Heart-beat and pulse-wave / by C.S. Roy and J.G. Adami.

Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Heart-beat and pulse-wave / by C.S. Roy and J.G. Adami. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    If therefore we consider the flow through the auriculo-ven- tricular orifice, we may divide it into four periods: the first, during ventricular systole, in which it is quite arrested, and in which, therefore, the auricles act as reservoirs ; the second, that of rapid flow through the orifice resulting from the resilience of the ventricle (for any rise of pressure in the auricles, which may take place as a result of the accumulation of blood during the previous period, must be so slight that it may safely be ignored) ; the third stage is that during which, whatever the amount of blood available, there must be a slowing owing to diminished resilience of the heart-wall, the resilience diminishing with the ventricular expansion (if the amount of blood avail- able be below a certain limit, the resilience of the wall of the ventricle may still suffice to produce a negative pressure, as above explained); the fourth phase is one of increased rapidity of flow through the orifice, owing to the successive contraction of the veins and auricle. Let us consider for a moment how our conclusions upon this subject bear upon the murmurs which, when present, are charac- teristic of mitral stenosis. In this condition a continuous murmur extending from the second to the succeeding first sound is of infrequent occurrence, whereas a murmur following the second sound, or a presystolic murmur, that is, one preceding the first sound, is common enough; or there may be a combina- tion of both, a pause intervening. With regard, first of all, to the murmur following the second sound. This occurs at a time when through the narrowed orifice there is a rapid inflow into the ventricles as a result of the resilience of its walls at the be- ginning of diastole. The velocity of inflow, which is the import- ant factor in the causation of this murmur, will not be diminished to any extent as the result of a limited amount of blood being available to enter the ventricle, seeing that in mitral stenosis there is congestion of the pulmonary veins, and the supply of blood is correspondingly large; but it must diminish with the diminution in suction power of the ventricle which necessarily accompanies its expansion. This diminution in suction explains the pause which in certain cases intervenes between the murmur following the second sound and that which precedes the first. Whatever conditions, moreover, lead to dilatation of the left
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