Heart rate variability parameters in patients with systemic sclerosis: association with disease characteristics and therapy

Aim. To study heart rate variability (HRV) parameters in patients with systemic sclerosis (SSc) and their relationship with disease characteristics and therapy. Material and methods. A study included 48 SSc patients and 43 healthy individuals. HRV was assessed using electrocardiography (ECG) data recorded at rest during quiet breathing (a 5-minute ECG fragment) and ambulatory 24-hour ECG monitoring. Results. According to 5-minute ECG recordings, in patients with SSc, an increase in heart rate (p=0.023) and changes in HRV frequency parameters were detected compared with the control group: a decrease in HFlog and HFn.u. (p=0.046 and p=0.027, respectively), an increase in LF (p=0.018) and the ratio LF/HF (p=0.016). According to ambulatory ECG monitoring data, patients with SSc have increased heart rate, decreased SDNNidx and pNN50 during the entire recording period and during the daytime, and a statistically significant decrease in most HRV parameters (meanNN, SDNN, SDNNidx, rMSSD and pNN50) at night. According to 5-minute ECG recordings, a relationship was found between heart rate (meanRR and meanHR) and the duration of Raynaud's syndrome (R=0.31, p=0.034; R=-0.30, p=0.043). In the presence of a history of heart damage in patients with SSc, according to ambulatory monitoring data, lower SDNNidxall, SDNNidxday, SDNNidxnight, pNN50night were noted, according to 5-minute ECG recordings — lower values of total power, LFmc2, LFlog, SD2. In the presence of lung damage, there is a higher heart rate according to meanRR, meanHR and meanNNday (according to 5-minute and ambulatory ECG recordings). Correlation between C-reactive protein (CRP) level of and SD2/SD1 were revealed according to 5-minute ECG recordings (R=-0.419, p=0.015), DFAα1 (R=-0.419, p=0.015). Patients with SSc taking calcium channel blockers (CCB) had higher values of HRV time parameters according to ambulatory ECG monitoring (p<0.05). Conclusion. SSc patients exhibited reduced frequency-domain, time-domain, and nonlinear HRV parameters in both short-term and 24-hour ECG recordings. A potentially unfavorable relationship was identified between nonlinear HRV parameters and C-reactive protein (CRP) levels, as well as correlations of heart rate (HR) with Raynaud’s syndrome duration, and HRV with lung and heart involvement. CCB therapy was associated with improved circadian rhythm of HRV.