Optimizing external cardiac-assist compressions in patients with atrial fibrillation by anticipating the next beat

Multiple empirical formulas predicting the next RR interval in centiseconds (CS) were tested on EKG strips obtained from 30 patients with atrial fibrillation (AF). The benefits of the formulas were related to the percentages of leg pulsations determined by computer to be effective when the formulas were utilized to initiate compressions in an external end-diastolic pneumatic compression boot. The use of averages of variable numbers of preceding RRs was found to be increasingly beneficial as the number of preceding beats averaged was increased from 1,2,3,5 to the 10th preceding beat with little additional benefit beyond the 10th beat. The following empiric method was the most effective (P < 0.001): the next RR equals the average of the last 10 RRs minus 4 cs if the last RR is within 10% of the average; if the last RR is < 90% of the average, the next RR is 110% of the average minus 4 cs; and if the last RR is greater than 110% of the average, the next beat is 88% of the average minus 4 cs. It was concluded that a computer-controlled monitor may improve the efficiency of external end- diastolic cardiac arrest in patients with AF.