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Biomedical subjects

F L Meijler

Publications and source records attributed to F L Meijler.

At least 109 records · Page 6Linked to original sources
PubMed1982

Cardiac function, fiber shortening, and dynamic geometry.

Many models for the study of the pump function of the heart emphasize the importance of cardiac geometry and detailed dimensional data. Because of the lack of accurate measuring techniques, approximate geometries such as shells of revolution have been applied. In this study, methods are presented that measure the dynamic geometry of the working, isolated canine heart by means of ultrasound-velocity tomography techniques. In addition, cardiac dimensions, intramural deformations, and fiber shortening have been measured dynamically in the in situ canine heart throughout the cardiac cycle with implanted radiopaque markers and biplane roentgen techniques. Results of regional contraction and relaxation patterns are presented. Epicardial fiber shortening between apex and base were computed and found to be dependent on the duration of the preceding RR interval.

Animals↗
PubMed1982

Clinical relevance of postextrasystolic potentiation.

The significance and clinical relevance of postextrasystolic potentiation resides in the fact that any change in duration of the cardiac cycle results in a change in the contractile behavior of the heart. Since neither a normal nor a diseased heart ever beats strictly regularly, postextrasystolic potentiation is continuously operative, and all hemodynamic or circulatory data obtained in the intact organism are affected by it. This means that postextrasystolic potentiation should be taken into account when cardiovascular clinical data are analyzed and subsequently used for diagnosis or treatment. Postextrasystolic potentiation used as an intervention for the evaluation of residual viable myocardium in scar tissue areas in patients with coronary heart disease may contribute to out insights in the prognosis of and therapeutic judgments in those patients. Postextrasystolic potentiation is a fundamental physiologic property of all myocardium under all circumstances and as such does not allow for integrating or averaging data obtained during more than one cardiac cycle, if cardiac rhythm has not been strictly regular. This fact is insufficiently appreciated in nuclear cardiology and two-dimensional echocardiography.

Animals↗
PubMed1980

Future of computerised electrocardiography.

The advent of computerised electrocardiography has been of prime importance for the storage and retrieval of data, but none of the available systems is of universal application for analysis of patterns. Future needs require hierarchical systems of increasing degrees of complexity, depending on the source of requests, and there should be appropriate provision for review by cardiologists before the final report is issued.

Computers↗
PubMed1980

The effect of verapamil on the calcium paradox.

Reperfusion of isolated rat hearts with calcium-containing medium after a short period of calcium-free perfusion results in irreversible cell damage (calcium paradox). Experiments were undertaken to determine whether the slow-channel calcium-antagonist drug verapamil protects calcium-deprived rat heart muscle against the consequences of readmitting calcium. Cell damage was quantitated in terms of creatine kinase (CK) release, depletion of endogenous creatine phosphate (CP) and adenosine triphosphate (ATP) stores, development of contracture as measured by longitudinal shortening of the left ventricle, and ultrastructural damage. Verapamil (1 mg/l) did not reduce the initial rate of CK release during reperfusion with calcium but reduced the initial rate at which myocardial CP and ATP stores were depleted and decreased the shortening of the longitudinal axis of the left ventricle. After 30 seconds of reperfusion the mean sarcomere length was significantly greater in the verapamil-treated hearts. These results can be interpreted to mean that inhibition of calcium inflex via the slow channels does not protect heart muscle against the deleterious effects of readmitting calcium after a period of calcium-free perfusion.

Adenosine Triphosphate↗
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↗