Two factors combine to increase your risk: chronic inflammation and shared risk factors.
Inflammatory substances called cytokines fuel joint destruction in RA and blood vessel damage in cardiovascular disease (CVD). Inflammation causes plaque to build up in the arteries, which slowly narrows the blood vessels and blocks blood flow, and is the main cause of heart attacks and strokes.

The second reason people with rheumatoid arthritis (RA) are more likely to develop heart disease, are shared risk factors such as these:

high blood pressure – A number of factors increase blood pressure in people with RA, including lack of exercise and medications used to treat the disease (such as NSAIDs and steroids). People with RA also have less elastic arteries that can narrow, letting less blood through and increasing blood pressure.

metabolic syndrome – Almost 40% of people with RA have metabolic syndrome, compared to less than 20% of people in general. This collection of symptoms, which includes obesity, high triglycerides and cholesterol, high blood pressure and high blood sugar, doubles the risk of cardiovascular disease.

obesity – Sore joints make it difficult to exercise, and lack of physical activity can lead to weight gain. Obesity is linked to CVD risk itself, as well as to cardiovascular risk factors such as high blood pressure and high blood sugar. Fat cells release inflammatory substances that contribute to inflammation throughout the body and the risk of cardiovascular disease.

smoking – People with RA are more likely to smoke than those without the disease. Not only has this habit been linked to more aggressive joint destruction, but smoking also accelerates blood vessel damage and contributes to artery narrowing. Smokers with RA have a 50% higher risk of cardiovascular events than non-smokers with RA.

Abnormal lipids – RA has an unusual effect on lipids or fats in the blood. Experts call it the “lipid paradox.” People with RA have high levels of triglycerides, low levels of low-density lipoproteins (LDL or “bad” cholesterol), and low levels of high-density lipoproteins (HDL or “good” cholesterol). Although low LDL is good for the heart, low HDL cholesterol and high triglycerides contribute to cardiovascular disease.