Article Text

Download PDFPDF
Repolarisation and refractoriness during early ischaemia in humans


OBJECTIVES To determine whether effective refractory period (ERP) shortens or lengthens in the first minutes of ischaemia in humans, and the relation between ERP changes and action potential duration (APD).

METHODS ERP and monophasic action potential duration (MAPD) were measured from a single left ventricular epicardial site in 26 patients undergoing coronary artery surgery. Cardiopulmonary bypass was instituted and normothermia maintained. Refractory period was determined by the extrastimulus technique at a basic cycle length of 500 ms, at four times (group 1, 15 patients) or two times (group 2, 11 patients) the preischaemic diastolic threshold. A three minute period of ischaemia was instituted by aortic cross clamping between the input from the pump oxygenator and the heart.

RESULTS After three minutes of ischaemia, mean (SEM) ERP lengthened from 232 (5) ms (control) to 246 (7) ms (p < 0.005) in group 1, and from 256 (10) ms (control) to 348 (25) ms (p < 0.005) in group 2. In the same time MAPD shortened from 256 (5) ms (control) to 189 (9) ms (p < 0.001) with no difference between groups. Thus postrepolarisation refractoriness developed during ischaemia. Before ischaemia, ERP showed a good correlation with APD (R 2 = 0.64) but by one minute of ischaemia the correlation was poor (R 2 = 0.29).

CONCLUSIONS These results show that during the first three minutes of global ischaemia in patients with coronary artery disease: (1) ERP lengthened in response to both a low and a high stimulus strength; and (2) there was a good correlation between ERP and APD before ischaemia, which was lost by one minute as APD decreased and ERP increased. These findings may have important implications in arrhythmogenesis.

  • refractoriness
  • ischaemia
  • repolarisation

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.