a. delay in the conduction of the con- 

 tractile stimulus (increase of the 

 space ac or P. V.) 



6. partial block 



c. total block (dissociation of auriculo- 

 ventricular rhythm with persistence 

 of ventricular rhythm) 



3. Premature contractions: 



a. auricular extrasystoles 



b. ventricular extrasystoles 



c. nodal extrasystoles 



4. Auricular tachysystole (auricular flut- 

 ter) 



5. Paroxystic tachycardia (auricular, 

 ventricular and nodal) 



6. Complete arrhythmia (auricular fib- 

 rillation) 



7. Cardiac alternations 



These are the alterations of rhythm of 

 which we have well-studied demonstrative 

 examples. Some of them, of great frequence, 

 indicate the affection of the organ in a very 

 high percentage of the infected. This is true, 

 in the first place, for the extrasystoles which 

 are the most common of the changes of 

 rhythm and constitute the best clinical symp- 

 tom for the estimation of the endemic index 

 of the disease. And the most frequent of 

 the arrhythmias are those of conductibility, 

 which among the many clinical features of 

 trypanosomiasis represent that which is ex- 

 clusively and peculiarly due to that disease. 

 This is one of the great pathologic curiosi- 

 ties of the new disease entity, and in this 

 chapter we find abundant valuable material 

 for exemplifying and fundamenting the best 

 theories of heart block, and for interpreting 

 in the future, perhaps with greater certainty, 

 the points that have remained open to dis- 

 cussion in this group of arrhythmias. 



Other alterations of rhythm, associated 

 like the two first with lesions of the muscle, 

 are less common and we have only a few 

 cases of them; in spite of this they are of 

 value to characterize the sequence of the 

 pathologic process and to better funda- 

 ment the admitted pathogenesis. Among 

 these are auricular tachycardia (auricular 



flutter) and auricular fibrillation. Why are 

 they less common in this immense accumu- 

 lation of morbid statistics with the most 

 varied forms of arrhythmia? Why is the 

 auricular fibrillation especially less common 

 when in the opiniou of all the cardiopathol- 

 ogists it is the most frequent persistent irreg- 

 ularity of the human heart, represented 

 perhaps by fifty per cent, of the clinical 

 cases. We believe that in trypanosomiasis 

 both are manifestations of the most advanc- 

 ed inflammatory processes of the myocard- 

 ium and are the expression of a terminal 

 condition rapidly followed by death. And, 

 as a matter of fact, in the cases of this kind 

 that we have observed up to the present 

 time lethal termination occurred in a short 

 time in the advanced conditions referred to. 



Let us now see what are the appearan- 

 ces of the different forms of arrhythmia in 

 the disease. 



1. Total tachycardias and bradycardias 

 (sinus arrhythmia). -Iht number of clinical 

 cases of trypanosomiasis is high in which 

 the cardiac rhythm is permanentlv accele- 

 rated or retarded, without the interference 

 of accidental factors which could cause those 

 anomalies. Usually these tachycardias and 

 bradycardias are accompanied by extrasys- 

 toles of variable frequency; however, cases 

 exist and are not rare in which protracted 

 examinations do not show the presence of 

 extrasystolic contractions, which are surely 

 widely separated and even absent during 

 long periods so that it is difficult to detect 

 them. In this way the acceleration or slow- 

 ing of the pulse with a regular succession 

 of the pulsations predominates among the 

 cardiac symptoms. 



It must be emphasized that in such 

 cases the auricles and ventricles pulsate at 

 the same rate so that there is not here a 

 sino-auriculo-ventricular dissociation. 



How is the pathogenesis of these arrhy- 

 thmias to be interpreted and how are their 

 relations with the disease to be determined? 

 Let us examine the clinical facts commenc- 

 ing with the tachycardias. 



