Chapter 11 / Cardiogenic Shock and Valvular Heart Disease 159
In the subset of patients who present in cardiogenic shock with left ventricular dys-
function and low cardiac output, the transvalvular gradient does not truly reflect the
severity of the stenosis. In these patients, resting transvalvular gradients are usually
modestly elevated because of the low transaortic flow rate. Therefore, calculation of the
aortic valve area is mandatory.
In cases of a technically difficult transthoracic study, valve area planimetry by TEE
can be helpful (28). This relatively new method for measuring valve area is still contro-
versial, however, and some authors question its validity in patients with heavily calci-
fied valves (29).
An evaluation of the change in valve area with a change in flow rate, by using phar-
macological stress echocardiography, may be helpful in a subgroup of patients with
aortic stenosis and coexisting significant left ventricular dysfunction. It is sometimes
difficult to separate patients with true, anatomically severe AS from those with a
reduced aortic opening owing to poor left ventricular function in the setting of only
mild to moderate aortic valve obstruction (i.e., “functional aortic stenosis”). If the
transaortic flow rate increases during dobutamine stress echocardiography, the resul-
tant increase in flow rate increases the degree of aortic valve opening when the primary
process is left ventricular dysfunction. In contrast, when severe valvular obstruction is
present, the aortic valve area remains unchanged with increased transaortic velocity
and pressure gradient. When there is no increase in flow rate, it remains unclear
whether the failure to increase flow rate results from an unresponsive myocardium or a
stiff aortic valve restricting an increase in ventricular outflow (30).
A patient with severe AS and poor left ventricular function may benefit from PBAV
or aortic valve replacement, whereas a patient with primary left ventricular dysfunction
and associated mild or moderate valvular disease may not (31,32). Although dobuta-
mine stress is not always applicable in patients in cardiogenic shock, it may be useful
in patients who are already on a regimen of catecholamines. In patients who recover
from cardiogenic shock, dobutamine stress testing is very useful for selecting those
who might benefit from surgery or PBAV.
TREATMENT
Medical therapy for patients with critical AS and cardiogenic shock should include
optimal ventilatory and inotropic support. Occasionally, an intra-aortic balloon pump is
required, providing there is no concomitant moderate or severe aortic regurgitation. Every
effort should be made to identify and treat the precipitating factors such as anemia, infec-
tion, arrhythmias, and an acute coronary event. It is not, however, recommended that med-
ical stabilization be the ultimate goal of treatment; these patients should have urgent or
emergency interventional therapy (PBAV or aortic valve replacement) as soon as possible.
Surgical therapy: The experience with emergency or urgent aortic valve replacement
(AVR) in patients with cardiogenic shock from critical aortic stenosis is limited. Aortic
valve replacement in these patients is associated with high mortality and morbidity
(33,34). Although AVR provides definitive and long-lasting relief of AS in some criti-
cally ill patients, surgeons consider most patients presenting with cardiogenic shock
and multiorgan failure to be too risky for cardiac surgery; thus, the only alternative for
these patients is PBAV.
Percutaneous balloon aortic valvuloplasty was reported in elderly patients with criti-
cal aortic stenosis and relative contraindications to surgery in several studies in the late
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