The 12-lead electrocardiogram helps to define the arrhythmic mechanism in patients with palpitations. However, in the setting of nondocumented palpitations the value of the electrophysiologic study (EPS) needs additional investigation. We investigated the utility of the EPS in patients with nondocumented palpitations. A total of 172 patients with normal electrocardiographic findings and nondocumented palpitations underwent an EPS. The clinical and electrophysiologic characteristics were assessed. The symptoms were long-lasting (>5 minutes) in 56%. Sudden onset was present in 99%, and termination was rapid in 65%. Neck palpitations were reported in 36%. The EPS findings were normal in 86 patients (50%); atrioventricular nodal reentrant tachycardia was induced in 43, orthodromic reentrant tachycardia in 9, and nonsustained atrial tachycardia/fibrillation (AT/AF) in 34. Long-lasting episodes, sudden termination, and neck palpitations predicted positive EPS findings and were associated with reentrant supraventricular tachycardia (p <0.001). The induction of AT/AF was associated with age >50 years and structural heart disease (p <0.001). After 53 ± 36 months of follow-up, 92% of patients with negative EPS findings were symptom free. Only 32% of patients with induced AT/AF remained free of symptoms (p <0.001). The recurrence of palpitations was more prevalent among patients with structural heart disease and aged >50 years (p <0.001). In conclusion, 50% of patients with nondocumented palpitations had positive EPS findings. A long duration, sudden termination, and neck palpitations, together with structural heart disease and age >50 years, predicted tachycardia inducibility and recurrence and could help in selecting patients suitable for EPS and ablation.
The long-term prognosis of patients with nondocumented palpitations has not been widely assessed. Both the clinical baseline characteristics and the results of the electrophysiologic study (EPS) can predict the long-term outcome of this population. The identification of clinical and/or EPS predictors of palpitation recurrence would help improve the treatment of these patients by improving their quality of life and, in some cases, survival. The purpose of the present study was to search for clinical pretest predictors of tachycardia induction during the EPS and to identify the clinical and EPS predictors of long-term recurrence.
Methods
Patients undergoing an EPS for nondocumented palpitations were considered for inclusion in the present prospective study. All patients provided written informed consent in accordance with institutional guidelines of the Hospital del Mar in Barcelona, Spain.
From January 2000 to December 2009, 172 consecutive patients with normal baseline electrocardiographic findings who had presented with sustained palpitations in the emergency room were referred to the Electrophysiology Unit. The patients were considered candidates for a comprehensive EPS if they had ≥2 of the 4 following clinical criteria: long-lasting palpitations (>5 minutes), sudden onset, sudden termination, and neck palpitations. In all patients, the documentation of the tachycardia was not obtained in the emergency room, nor after a systematic and extensive noninvasive evaluation, including 24-hour Holter monitoring in all patients, stress testing in 40%, and, in some cases, 7-day Holter monitoring. If sustained tachycardia was observed during noninvasive testing, the patient was excluded from the present study and underwent EPS/ablation if considered appropriate. All patients included had presented with palpitations of ≥5 seconds in duration (not suggesting isolate premature depolarizations) and were submitted to a specific questionnaire in the search for the clinical characteristics of the palpitations. Transthoracic echocardiography was performed in all patients to identify the presence of underlying structural heart disease (SHD).
A comprehensive EPS was performed using standard techniques. Quadripolar electrode catheters were positioned in the high right atrium for registration and atrial stimulation and in the right ventricular septum for His registration and ventricular/para-hisian stimulation. An octopolar electrode catheter was positioned into the coronary sinus for left atrial registration, if deemed necessary. At least 3 electrocardiographic leads and intracardiac electrograms were recorded and stored on the Bard (C.R. Bard, Lowell, Massachusetts) recording system. Bipolar intracardiac electrograms were filtered at 30 to 500 kHz and recorded from each electrode pair at a speed of 100 mm/s. The study protocol included programmed atrial stimulation with ≤3 extrastimuli and burst pacing. If tachycardia was not induced under basal conditions, the protocol was repeated after infusion of isoproterenol to ≤3 μg/kg/min. Patients with SHD also underwent programmed ventricular stimulation with ≤3 extrastimuli.
The diagnosis of orthodromic reentrant tachycardia using a retrograde accessory pathway and typical atrioventricular nodal reentrant tachycardia (AVNRT) were made according to the VA interval, tachycardia entrainment maneuvers from the right ventricle/His catheter, and the response to premature ventricular depolarization occurring when the His bundle was refractory. The diagnosis of atypical AVNRT was made according to the VA interval, earliest retrograde atrial activation site, VA linking, and response to entrainment of the tachycardia from the right ventricle/His catheter. The diagnosis of atrial tachycardia was made when a “VAAV” response to ventricular stimulation during tachycardia or the lack of VA linking was demonstrated. Induced runs of nonsustained atypical atrial flutter were considered in the group of induced nonsustained atrial tachycardia/fibrillation (AT/AF).
The results of the EPS were considered positive on the induction of sustained supraventricular tachycardia (SVT), including AVNRT, orthodromic reentrant tachycardia, AT/AF, and ventricular tachycardia or fibrillation. The EPS findings were also considered positive on the induction of short runs of nonsustained (>3 beats, <30 seconds) tachycardia if the patients identified those runs as their clinical palpitations. Patients with induced sustained arrhythmias were proposed for catheter ablative therapy. For the patients with induced AT/AF and those with induced nonsustained tachycardia, ablation was not indicated, because pharmacologic therapy had not yet been attempted. This was independent of whether the patients had identified tachycardia as their clinical palpitations.
The patients were followed up for the assessment of clinical recurrences. Clinical assessments were made by direct or telephone interviews at 3 and 6 months and subsequently every 12 months in all patients. This was independent of the EPS results. The following clinical and electrophysiologic characteristics were included and analyzed as predictors for positive EPS findings and/or clinical recurrences of the palpitations during follow-up: age, gender, sudden onset and termination of tachycardia, tachycardia duration of ≥5 minutes, neck palpitations, presence of SHD, previous attempt at ablation of any tachycardia, and type of arrhythmia induced during the EPS.
The categorical variables were compared using a chi-square test. Continuous variables (expressed as the mean ± SD) were compared using an unpaired Student’s t test (normal distribution). The predictors found during follow-up were evaluated using a Kaplan-Meier analysis. p Values ≤0.05 were considered statistically significant.
Results
A total of 172 patients fitting the inclusion criteria underwent a comprehensive EPS. The baseline main clinical characteristics of the population are listed in Table 1 . None of the patients with a previous ablation procedure (AVNRT in 5 patients, orthodromic reentrant tachycardia in 4 patients, and typical atrial flutter in 1 patient) had the index arrhythmia reinduced during the EPS. Of the 21 patients with SHD, 11 had hypertensive cardiomyopathy, 6 had ischemic cardiomyopathy, 2 had valvular disease, and 2 had idiopathic cardiomyopathy. Only 1 of the 21 patients with SHD had a diminished left ventricular ejection fraction (left ventricular ejection fraction <50%).
| Characteristic | Value |
|---|---|
| Age (years) | 46 ± 18 |
| Gender | |
| Male | 132 (77%) |
| Female | 40 (23%) |
| Heart disease | 21 (12%) |
| Previous ablation | 10 (6%) |
| Palpitation duration (min) | |
| <1 | 17 (10%) |
| 1–5 | 58 (34%) |
| >5 | 97 (56%) |
| Sudden onset | 171 (99%) |
| Sudden termination | 112 (65%) |
| Neck palpitations | 61 (35%) |
A total of 86 patients (50%) had normal EPS findings and 86 patients (50%) had inducible SVT. AVNRT was induced in 43 patients (25%). Orthodromic reentrant tachycardia using a concealed accessory pathway was induced in 9 patients (5%). Nonsustained runs of AT/AF identified by the patient as their clinical palpitations were observed in 34 patients (20%). Nonsustained runs of ventricular tachycardia or fibrillation (maximum of 6 beats) were observed in 14 patients; however, none associated it with their clinical symptoms. No complications related to the procedure were seen in our series.
The analysis of the clinical and palpitation characteristics predicting positive EPS findings is summarized in Table 2 . The duration of episodes of ≥5 minutes predicted positive EPS findings with a sensitivity of 77% and specificity of 71% (p <0.001) and also predicted the induction of reentrant SVT (AVNRT or orthodromic reentrant tachycardia) with a sensitivity of 92% and specificity of 60%. Sudden onset was not associated with tachycardia induction. In contrast, sudden termination predicted positive EPS findings with a sensitivity of 79% and specificity of 55% (p <0.001) and the induction of reentrant SVT with a sensitivity of 96% and specificity of 48%. Neck palpitations were associated with positive EPS findings, with a sensitivity of 44% and specificity of 77% (p <0.001) and with reentrant SVT induction with a sensitivity of 71% and specificity of 79%. To improve the accuracy of the statistically significant predictors for reentrant SVT induction, we considered the association of the best 2 individual predictors for both AVNRT and orthodromic reentrant tachycardia. The combination of sudden termination of tachycardia and the presence of long-lasting palpitations increased the accuracy for predicting reentrant SVT, with a sensitivity of 90% and specificity of 76%. Neither age nor gender predicted tachycardia inducibility during the EPS. However, when considering specific tachycardias individually, age >50 years was associated with induction of AT/AF, with a sensitivity of 73% and specificity of 67% (p <0.001). The presence of SHD was not associated with positive EPS findings but did predict the induction of AT/AF, with a sensitivity of 48% and specificity of 96% (p <0.001).
| Variable | Total (n = 172) | No Induction (n = 86) | Reentrant SVT (n = 52) | AT/AF (n = 34) | p Value |
|---|---|---|---|---|---|
| Age (years) | 46 ± 18 | 44 ± 17 | 38 ± 15 | 62 ± 14 | <0.001 ⁎ |
| Gender | 0.17 | ||||
| Male | 23% | 29% | 19% | 15% | |
| Female | 77% | 71% | 81% | 85% | |
| Duration (min) | |||||
| <5 | 44% | 66% | 8% | 41% | <0.001 † |
| >5 | 56% | 34% | 92% | 59% | |
| Sudden onset | 99% | 99% | 100% | 100% | — |
| Sudden termination | 65% | 47% | 96% | 65% | <0.001 † |
| Neck palpitations | 35% | 23% | 71% | 12% | <0.001 † |
| Structural heart disease | 12% | 4% | 4% | 47% | <0.001 ⁎ |
| Previous ablation | 6% | 8% | 2% | 6% | 0.38 |
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