Adenosine is a purine ribonucleoside with important roles in various physiological processes. A number of studies have indicated the importance of adenosine in cardiovascular diseases including syncope; however, the accurate determination of adenosine in human blood is challenging due to the molecule’s instability. In the present study, we report a simple method for the pre-treatment of blood samples and the development of a fast and efficient hydrophilic interaction chromatographic tandem mass spectrometry method for the analysis of adenosine in patient blood. During collection, samples were mixed directly with a solvent mixture containing 95% acetonitrile and 10 mM ammonium formate in a Vacutainer tube, resulting in successful prevention of adenosine metabolic processes and direct blood sample deproteinization. The method was validated according to bioanalytical industry guidelines and found to be accurate, repeatable, specific and sensitive with LLOQ 0.005 μg/mL, thus allowing its application in the analysis of real clinical samples.

Syncope represents a relatively uncommon symptom of supraventricular tachycardia (SVT). It is likely that an impaired autonomic vasomotor response to the hemodynamic stress of tachycardia is the determinant of hemodynamic changes leading to cerebral hypoperfusion and syncope. In this regard, tilt‐table test may detect abnormalities in the autonomic nervous function and predict the occurrence of syncope during SVT. Electrophysiology studies may reproduce the SVT, distinguish it from other life‐threatening ventricular tachyarrhythmias, and exclude other causes of syncope. Not infrequently mixed syncope mechanisms are revealed during the above diagnostic workup raising doubts about the operating mechanism in the clinical setting. In such cases of uncertainty, an implantable loop recorder, providing long‐term cardiac monitoring, may play a pivotal role in the establishment of the diagnosis, confirming the association of an arrhythmic event with the symptom. Herein, we present four such cases with recurrent unexplained syncope finally attributed to paroxysmal SVT guiding them to a potentially radical treatment through radiofrequency catheter ablation.

Background: The contribution of atrial and ventricular function in neurocardiogenic syncope (NCS) pathophysiology is elusive.Hypothesis: We assessed the influence of echocardiographic properties to the age of presentation and NCS recurrences. Methods:We assigned 124 patients with symptoms suggesting NCS, to those with syncope initiation at age <35 (group A, n = 56) and >35 years (group B, n = 68). Echocardiographic indices were measured before head-up tilt test (HUTT).Results: A total of 55 had positive HUTT (44%) with a trend favoring group A (p = .08). Group A exhibited lower left atrial (LA) volume index (17 ± 6 vs. 22 ± 11 ml/m 2 , p = .015), higher LA ejection fraction (69 ± 10 vs. 63 ± 11%, p = .008), LA peak strain (reservoir phase 41 ± 13 vs. 31 ± 14%, p = .001, contraction phase 27 ± 11 vs. 15 ± 10%, p < .001) and LA peak strain rate (reservoir phase 1.83 ± 1.04 vs. 1.36 ± 0.96 1/s, p = .012, conduit phase 2.36 ± 1.25 vs. 1.36 ± 0.78 1/s, p = .001). Group A showed smaller minimum right atrial (RA) volume, better RA systolic function, superior left ventricular diastolic indices, and lower filling pressures.Group A patients were more likely to have >3 recurrences (82.0% vs. 50.1%, p < .05).Conclusions: Patients with younger age of NCS onset and more syncopal recurrences manifest smaller LA and RA dimensions with distinct patterns of systolic and diastolic function and better LA reservoir and contraction properties. These findings may indicate an increased susceptibility to preload reduction, thereby triggering the NCS mechanism.

No abstract

Background: Radiofrequency (RF) ablation of the slow pathway (SP) in atrioventricular nodal reentry tachycardia (AVNRT) is occasionally complicated with atrioventricular block (AVB) often predicted by junctional beats (JB) with loss of ventriculo-atrial (VA) conduction. Methods:We analyzed retrospectively 153 patients undergoing ablation of SP for typical AVNRT. Results:The A(H)-A(RFd) and A(RFd)-A(CS) intervals were significantly shorter in RF applications causing JB than those without JB (33 ± 11 ms vs 39 ± 9 ms, P < 0.001, 14 ± 9 ms vs 20 ± 7 ms, P < 0.001, respectively). The A(H)-A(RFd) and A(RFd)-A(CS) intervals were also significantly shorter in RFs causing JB with VA block than those with VA conduction (29 ± 11 ms vs 35 ± 11 ms, P < 0.001, 8 ± 8 ms vs 17 ± 8 ms, P < 0.001, respectively). Patients > 70 years had shorter intervals (36 ± 11 ms vs 29 ± 8 ms, P = 0.012, 17 ± 8 ms vs 13 ± 7 ms, P = 0.027, respectively), while VA block was more common in this age group.