Abstract

Objective: To assess the haemodynamic effect of simultaneously adjusting atrioventricular (AV) and interventricular (VV) delays.

Method: 35 different combinations of AV and VV delay were tested by using digital photoplethysmography (Finometer) with repeated alternations to measure relative change in systolic blood pressure (SBP_rel) in 15 patients with cardiac resynchronisation devices for heart failure.

Results: Changing AV delay had a larger effect than changing VV delay (range of SBP_rel 21 v 4.2 mm Hg, p < 0.001). Each had a curvilinear effect. The curve of response to AV delay fitted extremely closely to a parabola (average R²  =  0.99, average residual variance 0.8 mm Hg²). The response to VV delay was significantly less curved (quadratic coefficient 67 v 1194 mm Hg/s², p  =  0.003) and therefore, although the residual variance was equally small (0.8 mm Hg²), the R² value was 0.7. Reproducibility at two months was good, with the SD of the difference between two measurements of SBP_rel being 2.5 mm Hg for AV delay (2% of mean systolic blood pressure) and 1.5 mm Hg for VV delay (1% of mean systolic blood pressure).

Conclusions: Changing AV and VV delays results in a curvilinear acute blood pressure response. This shape fits very closely to a parabola, which may be valuable information in developing a streamlined clinical protocol. VV delay adjustment provides an additional, albeit smaller, haemodynamic benefit to AV optimisation.