Results of the modified Fontan operation for congenital heart lesions in patients without preoperative sinus rhythm

Preoperative sinus rhythm has been a criterion for the Fontan operation. However, of 297 patients who underwent the Fontan operation between October 1973 and February 1984, 12 (4%) did not have sinus rhythm. The age at operation ranged from 4 to 34 years (median 15). Nine patients had a univentricular heart, two had tricuspid atresia and one had a complex form of transposition. In all 12 patients, 3 to 8 of the 10 proposed criteria for operability were not met. An atrioventricular (AV) conduction abnormality was present in seven patients, six with complete AV block and one with AV dissociation. The patient with complex transposition had complete AV block and atrial fibrillation. Postoperatively, all seven patients continued to have an AV conduction abnormality, and those with complete AV block had a permanent pacemaker implanted. Six of the 12 study patients had atrial flutter or fibrillation refractory to antiarrhythmic medications. Postoperatively, four of the six patients had sinus rhythm. Two of the six patients had complete AV block (including the patient with complex transposition) and both had a permanent pacemaker implanted. Three of the 12 patients died (mortality rate 25%). The nine survivors were followed up for 6 to 55 months; no late deaths occurred. All had marked clinical improvement. This study demonstrates that 1) complete AV block is not a contraindication to the Fontan operation, 2) some patients may not require AV synchrony postoperatively for survival, and 3) postoperative atrial flutter or fibrillation may cease or be easier to control after the Fontan operation.     

VVI起搏器工作停止后心房扩大和房室瓣反流的逆转

为探讨VVI起搏器工作停止后的心房结构和房室瓣反流情况，我们观察13例安植VVI起搏器后因多种原因起搏器工作停止又恢复正常窦性心律的心肌梗塞患者（A组）。对照组（B组）为年龄、病因、起搏器安植时程基本与A组匹配的心肌梗塞患者15例。用二维超声心动图测定左心房上下径，左右心房前后径，中侧径和容量。彩色多普勒异常反流束面积法测房室瓣返流面积，多普勒超声测主动脉瓣下速度时间积分（VTI）。结果A组起搏器停止工作半年后心房内径和房室瓣反流程度明显减小，VTI明显增大，B组在起搏器继续工作半年后，心房内径和返流面积略增大，VTI略减小，提示VVI右心室起搏可对心房结构和瓣膜产生不利作用。而起搏器工作停止后恢复窦性心律一段时间心房扩大和房室瓣反流可逆转，并可改善心输出量。     

Cardiac rhythm in atrial isomerism

Standard electrocardiograms from 126 consecutive patients with atrial isomerism were reviewed. Of 67 patients with left isomerism, 49 had sinus rhythm, 8 nodal rhythm and 10 atrioventricular (AV) block. Fifty-eight of 59 patients with right isomerism had sinus rhythm. Complete AV block was significantly more frequent in association with AV septal defect in left isomerism (5 of 45 patients) than in right isomerism (0 of 47 patients, p = 0.049). The P-wave axis was superior in 49% of patients with left isomerism but did not correlate with abnormalities of systemic or pulmonary venous connection. A significant shift of P-wave axis (more than 90 degrees) was seen on a subsequent electrocardiogram in 14 of 44 patients (32%) with left isomerism and 2 of 16 (13%) with right isomerism. Ambulatory electrocardiographic monitoring in 17 patients (14 with left isomerism) showed that only 4 had sinus rhythm throughout 24 hours. Only 1 patient with complete AV block received a permanent pacemaker. Despite the high incidence of electrocardiographic abnormalities, significant arrhythmias appear to be rare. The arrhythmias apparently do not influence the natural history of this condition or affect the outcome of palliative or corrective surgery. The prognosis is determined mainly or solely by the associated anatomic abnormalities.     

Comparison of first- and second-generation leadless pacemakers in patients with sinus rhythm and complete atrioventricular block

Introduction

The efficacy and safety of leadless cardiac pacemakers (LPMs) as an alternative to conventional transvenous cardiac pacing have been largely reported. The first generation of the Micra^TM transcatheter pacing system (VR; Medtronic) was able to provide single-chamber VVI(R) pacing mode only, with a potential risk of pacemaker syndrome in sinus rhythm patients. A second-generation system (AV) now provides atrioventricular synchrony through atrial mechanical (Am) sensing capability (VDD mode).

Objective

We sought to compare VR and AV systems in sinus rhythm patients with chronic ventricular pacing (Vp) for complete atrioventricular block.

Methods

All consecutive patients implanted with an LPM in our department for complete atrioventricular block were retrospectively screened. Patients with atrial fibrillation, sinus dysfunction, or Vp burden <20% at 1 month postimplantation were excluded. Patients were systematically followed with a visit at 1 month, and then at least once a year.

Results

A total of 93 patients—45 VR (2015–2020) and 48 AV (2020–2021)—were included. VR and AV patients had similar baseline characteristics, except for VR patients being older (80 ± 8 vs. 77 ± 9 years, p = 0.049). The mean Vp burden was 77% in the VR and 82% in the AV group (p = 0.38). In AV patients, the median AV synchronous beats rate was 78%, with 65% having a >66% rate. An E/A ratio <1.2 as measured on echocardiography was the only independent predictor of accurate atrial mechanical tracking (p = 0.01). One-year survival rate was similar in both groups. Five patients in the VR and 0 in the AV group eventually developed pacemaker syndrome within 1 year post-implantation (p = 0.02).

Conclusion

In sinus rhythm patients with chronic Vp for complete atrioventricular block implanted with an LPM, the atrial mechanical sensing algorithm allowed significant atrioventricular synchrony in most patients and was associated with no occurrence of—otherwise rare—pacemaker syndrome.     

选择性消融窦房结与房室结周围神经治疗阵发性心动过缓

目的探讨选择性消融窦房结与房室结周围神经,治疗缓慢性心律失常的方法与初步效果。方法选择症状严重,拟行起搏器治疗的阵发性心动过缓者,在X线与64排螺旋CT心脏解剖影像指导下,以手工或磁导航遥控操作,标测窦性心律心房激动顺序,围绕并避开心房最早激动位点和His束区域,记录心内电图神经组织电位,温控射频消融,观察消融反应,随访治疗效果。结果13例患者,男9例,女4例,年龄36.46±9.51(14～51)岁。1例有器质性心脏病,高度房室传导阻滞7例,病窦综合征4例,病窦综合征合并高度房室传导阻滞1例,窦性心动过缓1例,6例黑矇或晕厥。在窦房结和房室结周围均记录到神经组织电位,放电10～15s神经组织电位消失。消融中先出现迷走激惹效应,之后窦房结和房室结功能改善。12例术中心动过缓消失,1例失败。随访13±5.89(3～20)个月,2例复发,余症状消失,无并发症。结论选择性消融窦房结与房室结周围神经治疗迷走介导的缓慢心律失常,可行、安全、有效。     

Complete interatrial block in a left-atrial dependent atrioventricular node

Introduction : A middle-age woman underwent an electrophysiologic study due to recurrent atypical atrial flutter. Methods and Result : Radiofrequency ablation of cavotricuspid isthmus and anterior mitral line was performed. During energy delivery on the anterior left atrial wall, interatrial dissociation and complete block of the sinus impulse to the atrioventricular (AV) node was observed. AV node activation became dependent on a subsidiary left atrial rhythm. Conclusion : Anatomical location of intra and inter-atrial connections must be taken into account when performing extensive ablation procedures, specially in cases with prior cardiac surgeries.     

Studies on second-degree atrioventricular block during atrial fibrillation]

The degree of AV block after cardioversion in 80 episodes of atrial fibrillation in 61 patients who suffered from atrial fibrillation associated with second-degree AV block was observed. Only in 34 of the 80 episodes the electrocardiogram showed first-degree AV block. The remaining 46 had normal AV conduction. No second-degree block was found. It demonstrates that second-degree AV block during atrial fibrillation is not identical with that in sinus rhythm.     

Subcostal M-mode echocardiography of the right atrial wall in the diagnosis of cardiac arrhythmias

The M-mode echocardiogram of the right atrial (RA) wall can be easily recorded in each person from the subcostal location. In a normal RA wall motion pattern, atrial contraction is represented by a markedly prominent posterior motion. The presence or absence of atrial contractions in the subcostal RA wall echocardiogram, their amplitude, and their timing may help in the diagnosis of cardiac arrhythmias with the simultaneously recorded non-diagnostic electrocardiogram. Flat and hidden P waves can be accurately identified throughout the cardiac cycle. It is possible to distinguish between atrial, ventricular, and nodal premature beats and to recognize atrial fibrillation, atrial flutter, paroxysmal atrial tachycardia, paroxysmal atrial tachycardia with block, atrioventricular (AV) nodal tachycardia, and supraventricular tachycardias with aberrant ventricular conduction. The diagnosis of wandering pacemaker, AV dissociation, sinoatrial block, and AV block is facilitated. On the basis of study of 60 patients with various rhythm disturbances, it was concluded that analysis of the subcostal RA wall echocardiogram is a new, helpful noninvasive approach in the diagnosis of cardiac arrhythmias.     

Development of sinus node disease in patients with AV block: implications for single lead VDD pacing

OBJECTIVE: To investigate the incidence of sinus node disease after pacemaker implantation for exclusive atrioventricular (AV) block. DESIGN: 441 patients were followed after VDD (n = 219) or DDD pacemaker (n = 222) implantation for AV block over a mean period of 37 months. Sinus node disease and atrial arrhythmias had been excluded by Holter monitoring and treadmill exercise preoperatively in 286 patients (group A). In 155 patients with complete AV block, a sinus rate above 70 beats/min was required for inclusion in the study (group B). Holter monitoring and treadmill exercise were performed two weeks, three months, and every six months after implantation. Sinus bradycardia below 40 beats/min, sinoatrial block, sinus arrest, or subnormal increase of heart rate during treadmill exercise were defined as sinus node dysfunction. RESULTS: Cumulative incidence of sinus node disease was 0.65% per year without differences between groups. Clinical indicators of sinus node dysfunction were sinus bradycardia below 40 beats/min in six patients (1.4%), intermittent sinoatrial block in two (0.5%), and chronotropic incompetence in five patients (1.1%). Only one of these patients (0.2%) was symptomatic. Cumulative incidence of atrial fibrillation was 2.0% per year, independent of the method used for the assessment of sinus node function and of the implanted device. CONCLUSIONS: In patients undergoing pacemaker implantation for isolated AV block, sinus node syndrome rarely occurs during follow up. Thus single lead VDD pacing can safely be performed in these patients.     

Selective experimental chelation of calcium in the AV node and His bundle

There are P cells in the human and canine AV (atrioventricular) node which are virtually devoid of gap junctions. All other components of myocardial cellular connections are calcium-dependent except the gap junction. Direct perfusion of disodium EDTA through the AV node artery of 16 anaesthetized dogs produced three immediate effects: complete AV block, a rapid irregular atrial rhythm and a separate rapid irregular ventricular rhythm. The atrial arrhythmia was short in duration and sinus rhythm resumed, initially with complete AV and VA block; both waned until normal AV conduction returned in each dog. In 3 of the 16 dogs there was transient complete AV block during which two independent His potentials were separately associated with the atrial and ventricular complexes. When conducted sinus rhythm resumed, there was initially A-H prolongation (but not H-V). Atropine, propranolol and reserpine had no influence on any electrophysiologic effect of EDTA. Both tachycardias probably originate in P cells of the AV node, the irregularity being attributable to varying enhancement of automaticity plus functional disaggregation of P cells. AV block is attributed to failure of conduction between disaggregated P cells, which in turn must be an obligatory pathway for normal AV conduction, because of their anatomic interposition. The findings further suggest that the AV nodal P cells are the site of the normal 40 ms delay in AV conduction, and that they may be the site of origin of the His potential.     

Ventricular tachycardia masquerading as supraventricular tachycardia: A wolf in sheep''s clothing

It is generally assumed that if a wide QRS complex tachycardia has the same morphology on the 12-lead electrocardiogram as during sinus rhythm, the tachycardia is supraventricular. The author presents unique electrocardiographic data on four patients with QRS complex morphologies that are nearly identical during ventricular tachycardia and during sinus rhythm. The QRS complex duration during sinus rhythm was 140-180 msec and was the same as that of the tachycardia. The QRS complex morphology on the electrocardiogram was a right bundle branch block, left axis in three patients and right bundle branch block, normal axis in one patient. The mean ventricular tachycardia cycle length was 345 msec. The diagnosis of ventricular tachycardia was established by electrophysiologic testing in two patients and by atrial electrograms demonstrating AV dissociation in two patients. Thus, if the 12-lead electrocardiogram morphology of a wide QRS complex tachycardia is similar to that during sinus rhythm, it does not necessarily imply that the tachycardia is supraventricular. Ventricular tachycardia can occur with the same QRS complex morphology as occurs during sinus rhythm.     

Reversibility of hypotension and shock by atrial or atrioventricular sequential pacing in patients with right ventricular infarction

Hypotension and shock associated with heart block and other forms of atrioventricular (AV) dissociation frequently accompany right ventricular infarction (RVI). Such patients do not invariably improve with ventricular pacing. We evaluated the relative effects of AV dissociated rhythms (ventricular pacing or nodal rhythm) and AV synchronous rhythms (atrial pacing, AV sequential pacing, or return to normal sinus rhythm) in seven patients with RVI complicated by AV dissociation, who had hypotension or shock. Hemodynamic monitoring demonstrated the characteristic features of RVI in all patients. Restoration of AV synchrony resulted in a highly significant (p ≤ 0.001) increase in systolic blood pressure (88.0 ± 16.5 mm Hg to 133.0 ± 21.8 mm Hg), cardiac output (3.8 ± 0.9 L/min to 5.7 ± 0.9 L/min), and stroke volume (40.5 ± 6.9 cc to 61.0 ± 10.0 cc). We conclude that restoration of normal AV synchrony has a marked effect on stroke volume in this setting and that atrial or AV pacing can reverse hypotension and shock in RVI complicated by AV dissociation.     

AAI pacing mode: When is it indicated and how should it be achieved?

AAI pacing offers better hemodynamic characterstics than dual-chamber pacing and is the optimal mode for patents with sick sinus syndrome without AV conduction disorders. AAI pacing may be achieved by single-chamber atrial, by programming a dual-chamber pacemaker to the AAI mode, or by programming a dual-chamber pacemaker to DDD mode with a long AV delay. The annual incidence of AV block development in patients with sick sinus syndrome is low, probably 1-5%, but there is no method of detecting patients immune to future development of AV block. Chronotropic is often present in patients with sick sinus but the value of additional rate response is not yet established. Our recommendations for the choice of the method of pacing are discussed.     

Natural history of sinus node disease treated with atrial pacing in 213 patients: implications for selection of stimulation mode.

OBJECTIVES. This study was designed to analyze the incidence and determinants of complications and long-term survival in sinus node disease treated with atrial pacing. BACKGROUND. Knowledge of the natural history of sinus node disease treated with different pacing modes is imperfect, and controversy exists regarding the optimal pacemaker therapy. METHODS. A consecutive series of 213 patients with sinus node disease initially treated with atrial pacing was studied for a median follow-up period of 60 months. The end points studied were permanent atrial fibrillation, high grade atrioventricular (AV) block, P wave undersensing, pacing mode change, reoperation and death. Several prognostic factors were evaluated statistically and the survival rate was compared with that of a matched general population. RESULTS. The incidence rate of permanent atrial fibrillation during follow-up was 7% (1.4%/year). The risk of this arrhythmia increased substantially with age greater than or equal to 70 years at pacemaker implantation. Only 2 of the 15 patients who developed permanent atrial fibrillation required ventricular pacing. High grade AV block occurred in 8.5% (1.8%/year) and its incidence was much greater in patients with complete bundle branch block or bifascicular block (35%) than in patients without such conduction disturbances (6%). A change to ventricular or dual-chamber stimulation was necessary in 14% of all patients, primarily because of early lead dislodgment or high grade AV block. Surgical intervention with maintenance of atrial pacing was required in 7% of patients. The survival rates of 97% at 1 year, 89% at 5 years and 72% at 10 years did not differ significantly from those of a matched general population. CONCLUSIONS. In sinus node disease, atrial pacing can be successfully applied during long-term follow-up. Patients with complete bundle branch or bifascicular block in addition to sinus node disease should initially receive a dual-chamber pacemaker, but routine application of dual-chamber stimulation does not appear to be warranted.     

Orthostatic and exercise-induced advanced nodal atrioventricular block.

A 69-year-old woman was referred for asthenia and dizziness when walking in the last two months. No clinical abnormalities were found, and sinus rhythm was present when lying down. On orthostatism and walking, advanced AV block developed. Atropine and isoproterenol ameliorated the AV conduction abnormality, suggesting a nodal block. The patient remained asymptomatic after pacemaker implantation.     

Partial atrial electrical standstill: report of three cases and review of clinical and electrophysiological features

Three patients with partial atrial electrical standstill aredescribed. Serial electrocardiograms and electrophysiologicalstudies were performed after a clinical follow-up ranging fromfour to ten years. Two patients had valvular heart disease andone patient had a sick sinus syndrome. Case I presented, onthe admission electrocardiogram, an atrioventricular (AV) junctionalrhythm whereas paroxysmal atrial fibrillation had been previouslydocumented. Case 2, who had had long-standing atrial fibrillationpresented on admission absence of fibrillation waves and simulatedAV junctional rhythm. In case 3 with known sino-atrial block,electrocardiographic monitoring showed sinus rhythm with episodesof slow AV junctional rhythm. Atrial endocardial mapping showedan electrically silent area ranging from a small region nearthe sinus node (case 1) to the entire right atrium except fora discrete area near the tricuspid valve (case 2). AV dissociationbetween the electrical activity recorded in the remaining atriumand the junctional escape rhythm was present in every patient. The clinical and electrophysiological features of this entityare reviewed. This study emphasizes the limitations of the electrocardiogramin making the diagnosis of atrial standstill. However, partialatrial electrical standstill should be suspected in patientswith AV junctional rhythm or atrial fibrillation with fine waves.This diagnosis may have important therapeutic implications.     

Transvenous catheter ablation of the His bundle in ventricular tachycardia

The usefulness of transvenous catheter ablation of the His bundle in three patients with recurrent ventricular tachycardia (VT), in which the initiating mechanism was recognized during a rapid atrial rhythm, is reported. Tachycardia was refractory to conventional treatment and required transthoracic direct-current shocks in all patients. In patient No. 1 double tachycardia (atrial flutter and VT) was documented and VT was easily induced by rapid atrial pacing. In patients Nos. 2 and 3 initiation of VT during junctional reciprocating and atrial tachycardia, respectively, was observed. Interruption of the His bundle was performed by means of fulguration. Stable atrioventricular (AV) block was observed in patient No. 1 after the ablative procedure; patient No. 2 showed anterograde conduction over a posterior septal accessory pathway with no evidence of conduction over the normal conduction system in both the anterograde and retrograde directions. In patient No. 3, transient AV block was observed; AV conduction resumed 2 days later and the cardiac rhythm showed persistent ectopic atrial tachycardia with second-degree AV block. Patients Nos. 1 and 2 underwent pacemaker implantation, but patient No. 2 was not pacemaker dependent. After the procedure, VT no longer occurred in any of the patients (follow-up: 2 years, 5 months, and 6 months).     

Ventricular echo beats during ventricular pacing or junctional bradycardia: studies in the normal canine heart

In 15 adult dogs ventricular echoes were elicited during sinus rhythm by incremental ventricular pacing and during atrioventricular (AV) junctional rhythm by depressing simultaneously AV junctional automaticity and retrograde AV nodal conduction. Concomitant slowing of AV junctional automaticity and conduction was achieved by selective intranodal administration of verapamil. In three dogs incremental pacing from either ventricle failed to retrogradely activate the atria, and in each case the site of block was found to be in the AV node. In two dogs with retrograde atrial capture there was little or no rate-dependency of retrograde ventriculoatrial (VA) conduction. During incremental ventricular pacing a single ventricular echo beat was observed in 10 of the 12 dogs that had atrial capture, and the atrium appears to be an essential link in the production of each ventricular echo. Ventricular echo occurred when the time allotted for retrograde VA conduction amounted to 70 +/- 4% of the duration of the ventricular pacing cycle length. During AV junctional rhythm, a single ventricular echo was elicited in half of the dogs and in each of those cases intranodal verapamil produced a profound depression of retrograde VA conduction. These experiments suggest that retrograde AV nodal longitudinal dissociation occurs in the slow current-dependent cells of the AV node.     

Transient atrioventricular block after open-heart surgery for congenital heart disease

The records of 22 patients with transient atrioventricular (AV) block after open-heart surgery for congenital heart disease from 1972 to 1978 were reviewed to determine the natural history of this entity. Preoperatively, no patient had AV block; 3 had right bundle branch block (BBB), 1 had left BBB and 5 had nonspecific intraventricular conduction delay. Complete AV block developed in 20 patients and Mobitz II AV block in 2. Transient AV block occurred intraoperatively in 14 patients and within 48 hours postoperatively in 8; AV block persisted for greater than or equal to 48 hours postoperatively in all patients, for a mean of 7.3 days (range 2 to 28). During a follow-up of 5.5 years (range 2.5 to 10), late AV block developed in 2 patients. None of the 18 patients whose escape QRS complex morphology during AV block was similar to the final QRS complex during normal sinus rhythm or atrial fibrillation with AV conduction had late AV block, whereas 2 of the 4 in whom it differed did (p less than 0.01). There was no difference in the escape rate between the 2 groups. Thus, late development of high-grade AV block is infrequent among patients with transient postoperative AV block. An escape QRS complex during postoperative AV block that differs from the QRS complex seen on recovery of normal sinus rhythm or atrial fibrillation with anterograde conduction may identify those at high risk of late AV block.