@dlowan,
Preventive medicine and physical conditioning are effective ways of alleviating your fear.
Your anxiety (while not unfounded) is a bit unrealistic. You need to handle your anxiety before it turns into panic attacks and then some well meaning physician will start prescribing valium which only dulls your senses and makes you dependent.
If you get on with some good sense exercise and maybe even taking an aspirin every otherday, you can consider a cardiac condition as a maneageable condition even if you are eventually afflicted.
Your friend, more than likely, ws the recipient of a double dose of bad luck.
1His genes were probably a story of a family history replete with "dropping dsead" and heart attacks
2 Ill bet he had some dietary or life style issues.
Worrying about this can interfere with actually enjoying your life.