A new tool for doctors and patients will help predict how well four preventive therapies affect long-term risk of heart attacks and strokes, according to a special report published Friday by the American College of Cardiology and the American Heart Association.

The risk assessment tool, developed by the U.S. Department of Health and Human Services’ Million Hearts Initiative and the Centers for Medicare & Medicaid Services, allows a patient’s risk to be updated based on how they respond one or all four preventive therapies. It will be used in a federal study to determine whether financially rewarding doctors for reducing their patients’ risk results in fewer heart attacks and strokes.

Launched in 2012, the Million Hearts Initiative aims to prevent 1 million heart attacks and strokes by 2017  by emphasizing aspirin therapy, blood pressure control, cholesterol management and smoking cessation, known as the ABCS. It is led by the Centers for Disease Control and Prevention and CMS, and is supported by the AHA and ACC.

Each year, about 750,000 Americans have a heart attack  and nearly 800,000 have a stroke. Heart disease is the No. 1 cause of death in the United States, and stroke is No. 5.

The panel that developed the tool was led by Donald Lloyd-Jones, M.D., and David Goff, M.D., Ph.D., who this month becomes director of the National Heart, Lung, and Blood Institute’s Division of Cardiovascular Science. The pair also headed the ACC/AHA panel that created the risk assessment model released in 2013 as part of the organizations’ prevention guidelines.

The Million Hearts assessment tool will be used in a five-year study  that looks at Medicare patients at very high risk — more than 30 percent — for having a heart attack or stroke within a decade. Conducted by CMS’ Innovation Center, the study will compare 360 medical practices using the new tool to 360 practices that aren’t, and will reward practices in both groups for overall reductions in heart attack and stroke risk through Medicare and Medicaid payments.

“They’re assessing whether paying health systems and clinicians to achieve risk reduction actually results in lower cardiovascular event rates and therefore lower costs for Medicare,” said Lloyd-Jones, chair of the department of preventive medicine at the Northwestern Feinberg School of Medicine in Chicago.

Patients in practices using the new tool will receive an initial 10-year prediction of developing cardiovascular disease caused by atherosclerosis using the ACC/AHA assessment formula.

The new tool then goes a step further, giving doctors and patients a preview of how stopping smoking or starting aspirin, blood pressure-lowering medication or a statin may each or in combination affect their risk of a heart attack or stroke.

Strongly backed by medical research, these four preventive strategies are where patients “are going to get the most bang for their buck,” Lloyd-Jones said.

Then the “really innovative part” of the tool kicks in, he said. “After a clinician and patient have decided what they’re going to do, they can enter the new values at a follow-up visit and see the actual updated risk, not just what we would expect.”

Some patients may need more than one preventive therapy, Lloyd-Jones said. “They might benefit from a statin plus aspirin or a statin plus blood pressure control.”

Although physical activity, healthy eating, healthy weight and diabetes management are critically important for health and are part of every prevention visit, they are not currently emphasized in the Million Hearts model. Lloyd-Jones said that’s because interventions for those factors either “haven’t been measured in consistent ways” or they lack the highest-quality evidence that backs the four measures included in the tool.

Physical activity, healthy eating, healthy weight and diabetes are not emphasized in the new Million Hearts tool. Lloyd-Jones said that’s because those factors “haven’t been measured in consistent ways” and lack the high-quality evidence that backs the four measures included in the tool.

Although “everyone acknowledges that with all of these tools, the prediction of the risk is not exact, this can be a really useful tool,” Lloyd-Jones said.

According to the ACC and AHA, using prediction formulas to guide treatment “may represent the next wave in clinical practice to help target therapies to those in whom they will provide the greatest benefit.”