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Biomedical subjects

D E Ward

Publications and source records attributed to D E Ward.

At least 199 records · Page 11Linked to original sources
PubMed1983

A specular microscopic viewing system for donor corneas.

A system for routine specular microscopic assessment of donor corneal endothelium including a chamber that allows both storage and viewing of the donor tissue was evaluated. A specular microscope modified to enable noncontact scanning of donor cornea from the endothelial side was used. Forty-five human corneas were examined upon arrival at the eyebank. Storage in the new chamber was compared with that in standard vials for 13 paired corneas. This study demonstrates the feasibility and simplicity of routine specular microscopy on donor corneal tissue, and discusses its advantages.

Adolescent↗
PubMed1983

Characteristics of atrio-His conduction in the short PR interval, normal QRS complex syndrome. Evidence for enhanced slow-pathway conduction.

This study confirms the existence of accelerated conduction via a fast atrio-His pathway in patients with the so-called Lown-Ganong-Levine (LGL) syndrome. Additional slow AH pathway conduction was detected in about 50% of patients. Comparison of slow pathway conduction characteristics in the LGL syndrome with AH conduction in age-matched normals and patients with dual AV nodal pathways revealed that the 'slower' of dual AH pathways in LGL patients also exhibits relatively enhanced conduction. This finding cannot be explained by the presence of an anomalous AH pathway ('James' fibre') bypassing a normal AV node. It is suggested that a non-specific and as yet unknown effect causes enhanced conduction throughout the AV junction in patients with the LGL syndrome.

Adolescent↗
PubMed1983

Detachment of pacemaker active fixation helix.

The introduction of active fixation electrodes has been a major advance in permanent atrial and ventricular endocardial pacing. We report here an important complication in the use of one such device, the Medtronic transvenous unipolar screw-in ventricular lead (Model 6959).

Aged↗
PubMed1983

Occluded left main stem coronary artery. Report of five patients and review of published reports.

Five patients aged 24 to 62 years presenting with a long history of angina were found to have complete occlusion of the left main coronary artery. In one patient the right coronary artery was also completely blocked. All patients had a dominant right coronary artery which was significantly diseased in only one patient. Ventricular function was severely impaired in only one patient. These patients illustrate the importance of collateral information in this condition. Coronary bypass grafting was performed in three patients who are now symptomatic at follow-up between nine and 17 months.

Adult↗
PubMed1983

Diastolic mechanisms of impaired exercise tolerance in aortic valve disease.

In order to determine the significance of abnormalities of diastolic function in patients with left ventricular hypertrophy, exercise echocardiography to heart rates of 140 to 150 beats/min was performed in 18 normal subjects and 14 patients after aortic valve replacement. Simultaneous echo-, phono-, and electrocardiograms were recorded. Left ventricular cavity size was determined at end-diastole and end-systole. The timing of mitral valve opening and closure was measured, and hence left ventricular filling time derived, expressed either as ms/beat, or s/min when multiplied by heart rate. Isovolumic relaxation was taken as the interval between A2 and mitral valve opening. Systolic function, assessed from cavity dimensions, peak VCF, and QA2 interval was normal in all but two patients at rest and on exercise. Isovolumic relaxation was prolonged at rest in the patients to 85 +/- 8 ms (normal 69 +/- 9 ms), but left ventricular filling times were normal. With exercise, in normal subjects, isovolumic relaxation remained constant, but filling times dropped strikingly from 380 +/- 66 ms/beat, or 27 +/- 2 s/min at rest to 115 +/- 10 ms/beat or 16 +/- 2 s/min. In patients with left ventricular hypertrophy, isovolumic relaxation dropped on exercise to 41 +/- 15 ms. Filling periods were normal at rest, 367 +/- 67 ms/beat or 27 +/- 3 s/min, but failed to show the normal drop with exercise, being 240 +/- 44 ms/beat or 28 +/- 4 s/min. At heart rates above 120/min, separation between the two groups was complete. Thus, striking abnormalities of left ventricular filling can be demonstrated on exercise in patients with left ventricular hypertrophy. They appear to represent loss of mechanisms whereby rapid diastolic filling is achieved in the normal subject.

Aged↗
PubMed1982

The acute electrophysiological effects of intravenous metoprolol.

The cardiac electrophysiological effects of metoprolol were studied in ten patients (pts) aged 22-51 years undergoing intracardiac stimulation studies for paroxysmal palpitations. The following measurements were made: (1) basic sinus cycle length (SCL); (2) sinus node recovery time (SRT) following overdrive pacing; (3) atrio-His (A-H) and His-ventricular (H-V) conduction intervals during regular atrial pacing; (4) effective refractory periods of the atria (AERP), A-V node (AVERP) and ventricular myocardium (VERP); and (5) A-V nodal functional refractory period (AVFRP). All measurements were repeated 10-20 min after a slow bolus intravenous injection of metoprolol (0.2 mg/kg body weight). Results were analyzed by the Wilcoxon Signed Rank test. Highly significant increases in: SRT (932 +/- 166 to 1107 +/- 225 ms, p less than 0.001) and A-H (72 +/- 14 to 103 +/- 14 ms, p less than 0.001) were observed. There were also small increases of lesser significance in SCL (794 +/- 160 59 898 +/- 190 ms, p less than 0.01), AVERP (308 +/- 46 to 341 +/- 66 ms, p less than 0.02), and AVFRP (376 +/- 43 to 416 +/- 59 ms, p less than 0.01). Metoprolol did not affect the H-V interval, the AERP, or the VERP. These results are similar to those of other beta blockers.

Adult↗
PubMed1982

Electrophysiological characteristics of junctional pacemakers in congenital A-V block and following His bundle cryoablation.

The characteristics of the escape mechanism following surgically induced permanent A-V block were investigated and compared with those seen in congenital complete heart block (CHB). Six patients had undergone elective cryothermal ablation of the His bundle for supraventricular arrhythmias unresponsive to pharmacological and pacemaker techniques (group A) and 12 patients had congenital CHB (group B). In the 12 patients in group B the site of block was localized by His bundle electrocardiography to be proximal to the point of recording of the His potential. In 3 patients in group A in whom intracardiac studies were performed it was impossible to record an His potential. There were no significant differences between the control escape rate, junctional recovery time (JRT), and corrected junctional recovery time (cJRT) of the two groups. In group A there were no significant changes in these parameters following the administration of atropine, whereas isoproterenol significantly increased the rate of the subsidiary pacemaker (p less than 0.001) and shortened the JRT (p less than 0.02) and cJRT (p less than 0.02). In group B both atropine (A) and isoproterenol (I) significantly increased escape rate (A, p less than 0.001; I, p less than 0.001) and shortened JRT (A, p less than 0.01; I, p less than 0.001) and cJRT (A, p less than 0.01; I, p less than 0.001). It is concluded that the escape focus in patients with congenital CHB is situated in the A-V node. The escape rhythm following His bundle section is unpredictable and elective permanent pacemaker implantation is indicated.

Adolescent↗
PubMed1982

The long QT syndrome; effects of drugs and left stellate ganglion block.

Four patients, two with congenital QT prolongation (Romano-Ward syndrome) and two with acquired idiopathic QT prolongation not related to bradycardia, drug toxicity, electrolyte imbalance, or neurological disorder were investigated for the onset of recurrent palpitations and/or syncope. The effects on the measured QT interval of intravenously administered propranolol (QTp), an infusion of isoproterenol (QTi) and left stellate ganglion block (QTs) were assessed at identical atrial paced rates and during sinus rhythm, corrected for rate change (QTc). Propranolol shortened the QTc in all patients. The QTp shortened only in those with congenital QT prolongation. Isoproterenol lengthened the QTc in the three patients studied. However, the QTi lengthened in the congenital syndrome whereas it shortened in the acquired syndrome. The QTs was uninfluenced by left stellate ganglion block in all patients. It is suggested that the congenital and acquired forms can be differentiated by pharmacological interventions and that the efficacy of propranolol in the former may result from its ability not only to increase the threshold for ventricular fibrillation, but also its ability to shorten the QT interval.

Adult↗
PubMed1982

Unusual capture phenomena during interaction of dissociated sinus and junctional rhythms: spontaneous expression of intranodal duality and gap phenomenon.

A ten year old boy presented with an irregular pulse which was caused by AV dissociation with capture beats and pauses. Electrophysiologic studies revealed interaction between sinus rhythm and junctional rhythm. Capture beats were of several types. Early captures blocked below the His bundle but reset the junctional pacemaker causing pauses. Earlier sinus beats conducted with marked atrio His delay. Measurement of intervals during spontaneous rhythm demonstrated a type I gap phenomenon due to dual AH pathways. This case illustrates the value of electrophysiologic studies in analysing complex arrhythmias.

Arrhythmia, Sinus↗
PubMed1982

The use of active fixation electrodes for permanent endocardial pacing via a persistent left superior vena cava.

Two patients underwent permanent endocardial pacing for complete atrioventricular block. In each case a persistent left superior vena cava was either suspected or known to be present. An active fixation electrode was passed down the left superior vena cava and the tip positioned in the apex of the right ventricle. Stable ventricular pacing was achieved for the follow-up period of approximately six months. With the availability of such active fixation electrodes the presence of a persistent left superior vena cava no longer mandates insertion of an endocardial electrode via the right superior vena cava, when present, or implantation of an epicardial pacing system.

Adolescent↗
PubMed1982

The ventricular paced QT interval--the effects of rate and exercise.

Changes in the QT and QTc intervals in 19 patients were studied at a ventricular paced rate difference of 50 beats/min. In all patients the measured QT interval shortened as the pacing rate was increased, from a mean value of 441 ms to 380 ms (p less than 0.001), but when corrected for heart rate the QTc lengthened from a mean value of 518 ms to 575 ms. In 11 patients the QT interval was measured at rest and immediately following exercise sufficient to increase the atrial rate by approximately 50 beats/min at identical ventricular paced rates. In all patients exercise-induced QT interval shortening from a mean value of 433 ms to 399 ms (p less than 0.001). These results show first that Bazett's formula is unsuitable for correction of QT interval induced by ventricular pacing, and second that heart rate and changes in sympathetic tone independently influence the duration of the QT interval. It is suggested that these results are relevant to the design of physiological pacemakers in which the duration of the QT interval influences the discharge frequency of the pacemaker and to the consideration of ventricular pacing for the treatment of abnormal repolarization syndromes.

Adolescent↗
PubMed1982

Cardiac pacing in children.

Twenty patients aged between 12 months and 13 years underwent permanent pacemaker implantation. The main indication for pacing was post-surgical atrioventricular block. The complication rate was high and related mainly to infections and lead system problems. The use of small multiprogrammable pacemakers is expected to reduce the reoperation rate for system malfunction and elective replacement. Newer methods of electrode insertion and active fixation devices in smaller diameter leads make endocardial pacing a practical alternative to epicardial pacing in the larger child who did not require a pacing system at the time of surgery.

Adolescent↗
PubMed1982

Electrophysiological effects of sotalol--just another beta blocker?

The electrophysiological effects of intravenous sotalol hydrochloride (0.4 mg/kg) were assessed in 24 patients, including 13 with the Wolff-Parkinson-White syndrome, undergoing routine electrophysiological study. Fifteen to 30 minutes after sotalol administration there was a significant increase in sinus cycle length and in sinus node recovery time. There was a small increase in the AH interval, but the HV interval was unchanged. The QT and JT intervals, measured during sinus rhythm, were both increased. The atrial, ventricular, and atrioventricular nodal effective refractory periods were all prolonged, as was the atrioventricular nodal functional refractory period. In 13 patients with ventricular pre-excitation there was an increase of the accessory pathway anterograde and retrograde effective refractory periods. In 12 of these 13 sotalol was given during atrioventricular re-entrant tachycardia, resulting in termination in five. Tachycardia cycle length increased in all patients, with the major effect being in the atrioventricular direction. Though some of the effects seen in these patients are consistent with the beta adrenergic antagonist properties of sotalol, the effect on atrial, ventricular, and accessory pathway effective refractory periods and on ventricular repolarisation is not typical of that observed with other beta blockers but may be the result of lengthening of the action potential duration. These findings suggest that sotalol may be a more versatile antiarrhythmic agent than other beta receptor antagonists.

Adolescent↗