Análisis de la Sístole Eléctrica Ventricular de Ovinos I. Fenómenos de Despolarización

Abstract

Summary Analysis of electrical ventricular systole in the sheep. 1. Depolarization phenomena Over a time period from birth to one year a study was made of the ECG in sheep of the early maturing merino breed in order to determine the influence of physical maturation on the process of ventricular depolarization. The QRS complex undergoes an increase in length in the course of bodily development; the electrical potential, on the other hand, is significantly lower in the 1‐year old animal. The morphological structure also seems to be involved since in V10 the Q‐spike is absent in the newborn; it becomes more frequent with increasing age. The length of both the RR interval and the QT interval undergo and increase from 20 days of age; there also occurs a highly significant correlation between the two intervals. The length of ventricular activation showed, however, no significant correlation with the length of the cardiac cycle. Resumen Se han analizado ECG procedentes de ovinos de raza Merino Precoz, a lo largo de un periodo de tiempo comprendido entre el nacimiento y la edad de 1 año, con el fin de determinar la influencia de la maduración física sobre el proceso de despolarización ventricular. El complejo QRS experimenta un aumento en su duración a medida que se produce la maduración física; por el contrario, el voltaje se muestra significativamente inferior en los individuos de 1 año. También la morfología parece verse afectada ya que, en V10, la onda ‘q’ está ausente en los individuos recién nacidos, haciéndose más frecuente a medida que aumenta la edad. Tanto la durción del intervalo RR como del intervalo QT experimenta un incremento a partir de los 20 días de edad, obteniéndose, además, una correlación muy significativa entre ambos. Sin embargo, la duración de la activación ventricular no presenta correlación significativa con la duración del ciclo cardíaco. Zusammenfassung Analyse der elektrischen Herzkammersystole bei Schafen I. Depolarisationsphänomene Während einer Zeitperiode, die von der Geburt bis zum Alter eines Jahres geht, wurden Elektrokardiogramme untersucht, die von Schafen der Frühreifen‐Merino‐Rasse stammten zwecks Feststellung des Einflusses der physischen Reife auf den Prozeß der ventrikulären Depolarisation. Der QRS‐Komplex erfährt einen Zuwachs in seiner Länge im Laufe der Entwicklung der körperlichen Reife; die elektrische Spannung hingegen ist signifikant niedriger bei den einjährigen Individuen. Der morphologische Aufbau scheint ebenfalls betroffen zu sein, da bei V10 die Q‐Zacke bei den Neugeborenen ausblieb; sie wird häufiger mit zunehmendem Alter. Sowohl die Länge des Intervalls RR wie die des Intervalls QT erfahren einen Zuwachs ab einem Alter von 20 Tagen; dabei wird außerdem eine hochsignifikante Korrelation zwischen beiden Intervallen erzielt. Jedoch weist die Länge der ventrikulären Aktivierung keine signifikante Korrelation mit der Herzzykluslänge auf.

The normal electrocardiograms in the conscious newborn lambs in neonatal period and its progression

“…The wave and complex morphology was quite variable throughout the neonatal period. Various QRS patterns were found; however, no specific pattern predominated for a particular week of growth, contrary to that literature described [ 42 – 45 , 48 ]. In general, lambs that exhibited a particular pattern at birth, maintained this pattern until 35 days of age, but at a reduced voltage.…”

“…The values of certain parameters obtained from the six leads placed in the frontal plane and base-apex in this study were not available in the published literature for this age group of the Bergamasca breed. In general, our results differed to those obtained for adults, but were similar to those described by Tovar et al [ 42 – 45 ].…”

“…However, these characteristics could not be identified in our study; therefore, it is likely that the QRS duration increased over the initial 3 weeks of life to occur predominantly in the left ventricle or left ventricular hypertrophy. A decrease in QRS complex amplitude with advancing age was also observed by Tovar et al [ 42 , 43 ] which was explained by an increased degree of cancellation promoted by the development of the Purkinge network during the neonatal period. With the animal growth and consequents gains of body surface area and body weight, it also occurs the development of cardiac mass, and decreases in R-wave amplitude is related to the maturation of the His bundle and Purkinje cells, carrying to synchronous depolarization [ 38 , 47 ].…”

“…Ventricular repolarization is influenced by maturity, with a significant decrease in amplitude being recorded within 2 weeks of birth. According to Tovar et al [ 42 , 43 ], the most significant decrease in amplitude occurs within the first 4 days of birth. The high polarity of the T wave immediately after birth is probably the result of respiratory abnormalities caused by the birthing process and the immaturity of the autonomic tonus.…”

Avaliação cardiovascular do neonato ovino

“…De acordo com Piccione et al (42) há uma relação inversamente proporcional entre a idade e a frequência cardíaca até os 30 dias de vida. A frequência cardíaca superior, em relação aos adultos, em recém-nascidos de diversas espécies animais deve-se ao baixo volume sistólico durante o período neonatal (39,40 A diminuição da frequência cardíaca com o avançar da idade (42,43) e o consequente aumento do intervalo RR descrito em ovinos por Tovar et al (44), são reflexo das alterações nos mecanismos intrínsecos de controle da frequência cardíaca, não relacionadas ao tônus autonômico propriamente dito. A atuação intrínseca do sistema colinérgico e beta-adrenérgico na variabilidade da frequência cardíaca foi investigada em cordeiros recém-nascidos a partir da primeira a oitava semana de idade.…”