Heart rate variability in sick sinus syndrome: does it have a diagnostic role?

BACKGROUND: Hypothesis of our study was that the irregular rhythm of sick sinus syndrome (SSS) was characterized by an augmented HRV. Objective was to assess whether SSS patients had a typical HRV profile. METHODS: We screened all 1947 consecutive Holter ECGs performed in our Units of Vascular Medicine and Internal Medicine and Cardioangiology at the University of Palermo (Italy) from April 2010 to September 2014. Among these, we selected 30 patients with ECG criteria of SSS. They were compared to 30 patients without SSS matched for age, sex and comorbidities. RESULTS: The SSS group had a lower mean heart rate (HR) (P=0.003), and a longer mean NN max-min longer (P<0.0005) compared to control group. SSS group had higher mean pNN50 (P=0.043), mean RMSSD (P=0.006), mean SDNN (P=0.021), and mean SDNNi (P=0.005) as compared with control group. Moreover, HR ≤64.5 bpm, NN max-min>1355 msec, pNN50>16.08, RMSSD>50.2, SDNN>151.94, and SDNNi>71.1 showed a predictive value for diagnosis of SSS. The positivity of all 6 variables according to the aforementioned cut-offs ensured a positive predictive value of 100% and the negativity of all 6 variables had a negative predictive value of 94% for diagnosis of SSS. Among SSS patients, we did not observe any correlation between HR and HRV variables. CONCLUSIONS: SSS patients have a HRV profile characterized by: low HR, long NN max-min interval, and elevated pNN50, RMSSD, SDNN and SDNNi values with specific diagnostic cut-offs for diagnosis of SSS. Moreover, we found the absence of correlation between HR and all time-domain HRV variables in SSS patients.