Hello! Thank you for asking on HCM! Regarding your concern I would explain that
left ventricular dysfunction is the most wide and important chapter in cardiac pathology gallery. Almost every disease affecting the heart do involve to some degree LV function. Many different etiologies may be the reason:
(1)
ischemic heart disease (
unstable angina and
myocardial infarction),
(2)
valvular heart disease (valvular stenosis and/or regurgitation),
(3) different cardiomyopathies
(4) infective involvement of every cardiac component,
($) pericardial diseases
(5) persistent arrhythmia (atrial or ventricular),
(6) some systemic diseases, environmental factors (radiation, chemical compounds, etc), etc, etc.
So the list is ever lasting and expanding.
I don't know the medical history of your sister. If you bring some data, i could give a more concrete opinion.
Hope to have been helpful to you. Greetings!