Exercise Tolerance and Hemodynamic Studies After Replacement of Canine Mitral Valve With and Without Preservation of Chordae Tendineae
The effect of the mitral Starr-Edwards ball-valve prosthesis on cardiac function was investigated in the dog. Fifteen dogs were studied for the first 48 hours after replacement of the mitral valve (the chordae tendineae [see Figure in the PDF file] had been totally resected, partially resected, or preserved). The cardiac output and left atrial pressure were similar in these three groups of animals and in two animals subjected to sham operation. Ten dogs (five with intact chordae and five with excised chordae) were studied two months after the insertion of a Starr-Edwards prosthesis. In these animals normal hemodynamic values were obtained at rest and during infusion of acetylcholine, except for a marked (liastolic gradient across the prosthesis, which developed at high cardiac output and heart rate. Six dogs were able to complete a standard test of substantial, unrestrained, graded exercise and gave a normal heart rate response. Heart rate increased and was maintained during maximal efforts, to levels of about 300 beats/min, demonstrating that heart rate need not be a limit of cardiac performance. No evidence of left ventricular dysfunction or of a decrement in cardiac performance could be demonstrated in dogs early or late after replacement of the mitral valve with a Starr-Edwards prosthesis. The presence or absence of chordae tendineae was irrelevant to cardiac performance.
- © 1967 American Heart Association, Inc.