DELIUS, W., K.-E. HAGBARTH, A. HONGELL and B. G. WALLIN. General characteristics of sympathetic activity in h u m a n muscle nerves. Acta physiol. scand. 1972. 84. 65-81.Multiunit sympathetic activity was recorded from muscle nerve fascicles in the median or peroneal nerve of resting, relaxed human subjects. The impulses, which were reversibly abolished by a sympathetic ganglion blocking agent, were grouped in the pulse rhythm, and series of such pulse rhythmic bursts of impulses regularly appeared during spontaneously occurring blood pressure reductions, whereas temporary blood pressure elevations were associated with neural silence. The findings agree with the notion that the sympathetic muscle nerve activity recorded consists of vasoconstrictor impulses, the outflow of which is modulated by a strong phasic and tonic inhibitory baroreflex influence. The reflex delay from an arterial pulse wave to the corresponding inhibition of efferent sympathetic activity was 0.9-1.4 seconds, depending on the recording site. Several stimuli, such as sudden chest compression, a rapid deep breath or an electrical shock against the skin, caused a transient inhibition of the sympathetic discharges lasting a few seconds.

DELIUS, W., K.-E. HAGBARTH, A. HONGELL and B. G. WALLIN. Manoeuvres affecting sympathetic outflow in human skin nerves. Acta physiol. scand. 1972. 84. 177-186. W . a L n i m . 0 -E . . M. IIUKI and E. SIMOS, Antagonistic changes of blood flow and sympathetic activity in different vascular beds following central thermal stimulation. 11. Cutaneous and .i.isceral sympathetic activity during spinal heating and cooling in anesthetized rabbits and cats.

DELIUS, W., K.-E. HAGBARTH? -4. HONCELL and B. G. WALLIN. Manoeuvrcs affecting sympathetic oiitflow in human muscle n c r x s . hcta physiol. scand. 1972. 84. 82-94.Multi-unit sympathetic activit). was recorded in hunian muscle nerves, together with measurements of intra-arterial blood pressure and forearm or calf blood flow, during manoeuvres causing circulatory adjustments. Manoeuvres causing an increased vascular resistance in the forearm or calf were regularly associated with an increase in sympathetic outflow, proving that the neural activity was dominated by vasoconstrictor impulses. T h e inverse changes of blood pressure and sympathetic activity observed during Valsalva's manoeuvre and mental stress are explicable in terms of baroreflex control of the neural outflow. However, during muscle work and hyperventilation the relation between blood pressure and sympathetic activity was more complex, indicating that the baroreflex influence was superimposed or modified by other regulatory mechanisms. Some manoeuvres known to affect sympathetic outflow in skin nerves caused no appreciable change in sympathetic muscle nerve activity.

No abstract

Background-Recent studies indicate that MRI, after administration of gadolinium-diethylenetriamine pentaacetic acid, can identify nonviable areas in dysfunctional myocardium. We compared MRI hyperenhancement with PET as a gold standard for detection and quantification of myocardial scar tissue. Methods and Results-Thirty-one patients with ischemic heart failure (ejection fraction, 28Ϯ9%) were imaged with PET and MRI. Scar was defined as regionally increased MRI signal intensity 20 minutes after injection of 0.2 mmol/kg gadolinium-diethylenetriamine pentaacetic acid and as concordantly reduced perfusion and glucose metabolism as defined by PET. Sensitivity and specificity of MRI in identifying patients and segments (nϭ1023)