Rapid cooling contracture with cold cardioplegia.
BACKGROUND
Cold cardioplegia can induce rapid cooling contracture. The relations of cardioplegia-induced cooling contracture to myocardial temperature or myocyte calcium are unknown.


METHODS
Twelve crystalloid-perfused isovolumic rat hearts received three 2-minute cardioplegic infusions (1 mmol/L calcium) at 4 degrees, 20 degrees, and 37 degrees C in random order, each followed by 10 minutes of beating at 37 degrees C. Finally, warm induction of arrest by a 1-minute cardioplegic infusion at 37 degrees C was followed by a 1-minute infusion at 4 degrees C. Indo-1 was used to measure the intracellular Ca2+ concentration in 6 of these hearts. Additional hearts received hypoxic, glucose-free cardioplegia at 4 degrees or 37 degrees C.


RESULTS
After 1 minute of cardioplegia at 4 degrees, 20 degrees, and 37 degrees C, left ventricular developed pressure rose rapidly to 54% +/- 3%, 43% +/- 3%, and 18% +/- 1% of its prearrest value, whereas the intracellular Ca2+ concentration reached 166% +/- 23%, 94% +/- 4%, and 37% +/- 10% of its prearrest transient. Coronary flow was 5.7 +/- 0.2, 8.7 +/- 0.3, and 12.6 +/- 0.6 mL/min, respectively. Warm cardioplegia induction at 37 degrees C reduced left ventricular developed pressure and [Ca2+]i during subsequent 4 degrees C cardioplegia by 16% (p = 0.001) and 34% (p = 0.03), respectively. Adenosine triphosphate and phosphocreatine contents were lower after 4 degrees C than after 37 degrees C hypoxic, glucose-free cardioplegia.


CONCLUSIONS
Rapid cooling during cardioplegia increases left ventricular pressure, [Ca2+]i and coronary resistance, and is energy consuming. The absence of rapid cooling contracture may be a benefit of warm heart operations and warm induction of cardioplegic arrest.
Lahorra
J A
JA
Cardiac Surgical Unit, Massachusetts General Hospital, Harvard Medical School, Boston, USA.
Torchiana
D F
DF
Tolis
G
G
Bashour
C A
CA
Hahn
C
C
Titus
J S
JS
Geffin
G A
GA
Daggett
W M
WM
D000818:Animals; D001831:Body Temperature; D002118:Calcium / Q000032:analysis; D002314:Cardioplegic Solutions / Q000737:chemistry; D003080:Cold Temperature; D004734:Energy Metabolism; D006324:Heart Arrest, Induced; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D017682:Myocardial Stunning / Q000209:etiology*; D009206:Myocardium / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D017725:Ventricular Pressure
D002314:Cardioplegic Solutions; D002118:Calcium