Cardiovascular medicine
2 Adrenergic receptors mediate important
electrophysiological effects in human ventricular myocardium
M D Lowea, E Rowlandc, M J Brownb, A A Gracea
a Department of
Cardiology, Papworth Hospital, Papworth Everard, Cambridge CB3
8RE, UK, b Department of Medicine, University of Cambridge,
Cambridge, UK, c Department of
Cardiological Sciences, St George's Hospital Medical School, London,
UK
Correspondence to: Dr Grace ag{at}mole.bio.cam.ac.uk
Accepted 9 January
2001
OBJECTIVE
To define the effects of
2 adrenergic receptor stimulation on ventricular
repolarisation in vivo.
DESIGNProspective study.
SETTINGTertiary referral centre.
PATIENTS85 patients with coronary
artery disease and 22 normal controls.
INTERVENTIONSIntravenous and
intracoronary salbutamol (a 2 adrenergic receptor
selective agonist; 10-30 µg/min and 1-10 µg/min), and
intravenous isoprenaline (a mixed 1/2
adrenergic receptor agonist; 1-5 µg/min), infused during fixed
atrial pacing.
MAIN OUTCOME MEASURESQT intervals,
QT dispersion, monophasic action potential duration.
RESULTSIn patients with coronary
artery disease, salbutamol decreased QTonset and
QTpeak but increased QTend duration;
QTonset-QTpeak and
QTpeak-QTend intervals increased, resulting in
T wave prolongation (mean (SEM): 201 (2) ms to 233 (2) ms;
p < 0.01). There was a large increase in dispersion of
QTonset, QTpeak, and QTend which was more pronounced in patients with coronary artery diseasefor example, QTend dispersion: 50 (2) ms baseline
v 98 (4) ms salbutamol (controls), and 70 (1) ms baseline v 108 (3) ms salbutamol
(coronary artery disease); p < 0.001. Similar responses were
obtained with isoprenaline. Monophasic action potential duration at
90% repolarisation shortened during intracoronary infusion of
salbutamol, from 278 (4.1) ms to 257 (3.8) ms (p < 0.05).
CONCLUSIONS2
adrenergic receptors mediate important electrophysiological effects in
human ventricular myocardium. The increase in dispersion of
repolarisation provides a mechanism whereby catecholamines acting
through this receptor subtype may trigger ventricular arrhythmias.
Keywords:
2 adrenergic receptors;
ventricular
repolarisation;
QT dispersion;
salbutamol;
isoprenaline
© 2001 by Heart
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