Dear Concerned.,
Thanks for writing to us.
In your history you have not mentioned your age/duration since you have been smoking?have you also developed breathing difficulty during work outs?
In all probabalities it could be an Anginal attack /Angina pectoris we call in medical terms.
During excercise there will be increase in blood flow to the extremities and due to clogging of respiratory passage and /narrowing of various blood vessels due to your smoking habit , the airflow through bronchi getting reduced and blood flow through coronaries being reduced due to narrowing /clogging, there will be lack of oxygen and nutrients and also accumulation of metabolites in
cardiac musculature leading to Ischemia and pain .This needs to be immediately investigated.
Have you consulted any doctor/paramedic to check your Pulse/BP/breathing pattern at that time?Pls get your Vitals Checked in a nearby health centre.In addition get investigated by ECG/Chest X-ray/Baseline blood/Urine Examinations/Lipid Profile(Most Important).
These days even in secondary healthcare units they have Non invasive 64 slice CT Angiogram availability to delineate exactly the type and extent of lesions.Pls get investigated and consult a Cardiologist.
Coming to the immediate First Aid., you must be given coronary vasodilators such as sorbitrate/antiplatelet agents such as aspirin/oxygen/statins/ In Consultation with MD , be shifted to a Cardiac care centre for further management.
Prevention:-(1) immediately stop smoking habit/drinking habit.
(2)Reduce weight by dieting and regular excercise.
(3) Overall life style modifications including developing Type "B" personality if you are Type "A". (4) Regular follow up with your MD.

Wishing you a speedy recovery.,
Best regards.,
Dr Lt Cdr ASN Bhushan.,
Ex-navy