Cardiovascular System III

Cardiac Anatomy & X-Ray

• The area of skin innervated by one dorsal root is called a dermatome.
• The cardiac shadow in a chest X-ray is more prominent in an AP projection than in a PA projection.
• Wilhelm Conrad Röntgen created the first radiographic image in 1895 using X-rays generated from a cathode ray tube.
• The X-ray image demonstrates the position of the heart, which may be abnormal due to dextroposition, dextroversion, dextrocardia, or other changes in intrathoracic structures.
• An extreme case of abnormal cardiac position is Situs inversus totalis, where the heart is on the right and the liver is on the left.

Cardiac Cycle and Auscultation

• The cardiac cycle represents a complete heartbeat, from the beginning of one heartbeat to the next.
• The cycle consists of diastole (ventricular relaxation and filling) and systole (ventricular contraction and emptying).
• Two heart sounds are heard with the stethoscope: a "lub" (1st) sound and a "dub" (2nd) sound.
• The "lub" sound corresponds to the closure of the atrioventricular valves, while the "dub" sound corresponds to the closure of the semilunar valves.
• The valves are responsible for preventing backflow of blood during heart contractions.

Percussion and Auscultation

• Leopold Auenbrugger, a Viennese doctor, pioneered the technique of percussion to diagnose chest diseases.
• Rene Theophile Hyacinthe Laënnec, a French physician, invented the stethoscope in 1816.
• Auscultation helps identify leaking valves, known as "murmurs."
• The location of the valves and their auscultation points are shown in the provided image.

Coronary Sinus and Valves

• Various landmarks have been identified for the location of the coronary sinus origin, including where the oblique vein of the left atrium meets the great cardiac vein and at the valve of Vieussens.
• The coronary sinus empties into the right atrium near the crux cordis area.
• The atrial orifice of the coronary sinus can be partially covered by a Thebesian valve.

Coronary Venous Anatomy

• The coronary venous system drains oxygen-depleted blood from the myocardium.
• Coronary veins are considered low-resistance conduits that can alter their capacity to maintain venous pressure.
• The coronary venous system is comprised of the unique cardiac venous system and the minor cardiac venous system (Thebesian vessels).

Valvular Heart Disease

• Clinicians assess valvular function during auscultation, listening for pathological sounds called murmurs.
• Valvular heart disease refers to pathologies that affect the heart valves, which can be stenoses or insufficiencies.
• Stenotic valves harden and do not open properly, obstructing blood flow.
• Insufficient valves cannot close fully, leading to retrograde blood flow (regurgitation) during systole.

Fetal Circulation

• Fetal circulation features a different blood flow pattern through the heart.
• Blood bypasses the lungs in the fetus, with the foramen ovale connecting the right and left atria.
• The ductus arteriosus connects the pulmonary trunk to the aorta, shunting blood away from the pulmonary circulation.

Clinical Case Study

• Rupture of the papillary muscles, which are responsible for attaching the chordae tendineae to the ventricular wall, can lead to death.
• A blood clot traveling from the right inguinal vein to the lungs follows this path: Right inguinal vein to inferior vena cava to Right atrium to Right ventricle to pulmonary trunk.