Advances in Physiology Education, Vol 256, Issue 6 9-13, Copyright © 1989 by American Physiological Society
Use of frog ventricle to examine mechanical and electrical activity of heart
V. A. Knight, D. R. Richardson and B. Makoba
Department of Physiology, University of Transkei, Faculty of Medicine and Health Sciences, Southern Africa.
This report describes a Langendorff heart preparation, which utilizes frog
rather than mammalian hearts to demonstrate both mechanical and electrical
events of the cardiac cycle. The preparation is durable in that it can be
maintained for several hours while being perfused with room-temperature
solutions that are not supplemented with oxygen. Ventricular perfusion is
achieved via a fluid-filled reservoir coupled to a truncus arteriosus
catheter advanced into the ventricle. By varying the height of the
reservoir relative to the heart, changes in ventricular pressure and the
rate of ventricular pressure change during systole can be recorded by way
of a side port on the catheter tubing. The former is indicative of
Starling's law of the heart, whereas the latter is reflective of the
contractility. Electrical activity of the heart can be observed by
measuring injury potentials via a needle electrode inserted into the
ventricle. These are extracellular potentials that reflect ventricular
action potentials. In addition, surface electrodes placed on the ventricle
can be used to detect an integrated ventricular electrocardiogram.
Recording of ventricular pressure simultaneously with at least one of these
two electrical recordings allows a direct comparison of electrical and
mechanical events of the heart. In summary, the Langendorff frog heart
preparation is economical in terms of both financial cost and simplicity;
yet it enables a thorough examination of both electrical and mechanical
properties of the heart either as a student lab exercise or as a classroom
demonstration.
