Lecture 1 out 2

Clinical AnatomyOf Pericardium and Heart

Associate Professor

Dr. Alexey Podcheko

Upd. Fall 2014

Intended Learning OutcomesA. Pericardium: To know the organs of the middle mediastinum, To know parts of the pericardium, innervation and blood supply Surgical aspects of pericardial anatomy Clinical insights on pericardium

B. Heart: To know the external features of the heart. To know the chambers, valves, vessels, and related structures of

the heart including the pathway of blood flow. Describe the mechanism of the heart sounds formation. To know the layers of the heart wall (epicardium, myocardium,

and endocardium). To know the course and distribution of the coronary arteries and cardiac veins. To know  coronary dominance in regard to the posterior interventricular artery

(posterior descending artery; PDA). To know the cardiac plexus and its contribution to heart innervation on

cardiac myocardium, cardiac cycle, and coronary arteries. Outline the conducting system of the heart, including the location and function

of the SA node, AV node, AV bundle, and Purkinje fibers of the heart Clinical insights on heart pathology

Concept of the Middle Mediastinum•The mediastinum is the compartment of the thorax that occupies the space between the 2 lungs and their surrounding pleural sacs. Has 6 boundaries (Inferior, Superior, Right/Left Lateral boundaries, Anterior boundary, Posterior boundary)•Divided into two regions: I. Superior mediastinum (above the heart and pericardial sac on the level of T4-T5 intervertebral disc – brown dashed line, see below)II. Inferior mediastinum further divided into 3 subdivisions: 1. Anterior mediastinum

2. Middle mediastinum 3. Posterior mediastinum

I. Pericardium (3 parts): Visceral pericardium Parietal pericardium (Fibrinous) Pericardial cavity - space between the visceral and parietal pericardial

layers II. Oblique cardiac sinus. The posterior space within the serous

pericardium between the visceral pericardium andparietal pericardium. It is limited superiorly and on the right by the reflection between the visceral and parietal peritoneum between the arteries and veins (superiorly) and the superior and inferior vena cava (right lateral side), but is continuous with the the rest of the pericardial cavity to the sides and below.

III. Transverse pericardial sinus. Passageway that traverses the top of the heart between the parietal pericardiumcovering the arterial plane and the parietal pericardium covering the venous plane. This sinus arises as the heart folds and draws the venous end toward the arterial end during embryonic development.

Phrenic nerves. Descend from the neck to the diaphragm in the fibrous pericardium.Clinical Insights

Diaphragmatic Paralysis Pericardiacophrenic artery and pericardiacophrenic vein. Pass with

the phrenic nerve to supply the diaphragm. Heart. The muscular pump of the cardiovascular system that

pumps blood throughout the blood vessels of the pulmonary and systemic circuits.

Structures of the Middle Mediastinum

PERICARDIUM Is a fibroserous sac that encloses

the heart and the roots of the great vessels and occupies the middle mediastinum.

Is composed of the fibrous pericardium and serous pericardium.

Receives blood from the pericardiophrenic, bronchial, and esophageal arteries.

Is innervated by vasomotor and sensory fibers from the phrenic and vagus nerves and the sympathetic trunks.

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•The pericardium is a closed sac composed of two layers: Fibrous and Serous •The tough external layer, the fibrous pericardium, is continuous with (blends with) the central tendon of the diaphragm

PERICARDIUM: 2 layers

•The internal surface of the fibrous pericardium is lined with a glistening serous membrane, the parietal layer of serous pericardium. •This layer is reflected onto the heart at the great vessels - aorta, pulmonary trunk and veins, and superior and inferior venae cavae - as the visceral layer of serous pericardium. •The serous pericardium is composed mainly of mesothe-lium, a single layer of flattened cells forming an epithelium that lines both the internal surface of the fibrous pericardium and the external surface of the heart.

PERICARDIUM: Serous layer has 2 portions

•The fibrous pericardium is continuous superiorly with the tunica adventitia of the great vessels entering and leaving the heart and fusing with the pretracheal layer of deep cervical fascia.

PERICARDIUM: Fibrous pericardium

•The inferior wall (floor) of the fibrous pericardial sac is firmly attached and confluent (partially blended) centrally with the central tendon of the diaphragm. •The site of continuity has been referred to as the pericardiacophrenic ligament; however, the fibrous pericardium and central tendon are not two separate structures that fused together secondarily, nor are they separable by dissection. •As a result of the attachments just described, the heart is relatively well fixed in place inside this fibrous sac

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PERICARDIUM: Fibrous pericardium

•The pericardium is influenced by movements of the heart and great vessels, the sternum, and diaphragm•The fibrous pericardium protects the heart against sudden overfilling because it is so unyielding and closely related to the great vessels that pierce it superiorly•The ascending aorta carries the pericardium superiorly beyond the heart to the level of the sternal angle

PERICARDIUM: Fibrous pericardium

•The pericardial cavity is the potential space between opposing layers of the parietal and visceral layers of serous pericardium. •It normally contains a thin film of fluid that enables the heart to move and beat in a frictionless environment. •The visceral layer of serous pericardium makes up the epicardium, the outermost of three layers of the heart wall:

PERICARDIAL CAVITY

(epicardium, myocardium and endocardium)

•Extends onto the beginning of the great vessels, becoming continuous with the parietal layer of serous pericardium, where the aorta and pulmonary trunk leave the heart and where the superior vena cava, inferior vena cava, and pulmonary veins enter the heart. •The transverse pericardial sinus lies between Aorta+Pulmonary Trunk and SVC+RPV/LPV•the reflection of the serous pericardium around the RPV+LPV and IVC defines the oblique pericardial sinus

Epicardium and Pericardial Sinuses

•The transverse pericardial sinus is especially important to cardiac surgeons. •After the pericardial sac is opened anteriorly, a finger can be passed through the transverse pericardial sinus posterior to the aorta and pulmonary trunk.grafting.

Surgical Significance of the Transverse Pericardial Sinus

•By passing a surgical clamp or placing a ligature around these vessels, inserting the tubes of a coronary bypass machine, and then tightening the ligature, surgeons can stop or divert the circulation of blood in these large arteries while performing cardiac surgery, such as coronary artery bypass

The aortic cannula is seen at the most cephalad aspect of the field. Cardiopulmonary bypass is initiated through a straight venous cannula placed within the right atrial appendage

The arterial supply: mainly from pericardiacophrenic artery - branch of the internal thoracic artery (ITA), parallels the phrenic nerve to the diaphragmSmaller contributions of blood come from the: 1.Musculophrenic (branch of ITA) 2. Bronchial, Esophageal and Superior phrenic arteries - branches of the thoracic aorta 3. Coronary arteries (visceral layer of serous pericardium only), the first branches of the aortaThe venous drainage: Pericardiacophrenic veins, tributaries of the brachiocephalic (or internal thoracic) veins + azygos venous system.

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Blood Supply of the Pericardium

1. Phrenic nerves (C3 - C5), primary source of sensory fibers; pain sensations conveyed by these nerves are commonly referred to the skin (C3 - C5 dermatomes) of the ipsilateral supraclavicular region (top of the shoulder of the same side). 2. Vagus nerves, function uncertain.3. Sympathetic trunks, vasomotor

Nerve supply of the pericardium

•After passing through the diaphragm, the entire thoracic part of the inferior vena cava (approximately 2 cm) is enclosed by the pericardium. •Consequently, the pericardial sac must be opened to expose the superior part of the inferior vena cava•The same is true for the terminal part of the superior vena cava, which is partly inside and partly outside the pericardial sac.

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Exposure of the inferior vena cava and superior vena cava

•Inflammation of the pericardium (pericarditis) usually causes chest pain•The pain is sharp in quality and increases with inspiration. It radiates to the trapezius ridge and is partially relieved by sitting up•Pericarditis may also make the serous pericardium rough. Usually the smooth opposing layers of serous pericardium make no detectable sound during auscultation, but in pericarditis friction of the roughened surfaces sounds like the rustle of silk when listening with a stethoscope over the left sternal border and upper ribs (pericardial friction rub)•Heart sounds are understandably distant or muffled• A chronically inflamed and thickened pericardium may actually calcify, seriously hampering cardiac efficiency.

Clinical Correlations: Pericarditis, and Pericardial

Rub

Some Types of PericarditisAdhesive pericarditis with formation of plaquelike

fibrous thickeningsAdhesive mediastinopericarditis is result of

infectious pericarditis, previous cardiac surgery, or irradiation to the mediastinum

Constrictive pericarditis - scar that limits diastolic expansion and cardiac output, features that mimic a restrictive cardiomyopathy. Cardiac output is reduced at rest and heart has little if any capacity to increase its output in response to increased peripheral needs

Fibrinous pericarditis – due to accumulation of fibrin

Encircling all of the heart by massive pericardial calcific deposits

Chronic Constrictive Idiopathic Pericarditis

Acute suppurative pericarditis arising from direct extension of a pneumonia. Extensive purulent exudate is evident.

Fibrinous pericarditis

A 34-year-old Caucasian female who is being evaluated for proteinuria and a facial rash complains of chest pain. The pain is sharp in quality and increases with inspiration. It radiates to the trapezius ridge and is partially relieved by sitting up. Which of the following is the most likely cause of this patient’s chest pain?

A. Intimal hyperplasia of pulmonary arteries B. Aortic dissection C. Pericardial inflammation D. Non-infectious cardiac valve vegetations E. Cardiac tamponade

•Some inflammatory diseases produce pericardial effusion (passage of fluid from pericardial capillaries into the pericardial cavity, or an accumulation of pus). •As a result, the heart becomes compressed (unable to expand and fill fully) and ineffective. •Non-inflammatory pericardial effusions often occur with congestive heart failure

Clinical Correlations: Pericardial Effusion

Pericardial EffusionNormal CXR

•The fibrous pericardium is a tough, inelastic, closed sac that contains the heart + thin lubricating layer of pericardial fluid•If extensive pericardial effusion exists, the compromised volume of the sac does not allow full expansion of the heart, limiting the amount of blood the heart can receive, which in turn reduces cardiac output. •This phenomenon, cardiac tamponade (a.k.a. heart compression), is a potentially lethal condition because heart volume is increasingly compromised!!!!

Clinical Correlations: Cardiac Tamponade

•Hemopericardium is the presence of the blood in the pericardial cavity,•Also produces cardiac tamponade•Causes: a. perforation of a weakened area of heart muscle owing to a previous myocardial infarction (MI) or heart attack, •b. bleeding into the pericardial cavity after cardiac operations•c. from stab/gunshot wounds•This situation is especially lethal because of the high pressure involved and the rapidity with which the fluid accumulates. •The heart is increasingly compressed and circulation fails.

Clinical Correlations: Hemopericardium

Clinical signs:

1. The veins of the face and neck become engorged because of the backup of blood

2. Another sign of the tamponade is phenomenon of the “PULSUS PARADOXUS” -  paradoxic pulse or paradoxical pulse, is an abnormally large decrease in systolic blood pressure and pulse wave amplitude during inspiration. The normal fall in pressure is less than 10 mmHg during inspiration. When the drop is more than 10mm Hg, it is referred to as pulsus paradoxus. 

Clinical Correlations: Hemopericardium

In patients with pneumothorax - ‘air or gas in the pleural cavity’, the air may dissect along connective tissue planes and enter the pericardial sac, producing a pneumopericardium, which can be demonstrated radiographically.

Clinical Correlations: Pneumopericardium

air or gas in the pleural cavity

•Drainage of fluid from the pericardial cavity, pericardiocentesis, is usually necessary to relieve cardiac tamponade. •To remove the excess fluid, a wide-bore needle may be inserted through the left 5th or 6th intercostal space near the sternum. •This approach to the pericardial sac is possible because the cardiac notch in the left lung and the shallower notch in the left pleural sac leaves part of the pericardial sac exposed ‘the bare area’ of the pericardium.

Clinical Correlations: Pericardiocentesis

•The pericardial sac may also be reached by entering the infrasternal angle and passing the needle superoposteriorly. •the needle avoids the lung and pleurae and enters the pericardial cavity; however, care must be taken not to puncture the internal thoracic artery •In acute cardiac tamponade from hemopericardium, an emergency thoracotomy may be performed (the thorax is rapidly opened) so that the pericardial sac may be incised to immediately relieve the tamponade and establish stasis of the hemorrhage (stop the escape of blood) from the heart.

Clinical Correlations: Pericardiocentesis

End of Pericardium Part

ANATOMY of the HEART

Overview The right side receives

oxygen-poor blood from the body and tissues and then pumps it to the lungs to pick up oxygen and dispel carbon dioxide

Its left side receives oxygenated blood returning from the lungs and pumps this blood throughout the body to supply oxygen and nutrients to the body tissues

The heart=a muscular double pump with 2 functions

•The heart, slightly larger than a clenched fist, is a double, self-adjusting, suction and pressure pump, the parts of which work in harmony to propel blood to all parts of the body. •The right side of the heart (right heart) receives poorly oxygenated (venous) blood from the body through the superior vena cava and inferior vena cava and pumps it through the pulmonary trunk to the lungs for oxygenation.

Heart and Great Vessels: Part 1

•The left side of the heart (left heart) receives well-oxygenated (arterial) blood from the lungs through the pulmonary veins and pumps it into the aorta for distribution to the body.

Heart and Great Vessels

Cone shaped muscleFour chambers

Two atria, two ventriclesDouble pump – the ventriclesTwo circulations

Systemic circuit: blood vessels that transport blood to and from all the body tissues

Pulmonary circuit: blood vessels that carry blood to and from the lungs

Heart simplified…

Heart’s position in thorax

•The heart has four chambers: right and left atria and right and left ventricles. •The atria are receiving chambers that pump blood into the ventricles (the discharging chambers).

Heart Chambers

Valves: three tricuspid one bicuspid (cusp means flap)

“Tricuspid” valveRA to RV

Pulmonary or pulmonic valveRV to pulmonary trunk

(branches R and L)Mitral valve (the

bicuspid one)LA to LV

Aortic valveLV to aorta

Heart Valves

•The synchronous pumping actions of the heart's two atrioventricular (AV) pumps (right and left chambers) constitute the cardiac cycle.•For more details : https://www.youtube.com/watch?v=ABTvNR59K5Q

Cardiac Cycle

•The cycle begins with a period of ventricular elongation and filling (diastole) and ends with a period of ventricular shortening and emptying (systole). •Two heart sounds are heard with a stethoscope: a “lub” sound as the blood is transferred (sucked) from the atria into the ventricles and a “dub” sound as the ventricles expel blood from the heart.

Cardiac Cycle: Main Stages

•The heart sounds are produced by the snapping shut of the one-way valves that normally keep blood from flowing backward during contractions of the heart.

Cardiac Cycle: Heart Sounds

Called S1 and S2S1 is the closing of AV (Mitral and Tricuspid) valves at

the start of ventricular systoleS2 is the closing of the semilunar (Aortic and Pulmonic)

valves at the end of ventricular systoleSeparation easy to hear on inspiration therefore S2

referred to as A2 and P2Murmurs: the sound of flow

Can be normalCan be abnormal

Cardiac Cycle: Heart Sounds

Systole: contractionDiastole: fillingNormal rate: 60-100Slow: bradycardiaFast: tachycardia

***Note: blood goes to RA, then RV, then lungs, then LA, then LV, then body; but the fact that a given drop of blood passes through the heart chambers sequentially does not mean that the four chambers contract in that order; the 2 atria always contract together, followed by the simultaneous contraction of the 2 ventricles

Definition: a single sequence of atrial contraction followed by ventricular contraction

Cardiac Cycle: Heartbeat

•The wall of each heart chamber consists of three layers: •Endocardium, a thin internal layer (endothelium and subendothelial connective tissue) or lining membrane of the heart that also covers its valves. •Myocardium, a thick, helical middle layer composed of cardiac muscle. •Epicardium, a thin external layer (mesothelium) formed by the visceral layer of serous pericardium

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Heart Wall Layers

The walls of the heart consist mostly of thick myocardium, especially in the ventricles.

Heart Wall Layers

•Thickness of left ventricle myocardium is app. 10-15mm•Thickness of right ventricle myocardium is app. 3-5mm

The muscle fibers of the myocardium are anchored to the fibrous skeleton of the heart.

Heart Skeleton is a complex framework of dense collagen forming

a. four fibrous rings that surround the orifices of the valves

b. right and left fibrous trigone (formed by connections between rings)

c. membranous parts of the interatrial and interventricular septa

Heart Skeleton

The fibrous skeleton of the heart:

a. Keeps the orifices of the atrioventricular (AV) and semilunar valves patent and prevents them from being overly distended

b. Provides attachments for the leaflets and cusps of the valves.

c. Provides attachment for the myocardium,

d. Forms an electrical ‘insulator’ so that atria and ventricles may contract independently

Heart Skeleton Functions