CLINICAL SYNDBOMES 325 



lieves "the hyperthyroid heart can be distinguished from the nervous 

 cardiac affections by the fact that the high pulse rate lasts throughout 

 the whole day and night and is not due to reflex action alone." 



The rapid heart action is caused by a stimulation of the accelerator 

 nerve of the heart, coming from the sympathetic nerve, by the action 

 of the thyroid intoxication; the inhibitory fibers of the vagus may be 

 affected but to a lesser extent ; hence it is more marked in the sympathi- 

 cotonic and less marked in the vagotonic cases. The mechanical origin of 

 the tachycardia is no longer entertained. 



Investigators assert, according to Bram (c), that the stimulation of the 

 vagus, causing universal peripheral vascular dilatation, 1 occasions in- 

 creased thyroid vascularity and increased formation of thyroid substance ; 

 the latter thrown into the blood stimulates the vagus : thus a vicious cycle 

 is formed. 



Palpitation. This subjective sensation of the heart's action is some- 

 times very distressing. As is well known to students of cardiac disease, 

 it is largely independent of the pulse rate, being often less marked in 

 cases with marked tachycardia than in those with slight. Sometimes there 

 is an associated feeling of suffocation or swelling in the throat. It is 

 always a suggestive symptom of hyperthyroidism when it occurs in a 

 person without other discoverable cause; indeed, Mueller states that 

 "nearly a third of all cases of so-called nervous palpitation belong to this 

 disease." This is especially true of the incomplete hyperthyroidism when 

 only the cardiac symptoms are .very prominent. In the hyperthyroid 

 heart as well as in fully developed exophthalmic goiter, the increased pulsa- 

 tion is especially felt over the region of the right ventricle and at autopsy 

 there is present a marked hypertrophy and dilatation, especially of the 

 right ventricle. 



The Heart. The heart is often moderately dilated and may be hyper- 

 trophied from a prolonged thyroid intoxication. While the left ventricle 

 is most affected, the right, according to Kraus, is also sometimes enlarged. 

 In severe cases, late in the disease myocardial insufficiency may de- 

 velop and lead to a fatal termination. Auricular fibrillation is a common 

 accompaniment of this myocardial degeneration. Anginoid precordial 

 pain may occur, according to Marie and Bram, and be severe enough to 

 resemble true angina pectoris, particularly when associated with slight 

 unconsciousness. 



Upon physical examination the precordium is often prominent, espe- 

 cially when the disease has begun in early life. The whole anterior part of 

 the chest may heave from the forcible action of the heart and the move- 

 ment may be perceptible even through the clothing. The head and body 

 may be shaken with each heart beat (Musset's sign) as in true aortic 



1 The assumption that vagus stimulation causes "universal vascular dilatation" 

 rests upon very dubious physiological grounds. R. G. H. 



