December 10th, 2013
Co-Chairs of CVD Risk Guidelines Discuss a Difficult Case
University of Utah cardiology fellow Eric Lindley presents a challenging case to the co-chairs of the new 2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk: David Goff, Dean of the Colorado School of Public Health, and Donald Lloyd-Jones, Chairman of the Department of Preventive Medicine at Northwestern University.
Lindley: My patient is an asymptomatic 38-year-old white male who comes to the office concerned about his future CV risk. He is a lifetime nonsmoker and takes no medications. Asymptomatic and very active, he frequently rides his bike to and from work, and spends his weekends hiking and camping. By trade, he is a horticulturist, eats out of his garden in Oregon, and eats red meat approximately once a week.
The patient has a significant family history of early atherosclerotic disease. His father, uncles, and grandfathers had either an MI or a CABG when they were in their mid-to-late 40’s. His physical exam is unremarkable, with a normal BMI and blood pressure (systolic blood pressure <125 mm Hg). His total cholesterol has ranged over the last five years from 200-240, with his LDL <190, and his HDL hovering around 35-40.
He is reluctant to start a statin at this age, as he doesn’t want to start a medicine he’ll need for life unless the benefits truly outweigh the risk. Using the new lipid guidelines and risk calculator, his lifetime CVD risk is estimated at 50%. However, until he is age 40, no 10-year risk is calculated. Estimating for him in the future, and only changing his age in the calculator, leaving all other numbers the same, his 10-year CVD risk isn’t above 7.5% until he’s 53. Yet a significant number of his relatives have already had their events by the time they were 53.
Would you start a statin based on his lifetime risk alone?
Goff: I would be reluctant to recommend a statin based on his lifetime risk estimate alone, primarily because he expresses reluctance to take a life-long medicine at this point, he appears committed to a healthy lifestyle, and his short-term risk and short-term benefit are both estimated to be low. I would reinforce a healthy lifestyle and try to help him reduce his cholesterol further. You stated that his blood pressure is normal. If it were higher than optimal, that is, higher than 120 systolic or 80 diastolic, I would include an emphasis on the blood-pressure lowering benefits of more intensive lifestyle change to motivate adherence.
Lloyd-Jones: This is a very interesting scenario, and this is the kind of patient I encounter very frequently in my preventive cardiology clinic. First and foremost, we must respect his family history. This kind of premature CVD family history is not particularly well represented in any risk assessment approach from the broad population. He must be congratulated on trumping as much of his inherited risk as possible by following the healthy lifestyle he follows. He sounds like he is quite active and currently asymptomatic at a good workload. That he has stayed lean (“normal BMI”) is a good sign. If he wants to avoid medication, he should certainly be offered a referral to a nutritionist or dietician to explore options, explicitly including a vegan diet. But, at this point, I would not start a statin based solely on the lifetime risk estimate.
Would you wait until his 10-year risk exceeded 7.5% to start a statin?
Goff: Given his strong family history, I am concerned that the risk calculator might under-estimate his risk. All risk estimates are averages for people with the same values of the risk factors that are included in the model, but no one really has 7.5% of a heart attack or stroke. The patient will either have an event or not during the 10-year period. From that point of view, it is all or nothing!
The challenge is that it is difficult to predict who will have the event and who will not in a group with any specified level of risk, and when we examined the contribution to risk prediction of information regarding family history, that added value was quite small for the general population. Of course, most people don’t have the very strong family history of this patient. For him, I would be interested in discussing disease screening, especially if we were not able to achieve substantial reductions in his cholesterol through lifestyle change.
Lloyd-Jones: Let’s think about his risk. I would start by plugging in his risk factor levels with an age of 40. Recognizing that we have not quantitatively considered his family history, I get 10-year risk estimates in the range of 1.4% to 2.4% (if he were black it would be as high as ~3.1%). Lifetime risks are in the range of 46-50%. This is not where we prescribe a statin per the guidelines (despite what the media seems to think), this is where we start the risk discussion. And this is very much how I practice.
As you know, the guidelines provide 6 different things that should potentially be considered to color in our risk assessment. In this framework, the first 3 questions to ask, before we consider any additional testing, are:
- Is his LDL >160? Sounds like it sometimes is, so I would take this as an indicator that we should consider a statin now.
- Does he have a strong family history of premature CVD? Unequivocally, yes. This, for me as his physician, would provide strong justification for a statin now.
- Does he have a higher lifetime risk? I would say unequivocally, yes.
At this point, I would provide him with all of this information, answer any questions, and indicate that, on balance, I would favor starting a statin now. But first I would tell him my read on the statin safety data.
Would you do further testing such as an hsCRP or CAC score to determine his risk and possible need for a statin?
Goff: The Risk Assessment and Cholesterol Guidelines provide advice on how to proceed when one is uncertain about a risk-based treatment decision. We recommend that clinicians consider using information about several factors: family history of premature CVD, LDL-C > 160, lifetime risk, hsCRP, ABI, and CAC.
I am especially intrigued by the potential value of disease screening using CT to detect CAC. We know that people without CAC are at very low risk for clinical events, and people with CAC are at much greater risk. If he were interested in pursuing additional testing, I would consider getting a CAC score. Even without the CAC score, he has a very strong family history and a fairly high lifetime risk. If his LDL-C were to remain greater than 160 despite focus on a healthy lifestyle, the guidelines provide support for a decision to start statins. The risk-benefit discussion will be critical for this patient, because his short-term benefit is likely to be low, but his long-term benefit is likely to be great.
Lloyd-Jones: If he is still reluctant to take a statin, or would like to make our decision-making a little more concrete, here is what I would do next:
- Although these tests are mentioned for potential consideration in the guidelines, I would not personally measure CRP (too nonspecific) or ABI (very low yield at this age) in him.
- Off guidelines, I would next offer him a Lp(a) measurement. If that is high (>30 or so; which I suspect will be the case, given his family history), I would urge statin therapy. Lp(a) is actually our highest yield test for heritable premature CVD and I believe it would indicate intensive statin therapy if high in this scenario.
- If the Lp(a) is not elevated, or he is not convinced enough to start a statin in the instance that Lp(a) is high, I would offer him a CT scan for CAC scoring. This would be an important test, in many ways definitive for decision-making in such a scenario. In fact, this is the situation when I tend to use CAC scores. The average white male develops CAC at an age of 53 years, so if he has CAC now he is way ahead of his age/sex/race cohort and it would indicate a sufficient burden of coronary atherosclerosis to consider him at very high risk in the nearer term. If his CAC score is zero, this would be very reassuring that he should be at very low risk (<1%) for the next 5-10 years. I would feel compelled to tell him that he will have to pay out of pocket for the CAC score (typically $75-$300) and that there is some radiation exposure, typically equivalent to ~2 chest x-rays). If we can buy him 5 years, there might well be other medication options for risk reduction other than statins.
If, after all of this, he still does not want to take a statin, I would at least feel I had offered him the best possible information to help him make his decision. Regardless of his decision, optimal lifestyle modification must remain a critical component of his prevention regimen.