FACTS & HINTS
High-Yield Facts
Clinical Points
page 115
page 116
page 116
page 117
Cardiac Tamponade
Inflammation of the pericardium (pericarditis) can result in pericardial effusion, a leakage of fluid from the pericardial capillaries into the
pericardial cavity.
Similarly, stab wounds to the heart can result in the leakage of blood into the pericardial cavity.
As excess blood or fluid accumulates in the pericardial cavity, the heart becomes increasingly inhibited from expanding as it beats, and
blood flow to the ventricles is impeded.
This situation is called cardiac tamponade and is a potentially lethal condition.
Symptoms include distension of neck veins and a collapsing pulse, i.e., diastolic and systolic pressures become the same.Pericardiocentesis
Pericardiocentesis or drainage of fluid from the pericardial cavity is necessary to relieve cardiac tamponade.
A wide bore needle is inserted into the 5th or 6th intercostal space adjacent to the sternum (but not too close because of the presence of the
internal thoracic vessels).
This approach can be made because of the cardiac notch in the left lung and left parietal pleura, leaving the pericardial sac exposed.
A needle can also be inserted into the infrasternal angle, again being careful of the internal thoracic artery and its branches, and passed
superiorly and posteriorly to reach the pericardial sac.Cardiac Referred Pain
While the heart is generally insensitive to various stimuli, ischemia (lack of oxygen) and the resulting accumulation of metabolic products
registers as pain, typically in the left pectoral and substernal regions and over the medial aspect of the left shoulder and upper limb.
The axons of visceral afferent fibers from the heart typically enter spinal cord segments from T1 through T4 or 5 on the left side.
General sensory fibers from these areas also enter the same spinal cord segmentsCardiac Bypass Graft (CABG)
In this surgery, the patient has a blood vessel grafted into the coronary circulation to bypass an occlusion in one of the coronary arteries or
its branches.
In the past, the saphenous vein was commonly used in the bypass graft, because it is easily obtained from the lower limb and has lengthy
sections without valves or branches.
The internal thoracic artery is more frequently used to shunt blood from the aorta to branches of the coronary arteries beyond the occlusion.
This restores normal blood flow to the part of the heart distal to the blockage.Ventricular Septal Defects (VSDs)
The membranous part of the interventricular septum is the most common site of ventricular septal defects (VSDs).
VSDs account for 25% of all cardiac abnormalities.
It can be a result of any one of several developmental anomalies, such as failure of the embryonic endocardial cushions, which form part of
the septum, to fuse.
A left to right flow of blood occurs with this defect because of the strength of contraction of the left ventricle.
This increases the blood flow through the pulmonary trunk to the lungs and results in pulmonary hypertension (increased blood pressure)
and an enlarged heart.
This condition is potentially fatal if not corrected.Pathologies of the Aorta
Aneurysms of the ascending aorta
An aortic aneurysm is an enlargement of a weakened area of the aorta, in this case in the distal part of the ascending aorta.
Aneurysms are prone to rupture once they reach a certain size and 50% of patients who experience a rupture of a thoracic aortic
aneurysm die before reaching the hospital.
Ascending aortic aneurysms frequently cause dilation and leakage of the aortic valve, resulting in shortness of breath or even heart
failure.
They can also cause a dull pain beneath the sternum and/or pain radiating to the upper back.
Aortic dissection is a tearing of the internal wall of the aorta, with subsequent bleeding into the wall, as the result of an aneurysm,
atherosclerosis, or high blood pressure.
Coarctation of aorta is a birth defect in which the aorta is narrowed somewhere along its length, most commonly just past the point where
the subclavian artery arises.
This results in low blood pressure in branches of the aorta distal to the narrowing and high blood pressure in branches between the
narrowing and the heart.
People with this condition often have high blood pressure in the upper body and arms (or one arm) and low blood pressure in the
lower body and legs.
The intercostal arteries can become enlarged, since the anastomoses of the anterior intercostals (from the internal thoracic artery)
with the posterior intercostals can circumvent the narrowing.
Aortic coarctation is more common in some genetic conditions such as Turner syndrome but also can be associated with congenital
abranditemities of the aortic valve such as a bicuspid aortic valve.Valvular Insufficiencies
The mitral valve is the heart valve most frequently affected by disease.
It can be caused by endocarditis, myocarditis, rheumatic heart disease, or lupus erythematosus, or can result from a developmental
abranditemity.
The diseased mitral valve allows reversal of blood flow from the left ventricle to the left atrium (mitral regurgitation).
It is characterized by a high pitched murmur, loudest over the apex of the heart.
Narrowing of the pulmonary valve (stenosis) is caused by fusion of the valve cusps.
It can result from a developmental abranditemity or diseases such as rheumatic fever or endocarditis.