Retrograde Atrial Depolarization Research Articles

Ventricular Pacing in Pacemaker Bigeminy to Rule in/out Truncated Pacemaker-mediated Tachycardia

Pacemaker bigeminy is not an uncommon electrocardiographic finding in device clinics. However, such a pattern mandates the differentiation of important possible diagnostic considerations such as premature atrial contractions, oversensing the T wave or the QRS complex, dual AV nodal physiology, and retrograde atrial depolarization. We present a case of pacemaker bigeminy where ventricular pacing was used to exclude the truncated form of pacemaker-mediated tachycardia and reach a diagnosis of atrial bigeminy, which was crucial from the management’s perspective.

P172 AN ACCESSORY PATHWAY WITHOUT REENTRANT TACHYCARDIA

Abstract A 65–year–old patient, hypertensive, dyslipidemic, strong smoker. He has heart disease with hypokinetic evolution EF 47%, mild MI. Negative Dipyridamole–stress echocardiography dated January 2008. Recently atrial fibrillation (AF) is found and anticoagulant therapy was started. Dyspnea and weight loss occurred in past two months. Detected keratinizing squamous pulmonary Ca with negative markers. This injury was judged to be inoperable, and the patient get indications for chemotherapy and radiotherapy. The patient also starts complaining of dyspnea and chest pain on exertion: Not serological modification, not ischemic ECG. Echocardiogram LVEF 47–50% highlights diffuse hypokinesia, regular valves. Ergometric test was not evaluable for ischemia. Coronary angiography shows stenosis of proximal and middle anterior interventricular coronary and non–critical lesions of circumflex and right coronary. Ecodobutamine test was positive for ischemia and arrhythmias (AF and wide QRS tachycardias in recovery phase), but negative for angor. The patient was treated with CT and IVA I – II. angioplasty Monitoring shows AF with high penetrance, wide QRS tachycardia runs and very short TVNS. ECG 1: During atrial tachycardia, show broad QRS conduction to BBSX alternating with narrow QRS with the same RR interval. ECG 2. show fusion between the wavefront conducted with narrow QRS and that with wide QRS. These are supraventricular arrhythmias that run along the atrioventricular nodal pathway (NAV) in the narrow QRS tracts and take an accessory pathway in the wide QRS run. The Mahaim fibers have decremental conductivities like the AV node, therefore high ventricular frequencies does not occur AF appeared during ecodobutamine, but some beats were conducted by an anomalous path in a discontinuous way); they are generally directed from the atrium or the NAV, towards another part of the right ventricular conduction system, with atrium wave or NAV – RB, therefore the early activation of the RB generates a widened QRS, with a LBB morphology. ECG 3 Re–entry on Mahaim pathway, ventricular activation widened through Mahaim fiber, which generate LBB morphology with retrograde atrial depolarization. In this case there is no reentry, but we have an atrial tachycardia conducted alternately on an accessory pathway and across the NAV. Given the patient‘s clinical problems and the total absence of symptoms, the patient remains asymptomatic during therapy with amiodarone and beta–blocker.

Left ventricular diverticulum associated with two concealed atrioventricular accessory pathways.

A 27-year-old man with paroxysmal episodes of atrioventricular reciprocating tachycardia was referred for radiofrequency catheter ablation of a concealed atrioventricular accessory pathway (AP). Echocardiography revealed the presence of a finger-shaped inferior-basal left ventricular diverticulum (LVD), which was confirmed by CT scan (30 mm × 11 mm). The ablation procedure was performed using the CARTO3™ mapping system to identify the site of earliest retrograde atrial depolarization (ERAD) during ventricular pacing (cycle length = 400ms). This site corresponds to the atrial insertion of the AP. The resulting 3D map was merged with the CT-scan images (Panel B). The ERAD was located close to the tricuspid annulus, slightly lateral to the LVD projection (‘site 1’, Panel A). Radiofrequency application at site1 resulted in a significant increase (+40 ms) in the local stimulus-to-atrial-electrogram delay. A new 3D map was produced to verify the location of the ERAD, then located slightly septal...

Shortness of breath in a patient with complete heart block and permanent pacemaker: A case of effective pacemaker reprogramming

An 82-year-old frail woman with a prior history of hypertension, complete heart block, and dual permanent pacemaker (Sensia DR SEDR01, Medtronic Inc., Minneapolis, MN) presented to pacemaker clinic with symptoms of shortness of breath (SOB), dizziness, and “low pulse rate”. Pacemaker interrogation showed underlying normal sinus rhythm, sinus rate of around 74 beats/ min with atrial sensed events, and ventricular paced rhythm with frequent symptomatic premature ventricular complexes (PVC). Pacemaker parameters were DDD, lower rate limit (LRL) of 60 beats/min, and maximum tracking rate of 120 beats/min, along with paced/sensed AV delay of 300/250 ms. Also noted was high pacing threshold of 3.5 V at 1 ms in the atrial lead with normal sensing parameters. In view of these, the pacemaker mode was reprogrammed to VDD mode and the patient was given betablocker therapy for frequent PVCs. She presented to arrhythmia clinic a few weeks later because of worsening SOB, light-headedness, and transient ischemic attacklike symptoms. Electrocardiography (ECG) performed in the clinic showed ventricular paced rhythmwith retrograde P waves (Fig. 1). What was the underlying arrhythmia mechanism? What treatment options are available? 2. Discussion

Atrial Pacing During Radiofrequency Ablation of Junctional Ectopic Tachycardia

Radiofrequency catheter ablation (RFCA) was performed on a 5-year-old boy with congenital junctional ectopic tachycardia (JET) that was refractory to medical management. Because of the lack of retrograde atrial depolarization during tachycardia, radiofrequency energy was delivered during atrial overdrive pacing to confirm the presence of preserved atrioventricular (AV) conduction. Although the procedure was complicated by complete right bundle branch block after ablation of the para-Hissian region, the patient regained sinus rhythm accompanied by normal AV conduction. Rapid atrial pacing during RFCA of JET may be safely used to avoid AV block.

Reappraisal of electrical cure of atrioventricular nodal reentrant tachycardia — lessons from a modified catheter ablation technique

A modified catheter ablation technique was studied prospectively in 29 patients with atrioventricular (AV) nodal reentrant tachycardia. A His bundle electrode catheter was used for mapping and ablation. Cathodic electroshocks (100–250 J) were delivered from the distal two-electrodes (connected in common) of the His bundle catheter to the site selected for ablation. The optimal ablation site recorded the earliest retrograde atrial depolarization, simultaneous or earlier than the QRS complex, with absence of a His bundle deflection during AV nodal reentrant tachycardia. One additional electrical shock was delivered if complete abolition of retrograde VA conduction persisted for more than 30 min and AV nodal reentrant tachycardia was not inducible during isoproterenol and/or atropine administration. With a cumulative energy of 323 ± 27 J and a mean of 2.3 ± 0.5 shocks interruption or impairment of retrograde nodal conduction was achieved. Antegrade conduction, although modified, was preserved in 27 patients, with persistence of complete AV block in 2 patients. Two of the 27 patients still need antiarrhythmic agents to control tachycardia, the other 25 patients were free of tachycardia within a mean follow-up period of 13 ± 2 months (range 7 to 20 months). Twenty-three patients received late follow-up electrophysiological studies (3–6 months after the ablation procedures), and the AV nodal function curves were classified into 4 types. The majority of the patients ( 15 23 ) had loss of retrograde conduction. Among the 8 patients with prolongation of retrograde conduction, 4 patients still had antegrade dual AV nodal property but all without inducible tachycardia. In conclusion, preferential interruption or impairment of retrograde conduction was the major, but not the sole, mechanism of electrical cure of AV nodal reentrant tachycardia.

Demonstration of an Excitable Gap in the Common Form of Atrioventricular Nodal Reentrant Tachycardia

Premature ventricular depolarizations were introduced during sustained atrioventricular nodal reentrant tachycardia (“slow‐fast” type) in a single patient during electrophysiological study. Preexcitation of the atrium with retrograde His bundle capture occurred over an 85 msec range of coupling intervals between the last antegmde His bundle depolarization and the first retrograde His bundle depolarimtion associated luith the premature beat (H1 ‐ H2 interval). The interval between the retrograde His bundle depolarization (H2) and the retrograde atrial depolarization (A2) remained constant over this 85 msec excitable gap as the H1‐H2 interval decreased. This indicates the presence of fully excitable tissue luithin the retrograde fast pathway of the reentrant circuit during the tachycardia and demonstrates the utility of this technique for defining the extent and conduction properties of the excitable gap in reentrant arrhythmias

Nova técnica para tratamento da taquicardia por reentrada nodal: desconexão posterior do nó atrioventricular

No periodo de marco de 1987 a novembro de 1989, 20 pacientes com idade variavel entre 20 e 74 anos, 13 do sexo feminino, portadores de taquicardias por reentrada nodal (TRN) recorrentes e refratarias a terapeutica medicamentosa, foram submetidos a tratamento cirurgico. O estudo eletrofisiologico pre-operatorio demonstrou intervalo VA durante TRN menor que 40 ms e a despolarizacao atrial retrograda se iniciava na porcao anterior ao no AV. O mapeamento intra-operatorio feito durante estimulacao ventricular mostrou desplarizacao atrial retrograda posterior ao no AV. Independentemente do local mais precoce de ativacao atrial, anterior ou posterior ao no AV, em todos os casos a abordagem foi posterior, sendo realizada a desconexao posterior do no AV. Apos cardioplegia, a incisao foi realizada no atrio direito, a 2 mm do anel tricuspide, e paralela ao mesmo, iniciando-a a 2 mm atras do feixe de His, previamente localizado. A extensao posterior da incisao ultrapassou em 2 cm o ostio do seio coronario. Atraves dessa incisao, toda a regiao correspondente ao limite posterior do no AV foi separada das estruturas vizinhas, seio coronario, parede atrial direita, porcao postero-superior do ventriculo esquerdo, septo interventricular e porcao subanular do ventriculo direito. Em profundidade, a disseccao atingiu a parede do atrio esquerdo, na sua juncao com o anel correspondente. Todos os pacientes sobreviveram a intervencao e encontram-se assintomaticos. Antes da alta hospitalar, o teste eletrofisiologico pos-operatorio realizado com estimulacao atrial epicardica e com 1 e 2 extra-estimulos, durante ritmo sinusal, em 600 e 400 ms e apos bloqueio parasimpatico completo com atropina 0,01 mg/kg, nao induziu nenhuma forma de taquicardia nodal. A tecnica proposta e simples e curativa; o mapeamento intra-operatorio torna-se dispensavel; as conexoes posteriores do no AV sao indispensaveis no circuito de reentrada; a funcao do no AV, o intervalo PR e a frequencia de Wenckeback nao se alteram no pos-operatorio.

Discrimination of Retrograde from Anterograde Atrial Activation Using Intracardiac Electrogram Waveform Analysis

The prevention of pacemaker-mediated tachycardias requires a safe, reliable method for distinguishing retrograde from anterograde atrial activation by dual chamber pacemakers. In this study, a technique was developed to detect the morphological change that occurs in the waveform of the intra-atrial electrogram during retrograde atrial activation. The method employed for waveform analysis is based upon statistical correlation. In 19 patients undergoing electrophysiological studies, atrial electrograms were recorded from bipolar endocardial electrodes during sinus rhythm and 1:1 retrograde atrial depolarization while undergoing right ventricular pacing. Data were digitally sampled at 750, 1,000, and 1,500 Hz. Templates of anterograde atrial depolarization were constructed by signal averaging waveforms from an initial sinus rhythm passage. These were used for analysis of anterograde depolarizations from a subsequent passage of sinus rhythm and a passage of known retrograde atrial depolarization. In all 19 cases, a patient-specific threshold could be derived to separate anterograde from retrograde atrial depolarizations using 1,000 Hz and 1,500 Hz sampling rates. However, at a sampling rate of 750 Hz, separation of anterograde from retrograde atrial activation was possible in only 16/19 patients (84%). We conclude that correlation waveform analysis of a suitably sampled atrial electrogram is a reliable method of discriminating retrograde atrial depolarization from anterograde atrial depolarization in intracardiac electrograms.

Discrimination of antegrade and retrograde atrial depolarization by electrogram analysis

The inability of cardiac pacemakers to selectively reject retrograde P waves limits the usefulness of dual-chamber pacemakers (because of the possibility of endless loop tachycardias) and of antitachycardia devices which use a dual-chamber sensing algorithm. In order to determine selective sensing parameters, amplitude, slew rate, and configuration of antegrade and retrograde atrial electrograms were measured in 34 patients undergoing dual-chamber pacemaker implant—31 with unipolar and three with bipolar units. All antegrade and retrograde pairs were measurably different. All 34 cases had measurable antegrade/retrograde amplitude differences; 30 of the unipolar cases (96.8%) and all bipolar cases displayed antegrade/retrograde amplitude differences of at least 0.25 mV. Thirty of the unipolar cases (96.8%) and two bipolar cases had measurable slew rate differences. Conflguration differed in 14 of 31 (45.2%) of unipolar and in two bipolar cases. A combined criterion with 0.25 mV sensitivity steps (available in at least two presently avallable pacemakers) and 0.5 V/sec slew rate gradations (through the use of externally programmable filters) would allow the discrimination of retrograde from antegrade depolarizations in all 34 cases. With the use of amplitude and slew rate differences, it is therefore possible to reject retrograde P waves while sensing antegrade P waves with current technology.

Detection of Pathological Tachycardia by Analysis of Electrogram Morphology

Pacemaker recognition of pathological tachycardia relies on heart rate analysis. This can lead to misdiagnosis when sinus tachycardia exceeds the preset tachycardia response trigger rate. We have explored a method for automatic tachycardia diagnosis by analysis of bipolar endocardial electrogram morphology. Electrograms were recorded from 11 patients (pts) during sinus rhythm and during a total of 20 abnormal rhythms: retrograde atrial depolarization from ventricular pacing in six patients; atrioventricular reentry tachycardia in five patients with intermittent left bundle branch block in one of those; AV nodal reentry tachycardia in five patients and ventricular tachycardia in three patients. Posture and respiration were varied during all rhythms except ventricular tachycardia. The electrograms were then digitized and converted to a form in which the amplitudes were proportional to the rates of change of the original electrogram (equivalent to a first time derivative); the derived signal was then analyzed by a new gradient pattern detection (GPD) program. Analysis of the processed atrial signals by GPD resulted in automatic recognition of abnormal rhythms from sinus rhythm in all cases except for one patient's retrograde atrial depolarization. At the ventricular level, GPD successfully distinguished all abnormal rhythms from sinus rhythm including recognition of left bundle branch block and varying degrees of preexcitation. Respiratory and postural variation did not affect the recognition process. We conclude that electrogram GPD has successfully and automatically detected a variety of arrhythmias which can be treated by implantable pulse generators and may, therefore, be a useful adjunct to heart rate analysis in future generations of such antitachycardia pacemakers.

Ideal atrial lead positioning to detect retrograde atrial depolarization by digitization and slope analysis of the atrial electrogram.

In 10 patients with intact retrograde (V-A) conduction (mean retrograde conduction time 296 +/- 45 msec), bipolar atrial electrograms were recorded simultaneously from three atrial sites (high right atrium [HRA], low right atrium [LRA], and right atrial appendage [RAA]) during sinus rhythm (anterograde electrogram) and paced ventricular rhythm (retrograde electrogram). Atrial electrograms were digitized and analyzed by a special feature detection program which uses sequential slew-rate changes to discriminate different analogue signals. In all patients, it was possible to distinguish anterograde and retrograde atrial depolarizations using the analogue or digital signal recorded from one and usually two [HRA and RAA] lead sites. Digital signal recognition was machine-based and fully automatic, and could be applied to the prevention of pacemaker-mediated tachycardia if incorporated into future microprocessor-based pulse generators.

Shortening Of R-Pp Interval By Verapamil In Reciprocating Tachycardia

T he R-P’ interval in reciprocating tachycardia represents the temporal relationship between ventricular depolarization and retrograde atrial depolarization. This interval, however, does not reflect the A-V nodal conduction sequences during such a tachycardia, but is merely the end result of these sequences. The Ibllowing case reflects a shortening ofthe R-P’ interval following the intravenous administration of verapamil. The electrocardiogram (Fig 1, all strips of standard lead 2) was recorded from a 55-year-old woman with recurrent attacks ofsupraventncular tachycardia. Strip A was recorded during the attack. The R-R intervals measured 0.34 second, representing a rate of176 beats per minute. The P’ waves ofretrograde atrial activation were superimposed upon, and deform the T waves. The R-P’ interval measured from the beginning of the QRS complex to the sharp nadir of the P’ wave-the initial deformity of the T wave-was 0.21 second.

Comparison of the effects of atrial and ventricular stimulation on sinus node function in man

Although sinus node function has been evaluated during premature atrial stimulation, no study of retrograde ventriculoatrial sinus node activation following premature ventricular stimuli has been reported. The purpose of this study was to investigate the production of compensatory and noncompensatory pauses by premature ventricular contractions through a comparison of the effects of atrial and ventricular stimulation on sinus node function. Eleven patients in sinus rhythm were studied with programmed introduction of premature atrial and ventricular stimuli outside the ventricular vulnerable period. The onset of sinus node reset, duration of return sinus cycle (A2-A3) during reset, and estimated sinoatrial conduction times were recorded. Sinus node function during premature ventricular stimulation was approximated by utilizing the interval between the last sinus beat and onset of retrograde atrial depolarization (A1-A2 interval). The return cycle length (A2-A3) during sinus reset compared at equal A1-A2 intervals was significantly less with ventriculoatrial conduction (1,145 +/- 52 msec. atrial vs. 1,076 +/- 52 msec ventriculoatrial; P less than 0.01 by paired t test) and the estimated sinoatrial conduction time was significantly less with ventriculoatrial conduction (71 +/- 7 msec. atrial vs. 25 +/- 7 msec. ventriculoatrial; P less than 0.01 by paired t test). Ventriculoatrial sinus reset occurred later in the sinus cycle than atrial reset in three of seven patients with sinus reset produced by both atrial and ventricular prematures. This study shows that the effects of ventriculoatrial conduction on sinus node function are significantly different from those of atrial stimulation alone. The return sinus cycle length during reset and estimated sinoatrial conduction time are significantly reduced with ventriculoatrial conduction. Although the zones of sinus reset with atrial and ventricular stimulation are approximately equal, ventriculoatrial depolarization may produce sinus reset later in the sinus cycle in some cases.