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Biomedical subjects

F L Meijler

Publications and source records attributed to F L Meijler.

At least 91 records · Page 5Linked to original sources
PubMed1984

The concept of apparent cardiac arrest as a prerequisite for coronary digital subtraction angiography.

This study was undertaken to evaluate the possible use of digital subtraction applied after selective coronary arteriography. An identical position of the objects with and without contrast medium is an absolute requirement for the application of subtraction techniques. Because coronary arteries are in continuous motion, the subtraction technique cannot be applied without certain precautions. In our study, only images from corresponding moments in the cardiac cycle before and after contrast injection were matched for subtraction, that is, the concept of apparent cardiac arrest. To prevent variations in cardiac contractions due to varying RR intervals, heart rate was controlled by regular right atrial stimulation. Moreover, the stimulation rate and cine frequency were in synchrony, which was effected by triggering both on the frequency of the electric main alternating current (50 cycles/s). In this way, each cardiac cycle contains exactly the same number of frames at corresponding moments. A combination of the application of the concept of apparent cardiac arrest with the subtraction technique in 12 patients resulted in good quality images. Furthermore, better visualization of capillary filling with contrast material was obtained than with conventional coronary arteriography.

Capillaries↗
PubMed1984

Nonrandom ventricular rhythm in horses with atrial fibrillation and its significance for patients.

RR interval sequences during spontaneous atrial fibrillation in eight horses were analyzed as in previous studies in patients and dogs using histograms and serial auto-correlograms. In patients and dogs with spontaneous atrial fibrillation, ventricular rhythms were always random. In the horses, the histograms were skewed with median RR intervals of approximately 1,000 ms. A striking finding in these animals was the presence of long RR intervals up to 5,000 ms in duration. The shortest RR intervals lasted 400 to 600 ms. In contrast to findings in dogs and patients, the serial autocorrelograms showed periodicity that was reenforced by digitalis (n = 3), but eliminated by quinidine (n = 2) and atropine (n = 2). Quinidine and atropine eliminated the longer RR intervals, whereas digitalis increased the number of long RR intervals. In one horse, it was possible to measure intraarterial pressure, and large fluctuations in pressure were observed as the RR intervals varied from over 3,000 to less than 500 ms. It is postulated that these changes in blood pressure are associated with baroreceptor responses that may alter the electrophysiologic behavior of the atria and atrioventricular node. These changes cause the nonrandom patterns of ventricular rhythm in the horse. Because such very long RR intervals do not occur in human beings or dogs during atrial fibrillation, the random ventricular rhythm in these groups is maintained even during digitalis treatment.

Animals↗
PubMed1984

Baroreflex modulation of ventricular rhythm in atrial fibrillation.

The influence of bilateral carotid sinus nerve stimulation was studied in a patient with atrial fibrillation. Stimulation resulted after approximately 1.5 s in abrupt prolongation of the minimum, median and maximum RR-interval, and in greater RR-interval dispersion. Virtually no change was observed in the random character of the ventricular rhythm. The absence of demonstrable baroreflex modulation of the ventricular rhythm in atrial fibrillation is probably due to the relatively long latency of the reflex effect on atrioventricular conduction in relation to the duration of the RR-intervals.

Atrial Fibrillation↗
PubMed1984

How to keep the doctor away.

The current emphasis of Health Ministries in Western Europe on primary health care and individual responsibility for health life styles has been traced to a Canadian report entitled: "A new perspective on the health of Canadians" which appeared in 1974. The contents of this report are critically analyzed and show to be founded on misinterpretations of epidemiological data and on misunderstandings of the value of the scientific approach. It is the purpose of this article to expose the irrational nature of the Canadian report so as to prevent the further implementation of its recommendations.

Canada↗
PubMed1983

Contribution of the risk factor concept to patient care in coronary heart disease.

This article deals with the question of whether or not the risk factor concept, a principal aspect of preventive cardiology, has contributed to patient care in coronary heart disease. The risk factors considered are plasma cholesterol, high blood pressure, smoking, diabetes and marked obesity. With the exception of plasma cholesterol and diabetes, all of these factors enhance myocardial oxygen consumption and thus, in the presence of coronary insufficiency, promote myocardial ischemia. Their modification is therefore good general medical practice, even if not related to coronary atherosclerosis. Diabetes needs adequate medical treatment in patients both with and without coronary atherosclerosis. Because of the occasional occurrence of spontaneous regression of coronary atherosclerosis and the morphologic and functional complexity of coronary artery pathology, it has never been and probably never will be demonstrated that lowering plasma cholesterol levels by diet or other means will cause regression of coronary atherosclerosis. It follows that modification or treatment of risk factors is implemented for good medical reasons but does not demonstrably or predictably affect coronary artery disease. It is concluded that the contribution of the risk factor concept to patient care in coronary heart disease has been, and still is, trivial.

Blood Pressure↗
PubMed1983

Protective effect of nifedipine in myocardial ischemia assessed by phosphorus-31 nuclear magnetic resonance.

Calcium antagonists may protect the myocardium against the consequences of ischemia. Phosphorus-31 nuclear magnetic resonance (31P NMR) was used to study the effect of nifedipine on intracellular acidosis and high energy phosphate depletion during global ischemia. Isolated rat hearts were paced (300 beats/min), perfused with a modified Tyrode solution for 30 min, made totally ischemic for 30 min (37 degrees C) and then reperfused for 30 min. When required, nifedipine (1 mg/l) was added to the perfusion fluid 10 min before ischemia. During ischemia intracellular pH fell from 7.11 +/- 0.03 (mean +/- S.E.M.) to 5.88 +/- 0.04 in the untreated hearts (n = 6), and from 7.11 +/- 0.03 to 5.95 +/- 0.02 in the treated hearts (n = 6). During the first 20 min of ischemia, intracellular pH was significantly higher in the treated than in the untreated hearts (P less than 0.001). Myocardial creatine phosphate (CP) content was depleted after 15 min of ischemia in the untreated hearts, and after 20 min of ischemia in the hearts treated with nifedipine. Myocardial adenosine triphosphate (ATP) content was depleted after 20 min of ischemia in the untreated hearts; ATP content in hearts that received nifedipine amounted to 23.5 +/- 6.2% of control after 30 min of ischemia. In contrast with the untreated hearts, the nifedipine-treated hearts showed a rapid recovery of CP content during reperfusion. The results indicate that nifedipine protects the myocardium against the metabolic consequences of ischemia and reperfusion.

Adenosine Triphosphate↗