Risk of Death and Cardiovascular Events in Asian Patients With Atrial Fibrillation and Chronic Obstructive Pulmonary Disease: A Report From the Prospective APHRS Registry

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with an increased risk of adverse events in patients with atrial fibrillation (AF); however, few data are available on this topic in Asian populations.

METHODS AND RESULTS

Prospective observational study conducted on patients with AF enrolled in the Asia-Pacific Heart Rhythm Society (APHRS) AF Registry. The diagnosis of COPD was based on data reported in the case report form by the investigators. Cox-regression models were used to assess the 1-year risk of a primary composite outcome of all-cause death, thromboembolic events, acute coronary syndrome, and heart failure. Analysis on single outcomes and cardiovascular death was also performed. Interaction analysis was used to assess the risk of composite outcome and all-cause death in different subgroups. The study included 4094 patients with AF (mean±SD age 68.5±12 years, 34.6% female), of whom 112 (2.7%) had COPD. Patients with COPD showed a higher incidence of the primary composite outcome (25.1% versus 6.3%, P<0.001), all-cause death (14.9% versus 2.6%, P<0.001), cardiovascular death (2.0% versus 0.6%, P<0.001), and heart failure (8.3% versus 6.0%, P<0.001). On multiple Cox-regression analysis, COPD was associated with a higher risk of the primary composite outcome (hazard ratio [HR], 3.17 [95% CI, 2.05-4.90]), all-cause death (HR, 3.59 [95% CI, 2.04-6.30]), and heart failure (HR, 3.32 [95% CI, 1.56-7.03]); no statistically significant differences were found for other outcomes. The association between COPD and mortality was significantly modified by the use of beta blockers (Pint=0.018).

CONCLUSIONS

In Asian patients with AF, COPD is associated with worse prognosis. In patients with AF and COPD, the use of beta blockers was associated with a lower mortality.

REGISTRATION INFORMATION

clinicaltrials.gov Identifier: NCT04807049.

Adverse Events and Clinical Correlates in Asian Patients with Atrial Fibrillation and Diabetes Mellitus: A Report from Asia Pacific Heart Rhythm Society Atrial Fibrillation Registry

Aims. To evaluate the adverse events (and its clinical correlates) in a large prospective cohort of Asian patients with atrial fibrillation (AF) and diabetes mellitus (DM). Material and Methods. We recruited patients with atrial fibrillation (AF) from the Asia-Pacific Heart Rhythm Society (APHRS) AF Registry and included those for whom the diabetic mellitus (DM) status was known. We used Cox-regression analysis to assess the 1-year risk of all-cause death, thromboembolic events, acute coronary syndrome, heart failure and major bleeding. Results. Of 4058 patients (mean age 68.5 ± 11.8 years; 34.4% females) considered for this analysis, 999 (24.6%) had DM (age 71 ± 11 years, 36.4% females). Patients with DM had higher mean CHA2DS2-VASc (2.3 ± 1.6 vs. 4.0 ± 1.5, p < 0.001) and HAS-BLED (1.3 ± 1.0 vs. 1.7 ± 1.1, p < 0.001) risk scores and were less treated with rhythm control strategies compared to patients without DM (18.7% vs. 22.0%). After 1-year of follow-up, patients with DM had higher incidence of all-cause death (4.9% vs. 2.3%, p < 0.001), cardiovascular death (1.3% vs. 0.4%, p = 0.003), and major bleeding (1.8% vs. 0.9%, p = 0.002) compared to those without DM. On Cox regression analysis, adjusted for age, sex, heart failure, coronary and peripheral artery diseases and previous thromboembolic event, DM was independently associated with a higher risk of all-cause death (HR 1.48, 95% CI 1.00-2.19), cardiovascular death (HR 2.33, 95% CI 1.01-5.40), and major bleeding (HR 1.91, 95% 1.01-3.60). On interaction analysis, the impact of DM in determining the risk of all-cause death was greater in young than in older patients (p int = 0.010). Conclusions. Given the high rates of adverse outcomes in these Asian AF patients with DM, efforts to optimize the management approach of these high-risk patients in a holistic or integrated care approach are needed.

External Validation of COOL-AF Scores in the Asian Pacific Heart Rhythm Society Atrial Fibrillation Registry

Background

The COOL-AF (Cohort of Antithrombotic Use and Optimal International Normalized Ratio Levels in Patients with Atrial Fibrillation) risk scores for death, bleeding, and thromboembolic events (TEs) were derived from the COOL-AF cohort from Thailand and require external validation.

Objectives

The authors sought to externally validate the COOL-AF scores in the APHRS (Asia-Pacific Heart Rhythm Society) registry and to compare their performance in the ESC-EHRA (European Society of Cardiology-European Heart Rhythm Association) EORP-AF (EURObservational Research Programme in Atrial Fibrillation) General Long-Term Registry.

Methods

We studied 3,628 APHRS and 8,825 EORP-AF patients. Receiver operating characteristic (ROC) curves and Cox regression analyses were used to test the predictive value of COOL-AF scores and to compared them with the CHA2DS2-VASc and HAS-BLED scores.

Results

Patients in the EORP-AF were older, had a higher prevalence of male sex, and were at higher thromboembolic and hemorrhagic risk than APHRS patients. After 1 year of follow-up in APHRS and EORP-AF, the following events were recorded: 87 (2.4%) and 435 (4.9%) death for any causes, 37 (1.0%) and 111 (1.3%) major bleeding, and 25 (0.7%) and 109 (1.2%) TEs, respectively. In APHRS, the COOL-AF scores showed moderate-to-good predictive value for all-cause mortality (area under the curve [AUC]: 0.77; 95% CI: 0.71-0.83), major bleeding (AUC: 0.68; 95% CI: 0.60-0.76), and TEs (AUC: 0.61; 95% CI: 0.51-0.71), and were similar to the CHA2DS2-VASc and HAS-BLED scores. In EORP-AF, the predictive value of COOL-AF for all-cause mortality (AUC: 0.68; 95% CI: 0.65-0.70) and major bleeding (AUC: 0.61; 95% CI: 0.60-0.62) was modest and lower than in APHRS. In EORP-AF, the COOL-AF score for TE was inferior to the CHA2DS2-VASc score.

Conclusions

The COOL-AF risk scores may be an easy tool to identify Asian patients with AF at risk for death and major bleeding and performs better in Asian than in European patients with AF. (Clinical Survey on the Stroke Prevention in Atrial Fibrillation in Asia [AF-Registry]; NCT04807049).

Sex-related differences in presentation, treatment, and outcomes of Asian patients with atrial fibrillation: a report from the prospective APHRS-AF Registry

We aimed to investigate the sex-related differences in the clinical course of patients with Atrial Fibrillation (AF) enrolled in the Asia-Pacific-Heart-Rhythm-Society Registry. Logistic regression was utilized to investigate the relationship between sex and oral anticoagulant, rhythm control strategies and the 1-year chance to maintain sinus rhythm. Cox-regression was utilized to assess the 1-year risk of all-cause, and cardiovascular death, thromboembolic events, acute coronary syndrome, heart failure, and major bleeding. In the whole cohort (4121 patients, 69 ± 12 years,34.3% female), females had different cardiovascular risk factors, clinical manifestations, and disease perceptions than men, with more advanced age (72 ± 11 vs 67 ± 12 years, p < 0.001) and dyslipidemia (36.7% vs 41.7%, p = 0.002). Coronary artery disease was more prevalent in males (21.1% vs 16.1%, p < 0.001) as well as the use of antiplatelet drugs. Females had a higher use of oral anticoagulant (84.9% vs 81.3%, p = 0.004) but this difference was non-significant after adjustment for confounders. On multivariable analyses, females were less often treated with rhythm control strategies (Odds Ratio [OR] 0.44,95% Confidence Interval [CI] 0.38-0.51) and were less likely to maintain sinus rhythm (OR 0.27, 95% CI 0.22-0.34) compared to males. Cox-regressions analysis showed no sex-related differences for the risk of death, cardiovascular, and bleeding. The clinical management of Asian AF patients should consider several sex-related differences.

Integrated Care for Atrial Fibrillation Using the ABC Pathway in the Prospective APHRS-AF Registry

Background

The Atrial Fibrillation Better Care (ABC) has been proposed as an integrated approach to improve management in patients with atrial fibrillation (AF), based on 3 pillars: "A" Avoid stroke with Anticoagulation; "B" Better symptoms control; "C" Cardiovascular risk-factor and comorbidities management.

Objectives

This study sought to investigate the association with outcomes of ABC adherence in the prospective multinational Asia-Pacific Heart Rhythm Society (APHRS) Atrial Fibrillation registry.

Method

Cox-regression analyses adjusted for age, sex, CHA2DS2-VASc score, paroxysmal AF, chronic obstructive pulmonary disease, chronic kidney disease, cancer, dyslipidemia, and dementia were performed to investigate the association with outcomes. Primary outcome was a composite of all-cause death, any thromboembolic events, acute coronary syndrome or percutaneous interventional procedures, and advancing heart failure.

Results

Of the 4,013 included patients with AF (mean age 68 ± 12 years; 34.4% female); 38.6% were adherent to all 3 main ABC pillars. After 1 year of follow-up, adherence to the ABC pathway was associated with a low incidence of composite outcome (4.0% vs 8.5%, P < 0.001), all-cause and cardiovascular death, and advancing heart failure. On Cox regression analysis, ABC adherence was associated with a lower risk of primary outcome (HR: 0.72; 95% CI: 0.53-0.97), with risk reduction progressively higher with a higher number of ABC criteria attained. No significant interaction in the association was seen according to the different geographic areas (Pint = 0.217).

Conclusions

In a large contemporary cohort of Asian patients with AF, adherence to ABC pathway was associated with a reduction of the risk for adverse outcomes. (Clinical Survey on the Stroke Prevention in Atrial Fibrillation in Asia (AF-Registry; NCT04807049).

Prognosis and treatment of atrial fibrillation in Asian cities: 1-year review of the Asia-Pacific Heart Rhythm Society Atrial Fibrillation Registry

AIMS

The aim of this study is to describe the implementation of the current guidance for stroke prevention and treatment option in atrial fibrillation (AF) and to evaluate mortality and morbidity in relation to therapeutic decisions, including persistence with treatment at 1 year in Asia-Pacific regions.

METHODS AND RESULTS

We recruited 4664 patients consecutive in- and outpatients with AF who presented to cardiologists in five countries under the Asia-Pacific Heart Rhythm Society (APHRS) in whom 1-year follow-up was completed for 4003 (65.5% male; mean age 68.5 years). Oral anticoagulant (OAC) use remained high, 77% at follow-up, including 17% prescribed a vitamin K antagonist (VKA) and 60% a non-VKA oral anticoagulant (NOAC). At 1-year follow-up, 93% and 88% remained on a VKA or NOAC, respectively. With good adherence to OAC therapy, 1-year mortality was only 2.7%. Most deaths were non-cardiovascular (72.3%) and the 1-year incidence of stroke/transient ischaemic events (TIA) was low (<1%). Hospital readmissions were common for non-cardiovascular cases and atrial tachyarrhythmias. On multivariate analysis, independent baseline predictors of mortality and/or stroke/TIA/peripheral embolism were age, previous heart failure for >12 months, and malignancy. Independent predictors of mortality were age, chronic obstructive pulmonary disease, malignancy, and diuretic use. AF as a primary presentation was predictive of lower mortality and/or stroke/TIA/peripheral embolism as well as mortality.

CONCLUSION

In this 1-year analysis of the APHRS-AF registry, overall OAC use and persistence were high and were associated with low 1-year cardiovascular mortality and morbidity, but mortality and morbidity related to non-cardiovascular causes were high in AF patients, particularly from malignancy and pneumonia.

Quality indicators of the atrial fibrillation management from the European (EORP) and Asia-Pacific (APHRS) registries

Background

The 2020 ESC guideline for atrial fibrillation (AF) recommends universal quality indicators to identify areas for improvement in clinical practice. It also recommends using clinical registries to monitor clinical practice and identify areas for improvement. We have analysed two large comprehensive prospective clinical registries of patients with AF, the EURObservational Research Programme (EORP) and the Asia Pacific Heart Rhythm Society (APHRS), to compare the achievement of the ESC quality indicators in two major world populations.

Methods

The EORP and APHRS registries used the same electronic case report forms to collect data. T-test and Chi-squared test were used to compare registries. Logistic regression was used to identify pharmacological rate control therapy predictors in permanent AF. The model was adjusted for age, oral anticoagulation (OAC), EHRA and CHA2DS2-VASc scores, heart rate on the latest ECG and the region of recruitment (Europe or Asia) (STATA Corp, version 13).

Results

All 11096 EORP patients (59.3% males, age 69±11 years) and 5460 APHRS patients (66.3% males, age 68±12 years) had CHA2DS2-VASc and HAS-BLED scores documented at enrolment. The EORP register included a higher proportion of patients with CHA2DS2VASc ≥2 (81% vs 70%, p&lt;0.001). These patients had similar OAC use (87%) in both registries, but NOAC use was higher in the APHRS (67% vs 34%, p&lt;0.001), while dual antithrombotic use was more common in the EORP (14% vs 8%, p&lt;0.001). The Table lists paraments that may impact OAC prescription.

In patients with permanent AF, heart rate (82±20 vs 78±20, p&lt;0.001) and antiarrhythmic pharmacotherapy (9% vs 5%) was higher in the EORP registry. On logistic regression, independent predictors of rate control with antiarrhythmic pharmacotherapy were higher EHRA 3 score (adjusted odds ratio (aOR) 1.8; 95% confidence interval (CI) 1.3–2.5, p&lt;0.001); faster heart rate (aOR 1.01; 95% CI 1.00–1.02, p&lt;0.001); younger age (aOR 0.97; 95% CI 0.96–0.98, p&lt;0.001) and being recruited to the APHRS (aOR 0.56; 95% CI 0.40–0.79, p=0.001).

APHRS vs EORP patients with non-permanent AF were less symptomatic (EHRA score I in 56% vs 38%) with less frequent use of antiarrhythmics (25% vs 37%), rhythm-management interventions (32% vs 46%), but higher use of catheter ablation (p&lt;0.001 for all).

Conclusion

There are significant regional variations in achievement of the ESC quality indicator for AF. The variations may be due to differences in healthcare systems, but they may also reflect the population characteristics.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Since the start of EORP, the following companies have supported theprogramme: Abbott Vascular Int. (2011-2014), Amgen Cardiovascular(2009-2018), AstraZeneca (2014-2017), Bayer AG (2009-2018),Boehringer Ingelheim (2009-2019), Boston Scientific (2009-2012), TheBristol Myers Squibb and Pfizer Alliance (2011-2016), The Alliance DaiichiSankyo Europe GmbH and Eli Lilly and Company (2011-2017), Edwards(2016-2019), Gedeon Richter Plc. (2014-2017), Menarini Int. Op. (2009-2012), MSD-Merck & Co. (2011-2014), Novartis Pharma AG (2014-2017), ResMed (2014-2016), Sanofi (2009-2011), and SERVIER (2009-2018).The Atrial Fibrillation NETwork (AFNET), conducting the registryin Germany, received support from The Bristol Myers Squibb/PfizerAlliance (2014-2018) and the German Centre for CardiovascularResearch (DZHK).

Clinical utility and prognostic implications of the 4S-AF scheme: Report from Asia Pacific Heart Rhythm Society Atrial Fibrillation Registry

BACKGROUND

The 4S-AF classification scheme comprises of four domains (stroke risk [St], symptoms [Sy], severity of atrial fibrillation (AF) burden [Sb] and substrate [Su]), which has been recommended in the 2020 ESC guidelines to characterize and evaluate patients with AF.

OBJECTIVES

We aimed to determine whether the 4S-AF scheme would be useful for AF characterization and provides prognostic information in a large contemporary prospective Asian registry conducted by the Asia Pacific Heart Rhythm Society (APHRS).

METHODS

Among 4666 patients enrolled in APHRS registry, 3586 of them whose data about left atrial (LA) dimension and European Heart Rhythm Association (EHRA) symptom score were available have constituted as the study population. The 4S-AF score was calculated as the sum of each domain with a maximum score of 9. The clinical endpoint was defined as the 1-year composite risk of any thromboembolic event, ischaemic stroke, heart failure, acute coronary syndrome, significant coronary artery disease requiring coronary intervention and all-cause mortality.

RESULTS

Based on the 4S-AF domains, 86.7% were 'non-low risk' for stroke; 94.3% had EHRA Class I-II, 48.5% were newly diagnosed or paroxysmal AF; and only 8.4% had no cardiovascular risk factors or LA enlargement. The risk of clinical events was higher in patients who were 'non-low risk' for stroke (aOR 2.175, 95% CI 1.060-4.461), with permanent AF (aOR 1.579, 95% CI 1.106-2.225) and increasing points for substrate (aORs 2.376-4.968 from score 2 to 4). When compared to the first tertile of 4S-AF score (0-3 points), patients in the second tertile (4-5 points) had approximately 2.5-fold increase in adverse events (OR 2.478, 95% CI 1.678-3.661, p < .001), while those in the third tertile (6-9 points), had a 3.5-fold increase (OR 3.484, 95% CI 2.322-5.226, p < .001), both without significant differences between the 5 participating countries (p for interaction > .05). If all 4S-AF domains were appropriately treated, this was associated with a lower risk of composite clinical outcomes (aOR 0.384, p < .001; p for interaction for different countries = .234).

CONCLUSIONS

Categorization according to the 4S-AF scheme can be related to the risk of the composite adverse event rate in Asian AF patients, and appropriate treatments based on the 4S-AF scheme resulted in better clinical outcomes. These observations support the characterization and management according to the 4S-AF scheme in Asian patients.

From matrix nano- and micro-phase tougheners to composite macro-properties

In this paper, firstly, the morphology and toughness of a range of bulk epoxy polymers, which incorporate a second phase of well-dispersed silica nanoparticles and/or rubber microparticles, have been determined. Secondly, the macro-properties of natural-fibre reinforced-plastic (NFRP) composites based upon these epoxy polymers have been ascertained, using (i) unidirectional flax fibres or (ii) regenerated-cellulose fibres in the architecture of a plain-woven fabric. Thirdly, the toughening mechanisms which are induced in these materials by the presence of the silica nanoparticles, the rubber microparticles and the natural fibres have been identified. Finally, the values of the toughness of the bulk epoxy polymers and corresponding NFRPs have been quantitatively modelled. The increased toughness recorded for the bulk epoxy polymer due to the presence of the silica nanoparticles and/or rubber microparticles was indeed typically transferred to the NFRP composites when using such epoxies as the matrices for the fibres. Thus, the important role that may be played by modifications to the epoxy matrices in order to increase the toughness of the composites was very clearly demonstrated by these results. However, notwithstanding, the toughening mechanisms induced by the fibres were essentially responsible for the very high toughnesses of the NFRP composites, compared with the bulk epoxy polymers. The modelling studies successfully predicted the values of toughness of the bulk epoxy polymers and of the NFRP composites. These studies also quantified the extent to which each toughening mechanism, induced by the second-phase nano- and microparticles and the natural fibres, contributed to the overall values of toughness of the materials. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.

First clinical experience of the safety and feasibility of total subcutaneous implantable defibrillator in an Asian population

AIMS

The safety and feasibility of a subcutaneous implantable cardioverter-defibrillator (S-ICD) has been demonstrated in the treatment of life-threatening ventricular tachyarrhythmias (VT). Nonetheless, its safety and feasibility in an Asian population with smaller body-build is unclear.

METHODS AND RESULTS

Twenty-one Asian patients who underwent S-ICD from 1 April 2014 to 2 February 2015 in five institutions in Hong Kong and Singapore were retrospectively reviewed. Twenty-one patients with a mean age of 50.0 ± 14.1 years (range 29-77 years, 82.6% male) were included. Among them, 17 (81.0%) were Chinese, 3 (14.3%) were Malay, and 1 (4.8%) was Indian. Their mean body mass index was 23.0 ± 4.0 kg/m(2). An S-ICD was implanted for primary and secondary prevention in 13 (61.9%) and 8 (38.1%) patients, respectively. The indications included Brugada syndrome (n = 6, 28.6%), ischaemic cardiomyopathy (CMP, n = 6, 28.6%), dilated CMP (n = 4, 19.0%), hypertrophic CMP (n = 2, 9.5%), and idiopathic ventricular fibrillation (n = 2, 9.5%). Three patients (14.3%) had prior infected transvenous ICD. There were no acute complications but eight wound complications (persistent wound bleeding requiring intervention = 2; delayed wound healing: upper sternal wound = 3; generator site = 1; local wound infection = 2) were observed in six (28.2%) patients. After a mean follow-up of 107.2 ± 81.3 days (range of 14-254 days), one patient underwent three successful appropriate shocks for treatment of VTs. No inappropriate therapy was documented.

CONCLUSION

Our initial experience shows that S-ICD is a feasible treatment for VT among an Asian population with smaller body-build. There was nonetheless a relatively high rate of wound complications.

Pneumocystis carinii (jirovecii) pneumonia (PCP): the most common opportunistic infection observed in HIV/AIDS cases at the University Malaya Medical Centre, Kuala Lumpur, Malaysia

This retrospective study was conducted among 59 HIV/AIDS patients with opportunistic infections admitted to the University Malaya Medical Centre between 2000 and 2009. Fifty-five point nine percent of cases were Chinese, 25.4% were Malays, 11.9% were Indians and 6.8% were of unknown ethnic origin. The male:female ratio was 2.9:1 (44 males and 15 females). The highest prevalence (38.9%) occurred in the 30-39 year old age group. Men comprised 47.7% and women 53.3%; the majority of both were married. The majority of cases were Malaysians (89.8%) and the rest (10.2%) were immigrants. Most of the patients (18.6%) were non-laborers, followed by laborers (11.9%), the unemployed (5.1%) and housewives (3.4%). The most common risk factor was unprotected sexual activity (20.3%). The two most common HIV/AIDS related opportunistic infections were Pneumocystis carinii (jirovecii) pneumonia (PCP) (62.7%) and toxoplasmosis (28.8%). Seventy-two point nine percent of patients had a CD4 count <200 cells/microl and 5.1% had a CD4 count >500 cells/microl. Eleven point nine percent of cases died during study period. A low CD4 count had a greater association with opportunistic infections. Most of the patients presented with fever (44.1%), cough (42.4%) and shortness of breath (28.8%). Detection of the etiologic pathogens aids clinicians in choosing appropriate management strategies.

Novel electrogram device with web-based service centre for ambulatory ECG monitoring

INTRODUCTION

Arrhythmias are often intermittent, and a normal electrocardiogram (ECG) may not be diagnostic. The purpose of this study was to evaluate the usefulness of HeartWave500 (HW), a novel web-based ambulatory ECG monitoring device.

METHODS

A total of 120 patients from the National Heart Centre, Singapore were prospectively randomised in a three to one ratio to either HW or a standard transtelephonic (TT) event recorder. HW records five leads and transmits to an internet server, while TT transmits audio data to a central station. Monitoring was conducted for two weeks. The diagnostic yield was calculated in two ways: the percentage of patients successfully diagnosed as a function of time, and the absolute number of new diagnoses per patient per week.

RESULTS

33 patients (14 male, 19 female; mean age 49.6 + or - 11.1 years) were randomised to TT. 87 patients (32 male, 55 female; mean age 43.7 + or - 12.2 years) were randomised to HW. At the end of two weeks, the percentage of patients diagnosed with any arrhythmia was similar for both groups (66.7 percent for TT versus 67.8 percent for HW). There was a trend toward significance for the number of diagnoses per patient per week for Week 2 between TT and HW (0.58 + or - 0.75 versus 0.34 + or - 0.55, p is 0.06). Transmitted ECGs were read earlier for HW (18 minutes versus 1107 minutes, Mann-Whitney non-parametric test, p is less than 0.05). Transmitted recordings that were unreadable were also significantly lower for HW (8.0 percent versus 17.6 percent, chi-square test, p is less than 0.05).

CONCLUSION

HW and TT have similar diagnostic yields. There is a trend toward a shorter monitoring time for HW. The ability of HW to record and transmit via the web, the earlier review of data and low unreadable data make HW an attractive alternative to TT.

Electrocardiographical case. Young woman with frequent syncope attacks

A 29-year-old woman with frequent syncope attacks was referred for electrophysiological study and consideration for radio-frequency ablation of her ventricular arrhythmias. Her ECG showed features of right ventricular outflow tract premature contraction. Differential diagnoses for the causes of syncope in this patient include: right ventricular outflow tract tachycardia, arrythmogenic right ventricular dysplasia, and neurocardiogenic syncope. She underwent a tilt table test, which showed a malignant cardioinhibitory response. She developed abrupt syncope with 32 seconds of asystole during the test. She was given intravenous atropine and was resuscitated. A dual chamber rate-responsive pacemaker was implanted for her the next day. She was discharged well subsequently. Although the prognosis in patients with prolonged aystole in malignant vasovagal syncope is unknown, most doctors will still choose to implant a permanent pacemaker for patients with malignant neurocardiogenic syncope when the sinus arrest is prolonged.

Mutation Screening in KCNQ1, HERG, KCNE1, KCNE2 and SCN5A Genes in a Long QT Syndrome Family

Introduction: Long 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 wellcharacterised 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 Methods: The present study systematically screens the coding region of the LQTS-associated genes (KCNQ1, HERG, KCNE1, KCNE2 and SCN5A) for mutations using DNA sequencing analysis. Results: The mutational analysis revealed 7 synonymous and 2 nonsynonymous polymorphisms in the 5 ion channel genes screened. Conclusion: We did not identify any clear identifiable genetic marker causative of LQTS, suggesting the existence of LQTSassociated genes awaiting discovery. Key words: Arrhythmia, Ion channels, Long QT syndrome

Electrocardiographical case. Asymptomatic patient with deep T-wave inversions

A 45-year-old man was found to have an abnormal myocardial perfusion scan. He was asymptomatic, with no chest pain, breathlessness or palpitations. Clinical examination was unremarkable. The 12-lead electrocardiography (ECG) showed increased QRS voltage in leads V3-V6, and deep T-wave inversions noted in leads V3-V6, with an absence of septal Q waves. These ECG features were characteristic of apical variant hypertrophic cardiomyopathy (HCM). He underwent a coronary angiogram that revealed normal coronary arteries, and a left ventriculogram which showed apical HCM. Transthoracic echocardiography further confirmed the diagnosis. No drug therapy was instituted as he was asymptomatic. Apical HCM is discussed.

Mutation screening in KCNQ1, HERG, KCNE1, KCNE2 and SCN5A genes in a long QT syndrome family

INTRODUCTION

Long 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 METHODS

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

RESULTS

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

CONCLUSION

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

Electrocardiographical case. Acute severe chest tightness

The early diagnosis of acute myocardial infarction is crucial for the institution of appropriate reperfusion therapy. We describe a 56-year-old man who developed sudden onset of severe chest tightness. Inferior, posterior and right ventricular ST elevation myocardial infarction was diagnosed on electrocardiography (ECG). The ECG interpretation, differential diagnosis and management are discussed.

Electrocardiographical case. An elderly lady with chest pain. Diagnosis: isolated posterior myocardial infarct (MI)

A 72-year-old woman with diabetes mellitus, hypertension and dyslipidaemia presented with severe chest pain of four hours duration. Her electrocardiogram (ECG) showed tall R waves in leads V1-2, and ST segment depression in leads V1- 4, consistent with an isolated posterior myocardial infarction (MI). Emergency coronary angiogram showed an occluded left circumflex coronary artery, and primary angioplasty and stenting was performed. The ECG criteria for isolated posterior MI and pitfalls in using the conventional 12-lead ECG are discussed.

Electrocardiographical case. Elderly woman with sudden onset of post-operative dyspnoea

A 70-year-old Chinese woman developed breathlessness, tachycardia and hypotension on the fourth day after total hip replacement. 12-lead electrocardiogram (ECG) showed sinus tachycardia with ST depression in I, II, V5 and V6. The ECG changes of sinus tachycardia along with a typical history is suggestive of pulmonary embolism. Diagnosis, treatment and the use of IVC filter for pulmonary embolism are discussed.

Electrocardiographical case. Asymptomatic patient with ST-segment elevation

A 46-year-old man complained of recurrent episodes of giddiness which was not associated with chest pain or breathlessness. There was no family history of sudden death. Clinical examination was unremarkable.12-lead electrocardiogram (ECG) showed ST segment elevation in the right precordial leads, with coved ST segment elevation at its J point followed by a negative T wave with no isoelectric separation, specifically in V2. These ECG features are characteristic of the Brugada syndrome. He underwent a flecanide challenge which produced further elevation of ST segment at its J point and spontaneous ventricular ectopy. Electrophysiological studies induced ventricular fibrillation with 3 extra stimuli. An implantable cardioverter-defibrillator was implanted for prevention of sudden cardiac death. The Brugada syndrome is discussed.

Brugada-type ECG with polymorphic ventricular tachycardia: a red herring for isolated right ventricular infarction

We present a patient with Brugada-type ECG abnormalities and recurrent polymorphic ventricular tachycardia (VT). Subsequent investigations confirmed the diagnosis of isolated right ventricular myocardial infarction. The VT resolved after the 1st day and was not inducible subsequently. This case illustrates the importance of a careful study of the ECG to exclude other conditions in a patient with Brugada-type ECG abnormalities.

A case series of sotalol-induced torsade de pointes in patients with atrial fibrillation--a tale with a twist

INTRODUCTION

Sotalol is a potent antiarrhythmic often used in patients with atrial fibrillation. However, it has been associated with a risk of provoking other potentially dangerous arrhythmias, especially if used in high doses and in patients with uncorrected electrolyte imbalance or impaired renal and cardiac function.

CLINICAL PICTURE

We present 4 patients with atrial fibrillation treated with sotalol who developed torsade de pointes due to marked prolongation of the QT interval. While 1 patient had renal failure, all had normal left ventricular function. One patient had been treated with sotalol for more than 10 months before developing torsade de pointes precipitated by hypokalaemia, while another had tolerated sotalol for a 3-month period before the drug was discontinued, and only developed torsade de pointes when the drug was restarted 2 years later. Significantly, the doses used in all patients were relatively low, in contrast to most other reported cases where higher doses were used.

CONCLUSION

As with all antiarrhythmic therapy, these cases illustrate the need for close follow-up of patients treated with sotalol, even if relatively low doses are used. In addition, patients who had previously tolerated the drug well are still susceptible to its proarrhythmic effects.

Treatment of heart failure--role of biventricular pacing for heart failure not responding well to drug therapy

OBJECTIVE

Patients with heart failure may have conduction abnormalities in up to 30%, further aggravating cardiac output. Drugs worsen these abnormalities and resynchronisation therapy with biventricular pacing improves cardiac function by effecting a more coordinated and efficient ventricular contraction. We report here the technique of biventricular pacing and its results.

METHODOLOGY

Patients with NYHA Class III to IV heart failure, widened QRS (> or = 130 ms) complex on the ECG and impaired LVEF < or = 40% were enrolled.

RESULTS

Biventricular pacing was performed in 29 patients (26 males, three females) from August 1999 to December 2001. The mean age of the patients was 59.6 +/- 12.8 years and 62% had underlying ischemic heart disease. All were in NYHA class III or more. Twenty-three had LBBB, four RBBB and two had widened paced QRS complex. The QRS duration was 161 +/- 21 ms and LVEF was 22 +/- 8%. All the left ventricular leads were implanted successfully. The procedure time was 167.0 +/- 79.6 mins and the fluoroscopy time was 43.8 +/- 41.4 mins. There were no significant complications. The NYHA class improved from a mean of 3.1 to 2.0 and exercise time from 252 +/- 95 seconds to 392 +/- 152 seconds at six months post implant (p=0.049). On follow-up (one month to 28 months), 25 (86%) patients had improvement in heart failure symptoms and 26 (90%) of the patients remained alive.

CONCLUSION

Biventricular pacing can be safely performed and results in improvement in symptoms and exercise tolerance in heart failure patients with ventricular dyssynchrony not responding to drug therapy.

Immediate and mid-term safety and efficacy of single lead VDD pacemakers for patients with atrioventricular block and normal sinus node function--a single centre experience

INTRODUCTION

Single lead atrial synchronous ventricular pacing (VDD) is increasingly being used in place of conventional dual chamber pacing (DDD) for patients with atrioventricular block and preserved sinus node function. Compared to the latter, VDD pacemakers provide similar haemodynamic benefits derived from atrial synchronous pacing, with the added benefit of an easier implant procedure.

OBJECTIVE

To review the use, safety and efficacy of VDD pacing in a single tertiary referral centre.

MATERIALS AND METHODS

A review of all patients with atrioventricular block and normal sinus node function implanted with a VDD pacemaker over a 2-year period at a local tertiary cardiac referral centre. Data on complications, atrial sensing performance and maintenance of atrioventricular synchrony during implant and at subsequent follow-up visits were obtained from a prospectively maintained registry and analysed.

RESULTS

Forty-one patients (17 males, 24 females) with a mean age of 72 +/- 9 years received VDD pacing for various forms of high-grade atrioventricular block. The average implantation time was 46.8 +/- 17.1 minutes, and a pneumothorax in 1 patient was the only complication. Electrical measurements at implantation and subsequent follow-up visits revealed an initial rapid decrease in atrial signal amplitude (mean atrial P wave at implant 3.1 +/- 1.1 mV, predischarge 1.9 +/- 1.3 mV) which began to stabilise after 3 months, reaching a mean atrial P wave value of 1.3 +/- 0.3 mV at 24 months. The atrial sensing performance (percentage of atrial synchronous ventricular complexes) was 97% over a mean follow-up period of 9.9 months. Four patients (10%) developed paroxysmal atrial tachyarrhythmias. Sinus node dysfunction was not observed in any of our patients during the follow-up period.

CONCLUSION

In patients with atrioventricular block and preserved sinus node function, single lead VDD pacing is safe and effective in maintaining a physiological atrial synchronous pacing mode.

Clinical outcomes of patients with diabetes mellitus and acute myocardial infarction treated with primary angioplasty or fibrinolysis

OBJECTIVE

To compare the early and late outcomes of primary percutaneous transluminal coronary angioplasty (PTCA) with fibrinolytic treatment among diabetic patients with acute myocardial infarction (AMI).

DESIGN

Retrospective observational study with data obtained from prospective registries.

SETTING

Tertiary cardiovascular institution with 24 hour acute interventional facilities.

PATIENTS

202 consecutive diabetic patients with AMI receiving reperfusion treatment within six hours of symptom onset.

INTERVENTIONS

Fibrinolytic treatment was administered to 99 patients, and 103 patients underwent primary PTCA. Most patients undergoing PTCA received adjunctive stenting (94.2%) and glycoprotein IIb/IIIa inhibition (63.1%).

MAIN OUTCOME MEASURES

Death, non-fatal reinfarction, and target vessel revascularisation at 30 days and one year were assessed.

RESULTS

Baseline characteristics were similar in these two treatment groups except that the proportion of patients with Killip class III or IV was considerably higher in those treated with PTCA (15.5% v 6.1%, p = 0.03) and time to treatment was significantly longer (103.7 v 68.0 minutes, p < 0.001). Among those treated with PTCA, the rates for in-hospital recurrent ischaemia (5.8% v 17.2%, p = 0.011) and target vessel revascularisation at one year (19.4% v 36.4%, p = 0.007) were lower. Death or reinfarction at one year was also reduced among those treated with PTCA (17.5% v 31.3%, p = 0.02), with an adjusted relative risk of 0.29 (95% confidence interval 0.15 to 0.57) compared with fibrinolysis.

CONCLUSION

Among diabetic patients with AMI, primary PTCA was associated with reduced early and late adverse events compared with fibrinolytic treatment.

Myocardial infarction in Singapore: a nationwide 10-year study of multiethnic differences in incidence and mortality

INTRODUCTION AND METHODS

Cardiovascular diseases have progressively increased in importance as a major contributor of morbidity and mortality in Asia. However, many countries in Asia do not have nationwide systematically-collected and standardised data on myocardial infarction (MI). To accurately document the extent of atherosclerotic coronary heart disease in Singapore, a nationwide myocardial infarct registry was established in the mid-1986. Possible myocardial infarct events were identified through daily national lists of cardiac enzymes, hospital discharge codes, mortuary records and the national death registry. Data obtained from clinical history, cardiac enzymes and 12-lead electrocardiogram Minnesota codes were entered into an algorithm based on the WHO MONICA study. Cases identified as "definite" MI were included in the decade's review for this study.

RESULTS

From 1988 to 1997, 13,048 myocardial infarct events were diagnosed with 3367 deaths. There was a 39.1% decline in mortality, with an average decline of 6.5% per year [95% confidence intervals (CI), -3.9% to -9.1%]. However, the decline in incidence was only 20.8% with an average decline of 2.4% per year (95% CI, -6.6% to -1.2%). The highest incidence and mortality rates for both genders were seen in the Indians, followed by the Malays and the Chinese.

CONCLUSION

Over 10 years, from 1988 to 1997, we documented a significant fall in mortality from MI in Singapore. There was a smaller decline in the incidence of infarction. Singapore implemented a National Healthy Lifestyle Programme in 1992 as a 10-year effort. The disparity in the incidence and mortality may suggest that a more dramatic and immediate impact has taken place in mortality through therapeutic programmes; primary preventive programmes would be more difficult to evaluate and have a more gradual impact. Only with continual accurate data collection through the whole country, over a much longer period, can the relative value of preventive and therapeutic programmes in coronary heart disease be assessed.

Slow-infusion of calcium channel blockers in the emergency management of supraventricular tachycardia

OBJECTIVE

To compare the efficacy of verapamil and diltiazem as slow infusions in terminating spontaneous supraventricular tachycardia (SVT) in the emergency department (ED).

METHOD

Patients of at least 10 years of age who presented to our ED with regular narrow complex tachycardia not converted with a vagal manoeuvre with an ECG diagnosis of SVT were included. Those who were haemodynamically unstable were excluded. Patients were randomized to undergo either verapamil infusion at a rate of 1 mg/min to a maximum of 20 mg or diltiazem infusion at a rate of 2.5 mg/min to a maximum of 50 mg.

RESULTS

Eighty-one patients were randomized to receive verapamil infusion and 80 were randomized to receive the diltiazem infusion. There is no difference in success rate between verapamil (98.8%) and diltiazem (96.3%) infusion. The dose of medication required to convert 25,50 and 75% of SVTs were 4.0,5.0 and 8.0 mg for the verapamil infusion and 10.0,12.5 and 17.5 mg for the diltiazem infusion. There was one complication in each group.

CONCLUSION

Calcium channel blockers infusions were safe and efficacious in terminating spontaneous SVT. There was no difference between the success rates of verapamil and diltiazem infusions.

Two case reports on incessant left ventricular tachycardia: curative therapy with radiofrequency ablation

INTRODUCTION

Incessant ventricular tachycardia is a rare arrhythmia which can be life threatening. Treatment with anti-arrhythmic agents may occasionally fail.

CLINICAL PICTURE

We report 2 cases of incessant ventricular tachycardia. The first case was a young man with idiopathic left ventricular tachycardia who was in incessant ventricular tachycardia despite treatment with multiple anti-arrhythmic drugs and developed dilated cardiomyopathy. The second case was an asymptomatic girl with the incidental finding of an incessant ventricular tachycardia which originated from the left ventricular outflow tract.

TREATMENT AND OUTCOME

Both patients underwent electrophysiologic study and radiofrequency ablation with complete termination of the tachycardia.

CONCLUSION

Radiofrequency catheter ablation in experienced centres should be the first-line therapy for incessant ventricular tachycardia.

A case series of drug-induced long QT syndrome and Torsade de Pointes

INTRODUCTION

Torsade de Pointes (Tdp) is a form of polymorphic ventricular tachycardia in the setting of prolonged QT interval. Any drug that prolongs repolarisation, and hence QT interval, may cause Tdp. Predisposing factors of drug-induced Tdp include female sex, bradyarrhythmia and hypokalaemia.

METHODS

We retrospectively analysed the case notes of 13 patients with drug-induced LQTS from 1991 to 2000 from National Heart Centre and Changi General Hospital.

RESULTS

Causative drugs in the series were amiodarone (seven patients, 54%), sotalol (two patients), quinidine (one patient), phenothiazine (two patients) and astemizole (one patient). There were eight females and all were Chinese. The mean age was 72 +/- nine years. The patients commonly present with syncope (38%) and cardiac arrest (38%). The mean corrected QTC interval was 545 ms. The most common precipitating factor was hypokalaemia (31%). Nine patients require cardiopulmonary resuscitation and two patients (15%) died. Nine patients (69%) had underlying structural heart disease such as ischaemic heart disease, valvular heart disease and hypertensive heart disease. The left ventricular ejection fraction was normal in six patients. The onset of Tdp ranged from Day 2 to Day 5 in the seven patient with amiodarone-induced LQTS. These were inpatients who were given intravenous loading doses of amiodarone. Both patients with sotalol-induced LQTS were females on sotalol 80 mg and 240 mg per day with Tdp occurring on Day 2 and 10 months respectively.

CONCLUSION

Tdp is a potentially life-threatening arrhythmia. The list of torsadogenic drugs is ever expanding. Physicians need to know the drugs which can lead to Tdp. Careful assessment of risk-benefit ratio is important before prescribing such drugs. Amiodarone-induced Tdp is not uncommon in our local population. Initiation of a class III agent, especially amiodarone, should be done judiciously, with monitoring of the QT interval and avoidance of hypokalaemia.

Dual-site atrial pacing for atrial fibrillation in patients without bradycardia

Atrial pacing has been shown to delay the onset of atrial fibrillation (AF) when compared with ventricular pacing in patients with sick sinus syndrome. The role for pacing in the control of AF in patients without bradycardia is uncertain. We performed a randomized, crossover, single-blinded study in 22 patients (14 women, aged 63 +/- 10 years) with paroxysmal AF refractory to treatment with oral sotalol (202 +/- 68 mg/day) and no bradycardic indication for pacing. All patients received a dual-chamber pacemaker with 2 atrial pacing leads positioned at the high right atrium and coronary sinus ostium, respectively. Patients were randomized in a crossover fashion to be paced for 12 weeks, either with high right atrial (RA) pacing at 30 beats/min ("Off") or dual-site RA pacing with an overdrive algorithm that maintained atrial pacing at a rate slightly above the sinus rate ("On"). Treatment on resulted in a significantly higher percentage of atrial pacing and a reduction in atrial ectopic frequency than the treatment off period. The time to the first clinical AF recurrence was prolonged (15 +/- 17 to 50 +/- 35 days, p = 0.006), and total AF burden was reduced (45 +/- 34% vs 22 +/- 29%, p = 0.04) in the on-treatment phase. However, there was no difference in AF checklist symptom scores or overall quality-of-life measures. Dual-site RA pacing with continued sinus overdrive prolonged the time to AF recurrence and decreased AF burden in patients with paroxysmal AF. The absence of a major impact on symptom control suggests that pacing should be used as an adjunctive therapy with other treatment modalities for AF.

Comparison of effectiveness of an 8-mm versus a 4-mm tip electrode catheter for radiofrequency ablation of typical atrial flutter

An 8-mm catheter does not appear superior to 4-mm tip electrode for atrial flutter ablation. The potential advantage of allowing higher energy delivery on a larger surface is compensated by the lack of consistent contact with the endocardial surface.

Initial experience with an autocapture pacemaker system

INTRODUCTION

Autocapture management aims to extend pacemaker longevity without compromising on patient safety by automatically monitoring the pacing threshold and adjusting the pacemaker output for consistent capture. This paper describes our initial experience with the Pacesetter Regency pacemaker with autocapture management.

MATERIALS AND METHODS

Nineteen patients were implanted with single chamber pacemakers with autocapture management. Autocapture was programmed "ON" the day after implantation if Evoked Response (ER) amplitude was at least 2.8 mV. The patients were followed up at 2 weeks, 2 months and 6 months. At each visit, pacing threshold and lead impedance were measured. Autocapture was turned "ON" during follow-up if it had not been done previously.

RESULTS

In 16 out of 19 patients, autocapture could be turned "ON" the day after implantation. One patient had an ER signal that was less than 2.8 mV and 2 patients were in fast atrial fibrillation of more than 120 beats per minute which precluded ER signal testing. These patients could not have autocapture programmed "ON".

CONCLUSION

The benefits of autocapture management can only be realised if an ER signal of at least 2.8 mV is obtained. This requires intraoperative testing of the ER signal. Since there is no commercially available pacing system analyser presently that can measure this, modification of the standard implantation procedure with some prolongation of procedure time is needed.

The differential diagnosis of supraventricular tachycardia using clinical and electrocardiographic features

INTRODUCTION

Noninvasive determination of the mechanism of supraventricular tachycardia (SVT) is useful in order to decide on the appropriate mode of therapy. The aim of this study was to evaluate the usefulness of the clinical and electrocardiographic features in diagnosing the type of SVT.

METHODS

Design--A retrospective review of case records and electrocardiograms (ECG) of patients with definitive diagnosis of the mechanism of supraventricular tachycardia (SVT) made during electrophysiological study (EPS) and catheter ablation. Setting--A tertiary referral centre for electrophysiological studies and radiofrequency catheter ablation of arrhythmias. Sample--One hundred consecutive patients with SVT who had EPS and catheter ablation at our institution. Chief Outcome--Comparison of clinical and ECG pacemeters among 3 different types of SVT, namely atrioventricular nodal reentrant tachycardia (AVNRT), atrioventricular reentrant tachycardia (AVRT) and atrial tachycardia (AT).

RESULTS

There were 68 atrioventricular nodal reentrant tachycardia (AVNRT), 26 atrioventricular reentrant tachycardia (AVRT) and 6 atrial tachycardia (AT). AVRT had the earliest mean age of presentation at 26.8 +/- 11.9 years. Sex and age of onset of symptoms alone were, however, not valuable in diagnosing the type of SVT. P waves were more discernible in AVRT and AT than in AVNRT (69%, 67% and 44% respectively, P = 0.071). AVNRT had the shortest mean RP' interval (86.3 +/- 47.6 msec), while AT had the longest (187 +/- 80.6 msec, P < 0.0001). Conversely for mean P'R interval, AT had the shortest (125 +/- 30 msec), AVNRT had the longest (262.7 +/- 73.7 msec, P = 0.001). AVNRT had the smallest mean RP':P'R ratio (0.6 +/- 0.9), while AT had the largest (2.2 +/- 0.6, P = 0.001). The presence of pseudo r' in V1 and pseudo s' in II/III/aVF was diagnostic of AVNRT with a specificity of 90% and 100%, respectively, and positive predictive value of 97% and 100%, respectively.

CONCLUSION

Pseudo s' in II/III/aVF is highly predictive of AVNRT. Measurement of RP' and PR' interval and ratio are also useful in determining the SVT mechanism.

Electrocardiographic case: diagnosis of acute myocardial infarction in the presence of left bundle branch block

The electrocardiographic features associated with acute myocardial infarction (AMI) are often easily recognised. However, interpretation is made more difficult in the presence of confounding patterns such as a left bundle branch block (LBBB). This may result in missed cases which may otherwise have benefited from acute revascularisation therapy. Though not straightforward, the diagnosis of AMI in the presence of LBBB can be made with a reasonable amount of accuracy. We report a case of acute myocardial infarction with LBBB that was appropriately diagnosed and underwent acute revascularisation by angioplasty. A detailed knowledge of the typical electrocardiographic features associated with LBBB, especially the ST segment morphologies, is very important. This will greatly aid recognition of an evolving AMI and help us decide on the most appropriate therapy.

Pacemaker implantation in Singapore in 1997

INTRODUCTION

Previous reports on pacemaker implantation in Singapore have been from a single institution and hence may not accurately reflect the practice in Singapore. As part of the World survey on pacemaker implantation, a survey of all pacemaker implantations in Singapore in 1997 was performed.

METHOD

Information was obtained from the pacemaker manufacturers and a survey form was sent to all doctors involved in pacemaker implantation.

RESULT

In 1997, 206 pacemakers were implanted or replaced in Singapore. This gives a pacemaker rate of 69 per million. For new implants only, there were 61 implants per million. More detailed information regarding the patient and implantation was obtained in 160 (78%) patients. The mean age of the patients was 68.5 +/- 14.4 years (range 2-97 years). There were 142 (89%) new implants and 18 (11%) replacements. 62.5% of the patients were females. Seventy-nine percent of the patients were older than 60 years old and 17.5% were older than 80 years. Seventy-five percent of the pacemakers were single chamber pacemakers. Twenty-five percent were dual chamber pacemakers. Only 1.4% of the pacemakers used epi-myocardial leads and all these were in children. Heart block was the most common indication for pacing and consisted of 52.8% of the patients while 43.0% of patients were implanted for the sick sinus syndrome.

CONCLUSION

Pacemaker implantation in Singapore in 1997 was 69 per million. Heart block remains the most common indication for implant and single chamber pacing is still the most commonly used mode of pacing. The majority of the implants were in persons older than 60 years. With an increasing ageing population in Singapore, the implant rate for pacemakers will be expected to increase significantly.

Incessant ectopic atrial tachycardia and tachycardia-related cardiomyopathy: therapeutic options and potential for cure

Incessant ectopic atrial tachycardia (IEAT) is a rare cause of cardiomyopathy. Cardiomyopathy is reversible by curative ablation using surgery or radiofrequency current. We report our experience with 5 patients with IEAT. Three patients presented with palpitations and were diagnosed to have paroxysmal supraventricular tachycardia (2 patients) and atrial flutter with 1:1 conduction (1 patient), but 2 presented insidiously with congestive cardiac failure. All the initial echocardiograms showed left ventricular dysfunction. The patients underwent electrophysiological studies which confirmed the diagnosis of IEAT. The first patient had surgical cryoablation and the other patients had successful radiofrequency catheter ablation. Follow-up for 2 to 7 years has shown no recurrences. All patients had significant improvement in left ventricular function on echocardiography. In conclusion, curative ablation by surgery or radiofrequency current is safe and effective. Because of its low morbidity, radiofrequency catheter ablation should be the treatment of choice for IEAT, especially if complicated by tachycardia-related cardiomyopathy.

Treatment and prevention of sudden cardiac death--what have we learnt from randomised clinical trials?

Sudden cardiac death is most commonly caused by ventricular tachycardia or fibrillation. Three groups of patients at highest risk for sudden cardiac death are survivors of previous sudden cardiac death, those with recurrent documented episodes of sustained ventricular tachycardia and patients with recurrent syncope of unknown origin. The experience with antiarrhythmic drugs has been discouraging. Only beta-blockers have been shown to unequivocally reduce both arrhythmic and total mortality in randomised trials. Class I antiarrhythmic drugs increase mortality, especially in an ischemic substrate. Class III drugs such as sotalol and amiodarone have had variable success. Racemic sotalol has both beta-blocker as well as Class III actions and some of the benefits may be due to the former effect. D-sotalol which has only pure Class III action, increases mortality in the post myocardial infarction patient. Amiodarone is superior to Class I antiarrhythmic drugs for patients with previous cardiac arrest. In the high-risk myocardial infarction patient, it seems to reduce sudden death but not total mortality. In the cardiac failure patient, the effect of amiodarone on total mortality is controversial. Several randomised trials of implantable cardioverter-defibrillator (ICD) therapy versus drugs have however concluded that the ICD is superior to drugs in reducing total mortality. In comparison with many other high volume therapies used in medicine today, ICD is still a cost-effective therapy.

T wave alternans and acute rheumatic myocarditis: a case report

T wave alternans is an uncommonly recorded cardiac rhythm. We report here an unusual case of a 13-year-old girl with acute rheumatic carditis and acute nephritis, who developed T wave alternans associated with a prolonged QT interval. These electrocardiographic changes were evident only after the initial acute stage of the disease process and should be borne in mind for patients with acute rheumatic carditis as they may be associated with more malignant arrhythmias.

Curative therapy of cardiac tachyarrhythmias with catheter ablation--a review of the experience with the first 1000 patients

INTRODUCTION

Cardiac tachyarrhythmias present as supraventricular or ventricular tachycardia. Catheter ablation has completely revolutionised the treatment of patients with these arrhythmias.

METHOD

We reviewed the experience of radiofrequency catheter ablation in a single centre.

RESULTS

A total of 1,022 patients underwent radiofrequency catheter ablation from October 1991-December 1997. There were 480 patients who had AV nodal re-entrant tachycardia, 429 patients with accessory pathways, 7 patients with both AV nodal re-entrant tachycardia and accessory pathways, 4 patients with both AV nodal re-entrant tachycardia and atrial tachycardia. Twenty-seven patients had atrial tachycardia ablation, 28 had atrial flutter ablation and 11 patients had AV node ablation for atrial fibrillation. The mean age of the supraventricular tachycardia patients was 41 +/- 15 years (10-80 years). The mean duration of procedure was 108 +/- 60 minutes (15 to 480 minutes) and the mean fluoroscopy time was 19 +/- 17 minutes (3-122 minutes). Another 14 patients had ablation for right ventricular outflow tract ventricular tachycardia and 22 patients had ablation for idiopathic left ventricular tachycardia. The mean age of the ventricular tachycardia patients was 35 +/- 14 years (19-65 years). The mean duration of the ventricular tachycardia ablation procedure was 185 +/- 63 minutes (110-285 minutes) and the duration of fluoroscopy was 33 +/- 16 minutes (range 14-68 minutes). Of the 1,022 patients, 1,002 (98%) of the patients were successfully ablated. There were significant complications in less than 1% of the patients and no mortality associated with the procedure. The recurrence rate was 5% and could be successfully reablated when the procedure was repeated.

CONCLUSION

Radiofrequency catheter ablation is thus an extremely safe and successful procedure and has replaced drug therapy as the treatment of choice for patients with supraventricular tachycardia and non-ischaemic ventricular tachycardia. It provides curative therapy without the need for life-long drug therapy.

The Brugada syndrome in a Chinese population

Sudden cardiac death has been reported in patients with a unique electrocardiographic (ECG) abnormality showing right bundle branch block and ST segment elevation in the precordial leads. This syndrome was first described by Brugada and Brugada and has not been previously described in a Chinese population. We report here the first three cases in Singapore. The first patient was a 49-year-old man who presented with syncope, associated with generalized convulsions. The second patient was a 25-year-old man who complained of palpitations but no syncope. The third patient was a 77-year-old man who presented with recurrent episodes of syncope and collapsed with ventricular fibrillation. All patients had no past cardiac or drug history of note. The neurological examination and investigations were normal. All three patients showed a unique right bundle branch block pattern with ST segment elevation in leads V1-3. The echocardiogram and 24-h ambulatory ECG monitoring, were normal. Single vessel disease was present in the third patient. Electrophysiological studies performed in all three patients were able to induce ventricular fibrillation. The patient with resuscitated cardiac death underwent an implantable cardioverter defibrillator implantation. The importance of this syndrome is that the recognition of the unique ECG pattern enables early identification and treatment of these patients.

Interventional electrophysiology and its role in the treatment of cardiac arrhythmia

Cardiac arrhythmias can present as benign ectopics or as life-threatening arrhythmias and sudden cardiac death. Clinical cardiac electrophysiology is the study of the electrophysiology of the heart and all aspects of management of cardiac arrhythmias. The invasive electrophysiological study was initially purely diagnostic, but recent advances in technology has allowed us to intervene and hence the term interventional electrophysiology. The interventional therapies include permanent pacing for bradyarrhythmias, arrhythmia surgery for arrhythmias, percutaneous catheter ablation and implantable devices for tachyarrhythmias. The treatment of bradyarrhythmias with permanent pacemaker implantation represents the first interventional therapy for patients with cardiac arrhythmias. From 1973 to June 1996, a total of 791 pacemakers have been implanted at the Singapore General Hospital. Previously, patients with tachyarrhythmias could only be cured by open heart surgery utilising intraoperative map guided surgery and ablation of the arrhythmia. Only 17 patients with supraventricular tachycardia (SVT) and 3 patients with VT have undergone this procedure. Catheter ablation has completely revolutionised the treatment of these patients. From October 1991 until December 1996, 860 patients have undergone radiofrequency (RF) catheter ablation for SVT and non-ischaemic VT. Ninety-eight per cent of the patients with SVT have been successfully ablated and 94% of the patients with VT were successfully ablated. RF ablation has become the technique of choice to cure patients with recurrent paroxysmal SVT due to AV re-entrant tachycardia using an accessory pathway, AV nodal re-entrant tachycardia, atrial tachycardia and atrial flutter. It is also used for AV nodal ablation followed by pacemaker insertion or AV nodal modification in patients with poorly controlled atrial fibrillation. Patients with idiopathic non-ischaemic VT arising from the left ventricle or right ventricular outflow tract can similarly be cured. For all these patients, RF ablation offers curative therapy, thus eliminating recurrent symptoms, life-threatening attacks, tachycardia cardiomyopathy and need for life-long drug therapy. For patients with resuscitated sudden cardiac death or at high risk for sudden death, the implantable cardioverter defibrillator (ICD) is the only technique that has significantly improved survival from sudden cardiac death. Since August 1992, 11 patients have had the ICD implanted, with 9 surviving. The 2 deaths were due to cardiac failure and not to sudden death. Thus the ICD can prevent sudden death, but the main limitation is the cost of the device and it is not suitable in patients who have severe heart failure. In conclusion, interventional electrophysiology represents a tremendous leap forward in the management of cardiac arrhythmias. With catheter ablation, it offers a safe curative therapy for patients with recurrent SVTs and VTs and with the ICD, prevents sudden cardiac death in patients who have been resuscitated from it or who are at risk for it. The future will see us improving our success in ablating patients with monomorphic ischaemic VT and even atrial fibrillation, and the role of prophylactic ICDs in high risk patients will be better defined.