29 :The Middle Mediastinum, Heart and Pericardium and the Superior Mediastinum

Clinical Anatomy:

Pericarditis: Inflamation of the pericardium can be:

Infective,
Degenerative
Malignant.

It can occur on its own or as a part of a heart condition as in rheumatic pericarditis. The pain is felt diffusely posterior to the sternum i.e. substernal pain. It commonly radiates to the shoulder, side of neck and to the submandibular regions.

Pericardial effusion: Fluid in the pericardial sac may be due to inective pericarditis , trauma, degenerative disorder or malignancy. If extensive the fluid may embarass the action of the heart by compressing it. This is called cardiac tamponade. Circulation may fail completely causing death. When the IVC and SVC are compressed the veins in the periphery swell and show on the surface with edema. The organs like the liver e.t.c. get engorged and may fail, and brain edema may cause neurological deficits

Pericardiocentesis : Drainage of fluid from the pericardial cavity may be done for diagnostic purposes or to ease the compression of the heart. A wide bore needle may be inserted through the 5 th or 6 th intercostal space near the sternum or through the infrasternal angle directed towards the left. Care must be taken not to injure the internal thoracic artery.

Coronary Arteries

The branches of the coronary arteries are end arteries in the sense that they supply regions of cardiac muscle

without significant overlap, from other large branches. Although there is a rich anastomosis between arteries, this

blood supply is inadequate for the requirements of cardiac muscle when there is sudden occlusion of a major branch.

Consequently, the region supplied by the occluded branch becomes infarcted (rendered bloodless and soon undergoes necrosis.

An area of myocardium that has undergone necrosis is called an infarct.