FACTS & HINTS
High-Yield Facts
Clinical Points
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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 increasinglyinhibited from expanding as it beats, and blood flow to the ventricles is impeded.
This situation is called cardiac tamponade and is a potentiallylethal 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 cavityis necessaryto relieve cardiac tamponade.
Awide 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. Aneedle can also be inserted into the infrasternal angle, again being careful of the internal thoracic arteryand its branches, and passed superiorlyand posteriorlyto reach the pericardial sac.
Cardiac Referred Pain
While the heart is generallyinsensitive to various stimuli, ischemia (lack of oxygen) and the resulting accumulation of metabolic products registers as pain, typicallyin 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 typicallyenter spinal cord segments from T1 through T4 or 5 on the left side.
General sensoryfibers from these areas also enter the same spinal cord segments
Cardiac Bypass Graft (CABG)
In this surgery, the patient has a blood vessel grafted into the coronarycirculation to bypass an occlusion in one of the coronaryarteries or its branches.
In the past, the saphenous vein was commonlyused in the bypass graft, because it is easilyobtained from the lower limb and has lengthy sections without valves or branches.
The internal thoracic arteryis more frequentlyused to shunt blood from the aorta to branches of the coronaryarteries 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 anyone of several developmental anomalies, such as failure of the embryonic endocardial cushions, which form part of the septum, to fuse.
Aleft 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 pulmonarytrunk to the lungs and results in pulmonaryhypertension (increased blood pressure) and an enlarged heart.
This condition is potentiallyfatal 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 theyreach a certain size and 50% of patients who experience a rupture of a thoracic aortic aneurysm die before reaching the hospital.
Ascending aortic aneurysms frequentlycause dilation and leakage of the aortic valve, resulting in shortness of breath or even heart failure.
Theycan 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 commonlyjust past the point where the subclavian arteryarises.
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 bodyand arms (or one arm) and low blood pressure in the lower bodyand 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 frequentlyaffected bydisease.
It can be caused byendocarditis, 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 bya high pitched murmur, loudest over the apexof the heart. Narrowing of the pulmonaryvalve (stenosis) is caused byfusion of the valve cusps.
It can result from a developmental abranditemityor diseases such as rheumatic fever or endocarditis.
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Stenosis of the pulmonaryvalve leads to right ventricular hypertrophyand heart failure, if not corrected surgically.
Mnemonics
Memory Aids
PV2L: Pulmonaryvalve heard over 2nd left intercostal space
AV2R:Aortic valve heard over 2nd right intercostal space
Memory Aids
To remember the cusps of the aortic and pulmonaryvalves: A= P and P = A
A(ortic) = Posterior, Right and Left
P(ulmonary) = Anterior, Right and Left
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