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100 Pressure vs flow as a guide for pacemaker optimisation? The acute haemodynamic effects of changes to atrioventricular delay
  1. C H Manisty,
  2. B Unsworth,
  3. R Baruah,
  4. P Pabari,
  5. Z I Whinnett,
  6. J Mayet,
  7. D P Francis
  1. Imperial College, St. Marys Hospital, London, UK

Abstract

Background Non-invasive blood pressure monitoring by continuous finger photoplethysmography (Finometer) may have value in pacemaker optimisation. However, the immediate increment in blood pressure seems to diminish somewhat in the initial minute: it is unclear whether this is due to an (undesirable) fall in stroke volume or a (desirable) compensatory reduction in peripheral resistance.

Methods and Results We studied this question by measuring beat-by-beat stroke volume (flow) using Doppler echocardiography, and blood pressure using continuous finger photoplethysmography, during and after atrioventricular delay adjustment from 40 to 120 ms in 19 subjects with cardiac pacemakers. Quintuplicate experimental runs were performed. Blood pressure and stroke volume (flow) both increased immediately (p<0.00001 within one heartbeat). The immediate pressure increment correlated strongly with the immediate flow increment (r=0.74, p=0.0001). Pressure showed a partial decline a few seconds later (average rate 0.65 mm Hg/beat, r=–0.98, p<0.0001), in contrast, flow did not decline (p=NS), Abstract 100 figure 1. Signal-to-noise ratio was significantly better for pressure than flow (6.3±3.6 vs 2.1±1.4, p<0.0001), Abstract 100 figure 2.

Conclusions Improving atrioventricular delay immediately increases blood pressure; however this effect decays slightly over the subsequent minute. This is due to compensatory vasodilatation rather than a reduction in cardiac function. Pressure changes are simpler to measure and easier to distinguish from random variation than Doppler measurements of flow, but are best measured immediately, before the vascular compensation.

  • Pacemaker optimisation
  • pressure
  • flow

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