Effect of mild chronic hypoxia on the infantile heart: ECGs of guinea pigs pre- and postnatally treated with carbon monoxide.

: Contrary to rats, developing guinea pigs don't react with a hypertrophy of their hearts following sublethal chronical intoxication with CO (200 ppm in room air applied to the pregnant mothers and subsequently to the infant animals). Since birth weight and postnatal growth remained in normal ranges, tissue oxygenation must have been sufficient despite a concentration of 30 +/- 4.5% COHb. Hence, ECGs didn't show characteristic parameters of heart hypertrophy. However, alterations of QRS vector loops consist in a more pronounced but retarded rightward accentuation during the first 4 days of life and afterwards in an accelerated turnover to the left relative to controls. We suppose a pathological volume loading of both the ventricles during the first week of postnatal life, caused by the chronically acting hypoxia.