C h a p t e r 1 9
Disorders of Cardiac Function
467
tamponade is pulsus paradoxus, or an exaggeration
of the normal variation in the systolic blood pressure.
Pulsus paradoxus is defined as a 10 mm Hg or more
fall in the systolic blood pressure that occurs with inspi-
ration.
42,43
Normally, the decrease in intrathoracic pres-
sure that occurs during inspiration accelerates venous
flow, increasing right atrial and right ventricular filling.
This causes the interventricular septum to bulge to the
left, producing a slight decrease in left ventricular filling,
stroke volume output, and systolic blood pressure. In
cardiac tamponade, the left ventricle is compressed from
within by movement of the interventricular septum and
from without by fluid in the pericardium (Fig. 19-17).
This produces a marked decrease in left ventricular fill-
ing and left ventricular stroke volume output following
inspiration.
Computed tomography (CT) and magnetic resonance
imaging (MRI) are useful adjuncts to echocardiography
in cardiac tamponade. The ECG often reveals nonspe-
cific T-wave changes and low QRS voltage. Usually only
moderate to large effusions can be detected by chest
radiography.
Closed pericardiocentesis, in which fluid is removed
from the pericardial sac through a needle inserted
through the chest wall, may be an emergency lifesaving
measure in severe cardiac tamponade. Open pericardio-
centesis may be used for recurrent or loculated effusions
(i.e., those confined to one or more pockets in the pleu-
ral space), during which biopsies can be obtained and
pericardial windows created. As with pericardial effu-
sion, laboratory evaluation of the pericardial fluid may
be used to identify the causative agent.
Constrictive Pericarditis
In constrictive pericarditis, fibrous scar tissue develops
between the visceral and parietal layers of the serous
pericardium. In time, the scar tissue contracts and inter-
feres with diastolic filling of the heart, at which point
cardiac output and cardiac reserve become fixed. It is
most commonly associated with inflammation resulting
from infections, mediastinal radiation, or cardiac surgi-
cal trauma.
The condition is characterized by high venous pres-
sure, low cardiac output, narrow pulse pressure, and
fluid retention.
44
Ascites is a prominent early finding
and may be accompanied by pedal edema, dyspnea on
exertion, fatigue, and jugular venous distention. The
Kussmaul sign is an inspiratory distention of the jugu-
lar veins (opposite of normal physiology) caused by the
inability of the right atrium, encased in its rigid peri-
cardium, to accommodate the increase in venous return
that occurs with inspiration. Exercise intolerance, mus-
cle wasting, and weight loss develop in end-stage con-
strictive pericarditis. Surgical removal or resection of
the pericardium (i.e., pericardiectomy) is the treatment
of choice.
Pericardium
Left
ventricle
Normal
expiration
Normal
inspiration
Tamponade
(in inspiration)
FIGURE 19-17.
Effects of respiration and cardiac tamponade
on ventricular filling and cardiac output. During inspiration,
venous flow into the right heart increases, causing the
interventricular septum to bulge into the left ventricle.
This produces a decrease in left ventricular volume, with
a subsequent decrease in stroke volume output. In cardiac
tamponade, the fluid in the pericardial sac produces further
compression of the left ventricle, causing an exaggeration of
the normal inspiratory decrease in stroke volume and systolic
blood pressure.
SUMMARY CONCEPTS
■■
The major threat of pericardial disorders,
which include acute and chronic or recurrent
pericarditis, pericardial effusion, cardiac
tamponade, and constrictive pericarditis, is
compression of the heart chambers.
■■
Acute pericarditis may be infectious in origin
or it may be due to systemic diseases. It is
characterized by pleuritic chest pain, fever, ECG
changes, and pericardial friction rub. Recurrent
pericarditis, which is usually associated with
autoimmune disorders, often produces few
symptoms.
■■
Pericardial effusion, either acute or chronic, refers
to the accumulation of fluid or exudate in the
pericardial cavity. It can increase intracardiac
pressure, compress the heart, and interfere with
venous return to the heart.The amount of fluid
(continued)
