Boon Yew Tan

Fragmented QRS complexes predict right ventricular dysfunction and outflow tract aneurysms in patients with repaired tetralogy of Fallot.

BACKGROUND Fragmented QRS complexes (fQRS) correlate with myocardial scar, and may predict arrhythmias in patients with repaired tetralogy of Fallot (TOF). We investigated the relationship between fQRS in operated TOF patients with right ventricular (RV) dysfunction and RV outflow tract (RVOT) aneurysm. METHODS We studied 56 operated TOF patients with moderate/severe pulmonary regurgitation, referred for cardiac magnetic resonance imaging (MRI) over a 4.5 year period. The presence of fQRS (additional notches in the R/S wave in ≥ 2 contiguous leads on the ECG) was correlated with MRI findings. RESULTS fQRS was observed in 44 (78.6%) patients. Patients with fQRS had significantly larger RV end diastolic volume index (RVEDVi; 162 ml vs 141 ml, p=0.028) and RV end systolic volume index (RVESVi; 88 ml vs 70 ml, p=0.031). Increasing number of leads with fragmentation was independently associated with increasingly lower RV ejection fraction (adjusted co-efficient -0.97, 95%CI -1.83 to -0.12, p=0.026), greater pulmonary regurgitation fraction (1.65, 0.28 to 3.01, p=0.019), larger RVEDVi (6.78, 2.00 to 11.56, p=0.006) and RVESVi (5.41, 1.66 to 9.15, p=0.005). Anterior fragmentation correlated most significantly with RV dysfunction (p<0.05). fQRS had no significant association with LV dysfunction. Presence of any fQRS (OR 17.5, 95%CI 2.1-147.8, p=0.009) and inferior fQRS (OR 9.0, 95%CI 2.7-30.1, p<0.001) were found to be significant predictors for RVOT aneurysm. CONCLUSIONS The presence of fQRS on the ECG is significantly associated with RV dysfunction and RVOT aneurysms in repaired TOF patients. Increasing burden of fragmentation, especially in the anterior leads, is associated with increasing RV dysfunction.

Pacing Trends over a Decade in a National Registry

Permanent cardiac pacing is the treatment of choice in patients with symptomatic bradyarrhythmias. The SCDB is a prospective registry of interventional cardiac procedures done in Singapore since July 2000. This report looks at the data from NHC during the period from 2000–2010. There were 1724 pacemakers implanted during the 10 year with almost yearly increase in the number of pacemakers implanted at this single centre. The mean age of the patients was 69.86 years+12.2 old (median 71 years old, range 11–98 years). Over the 10 year period, there were more females (54.2% females vs 45.8% males). Sick sinus syndrome remains the most common indication for pacemaker implantation (60.7%) and the second most common indication was AV block (35.3%). This trend was consistently seen over the decade. The number of females was higher in the sick sinus syndrome group (59.8% females vs 40.2% males) whereas the proportion of males was higher in the complete heart block group (46.5% females vs 53.5% males). In conclusion, there is an increase in the number of pacemakers implanted likely due to an aging population. Females remain consistently higher and sick sinus syndrome remains the most important indication for pacing. With the rapidly aging population, it would be expected that this trend would continue to increase over the next decade.

Brugada Syndrome and SCN5A-Encoded Cardiac Sodium Channel Mutations in Singapore

Introduction:This study aims to characterize patients with Brugada syndrome (BrS) in Singapore, and its association with SCN5A-encoded cardiac sodium channel mutations.Methods:The study population consisted of 30 unrelated individuals (28 males, 93%) with either spontaneous or drug induced type 1 coved ST-segment elevation in leads V1–V3.Results:The mean age of symptom onset was 40.8 years (SD 13.5, min 11, max 72). The mean follow up duration was 3.6 years. Nine patients had an ICD implanted, none had appropriate ICD shocks.Mutation in the SCN5A gene was found in 5 out of the 30 individuals (16.7%). The PR interval in SCN5A mutation carriers was significantly prolonged (201.40 +/− 28.35 ms vs 168.92 +/− 27.67 ms, p=0.024). One individual had compound heterozygous mutation and presented with syncope and VT at the age of 11. A total of 6 mutations were identified, four of which were novel (67%).Conclusion:In this study, a mutation in the SCN5A gene was found in 16.7% of patients with BrS. The presence of a SCN5A mutation results in a longer PR interval. Compound heterozygosity in one individual appears to confer a more severe phenotype and an earlier onset of symptoms.

In a Multi-Ethnic Pacemaker Population, Are There Age Related, Gender or Ethnic Differences in Intracardiac Electrogram Amplitudes?

Background: The impact of age, gender and ethnicity on intracardiac electrogram amplitudes has not been widely studied. With a multi-ethnic population of pacemaker implanted patients in Singapore, we aim to determine if any of the above factors affect intracardiac electrogram amplitudes. Methods: 1813 consecutive patients with pacemakers implanted at National Heart Centre Singapore were studied. Results: Mean age at implant was 70.1±12.3 (SD) years. 54% were females. The 3 major ethnic groups were Chinese 79.6%, Malays 9.5% and Indians 6.6%. Types of pacemakers implanted: VVI/R (46.4%), DDD/R (43.7%), VDD (7.9%), AAI/R (2.0%). All atrial leads were placed at the right atrial appendage. 70% of ventricular leads were placed at the apex with the remainder in the right ventricular mid to high septum. Mean R wave amplitude in mV in females 10.8±4.2 (SD), males 11.1±4.5 (SD). R wave in mV by ethnicity: Chinese 10.9±4.4 (SD), Malays 11.0±3.9 (SD), Indians 11.5±4.4 (SD). Mean P wave amplitude in mV in females 2.9±1.4 (SD), males 3.1±1.5 (SD). P wave in mV by ethnicity: Chinese 3.0±1.5 (SD), Malays 2.9±1.4 (SD). Indians 2.9±1.3 (SD). There were no statistical differences in R or P wave amplitudes by age, gender or ethnic group. Conclusion: In our population, there were no differences in intracardiac electrogram amplitude in the ventricle or atrium between the different ethnic, age and gender groups.