TOWNSHIP 3 RANGE 11 – A rare heart condition killed a Massachusetts fly fisherman whose body was found Thursday in the West Branch of the Penobscot River just northwest of Piscataquis County’s Little Ambejackmockamus Falls, state officials said Friday.

Charles H. Zimmerman, 51, of Upton, Mass., died Thursday from cardiac tamponade, a condition that occurs in approximately two out of 10,000 people, according to a spokesman for the state medical examiner’s office and the Medline Plus Web site.

Dr. Margaret Greenwald, chief medical examiner, performed the autopsy.

Cardiac tamponade is the compression of the heart caused by blood or fluid accumulation in the space between the myocardium – the muscle of the heart – and the pericardium, the outer covering sac of the heart, according to the Web site.

In this condition, blood or fluid collects within the pericardium and prevents the ventricles from expanding fully so they cannot adequately fill or pump blood, the site states.

Symptoms include anxiety, restlessness, discomfort, difficulty breathing, rapid breathing, fainting, light-headedness, chest pains and gray or blue skin.

Cardiac tamponade is an emergency condition that requires immediate hospitalization and many cases are not preventable, the site states.

Three fishermen from Sanford working the north bank of the river Thursday found Zimmerman floating face-down in the river in about 3 feet of water about three-tenths of a mile south of Chewonkis Big Eddy Campground, 8027 Golden Road, at about 11 a.m.

Two went to the campground and had workers there call 911 at about 11:15 a.m., Game Warden Joel Wilkinson said. Game wardens retrieved Zimmerman’s body about two hours later.

Investigators believed Zimmerman, who was staying at a Millinocket motel and had parked his vehicle near where his body was found, slipped under the water accidentally or suffered a medical problem, such as a heart attack.

Zimmerman was found in shallow and slow-moving water, but the body, which was about 40 feet from the river’s north bank, could have drifted from another, more violent point in the river.

Zimmerman also was wearing waders that drained, making it unlikely that their weighing him down contributed to his drowning.

He is survived by his wife, who was in Massachusetts at the time of his death. His body will be released to a funeral home upon the family’s request, the spokesman said.