Effects of adenosine on wavelength of premature atrial complexes in patients without structural heart disease

A novel association of adenosine deaminase with paroxysmal atrial fibrillation: a propensity score analysis from a case-control study

BACKGROUND

Prior work has identified age, body mass index, underlying heart disease, and other comorbidities as risk factors for atrial fibrillation. To date, studies have examined single baseline measures of traditional risk factors, and data on biomarker associations are lacking.

OBJECTIVE

We sought to explore novel biochemical measures possibly associated with incident PAF after balancing the traditional risk factors.

METHODS

Men or women aged ≥18 years that were hospitalized between 1(st) Jan. 2010 and 31(st) Dec. 2013 for paroxysmal atrial fibrillation (PAF) and for health checkup (non-PAF) were included. We used propensity score methods to mitigate the influence of the nonrandom selection of PAF and non-PAF patients. Logistic regression was applied for analysis of risk factors for PAF.

RESULTS

A total of 1,802 eligible patients were identified, in whom, 895 patients had at least one exclusion criterion. After excluding these patients, the total analytic cohort numbered 907 patients. Of these, 779 patients were for control group and 128 patients were for PAF group. Propensity score matching was used to obtain a balanced cohort of 124 patients per group. The PAF and non-PAF groups were well matched on demographic and clinical characteristics after propensity matching. Risk factors for PAF on multivariate stepwise logistic regression model included adenosine deaminase (ADA) [odds ratio (OR) =0.9160, P=0.015, 95% confidence interval (CI): 0.8536-0.9829], mitral valvular regurgitation (OR =3.4611, P=0.001, 95% CI: 1.7000-7.0467) and left atrial diameter (OR =1.0913, P=0.001, 95% CI: 1.0387-1.1465). Only the ADA was a protective factor for the occurrence of PAF.

CONCLUSIONS

The ADA seems to be associated with PAF. The current study provides new insights into the prevention and treatment of PAF.

Induction of atrial fibrillation with adenosine during a transesophageal electrophysiology study to risk stratify a patient with asymptomatic ventricular preexcitation

An asymptomatic adolescent male athlete was incidentally found to have ventricular preexcitation on electrocardiogram during a sports preparticipation physical. A transesophageal electrophysiology study (TEEPS) was performed after an exercise stress test failed to delineate the patient's risk of sudden cardiac death. The TEEPS was favored in this case over a transvenous electrophysiology study due to reduced invasiveness. The goal of the TEEPS was to place the patient into atrial fibrillation (AFib) and evaluate the shortest preexcited RR interval during AFib, thereby assessing the risk of his accessory pathway. Conventional pacing modalities were unable to induce AFib. During atrial burst pacing, adenosine was then administered, which successfully induced AFib. This case highlights adenosine's potential to induce atrial fibrillation during transesophageal electrophysiology studies when atrial pacing alone was unable to do so.

Adenosine-insensitive focal atrial tachycardia: evidence for de novo micro-re-entry in the human atrium

OBJECTIVES

The purpose of this work was to describe the entity and mechanism of adenosine-insensitive focal atrial tachycardia (AT).

BACKGROUND

The majority of regular focal ATs demonstrate properties consistent with triggered activity, including termination by adenosine. Less commonly, AT may be due to enhanced automaticity, which is transiently suppressed by adenosine. Small re-entrant circuits may also give rise to focal AT, but limited data exist regarding this entity as a de novo arrhythmia in the human atrium.

METHODS

Eighty cases of focal AT were mapped in the electrophysiology laboratory and challenged with adenosine. Adenosine-sensitive and -insensitive groups were compared with regard to demographics, anatomical distribution, and electrogram characteristics at the tachycardia origin.

RESULTS

In response to adenosine, termination occurred in 67 cases (84%), transient suppression in 5 (6%), 6 were insensitive (8%), and 2 exhibited nonspecific responses. Adenosine-insensitive AT arose near the pulmonary vein ostia (4) and from the right atrium (2), whereas adenosine-sensitive AT arose from a wide distribution in both atria. Electrograms at the site of origin for adenosine-insensitive AT were highly fractionated, with longer durations and lower amplitudes compared with AT that terminated or was transiently suppressed. The electrograms at the origin of adenosine-insensitive ATs comprised 22% to 69% of the tachycardia cycle length, compared with 4% to 21% for adenosine-sensitive ATs. In 3 adenosine-insensitive ATs, entrainment was demonstrated with post-pacing intervals equivalent to the tachycardia cycle length.

CONCLUSIONS

The characteristics of adenosine-insensitive focal AT differ from adenosine-sensitive AT and are consistent with small re-entrant circuits. These data provide evidence that focal re-entry is a mechanism of AT and has an electropharmacologic profile that differs from AT due to automaticity and triggered activity.

Anisotropic effects of sodium channel blockers on the wavelength for ventricular excitation in dogs

The purpose of this study was to determine the anisotropic effects of sodium channel blockers on wavelength (WL) and proarrhythmia. In 18 anesthetized, open chest dogs, a 64-electrode array was placed on the left ventricle and the ventricle was constantly paced. Disopyramide, lidocaine or flecainide was intracoronarily administered. Conduction velocity (theta) and activation-recovery interval (ARI) were measured in the longitudinal (L) and transverse (T) directions. Flecainide markedly decreased thetaL, but did not alter thetaT or ARIs in either direction. As a result, the wavelength was significantly shortened only in the L direction. Disopyramide or lidocaine did not show direction-dependent effects on theta or WL. In 3 of 6 dogs with flecainide exposure, ventricular fibrillation (VF) developed. However, no VF occurred with disopyramide or lidocaine. Accordingly, the WL is dependent on the fiber orientation of myocardium. The anisotropic shortening of the WL may explain the character of the proarrhythmia observed with flecainide.

Electrophysiological effect of adenosine triphosphate and adenosine on atrial and ventricular action potential duration in humans

Bolus injection of adenosine triphosphate (ATP) or adenosine is widely used clinically for terminating supraventricular tachycardia. However, bolus injection of these drugs has been reported to provoke atrial fibrillation (Afib). The effects of ATP and adenosine on the monophasic action potential duration (MAPD) of atrial and ventricular muscle was investigated, as well as the changes in the spatial distribution of atrial functional refractoriness caused by adenosine. Bolus injection of ATP and adenosine shortened atrial MAPD; no change was observed in the ventricle. Because local f-f intervals during atrial fibrillation correlate with the atrial refractory period, changes in mean f-f intervals in the right atrial appendage, His bundle region, coronary sinus ostium and distal coronary sinus were compared before and after injection of adenosine during induced Afib. Maximal shortening of f-f intervals was observed in the right atrial appendage. Inhomogeneous shortening of atrial refractoriness may account for the Afib following bolus injection of ATP or adenosine.

Effects of adenosine on local stimulus-response latency and induction of atrial fibrillation by premature stimuli

Premature atrial stimuli delivered during the relative refractory or "vulnerable" period exhibit increased local stimulus-response latency and may occasionally induce atrial arrhythmias. The use of adenosine to treat supraventricular tachycardias may also provoke atrial arrhythmias. In this study we investigated the effects of adenosine on the latency of premature complexes in relation to repolarization and induction of atrial arrhythmias in 14 patients without structural heart disease. A monophasic action potential catheter was used for recording in the right atrium and introducing premature stimuli (S2) at twice diastolic threshold after eight paced (S1) complexes. At short coupling intervals, S2 latency increased relative to S1 latency. S2 was delivered repeatedly at a fixed coupling interval (producing maximal local response latency) and adenosine (6 mg) was given intravenously. Adenosine decreased S2 latency significantly (23+/-5 to 11+/-3 ms, P<0.01), to values similar to S, latency. However, despite the decrease in S2 latency, the combination of adenosine and S2 more often resulted in transient atrial arrhythmias (11 of 14 patients vs 2 of 14 patients without adenosine, P<0.05). Adenosine had no effect on S, latency (9+/-2 vs. 9+/-2 ms) but decreased monophasic action potential duration from 202+/-37 to 158+/-38 ms (P<0.01). Adenosine was also given to 10 patients with S2 introduced at a coupling interval 40-50 ms less than the baseline effective refractory period. This resulted in a decrease in atrial refractoriness and capture of S2 in all cases. Latency for S2 was significantly greater than Si latency (21+/-12 vs. 9+/-2 ms, P<0.01) and transient atrial arrhythmias were induced in 9 of 10 patients. We conclude that for a given S2 coupling interval, adenosine decreases local stimulus-response latency but increases atrial vulnerability to transient atrial arrhythmias. Decreased latency may be related to a shift in the zone of relative refractoriness associated with an adenosine-mediated decrease in monophasic action potential duration. Induction of atrial arrhythmias in the presence of adenosine occurs independently of increased latency and is therefore not dependent on S2 falling within the relative refractory period at the site of stimulation.

Electrophysiologic effects of adenosine in patients with supraventricular tachycardia

BACKGROUND

We correlated the electrophysiologic (EP) effects of adenosine with tachycardia mechanisms in patients with supraventricular tachycardias (SVT).

METHODS AND RESULTS

Adenosine was administered to 229 patients with SVTs during EP study: atrioventricular (AV) reentry (AVRT; n=59), typical atrioventricular node reentry (AVNRT; n=82), atypical AVNRT (n=13), permanent junctional reciprocating tachycardia (PJRT; n=12), atrial tachycardia (AT; n=53), and inappropriate sinus tachycardia (IST; n=10). There was no difference in incidence of tachycardia termination at the AV node in AVRT (85%) versus AVNRT (86%) after adenosine, but patients with AVRT showed increases in the ventriculoatrial (VA) intervals (13%) compared with typical AVNRT (0%), P<0.005. Changes in atrial, AV, or VA intervals after adenosine did not predict the mode of termination of long R-P tachycardias. For patients with AT, there was no correlation with location of the atrial focus and adenosine response. AV block after adenosine was only observed in AT patients (27%) or IST (30%). Patients with IST showed atrial cycle length increases after adenosine (P<0.05) with little change in activation sequence. The incidence of atrial fibrillation after adenosine was higher for those with AVRT (15%) compared with typical AVNRT (0%) P<0.001, or atypical AVNRT (0%) but similar to those with AT (11%) and PJRT (17%).

CONCLUSIONS

The EP response to adenosine proved of limited value to identify the location of AT or SVT mechanisms. Features favoring AT were the presence of AV block or marked shortening of atrial cycle length before tachycardia suppression. Atrial fibrillation was more common after adenosine in patients with AVRT, PJRT, or AT. Patients with IST showed increases in cycle length with little change in atrial activation sequence after adenosine.