492
U N I T 5
Circulatory Function
The cardinal symptoms of systolic failure are dyspnea,
fatigue, and peripheral edema. Other symptoms include
orthopnea and paroxysmal nocturnal dyspnea, signs of
jugular venous distention and cardiac enlargement.
22
Preserved Ejection Fraction Heart Failure.
Although
heart failure is commonly associated with impaired sys-
tolic function, in approximately half of the cases systolic
function is preserved (EF > 50%) and heart failure results
from an inability of the left ventricle to fill sufficiently
during diastole.
23–25
Hypertension remains the leading
cause of diastolic dysfunction. Other conditions that
cause diastolic dysfunction include those that impede
filling of the ventricle (e.g., pericardial effusion, con-
strictive pericarditis), increase ventricular wall thickness
and reduce chamber size (e.g., myocardial hypertrophy,
hypertrophic cardiomyopathy), or delay diastolic relax-
ation of the ventricle (e.g., aging, hypertension).
25
The
prevalence of diastolic failure increases with age and is
higher in women than men, and in persons with obesity,
hypertension, and diabetes. Aging is often accompanied
by a delay in relaxation of the heart during diastole such
that diastolic filling begins while the ventricle is still
stiff and resistant to stretching. A similar delay in filling
occurs in myocardial ischemia, resulting from a lack of
energy to break the bonds that form between the actin
and myosin filaments and to pump calcium out of the
cytosol and back into the sarcoplasmic reticulum.
23
With diastolic dysfunction, ventricular relaxation
and distensibility are impaired leading to an increase
in intraventricular pressure at any given volume.
The elevated pressures are transmitted backward from
the left ventricle into the left atrium and pulmonary
venous system, causing pulmonary congestion and a
decrease in lung compliance, which increases the work
of breathing and evokes symptoms of dyspnea. Cardiac
output is decreased, not because of a reduced ventricu-
lar EF as seen with systolic dysfunction but because of a
decrease in ventricular filling. Diastolic function is fur-
ther influenced by the heart rate, which determines how
much time is available for ventricular filling. An increase
in heart rate shortens the diastolic filling time. Thus,
diastolic dysfunction can be aggravated by tachycardia
and improved by a reduction in heart rate, which allows
the heart to fill over a longer period of time.
Left-sided versus Right-sided Heart
Dysfunction
The clinical manifestations of heart failure depend upon
which heart chamber (i.e., the left or right) is dysfunc-
tional (Fig. 20-5). An important feature of the circula-
tory system is the fact that the left and right ventricles
function as two pumps that are connected in series. To
function effectively, the left and right ventricles must
maintain equal outputs. Although the initial event that
leads to heart failure may be primarily left or right ven-
tricular in origin, heart failure usually progresses over
time to involve both ventricles.
Left Ventricular Dysfunction.
The clinical features of
heart failure affecting the left ventricle result from a
diminished cardiac output with a resultant decrease in
Right ventricular failure
Congestion of peripheral tissues
Liver congestion
Dependent
edema
and ascites
Signs related
to impaired liver
function
Anorexia, GI distress,
weight loss
Left ventricular failure
Pulmonary congestion
Decreased cardiac output
Activity
intolerance
and signs of
decreased
tissue
perfusion
Pulmonary
edema
Impaired gas
exchange
Cough with
frothy sputum
Orthopnea
Paroxysmal
nocturnal dyspnea
Cyanosis
and signs of
hypoxia
GI tract
congestion
FIGURE 20-5.
Manifestations of right and left ventricular failure. GI, gastrointestinal.
