Aims: In this study, we apply non-invasive blood pressure (BP) monitoring, by continuous finger photoplethysmography (Finometer), to detect directly haemodynamic responses during adjustment of the atrioventricular (AV) delay of cardiac resynchronization therapy (CRT), at different heart rates.
Methods and results: Twelve patients were studied with six re-attending for reproducibility assessment. At each AV delay, systolic BP relative to a reference AV delay of 120 ms (SBPrel) was calculated. We found that at higher heart rates, altering the AV delay had a more pronounced effect on BP (average range of SBPrel=17.4 mmHg) compared with resting rates (average range of SBPrel=6.5 mmHg), P<0.0001. Secondly, peak AV delay differed between patients (minimum 120 ms, maximum 200 ms). Thirdly, small changes in AV delay had significant BP effects: programming AV delay 40 ms below the peak AV delay reduced SBPrel by 4.9 mmHg (P<0.003); having it 40 ms above the peak decreased SBPrel by 4.4 mmHg (P<0.0005). Finally, the peak AV delay is highly reproducible both on the same day and at 3 months (Bland-Altman difference: 3+/-8 ms).
Conclusions: Continuous non-invasive arterial pressure monitoring demonstrates that even small changes in AV delay from its haemodynamic peak value have a significant effect on BP. This peak varies between individuals, is highly reproducible, and is more pronounced at higher heart rates than resting rates.