Ons hart en de evolutie; vorm en functie van zoogdierharten vrijwel identiek

Charles Darwin werd 200 jaar geleden geboren en dit is een goede aanleiding om bij de evolutie van het zoogdierhart stil te staan. Alles wat leeft en bloeit op aarde is ontstaan en wordt toegeschreven aan het proces dat evolutie heet. De mens, een product van die evolutie, heeft alle kenmerken van een zoogdier. Wat is de samenhang tussen vorm en functie van het zoogdierhart in relatie tot de evolutie? Het blijkt dat alle morfologische en functionele eigenschappen van het hart van alle zoogdierrassen nagenoeg identiek zijn. De consequentie hiervan is dat kennelijk het zoogdierhart niet of nauwelijks betrokken is geweest bij de differentiatie van zoogdieren, van muis tot walvis en dus de mens incluis. Dat betekent dat het hart, al bij het ontstaan van het allereerste zoogdier dezelfde bouw en functie moet hebben gehad, als nu bij alle bestaande zoogdiersoorten worden aangetroffen. Dit leidt tot de o.i. onontkoombare conclusie dat het ‘oerzoogdier’, dus voordat de enorme differentiatie van zoogdieren door aanpassing aan klimaat of bodemgesteldheid heeft plaats gevonden, al een hart moet hebben gehad dat in alle opzichten uitstekend voldeed en tijdens die aanpassing niet of nauwelijks gewijzigd hoefde te worden

Archetype, adaptation and the mammalian heart

Forty years ago, we started our quest for 'The Holy Grail' of understanding ventricular rate control and rhythm in atrial fibrillation (AF). We therefore studied the morphology and function of a wide range of mammalian hearts. From mouse to whale, we found that all hearts show similar structural and functional characteristics. This suggests that the mammalian heart remained well conserved during evolution and in this aspect it differs from other organs and parts of the mammalian body. The archetype of the mammalian heart was apparently so successful that adaptation by natural selection (evolution) caused by varying habitat demands, as occurred in other organs and many other aspects of mammalian anatomy, bypassed the heart. The structure and function of the heart of placental mammals have thus been strikingly conserved throughout evolution. The changes in the mammahan heart that did take place were mostly adjustments (scaling), to compensate for variations in body size and shape. A remarkable scaling effect is, for instance, the difference in atrioventricular (AV) conduction time, which is vital for optimal cardiac function in all mammais, small and large. Scaling of AV conduction takes place in the AV node (AVN), but its substrate is unknown. This sheds new light on the vital role of the AVN in health and disease. The AVN is master and servant of the heart at the same time and is of salient importance for our understanding of supraventricular arrhythmias in humans, especially AF. In Information Technology a software infrastructure called 'enterprise service bus' (ESB) may provide understanding of the mammalian heart's conservation during evolution. The ESB is quite unspecific (and thus general) when compared with the specialised components it has to support. For instance, one of the functions of an ESB is the routing of messages between system nodes. This routing is independent and unaware of the content of the messages. The function of the heart is likewise independent and unaware of the routing of blood (oxygen) and of the specialised components of the mammalian body it has to support. Conclusions: Evolution seems to have bypassed the heart, which is in contrast to the sometimes similarly looking, but yet quite differently functioning of the other organs of the mammalian body

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 medica I 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 he art disease has been, and still is, trivial

Atrioventricular conduction versus heart size from mouse to whale

In normal sinus rhythm, the atrioventricular (AV) conduction system introduces an appropriate delay between atrial and ventricular excitation and contraction. This delay, the AV or PR interval, increases with the size of the animal and, thus,of the heart. This increase, however, is relatively small in comparison with the difference in the sizes of the body and the heart. For instance, the PR interval is only twice as long in mammals such as the elephant or the whale as it is in human beings. Comparison of the AV nodal electrophysiologic properties with the size of the heart in a number of mammalian species raises rather interesting questions regarding the functional properties of the AV conduction system

Sur l'action de l'acéthylcholine, de l'atropine et du potassium sur le coeur de la grenouille

Beaucoup d'expériences ont déjà été exécutées sur l'action stimulante de l'acétylcholine (ACH) sur le creur..

Contractility of isolated hearts from myxedematous rats

HYPOTHYROIDISM is often complicated by coronary sclerosis and cardiac failure. It is generally believed that the coronary sclerosis is mainly caused by the disturbed lipoid metabolism. The cardiac failure, however, is less well understood. Our findings demonstrate that current concepts about cardiac insufficiency in myxedematous patients are not likely to be true. Thyroid hormone is a specific factor which has a direct (or viaunknown intermediates) important influence on rate and contractility of heart-muscle

Prof. Dirk Durrer, godfather of Dutch cardiology : A personal note

Scene from grand opening of arboretum on UNL East Campu

Kun jij een aardappel maken?

Rede uitgesproken bij de aanvaarding van het ambt van gewoon Hoogleraar in de ziekten van hart en bloedvate

Comparative aspects of the dual role of the human atrioventricular node

As well as transmitting the impulse from the atria to the ventric1es the atrioventricular node has two other important functions namely: (a) synchronisation of atrial and ventricular contractions by a varying delay; and (b) protection of the ventricles from rapid atrial arrhythmias. The relative importance of these two functions appears to differ in large and small mammalian hearts. In small mammals synchronisation of atrial and ventricular contractions is the major function of the atrioventricular node, whereas protection from rapid atrial arrhythmias may be its most important function in large mammals. Atrioventricular conduction time in sinus rhythm is ten times longer in the whale (500 ms) than in the rat (50 ms). A whale heart, however, is about 100000 times heavier than a rat heart. During atrial fibrillation the ventricular rate in a dog heart is only three times faster than in a horse, whereas a horse heart may be 40 times as heavy as that of a dog. Hence there is a considerable discrepancy between the size of the mammalian heart and the functions of its atrioventricular node. Analysis of several anatomical and functional aspects of atrioventricular conduction systems in mammals of all sizes showed that the importance of the delaying role of the atrioventricular conduction system diminishes as the size of the mammal increases, whereas the protective role of the atrioventricular node probably increases. The function of the human atrioventricular node seems to be intermediate between that of the small and large mammals