Analysis of sinus cycle variation: a new method for evaluation of suspected sinus node dysfunction.

Momentary sinus cycle variations in 30 patients with unequivocal sinus node disease (SND) were compared with those found in 18 healthy control subjects to assess their potential diagnostic value. The range of variation of sinus cycle length (SCL; standardized by dividing by mean SCL) and the maximal change in SCL between any two consecutive cycles (max delta SCL) were measured in short (about 1 minute) continuous ECG recordings from invasive electrophysiologic investigations. Age-stratified reference values from 1 minute surface ECG recordings obtained at rest during quiet breathing in about 70 healthy persons were applied. For diagnosing SND, an increased standardized variation range had a sensitivity of 63%, a specificity of 94%, and a predictive value of a positive test of 95%. The corresponding figures for an increased max delta SCL were 77%, 78%, and 85%, respectively. A combination of increased range of variation and increased max delta SCL was observed in 63% of the patients but not in any healthy subject, which gives a specificity and a predictive value of a positive test of 100% for this combination.