Atrioventricular Nodal Reentrant Tachycardia with Advanced Infra-Hisian Atrioventricular Block

We report a case of 78-year-old man admitted to the hospital due to palpitations and lightheadedness. On EKG advanced atrioventricular block with ventricular rate of 37 beats per minute was noted. On electrophysiology study a common type of atrioventricular nodal reentrant tachycardia was inducible with maintenance of advanced AV block. Radiofrequency ablation of slow pathway followed by placement of a permanent pacemaker resulted in elimination of tachycardia and resolution of symptoms.     

Atrioventricular Block Precipitated by Isoproterenol

An isoproterenol infusion was administered during an electrophysiologic study (EPS) in a patient with a history of near syncope, left bundle branch block, and no documented atrioventricular (AV) block. Isoproterenol precipitated classic 2:1 Infra‐Hisian AV block most probably proximal to the site of recording a His–Purkinje potential consistent with right bundle branch activity. Paroxysmal AV block also occurred during isoproterenol washout at a different site located distal to the presumed right bundle branch potential. Isoproterenol may be valuable diagnostically in an occasional patient suspected of AV block in whom an EPS is unrevealing and a drug challenge is negative.     

QRS Alternans with 2:1 Atrioventricular Conduction Block: What Is the Mechanism?

An 81‐year‐old woman was admitted for symptomatic bradycardia. On admission, the ECG exhibited QRS alternans, narrow QRS complex and left bundle branch block with 2:1 AV block. The patient soon had complete AV block and underwent a pacemaker implantation. An appropriate mechanism for explaining those ECG findings might be 4:1 conduction over the left bundle branch and 2:1 conduction over the right bundle branch. An ECG pattern exhibiting QRS alternans with a narrow QRS complex and bundle branch block with 2:1 AV block may suggest the coexistence of both bundle branch blocks and a high risk of complete AV block.     

Reversible,Complete Atrioventricular Block Caused by Primary Cardiac Lymphoma in a Nonimmunocompromised Patient

PCL in a Nonimmunocompromised Patient Primary cardiac lymphoma (PCL) is a rare entity that commonly presents as a heart rhythm disorder. We describe a previously healthy, immunocompetent patient presenting with complete atrioventricular block (AVB). The patient was found to have a cardiac mass on magnetic resonance imaging and underwent percutaneous biopsy eventually diagnosing PCL. After pacemaker implantation, the patient's tumor responded rapidly to chemotherapy and the AVB completely resolved. In otherwise healthy patients presenting with AV block, cardiac tumor should be considered. Additionally, if PCL is diagnosed and the patient is clinically stable with AVB, it may be reasonable to delay pacemaker implantation until the clinical response to chemotherapy is evaluated. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1386‐1389, December 2012)     

Total Atrioventricular Block with Syncopes Complicating Carbamazepin Therapy

ABSTRACT. A case of carbamazepine-induced intermittent total atrioventricular block with asystole and Stokes-Adams attacks is reported. The diagnosis was proved by repeated administration of carbam-azepine after insertion of a demand pacemaker. If syncopes occur or change nature in a patient treated with carbamazepine, evaluation of cardiac conduction is recommended.     

Sinus Tachycardia with Atrioventricular Block:

Sinus Tachycardia with AV Block During VVS. Introduction : Neurocardiogenic (vasovagal) syncope is characterized by hypotension and bradycardia. The presence of sinus tachycardia along with AV block during syncope in patients with neurocardiogenic syncope has not been described previously.
Methods and Results : Two female patients (18 and 16 years old) with recurrent syncope and documented sinus tachycardia at the time of syncope are described. Patient 1 had recurrent episodes of syncope. During one of these episodes, which occurred while she was being monitored, sinus tachycardia along with high-grade AV block was seen at the time of syncope and hypotension. Patient 2 had a history of recurrent syncope and seizure. During one of these episodes, she was documented to have ventricular asystole lasting for about 39 seconds. The sinus rate was 480 msec at the beginning, before slowing down to 960 msec prior to restoration of sinus rhythm with 1:1 AV conduction. The same scenario was repeated during head-up tilt testing. Both patients were treated successfully with oral disopyramide and, during a follow-up of 28 months and 9 months, have remained symptom-free.
Conclusion : Sinus acceleration along with high-grade AV block during syncope and hypotension can occur in some patients with neurocardiogenic syncope. The exact mechanism of this phenomenon is unclear.     

Correlation between Transient Hypotension and Exclusively Exercise-induced Symptoms of Two-to-One Atrioventricular Block

A 62-year-old woman with activity-dependent two-to-one atrioventricular block (2:1AVB) and a normal left ventricular ejection fraction was referred to our department for the evaluation of exclusively exercise-induced marked symptoms. The treadmill test helped establish a clear correlation between 2:1AVB and symptoms. The test results demonstrated that exercise-induced marked symptoms were attributed to abrupt transient hypotension combined with relative bradycardia, probably due to increased diastolic mitral and tricuspid regurgitation because of 2:1AVB during moderate-to-heavy exercise. After pacemaker implantation for 2:1AVB, the symptoms and transient hypotension disappeared, and her exercise capacity improved.     

Symptomatic Atrioventricular Block in an Atriofascicular Pathway Inserting into the Left Bundle Branch Without Apparent Atrioventricular Node Function

Atriofascicular Pathway with AV Block. We report a patient with symptomatic AV block associated with conduction solely through an atriofascicular pathway that inserted into the left bundle branch. There was no apparent conduction present through the AV node. There was, however, passive activation through the His-Purkinje system. His-bundle pacing demonstrated normal conduction through both right and left bundles. This is the first report of such a case.     

Intra‐Atrial Conduction Block Mimicking Atrioventricular Nodal Block After Multiple Catheter Ablation Procedures for Atrial Tachycardia in a Patient with Cardiomyopathy

Intra‐Atrial Conduction Block . A 42‐year‐old woman with a history of cardiomyopathy and multiple ablation procedures for atrial tachycardia developed intra‐atrial conduction block that mimicked atrioventricular (AV) nodal block during radiofrequency ablation at the cavotricuspid isthmus. She was treated with atrial pacing (from the coronary sinus), which overcame intra‐atrial conduction block and resulted in AV nodal conduction. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1258–1261, November 2012)     

Paradoxical Shortening of the Second PR Interval During 3:2 Atrioventricular Nodal Block

Paradoxical Shortening in Second-Degree AV Block. A patient with 3:2 second-degree AV block after acute inferior wall myocardial infarction showed consistent PR interval shortening on the second conducted beat in each periodicity. Intracardiac electrophysiologic evaluation revealed that the site of block was nodal. A typical Wenckebach pattern with prolongation of the AH interval was noted. The shorter PR resulted from a paradoxical shortening of the HV interval in the second beat, most likely due to supernormal conduction in the setting of concomitant trifascicular disease.     

Electrophysiologic Characteristics and Radiofrequency Catheter Ablation in Atrioventricular Node Reentrant Tachycardia with Second-Degree Atrioventricular Block

Second-Degree AV Block During AVNRT. Introduction : Detailed electrophysiologic study of AV nodal reentrant tachycardia (AVNRT) with 2:1 AV block has been limited.
Methods and Results : Six hundred nine consecutive patients with AVNRT underwent electrophysiologic study and radiofrequency catheter ablation of the slow pathway. Twenty-six patients with 2:1 AV block during AVNRT were designated as group I, und those without this particular finding were designated as group II. The major findings of the present study were: (1) group I patients had better anterograde and retrograde AV nodal function, shorter tachycardia cycle length (during tachycardia with 1:1 conduction) (307 ± 30 vs 360 ± 58 msec, P < 0.001), and higher incidence of transient bundle branch block during tachycardia (18/26 vs 43/609, P < 0.001) than group II patients: (2) 21 (80.8%) group I patients had alternans of AA intervals during AVNRT with 2:1 AV block. Longer AH intervals (264 ± 26 vs 253 ± 27 msec, P = 0.031) were associated with the blocked beats. However, similar HA intervals (51 ± 12 vs 50 ± 12 msec, P = 0.363) and similar HV intervals (53 ± 11 vs 52 ± 12, P = 0.834) were found in the blocked and conducted beats; (3) ventricular extrastimulation before or during the His-bundle refractory period bundle could convert 2:1 AV block to 1:1 AV conduction.
Conclusions : Fast reentrant circuit, rather than underlying impaired conduction of the distal AV node or infranodal area, might account for second-degree AV block during AVNRT. Slow pathway ablation is safe and effective in patients who have AVNRT with 2:1 AV block.     

Congenital Complete Atrioventricular Block and Preexcitation Syndrome: A Well-Matched Partner

A patient who had been previously diagnosed with congenital complete atrioventricular block (CCAVB) twenty years ago developed atrioventricular (AV) conduction through an accessory pathway (AP). With enhanced sympathetic tone (exercise, isoproterenol), 1:1 conduction down the AP occurred. An electrophysiologic study confirmed a suprahissian AV block and the presence of an AP. The AP was located on the left side and posterior. The absence of retrograde conduction through the AP and also a long conduction time were demonstrated.     

Paroxysmal Atrioventricular Block in a Relatively Young Patient with COVID-19

Cardiac involvement has been reported in patients with coronavirus disease 2019 (COVID-19). We herein report a 41-year-old man who presented with recurrent paroxysmal atrioventricular block without showing significant cardiac injuries or comorbidities. The patient was diagnosed with COVID-19 and admitted to our hospital, where he was noted to have paroxysmal atrioventricular block. Cardiac biomarkers, echocardiography, and cardiac magnetic resonance imaging findings were fairly normal. An endomyocardial biopsy performed before the implantation of a permanent pacemaker revealed mild myocardial fibrosis without inflammatory infiltrates. The unusual myocardial involvement of the novel coronavirus was suspected.     

Progressive Atrioventricular Conduction Block in a Mouse Myotonic Dystrophy Model

Introduction: Myotonic dystrophy is caused by expansion of a CTG trinucleotide repeat on human chromosome 19, and leads to progressive skeletal myopathy and atrioventricular conduction disturbances. A murine model of myotonic dystrophy has been designed by targeted disruption of the myotonic dystrophy protein kinase (DMPK) gene. The DMPK-deficient mice display abnormalities in A-V conduction characteristics, similar to the human cardiac phenotype. The purpose of this study was to determine whether age-related progression of A-V block occurs in a mouse model of DMPK-deficiency.Methods and Results: Surface ECGs and intracardiac electrophysiology (EP) studies were performed in 60 immature and 90 adult homozygous (DMPK), heterozygous (DMPK), and wild-type (WT) DMPK control mice. Complete studies were obtained on 141 of 150 mice. The RR, PR, QRS, and QT intervals were measured on ECG. Sinus node recovery time, AV refractory periods, paced AV Wenckebach and 2:1 block cycle lengths, atrial and ventricular effective refractory periods were compared between genotypes and age groups. There were no differences in ECG intervals or EP findings in the young mutant mice, but progressive PR prolongation in older mice. The A-V conduction defects are also sensitive to DMPK gene dosage. Adult DMPK mice develop 1°, 2° and 3° A-V block, whereas DMPK mice develop only 1° heart block.Conclusion: These data demonstrate that both age and DMPK dose are important factors regulating cardiac conduction in myotonic dystrophy. This mouse model of DM is remarkably similar to the human phenotype, with age-related progression in atrioventricular conduction defects.     

III度房室阻滞患者VVI起搏时运动耐力和心力储备的研究

采用心肺运动试验的方法，对１６例ＶＶＩ起搏的ＩＩ度房室阻滞患者行最大症状限制性运动试验，以测定病人的心力储备和耐力储备。结果表明病人运动时心脏指数较运动前增加１倍。最大作功８８．６±１６．３６Ｗ／ｍｉｎ，最大氧耗量１７．３８±４．４８ｍｌ／ｍｉｎ。１６例中有９例未测出无氧阈。极量运动时每个病人都出现运动性心律失常。认为ＶＶＩ起搏的患者极量运动时病理生理特点是低无氧阈、低最大氧耗量、低心输出量、低全身耐力。     

Effects of Blocked Atrial Beats on the Atrioventricular Nodal Recovery Property

AVN Recovery Property After Blocked Atrial Beats. Introduction: Blocked atrial beats (A_B) usually have concealed AV nodal penetration, which can change the nodal conduction time (AH) of a subsequent beat. However, without an output marker it is difficult to assess their effect on the node. In this report we used all possible parameters as nodal resting time after A_B and plotted them against the AH of testing beats to study their effects on the node. Methods and Results: Atrial extrastimulation studies were done in 21 patients in whom one blocked atrial heat (A_2B) was observed. Nodal recovery curves were obtained for basic pacing (A₁), after a conducted premature heat (A₂), and after A_2B. In six patients there were 2 to 3 consecutively blocked beats (A_nB) and recovery curves were constructed after each A_nB. Nodal recovery curves were plotted with AH of the testing beat against different nodal resting parameters and fitted to a single exponential equation. We found contradicting phenomena when using different formats. (1) For recovery curves of A_2B, there was a rightward shift from that of the basic curve when using H₁A₃ or A₁A₃ as the gauge (depression phenomenon). On the contrary, there was a leftward shift of the curves when using A_2BA₃ (facilitating phenomenon). (2) For recovery curves after multiple blocked beats there was a marked rightward shift of all curves except A_(n-1)BA_n -curves, which were all leftward shifted. Conclusion: Because these contradicting phenomena were dictated by the presenting formats, the terms “depression” and “facilitation” cannot he considered intrinsic AV nodal properties outside of the strict context of the pacing protocol and the format of data presentation.     

导管射频消融术中出现Ⅲ度房室阻滞的预后与对策

为了探讨导管射频消融术中出现的Ⅲ度房室阻滞 (AVB)转为永久性Ⅲ度AVB的预测指标与合理对策 ,回顾性地分析了 10年来遇到的 16例患者。术中终止放电后很快恢复了房室传导而术后次日再次发生Ⅲ度AVB 8例 (A组 ) ,终止放电后直至出院 (住院 30～ 80d)始终未恢复房室传导 8例 (B组 )。并对两组的以下指标进行比较 :①性别 ;②年龄 ;③术中发生Ⅲ度AVB的次数 ;④放电中出现连续非 1∶1结性搏动数 ;⑤终止放电后Ⅲ度AVB的持续时间 ;⑥次日再出现Ⅲ度AVB的持续时间 ;⑦是否使用激素。结果表明放电中连续的非 1∶1结性搏动数及Ⅲ度AVB持续的时间是可靠的预测指标 ,一旦出现必须在 3跳内停止放电 ,观察期为一个月 ,否则应安置永久起搏器。