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Biomedical subjects

A A Adgey

Publications and source records attributed to A A Adgey.

At least 19 recordsLinked to original sources
PubMed1995

Sudden cardiac death and substance abuse.

There has been a steady increase in the number of deaths occurring from volatile substance abuse per year. The majority of deaths are in males, the peak age group being 15-19 years. Fuel gases i.e. cigarette lighter refills (butane), propane and gasoline and other solvents such as typewriter correction fluid, dry-cleaning fluids (trichloroethane) and fire extinguishers (bromochlorodifluoromethane) are responsible for approximately 60% of these deaths. Volatile substances sensitise the heart to circulating catecholamines, such that sudden alarm or exercise may precipitate sudden death. The main mechanism of cardiac arrest is a cardiac arrhythmia, but anoxia, respiratory depression and vagal stimulation along with aspiration of vomit or trauma may be contributing factors to the sudden death. In addition, particularly butane gas inhalation may be associated with severe laryngeal oedema and laryngospasm. Resuscitation from sudden death associated with volatile substance abuse is rare, since the majority of deaths are unwitnessed. It is suggested that cardiac arrhythmias should be treated conventionally. Sympathomimetic drugs should be avoided. Early during the resuscitation process, beta-adrenergic blocking agents should be administered to protect the catecholamine-sensitised heart. Early intubation in the management of the cardiac arrest should be avoided, if the inhalational agent is known to be associated with laryngospasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1995

Body surface ECG potential maps in acute myocardial infarction.

An algorithm for the early detection of acute myocardial infarction (MI) using body surface electrocardiographic potential mapping has been developed. The mapping system consists of a 64-hydrogel electrode harness applied rapidly to the anterior chest, from which electrocardiographic signals are stored on a memory card and processed by computer. At each of the 64 points, QRS and ST-T isointegrals and 10 other features of the QRST segment are measured. Using these measurements, new variables are derived that express the shape of the three-dimensional geometric surface of the map. The isointegrals, features, and shape variables are used in a variety of techniques to discriminate between MI and control subjects. Maps were recorded from 69 patients at initial presentation of chest pain suggestive of acute MI and from 80 healthy control subjects. Using a multiple logistic regression technique, 14 variables were identified that correctly classified 79 of the 80 control subjects (specificity, 98.8%) and 65 of the 69 MI patients (sensitivity, 94.2%). The algorithm based on these 14 variables was applied prospectively to maps recorded on a further 48 control subjects and 59 patients with acute MI. Of the MI patients, 31 had inferior, 13 inferoposterior, 10 anterior, 2 posterior, 1 lateral, 1 inferior with right bundle branch block, and 1 anterior non Q wave MI. The algorithm correctly classified all 48 control subjects (specificity, 100%) and 57 of the 59 MI patients (sensitivity, 96.6%). Marked differences in the three-dimensional geometric map surfaces between the control subjects and MI patients were demonstrated. Variables derived from these surfaces form the basis of an algorithm with a high sensitivity and specificity for the automated detection of acute MI. The design of adaptive algorithms and their application to patients with chest pain and atypical electrocardiographic changes, particularly ST depression, may lead to the earlier detection of MI and greater numbers of patients receiving thrombolytic therapy.

Adolescent↗
PubMed1995

An esophageal and gastric approach to ventricular pacing.

Using a unipolar esothoracic pacing system (where current passes from a point source positioned in the distal esophagus to a chest wall pad) and pulse duration of 50 msec, satisfactory 1:1 ventricular capture was obtained in 57 (86%) of 66 patients, with a mean threshold current of 27.7 mA at an optimal depth of 40.3 cm from the lower lip. When the unipolar esothoracic and bipolar transesophageal ventricular pacing systems were compared, the bipolar system was associated with a lower success rate and higher threshold current. When unipolar esothoracic pacing and gastrothoracic pacing (where current passes from a point source positioned in the stomach to a chest wall pad) were compared in 23 patients with bradyarrhythmia, ventricular capture was achieved using gastrothoracic pacing in 22 patients (96%) and esothoracic pacing in 21 (91%): gastrothoracic pacing required less current (16.0 mA +/- SD 7.2 vs 25.8 mA +/- SD 8.6). Optimal ventricular capture occurred using a unipolar gastrothoracic pacing electrode inserted to an average depth of 44.3 cm together with a high impedance chest pad (250 omega) placed in the fourth interspace at the left sternal edge, with 50-msec current pulses and a mean threshold of 16.0 mA. Thus, using a gastroesophageal electrode system, ventricular pacing can be achieved successfully, and the availability of such a system could play a major role in resuscitation of patients from severe bradyarrhythmias.

Bradycardia↗
PubMed1995

Esophageal countershock: anthropometric determinants of impedance.

OBJECTIVE: To examine the use of a novel esophageal electrode system for countershock of atrial and ventricular tachyarrhythmias, with particular regard to the measurement of transesophageal and transthoracic impedances and their association with anthropometric variables. METHODS: Transesophageal cardioversion was attempted during 131 episodes of arrhythmia in 105 patients (including 109 episodes of atrial fibrillation). The esophageal system also used in 29 patients undergoing electrophysiologic studies for investigation of ventricular tachyarrhythmias. Transesophageal and transthoracic impedances were estimated during passage of a high-frequency, low-amplitude current between the respective electrodes. Impedance estimates were associated with anthropometric measurements using linear regression (least-squares method). RESULTS: In the group of patients undergoing attempted transesophageal cardioversion, the mean estimated transesophageal impedance of 52.6 +/- 11.7 omega was significantly lower than the mean estimated transthoracic impedance of 63.1 +/- 16.4 omega (n = 104, p < 0.01). For all the patients, transesophageal impedance was associated with weight, body mass index, and chest circumference (all r > or = 0.65, p < 0.01). Transthoracic impedance was associated with the same factors (all r > or = 0.55, p < 0.01). CONCLUSION: This esophageal electrode system results in lower impedance values for countershock between the esophagus and the cutaneous cardiac apex in comparison with standard transthoracic cutaneous electrode placement. Both techniques are dependent on anthropometric factors.

Adult↗
PubMed1995

Systemic lupus erythematosus presenting as effuso-constrictive pericarditis.

We describe a 62-year-old woman in whom systemic lupus erythematosus presented as life-threatening effuso-constrictive pericarditis. Surgical drainage of the pericardium was required and the patient made a satisfactory recovery. At six-months follow-up, while taking hydroxychloroquine and a non-steroidal anti-inflammatory agent, she remains well.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1994

Asystolic arrest as a presentation of sarcoidosis.

A 41-year-old man who presented with a history of sudden loss of consciousness suffered two further episodes during which asystole was documented. Subsequent investigations included exercise stress testing, thallium scintigraphy, electrophysiological studies, CT-scan of chest, Kveim test and a gallium-67 scan, which led to a presumptive diagnosis of averted sudden death as a first presentation of sarcoidosis with primary cardiac involvement.

Adult↗
PubMed1994

Use of the gastro-oesophageal route for the rapid establishment of ventricular pacing.

A novel approach to emergency ventricular pacing has been developed using a gastro-esophageal electrode. The polythene electrode was passed into the stomach, after which the electrode tip was positioned in the gastric fundus. Ventricular pacing was performed using a cathode mounted on the electrode tip; the indifferent electrode (anode) was either a chest pad or a proximal ring electrode. Ventricular capture was easily achieved in three emergency cases of severe bradyarrhythmia.

Adult↗
PubMed1994

Discriminant function analysis of body surface potential maps in acute myocardial infarction.

Using a newly developed 64-electrode portable mapping device, QRS and ST-T isointegral maps were compared in 194 control subjects and 101 patients. One hundred ninety-four control subjects (mean age, 48 years; 120 men) with no history of cardiac disease were selected randomly and mapped. One hundred one patients (mean age, 62 years; 77 men) were mapped at presentation of chest pain suggestive of first myocardial infarction (MI); all patients had classic 12-lead electrocardiographic findings--46 with anterior and 55 with inferior MI. The diagnosis was confirmed in all cases by a significant rise in serial cardiac enzymes. The mean delay between onset of chest pain to map recording was 163 minutes. Of the 101 patients, 78 were first mapped outside the hospital. Applying discriminant function analysis to the isointegral measurements made on the control subjects and on the first map of MI patients achieved a correct classification of 97% of the control subjects (189 of 194) and 72% of the anterior (33 of 46) and 76% of the inferior (42 of 55) MI groups. This preliminary study suggests that discriminant function analysis, based on isointegral maps, not only provides a method of separating control subjects from MI patients but that it can also differentiate between types of infarct. Further studies are required to improve the predictive values of discriminant function and to extend the methodology to assess both the site and size of MI.

Adult↗
PubMed1994

Assessment of ability of levcromakalim and sodium nitroprusside to reverse the cardiovascular effects of nitric oxide synthase inhibition in the anaesthetised pig.

OBJECTIVE: The aim was to test the ability of levcromakalim, a potassium channel opener, and sodium nitroprusside, a nitric oxide donor, to reverse the systemic and pulmonary vasoconstrictor actions of NG-nitro-L-arginine methyl ester (L-NAME), and thus to restore cardiac output in anaesthetised pigs. METHODS: In separate groups of pigs administration of a bolus of L-NAME (10 mg.kg-1) was followed either by no further agent (control group; n = 8) or by increasing bolus doses of levcromakalim (10, 20, and 40 micrograms.kg-1; n = 8) or by increasing infused doses of sodium nitroprusside (1, 2, and 4 micrograms.kg-1.min-1 for 15 min at each dose). The same doses of levcromakalim and sodium nitroprusside were also given to pigs (n = 6 in each group) which had been pretreated with saline rather than L-NAME. The changes in systemic and pulmonary haemodynamic indices and cardiac output as a result of each intervention were measured at each stage and compared between and within drug groups. RESULTS: In each group, the bolus of L-NAME caused increases in systemic vascular resistance, mean arterial pressure, pulmonary vascular resistance, and mean pulmonary artery pressure, and a reduction in cardiac output. These effects were significantly different from pretreatment values at 15 min, and were maintained for at least 60 min when no further agent was given. The subsequent administration of levcromakalim caused significant reductions in systemic vascular resistance and mean arterial pressure, the effects being greater than in animals that had been pretreated with saline rather than L-NAME. Pulmonary vascular resistance and mean pulmonary artery pressure were also reduced, but to a lesser degree. Cardiac output was partially but significantly restored. The subsequent administration of sodium nitroprusside caused significant reductions in systemic vascular resistance, mean arterial pressure, pulmonary vascular resistance, and mean pulmonary artery pressure. These effects were significantly greater than those in animals that had been pretreated with saline rather than L-NAME. Cardiac output was weakly, though significantly restored. CONCLUSIONS: Increased systemic vascular resistance following a bolus of L-NAME (10 mg.kg-1) is reversed by subsequent administration of levcromakalim (10-40 micrograms.kg-1) or sodium nitroprusside (1-4 micrograms.kg-1.min-1) associated with partial restoration of cardiac output. The degree to which cardiac output is restored by these two agents is limited by a concomitant reduction in preload.

Amino Acid Oxidoreductases↗
PubMed1994

Time delays to lytic therapy and outcome in 100 consecutive patients with a history suggestive of acute myocardial infarction in an area with access to a mobile coronary care unit.

Time delays to fibrinolytic treatment and outcome were assessed in 100 consecutive patients, with suggestive symptoms and electrocardiographic changes of acute myocardial infarction, admitted to the coronary care unit of this hospital. All patients admitted from out-of-hospital had access to a mobile coronary care unit. Initially, 40 patients called a general practitioner, 30 called the '999' operator, 12 called the mobile coronary care unit, 10 reported directly to the Accident and Emergency Department, seven were in-hospital and one spoke to the general practitioner's receptionist. Subsequently, 59 patients were attended by the mobile coronary care unit, 34 were admitted via the Accident and Emergency Department and seven had symptoms in-hospital. Thrombolytic therapy was initiated in 45/59 (76%) patients by the mobile coronary care unit staff and in 29/34 (85%) patients in the Accident and Emergency Department by cardiac staff. The remaining 26 patients received thrombolytic treatment in the hospital coronary care unit or cardiac department. The mean (+/- SEM) time from symptom onset to the initiation of thrombolytic therapy was 127 (+/- 11 min) for those patients treated by the mobile coronary care unit staff and for those treated in the Accident and Emergency Department was 187 (+/- 13 min) (P = 0.005). Multiple regression analysis showed significant reductions in total time delay if patients received thrombolytic therapy by the mobile coronary care unit staff out-of-hospital, when chest pain began in-hospital, or if patients had a previous myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulances↗
PubMed1994

Comparison of the ability of nicardipine, theophylline and zaprinast to restore cardiovascular haemodynamics following inhibition of nitric oxide synthesis.

1. The use of pharmacological inhibitors of nitric oxide (NO) synthesis to treat patients with septic shock is limited by the observation that they cause a fall in cardiac output in some subjects. The aim of this work was to investigate this fall and to test whether it was reversible by subsequent administration of nicardipine, theophylline or the cyclic GMP-selective phosphodiesterase inhibitor, zaprinast (M&B 22948). 2. In pentobarbitone-anaesthetized pigs, haemodynamic indices were measured before and after intravenous administration of NG-nitro-L-arginine methyl ester (L-NAME) in a dose-response protocol (0.2-20 mg kg-1; n = 6) and as a single bolus of 10 mg kg-1 either alone or followed by increasing doses of nicardipine, theophylline or zaprinast (n = 8 in each group). 3. L-NAME caused a dose-dependent rise in systemic vascular resistance and mean systemic arterial pressure and a dose-dependent fall in cardiac output. A single bolus of L-NAME (10 mg kg-1) produced these effects within 15 min. 4. Subsequent administration of nicardipine (0.05-0.2 mg kg-1) caused complete reversal of systemic vasoconstriction and hypertension and in doing so completely restored cardiac output. Theophylline (7.5-10 mg kg-1) partially reversed the rise in systemic vascular resistance and partially restored cardiac output but the effect was small compared to that of nicardipine. Zaprinast (1-5 mg kg-1) had no significant effect on any of these variables. 5. These results suggest that reduced cardiac output following inhibition of NO synthesis is an effect of increased afterload on the heart and is reversible by nicardipine and to a lesser extent by theophylline.These findings may have potential value for those using NO synthase inhibitors to treat patients with septic shock.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1994

Transesophageal electroventilation. Optimization and improvement.

For electroventilation, short duration pulse trains (0.1 ms) were applied between two axillary pads (transchest) and compared with transesophageal electroventilation where pulses passed between the same pads to an esophageal electrode in apneic, pentobarbitone-anesthetized pigs. Significantly greater tidal volumes were produced by transesophageal electroventilation in comparison with transchest. As measured by maintained tidal volumes, duration of inspiratory air flow, peak flow, percentage hemoglobin oxygen saturation (%SaO2), and end tidal carbon dioxide concentration (ETCO2), the optimal requirements for transesophageal electroventilation were pulse frequency 40 Hz, 0.7 s duration pulses, at 60 to 100 V, pulse width 0.1 ms, with the esophageal electrode proximal to the gastroesophageal junction without producing brachial plexus stimulation. The efficiency of transesophageal electroventilation falls off rapidly following ventricular fibrillation. Thus, the application of this technique would be in respiratory arrest with maintained circulation, eg, in drug-induced respiratory depression, severe smoke inhalation, severe emphysema, high cervical cord lesion, and weaning from prolonged mechanical ventilation.

Animals↗
PubMed1994

Portable cardiac mapping assessment of acute ischaemic injury.

A portable cardiac mapping system is used to improve the accuracy of diagnosis of acute ischaemic injury outside hospital. Patients presenting chest pain suggestive of myocardial infarction (MI) were mapped by attendant medical personnel operating from a mobile coronary unit. These first MI maps were compared against average normal maps using QRS and ST-T isointegral values. Discriminant function analysis performed on the parameters achieved a sensitivity of 90% and a specificity of 96%.

Body Surface Area↗