Long-term myocardial preservation: beneficial and additive effects of polarized arrest (Na+-channel blockade), Na+/H+-exchange inhibition, and Na+/K+/2Cl- -cotransport inhibition combined with calcium desensitization.
BACKGROUND
Polarized arrest, induced by tetrodotoxin (TTX) at an optimal concentration of 22 micromol/L, has been shown to reduce ionic imbalance and improve myocardial preservation compared with hyperkalemic (depolarized) arrest. Additional pharmacologic manipulation of ionic changes (involving inhibition of Na+ influx by the Na+/H+ exchanger [HOE694] and Na+/K+/2Cl- cotransporter [furosemide], and calcium desensitization [BDM]) may further improve long-term preservation. In this study, we (i) established optimal concentrations of each drug, (ii) determined additive effects of optimal concentrations of each drug and (iii) compared our optimal preservation solution to an established depolarizing cardioplegia (St Thomas' Hospital solution No 2: STH2) used during long-term hypothermic storage for clinical transplantation.


METHODS
The isolated working rat heart, perfused with Krebs Henseleit (KH) buffer was used; cardiac function was measured after 20 min aerobic working mode perfusion. The hearts (n=6/group) were arrested with a 2 ml infusion (for 30 sec) of the polarizing (control) solution (22 micromol/L TTX in KH) or control+drug and subjected to 5 hr or 8 hr of storage at 7.5 degrees C in the arresting solution. Postischemic function during reperfusion was measured (expressed as percentage of preischemic function).


RESULTS
Dose-response studies established optimal concentrations of HOE694 (10 micromol/L), furosemide (1.0 micromol/L) and BDM (30 mmol/L) in the polarizing (control) solution. Sequential addition to the control solution (Group I) of optimal concentrations of HOE694 (Group II), furosemide (Group III), and BDM (Group IV) were compared with STH2 (Group V); postischemic recovery of aortic flow was 29+/-7%, 49+/-6%*, 56+/-2%*, 76+/-3%*, and 25+/-6%, respectively (*P<0.05 vs. I and V). Creatine kinase leakage was lowest, and myocardial ATP content was highest in Group IV.


CONCLUSIONS
A polarizing preservation solution (KH+TTX) containing HOE694, furosemide, and BDM significantly enhanced long-term preservation compared with an optimized depolarizing solution (STH2) used clinically for long-term donor heart preservation.
Snabaitis
A K
AK
Cardiovascular Research, The Rayne Institute, St Thomas Hospital, London, United Kingdom.
Chambers
D
D
D000227:Adenine Nucleotides / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates; D002122:Calcium Chloride; D002314:Cardioplegic Solutions; D003402:Creatine Kinase / Q000378:metabolism; D004734:Energy Metabolism; D006146:Guanidines / Q000494:pharmacology; D006321:Heart / Q000187:drug effects; D006323:Heart Arrest / Q000139:chemically induced; D008274:Magnesium; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009926:Organ Preservation / Q000379:methods*; D011188:Potassium; D011189:Potassium Chloride; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors; D013450:Sulfones / Q000494:pharmacology; D013779:Tetrodotoxin
D000227:Adenine Nucleotides; D001639:Bicarbonates; D002314:Cardioplegic Solutions; D006146:Guanidines; D017923:Sodium-Hydrogen Exchangers; C041711:St. Thomas' Hospital cardioplegic solution; D013450:Sulfones; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; D013779:Tetrodotoxin; D012965:Sodium Chloride; D011189:Potassium Chloride; D003402:Creatine Kinase; D008274:Magnesium; D002122:Calcium Chloride; D011188:Potassium