The isolated human pectinate muscle: a reliable preparation of human cardiac tissue.

We have developed an anatomically and functionally intact preparation of isolated pectinate muscles from readily-available surgical specimens of human right atrial appendage. Individual pectinate muscles (2-3 per specimen) are dissected free and mounted in a tissue bath. Field stimulation is used for electrical pacing, and isometric contractions are recorded. The pectinate muscle develops a stable and large force of contraction and hence is superior to strips cut from atrial appendage specimens. Isolated pectinate muscles develop spontaneous beating or can be induced to beat spontaneously by brief periods of electrical pacing or transient exposure to epinephrine or histamine. Spontaneously-beating muscles increase their rate and force of contraction in response to drugs which have positive chronotropic and inotropic effects in the whole heart. Because the force of contraction of the pectinate muscle is a function of the rate of beating, inotropic effects of agents should also be evaluated in preparations which are electrically paced at a constant rate.