Demand dynamic cardiomyoplasty: Mechanograms prove incomplete transformation of the rested latissimus dorsi

Background. In dynamic cardiomyoplasty, standard stimulation produces high fatigue resistance but also undesirable dynamic characteristics of the lati ssimus dorsi (LD). Based on results of intermittent stimulation in animals we introduced demand stimulation, a lighter regimen of LD activity-rest sti mulation, and the mechanogram, a noninvasive method to determine the contra ctile characteristics of LD wrap. Methods. Surgery and standard stimulation was according to the technique of Carpentier and Chachques, demand stimulation and LD wrap mechanogram were as we previously described. The LD contraction is synchronized to heart sys tole by mechanogram and echocardiography, and extent of transformation by t etanic fusion frequency analysis. A total of 22 patients were studied to da te. Data for the 8 subjects who attained 6-month follow-up are reported. Fo ur of them were lightly stimulated from the conditioning period, whereas 4 others were converted to light and then demand stimulation after years of s tandard stimulation. Patients were followed up with respect to survival, fu nctional class, hospital admission rate, medication used, cardiopulmonary e xercise testing, and LD wrap mechanography. Results. Latissimus dorsi wrap slowness reverses by the activity-rest regim en, even after years of standard stimulation (Tetanic fusion frequency of 1 1 +/- 2 Hz after standard stimulation vs 30 +/- 3 Hz after demand regimen, p < 0.0001). After demand dynamic cardiomyoplasty there are no deaths. Qual ity of life is substantially improved with significant reduction of heart f ailure symptoms (New York Heart Association class: preoperative 3.0 +/- 0.0 , post-demand dynamic cardiomyoplasty 1.5 +/- 0.2, p < 0.0001). In the subg roup of patients lightly stimulated from LD conditioning, exercise capacity tends to increase over preoperative values more than 2 years after operati on (VO2 max: preoperative 12.3 +/- 0.7 vs 16.6 +/- 1.7 post-demand dynamic cardiomyoplasty, p 0.05). Conclusions. Demand stimulation and mechanography of the LD wrap are safe p rocedures that could offer long-term benefits of dynamic cardiomyoplasty to patients with pharmacologically intractable heart failure. (Ann Thorac Sur g 2000;70:67-73) (C) 2000 by The Society of Thoracic Surgeons.