MKSAP quiz: Primary prevention

This month's quiz asks readers to evaluate a 69-year-old man with hypertension, atrial fibrillation, and type 2 diabetes to choose appropriate primary prevention for cardiovascular disease.

A 69-year-old man is evaluated during a routine visit. He is asymptomatic. Medical history is remarkable for hypertension, atrial fibrillation, and type 2 diabetes mellitus. He has a 25-pack-year smoking history but quit smoking 3 years ago. Medications are amlodipine, metoprolol, rivaroxaban, and atorvastatin.

Physical examination, including vital signs, is normal.

His estimated 10-year risk for atherosclerotic cardiovascular disease (ASCVD) according to the Pooled Cohort Equations is 14.6%.

Which of the following is most appropriate for primary prevention of ASCVD in this patient?

A. Add aspirin
B. Add fish oil
C. Switch rivaroxaban to aspirin
D. No further intervention

MKSAP Answer and Critique

The correct answer is D. No further intervention. This item is available to MKSAP 18 subscribers as item 78 in the General Internal Medicine section. More information about MKSAP 18 is available online.

No further intervention is the most appropriate management of this patient. Although he has a 10-year risk for atherosclerotic cardiovascular disease (ASCVD) of 14.6%, he is at high risk for bleeding with the addition of aspirin therapy. The U.S. Preventive Services Task Force recommends low-dose aspirin for the primary prevention of ASCVD and colorectal cancer in adults aged 50 to 59 years with a 10-year ASCVD risk of 10% or higher who do not have an increased risk for bleeding, have a life expectancy of at least 10 years, and are willing to take low-dose aspirin daily for at least 10 years. Patients aged 60 to 69 years may also benefit from aspirin; however, the net benefit is smaller because of the increased risk for bleeding in this population. In addition to increasing age, male sex and use of anticoagulants or NSAIDs increase the risk for bleeding. Many patients with cardiovascular disease who are eligible for secondary prevention with aspirin therapy also require long-term oral anticoagulant therapy for atrial fibrillation. In these patients, the addition of aspirin to anticoagulant therapy provides some additional protection against cardiovascular events, but the risk for major bleeding is significantly increased. Aspirin is not generally recommended in these patients, and the American College of Cardiology/American Heart Association specifically recommend against the use of low-dose aspirin for primary prevention in patients at increased risk for bleeding, including those on anticoagulant therapy. Although this patient's risk for ASCVD is higher than 10%, he is already receiving anticoagulant therapy with rivaroxaban; therefore, the potential benefits of aspirin therapy for primary prevention of ASCVD are likely outweighed by the increased risk for bleeding.

High doses of fish oil increase bleeding time in vitro by suppressing platelet-activating factor, but this mechanism has not been associated with higher rates of clinical bleeding, even when the supplement is combined with aspirin or warfarin. However, a 2018 systematic review concluded that omega-3 fatty acid supplementation does not reduce heart disease, stroke, or death; therefore, fish oil supplementation cannot be recommended.

Switching rivaroxaban to low-dose aspirin is not recommended because this patient is at high risk for atrial fibrillation–related stroke. For this patient, anticoagulant therapy is significantly superior to aspirin in reducing his risk for stroke.

Key Point

  • In the primary and secondary prevention of cardiovascular events, the addition of aspirin to long-term anticoagulation is associated with significantly increased bleeding events and is not routinely recommended.