Use of adenosine in patients hospitalized in a university medical center.

PURPOSE: Adenosine is a useful agent for the diagnosis and termination of tachycardias. The purpose of this study was to identify the rhythms for which adenosine is prescribed in hospitalized adults and to identify the reasons for its misuse. PATIENTS AND METHODS: Data were collected from the medical records of 100 patients who received intravenous adenosine while hospitalized at a university medical center. The characteristics of the patients, rhythms treated with adenosine, and dosages of adenosine were analyzed. In addition, internal medicine house officers were administered a questionnaire referring to an electrocardiogram of atrial fibrillation with a rapid ventricular response. RESULTS: The arrhythmias for which adenosine was administered consisted of regular, narrow-QRS complex tachycardias in 33% of patients; atrial fibrillation in 32% of patients; regular, wide-QRS complex tachycardias in 23% of patients; atrial flutter in 10% of patients, and multifocal atrial tachycardia in 2% of patients. The mean (+/-SD) number of doses of adenosine given to each patient was 1.6+/-0.8, and the mean dose of adenosine was 7.8+/-2.8 mg. Internal medicine house officers prescribed 70% of the doses of adenosine and were as likely to use it for patients with atrial fibrillation as were surgical house officers. There was a 2% incidence of proarrhythmia, including asystole and polymorphic ventricular tachycardia. Thirty-one percent of the 100 house officers in our survey misdiagnosed a 12-lead electrocardiogram of rapid atrial fibrillation as paroxysmal supraventricular tachycardia, suggesting that adenosine may have been misused for atrial fibrillation because of errors in rhythm diagnosis. Only 5% of those who correctly diagnosed atrial fibrillation also answered that adenosine would be likely to terminate the arrhythmia, suggesting that a misunderstanding that adenosine terminates atrial fibrillation is not a common reason for its misuse. CONCLUSIONS: Approximately 40% of hospitalized adults who are treated with adenosine receive the medication unnecessarily for atrial fibrillation or atrial flutter, and this misuse results in unnecessary expenses and risks of adverse effects. The primary reason that adenosine is misused for atrial fibrillation is the inability to recognize that rhythm on an electrocardiogram. House officers need additional education on the electrocardiographic recognition of atrial fibrillation.

Spatial resolution of atrial pace mapping as determined by unipolar atrial pacing at adjacent sites.

BACKGROUND: The purpose of this study was to examine the spatial resolution of unipolar atrial pace mapping by pacing at adjacent sites within the coronary sinus and the right atrium. METHODS AND RESULTS: Unipolar pacing from each pole of a quadripolar catheter was performed in the coronary sinus (n = 29) and in the right atrium (n = 10). Pacing from the distal electrode was used to simulate the site of origin of an atrial tachycardia. These P waves were compared with the P waves generated by unipolar pacing from each of the three proximal electrodes. The P waves were analyzed for changes in amplitude, duration, and configuration. Pacing within the coronary sinus resulted in significant changes in amplitude and duration at distances of 17 and 21 mm from the distal pole, respectively. Similarly, pacing in the right atrium resulted in significant changes in amplitude and duration at distances of 17 and 32 mm from the distal pole, respectively. No significant changes in configuration were noted in the coronary sinus in any lead at packing sites < or = 32 mm from the distal pole. Configurational changes were noted in the right atrium at pacing sites 17 mm from the distal pole. CONCLUSIONS: The spatial resolution of unipolar atrial pace mapping is approximately 17 mm. These findings indicate that mapping techniques that depend on the accurate discrimination of P-wave morphology, such as pace mapping or concealed entertainment, are likely to be imprecise when used in the atria.

Atrioventricular node properties in patients with accessory pathways.

A study during the era of surgical ablation suggested that atrioventricular (AV) nodal conduction is faster in patients with accessory pathways than in controls. In the present study, AV nodal characteristics were studied in 30 patients who underwent radiofrequency ablation of an accessory pathway and compared to 23 control patients. Sinus cycle length, AH and HV intervals, AV block cycle length, ventriculoatrial (VA) block cycle length, AV nodal effective refractory period, and VA effective refractory periods were measured in control and postablation accessory pathway patients before and after autonomic blockade with 0.04 mg/kg of atropine and 0.2 mg/kg of propranolol. The mean sinus cycle length in the control and accessory pathway groups did not differ significantly at baseline (798 +/- 211 and 766 +/- 156 msec, respectively) or after autonomic blockade (654 +/- 98 and 649 +/- 108 msec, respectively). The mean AH interval in the accessory pathway group (77 +/- 15 msec) was significantly shorter than in the control group (91 +/- 22 msec; p < 0.05) at baseline; however, there was no difference after autonomic blockade. No other significant differences were observed between the accessory pathway and control groups. These results demonstrate that AV nodal properties of patients with accessory pathways are not significantly different from controls and suggest that previously reported differences may have been due to selection bias.

Reasons for prolonged or failed attempts at radiofrequency catheter ablation of accessory pathways.

OBJECTIVES: The purpose of this study was to categorize the reasons for a prolonged or failed procedure in a series of patients undergoing catheter ablation of an accessory pathway. BACKGROUND: Radiofrequency ablation of accessory pathways at times requires a lengthy procedure or a second ablation session, or both, and not prior studies have systematically investigated the reasons for this. METHODS: In a consecutive series of 619 patients undergoing catheter ablation of an accessory pathway, the mean ablation time +/- SD was 68 +/- 64 min. The subjects of this study were 14 patients who had an ablation time >2 SD greater than the mean (>196 min) and 51 patients who required a second ablation session for a successful outcome. The accessory pathway in the 65 patients in this study was located in the right free wall in 19 patients (29%), septum in 14 (22%) and left free wall in 32 (49%). RESULTS: The primary reasons for a lengthy or failed ablation attempt were 1) inability to position the ablation catheter at the effective target site (16 patients, 25%); 2) instability of the ablation catheter or inadequate tissue contact at the target site, or both (15 patients, 23%); 3) mapping error due to an oblique course of the accessory pathway (7 patients, 11%); 4) failure to recognize a posteroseptal accessory pathway as being left-sided instead of right-sided (4 patients, 6%); 5) other errors in accessory pathway localization (6 patients, 9%); 6) epicardial location of the accessory pathway (5 patients, 8%); 7) recurrent atrial fibrillation (2 patients, 3%); 8) occurrence of a complication (2 patients, 3%); 9) unusual right-sided accessory pathway that inserted in the anterior right ventricle, 2 cm away from the lateral tricuspid annulus (1 patient, 1.5%); and 10) unexplained factors (7 patients, 11%). The most common effective strategies employed to achieve a successful outcome in these patients were 1) substitution of a more experienced operator; 2) use of ablation catheters of varying configurations; 3) switching from a retrograde aortic to a trans-septal approach; 4) switching from an inferior to a superior vena caval approach; 5) use of a 60-cm guiding sheath; 6) detailed mapping of the atrial or ventricular insertion of the accessory pathway; and 7) searching within the coronary sinus for a presumed accessory pathway potential. CONCLUSIONS: A lengthy or failed attempt at catheter ablation of an accessory pathway may be due to a variety of reasons, the most common of which are problems related to some aspect of catheter manipulation and errors in accessory pathway localization. Knowledge of the most common reasons for a lengthy or ineffective procedure may facilitate successful outcome of accessory pathway ablation.

Atrial electrogram characteristics in patients with and without atrioventricular nodal reentrant tachycardia.

BACKGROUND: Multicomponent atrial electrograms and "slow pathway potentials" are helpful in identifying target sites for radiofrequency catheter ablation of the slow pathway in patients with atrioventricular (AV) nodal reentrant tachycardia. The purpose of this study was to compare the atrial electrograms recorded at various locations in the right atrium in patients with and without AV nodal reentrant tachycardia to assess the specificity of multicomponent atrial electrograms and possible slow pathway potentials both for the posteroseptal right atrium and for patients with AV nodal reentrant tachycardia. METHODS AND RESULTS: In 25 patients with AV nodal reentrant tachycardia and 23 control patients without AV nodal reentrant tachycardia or dual AV nodal physiology, atrial electrograms with an AV ratio of < or = 1:2 were recorded at the posteroseptal right atrium near the coronary sinus ostium and in the right atrium near the posterior, lateral, and anterior aspects of the tricuspid annulus. Attempts were made to identify broad, multicomponent, and double atrial electrograms. There were no significant differences between the patients with and without AV nodal reentrant tachycardia in the mean number of deflections in the atrial electrograms or in the mean duration of the atrial electrograms recorded at any of the atrial sites. In all patients, the number of atrial electrogram deflections and the atrial electrogram duration were significantly greater at the posteroseptal position than at the other three atrial sites. The prevalence of potentials with the appearance of slow pathway potentials in the posterior septum was similar in patients with and without AV nodal reentrant tachycardia (68% and 70%, respectively). The prevalence of these potentials was 6% to 25% at the other three atrial sites (P < .005 compared with the posterior septum). CONCLUSIONS: The atrial electrogram characteristics that have been found to be useful in identifying effective posteroseptal slow pathway ablation sites in patients with AV nodal reentrant tachycardia are equally prevalent in patients without AV nodal reentrant tachycardia or dual AV nodal physiology. Atrial electrograms in the posteroseptal area are broader and contain more deflections than at other areas in the right atrium, possibly because of conduction properties of the posterior transitional zone that are independent of the presence of AV nodal reentrant tachycardia.

Assessment of pacing maneuvers used to validate anterograde accessory pathway potentials.

Four pacing maneuvers have been proposed to validate an anterograde accessory pathway potential (APP): (1) atrial pacing to induce complete block between the atrial electrogram and the APP; (2) ventricular pacing to advance the APP without altering the timing of the atrial electrogram; (3) atrial pacing to induce complete block between the APP and the ventricular electrogram; and (4) ventricular pacing to advance the ventricular electrogram without altering the timing of the APP. The purpose of this study was to assess these validation techniques by applying them to electrograms that simulated APPs but which were known to be atrial in origin. In 32 patients undergoing an electrophysiology procedure, a split atrial electrogram containing two components separated by at least 30 msec (mean 54 +/- 15 msec) was recorded. Using an atrial extrastimulus technique, complete block between the two components of the atrial electrogram (criterion 1) could never be induced, but complete block between the second component of the atrial electrogram and the ventricular electrogram (criterion 3) consistently was induced. Using a ventricular extrastimulus technique, the second component of the atrial electrogram consistently could be advanced by 10 to 40 msec without altering the timing of the first component (criterion 2). In addition, with ventricular pacing, the ventricular electrogram consistently was advanced without altering the timing of the two components of the atrial electrogram (criterion 4). In conclusion, among the four pacing maneuvers used to validate an anterograde APP, the only one that may be specific for an APP is the ability to induce complete block between the atrial electrogram and the APP.