A heart attack ended up killing Venezuelan president and longtime cancer sufferer Hugo Chavez, a source close to Chavez revealed. And cancer experts say that's not unusual…Anti-cancer drugs such as anthracyclines, a mainstay of breast cancer chemo, as well as newer medications such as the drug Herceptin may cause heart damage by weakening the heart muscle, Dr. Timothy Moynihan, an oncologist at the Mayo Clinic in Minnesota said in a statement on the clinic's website.

ABC News by Karen Keller

Tags: ABC News, anthracyclines, anti-cancer drugs, Breast Cancer, Cardiology, Dr. Timothy Moynihan, heart attack, heart damage, Herceptin, Hugo Chavez, Mayo Clinic Rochester