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Biomedical subjects

N Twidale

Publications and source records attributed to N Twidale.

30 records · Page 2Linked to original sources
PubMed1989

Results of cardiopulmonary resuscitation in adult patients managed in a teaching hospital: clinical outcome and implications.

OBJECTIVE: To assess the impact and clinical implications of therapeutic strategies for managing sudden cardiac arrest in a teaching hospital. METHOD: A prospective audit of the results of out-of-hospital and in-hospital cardiac arrest. RESULTS: Compared with other studies, our results for resuscitation of out-of-hospital cardiac arrest were poor, only 5% of patients being discharged. This probably relates to the inability to revert ventricular tachycardia or ventricular fibrillation promptly by defibrillation. Improving access to defibrillation at the scene of cardiac arrest could improve the results of out-of-hospital cardiac arrest. In contrast, among patients with in-hospital cardiac arrest. In contrast, among patients with in-hospital cardiac arrest, 14% of patients in monitored wards, and 24% of patients in unmonitored wards, were discharged (P less than 0.05). When cardiac arrest is not associated with acute myocardial infarction, survivors require thorough investigation and treatment to prevent recurrence.

Adult↗
PubMed1988

Direct identification of parameters in a mathematical model describing conduction through the atrioventricular node.

Function of the atrioventricular node is assessed during intracardiac electrophysiology study by relating the output intervals A2H2 and H1H2 to the input A1A2, where A and H are, respectively, atrial and His bundle electrograms recorded by catheter. The H1H2 curves have been previously deduced from a model describing the A2H2 curves. Because of presence in a few cases of different behaviour of A2H2 and H1H2, this study aimed to establish a more suitable model of H1H2 independently of A2H2 for the particular case of a single transmission pathway. The two models were compared by calculation of standard error of the estimate. As a first approximation, the deduced model may be sufficient. However, the standard error of the estimate was less with the direct algorithm, which is therefore the more suitable for further development, particularly for recognition and modelling of conduction over multiple pathways through the atrioventricular node.

Adult↗
PubMed1988

Clinical implications of electrophysiology study findings in patients with chronic bifascicular block and syncope.

Electrophysiology study was performed in 93 patients with bifascicular block and unexplained syncope. Clinical evidence of organic heart disease was present in 33 (35%). Electrophysiological abnormalities were detected in 45 patients (48%). Of these, 36 had distal conduction disease, including 28 with an HV interval greater than 55 ms (mean 76.4 ms), and eight who developed infraHisian block following either intravenous procainamide (four) or atrial pacing (four). Sick sinus syndrome was evident in six patients and a further two had carotid sinus hypersensitivity. Sustained monomorphic ventricular tachycardia (VT) was induced in only three patients, two of whom also had prolonged HV interval. Among the 93 patients, 45 had therapy which was guided by positive findings at electrophysiology study (Group 1). Of these, 42 received permanent pacemakers, two were treated with combined permanent pacing and antiarrhythmic drug therapy, and one was treated with antiarrhythmic drug alone. In addition, eight patients without electrophysiologic abnormalities were treated empirically by pacing (Group 2). Finally, 40 patients without electrophysiologic abnormalities received no specific therapy (group 3). At a mean follow-up of 39 months (range two-125 months), recurrence of syncope had occurred in 4% of Group 1 patients, and 25% of Group 3 patients (p less than 0.05). No patient in Group 2 had had recurrence. Total mortality was 40%, including 47% of patients in Group 1, 25% of Group 2, and 35% of Group 3. Death was sudden in seven patients. We concluded that among patients with bifascicular block and syncope, therapy directed by findings at electrophysiology study was associated with symptomatic improvement, but mortality was not significantly influenced.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Programmed stimulation after anterior myocardial infarction complicated by bundle branch block--late ventricular tachyarrhythmias and outcome.

One hundred and thirty consecutive patients with anterior myocardial infarction complicated by bundle branch block were retrospectively analyzed. Sixty died within 1 week of infarction. Of the remaining 70 patients, 36 had electrophysiology study with programmed stimulation 8-90 (mean 20) days after infarction. Of these, nine patients (35%) who clinically had not manifested either ventricular tachycardia or ventricular fibrillation more than 72 hours after infarction, had inducible ventricular tachycardia which was sustained more than 30 seconds in eight patients. By contrast, assessment of atrioventricular conduction added little to clinical management, long-term follow-up, extending up to 127 months, was available both in those patients whose therapy was directed by electrophysiology study, and was assessed among the other 34 patients who survived at least 7 days after myocardial infarction, but who did not undergo electrophysiology study. While the overall mortality was 55%, the majority of deaths (22/35) occurred within 4 months of infarction and many long-term survivors enjoy a gratifying quality of life. Although programmed stimulation in survivors of anterior myocardial infarction complicated by bundle branch block may identify a high risk subgroup, a prospective randomized trial is required to define the utility of more aggressive stimulation protocols following NASPE recommendations, to identify subgroups of patients in whom newer therapeutic interventions, including antiarrhythmic agents, electrical devices and surgery may be indicated.

Adult↗
PubMed1988

Plasma atrial natriuretic polypeptide concentrations during and after reversion of paroxysmal supraventricular tachycardias.

Plasma concentrations of immunoreactive atrial natriuretic polypeptide were raised in 22 of 23 patients with paroxysmal supraventricular tachycardia and in all seven patients with atrial flutter. Plasma concentrations of atrial natriuretic polypeptide rose soon after the onset of supraventricular tachycardia. A sample taken 30 minutes after reversion to sinus rhythm (pharmacological or non-pharmacological) showed a significant fall in 19 of the 23 patients with paroxysmal supraventricular tachycardia and all seven patients with atrial flutter. Because atrial natriuretic polypeptide has powerful natriuretic and diuretic properties, an increase may contribute considerably to the polyuria that is often associated with episodes of supraventricular tachycardia.

Adolescent↗
PubMed1988

Computer algorithm for modeling transmission over one or two conduction pathways through AV node.

The goal of this study was to develop and test models of conduction through the atrioventricular node, particularly to encompass possible transmission over multiple pathways. Output from the atrioventricular node was related to its input, the variable coupling interval of a single extrastimulus introduced to scan diastole during programmed atrial stimulation. Trials were performed three times in 15 patients after pacing for eight beats at 100 beats/min. Hyperbolic and exponential functions were used to model trial data. For conduction over a single pathway, the standard error of the estimate was less with the exponential than with the hyperbolic model. The preferred exponential model had the general form A2H2 = K1 + K2 exp(-A1A2/K3), with K1, K2, K3 being the parameters fitted. The algorithm describing transmission over two pathways minimized sums of squares of deviations from two such exponential functions, with potential "bifurcation" points between the functions being those farthest from the computed single curve of best fit. The model predicted (R2 greater than 0.90) that 43% of the trials showed single conduction pathways and the remaining 57% showed dual pathways. A cardiologist who independently examined the data discarded eight trials because of insufficient data or scatter and agreed with presence of two pathways and the point of discontinuity in plots in 81% of trials. The reasons for discordance were minor and thus the model was reasonably verified.

Adolescent↗
PubMed1988

Procainamide administration during electrophysiology study--utility as a provocative test for intermittent atrioventricular block.

The utility of procainamide, up to 10 mg/kg IV, as a provocative test for intermittent high degree atrioventricular (AV) block was evaluated in a total of 89 patients. Forty two patients had resting 1:1 AV conduction but had bifascicular block and a history of syncope. High degree AV block had not been documented in anyone. Before procainamide, the HV interval was greater than 60 ms in 17 of the 42 patients but no patient developed infra-Hisian block with fixed rate atrial pacing or following programmed atrial extrastimuli. Procainamide administration lengthened the mean HV interval by 11.9 ms and in seven (14%) the HV increment was marked, 15-75 ms. Furthermore, four (9.5%) of these 42 patients developed second or third degree infra-Hisian block and in two of these four patients, the HV prior to procainamide administration was normal or only mildly prolonged (less than 60 ms). The findings were compared to those in three "control" groups. Among four patients with bifascicular block, previously documented transient AV block but 1:1 AV conduction at the time of study, three developed high degree AV block following procainamide. Among five patients with bifascicular block but without syncope nor documented high degree AV block, the mean HV interval lengthened by 18.8 ms and in three the HV increment was 24-30 ms. In another 38 patients with neither syncope nor an intraventricular conduction defect, the mean HV interval lengthened by 5.3 ms and in two cases by 20-25 ms. Most importantly, high degree AV block was never observed in the latter two groups. During follow-up of up to 10 years (mean 46 months), three of the seven patients in whom procainamide provoked high degree AV block have subsequently progressed to fixed complete AV block. Although the incidence of provocation of AV block was relatively low, it was concluded that, among patients with possible intermittent AV block, administration of procainamide as a test of distal conduction has limited value but is still useful, and may provide information additional to that obtained from mere assessment of the HV interval.

Adolescent↗
PubMed1987

Clinical electrophysiology study in patients with syncope of undetermined etiology.

The periodicity of symptoms in patients who present with syncope restricts the diagnostic value of prolonged electrocardiographic monitoring and furthermore, demonstration of arrhythmias in the absence of symptoms may not enable a firm diagnosis. Because of this, electrophysiology study is often necessary. A series of 89 consecutive patients with syncope of unknown origin is reported, highlighting the value and limitations of this technique. A diagnostic yield of 35% was found, with the majority having abnormalities of atrioventricular conduction. The presence of organic heart disease, 12-lead electrocardiographic abnormalities and a number of syncopal episodes did not influence the diagnostic utility of electrophysiology study. Patient follow-up suggested that therapeutic decisions based on the findings of electrophysiology study provide satisfactory symptomatic relief in a high percentage of cases, with a recurrence rate of 25% at mean follow-up of 14 months.

Adolescent↗
PubMed1987

Ventricular standstill complicating cardiac catheterization.

A patient is described in this paper who developed repeated episodes of ventricular standstill during left heart catheterization. The patient had a resting pattern of right bundle branch block with left anterior fascicular block; subsequent electrophysiology study was normal. Ventricular standstill during catheterization was apparently due to catheter-related trauma of His bundle connections.

Aged↗
PubMed1985

Recurrent cholangitis caused by hepatocellular carcinoma.

A patient is described with recurrent cholangitis and longstanding alcoholic cirrhosis. The cause of the cholangitis was found to be intraductal biliary tract invasion by hepatocellular carcinoma. A review of the literature suggests that this is an unusual manifestation of a common malignancy.

Ampicillin↗