Mechanism of syncope in patients with positive adenosine triphosphate tests.
OBJECTIVE
We prospectively evaluated the mechanism of syncope in patients with positive adenosine triphosphate (ATP) tests (defined as the induction of atrioventricular [AV] block with a ventricular pause >/=6 s after an intravenous bolus of 20 mg ATP).


BACKGROUND
Patients with unexplained syncope tend to have more positive ATP tests results than those without syncope.


METHODS
An implantable loop recorder (ILR) was inserted in 36 ATP-positive patients (69 +/- 10 years; 22 women; median of 6 syncopal episodes); 15 of them also had a positive response to tilt testing.


RESULTS
During the follow-up of 18 +/- 9 months, 18 patients (50%) had syncopal recurrence and 16 (44%) had an electrocardiographically documented episode: AV block (n = 3: paroxysmal in 2 and permanent in 1), AV block followed by sinus arrest (n = 1), sinus arrest (n = 5), sinus bradycardia <40 beats/min (n = 2), normal sinus rhythm (n = 2), sinus tachycardia (n = 1), rapid atrial fibrillation (n = 1), and ectopic atrial tachycardia (n = 1). Bradycardia was documented in a total of 11 cases (69%), and a long ventricular pause (4 to 29 s) was present in eight cases (50%). All three patients with ILR-documented AV block had previously had a negative tilt test, whereas seven of eight with ILR-documented sinus bradycardia or sinus arrest had previously had a positive tilt test.


CONCLUSIONS
In patients with adenosine-sensitive syncope, the mechanism of syncope is heterogeneous, although bradycardia is the most frequent finding. Adenosine triphosphate-induced AV block predicts AV block as the mechanism of spontaneous syncope in only a few tilt-negative patients.
Donateo
Paolo
P
Department of Cardiology, Ospedali del Tigullio, Lavagna, Italy.
Brignole
Michele
M
Menozzi
Carlo
C
Bottoni
Nicola
N
Alboni
Paolo
P
Dinelli
Maurizio
M
Del Rosso
Attilio
A
Croci
Francesco
F
Oddone
Daniele
D
Solano
Alberto
A
Puggioni
Enrico
E
D000255:Adenosine Triphosphate / Q000008:administration & dosage; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000150:complications / Q000503:physiopathology*; D003935:Diagnostic Techniques, Cardiovascular; D003943:Diagnostic Techniques, Neurological; D005260:Female; D006327:Heart Block / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D020007:Implants, Experimental; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012008:Recurrence; D013575:Syncope / Q000209:etiology* / Q000503:physiopathology*
D000255:Adenosine Triphosphate