Parameters of vascular resistance, perfusion pressure, and blood flow were measured as the temperature of the isolated gracilis (dog) muscle and perfusing blood was lowered continuously from approximately 37.5 C to 25 C. The rate of change of temperature varied from 4.20 C/min to 0.13 C/min. At the rapid rate of lowering the temperature, the vascular resistance of the muscle decreased and then increased. As the rate of lowering the temperature was decreased this response progressively changed to only an increased resistance. Eight experiments were performed in which the potassium concentration of the venous whole blood and plasma was determined as the temperature of the muscle was lowered. There was no significant change in the mean potassium concentration of the venous whole blood during hypothermia. However, the potassium concentration of the plasma decreased continuously as the temperature was lowered. Correlation coefficients between the change in peripheral resistance and the potassium concentration of the plasma appeared to be significant at the 5% level.
Genetic channelopathies can predispose individuals to life-threatening arrhythmias. Two such channelopathies are long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). To the best of our knowledge, we present the first case of LQTS with novel combined genetic mutations of KCNH2 and cardiac ryanodine receptor (RYR2) genes.
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