Background In atrial fibrillation (AF), VV optimisation of biventricular pacemakers can be examined in isolation. We used this approach to evaluate the internal validity of three VV optimisation methods.
Methods 20 patients (16 men, age 75±7) in AF were optimised, at two paced heart rates, by LVOT VTI (flow), non-invasive arterial pressure, and ECG (minimising QRS duration). Each optimisation method was evaluated by: singularity (unique peak of function), reproducibility of optimum, and biological plausibility of the distribution of optima.
Results The reproducibility (SD of the difference, SDD) of the optimal VV delay is 10 ms for pressure, vs 8 ms (p=NS) for QRS and 34 ms (p<0.01) for flow. Singularity of optimum is 85% for pressure, 63% for ECG and 45% for flow (χ2=10.9, p<0.005). The distribution of pressure optima is biologically plausible, with 80% LV pre-excited (p=0.007). The distributions of ECG (55% LV pre-excitation) and flow (45% LV pre-excitation) optima are no better than random (p=NS). The pressure-derived optimal VV delay is unaffected by the paced rate: SDD between slow and fast heart rate is 9 ms, no different from the reproducibility SDD at both heart rates, (p=NS).
Conclusions Using non-invasive arterial pressure, VV delay optimisation is achievable with good precision, satisfying all 3 criteria of internal validity, and the optimum is unaffected by heart rate. Neither QRS minimisation nor LVOT VTI satisfy all validity criteria and are therefore weaker candidate modalities for VV optimisation.
- Biventricular pacemaker
- internal validity