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Background: The aim of our study was to assess the real life cardiac resynchronization therapy (CRT) fusion left ventricular (LV) only pacing in patients with normal AV conduction (NAVc) without right ventricular (RV) lead. Methods: Consecutive NAVc patients with CRT indication were implanted with a right atrium RA/LV DDD pacing system. Complete follow-up at 1, 3 and every 6 months thereafter included echocardiography and stress testing. Results: We analysed 55 patients (62 &plusmn, 11 years). All patients were responders with significant LV reverse remodelling (LV end-diastolic volume 193.7 &plusmn, 81 vs. 243.2 &plusmn, 82 mL at baseline, p &lt, 0.002) and increased LV ejection fraction (38 &plusmn, 7.9% vs. 27 &plusmn, 5.2% at baseline, p &lt, 0.001). Mitral regurgitation decreased in 38 patients (69%). During follow-up (35 &plusmn, 18 months), 20 patients (36%) needed reprogramming sensed/paced AV delay or maximum tracking rate (MTR) because of inadequate or lost LV capture at exercise test, personalized programming to achieve up to 100% fusion pacing was used in all patients. One patient developed Mobitz II second degree AV block and triple chamber CRT-P upgrade was performed, defibrillator upgrade was not necessary. Conclusions: LV only pacing CRT-P without RV lead showed a positive outcome in carefully selected patients.

TAVR patients given pacemakers operating in mandatory DDD mode had more ventricular pacing, heart failure hospitalization, and mortality compared with AAI-DDD or VVI modes. AV conduction disturbances are often transient after TAVR. Minimizing ventricular pacing where possible avoids the risk of pacemaker-induced cardiomyopathy. Pacemaker specialists should be consulted for any TAVR patient with mild rhythm abnormalities given the high incidence of AV block.

Atrioventricular (AV) block is an AV conduction disorder that can manifest in various settings, with varying symptomaticity and severity. The electrocardiogram is a key diagnostic tool for management, and careful interpretation is necessary to institute the correct management. We described two cases of patients with bradycardia due to AV blocks and discussed the electrocardiogram interpretation and management.

Three-dimensional reconstruction of digitized histological serial sections of the cardiac conduction system yielded two accessory pathways in a case of a 24-day-old male infant who died after a short period of illness with ECG findings of Wolff-Parkinson-White syndrome. In infants, the differential diagnosis of possible accessory pathways connecting the AV conduction system, atrial or ventricular septum includes dispersed conduction system tissue without connecting features. This is why three-dimensional reconstruction is necessary in order to refute or establish connectivity of cell groups as found in histological serial slice images.

Pharmacological stress tests using dipyridamole are considered to be safe. However, cases of atrioventricular (AV) block have been reported. We retrospectively analyzed ECG at baseline and during dipyridamole stress tests of 2010 consecutive patients (patients with second or third degree AV block were excluded). At baseline, 350 (17.4%) patients had conduction abnormalities. Following dipyridamole infusion 16 patients (0.8%) developed a transient change in AV conduction (15 patients) and or sinus arrest (1 patient). Compared to patients without baseline conduction abnormalities, patients with any conduction abnormalities at baseline were at a higher risk for the development of AV block after dipyridamole infusion [0.3% vs 3.14%, respectively; P

Nowadays, slow pathway ablation is the first-line therapy for atrioventricular nodal reentrant tachycardia (AVNRT). However, it may cause inadvertent AV block especially inpatients with a prolonged PR interval on the baseline ECG. Retrograde fast pathway ablation may be attempted in such AVNRT patients as an alternative approach to maintain the original AV conduction over the slow pathway.

Background Symptomatic second-degree atrioventricular (AV) block is typically treated by implantation of a pacemaker. An otherwise healthy AV conduction system can nevertheless develop AV block due to interference from junctional extrasystoles. When present with a high burden, these can produce debilitating symptoms from AV block despite an underlying normal AV node and His–Purkinje system properties. Objective The purpose of this study was to describe a catheter ablation approach for alleviating symptomatic AV block due to a ventricular nodal pathway interfering with AV conduction. Methods Common clinical monitoring techniques such as Holter and event recorders were used. Standard electrophysiological study techniques using multipolar recording and ablation catheters were utilized during procedures. Results A 55-year-old woman presented with highly symptomatic, high-burden second-degree AV block due to concealed and manifest junctional premature beats. Electrophysiological characteristics indicated interference of AV conduction due to a concealed ventricular nodal pathway as the cause of the AV block. The patient's AV nodal and His–Purkinje system conduction characteristics were otherwise normal. Radiofrequency catheter ablation of the pathway was successful in restoring normal AV conduction and eliminating her clinical symptoms. Conclusion Pathways inserting into the AV junction can interfere with AV conduction. When present at a high burden, this type of AV block can be highly symptomatic. Catheter ablation techniques can be used to alleviate this type of AV block and restore normal AV conduction.

The goal of this study was to investigate the electrocardiographic and chronobiological features of paroxysmal atrioventricular (AV) block (PAVB) using data from ambulatory electrocardiography (AECG). The study population consisted of five men and six women aged from 47 to 82 years of age. Main presenting symptoms were pre-syncope in five patients (45.5%) and syncope in three patients (27.3%). Organic cardiovascular diseases were seen in eight patients (72.7%), and AV conduction disturbances were seen in six patients (54.5%), such as right bundle branch block, first to second degree AV block on standard 12-lead electrocardiography. Incidence of PAVB events were 1-329 (37.9±98.0) episodes/patient/day, and the maximum pause during Holter recordings was 3.3-12.4 (6.39±3.09) seconds. This maximum pause caused by intrinsic AV block was longer than that of vagally mediated AV block (8.4±3.2 sec vs 4.7±1.0 sec, p

Snake venom toxicities comprise mainly bleeding disorders and nephrotoxicity. Cardiotoxicity is a rare manifestation of snake bite. We describe the case of a previously healthy 23- year-old man who developed coagulopathy and AV node dysfunction following snake bite. Electrocardiography showed all variations of AV conduction dysfunction. This is the first account of AV node dysfunction caused by a snake bite with cardiotoxicity presenting as atrioventricular block.

More than half a century has passed since the concept of dual atrioventricular (AV) nodal pathways physiology was conceived. Dual AV nodal pathways have been shown to be responsible for many clinical arrhythmia syndromes, most notably AV nodal reentrant tachycardia. Although there has been a considerable amount of research on this topic, the subject of dual AV nodal pathways physiology remains heavily debated and discussed. Despite advances in understanding arrhythmia mechanisms and the widespread use of invasive electrophysiologic studies, there is still disagreement on the anatomy and physiology of the AV node that is the basis of discontinuous antegrade AV conduction. The purpose of this paper is to review the concept of dual AV nodal pathways physiology and its varied electrocardiographic manifestations.

Background Adaptive AV shortening algorithms have demonstrated QRS duration (QRd) narrowing in traditional cardiac resynchronization therapy (CRT) patients. Multipoint pacing (MP) has also demonstrated benefit in these patients. An additional site of activation via intrinsic conduction of the septum may further contribute to CRT response, however incorporation of all of these strategies together has yet to be developed or investigated. Objective We developed and tested a method combining MP-CRT and controlled septal contribution to create MP-Fusion encouraging 4 ventricular activation sites for CRT patients utilizing measurements from intracardiac electrograms and incorporation of an AV delay shortening algorithm (Sync-AVTM Abbott laboratories, Sylmar Ca.) Methods Patients with intact AV conduction Results 13 (N=17) patients were analyzed 65.5 +/- 8.3 years. (M:F /Age/) Mean baseline QRSd was 148ms (+/-22.14). Programming utilizing the MP-fusion algorithm yielded a QRSd of 113.23ms (+/-17.14) (P Conclusion The simple use of MP-fusion demonstrated significant QRSd narrowing in all patients tested. A randomized trial with larger sample size and outcome measures in addition to QRSd is warranted.

It is commonly believed that intermittently conducting accessory pathways are not capable of rapid conduction and thus ablation is not necessary. A 74-year-old male with a prolonged first degree AV block and episodes of 2:1 AV block conduction on Holter with a relatively wide QRS presented to the

QRS-Based Optimization of Cardiac Resynchronization Background Optimization of atrioventricular (AV) and interventricular (VV) intervals may improve cardiac resynchronization therapy (CRT) response but is a complex task. Fusion with intrinsic conduction may increase the benefit of CRT. The aim was to describe fusion-optimized intervals (FOI), a new method of optimizing CRT based on QRS duration. Methods and Results Seventy-six consecutive patients with preserved AV conduction who received CRT were prospectively included. The AV interval was optimized by searching the narrowest QRS obtained within the fusion band during left ventricular (LV) pacing. The VV interval was then adjusted, comparing QRS duration in simultaneous biventricular, LV preexcitation (−30 milliseconds), right ventricular (RV) preexcitation (−30 milliseconds) and LV-only pacing. A substudy in 31 patients evaluated the invasive LV +dP/dtmax. The best fusion-optimized AV interval was 136 ± 30 milliseconds during atrial sensing and 192 ± 35 milliseconds during atrial pacing. The best QRS was obtained with simultaneous biventricular pacing in 28 patients (37%), LV preexcitation in 22 (29%), LV-only in 20 (26%), and RV preexcitation in 6 (8%). Baseline QRS was shortened more by FOI (59 ± 19 milliseconds) than by nominal settings (40 ± 21 milliseconds; P 10% shortening of the baseline QRS with FOI; none prolonged the QRS duration by FOI compared to nominal settings. All echocardiographic asynchrony parameters were corrected by FOI. Baseline +dP/dtmax improvement was greater in FOI (127 ± 95 mmHg/seconds) than in nominal settings (102 ± 71 mmHg/seconds; P = 0.05). Conclusion The FOI method is feasible, further reduces QRS duration, and improves acute hemodynamic response compared to nominal programming of CRT.

We present a 51 years old male patient with recurrent syncope. Patient had baseline RBBB, LAFB and atrial fibrillation with normal holter study for 24 h period. Post DC cardioversion he went to first degree AV block in addition to baseline RBBB + LAFB, an evidence of trifascicular block. This was confirmed on EP study and patient underwent permanent pacemaker implantation. Doing well on follow up. The moral of story is that if a patient has AF with controlled rates, AV conduction disease should be ruled out as a cause for syncope and we should not ignore the facts about rhythm disturbances which can be seen post DC cardioversion of AF.

The gap phenomenon is an unusual phenomenon in electrophysiology arising from the interaction of different refractory periods of different levels of the conduction system. We present a case where there is an interesting interaction between AV conduction gap and AH jump due to the coexistence of dual AV nodal physiology. We also briefly discuss the other mechanisms of gap phenomenon that have been described in this setting.

We present two patients with paroxysmal atrial fibrillation on class 1C antiarrhythmic drugs without concomitant atrioventricular (AV) nodal blocking agents who developed atrial flutter with 1:1 AV conduction. Their electrocardiogram revealed wide complex tachycardia with rates >200/minute. Atrial flutter with 1:1 conduction in the presence of class IC antiarrhythmic drugs may present a diagnostic challenge. These cases illustrate the importance of coadministering an AV nodal blocking agent with class IC antiarrhythmic agents in patients with atrial fibrillation. The differential diagnosis of wide complex tachycardia in patients taking class IC agents should include atrial flutter with 1:1 AV conduction.

Cardiac pacing has been used for the treatment of symptomatic bradyarrhytmias, mostly sinus node dysfunction or advanced auriculoventricular conduction block. Technological advances have permitted the correction of rhythm and conduction disturbances by mode selection and algorithms that intend to simulate the natural function of the heart. Multiple clinical trials have assessed the efficacy and safety of different modes and favor atrial based stimulation modes, intrinsic AV conduction and the reduction unnecessary right ventricular pacing. Other conditions can benefit from the selection of specific modes.

A quadripolar catheter was placed at the Hisbundle region. At baseline, the patient was in sinus rhythmwith 2:1 AV block with RBBB on conducted beats (see Fig. 1A). Intracardiac recordings demonstrated infra-Hisian block with nonconducted beats (Fig. 2). Intermittently, 1:1 AV conduction would resume, sometimes, but not always, following a premature atrial contraction (PAC) with RBBB aberrancy, followed by LBBB with the 1:1 conducted beats (see Fig. 1B

Background Paroxysmal atrioventricular block (P-AVB) is a well-known cause of syncope; however, its underlying mechanism is difficult to determine. This study aimed to evaluate a new ECG index, the “vagal score (VS),” to determine the mechanism of P-AVB. Methods We evaluated the VS in 20 patients with P-AVB (13 men, 7 women; aged 25–78 years [mean, 59.3 years]). The VS was developed by assigning 1 point each for the following: (1) no AVB or intraventricular conduction disturbance on the baseline ECG, (2) PR prolongation immediately before P-AVB, (3) sinus slowing immediately before P-AVB, (4) initiation of P-AVB by PP prolongation, (5) sinus slowing during ventricular asystole, and (6) resumption of AV conduction with PP shortening, and by assigning –1 point each for (7) the initiation of P-AVB by a premature beat, and (8) resumption of AV conduction by an escape beat. Based on the clinical situations and electrophysiologic findings, we considered the mechanism of P-AVB as vagally mediated or intrinsic conduction disease (ICD). Results The VS ranged from 5 to –2 points for each patient. Five patients with a definite vagally mediated P-AVB had high VSs (3–5 points). We observed characteristic ECG findings of ICD consisting of changes in AV conduction by an extrasystole and/or escape beat in only 5 of the 6 patients (83%) with a low VS (1 to –2). Conclusions The VS is simple and potentially useful for determining the mechanism of P-AVB. P-AVB with a VS ≥3 strongly suggested a vagally mediated mechanism.

The most common manifestation of Lyme carditis is a varying degree of atrioventricular (AV) conduction block. This case describes a 45-year-old male with third-degree AV block due to Lyme carditis. Treatment with intravenous antibiotics resulted in complete normalization of AV conduction, thereby averting permanent pacemaker implantation.

Atrioventricular (AV) delay optimization in sequential and biventricular (BiV) pacing, although widely recommended, is often poorly performed in clinical practice as an improper setting can reduce the success of the stimulation. Despite the several methods proposed, the AV delay is frequently programmed in an empirical way or left to a predefined value (usually the manufacturer's setting), without considering the different variables involved in this context, concerning the intra- and interindividual variability of the electromechanical events, the peculiarities of the several cardiopathies, the spontaneous interatrial and AV conduction, the pharmacological therapy, and the pacing mode. The manuscript illustrates the physiological bases of the optimization, describes why and how to programme the best AV delay at rest and during daily activities and discusses critically all methods proposed, divided into three groups: predefined formulas, iterative attempts, and automatic settings. The manuscript is not only a review because it tries to clarify this complex topic, stating the fundamental concept in BiV pacing; the optimal AV delay should be short enough to have always a pre-exitated stimulation and contemporary an optimal left ventricular filling. The paper suggests new purposes and new solutions for this goal, it shows the limits of the actual guidelines and the disappointing results obtained in several studies by automatic methods, goading to find new algorithms.

This study investigated long-term outcome of catheter ablation of right anteroseptal atrio-ventricular (AV) accessory pathways (AP) located close to the His bundle. Methods Between April 2003 and June 2011, 26 patients (6 females, age 35±13 years) underwent catheter ablation of right anteroseptal AP. These APs represented 10% of all 248 APs ablated within the given reference period. Elimination of AP conduction in both directions and preservation of normal AV conduction were the ablation procedure endpoints. Results First ablation was effective in 18 (69%) patients. After repeat ablation, AP was permanently eliminated in 22 (85%) patients (one, two, and three ablation procedures in 16, 5, and 1 patient, respectively). Ablation failed in 4 patients (1 procedure in 3 patients, 2 procedures in 1 patient). During 56±27 (4–102) month follow-up period since the last ablation, no late AP conduction recovery was found, and no late advanced AV block occurred. Post-ablation AV node Wenckebach point was present at the pacing rate of 176±26 (130–230) beats per minute. Of the two engaged operators, more experienced operator successfully accomplished first, second, and third ablation procedure in 14/16 (88%), 5/5 (100%), and 1/1 (100%) patients, respectively, the latter operator attained successful ablation in 4/10 (40%) and 1/2 (50%) patients at the first and second ablation procedures, respectively. Conclusion Ablation of right anteroseptal AP close to the His bundle is feasible and safe. Late advanced AV block was not observed. Individual operator's experience influenced ablation efficacy.

A 58-year-old woman received a dual chamber pacemaker (Medtronic) for sick sinus syndrome. Given intact AV conduction the Managed Ventricular Pacing mode algorithm (MVP) was programmed. The day after, she suffered from palpitations. Her ECG showed a possible loss of atrial capture accompanied by atrial undersensing. Telemetry-supported pacemaker control confirmed the loss of capture. Undersensing of atrial signal was functional, related to long atrial refractory period in MVP mode algorithm. Device algorithms could induce false suspicions. Awareness about the different pacing algorithms can be useful in order to avoid erroneous interpretations and to correct potential malfunctioning.

Background Dual-chamber pacemaker systems can lead to two forms of pacemaker-facilitated tachycardia: pacemaker-mediated tachycardia (PMT) and tracking of sinus or atrial tachycardia. Current pacemaker algorithms cannot always differentiate between these two tachycardias. Objective The purpose of this study was to investigate a novel algorithm for distinguishing the two mechanisms of pacemaker-facilitated tachycardia, which is based on the specific termination response to postventricular atrial refractory period (PVARP) extension. Methods We prospectively tested our algorithm using the Medtronic Virtual Interactive patient (VIP) II simulator (version 1.53) and a Medtronic Adapta ADDR01 dual-chamber pacemaker. Results Thirty-five scenarios that triggered "PMT detection" by the device were evaluated. All 12 scenarios of atrial tachycardias with intact AV conduction terminated with a Vp-Ar-Vs (V-A-V) response as a result of PVARP extension. Of the 11 scenarios of atrial tachycardia with complete heart block, all terminated with a Vp-Ar-As-Vp response. All four episodes of PMT with intact AV conduction terminated with a Vp-Ar-As-Vs (V-A-A-Vs) response. Of the eight episodes of PMT with complete heart block, all terminated with a Vp-Ar-As-Vp response. Conclusion In the presence of intact AV conduction, the V-A-V response to PVARP extension is specific to atrial (or sinus) tachycardia, whereas the V-A-A-Vs response is specific to PMT. Recognizing the difference between the two forms of pacemaker-facilitated tachycardias has important implications for pacemaker programming.

Background: The independent activation of the atria and ventricles, AV dissociation, is a common phenomenon that occurs during a wide variety of electrophysiologic circumstances. The clinical significance of AV dissociation is often misunderstood. Methods: This article examines the basis and clinical implications of AV dissociation. Results: AV dissociation is often an obligatory, secondary phenomenon, and should not be construed as the primary disorder; it may be due to either the AV conduction system being completely blocked (3° AV block) or the P wave and the QRS complex being generated from separate sources (usually, the AV junction or ventricle) but occurring close together during the physiologic refractory period of each other. The latter may happen in junctional or ventricular arrhythmias including escape or accelerated rhythm, tachycardia, or premature beats. Conclusion: The crucial clinical point is not the AV dissociation itself, but that an underlying triggering primary disorder is present and should be identified. Ann Noninvasive Electrocardiol 2011;16(3):227–231

An 85-year old Thai woman was admitted to the hospital for dyspnea. Her ECG showed complete atrioventricular (AV) block. Her laboratory data upon admission revealed low serum thyroxine level and elevated thyrotropin level. Levothyroxine was started, and the AV conduction block was supported by a temporary pacemaker. At the end of the second week, her free T4 fell within normal range. The temporary pacemaker was subsequently removed. She was discharged without permanent pacing. This case demonstrated that hypothyroidism can cause complete atrioventricular block. Levothyroxine replacement can restore AV conduction in the hypothyroid patient.

We describe a case of advanced atrioventricular (AV) block, in which treatment with cilostazol was effective in recovering the AV conduction. The patient was referred to our hospital for close examination of the advanced AV block and permanent pacemaker implantation. Although the patient had experienced third-degree AV block with occasional AV synchrony for more than two days, the AV conduction completely recovered after treatment with oral cilostazol at 200 mg/day. Here we discuss the possible mechanism of the improvement in the AV conduction by cilostazol.

This case review presents various manifestations of extra long PR intervals, an interesting form of atrioventricular (AV) block first described in 1977. All patients in this study had organic heart diseases and various combinations of multilevel conduction impairment. Perhaps the most common cause of chronic AV conduction impairment is the ill-defined degenerative and/or fibrotic damage to the intraventricular conduction system.

A 28‐year‐old previously healthy male presented with nonprodromal syncope and a 4‐day history of chest pain, shortness of breath, and malaise. His ECG showed rapidly progressive high‐degree AV block. His Suspicious Index in Lyme Carditis (SILC) score was 8, indicating high risk for Lyme carditis. Lyme serology revealed to be positive (anti‐Lyme IgM). During the second day of hospitalization, the patient deteriorated his AV conduction, and a temporary–permanent pacemaker was implanted allowing ambulating in hospital the very same day. Temporary–permanent pacemakers for the management of transient high‐degree heart block associated with Lyme carditis were only occasionally used in the past.

Radiofrequency catheter ablation treats resistant nodal re-entrant tachycardia but carries a risk to AV conduction system and its vessels. We aimed to study the origin of the A-V nodal artery (AVNA) and its course within the posterior septal space (PSS).Twenty embalmed human hearts of both sexes (16 males) age, 25-60 years, were dissected to study the PPS and its arteries down to their destination.The PSS is a four sided pyramidal space, at the crux of the heart, with its base made of the pericardium. It is made of four; right upper and lower and left upper and lower walls corresponding to the right atrium and ventricle and left atrium and ventricle, respectively. The right coronary artery (RCA) crossed the base from the right to the left angle, to lie inferior and adherent to the terminal part of the coronary sinus (CS). The posterior interventricular artery, the ventricular branches of the RCA, the middle cardiac vein and the ventricular veins, all crossed the base of the space to their final destination. AVNA originated from either the RCA itself or one of its branches. Double AVNA was encountered in 14 specimens with the upper artery larger and passed between the right and left atria and the lower artery smaller and crossed the space adjacent to the right ventricle.These findings highlight the importance of the PSS and its structural relations, in particular to the AVNA, that should be considered during various interventional procedures.

The atrioventricular node (AVN) has mystified generations of investigators over the last century and continues today to be at the epicenter of debates among anatomists, experimentalists, and electrophysiologists. Over the years, discrepancies have remained in regard to correlating components of AVN structure to function, as evidenced by studies from microelectrodes, optical mapping, and the electrophysiology laboratory. Historically, the AVN has been defined by classical histological methods; however, with recent advances in molecular biology techniques, a more precise characterization of structure is becoming attainable. Distinct molecular compartments are becoming apparent based on connexin staining and genotyping, providing new insight into previously characterized functional aspects of the AVN and its surrounding structures. Advances in optical mapping have provided a unique opportunity for correlating structure and function--unmasking properties of the native AVN pacemaker and providing further insight into basic mechanisms involved in AV conduction. Additionally, procurement of explanted human hearts have provided a unique opportunity to further characterize the human AVN structurally and functionally with both molecular biology techniques and optical mapping. With the elucidation of basic elements of both structure and function via molecular investigation and optical mapping, new opportunities are becoming apparent in utilizing the unique properties of the AVN for pursuing novel clinical applications relevant to clinical electrophysiology.

Udgivelsesdato: 2008-Mar AIMS: Several clinical studies have shown that, in patients with intact atrioventricular (AV) conduction, unnecessary chronic right ventricular (RV) pacing can be detrimental. The managed ventricular pacing (MVP) algorithm is designed to give preference to spontaneous AV conduction, thus minimizing RV pacing. The clinical outcomes of MVP are being studied in several ongoing trials in patients undergoing a first device implantation, but it is unknown to what extent MVP is beneficial in patients with a history of ventricular pacing. The purpose of the Prefer for Elective Replacement MVP (PreFER MVP) study is to assess the superiority of the MVP algorithm to conventional pacemaker and implantable cardioverter-defibrillator programming in terms of freedom from hospitalization for cardiovascular causes in a population of patients exposed to long periods of ventricular pacing. METHODS AND RESULTS: PreFER MVP is a prospective, 1:1 parallel, randomized (MVP ON/MVP OFF), single-blinded multi-centre trial. The study population consists of patients with more than 40% ventricular pacing documented with their previous device. Approximately, 600 patients will be randomized and followed for at least 24 months. The primary endpoint comprises cardiovascular hospitalization. CONCLUSION: The PreFER MVP trial is the first large prospective randomized clinical trial evaluating the effect of MVP in patients with a history of RV pacing.

Background: Managed Ventricular Pacing (MVP) and Search AV+ (SAV+) are two pacing algorithms designed to reduce ventricular pacing, MVP promotes conduction by operating in AAI/R mode with backup ventricular pacing during atrioventricular block (AVB). SAV+ operates in DDD/R mode with a nominal AV extension of 290 ms during atrial sensing and 320 ms during atrial pacing. The reduction in ventricular pacing was compared with these two algorithms in pacemaker patients. Methods: The EnRhythm and EnPulse clinical studies assessed the Percentage of ventricular pacing (% VP) after 1 month. Each patient's AVB status was assigned using the following hierarchical categories: persistent third-degree AVB (p3AVB), episodic third-degree AVB (e3AVB), second-degree AVB (2AVB), first-degree AVB (1AVB), and no AVB (nAVB). The% VP was tabulated for each AVB status category. Results: Data were available from 322 patients of whom 129 received DDD(R) pacing with the MVP algorithm activated and 193 patients with DDD(R) pacing and the SAV+ function activated, each for a month period. MVP resulted in a significantly lower median % VP than SAV+ in all AVB categories except for p3AVB: nAVB (0.3 vs 2.9, P < 0.0001), 1AVB (0.9% vs 80.6%. P < 0.0001), 2AVB (37.6 vs 99.3. P < 0.002), e3AVB (1.2 vs 42.2, P = 0.02), p3AVB (98.9 vs 100, P = 1.00). Conclusion: MVP resulted in a greater reduction in% VP than SAV+ across all patient groups except persistent third-degree AV block. The greatest reduction in%VP was observed in patients with mildly impaired AV conduction. (Less)

The atrioventricular (AV) node allows ante- and retrograde conduction between atria and ventricles. It is commonly assumed that these AV nodal conduction properties go hand in hand. However, ante- and retrograde AV conduction can be completely independent from each other in individual patients. We report about a patient with permanent AV block III degrees requiring implantation of a pacemaker. As soon as a dual-chamber device was connected to the implanted leads, a tachycardia started at the maximum tracking rate, which was subsequently reprogrammed from 120 to 170 bpm. Non-invasive electrophysiologic testing showed that this patient demonstrated 1:1 ventriculoatrial (VA) conduction up to 170 bpm leading to endless loop tachycardia (ELT) while the antegrade AV block III degrees persisted. This case impressively illustrates that one has to take into account that patients with antegrade AV block III degrees may still have a high VA conduction capacity leading to ELT. Dual-chamber devices therefore have to be programmed accordingly, activating dedicated reactions after ventricular premature beats and automatic ELT detection and termination algorithms.

Based on their established role in the generation of spontaneous activity in pacemaker cells and control of cardiac rate, funny/hyperpolarisation-activated, cyclic nucleotide gated 4 (HCN4) channels are natural candidates in the search for causes of sinus arrhythmias. Investigation of funny current-related inheritable arrhythmias has led to the identification of several mutations of the HCN4 gene associated with bradycardia and/or more complex arrhythmias. More recently, the search has been extended to include auxiliary proteins such as the minK-related peptide 1 (MiRP1) β-subunit. All mutations described so far are loss-of-function and in agreement with the role of funny channels, the predominant type of arrhythmia found is bradycardia. Funny channel-linked arrhythmias, however, also include atrioventricular (AV) block and atrial fibrillation, in agreement with an emerging new concept according to which defective funny channels have a still unexplored role in impairing AV conduction and triggering atrial fibrillation. Also, importantly, recent work shows that HCN4 mutations can be associated with cardiac structural abnormalities. In this short review I briefly address the current knowledge of funny/HCN4 channel mutations and associated sinus and more complex arrhythmias.

Complete atrioventricular (AV) block is defined as interruption in the transmission of the cardiac impulse from the atria to the ventricles due to an anatomical or functional impairment in the AV conduction system. The conduction disturbance can be transient or permanent.

Background: In patients requiring permanent pacing, preservation of intrinsic ventricular activation is preferred whenever possible. The Search AV+ (SAV+) algorithm in Medtronic EnPulse(TM) dual-chamber pacemakers can increase atrioventricular (AV) intervals to 320 ms in patients with intact or intermittent AV conduction. This prospective, multicenter study compared the percentage of ventricular pacing with and without AV interval extension. Methods: Among 197 patients enrolled in the study, the percentage of ventricular-paced beats was evaluated via device diagnostics at the 1-month follow-up. Patient cohorts were defined by clinician assessment of conduction via a 1:1 AV conduction test at the 2-week follow-up. The observed percentage of ventricular pacing with SAV + ON and the predicted percentage of ventricular pacing with SAV + OFF were determined from the SAV + histogram data for the period between the 2-week and 1-month follow-up visits. Results: Of 197 patients, 110 (55.8%) had intact 1:1 AV conduction, of which 109 had 1-month data. SAV + remained ON in 991109 patients; 10 patients had intrinsic A-V conduction intervals beyond SAV + nominal and therefore SAV + disabled. The mean percentage of ventricular pacing in the 109 patients was SAV+ ON = 23.1% (median 3.7%) versus SAV + OFF = 97.2% (median 99.7%). In 87 patients without 1:1 AV conduction, SAV + was programmed OFF in 6, automatically disabled in 52, and remained ON in 29. In 8 of these patients, 80-100% reduction in ventricular pacing was observed with SAV + ON. Conclusion: The Search AV+ algorithm in the EnPulse pacemaker effectively promotes intrinsic ventricular activation and substantially reduces unnecessary ventricular pacing. (Less)

The Cardiostim team and Prof. Aladar Ronaszeki organised an educational meeting in Budapest from April 6 to 8 entitled “Pacing and Haemodynamics: Art of Timing”. This European congress has been an opportunity to discuss the haemodynamic effects of the various modes of pacing available, and more specifically Cardiac Resynchronisation Therapy (CRT) for heart failure patients. The reader will find below the 101 abstracts selected among the 156 received, printed in three different sections: conventional pacing, CRT, and a small set of abstracts on ablation techniques, which will not receive comment. Many investigations have demonstrated the deleterious effects of right ventricular (RV) apical pacing. Padeletti et al. (for the WHERE study) elegantly show the benefit of preserving spontaneous AV conduction in comparison with RV apical pacing, in DDD paced patients, via PEA measurements. PEA, which has been demonstrated to be closely correlated with LV d P /d t , significantly increases when patients are not RV paced, and decreases when they are RV paced. PEA variations parallel clinical outcomes and echo parameter values. When pacing is necessary, there is still controversy about the optimal RV pacing site. Direct His bundle pacing is feasible and safe (Catanzariti et al.), but requires normal function of the bundle branches and Purkinje system. Implantation is also difficult to perform. Long term reliability of His pacing is unknown. For Kutarski et al., RV outflow tract (RVOT) pacing is preferable to RV apical pacing. But for van Gelder, RV apical pacing is preferred for CRT patients. In our experience, RVOT and RV apical pacing provide similar haemodynamic results on average, but may induce significant individual differences. To help to understand individual requirements, one of the main targets for manufacturers is to propose haemodynamic sensors that could evaluate and guide the benefits of various pacing sites, such as …

Implantable cardioverter defibrillators (ICDs) reduce sudden arrhythmic death risk but when these devices are programmed DDD and pace in the right ventricle (RV), they can be associated with increased mortality and heart failure morbidity compared to an ICD programmed to back-up RV. An ideal ICD would provide effective treatment for life-threatening tachyarrhythmias, reduce unnecessary RV pacing and maintain AV synchrony. The Inhibition of Unnecessary RV Pacing with AV Search Hysteresis (AVSH) in ICDs (INTRINSIC RV) study will assess whether an ICD programmed to DDDR with AVSH is equal to an ICD programmed to VVI with regard to mortality, heart failure hospitalizations, and several predefined secondary enpoints. AVSH allows intrinsic AV conduction beyond the programmed AV delay to help minimize ventricular pacing. INTRINSIC RV, a multi-center, randomized, prospective trial will enroll >1,200 participants who receive a Guidant VITALITY AVT ICD. ICDs are programmed initially to DDDR AVSH 60–130. Then, after a week, if the %RV pacing

Woldemar Mobitz, an early 20th century German internist, analyzed arrhythmias by graphing the relationship of changing atrial rates and premature beats to AV conduction. Through an astute mathematical approach, he was able to classify second-degree atrioventricular block into 2 types, subsequently referred to as Mobitz type I (Wenckebach) and Mobitz type II (Hay). Type I AV block was most often due to digitalis and was reversible. There were no associated pathological findings. Type II AV block frequently progressed to complete AV block and was associated with seizures, death, and pathological findings.

A 63-year-old man undergoing treatment for Parkinson's disease and with no history of cardiac disease showed a newly emergent arrhythmia during a follow-up visit. The 12-lead ECG suggested atrial flutter with a cycle length of 180 ms (330 cycles/min or 5.5 Hz) pattern in all the leads. With an intrinsic ventricular rate of 86 bpm, the initial machine-based assessment was atrial flutter with 4:1 AV conduction. Multiple ECGs were recorded and a closer scrutiny of the serially recorded digital ECG waveforms manually helped in ruling out the arrhythmia and diagnosing it as a Parkinson's tremor-induced artifact.