228
CARDIOVASCULAR PHYSIOLOGY CONCEPTS
■ FIGURE 9.14 Changes in cardiac pressures and volumes associated w ith chronic mitral valve regurgita-
tion in the absence of systolic failure. The le ft panel shows that during ventricular contraction, the left
ventricle ejects blood back into the left atrium as well as into the aorta, thereby increasing left atrial pres-
sure (
LAP
), particularly the
v
wave. The aortic pressure (AP) and left ventricular pressure
(LAP)
may fall
in response to a reduction in the net volume of blood ejected into the aorta; a systolic murm ur is present
between S, and just beyond S2. The rig ht panel shows the effects of mitral valve regurgitation
(red loop)
on the left ventricular
(LV)
pressure-volume loop. End-systolic volume is reduced because of decreased
outflow resistance (afterload); end-diastolic volume is increased because increased left atrial pressure
increases ventricular filling; stroke volume is greatly enhanced. There are no true isovolumetric phases
because blood flows across the valve whenever there is a pressure difference across the valve.
and volume increase. In chronic mitral regur-
gitation, volume overload causes the ventri-
cle to undergo dilation, thereby increasing its
compliance. This dilation would cause wall
stress (afterload) to increase if it were not for
the reduced outflow resistance that tends to
decrease afterload during ejection. The net
effect of these changes is that the width of
the pressure-volume loop (stroke volume) is
increased; however, ejection into the aorta is
reduced by the regurgitant fraction.
In summary, mitral regurgitation is charac-
terized by a tall
v
wave, a systolic murmur,
increased stroke volume but reduced net
ventricular outflow into the aorta, ventricu-
lar dilation, no true isovolumetric phases,
increased ventricular filling pressures, and
increased left atrial and pulmonary vascular
pressures.
PULMONIC AND TRICUSPID VALVE
REGURGITATION
Pulm onic regurgitation produces changes
to
the
right side
of the
heart
that
are
analogous to those produced on the left side
of the heart by aortic regurgitation. Regur-
gitation across the pulm onic valve leads to
increased pulm onary artery pulse pressure,
increased
right
ventricular
end-diastolic
volum e and pressure, and a diastolic mur-
mur. There is no true isovolum etric phase
during right ventricular systole and dias-
tole. Because the right ventricle becom es
volum e overloaded, it responds by dilating,
and right atrial and system ic venous pres-
sures increase.
Tricuspid
regurgitation
causes
a
tall
v
wave in the right atrial pressure tracing, an
overall increase in right atrial volum e and
system ic venous pressures, and a systolic
murmur. Right ventricular stroke volum e
is increased, but ejection into the pulm o-
nary artery may be reduced because of the
large volum e of blood ejected into the right
atrium during ventricular systole. Reduced
ejection into the pulmonary artery decreases
left ventricular filling and stroke volume,
leading to activation of neurohumoral com -
pensatory m echanisms.
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