HEMODYNAMIC-EFFECTS IN ACUTE CARDIOMYOPLASTY OF DIFFERENT WRAPPED MUSCLE ACTIVATION TIMES AS MEASURED BY PRESSURE-VOLUME RELATIONS

Background: Correct timing of mechanical interaction between wrapped l atissimus dorsi muscle (LDM) and the heart during cardiac systole has been poorly understood and remains a controversial issue. Therefore, l eft ventricular pressure-volume relations were analyzed in acute cardi omyoplasty while changing the synchronization delays. Methods: Effects of different delays between the sensed cardiac R wave and wrapped mus cle contraction were studied in goats submitted to acute left cardiomy oplasty. Conductance and micromanometer catheters were used to evaluat e hemodynamics. Systolic contribution of the wrapped muscle was studie d in preassisted and assisted beats, whereas diastolic effects were st udied in assisted and postassisted beats. Results: At best settings, c ardiomyoplasty resulted in a significant (p < 0.05) increase in left v entricular ejection fraction (from 42.2 +/- 9.2 to 56.7% +/- 13%), in stroke work (from 2769 +/- 1140 to 4271 +/- 1717 gm/m(2)), in dP/dt (f rom 1185 +/- 342 to 1510 +/- 285 mmHg/sec), in end-systolic pressure ( from 93.5 +/- 22.5 mmHg to 97.3 +/- 22.3 mmHg), and in peak ejection r ate (from 282 +/- 64 to 533 +/- 241 mL/sec). Stroke volume showed a me an increase of 35% (from 42.2 +/- 9.9 mL to 56.9 +/- 20.1 mL) during a ssisted beats. Diastolic function was not substantially impaired at op timal stimulation delay. Incorrect timing of LD contraction resulted i n suboptimal improvement or no change in comparison with unassisted he modynamics. Conclusions: Our study documents support of cardiac perfor mance by LDM. Incorrect timing of heart/wrapped muscle interaction led to suboptimal hemodynamic results. Muscle contraction timing is an im portant factor in cardiomyoplasty outcome.