Download 02 Cardiac Anatomy

Essential
Cardiac Anatomy and Physiology
Tobias Schaeffter
Division of Imaging Sciences and Biomedical Engineering
King’s College London
Learning objectives
•  Provide an overview on Heart Anatomy,
Conducting System and Physiology
•  Provide terminology of the external and internal
features of the heart
•  Show imaging examples of cardiac anatomy and
physiology
Heart Anatomy
•  Approximately the size of your fist
–  Weight = 250-300 grams
•  Location
–  In the mediastinum between the lungs
–  Superior surface of diaphragm
–  ⅔ of it to the left of midsternal line
Anatomical Features of the Heart
•  Muscular organ with 4 internal
chambers
–  2 atria
(lt. atrium & rt. atrium)receive blood from veins
–  2 ventricles
(lt. ventricle & rt. ventricle)pump blood into arteries
•  Superior aspect of heart is the “base”, where the blood
vessels attach;
•  Inferior is the “apex”, which rests on the relaxed diaphragm
Coverings of the Heart
•  Pericardium – a double-walled sac around the heart
•  Fibrous pericardium (pericardial sac) – outer layer that
protects & anchors
•  Serous pericardium – double layered membrane with
“pericardial fluid”
–  Protects and anchors the heart
–  Allows for the heart to work relatively friction-free
Layers of the Heart Wall
•  Epicardium – visceral
pericardium
•  Myocardium – cardiac
muscle layer forming the
bulk of the heart
•  Endocardium – endothelial
layer of the inner
myocardial surface
Layers of Heart Wall
§  Epicardium (a.k.a. visceral pericardium)
§  Myocardium
§  Endocardium
Cardiac muscle tissue
•  Cardiac muscle consists
of heart muscle cells
(cardiomyocytes) which
are connected by
intercalated discs to work
as one functional organ
•  Intercalated discs support
synchronised contraction
of cardiac tissue.
MR-DTI
Heart Anatomy
•  External markings
–  Apex - pointed inferior region
–  Base - upper region
–  Coronary sulcus (feature that separates atria from ventricles)
–  Anterior and posterior interventricular sulcus (feature that separates
right and left ventricles)
•  Internal divisions
–  Atria (superior) and
ventricles (inferior)
–  Interventricular and
interatrial septa
Cardiac CT
External Features
§  Auricles
§  Coronary sulcus – contains the
coronary sinus
§  Anterior interventricular sulcus –
contains coronary vessels
§  Posterior interventricular sulcus –
contains coronary vessels
Atria of the Heart
•  Atria - receiving chambers of the heart
–  Receive venous blood returning to heart
–  Separated by an interatrial septum (wall)
•  Fossa ovalis - remnant of foramen ovale (opening in interatrial
septum in fetus)
•  Pectinate muscles mark atrial walls
•  Pump blood into ventricles
•  Blood enters right atria from superior and inferior
venae cavae and coronary sinus
•  Blood enters left atria from pulmonary veins
Internal Structures
Cardiac MR
SVC
Interatrial septum
Fossa ovalis
Lt Atrium
Rt Atrium
Pectinate
muscles
Bicuspid (mitral)
valve
Coronary sinus
(opening)
Chordae tendineae
Tricuspid valve
Chordae tendineae
Papillary muscle
Papillary muscle
IVC
Deoxygenated
blood
Pulmonary
veins
Oxygenated
blood
Internal Structures
Cardiac MR
Ventricles of the Heart
•  Ventricles are the pumping chambers of the heart
•  Papillary muscles and trabeculae carneae muscles mark
ventricular walls
•  Separated by an interventricular septum
–  Contains components of the conduction system
•  Right ventricle pumps blood into the pulmonary trunk
•  Left ventricle pumps blood into the aorta
–  3xThicker myocardium due to greater work load
•  Pulmonary circulation supplied by
right ventricle is a much low pressure
system requiring less energy
•  Systemic circulation supplied by
left ventricle is a higher pressure
system and thus requires more forceful
contractions
Heart Valves
•  Heart valves ensure unidirectional
blood flow through the heart
•  Two major types
–  Atrioventricular valves
–  Semilunar valves
•  Atrioventricular (AV) valves lie between
the atria and the ventricles
–  R-AV valve = tricuspid valve
–  L-AV valve = bicuspid or mitral valve
•  AV valves prevent backflow of blood
into the atria when ventricles contract
•  Chordae tendineae anchor AV valves to
papillary muscles of ventricle wall
–  Prevent prolapse of valve back into atrium
Fibrous Skeleton
•  Surrounds all four valves
–  Composed of dense connective tissue
•  Functions
–  Anchors valve cusps
–  Prevents overdilation of valve openings
–  Main point of insertion for cardiac muscle
–  Blocks direct spread of electrical impulses
Aorta (ascending)
Pulmonary artery
Pulmonary trunk
Pulmonary semilunar
valve
Aortic semilunar valve
Trabeculae
carneae
Lt ventricle
Rt ventricle
Interventricular
septum
Atrioventricular Valve Function
Semilunar Valve Function
Semilunar Heart Valves
•  Semilunar valves prevent backflow of blood into
the ventricles
•  Have no chordae tendinae attachments
•  Aortic semilunar valve lies between the left
ventricle and the aorta
•  Pulmonary semilunar valve lies between the
right ventricle and pulmonary trunk
Atrioventricular
(AV) valves
§  Tricuspid
§  Bicuspid
Semilunar
valves
Heart Valves
Cardiac US
3D reconstruction of the heart. To the left 2D
US-images from the same dataset, showing
tricuspid and mitral valves (above) and aortal
and mitral valve (below) (source Wikipedia)
Heart sounds (“lub-dup”) due to valves closing
“Lub” - closing of atrioventricular valves
“Dub”- closing of semilunar valves
Heart Defects
Conducting System
•  Cardiac muscle tissue has intrinsic ability to:
–  Generate and conduct impulses
–  Signal these cells to contract rhythmically
•  Conducting system
–  A series of specialized cardiac muscle cells
–  Sinoatrial (SA) node sets the inherent rate of
contraction
•  “Autorhythmic (conducting) cells”
–  spontaneously generate action potentials
Conducting System
SA node (“pacemaker”) à
à AV node à
à AV bundle (of His) à
à  Bundle branches à
à Purkinje fibers
Innervation
•  Heart rate is altered by
external controls
•  Nerves to the heart
include:
–  Visceral sensory fibers
–  Parasympathetic
branches of the vagus
nerve
–  Sympathetic fibers –
from cervical and upper
thoracic chain ganglia
Heart Excitation Related to ECG
Figure 18.17
Electroanatomical Mapping
Movement of blood through heart & heart sounds
§  The activity of the conduction system results in the contraction (systole)
& relaxation (diastole) of the heart chambers
§  atria will contract as ventricles remain relaxed (atrial systole/ventricular
diastole). Blood moves from atria to ventricles
§  as atria relax, ventricles begin to contract (atrial diastole/ventricular
systole). The AV valves (tricuspid & bicuspid/mitral) close to prevent
backflow of blood into atria. The closing of the valves makes a sound –
“Lub”
§  as blood moves from ventricles to arteries (pulmonary trunk & aorta),
pressure will increase in the arteries and decrease in the ventricles.
Semilunar valves will then shut à “Dupp” as ventricles relax
§  all 4 chambers will be in diastole, and then cycle begins again
Electrocardiography
Cardiac Cycle
•  Cardiac cycle refers to all events
associated with blood flow through the
heart
–  Systole – contraction of heart muscle
–  Diastole – relaxation of heart muscle
Phases of the Cardiac Cycle
•  Ventricular filling
–  Heart blood pressure is low as blood enters atria
and flows into ventricles
–  AV valves are open, then atrial systole occurs
Phases of the Cardiac Cycle
•  Ventricular systole
–  Atria relax
–  Rising ventricular pressure results in closing of
AV valves
–  Isovolumetric contraction phase
–  Ventricular ejection phase opens semilunar
valves
Phases of the Cardiac Cycle
•  Isovolumetric relaxation – early diastole
–  Ventricles relax
–  Backflow of blood in aorta and pulmonary trunk
closes semilunar valves
•  Dicrotic notch – brief rise in aortic pressure
caused by backflow of blood rebounding off
semilunar valves
Phases of the Cardiac Cycle
Pressure-Volume Loop
Pressure-volume loop of left ventricle
Cardiac Output (CO) and
Reserve
•  CO is the amount of blood pumped by each
ventricle in one minute
•  CO is the product of heart rate (HR) and stroke
volume (SV)
•  HR is the number of heart beats per minute
•  SV is the amount of blood pumped out by a
ventricle with each beat
•  Cardiac reserve is the difference between
resting and maximal CO
Cardiac Output: Example
Left ventricular chamber assessment
•  CO (ml/min) = HR (75 beats/min) x SV (70 ml/beat)
quantitativ
e: discs
contiguous stack of short axis slices
Simpsons
rule
of
•  CO = 5250 ml/min (5.25 L/min)
Short axis cine stack
•
p4CH
•
LV Volumes
Papillary muscles: either
SAX
stack
included
or excluded in LV
volumes (report to specify)
•
LVOT included in LV volume: the
contour is drawn to include the
outflow tract to the level of the
aortic valve cusps.
•
The highest basal slice: can be
identified when more than 50% of
the blood volume is surrounded by
myocardium
every slice has a defined thickness (8mm)
bbb= 0mm
gap between the slices
Regulation of Stroke Volume
•  SV = end diastolic volume (EDV) minus
end systolic volume (ESV)
•  EDV = amount of blood collected in a
ventricle during diastole
•  ESV = amount of blood remaining in a
ventricle after contraction
Factors Affecting Stroke Volume
•  Preload – amount ventricles are stretched
by contained blood
•  Contractility – cardiac cell contractile force
due to factors other than EDV
•  Afterload – back pressure exerted by
blood in the large arteries leaving the heart
Preload and Afterload
Pressure-Volume Loop
SYSTOLIC PRESSURE CURVE
After-load
Pre-load
PRESSURE
Isotonic (Ejection) Phase
Isovolumetric
Phase
Stroke
Volume
DIASTOLIC
PRESSURE CURVE
End Systolic Volume End Diastolic Volume
Extrinsic Factors Influencing
Stroke Volume
•  Contractility is the increase in contractile
strength, independent of stretch and EDV
•  Increase in contractility comes from:
–  Increased sympathetic stimuli
–  Certain hormones
–  Ca2+ and some drugs
Major Vessels of the Heart
•  Vessels returning blood to the heart include:
–  Superior and inferior venae cavae
•  Open into the right atrium
•  Return deoxygenated blood from body cells
–  Coronary sinus
•  Opens into the right atrium
•  Returns deoxygenated blood from heart muscle (coronary veins)
–  Right and left pulmonary veins
•  Open into the left atrium
•  Return oxygenated blood from lungs
Pathway of Blood Through the Heart and Lungs
Blood Flow Through the Heart
Major Vessels of the Heart
Vessels conveying blood away from the heart include:
–  Pulmonary trunk
•  Carries deoxygenated blood from right ventricle to lungs
•  Splits into right and left pulmonary arteries
–  Ascending aorta
•  Carries oxygenated blood away from left atrium to body organs
•  Three major branches
–  Brachiocephalic
–  Left common carotid,
–  Left subclavian artery
4D MR-Flow
Coronary Circulation
•  Coronary circulation
–  The functional blood supply to the heart
muscle itself
–  R and L Coronary arteries are 1st branches
off the ascending aorta
–  Coronary sinus (vein) empties into R. atrium
•  Collateral routes ensure blood delivery to
heart even if major vessels are occluded
Coronary Circulation - Arteries
•  Right Coronary Artery
–  Supplies blood to
•  Right atrium and posterior surface of both ventricles
–  Branches into the
•  Marginal artery - extends across surface of R. ventricle
•  Posterior interventricular artery
•  Left Coronary Artery
–  Supplies blood to
•  Left atrium and left ventricle
–  Branches into
•  Circumflex artery
•  Left Main
Cardiac MRA
Cardiac CTA
Coronary Circulation: Arterial Supply
Perfusion
Data Courtesy S. Plein
Stress
PET/MR
Rest
Data Courtesy E. Nagel
Coronary Circulation - Veins
Coronary sinus:
•  Vein that empties into right atrium
•  Receives deoxygenated blood from:
–  Great cardiac vein - on anterior surface
–  Posterior cardiac vein
•  Drains area served by circumflex
–  Middle cardiac vein
•  Drains area served by posterior interventricular artery
–  Small cardiac vein
•  Drains blood from posterior surfaces of right atrium and ventricle
Coronary Vein MRA
Coronary Circulation: Venous Supply
Learning objectives
•  Provide an overview on Heart Anatomy,
Conducting System and Physiology
•  Provide terminology of the external and internal
features of the heart
•  Show imaging examples of cardiac anatomy and
physiology
Readings
•  Achilles J. Pappano, Withrow Gil Wier, Matthew
N. Levy; Cardiovascular Physiology; Mosby;
9th edition 2006
•  Elaine N. Marieb, Essentials of Human
Anatomy and Physiology, Pearson Education ;
10th edition 2010
•  Lauralee Sherwood. Human Physiology: From
Cells to Systems; Brooks Cole; 8th edition,
2012
•  Robert F. Schmidt, Gerhard Thews, Human
Physiology, Springer 1989
•  Many slides from www.slideworld.org