The reelin pathway components disabled-1 and p35 in gangliogliomas--a mutation and expression analysis

Focal epilepsies in young patients are frequently associated with differentiated glioneuronal tumours. Dysplastic neurones represent a characteristic neuropathological feature of gangliogliomas, the most common entity encountered in this group. Here, we have analysed two major components of the reelin pathway involved in neuronal migration and cortical development, that is, p35 and disabled-1 (dab1), in gangliogliomas. Genomic structures of human dab1 and p35 were identified 'in silico' using the HTGS databank, NCBI BLAST 2.1. DNA sequence analysis was carried out in gangliogliomas obtained from 29 epilepsy patients vs. peripheral blood DNA from non-affected control individuals (n = 100). Gene expression of dab1 and p35 was determined by real-time RT-PCR (reverse transcriptase polymerase chain reaction) in gangliogliomas (n = 14) vs. non-neoplastic central nervous system tissue (n = 20). The human dab1 gene contains 13 coding exons and is located on chromosome 1p31-32. A single coding exon constitutes the human p35 gene, which is located on chromosome 17q11.2. A novel homologueous genomic region on chromosome 2 has to be taken into account for future studies on p35. One ganglioglioma patient showed a unique polymorphism in the p35 gene. The single base exchange (C to A) at nucleotide 904 of the p35 cDNA (GenBank X80343, start ATG, codon 302) results in a leucine-isoleucine amino acid substitution. No mutations of the dab1 and p35 genes in gangliogliomas were observed. However, significantly lower levels of dab1 and p35 gene transcripts were detected in gangliogliomas compared to controls (dab1 28.24%, t-test P < 0.001; p35 21.28%, t-test P < 0.001, in gangliogliomas vs. controls). Our data suggest that mutational events of dab1 and p35 are not involved in the molecular pathogenesis of gangliogliomas. A potential functional role of these developmentally regulated genes for the formation of epileptogenic glioneuronal lesions remains to be elucidated.

Ethnic variations in female vulnerability after an acute coronary event

OBJECTIVE

To determine the ethnic variation of short and long term female vulnerability after an acute coronary event in a population of Chinese, Indians, and Malays.

DESIGN

Population based registry.

PATIENTS

Residents of Singapore between the ages of 20-64 years with coronary events. Case identification and classification procedures were modified from the MONICA (monitoring trends and determinants in cardiovascular disease) project.

MAIN OUTCOME MEASURES

Adjusted 28 day case fatality and long term mortality.

RESULTS

From 1991 to 1999, there were 16 320 acute coronary events, including 3497 women. Age adjusted 28 day case fatality was greater in women (51.5% v 38.6%, p < 0.001), with a larger sex difference evident among younger Malay patients. This inequality between the sexes was observed in both the pre-hospitalisation and post-admission periods. Among hospitalised patients, women were older, were less likely to have suffered from a previous Q wave or anterior wall myocardial infarction, and had lower peak creatine kinase concentrations. Case fatality was higher among women, with adjusted hazard ratios of 1.64 (95% confidence interval (CI) 1.43 to 1.88) and 1.50 (95% CI 1.37 to 1.64) for 28 day and mean four year follow up periods. There were significant interactions of sex and age with ethnic group (p = 0.017). The adjusted hazards for mortality among Chinese, Indian, and Malay women versus men were 1.30, 1.71, and 1.96, respectively. The excess mortality among women diminished with age.

CONCLUSION

In this multiethnic population, both pre-hospitalisation and post-admission case fatality rates were substantially higher among women. The sex discrepancy in long term mortality was greatest among Malays and in the younger age groups.

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.

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.

Gender differences in outcome after an acute myocardial infarction in Singapore

OBJECTIVES

To characterise gender and age-related differences in presentation and outcome after an acute myocardial infarction (AMI).

DESIGN

Data were derived retrospectively from the Singapore Myocardial Infarction Registry from 1988 through 1997. This database comprised all AMI cases for ages between 20 and 64 years (group A). For approximately three months a year, data were also collected for all AMI cases above the age of 64 years (group B). There were 13,048 and 4,425 cases in groups A and B respectively.

RESULTS

In age - standardised AMI rates, males outnumbered females by a factor of 4.0 and 1.7 for groups A and B respectively.The median age of presentation was higher in females for both age groups being 58 years versus 54 years for group A and 75 years versus 72 years for group B. Younger females had worse survival at 28 days and were more likely to have prior ischaemic heart disease and require resuscitation. They were also more likely to have atypical symptoms. Previous myocardial infarction was not different between the sexes in both groups. Among the older age group, there was no gender difference in prior ischaemic heart disease, 28-day survival and requirement for resuscitation.

CONCLUSION

Women who have AMI tend to be older than men. Gender differences are age-specific. Women who are 64 years and below have more atypical symptoms, prior ischaemic heart disease and worse prognosis than men after AMI. These differences are not seen in those over the age of 64.

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.

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.

Effects of baclofen on striatal 5-HT mediated by the nigrostriatal dopamine system

In rats, baclofen injected unilaterally into the substantia nigra increased dopamine (DA) and serotonin (5-HT) levels in the ipsilateral striata. Homovanillic acid levels first decreased and then increased to a maximum after 4 h. The content of 3,4-dihydroxyphenylacetic acid also increased after a latency of about 1 h. The effects of baclofen on striatal DA metabolism are consistent with the assumption that impulse flow in these DA neurones was diminshed by the drug. DA metabolites were also found in greater quantities in the contralateral striata, probably owing to compensatory activation of these DA neurones. Baclofen injected intranigrally did not increase the striatal 5-HT content in rats with a 6-hydroxydopamine-induced lesion of the nigrostriatal DA pathway. Our results suggest the presence of DA receptors on striatal 5-HT terminals or on interneurones synapsing axo-axonally with them.