ECHOCARDIOGRAPHIC STUDY OF HEART-RATE IN DOG AND CAT FETUSES IN-UTERO

The heart rate of dog and cat fetuses in utero was studied using real- time B and M mode ultrasonography. Fifteen bitches and 15 queens were monitored from day 19 after the luteinizing hormone (LH) peak in the b itch, and from day 15 after the first mating in the cat, up to parturi tion, using a 7.5 MHz linear transducer. The first fetal cardiac movem ents and the cardiac frequency were detected from days 23 and 29 after the LH peak and from days 18 and 25 after mating, in the bitch and in the queen, respectively. In bitches, heart rates were higher 1230.2 /- 15.4 beats per minute (b.p.m.)] than values previously reported. In itial average values were 214 +/- 13.3 b.p.m. and these significantly increased thereafter, with an average of 238.2 +/- 16.1 b.p.m. at day 40. A reduction was noted near parturition. In queens, the average val ues recorded were 228.2 +/- 35.5 b.p.m. Contrary to what has been obse rved in the bitch, the cardiac frequencies remained stable during preg nancy.