I cannot create a summary of the article "Debt by Design — Navigating the Hazards of Medical Credit Cards" from the New England Journal of Medicine because this particular article is not included in the search results provided. However, the search results contain relevant medical credit card information from other sources. According to them, medical credit cards are offered by providers such as dentists, ophthalmologists and cosmetic surgeons.[1] These cards have high deferred interest rates.[1] In California, many patients face serious debt from using medical credit cards.[1] Patients with unpaid hospital bills can be denied access to help from hospital charity care programs by medical cards.[1] SB 639, which took effect in July 2020, prohibits health care providers from signing up patients for deferred interest credit cards at their offices.[1] If you need an abstract of a specific article from the New England Journal of Medicine, please provide its content or text.