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Biomedical subjects

R A Spurrell

Publications and source records attributed to R A Spurrell.

At least 73 records · Page 4Linked to original sources
PubMed1979

Patterns of atrial activation during right ventricular pacing in patients with concealed left-sided Kent pathways.

A 'concealed' accessory pathway was suspected in 12 patients because of eccentric left atrial activation during tachycardia. Retrograde conduction during ventricular pacing may occur over the atrioventricular node, the accessory pathway, or both. There were 4 patterns of ventriculoatrial conduction in response to ventricular extrastimuli (V2) at various coupling intervals: (1) exclusive accessory pathway conduction throughout the cardiac cycle in 2 patients; (2) exclusive accessory pathway conduction at long coupling intervals and exclusive atrioventricular node conduction at short coupling intervals in 2 patients; (3) variably fused accessory pathway/atrioventricular node conduction at long coupling intervals but exclusive accessory pathway conduction at short coupling intervals in 4 patients; (4) fused accessory pathway/atrioventricular node conduction at long coupling intervals but exclusive atrioventricular node conduction at short coupling intervals in 4 patients. With increased prematurity of V2 the ventricle to right atrial interval prolonged conspicuously in 11 of 12 patients whereas the ventricle to left atrial interval remained constant until the refractory period of the accessory pathway in all but 2 instances where intraventricular delay occurred. This study emphasises the importance of left atrial recordings in these patients.

Adult↗
PubMed1979

Ectopic ventricular tachycardia in association with a concealed accessory pathway.

Ventricular tachycardia may result in retrograde atrial depolarization. In all previous examples studied by intracardiac recording techniques retrograde conduction to the atria has been thought to occur via the normal conduction system. In the patient reported here, 1 : 1 retrograde conduction with atrial preexcitation during ventricular tachycardia indicated the presence of a concealed accessory pathway. This was confirmed by the phenomenon of exact atrial capture. The achievement of atrioventricular dissociation during tachycardia by atrial overdrive pacing excluded a reentrant tachycardia involving such a pathway. The widely variable H--V interval in the presence of a constant V--A interval during tachycardia suggested anterograde His bundle depolarization following atrial activation over the accessory pathway. This hypothesis was supported by the long V--H interval during tachycardia and the relationship of the ventricular, atrial and His bundle electrograms of the first and least beat of the tachycardia. This report illustrates the value of careful electrophysiological investigation in evaluating the relationship of an accessory pathway to the tachycardia mechanism.

Electrophysiology↗
PubMed1979

Ventricular preexcitation due to anomalous nodo-ventricular pathways: report of 3 patients.

3 patients with paroxysmal palpitations had surface electrocardiographic evidence of type B preexcitation with a small positive delta wave in lead V1. At study all patients had an abnormally short H-V interval. Programmed atrial premature stimuli at progressively shorter coupling intervals resulted in prolongation of AV conduction time and increasing preexcitation. In 2 patients early atrial premature stimuli elicited atrial echo beats or sustained tachycardia with preexcited QRS complexes. In these patients the accessory pathway did not appear to be involved in the tachycardia circuit. It is postulated that the site of reentry is within the AV node with preexcitation occurring as the result of conduction in an anomalous node-ventricular pathway. In the 3rd patient, preexcitation occurred within a restricted range of coupling intervals of an atrial premature stimulus. The electrophysiological responses of nodo-ventricular and His-ventricular pathways to atrial stimulation are compared and contrasted.

Adult↗
PubMed1978

Comparative peripheral and coronary haemodynamic effects of rimiterol and isoprenaline.

1. Rimiterol and isoprenaline produced significant dose-related increases in cardiac output. 2. These changes in cardiac output were accompanied by increases in heart rate and myocardial oxygen consumption which were similar for each drug and dose-related. 3. Isoprenaline in contrast with rimiterol produced direct coronary vasodilation, i.e. coronary vasodilation in excess of that required to meet increases in myocardial oxygen demands. 4. It is suggested that the beta-adrenergic receptors in the human coronary vasculature are mainly of the beta1 type. 5. Rimiterol, because it does not produce direct coronary vasodilation may be preferable to isoprenaline in the treatment of low-cardiac output syndrome where there is regional myocardial ischaemia, since it would be less likely to produce a "coronary steal" effect.

Adult↗
PubMed1978

Gaps in anterograde conduction in patients with the short PR interval, normal QRS complex syndrome.

Of 8 patients with the short PR interval, normal QRS complex syndrome studied recently, 3 reported here displayed gaps in anterograde conduction. Atrial premature beats at decreasing coupling intervals conducted with minimal AH prolongation until a zone within the cardiac cycle was reached where conduction failed at a supra-Hisian level. Conduction resumed at earlier atrial coupling intervals and was associated with a sudden increase in the AH interval and the appearance of atrial echo beats with earliest atrial activation on the proximal coronary sinus electrogram. It is suggested that the failure of anterograde conduction at relatively late atrial coupling intervals was caused by a short AH functional refractoriness produced by the pre-excitation of the lower AV junction by a partial AV nodal bypass. Conduction resumed only when early atrial premature beats found the extranodal pathway refractory and were transmitted with decremental delay through the AV node.

Adult↗
PubMed1978

Re-entrant tachycardia using two bypass tracts and excluding AV node in short PR interval, normal QRS syndrome.

In patients with the short PR interval, normal QRS complex syndrome, paroxysmal tachycardias are usually the result of circus movement involving the AV node and a partial or complete AV nodal bypass. We report 2 patients with this syndrome who suffered distressing rapid paroxysms of tachycardia but in whom there was evidence of a concealed direct VA connection. In both patients, tachycardia was initiated with critical AV prolongation distal to the His bundle, in response to programmed atrial premature stimuli. The constancy of the timing of the atrial echo from the onset of the QRS complex in the presence of a varying HV interval is evidence for involvement of the ventricles in the re-entry pathway. In addition, in both patients the appearance of left bundle-branch block during tachycardia was associated with appropriate prolongation of tachycardia cycle length consistent with the presence of a direct VA connection. The short AH interval during tachycardia and the absence of critical AH prolongation suggests the participation of a rapidly conducting pathway in the anterograde limb of the tachycardia circuit.

Adult↗
PubMed1978

Positive myocardial scintigraphy at the bedside--evaluation using a portable gamma camera.

A study was undertaken to evaluate the role of positive infarct scintigraphy in the diagnosis of acute myocardial infarction (AMI), using Technetium99m stannous pyrophosphate (Tc-PYP) and a portable gamma camera. Sixty-one patients admitted to the Coronary Care Unit (CCU) with a presumptive diagnosis of AMI or ischaemic cardiac pain were studied. Positive scans were present in 24/25 (96%) patients with AMI and new Q waves, and in 10/12 (83%) patients with AMI and no Q waves. Nine of eleven (82%) patients with chest pain and no infarction had negative scans. Of thirteen patients with unstable angina, ten (77%) had positive scans. A further eight patients undergoing coronary artery bypass surgery for angina pectoris were studied pre- and postoperatively. Two patients had strongly positive postoperative scans. The Tc-PYP scan is valuable in the detection of peri-operative infarction following coronary artery surgery, and in patients with unstable angina the technique may detect small amounts of myocardial necrosis undetectable by more conventional means. When the diagnosis of infarction is obvious from the ECG, enzymes, or a combination of the two, the Tc-PYP scan provides no extra information helpful in patient management.

Acute Disease↗
PubMed1978

Haemodynamic effects of isosorbide dinitrate in patients with congestive cardiac failure at rest and during submaximal supine exercise.

Eight patients with chronic congestive cardiac failure secondary to ischaemic heart disease performed submaximal supine exercise before and after 5 mg sublingual isosorbide dinitrate (ISDN) at the time of cardiac catheterisation. Exercise before ISDN produced a poor response in left ventricular performance. After ISDN this response was significantly improved. Compared with the control exercise period cardiac index (CI) increased from mean 2.9 to 3.5 l/mn/m2 (p = less than 0.0025), stroke volume index (SVI) from mean 24 to 29 ml/m2 (p = less than 0.0005) and left ventricular stroke work index (LVSWI) from mean 22 to 28 g-m/m2 (p = less than 0.0025). Although ISDN reduced LVEDP significantly at rest, there were associated small but significant falls in CI, SVI and LVSWI. The improvement in exercise cardiac index was related to the ejection fraction, or the ejection fraction of the contractile section where a left ventricular aneurysm was present. ISDN may be effective in improving exercise tolerance in ambulant patients with chronic congestive cardiac failure.

Administration, Oral↗
PubMed1978

Arrhythmias in ambulatory persons. A review and experience of 1,000 consecutive recordings.

The value of 24-hour ambulatory monitoring of the ECG for the diagnosis of symptoms of dizziness, palpitations and syncope is controversial. In this study results from a hospital-based, clinical service have been analysed. Of 1,000 consecutive dynamic electrocardiograms (DCG), 678 were performed for assessment of dizziness, syncope or palpitations in 405 patients. 36 of the patients had pacemakers. 60 DCGs were technically inadequate. The recordings were classified according to the correspondence between DCG findings and symptoms noted in the patient diary: (I) Completely diagnostic: significant arrhythmias (SA) corresponding to diary symptoms - 99 recordings. (II) Incompletely diagnostic: (a) absence of SA in the presence of diary symptoms - 90 recordings; (b) presence of SA but no diary symptoms - 197 recordings; (c) presence of SA corresponding to symptoms other than that for which the DCG was indicated - 52 recordings. (III) Non-diagnostic: absence of both SA and diary symptoms - 180 recordings. Incompletely diagnostic categories were regarded as clinically valuable in that they either excluded a cardiac arrhythmia as a cause of symptoms (group IIa) or they revealed SA which did not correspond to diary symptoms (group IIc). The absence of symptoms corresponding to SA was ascribed to poor diary keeping in 54 of 197 recordings. These results are discussed in the context of the findings in normal and symptomatic patients. A clinical 24-hour ambulatory ECG monitoring service provided useful diagnostic information in 65% of recordings and 74% of patients.

Adolescent↗
PubMed1977

Ambulatory monitoring of the electrocardiogram: an important aspect of pacemaker surveillance.

Of the 353 patients followed in the pacemaker surveillance clinic between July 1976 and July 1977, 25 patients complained of episodes of dizziness and faintness. 20 of these had normal pacing function and pacemaker parameters at routine clinic testing. 18 patients had 'demand' units and 2 had fixed-rate pacemakers. The indication for permanent pacing was complete heart block in 16 patients and sinoatrial disease in 5 patients. At clinic follow-up, there was unequivocal evidence of vertebrobasilar insufficiency in 5 patients and postural hypotension in 4 patients. In 11 patients, the cause of presyncope was not evident at the clinic. All patients were monitored by 24-hour tape recording until an episode of pre-syncope occurred. In 8 patients, there was evidence of intermittent failure to pace associated with the episodes of presyncope. In 2 patients, an additional cause for presyncope was found at clinic examination. Ambulatory 24-hour tape monitoring of the electrocardiogram is an important adjunct to pacemaker follow-up especially when other methods such as transtelephone monitoring are not available in the United Kingdom. Routine electronic testing of pacemaker function does not always reveal intermittent abnormalities related to changes in threshold or unstable electrode positions.

Ambulatory Care↗
PubMed1976

Pacing techniques in the management of supraventricular tachycardias. Part 2. An implanted atrial synchronous pacemaker with a short atrioventricular delay for the prevention of paroxysmal supraventricular tachycardias.

An implanted atrial synchronous pacemaker with an atrioventricular delay of 30 msec is described. This pacemaker was implanted into a patient with paroxysmal supraventricular tachycardia due to an intra AV nodal reciprocal mechanism. The pacemaker was able to trigger from atrial potentials following atrial premature beats down to a coupling time of 300 msec. Following each triggering atrial potential, a ventricular stimulus was applied 30 msec later thereby producing a ventricular premature beat in response to each sinus beat or each atrial premature beat. Retrograde conduction from this atrial premature beat blocked the re-entry mechanism within the AV node and prevented the initiation of tachycardia. A detailed discussion on all parameters of function of this pacemaker is presented.

Action Potentials↗
PubMed1975

Pacing techniques in the management of supraventricular tachycardias. Part 1. The use of high frequency stimulation (HFS) in the management of paroxysmal supraventricular tachycardia.

Using techniques for programmed electrical stimulation of the heart, seven patients with paroxysmal supraventricular tachycardia have been studied and shown to have a reciprocal mechanism as the most likely basis for the tachycardia. In four patients it was found that the tachycardia could be terminated by single right atrial premature beats and in three patients two right atrial premature beats were required. A variable zone for tachycardia termination was found when single or double stimuli were used and so a system for introducing high frequency stimuli at 100 or 1000 stimuli/sec for a given duration is described. Using this system a wider range of the cardiac cycle could be covered, thereby increasing the likelihood of producing correctly timed premature beats. The results of using this system are presented and its practical usage discussed.

Adult↗