European Journal of Cardio-Thoracic Surgery, Vol 2, 167-171, Copyright © 1988 by European Association for Cardio-thoracic Surgery
Intraoperative assessment of myocardial revascularisation for the relief of ischaemia using monophasic action potential recordings
T Treasure, P Taggart, P Sutton and W O'Brien
Middlesex Hospital, London, UK.
We have been concerned with developing a method of assessing regional
myocardial perfusion which is simple, quick and without hazard to the
patient. Monophasic action potential (MAP) recordings provide a highly
sensitive measure of localised myocardial ischaemia. We have developed a
hand-held pressure contact silver/silver chloride electrode for recording
MAP signals from the left ventricular epicardium. The design enables it to
slide within the pericardium on the left ventricle/epicardium with minimal
displacement of the heart. Three protocols were adopted providing different
permutations of atrial pacing and graft occlusion. Protocol 1: after
discontinuing bypass, atrial pacing was established. After 90 s, all grafts
were occluded for a period of 90 s. Protocol 2: after discontinuing bypass,
all grafts were occluded for 90 s in the absence of pacing. Protocol 3:
atrial pacing was established for 60 s before grafting and bypass and
repeated subsequent to grafting and discontinuing bypass. Our results show
that the most promising method is protocol 3. The most important results
were that when heart rate is taken into account, the ischaemic changes in
the MAP were significantly less impressive (P less than 0.05) following
grafting. With further refinement, this technique may be applicable to the
assessment of individual grafts.
