What are the causes of ST segment depression in V1 , V 2, and V3 in inferior myocardial infarction ?

ST segment depression is a fairly common observation in anterior precardial leads. It   is  due to

1.  Pure electrical phenomenon (Referred to as reciprocal changes)*
2.  Additional  ischemia in LAD territory
3.  It could imply  the IRA  is  a critically occluded  LCX and STEMI is actually an   infero -posterior STEMI
4.  Simply  indicate a  multi vessel disease.
5. Many times  reciprocal changes may simply indicate extensive nature of the  index  inferior MI.

How to differentiate reciprocal ischemia from true  remote ischemia ?*

• Logically true ischemia patients  should suffer from double dose of angina (Infarct pain plus ischemic). Most of these patients will present in a   scenario of  post infarct persistent  angina . Patients with   pure electrical reciprocal  changes are relatively  quiet and  severe distress is uncommon.
• In true ischemia  , both patterns are  not temporally related  in time. If its a  pure electrical phenomenon they should be linked in time .
• Disproportionate ST segment depression  (ST elevation  in inferior lead  is  2 mm  while ST depression in v1,v2, v3 is >  3 mm )
• Persistence of ST depression even after thrombolysis  or PCI to IRA.
• Worsening with thrombolysis would suggest ST depression in V1V2 and v3  is indeed an  episode of  true NSTEMI  of LAD , where thrombolysis is contraindicated. (Also  read  – A  related article  dual acute coronary syndrome in this site )
• Echocardiogram will give us a clue .One can  detect ischemic the wall motion defect in the segment in dispute .(Reciprocals do not show WMA )
• Coronary angiogram   would provide   definite  answer to the speculations in most  . Still , it may   require a FFR  to confirm ischemia in the contra lateral artery.