Increased peripheral chemoreceptors sensitivity and exercise ventilation in heart transplant recipients.
BACKGROUND
Heart failure is characterized by increased ventilation during exercise, which is positively related to increased peripheral and central chemoreceptor sensitivity. Heart transplantation does not normalize the ventilatory response to exercise, and its effects on the chemoreflex control of ventilation remain unknown. We tested the hypothesis that chemoreceptor sensitivity is increased in heart transplant recipients (HTRs) and linked to exercise hyperpnea.


RESULTS
We determined the ventilatory, muscle sympathetic nerve activity (MSNA), and circulatory responses to isocapnic hypoxia and hyperoxic hypercapnia 7+/-1 years after transplantation in 19 HTRs with a normal left ventricular ejection fraction of 60+/-2%. Results were compared with those of 11 closely matched referent subjects. Sixteen patients and 10 referent subjects also underwent cycle ergometer exercise tests. HTRs compared with referent subjects presented higher MSNA (52+/-4 versus 34+/-3 bursts/min; P<0.01) and heart rates (83+/-3 versus 68+/-3 bpm; P<0.01) during room air breathing. The ventilatory response to hypoxia was higher in HTRs than in referent subjects (P<0.01, ANOVA). The increase in MSNA also was more marked during hypoxia in the HTRs than in the referent group (P<0.05, ANOVA). Responses to hyperoxic hypercapnia did not differ between the HTRs and the referent group. The ventilatory response to exercise, characterized by the regression slope relating minute ventilation to CO2 output, was steeper in HTRs than in referent subjects (38+/-2 versus 29+/-1 L/mm Hg; P<0.01). Exercise ventilation in HTRs was related to the ventilatory response to isocapnic hypoxia (r=0.57; n=16; P<0.05) and to the ventilatory response to hyperoxic hypercapnia (r=0.50; n=16; P<0.05).


CONCLUSIONS
Peripheral chemoreceptor sensitivity is increased in HTRs and is related to exercise hyperpnea after heart transplantation.
Ciarka
Agnieszka
A
Department of Cardiology, Erasme University Hospital, 1070 Brussels, Belgium. Agnieszka.Ciarka@ulb.ac.be
Cuylits
Nicolas
N
Vachiery
Jean-Luc
JL
Lamotte
Michel
M
Degaute
Jean-Paul
JP
Naeije
Robert
R
van de Borne
Philippe
P
D016022:Case-Control Studies; D002628:Chemoreceptor Cells / Q000502:physiology*; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D016027:Heart Transplantation / Q000502:physiology*; D006801:Humans; D006935:Hypercapnia; D000860:Hypoxia; D008297:Male; D008875:Middle Aged; D012123:Pulmonary Ventilation