The heart rate with exercise in patients with auricular fibrillation.

In a previous article (Knox, 1940) an accurate method of recording the changes in heart rate during exercise was described, and results were given for normal subjects performing a brief light step-test. This technique has now been applied to patients with auricular fibrillation. The present series consists of twenty-two tracings from thirteen ambulant patients with fibrillation. The standard exercise was five ascents of two steps each ten inches high, the rate of stepping being 96 a minute. The exercise began and ended in the sitting posture and its total duration was about twenty seconds. The heart beats were electrically recorded on a smoked drum throughout exercise and were counted in five-second periods to the nearest tenth of a beat. The clinical condition of the patients with fibrilla-tion was classified as good, fairly good, fair, or poor on the basis of the functional capacity classification ofthe American Heart Association (1926). This was called the patients' " Exercise Tolerance Group." In addition, the patients were also grouped according to whether they were receiving digitalis or not. Full details of the method of calculating the various heart rate indices were given in the previous article and only a summary need be given here. The initial rate is the heart rate averaged over the ten seconds immediately preceding exercise. The maximum rate is the highest rate observed during exercise averaged over a five-second period. The acceleration of the heart rate is calculated by subtracting the rate in the five seconds immediately preceding exercise from the maximum rate, and dividing the result by the time taken to reach the maximum rate. The post-exercise rate is the heart rate averaged over a thirty-second period beginning five seconds after exercise ends. RESULTS The heart-rate indices. The figures for the various heart-rate indices of the fibrillation cases in the different " Exercise Tolerance Groups " are shown in Table I. For comparison, the mean results for 100 normal subjects (75 men and 25 women) are also included in this table. It can be seen that there was no correlation between any of these heart rate indices and the patient's clinical condition. This was not unexpected, as the number of patients in each group is very small and in addition the completely irregular ventricular rhythm present in fibrillation produces sudden arbitrary changes in heart rate in the successive five-second intervals counted. Certain general characteristics, however, can be seen in …