AUGMENTED PERIPHERAL CHEMOSENSITIVITY AS A POTENTIAL INPUT TO BAROREFLEX IMPAIRMENT AND AUTONOMIC IMBALANCE IN CHRONIC HEART-FAILURE

Background The precise mechanisms responsible for the sympathetic over activity and blunted baroreflex control in chronic heart failure (CHF) remain obscure. Augmented peripheral chemosensitivity has recently be en demonstrated in CHF, We evaluated the relation between peripheral c hemoreflex sensitivity and autonomic activity in patients with CHF. Me thods and Results We studied in 26 stable patients with CHF the periph eral chemosensitivity (ventilatory response to hypoxia using transient inhalations of pure nitrogen), autonomic balance (spectral analysis o f heart rate variability [HRV]), and baroreflex sensitivity (bolus phe nylephrine method and alpha index). To determine whether transient ina ctivation of peripheral chemoreceptors might influence autonomic balan ce, 12 patients underwent a second study during which they breathed 10 0% O-2. Peripheral chemosensitivity correlated inversely with HRV powe r within the low-frequency band (0.04 to 0.15 Hz) (r=-.52, P=.006) and inversely with baroreflex sensitivity (r=-.60, P=.005). When the pati ents were divided into two groups according to the chemosensitivity of age-matched normal controls (above and below mean+2 SDs of chemosensi tivity of control subjects), those above the normal range revealed mor e impaired autonomic balance, ie, lower baroreflex sensitivity (1.4+/- 1.3 versus 5.0+/-1.5 ms/mm Hg, P<.0001) and depressed values of low-fr equency power (2.5+/-1.8 versus 4.1+/-0.8 ln ms(2), P<.005) compared w ith those with normal chemosensitivity. Transient hyperoxia did not al ter heart rate or systolic pressure but resulted in an increase in HRV and an improvement in baroreflex sensitivity. Conclusions A link betw een increased peripheral chemosensitivity and impaired autonomic contr ol, including baroreflex inhibition, is demonstrated. The clinical imp ortance of this phenomenon warrants further investigation.