ischaemic preconditioning of the human heart. - Leicester Research ...

human myocardium However, atria] and ventricular myocardiurn possess characteristics
of their own that may influence the susceptibility to ischaemia/reperfusion injury and as a
consequence
results from one may not be applicable to the other. Thus, for example, the
reported differences in the distribution of potassium channels [5,132], which contribute to
the charactenstic differences between atrial and ventricular action potentials, may
determine a different response to ischaemia/reperfusion. Undoubtedly, KATpchannels are
present in both atnurn and ventricle [1321, although their density in both tissues is
unknown. It must also be mentioned that the preparation is superfused ("simulated
ischaemia") as opposed to being artenally perfused and simulated ischaernia is achieved
by removal of oxygen and blocking glycolytic ATP production with 2-deoxyglucose.
This results in metabolic conditions within the myocardium that may be different than
that which occurs in the myocardium during clinical ischaernia.
Another possible limitation might be that right atrial appendages were obtained
from patients subjected to various medical treatments (e. g. nitrates, P-blockers, calcium
antagonists) and that in principle may have influenced ischaemia/reperfusion injury and
the protection induced by preconditioning. However, it should be emphasized, that all
medication was stopped the day before surgery when specimens were taken for the study
and that significant effect of the medication was unlikely since all preparations responded
to ischaemia/reperfusion
with a similar degree of injury. It should be mentioned that the
preparation used in this study was not electrically stimulated (i. e. non-beating) and
therefore one should be cautious when extrapolating to the in vivo situation.
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