In a letter sent this week to Senate Majority Leader Mitch McConnell (R-Kentucky) and House Speaker Paul Ryan (R-Wisconsin), American Heart Association CEO Nancy Brown stressed the AHA’s continued commitment to patients with heart disease and stroke who are covered under the Affordable Care Act.

In the seven-page letter, Brown laid out the AHA’s position on the potential repeal and replacement of provisions contained in President Obama’s signature health law. Congressional leaders and President-elect Donald Trump have made ACA repeal a top priority during the first 100 days of the new Congress and administration.

Individuals currently insured under the ACA have expressed concern that they will be unable to pay daunting medical expenses if the law is dismantled. Patients with chronic diseases such as cardiovascular disease could be particularly hard hit.

Before the law was passed in 2010, many patients with pre-existing conditions like congestive heart failure, coronary artery disease, bypass surgery and stroke were precluded from health insurance coverage because of medical underwriting rules in most states. Under the ACA, heart disease and stroke patients are protected from discrimination based on their health condition.

The protections the law provides are critical, Brown wrote, and include the non-discrimination clause; guaranteed renewability for patients regardless of health status; caps on annual out-of-pocket expenses; and no annual or lifetime limits on coverage. She noted that reversing these protections would impact millions of Americans.

Brown also spoke about the necessity of providing coverage options for low-income people in states that elected not to expand their Medicaid programs.

In a separate joint letter to Congress on Thursday, the AHA, American Cancer Society Cancer Action Network, American Lung Association, American Diabetes Association and the National Multiple Sclerosis Society stressed the need to preserve the pre-existing conditions protections.