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Biomedical subjects

W S Teo

Publications and source records attributed to W S Teo.

At least 73 records · Page 4Linked to original sources
PubMed1992

Surgery for cardiac arrhythmias.

From March 1989 to March 1991, 17 patients underwent curative surgical ablation of cardiac arrhythmias at the Singapore General Hospital. In the supraventricular tachycardia group, 13 patients with the Wolff-Parkinson White syndrome (WPW) underwent surgical ablation of the accessory conduction pathway by the classical endocardial approach. Two patients who had atrioventricular nodal tachycardia (AVNRT) underwent surgical dissection around the atrioventricular node to divide one of the dual conduction pathway responsible for the tachycardia. In the ventricular tachycardia group, two patients underwent surgical ablation of the arrhythmic focus. There was no operative mortality in the supraventricular tachycardia group and there were no late deaths to date. All these patients underwent electrophysiological study just before discharge and most of them had a repeat test six months later. In the Wolff-Parkinson White group, surgical ablation was completely successful in 12 patients (92%), preexcitation recurred in one patient (8%) but non had recurrence of supraventricular tachycardia. The two patients who had atrioventricular nodal tachycardia were completely cured of recurrent supraventricular tachycardia and had normal atrioventricular conduction. In the ventricular tachycardia group, one was cured with no recurrence of tachycardia, is not on medication and is in New York Heart Association Class I status. The other died postoperatively of recurrent ventricular tachycardia and low cardiac output syndrome.

Adult↗
PubMed1992

Lipid screening in a volunteer population in Singapore.

Coronary risk profile screening was performed in 1065 volunteers during the National Heart Week 1988 as part of the National Heart Association's campaign against the increasing incidence of ischaemic heart disease. Of particular importance was the use of a desktop analyser for lipid screening of total cholesterol and high density lipoprotein (HDL) cholesterol. It was found that the mean serum cholesterol was 211 +/- 39.5 mg/dl, with 62% of the participants having a total cholesterol greater than 200 mg/dl and 23.1% having a total cholesterol greater than 240 mg/dl. For HDL cholesterol, the mean was 48.4 +/- 17 mg/dl, with 18.7% of the participants having a low HDL cholesterol of less than 35 mg/dl. The male Indians had a significantly lower HDL cholesterol compared to male Malays. Three or more risk factors for coronary artery disease was present in 21.7% of Chinese, 41.2% of Malays and 50% of Indians. We conclude therefore that a proportion of this volunteer population, the majority of which have no overt heart disease, is at risk from coronary artery disease from an elevated cholesterol or low HDL cholesterol level. A follow-up of 90 participants who were initially detected to have an elevated cholesterol in 1986, however, showed that only 54.4% still had an elevated cholesterol of greater than 240 mg/dl, thus suggesting that early detection may help to reduce this risk.

Age Factors↗
PubMed1992

Sudden cardiac death in the Wolff-Parkinson-White syndrome.

Sudden death in the Wolff-Parkinson-White syndrome is an uncommon event but strikes in otherwise healthy children or young adults, often without much warning. They tend to occur in symptomatic but have also been reported in asymptomatic individuals. Several studies have been done profiling the sudden death survivor in the Wolff-Parkinson-White syndrome. In general, they tend to be symptomatic, have a short RR interval between preexcited beats during atrial fibrillation, have multiple pathways and may be associated with familial occurrence and Ebstein's anomaly. Several noninvasive investigations can help to assess the risk for sudden death, but the gold standard remains the use of electrophysiological testing. The management of patients with documented ventricular fibrillation or resuscitation from sudden death is unquestionably ablation of the accessory pathway but for the asymptomatic patients, it is still controversial whether they should be routinely studied by electrophysiological studies.

Death, Sudden, Cardiac↗
PubMed1991

Epicardial mapping in patients with "nodoventricular" accessory pathways.

Some patients with electrophysiologic features suggesting nodoventricular fibers have been shown to have right parietal atrioventricular (AV) accessory pathways with decremental conduction properties intraoperatively. The experience with 11 patients (7 women and 4 men, mean age +/- standard deviation 25 +/- 5 years) who had electrophysiologic features consistent with a nodoventricular pathway and who underwent operative correction was reviewed. At electrophysiologic study, all patients had absent or minimal preexcitation in sinus rhythm. During atrial pacing and extrastimulus testing, maximal preexcitation with left bundle branch block morphology developed and the AH and AV intervals progressively prolonged. Preexcited tachycardia was initiated in all patients (AV reentrant tachycardia in 10 patients and AV node reentrant tachycardia in 1 patient). At operation all patients had a right parietal accessory pathway demonstrated. Intraoperative mapping demonstrated the earliest site of ventricular activation during anterograde preexcitation to be at the midanterior right ventricle, consistent with insertion of these pathways into the right bundle branch system, in 7 patients. The ventricular insertion was at the AV groove in 4 patients, in keeping with the typical Wolff-Parkinson-White syndrome. Retrograde conduction over the pathway was not demonstrated in any patient. Two patients had evidence of a second accessory AV pathway in the left paraseptal region. Operative AV node ablation was electively performed in 2 patients without affecting preexcitation in either case. In 1 of these patients, accessory pathway conduction was temporarily abolished by ice mapping in the right anterolateral AV groove.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Characteristics of accessory pathways exhibiting decremental conduction.

The prevalence, electrophysiologic characteristics and functional significance of decremental conduction over an accessory pathway were examined in this retrospective study of 653 patients who had an accessory pathway demonstrated at electrophysiologic study. Decremental conduction was identified in 50 patients (7.6%). In 15 patients with anterograde decremental conduction, the accessory pathway was right parietal or septal in 14 patients and left parietal in 1 patient. In the 40 patients with retrograde decrement, the accessory pathway was left parietal in 19, posteroseptal in 13, right parietal in 2 and right anteroseptal in 6 patients. Anterograde conduction over the accessory pathway was absent in 11 of the 40 patients with retrograde decrement. Retrograde conduction over the accessory pathway was absent in 9 patients with anterograde decrement. There was no significant difference in the accessory pathway effective refractory period, or shortest cycle length with 1:1 conduction over the accessory pathway in anterograde and retrograde directions. The shortest RR interval in atrial fibrillation between 2 preexcited QRS complexes was longer in patients with anterograde decremental conduction than in a control group of patients with anterograde-conducting accessory pathways without decremental properties. These data demonstrate that decremental conduction over accessory pathways is uncommon. Anterograde decremental conduction usually occurs in right-sided or septal pathways that often do not conduct in the retrograde direction.

Adolescent↗
PubMed1991

Predictive accuracy of electrophysiologic localization of accessory pathways.

Operative ablation of accessory pathways depends critically on preoperative localization when technical limitations preclude complete intraoperative mapping. To assess the accuracy of localization, 345 patients undergoing operative ablation were studied; 316 (91.6%) had a single accessory pathway and 29 (8.4%) had multiple accessory pathways. The electrophysiologic study was diagnostically complete and accurate in 294 patients (93%) with a single accessory pathway and 19 (61%) with multiple accessory pathways. A left lateral accessory pathway was most accurately localized with excellent sensitivity (99%) and positive predictive value (98.5%). Diagnostic errors occurred in 33 patients because of 1) incorrect localization (n = 16), 2) failure to detect a second pathway (n = 9), and 3) diagnosis of a second pathway not verified intraoperatively (n = 8). Multiple pathways were more prevalent in the group with errors (33.3% vs. 5.8%, p = 0.0001), as were unidirectional pathways (48.5% vs. 24.3%, p = 0.003). It is concluded that preoperative localization of accessory pathways is sufficiently accurate to allow intraoperative mapping to be brief and focused.

Adult↗
PubMed1991

Hypothesis testing as an approach to the analysis of complex tachycardias--an illustrative case of a preexcitation variant.

The correct elucidation of the electrophysiological substrate and mechanism(s) responsible for a complex arrhythmia requires a systematic approach to the analysis of the electrophysiological data. One approach calls for the formulation of a set of hypotheses that could explain the data obtained during the study. The hypotheses are then tested for compatibility with phenomena observed and the one that agrees with the majority of the findings would represent the most tenable explanation. We present the case of a young girl with a wide QRS complex tachycardia and a history of ventricular preexcitation that illustrates this approach. The complexities were resolved only after intraoperative analysis and surgical ablation of a right-sided accessory pathway with decremental properties, and provides further insight into our understanding of the nodoventricular Mahaim fiber.

Anti-Arrhythmia Agents↗
PubMed1991

Pacing experience with the atrial screw-in leads at the Singapore General Hospital.

This is a retrospective study of atrial screw-in leads implanted at the Singapore General Hospital from January 1988 to August 1990. There were 21 (13 female and 8 male) consecutive patients, with age ranging from 17 to 79 years (mean 55 years). Thirteen patients had sick sinus syndrome and the remaining eight patients had high grade AV block. Eleven patients had AAI, six had DDD and four had DDDR pacing modes respectively. Three different models of unipolar screw-in leads were used. Eight patients had Medtronic Model 6957, seven had Medtronic Model 4057 and six had Siemens-Pacesetter Model 1007 pacing leads implanted. At the time of implant, the measured P wave amplitudes ranged from 1 to 4.8 mV (2.5 +/- 1.1 mV) and the pacing thresholds ranged from 0.5 to 2.3 volts (1.21 +/- 0.51 volts). There were no acute complications at the time of implant. On follow-up ranging from one month to two years, two patients had inadequate sensing in the atrium and one patient had high pacing threshold. There were no lead dislodgement. In conclusion, these screw-in leads can be safely used in the atrium with acceptable pacing characteristics.

Adolescent↗
PubMed1991

Catheter ablation of idiopathic exercise-induced right bundle branch block and left axis deviation ventricular tachycardia.

Catheter ablation of ventricular tachycardia was performed in a patient without evidence of structural heart disease. ECG showed ventricular tachycardia and a right bundle branch block QRS configuration with left axis deviation induced by exercise and atrial pacing. At electrophysiology, presystolic activation was found in the low septal region of the left ventricle. Radiofrequency energy delivered to this site failed to prevent tachycardia. Three direct current shocks (total energy 400 J) delivered in this region rendered the tachycardia noninducible. There were no complications. During the follow-up period of six months the patient has remained free from arrhythmia on no medication. This report expands the use of catheter ablation to patients with idiopathic ventricular tachycardia ('verapamil responsive' ventricular tachycardia) originating in the left ventricle.

Bundle-Branch Block↗
PubMed1990

Feasibility of long-term electrocardiographic monitoring with an implanted device for syncope diagnosis.

Patients with infrequent recurrent syncope undiagnosed after extensive noninvasive and invasive testing pose a diagnostic and therapeutic dilemma. The purpose of this pilot study was to assess the feasibility of using an implanted, long-term monitor as an aid to diagnosis in these patients. This was done using commercially available pacemakers with monitoring functions. Sixteen patients (eight males and eight females), aged 59.7 +/- 17 years who had unexplained syncope despite a 12-lead electrocardiogram, repeated Holter monitoring, exercise testing, echocardiography, an electrophysiological study, and a tilt test (n = 6), were entered into the study. Patients had experienced a mean of 3.1 +/- 1 episodes of syncope in the 12 months prior to the study. All provided a history suggestive of Stokes-Adams attacks and were referred for consideration of pacemaker implantation. Two patients had ischemic heart disease and one patient had a long QT interval. Patients had an Intermedics Nova II or Medtronic Quintech DPG pulse generator capable of recording sensed and paced events implanted with a single right ventricular lead. Syncope or presyncope occurred in ten patients (62%) 4.9 +/- 4.2 months after pacemaker implantation. Bradycardia was detected in six patients and four patients had no arrhythmia. In addition to bradycardia, one patient also had tachycardia detected. Pacing therapy resulted in symptom relief in all six patients with syncope or presyncope due to bradycardia. Complications of pacemaker implantation (lead insulation failure) occurred in two patients. One of these patients subsequently had an infection of the generator pocket with associated systemic sepsis.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1990

Ventricular septal rupture in acute myocardial infarction.

This is a review of 31 patients with ventricular septal rupture occurring in myocardial infarction which have been managed at the Singapore General Hospital. Ventricular septal rupture occurs more frequently in the elderly, in females and those presenting with the first myocardial infarction. Very few have a prior history of stable angina pectoris before the myocardial infarction. Sudden deterioration as manifested by an increase in heart rate, fall in blood pressure and signs of right heart failure in a patient with acute myocardial infarction (AMI) especially if accompanied by a systolic murmur should encourage a search for a mechanical cause, especially a ventricular septal rupture. 2D echocardiography or Swan-Ganz catheterisation are 100% diagnostic and can be easily and rapidly done at the bedside. Medical management includes vasodilator therapy and inotropic support. Intra-aortic balloon counterpulsation is especially useful and was instituted in 6 patients. Early surgical repair of the ventricular septal defect is important if overall prognosis of these patients is to be improved. Our operative survival of 42.9% is comparable to others, considering that without surgery all have died. Survival appears to be related to the site of the myocardial infarction (very poor prognosis in inferior myocardial infarction), operative treatment (no survivors if treated conservatively) and the mode of presentation (poor prognosis in patients who develop a ventricular septal rupture while in hospital).

Aged↗
PubMed1990

Anti-arrhythmic surgery for atrioventricular junctional and atrioventricular re-entrant tachycardia--a report of six cases.

Since 15th March 1989, six patients with recurrent supraventricular tachycardia (SVT) had antiarrhythmic surgery performed. There were 4 males and 2 females, ages ranged from 23 to 62 years (mean 41 years). Two of these patients with the Wolff Parkinson White (WPW) syndrome also had syncope. Five of these patients had atrioventricular re-entrant tachycardia (AVRT) involving the bypass tracts. Two patients with the WPW syndrome had persistent antegrade conduction, two had intermittent conduction and the last patient had no antegrade conduction via the bypass tract. The bypass tracts were localised at the left free wall in all the five patients. Only one patient had atrioventricular junctional re-entrant tachycardia (AVJRT) of the slow-fast type. The indications for surgery for these patients include failed medical therapy, "dangerous" arrhythmias and patient's preference. All the patients had surgery performed using the endocardial dissection technique on the cardioplegic heart. There were no perioperative mortality and morbidity. All the patients were discharged within 2 weeks. To date, none of the patients had clinical recurrence of SVT and only one patient remained in atrial fibrillation and is on digoxin. In conclusion, antiarrhythmic surgery should be considered for patients with "symptomatic" palpitations as it is curative with a resumption to normal life.

Adult↗