CARDIOMETRIC STUDIES ON CHILDREN V. VARIABLE P-R INTERVAL AND VARIATIONS OF HEART SOUMS AND VENTRICULAR SYSTOLE1

Autor: William E. Poel, Carroll E. Palmer
Rok vydání: 1942
Předmět:
Zdroj: Child Development. 13:269-278
ISSN: 1467-8624
0009-3920
DOI: 10.1111/j.1467-8624.1942.tb05610.x
Popis: It is known that the duration of the diastolic period preceding the auricular contraction plays a large part in determining the next stroke output, and therefore the duration of ventricular systole. However, available literature does not mention the effect on the cardiac output and ventricular systole, of variations in the time interval between auricular and ventricular contractions (that is, variations of the AsVs or P-R interval). Wright, in his Applied Physiology (6, p. 403) says: "On the average, auricular systole is said to contribute thirty-five per cent of the total ventricular output . . . the exact proportion depending on the time in diastole at which auricular systole occurs, the vigor of auricular systole, and the completeness with which the ventricle is already filled. ... An auricular contraction early in diastole may contribute up to sixty percent of the ventricular output, whereas at the end of a long diastole, the ventricle may already be so full that the auricle can contribute relatively little." Simultaneously recorded electrocardiograms and stethograms, obtained in a case of A-V nodal escape and nodal rhythm presented in the preceding report of this series, offered an unusual opportunity to study the effect of variations of the As-Vs or P-R interval on the duration of ventricular systole in an organically normal heart. The stethographic data and tracings herein presented also added significantly to our understanding of the relationship between variations in the time intervals of successive auricular and ventricular contractions, and the character of the changes in the heart sounds produced by those variations. The case reported is that of a clinically normal white girl 16 years of age, in whom transition from sinus rhythm to A-V nodal rhythm or periods of A-V nodal escape occurred spontaneously or were induced in a number of ways described. Technique. Stethographic tracings were taken routinely at the mitral, tricuspid, aortic, and pulmonic areas. A Sanborn Stetho-Cardiette was used throughout the study. The machine is arranged to record simultaneously both the sound track and the electrocardiogram on a 6 cm. bromide-paper record. Stethograms were always run simultaneously with Lead II, at a film speed of 75 rmm. per sec. The length of all desired electrocardiographic and stethographic intervals was measured in halfmillimeters, dropping all smaller fractions. The measurement was multiplied by 1.333 to calculate time duration in hundredths of a second.2 The sound tracings were taken with the standard microphone and medium sized bell supplied by the manufacturers.
Databáze: OpenAIRE
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