Normal heart,fetal elkhatib

M.elKhatib

Understand the normal anatomy of the heart.

Understand the size, shape, location and orientation of the heart.

Understand and locate the cardiac valves.

Understand the route of blood flow through the heart and lungs.

• The heart size is usually referred to as the size of the persons fist.

• The heart is located mid sternal with approximately 2/3 of the heart mass on the left side.(levocardia)

•The heart is a muscular, hollow cone shaped organ.

• In a normal heart, the apex of the heart faces to the left.

• There are conditions when the heart does not face this way such as dextrocardia,mezocardia

The heart has four chambers that are divided into 2 areas.

The first is the atria which has two chambers, the right atrium (RA) and the left atrium (LA).

The atriums are located on the top half of the heart and are less muscular then the ventricles.

They bring blood into the heart. The right side or RA brings de-oxygenated blood into the heart and the left side (LA) brings oxygenated blood back into the heart.

The second area is the ventricles which is split into the Right Ventricle (RV) and the Left Ventricle (LV).

The ventricles are located at the bottom of the heart. The ventricles are more muscular then the atriums

because they are the pumping chambers. The RV pumps the de-oxygenated blood to the lungs

to be oxygenated. The LV pumps the oxygenated blood to the body so

that they can oxygenate the organs and tissues.

There are two types of valves in the heart; Atrioventricular valves and semilunar valves.There are two atrioventricular valves in the heart. The first is the tricuspid valve which is located on the right side of the heart.It separate the right atrium from the right ventricle. This valve has three leafletsThe second is the mitral valve. Located on the left side of the heart, it separates the left atrium from the left ventricle. The mitral valve is bicuspid and has two leaflets.

The Pulmonary Valve (PV) is described as a semilunar valve. It separates the Right Ventricle (RV) from the Pulmonary Artery (PA).

The Aortic Valve (AoV) is also described as a semilunar valve. It separates the Left Ventricle (LV) from the Aorta (Ao).

The heart is made of three tissue layers:

• Endocardium• Myocardium• Pericardium

The outer layer of the heart is called the Pericardium. The pericardium is a double layered sac. The outer sac

is made of fibrous tissue and adheres to the diaphragm and coats the great vessels (pulmonary artery and aorta) to ensure that they stay in the correct position and to protect them.

The inner layer is serous and secretes a substance called pericardial fluid. This stops friction between the layers of the heart.

When the fluid builds up, it can cause pericarditis or cardiac tamponade. If the fluid leaks, it can cause a pericardial rub.

The second layer is the Myocardium which is an involuntary muscle and is branched in appearance.

The contraction of the heart and ejection of blood to both the systemic and pulmonary circulations is the myocardium's responsibility.

Lastly is the Endocardium which is a single thin layer of endothelium that lines the inside of the myocardium.

The blood from the body, or systemic blood comes back to the heart via the Inferior Vena Cava (IVC)

The blood from the head returns to the heart via the Superior Vena Cava (SVC)

From the IVC and SVC, the blood which is de-oxygenated or desaturated enters the right atrium (RA).

The right atrium also receives a flow of de-saturated blood from the coronary sinus

RA connects to the RV via the tricuspid valve RV is a pumping chamber and pumps blood through the

pulmonary valve, up the main pulmonary artery, divides to the left and right pulmonary artery, to the respective left and right lungs.

In the lungs, the blood is re-oxygenated and returns to the heart via the 4 pulmonary veins (PV)

The 4 Pulmonary Veins connect to the Left Atrium (LA) The LA is connected to the Left Ventricle (LV) via the mitral

valve (Bi-leaflet) LV is also a pumping chamber and pumps the oxygenated

blood through the aortic valve, up the aorta and to the head and body.

The aorta has many important arteries that come off it.

The first is the coronary arteries which come off at the base of the aorta and supplies the hearts muscle with oxygenated blood.

Further up the aorta just after the ascending aorta, we come to the aortic arch. Off the aortic arch, there are three main branches.

• The first main artery that comes off the arch of the aorta is the brachiocephalic artery which is short and splits off to the right subclavian and right common carotid artery.• The right subclavian artery supplies the right arm while the right common carotid artery supplies the head. • The second branch is the left common carotid artery. This artery also supplies the head on the other side.• Both common carotid arteries branch further up to become the external carotid artery (ECA) and internal carotid artery (ICA)• The last in the left subclavian artery which supplies blood to the left arm.

Atrial contraction Isovolumetric contraction Ejection Isovolumetric relaxation Passive filling

What is the difference?Lungs are not used – high PVR, amniotic fluidPlacenta responsible for oxygenation, nutrition and removal of wasteUse of foetal shunts

Ductus Venosus Foramen Ovale Ductus arteriosus

Oxygenated blood from placenta via umbilical vein Separates at liver Connects to IVC via ductus venosus Liver has high o2 demand – mixture of

de/oxygenated blood Foetal haemoglobin has a high affinity for o2 High cardiac output

Blood flows from IVC to RA Eustachian valve/crista dividens direct blood

toward foramen ovale Intra atrial communication One way Right to left shunting across PFO

Communication between PA and Ao Deoxygenated blood from SVC flows RA>RV>PA High PVR Blood follows path of least resistance Blood passes into descending aorta via the ductus

arteriosus

2/3 of LV output perfuses upper limbs and brain Remaining 3rd mixes with blood from ductus

arteriosus and perfuses lower body Lower body saturations approx 55% Foetal haemoglobin has a high affinity for o2 High cardiac output

First breath!! Lungs and alveoli expand Rapid fall in pulmonary vascular resistance Amniotic fluid moves into interstital space and

absorbed by pulmonary capillaries and lymphatic system

Increased pulmonary venous return Increase in left atrial pressure Higher than RAP leads to functional closure of FO Umbilical cord tied and cut/clamped Arteries and veins constrict Become fibrous DA becomes ligamentum venosum

Increase in o2 concentration Decrease in prostaglandin levels Constriction of smooth muscle Ductus arteriosus begins to close with 12-24

hours

Some patients born with CHD will have a condition that is incompatible with life

Death will occur if no intervention Life is made possible by partially maintaining the

foetal circulation ‘Duct-dependent’

Require patency of the ductus arteriosus for mixing of blood or maintaining blood flow

Typical conditions include coarctation of the aorta (CoA), transposition of the great arteries (TGA) and hypoplastic left heart syndrome (HLHS)

Duct patency maintained via IV prostaglandin infusion @ 5-20ng/kg/min until palliative or corrective interventions available

The normal anatomy of the heart.

The size, shape, location and orientation of the heart.

The cardiac valves.

The route of blood flow through the heart and lungs.