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Biomedical subjects

D P Myburgh

Publications and source records attributed to D P Myburgh.

At least 19 recordsLinked to original sources
PubMed1991

A comparative study of atenolol, nifedipine and their combination in the treatment of hypertension.

The antihypertensive effects, as assessed by clinical and ambulatory blood pressure measurement, of nifedipine slow-release (SR), atenolol and the two in combination were evaluated in 28 known hypertensives in a placebo-controlled, double-blind, randomised cross-over trial. Clinical blood pressure was significantly lower on combination therapy (P less than 0.025) than on either agent alone, although all therapeutic agents reduced blood pressure significantly when compared with placebo (P less than 0.01). All ambulatory blood pressure measurements obtained on any therapeutic agent were significantly lower than those obtained on placebo (P less than 0.01). The mean daytime (08h00-17h00) ambulatory blood pressure measurement as well as the percentage of this monitoring period during which patients were hypertensive were significantly lower (P less than 0.01) on combination therapy than on nifedipine SR. A similar pattern was observed for 24-hour ambulatory blood pressure measurements. Headache was the most significant adverse effect. This was most common with nifedipine SR, less common with combination therapy and least common with atenolol. Combination therapy with nifedipine SR and atenolol is therefore a viable therapeutic alternative in the treatment of patients with benign essential hypertension.

Adult↗
PubMed1991

Observer accuracy and confirmation of the important role of abnormal ST/T time course behavior in the evaluation of stress electrocardiograms.

Routine exercise electrocardiography has been criticized for yielding too many so-called "false-positive" results. Recent studies in our institution indicate that evaluation of the time course behavior of ST segment and T wave (ST/T) changes after cessation of exercise differentiates ischemic from non-ischemic ("false-positive") stress electrocardiograms (SEs). Our method of assessing time course behavior is clarified. The principal aim of this study was to determine the accuracy of experienced observers in making this differentiation. Records of consecutive patients undergoing coronary arteriography over a 2 year period were reviewed and 30 with SEs judged positive for ischemia by the widely accepted ST/T configurational criteria alone were selected at random for the investigation. Sixteen subjects had normal coronary angiograms and had therefore previously been regarded as having false-positive SEs. Fourteen patients had at least one significantly (> 70%) stenosed coronary artery which was our yardstick for ruling that true myocardial ischemia, due to epicardial coronary artery disease (CAD), was present. Five observers, familiar with post-exercise ST/T time course patterns, independently and "blindly" analyzed all 30 configurationally abnormal SEs. Observers were informed only of the patient's age and sex; they were thus unaware of symptoms, exercise variables, coronary anatomy and the number of patients in the 2 groups. The observer consensus for ischemia of SEs using time course analysis was: total test accuracy 87%, sensitivity 79%, specificity 94%, positive predictive value 92% and negative predictive value 83%. Because all 30 patients had ST/T abnormalities, results of the sample for ischemia based on configurational criteria alone were sensitivity 100%, specificity 0% and positive predictive value 47%. We concluded that time course analysis plays a crucial role in evaluating SEs and that exercise electrocardiography remains a safe, cost-effective and reliable method of screening many asymptomatic, as well as symptomatic, subjects for CAD.

Coronary Angiography↗
PubMed1991

Post-exercise time-course analysis of ST segment and T wave changes: an important contribution to the role of stress electrocardiography in aircrew.

Flight surgeons recognize that ongoing vigilance is necessary to detect coronary artery disease (CAD) in aircrew. Regular physical examinations with only a resting electrocardiogram, albeit having a very low predictive value for detection of CAD in asymptomatic subjects, are now widely practised. Routine stress electrocardiography has been criticized for yielding too many so-called "false positive" results because ST/T changes that develop during and after exercise are prevalent. Recent studies in our institution indicate, however, that the time-course behavior patterns of these ST/T configurational "abnormalities" after exercise are different from those reflecting myocardial ischemia due to epicardial CAD. Time-course analysis increases the predictive value of exercise testing and has dramatically decreased the number of asymptomatic aircrew being subjected to coronary arteriography in our institution. Routine exercise electrocardiography provides a reliable, cost-effective means of detecting aircrew with CAD and a baseline for comparison at subsequent examination, and we strongly recommend that it be universally reinstated.

Adult↗
PubMed1990

Evaluation of the post-exercise time-course behaviour of ST-segment and T-wave changes in the elimination of the false-positive stress ECG.

Routine stress ECG has been criticised for yielding too many so-called false-positive results because ST-segment and T-wave (ST/T) changes that develop during and after exercise are prevalent. Recent studies in our institutions indicate that the time-course behaviour patterns of ST/T configurational abnormalities after exercise reflecting myocardial ischaemia are different from those that do not. The epicardial coronary arteries of 111 patients, who had positive stress tests for ischaemia based on ST/T configurational changes alone but were considered non-ischaemic when the ST/T time-course behaviour was analysed, were assessed. Of these patients, 102 had normal coronary arteries, 7 had insignificant stenoses and only 2 had significant coronary artery diseases. ST/T abnormalities on stress testing with a non-ischaemic time-course pattern should be regarded in the same category as ST segments that remain normal as far as the detection of myocardial ischaemia due to epicardial coronary artery disease is concerned. This policy has resulted in an improved predictive value of exercise testing and has considerably decreased the number of patients subjected to coronary arteriography in our institutions. The assessment of the post-exercise stress ECG remains the most practical and cost-effective method for detecting ischaemic heart disease.

Adolescent↗
PubMed1990

Bezafibrate and simvastatin (MK-733) in the treatment of primary hypercholesterolaemia.

Simvastatin, a new 3-hydroxy-3-methylglutaryl co-enzyme A reductase inhibitor, was compared to bezafibrate, a fibric acid derivative, in an open cross-over placebo-controlled study. Bezafibrate was administered as a 200 mg dose 3 times daily, while simvastatin dosage ranged from 10 mg to 40 mg once daily at night. Bezafibrate produced a non-significant 13.1% (P = 0.113) decrease in total cholesterol (TC), a 20.7% (P less than 0.05) decrease in low-density lipoprotein cholesterol (LDL-C), an increase of 26.5% (P less than 0.01) in high-density lipoprotein cholesterol (HDL-C) and an improvement in the HDL:LDL ratio of 77.3% (P less than 0.01). Simvastatin 10 mg and 20 mg daily reduced TC by 18.6% and 22.6%, respectively, and LDL-C by 23.9% and 28.6% respectively (P less than 0.01), while no significant increase was noted in HDL-C. Simvastatin 40 mg daily reduced TC and LDL-C by 27.1% and 37.6%, respectively (P less than 0.01), increased HDL-C by 32.0% (P less than 0.05) and improved on the HDL:LDL ratio by 130.8% (P less than 0.01). This showed improvements over bezafibrate of 13.5% for TC, 18.9% for LDL-C, 6.0% for HDL-C and 55.8% for HDL:LDL ratio. It was concluded that simvastatin was well tolerated and had significant hypocholesterolaemic effects when taken once daily.

Adult↗
PubMed1990

Effects of therapy with diet and simvastatin on atherosclerosis in hypercholesterolemic patients.

We evaluated the effect of cholesterol reduction on atherosclerotic coronary artery lesions using diet and simvastatin, a potent HMG CoA reductase inhibitor. Fifteen subjects aged 28-69 years (mean 44), each of whom demonstrated significant (greater than 50%) narrowing of a coronary artery and a baseline cholesterol level greater than 278 mg/dl, were studied. Coronary arteriography was performed prior to and after 20 +/- 2.5 months of therapy. A 42% reduction in total serum cholesterol, a 52% reduction in LDL cholesterol, and an 87% increase in the HDL/LDL cholesterol ratio (p less than 0.01) were achieved. Pretreatment and posttreatment angiograms were reviewed by three experienced angiographers with temporal order masked. Improvement in the overall status of coronary atherosclerotic lesions was demonstrated in two patients (13%), while deterioration occurred in one patient (7%). No overall change was found in the remaining 12 patients (80%). We conclude that a cholesterol-lowering regimen using a nonatherogenic diet and simvastatin therapy may at least stabilize coronary atherosclerosis.

Adult↗
PubMed1990

The aeromedical implications of atrial fibrillation.

A retrospective study was undertaken to determine the incidence of spontaneous atrial fibrillation (AF) in a group of asymptomatic pilots. The electrocardiograms of 13,037 aircrew members accumulated between 1964 and 1986 were reviewed and those coded for AF were extracted. In each case an attempt was made to investigate factors relating to the onset, course, and prognosis of the AF. Eight subjects (mean age 50.1 years) were found to have AF. Of this group, two had a single isolated episode of AF for which a specific precipitating factor was implicated, three had recurrent paroxysmal AF of which one progressed to chronic persistent AF, and three had chronic persistent AF from the outset. The mean follow-up period for the eight subjects was 13.6 years. The two pilots who had isolated attacks of AF have thus far had no subsequent episodes of AF. Five of the remaining six have been completely well, while one required treatment for an embolus to his left leg. Concerning the aeromedical implications, we believe that pilots demonstrating single isolated episodes of AF in the presence of a normal heart, and in whom recovery is complete, should be allowed to return to full aviation duties on a waiver clause. Patients with chronic AF, lone AF, or paroxysmal AF should be excluded from all flying duties.

Adult↗
PubMed1979

The efficacy of sotalol in suppressing ventricular ectopic beats.

Sotalol (Sotacor) is a beta-adrenergic receptor blocking agent, which in addition possesses class III anti-arrhythmic properties. In this study we report on the clinical effectiveness of sotalol in the suppression of ventricular ectopic beats in 20 patients suffering from ischaemic heart disease. Sotalol was compared with placebo and efficacy was determined by Holter tape monitoring. Sotalol produced an 88,5% (P < 0,001) reduction in ectopic beat frequency at the optimal titrated dosage, with relatively few physical or biochemical side-effects. In situations where ventricular anti-arrhythmic therapy is deemed necessary, especially if long-term use is considered, sotalol seems to be the agent of choice.

Adult↗
PubMed1979

Prognostic significance of ventricular ectopic beats in chronic ischaemic heart disease.

Holter studies were performed periodically over a period of up to 7 years (mean 33 months) in 175 post-myocardial infarction patients. According to the number of ventricular ectopic beats (VEBs), the patients were classified into two main groups: those with few VEBs, i.e. less than 8 per hour, and those with many, i.e. 8 or more per hour. By comparing the number of ectopic beats during the different monitoring sessions, it was found that individual patients tended to remain in their originally allocated groups. Patients with frequent VEBs were more likely to die suddenly, the difference being significant (P < 0,001). No association could be demonstrated between recurrent non-fatal myocardial infarction and ectopic beat frequency (P > 0,10).

Adult↗
PubMed1978

The anti-arrhythmic efficacy of perhexiline maleate, disopyramide and mexiletine in ventricular ectopic activity.

The anti-arrhythmic efficacy of perhexiline maleate, disopyramide and mexiletine has been evaluated in 27 patients with chronic ischaemic heart disease who exhibited frequent ventricular ectopic beats (i.e. greater than or equal to 8/h). Holter tape recordings were made during normal working hours before, during and after the sequential administration of the three drugs. Each drug was administered to each patient for a 2-month period. The drug had to be discontinued in 4 cases because of side-effects. A significant reduction (P less than 0,001) in ectopic beat frequency occurred with all three drugs. No significant difference in anti-arrhythmic potency could be demonstrated between the drugs.

Adult↗
PubMed1978

Long-term effect of perhexiline maleate on ventricular ectopic activity.

The effectiveness of perhexiline maleate in the suppression of ventricular ectopic activity has been studied in 10 patients after myocardial infarction. Before treatment all patients exhibited frequent ectopic beats, i.e. more than 8 per hour. Numerous Holter magnetic tape recordings were made over a 9 - 10-month period of treatment. During the entire period of monitoring significant suppression of ectopic activity was observed in 5 patients and transient suppression in 4, of whom 3 subsequently showed a transient increase. The drug was discontinued in 1 patient because of nausea, anorexia and weight loss. No other adverse effects were encountered.

Anti-Arrhythmia Agents↗
PubMed1978

Repetitive ventricular ectopic activity in chronic ischaemic heart disease.

The characteristics of repetitive ventricular ectopic activity in 175 ambulatory patients after myocardial infarction are analysed. A total of 1 500 magnetic tape recordings were made on these patients over a period of up to 8 years. In the group of patients exhibiting few ectopic beats, i.e. less than 8/h, the incidence of ventricular salvoes and tachycardia was 9% and 4% respectively, whereas in the group exhibiting many ectopic beats, i.e. greater than or equal to 8/h, the incidence of ventricular salvoes and tachycardia was 60% and 30% respectively. Even though only 1 patient in the first group, exhibiting repetitive ventricular ectopic activity, died, in contrast to 10 in the second group, this is not of statistical significance. The coupling intervals between preceding normal sinus beats and beats which led to repetitive ventricular discharge were clustered between the shortest and the longest coupling intervals which did not lead to salvoes and tachycardia.

Adult↗
PubMed1977

Persistent ventricular ectopic beats: a long-term study.

Electrocardiograms of 8 000 flying personnel, who had been undergoing routine medical examinations from 1963 to 1976, were analysed for the presence of ventricular ectopic beats (VEB). Those in whom VEB persisted, i.e. VEB of the same form recorded in two or more tracings taken at least 1 year apart, were carefully examined for the presence of cardiovascular disease and followed up. VEB were detected in 178 (2,2%) of the 8 000 subjects. Of the 98 subjects followed up after VEB had been detected, 54 (55%) showed persistence of this arrhythmia. Significant cardiovascular disease, i.e. ischaemic heart disease, hypertension or atrial fibrillation, developed in 15 (27%) of these subjects at some time during the study. No instances of sudden death occurred over a mean follow-up period of 8,3 years, even though complex (multiform, repetitive or alternating) VEB were recorded in 20 (37%) of the 54 subjects.

Adolescent↗