Maximum hyperemia is needed to correctly measure FFR. This is most often achieved by giving adenosine intravenously (IV) or by intracoronary bolus.1 The disadvantages of intravenous administration of adenosine are the need for a separate access point, the longer time to onset of hyperemia and an intensely unpleasant feeling in the chest or throat of the patient. IC bolus administration of adenosine has other drawbacks in that it only creates hyperemia for a few seconds and it does not allow for performance of a pressure- pullback recording.2
The principle of FFR is based upon the presence of true maximum hyperemia, which requires a hyperemic stimulus. If full maximum hyperemia is not present, FFR is overestimated and stenosis severity underestimated.
The ideal hyperemic stimulus should be easy to administer, have a short onset until maximum hyperemia is achieved, have a duration long enough to enable pressure pullback recordings (a few minutes), have few side effects, and be eliminated within a few minutes.3
In 2009 the principle of continuous infusion of hyperemic agent via a standard microcatheter was shown to be safe, effective and faster in inducing optimal steady-state hyperemia than the standard IV infusion method.4
This was achieved using less than 5% of the standard IV dosage of adenosine, which may offer significant savings to routine practice.
Continuous IC infusion offers the combined benefits of IV infusion and IC bolus. It is compatible with pull-back during hyperemia whilst providing confidence in results from prolonged, maximal hyperemia. Need for FFR Infusion Microcatheters. IC infusion of adenosine is also compatible with radial procedures, offers a fast & targeted drug delivery, and ticks all the boxes for the ideal hyperemic stimulus. Despite these advantages the IC infusion method has not been widely adopted due to the absence of devices specifically designed for this purpose. The continuous IC infusion method could be made simple and practicable for everyday application by an OTW FFR Infusion Microcatheter such as HYPEREM™IC (www.hyperemicstudy.com).