A higher pacing rate more effectively reduces central blood pressure in patients with sick sinus syndrome and hypertension

Central blood pressure (BP) and arterial stiffness are independent predictors of cardiovascular risk. Clinically, peripheral BP is commonly measured, yet, it may exhibit inverse changes relative to central BP in response to alterations in heart rate (HR). In patients with sick sinus syndrome (SSS), pacemakers are used to alleviate symptoms of bradycardia, however, an optimal pacemaker base rate (PBR) strategy remains unclear. Of note, no studies have explored the long-term effects of different PBR strategies on central haemodynamic parameters.

To evaluate the effect of three different PBR strategies on central BP parameters via pulse wave analysis (PWA) and pulse wave velocity (PWV) in a randomised single-centre cross-over study.

Patients with hypertension and a dual-chamber permanent cardiac pacemaker implanted due to SSS with preserved atrioventricular conduction (atrial pacing >95% and ventricular pacing <1%) were included in the study. Following data collection and randomization, patients had their PBR set to either 55 or 75 bpm for two months. Then, after a two-week wash-out period with patients' pre-study PBR, a second two-month period with alternate settings (those initially at 55 bpm were adjusted to 75 bpm, and vice versa) followed. A non-invasive oscillometric cuff-based device (Sphygmocor XCEL, AtCor Medical) was used for PWA to derive central aortic pressures and applanation tonometry to measure arterial stiffness (PWV) prior to randomisation, after the two-month study period, at the end of the wash-out period, and upon conclusion of the study. Measurements taken at baseline with a PBR of 65 bpm were used to form the mid HR group, whilst measurements taken at 55 and 75 bpm were used for low and high HR groups, respectively.

Twenty-two patients with a mean age of 75 (±4) years, a BMI of 30 (±5) kg/m² who were predominantly female (73%) were included in the study.

Table 1 describes haemodynamic measurements in study groups. Briefly, there were no statistically significant differences in peripheral systolic BPs (Figure 1A) between study groups (p=0.15). Central systolic BPs (Figure 1B) decreased significantly with increasing pacemaker base rates (p=0.04). Central pulse pressure (Figure 1C) also decreased significantly with increasing HRs (p<0.01). No significant inter-group differences were seen when comparing arterial stiffness (PWV, Figure 1D, p=0.08). Lastly, in a linear regression analysis, baseline PWV was not associated with the degree of changes seen in central BP or PP (p=0.84 and p=0.25, respectively).

In older SSS patients with hypertension, opting for a higher anti-bradycardia PBR can enhance central BP control without increasing arterial stiffness. As central BP is independently associated with cardiovascular risk, future studies exploring effects of different PBR strategies on cardiovascular events and mortality are warranted.Figure 1  Table 1