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Biomedical subjects

M M Laks

Publications and source records attributed to M M Laks.

At least 91 records · Page 5Linked to original sources
PubMed1979

The electrophysiologic effects of intravenous propranolol in the Wolff-Parkinson-White syndrome.

Fourteen patients with the Wolff-Parkinson-White (WPW) syndrome were studied by means of intracardiac stimulation techniques, before and after the intravenous administration of propranolol, 0.1 mg./Kg. There were no significant change, or only a slight increase, in the effective refractory periods of all parts of the re-entry tachycardia circuit studied, in either anterograde or retrograde directions. Re-entry tachycardia was initiated in nine patients in the control state, and in 10 patients after propranolol. The rate of re-entry atrioventricular node-accessory pathway tachycardia was decreased, but by only 10 per cent. The duration and outer limit of the tachycardia zone of atrial extrastimuli were not significantly decreased. Propranolol, by rapid intravenous infusion administration, is unlikely to be effective primary therapy for PSVT in the WPW syndrome.

Adolescent↗
PubMed1979

Increased ejection fraction produced by a long-term subhypertensive infusion of norepinephrine in the conscious dog.

Five mongrel dogs with chronically implanted catheters in the left atrium, mid-thoracic aorta, and right atrium were continuously infused with subhypertensive doses of norepinephrine for 3 months. Left ventricular cineangiography, determinations of aortic pressure, and cardiac output were performed in the conscious dog. After 3 months of continuous norepinephrine infusion, stroke volume increased from 38 +/- 3.0 to 67 +/- 8.0 ml. (p less than .01), the left ventricular end-diastolic volume increased from 72 +/- 6.4 to 89 +/- 12.9 ml. (p less than .05), and the ejection fraction increased from 52 +/- 3.6 to 76 +/- 3.6% (p less than .005). We postulate that norepinephrine results in an increased myocardial function by producing physiological myocardial hypertrophy.

Animals↗
PubMed1979

Comparison of ejection fraction and segmental circumferential fiber shortening velocity in the anesthetized and conscious canine.

A chronically and transseptally implanted left atrial catheter was utilized to perform repeated cineangiography in the conscious dog. The advantage of this preparation is that catheter placement does not require a thoracotomy. Left ventricular function was compared in the same pentobarbital-anesthetized and conscious dog. Anesthesia significantly depressed myocardial function as was demonstrated by a decrease in ejection fraction and segmental circumferential fiber shortening velocity (VCF) and an increase in end-diastolic volume. In addition, no difference in Vcf occurred between the base and the apex. Since anesthesia produced regional difference in the degree of depression of VCF, we conclude that anesthesia will produce patterns of ventricular contraction which are variable and unpredictable. Consequently, we recommend the use of the conscious dog and this preparation in order to evaluate myocardial function.

Anesthetics↗
PubMed1977

A new method for internal calibration of left ventricular cineangiography.

Previous methods of internal calibration for cineangiography have made use of reference objects such as catheters or wires of known length or diameter. Such devices have either insufficient X-ray resolution, or require a specific orientation within the ventricle which is difficult to confirm. External calibration methods, while eliminating these errors, can only estimate actual position of the left ventricle. The use of a Swan-Ganz balloon catheter as a calibration object diminishes these problems. When positioned within the left ventrical and filled with a radiopaque medium, the balloon is of sufficient size and density to avoid errors induced by previously employed objects. The inflated balloon geometry is simple and reproducible. The use of this internal calibration catheter markedly diminishes major sources of errors in the determination of ventriculograms for both dogs and humans.

Animals↗
PubMed1977

Relationship between the electrical (electrocardiographic) and mechanical (echocardiographic) events in Wolff-Parkinson-White syndrome.

Studies using epicardial mapping on patients with Wolff-Parkinson-White syndrome have demonstrated that the delta vector of the electrocardiogram is a detector of the location of at least one bypass tract. In order to relate the electrical activities (preexcitation) with the mechanical activity (septal and ventricular wall motion), echocardiographic strip-chart recordings were obtained in 22 patients with Wolff-Parkinson-White syndrome. Our studies indicated that in the majority of patients with Wolff-Parkinson-White syndrome, left ventricular and septal contraction is normal, suggesting that normal activation predominates and that the determinants of abnormal septal wall motion are (1) the location (right ventricular free lateral wall or septrum) and (2) the degree (duration of the QRS complex greater than 130 msec) of ventricular preexicitation.

Adolescent↗
PubMed1977

Wolff-Parkinson-White syndrome. Alterations in electrophysiologic characteristics of the bypass tract secondary to ischemia.

Accurate electrocardiographic diagnosis of myocardial ischemia or infarction is difficult in patients with the Wolff-Parkinson-White syndrome; however, myocardial ischemia may also have profound effects on the electrophysiologic characteristics of the bypass tract in these patients. Comparison of studies performed during and two months following an episode of significant myocardial ischemia demonstrated substantial prolongation of the refractoriness of the bypass tract during the period of ischemia. Bypass refractoriness was prolonged by 196 msec, yet atrioventricular nodal refractoriness was not significantly different from normal. These studies, therefore, suggest that, on occasion, the presence of acute myocardial ischemia may, in fact, obscure the electrocardiographic diagnosis of the Wolff-Parkinson-White syndrome.

Aged↗
PubMed1976

Technique for serial right and left ventricular endocardial biopsy in dogs.

A method is described for obtaining left and right ventricular endocardial biopsies repeatedly over a period of 3-6 mo in the dog. The left ventricular endocardial biopsy technique consists of the placement of a catheter via the venous route across the atrial septum and into the left ventricle. The biopsy catheter is in turn placed within this transseptal catheter. Tissues obtained by this method were satisfactory for both light and electron microscopic examination. At postmortem examination, only minimal and insignificant damage existed at the biopsy site. Consequently, we recommend this technique for the study of progressive pathologic changes in the endocardium that occur during the course of an experiment which can be identified and quantified in comparison to the control state.

Animals↗
PubMed1976

Technique for the performance of repeatable renal clearances in the conscious male dog.

A preparation for performance of renal clearances in the conscious dog is described. The important aspect of the technique is the use of a Pavlov sling and a specially designed restraining apparatus. Of most importance is the use of a 7 French Swan-Ganz balloon-tipped catheter for urinary bladder catheterization. The use of male dogs obviated the need for an episiotomy. No special training of the animals was required. The animals tolerated long-term and repeated catheterization without any evidence of infection or trauma.

Aminohippuric Acids↗
PubMed1976

Recurrent reciprocating tachycardias in the Wolff-Parkinson-White syndrome; control by the use of a scanning pacemaker.

Frequent episodes of arrhythmias in patients with the Wolff-Parkinson-White syndrome are sometimes unresponsive to medical management. Recent emphasis has been placed on the role of surgery as a means of effectively controlling these patients' tachyarrhythmias; however, in some patients the use of permanent pacing has been espoused as an effective means of controlling arrhythmias. This report documents the efficacy of a new pacemaker with rate-scanning features, which offers significant technical advantages. Subsequent follow-up has documented the efficacy of this unit in the management of a young woman with type-A Wolff-Parkinson-White syndrome and previously intractable arrhythmias.

Adult↗
PubMed1975

The Wolff-Parkinson-White syndrome: pharmacologic effects of procaine amide.

The effect of procaine amide, 10 mg. per kilogram via intravenous infusion, was studied in 13 patients with the WPW syndrome. The delta wave was eliminated by procaine amide in 10 and modified in three patients. This effect lasted between 30 minutes and 8 1/2 hours and was unrelated to the total dose administered. Anterograde A-V conduction was assessed by atrial pacing with increasing rates. More rapid atrial pacing rates with 1:1 A-V conduction were observed in patients who maintained rather than lost their delta wave during pacing. Ventriculoatrial conduction was assessed with ventricular pacing at increasing rates; ventricular conduction time was fixed regardless on the pacing rate. Procaine amide significantly prolonged V-A conduction time in six and blocked V-A conduction in one patient. In addition, A-V and V-A refractory periods were measured by the extrastimulus technique. Two types of responses were observed: (1) Type I or (2) line of identity. A-V nodal refractoriness was observed to be within the normal range. Procaine amide converted anterograde line of identity responses to Type I responses in all patients who had their delta waves eliminated. In this patient group, bypass refractoriness was shorter than A-V nodal refractoriness. Procaine amide was not observed to alter significantly normal A-V conduction as assessed by atrial pacing or A-V refractory period measurements. Furthermore, a significant disparity between the effects of procaine amide on anterograde and retrograde bypass refractoriness was observed. Tachycardias could be induced in nine of the 13 patients with a mean rate of 167.2 +/- 7.9 beats per minute; delta waves were abent during all episodes of tachycardia. Procaine amide prevented tachycardia induction in six of the none patients. Procaine amide therefore demonstrates electrophysiologic effects which would be beneficial for prevention or treatment of reciprocating tachycardias in the WPW syndrome. Moreover, procaine amide would be an ideal agent for the prevention of rapid ventricular rates in patients with the WPW syndrome and atrial fibrillation.

Adolescent↗