Clinical disorders of the heart beat : a handbook for practitioners and students / by Thomas Lewis.

  • Thomas Lewis
Date:
1920
Catalogue details

Licence: In copyright

Credit: Clinical disorders of the heart beat : a handbook for practitioners and students / by Thomas Lewis. Source: Wellcome Collection.

    63/148 (page 47)
    action which often follows exercise, they are frequent in the predisposed. As we shall subsequently see, this knowledge may often be used advantageously to induce premature beats in patients predisposed to them. Suspension of respiration for a period compatible with comfort often suffices. The pathological beats are in evidence either in the apnoeic stage •or shortly after the resumption of respiration. Posture is often a potent factor. Patients who exhibit numerous premature contractions while standing may soon lose them in recumbency, and this happens despite a slight decrease of heart rate in the last position. In other patients, pressure upon the abdomen may abolish them. Observations go to show that extrasystoles are not caused by nervous impulses playing upon a healthy organ ; but it seems to be true that, if the heart manifests extra¬ systoles from time to time, nervous impulses, especially those ■of sympathetic origin, may exaggerate the tendency. The recognition of premature contractions. The work accomplished by premature beats is small, because the periods of rest that precede them are short. They may or may not raise the aortic valves. Accompanying the premature beat, a feeble pulsation or a prolonged pause is noted in the arterial pause ; auscultation reveals early first and second sounds when the aortic valves are forced, but only an isolated and premature first sound if the ven¬ tricular pressure fails to top the arterial. The consequent grouping of sounds in threes and fours is comprehended when the nature and degree of the corresponding arrhythmia are discerned. The commonest arrangements of pulsations and sounds are described in the following paragraphs, and are illustrated by the accompanying diagram and tracings.