The Journal of Thoracic and Cardiovascular Surgery, Vol 88, 424-431, Copyright © 1984 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Optimal intraoperative protection of myocardium distal to coronary stenoses
NA Silverman, G Schmitt, S Levitsky and H Feinberg
Metabolic evidence of improved delivery of cardioplegic solutions by
adjuvant use of nitroglycerin (NTG) and reinfusing these solutions distal
to an obstructed coronary artery was sought in 40 dogs subjected to cold
cardioplegic arrest. The left anterior descending coronary artery was
occluded prior to initiating arrest by intra-aortic root infusion.
Cardioplegic solution was reinfused with the left anterior descending
occluded throughout ischemia (Group I), or with this artery reopened, to
simulate a completed distal anastomosis (Group II). Serial biopsy specimens
of the left ventricular apex were assayed for adenosine triphosphate and
creatine phosphate, while specimens from the posterior left ventricular
wall served as controls. Regional myocardial temperatures were recorded
throughout ischemia. Half of the hearts in each group received 300
micrograms of nitroglycerin in the cardioplegic solution. Adenosine
triphosphate was preserved in myocardium distal to a patent coronary artery
whether nitroglycerin was added to the cardioplegic solution or not
(control, control + NTG). Moreover, nitroglycerin did not prevent the 26%
to 34% (p less than 0.05) decline in adenosine triphosphate levels when the
left anterior descending remained obstructed throughout ischemia (Group I,
I + NTG). However, opening the left anterior descending for reinfusion of
cardioplegic solution allowed adenosine triphosphate to be preserved at
end-ischemia (Group II, II + NTG). In addition, the metabolic reperfusion
injury manifested by a 37% (p less than 0.01) decline in adenosine
triphosphate levels after aortic unclamping (Group II) was obviated when
nitroglycerin was added to the cardioplegic solution delivered in this
manner (II + NTG). The depletion of cardioplegic solution stores during
ischemia was more severe in the experimental groups than in controls (p
less than 0.05). These metabolic changes did not correlate with regional
myocardial temperature gradients. The data indicate that myocardium
jeopardized by coronary stenoses can be preserved as well as myocardium
supplied by a patent coronary artery by adjuvant use of nitroglycerin and
varying the mode of delivery of the cardioplegic solution.
