Episode 136. Coronary Calcium Score with Dr Alistair Fyfe
The corner stone of cardiovascular disease prevention is the identification of high-risk asymptomatic individuals. In this regard coronary artery calcium is a highly specific marker of atherosclerosis and can be quantified using non contrast CT scanning which provides an accurate measure of atherosclerotic burden. Coronary artery disease is the single leading cause of disease morbidity and mortality in Australia and is responsible for approximately one in 10 deaths furthermore half the individuals with coronary artery disease will present with a myocardial infarction or death.
The compelling reason for undertaking coronary artery calcium scoring is to identify asymptomatic at-risk individuals who are likely to benefit from early detection, risk factor intervention and treatment of coronary artery disease.
In Australia risk assessment is recommended using the National Vascular Disease Prevention Alliance tool based on the Framingham Risk Equation. This risk stratification is drawn upon to guide the decision for calcium scoring which according to the Cardiac Society of Australia and New Zealand is recommended for asymptomatic intermediate risk patients or where there may be other strong evidence supporting its ability to improve cardiovascular risk assessment. High risk individuals may be better assessed by means of stress testing.
The calcium score is determined by non-contrast CT scanning and is complete within about ten minutes delivering just a little over 1 mSv of radiation equivalent to the annual background radiation we are exposed to. Using the Agatston method the volume and density of calcium is calculated and computed as a score. Again drawing upon The Cardiac society of Australia and New Zealand calcium scores may be interpreted as follows: A measurement of 0 is very low risk of coronary disease, a score of 1-100 is low risk, a measure of 101-400 is considered moderate risk and a patient lying within the 75th percentile of this group is at moderately high risk. Measurement over 400 denotes a high risk.
Multiple studies including the Multiethnic Study of Atherosclerosis (MESA) have confirmed the long-term prognostic value of CT calcium scores with over ten years of prospective follow up.
The value of calcium scoring lies in its ability to improve the accuracy of risk prediction. It helps to identify individuals who may benefit from more aggressive primary prevention measures; including the use of low dose aspirin that may otherwise not be recommended for primary prevention, as well as aggressive lipid management with statin therapies.
Given the importance of detecting asymptomatic coronary heart disease I was interested in pursuing the conversation further with one of the US expert cardiologists Dr Alistair Fyfe who has been practicing cardiology for over 38 years after graduation from the University of Tasmania.
Alistair has worked in Canada as well as the United States and is in Dallas, Texas where he has affiliations with Medical City Dallas and White The Heart Hospital Baylor Plano and is Medical Director of Blue Cross and Blue Shield of Illinois, Montana, New Mexico Oklahoma, and Texas not bad for a home-grown lad.
He is currently busy writing a contributing chapter to a soon to be published book titled: "The Implementation of Personalised Precision Medicine”, which, if I know Alistair will be excellent and a must read.
Given his expertise I was curious to learn a little more about its application and how a measured coronary calcium score should influence our approach to patient management.
I know you will find this conversation with Alistair very interesting. Please welcome him to the podcast.
References:
Dr Alistair Fyfe - on google and LinkedIn Coronary artery calcium in primary prevention
Chuah.www1.racgp.org.au When not to use calcium scoring
www.ausdoc.com.au Polonsky et al.
Coronary artery calcium score and risk classification for coronary heart disease prediction.