hi and welcome.
well if you have no other risk factors for heart diseases and your cardiologist has done all the preliminary tests and they all are clear , then there is no need to worry.
you mentioned arrythmia
... what exactly do u mean by that. do you feel black outs, change in your pulse rate and regularity ... any episode of syncope
or palpitations or a missed beat .. or is it just the apprehension.
too much daily stress
of our life has impact on our heart because too much neurotransmitters
released form our nerves can increase our heart rate
and gives us feeling of apprehension . if there is no chest heaviness especially on exertion , and no shortness of breath
then it is of no significance. but if you have any of the symptoms i mentioned then its prudent to have a holters monitoring for 24 to 48 hours that will reveal any rhythm disturbance . causes can be sort out accordingly.
its also ideal that blood pressure should be controlled and any anxiety
relieved because it can cause the most common of the rhythm disturbance called SVT. i would suggest you meet a senior cardiologist and it will help . take care and best regards