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 !)