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Chapter: Clinical Cases in Anesthesia : Aortic Stenosis

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).

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

 

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