DDD Pacemaker Research Articles

Routine use of biventricular pacing is not warranted for patients with heart block.

Ventricular pacing can be lifesaving for patients with complete atrioventricular block (AVB). Since the introduction of permanent transvenous cardiac pacing >40 years ago, the right ventricular (RV) apex has been the preferred site for ventricular stimulation. This location provides good fixation and low capture thresholds. However, RV apical pacing may induce cardiac dyssynchrony. Hence, it has been suggested that all patients with symptomatic AVB (regardless of current indication for biventricular pacing), with anticipated high RV pacing burden, should receive preventive biventricular pacing. In this article, we review the physiological effects of RV pacing, data from observational studies (Table I in the Data Supplement),1–6 and available randomized trials comparing biventricular versus RV pacing (Table).7–16 View this table: Table. Randomized Controlled Studies Comparing Right Ventricular and Biventricular Pacing Response by Fang et al on p 738 Since the initial report of the use of endocardial pacing to treat complete AVB by Furman and Schwedel in 195917, pacemakers have evolved dramatically into complex devices with the ability to sequentially pace the atrium and both ventricles. Between 1993 and 2009, 2.9 million patients received a permanent pacemaker in the United States.18 During this time, overall pacemaker use increased by 55.6%. However, although the use of dual chamber (DDD) pacemakers increased by at least 40%, the use of single-chamber ventricular (VVI) pacemakers decreased ≈50%,18 despite the evidence from large pacing trials19–21 indicating no major differences in outcomes between single and dual chamber pacing modes. In fact, by 2009, DDD pacemakers accounted for 82% of all implants (VVI for only 14%).18 These statistics speak loudly about the impact of technology on daily clinical practice. A similar quandary now exists with regards to biventricular pacing. We suggest that the global utilization of biventricular pacing for all …

Inny scenariusz hamowania kardiostymulatora typu DDD. Czy zawsze winne są elektrody unipolarne?

We present 24-hour electrocardiography recording with observed DDD pacemaker pacing inhibition. Discussed Holter monitoring fi ndings are puzzling and may result from pacemaker sensing malfunction. However, its aetiology may be diverse. The detailed explanation of underlying mechanisms is provided and literature is reviewed.

Torsade de pointes in a patient with complete atrioventricular block and pacemaker failure, misdiagnosed with epilepsy

A case of torsade de pointes (TdP) with complete atrioventricular block and pacemaker failure that was misdiagnosed as epilepsy is presented herein. An 82-year-old female with recurrent seizure-like attacks showed epileptiform discharge during an electroencephalogram recording. A long QT interval and severe hypokalemia induced runs of TdP, which was related to pacemaker lead fracture, was detected during Holter recording and accompanied with episodes of seizures. After a DDD pacemaker with a new ventricular lead was replaced, there was no recurrence of any seizure-like attacks. Bradycardia-mediated TdP associated with complete atrioventricular block should not be missed in patients with recurrent seizure-like attacks even after pacemaker implantation.

Prevalence of E/A wave fusion and A wave truncation in DDD pacemaker patients with complete AV block under nominal AV intervals.

AimsOptimization of the AV-interval (AVI) in DDD pacemakers improves cardiac hemodynamics and reduces pacemaker syndromes. Manual optimization is typically not performed in clinical routine. In the present study we analyze the prevalence of E/A wave fusion and A wave truncation under resting conditions in 160 patients with complete AV block (AVB) under the pre-programmed AVI. We manually optimized sub-optimal AVI.MethodsWe analyzed 160 pacemaker patients with complete AVB, both in sinus rhythm (AV-sense; n = 129) and under atrial pacing (AV-pace; n = 31). Using Doppler analyses of the transmitral inflow we classified the nominal AVI as: a) normal, b) too long (E/A wave fusion) or c) too short (A wave truncation). In patients with a sub-optimal AVI, we performed manual optimization according to the recommendations of the American Society of Echocardiography.ResultsAll AVB patients with atrial pacing exhibited a normal transmitral inflow under the nominal AV-pace intervals (100%). In contrast, 25 AVB patients in sinus rhythm showed E/A wave fusion under the pre-programmed AV-sense intervals (19.4%; 95% confidence interval (CI): 12.6–26.2%). A wave truncations were not observed in any patient. All patients with a complete E/A wave fusion achieved a normal transmitral inflow after AV-sense interval reduction (mean optimized AVI: 79.4 ± 13.6 ms).ConclusionsGiven the rate of 19.4% (CI 12.6–26.2%) of patients with a too long nominal AV-sense interval, automatic algorithms may prove useful in improving cardiac hemodynamics, especially in the subgroup of atrially triggered pacemaker patients with AV node diseases.

0446: Septal right ventricular lead positioning and optimized DDD pacing versus intrinsic conduction in sinus node disease: an echocardiographic study. The optimist trial

Preserved intrinsic conduction in paced sinus node disease (SND) patients seems to be associated with a better outcome when compared with apical right ventricular (RV) DDD pacing.The prospective, multicenter, randomized OPTIMIST study was designed to compare RV lead positioning in the septum to preserved intrinsic conduction in chronically paced SND patients. SND patients with a class I indication were implanted with a DDD pacemaker (St. Jude medical), the RV lead being located in the midseptum. The algorithm VIP™ (Ventricular Intrinsic Preference) was programmed « on » in all patients at hospital discharge. After a 6 weeks observational period, patients with a ventricular pacing percentage inferior to 10% were randomized in 2 parallel groups: VIP « on » (preserved natural conduction - group 1) or « off » with AV delay optimization (RV pacing - group 2). Patients were followed every 6 months with echocardiography through 18 months. The primary endpoint was the left ventricular end-systolic diameter (LVESD) (Corelab analysis), with a non inferiority hypothesis. 216 patients mean age 76.07±9.45 were included and 167 randomized. The baseline characteristics were comparable in group 1 and 2 including left ventricular ejection fraction, LVEF (62.4±12.6 vs 64.4±8.7%), LVESD (32.7±8.5 vs 32.5±9.3mm) and 6 weeks RV pacing percentage (1.81±1.92 vs 2.15±2.07%). At the end of FU, as expected the percentage of RV pacing was significantly higher in group 2 (78.9±31.6 vs 7.9±17.4%). The LVEF was 62.3±10.1% in group 1 and 60.9±10.9% in group 2 (NS) and the LVESD was 31.9±7.23mm in group 1 and 31.26±7.21mm in group 2 (NS).The non-inferiority hypothesis was validated (p=2.572e-06 for a delta = 4.785). AF burden was not different between the 2 groups. When implanting the RV lead in the midseptum, DDD pacing with high percentage of RV capture was not associated with LV echocardiographic deterioration as compared to preserved intrinsic conduction pacing mode. January 17 th , Saturday 2015

Successful Implantation of Bipolar Epicardial Leads and Dual Chamber Pacemaker in Infant After Postoperative Atrioventricular Heart Block

Total atrioventricular (AV) block is inconvenient and serious complication of open heart surgery. Permanent total AV block requires the implantation of permanent pacemaker in order to allow normal hemodynamics and patient’s survival. In infancy additional challenge is the surgical approach, the selection of electrodes and PM, as well as place of implantation. We are publishing case report of successful double-chamber DDD pacemaker implantation at an infant born with Fallot tetralogy and with low birth weight due to complete AV block after primary surgical correction of these congenital defects.

Comparison of early effects of right ventricular apical pacing on left ventricular functions in single and dual chamber pacemakers

Abstract Objectives Our study aimed to demonstrate the early negative impact of right ventricular apical pacing induced by single (VVI) and dual chamber (DDD) pacemakers on LV functions in patients with preserved EF. And to assess that single brain natriuretic peptide (BNP) after 2 months of implantation is correlated to ventricular dyssynchrony. Methods 40 patients with implanted VVI and DDD pacemakers were examined before implantation and again after 2 and 6 months of implantation for BNP, left ventricular (LV) systolic and diastolic functions by echocardiography and pulsed tissue Doppler. After 6 months, patients with DDD pacemakers were crossed over to VVI mode of pacing for 2 weeks with lower rate programed to 60 beat per minute then sample for BNP was collected again. Results There was no statistically significant difference in LV systolic and diastolic functions except for myocardial performance index (MPI) with ( P value of 0.03). Mean BNP level in VVI pacing was higher than DDD pacing after two months with P value = 0.001 while comparison after 6 months showed P value = 0.023. There was a statistically significant difference between both groups in results of aortic preejection delay (APED) ( P value of r = 0.651 and P value = 0.001) and pacing percentage ( r = 0.687 and P value = 0.00). Conclusion Loss of atrioventricular synchrony in VVI mode leads to a significant difference in LV dyssynchrony between both groups. BNP level is correlated to LV dyssynchrony and pacing percentage.

Long-term follow-up after pacemaker implantation via persistent left superior vena cava

The persistent left superior vena cava (PLSVC) is a relatively common con-genital venous return anomaly. It may have serious clinical implications especially in case of pacemaker/cardioverter-defibrillator implantation, venous catheter insertion, radio-frequency ablation and cardiac surgery. There is also some evidence that PLSVC may be accompanied by arrhythmias. The aim of this report is to present the effectiveness and safety of cardiac pacing via PLSVC, clinical outcome and appearance of arrhythmias in a long-term follow-up. Four cases of pacing electrodes implanted via PLSVC in patients without any other cardiac congenital heart anomalies were observed for at least 6 years. There was 1 patient with AAI, 2 patients with VVI, and 1 with DDD pacemaker. Atrial electrodes were implanted on the free right atrial wall, 2 ventricular electrodes were implanted in right ventricular outflow tract, 1 in postero-lateral cardiac vein. During the mean 110 months of observation, pacing was efficient. One patient underwent an upgrade from AAI to biatrial pac-ing due to progressive interatrial conduction delay during the follow-up. No other intervention or pacemaker related events were noticed except for battery replacement. The presence of PSVC may complicate implantation, but it does not influence the long-term follow-up of pacing parameters.

Automated functional imaging in atrioventricular delay time optimisation in patients with dual chamber pacemakers

Optimisation of atrioventricular (AV) delay time has positive effects on left ventricular (LV) functions in patients with a DDD pacemaker. However, the method used for optimisation is still debated. To evaluate the effect of different AV delay times on various LV systolic performances by using automated functional imaging (AFI) in patients with a DDD pacemaker and preserved LV systolic function. The study population consisted of 40 patients with a DDD pacemaker implanted for third degree AV block and preserved LV systolic function (19 men; mean age 64.3 ± 10.9 years). During each pacing period, blood samples were taken for the measurement of B-type natriuretic peptide (BNP) levels, and telemetric and echocardiographic evaluations were performed to all patients. Also peak systolic global longitudinal strain (PSGLS) was calculated using the AFI method. No significant differences except for LV outflow tract-velocity time integral (LVOT-VTI) were observed in pulse wave Doppler parameters with different AV delay times. PSGLS were better at 150 and 200 ms AV delay times compared to 100 ms (p < 0.001 for 100-150 ms and 100-200 ms). Similarly, LVOT-VTI values were significantly higher at 150 and 200 ms AV delay times compared to 100 ms (for 100-150 ms, p = 0.017 and for 100-200 ms, p = 0.013). Also there was a significant reduction in BNP levels at 150 ms and 200 ms compared to 100 ms AV delay time (for 100-150 ms, p = 0.001, and for 100-200 ms, p < 0.001). In patients with an implanted DDD pacemaker and preserved LV systolic function, increasing AV delay time has beneficial effects on LV systolic performance in the acute phase, as shown by the AFI method in our study.

High-degree atrioventricular block in patients with preexisting bundle branch block or bundle branch block occurring during transcatheter aortic valve implantation.

Transcatheter aortic valve implantation (TAVI) has become the standard therapy for high-risk and non-operable patients with severe aortic stenosis. However, the procedure involves several adverse effects, such as rhythm and conduction disturbances. Patients with postprocedural left bundle branch block may have an increased mortality risk, whereas patients with preprocedural right bundle branch block display a higher rate of postinterventional bradyarrhythmias. The purpose of this study was to investigate the occurrence of high-degree atrioventricular block (AVB) in patients with preexisting bundle branch block (BBB) or BBB occurring during TAVI. In this prospective single-center study, 50 consecutive patients undergoing TAVI with the Medtronic CoreValve Revalving System were included. Of these patients, 17 with preexisting BBB or BBB occurring during TAVI received a primary prophylactic permanent DDD pacemaker, programmed to the SafeR-mode and featuring dual-channel event counters as well as stored intracardiac electrograms. Pacemaker readouts and intracardiac electrograms were analyzed for the occurrence of high-degree AVB. Ten of 17 patients (58.8%) with preexisting BBB or BBB occurring during TAVI developed episodes of high-degree AVB that were immediately terminated due to switch into DDD backup pacing. In 5 of the cases (29.4%), the first documented episode of high-degree AVB occurred after hospital discharge. Mean follow-up period was 578.1 ± 294.9 days. Development of high-degree AVB is a common complication in patients with preexisting BBB or BBB occurring during TAVI. Accordingly, intensified monitoring might be reasonable, especially in patients treated with the self-expandable Medtronic CoreValve Revalving System.

Remote-controlled magnetic navigation and ablation of atrial flutter in a patient with an extracardiac total cavopulmonary connection

Atrial tachycardias (AT) may occur in up to 50 % of patients following modifications of the Fontan operation [1]. The main challenge in patients with an extracardiac total cavopulmonary connection (TCPC) is the access to relevant structures such as the right atrium. Remote magnetic navigation (RMN) may offer the possibility to reach even complex anatomy without the risk of perforation or other complications [2]. A 28-year-old patient with double inlet left ventricle (LV), rudimentary right ventricle (RV), ventricular septal defect (VSD), pulmonary stenosis and ventriculo-arterial discordance had undergone a modified Fontan operation with connection of the pulmonary artery to the right atrium (RA) at the age of 5 years. Three years later, he began to suffer from recurrent ATs which necessitated antiarrhythmic drug (AAD) therapy with amiodarone as well as multiple cardioversions. In 2010, at the age of 25 years, the patient underwent a Fontan conversion operation [3] with a 20-mm extracardiac Goretex total cavopulmonary connection (TCPC). A DDD pacemaker with epicardial leads was implanted for sinus node dysfunction. Two years later, the patient began to suffer again from recurrent symptomatic tachycardia which was documented on the pacemaker Holter. He was taken to the electrophysiological lab for further evaluation and treatment. After venous and arterial puncture, an 8-polar steerable diagnostic catheter was introduced inside the conduit (XPT, C.R. Bard, Lowell, MA; USA). The right atrium could be sensed and captured via this access site. Mapping and ablation was performed with the use of the magnetic navigation system (Niobe II, Stereotaxis Inc, St Louis, MO) and a 3D mapping system (Carto3 RMT, Biosense Webster, Diamond Bar, CA, USA). A 7F irrigated-tip ablation catheter (Navistar RMT Thermocool, Biosense Webster) was introduced via a retrograde aortic approach into the RV. Using RMN, the LV was accessed via the VSD and finally the right and left atrium retrogradely passing the AV-valves (Fig. 1a). 3D-image integration with a previously performed CT scan (Fig. 1b) was used to facilitate the access. The atria were mapped in sinus rhythm (SR) and a scar area was delineated in the antero-lateral RA (Fig. 1c). Using programmed atrial stimulation, AT was induced with a cycle length (CL) of 480 ms and 1:1 AV conduction which corresponded to the pacemaker Holter recorded CL. Positive entrainment was confined to a limited zone of fractionated electrograms on the border region of the scar area, suggesting a localized re-entry mechanism. Irrigated radiofrequency (RF) energy with a maximum power of 38 W, a maximum temperature of 43 C and a flow rate of 30 ml/min was delivered in this zone and achieved termination to SR. For substrate modification, we then performed an ablation of all fragmented signals around the scar zone. After ablation, programmed stimulation and bursts failed to reinduce AT. The total procedure time was 200 min, with a total fluoroscopy time of 9 min and a fluoroscopy dose of 719 cGy/cm (with a total dose including the preinterventional CT scan of 735.1 cGy/cm). The patient has remained free from recurrent arrhythmia off AAD for the last 18 months. This was documented on the pacemaker Holter. S. Ammar (&) I. Deisenhofer T. Reents G. Hessling Deutsches Herzzentrum Munchen, Technische Universitat Munchen, Lazarettstrasse 36, 80636 Munich, Germany e-mail: ammar@dhm.mhn.de

Pacemaker diagnostics in atrial fibrillation: limited usefulness for therapy initiation in a pacemaker practice.

We aimed to determine the practical value of pacemaker diagnostics for atrial fibrillation (AF) in an unselected general pacemaker practice, specifically workflow and initiation of anticoagulation or antiarrhythmic drug (AAD) therapy. We prospectively followed consecutive pacemaker interrogations over a period of 1 year to identify patients with AF (burden from 1% to 99%). We contacted referring physicians with AF details, and then determined whether the information resulted in therapeutic changes. Of the 1,100 pacemakers interrogated, 728 were dual chamber (DDDs) with AF diagnostic capability. AF was recorded in 73 (10%) but seven had limited information, leaving 66 patients; of these, 42 (63%) patients were already anticoagulated and in five (7%) patients, anticoagulation had been stopped because of complications. Initial diagnosis of AF was made by the pacemaker in 17 patients (26% of 66; 2% of 728); four (6% of 66) patients were newly initiated on anticoagulation. Of the 66 patients, 17 patients were already on AADs; 49 (74%) had satisfactory rate control or had other issues; only two (3% of 66; 0.3% of 728) received new AADs. Of 728 patients with DDD pacemakers, only 17 were newly discovered to have AF, and six (0.8%) had changes in medications based on the pacemaker data. Adding pacemaker-derived data to existing clinical information had little therapeutic impact, due to a combination of cumbersome workflow, and because AF was usually known to practitioners. Developments in automated monitoring systems may provide more accessible and therapeutically useful information.

Influence of Atrioventricular Optimization on Hemodynamic Parameters and Quality of Life in Patients with Dual Chamber Pacemaker with Ventricular Lead in Right Ventricular Outflow Tract

The aim of this study was to ascertain whether individual atrioventricular delay (AVD) optimization using impedance cardiography (ICG) offers beneficial hemodynamic effects as well as improved exercise tolerance and quality of life in patients with requiring constant right ventricular pacing. There were 37 patients with advanced AV block included in the study. Several examinations were performed at the beginning. Next, the optimization of AVD by ICG was done. The next step of the study patients have been randomized into optimal AVD group (AVDopt) or factory setting group (AVDfab). After 3 months, the follow-up all data were collected again and crossover was performed. After another 3 months, during the final follow-up all these measures were repeated. In 87.5% patients, AVDopt were different than factory value. Cardiac output (CO), cardiac index (CI), and stroke volume (SV) were significantly (P < 0.001) higher in AVDopt group than in AVDfab group (CO: 6.0 ± 1.4 L/minute vs. 5.3 ± 1.2 L/minute; SV: 85.8 ± 25.7 mL vs.76.9 ± 22.5 mL; CI: 3.2 ± 0.7 L/minute/m(2) vs. 2.7 ± 0.6 L/minute/m(2) ). There was a statistical significant (P < 0.05) reduction of proBNP and NYHA class in patients with AVDopt compared to AVDfab (proBNP: 196.4 ± 144.7pg/mL vs. 269.4 ± 235.8 pg/mL; NYHA class: 1.7 ± 0.5 vs. 2.3 ± 0.6). Six-minute walking test was significantly (P < 0.05) higher in AVDopt group (409 ± 90 m) than in AVDfab group (362 ± 93 m). There were no statistically significant differences in echocardiographic parameters between AVDopt and AVDfab settings. Our study results suggest that AVD optimization in patients with DDD pacemaker with ICG improves hemodynamic when compared to the default factory settings. Furthermore, optimally programmed AVD reduces BNP and improves exercise tolerance and functional class.

Bidirectional Ventricular Tachycardia?

A 65-year-old woman was admitted to the hospital because of a syncopal episode with documented transient complete atrioventricular block. A DDD pacemaker was implanted. Post implantation, the patient was diagnosed with bidirectional ventricular tachycardia. Analysis of the arrhythmia and differential diagnosis is performed.

Automated Functional Imaging in Atrioventricular Delay Time Optimization in Patients with Dual Chamber Pacemakers

OP-020 Optimization of atrioventricular (AV) delay time has positive effects on left ventricular functions in patients with DDD pacemaker. Although echocardiographic methods are still the most commonly used ones for the optimization of AV delay time, the gold standard method used for optimization

Bachmann's bundle pacing not only improves interatrial conduction but also reduces the need for ventricular pacing

Background: Patients treated for sick sinus syndrome may have interatrial conduction disorder, what often leads to atrial fibrillation. Moreover, up to 20% of them have atrioventricular conduction delay which worsens over time and is responsible for the need of ventricular pacing. Implantation of atrial lead in right atrium appendage (RAA) is the reason for longer interatrial and atrioventricular conduction time even in patients without prior disorders. Purpose: The aim of this study was to assess influence of atrial pacing site on interatrial and atrioventricular conduction and the percentage of ventricular pacing in population with SSS implanted with DDD pacemaker. Methods: The study group consisted of 107 patients (64 F, 43 M) aged 71,2±18,7 years. Patients were divided in two groups: group I (n=51) with RAA pacing, group II (n= 56) with Bachmann's area pacing. Differences in atrioventricular conduction in sinus rhythm and AAI 60 and 90/min pacing were assessed. Also P wave width at sinus rhythm and during atrial pacing as well as percentage of ventricular stimulation were compared. P wave morphology was studied in surface ECG leads I and II. Results: There were no differences in baseline P wave duration in sinus rhythm between the groups (99.7±16 ms vs 103.0±28 ms, p=n.s.). Atrial pacing 60 bpm revealed longer P wave duration with atrial lead location in RAA in comparison to Bachmann's bundle region (141.1±24.3 vs 107.2±14.2 ms, p<0.01). In group II the P wave morphology was more comparable with sinus P wave. The differences between atrioventricular conduction time during sinus rhythm and atrial pacing at 60 and 90 bpm were significantly longer in patients with RAA vs. Bachmann's pacing (42.1±16 vs 8±7 ms p<0.01 and 68±32 vs 22±11 ms p<0.005, respectively). The percentage of ventricular pacing was higher in group I (19±1 vs 3±3%, p<0,01). Conclusions: 1. Right atrium appendage pacing in SSS pts promotes atrioventricular conduction disorder which results in higher percentage of ventricular pacing in DDD mode. 2.The Bachmann's bundle region pacing of right atrium results in less pronounced interatrial and atrioventricular conduction delay.

Very late effects of dual chamber pacing therapy for obstructive, hypertrophic cardiomyopathy

Background: The very long-term effects of dual chamber pacing as a primary treatment for hypertrophic obstructive cardiomyopathy (HOCM) are poorly known and controversial. Objective: To examine the intermediate- and long-term clinical and hemodynamic effects of permanent, dual chamber pacing in patients presenting with HOCM. Methods: Between 1991 and 2007, 51 patients (mean age = 59±14 years) presenting with HOCM and New York Heart Association (NYHA) functional class ≥ 2 despite optimal medical therapy, underwent implants of DDD pacemakers with or without defibrillator and were followed for 11.5 years (range 0.4 - 21.8). Results: During follow-up, no patient underwent myectomy or septal alcohol ablation. NYHA functional class and other disease manifestations decreased significantly between 1 and 2 years of follow-up and remained stable thereafter. The left intraventricular (LV) gradient decreased by a mean of 78% between 1 and 2 years, to reach 89% at the end of follow-up, along with the disappearance of systolic anterior motion of the mitral valve. Mean LV ejection fraction decreased from a mean of 64±8% before pacing to 56±9% at the end of follow-up (P=0.05), while LV end-diastolic diameter did not change significantly. The 5- and 10-year actuarial survival rates were 90 and 65%, respectively. Among 22 deaths, 10 were due to cardiovascular and 12 to non-cardiovascular causes; 2 patients underwent cardiac transplantation after 8 and 13 years of DDD pacing, respectively. Conclusions: In this sample of patients suffering from HOCM, DDD pacing alleviated symptoms and improved hemodynamic function over the very long term. The merits of this treatment should be revisited in a controlled trial.

GW24-e1129 The analysis of cardiac resynchronisation therapy in right ventricular pacing patients

ObjectivesAcording an investigaion of 417 Grade A hospitals in China of recent 10 years, pacemaker implantation has been raising at an average of 11% per year. Overwhelming majority were received...

Recurrent syncope: a slow heart rate?

Answer to the rhythm puzzle The ECG shows a total atrioventricular block with junctional escape complexes, although the ninth QRS complex may be conducted. The second and eighth QRS complexes result from a retrogradely conducted P wave (Fig. 2). This mechanism, in which an escape complex is followed by a conducted complex, is called an escape-capture bigeminy. This only happens if the R-P interval of the retrograde P wave is long enough (along the slow AV nodal pathway) to be conducted back to the ventricles along the fast AV nodal pathway. When the P wave is caused by retrograde conduction along the fast AV nodal pathway, anterograde AV nodal conduction is blocked, resulting in a blocked P wave (after the third, fifth and (probably) tenth QRS complex). Fig. 2 Ladder diagram of a retrograde P wave conducted back to the ventricles and a blocked retrograde P wave Lithium intoxication was diagnosed based on the clinical symptoms (sinus node dysfunction and lethargy) and on a serum level of 0.88 mmol/l which is considered to be toxic at this age. Since lithium treatment was considered to be the most beneficial therapy for this patient, a DDD pacemaker was implanted. This was done successfully and without any complications, after which she was discharged from our centre.

Recurrent syncope: a slow heart rate?

Answer to the rhythm puzzle The ECG shows a total atrioventricular block with junctional escape complexes, although the ninth QRS complex may be conducted. The second and eighth QRS complexes result from a retrogradely conducted P wave (Fig. 2). This mechanism, in which an escape complex is followed by a conducted complex, is called an escape-capture bigeminy. This only happens if the R-P interval of the retrograde P wave is long enough (along the slow AV nodal pathway) to be conducted back to the ventricles along the fast AV nodal pathway. When the P wave is caused by retrograde conduction along the fast AV nodal pathway, anterograde AV nodal conduction is blocked, resulting in a blocked P wave (after the third, fifth and (probably) tenth QRS complex). Fig. 2 Ladder diagram of a retrograde P wave conducted back to the ventricles and a blocked retrograde P wave Lithium intoxication was diagnosed based on the clinical symptoms (sinus node dysfunction and lethargy) and on a serum level of 0.88 mmol/l which is considered to be toxic at this age. Since lithium treatment was considered to be the most beneficial therapy for this patient, a DDD pacemaker was implanted. This was done successfully and without any complications, after which she was discharged from our centre.