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Mechanism of syncope in patients with positive adenosine triphosphate tests

Paolo Donateo, MD^*, Michele Brignole, MD^*,*, Carlo Menozzi, MD, Nicola Bottoni, MD, Paolo Alboni, MD, Maurizio Dinelli, MD, Attilio Del Rosso, MD, Francesco Croci, MD^*, Daniele Oddone, MD^*, Alberto Solano, MD^* and Enrico Puggioni, MD^*

^* Ospedali del Tigullio, Lavagna, Italy
Ospedale S. Maria Nuova, Reggio Emilia, Italy
Ospedale Civile, Cento, Italy
Ospedale S. Pietro Igneo, Fucecchio, Italy

View larger version (23K): [in a new window]   Figure 1 The figure shows the syncopal event observed in Patient no. 1. (A) Heart rate trend during the whole 21-min loop recording. The heart rate is initially stable at 80 beats/min and then suddenly falls at the time of syncope. (B) Expanded electrocardiographic recording at the time of the syncopal event. The onset of atrioventricular block is sudden, with no change in the PP interval; the main pause lasted 12 s.

View larger version (17K): [in a new window]   Figure 2 The figure shows the result of the adenosine triphosphate (ATP) test performed in Patient no. 2. Continuous tracings of the electrocardiogram and non-invasive blood pressure (BP) (Finapres method) are shown. The bolus of ATP causes abrupt third-degree atrioventricular (AV) block with long ventricular asystoles of 5.2, 6.0, and 4.5 s. The sinus rate increases during the block. Thus, the effect of the drug is limited to the AV conduction system. Systolic blood pressure dropped from an initial value of 140 mm Hg to values ranging between 80 and 110 mm Hg.

View larger version (17K): [in a new window]   Figure 3 The figure shows the electrocardiographic recording of the syncopal event observed in the same patient as in Figure 2 (Patient no. 2). The onset of atrioventricular block is sudden, with a long ventricular asystole of 7 s. The sinus rate increases during the spontaneous event. The increase in sinus rate during the episode argues against the presence of a vagal reflex. The noise recorded probably reflects jerking movements of the patient during syncope.