title: Control of ventricular unloading using an electrocardiogram-synchronized Thoratec paracorporeal ventricular assist device.
abstract: OBJECTIVE
  Current pulsatile ventricular assist devices operate asynchronous with the left ventricle in fixed-rate or fill-to-empty modes because electrocardiogram-triggered modes have been abandoned. We hypothesize that varying the ejection delay in the synchronized mode yields more precise control of hemodynamics and left ventricular loading. This allows for a refined management that may be clinically beneficial.
  
  
  METHODS
  Eight sheep received a Thoratec paracorporeal ventricular assist device (Thoratec Corp, Pleasanton, Calif) via ventriculo-aortic cannulation. Left ventricular pressure and volume, aortic pressure, pulmonary flow, pump chamber pressure, and pump inflow and outflow were recorded. The pump was driven by a clinical pneumatic drive unit (Medos Medizintechnik AG, Stolberg, Germany) synchronously with the native R-wave. The start of pump ejection was delayed between 0% and 100% of the cardiac period in 10% increments. For each of these delays, hemodynamic variables were compared with baseline data using paired t tests.
  
  
  RESULTS
  The location of the minimum of stroke work was observed at a delay of 10% (soon after aortic valve opening), resulting in a median of 43% reduction in stroke work compared with baseline. Maximum stroke work occurred at a median delay of 70% with a median stroke work increase of 11% above baseline. Left ventricular volume unloading expressed by end-diastolic volume was most pronounced for copulsation (delay 0%).
  
  
  CONCLUSIONS
  The timing of pump ejection in synchronized mode yields control over left ventricular energetics and can be a method to achieve gradual reloading of a recoverable left ventricle. The traditionally suggested counterpulsation is not optimal in ventriculo-aortic cannulation when maximum unloading is desired.
authors: Institute for Dynamic Systems and Control, ETH Zurich, Zurich, Switzerland. raffael.amacher@idsc.mavt.ethz.ch
authors: Raffael
authors: R
authors: Amacher
authors: Alberto
authors: A
authors: Weber
authors: Henriette
authors: H
authors: Brinks
authors: Shannon
authors: S
authors: Axiak
authors: Antonio
authors: A
authors: Ferreira
authors: Lino
authors: L
authors: Guzzella
authors: Thierry
authors: T
authors: Carrel
authors: James
authors: J
authors: Antaki
authors: Stijn
authors: S
authors: Vandenberghe
mesh_terms: D000818:Animals; D001011:Aorta / Q000503:physiopathology; D062186:Arterial Pressure; D004195:Disease Models, Animal; D004562:Electrocardiography; D006339:Heart Rate; D006353:Heart-Assist Devices; D011474:Prosthesis Design; D011652:Pulmonary Circulation; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D012756:Sheep; D013318:Stroke Volume; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology / Q000628:therapy*; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
keywords: 27; ECG; LV; LVAD; VAD; electrocardiogram; left ventricle; left ventricular assist device; ventricular assist device