Chronotropic incompetence in young patients with late postoperative atrial flutter: a case-control study.
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AIMS: Atrial flutter causes late postoperative morbidity in congenital heart disease (CHD). Sinoatrial node dysfunction is associated with late postoperative atrial flutter, but pacing interventions driven by minimum heart rates (HR) have yielded mixed results. METHODS AND RESULTS: A retrospective case-control study was used to test the hypothesis that late postoperative atrial flutter is associated with chronotropic incompetence in active young CHD patients. Control CHD patients aged < or =18 years without documented supraventricular ectopy (n = 42) were matched with 42 patients (cases) having atrial flutter onset > or =6 months postoperatively. Minimum, average, and maximum non-flutter HRs were obtained from outpatient ambulatory 24 h ECG (Holter) recordings and graded exercise tests. Chronotropic competence was assessed using percentage of age-specific predicted maximum HR achieved, and calculated chronotropic index. Effects of rate-adaptive programming and maximum atrial pacing rates were analysed in 19 permanently paced cases. Least square estimates of minimum HRs were similar in cases and controls (54+/-2 vs. 52+/-2 bpm). Average HRs were lower in cases (75+/-2 vs. 81+/-2 bpm, P=0.02). Cases and controls differed most significantly with respect to percentage of predicted maximum HR achieved (67+/-2 vs. 80+/-2%, P < 0.001). This difference remained highly significant when the data were adjusted for age, sex, permanent pacing, and negatively chronotropic medication usage at the time of testing. Among paced patients, atrial flutter was significantly less likely to be observed in the setting of rate-adaptive pacing [odds ratio (OR) = 0.36; P < 0.05], and the likelihood of detecting atrial flutter decreased relative to the maximum programmed atrial pacing rate (OR 0.87 for every 5% increment in maximum pacing rate relative to maximum predicted HR for age; P < 0.05). CONCLUSION: Late postoperative atrial flutter is associated with chronotropic incompetence in paediatric CHD patients. (+info)
Long term management of atrial arrhythmias in young patients with sick sinus syndrome undergoing early operation to correct congenital heart disease.
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AIMS: The objective of our study was to evaluate the clinical outcome of patients with operated congenital heart disease (CHD), post-operative sinus node dysfunction and atrial tachyarrhythmias (AT) who had a new generation of DDDRP pacemakers (Model AT501, Medtronic Inc., MN, USA) able to deliver preventive atrial pacing and antitachycardia pacing (ATP) therapies. METHODS AND RESULTS: Fifteen CHD patients (mean age 17+/-9 years, eight after Mustard operation, five after extracardiac Fontan operation and two after atrial septum repair) received a dual-chamber pacemaker with transvenous (eight patients) or epicardial leads (seven patients). In the year before implantation, all patients had symptomatic AT (palpitations), eight patients required hospitalization and five required electrical cardioversion. Pacing prevention algorithms were enabled in all patients, and ATP therapies in six patients. During a mean follow-up of 30 months (range 24-44), three patients (two Fontan, one Mustard) died of CHF, whereas AT required hospitalization in three patients (two Fontan, one atrial septum repair). Only seven patients had symptomatic AT. One hundred and twenty-five AT episodes were treated by ATP in three patients, with an overall termination efficacy of 43.2%. In one patient, atrial lead noise induced inappropriate AT detection that resulted in ATP delivery. Several AT episodes were not treated owing to their very short duration, atrial undersensing, or 1:1 atrioventricular conduction. CONCLUSIONS: Our experience with antitachycardia pacemakers in CHD patients with post-operative sick sinus syndrome after biventricular correction or palliation shows that these devices are safe and that atrial pacing may play a role in AT prevention and treatment. (+info)
Role of the low amplitude potential in the initial P wave signal-averaged electrocardiogram [corrected] in sick sinus syndrome.
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BACKGROUND: The cause of abnormally low amplitude of the initial P wave signal-averaged electrocardiogram (P-SAECG) in patients with sick sinus syndrome (SSS) is unknown. METHODS AND RESULTS: Thirteen normal patients (Group C) and 33 with SSS (Group S) were examined. The root mean square amplitude for the initial 30 ms (EP30) and the duration of below-4 microV signals of the filtered P waves (ED4) were measured using the P-SAECG. The interval from an atrial potential on the sinus-node electrogram (SNE) to P wave onset (AS-P), and the interval from the P wave to the atrial potential on the His-bundle-electrogram (P-AH) were measured in the electrophysiological study. The sino-atrial conduction time was measured by a conventional method (indirect sino-atrial conduction time (SACTi)) and using SNE (direct sino-atrial conduction time (SACTd)). The EP30 was significantly lower and the ED4 significantly longer in Group S. The AS-P was significantly longer in Group S (p<0.01), but the P-AH was not different. In Group S, the AS-P was significantly correlated with EP30 and ED4 (p<0.01), but the P-AH was uncorrelated. The SACTi was significantly correlated with EP30 and ED4 (p<0.05), but the SACTd was uncorrelated. CONCLUSION: The abnormality of the initial portion of the P-SAECG observed in SSS appears to be due to disturbed conduction through the atrial myocardium around the sino-atrial node. (+info)
Bioartificial sinus node constructed via in vivo gene transfer of an engineered pacemaker HCN Channel reduces the dependence on electronic pacemaker in a sick-sinus syndrome model.
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BACKGROUND: The normal cardiac rhythm originates in the sinoatrial (SA) node that anatomically resides in the right atrium. Malfunction of the SA node leads to various forms of arrhythmias that necessitate the implantation of electronic pacemakers. We hypothesized that overexpression of an engineered HCN construct via somatic gene transfer offers a flexible approach for fine-tuning cardiac pacing in vivo. METHODS AND RESULTS: Using various electrophysiological and mapping techniques, we examined the effects of in situ focal expression of HCN1-DeltaDeltaDelta, the S3-S4 linker of which has been shortened to favor channel opening, on impulse generation and conduction. Single left ventricular cardiomyocytes isolated from guinea pig hearts preinjected with the recombinant adenovirus Ad-CMV-GFP-IRES-HCN1-DeltaDeltaDelta in vivo uniquely exhibited automaticity with a normal firing rate (237+/-12 bpm). High-resolution ex vivo optical mapping of Ad-CGI-HCN1-DeltaDeltaDelta-injected Langendorff-perfused hearts revealed the generation of spontaneous action potentials from the transduced region in the left ventricle. To evaluate the efficacy of our approach for reliable atrial pacing, we generated a porcine model of sick-sinus syndrome by guided radiofrequency ablation of the native SA node, followed by implantation of a dual-chamber electronic pacemaker to prevent bradycardia-induced hemodynamic collapse. Interestingly, focal transduction of Ad-CGI-HCN1-DeltaDeltaDelta in the left atrium of animals with sick-sinus syndrome reproducibly induced a stable, catecholamine-responsive in vivo "bioartificial node" that exhibited a physiological heart rate and was capable of reliably pacing the myocardium, substantially reducing electronic pacing. CONCLUSIONS: The results of the present study provide important functional and mechanistic insights into cardiac automaticity and have further refined an HCN gene-based therapy for correcting defects in cardiac impulse generation. (+info)
Suppression of atrial fibrillation by atrial pacing.
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BACKGROUND: Atrial fibrillation (AF) is a common arrhythmia in patients with an implanted pacemaker, but the role of atrial pacing in preventing AF is still unclear. METHODS AND RESULTS: Sixty-six patients (67.8+/-12.1 years) were enrolled: 54 with sick sinus syndrome (SSS), 11 with atrioventricular blocks (AVB), and 1 with SSS and AVB. The prevalence of AF was investigated. In 22 patients with AF, the AF burden was estimated under "back-up pacing" (40-50 beats/min), then under "atrial pacing" (60-85 beats/min). The prevalence of AF in the SSS group tended to be higher than that in the AVB group (48.1% vs 18.2%, p=0.06). The AF burden in patients with a percentage of atrial pacing (% atrial pacing) <50% was significantly greater than that in patients with % atrial pacing >or=50% (12.5+/-21.1% vs 4.2+/-10.3%, p<0.05). AF disappeared immediately after "atrial pacing" in 4 patients (18.2%). In 9 patients (40.9%), the AF burden decreased gradually, and AF disappeared in 6 patients (27.3%) after 207.9+/-130.2 days. CONCLUSION: The prevalence of AF may be higher in patients with SSS than in those with AVB. Atrial pacing has a preventive effect on AF, and the effect of atrial pacing is not always immediate but is progressive in some patients. (+info)
Clinical and electrophysiological characteristics of binodal disease.
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BACKGROUND: Although coexistence of atrioventricular conduction disturbances with sick sinus syndrome (SSS), so-called binodal disease (BND), is a frequently encountered disorder, its clinical significance and electrophysiological characteristics remain unknown. METHODS AND RESULTS: One hundred and seven patients with SSS were divided into BND (n=30) and N-BND groups (n=77). Sinus cycle length, sinus node recovery time (SRT), sino-atrial conduction time (SACT), the number of isolated sinus node electrograms, atrio-His (AH) interval, His-ventricular (HV) interval, intra-atrial conduction time (PA intervals) and QRS width were measured. In addition, the prevalence of bundle-branch block was obtained. The parameters of sino-atrial and intra-atrial conduction were significantly longer in the BND group: SRT (5,070+/-2,628 vs 3,122+/-1,856 ms, p<0.05), SACT (115+/-30 vs 87+/-21 ms, p<0.05), PA intervals (56+/-13 vs 41+/-8 ms, p<0.05). The BND group was more likely to have atrial fibrillation than the N-BND group (83.3% vs 53.2%, p<0.01). HV interval, QRS width and the prevalence of associated bundle-branch block did not differ between the 2 groups. CONCLUSION: BND patients not only had sino-atrial and atrioventricular node dysfunction, but also widespread atrial conduction disturbances. Thus, in the clinical setting BND should be categorized as severe SSS. (+info)
A novel technique for right ventricular lead placement in a patient with a persistent left superior vena cava.
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Persistent left superior vena cava is the most common venous anomaly of the thorax. If unrecognized, it could lead to catheter malplacement and even vascular injuries. We describe a novel use of a Worley sheath for the delivery of a right ventricular (RV) endocardial pacing lead in a 65-year-old male with a persistent left superior vena cava. After failed attempts with the standard stylets, use of the Worley sheath aided successful lead deployment. We conclude that when used appropriately, the Worley sheath is a tool that could be helpful in pacing lead placement in patients with persistent left superior vena cava. (+info)
Single-chamber ventricular pacing increases markers of left ventricular dysfunction compared with dual-chamber pacing.
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AIMS: Large randomized trials comparing DDD with VVI pacing have shown no differences in mortality, but conflicting evidence exists in regard to heart failure endpoints. Here we evaluated the effect of pacing mode on serum levels of brain natriuretic peptide (BNP) and amino-terminal-proBNP (NT-proBNP). Methods Forty-one patients (age 73 +/- 10 years) with dual-chamber pacemakers were included in a prospective, single-blind, randomized crossover study evaluating the impact of DDD(R)/VDD versus VVI(R) mode on objective and functional parameters. Data were collected after a 2-week run-in phase and after 2 weeks each of VVI(R) and DDD(R)/VDD pacing or vice versa. Results BNP and NT-proBNP levels during DDD(R)/VDD stimulation (151 +/- 131 and 547 +/- 598 pg/mL) showed no change compared with baseline (154 +/- 130 and 565 +/- 555 pg/mL), but a significant 2.4-fold increase was observed during VVI(R) mode [360 +/- 221 and 1298 +/- 1032 pg/mL; P < 0.001 compared with DDD(R)/VDD]. The assessment of functional class, the presence of pacemaker syndrome [49% in VVI(R) mode] and the patients' preferred pacing mode showed significant differences in favour of DDD(R)/VDD pacing. CONCLUSION: Patients can differentiate between DDD(R)/VDD and VVI(R) pacing, and prefer the former. Compared with DDD(R)/VDD pacing, VVI(R) stimulation induces a two- to three-fold increase in serum BNP and NT-proBNP levels. (+info)