Thursday, April 27, 2006

Screening for CAD: Part 1

Coronary artery disease (CAD) is a disease that kills. It is certainly the no 2 killer in Malaysia. Road traffic accidents are number 1 and we should do something about those too. Although we know so much about it, we do not know the cause. It is likely to be a combination of factors and genetics. Since we do not have a single cause, we are unable to find a cure, and so we are left with a strategy of trying to work out all the risk factors and try and get rid of the risk factors, in an attempt to reduce the incidence of CAD.

To add to our difficulty, we know that not all atheromas are the same. Some atheroma are "safe" atheromas and some are vulnerable atheromas. Vulnerable in the sense that they are the ones prone to cause a heart attacks. We use to think that vulnerable plaques rupture to cause heart attacks (coronary thrombosis). That may not be the only mechanism. We also know that some plaques erode, and the dowstream thrombus occlude smaller coronary branch vessels to cause an infarct (heart attacks), mostly of the subendocardial variety (by the old nomenclature) or NSTEMI by the current nomenclature.

The task remains as to how to halt this disease. Screening of asymptomatic adults, males above 40yrs and females above 50 yrs, is one way, paying particular attention to those with 2 or more coronary risk factors (refer to earlier article on coronary risk factors and prevention). As written earlier, screening test include the ECG, stress ECG, stress Echocardiogram, stress radionuclide scans, CT coronary angiograms and MRI coronary angiograms. The last two are still undergoing tremendous improvement and refinement. The first 5 screening test named, will certainly help to detect significant atheromas, but does not seperate the vulnerable ones. There is much work using the MRI coronary angiogram to define vulnerable plaques, and the work certainly look promising. The work on using CT coronary angiogram to identify soft plaques is still very early and certainly needs much improvement.

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