Registration and interpretation of cardiovascular activity in the normal infant

122

THE

AMER.ICAN

IXEART

JOURNAL

The third paper shows, by means of heart-lung preparations, employing the tests used in the first paper for comparing capacity for work, that this function diminishes when thyroxin i,s fed to the animals for ten days prior to the making of the preparation and that with longer feeding (three weeks) the decline is greater. Furthermore, the seusitivity to strophanthin of hearts of cats which have been receiving thyroxin for longer than three weeks is markedly increased. The conflicting reports of earlier workers on the question of whether thyroxin increases the sensitivity of the heart to the action of strophanthin are explainable because, when thyroxin has been fed for less than two weeks, no change from normal is found. J. M. 8. Segura, Angel the Normal

S.: Registration Infant. Rev.

and Interpretation argent. d. cardiol.

of Cardiovascular 3: 3, 1936.

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The most striking result obtained by recording optically the heart sounds in 120 normal infants from birth to two years of age was the finding of three sounds per cycle in a great proportion (38 per cent). The moment of occurrence of this third sound and its time relation with the ordinary first and second heart sound and with the P-wave of the electrocardiogram sufficiently warrant the assumption that it is due to auricular systole. The phonocardiographic records show that the first heart sound of infants and young children has a duration ranging between 0.064 and 0.172 sec., with the majority of the results falling between 0.10 and 0.14 sec., the fundamental frequency being very constantly of about 40 per second. The first heart sound is the most intense on the mesocardiac area. The second heart sound lasts for between 0.045 and 0.164 sec., the majority of the results ranging from 0.055 to 0.10 sec., its fundamental frequency being also about 40 per second. The auricular sound (visible in 38 per cent of the cases and easily recognizable as vestigial vibration in another 31 per cent of the total number) is 0.06-CO.001 It lasts for about 0.057 sec. and shows sec. before the onset of ventricular systole. a fundamental frequency of about 40 per second (averagez39k0.68). The intensity of the auricular sound is the lowest as compared with that of the other sounds. No true reduplication of either the first or the second sound was ever recorded. There was no instance in the records of the so-called physiological third heart sound. The duration of the silent periods between the first and second sounds and between the second and the following first was practically the same in all cases. AUTHOR. Segura, A. S.: Registration and Interpretation Normal Infant. Rev. argent. de cardiol.

of Cardiovascular 3: 85, 1936.

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Ponla&lar P&e.-Optical tracings (Frank’s method) of the fontanellar pulse are easily obtained in infants after the lirst month of life. The record is somewhat similar to that of the central arterial pulse recorded in adults. It affords important information concerning the rhpthmicity of the heartbeat and (if recorded with the heart sounds) the approximate duration of the isometric contraction and ejection phases. The fontanellar pulse starts between 0.04 to 0.05 sec. after the first heart sound, this interval increasing with the age. The same relation can be found with the top of the R-wave of the electrocardiogram simultaneously recorded. The ascending limb is relatively steep, forming a 95” to 110° angle with the horizontal. Pernor& and Tibia1 B&e&-An optical record may be obtained by means of a pneumatic cuff, a sphygmoscope, and a segment capsule. The record in both cases