Angiography: CT not as effective as conventional

There is no conclusive evidence that CT angiography is life-saving

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Every physician who advertises CT angiography points out that it is painless and takes less time

Risks from radiation exposure are significant when radiation is used for mass screening

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Whole-body CT scanning technology fell by the wayside thanks to the uncompromising stand of professional associations and regulatory agencies which highlighted its dangers. But some specialists widely practise cardiac CT tests such as calcium scoring and CT angiography though independent assessments have not proved their effectiveness.

During conventional angiography, the physician threads a thin catheter through the groin artery into the heart, injects a contrast medium and takes x-ray pictures.

These pictures show whether narrowing or blockages in the artery impede the flow of blood. For those with severe blockage, the options are angioplasties possibly with insertion of stents or bypass surgeries.

Risk of bleeding

During cardiac catheterization, there is some risk of bleeding, and a tiny risk for major complications, such as heart attack, stroke, even death.

Every physician who advertises CT angiography points out that it is painless, takes less time and is an attractive option. According to the New York Times, more than 1,000 cardiologists and hospitals installed CT scanners in the U.S. There is undeniable financial incentive to order too many of these tests.

A comparison

The owners argue that the test is cheap, at about $600, paid for by insurers as against $ 4,000 for a cardiac catheterization done at their local hospital.

However, there is no conclusive evidence that CT angiography leads to treatment that saves lives (Health Affairs, Nov/Dec 2008). Conventional angiography remains the gold standard.

Risks from radiation exposure, though small to an individual, are significant when radiation is used for mass screening. There was broad consensus that radiation exposure from CT is of concern.

In India, certain private hospitals advertise CT angiography as very beneficial; none of them refers to radiation risks. Everyone praises the technology. A private hospital used a letter from a member of the faculty of a premier medical research centre to substantiate correlation between CT angiography and conventional angiography!

I sought his reaction to this crude anecdotal approach.

“I routinely write letters to people who have done investigation and what I have done was just to let them know what was the outcome.

“I did not think in my wildest dream that they will utilise it to advertise my letter. I was not aware of it. They are commercial organisations and medicine in a private hospital has become good money making art/business,” he responded to my e-mail.

Pro-screening physicians formed the Screening for Heart Attack Prevention and Education (SHAPE) task force. They want non-invasive imaging of all asymptomatic men (aged 45-75 years) and women (55-75years) except those at very low risk (Archives of Internal Medicine, May 26, 2008).

Evidence of the effectiveness of this recommendation is scanty. These specialists propose the existence of “vulnerable plaques.” The difficulty is that CT cannot identify them.

No clinical utility

“I do not think ‘vulnerable plaque’ has been shown to have any clinical utility,” Dr. Rita Redberg, Professor of Medicine at University of California, San Francisco, responded when I sought her views on promotion of CT by the Indian private hospitals and the SHAPE guidelines.

CT angiography is not as effective as conventional angiography. Those knowledgeable in the field must take the lead in exposing the tendency of hospitals to exploit the “worried well.”