New configuration of double cardiomyoplasty based on studies of the length-tension properties of the latissimus dorsi muscle.

A new configuration of double cardiomyoplasty was designed according to studies of the length-tension properties of the linear latissimus dorsi muscle. Four dogs had both their right and left latissimus dorsi muscles dissected from the chest wall and attached to a tensiometer to measure force of contraction. The maximum active tension obtained with stimulation of the linear latissimus dorsi muscle was observed when the muscle was at its resting anatomic length and up to 5% above this length. Eight dogs had a double cardiomyoplasty in which the resting anatomic length of both muscles was maintained. Control hemodynamic parameters obtained with the muscles at rest were compared with stimulated muscle protocols. In a normal heart state, stimulation of the double cardiomyoplasty increased the cardiac output 32% (p < 0.05), the stroke volume 39% (p < 0.05), and the left ventricular pressure 42% (p < 0.05). When acute heart failure was induced with high-dose intravenous propranolol (5 mg/kg), stimulation of the double cardiomyoplasty increased the cardiac output 32% (p = 0.01), the stroke volume 32% (p < 0.05), rate of pressure rise 39% (p < 0.01), and myocardial thickening 39% (p < 0.01). The study demonstrated that this configuration of double cardiomyoplasty provides significant hemodynamic assistance in the normal and acutely failing canine heart.