Current permanent right ventricular and right atrial endocardial pacing leads are implanted utilizing a central lumen stylet. Right ventricular apex pacing initiates an abnormal asynchronous electrical activation pattern, which results in asynchronous ventricular contraction and relaxation. When pacing from right atrial appendage, the conduction time between two atria will be prolonged, which results in heterogeneity for both depolarization and repolarization. Six patients with Class I indication for permanent pacing were implanted with either single chamber or dual chamber pacemaker. The SelectSecure 3830 4-French (Fr) lumenless lead and the SelectSite C304 8.5-Fr steerable catheter-sheath (Medtronic Inc., USA) were used. Pre-selected pacing sites included inter-atrial septum and right ventricular outflow tract, which were defined by ECG and fluoroscopic criteria. All the implanting procedures were successful without complication. Testing results (mean atrial pacing threshold: 0.87 V; mean P wave amplitude: 2.28 mV; mean ventricular pacing threshold: 0.53V; mean R wave amplitude: 8.75 mV) were satisfactory. It is concluded that implantation of a 4-Fr lumenless pacing lead by using a streerable catheter-sheath to achieve inter-atrial septum or right ventricular outflow tract pacing is safe and feasible.
Cardiac Pacing, Artificial/*methods ; Electrodes, Implanted ; Equipment Safety ; Pacemaker, Artificial ; Prosthesis Implantation/methods ; Sick Sinus Syndrome/*therapy

Aged ; Cardiac Care Facilities ; trends ; Cardiac Resynchronization Therapy ; trends ; utilization ; Cardiac Resynchronization Therapy Devices ; trends ; utilization ; Death, Sudden, Cardiac ; prevention & control ; Defibrillators, Implantable ; trends ; utilization ; Electric Countershock ; trends ; utilization ; Female ; Heart Failure ; therapy ; Humans ; Male ; Middle Aged ; Retrospective Studies ; Singapore ; Stroke Volume ; Tachycardia, Ventricular ; therapy ; Tertiary Care Centers

INTRODUCTIONLong QT syndrome (LQTS), an inherited cardiac arrhythmia, is a disorder of ventricular repolarisation characterised by electrocardiographic abnormalities and the onset of torsades de pointes leading to syncope and sudden death. Genetic polymorphisms in 5 well-characterised cardiac ion channel genes have been identified to be responsible for the disorder. The aim of this study is to identify disease-causing mutations in these candidate genes in a LQTS family.

MATERIALS AND METHODSThe present study systematically screens the coding region of the LQTS-associated genes (KCNQ1, HERG, KCNE1, KCNE2 and SCN5A) for mutations using DNA sequencing analysis.

RESULTSThe mutational analysis revealed 7 synonymous and 2 non-synonymous polymorphisms in the 5 ion channel genes screened.

CONCLUSIONWe did not identify any clear identifiable genetic marker causative of LQTS, suggesting the existence of LQTS-associated genes awaiting discovery.

Adolescent ; Adult ; Child ; DNA Mutational Analysis ; ERG1 Potassium Channel ; Ether-A-Go-Go Potassium Channels ; analysis ; genetics ; Female ; Frameshift Mutation ; Humans ; KCNQ1 Potassium Channel ; analysis ; genetics ; Long QT Syndrome ; genetics ; Male ; Middle Aged ; Muscle Proteins ; analysis ; genetics ; NAV1.5 Voltage-Gated Sodium Channel ; Polymorphism, Genetic ; genetics ; Potassium Channels, Voltage-Gated ; analysis ; genetics ; Sodium Channels ; analysis ; genetics ; Trans-Activators

OBJECTIVEThe present study retrospectively evaluated the reliability of detecting atrial tachyarrhythmias (ATA), the efficacy of automatic atrial antitachycardia pacing (ATP) and the performance of atrial preventive pacing (APP) algorithms in an implanted antitachycardia DDDRP pacemaker for patients with sick sinus syndrome and paroxysmal ATA.

METHODSIn all 24 patients, a DDDRP pacemaker (Medtronic AT500/AT501) was implanted. APP algorithms were switched on at the implanting physician's discretion. During each pacemaker follow-up, information was saved to disk and the ATA burden between those patients with APP algorithms switched "ON" and "OFF" were compared. Reliability of ATA detection was determined by reviewing the stored electrograms and ATP efficacy was also reviewed. Both the pacemaker memory data and manual EGM retrieval were used for the analysis.

RESULTSComplication-free survival at (17.63 +/- 8.79) months was 100%. In 12 patients APP was not turned "ON" until the latest follow-up, in 6 patients APP was switched "ON" at their first visit after implantation, and in another 6 patients APP was switched "ON" after a median follow-up of 9.29 months. There were 97 367 episodes of ATA detected by the devices, of those with stored atrial electrograms the correct classification of ATA was (76.77 +/- 20.52)%. The percentage of atrial pacing with APP algorithms turned on was (87.95 +/- 20.93)%, which was significantly higher than that in patients with APP "OFF" (50.73 +/- 34.46)% (P < 0.01). ATP efficacy was (50.27 +/- 19.29)%. However, the ATA burden (14.73% vs 16.52%, or 7.52 hours vs 6.58 hours per week, P > 0.05) and the longest duration of single ATA episode (27.27 hours vs 20.75 hours, P > 0.05) were not significantly different between those patients with APP "ON" and "OFF". No proarrhythmic effect or major cardiovascular event was observed.

CONCLUSIONSThe antitachycardia DDDRP pacemaker correctly detects and diagnoses about 75% of the ATA episodes, while the ATP therapy successfully terminates atrial tachycardia or flutter in about 50% of attacks. However, there is no difference in ATA burden with the APP algorithms and high incidence of atrial pacing. As a non-curative therapy strategy, this high-cost device may only be used in strictly selected indication patients in addition to other treatments of ATA.

Aged ; Aged, 80 and over ; Algorithms ; Atrial Fibrillation ; diagnosis ; prevention & control ; therapy ; Cardiac Pacing, Artificial ; methods ; Electrophysiologic Techniques, Cardiac ; Female ; Follow-Up Studies ; Humans ; Male ; Middle Aged ; Pacemaker, Artificial ; Retrospective Studies ; Treatment Outcome

Current permanent fight ventricular and fight atrial endocardial pacing leads are implanted utilizing a central lumen stylet. Right ventricular apex pacing initiates an abnormal asyno chronous electrical activation pattern, which results in asynchronous ventricular contraction and re-laxation. When pacing from right atrial appendage, the conduction time between two atria will be prolonged, which results in heterogeneity for both depolarization and repolarization. Six patients with Class Ⅰ indication for permanent pacing were implanted with either single chamber or dual chamber pacemaker. The SelectSecure 3830 4-French (Fr) lumenless lead and the SelectSite C304 8.5-Fr steerable catheter-sheath (Medtronic Inc., USA) were used. Pre-selected pacing sites included inter-atrial septum and right ventricular outflow tract, which were defined by ECG and fluoroscopic criteria. All the implanting procedures were successful without complication. Testing results (mean atrial pacing threshold: 0.87 V; mean P wave amplitude: 2.28 mV; mean ventricular pacing threshold:0.53V; mean R wave amplitude: 8.75 mV) were satisfactory. It is concluded that implantation of a 4-Fr lumenless pacing lead by using a streerable catheter-sheath to achieve inter-atrial septum or right ventricular outflow tract pacing is safe and feasible.

Transvenous implantable cardioverter defibrillators are a type of implantable cardiac device. They are effective at reducing total and arrhythmic mortality in patients at risk of sudden cardiac death. Subcutaneous implantable cardioverter defibrillators (S-ICDs) are a new alternative that avoids the disadvantages of transvenous lead placement. In this case series, we report on the initial feasibility and safety of S-ICD implantation in Singapore.
Adult ; Death, Sudden, Cardiac ; prevention & control ; Defibrillators, Implantable ; statistics & numerical data ; Electrophysiology ; Follow-Up Studies ; Humans ; Male ; Middle Aged ; Patient Safety ; Prosthesis Implantation ; Singapore ; Tachycardia, Ventricular ; Ventricular Fibrillation

INTRODUCTIONDevice therapy is efficacious in preventing sudden cardiac death (SCD) in patients with reduced ejection fraction. However, few who need the device eventually opt to undergo implantation and even fewer reconsider their decisions after deliberation. This is due to many factors, including unresolved patient barriers. This study identified the factors that influenced patients' decision to decline implantable cardioverter defibrillator (ICD) implantation, and those that influenced patients who initially declined an implant to reconsider having one.

METHODSA single-centre survey was conducted among 240 patients who had heart failure with reduced ejection fraction and met the ICD implantation criteria, but had declined ICD implantation.

RESULTSParticipants who refused ICD implantation were mostly male (84%), Chinese (71%), married (72%), currently employed (54%), and had up to primary or secondary education (78%) and monthly income of < SGD 3,000 (51%). Those who were more likely to reconsider their decision were aware that SCD was a consequence of heart failure with reduced ejection fraction, knowledgeable of the preventive role of ICDs, currently employed and aware that their doctor strongly recommended the implant. Based on multivariate analysis, knowledge of the role of ICDs for primary prophylaxis was the most important factor influencing patient decision.

CONCLUSIONThis study identified the demographic and social factors of patients who refused ICD therapy. Knowledge of the role of ICDs in preventing SCD was found to be the strongest marker for reconsidering ICD implantation. Measures to address this information gap may lead to higher rates of ICD implantation.

Cross-Sectional Studies ; Death, Sudden, Cardiac ; prevention & control ; Defibrillators, Implantable ; Female ; Heart Failure ; mortality ; physiopathology ; therapy ; Humans ; Male ; Middle Aged ; Primary Prevention ; methods ; Risk Factors ; Singapore ; epidemiology ; Stroke Volume ; physiology ; Survival Rate ; trends

INTRODUCTIONRemote monitoring of cardiac implantable electronic devices (CIED) has been shown to improve patient safety and reduce in-office visits. We report our experience with remote monitoring via the Medtronic CareLink(®) network.

METHODSPatients were followed up for six months with scheduled monthly remote monitoring transmissions in addition to routine in-office checks. The efficacy of remote monitoring was evaluated by recording compliance to transmissions, number of device alerts requiring intervention and time from transmission to review. Questionnaires were administered to evaluate the experiences of patients, physicians and medical technicians.

RESULTSA total of 57 patients were enrolled; 16 (28.1%) had permanent pacemakers, 34 (59.6%) had implantable cardioverter defibrillators and 7 (12.3%) had cardiac resynchronisation therapy defibrillators. Overall, of 334 remote transmissions scheduled, 73.7% were on time, 14.5% were overdue and 11.8% were missed. 84.6% of wireless transmissions were on time, compared to 53.8% of non-wireless transmissions. Among all transmissions, 4.4% contained alerts for which physicians were informed and only 1.8% required intervention. 98.6% of remote transmissions were reviewed by the second working day. 73.2% of patients preferred remote monitoring. Physicians agreed that remote transmissions provided information equivalent to in-office checks 97.1% of the time. 77.8% of medical technicians felt that remote monitoring would help the hospital improve patient management. No adverse events were reported.

CONCLUSIONRemote monitoring of CIED is safe and feasible. It has possible benefits to patient safety through earlier detection of arrhythmias or device malfunction, permitting earlier intervention. Wireless remote monitoring, in particular, may improve compliance to device monitoring. Patients may prefer remote monitoring due to possible improvements in quality of life.

Aged ; Arrhythmias, Cardiac ; diagnosis ; Defibrillators, Implantable ; Female ; Follow-Up Studies ; Humans ; Male ; Middle Aged ; Monitoring, Physiologic ; methods ; Pacemaker, Artificial ; Patient Safety ; Pilot Projects ; Prospective Studies ; Quality of Life ; Remote Consultation ; methods ; Singapore ; Surveys and Questionnaires

INTRODUCTIONThe use of non-fluoroscopic systems (NFS) to guide radiofrequency catheter ablation (RFCA) for the treatment of supraventricular tachycardia (SVT) is associated with lower radiation exposure. This study aimed to determine if NFS reduces fluoroscopy time, radiation dose and procedure time.

METHODSWe prospectively enrolled patients undergoing RFCA for SVT. NFS included EnSiteTM NavXTM or CARTO® mapping. We compared procedure and fluoroscopy times, and radiation exposure between NFS and conventional fluoroscopy (CF) cohorts. Procedural success, complications and one-year success rates were reported.

RESULTSA total of 200 patients over 27 months were included and RFCA was guided by NFS for 79 patients; those with atrioventricular nodal reentrant tachycardia (AVNRT), left-sided atrioventricular reentrant tachycardia (AVRT) and right-sided AVRT were included (n = 101, 63 and 36, respectively). Fluoroscopy times were significantly lower with NFS than with CF (10.8 ± 11.1 minutes vs. 32.0 ± 27.5 minutes; p < 0.001). The mean fluoroscopic dose area product was also significantly reduced with NFS (NSF: 5,382 ± 5,768 mGy*cm2 vs. CF: 21,070 ± 23,311 mGy*cm2; p < 0.001); for all SVT subtypes. There was no significant reduction in procedure time, except for left-sided AVRT ablation (NFS: 79.2 minutes vs. CF: 116.4 minutes; p = 0.001). Procedural success rates were comparable (NFS: 97.5% vs. CF: 98.3%) and at one-year follow-up, there was no significant difference in the recurrence rates (NFS: 5.2% vs. CF: 4.2%). No clinically significant complications were observed in both groups.

CONCLUSIONThe use of NFS for RFCA for SVT is safe, with significantly reduced radiation dose and fluoroscopy time.

Adolescent ; Adult ; Aged ; Aged, 80 and over ; Catheter Ablation ; methods ; Child ; Female ; Fluoroscopy ; Humans ; Male ; Middle Aged ; Prospective Studies ; Radiation Dosage ; Radiation, Ionizing ; Tachycardia, Atrioventricular Nodal Reentry ; therapy ; Tachycardia, Supraventricular ; therapy ; Treatment Outcome ; Young Adult