Efficacy of adenosine in terminating catecholamine-dependent supraventricular tachycardia

Imaging of adenosine bolus transit following intravenous administration: insights into antiarrhythmic efficacy

OBJECTIVE

To study the effects of the site of intravenous injection of adenosine and to assess the site of action of adenosine in the heart by correlating cardiac effects with bolus transit.

METHODS

Ten patients undergoing routine technetium (Tc-99m) gated blood pool ventriculography consented to the coadministration of intravenous adenosine. The dose of adenosine required to produce heart block during sinus rhythm was determined following antecubital vein administration. This dose (6-18 mg) was mixed with Tc-99m and given first into the same antecubital vein (proximal injection) and then repeated into a hand vein (distal injection). The ECG was recorded and the transit of the bolus was imaged using a gamma camera.

RESULTS

Heart block occurred in all 10 patients (second degree in seven, first degree in three) at (mean (SEM)) 17.5 (1.0) seconds after the proximal injection of adenosine. Distal injection produced heart block in six patients (second degree in two, first degree in four) at 21.9 (4.4) seconds (p < 0.01). In eight of 10 patients the electrophysiological effects were less with distal injection. The onset of heart block was close to the time of peak bolus Tc-99m activity in the left ventricle. Peak bolus activity was delayed (by about three seconds) and the duration of bolus activity in the left ventricle was increased with distal injection compared with proximal injection, at 17.2 (4.2) v 9.2 (3.1) seconds, p < 0.01.

CONCLUSIONS

The lesser electrophysiological effects of adenosine following distal intravenous injections were associated with delay in transit time and dispersion of the bolus. The correlation of adenosine induced heart block with bolus activity in the left heart indicated dependence on coronary arterial delivery of adenosine to the atrioventricular node.

Effect of adenosine and verapamil in catecholamine-induced accelerated atrioventricular junctional rhythm: insights into the underlying mechanism

Accelerated AV junctional rhythm is postulated to be due to enhanced automaticity of a high AV junctional focus. The adenosine response of this rhythm was tested in 17 patients (7 males, 12-83 years). The indications of electrophysiology study were nonspecific palpitation (n = 5), unexplained syncope (n = 6), postablation of accessory pathways (n = 4), and postmodification of AV nodal reentry tachycardia (n = 2). The sinus node and AV nodal functions were normal. Pacing and programmed electrical stimulation failed to induce any arrhythmia at baseline. The accelerated junctional rhythm (cycle length = 553 +/- 134 ms) was initiated spontaneously in all patients after isoproterenol infusion (1-2 micrograms/min). It was not suppressible by overdrive pacing. Cessation of isoproterenol infusion terminated the rhythm in all patients. Adenosine (6 mg) reproducibly terminated the accelerated junctional rhythm in all patients. In six patients, adenosine suppressed the junctional rhythm without producing AV nodal block. In the other 11 patients, the junctional rhythm was terminated prior to the occurrence of AV nodal block. Verapamil was tested in ten patients and 5 mg of intravenous verapamil terminated the junctional rhythm in all patients. In conclusion, the mechanism of catecholamine-induced accelerated AV junctional rhythm is most likely enhanced automaticity, and catecholamine-induced accelerated AV junctional automaticity is sensitive to adenosine and verapamil. Adenosine appears to have differential effects on catecholamine-enhanced AV junctional automaticity and AV nodal conduction. This suggests that, under catecholamine stimulation, adenosine may have different mechanisms of action on AV nodal conduction and automaticity.

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.

Influence of beta-adrenergic and vagal activity on the effect of exogenous adenosine on supraventricular tachycardia termination

Adenosine, which binds to cell surface receptors and couples with guanosine triphosphate-binding inhibitory proteins (G(i)), is potent in terminating supraventricular tachycardia (SVT). However, whether the differences in autonomic tone will influence this effect remains unknown. This study was designed to investigate the role of beta-adrenergic and vagal activity on the action of adenosine. Forty patients with clinically documented SVT (22 with atrioventricular node reentrant tachycardia and 18 with atrioventricular reciprocating tachycardia) were divided into 4 groups with 10 patients in each group. In groups 1 and 2, adenosine was intravenously injected during the baseline state and during infusion of isoproterenol (2 and 4 microg/min, respectively). Group 2 patients received atropine (0.04 mg/kg) injection before isoproterenol infusion. In groups 3 and 4, intravenous injection of adenosine was given during the baseline state and after injection of atropine (0.02 and 0.04 mg/kg, respectively). Group 4 patients received propranolol (0.2 mg/kg) before atropine injection. The minimal dose of adenosine to terminate tachycardia during isoproterenol infusion of 2 microg/min was greater than that during the baseline state in both groups 1 and 2. The minimal dose of adenosine during isoproterenol infusion with 4 microg/min was higher than that with 2 microg/min in group 2, but not in group 1 patients. In both groups 3 and 4, the minimal dose of adenosine required to terminate tachycardia during atropine injection with 0.02 mg/kg was greater than that during the baseline state. The minimal effective dose of adenosine during atropine injection with 0.04 mg/kg was higher than that with 0.02 mg/kg in group 4, but not in group 3 patients. In conclusion, either limb of the autonomic nervous system may modulate the adenosine dosage required for termination of SVT. Patients taking drugs such as beta blockers or vagolytic agents may need alterations in the dose of adenosine for therapy.

Management of paroxysmal atrioventricular nodal reentrant tachycardia in the critically ill surgical patient

OBJECTIVES

Paroxysmal atrioventricular nodal reentrant tachycardia is an infrequently encountered supraventricular arrhythmia that continues to present difficult management problems in the critically ill surgical patient. The purpose of this study was to evaluate the efficacy of a new treatment algorithm involving the sequential administration of different classes of antiarrhythmic agents until conversion to sinus rhythm was achieved.

DESIGN

Nonrandomized, consecutive, protocol-driven descriptive cohort.

SETTING

University hospital surgical and trauma intensive care unit (ICU).

PATIENTS

During an 11-month period, we prospectively evaluated all hemodynamically stable patients who sustained new-onset atrioventricular nodal reentrant tachycardia.

INTERVENTIONS

Vagal maneuver, followed by the rapid, sequential infusion of antiarrhythmic agents (i.e., adenosine, verapamil, and esmolol, respectively) until the arrhythmia was terminated.

MEASUREMENTS AND MAIN RESULTS

Twenty-seven patients (4% of all admissions) were evaluated, including 16 trauma patients (injury Severity Score of 20 +/- 8) and 11 general surgical patients (Acute Physiology and Chronic Health Evaluation II score of 17 +/- 7). Time from ICU admission to onset of atrioventricular nodal reentrant tachycardia was 4.5 +/- 5 days (median 2.5). Arrhythmia termination was achieved in all patients within minutes (mean 13 +/- 10 [SD]). Incremental sequential adenosine administration alone, however, was successful in affecting conversion to sinus rhythm in only 44% of initial episodes of atrioventricular nodal reentrant tachycardia (95% confidence interval 21% to 67%). A total of 14 (52%) patients developed 38 relapses of paroxysmal supraventricular tachycardia in the ICU after initial conversion to sinus rhythm. These relapses required additional antiarrhythmic therapy. Adenosine was only effective in 34% of the relapses (95% confidence interval 17% to 53%). Seven (50%) of these 14 patients developed multiple relapses. However, only two patients were receiving suppressive calcium-channel or beta-adrenergic receptor blockade at the time of relapse.

CONCLUSIONS

The use of a multiagent algorithm was effective for the initial conversion of new-onset atrioventricular nodal reentrant tachycardia to sinus rhythm in critically ill surgical and trauma patients. This preliminary report suggests that adenosine has marginal efficacy in the critically ill surgical or trauma patient. Given the high frequency of relapses, regardless of the agents used to achieve initial control, suppression therapy for the arrhythmia during the period of maximal cardiovascular stress is essential.

Correlation of P-wave polarity with underlying electrophysiologic mechanisms of long RP' tachycardia

Analysis of surface electrocardiograms from patients with long RP' tachycardia due to either atypical atrioventricular node reentrant tachycardia, permanent junctional reciprocating tachycardia, or low atrial tachycardia was performed. Although a negative P wave in the inferior leads is common to all 3 mechanisms, the results suggest that a positive or isoelectric P wave in electrocardiographic lead I strongly supports a diagnosis of atypical atrioventricular node reentrant tachycardia, whereas a negative or biphasic P wave in lead I argues against this mechanism.

Spectrum of electrophysiologic and electropharmacologic characteristics of verapamil-sensitive ventricular tachycardia in patients without structural heart disease

Verapamil-sensitive ventricular tachycardia (VT) is a well-recognized clinical entity that some authorities believe may result from triggered activity. Despite its uniform response to verapamil, however, there is evidence that this uncommon form of VT may not be as homogeneous as first believed. Standard intracardiac electrophysiologic techniques were used to study verapamil-sensitive VT in 32 patients (aged 38 years +/- 20 years) without evidence of structural heart disease. More than half of these patients (69%) exhibited VT with a right bundle branch block-type QRS pattern, with the remainder (31%) displaying VT with a left bundle branch block pattern. In 31% of the patients the VT could be induced by fixed-cycle length atrial pacing, whereas in 59% of patients fixed-cycle length ventricular pacing was necessary. A critical range of cycle lengths for VT induction was required in 66% of the patients. Ventricular tachycardia was initiated with single atrial premature extrastimuli in 16% of patients, single ventricular extrastimuli in 50% of patients, and double ventricular premature extrastimuli in 9% of patients. Ventricular tachycardia displaying cycle-length alternans was observed in 28% of patients. In only 19% of patients was it possible to entrain VT during pacing from the right ventricular apex. Isoproterenol infusion was required for tachycardia induction in 50% of patients, 44% of whom had VT with a left bundle branch block QRS pattern, with the remaining 56% exhibiting VT with a right bundle branch block pattern. Beta-adrenergic blockers suppressed 53% of verapamil-sensitive VT in patients tested, whereas adenosine terminated VT in 50% of patients, with 81% of these patients exhibiting either a left bundle branch block QRS pattern or isoproterenol dependence. Ventricular tachycardia exhibiting a left bundle branch block pattern was more likely to be isoproterenol dependent (p <0.05) and adenosine sensitive (p <0.001). However, verapamil-sensitive, catecholamine-dependent VT was no more likely to be adenosine sensitive than the catecholamine-independent form of the arrhythmia (p >0.5). Verapamil-sensitive VT exhibits properties expected of both a reentrant and triggered arrhythmia, and it is inconsistently dependent on both exogenous catecholamines for induction and intravenous adenosine for termination. Verapamil-sensitive VT encompasses a heterogeneous group of tachycardias that may result from multiple cellular electrophysiologic mechanisms.

Atrioventricular node reentry: current concepts and new perspectives

With the advent of RF catheter modification of AV node conduction for the treatment of AV node reentrant tachycardia, considerable advances have been made with better understanding of the AV junctional anatomy, electrophysiology, and mechanism responsible for AV node reentrant tachycardia. Future studies should be designed to uncover the basic cellular electrophysiological mechanisms responsible for fast and slow AV node conduction, to define the exact tissue components of the reentrant circuit in order to make ablative procedures safer, and to study the long-term effects of RF catheter ablation on AV conduction. Special caution should be directed toward pediatric patients with more stringent indications for catheter ablation of the AV junctional area in these patients.