Effects of electrical stimulation postcardiomyoplasty in a model of chronic heart failure: Hemodynamic results after daily 12-hour cessation versus anonstop regimen

The hemodynamic effects of cardiomyoplasty (CMP) have been investigated in many centers, but the question of whether it is necessary to stimulate the latissimus dorsi muscle (LDM) 24 hours a day has not been answered. The mai n goal of our investigation was to determine whether hemodynamic results af ter CMP were impaired when continuous electrical stimulation (ES) was off f or 12 hours a day. A model of chronic heart failure was created in 12 sheep by performing an arteriovenous anastamosis and administering doxorubicin. Two weeks after the anastomosis, CMP was performed in eight sheep (experime ntal series); ES training was begun at 2 weeks after CMP. After completion of the initial ES conditioning (8 weeks after CMP), one group of sheep cont inued to receive ES 24 hours daily. Another group of sheep had only 12 hour s of ES daily. Hemodynamic parameters were investigated 2 weeks later with the stimulator turned on and then off With doxorubicin administration, arte riovenous anastamosis created a stable model of biventricular heart failure (right atrial pressure 20 +/- 3 mmHg vs 6 +/- 2 mmHg at baseline; pulmonar y capillary wedge pressure 18 +/- 3 mmHg vs 9 +/- 2 mmHg; left ventricular end-diastolic area 15.2 +/- 1.2 cm(2) vs 6.4 +/- 0.7 cm(2); left ventricula r ejection fraction 0.38 +/- 0.6 vs 0.65 +/- 0.7). Cardiomyoplasty improved hemodynamic status in all eight experimental sheep. However, when the inve stigation was performed with the stimulator off, this improvement was stati stically insignificant. With stimulation on, there was decreased right atri al pressure, pulmonary capillary wedge pressure, left ventricular end-diast olic volume, and increased left ventricular ejection fraction. With the sti mulator turned off for 12 hours daily, hemodynamic measurements did not dif fer from data with continuous ES for 24 hours daily. Because hemodynamic re sults do not seem to be impaired, we recommend daily, periodic cessation of stimulation to prevent damage to the LDM after CMP.