Why 3-24h ?
The famous & popular 3-24 hr time window for pharmaco-invasive strateg(PIPCI) was adopted blindly from STREAM (prehospital tenecteplase + PCI <6-24h in <3h presenters) and FAST-MI trials assuming uniform IRA patency. It fails to stress the importance Initial time window to lysis, and its response . This makes the distinction between rescue vs routine pharmaco invasive PCI a hazy excercise . Thus, both inappropriately delayed or a hastily-routine PCI becomes all too common.
The 24-hour upper cutoff in pharmacoinvasive strategy serves to prevent reocclusion, or to address any residual stenosis . It is not meant for myocardial salvage, which is irrelevant if lysis was successful.
Mind you, IRA optimisation is not a time bound emergency in a well recannalised vesseel. In fact, PCI is not an absolute neccesity for long term IRA patency. With TIMI 3 flow ,and in the absence of any ischemic substrate , there is no need to chase the 24 hr time window. If lysis achieves complete( or almost complete) IRA patency, PCI can safely extended to 48-72 hours, or even permanent deferral (No-PCI , stand alone thrombolysis’ ) in stable patients with optimal medical therapy.
An intresting study is published , from my institute in the current issue of AJC with a title. Extended Pharmacoinvasive PCI Compared to Primary PCI: Insights From Madras Medical College STEMI Registry . This study argues for extending the time window for pharmacoinvasive strategy to 48 hrs. (It could still be higher.) It suggests , this flexibility suits the LMIC, due to logistical realities. ( Glad to be listed as a co-athour)
Link to the PDF of the article
I am sure, this study, demands to reset the 24 hr upper limit of cut off for pharmaco invasive strategy.Looking beyond this study, there is an urgent need to clarify the specifc purpose of the generalised time window of “3 to 24” hr time window in pharmaco invasive strategy.
A call for new sub defintions in the time windows in PIPCI
1.Successful Lysis* (TIMI 2-3, in about 70%): Routine angiography/PCI 3-24h (prevent reocclusion/residual stenosis) .Extendable to 48-72h + is possibel. Permanent deferral if the pateint and myocardiumare , with a patent IRA . (Implying no need for further salvage at all , we should allow a green corridor for patients with successful standalone thromolysis to exit the hospital without a PCI ) Doing a PCI onlu t0 prevent fear of reocclusion in the first 30 days is not backed with good data.
2.Failed Lysis* (TIMI 0-1, 30%): Rescue PCI immediately (<3-6h post-lysi, like PPCI) Here the time window should be hastened and can never afford to extend it, at any stretch of imagination.
* Ironically, the 24hr cut of has no place in both the above subsets. (May be in failed lysis , 24 hr cut off might apply , again it is 12 hr longer than primary PCI )
Final message
Time is no longer the muscle , if the Intial lysis is suscessful .
What is the purpose of “24-hour” upper limit cut of time in pharmaco invasive strategy ? The 24 hr is not universally valid. Pharmaco Invasive strategy time windows need to be based on timing and efficacy of the Initial lysis.
Postamble
Commenting this paper as a third person : (With due respect to all the authours )
One limitation in this study is to be admitted. I think, the generalised comparative efficacy of extended PIPCI with primary PCI can not be made, for the simple reason, the extension of time window is possible only in patients who had successful lysis. This study may ideally be concluded as “3-24h pharmacoinvasive PCI can be extended to 48h if the initial lysis successful” . Further, If initial lysis fails (30% TIMI 0-1), any extension is contraindicated and requires immediate rescue PCI akin to PPCI. Also, data regarding non-IRA intervention might help understand the importance of the extension of the time window better.
Dr.S.Venkatesan MD 