Adenosine and Clinical Forms of Neurally-Mediated Syncope

Abstract

nus bradycardia and/or atrioventricular block.For patients with typical VVS, a combination of neural outflow and purinergic activation is likely. Letters J A C C V O L . 6 6 , N O . 2 , 2 0 1 5 J U L Y 1 4 , 2 0 1 5 : 2 0 2 -7 R E F E R E N C E S 1. Deharo JC, Mechulan A, Giorgi R, et al. Adenosine plasma level and A2A adenosine receptor expression: correlation with laboratory tests in patients with neurally mediated syncope. Heart 2012;98:855-9. 2. Deharo JC, Guieu R, Mechulan A, et al. Syncope without prodromes in patients with normal heart and normal electrocardiogram: a distinct entity. J Am Coll Cardiol 2013;62:1075-80. 3. Brignole M, Deharo JC, De Roy L, et al. Syncope due to idiopathic paroxysmal atrioventricular block: long-term follow-up of a distinct form of atrioventricular block. J Am Coll Cardiol 2011;58:167-73. 4. Saadjian AY, Gerolami V, Giorgi R, et al. Head-up tilt induced syncope and adenosine A2A receptor gene polymorphism. Eur Heart J 2009;30:1510-5. 5. Sutton R, Brignole M. Twenty-eight years of research permit reinterpretation of tilt-testing: hypotensive susceptibility rather than diagnosis. Eur Heart J 2014;35:2211-2. Early Repolarization A Risk Factor in Brugada SyndromeConte et al. (1) reported their long-term results of implantable cardioverter-defibrillator therapy in Brugada syndrome (BS). The investigators noted that 4 patients experienced an electrical storm and 1 (Patient #3) had a "fragmentation of the QRS complex (f-QRS)." In fact, this patient's electrocardiogram (ECG) showed a spike mainly at the terminal portion of all QRS complexes. After ajmaline challenge, a coved-type ECG was induced, and the spike disappeared, unmasking an S wave in leads V 4 to V 6 .We believe that the terminal QRS spike may signify early repolarization (ER) rather than f-QRS in this BS patient. Unlike in myocardial infarction, f-QRS has

Spare Adenosine A2a Receptors Are Associated with Positive Exercise Stress Test in Coronary Artery Disease

“…While the K D for A 2A R of the agonist used here to mimic adenosine was similar in patients and controls, the EC 50 value (related to the biological effect triggered by the Spare A 2A R was first observed in guinea pig cardiac tissue using an irreversible A 2A R antagonist to block response to various agonists (13). Here, we used an agonist-like monoclonal antibody and provided further evidence for the presence of spare A 2A R on the surface of human mononuclear cells in relation to cardiac dysfunction, spare A 2A R having already been observed in a context of neurocardiogenic syncope, but not in healthy subjects (14,15,18).…”

“…The presence of spare A 2A R in CAD patients and its role in CAD pathophysiology in which the regulation of myocardial blood flow is altered have never been addressed, and we hypothesized that spare A 2A R is present in CAD patients to try to correct myocardial ischemia. We therefore undertook in this study to test the pharmacological characteristics of A 2A R present on peripheral blood mononuclear cells (PBMC) because i) this cell population is readily accessible compared with coronary tissues and ii) properties of A 2A R on PBMC appear to be similar to those of A 2A R in heart tissue as changes in PBMC-surface expression of A 2A R occur in cardiovascular diseases are associated with adenosine metabolism abnormalities (16)(17)(18), which suggests that regulation of A 2A R expression may be a systemic mechanism.…”

Rapid Measurement of Adenosine Concentration in Human Blood Using Fixed Potential Amperometry: Comparison with Mass Spectrometry and High- Performance Liquid Chromatography

“…This high APC is responsible for the drop in blood pressure and loss of consciousness. Conversely, low adenosine is associated with sudden syncope [2,3]. This last kind of syncope has a more pejorative prognosis because lacking prodromes and because the cause of loss of consciousness is often atrio-ventricular block [3].…”

“…Adenosine is an ATP derivative that is implicated in a lot of cardiovascular and neurological diseases including neurocardiogenic syncope [1][2][3], coronary artery diseases [4,5], neuropathic pain [6], septic shock [7] and severe systemic inflammatory response [8]. Thus, measurig adenosine in blood may be helpful for some pathologies.…”

“…Thus, measurig adenosine in blood may be helpful for some pathologies. As example measuring adenosine in blood help to distinguish patient's vasovagal syncope (VVS) that have high adenosine plasma concentration (APC) from patients with sudden syncope that have low APC and more pejorative prognostic [2].…”