Calculating Cardiovascular Disease: How Well Do Your Risk Factors Predict Your Risk?
As time goes on, artery disease slowly and steadily gets worse, until the inflammation ("plaque") becomes vulnerable and dangerous. Risk factors are the forces that drive this disease forward. Since the 1960s, doctors have made valiant attempts to plug numbers into calculators to figure out someone's risk of having a cardiovascular event (a heart attack, stroke or sudden death). But do those risk calculators really work?
THE BIGGEST KILLER:
Cardiovascular disease means heart attacks, strokes and sudden death. We refer to these as "events." CV disease is responsible for 30% of deaths globally (1) and 33% of deaths in America every year (2). 40% of first events are sudden death (3). Recurrent events are fatal 40-50% of the time (2,3).
Every hour 17 Americans younger than 65 die from CV disease (2).
WHO IS SAFE?
Only about 5-10% of young and middle age Americans have no risk factors (4). 90-95% have at least one risk factor. The percentage of older Americans with one or more risk factors is even higher.
cholesterol can be normal:
Half of heart attack victims have a normal cholesterol (5).
When the vast majority of a population has risk factors, those risk factors lose their power to predict who will have an event. For example, if everyone smoked cigarettes, then cigarette smoking would disappear as a risk factor for lung cancer. This is why risk calculators based on risk factors like cholesterol values and blood pressure and weight are not very effective at identifying people who are at risk for CV events. Over 90% of Americans have risk factors (4). And we're gaining weight every year.
What about people who have no major risk factors? In a study of 1779 middle-aged people who had no major risk factors (non-smokers without high cholesterol or diabetes or high blood pressure), even though 95% had low risk by using risk calculators, 50% had sub-clinical atherosclerosis (6). By sub-clinical atherosclerosis we mean plaque that is not bad enough to cause obstruction, or not bad enough to need a surgical procedure. In the illustration above, only the "obstructive" plaque is considered surgically significant. "Vulnerable plaque" causes most heart attacks.
The major risk calculators use risk factors from population studies to calculate the probability of having events like heart attacks or strokes. Although risk calculators have been validated with large populations, using them for an individual can give a false sense of security. Risk calculators are not as sensitive as looking directly at the arteries (7, 9-11). Even so, risk calculators are popular with doctors (8). Risk calculators can never answer the question, "Do I have artery disease?" Artery tests can.
do you have artery disease? look at the arteries
A heart calcium scan, with the proper equipment and technique, is more sensitive than risk calculators (7, 9-11).
There are two good non-invasive ways to assess how much plaque is in the arteries: CT calcium scores and ultrasound.
CT calcium scans can’t find calcium if your plaque hasn’t calcified yet. They can miss artery disease in patients younger than 45.
Another problem with CT scans is that they are currently being done by many hospitals with older sub-standard equipment. When the CT detection ring moves around the patient's chest too slowly, because the coronary arteries are in motion with every heart beat, pictures of the arteries can be blurred by "motion artifact." So these slower CT heart scans are not as sensitive in detecting calcium as the Electron Beam CT (EBCT) with no moving parts, which captures images at the speed of light. These old out-dated CT machines are (like stress tests and executive physicals) often giving high-risk patients a false sense of security by the telling them their arteries are OK, when their actual calcium scores are much higher.
After screening mammograms locate calcified lesions in the breast, ultrasound technology is employed to get a better picture of the actual breast tissue. In the same way, we use ultrasound technology to get a close-up picture of plaque in the peripheral arteries after calcium has been identified by screening CT heart scans. Combining the CT information from the heart arteries with the ultrasound data from peripheral arteries provides the most thorough and comprehensive non-invasive trending technology available today.
The most important question a doctor can ask is whether plaque is getting worse with therapy, or getting better. When we follow the effects of lifestyle and bio-marker changes on the actual plaque itself, our therapeutic decision-making process has the traction that can only come from the linking together of cause-effect relationships. This is the power of personalized medicine.
CardioSound can help determine if you are at risk.
Why has early screening (looking for heart disease before a heart attack) been so controversial?
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World Health Organization http://www.who.int/mediacentre/factsheets/fs317/en/index.html
National Vital Statistics Reports, 61:4 May 8, 2013 Data is available at the National Center for Health Statistics website: http://www.cdc.gov/nchs/deaths.html
Christian T. Ruff, et al. Long-term risk and prognosis of recurrent cardiovascular events in the REACH registry. J Am Coll Cardiol. 2012;59(13s1):E1521-E1521. doi:10.1016/S0735-1097(12)61522-8
Stamler, et al. Low risk-factor profile and long-term cardiovascular and non-cardiovascular mortality and life expectancy: Findings for 5 large cohorts of young adult and middle aged men and women JAMA 1999:282:2012-2018
Sachdeva et al. Lipid levels in patients hospitalized with coronary artery disease: an analysis of 136,905 hospitalizations in Get With The Guidelines. Am Heart Journal. 2009;157(1):111-117.e2.
Fernández-Friera L et al. Normal LDL-cholesterol levels are associated with subclinical atherosclerosis in the absence of risk factors. J Am Coll Cardiol 2017 Dec 19; 70:2979. (http://dx.doi.org/10.1016/j.jacc.2017.10.024)
Framingham-based risk calculators tend to miss too many high-risk people. Doneen AL, Bale BF, ISA June 15, 2009
A recent task force paper reviewed the evidence for screening by using EKGs, nuclear stress tests and stress echocardiograms to find coronary disease in low-risk patients with no symptoms. They found no evidence supporting the use of these methods. They failed to address the well-documented evidence for screening by using CT heart calcium scans, but they did recommend using risk calculators. Chou, Cardiac screening with electrocardiography, stress echocardiography or myocardial perfusion imaging: Advice for high-value care from the American College of Physicians. Ann Intern Med. 2015;162:438-447
This excellent prospective study of 44,000 patients with no symptoms and no history of coronary disease compares the relative predictive value of risk factors versus heart calcium scores. "Our study findings support a paradigm shift in CVD risk assessment from RF-based (risk factor) approach to detection of sub-clinical atherosclerosis burden as evident by the fact that a significant proportion of those with no RF (risk factors) have a severe amount of coronary atherosclerosis and have a high risk for all-cause mortality. The higher precision of CAC (coronary artery calcium) relative to RFs (risk factors) for identifying at-risk individuals may be because of the fact that CAC is a measure of actual disease that occurs further down the causal pathway than the presence of RFs that are mere surrogates for this process." (parentheses and italics added) Nasir, et al. Interplay of coronary artery calcification and traditional risk factors for the prediction of all-cause mortality in asymptomatic individuals. Circ Cardiovasc Imaging. 2012;5:467-473
The MESA trial showed that the heart calcium score “alone was better than all the other risk factors combined for risk prediction.” Sharma, et al, Cardiac risk stratification: Role of the coronary calcium score. Vasc Health Risk Manag. 2010; 6: 603–611. Published online 2010 Aug 9. PMCID: PMC2922321 PMID: 20730016
Quote: “Our data suggest that the presence of CAC (coronary artery calcium) is associated with increased CHD eventw (all and hard) across all levels of RF (risk factor) burden, even among individuals with no RFs. In contrast, among the 50% of the population with CAC0 (no calcium), although RFs are associated with higher relative risk, the absolute risk of a CHD event over mean 7.1 years of follow-up in this group remains low.” We would add this caveat: Low risk doesn’t mean no risk. We do see people have events with 0 calcium scores. Silverman, et al. Impact of coronary artery calcium on coronary heart disease events in individuals at the extremes of traditional risk factor burden: the Multi-Ethnic Study of Atherosclerosis European Heart Journal (2014) 35, 2232–2241 doi:10.1093/eurheartj/eht508