Left ventricular performance during by-pass or distension of the right ventricle.

• The close anatomical relationship between the two ventricles of the heart implies some kind of functional effect upon each other. This effect could be manifested in at least two different ways. An indirect "hemodynamic" effect could be exercised by one ventricle upon the other, because differences in the output of the one ventricle may affect the input to the other ventricle. A direct or "mechanical" effect could also be expected because of anatomical connections. Common muscular bundles encircle both ventricles and it is difficult to believe, for example, that a change in the strength of contraction could be limited strictly to the part of these bundles that extends over one of the ventricles. The degree of distension of the wall of one ventricle may be expected also to affect the function of the other ventricle. A limited number of studies has been published, referring to the effect of by-passing or distending the right ventricle on the dynamics of the circulation. Grodins et al. replaced the right ventricle by a Sigmamotor pump in order to study the response of systemic pressure to variations of right heart output. They found that the arterial systemic pressure was a positive function of the pump output. Guyton et al." used a partial right heart by-pass preparation and pointed out the dependence of cardiac output upon several heart parameters. On the other hand, Taquini et al. constricted the lumen of