Ok. I didn't expect this when I googled "heart growling." So, I have parasites (likely nematodes) that I've been working on for over a year with limited success. I've had not much help from physicians locally since, though my eosinophils are high, my stool sample is negative. Anyway, I continue to feel the parasites moving in my gut, usually after I eat, but sometimes at night as well. I've treated them myself during this time with various herbal protocols. These have help, but not resolved my problem. So, my concern is these parasites have made their way into my heart or perhaps other tissues or organs. Or maybe its just a weakening heart. I'm 54, have been through a lot of stress since July 2012 when my wife was diagnosed with breast cancer at stage 4. She died in November 2014. Now I'm raising our 12 yr old son alone. I was diagnosed with mildly leaky valves, mitral and tricuspid, in April 2013. Why does a heart growl? In may case, usually several hours after I've had exercise.