8 Cardiac Anatomy and Physiology Flashcards
Describe the anatomy of the thorax.
The heart is located in the middle mediastinum in the left side of the thorax. It is located between the lungs (the lungs are located within the pleura) within the ribcage.
The mediastinum is located between the lungs in the centre of the thorax. The superior mediastinum contains the great vessels. The inferior mediastinum is divided into the anterior, middle and posterior mediastinum. The middle mediastinum contains the heart and the pericardium.
The heart is located within the pericardium. The pericardium is divided into the outer fibrous pericardium and the inner serous pericardium which is further divided into the parietal layer and the visceral layer.
Describe the anatomy of the blood vessels in the thorax.
The ascending aorta, which supplies the coronary arteries, becomes the aortic arch, which supplies the brachiocephalic, left common carotid, and left subclavian arteries, becomes the descending aorta, which supplies the organs in the thorax.
The pulmonary artery divides into the left and right pulmonary arteries which drain the RV and supply the lungs.
The SVC arises from the right and left brachiocephalic veins supplies the RA with blood from the upper body. The IVC supplies the RA with blood from the lower body.
The four pulmonary veins drain the lungs and supply the LA.
The internal thoracic, intercostal, brachiocephalic, subclavian and azygos vessels supply other parts.
What occurs in cardiac embryology?
In weeks 1-3, the cardiogenic area forms in the mesoderm. The cardiogenic area forms the primitive heart tube.
In weeks 4-6, the primitive heart tube loops and the chambers form. In weeks 5-6, the IAS, IVS and atrioventricular septum form to form the chambers.
In weeks 7-12, the chambers divide and the valves develop. In weeks 7-8, the aorta and PA develop. In weeks 8-12, the valves develop.
In weeks 13-16, the chambers and valves further develop. In weeks 17-38, the heart grows and adapts.
What is the flow of blood like in the fetus, the neonate, and the adult?
In foetuses, a foramen ovale is present, allowing blood to flow from the RA to the LA, via the IAS, to bypass the lungs. In neonates, the foramen ovale closes because the lungs develop and the LA pressure increases. In adults, the foramen ovale becomes the fossa ovalis, or, a PFO.
In foetuses, a ductus arteriosus is present, allowing blood to flow from the PA to the aorta to bypass the lungs. In neonates, the ductus arteriosus closes and forms the ligamentum arteriosum. In adults, it can become a PDA.
In foetuses, the eustachian valve directs blood from the TV to the foramen ovale. In adults, the foramen ovale closes so the eustachian valve loses its function.
Described the flow of blood through the heart.
Oxygenated blood from the lungs enters the LA via the four pulmonary veins, then enters the LV via the MV, and then exits the LV via the AV and the aorta to travel to the body. Deoxygenated blood from the body enters the RA via the SVC and IVC, then enters the RV via the TV, and then exits the RV via the PV and PA to travel to the lungs.
Describe the anatomy of the coronary arteries.
The coronary arteries originate from the sinuses of Valsalva. The LCA divides into the LAD and LCx. The LAD divides into the diagonal branches and the LCx divides into obtuse marginal branches. The RCA normally supplies the PDA (dominance).
Describe the anatomy of the valves.
The AV has three cusps (RCC, LCC and NCC) which open during systole and close during diastole.
The MV has two leaflets (anterior and posterior) which open during diastole and close during systole.
The TV has three leaflets/cusps (anterior, posterior and septal) which attach to the three papillary muscles via the chordae tendineae. The TV opens during diastole and closes during systole.
The PV has three leaflets/cusps (anterior, left and right). The PV opens during systole and closes during diastole.
Describe the anatomy of the mitral valve and its apparatus.
The MV has two leaflets (anterior and posterior) which open during diastole and close during systole. The leaflets are divided into three scallops (A1, A2, A3 and P1, P2, P3) from the anterolateral commissure to the posteromedial commissure.
The base of the leaflets attach to the mitral annulus. The anterior leaflet is longer from base to tip but the posterior leaflet is longer along the length of its attachment to the annulus.
The leaflets attach to the two papillary muscles (anterolateral and posteromedial) via the chordae tendineae. The papillary muscles supply chordae tendineae to both leaflets. There are three groups of chordae tendineae (first, second/strut, third/basal). The chordae tendineae prevent MV prolapse.
The leaflets close during diastole (coaptation) and overlap by a few mm (apposition).
Describe the anatomy of the chambers.
The LA is posterior to the other chambers and superior to the LV. The LA is smooth walled with a LAA.
The LV is anterior and inferior to the LA but posterior and lateral to the RV. The LV is symmetrical with a wide base and a narrow apex. The LV is the biggest in size, wall thickness and mass.
The RA is anterior to the LA and superior to the RV. The RA is smaller and more irregular than the LA.
The RV is anterior to the other chambers, inferior to the RA and medial to the LV. The RV is triangular (crescent) shaped. The RV is more trabeculated than the LV and has a moderator band.
Described the anatomy of the pericardium.
The pericardium is a double layered sac surrounding the heart. The pericardium is divided into the outer fibrous pericardium and the inner serous pericardium which is further divided into the parietal layer (continuous with the fibrous pericardium) and the visceral layer (the epicardium).
The pericardial space is located between the parietal layer and the visceral layer. It holds the pericardial fluid.
Pericarditis can cause a pericardial effusion which can cause cardiac tamponade. Long term inflammation can cause pericardial constriction.
What are the normal anatomical variants?
A LV false tendon is a fibromuscular band in the LV which connects the papillary muscles to the IVS or LV free wall.
A moderator band is a muscular ridge in the RV which connects the RV free wall to the IVS.
A eustachian valve is an embryological remnant in the RA. It is a flap at the junction of the RA and IVC.
A Chiari network is an embryological remnant of the sinus venosus. It forms a web across the RA.
A Crista Terminalis is a muscular ridge in the RA which runs between the SVC to the IVC.
Lambl’s excrescences are small filamentous strands on the ventricular side of the AV.
Lipomatous hypertrophy of the IAS is characterised by a build up of non-encapsulated fat in the IAS.
An IAS aneurysm is a bulge in the IAS which protrudes into the RA or LA.
Dilated coronary sinuses and aneurysmal coronary arteries can look like cystic masses.
What are the 3 atrial phases?
Resevor, conduit and contractile.
During ventricular systole, the LA acts as a reservoir for blood from the lungs. Strain >30%.
During early ventricular diastole, the LA acts as a passive conduit (channel), allowing blood to enter the LV. Strain >15%.
During late ventricular diastole, the LA contracts to increase LV filling. Strain >10% (or >14%).
What is the pathophysiology of eccentric hypertrophy and concentric hypertrophy?
Eccentric hypertrophy is secondary to chronically increased preload. Volume overload (e.g. MR, AR, high CO states) causes LV dilatation via cardiomyocyte lengthening. Dilatation is greater than hypertrophy so the LV becomes elliptical in shape with increased internal size. Ultimately, it causes systolic dysfunction and HFrEF.
Concentric hypertrophy is secondary to chronically increased afterload. Pressure overload (e.g. hypertension, AS) causes LV hypertrophy via cardiomyocyte thickening. The hypertrophy causes the LV to become round in shape an increased wall thickness (and RWT), increased mass, but decreased internal size. Ultimately, it causes diastolic dysfunction and HFpEF and then systolic dysfunction and HFrEF.
What are the four phases of the cardiac cycle?
Isovolumetric contraction, ventricular ejection, isovolumetric relaxation and ventricular filling.
In isovolumetric contraction the LV pressure increases and becomes greater than the LA pressure so the MV closes. The AV is still closed so the LV pressure continues to increase but the LV volume stays constant (the middle to the end of the QRS complex)
In ventricular ejection, the LV pressure increases and becomes greater than the aortic pressure so the AV opens. Blood flows from the LV into the aorta. The LV volume decreases but the LV pressure continues to increase, peak, then decrease (the end of the QRS complex to the middle to the end of the T wave)
In, isovolumetric relaxation, the LV pressure decreases and becomes less than the aortic pressure, so the AV closes. The LV pressure continues to decrease the LV volume stays constant (the middle to the end to the end of the T wave).
In ventricular filling, the LV pressure decreases and becomes less than the LA pressure so the MV opens. Blood flows from the LA into the LV. At the end of ventricular filling, atrial systole increases ventricular filling (the end of the T wave to the middle of the QRS complex). Atrial systole occurs during this period.
Wigger’s Diagram.
What are the normal cardiac pressures?
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