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How does un-accoustomed exertion trigger an acute coronary syndrome ?

Posted Nov 26 2011 11:51am

Exertion and  acute coronary syndrome (ACS) has a tricky relationship. On the one  hand, it  would  appear they are not related at all  as only a miniscule of patients   give history of recent severe exertion prior to ACS   , while  few others  tell us  a clear- tale of   unaccustomed  exertion ,  just prior to the onset of chest pain.

Here is case history  of a  man  who was rushed to our  ER from  Madras central station ( Our hospital is located just opposite to it !  )

A  48 year bank officer  was  about to board  a train to Patna   . It was a rainy  November  evening ,  his car got struck in traffic .He along with  his family members were rushing to catch the rain  .He had  to run fast with his heavy luggage  .Even as they boarded  the train successfully and occupied their  seats  ,   within minutes  he  developed intense chest pain and sweating . The distressed family de-boarded the train and was rushed to our hospital  . Yes  you guessed it right   . . . he  was showing an extensive ST elevation  in anterior leads on arrival.

So what  has  happened ?  What is the coronary hemo-dynamics during heavy unusual physical exertion ?

The above patient did  not have any obvious risk factor . He vaguely recalled ,   one if his family doctors telling him ,  he had borderline high BP and was never prescribed a  drug . His wife told us  he has been a emotionally  liable individual .

It is well  known  , sudden exertion in an  emotional  milieu   would  result  in  intense  adrenergic drive  . (Here the emotion was anxiety/ fear of missing the train )  Adrenergic drive was  amplified with the  isometric exercise (heavy suitcases ) ,   shoots the intra  coronary blood pressure (normal 45-60mmhg)  into  dangerous spikes . (By the way , what happened to  coronary auto regulation  ?) . We also  realise simple raise  of  intra coronary pressure alone is not sufficient  .These patient  will  harbor at least some degree of  atherosclerosis  which face a  shearing stress and give way /tear  or fissure resulting in  a sudden substrate for intra coronary  thrombosis.  Some of them may manifest  only  as coronary vasospasm  .When sustained  it can also result in a full-blown acute coronary syndrome.

The concept of trigger vs risk factor

One should remember  both physical and mental exertion   act  mainly as a  trigger (They are not  major risk factors  like DM/HT/Smoking /Dyslipedemia) . All that is required ,  for  this   vulnerable population  to fire  is a trigger.  Physical exertion ( especially  isometric)  when  associated with  emotionally charged  brain  sends a  perfect  invitation  for an impending  ACS !

Another example  for untoward  effects of  exertion

A middle aged man who had  impaired glucose intolerance and dyslipdemia  was referred for an  EST.He did complete  12 minutes of  Bruce  protocol  comfortably . But  on the same day evening  ,  he felt  uneasy  and came to our ER ,   only to record a full blown STEMI .

These events may be rare but if properly understood   these  patients can teach  us  few   lessons in the genesis of ACS and coronary hemodynamics .

Special  issues  about   exertion in post PCI patients

One of the purpose of doing  PCI  for CAD  is to improve the  functional  capacity  (and possibly to prevent future ACS) . Paradoxically ,  we  continue  to have  some apprehension about subjecting post PCI  patients  into early stress testing . (I remember reading some guidelines that advice us to  avoid stress testing strictly for 6 months post PCI  ! Is it true ?)

If a  cardioloigst  is  not too comfortable  putting their  patients  into a  treadmill  post PCI ,  it only implies they doubt their efficacy ! It   would  also imply  these  patients   should  not be allowed to exert to their full capacity in day to day  life events as well .(Attention  cardiologists   . . . Yeh  . . . we have a  fundematal problem on our hand !)


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