Ask someone about their cholesterol level and the odds are pretty good that they can at least tell you whether their cholesterol is “normal” or “high”. Knowing your cholesterol level has become virtually synonymous with predicting whether you are at risk for a heart attack or stroke. But the reality is that using your cholesterol level to predict the presence of atherosclerosis is actually a bit less effective than saving yourself the pain of a needle stick and just flipping a coin instead. Now, a study published this month in the Journal of the American College of Cardiology found that more than half of individuals considered to be at low risk had evidence of plaque developing in their arteries.
The study looked at 4,184 participants who were considered to be at low cardiovascular risk. That means that they had a total cholesterol level below 240 with and LDL cholesterol below 160 and an HDL level above 40. They also had a normal fasting blood sugar (below 126) and a normal blood pressure (below 140/90). None of the participants were smokers. In general, people in this group would be considered “low risk” and would not be told that they should be taking medication, such as a statin, to lower their risk factors.
A smaller sub-group of 740 participants had very low risk factor levels. These participants had a blood pressure below 120/80, a fasting blood sugar below 100 and total cholesterol less than 200.
The researchers used ultrasound of the carotid artery , iliofemoral artery and abdominal aorta along with Coronary Calcium Scans to identify the present of atherosclerotic plaque.
What they found was that 49.7% of the participants with no cardiovascular risk factors has detectable plaque in their arteries. And, the average age in this group was only 45 years old!
Among those who were considered “low risk” the researchers “identified subclinical atherosclerosis in nearly 60% of middle-aged individuals classified as low risk according to traditional risk scales, with multiple vascular sites affected in 41%.” Clearly, these findings show a significant disconnect between conventional cardiovascular risk factors and the presence of atherosclerosis.
Treatment guidelines to date have mainly focused on treating those patients with high risk as measured by those conventional risk factors rather than looking directly at the arteries to determine the presence of plaque. But it is plaque that causes heart attacks and stroke and, as this study demonstrates, your blood tests just don’t adequately predict the presence of plaque. Imagine you have two patients, one with a cholesterol of 270 and the other with a cholesterol of 160. A Coronary Calcium Scan shows that the patient with the higher cholesterol has no detectable plaque and is therefore at very low risk for a heart attack. The patient with the lower cholesterol has extensive plaque on his scan and is at high heart attack risk. The treatment guidelines say you should only prescribe a statin to the high cholesterol patient. He probably won’t benefit from it. Meanwhile, you are going to have to explain to the low cholesterol patient why he eventually had a heart attack that you didn’t think needed to be prevented.
In an editorial accompanying the study Drs Vijay Nambi and Deepak Bhatt suggest that it is “Time to Take a Selfie” of our arteries to directly look for plaque rather than guessing at it with risk factors. As the authors state, “this elegant analysis…demonstrates that subclinical atherosclerosis is highly prevalent, even in individuals with ‘normal’ values for conventional cardiovascular risk factors”. They further state that “the findings from the current analysis underscore the need to start using advances in imaging, biomarkers and genetics to re-examine the definition of ‘optimal’ cardiovascular health”.