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Biomedical subjects

R M Kam

Publications and source records attributed to R M Kam.

12 recordsLinked to original sources
PubMed2000

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.

Bundle-Branch Block↗
PubMed2000

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.

Adolescent↗
PubMed2000

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.

Aged↗
PubMed1999

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.

Adolescent↗
PubMed1999

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.

Adrenergic beta-Antagonists↗
PubMed1999

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.

Adolescent↗
PubMed1997

Transient right bundle branch block causing R wave attenuation postdefibrillation.

Transient and significant decrease in R wave amplitude, associated with transient right bundle branch block, was noted to occur after defibrillation in a defibrillator patient. The mechanism is probably stunning of the right bundle branch, causing right intraventricular conduction delay and decrease in signal amplitude reaching the endocardial sensing dipoles.

Bundle-Branch Block↗
PubMed1995

Outpatient coronary angiography using 7 French catheters in Singapore.

PURPOSE: Out-patient coronary angiogram (OCA) is commonly performed in many centres using 5 or 6 French (F) catheters. Though this small catheter may reduce bleeding complications, manipulatability and adequate vessel visualisation are problems which may increase procedure time. 7 or 8 F catheters have been used in Caucasians. We report our experience with OCA using 7 F catheters in an Asian centre. METHODS: Sixty-six patients with low procedural risk were consecutively recruited. They were pre-medicated with oral diazepam. Selective coronary angiogram (SCA) and left ventriculogram were performed via the femoral artery. Parenteral heparin was administered after the arterial puncture. After the procedure, haemostasis was secured by at least ten minutes of manual compression. The patients were immobilised for six hours and thereafter encouraged to walk for about an hour. The groin was inspected by a doctor before discharge and reviewed the following day. RESULTS: The age ranged from 27 to 73 years with a mean of 52.6. There were 48 men and 18 women. Seventeen patients had previous SCA or angioplasty. There was no significant coronary artery disease (CAD) in 26 patients (39.4%). Thirteen patients (19.7%) had minor CAD, 20 (30.3%) had single or double vessel and 7 (10.6%) had triple vessel disease. The mean procedural time was 16.6 +/- 7.3 minutes, ranging from 7 to 54. Seven (10.6%) of the patients had a small haematoma prior to discharge. None of the haematoma deteriorated at review. We did not find sex, age, history of diabetes mellitus or hypertension, height, weight, body mass index, use of anti-platelet agents, systolic blood pressure at and after the procedure and coronary artery anatomy to be associated with an increased risk of haematoma. The estimated cost savings for a non-subsidized patient was S$285 and for a subsidized patient was S$66. CONCLUSION: We conclude that OCA using 7 F catheters is a safe and efficacious procedure in our patients.

Adult↗
PubMed1995

Upright tilt table testing in the evaluation of syncope.

OBJECTIVES: To review our experience with the upright tilt table test for the diagnosis of vasovagal syncope in a group of unselected patients with a history of syncope or presyncope. METHODS: 179 patients with a history of syncope or presyncope were subjected to upright tilt test. After carotid sinus massage to exclude carotid sinus hypersensitivity, the patients were tilted on a motorised tilt table with footplate support to an angle of sixty to seventy degrees for thirty minutes. If syncope was not induced, isoprenaline was then infused for a further fifteen minutes. A positive response was defined as fulfilling at least two out of three criteria: (i) syncope or presyncope similar to the spontaneous episodes of syncope, (ii) relative slowing of the heart rate at the onset of symptoms, (iii) drop of systolic pressure to less than 90 mmHg or by more than 50 mmHg. STATISTICAL METHODS: Continuous variables are expressed as mean values +/- one standard deviation and analysed for statistical significance by the unpaired Student's t-test. Chi-squared test with continuity correction was used for dichotomous variables. RESULTS: Ninety-four patients (53%) were positive for vasovagal syncope. Fourteen patients (8%) were positive at baseline tilt. An additional 80 patients (45%) were positive with the use of isoprenaline. Ten percent of the positive responses were purely cardioinhibitory, 10% purely vasodepressor and 80% mixed. The commonest cardiac rhythm during a positive response was junctional rhythm (46%) followed by sinus rhythm (44%). Sinus arrest with ventricular standstill occurred in only 5%. Accelerated idioventricular rhythm, 2:1 atrioventricular block and ventricular bigeminy accounted for the remaining 5%. CONCLUSION: The upright tilt table test is useful for the diagnosis of vasovagal syncope.

Adolescent↗
PubMed1994

Massive acute pulmonary embolism in protein S deficiency--a case report.

A young man with a history of deep vein thrombosis and pulmonary embolism 11 years ago presented again with acute pulmonary embolism and was treated initially with intravenous heparin at our institution. Five days later he had another massive bout of pulmonary embolism causing hypotension. Pulmonary angiography confirmed the presence of thrombi in both pulmonary arteries, with complete obstruction of the left pulmonary artery. He was treated successfully by emergency pulmonary embolectomy. Blood investigations later confirmed the diagnosis of protein S deficiency and he was started on warfarin therapy for life. Massive pulmonary embolism should be treated aggressively. Thrombolytic therapy accelerates clot lysis, reduces pulmonary pressures, restores pulmonary capillary volume and reverses right heart failure faster than heparin alone. There is also a trend towards decreased mortality with thrombolysis. In the presence of shock, the patient should be resuscitated and if facilities for emergency embolectomy are available, surgery is a viable alternative to thrombolysis, especially if the clot burden is massive. In young patients with recurrent venous thromboembolism in the absence of obvious predisposing factors, it is important to exclude inherited plasma protein deficiencies of protein S, protein C, antithrombin III, plasminogen and fibrinogen.

Acute Disease↗