Patients who were treated for breast cancer or lymphoma are more than three times at risk of developing congestive heart failure compared with patients who did not have cancer finds a study. Congestive heart failure is when the heart muscle does not pump blood as well as it should. The researchers found that risk of increased heart failure occurred as early as one year after cancer diagnosis but continued 20 years after patients completed cancer treatment. Overall one in 10 cancer patients developed heart failure by 20 years after cancer diagnosis. The majority of patients do not develop heart failure