Welcome to HCM
Aftergoing thriugh history of your mother,she has Ischemic heart disease
and treated by stent in coronary but we need to know status of other coronary arteries and condition of colateral blood flow.
This is left ventricular function called Ejection Fraction
20%.This means she has heart failure
She should continue to take regular medicines as advised by treating cardiologist life long.
Why pace maker is advised there are certain indications if any one is there this helps,like if there is heart block( CHB),some time in poor heart function it is done for resynchronization to improve heart function.
In patients of low EF and if there are arrythmia
risk of sudden death is there which is taken care by AICD ( D Fib) ,I can understand your concern but discuss with your cardiologist advantages and think and take appropiate decision as these interventions are expensive.
Even heart transplantation