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Biomedical subjects

R W Wald

Publications and source records attributed to R W Wald.

34 records · Page 2Linked to original sources
PubMed1980

Vagal techniques for termination of paroxysmal supraventricular tachycardia.

Maneuvers that reflexly increase vagal tone were deployed to terminate the tachycardia in 68 consecutive patients with paroxysmal supraventricular tachycardia. The order and success rate of the protocol was as follows: 57 episodes were terminated with carotid sinus pressure alone or after pretreatment with edrophonium, 5 were terminated with the Valsalva maneuvers and 6 were terminated with phenylephrine. Potency testing showed that phenylephrine evoked the greatest increase in vagal tone. All cases demonstrated slowing of tachycardia ranging from 40 to 220 ms +/- standard error of the mean (mean 79.0 +/- 3.8 ms) followed by abrupt termination. Pauses after termination ranged from 900 to 3,300 ms (mean 1,683.8 +/- 66.6) with 54 patients showing pauses of 2,000 ms or less. Termination was highly reproducible showing an overall success of 148 (92 percent) of 160 trials among 22 selected cases. The extent of increased vagal tone needed to terminate paroxysmal supraventricular tachycardia was raised by augmented sympathetic tone (infusion of isoproterenol) and decreased by reduced sympathetic tone (pretreatment with propranolol). Thus, paroxysmal supraventricular tachycardia can be rapidly, safety and consistently terminated by maneuvers that reflexly increase vagal tone.

Adolescent↗
PubMed1980

Effect of intracoronary glyceryl trinitrate on perfusion distribution in the collateralised human myocardium.

The effect on myocardial perfusion distribution of intracoronary glyceryl trinitrate in a dose (60 micrograms) insufficient to cause alterations in systemic blood pressure or heart rate was studied in eight patients with angiographically demonstrated collaterals from the left coronary system to the distal right coronary artery. Double isotope imaging using technetium-99m and iodine-131 labelled albumin macroaggregates allowed each patient to serve as his own control. The reproducibility of the imaging and data handling techniques was shown in 12 control patients. Glyceryl trinitrate caused a significant diminution in the collateral-mediated fractional perfusion while increasing that of the native coronary bed.

Collateral Circulation↗
PubMed1980

Unidirectional block in Purkinje fibers.

Three methods of inducing focal conduction disturbances in free-running sheep Purkinje fibers (symmetric and asymmetric focal cooling and asymmetric focal crushing) were explored in 50 preparations. Complete unidirectional block was induced in only a minority of symmetrically cooled preparations whereas the asymmetric lesions generated this conduction disturbance in 80-85% of preparations. The block was more stable when induced by crushing than by asymmetric cooling but was more readily reversible with the latter. The direction of block coincided with the least abrupt gradient in the intensity of the lesion (82-94%), was reversible upon reorientation of the cooling lesion, and was independent of anatomic orientation or pre-existing asymmetries of conduction. The models of unidirectional block described in this paper may be useful in the elucidation of the mechanism of asymmetric conduction disturbances and in studies of the mechanism of action of antiarrhythmic drugs.

Action Potentials↗
PubMed1980

Valsalva termination of ventricular tachycardia.

Nine patients with recurrent ventricular tachycardia (VT) that could be repeatedly terminated by a Valsalva maneuver are described. In two, the tachycardia would cease for only a few seconds and then resume, whereas in seven, the tachycardia could be permanently and reproducibly terminated with a Valsalva maneuver. In all patients the tachycardia ended during the strain phase of the Valsalva maneuver, when blood pressure and radiographic measurement indicated that cardiac dimensions had been reduced dramatically. The speed with which the Valsalva maneuver terminated VT incresed in direct proportion to the strain pressure. Maneuvers such as standing or nitroglycerin, which independently reduce cardiac dimensions, enhanced the potency of the Valsalva maneuvers. Pretreatment with atropine or propranolol in four patients did not alter the response of VT to the Valsalva maneuver. Thus, it appears that a strong Valsalva maneuver can terminate some forms of VT, most likely related to an abrupt reduction in cardiac dimensions.

Adolescent↗
PubMed1980

Effects of respiration and posture on paroxysmal supraventricular tachycardia.

The capacity of deep inspiration and the dependent body position to terminate episodes of tachycardia was studied in 11 patients with recurrent paroxysmal supraventricular tachycardia (PSVT). In eight patients, a deep inspiration and a dependent position repeatedly terminated episodes of PSVT. Reasons for failure were found in the other three patients. A deep inspiration or assumption of a dependent position dramatically raised arterial blood pressure and terminated episodes of PSVT by reflexly increasing vagal drive. The magnitude of the rise in blood pressure was directly proportional to the depth of the inspired volume and to the extent of body dependency. The upright position attenuated the respiratory-induced increase in blood pressure and blocked PSVT termination. Likewise, vagal blockade with atropine did not affect the effects of respiration or dependent position on blood pressure but prevented termination of PSVT.

Adult↗
PubMed1980

The effect of antiarrhythmic drugs on depressed conduction and unidirectional block in sheep Purkinje fibers.

We studied the effect of therapeutic concentrations of lidocaine, procainamide, quinidine, propranolol, and diphenylhydantoin on two models of depressed conduction and unidirectional block produced by asymmetric focal cooling and crushing in sheep Purkinje fibers. All drugs were shown to induce reversible deterioration of conduction. Unidirectional block was converted to bidirectional block with each drug. Improvement of conduction was rare and conversion of unidirectional block to bidirectional conduction never was observed. These experiments suggest that all five drugs may act by a uniform mechanism of action in some reentrant ventricular arrhythmias involving a zone of depressed conduction or unidirectional block within the Purkinje network.

Animals↗
PubMed1979

Management of intractable ventricular tachyarrhythmias after myocardial infarction.

Twenty-five patients with recent or old myocardial infarction were studied because they had life-threatening ventricular arrhythmias that required repeated cardioversions and were intractable to medical management. All patients had had a large anterior infarction a mean of 4.6 weeks before the emergence of the arrhythmias and all had severe left ventricular dysfunction. Cardiac catheterization or autopsy revealed a left ventricular aneurysm in 18 of 18 patients and obstruction of the left anterior descending coronary artery in 20 of 20 patients. Of 16 patients treated surgically with aneurysm resection or coronary bypass grafting, or both, 10 (62 percent) were alive after 3 to 39 (mean 26) months of follow-up. The perioperative mortality rate was 31 percent and only one patient died during the postoperative follow-up period 4 months after discharge from the hospital. By contrast, all nine medically treated patients died either in the hospital (four patients) or suddenly within 2 months of discharge (five patients). Ventricular fibrillation was documented as the cause of death in five of these patients. Surgical intervention was found to improve significantly the survival of these patients (P less than 0.02). The perioperative mortality rate was lower when at least 4 weeks had elapsed from acute infarction to surgery (10 versus 67 percent) and when the procedure included coronary bypass grafting (13 versus 50 percent), although these differences were not statistically significant (P greater than 0.05).

Adult↗
PubMed1979

Carotid sinus massage induced elimination of rate related bundle branch block during paroxysmal atrial tachycardia: a simple method of proving bypass tract participation in the tachycardia.

Four cases of paroxysmal atrial tachycardia are described in whom rate related left bundle branch block (LBBB) was often present which persisted indefintely and showed no signs of spontaneous disappearance. Transient slowing of the tachycardia by carotid sinus massage in each case eliminated LBBB and this led to tachycardia acceleration. The tachycardia acceleration was traceable to a shortening in ventriculoatrial conduction. These observations proved the participation of a left sided bypass tract in the tachycardia circuit in each of these cases.

Bundle-Branch Block↗
PubMed1978

Myocardial perfusion imaging with thallium-201: correlation with coronary arteriography and electrocardiography.

Myocardial perfusion imaging with thallium-201 and electrocardiography with the subject at rest and undergoing submaximal treadmill exercise were performed in 19 men and 3 women. Selective coronary arteriography and left ventriculography showed that 7 had normal coronary arteries and 15 had coronary artery disease.The 11 persons with electrocardiographic evidence of an old myocardial infarct (q waves) had a perfusion defect at rest in the area of the infarct and a segmental abnormality of wall motion apparent on the left ventriculogram corresponding to the perfusion defect.MYOCARDIAL PERFUSION IMAGING AND ELECTROCARDIOGRAPHY WERE EQUALLY SENSITIVE IN DETECTING CORONARY ARTERY DISEASE IN EXERCISING INDIVIDUALS: perfusion defects were noted in 7 of the 15 persons with coronary artery disease, and diagnostic ST-segment depression was present in 8 of the 15. Combination of the results of the two tests with exercise permitted the identification of 11 of the 15 persons and improved the sensitivity. Combination of the results of rest and exercise imaging and electrocardiography permitted the identification of 94% of the patients with coronary artery disease.Myocardial perfusion imaging with (201)TI in the subject at rest is a sensitive indicator of previous myocardial infarction. Imaging after the subject has exercised is a useful adjunct to conventional exercise electrocardiography, especially in those whose exercise electrocardiogram is non-interpretable.

Adult↗
PubMed1978

Demand pacemaker slowing: a simple bedside technique.

We present a simple noninvasive bedside technique to slow gradually any R-wave inhibited ventricular demand pacemaker up to one-half its original rate for indefinite periods of time. Gradual pacemaker slowing allows accurate diagnostic observations and therapeutic interventions in pacemaker-induced arrhythmias and may possibly be used in the management of unstable angina in patients with ventricular demand pacemakers.

Aged↗
PubMed1978

Self-conversion of supraventricular tachycardia by rapid atrial pacing.

The use of pacemakers in the treatment of tachycardias is one of the most exciting and rapidly expanding applications of cardiac pacing. One of the more recent developments in this field has been the use of patient-activated radio frequency transmitted rapid atrial stimulation (RAS) in the treatment of paroxysmal supraventricular tachycardia (PSVT). Based on the previously established ability of asynchronous atrial pacing to interrupt a variety of re-entrant supraventricular rhythm disturbances, this modality of treatment is gaining increasing applicability in patients with PSVT associated with debilitating symptoms or other severe cardiovascular consequences in whom standard pharmacological regimens have either failed or are impossible to maintain for indefinite periods. This report describes our experience with five patients who underwent implantation of RAS units. The detailed electrophysiological studies required to ensure success and avoid any possible future complications are described. Over a follow-up period of four months to four years (mean 16 months) very few problems arose in the use of these units which have immeasurably improved the quality of life of the recipients. Our experience with RAS units has led to a few suggestions for future improvement and these are outlined in this report. The excellent patient acceptance and the reliability of this technique in terminating episodes of PSVT should, in the future, render RAS the treatment of choice in certain selected patients suffering from this common disorder.

Adult↗
PubMed1978

Technetium-99m stannous pyrophosphate scintigraphy in patients with calcification within the cardiac silhouette.

Technetium-99m stannous pyrophosphate scintiscanning was performed in 22 patients with radiographically detected calcification within the cardiac silhouette. All but one of these scintigrams showed a localised area of increased activity similar to that ordinarily seen in acute myocardial infarction. Scintiscans in 3 patients after removal of the calcified aortic valve reverted to negative. It was concluded that this technique for acute infarct detection may yield false positive results in the presence of cardiac calcification.

Calcinosis↗
PubMed1977

Recurrent paroxysmal supraventricular tachycardia: a complication of ventricular pacing in a patient with occult Wolff-Parkinson-White syndrome.

A 60 year old man suffering from syncope believed to be due to the sick sinus syndrome was treated with a permanent demand ventricular pacemaker. This led to almost continous bouts of paroxysmal supraventricular tachycardia (SVT) over the ensuing two years, mistakenly believed to be part of the sick sinus syndrome. Careful study showed that this man had a type A Wolff-Parkinson-White accessory atrioventricular connection which consistently conducted retrogradely, but only rarely antegradely, during applications of carotid sinus massage. Episodes of SVT were repeatedly induced whenever ventricular-paced impulses captured the atria retrogradely. All episodes of SVT stopped when the ventricular pacemaker was removed. Following insertion of an atrial pacemaker, the patient had no episodes of SVT or syncope over a nineteen month follow-up period. This case illustrates the care required in selecting a proper site for protective pacing in patients who suffer from paroxysmal SVT.

Heart Conduction System↗
PubMed1977

Termination of ventricular tachycardia by an increase in cardiac vagal drive.

Out of 12 patients in whom phenylephrine terminated ventricular tachycardia, four were selected for detailed studies of its mechanism of action. Pretreatment with edrophonium (15-20 mg, i.v.) decreased, while atropine (2.4 mg, i.v.) increased by at least a factor of two, the dose of phenylephrine required to break ventricular tachycardia. Carotid sinus massage following pretreatment with edrophonium in unusually high (15-20 mg, i.v.) doses broke ventricular tachycardia in all four patients. The evidence presented supports the assumption that a vagal mechanism caused both instances of termination. These findings significantly alter our interpretation of vagal interventions in the bedside clinical diagnosis of wide QRS complex tachycardias.

Atropine↗