Resetting of the cardiopulmonary baroreflex 10 years after surgical repair of coarctation of the aorta.
OBJECTIVE
To characterise cardiopulmonary baroreflex responses and examine the effects of a 45 minute cycling bout late after successful repair of coarctation of the aorta.


METHODS
10 young adults (mean (SEM) age 18.1 (2.6 years)) operated on for coarctation of the aorta 12.7 (3.5) years earlier, and 10 healthy controls.


METHODS
Forearm blood flow (venous occlusion plethysmography) and vascular resistance, left ventricular internal diastolic diameter, and central venous pressure estimated from an antecubital vein were measured in the supine position at baseline and during five minute applications of lower body negative pressure (LBNP) at -15 mm Hg (LBNP(-15)) and -40 mm Hg (LBNP(-40)). Venous samples were obtained at baseline and during LBNP(-40) for noradrenaline (norepinephrine), adrenaline (epinephrine), renin activity, and aldosterone. The tests were repeated after 45 minutes of moderate exercise.


RESULTS
Baseline heart rate (78 (9) v 64 (6) beats/min), echocardiographic cardiac output (6.9 (1.1) v 5.0 (0.2) l/min), shortening fraction (41.7 (1.8)% v 33.3 (1.3)%), and forearm blood flow (3.4 (0.4) v 2.3 (0.3) ml/100 g/min) were higher in the coarctation group than in the controls (p < 0.05). Changes in forearm blood flow and forearm vascular resistance from baseline to LBNP(-40) were similar in both groups, but the relation between forearm vascular resistance and estimated central venous pressure or left ventricular internal diastolic diameter was shifted downward in the coarctation group. Plasma adrenaline was increased in the coarctation group (baseline: 3.2 (0.6) v 2.4 (0.3) pmol/l in controls; LBNP(-40): 687 (151) v 332 (42) pmol/l) (p < 0.05). Both groups showed a similar downward displacement of forearm vascular resistance (p < 0.05) after exercise.


CONCLUSIONS
There appears to be resetting of the cardiopulmonary baroreflex to a lower forearm vascular resistance in young adults operated on for coarctation of the aorta, associated with hyperdynamic left ventricular function. Raised circulating adrenaline could contribute to the lower forearm vascular resistance.
Johnson
D
D
Cardiology Unit, Ste-Justine Hospital, Montreal, Quebec, Canada.
Perrault
H
H
Vobecky
S J
SJ
Trudeau
F
F
Delvin
E
E
Fournier
A
A
Davignon
A
A
D000293:Adolescent; D000328:Adult; D001017:Aortic Coarctation / Q000150:complications / Q000503:physiopathology* / Q000601:surgery; D017704:Baroreflex; D001794:Blood Pressure; D016022:Case-Control Studies; D002395:Catecholamines / Q000097:blood; D015444:Exercise / Q000502:physiology; D005500:Follow-Up Studies; D006439:Hemodynamics; D006801:Humans; D006973:Hypertension / Q000209:etiology; D012084:Renin-Angiotensin System / Q000502:physiology; D014655:Vascular Resistance
D002395:Catecholamines