Rapid Measurement of Adenosine Concentration in Patients With Syncope

Rationale and aim Until now, a barrier to the widespread evaluation of adenosine in clinical practice has been the difficulty of obtaining rapid reliable measures. Indeed, owing to its short half-life in the blood, adenosine is not easy to sample and measure. At the time of venepuncture, a stop solution - not commercially available - must be utilized in order to inhibit the degradation of adenosine in body fluid. After plasma deproteinization, adenosine concentration is evaluated by means of high-performance liquid chromatography.

A rapid method has recently been developed which consists of measuring adenosine concentration in whole blood instead of plasma by means of Mass Spectrometry (LC-MS/MS). In brief, whole blood is collected after finger puncture and a drop is deposited on a blot paper (Whatman). After the extraction of adenosine by means of a mixture consisting of methanol and internal standard, its concentration is measured by LC-MS/MS. This method is rapid, well accepted by the patient, not expensive, and easily replicable. Comparison between the two above-mentioned methods in 20 healthy subjects and in patients with vasovagal syncope has shown an acceptable correlation, with a r=0.65 and p<0.01. The mean adenosine concentration was significantly higher in vasovagal syncope patients than in controls (3.1 µM versus 0.60 µM, p<0.001). However, the above results need to be replicated in a larger sample of patients and controls before the blot paper method of measurement of adenosine can replace the standard method.

In this study denosine plasma levels was assessed in a larger unselected cohort of patients affected by non-cardiac syncope and compared the results with healthy controls.

Study design The rapid method of adenosine dosage in whole blood was assessed in patients with syncope and in controls. The study was performed in patients referred to Istituto Auxologico Italiano. The blood sample was be shipped to the Laboratory of Biochemistry, Timone Hospital 264 Rue Saint-Pierre, 13385 Marseille, France for analysis Syncope group: patients referred to the Syncope Unit of Auxologico with a diagnosis of possible or certain reflex syncope (class I diagnostic criteria of ESC guidelines) after exclusion of competing diagnoses.

There syncope patients are subdivided in 3 predefined subgroups: