Primary PCI (pPCI) is probably* the best modality in the management of STEMI .
( *Probably because , we know “Time” ( fate !) is still the most crucial determinate of ultimate outcome of STEMI )
Any experienced interventional cardiologist will be aware of the surprises and difficulties they encounter during primary PCI.
The pPCI is all about opening up the IRA rapidly and wheel out the patient from cath lab at the earliest.
But , ironically , an often under- reported issue is the difficulty in identifying IRA itself !
One may wonder , how this can happen ?
Following difficulties can occur in identifying IRA during primary PCI*
(* There are some hyper-talented cardiologists who would never consider IRA recognition as an issue .This article is not meant for them.)
The problems can range anything between the following queries
- Where is the IRA?
- Is that the IRA?
- No IRA ?
- Multiple IRAs !
Angiographic encounters during pPCI and IRA trouble shooting .
- When there is diffuse multivessel disease.
- Thrombus vs eccentric plaque both showing intra luminal filling defect .
- Thrombus spill over to adjacent branch or A mid LAD lesion with stagnating thrombus extending to LCX ostium mimicking two IRA
- A bifurcation lesion with both LAD and LCX ostial occlusion.
- Multiple active looking plaques with thrombus
- STEMI in patients with preexisting CAD . Is it a CTO ? ATO ? (Acute total occlusion ) A CTO ,which is fed by collaterals from contralateral artery , if this feeding vessel is occluded even partially , STEMI will occur in CTO territory . Here , for rapid salvage you need to open the vessel that feeds the CTO territory.
- Post CABG and post PCI form a special subset . Some times it is very difficult or even impossible to label a graft as an IRA
Finally and most importantly , when there is no visible lesion in any of the coronary arteries and look near normal ! Is that no IRA ? or Wrong diagnosis of STEMI ? Every one blinks in cath lab . The consultant howls the fellow to verify the ECG . Finally it may well turn out to be an early repolarisation syndrome . These are wages we often pay for the modernity !
How to approach the situation when one is confused with identifying the IRA ?
The good old ECG will come to our rescue sometimes. Realise in a multivessel CAD , ECG is also vested with errors.
Echocardiography rarely gives a convincing answer to localise IRA. (Segmental overlap , preserved sub epicardial contraction , residual ischemia all tend to confound )
Most confusions occur between LAD and diagonal /LCX as there can be a huge overlap in the ECG territory anterolateral segments
In a infero posterior STEMI, if you have both RCA / LCX lesion and you wonder which is the IRA it is easy to solve by looking for RV involvement. (LCX lesions however dominant they are . 99/100 times can not infarct the RV significantly !)
If the lesion is in PDA the issue is made simple.
Doing a primary PCI blindly without knowing the IRA
This is modern-day cardiology at its scientific low ! . Cardiologists indulge in such things much more commonly than one would imagine.
Probably they would reason , it is safe to stent every vessel that is potentiality an IRA , rather than missing it. Though the concept of multivessel stenting in STEMI may help patients with complicated MI , like pump failure , it generally increases risk of primary PCI outcome in otherwise stable STEMI. Primary PCI procedure must be as short as possible. The other option is to do plain balloon angioplasty in less deserving vessels.
Important considerations in the setting of complex multivessel CAD during pPCI .
- Fall back on medical therapy
- Staged PCI
- Deferred or Immediate CABG
- Hybrid procedures like PCI with CABG
Final message
IRA identification can indeed be a difficult task during primary PCI. Sound knowledge and experience about coronary anatomy and its draining territories especially in the setting of multivessel CAD is essential to avoid errors.
Dr.S.Venkatesan MD 
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