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Preload-adjusted maximal power: a novel index of left ventricular contractility in atrial fibrillation
  1. M Takagaki1,
  2. P M McCarthy2,
  3. M Chung3,
  4. J Connor4,
  5. R Dessoffy1,
  6. Y Ochiai1,
  7. M Howard1,
  8. K Doi1,
  9. M Kopcak5,
  10. T N Mazgalev3,
  11. K Fukamachi1
  1. 1Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
  2. 2Department of Thoracic and Cardiovascular Surgery, George and Linda Kaufman Center for Heart Failure, Cleveland Clinic Foundation
  3. 3Department of Cardiovascular Medicine, Cleveland Clinic Foundation
  4. 4Department of Biostatistics and Epidemiology, Cleveland Clinic Foundation
  5. 5Biological Resources Unit, Lerner Research Institute, Cleveland Clinic Foundation
  1. Correspondence to:
    Dr Kiyotaka Fukamachi, Department of Biomedical Engineering/ND20, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA;


Background: Left ventricular contractility in atrial fibrillation is known to change in a beat to beat fashion, but there is no gold standard for contractility indices in atrial fibrillation, especially those measured non-invasively.

Objective: To determine whether the non-invasive index of contractility “preload-adjusted PWRmax” (maximal ventricular power divided by the square of end diastolic volume) can accurately measure left ventricular contractility in a beat to beat fashion in atrial fibrillation.

Methods: Atrial fibrillation was induced experimentally using 60 Hz stimulation of the atrium and maintained in 12 sheep; four received diltiazem, four digoxin, and four no drugs (control). Aortic flow, left ventricular volume, and left ventricular pressure were monitored simultaneously. Preload-adjusted PWRmax, the slope of the end systolic pressure–volume relation (Emax), and the maximum rate of change of left ventricular pressure (dP/dtmax) were calculated in a beat to beat fashion.

Results: Preload-adjusted PWRmax correlated linearly with load independent Emax (p < 0.0001) and curvilinearly with load dependent dP/dtmax (p < 0.0001), which suggested the load independence of preload-adjusted PWRmax. After five minutes of diltiazem administration, preload-adjusted PWRmax, dP/dtmax, and Emax fell significantly (p < 0.0001) to 62%, 64%, and 61% of baseline, respectively. Changes were not significant after five minutes of digoxin (103%, 98%, and 102%) or in controls (97%, 96%, and 95%).

Conclusions: Preload-adjusted PWRmax correlates linearly with Emax and is a useful measure of contractility even in atrial fibrillation. Non-invasive application of this method, in combination with echocardiography and tonometry, may yield important information for optimising the treatment of patients with atrial fibrillation.

  • atrial fibrillation
  • preload-adjusted maximal power
  • contractility
  • sheep
  • ABD, automated border detection
  • AIC, Akaike information criteria
  • BIC, Bayesian information criteria
  • Emax, slope of ESPVR
  • ESPVR, end systolic pressure volume relation;
  • dP/dtmax, maximum rate of change in left ventricular pressure
  • PWRmax
  • maximal ventricular power
  • VED
  • end diastolic volume

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