1904-5.] Dr W. T. Ritchie on Complete Heart-block. 
1085 
Complete Heart-block, with Dissociation of the Action 
of the Auricles and Ventricles. By W. T. Ritchie, 
M.D., F.R.C.P.E. Communicated by Dr George A. Gibson. 
(Read July 3, 1905.) 
The ventricular rhythm differs from the auricular, firstly, on the 
occurrence of a ventricular extra-systole, and, secondly, in cases 
where there is allorhythmia due to depression of conductivity of the 
heart muscle. When conductivity is depressed, the contraction 
stimulus at regular or irregular intervals may he blocked at the 
auriculo-ventricular muscle bridge ; so that whereas some stimuli 
induce both auricular and ventricular systole, others induce auricular 
systole alone, the ventricular systole being missed. That con- 
dition, incomplete heart-block, is of not infrequent occurrence in 
the human heart, and has been graphically recorded by Mackenzie 
(1), Finkelnburg (2), and other writers. 
The block at the auriculo-ventricular bridge may, however, be 
complete, as after the application of a Stannius’s ligature around 
the auriculo-ventricular junction of the frog’s heart. Bering (3) 
has conclusively proved the contention of His (4) and Max 
Humblet (5), namely, that complete heart-block occurs after section 
of the auriculo-ventricular muscle bundle (or bridge) of His. The 
auricles then continue to contract rhythmically, whilst, the con- 
duction of contraction stimuli being completely blocked by the 
division of that bridge, the ventricles manifest their inherent 
power of automatically generating contraction stimuli, and beat 
less frequently than the auricles and with an independent rhythm. 
Persistent bradycardia in man, with a pulse rate of 30 to 36 
beats per minute, is probably in every instance the result of a 
lesion at the auriculo-ventricular bridge. In the cases of brady- 
cardia recorded by Adams (6), Stokes (7), and many subsequent 
writers, there is, however, no conclusive evidence of complete 
dissociation of the ventricular rhythm from the auricular. Complete 
heart-block in man has been demonstrated by few observers. 
