LEFT STELLATE GANGLION BLOCK IMPAIRS LEFT-VENTRICULAR FUNCTION

Stellate ganglion block (SGB) is an established procedure for the diag nosis and treatment of chronic pain. SGB results in an acute sympathet ic denervation of a part of the left ventricular (LV) wall innervated by the blocked ganglion, which may impair regional contractility. The resulting imbalance of myocardial contrac tility in different LV regio ns may affect LV function adversely by increasing LV asynchrony. Seven anesthetized open chest dogs were instrumented for measurement of aor tic and LV pressure (tip manometers), cardiac output (CO, thermodiluti on), and regional LV wall thickness (WT, sonomicrometry) in the antero apical (predominantly innervated by the right stellate ganglion) and p osterobasal wall(left stellate ganglion). The contractility of both re gions was assessed using the relationship between preload recruitable stroke work and end-diastolic WT relationship (M(W)). The timing of re gional myocardial wall motion was evaluated by means of the phase of t he first harmonic of the Fourier transform of the WT signals, LV async hrony by the phase difference (PD) between bath regions, and LV diasto lic function by the time constant of isovolumic relaxation (tau). Meas urements were performed before and after left SGB (LSGB). Mean arteria l pressure was 105 +/- 25 (mean +/- SD) before and 97 +/- 10 mm Hg aft er LSGB (not significant). CO remained unchanged (3.09 +/- 1.03 vs 2.9 3 +/- 1.07 L/min). LSGB significantly reduced contractility in the pos terobasal myocardium (M(W) -162 +/- 26 vs -80 +/- 7 mm Hg; P < 0.01), accompanied by a delay of regional wall motion within the cardiac cycl e (phase 202 +/- 18 vs 223 +/- 17 degrees; P < 0.01). In contrast, ant eroapical wall function was unaffected by LSBG. Consequently, myocardi al asynchrony increased (PD 20 +/- 20 vs 45 +/- 20 degrees;P < 0.01), paralleled by an impairment of LV diastolic function (tau 26 +/- 3 vs 32 +/- 3 ms; P < 0.01). These hemodynamic effects of LSGB may be parti cularly relevant in patients with compromised hearts in whom LV functi on partially depends on a high sympathetic tone.