Sildenafil Does Not Influence Autonomic Neurocardiac Control Assessed by Standard Measurements of Heart Rate Variability
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To the Editor:
Recently, an excellent study by Phillips and colleagues1 showed a significant increase in muscle sympathetic nerve activity (MSNA) in healthy young men after a single 100-mg dose of sildenafil. The MSNA increase did not, however, result in an increase in heart rate, from which the authors concluded that the sympathetic activation they observed was selective for the vascular sympathetic drive only. Given the highly differentiated nature of autonomic efferent activity, the measurement of MSNA as a pure index of peripheral sympathetic outflow might allow no definitive conclusions to be made about the autonomic control of the sinoatrial node.
A noninvasive method for evaluating autonomic neurocardiac control involves standardized investigations of heart rate variability (HRV). We recently …