest impact on the diagnosis and treatment of coronary artery disease and will significantly change how we practice medicine in the years to come.
Coronary artery disease (CAD), also known as atherosclerotic heart disease, is narrowing of the blood vessels that supply the heart muscle with blood and oxygen. It remains the leading cause of death in the United States with 1 person dying from a CAD-related event each minute. Clinical manifestations of CAD include sudden death, myocardial infarction (aka, heart attack), and stable and unstable angina pectoris. Unfortunately for patients and physicians, the disease does not always present in a characteristic way. The classic presentation is crushing substernal chest pain/pressure. However, there are many other diseases that mimic the symptoms of CAD, and CAD can manifest without chest pain in up to a third of patients. Because of the protean symptoms and current workups of this disease, small but significant subsets of the 6.5 million U.S. patients who present to the emergency department each year with chest pain are either admitted unnecessarily for observation or erroneously discharged.
In the past, work-up for CAD has traditionally involved careful history and physical followed by EKG, blood work analysis, echocardiography, and nuclear medicine stress testing (all of which assess indirect evidence of vessel stenosis/occlusion by evaluating for cardiac muscle damage). Traditionally, those patients with atypical or indeterminate results from the above exams have gone on to coronary angiography, which requires placement of a small catheter from the groin or arm through the arterial system of the abdomen and/or chest followed by catheterization and injection of contrast material directly into the arteries that supply the heart. Ultimately, 40-50% of patients who undergo this at least semi-invasive test demonstrate normal coronary arteries, indicating that their chest pain is not arising from CAD. If only there was a reproducible, non-invasive test for excluding patients that do not have the disease, the cost, length of stay, and potential complications associated with cardiac catheterization could be diminished. Enter coronary computed tomographic angiography (CCTA).
CCTA is the new CT technology alluded to above which allows direct visualization of the coronary arteries without the risks associated with catheter placement into the arterial system as the contrast in CCTA is injected into an arm vein instead. It allows rapid identification of presence/absence, extent, and characterization of CAD as well as other potential deadly diseases that also cause chest pain, such as pulmonary embolism, congenital vascular anomalies, or thoracic aortic dissection.
This new technology, while still very promising, is not without its faults: itís technically demanding with little room for error, requires the injection of intravenous contrast material, often involves a higher radiation dose than a standard CT of the chest, may require slowing of the heart rate with medication, and cannot consistently image patients with atrial fibrillation, pacemakers, or who are morbidly obese. But despite these (probably temporary) shortcomings, we truly are one step closer to Star Trek.
For more information about Coronary CT Angiography, click here.