Chronic stable ischaemia protects against myocyte damage during beating heart coronary surgery.
OBJECTIVE
Many patients with coronary artery disease demonstrate chronic resting ischaemic myocardial dysfunction. We have investigated whether this ischaemia influences the myocardial damage caused by the period of coronary occlusion involved in beating heart surgery.


METHODS
Thirty-three patients with chronic stable angina and normal left ventricular ejection fraction were studied. To make our model clinically appropriate, we included patients with a wide range of ischaemic times, ages and in a subset of 10 patients a surgical preconditioning protocol. Myocyte injury was assessed from venous Troponin T release measured on days 1, 2, and 3. We used intraoperative transoesophageal M mode echocardiograms and simultaneous high-fidelity left ventricular pressure to assess whether patients were demonstrating the functional effects of ischaemia (asynchronous regional contraction with reduced mechanical function).


RESULTS
Patients demonstrated the functional effects of resting ischaemia and 17 did not. Patients with resting ischaemia had lower preoperative values of regional peak power and work and all three variables increased significantly with surgery. Venous Troponin T levels at 48 and 72 h postoperatively were lower in those with preoperative resting ischaemia (median (interquartile range) 0.13 (0.08-0.20) vs 0.21 (0.13-0.69) for 48 h and 0.10 (0.08-0.19) vs 0.26 (0.12-0.51) for 72 h). Stepwise multiple linear regression of total postoperative troponin release (measured as the area under the curve of troponin release) demonstrated two independent determinants (R squared for model 0.40): longer ischaemic time, and increasing values of cycle efficiency. The surgical ischaemic preconditioning protocol and preoperative collaterals were not independent determinants.


CONCLUSIONS
In patients with chronic coronary artery disease, stable preoperative ischaemia may thus represent a naturally occurring form of myocardial protection, whose presence reduces Troponin T release after beating heart surgery. This protection is different in nature from classical ischaemic preconditioning.
Carr-White
Gerald
G
Department of Academic Cardiac Surgery, Royal Brompton and Harefield Hospitals NHS Trust, Sydney Street, London, UK. g.carr-white@virgin.net
Koh
Tat
T
DeSouza
Anthony
A
Haxby
Elizabeth
E
Kemp
Michael
M
Hooper
James
J
Gibson
Derek
D
Pepper
John
J
D000368:Aged; D002315:Cardiopulmonary Bypass; D003097:Collateral Circulation; D001026:Coronary Artery Bypass / Q000379:methods*; D003327:Coronary Disease / Q000601:surgery*; D017548:Echocardiography, Transesophageal / Q000379:methods; D005260:Female; D006801:Humans; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D008875:Middle Aged; D032342:Muscle Cells / Q000473:pathology*; D011300:Preoperative Care / Q000379:methods; D020107:Troponin T / Q000097:blood; D016277:Ventricular Function, Left
D020107:Troponin T