jueves, 19 de junio de 2008

Heart Disease Screening

EKG? Stress test? Echocardiogram? Nuclear stress test? Angiogram? CT scan? Which test is the best for checking for heart disease, also known as coronary artery disease (CAD)? The best way to look at the heart is directly. Short of an autopsy, there is no other way. So what do you do?

Thanks to modern medical technology a electron-beam computed tomography (EBCT) scan (also called fast CT) of the heart is able to show heart vessels coronary artery calcium (CAC), hard plaque that causes blockage. An angiogram/ cardiac catherization shows actual blockages. This is invasive requiring injection of dye into a main artery to view the coronary arteries, and is the gold standard for detecting CAD. The heart scans are noninvasive, and give a rather good look at CAC (hard plaque) in heart vessels which can also be a predict cardiac events like heart attacks.

The most current consensus document (2007) from the American
College of Cardiology Foundation and American Heart Association does not recommend the scan for asymptomatic people with a high risk of coronary artery disease, or for those at low risk, nor as a screening tool. It is considered reasonable in the asymptomatic with intermediate risk, and for the symptomatic person prior to an angiogram for definitive diagnosis.

The document also cites studies that compare fast CT with EKG stress test, nuclear perfusion scan, stress echocardiogram and angiogram. "The accuracy of fast CT was significantly higher than either treadmill testing or technetium stress in the diagnosis of obstructive CAD." Other studies included angiography (the gold standard), fast CT, EKG, and nuclear (with thallium and technetium) exercise stress testing. The fast CT correlated closer with the angiogram than the other tests especially if the CAC score from the fast CT was over 100. If arteries are occluded more than 50%, this will likely show on the fast CT. "Three studies have documented that CAC is a rapid and efficient screening tool for patients admitted to the emergency department with chest pain and nonspecific electrocardiograms."

So why are cardiologists continuing to pass on recommending the fast CT? Is it because it is more convenient for the doctor to do the other tests because they are more "readily available" like in the doctor's office or nearby hospital? It seems like a fast CT could be just as "readily available". Do they get paid more for these other tests that may yield less information like the specific areas where CAD may be localized?

The fast CT sounds too good to be true. Is it? Does it give more accurate information about heart vessel blockage in 10 minutes than the other tests mentioned, excluding the angiogram? I have been watching my vessels with fast CT for about 5 years now. I felt that my family history of heart disease and my risk factors warranted more than an EKG or stress test which have also been done. Both failed to correlate with the findings of the fast CT.