Cardiac Physiology and Extras Flashcards
Cardiac Cycle
the sequence of events that make up one heartbeat
0.75-1 sec on length; duration of a cardiac cycle determines heart rate
about 1/3 is spent in systole, and 2/3 is spent in diastole
Stroke Volume
the amount of blood ejected from the heart in one contraction (mm)
end diastolic volume minus end systolic volume
measured on an echocardiogram
Cardiac Output
stroke volume X heart rate (L/min)
(end diastolic volume minus end systolic volume) X heart rate
Ejection Fraction
the percentage of blood ejected from the ventricle in one contraction; measures the amount of blood hat the ventricle can eject compared to what it contains prior to ejection
stroke volume/end-diastolic volume
(end-diastolic volume minus end-systolic volume)/ end-diastolic volume
assesses ventricular function
normal is 55-60%
Diastole
relaxation phase; ventricles fill
Frank-Starling Relationship
the more that a myocyte is stretched, the more it can contract; therefore, increased ventricle filling (more blood in the ventricle, stretches the ventricle out) leads to increased stroke volume
Diastolic Dysfunction
impaired relaxation/stretch caused by thickness or stiffness of the ventricle wall, decreasing ventricular filling
normal compliance (determined by the ability of myocardial cells to stretch) of the ventricle is necessary to achieve optimal filling
Systole
ventricle contraction and ejection
work of the heart
begins in isovolumetric contraction, just before the semilunar valves open
Preload
the filling pressure of the heart; mechanically it is the initial stretching of myocytes prior to contraction
can be increased by anything that increases the volume of blood delivered to the ventricle
can be decreased by diminished compliance (stiffness) of the ventricle, with impaired relaxation, or by a decrease in volume delivered to the ventricle
Afterload
the pressure against which the ventricle contracts; or, as the aortic pressure for the left ventricle
Sympathetic Nervous System Effect on the Heart
causes peripheral vasoconstriction
increases peripheral resistance
increases heart rate and cardiac output
Parasympathetic Nervous System Effect on the Heart
fibers in the vagus nerve affect the SA and AV nodes (bearing down stimulates vagus and parasympathetic response)
slows heart rate
decreases force of atrial contraction
Eisenmenger Syndrome
when a left-to-right shunt switches to ta right-to-left shunt
the left-to-right shunt causes damage to the vasculature of the lungs overtime
non-oxygenated blood moves from the right atrium into the left atrium and is sent to the body
the body does not get enough oxygen, resulting in cyanosis and clubbing
Four Congenital Abnormalities of Tetrology of Fallot
ventricular septal defect
RV infundibular stenosis - thickening of the pulmonary valve
a dilated, misplaced aorta (right sided aortic arch 25%, and anomalous left anterior descending coronary artery form right cusp 7-9%)
right ventricular hypertrophy - thickening of right ventricular wall
High levels of hemoglobin and hematocrit are evidence of
cyanosis
