Myocardium

Question 1

Mediastinal locations in supine position

Answer 1

(lying face upward) Abdominal viscera push mediastinum superiorly.

• Arch of aorta lies sup to transverse thoracic plane
• Bifurcation f trachea is transected by transverse thoracic plane
• Central tendon of diaphragm (diaphragm surface) lies at level of xiphisternal junction and T9

Question 2

Mediastinal locations standing or sitting

Answer 2

Abdominal viscera drawn down by gravity and soft structures of the mediastinum are supported by these.

• Arch of aorta is transected by transverse thoracic plane
• tracheal bifurcation lies inferior to transverse thoracic plane
• central tendon of diaphragm may fall to level of middle of xiphoid process and T9 or T10

Question 3

Mediastinoscopy

Answer 3

With endoscope (mediastinoscope), surgeons can see much of mediastinum and conduct small surgical procedures. (e.g. check mediastinal lymph nodes to see if cancer has metastasized from a bronchogenic carcinoma)

Question 4

Widening of mediastinum

Answer 4

Any structure in mediastinum may contribute.

• hypertrophy (enlargement to heart) due to congestive heart failure
• malignant lymphoma ij mediastinal lymph nodes
• hemorrhage into mediastinum after head on collision

Question 5

Transverse pericardial sinus surgical significance

Answer 5

Once pericardium is open, a finger can be passed through transverse pericardial sinus posterior to ascending aorta and pulmonary trunk.

• can put a clamp or ligature around these and stop or divert blood circulation in these arteries
  (e. g. during coronary artery bypass grafting)

Question 6

Exposing venae cavae

Answer 6

The inferior venae cavae is enclosed within the pericardium after ascending through the diaphragm, so the pericardium must be opened to expose in surgery.

Question 7

Pericarditis

Answer 7

Inflammation of pericardium. Usually causes chest pain. May make serous pericardium rough.
Rough rubbing (pericardial friction rub) of pericardium may be audible with a stethoscope if one listens over left sternal border and upper ribs.
Chronically inflamed and thickened may calcify,

Question 8

Pericardial Effusion

Answer 8

Inflammatory diseases pass fluid from pericardial capillaries to pericardial cavity, or may be caused by an accumulation of puss. Heart becomes compressed and unable to expand fully and ineffective.
(often seen in congestive heart failure)

Question 9

Cardiac tamponade

Answer 9

Heart compression is compromised by excessive pericardial effusion. Potentially lethal.

Question 10

Hemopericardium

Answer 10

Hemopericardium occurs when blood is in the pericardial cavity, causing cardiac tamponade, and may be from perforation of weakened area of heart muscle after a heart attack.
May also occur after cardiac operations or from stab wounds.
Circulation fails and of face and neck swell due to back up of blood beginning with where the superior vena cava enters pericardium

Question 11

Pericardiocentesis

Answer 11

Drainage of fluid from pericardial cavity to relieve cardiac tamponade. Either drained through

• 5th or 6th intercostal space due to cardiac notch in the left lung and pleural sack leaving pericardium exposed
• infrasternal angle next to the xiphoid by passing needle superoposteriorly (care taken not to puncture internal thoracic artery.

Question 12

Dextrocardia

Answer 12

Position of heart completely reversed so apex is to the right. Most common positional abnormality of the heart.

• mirror imaging of great vessels and arch of aorta
• may also affect thoracic and abdominal viscera (situs inversus) or only heart (isolated dextrocardia)