Maximum Cardiac Assistance by Latissimus Dorsi Muscle Stimulation by Optimization of Delays, Frequencies and Pulses

To determine optimal parameters for vascular delayed latissimus dorsi muscle (LDM) stimulation, we hypothesized that appropriate pattern of synchronization delay, frequency and number of pulses per burst would improve benefits in cardiomyoplasty. In six dogs, vascular delay of left LDM and induction of myocardial dysfunction were performed 2 weeks before standard cardiomyoplasty. LDM was progressively conditioned for 9 weeks. The interventions were divided into 3 groups of Delay (25, 50, 75, 100 ms; between QRS and muscle stimulation), Frequency (20, 30, 40, 50, 60 Hz; each examined at 6 pulses), and number of Pulses (4, 6, 8, 10 burst-pulses at 50 Hz). With LDM stimulation, pressures and flows were significantly increased in all except 100 ms delay group. 25 ms synchronization delay at 50 Hz and 6-10 pulses, LDM stimulation caused the highest increases in peak aortic pressure (18.3±1.4 mmHg), peak left ventricular pressure (22.4±2.4 mmHg), LV +dP/dt (276.3±166.4 mmHg/sec), stroke volume (8.0±3.3 ml), stroke work (13.0±2.8 gm⋅m), stroke power (135.0±17.8 gm⋅m/sec), and peak aortic flow (4.5±0.8 l/min) when assisted beats were compared to unassisted beats. At prolonged synchronization delay and highest burst pulses, the diastolic properties are compromised and at a relative shorter delay, higher frequency and bursts pulses showed maximum systolic improvements.