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F L Meijler

Publications and source records attributed to F L Meijler.

18 recordsLinked to original sources
PubMed1978

Postextrasystolic relaxation in the dog heart.

Left ventricular relaxation was studied in 8 dogs using parameters derived from the left ventricular pressure: the fastest pressure fall and the time constant of pressure decline. Effects of extrasystolic rhythm interventions were examined on the relaxation parameters of the post-relative to the preextrasystolic beat. Postextrasystolic potentiation of these parameters could not be demonstrated. Possible influences of physiologic variables as peak left ventricular pressure, endiastolic aortic and enddiastolic left ventricular pressure on relaxation mechanism were evaluated. The nonselective description of myocardial relaxation by pressure derived parameters is discussed.

Animals↗
PubMed1976

Atrial rhythm during ventricular fibrillation in the dog.

Depolarization of the atrioventricular junctional tissues and of the atrial septum was examined in the perfused dog heart before and during ventricular fibrillation by (1) recording the potentials from the junctional tissues in the regions of the interatrial and interventricular septum and examining the relationship of activity at these sites to atrial depolarization, (2) computing histograms and autocorrelograms of atrial firing intervals to study atrial rhythmicity, and (3) plotting the sequence of atrial septal depolarization. The junctional tissue was generally randomly depolarized by the fibrillating ventricles. The histograms and autocorrelograms indicate that during ventricular fibrillation the atrial depolarization intervals do not remain constant, but vary widely. This seems to be due to the retrograde excitation from the junctional tissues. Plots of the depolarization sequences of the interatrial septum also indicate that retrograde depolarization takes place. The junctional tissues decrease the number of impulses that can pass from ventricle to atrium, and they similarly decrease the number of impulses that pass in an antegrade direction during atrial fibrillation.

Animals↗
PubMed1976

Postextrasystolic potentiation in man.

Postextrasystolic potentiation (PESP) is a pre- and afterload-independent property of the myocardium. Therefore it has been used to study left ventricular (LV) contractile state in patients with coronary heart disease and normals. Using a computer-controlled cardiac stimulator, regular rhythms with just above sinus frequency were applied to the right atrium and interrupted after every 20th beat by one shorter interval after varying delays. The next stimulus interval was corrected in such a way that the resulting R-R interval was the same as the basic R-R interval. Control of the postextrasystolic R-R interval is a prerequisite for meaningful and quantitative evaluation of PESP. Of 166 basic and postextrasystolic beats in 12 patients LV pressures (P), obtained with a catheter tipmanometer, were analyzed. There was no significant difference in enddiastolic P between pre- and postextrasystolic beats. Peak dP/dt, time to peak dP/dt, (dP/dt)/P at a left ventricular P of 50 mm Hg and Vmax were used as indices of left ventricular contractile state. It was found that on increasing prematurity of the extrasystolic beat, there was a progressive and reproducible increase of these indices (selfevidently a decrease in the case of the time to reach peak dP/dt). Using Vmax as an index of contractile state, no significant PESP could be demonstrated in the two patients with very enlarged left ventricular volumes and depressed ejection fractions. PESP, elicted in this (only allowable) way, is an integral, quantitative and reproducible method for LV contractility estimation in man.

Adult↗
PubMed1975

An automated ECG-system in a large hospital: coding, storage and retrieval of tracings.

This paper describes an automated ECG-system as it is used in the 1000-bed University Hospital Utrecht, The Netherlands. The system involves a "hybride" approach, combining computer analysis of the ECG by means of the Pipberger program with the reading by a cardiologist via a specially developed coding system. Up until now (since January 1, 1972) 35,000 ECGs have been handled systematically at a rate of approximately 100 ECGs per working day. All the ECGs, together with the ECG-diagnoses and other relevant data of the patient are stored and can be retrieved whenever wanted. The system enables comparison of computer analysis and cardiologist's reading of the ECG. The boundary between reliable computer analysis and the necessity of human reading and verification lies with the normal ECGs. This apparently meagre result of the computer ECG-analysis for hospital use is, however, a great achievement for its use in epidemiological studies.

Electrocardiography↗
PubMed1975

Hydrogen ion changes and contractile behavior in the perfused rat heart.

The effect of acid-base alterations was analyzed using isolated rat hearts perfused at constant coronary perfusion pressure, and stimulated to contract at constant rat. The amount of shortening in the major axis and its derivative were measured to assess myocardial contractility. Both the 'respiratory' and 'metabolic' alterations affected the contractile behavior to the same extent. In the physiological range studied by us, acidosis depresses and alkalosis increases myocardial contraction. However acidosis seems to depress contractility more than the enhancement produced by the same change in pH towards the alkalotic side. When either amount of shortening or max dl/dt was plotted as a function of hydrogen ion acitvity (aH+) a linear correlation was obtained, either with pure 'metabolic' or 'respiratory' acid-base induced alterations (correlation coefficients higher than -.95; P less than .01). Our findings suggest that in the range studied by us, contraction of the perfused rat heart following acid-base alterations, is a linear function of hydrogen ion activity.

Acid-Base Equilibrium↗