Clinical significance of second degree Wenckebach type sinoatrial block identified during Holter monitoring in patients with symptoms suggestive of arrhythmia.

Aims To determine the clinical significance of the sinoatrial block II square of the Wenckebach type (block W) identified during Holter monitoring. Methods and results The study included 300 patients (mean age 54 +/- 17 years; 130 women) with symptoms suggestive of arrhythmia who underwent Holter monitoring. Block W was identified by a dedicated computer program and subsequently confirmed by a cardiologist. Block W was diagnosed in 88 patients (29%). It occurred only during sleep in 37 (12%) patients and during both daytime activity and sleep in 51 (17%) patients. Block W only during sleep happened predominately in young patients aged between 20 and 30 years, whereas episodes that occurred during both daytime and sleep were found mainly in patients between 60 and 70 years of age. Prospective observation time averaged 41 +/- 11 months, and the time to the diagnosis of sinus node disease was 26 +/- 10 months. Cox multivariate analyses showed that block W during both daytime and sleep is an independent predictor for the future diagnosis of sinus node disease [hazard ratio-13.6 (5.2-35.5); P < 0.0001]. Age-specific analyses confined this effect to the patients >= 50 years of age. The results also suggest that in patients >= 50 years of age block W during both daytime and sleep maybe related to a significant improvement in survival [hazard ratio-0.03 (0.007-0.16); P < 0.0001]. Conclusion Block W during daytime activity in patients with symptoms suggestive of arrhythmia indicates an increased likelihood of the future diagnosis of sinus node disease.