What are causes of dyspnea in aortic stenosis? Which stage of disease the symptom will appear?

Causes of dysnea in AS -

•Dysnea occurs because of pulmonary congestion which occurs due to raised LVEDP as a result of decreased LV compliance.(Please refer to pathophysiology explanation in case discussion AS )

•Occurs when preload reserve is exhausted

•Dysnea is more so on exertion as it is typically described as dysnea on exertion DOE due to limited cardiac output during exercise,increase in heart rate leading to myocardial O2 demand supply mismatch causing ischaemia,tachycardia causing decreased diastolic time and decreased coronary filling.All these eventually lead to raised LVEDP.

•Diastolic dysfunction from LV hypertrophy or ischaemia

•Systolic dysfunction from afterload mismatch (AS)

•Ischaemia

Symptoms occur in AS at various stages of the disease process like

•When the initial flow velocity is <3m>
•When it is >4m/s ,70% chance of AVR in next 2 years

In bicuspid valves –symptoms appear earlier, in 40 years of age

In degenerative old patients –may appear late in 60 or more years of age

Asymptomatic AS – there exists this entity as well wherein  patients may first get their symptoms while doing exercise tests in hospital.