Longevity decoded: Insights from power consumption analyses into device construction and their clinical implications

Figures

• 

  Figure 1. Effects of RV pacing parameters on Resonate X4 longevity. Plots produced with figures obtained from the online longevity calculator provided by Boston Scientific for the Resonate X4 G447 CRT‐D. The reciprocal of longevity is linearly related to the base rate (A) and percentage (B) of pacing, and the square of the output amplitude (C) and (D). The reciprocal of longevity appears to be related to the reciprocal of impedance (E) and pulse width (pw) (F) through an inverted negative exponential rise to a plateau, and the two factors affect each other's relationship. RV = right ventricular [Color figure can be viewed at http://wileyonlinelibrary.com]

• 

  Figure 2. Effects of the pw: impedance (with or without adjustment for internal resistance) ratio on Resonate X4 longevity. (A) and (B) For a fixed pacing amplitude, the pw: impedance ratio does not consistently predict the reciprocal of longevity. (C) Iso‐longevity curves suggest a correction term, an internal resistance, needs to be added to the load impedance to give an adjusted impedance. (D) and (E) The pw: adjusted impedance ratio consistently predicts the reciprocal of longevity. (F) The plot of the reciprocal of longevity against the total pacing power for the settings in the Viva Quad XT manual incorporating the estimated internal resistance and pacing capacitance is a straight line. The slope of the line is the reciprocal of the usable battery energy 1/W∘. The horizontal intercept is the negative value of the background power P 00. pw = pulse width [Color figure can be viewed at http://wileyonlinelibrary.com]

• 

  Figure 3. Effects of LV pacing amplitude, pulse width (pw), and impedance (with or without adjustment for internal resistance) on the longevity of the Quadra Assura MP CRT‐D. The parameters of pacing were altered from the default values of 2.5 V, 0.5 ms, and 500 Ω. (A) The plot of the reciprocal of longevity against LV amplitude comprises three rising steepening straight line segments separated by widening abrupt jumps. The line segments have a common vertical intercept and slopes proportional to the LV amplitude at their upper ends, which lie on a parabola. (B) The plot of the reciprocal of longevity against the square of LV amplitude comprises three rising flattening convex curve segments separated by widening abrupt jumps and whose upper ends lie on a straight line. (C) The reciprocal of longevity is linearly related to the LV pw. (D) The plots of the reciprocal of longevity against the reciprocal of LV impedance are a series of convex upward curves with curvature positively with the LV amplitude. (E) The plots of the reciprocal of longevity against the pw: adjusted LV impedance (with the addition of an estimated internal resistance) are still a series of convex upward curves, but have…

• 

  Figure 4. Plots of the reciprocal of longevity against pacing parameters or their derivatives for the Platinium 4LV SonR CRT‐D. β1 and β2 = regression coefficients; CRT‐D = cardiac resynchronization therapy defibrillator; LV = left ventricle; LVc = LV pacing capacitor peak voltage; LVp = LV pacing amplitude; P00: background power; pw = pulse width; RV = right ventricle; RVc = RV pacing capacitor peak voltage; RVp = RV pacing amplitude; W∘ = usable battery energy (see the main text and Appendix E for details) [Color figure can be viewed at http://wileyonlinelibrary.com]

• 

  Figure 5. Effects of shock therapy frequency on CRT‐D longevity. (A), (C), (E) The plot of the reciprocal of longevity 1/t∘ against shock frequency fs comprises straight lines. For Resonate X4 and Platinium 4LV SonR, the slope of the plot changes abruptly at fs = 4 and 2 spyr, respectively. (B) For Resonate X4, a higher fs shifts the plot of 1/1t∘t∘ against the square of RV amplitude upwards parallelly. The change Δ(1/t∘) is larger for Δfs=8−4 than for Δfs=4−0. (D) For Platinium 4LV SonR, a higher fs shifts the plot of 1/t∘ against LV pacing power upwards parallelly. The change Δ(1/t∘) is larger for Δfs=4−2 than for Δfs=2−0. (F) For Intica 7 HF‐T (QP), the plots of 1/t∘ against the total pacing power for different values of fs are roughly parallel. The line for fs=16 appears to be an outlier. LV = left ventricular; RV = right ventricular [Color figure can be viewed at http://wileyonlinelibrary.com]

• 

  Figure 6. Effect on longevity by the calculated total pacing power for the Viva Quad XT and other cardiac resynchronization therapy defibrillator models for the same settings [Color figure can be viewed at http://wileyonlinelibrary.com]