PHILADELPHIA – The American College of Cardiology Foundation and the American Heart Association have endorsed stepwise guidelines for using nuclear imaging to manage and diagnose heart failure, but they do not obviate the need for the hands-on patient examination, said Dr. Alfred Bove of Temple University, Philadelphia.
“The beginning of management of a patient with heart failure is clinical,” Dr. Bove said. “We have to understand the patient's status. I always think it's important to put a stethoscope there first.” That provides a basis for interpreting data generated by subsequent imaging, as called for in the ACCF/AHA guidelines (J. Am. Coll. Cardiol. 2009;53:1343-832), he said.
“The first thing we're trying to understand is both the etiology of ventricular dysfunction and actual function when a patient shows up with symptoms of congestive heart failure to determine whether it is ischemic, dilated, valvular, or congenital,” he said. “We need imaging to sort out these etiologies.”
Ejection fraction is a key measure to determine left ventricle function, as are left ventricle dimensions, he said. “We are always looking at diastolic dimensions in particular; the degree of hypertrophy; whether there's any evidence of coronary disease or coronary stenosis or valvular stenosis or insufficiency; and finally, with congenital heart disease, the presence of shunts.”
The guidelines first recommend obtaining a two-dimensional echocardiogram. “It will tell us what the ejection fraction is, and tell us about valve size and function,” he said
The guidelines then “jump” to radionuclide ventriculography to assess ejection fraction and volume. In a patient with ischemic cardiomyopathy, coronary arteriography can help evaluate indications for revascularization, he said.
In the patient with no history of coronary disease, myocardial perfusion imaging (MPI) can determine the presence of perfusion defects. “We can use that as a basis to go forward to do some further studies,” he said. But in the patient with nonischemic cardiomyopathy and no history of coronary disease, MPI can also have a high number of false-positive readings. “We're more interested here in getting ejection fraction and some measure of heart size from the imaging as well as perfusion,” Dr. Bove said.
The guidelines also call for appropriate follow-up with gated SPECT (single-photon emission CT) or MUGA (multiple gated acquisition) because echocardiography is inconclusive in about 20% of patients, particularly those who are obese or have large chests, Dr. Bove said. “In many cases [when] we see someone with borderline ejection fraction, we send that person for a gated scan and it comes back normal,” he said.
A gated SPECT or MUGA scan provides an “important second backup in left ventricle measures,” particularly in patients whose echocardiograms are of poor quality, he said.
In cases of suspected ischemic cardiomyopathy, the ACCF/AHA guidelines call for coronary CT angiography. “This has a very good negative predictive value,” Dr. Bove said. “If we get a negative CT angiogram, we can be pretty comfortable in saying this is not an ischemic cardiomyopathy.”
When the case mandates further study, MRI can help evaluate structural anomalies in the myocardium. “When there's a question of etiology in the absence of coronary disease, the MRI becomes very important in assessing the etiology of the myocardial dysfunction,” he said.
Dr. Bove disclosed that he is a consultant to Insight Telehealth Systems.
In cases of suspected ischemic cardiomyopathy, the guidelines call for coronary CT angiography.
Source DR. BOVE