Hello and thank you for using HCM. I carefully read your question and I understand your concern.I will try to ecplanin you something and give you some advises.
As you describe, my opinion is that we are dealing with an rhythm issue. Someone might feel fast and pounding heart beats for different reasons.
It might be to simple
sinus tachycardia when you heart just beats regularly over 100 beat for minute. Its normal resting rate is between 60-100 beat for minute. Normal sinus tachycardia might happen for different reasons from simple emotional stress to
anemia,
hyperthyroidism ect.
This abrupt, sudden fast heart beating might be a different rhythm issue like supra-
ventricular tachycardia or atrial
fibrillation. You feel exactly like your heart is running very fast in a regular or irregular caotic way.They give this sensation like
anxiety or difficulties in breathing deeply. They might happen for the same reasons like sinus tachycardia.
The rhythm issues are independent from
hypertension. You might have hypertension and not have rhythm problems and you might have rhythm problems when your blood pressure is normal .So, if i was your treating doctor i will recommend you make some examinations like a blood analyses, your thyroid hormons, electrocardiogram, echo-cardiography and a holter monitoring to see what kind of rhythm problem is this.
In mean time avoid caffeine products and alcohol because they exacerbate you symptoms.
Hope I was helpful. Best regards.