What are
the symptoms and long-term prognosis of aortic stenosis?
The classic symptoms in patients with severe
aortic stenosis (AS) are angina, syncope and congestive heart failure (CHF).
Life expectancy in untreated cases is approximately 5 years after developing
angina, 3 years after developing syncope, and 2 years after developing CHF.
Angina is the initial symptom in 50–70% of patients, but only about 25–50% have
coronary artery disease (CAD). Patients without CAD develop angina because of
inadequate oxygen delivery to a hypertrophied myocardium.
Concentric hypertrophy occurs in AS as the left
ventricular wall thickness increases in a symmetrical fashion. The advantage of
the hypertrophied myocardium is that greater intraventricular pressures may be
generated with lower wall tension. The relationship between intra-cavitary
pressure (P), wall tension (T), left ventricular radius (R), and wall thickness
(h) is described by the Law of Laplace:
T = P × R/2h
Tension generation in the myocytes is the most
inefficient way of performing cardiac work because it requires large amounts of
oxygen. In addition, oxygen delivery is decreased because of the lower coronary
perfusion pressure (CPP):
CPP =
diastolic aortic pressure – left ventricular end-diastolic pressure
As the AS becomes more severe, a decrease in
the diastolic aortic pressure compromises the CPP even more. The hyper-trophied
myocardium also results in decreased left ventricu-lar compliance and higher
left ventricular filling pressures. The neovascularization of the
pressure-overloaded heart has also been shown to be inadequate for the degree
of hypertro-phy. Finally, the isovolumic phase of relaxation is
inappropri-ately long, shortening diastole, and leaving less time for coronary
perfusion. For all these reasons, patients with AS are prone to developing
myocardial ischemia during anesthesia.
Syncope is the initial symptom of AS in 15–30%
of patients. It is usually exertional, and is caused by exercise-induced
vasodilation in the face of a fixed cardiac output. CHF portends the worst
long-term prognosis. At this time, the heart has exceeded its ability to
compensate for pressure work with myocardial hypertrophy. The heart then
progres-sively dilates, and symptoms of left ventricular failure appear.
Classic
Symptoms of Aortic Stenosis
o
Angina
o
Syncope
o
Congestive
heart failure
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.