Disturbances of the Heart | Page 5

not now sufficient to state that the heart is acting irregularly, or that the pulse is irregular; the endeavor should be to determine whit causes the irregularity, and what kind of irregularity is present.
CLINICAL INTERPRETATION OF PULSE TRACINGS
A moment may be spent on clinical interpretation of pulse tracings. It has recently been shown that the permanently irregular pulse is due to fibrillary contraction, or really auricular fibrillation--in other words, irregular stimuli proceeding from the auricle--and that such an irregular pulse is not due to disturbance at the auriculoventricular node, as believed a short time ago. These little irregular stimuli proceeding from the auricle reach the auriculoventricular node and are transmitted to the ventricle as rapidly as the ventricle is able to react. Such rapid stimuli may soon cause death; or, if for any reason, medicinal or otherwise, the ventricle becomes indifferent to these stimuli, it may not take note of more than a certain portion of the stimuli. It then acts slowly enough to allow prolongation of life, and even considerable activity. If such a heart becomes more rapid from such stimuli, 110 or more, for any length of time, the condition becomes very serious. Digitalis in such a condition is, of course, of supreme value on account of its ability to slow the heart. Such irregularity perhaps most frequently occurs with valvular disease, especially mitral stenosis and in the muscular degenerations of senility, as fibrosis.
Atropin has been used to differentiate functional heart block from that produced by a lesion. Hart [Footnote: Hart: Am. Jour. Med. Sc., 1915, cxlix, 62.] has used atropin in three different types of heart block. In the first the heart block is induced by digitalis. This was entirely removed by atropin. In the second type, where there was normal auricular activity, but where the ventricular contractions were decreased, atropin affected an increase in the number of ventricular contractions, but did not completely remove the heart block. He adopted atropin where the heart block was associated with auricular fibrillation. The number of ventricular contractions was increased, but not enough to indicate the complete removal of the heart block.
Lewis [Footnote: Lewis: Brit. Med. Jour., 1909, ii, 1528.] believes that 50 percent of cardiac arrhythmia originates in muscle disturbance or incoordination in the auricle. These stimuli are irregular in intensity, and the contractions caused are irregular in degree. If the wave lengths of the pulse tracing show no regularity- -if, in fact, hardly two adjacent wave lengths are alike--the disturbance is auricular fibrillation. Injury to the auricle, or pressure for any reason on the auricle, may so disturb the transmission of stimuli and contractions that the contractions of the ventricle are very much fewer than the stimuli proceeding from the auricle. In other words, a form of heart block may occur. Various stimuli coming through the pneumogastric nerves, either from above or from the peripheral endings in the stomach or intestines, may inhibit or slow the ventricular contractions. It seems to have been again shown, as was earlier understood, that there are inhibitory and accelerator ganglia in the heart itself, each subject to various kinds of stimulation and various kinds of depression.
Both auricular fibrillation and auricular flutter are best shown by the polygraph and the electrocardiograph. The former is more exact as to details. Auricular flutter, which has also been called auricular tachysystole, is more common that is supposed. It consists of rapid coordinate auricular contractions, varying from 200 to 300 per minute. Fulton [Footnote: Fulton, F. T.: "Auricular Flutter," with a Report of Two Cases, Arch. Int. Med., October, 1913, p. 475.] finds in this condition that the initial stimulus arises in some part of the auricular musculature other than the sinus node. It is different from paroxysmal tachycardia, in which the heart rate rarely exceeds 180 per minute. In auricular flutter there is always present a certain amount of heart block, not all the stimuli reaching the ventricle. There may be a ratio of auricular contractions to ventricular contractions, according to Fulton, of 2:1, 3:1, 4:1 and 5:1, the 2:1 ratio being most common.
Of course it is generally understood that children have a higher pulse rate than adults; that women normally have a higher pulse rate than men at the same age; that strenuous muscular exercise, frequently repeated, without cardiac tire while causing the pulse to be rapid at the time, slows the pulse during the interim of such exercise and may gradually cause a more or less permanent slow pulse. It should be remembered that athletes have slow pulse, and the severity of their condition must not be interpreted by the rate of the pulse. Even with high fever the pulse of an athlete may be slow.
Not enough investigations have been made of the rate of the pulse during sleep under various conditions. Klewitz [Footnote: