Biventricular function in exercise during autonomic (thoracic epidural) block.

Area of Science:

• Cardiology
• Anesthesiology
• Physiology

Background:

• Thoracic epidural anesthesia (TEA) blocks cardiac sympathetic fibers, reducing ventricular systolic function and pulmonary arterial elastance.
• Previous studies showed TEA did not alter cardiac output or systemic hemodynamics at rest with controlled heart rate.

Purpose of the Study:

• To investigate the effects of cardiac sympathicolysis via TEA during physical stress and increased oxygen demand.
• To assess the impact of TEA on biventricular function and hemodynamics during dynamic exercise.

Main Methods:

• A crossover design study involving 12 patients undergoing thoracic surgery.
• Patients performed dynamic ergometric exercise tests with and without TEA.
• Hemodynamics and biventricular function were monitored using echocardiography and Doppler imaging.

Main Results:

• TEA attenuated right ventricular (RV) and left ventricular (LV) systolic function (RV S': -21%, LV S': -14%).
• TEA decreased heart rate, stroke volume index, cardiac index, and mean arterial pressure, but not systemic vascular resistance.
• Exercise significantly augmented biventricular systolic and diastolic function, with no significant interaction with TEA, except for rate-pressure product and LV end-diastolic velocity.

Conclusions:

• Cardiac sympathetic blockade with TEA reduces LV and RV systolic function.
• TEA did not blunt exercise-induced increases in LV and RV function, indicating other regulatory mechanisms are involved.
• Additional mechanisms beyond the cardiac sympathetic nervous system regulate cardiac function during dynamic exercise.