ABSTRACT
Uremic cardiac autonomic nervous system alterations have not been well described, although it is as remarkable as cardiac autonomic neuropathies observed in diabetes mellitus and congestive heart failure. Heart rate variability (HRV), one of the most promising markers of cardiac autonomic activity, has been shown to be markedly decreased in most patients with chronic renal failure (CRF). In CRF patients, a few studies have reported the prognostic value of HRV as well as several variables responsible for low HRV, both of which need to be examined by more studies in a larger sample size. Hemodialysis (HD) may remove some metabolic agents interfering with HRV, but there are not a few patients on maintenance HD who show markedly reduced HRV. On the other hand, 123Imetaiodobenzylguanidine (MIBG) has been recently developed to image cardiac sympathetic innervation. Because myocardial MIBG kinetics reflects the reuptake, storage, and release of norepinephrine in cardiac presynaptic sympathetic nerves, mainly in the left ventricular myocardium, HRV and MIBG variables reflect different aspects, that is, sinus node versus left ventricular myocardium and postsynaptic versus presynaptic side. Several studies have demonstrated markedly rapid MIBG clearance from the heart in CRF patients without diabetes mellitus, coronary artery disease, and heart failure. Thus, the abnormalities in HRV and MIBG observed in previous studies suggest that uremic autonomic neuropathy is characterized by sympathetic overactivity with parasympathetic nervous system dysfunction, which are common in congestive heart failure. Furthermore, several
investigators have demonstrated that kidney transplantation improves HRV and MIBG variables in most patients with CRF on dialysis. Observations about possible improvement in HRV and MIBG measures by renal transplantation may afford excellent insight into not only the pathophysiology of uremic cardiac autonomic neuropathy, but also the recovery process of cardiac autonomic nervous system in patients with congestive heart failure.
