Transcript Document 7215299

Basic Cardiology
The Heart
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Pericardium
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Epicardium
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Myocardium
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atrial muscle
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ventricular muscle
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conductive tissue
Endocardium
The Heart
Myocardium
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branch
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intercalated disks with gap junctions
Intercalated Disc
Electrical Stimulation of the Heart
Sinoatrial (SA) Node
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Right atrium
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Inherent rhythm 80-100
bpm)
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Usually sets the heart
rate (sinus rhythm)
Internodal & Interarterial
Pathways
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Internodal
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Anterior
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Middle (Wenckebach
branch)
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Posterior
Interatrial
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Anterior Interarterial
band or Bachmann’s
bundle
Atrioventricular (AV)
Junction
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AV Node
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Located at the base of the
right atria near the
interventricular septum
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Smaller cells, fewer gap
junctions, slower
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Maximal rate is ~230 per
minute; also maximal
ventricular rate
AV Junction
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AV Bundle or Bundle of His
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Only cellular connection
between atria and ventricles
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Together with AV node make
up the AV junctional tissue
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Intrinsic heart rate of 40-60
bpm
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If SA node fails, AV junctional
tissue can control heart rate
Slows down the cardiac impulse
Bundle Branches
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Right and left branches
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Two left branches (sometimes three)
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Left anterior fascicle or left
anterior bundle branch; thinner,
carries impulses to septum, left
anterior wall, and anterior papillary
muscle
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Left posterior fascicle or l. post.
bundle branch; thicker, carries
impulses to posterior, inferior, left
ventricular free wall and posterior
papillary m. with dual blood
supply, less likely to become
ischemic,
Both left and right BB travel down
towards the apex of the heart where they
fan out into Purkinje fibers
Purkinje Fibers
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Pass through the ventricular
myocardium
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Contraction starts at the
apex
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Fast rate of action potential
generation, numerous
sodium ion channels and
mitochondria and fewer
myofibrils
Electrical Stimulation of the
Heart
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Video
“If you understand the normal physiologic stimulation of
the heart, you have the basis for understanding the
abnormalities of heart rhythm and conduction the
produce distinctive ECG patterns.” p. 5
Electrocardiogram
SA node
AV node
Atrial depolarization
Bundle branches
Ventricle depolarization
Ventricle repolarizatio
Purkinje fibers
Electrocardiogram
Rhythms
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Normal conduction
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Sinus Rhythm
Abnormal conduction
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Junctional rhythm
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e.g. escape
pacemaker
Ventricular rhythm
Cardiac Conductivity
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SA node - slow
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Internodal pathways - fast
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AV node - slow
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Purkinje fibers - faster
Cardiac Automaticity
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Automaticity
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SA node - primary pacemaker
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Other sites e.g. AV junction
Certain conditions increase the automaticity of ectopic
pacemakers
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Ectopic = outside of the sinus node pacemaker (nonsinus)
Abnormalities
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AV heart block = blockage of stimuli through AV junction
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Bundle Branch Block = disease of bundle branches
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ST segment changes = damage to ventricular muscle
Coronary Arteries
Coronary Arteries
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The Left Main (LM)
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Left Anterior Descending (LAD)
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Left Circumflex (LCX).
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The Right Coronary Artery (RCA)
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The RCA on the posterior part of the
heart is often called the Posterior
Descending Artery (PDA), in most
cases it originate from the RCA but in
some cases it comes from LCX.
Coronary Artery Perfusion
LAD
Supply the anterior septum, the
anterior wall, and in most cases apex.
9 o'clock to 1 o'clock.
Supply the lateral wall
LCX
2 o'clock to 4 o'clock
RCA
Supply the posterior lateral segments,
the inferior segments, and the posterior
septum.
5 o'clock to 8 o'clock
Class Organization
1. Resting 12 lead ECG
1. Understanding normal 12 lead ECG and conditions that cause
abnormal depolarization and repolarization
2. Recognizing abnormal rhythms and AV conduction
disturbances
3. Associating the ECG arrhythmia with its pathology
2. Exercise ECG
1. Recognizing abnormal rhythms and AV conduction
disturbances
2. Associating the ECG arrhythmia with its pathology