Clinical performance of implantable cardioverter-defibrillator lead monitoring diagnostics.

BACKGROUND: Implantable cardioverter-defibrillator (ICD) lead monitoring diagnostic alerts facilitate the diagnosis of structural lead failure. OBJECTIVE: The purpose of this study was to prospectively study the performance of Medtronic ICD lead monitoring alerts. METHODS: A prespecified ancillary substudy, World-Wide Randomized Antibiotic Envelope Infection Prevention Trial, was conducted in patients with an ICD with all available alerts enabled. The investigators reported possible lead system events (LSEs), with or without an alert. An independent committee reviewed all data and classified events as lead failure, other LSE, or nonlead system events (NLEs). RESULTS: In 4942 patients who were followed for 19.4 ± 8.7 months, there were 124 alerts (65 LSEs, 59 NLEs) and 19 LSEs without an alert. Lead monitoring alerts had 100% sensitivity for the 48 adjudicated lead failures (95% confidence interval 92.6%-100%) and for 10 events adjudicated as either lead failure or connection issue. The positive predictive value of alerts for lead failure was 38.7% (48 of 124). For 34 pace-sense lead failures, an alert that incorporated oversensing was more sensitive than the pacing impedance threshold alert (33 patients [97.1%] vs 9 patients [26.5%]; P < .0001). However, the sensitivity was only 13.6% for lead dislodgments or perforations. Inappropriate shocks occurred in 2 patients with pace-sense lead failure (5.9%). No patient had unnecessary lead replacement for any of the NLEs. CONCLUSION: In this first real-world prospective study, lead monitoring alerts had 100% sensitivity for identifying lead failures. Although their positive predictive value was modest, no false-positive alerts resulted in an unnecessary lead replacement. For the diagnosis of pace-sense lead failure, an alert for oversensing was more sensitive than a pacing impedance threshold alert. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02277990.

Long-term cerebral thromboembolic complications of transapical endocardial resynchronization therapy.

PURPOSE: Cardiac resynchronization therapy (CRT) is an established therapeutic option in selected heart failure patients (pts). However, the transvenous left ventricular (LV) lead implantation remains ineffectual in a considerable number of pts. Transapical LV (TALV) lead implantation is an alternative minimally invasive, surgical, endocardial implantation technique. The aim of the present prospective study is to determine the long-term outcome, including the cerebral thromboembolic complications, of pts who underwent TALV lead placement. METHODS: Twenty-six CRT candidates (19 men (78 %); mean age 61 ± 10 years) with a previously failed transvenous approach underwent TALV lead placement as a last resort therapy. The following data was collected: mortality rate, reoperation rate, and cerebrovascular event rate. Patients underwent a cerebral CT scan to determine any possible cerebrovascular event related to the presence of the TALV lead. RESULTS: Eleven out of 26 (47 %) patients survived after a median follow-up of 40 ± 24.5 months. Major acute ischemic stroke occurred in two cases, while in one case transient ischemic stroke was observed. Cerebral CT scan examination performed in asymptomatic patients revealed chronic ischemic lesions with minimal extension in two patients. Reoperation occurred in one case due to TALV lead fracture. CONCLUSIONS: This is the first study reporting the long-term outcome, mortality, and thromboembolic event rate exclusively after TALV lead implantation. Patients who underwent TALV lead implantation have a comparable long-term mortality rate to conventional CRT, although a major ischemic cerebrovascular event after TALV lead implantation is worrisome and has an impact on the outcome.

[Catheter ablation of ventricular tachycardias]. / Kamrai tachycardiák katéterablatiós kezelése.

Catheter ablation of ventricular tachycardias emerged significantly as standard therapy in the past 20 years. In this review recent advances in catheter ablation of ventricular tachycardias are discussed. The authors first present in details the technical aspects of ablation strategies, main indications and contraindications of ventricular tachycardia ablation and the necessary pre- and postinterventional diagnostic tests. Outcome is also discussed in different forms of ventricular tachycardias in detail. The authors summarize the safety and efficacy of catheter ablation of ventricular arrhythmias. They recommend that ablation of ventricular tachycardias should be considered earlier in patients with and without structural heart disease.

Alternative techniques for left ventricular pacing in cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) is an important treatment modality for a well-defined subgroup of heart failure patients. Coronary sinus (CS) lead placement is the first-line clinical approach but the insertion is unsuccessful in about 5-10% of the patients. In recent years, the number of CRT recipients and the considerable need for left ventricular (LV) lead revisions increased enormously. Numerous techniques and technologies have been specifically developed to provide alternatives for the CS LV pacing. Currently, the surgical access is most frequently used as a second choice by either minithoracotomy or especially the video-assisted thoracoscopy. The transseptal or transapical endocardial LV lead implantations are being developed but there are no longer follow-up data in larger patient cohorts. These new techniques should be reserved for patients failing conventional or surgical CRT implants. In the future, randomized studies are needed to asses the potential benefits of some alternative LV pacing techniques and other new technologies for LV lead placement are expected.

Could successful cryoballoon ablation of paroxysmal atrial fibrillation prevent progressive left atrial remodeling?

BACKGROUND: Radiofrequency catheter ablation of atrial fibrillation (AF) has been proved to be effective and to prevent progressive left atrial (LA) remodeling. Cryoballoon catheter ablation (CCA), using a different energy source, was developed to simplify the ablation procedure. Our hypothesis was that successful CCA can also prevent progressive LA remodeling. METHODS: 36 patients selected for their first CCA because of nonvalvular paroxysmal AF had echocardiography before and 3, 6 and 12 months after CCA. LA diameters, volumes (LAV) and LA volume index (LAVI) were evaluated. LA function was assessed by: early diastolic velocities of the mitral annulus (Aa(sept), Aa(lat)), LA filling fraction (LAFF), LA emptying fraction (LAEF) and the systolic fraction of pulmonary venous flow (PVSF). Detailed left ventricular diastolic function assessment was also performed. RESULTS: Excluding recurrences in the first 3-month blanking period, the clinical success rate was 64%. During one-year of follow-up, recurrent atrial arrhythmia was found in 21 patients (58%). In the recurrent group at 12 months after ablation, minimal LAV (38 ± 19 to 44 ± 20 ml; p < 0.05), maximal LAV (73 ± 23 to 81 ± 24 ml; p < 0.05), LAVI (35 ± 10 to 39 ± 11 ml/m2; p = 0.01) and the maximal LA longitudinal diameter (55 ± 5 to 59 ± 6 mm; p < 0.01) had all increased. PVSF (58 ± 9 to 50 ± 10%; p = 0.01) and LAFF (36 ± 7 to 33 ± 8%; p = 0.03) had decreased. In contrast, after successful cryoballoon ablation LA size had not increased and LA function had not declined. In the recurrent group LAEF was significantly lower at baseline and at follow-up visits. CONCLUSIONS: In patients whose paroxysmal atrial fibrillation recurred within one year after cryoballoon catheter ablation left atrial size had increased and left atrial function had declined. In contrast, successful cryoballoon catheter ablation prevented progressive left atrial remodeling.

Coupled pacing controls rapid heart rates better than paired pacing during atrial fibrillation.

AIMS: Delivery of a ventricular extrastimulus shortly after the effective refractory period (ERP) of a sensed (coupled pacing; CP) or a paced (paired pacing; PP) ventricular event can instantly decrease the mechanical pulse rate (MPR) during rapidly conducting atrial fibrillation (AF). We compared the short-term rate-controlling effects of CP and PP during AF with rapid ventricular rates. METHODS AND RESULTS: Sixteen patients with ongoing, spontaneous AF were examined. Mechanical pulse rate was registered via arterial pressure tracings. During CP a coupling interval (CI) of ERP+20 ms was used to reach an optimal haemodynamic effect. Paired pacing was started at a basic cycle length (CL) of 500 ms followed by an extrastimulus with an CI of ERP+20 ms. Drive train was changed at 50 ms increments until the lowest MPR was reached. Proarrhythmic effects were characterized by the number of premature ventricular complexes (PVCs). Mechanical pulse rate significantly decreased in all patients during CP (113 ± 9 vs. 58 ± 4/min). Using CP the controlled rhythm remained irregular (CL range: 896 ± 24-1452 ± 67 ms) while no PVCs were observed. With different drive trains PP resulted in different regular MPRs (range 62 ± 6-80 ± 4/min), but the lowest MPR achieved was significantly higher in the PP group than in the CP. Paired pacing caused premature beats in nine patients (56%) resulting in loss of continuous MPR control. CONCLUSIONS: Both CP and PP can reduce the MPR during rapidly conducting AF. Coupled pacing is more applicable, but PP has the advantage to achieve different target heart rates. Paired pacing has more proarrhythmic effects as compared with CP.

Comparison of the efficacy of two surgical alternatives for cardiac resynchronization therapy: trans-apical versus epicardial left ventricular pacing.

BACKGROUND: Epicardial pacing lead implantation is the currently preferred surgical alternative for left ventricular (LV) lead placement. For endocardial LV pacing, we developed a fundamentally new surgical method. The trans-apical lead implantation is a minimally invasive technique that provides access to any LV segments. The aim of this prospective randomized study was to compare the outcome of patients undergoing either trans-apical endocardial or epicardial LV pacing. METHODS: In group I, 11 end-stage heart failure (HF) patients (mean age 59.7 ± 7.9 years) underwent trans-apical LV lead implantation. Epicardial LV leads were implanted in 12 end-stage HF patients (group II; mean age 62.8 ± 7.3 years). Medical therapy was optimized in all patients. The following parameters were compared during an 18-month follow-up period: LV ejection fraction (LVEF), LV end-diastolic diameter (LVEDD), LV end-systolic diameter, and New York Heart Association (NYHA) functional class. RESULTS: Nine out of 11 patients responded favorably to the treatment in group I (LVEF 39.7 ± 12.5 vs 26.0 ± 7.8%, P < 0.01; LVEDD 70.4 ± 13.6 mm vs 73.7 ± 10.5 mm, P = 0.002; NYHA class 2.2 ± 0.4 vs 3.5 ± 0.4, P < 0.01) and eight out of 12 in group II (LVEF 31.5 ± 11.5 vs 26.4 ± 8.9%, P = < 0.001; NYHA class 2.7 ± 0.4 vs 3.6 ± 0.4, P < 0.05). During the follow-up period, one patient died in group I and three in group II. There was one intraoperative LV lead dislocation in group I and one early postoperative dislocation in each group. None of the patients developed thromboembolic complications. CONCLUSIONS: Our data suggest that trans-apical endocardial LV lead implantation is an alternative to epicardial LV pacing.

[Cardiac resynchronization therapy for patients with atrial fibrillation]. / Kardiális reszinkronizációs terápia pitvarfibrilláló betegekben.

Atrial fibrillation and chronic heart failure are two major and even growing cardiovascular conditions that often coexist. Cardiac resynchronization therapy is an important, device-based, non-pharmacological approach in a selected group of chronic heart failure patients that has been shown to improve left ventricular function and to reduce both morbidity and mortality in large randomized trials. The latest European and American guidelines have considered atrial fibrillation patients with heart failure eligible for cardiac resynchronization therapy. This review summarizes current literature concerning the following topics: prognostic relevance of atrial fibrillation in heart failure, effects of cardiac resynchronization therapy in atrial fibrillation, relevance and strategies of rhythm and rate control in this group of patients. Authors explain how atrial fibrillation may interfere with the delivery of adequate cardiac resynchronization therapy, how to reduce the burden of atrial tachyarrhythmias, and finally present a brief overview.

Feasibility of percutaneous implantation of transapical endocardial left ventricular pacing electrode for cardiac resynchronization therapy.

Failure of coronary sinus lead implantation for resynchronization therapy requires alternative approaches. For such events we have developed a transapical implantation technique as a feasible alternative. We report the outcome of this technique and its evolution from a minithoracotomy to a percutaneous approach. Twenty patients underwent alternative resynchronization therapy with transapical endocardial left ventricular (LV) pacing lead implantation in a multicentre, international study between October 2007 and March 2010. Eighteen patients underwent minithoracotomy and transapical puncture under direct observation. Two recent patients had transthoracic echocardiography-guided percutaneous apical puncture to enter the LV cavity. A 19 or 21 ga needle and two-stage Seldinger dilatation with 4 and 7 Fr sheaths were then used to introduce the lead. In the two patients with closed-chest insertion of the electrode there was no puncture related bleeding or lung damage. Lead dislocation occurred in two minithoracotomy patients. Repositioning was performed without re-opening the pleural cavity. One patient developed right-sided implanted cardiac defibrillator lead endocarditis requiring complete system removal. Twelve patients have >1 year follow-up; all have sustained and significant improvement in LV dimensions (diastolic Δ4.2 ± 2.9, systolic Δ7.2 ± 5.8 mm), ejection fraction (Δ9.5 ± 9.6%), and functional status (Δ1.1 ± 0.3). Transapical placement of LV endocardial pacing lead is an effective alternative strategy for cardiac resynchronization. A closed-chest, percutaneous approach is feasible and should offer even less invasive intervention.

Extrasystolic stimulation with bi-ventricular pacing: an acute haemodynamic evaluation.

AIMS: Cardiac resynchronization therapy (CRT) by means of biventricular pacing (BiVP) is well established as a treatment for patients with heart failure (HF). Post-extrasystolic potentiation, (PESP) which involves a transient increase in myocardial contractility following a ventricular extrasystole, can be achieved using extrasystolic stimulation (ESS). On this basis, ESS has been proposed as a therapeutic. We assessed acute haemodynamic effects of ESS in the context of BiVP. METHODS AND RESULTS: Patients (n = 15, left ventricular ejection fraction < 40%, QRS ≥ 125 ms) with HF, received BiVP in combination with right ventricular (RV) ESS (single stimulus or pulse train). Left ventricular (LV) and peripheral arterial pressures were recorded and dP/dt was monitored. Addition of RV ESS to BiVP pacing led to a 21% increase in maximum (max) dP/dt (P < 0.001) and an 8.5 mm Hg increase in a systolic arterial pressure (P < 0.001). The modest fall in end-diastolic pressure (3.3 mmHg, P < 0.001) observed during ESS and BiVP was prevented by maintaining baseline sinus rate. Varying ESS modes or pacing outputs was not associated with differences in haemodynamic parameters. CONCLUSIONS: Biventricular pacing in combination with ESS, with maintenance of sinus rate, improves myocardial contractility in patients undergoing CRT.

[Effectiveness of D,L-sotalol in post-ablative atrial arrhythmias in patients with atrial fibrillation treated with radiofrequency ablation]. / D,l-sotalol hatásossága postablatiós arrhythmiák kezelésében, pitvarfibrilláció miatt rádiófrekvenciás ablatióval kezelt betegeknél.

UNLABELLED: Left atrial tachycardia is the most common arrhythmia developing after pulmonary vein (PV) isolation in patients with atrial fibrillation. AIM: To compare the clinical effectiveness of class Ic propafenone and class III D,L sotalol in antiarrhythmic treatment of post-ablation left atrial tachycardias. METHODS AND RESULTS: A total of 75 consecutive patients with an age of 55.4 +/- 7.14 (mean +/- SD) years underwent real electrical isolation of the pulmonary veins. Beside electroanatomical guidance, a circular mapping catheter was used to achieve total electrical disconnection of the pulmonary veins from left atrium at the antrum level. After procedure, the antiarrhythmic drug therapy was continued with the tendency to taper down during follow up visits. These were scheduled 1 and later 3 monthly after PV isolation. After the first 3 months follow-up period, left atrial tachycardia occurred in 21 patients (31.3 %). 11 of them were on propafenone therapy, 6 were on sotalol therapy and 4 patients with left atrial tachycardia received amiodarone. In the first and third group, after developing left atrial tachycardia, the 1C class drug or amiodarone was changed to III D,L sotalol. In the second group, after developing left atrial tachycardia, the III D,L sotalol was changed to 1C class drug. 9 months later, in III D,L sotalol treated group of left atrial tachycardia patients (15), the drug was considered effective in 12 patients. CONCLUSION: In prevention of left atrial tachycardia occurred after PV isolation, sotalol is not more effective than 1C class propafenone. Otherwise, III D,L sotalol seems to be effective in anti-arrhythmic treatment of developed post-ablation in late left atrial tachycardias.

A novel approach for endocardial resynchronization therapy: initial experience with transapical implantation of the left ventricular lead.

BACKGROUND: Coronary sinus lead placement for transvenous left ventricular (LV) pacing in cardiac resynchronization therapy (CRT) has a significant failure rate at implant and a considerable dislocation rate during follow-up. For these patients epicardial pacing lead implantation is the most frequently used alternative. Recent data support endocardial lead implantation through the atrial septum and the mitral valve, because this method provides further hemodynamic advantages. On the other hand transseptal CRT carries a significant risk for device related infective endocarditis of the mitral valve. The aim of this prospective, nonrandomized study was to demonstrate the feasibility of a fundamentally new approach for endocardial LV lead implantation. METHODS: We performed 12 transapical LV lead implantations in 10 end-stage heart failure patients. In each operation an active fixation lead was placed into the LV cavity using standard Seldinger technique through the LV apex. By use of a J-shaped guide wire, the tip of the lead was positioned and fixed into the basal-lateral segment of the LV under fluoroscopy guidance. Pacing parameters were assessed and found to be optimal in all patients. The lead was conducted through the chest wall near the apex into a subcutaneous tunnel up to the pocket of the previously implanted device. After surgery the patients are anticoagulated with target anticoagulation level identical to mechanical valve prostheses. RESULTS: In 8 patients there were no major or minor complications related to this new technique. During the follow-up period (mean 7.2 +/- 4.1 months) all patients responded favorably to the treatment. One lead dislocation and 1 pocket infection were detected; the lead repositioning and replacing could be performed without reopening of the pleural cavity. CONCLUSIONS: The potential advantages of this new technique are that it is minimally invasive, endocardial, and does not involve the mitral valve. LV lead repositioning can also be performed minimally invasively.

Cavotricuspid isthmus ablation with large-tip gold alloy versus platinum-iridium-tip electrode catheters.

BACKGROUND: Gold has excellent electrical conductive properties and creates deeper and wider lesions than platinum-iridium during radiofrequency (RF) ablation in vitro. We tested the maximum voltage-guided technique (MVGT) of cavotricuspid isthmus (CTI) ablation using two 8-mm tip catheters containing gold (group G) or platinum-iridium (group PI). METHODS: We enrolled 31 patients who underwent CTI ablation. In group G (n = 15) CTI ablation was performed with a gold-tip ablation catheter, while in group PI (n = 16) a platinum-iridium tip was used. Ablation was guided by CTI potentials with the highest amplitude until achievement of bidirectional block (BIB). If BIB was not achieved after 10 RF applications, RF was delivered via a 3.5-mm irrigated-tip catheter. Success rate, procedure duration, duration of fluoroscopic exposure, and number of RF applications were measured. RESULTS: BIB was achieved in all patients in group G, while in group PI an irrigated tip was used in four patients (0% vs 25%, P < 0.001). These four patients required a total of 21 additional RF applications (5.25 +/- 2.22). Procedure time (56.4 +/- 12 vs 73.1 +/- 15 minutes P < 0.05) and fluoroscopic explosure (4.9 +/- 2.3 vs 7.1 +/- 3.8 minutes, P < 0.01) were shorter in group G than in group PI. Mean number of RF applications was lower (4.6 +/- 1.9 vs 6.6 +/- 3.1 P < 0.001) and total RF duration shorter (280 +/- 117 vs 480 +/- 310 seconds) in group G than in group PI. No difference was observed in the number of recurrences at a 6 month-follow up (1 in group G vs 1 in group PI). CONCLUSION: Using the MVGT of CTI ablation, gold-tip catheters were associated with shorter procedural and fluoroscopic times, and fewer RF applications.

[New method for the treatment of atrial fibrillation: circumferential cryoballoon ablation of the pulmonary vein]. / A paroxizmális pitvarfibrilláció kezelésének új módszere: cryoballonos pulmonalis véna cirkumferenciális ablatiója.

Atrial fibrillation is the most frequent arrhythmia with increasing prevalence. Given a limited success rate of drug therapy for atrial fibrillation, interventional treatment options have been developed during the last years. Catheter ablation of atrial fibrillation (until recently the mostly used energy source was radiofrequency energy) has been established as an important therapeutic alternative. Depending on interpersonal (both on patient and operator side) and technical variabilities using radiofrequency energy potentially life-threatening complications such as pulmonary vein stenosis or atrio-esophageal fistulas may occur. Cryoenergy is a novel energy source for transcatheter ablation eliminating the arrhythmia substrate by freezing. The cornerstone of catheter ablation for atrial fibrillation is electrical isolation of the pulmonary veins. During cryoballoon ablation the targeted pulmonary vein transiently occluded by the inflated balloon catheter and using this method a circumferential lesion is created. The success rate of cryoballoon ablation is comparable with the radiofrequency ablation with increased safety. We performed the first cryoballoon ablations for patients with paroxysmal atrial fibrillation in Hungary. On this occasion we review the potential advantages of this technique which may serve as basis for its widespread use in the future.

[Electroanatomical mapping systems in catheter ablation of cardiac arrhythmias]. / Elektroanatómiai térképezô rendszerek a ritmuszavarok katéterablatiós kezelésében.

Due to the recent technical development of the past years, most cardiac electrophysiological laboratories are equipped with computer-based electroanatomical mapping systems that precisely describe both the temporal and spatial characteristics of cardiac activation. This development has also been driven by the need for increased accuracy in arrhythmia localization as required for catheter ablation. Computer-based electroanatomical mapping systems are able to reconstruct cardiac anatomy and provide a straightforward representation of chamber activation. These systems capture and display details of intracardiac physiology and mark the site of interventions. Nowadays, several mapping technologies are available in the electrophysiological labs: CARTO XP, EnSite NavX and Array, Real-time Position Management. In this paper we aim to briefly present the principal technological and practical characteristics of these mapping systems regarding eligibility, ability and limitations. The development of computer-based mapping technologies is also discussed in detail, since future systems will be able to display any parametric process including vectors, strains, contraction patterns etc., a wide variety of physiologic parameters beyond activation times and voltage. Using electroanatomical mapping systems, the specific recording of both anatomy and physiology has contributed substantially to the expansion of ablation to atypical atrial flutters, ventricular tachycardia, congenital heart-disease-related arrhythmias and atrial fibrillation. While the technology is already facilitating, the obvious down-side to this technological explosion is cost. Subsequent studies will be needed, however, to show that this translates into improved outcomes and cost savings.

[Implantation of subcutaneous defibrillator in a patient treated for recidive endocarditis, previously operated for tetralogy of Fallot]. / Szubkután defibrillátorrendszer implantációja recidív endocarditisszel kezelt, korábban Fallot-tetralógia miatt mutött fiatal betegnél.

UNLABELLED: Implantable cardioverter-defibrillator implantation is an important adjunct in the management of these patients, although cardiac device endocarditis is an infrequent, but potentially lethal infectious complication. Cure of cardiac device endocarditis is achievable in the large majority of patients treated with an aggressive approach of combined antimicrobial treatment and complete cardiac device removal. Re-implantation of the device requires additional caution, but still associated with increased risk for recurrences. AIM: The aim of this case presentation is to demonstrate the feasibility of permanent subcutaneous defibrillation system in a patient with recurrent endocarditis. METHOD: In our case a 37-year-old patient--operated several times due to Fallot tetralogy, with permanent pacemaker and later implantable cardioverter defibrillator, requiring several replacements--was treated with recurrent device endocarditis. After device explantation and long-term standard antibiotic treatment, in order to decrease further risk for the development of recurrent endocarditis, we implanted a defibrillation system with an individually designed subcutaneous lead configuration. CONCLUSION: This case report suggests that individually tailored defibrillator lead configuration is a feasible option for patients until a fully automatic effective subcutaneous system will be available.

Mid-term echocardiographic follow up of left ventricular function with permanent right ventricular pacing in pediatric patients with and without structural heart disease.

BACKGROUND: Chronic right ventricular apical pacing may have detrimental effect on left ventricular function and may promote to heart failure in adult patients with left ventricular dysfunction. METHODS: A group of 99 pediatric patients with previously implanted pacemaker was studied retrospectively. Forty-three patients (21 males) had isolated congenital complete or advanced atrioventricular block. The remaining 56 patients (34 males) had pacing indication in the presence of structural heart disease. Thirty-two of them (21 males) had isolated structural heart disease and the remaining 24 (13 males) had complex congenital heart disease. Patients were followed up for an average of 53 +/- 41.4 months with 12-lead electrocardiogram and transthoracic echocardiography. Left ventricular shortening fraction was used as a marker of ventricular function. QRS duration was assessed using leads V5 or II on standard 12-lead electrocardiogram. RESULTS: Left ventricular shortening fraction did not change significantly after pacemaker implantation compared to preimplant values overall and in subgroups. In patients with complex congenital heart malformations shortening fraction decreased significantly during the follow up period. (0.45 +/- 0.07 vs 0.35 +/- 0.06, p = 0.015). The correlation between the change in left ventricular shortening fraction and the mean increase of paced QRS duration was not significant. Six patients developed dilated cardiomyopathy, which was diagnosed 2 months to 9 years after pacemaker implantation. CONCLUSION: Chronic right ventricular pacing in pediatric patients with or without structural heart disease does not necessarily result in decline of left ventricular function. In patients with complex congenital heart malformations left ventricular shortening fraction shows significant decrease.