Clinical significance of chemosensitivity in chronic heart failure: influence on neurohormonal derangement, Cheyne-Stokes respiration and arrhythmias. 
Increased chemosensitivity has been observed in HF (heart failure) and, in order to clarify its pathophysiological and clinical relevance, the aim of the present study was to investigate its impact on neurohormonal balance, breathing pattern, response to exercise and arrhythmic profile.  A total of 60 patients with chronic HF [age, 66+/-1 years; LVEF (left ventricular ejection fraction), 31+/-1%; values are means+/-S.E.M.] underwent assessment of HVR (hypoxic ventilatory response) and HCVR (hypercapnic ventilatory response), neurohormonal evaluation, cardiopulmonary test, 24-h ECG monitoring, and assessment of CSR (Cheyne-Stokes respiration) by diurnal and nocturnal polygraphy.  A total of 60% of patients had enhanced chemosensitivity.  Those with enhanced chemosensitivity to both hypoxia and hypercapnia (i.e. HVR and HCVR), compared with those with normal chemosensitivity, had significantly (all P<0.01) higher noradrenaline (norepinephrine) and BNP (B-type natriuretic peptide) levels, higher prevalence of daytime and night-time CSR, worse NYHA (New York Heart Association) class and ventilatory efficiency [higher VE (minute ventilation)/VCO(2) (carbon dioxide output) slope], and a higher incidence of chronic atrial fibrillation and paroxysmal non-sustained ventricular tachycardia, but no difference in left ventricular volumes or LVEF.  A direct correlation was found between HVR or HCVR and noradrenaline (R=0.40 and R=0.37 respectively; P<0.01), BNP (R=0.40, P<0.01), N-terminal pro-BNP (R=0.37 and R=0.41 respectively, P<0.01), apnoea/hypopnoea index (R=0.57 and R=0.59 respectively, P<0.001) and VE/VCO(2) slope (R=0.42 and R=0.50 respectively, P<0.001).  Finally, by multivariate analysis, HCVR was shown to be an independent predictor of both daytime and night-time CSR.  In conclusion, increased chemosensitivity to hypoxia and hypercapnia, particularly when combined, is associated with neurohormonal impairment, worse ventilatory efficiency, CSR and a higher incidence of arrhythmias, and probably plays a central pathophysiological role in patients with HF.