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 (SBPrel) in 15 patients with cardiac resynchronisation devices for heart failure.
Results: Changing AV delay had a larger effect than changing VV delay (range of SBPrel 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 SBPrel 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.
- AV, atrioventricular
- CARE-HF, Cardiac Resynchronization-Heart Failure
- COMPANION, Comparison of Medical Therapy, Pacing and Defibrillation in Chronic Heart Failure
- NYHA, New York Heart Association
- SBP, systolic blood pressure
- SBPrel, relative change in systolic blood pressure
- VV, interventricular
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↵* Also The Royal Brompton Hospital, London, UK
Published Online First 18 May 2006
Competing interests: We acknowledge support from the British Heart Foundation, Medtronic and the Coronary Flow Trust. Dr Whinnett (FS/05/068), Dr Davies (FS/05/006) and Dr Francis (FS/04/079) are British Heart Foundation fellows. Our institution has filed a patent involving some of the techniques described in this paper.