Patho II:
10/11/21
Cardiac Pathophysiology:
Heart:
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Heart Structure:
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Blood Flow through
the Heart:
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Size of a fist
o Base: upper portion
o Apex: pointed end
Acute Coronary Syndrome (ACS)
o Due to ischemia (low oxygen to cardiac muscle)
Myocardial Infarction (MI)
o Prolonged ischemia leading to cell death
Tissue Layers:
o Epicardium – outer layer
o Myocardium – cardiac muscle
o Endocardium – inner lining of heart
Coronary circulation:
o Right coronary artery: supplies right side of heart (right atrium and
ventricle, SA and AV nodes)
o Left coronary artery: supplies blood to the left side of heart
 LAD (left anterior descending): branches from left
coronary; supplies blood to front of left side of heart
Four chambers:
o Atria: receiving chambers
 Right atrium: receives blood from superior/ inferior vena
cava and coronary sinus >> tricuspid valve
 Left atrium: receives blood from pulmonary veins >>>
mitral valve (bicuspid valve)
o Ventricles: pumping chambers (pump blood outside the heart to
lungs or systemic circulation)
 Right ventricle: pumps blood to lungs
 Left ventricle: pumps blood to body
 Ventricular walls thicker than atrial walls
DEOXYGENATED blood enters from systemic circulation to RIGHT side of
heart from SUPERIOR/ INFERIOR VENA CAVA
Blood empties into RIGHT ATRIUM
RIGHT ATRIUM pumps blood through TRICUSPID VALVE to RIGHT
VENTRICLE
RIGHT VENTRICLE pumps blood through PULMONIC VALVE to PULMONARY
ARTERIES
PULMONARY ARTERIES carry blood to lungs for gas exchange
OXYGENATED blood returns from lungs to heart through PULMONARY
VEINS
PULMONARY VEINS empty into LEFT ATRIUM
LEFT ATRIUM pumps blood through MITRAL VALVE to LEFT VENTRICLE
LEFT VENTRICLE pumps blood through AORTIC VALVE to AORTA
AORTA carries blood to rest of body
Circulation Cont.:
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Cardiac Muscle
Action Potential:
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Two Circuits:
o Pulmonary: low pressure; Right ventricle to Left atrium
o Systemic: high pressure; Left ventricle to Right Atrium
Systolic: contraction (SBP)
Diastolic: relaxation (DBP)
Phase 0: fast SODIUM channels open and increased potential from -90mV
to 20mV
Phase 1: PEAK, abrupt CLOSURE of fast SODIUM channels
Phase 2: PLATEAU, slow SODIUM-CALCIUM channels
Phase 3: REPOLARIZATION, K+ channels open
Phase 4: RESTING POTENTIAL, Na+/ K+ PUMP
Refractory Period:
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Allows heart to relax w/o being reactivated
Allows heart to fill with blood
Protects against fatal arrhythmias
Absolute Refractory Period: cells cannot be restimulated; phases 0-2 (part
of 3)
Dysrhythmias
(Arrhythmias):
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Disruption in electrical signal
o Supraventricular: SA node, AV node, atria
o Ventricular: Bundle of His, Purkinje fibers, ventricles
o Tachyarrhythmia: rapid heartbeat that may be regular or
irregular, but is out of proportion to age and level of exertion or
activity
o Bradyarrhythmia: slower-than-expected heart rate, generally
beating fewer than 60 beats per minute
Block
o Most commonly at AV node
Ectopic pacemaker
o Outside normal conduction pathway
 PVC (premature ventricular contraction) – extra
heartbeats that begin in one of your heart’s ventricles
 Symptoms: fluttering, skipped/ missed beats,
pounding
 Causes: heart disease or bodily changes can
make cells electrically unstable; scarring may
also cause electrical impulses to be misrouted
 Risk factors: caffeine, tobacco, alcohol;
hypertension; anxiety; heart disease; risk
increases if taking ANTIHISTAMINES or
DECONGESTANTS
 Complications: cardiomyopathy (weaking of
heart muscle); arrhythmias
Electrical activity of the heart:
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Electrocardiogram:
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Coronary
Circulation:
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o X-axis: time (duration)
o Y-axis: millivolts (voltage)
Standard waveforms:
o P wave: atrial depolarization
o QRS complex: ventricular depolarization
o T wave: ventricular repolarization
12-Lead ECG: provides twelve diff. vies of electrical activity of the heart
Cardiac muscle requires constant supply of O2 and nutrients to function
properly
Blood flow is GREATEST during DIASTOLE
o REDUCED during SYSTOLE (due to contraction and compression of
cardiac vessels)
Collateral circulation will form if an artery becomes obstructed
o offers an important alternative source of blood supply when the
original vessel fails to provide sufficient blood; may avoid MI
SA node supplied by the RCA (right coronary artery) and LCA (left coronary
artery)
AV node supplied by RCA (blockage of RCA can lead to conduction issues >
dysrhythmias
Blockage of LCA can lead to LV dysfunction and possible CHF