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

patients were randomized into two groups. Patients randomized to preconditioning
received a preconditioning stimulus of two 3 minute periods of cross-clamping separated
by 2 minutes of reperfusion prior to the long 10 minute ischaemic insult. The control
patients received 10 minutes cross-clamping with fibrillation only. During the 10 minutes
cross-clamping the first distal aorto-coronary anastomosis was performed. Myocardial
ATP was determined from biopsy specimens taken at the onset of cardiopulmonary
bypass, at the end of preconditioning, and at the end of the 10 minute ischaernic insult.
Preconditioning resulted in a significant depiction of the myocardial ATP content. The
ten minutes of ischaernia resulted in a significant depletion of ATP in the controls.
Ischaernic preconditioning appeared to slow down the rate of myocardial ATP depletion
in the preconditioned group to such an extent that at the end of the 10 minutes ischaemic
insult, preconditioned hearts had a significantly higher ATP content than the controls.
This was in keeping with the metabolic changes that have already been dcmonstrated in
animal models [2521. Yellon's group has also investigated whether preconditioning alters
the release of troponin T, a reliable and sensitive marker of myocardial damage, in
patients undergoing coronary arlery bypass surgery using the same preconditioning
protocol. They found that the preconditioned patients released significantly less troponin
T into the blood at 72 hours post surgery [1461. However, subsequent investigators
[161,2421 have failed to show any benefit from preconditioning when used in similar
models in the presence of cardioplegia. Therefore the evidence that ischaernic
preconditioning protects the human heart still remains scant and conflicting.
32