Unilateral changes of sympathetic tone to the heart impair left ventricular function

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Abstract
Different regions within the left ventricle are preferentially supplied by the left or right sympathetic system. In order to characterize different influences of left vs right sympathetic lateralization on LV function, haemodynamic effects of right and left stellate ganglion stimulations (RSGS and LSGS) as well as a right sympathetic block (RSB) were compared. Seven alpha-chloralose anaesthetized open chest dogs were instrumented for measurement of LV pressure (tip manometers) and regional LV wall thickness (WT, sonomicrometry) in the antero-apical wall (AW, innervated by right stellate ganglion) and postero-basal wall (PW, left stellate ganglion). Timing of regional myocadial wall motion was evaluated by the phase of the first Fourier transform of the WT signals, LV asynchrony by the phase difference (phi) between both regions, and LV diastolic function by the time constant of isovolumic relaxation (tau). Measurements were performed before and after RSB (5 ml of lidocaine 1%); in 6 dogs of this group, RSGS and LSGS (4 V, 0.2 ms, 20 Hz) were performed before RSB. In order to investigate a regional inotropic stimulation without systemic effect, 6 additional dogs received intracoronary noradrenaline injections (NIC, 0.25 microgram) into the left circumflex artery perfused myocardium. LSGS and NIC led to an earlier PW-motion within the cardiac cycle (phase reduction by 40.0 +/- 15.0 degree (SEM) and 55.5 +/- 11.2 degrees) and RSGS induced an earlier AW-motion (by 33.7 +/- 15.2 degrees). After RSB, AW-motion was delayed (38.1 +/- 9.2 degrees). The consequence was an asynchronous wall motion pattern after all interventions (change in phi: LSGS-64.7 +/- 18.7 degrees, RSGS 41.1 +/- 15.7 degrees, NIC -74.5 +/- 17.4 degrees, RSB -52.6 +/- 14.6 degrees), and a prolonged relaxation (tau increase: RSGS 9.4 +/- 1.9, NIC 8.3 +/- 1.5, RSB 3.7 +/- 0.8 ms). Unilateral increases as well as decreases of sympathetic tone to the heart result in an asynchronous wall motion pattern and an impaired LV relaxation.