Are Heart Scans Suitable for Everyone?

Often a patient may be suspected of having symptoms of heart disease , diagnostic tests such as computed tomography (CT) angiograms or nuclear stress tests may be recommended by their medical practitioner.

Being a heart-imaging test , a coronary CT angiogram can detect whether fatty or calcium deposits have accumulated in the arteries, which supply blood to the heart muscle. Whereas nuclear stress tests can find out if there is a lack of blood flow in the heart muscle, which could mean a blockage in a heart artery.
However, in a scientific advisory released on February 2, 2009 in the Journal Circulation by the American Heart Association (AHA) suggested that doctors must use these tests with discretion and avoid screening their patients frequently for cardiac problems . Doctors are also advised to weigh risks and benefits before they recommend their patients since even such low-dose radiation does has the potential to cause cancer.
The AHA points out, heart scan recommendation should not be given to a patient who is at low risk of having heart disease and who does not have symptoms of heart disease. Doctors should have careful consideration and advice their patients for cardiac imaging only when this would potentially benefit the patients.
It definitely is not the intention of the AHA to scare the public that these diagnostic tests are dangerous and should not be used at all. What they mean is that the right tests should be used in the right patient.
Medical imaging techniques are the largest source of controllable radiation exposure of Americans, and so doctors must be aware of the potential harm from even small doses of radiation
As far as possible, doctors should tackle clinical question from their patients without using ionizing radiation. However, if the doctors are certain that ionizing radiation is necessary, they should make every effort to minimise the radiation dose.
In United States, there is no federal regulation of radiation dose, the only exception being for mammograms (for breast cancer). It is left to the doctors and medical facilities to determine the appropriate use of the scanning equipment and radiation dose .

Is Cardiac CT Angiography a Proper Substitute for Conventional Procedures?

In a study by researchers the conclusion was that - Cardiac CT angiography misclassifies diagnosis of coronary stenosis in too many patients to replace conventional invasive imaging. The noninvasive technique had a diagnostic accuracy of 93% for coronary obstruction and identified patients who subsequently underwent revascularization at least as well as conventional angiography (area under the curve 0.84 versus 0.82, P=0.36), Joao A.C. Lima, M.D., of Johns Hopkins Hospital, and colleagues found in a prospective, international trial of symptomatic patients. CT angiography's positive predictive value of 91% and a negative predictive value of 83% didn't measure up, they reported in the November issue of the New England Journal of Medicine.

The 13% misclassification indicates that "multidetector CT angiography cannot be used as a simple replacement for conventional coronary angiography,".

Earlier studies on CT angiography have had widely varying results for determining coronary obstruction , likely because of limitations in selection of patients, small sample size, single-center study design, and CT technology .

This study compared 64-row, 0.5-mm multidetector CT angiography and conventional coronary angiography in 291 patients referred for conventional angiography because of suspected symptomatic coronary artery disease .

The participants underwent blinded calcium scoring and CT angiography before conventional coronary angiography and only those with calcium scores of 600 or less were included in the study.

Another area to examine is the fact that cardiac imaging leads to unnecessary procedures and the "equipment bombards patients with radiation many orders of magnitude greater that that of traditional radiographs ."

The findings could not answer questions of use in asymptomatic patients, the results should not be used to support screening for asymptomatic coronary artery disease