Thursday, October 10, 2013

What is CIMT's Role in Screening for Heart Disease?

It turns out that those with diabetes, chronic kidney disease or rheumatoid arthritis (RA) have a greater risk of heart disease than those without.  But how do you separate those with heart disease from those without?  You can't go about giving everyone a stress test which only turns positive if there's reversible ischemia (loss of blood flow).  And you can't go about giving everyone a coronary artery calcium (CAC) scan which only looks for calcium deposition, possibly prior to onset of ischemia, especially due to the radiation exposure.  Besides, earlier studies have suggested that knowledge of one's CAC score doesn't impact or change our lifestyle.  And after all, isn't that why we do tests?  Because the results will change our decision making?

So we're looking for a (repeatable) method to screen for subclinical atherosclerosis since a lipid panel, even with newer markers, isn't enough to accurately predict one's risk.  It turns out that carotid ultrasound, especially for carotid intima media thickness (CIMT) fits the bill as it is easily performed, non-invasive, repeatable & requires no ionizing radiation.  The bigger question then is how well does it detect subclinical atherosclerosis?

In a study to be published next month in the Annals of Rheumatic Disease, the authors concluded that CIMT is better than CAC at detecting subclinical atherosclerosis in patients with RA.  To arrive at their conclusion, the authors studied 104 patients w/RA for 11yrs on average who had no history of heart disease.  23 of 40 patients were found to have carotid disease despite having CAC score of 0 while 29 of 38 patients w/CAC 1-100 had severe carotid disease, using CIMT greater than 0.9mm as cut off.  Using other calculators for heart disease risk, carotid ultrasound identified 70 of 72 who met definition for high risk.

Current appropriate use guidelines don't recommend CIMT for low risk or high risk patients, nor for serial monitoring.  However, we may soon find it to be useful in those disease populations with greater risk than average.  Of course, this restriction is when someone else has to foot the bill.  It only costs $150-200 if you can afford to pay out of pocket.  Good peace of mind, if you ask me, but again, only if you're willing to commit to a lifestyle change if subclinical atherosclerosis is found.  As for me, I don't need a test to tell me what I should be doing anyway. 

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