Effect of local cardiac sympathectomy on regional myocardial contraction

To investigate the response of locally sympathectomized myocardium to sympathetic stimulation, 90% phenol solution was painted on the left ventricular anterior wall surface in 13 open chest anesthetized dogs. Two pairs of ultrasonic crystals were implanted into the mid-myocardium and the left ansa subclavia was stimulated (LSS) at a frequency of 4 Hz. Heart rate, left ventricular systolic pressure and peak dP/dt increased following LSS before and after phenol application. After phenol application, the increase in peak dP/dt was significantly lower than before phenol application (p less than 0.01) despite similar increases in both heart rate and left ventricular systolic pressure. Before phenol application, norepinephrine (NE) overflow was observed following LSS (1.60 ng/ml) but after phenol application NE overflow decreased to 0.45 ng/ml, indicating that phenol interrupted sympathetic nerve conduction. During LSS, in both anterior and posterior walls, %shortening (%dL) increased from 13 +/- 1 (mean +/- SE) to 22 +/- 3% and 12 +/- 1 to 20 +/- 2%, respectively. After phenol application, LSS caused an increase of %dL in the posterior wall from 10 +/- 1 to 17 +/- 2%, while in the anterior wall it decreased from 15 +/- 2 to 8 +/- 3%. At the end of the experiment, when NE was infused to maintain the left ventricular systolic pressure similar to that obtained during LSS, %dL increased from 15 +/- 2 to 21 +/- 3% in the anterior wall. Pressure-length loop during LSS showed an early systolic expansion in the phenol treated anterior wall which disappeared during NE infusion.(ABSTRACT TRUNCATED AT 250 WORDS)