Bainbridge Reflex

Bainbridge Reflex

Bainbridge Reflex was described over a century back, in 1918 as the influence of venous filling on the heart rate [1]. It was noted as an increase in heart rate in response to a rise in central venous pressure. Mechanoreceptors for the Bainbridge reflex are located at the junction of the right atrium and the caval veins and at the junction of pulmonary veins and the left atrium [2]. It is also known as Bainbridge effect and sometimes called the atrial reflex. Efferent arm of the reflex could involve both parasympathetic withdrawal and sympathetic enhancement.

Axial stretch has been shown to increase spontaneous pacemaker activity in isolated rabbit sinoatrial node cells [3]. This could also contribute to the Bainbridge effect. Increase in inspiratory heart rate in respiratory sinus arrhythmia has been attributed to the Bainbridge reflex in response to increased venous return as the intrathoracic pressure falls. Bainbridge reflex is thought to counter the effect of baroreceptor reflex which causes bradycardia in response to increased arterial pressure.

References

1. Bainbridge FA. The influence of venous filling upon the rate of the heart. J Physiol. 1915 Dec 24;50(2):65-84. doi: 10.1113/jphysiol.1915.sp001736. PMID: 16993330; PMCID: PMC1420590.
2. Hakumäki MO. Seventy years of the Bainbridge reflex. Acta Physiol Scand. 1987 Jun;130(2):177-85. doi: 10.1111/j.1748-1716.1987.tb08126.x. PMID: 3300168.
3. Cooper PJ, Lei M, Cheng LX, Kohl P. Selected contribution: axial stretch increases spontaneous pacemaker activity in rabbit isolated sinoatrial node cells. J Appl Physiol (1985). 2000 Nov;89(5):2099-104. doi: 10.1152/jappl.2000.89.5.2099. PMID: 11053369.