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Biomedical subjects

D B Shaw

Publications and source records attributed to D B Shaw.

At least 19 recordsLinked to original sources
PubMed1991

Clinical trials of a dual-sensor diagnostic pacemaker.

The results of clinical trials of a dual-sensor diagnostic pacemaker are described. The system monitors and records intraventricular electrical and pressure waveforms using a special lead incorporating bipolar electrodes together with a piezoelectric pressure transducer. The recorded waveforms, which are shown in conjunction with Holter recordings made simultaneously, demonstrate the value of pressure measurements and illustrate several cardiac events, including an ECG pause, bradycardia, a pressure pause, ectopic beats and tachycardia. The pacing function of the device is shown and capture is demonstrated.

Arrhythmias, Cardiac↗
PubMed1990

A dual-sensor diagnostic pacemaker for ambulatory cardiac monitoring.

Unexplained blackouts are a very common medical problem. Some patients presenting themselves at hospital with such symptoms have underlying bradycardia or extreme tachycardia with a profound decrease in cardiac output. Modern treatment of these patients may be highly effective but accurate diagnosis of their exact condition may be needed. A novel ambulatory dual-sensor diagnostic pacemaker has been developed to meet this requirement. The device monitors intracardiac ECG and intraventricular pressure through a special lead introduced perveneously into the right ventricle and detects and counts events such as bradycardia, tachycardia, pauses in the electrical or pressure signals and electrical interference. Analogue recordings of the electrical and pressure waveforms of 16 of these events can be made during the operating period of 3 weeks and pacing is incorporated via a specially-adapted commercial pacemaker if a prolonged episode of bradycardia or a pause is sensed. The device forms part of a complete diagnostic system also incorporating a computer which is used to set up the parameters of the diagnostic pacemaker and to display and analyse the recorded data.

Diagnosis, Computer-Assisted↗
PubMed1987

Chronic sinoatrial disorder (sick sinus syndrome): a possible result of cardiac ischaemia.

Postmortem angiography was used to examine the blood vessels supplying the sinoatrial node in 25 subjects with chronic sinoatrial disorder (group 1). The results were compared with similar studies in 54 subjects who died of heart block and in whom sinus node function was normal (group 2). Although no significant lesion obstructing the blood flow to the sinus node was seen in the majority of those in group 1, there were abnormalities in seven cases, with reduced filling of the sinus node artery in five. In group 2 the sinus node artery filled normally in all cases despite major disease of the parent vessel in three. The combination of contralateral coronary artery disease with extensive atrial anastomoses was actively sought because this arrangement might predispose to a steal phenomenon. Such conditions were fully met in three cases in group 1 and two cases in group 2, and were found to a lesser extent in a further two cases in group 1 and three in group 2. Although coronary artery disease was unlikely to be the principal cause of sinus node dysfunction in most of the cases studied it was relatively common and may have been a factor in about one third. Improved survival after myocardial infarction may increase the number of patients with chronic sinoatrial disorder of ischaemic origin.

Aged↗
PubMed1985

Survival in second degree atrioventricular block.

Two hundred and 14 patients with chronic second degree heart block were seen and followed up in the Devon Heart Block and Bradycardia Survey between 1968 and 1982. The patients were divided into three groups according to the type of block. In group 1 there were 77 patients with Mobitz type I block (mean age 69 years), in group 2, 86 patients with Mobitz type II block (mean age 74 years), and in group 3, 51 with 2:1 or 3:1 block (mean age 75 years). The five year survival was similar in all groups, being 57%, 61%, and 53% in groups 1, 2, and 3 respectively. The presence or absence of bundle branch block did not appear to influence prognosis. In particular, patients in group 1 without bundle branch block did not fare any better than those in group 2 both with and without bundle branch block. One hundred and three of the patients were fitted with pacemakers, the proportion being greatest in group 2. In each group a significantly larger number of paced patients survived than unpaced. The five year survival for all the paced patients in the study was 78% compared with 41% for the unpaced. Since the paced patients were slightly younger than the unpaced two age matched groups of 74 patients each were selected from the paced and unpaced patients, but the five year survival of those paced was still significantly better. It is concluded that in the patients in the present study chronic Mobitz type I block has a similar prognosis to that of Mobitz type II block. Unpaced patients with both types did very badly, whereas those fitted with pacemakers had a five year survival similar to that expected for the normal population. These results refute the benign reputation of chronic Mobitz type I block and imply that patients with this condition should be considered for pacemaker implantation on similar criteria to those adopted for patients with higher degrees of block.

Adult↗
PubMed1984

Sinus node arrest and sino--atrial block.

Current epidemiological data suggest that sinus node dysfunction is a relatively uncommon condition in the pilot age group. Symptomatic pauses of any mechanism suggest disqualification from flying duties. Asymptomatic pauses (representing sino-atrial block or sinus node arrest) demand further investigation and regular follow-up. Idiopathic pauses greater than 2.5 s on an ambulatory ECG is abnormal and is likely to deny flying status.

Aerospace Medicine↗
PubMed1984

Anesthesia for obstetric emergencies.

Anesthesia in an emergency presents an additional risk to the mother and may have some possibly harmful effects on the stressed fetus. The risk to the mother can be reduced by using regional anesthesia, whenever reasonable, and by taking measures to minimize the risk of aspiration of vomitus. The stressed fetus can be assisted, if not by a rapid delivery, by giving the mother oxygen to oxygenate the fetus and possibly by improving intervillous perfusion with a regional anesthetic.

Anesthesia, Obstetrical↗
PubMed1983

Unexplained syncope--a diagnostic pacemaker?

We describe our initial experience with a pacemaker which performs the dual function of registering episodes of cardiac arrest and pacing the heart when necessary. The apparatus has a prolonged escape interval (2.30-2.65 seconds) and is capable of counting up to 128 "events." Twenty-five patients complaining of infrequent episodes of loss of consciousness have been studied. Blackouts ceased and episodes of ventricular standstill were recorded in 14 cases; the unit helped to establish a non-cardiac etiology for the attacks in two cases. It is suggested that a bradycardia-recording facility incorporated into a programmable pacemaker would provide a much needed tool in the diagnosis and management of patients with infrequent episodes of loss of consciousness in whom a cardiac mechanism is suspected but unproven.

Aged↗
PubMed1976

Myocardial infarction: a comparison between home and hospital care for patients.

To compare the results of home and hospital treatment in men aged under 70 years who had suffered acute myocardial infarction within 48 hours 1895 patients were considered for study in four centres in south-west England. Four-hundred-and-fifty patients were randomly allocated to receive care either at home by their family doctor or in hospital, initially in an intensive care unit. The randomised treatment groups were similar in age, history of cardiovascular disease, and incidence of hypotension when first examined. They were followed up for up to a year after onset. The mortality rate at 28 days was 12% for the random home group and 14% for the random hospital group; the corresponding figures at 330 days were 20% and 27%. On average, older patients and those without initial hypotension fared rather better under home care. The patients who underwent randomisation were similar to those whose place of care was not randomised, except that the non-randomised group contained a higher proportion of initially hypotensive patients, whose prognosis was poor wherever treated. These results confirm and extend our preliminary findings. Home care is a proper form of treatment for many patients with acute myocardial infarction, particularly those over 60 years and those with an uncomplicated attack seen by general practitioners.

Adult↗