Dr. Patrick Owens:

This can be done in two ways, one of which is to say that the thrombolytic trials, that is, those trials that have studied thrombolysis as an effective treatment for unblocking an artery, suggest that thrombolysis alone gives about a 50-50 chance of unblocking the artery. This ratio can be increased a little by giving other medications. While we routinely give these medications, one is still talking about a 55% to 65% chance of opening the artery. Primary PCI gives as close as one can get to a guarantee that the artery will be open. Patency rates, the rate at which the artery is rendered open, would approximate to around 95%. That is one way of expressing the comparison.

Primary PCI is clearly a highly superior treatment for opening the artery. The critical issue is that it takes longer to do using primary PCI because of the transfer time. It is for this reason that the whole concept of the time delay to treatment has come to the fore. While this is something of a generalisation, essentially what the figure of 90 minutes represents is the time point beyond which there is no superior benefit from primary PCI.

That does not mean, however, that at 89 minutes one accrues the entire benefit. It means that the benefit arguably is one ninetieth of what it might otherwise be. The 90 minute goal has become a hackneyed phrase and its meaning must be seen in those terms. It is a question of relative benefit and the relative benefit is felt to be lost once the 90 minutes has elapsed, but the benefit is so much greater if one is at 60 minutes. Perhaps an under-emphasised element of having a primary PCI unit in Waterford is that people from all over the south east, including south Tipperary and west Waterford, are within the 90 minute window for Cork, for example, or for St. James's but they are within a 60 minute window from Waterford and arguably a 30 minute window and that implies a much greater benefit from the procedure.