ST segment depression is a fairly common observation in anterior precardial leads. It is due to
- Pure electrical phenomenon (Referred to as reciprocal changes)*
- Additional ischemia in LAD territory
- It could imply the IRA is a critically occluded LCX and STEMI is actually an infero -posterior STEMI
- Simply indicate a multi vessel disease.
- 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.