Arteriosclerosis of the aorta, of the coronary arteries, or of both, is practically always found in cases dying of various cardiac irregularities other than those the result of rheumatic cardiac lesions. It is not that arteriosclerosis causes the cardiac lesions (although the thickening of the walls of the coronary arteries does interfere mechanically with the nutrition of the heart muscle), but the arteriosclerosis is a part of the tissue reaction in the arteries to some set of causes affecting the whole body. It is true when one boils down the question to its last analysis, general arteriosclerosis may mechanically so interfere with the blood supply to tissues that the tissue is thrown out of function either in the reduction or even loss of function. So it may be that occasionally the arteriosclerosis in the arteries supplying the heart is really responsible for the cardiac irregularity. The past few years have been fruitful ones in increasing our knowledge of the various irregularities of the heart. We can do no more than sketch briefly some of them in relation to arteriosclerosis. The chief irregularities are (1) auricular flutter, (2) auricular fibrillation, (3) ventricular fibrillation, (4) auricular extrasystole, (5) ventricular extrasystole, (6) heart block, partial or complete. =Auricular Flutter= Auricular flutter is an abnormal rhythm characterized by very rapid, but rhythmic auricular contractions usually 250 to 300 per minute. The auricular contractions are so rapid that the ventricle can not respond, so that an electrocardiagram of a heart in such a state (Fig. 40) shows the ventricle beating regularly but at a much slower rate than the auricle. [Illustration: Fig. 40.--(After Hart.)] The majority of cases exhibiting this peculiar rhythm are over 40 years of age. In many cases sclerosis of the coronary arteries as a part of general arteriosclerosis has been found. Auricular flutter can be suspected when the pulse is regular or not particularly irregular and a fluttering, rapid pulsation is seen in the jugular vein on the right side. One can only be sure of the condition by making graphic records of the heart. Attacks usually come on suddenly and may disappear as suddenly, suggesting paroxysmal tachycardia. The patient feels a commotion in his chest, dyspnea, precordial distress, etc. The attack may last for weeks or months, in which case the patient may carry on his usual work but be conscious of palpitation in his chest. One may safely assume that the flutter is a sign of a failing myocardium and sooner or later the heart will pass to the graver stage of auricular fibrillation. =Auricular Fibrillation=