Cardiac complications are well known in Lyme disease. It frequently causes chest pain and palpitations, and occasionally can cause heart block with Lyme carditis, which can be fatal. Rarely, patients will develop a cardiomyopathy, where the heart muscle becomes weak, leading to severe congestive heart failure. That was the case with Dr Neil Spector, an MD who developed Lyme disease, and had difficulty getting diagnosed because of insensitive blood tests, along with denial of the disease by the medical profession in his home state. I discuss Lyme and cardiomyopathy on pages 272-275 of "Why Can't I Get Better?", in chapter 10, Lyme and Mitochondrial Dysfunction.