Effect of beta blockade on the neurohumoral and cardiopulmonary response to dynamic exercise in cardiac transplant recipients.
OBJECTIVE
To determine the effects of a small dose of beta blocker on neurohumoral and cardiopulmonary responses after cardiac transplantation.


BACKGROUND
Cardiac transplant recipients have a reduced exercise capacity and abnormal cardiovascular responses to exercise. The sympathoadrenal response to exercise has been shown to be abnormal with high venous noradrenaline. The effect of beta blockade on these neurohumoral mechanisms has not been defined.


METHODS
10 non-rejecting cardiac transplant recipients were studied. Patients carried out graded exercise to a symptom limited maximum. Blood samples were taken during exercise. Concentrations of noradrenaline, adrenaline, and atrial natriuretic peptide and plasma renin activity were measured. The next day, the exercise and sampling procedure were repeated after an oral dose of propranolol (40 mg).


RESULTS
Patients tolerated exercise poorly after beta blockade, which was reflected in the maximum workload reached. Heart rate and blood pressure were significantly higher at rest and during exercise before beta blockade. Although there was no significant difference when resting, mean (SEM) noradrenaline concentrations during peak exercise were higher after beta blockade (16.2 (2) v 23.6 (2.9) nmol/l, p = 0.001). Adrenaline concentrations at peak exercise were also greater after beta blockade (0.89 (0.31) v 1.18 (0.38) nmol/l, p = 0.055). Atrial natriuretic peptide concentrations tended to be higher after beta blockade (118.75 (50.2) v 169.79 (39.3) pmol/l, p = 0.36). There was no significant change in plasma renin activity.


CONCLUSIONS
A small oral dose of a competitive beta blocker such as propranolol has an adverse effect on exercise tolerance and cardiovascular response to exercise in cardiac transplant recipients. There are also increased concentrations of circulating noradrenaline and therefore, sympathetic activity during exercise. beta blockers should be used with caution in cardiac transplant recipients.
Kushwaha
S S
SS
Department of Cardiology, Harefield Hospital, Middlesex.
Banner
N R
NR
Patel
N
N
Cox
A
A
Patton
H
H
Yacoub
M H
MH
D000284:Administration, Oral; D000328:Adult; D009320:Atrial Natriuretic Factor / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects; D015444:Exercise / Q000502:physiology*; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D016027:Heart Transplantation / Q000502:physiology*; D006801:Humans; D008168:Lung / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D018377:Neurotransmitter Agents / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood; D011433:Propranolol / Q000008:administration & dosage / Q000494:pharmacology*; D012083:Renin / Q000097:blood
D018377:Neurotransmitter Agents; D009320:Atrial Natriuretic Factor; D011433:Propranolol; D012083:Renin; D009638:Norepinephrine