tAkOXVSMAL IRREGULARITV OF THE HEART ^ 



rapid than the pulse taken by the finger which, as has been stated, was 

 given as about fifty a minute during the irregular periods. 



Even when these small beats are taken into account, the rhythm of 

 the heart is very irregular ; for example, during a succession of rapid 

 contractions in Fig. 3, the interval between successive pulses varies from 

 0*25 sec. to 0'4i sec. There exists no such "regular irregularity" as has 

 been described under the terms Pulsus bigeminus or trigeminus. In 

 these one normal pulsation is followed regularly by one or two move- 

 ments ot smaller dimensions, but in our tracings no such sequence is to 

 be made out. 



Even more striking than the irregularity in the pulse rhythm in this 

 case is the marked variation in the strength of the beats. This variation 

 in strength is of course a very common phenomenon in irregularity of 

 the heart. In the numerous tracings published of late years by Wencke- 

 bach, Mackenzie, Cushny and others, this variation in strength is 

 universally noted. But in most of these the strength of the beat varies 

 directly with the length of the preceding interval ; the ventricle accumu- 

 lates more energy during a long interval, and, at the same time, receives 

 more blood from the auricle, and these two factors together cause a very 

 powerful contraction and a very large output of blood. In this case, 

 however, the size of the pulse bears no relation to the length of the pre- 

 ceding interval. It is true that when there has been a great fall in the 

 pressure from the absence of or the inefficiency of the preceding beat, the 

 next contraction is often very large, but this is obviously not the 

 determining factor in most instances, for a strong contraction is often 

 preceded by a shorter interval than a smaller one, and, in other cases, 

 two intervals of equal length are followed by pulsations of very different 

 height. The variations in the size of the pulse must therefore be due not 

 to different degrees of recuperation in the contracting power of the 

 ventricle, but rather to variations in the amount of blood which it 

 receives during its diastole from the auricle. The amount of blood 

 entering the ventricle may be altered by a variety of causes. One 

 condition which occasionally causes pulses of different sizes is where the 

 ventricle and auricle are beating at different rates. For example, if the 

 auricle beats three times to the ventricle's twice, one of the auricular 

 beats discharges no blood into the ventricle, because the auricle contracts 

 against the contracted ventricle. The next pulse is correspondingly 



(lOl) 



