Biomedical subjects
J G Sloman
Publications and source records attributed to J G Sloman.
Recent concepts in the management of ischaemic cardiac syndromes.
Ischaemic heart disease is the most important cause of death in our society. Knowledge of the natural history of the various ischaemic syndromes leads to better management, with emphasis on prevention of cardiac necrosis rather than management of its sequelae. This article is from the Department of Cardiology, Royal Melbourne Hospital.
The malfunctioning pacemaker system. Part I.
The success of an implanted cardiac pacemaker is dependent upon the establishment of a harmonious relationship between the artificial pacemaker and the human receiver. Failure of a pacemaker system may arise from an electronic or mechanical defect within the pacemaker, a physiologic problem, or from a poor relationship between the normal function of both. Such malfunctions may necessitate the repair, replacement, or repositioning of a pacemaker component or removal of a source of external interference. True pacemaker malfunctions must be clearly distinguished from pseudo-malfunctions, where there is no pacemaker system defect. These situations may, variously, require the repair of faulty testing equipment, reassessment of falsely interpreted test data, or treatment of the patient for an unrelated disorder. This paper outlines a system for investigating patients with suspected pacemaker malfunction. For simplicity, only malfunctions associated with the ventricular inhibited pacing system will be discussed.
The malfunctioning pacemaker system. Part III.
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The malfunctioning pacemaker system. Part II.
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An assessment of the clinical use of glyceryl trinitrate in a hospital outpatient population.
Despite the availability of information on the use of glyceryl trinitrate (GTN) in standard texts, in practice many patients fail to obtain maximum benefit from GTN. This study of an Outpatient population, documents the patients' knowledge of the use and precautions which should apply to GTN and records the ways in which these patients took the drug. Fifty patients who regularly took GTN (greater than 5 tablets per week) were asked a series of questions by the same interviewer. Forty-nine of the 50 patients took GTN for the relief of chest pain, but only 34 patients knew that the drug could be used to prevent chest pain. Although 48 patients kept their bulk supply of GTN in the original container, over 40% transferred some or all of the tablets to other containers and locations. Seventy per cent of patients knew that GTN tablets deteriorate with time. However, knowledge of the factors which influence the rate of deterioration was lacking. Less than half the patients knew that the prompt relief of pain or the local effects on the buccal mucosa could be used as simple tests of the activity of tablets. It is recommended that all physicians should take more time to explain to their patients how to use glyceryl trinitrate correctly.
Multiform ventricular tachycardia.
Electrophysiological studies were performed in three patients with chronic recurrent ventricular tachycardia (VT) associated with coronary artery disease. In each case the ventricular origin of the tachycardia was confirmed and induction of tachycardia by programmed stimulation suggested a re-entry mechanism. Multiple types of ventricular tachycardia were observed which differed in cycle length, QRS morphology, timing of local epicardial and endocardial ventricular electrograms and the use of the specialized conduction system for propagation. There was evidence of one or more re-entry circuits arising in or near previously infarcted areas, with features of cycle length alternation, change in exit points and variations in subsequent conduction through the myocardium and specialized conduction tissues. These findings suggest multiform VT can be due to a number of factors. A modified surgical approach is recommended for management of medically refractory VT when there is evidence of multiple types.
Chronic diphenylhydantoin therapy does not reduce plasma 25-hydroxy-vitamin D.
A randomized controlled study was performed to investigate the effect of 2 years' monitored diphenylhydantoin (DPH) therapy on plasma 25-hydroxyvitamin D (25-OHD) in non-epileptic, non-institutionalized subjects. Mean +/- SEM plasma 25-OHD of 18 DPH-treated subjects at the end of 2 years' drug treatment was 59 +/- 8 nmol/l (23.6 +/- 3.2 ng/ml), which was not decreased compared to that of eighteen control subjects (54 +/- 8 nmol/l, 21.6 +/- 3.2 ng/ml). In addition, mean plasma 25-OHD had not changed 1 month after ceasing DPH. The treated group had a higher mean serum alkaline phosphatase (SAP) during DPH treatment, attributable to hepatic enzyme induction. It is concluded that therapeutic doses of DPH without other anticonvulsants do not have a clinically significant effect on plasma 25-OHD.
Chronic recurrent ventricular tachycardia--an electrophysiological study.
Electrophysiological techniques were used to study 17 patients with chronic recurrent ventricular tachycardia. Twelve of the patients had coronary disease, while eight had pre-existing intraventricular conduction defects. The site of origin of the tachycardia as deduced by analysis of the QRS morphology correlated well with the electrocardiographic evidence of the site of the old infarction. Ventricular tachycardia was induced by pacing techniques in eight patients while it occurred spontaneously during the study in two others. In only four of the eight patients in whom tachycardia was induced, could the arrhythmia be reinduced; the arrhythmia could not be reproduced in one, while reproducibility was not assessed in the remaining three. Tachycardia was terminated by pacing techniques in six patients and by DC cardioversion in four. Ventricular tachycardia was initiated with a run of "torsade de pointes" in four patients. Ventricular tachycardias with varying morphology were observed in three patients. Electrophysiological study was of significant benefit in patient management in 14 of the 17 patients, particularly those with pre-existing intraventricular conduction defects, undocumented tachycardia or undocumented syncope.
The use of balloon-tipped electrodes for permanent cardiac pacing.
A new balloon-tipped ventricular endocardial electrode for permanent artificial cardiac pacing is described. Following transvenous insertion of the electrode to the right ventricular apex, the distal balloon is inflated with contrast material in order to wedge the electrode tip between or beneath trabeculae and prevent displacement. fifty-nine electrodes were implanted, including a second generation type incorporating a wedge tip as well as the balloon. The incidence of displacement was 17% with 10% of cases being early, and 7% late. Early in the series, 50% Urografin was used to inflate the balloon and this resulted in premature deflation and early electrode displacement in two of the nine patients. When the concentration of Urografin was reduced, the balloon remained inflated for a longer period and the incidence of early displacement was reduced to 8%. However, there was still a late displacement of 8%. Only one wedge-tipped balloon electrode displaced. This electrode had a faulty sealing mechanism and the balloon could not be adequately inflated. There was a 3% incidence of early and a 3% incidence of late threshold problems with the electrode. However, name of the wedge-tipped balloon electrodes exhibited this problem. It was concluded that this new electrode did not fulfill its objectives. The total electrode failure rate, including displacements and episodes of high threshold was approximately 24%.
Similar QRS morphology in sinus rhythm and ventricular tachycardia.
A 74-year-old man with coronary artery disease and bifascicular block suffered recurrent tachycardia. Although the similarity of QRS morphology in tachycardia and sinus rhythm suggested a supraventricular origin, His bundle electrocardiography and programmed stimulation showed a ventricular origin. Digitalis toxicity was not an etiological factor and there was no evidence to suggest a His bundle tachycardia. The case illustrates that in occasional circumstances the onset of ventricular tachycardia may produce no change in QRS morphology thus making the diagnosis by conventional electrocardiographic criteria difficult.
Sinus arrhythmia in acute myocardial infarction.
Sinus arrhythmia, defined by means of a calculation of variance of the R-R interval on admission to hospital, was present in 73 of 176 patients admitted to a coronary care unit with acute myocardial infarction. These patients had a lower hospital mortality. They tended to have a higher incidence of inferior infarction, and a lower incidence of anterior infarction, and to have smaller infarcts as measured by the Norris index. The main difference between patients with sinus arrhythmia and without sinus arrhythmia related to heart rates on admission to hospital, the patients with the former having slower heart rates at that time.
Acute myocardial infarction in women. The influence of age on complications and mortality.
The prognostic implications of a past history of ischaemic heart disease, site of infarction, ectopic ventricular dysrhythmias (ventricular premature beats (VPB) more than one in 10 sinus beats, and/or ventricular tachycardia (VT), ventricular fibrillation (VF), atrioventricular blocks (AVB), bundle branch blocks (BBB)) and the occurrence of electrical and/or mechanical complications during stay in the Coronary Care Unit (CCU) were analysed in 154 women with definte (WHO Class 1) acute myocardial infarction, admitted sequentially to the CCU over a four-year period. The prognosis in these women was then compared with the prognosis in a group which represented the general male population in the CCU and an age-matched group of men. The results showed that the long-term prognosis in women with acute myocardial infarction is remarkably similar to age-matched groups of men.
Disopyramide in myocardial infarction.
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The prognostic value of the HV interval in patients with acute myocardial infarction and bundle branch block.
HV intervals were measured in 42 of 119 patients in the acute phase of myocardial infarction associated with bundle branch block (BBB). The mean HV intervals of patients with right, left and incomplete bilateral BBB were similar. The hospital and subsequent mortality of patients with prolonged HV intervals did not differ significantly from that of patients with normal HV intervals. The HV interval appeared to remain stable over the following months in most patients in whom it was remeasured. We conclude that the HV interval cannot be used to select patients who might benefit from prophylactic long term pacing.
Thyroid hormone levels and protein binding in patients on long-term diphenylhydantoin treatment.
The effect of long-term diphenylhydantoin (DPH) treatment on thyroid hormone concentrations and protein binding was determined in a randomized controlled trial. As has been demonstrated previously, total thyroxine (T4) concentrations were significantly depressed in patients on DPH. There was no significant effect on indirect indices of protein binding of thyroid hormones, and the free thyroxine index (FTI) was also significantly depressed. Triiodothyronine (T3) and thyrotrophin (TSH) concentrations were either unaffected, or only very slightly affected by DPH. Significant effects on the FTI were still apparent 4 weeks after discontinuing treatment. It is concluded that the depression of total T4 levels observed in vivo is not due solely to diminished protein binding, but may instead be largely explained by reports suggesting enhanced degradation of T4 following DPH therapy.
Exercise induced tachycardia after cessation of practolol therapy.
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Cardiac arrest.
Cardiac arrest is easily recognized clinically and requires immediated cardiopulmonary resuscitation (CPR) by well trained personnel. The importance of prophylaxis is emphasized in high risk patients. The ABC regime of CPR and the technique of blind defibrillation are recommended in the management of cardiac arrest. Good results may be expected with ventricular fibrillation associated with some correctable factor or myocardial infarction. With a satisfactory CPR technique and prompt resuscitation, the incidence of complications is low.