Augmentor action of the sympathetic cardiac nerves in man

During surgical procedures involving the upper thoracic sympathetic trunk in man, systolic and diastolic pressures were recorded during electrical stimulation. Significant and frequently profound elevation in systolic pressure, with little change in diastolic pressure, resulted in a marked increase in pulse pressure which has been designated as an augmentor response. Cardiac acceleration was an accompanying but less impressive response. The upper four or five thoracic segments mediate both the chronotropic and the inotropic action of the sympathetics but the T1 to T3 levels are the most significant. Corollary observations in animal experiments indicate the response is related to increased force of myocardial contraction with consequent increased systolic ejection.