Consecutive administration of atropine and isoproterenol for the evaluation of asymptomatic sinus bradycardia.
OBJECTIVE
Sinus node function is commonly evaluated by the atropine test. The isoproterenol test is less used. The aim of this study was to evaluate chronotropic reserve in patients with asymptomatic sinus bradycardia using the combined administration of atropine and isoproterenol.


RESULTS
A total of 100 patients were studied, 18-70 years old, with permanent, asymptomatic, sinus bradycardia and no detectable cardiac disease. The standard administration protocols for atropine and isoproterenol were used and successive heart rate recorded. Patients were stratified into three groups: Group A (control), showing normal response to atropine and isoproterenol; Group B, demonstrating abnormal response to atropine; Group C, with abnormal response to atropine and isoproterenol. No statistically significant difference was observed between Groups A and B (P = 0.11), whereas Group C differed statistically from both Groups A (P < 0.000001) and B (P = 0.000003) to a significant extent. By the end of the 3-year follow-up period, 47% of the Group C patients had undergone permanent pacemaker implantation (DDDR)--Kaplan-Maier survival curves predict only 35% survival without pacing--whereas none did so in Groups A and B.


CONCLUSIONS
In patients with deficient chronotropic response to atropine administration, isoproterenol tests could differentiate those with inadequate chronotropic reserves, possibly requiring preventive pacemaker implantations.
Vavetsi
Spiridoula
S
1Cardiology Department, Thriasio General Hospital of Elefsina, G. Gennimatas Avenue, Elefsina, Athens, Greece. rvav1962@yahoo.gr
Nikolaou
Nikolaos
N
Tsarouhas
Konstantinos
K
Lymperopoulos
Georgios
G
Kouzanidis
Ioannis
I
Kafantaris
Ioannis
I
Antonakopoulos
Athanasios
A
Tsitsimpikou
Christina
C
Kandylas
John
J
D000293:Adolescent; D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage; D001285:Atropine / Q000008:administration & dosage*; D001919:Bradycardia / Q000175:diagnosis*; D004562:Electrocardiography / Q000187:drug effects* / Q000379:methods*; D005260:Female; D006801:Humans; D007545:Isoproterenol / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013566:Sympathomimetics / Q000008:administration & dosage; D055815:Young Adult
D000889:Anti-Arrhythmia Agents; D013566:Sympathomimetics; D001285:Atropine; D007545:Isoproterenol