Anatomy/Physiology Flashcards
Acute Marginal Artery
supplies right ventricle
Post. descending/interventircular artery
supplies posterior 1/3 of IV septum and posterior walls of ventricles
Left anterior descending artery
supplies anterior 2/3 of IV septum, anterior papillary muscles and anterior surface of left ventricle
Left Circumflex coronary artery
supplies lateral and posterior walls of left ventricle
Blood supply for SA and AV nodes
Right Coronary Artery - infarct can cause nodal dysfx
Right Dominant Circulation
85% population, posterior descending artery arises from RCA
Left Dominant Circulation
8% of population, posterior descending artery arises from LCA
Codominant circulation
7% of population, posterior descending artery arises from both Left Circumflex artery and RCA
Peak of coronary blood flow
Early Diastole
Most posterior part of heart
Left Atrium, enlargment can cause dysphagia or hoarseness (compresses Left reccurrent laryngeal)
Cardiac Output
SV * HR -or-
rate of O2 consumption)/(arterial O2 content-venous O2 content
Mean Arterial Pressure
MAP = CO * TPR
2/3DBP + 1/2SBP
Pulse Pressure
systolic - diastolic
proportional to SV
inversely proportional to arterial compliance
Stroke Volume
EDV-ESV
Cardiac Output during exercise
Early - CO is maintained by increase HR and SV
Late - CO is maintained by increased HR only (SV plateaus)
Causes for increased Pulse Pressure
Hyperthyroidism, Aortic regurgitation, arteriosclerosis, obstructive sleep apnea, transiently with exercise
Causes for decreased Pulse Pressure
aortic stenosis, cardiogenic shock, cardiac tamponade, and advanced heart failure
Causes for increased stroke volume
increased contractility, increased preload, or decreased afterload
anxiety, pregnancy, exercise
Increased intracellular Calcium
increases contractility
Decreased Extracellular Sodium
increases contractility because it decreases the Na/Ca exchanger
Catecholamines effect on Heart
Increases activity of calcium pump in sarcoplasmic reticulum
Digitalis on Contractility
blocks Na/K pump thus increase intracellular Na and decreasing Na/Ca exchanger therefore INCREASING intracellular Calcium
Ways to decrease contractility and stroke volume
beta-1 blockade, HF with systolic dysfunction, acidosis, hypoxia/hypercapnea, non-dihydropyridine CCB
Increase of myocardial O2 demand
increased afterload, increased contractility, increased heart rate, increased ventricular diameter
Preload
depends on venous tone and circulating blood volume
approximated by ventricular EDV
Venodilators
nitroglycerin, decreases preload
Afterload
approximated by MAP
Compensation for increased afterload
LV compensates by thickening (hypertrophy) to decrease wall tension
Drugs that decrease both preload and afterload
ACE-inhibitors and ARBs
Vasodilators
hydralazine, decrease afterload
Wall Tension
Associated with Afterload
Pressureradius) / (2wall thickness
Ejection Fraction
EF = (SV)/(EDV) or (EDV-ESV)/EDV
left ventricular EF is an index of ventricular contractility
Normal EF
> 55%
EF in systolic heart failure
<55%
EF in diastolic heart failure
normal, >55%
Pressure =
Pressure = flow * resistance
Resistance of vessels in series
TR = R1+R2+R3…
Resistance of vessels in parallel
1/TR = 1/R1 + 1/R2 + 1/R3….
Causes of increased viscosity of blood
polycythemia, hyperproteinemic states (multiple myeloma), spherocytosis
Causes of decreased velocity of blood
ANEMIA
Resistance equation
(8(viscosity)length) / (pi*r^4)
Type of vessel that accounts for majority of TPR
arterioles, they regulate capillary flow
Inotropy
Strength of contraction
(+) inotropy
catecholamines, digoxin
negative inotropy
uncompensated heart failure and narcotic overdose
Decreases venous return
acute hemorrhage, spinal anesthesia
Increases venous return
fluid infusion, sympathetic activity
Increases TPR
vasopressors
Decreases TPR
Exercise and AV shunt
S1
mitral and tricuspid valve closure. Loudest at mitral area
S2
aortic and pulmonary valve closure, loudest at left sternal border
S3
Early diastole during rapid ventricular filling phase
associated with mitral regurgitation and CHF
more common in dilated ventricles
Heart sound normal in children and pregnant women
S3
S4
atrial kick - in late diastole, High atrial pressure. associated with ventricular hypertrophy. Left atrium must push against stiff LV wall.