. Clinical disorders of the heart beat : a handbook for practitioners and students . f the normal rhythm, then, while it is active, the newcentre dominates the movements of the whole heart. Suchare the paroxysms which we are about to study ; they consistof sudden accelerations of heart rate in response to theawakening of new and pathological impulses. The paroxysms * In so defining it I have purposely excluded all accelerations of normalor sinus rhythm, for these are dependent upon altered innervation. I havealso excluded two forms of tachycardia, which are closely related to thatdescribed in


. Clinical disorders of the heart beat : a handbook for practitioners and students . f the normal rhythm, then, while it is active, the newcentre dominates the movements of the whole heart. Suchare the paroxysms which we are about to study ; they consistof sudden accelerations of heart rate in response to theawakening of new and pathological impulses. The paroxysms * In so defining it I have purposely excluded all accelerations of normalor sinus rhythm, for these are dependent upon altered innervation. I havealso excluded two forms of tachycardia, which are closely related to thatdescribed in the present chapter ; one, which is regular, but in which theauricular rate exceeds 200 per minute (see Chapter VI) ; the other, which isirregular (see Chapter VII). 56 Chapter V. may be regarded both clinically and pathologically as formedessentially of a regular series of premature beats. The newimpulses are elaborated in a single focus, whence the regularityof the series, and this focus lies, usually or always, at a pointwhich is removed from the pacemaker.* Fig. 34 opens with. ■x. v Fig. 34. A diagrammatic representation of a short paroxysm of prematureauricular beats ; a paroxysm of tachycardia. The abnormal auricular beatsare broken in their centres. Each yields a ventricular response. The firstabnormal beat occupies the same position in relation to preceding eventsas does that of Fig. 23. The short paroxysm ends in a pause y. y islonger than x. three normal heart beats, and the fourth auricular contraction(p) is premature. Up to this point the diagram is identicalwith that shown in Fig. 23f ; it differs from the earlier picturein the repetition of the abnormal contraction, five such beatsfollowing each other in rapid and regular succession. In eachinstance the ventricle responds. The paroxysm terminates,and its end is marked by a pause (y) which is longer than thepause (x) intervening between the beats of the normalrhythm J ; its length is generally that of the pause w


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