CLINICAL CHARACTERISTICS OF CHRONIC HEART-FAILURE PATIENTS WITH AN AUGMENTED PERIPHERAL CHEMOREFLEX

Aims The peripheral chemoreflex may be augmented in chronic heart fail ure and may play a role in its pathophysiology including the mediation of exercise hyperpnoea and sympathetic activation. The objective of t his study was to characterize the patients with an augmented periphera l chemoreflex. Methods and results Peripheral chemoreflex sensitivity was assessed by measuring the ventilatory response to hypoxia using tr ansient inhalations of purl nitrogen in 50 patients with chronic heart failure (age 58.7 +/- 12.1 (SD) years; radionuclide left ventricular ejection fraction 26.5 +/- 13.0%). The peripheral chemoreflex of 12 he althy controls with similar demographic characteristics was 0.272 +/- 0.201 l.min(-1).%Sao(2)(-1) compared with 0.673 +/- 0.410 l.min(-1).%S ao(2)(-1) (P<0.0001) in the chronic heart failure patients. Using 2 st andard deviations above the mean level of the controls' peripheral che moreflex sensitivity as the upper limit of normal, we defined an augme nted chemoreflex as greater than 0675 l.min(-1).%Sao(2)(-1). Twenty of the chronic heart failure patients (40%) demonstrated such an augment ed peripheral chemoreflex. Compared with patients with peripheral chem oreflex sensitivity within the normal range, they had a reduced peak o xygen consumption during cardiopulmonary exercise (15.1 +/- 4.4 vs 18. 5 +/- 58 ml.kg(-1).min(-1), P = 0.02), reduced radionuclide left ventr icular ejection fraction (21.8 +/- 11.8 vs 29.4 +/- 13.1%, P = 0.046) and were in a worm New York Heart Association functional class (2.8 vs 2.4, P = 0.05). The ventilatory response to exercise, as characterize d by the regression slope relating minute ventilation to carbon dioxid e output during exercise, was also higher (40.48 +/- 9.32 vs 34.54 +/- 7.19, P = 0.02), consistent with the role of the peripheral chemorefl ex in mediating exercise hyperpnoea. There was also an increased propo rtion of patients with non-sustained ventricular tachycardia in the gr oup with an augmented peripheral chemoreflex (61% vs 21%, chi-squared 7.08, P<0.01). No difference was seen in the age, height, weight and l ung function measurements of these patients compared with the normal c hemoreflex group. Conclusion An augmented peripheral chemoreflex is a common finding in chronic heart failure patients, one associated with increasing severity and with the exercise hyperpnoea seen in the condi tion. That there was an excess of patients with non-sustained ventricu lar tachycardia in the group with an augmented peripheral chemoreflex may be related to the chemoreflex-driven sympathetic stimulation. The peripheral chemoreflex may be important in the pathophysiology of chro nic heart failure, both in terms of symptoms and exercise limitation.