R-R variability from standard 12 lead ECG may be useful for assessment of autonomic nervous function.

Many conditions such as aging, diabetic neuropathy and ischaemic heart disease are assoc ia ted wi th reduc t ions in hear t r a te var iab i l i ty (HRV) . Reduced HRV, in tu rn , has been associated with increased mortality (1) . There has been d iscuss ion of lowered HRV as a potent ia l therapeut ic ta rge t (2) . Trad i t iona l t echniques o f eva lua t ing HRV involve acquis i t ion of con t inuous ECG record ings fo r var iab le per iods o f t ime fol lowed by fair ly complex computer-based mathemat ica l p rocess ing . At tempts have been made to reduce the dura t ion of the ECG record ing . The power spec t ra l measures of HRV der ived f rom 2 min record ings a re wel l cor re la ted wi th those f rom 24 h record ings (3 ) . In a t l eas t one longi tud ina l ep idemio log ica l s tudy, variat ions in the RR intervals f rom the 12 lead ECG predic ted morta l i ty (4) but , th is was no t l inked to changes in au tonomic funct ion. A recent s tudy indicated that the average absolute difference in RR intervals or the roo t mean square o f the s tandard deviation of RR intervals from a continuous 10 ECG could reasonably pred ic t ca rd iac vaga l tone der ived f rom a 5 min ECG recording (5). HRV derived from a standard 12 lead ECG is cos t -ef fec t ive and wi l l be usefu l in poor count r ies . Th is s tudy therefore evaluated the extent to which RR var iab i l i ty der ived f rom s tandard 12 lead ECG correlated with HRV in the frequency domain der ived f rom a cont inuous 5 min ECG recording in supine pos ture .