The coronary calcium score ( for example as done with a EBCT heart scan) is well recognized as a tool to estimate cardiac risk, a higher score meaning a higher risk.
Coronary calcification is by definition coronary artery disease. Calcification may be in the media of arteries or in the intima. Intimal calcification may be dense as is found in fibrous, basically stable plagues which are not prone to rupture and cause an acute coronary event. Spotty calcification can be found in soft, vulnerable plaques that are at risk of rupture.
Serial calcium scans on patients taking statins have shown increase in coronary calcification and yet there is more than abundant evidence that statins ( at least in secondary prevention) can reduce plaques and decrease the risk of coronary events,a situation referred to by some as the "statin paradox" or the "plaque paradox".
A possible explanation to this alleged paradox may be found in a study (1) from Cleveland Clinic in which the authors analyzed intravascular ultrasound images of patients from 8 clinical trials.
Patients with coronary artery disease treated with statins show an increase in coronary calcification.The so-called high intensity statins bring about more increase in calcification while also causing the greatest regression of plaques. The increase in calcification may be one mechanism by which statin therapy stabilizes plagues and makes them less likely to rupture. So serial calcium scans in a patient taking a statin demonstrating increased calcification may not be a warning of increased risk at all.
Quoting Cleveland Clinic's Dr . Steve Nissen:
"This is an important observation that tells us statins work to stabilize plaques by converting softer,cholesterol -laden plaques that are prone to rupture into more stable calcified plaques that are relatively inert.It explains the paradox of why serial measurements of calcium doesn't necessarily work to track the progression of disease and it explains to some extent how statins work.
Internists who like to talk about mechanisms and how things work may find this a compelling story but as an accompanying editorial (3) said this is a hypothesis generating study,causality cannot be inferred and the techniques used have multiple limitations. Human are pattern seeking story telling creatures and this story might catch on-at least until something better comes along.
Shifting gears-there are at least 3 articles that have reported that long time endurance exercisers have higher calcium scores than age matched sedentary controls controls,an observation offered by some authors as more proof that too much exercise is not good. Juxtaposed to that is the epidemiologic evidence that longtime endurance exercise decreases the risk of a coronary event and that elite athletes life longer than sedentary colleagues and yet more calcium in the athletes.Another plaque paradox?
Merghani and co-authors studied 152 maters athletes ( ages 51-63) They found that "most" )( 60%) of the lifelong exercisers has a normal CT coronary angiogram as did a similar number of the controls. However they also reported that the male athletes were more likely to have a CAC score of 300 or more compared to the sedentary controls.The plaques in the athletes were predominately calcific.
Similar results were reported by V.L. Aengevaeren et al (2) who studied 284 lifelong exercisers. In regard to their findings they said:
"The most active group did however had a more benign composition of plaques with fewer mixed plaques and more often only calcified plaques.These observation may explain the increased longevity of endurance athletes despite the presence of more coronary atherosclerotic plaques in the most active participants ".
Eijsvogels and co-workers published an excellent, detailed and extensively referenced review( 4) of the possible harmful effects of acute and chronic exercise . They only briefly mention what was then the preliminary evidence that longtime runners have higher calcium scores as their review preceded Puri's work as well as that of Aengevaren and Merghani
1.Puri, R Impact of statins on serial coronary calcifications during atheroma progression and regression. J Am Coll Cardio 2015;65, 1273-1282
2 Aengevaren VL et al The Relationship between lifelong exercise volume can coronary atherosclerosis in Athletes. Circulation 2017 april 27
3. Shaw LJ The Never Ending story on Coronary Calcium.Is it predictive,punitive or protective? Editorial Comment J of Amer Coll Cardio, 2015 ,65 no 15 1283-1285
4. Eijsvogels,TMN et al Are there deleterious cardiac effects of acute and chronic endurance exercise? Physiol Rev 96 99-125,2015
2 comments:
What is the point, then, of having a coronary calcium test?
I was not clear in my comments.
Coronary calcification(CC) by definition is coronary artery disease and does indicate a CV event risk is elevated above that in someone without CC.There is ample evidence that long time endurance athletes have increased coronary calcium scores.There is also good evidence indicating that long time endurance athletes seem to live longer than non exercisers and even longer than more moderate exercisers.DeFina's data indicated that life long exercisers did not show increased risk of CV events and seem to enjoy a lower allcause and CV death risk than non exercisers even though their CC scores were higher.Possible analogy to the observation that longer,and more potent statin use is associated with more CC but lower CV mortality.Statins are postulated to basically increase the "good type" of CC,which is calcium in the media of the artery and by some mechanism is associated with stabilization of plaques and decreased heart attacks. DeFina and the senior author,Ben Levine,suggest a similar mechanism may be at work in the high exercise group.
The 2018 ACA/AHA recommendation on use of coronary calcium determination was that it was useful in persons with intermediate risk of a CV event in regard to statin use and other risk modifications.Some find it useful in the evaluation of chest pain as a calcium score of zero has good negative predictive value.
James
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