Effect of local cardiac sympathectomy on regional myocardial contraction.

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Abstract
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 < 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. These observations indicated that the abnormal pressure/length loop was derived from the delayed contraction in the phenol treated region.