6 8
CARDIOVASCULAR PHYSIOLOGY CONCEPTS
LV
Pressure
(mmHg)
LV
Volume
(ml)
LV
Pressure
(mmHg)
a
b
c
d
a
■ FIGURE 4.4 Ventricular pressure-volume loops. The left ventricular pressure-volume loop (bottom
panel) is generated by plotting ventricular pressure against ventricular volume at many different cor-
responding points during a single cardiac cycle (upper panel), a, ventricular filling;
b,
isovolumetric
contraction; c, ventricular ejection;
d,
isovolumetric relaxation; EDl/and
ESV,
left ventricular end-diastolic
and end-systolic volumes, respectively;
EDPVR,
end-diastolic pressure-volume relationship;
ESPVR,
end-systolic pressure-volume relationship;
SV,
stroke volume (EDV - ESV).
The units for cardiac output are expressed
as either milliliters/minute (mL/min) or liters/
min. The units for SV are mL/beat, and the
units for heart rate are beats/min. In a rest-
ing adult, cardiac output typically ranges
from 5 to 6 L/min. Sometimes cardiac output
is expressed as a cardiac index, which is the
cardiac output divided by the estimated body
surface area (BSA) in square meters. Several
different formulas can be used to estimate
BSA. One formula is BSA (m2) equals the
square root of the (height [cm] times weight
[kg] divided by 3600); BSA = (cm • kg/3600)1/2
(Mosteller formula). Calculating the cardiac
index normalizes cardiac output to individu-
als of different size. A normal range for car-
diac index is 2.6 to 4.2 L/min/m2.
PROBLEM 4-1
Calculate left ventricular SV in
milliliters/beat when the cardiac output
is 8.8 L/min and the heart rate is
110 beats/min.
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