title: Wave energy patterns of counterpulsation: a novel approach with wave intensity analysis.
abstract: BACKGROUND
  In counterpulsation, diastolic augmentation increases coronary blood flow and systolic unloading reduces left ventricular afterload. We present a new approach with wave intensity analysis to revisit and explain counterpulsation principles.
  
  
  METHODS
  In an acute porcine model, a standard intra-aortic balloon pump was placed in descending aorta in 4 pigs. We measured pressure and velocity with probes in left anterior descending artery and aorta during and without intra-aortic balloon pump assistance. Wave intensities of aortic and left coronary waves were derived from pressure and flow measurements with synchronization correction.
  
  
  RESULTS
  We identified predominating waves in counterpulsation. In the aorta, during diastolic augmentation, intra-aortic balloon inflation generated a backward compression wave, with a "pushing" effect toward the aortic root that translated to a forward compression wave into coronary circulation. During systolic unloading, intra-aortic balloon pump deflation generated a backward expansion wave that "sucked" blood from left coronary bed into the aorta. While this backward expansion wave translated to reduced left ventricular afterload, the "sucking" effect resulted in left coronary blood steal, as demonstrated by a forward expansion wave in left anterior descending coronary flow. The waves were sensitive to inflation and deflation timing, with just 25 ms delay from standard deflation timing leading to weaker forward expansion wave and less coronary regurgitation.
  
  
  CONCLUSIONS
  Intra-aortic balloon pumps generate backward-traveling waves that predominantly drive aortic and coronary blood flow during counterpulsation. Wave intensity analysis of arterial circulations may provide a mechanism to explain diastolic augmentation and systolic unloading of intra-aortic balloon pump counterpulsation.
authors.affiliation: Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan. pjlu888@yahoo.com
authors.forename: Pong-Jeu
authors.initials: PJ
authors.lastname: Lu
authors.forename: Chi-Fu Jeffrey
authors.initials: CF
authors.lastname: Yang
authors.forename: Meng-Yu
authors.initials: MY
authors.lastname: Wu
authors.forename: Chun-Hao
authors.initials: CH
authors.lastname: Hung
authors.forename: Ming-Yao
authors.initials: MY
authors.lastname: Chan
authors.forename: Tzu-Cheng
authors.initials: TC
authors.lastname: Hsu
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000503:physiopathology*; D001794:Blood Pressure; D003326:Coronary Circulation; D003971:Diastole; D006439:Hemodynamics; D007423:Intra-Aortic Balloon Pumping; D023421:Models, Animal; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D013552:Swine; D013556:Swine, Miniature; D013599:Systole; D013997:Time Factors