Accuracy of heart rate assessment in atrial fibrillation.

OBJECTIVE: To determine the most accurate technique to measure the heart rate during atrial fibrillation by use of three counting intervals, 15, 30, and 60 seconds, and two methods, apical and radial pulse measurement.

DESIGN: A quasi-experimental, repeated measures factorial design was used to determine absolute error (amount of error ignoring direction of error) between heart rates obtained from six randomly ordered pulse measurements taken of one man in chronic atrial fibrillation by the 94 nurses in the sample and the heart rate recorded by simultaneous electrocardiographic (ECG) and plethysmographic (pleth) recordings.

SUBJECTS: Nurses in four groups comprised the sample; registered nurses (N = 29), licensed practical nurses (N = 23), nursing students (N = 21), and registered nurses with advanced degrees who are clinical specialists and in faculty positions.

RESULTS: The heart rate of the man varied from 57 to 111 beats/min (mean 81 beats/min). The mean absolute error rates for the six measurements ranged from 8 beats/min to 20 beats/min, all considered to be important when a 10% error was used as the criteria for clinical significance. The apical method was significantly more accurate than the radial method regardless of whether the ECG or pleth standard was used (ECG--F1.90 = 72.91, p less than 0.0001; pleth--F1.144 = 4.68, p = 0.036). The 60-second counting interval was significantly more accurate regardless of the standard (ECG--F2.180 = 5.19, p = 0.006; pleth--F2.88 = 3.95, p = 0.02).

CONCLUSIONS: Atrial fibrillation occurs in 2% to 4% of people over 60 years of age and is one of the most difficult dysrhythmias to count. Accurate counts are important when making clinical decisions, yet measurement of heart rate in this study was quite inaccurate. The 60-second count and the apical method were the most accurate statistically, although differences in counting interval error rates were not clinically significant.