When is an optimization not an optimization? Evaluation of clinical implications of information content (signal-to-noise ratio) in optimization of cardiac resynchronization therapy, and how to measure and maximize it

Punam A. Pabari*, Keith Willson, Berthold Stegemann, Irene E. van Geldorp, Andreas Kyriacou, Michela Moraldo, Jamil Mayet, Alun D. Hughes, Darrel P. Francis

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

37 Citations (Web of Science)


Impact of variability in the measured parameter is rarely considered in designing clinical protocols for optimization of atrioventricular (AV) or interventricular (VV) delay of cardiac resynchronization therapy (CRT). In this article, we approach this question quantitatively using mathematical simulation in which the true optimum is known and examine practical implications using some real measurements. We calculated the performance of any optimization process that selects the pacing setting which maximizes an underlying signal, such as flow or pressure, in the presence of overlying random variability (noise). If signal and noise are of equal size, for a 5-choice optimization (60, 100, 140, 180, 220 ms), replicate AV delay optima are rarely identical but rather scattered with a standard deviation of 45 ms. This scatter was overwhelmingly determined (rho = -0.975, P <0.001) by Information Content, Signal/Signal+Noise, an expression of signal-to-noise ratio. Averaging multiple replicates improves information content. In real clinical data, at resting, heart rate information content is often only 0.2-0.3; elevated pacing rates can raise information content above 0.5. Low information content (e.
Original languageEnglish
Pages (from-to)277-290
JournalHeart Failure Reviews
Issue number3
Publication statusPublished - May 2011


  • Cardiac resynchronization therapy
  • Biventricular pacemaker
  • Optimization
  • Echocardiography
  • Velocity-time integral
  • Blood pressure

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