Effects of high potassium cardioplegia and hypothermia on myocardial compliance and distribution of water and potassium. II. The hypertrophied canine heart.

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High potassium solution for elective car?ioplegia associated with hypothermia has been shown to be effective for electromechanical arrest and myocardial presemation. The extracellular space (ECS), intracellular potassium, percentage of water change, and ventricular compliance were measured after I hour of reperjksion following I hour of high (35 mEq/liter) and low (5 mEqlliter) potassium (K’) cardioplegia employing normothermia and hypothermia in the isolated per@sed hypertrophied heart. The ECS measured with ‘H inulin in the hypertrophied control group was 27.80 -C 0.1% with total water content of 81. I I!I 0.4%, both of which were higher than the previously measured normal myocardium (p < 0.05). High potassium hypothermic arrest and reperjkion showed no change in ECS or intracellular K+ in normal hearts but produced an increase in EC’S (35.2 k 3.0) (p < O.OOI) and intracellular potassium in the hypertrophied group. Low potassium hypothermic arrest and reperfirsion showed no change in EC’S and increase in intracellular K’ in normal hearts but produced increased ECS (45.0 + 3.3%) and intercellular K’ in hypertrophied hearts (P < 0.05). High potassium normothermic arrest and reperjksion showed increased ECS and intracellular potassium in both normal hearts, ECS = 27.8 + 0.1% Cfour dogs) (p < 0.05) and hypertrophied hearts, ECS = 55.7 + 1.2% (P < 0.05). Compliance measurements in hypertrophied hearts showed no change with hypothermic high and low potassium arrest but decreased compliance (I’ < 0.05) when normothermic high K’ arrest was employed. Postperfusion shiffs of potassium in the reper@sion period suggest decreased potassium eflux and +-reasedjuid shift in all groups except the normal myocardium protected with hypothermic high K’ solution. Although d@rent from controls, hypertrophied hearts protected with hypothermic high K’ solution showed less juid shifts and potassium e&x than did the hypertrophied hypothermic low K’ or hypertrophied normothermic high K+ groups. The hypertrophied heart is more susceptible to &id and potassium shifts afier potassium arrest than is the normal heart with high K’ hypothermic arrest producing the least amount of changes.