Cardiogenic Shock - Diagnosis and Treatment

234 Part VI / Other Cardiac Disease
pressure, including hepatomegaly and systemic edema (Table 1). Unlike patients with
tamponade, patients with constrictive pericarditis have increased systemic venous pres-
sure during inspiration (Kussmaul’s sign). Shock is rare in constrictive pericarditis, but
hypotension is occasionally observed.
The rigid shell that surrounds the heart in patients with constrictive pericarditis
prevents the transmission of respiratory variations in transthoracic pressure into the
pericardial sac. In contrast to tamponade, constrictive pericarditis limits only late,
and not early, diastolic filling. Because of the rigidity of the pericardial sac, ventricu-
lar relaxation is rapid and is followed by a deep fall in early diastolic pressure. This
produces an early diastolic dip in ventricular pressure, with a corresponding promi-
nent Y descent in atrial and systemic venous pressures. The early fall in intracardiac
pressure is followed by rapid filling, producing the typical dip and plateau configura-
tion of the ventricular diastolic pressure tracing. These findings are easily recognized
on intracardiac pressure recordings and are useful for the differential diagnosis
between tamponade and constriction. Calcification of the pericardial sac strongly
supports the diagnosis of constriction and is better detected by CT or MRI than by
echocardiography.
Noninvasive Quantification of Pericardial Fluid Volume
The size of the effusion is a strong predictor of outcome for patients with cardiac
tamponade and is superior to other outcome predictors such as right-heart diastolic col-
lapse, distension of the superior vena cava, and respiratory flow variations (27). Nonin-
vasive quantification of pericardial effusion can therefore be beneficial in assessing the
need for pericardiocentesis in patients without overt tamponade. However, the com-
monly used methods for quantification of pericardial fluid volume by echocardiogra-
phy are not satisfactory, being based on M-mode echocardiographic findings or
involving complex calculations (28,29).
We measured the anteroposterior pericardial sac diameter before pericardiocentesis
in 83 procedures and found that it correlated well with effusion size (8). Our method
was more accurate in predicting the size of larger versus smaller effusions. However,
this disadvantage is not clinically important because in patients with smaller effusions,
the decision to intervene depends not on size but on the hemodynamic effects of the
effusion or other clinical parameters (e.g., suspicion of purulent pericarditis or a need
for diagnostic aspiration).
Cardiac Catheterization
Cardiac catheterization can provide important hemodynamic information on sta-
ble patients with pericardial effusion, but it is rarely indicated in hemodynamically
unstable patients with clinical and echocardiographic findings typical of cardiac
tamponade. Tamponade may develop, however, during cardiac catheterization and
other invasive procedures in the catheterization laboratory and in patients undergo-
ing balloon pericardiostomy.
The typical findings in patients with cardiac tamponade are elevated intrapericardial
and right atrial pressures, which decline during inspiration. Right atrial pressure typi-
cally has a systolic X descent, with an absent or nearly absent diastolic Y descent. Nor-
mal right atrial pressure in the presence of pericardial effusion suggests a nontense
effusion or a low-pressure tamponade.
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