Ventriculophasic Reflex

This is part of: Supraventricular Rhythms

Ventriculophasic reflex during second degree AV block type I. The PP interval that follow upon the blocked sinus beat is prolonged.[1]

Ventriculophasic reflex is a phenomenon that can be seen during AV block or during ventricular extrasystoles in bigemini. It describes the sinus arrhythmia that exists during a irregular rhythm. The phenomenon has been described by Erlanger and Blackman in 1910 [2]. Different theories have been postulated to explain the phenomenon (a.o. by Wenkebach), but the theory as published by Rosenbaum and Lepeschkin in 1955 [1] is the most accepted.

A positive chronotropic (accelerating) effect on the ventricular contraction is probably caused by stretch on the right atrium by contraction of the ventricles. A negative chronotropic effect (slows down) is probably caused by a vagal reflex caused by stimulation of the carotic arterial baroreceptors by the pressure wave. The result of these two effects determines whether the P-P interval that surrounds the extra beat is shorter or longer than the P-P interval that surrounds the missing beat.

The baroreflex influences both the sinusnode and the AV node and thus both sinus rate and atrioventricular conduction can be influenced.

References

1. ROSENBAUM MB and LEPESCHKIN E. The effect of ventricular systole on auricular rhythm in auriculoventricular block. Circulation. 1955 Feb;11(2):240-61. DOI:10.1161/01.cir.11.2.240 |

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