Effects of Sotalol on His-Purkinje Conduction and Refractoriness in Humans

BACKGROUND: The effects of sotalol on refractoriness in human ventricular and atrial muscles have been well established, but the drug's effect on the electrical properties of the His-Purkinje system in humans is not known, especially whether sotalol's effect is due solely to its action on prolonging repolarization or in combination with its beta-blocking properties. We studied the electrophysiologic effects of intravenous sotalol and propranolol in patients undergoing electrophysiologic studies of cardiac arrhythmias. METHODS AND RESULTS: We studied 22 patients (19 men, 3 women; mean age, 60 +/- 6 years) who had coronary artery disease and assessable anterograde, retrograde, or both, His-Purkinje system function. Fifteen patients underwent electrophysiologic studies before and after intravenous sotalol (1.5 mg/kg), and 7 patients underwent electrophysiologic studies before and after intravenous propranolol (0.15 mg/kg). Both sotalol and propranolol had no significant effect on the H-V interval, but sotalol significantly increased ventricular refractoriness and His-Purkinje refractoriness, both in anterograde and retrograde conduction, whereas propranolol did not, Sotalol's effect on His-Purkinge refractoriness also caused atrioventricular block distal to the His bundle during atrial pacing at a moderately fast rate. Sotalol was not effective in preventing bundle branch re-entry tachycardia, nevertheless, it increased cycle length of bundle branch re-entry tachycardia by increasing refractoriness. CONCLUSIONS: Sotalol increased His-Purkinje refractoriness in humans but had no effect on His-Purkinje conduction. The drug must be used judiciously in patients with a diseased His-Purkinje system because it may cause atrioventricular block distal to His at fast heart rates. Sotalol had no effect on macrore-entry utilizing bundle branches.     

Evaluation of Patients with Bundle Branch Block and "Unexplained" Syncope: A Study Based on Comprehensive Electrophysiologic Testing and Ajmaline Stress

Thirty-five patients with bundle branch block (BBB) and unexplained syncope underwent electrophysiologic study (EPS) including programmed ventricular stimulation and ajmaline administration (1 mg/kg, IV) to induce infra-His block. A prolonged HV interval (greater than 55 ms) was present in 16 of the 35 patients. Ajmaline-induced HV block occurred in 12 patients (complete HV block in 10, and 2:1 HV block in two). Monomorphic ventricular tachycardia (VT) was inducible in nine (25.7%) and polymorphic VT in two patients (5.7%). Left ventricular ejection fraction (LVEF) was less than 40% in five patients (45.5%) with inducible VT. Two patients had an unexpected co-existence of inducible HV block and VT. The remaining 14 patients (40%) had no detectable abnormality. The incidence of inducible VT was higher (45% vs 13.3%), and the presence of negative studies was lower (30% vs 53.3%) in patients with structural heart disease (n = 20), when compared to those with no significant heart disease (n = 15) (differences not significant [NS]). During a mean follow-up period of 16.5 +/- 9.2 months, all the patients with inducible HV block have been asymptomatic after having received permanent pacemakers. Patients with inducible monomorphic VT (except one with poor left ventricular function who died suddenly) have also been asymptomatic on antiarrhythmic drugs. Of the remaining patients, seven with normal EPS, two with prolonged HV intervals but no inducible HV block (despite being given permanent pacemakers) and one patient with polymorphic VT on antiarrhythmic drugs continue to have recurrent syncope. Approximately 60% of patients with BBB and unexplained syncope have clinically significant electrophysiologic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Role of Electrophysiologic Studies in the Management of Patients with Unexplained Syncope

We evaluated the frequency and type of electrophysiologic abnormalities in an unselected population of consecutive patients with unexplained syncope. Fifty patients were entered in the study; all had 24-hour dynamic electrocardiographs (Holter) recordings and underwent complete electrophysiological studies. An abnormal electrophysiologic study was found in 74% of the patients. Sinus node abnormality was observed in 30%, abnormal AV node function in 14%, long HV in 10%, block distal to H during rapid atrial pacing in 6%, paroxysmal supraventricular tachycardia in 12%, ventricular tachycardialfibrillation in 8%, and hypersensitive carotid sinus syndrome in 24%. There was no correlation between Holter and electrophysiologic study findings except for the presence of paroxysmal sustained supraventricular tachycardia. Based on clinical, Holter monitoring, and electrophysiologic findings, 38% were treated by antiarrhythmic drugs, 40% received permanent pacemakers, and. 22% were not treated at all. During follow-up (23 ± 13 months), 9 patients (18%) experienced recurrent syncope or death.     

Hereditary Long QT Syndrome Associated with Cardiac Conduction System Disease

This report describes the cardiac conduction abnormalities, detected by invasive electrophysiological study, in two identical siblings with symptomatic congenital long QT syndrome. Both patients had evidence of intra-Hisian conduction delay in response to programmed atrial stimulation and pacing induced infranodal block was seen in one of the two patients. The response of the observed conduction delay to autonomic interventions is described. The observed electrophysiologic abnormalities are consistent with previously reported pathological findings and document the association of functional conduction system disease with congenital QT prolongation.     

Intravenous Adenosine Triphosphate Disodium: Its Efficacy and Electrophysiologic Effects on Patients with Paroxysmal Supraventricular Tachycardias

We studied the electrophysiologic effects of intravenous adenosine triphosphate disodium (ATP-2Na) on 17 patients with paroxysmal supraventricular tachycardias (PSVTs). One patient had sinus node (SN) reentry, two had intraatrial (IA) reentry, 7 patients had AV nodal reentry and seven had atrioventricular reentrant tachycardias (AVRTs) with accessory pathways (APs). ATP-2Na was injected during ventricular pacing in patients with AV nodal reentry and AVRTs with APs. A bolus injection of ATP-2Na terminated all the PSVTs within 50 s except for one case of IA reentry (case 2). The sites of block at termination were the atrium in SN reentry and IA reentry, between A and H (AH) or between H and A (HA) in AV nodal reentry, and AH block in all the PSVTs with APs. The sites of action on the patients with AV nodal reentry were both the antegrade and retrograde pathways, while the modes of block were Mobitz type I and type II, respectively. ATP-2Na during ventricular pacing in patients with AV nodal reentry produced Mobitz type II ventriculoatrial block (VAB) in four of seven cases. ATP-2Na during ventricular pacing in patients with AVRTs with APs produced changes of atrial activation sequences in two patients, induction of PSVT in two patients, and Mobitz type II VA block in three patients. The former two phenomena suggested a retrograde AV nodal block and raised the possibility of a simple test for retrograde atrial fusion during ventricular pacing in patients with WPW syndrome. Chest discomfort of short duration was most commonly noted after ATP-2Na administration.     

急性下壁梗死发生房室传导阻滞的时间与预后关系

目的观察急性下壁心梗时，心电图检查和希氏束检查房室传导阻滞发生的时间和对预后的影响。方法患者24例，分为：(1)单纯下壁组；(2)下壁后壁或右室组；(3)下壁合并前、侧壁组。均行心电图及希氏束电图检查。结果三组房室传导阻滞发生率相似，多数房室传导阻滞在急性心肌梗死起病后12h内出现(81．8％)。阿托品和异丙肾上腺素治疗14例，AVB都有不同程度的改善，预后良好。结论急性下壁与合并其他部位心梗的AVB发病率相似，大部分出现时间为12h以内，多数AVB未用起搏治疗获得良好预后。     

Transesophageal Electrophysiologic Study to Determine the Inducibility After Successful Ablation of Supraventricular Tachycardia in Children

Background: Radiofrequency ablation has become first-line therapy for supraventricular tachycardia in all age groups, but there has been a concern regarding the long-term effectiveness of the procedure in children. This study aimed to determine the inducibility after successful ablation of supraventricular tachycardia in children; assessment was performed using a transesophageal electrophysiologic study.
Results: A total of 63 patients who had been treated successfully for supraventricular tachycardia with radiofrequency ablation were included in the study. A transesophageal electrophysiologic study was performed 2 months after radiofrequency ablation. Tachycardia was induced in nine of 34 symptomatic and five of 29 asymptomatic patients by a transesophageal electrophysiologic study. Ten patients had recurrence of the same type of supraventricular tachycardia seen previously, and two had a new type of arrhythmia during a transesophageal electrophysiologic study. Tachycardia inducibility rate was 16% in all patients, 22.8% in patients with atrioventricular reentrant tachycardia, and 8% in patients with atrioventricular nodal reentrant tachycardia.
Conclusion: Radiofrequency ablation is a safe and effective method to manage children with supraventricular tachycardia, but patients must be observed for recurrence and new arrhythmias. Sustained tachycardia may also be induced in asymptomatic patients. A transesophageal electrophysiologic study is effective and safe for follow-up of radiofrequency ablation for assessment, diagnosis, and treatment of patients.     

Ventricular arrhythmias in the long-term postoperative stage of tetralogy of Fallot

Arrhythmias were studied in 40 patients in the long-term stage after corrective surgery of tetralogy of Fallot. Holter monitoring showed ventricular dysrhythmias in 30 cases. Lown's grade 3 was found in 9, 4a in 5, and 4b in 5 cases. Five patients had ventricular arrhythmias of Lown's 3 or higher grade both in the treadmill stress test and in the Holter ECG. Twenty patients with ventricular arrhythmias of Lown's grade 3 or higher ones were associated with severer hemodynamic, and clinical abnormalities than those with ventricular arrhythmias of lower grade. Supraventricular arrhythmias or bifascicular block are also found in the group with complex ventricular arrhythmias but no cardiac arrest from sinus standstill or complete heart block was observed. Both the age at operation and the years after the corrective surgery were related to the incidence of ventricular arrhythmias of higher grades. Two patients with nonsustained ventricular tachycardia died suddenly during 2 years' follow up period. Tachyarrhythmia seems a major cause of sudden death after repair of tetralogy of Fallot. An electrophysiologic study may be reasonably indicated to prevent sudden cardiac death.     

Clinical electrophysiologic effects of a single high oral dose of amiodarone

Summary— Several recent reports have described the antiarrhythmic effects of a single high oral dose of amiodarone but clinical electrophysiologic effects have not been reported. The present study was performed to assess electrophysiologic effects in 12 patients. After baseline electrophysiologic studies (EPS) patients were administered a single oral dose of 30 mg/kg of amiodarone. EPS was repeated 7.5 ± 0.5 hours later. Plasma levels of amiodarone and its metabolite desethylamiodarone were determined at the time of the second EPS. Holter monitoring was performed for 24 hours after amiodarone administration. Amiodarone significantly increased the following parameters: corrected QT interval (+4.5%), functional refractory period of the right atrium (+7%); AH interval (+12.3%), effective refractory period of the atrioventricular node (+18.5%), and cycle length of Wenckebach block (+8.4%). These effects were not correlated with plasma levels of amiodarone and desethylamiodarone. Holter monitoring detected no significant bradycardia or arrhythmia. These findings indicate that the effects of a single high oral dose of amiodarone are the same as those known to be induced by acute intravenous administration.     

Phenytoin in the Treatment of Inducible Ventricular Tachycardia: Results of Electrophysiologic Testing and Long-Term FoUow-Up

Phenytoin treatment of inducible ventricular tachyarrhythmias was assessed by serial electrophysiologic studies (EPS) in 64 patients with spontaneous ventricular tachycardia, cardiac arrest, or symptoms compatible with a ventricular tachyarrhythmia. Coronary artery disease was the primary cardiac disease in 75% of the patients. All subjects had either inducible ventricular tachycardia (greater than or equal to 10 repetitive beats) or ventricular fibrillation at electrophysiologic study. Phenytoin was administered intravenously in 38 studies and orally in 31 studies. The mean serum phenytoin level was 19.5 +/- 4.7 mcg/ml. Only seven patients (11%) had a negative electrophysiologic study (less than or equal to 10 repetitive beats) after the administration of phenytoin and were classified as phenytoin responders (group I). The remaining 54 patients (89%) were classified as nonresponders (group II). For the nonresponders, phenytoin increased the cycle length of identical monomorphic ventricular tachycardias from a mean of 31 ms to a mean of 327 ms (p less than 0.001). For the four patients tested receiving both intravenous and oral phenytoin, the intravenous response always predicted the oral response. For the seven patients in whom electrophysiologic study indicated phenytoin efficacy, two are alive and arrhythmia-event free, two had sudden death when the regimen was changed (one case, quinidine added; one case, subtherapeutic serum level), and three died from nonarrhythmic causes. For the 10 patients treated empirically with phenytoin, either alone (seven patients) or in combination with another antiarrhythmic agent (three patients), four died secondary to an arrhythmic event.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ventricular Pacing in Children

Ventricular pacing in children. Ventricular pacing was performed in forty-one children ranging from one day to twenty years of age (median age = 10). Weight of the recipient at implant ranged from 2 kg. to 86 kg. Indications included presyncope, syncope, dyspnea on exertion, congestive heart failure, postoperative infra-Hisian heart block, and inadequate cardiac rate during pharmacotherapy. Four patients died during follow-up, but no deaths were attributable to pacemaker management. In contrast, 66% of the patients required more than one pacemaker related-operative procedure, and 43% of leads implanted failed by 48 hours. Indications for permanent cardiac pacing in this population at this time are symptomatic congenital AV block, symptomatic sinus node disease, and AV block in the postoperative period. Technological developments which might reduce complications seen in this population and electrophysiologic techniques which may better define indications for pacing in children are also reviewed.     

Electrophysiologic Findings in Carotid Sinus Massage

Thirty patients with carotid sinus syndrome were electrophysiologically studied. In 14 patients carotid sinus massage was performed during atrial and ventricular stimulation, and the conduction times were measured. The AH-time was prolonged by more than 120ms in 6 patients(20%); the HV-time was prolonged in 6 patients by more than 55 ms (20%); 5 patients had bundle branch block (16.7%); The sinus node recovery time was prolonged in 7 out of 27 patients (26%). Ten patients (33%) did not have additional electrophysiologic abnormalities. There was a predominance of carotid sinus syndrome on the right side. During carotid sinus massage there was a significant increase of the AH-time, but there were no significant changes of the HV-time or the width of the QRS-complexes. Twenty-one patients developed an atrial asystole and 9 patients an atrial bradycardia and an additional AV-block. There was a longer AH-time and a longer prolongation of the AH-time in the patients who developed an AV-block. Twelve out of 14 patients (85.7%) developed an AV-block during carotid sinus massage and atrial pacing. During ventricular pacing 5 of 14 patients (35.7%) revealed a complete retrograde block before carotid sinus massage and 5 of the remaining 9 patients developed a total retrograde block during carotid sinus massage. Consequently, in 71.4% of the patients with carotid sinus syndrome complete retrograde conduction block and atrial asystole can be expected during attacks of ventricular asystole and simultaneous ventricular pacing. In conclusion, there is a high incidence of additional disturbances of the sinus node function and AV-conduction in patients with carotid sinus syndrome. AAI pacemakers are contraindicateddue to the common development of additional A V-block during carotid sinus massage. Physiologic pacing might contribute to better hemodynamics, particularly in patients with the mixed type of carotid sinus syndrome.     

Analysis of Atrioventricular Nodal Reentrant Tachycardia with Variable Ventriculoatrial Block: Characteristics of the Upper Common Pathway

Background: The precise nature of the upper turnaround part of atrioventricular nodal reentrant tachycardia (AVNRT) is not entirely understood.
Methods: In nine patients with AVNRT accompanied by variable ventriculoatrial (VA) conduction block, we examined the electrophysiologic characteristics of its upper common pathway.
Results: Tachycardia was induced by atrial burst and/or extrastimulus followed by atrial-His jump, and the earliest atrial electrogram was observed at the His bundle site in all patients. Twelve incidents of VA block: Wenckebach VA block (n = 7), 2:1 VA block (n = 4), and intermittent (n = 1) were observed. In two of seven Wenckebach VA block, the retrograde earliest atrial activation site shifted from the His bundle site to coronary sinus ostium just before VA block. Prolongation of His-His interval occurred during VA block in 11 of 12 incidents. After isoproterenol administration, 1:1 VA conduction resumed in all patients. Catheter ablation at the right inferoparaseptum eliminated antegrade slow pathway conduction and rendered AVNRT noninducible in all patients.
Conclusion: Selective elimination of the slow pathway conduction at the inferoparaseptal right atrium may suggest that the subatrial tissue linking the retrograde fast and antegrade slow pathways forms the upper common pathway in AVNRT with VA block.     

Identification of the conduction system in corrected transposition and common ventricle at operation.

The high incidence of surgically induced heart block in patients with levotransposition of the great arteries is now better understood because of recent anatomic demonstration of an unusual anterior location of the atrioventricular specialized conducting tissue. The two cases reported herein proved electrophysiologic confirmation of this previously described anatomy. The specialized conducting bundle was easily and consistently identified and then avoided in successful surgical correction in one patient with common ventricle, type A-3, and in another with corrected transposition, large ventricular septal defect, and valvular pulmonary stenosis. Electrophysiologic identification of the atrioventricular conduction tissue at the time of operation may decrease the incidence of heart block and offers additional optimism for successful correction of levotransposition complexes.     

Mechanism of atrial flutter occurring late after orthotopic heart transplantation with atrio-atrial anastomosis

OBJECTIVE: We sought to better define the electrophysiologic mechanism of atrial flutter in patients after heart transplantation. BACKGROUND: Atrial flutter is a recognized problem in the post-cardiac transplant population. The electrophysiologic basis of atrial flutter in this patient population is not completely understood. METHODS: Six patients with cardiac allografts and symptoms related to recurrent atrial flutter underwent diagnostic electrophysiologic study with electroanatomic mapping and radiofrequency catheter ablation. Comparison was made with a control non-transplant population of 11 patients with typical counterclockwise right atrial flutter. RESULTS: In each case, mapping showed typical counterclockwise activation of the donor-derived portion of the right atrium, with concealed entrainment shown upon pacing in the cavotricuspid isthmus (CTI). The anastomotic suture line of the atrio-atrial anastomosis formed the posterior barrier of the reentrant circuit. Ablation of the electrically active, donor-derived portion of the CTI was sufficient to terminate atrial flutter and render it noninducible. Comparison with the control population showed that the electrically active portion of the CTI was significantly shorter in patients with transplant-associated flutter and that ablation was accomplished with the same or fewer radiofrequency lesions. CONCLUSIONS: Atrial flutter in cardiac transplant recipients is a form of typical counterclockwise, isthmus-dependent flutter in which the atrio-atrial anastomotic suture line forms the posterior barrier of the reentrant circuit. Ablation in the donor-derived portion of the CTI is sufficient to create bidirectional conduction block and eliminate this arrhythmia. Ablation or surgical division of the donor CTI at the time of transplantation could prevent this arrhythmia.     

Evoked potentials investigation of visual dysfunction after methanol poisoning

OBJECTIVE: To present results of electrophysiologic investigations of the visual toxicity observed during the early stage of methanol poisoning. DESIGN: Retrospective, clinical study. SETTING: A 7-bed intensive care unit in a university hospital. PATIENTS: Nineteen patients admitted with a diagnosis of acute methanol poisoning. INTERVENTIONS: Visual evoked potentials were obtained within the first 48 hrs after admission; a clinical follow-up examination was performed in 11 patients, and 12 patients were followed up by visual evoked potentials beyond the same delay. Correlations between the occurrence of an optic neuropathy and clinical, biological, and electrophysiological data were studied. MEASUREMENTS AND MAIN RESULTS: A significant correlation was found between arterial pH and blood formate concentration (r2 = 0.58, p = .003), between blood formate and bicarbonate concentrations (r2 = 0.36, p = .02), and between delay from ingestion and blood formate concentration (r2 = 0.44, p = .017). Clinical outcome was correlated not only with the bicarbonate (p = .007), formate (p = .018), and methanol (p = .03) concentrations and arterial pH (p = .004) but also with a well-defined electrophysiologic pattern during the acute stage. An index of global cortical functioning > or =3 was associated with death, whereas a global cortical functioning index < or =2 was associated with survival (p = .0058). Moreover, a statistically significant difference in long-term visual impairment was found between the subgroup with abnormal wave III morphology or a global cortical functioning index of 1-2 and the subgroup with normal wave III morphology and a global cortical functioning index <1 (p = .015). Results of the electrophysiologic studies were expressed as retinal dysfunction and optic nerve injury. Five patients had normal findings on electrophysiologic examination. Ten patients had early signs of retinal dysfunction that were fully reversed in the eight patients who were followed. Ten patients had persistent electrophysiologic signs of optic neuropathy. CONCLUSIONS: Although reversible retinal dysfunction is evident in the early stage of human methanol poisoning, its absence does not preclude development of optic neuropathy. The occurrence of optic neuropathy and early electrophysiologic data are correlated.     

The Incidence of Retrograde Conduction in Children

With the increasing use of "physiological" pacemakers in the pediatric age group, retrograde conduction in children has become of clinical importance. Pacemakers which sense atrial depolarization may sense "retrograde" P waves. The pacemaker may then act as the antegrade limb of a reciprocating tachycardia circuit, while the patient's own conduction system acts as the retrograde limb. We reviewed the data of 127 patients who underwent antegrade and retrograde electrophysiologic study at Texas Children's Hospital, with regard to retrograde conduction. Sixty percent of the patients had ventriculo-atrial conduction through the A-V node; the incidence of retrograde conduction in patients after surgical correction of a tetralogy of Fallot was significantly lower (33%). None of the patients with third-degree A-V block had retrograde conduction. The mean retrograde conduction time was 162 ms (range 70-335 ms) at the slowest pacing rate and 257 ms (range 80-475 ms) at the fastest pacing rate. This high incidence of retrograde conduction and the variability of conduction times must be taken into account when "physiological" pacemakers are to be implanted.     

Predictive value of early electrophysiologic testing in determining long-term outcome with amiodarone treatment in patients with sustained ventricular tachycardia

This prospective study sought to determine whether programmed ventricular stimulation before hospital dismissal in patients who had received a loading dose of amiodarone would identify those at risk for recurrent ventricular arrhythmias. Between January 1985 and January 1989, 64 patients (55 men and 9 women; mean age, 64 years) with a history of sustained ventricular tachycardia (VT) or ventricular fibrillation were referred to our institution for electrophysiologic testing. Of these patients, 52 had coronary artery disease, 11 had dilated cardiomyopathy, and 1 had hypertrophic cardiomyopathy. Of the 64 patients, 47 had baseline tests while no drugs were administered and repeated electrophysiologic testing after 10 days of amiodarone loading (1.2 g/day). The other 17 patients had no baseline study because of instability of their arrhythmias but underwent electrophysiologic testing after amiodarone loading. Follow-up ranged from 7 to 1,536 days (mean, 652 days). During the follow-up period, recurrent arrhythmias were detected in 22 patients. Of the 64 patients, 14 had suppression of VT. Of 43 patients in whom the cycle lengths of VT were determined both at baseline and after amiodarone therapy, 20 had an increase of 100 ms or more, and 23 had no substantial change. The mean ejection fraction was 31%. Of a total of 16 deaths in the series, 8 were sudden. Suppression of VT during amiodarone therapy suggested a lower rate of fatal and nonfatal recurrent arrhythmias, but the difference was not statistically significant. An increase in the cycle length of VT did not predict an improved outcome. The age of the patient and the presence of a left ventricular aneurysm were slightly predictive of mortality.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cough Syncope Presenting as Mobitz Type II Atrioventricular Block—An Electrophysiologic Correlation

A 34-year-old man with a history of cough syncope exhibited Mobitz type II atrioventricular block with a narrow QRS complex on Holter monitoring. The baseline electrophysiologic study was normal. No significant atrioventricular block could be induced with carotid sinus massage, neck suction, or intravenous propranolol. However, coughing reproduced Mobitz type II atrioventricular block, which was found to be above the His bundle on the His bundle electrogram. A review of the mechanism of cough syncope is also presented.     

Paroxysmal Complete Heart Block due to Bradycardia-dependent, "Phase 4" Fascicular Block in a Patient with Sinus Node Dysfunction and Bifascicular Block

A 34-year-old man with ankylosing spondylitis was admitted to the hospital because of syncopal attacks and heart block. Standard ECG, telemetry and an invasive electrophysiologic examination demonstrated right bundle branch block with left anterior fascicular block, sinus node dysfunction with spontaneous slowing of the sinus rate and, as a result, complete infrahisian atrioventricular block in the remaining fascicle at sinus rates below 57 beats per minute. Infrequent supraventricular extrasystoles and abruptly terminated atrial pacing led to the same result. Atrioventricular conduction resumed after three-to-four blocked atrial impulses with successively increasing rate. Pacemaker treatment provided complete symptomatic relief.