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 latissimus dorsi muscle (LDM) and the heart during cardiac systole has been poorly understood and remains a controversial issue. Therefore, left ventricular pressure-volume relations were analyzed in acute cardiomyoplasty while changing the synchronization delays.

METHODS

Effects of different delays between the sensed cardiac R wave and wrapped muscle contraction were studied in goats submitted to acute left cardiomyoplasty. Conductance and micromanometer catheters were used to evaluate hemodynamics. Systolic contribution of the wrapped muscle was studied in preassisted and assisted beats, whereas diastolic effects were studied in assisted and postassisted beats.

RESULTS

At best settings, cardiomyoplasty resulted in a significant (p < 0.05) increase in left ventricular ejection fraction (from 42.2 +/- 9.2 to 56.7% +/- 13%), in stroke work (from 2769 +/- 1140 to 4271 +/- 1717 gm/m2), in dP/dt (from 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 rate (from 282 +/- 64 to 533 +/- 241 mL/sec). Stroke volume showed a mean increase of 35% (from 42.2 +/- 9.9 mL to 56.9 +/- 20.1 mL) during assisted beats. Diastolic function was not substantially impaired at optimal stimulation delay. Incorrect timing of LD contraction resulted in suboptimal improvement or no change in comparison with unassisted hemodynamics.

CONCLUSIONS

Our study documents support of cardiac performance by LDM. Incorrect timing of heart/wrapped muscle interaction led to suboptimal hemodynamic results. Muscle contraction timing is an important factor in cardiomyoplasty outcome.