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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

Coronary care follow-up study: acute care required immediately following thrombolytic therapy.

We carried out a prospective survey of the outcome of patients with 'suspected myocardial infarction', in order to determine where they should be nursed. The delay between onset, admission, transfer to the CCU, the sequelae and side-effects of thrombolytic therapy were noted and were documented prospectively. Of 217 admissions to CCU with a history of chest pain and suspected acute myocardial infarction during a four-month period (mean age was 62.8 years range 31 to 86 years) 202 fulfilled the criteria for suspected myocardial infarction. Streptokinase was given in 129 and alteplase in one patient. The delay between onset of pain and admission was < 4 h in 73, 4 to 12 h in 30 and > 12 h in 23. Elderly patients were just as likely as younger ones to receive thrombolytic therapy (Chi 2 = 3.6; P = 0.6). An eventual diagnosis of acute myocardial infarction was made in 133 of whom 100 received streptokinase. Dysrhythmia or shock was encountered in one-third of those given streptokinase and a quarter of the remainder. Reactions to streptokinase were recorded in 32 mainly hypotension or bradycardia alone or in combination. Forty-five per cent experienced either cardiac complications or drug reactions or both. During one month there were 57 admissions, 50 of whom arrived by ambulance. The mean delay between call out and arrival in the A&E department was 55 min. We concluded patients who are given thrombolytic therapy need close supervision and they should be nursed in a CCU or its equivalent.

Adult

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

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

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

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

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

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

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

Survival in sinoatrial disorder (sick-sinus syndrome).

A total of 381 patients with established (156) or potential (225) sinoatrial dysfunction were included in a 10-year prospective survey to determine the course of the disease and the benefits of pacing. With the exclusion of nine patients who were lost to follow-up, 61 were fitted with pacemakers. The overall survival of patients with established and potential dysfunction was similar and apparently indistinguishable from that of the normal population. Pacemaker implantation had little discernible effect on mortality though it reduced some incapacitating symptoms. These findings suggest that sinoatrial dysfunction is a relatively benign condition. Hence pacing should probably not be adopted as a routing measure but be reserved for patients with troublesome symptoms.

Cardiac Pacing, Artificial

Sudden death in hypertrophic cardiomyopathy: associated accessory atrioventricular pathways.

Sudden death is a known but unpredictable complication of hypertrophic cardiomyopathy. We describe two patients who both had a strong family history of the disorder complicated by sudden death. Necropsy disclosed accessory bypass tracts, concealed in one and previously suspected in the other. One died from ventricular fibrillation and the other, who died outside hospital, had previously complained of palpitation. Arrhythmia complicating pre-excitation appears to be one of the factors responsible for sudden death in hypertrophic cardiomyopathy.

Adolescent