title: Myocardial function after polarizing versus depolarizing cardiac arrest with blood cardioplegia in a porcine model of cardiopulmonary bypass.
abstract: OBJECTIVE
  Potassium-based depolarizing St Thomas' Hospital cardioplegic solution No 2 administered as intermittent, oxygenated blood is considered as a gold standard for myocardial protection during cardiac surgery. However, the alternative concept of polarizing arrest may have beneficial protective effects. We hypothesize that polarized arrest with esmolol/adenosine/magnesium (St Thomas' Hospital Polarizing cardioplegic solution) in cold, intermittent oxygenated blood offers comparable myocardial protection in a clinically relevant animal model.
  
  
  METHODS
  Twenty anaesthetized young pigs, 42 ± 2 (standard deviation) kg on standardized tepid cardiopulmonary bypass (CPB) were randomized (10 per group) to depolarizing or polarizing cardiac arrest for 60 min with cardioplegia administered in the aortic root every 20 min as freshly mixed cold, intermittent, oxygenated blood. Global and local baseline and postoperative cardiac function 60, 120 and 180 min after myocardial reperfusion was evaluated with pressure-conductance catheter and strain by Tissue Doppler Imaging. Regional tissue blood flow, cleaved caspase-3 activity, GRK2 phosphorylation and mitochondrial function and ultrastructure were evaluated in myocardial tissue samples.
  
  
  RESULTS
  Left ventricular function and general haemodynamics did not differ between groups before CPB. Cardiac asystole was obtained and maintained during aortic cross-clamping. Compared with baseline, heart rate was increased and left ventricular end-systolic and end-diastolic pressures decreased in both groups after weaning. Cardiac index, systolic pressure and radial peak systolic strain did not differ between groups. Contractility, evaluated as dP/dtmax, gradually increased from 120 to 180 min after declamping in animals with polarizing cardioplegia and was significantly higher, 1871 ± 160 (standard error) mmHg/s, compared with standard potassium-based cardioplegic arrest, 1351 ± 70 mmHg/s, after 180 min of reperfusion (P = 0.008). Radial peak ejection strain rate increased and the load-independent variable preload recruitable stroke work was increased with polarizing cardioplegia after 180 min, 64 ± 3 vs 54 ± 2 mmHg (P = 0.018), indicating better preserved left ventricular contractility with polarizing cardioplegia. Phosphorylation of GRK2 in myocardial tissue did not differ between groups. Fractional cytoplasmic volume in myocytes was reduced in hearts arrested with polarizing cardioplegia, indicating reduction of cytoplasmic oedema.
  
  
  CONCLUSIONS
  Polarizing oxygenated blood cardioplegia with esmolol/adenosine/magnesium offers comparable myocardial protection and improves contractility compared with the standard potassium-based depolarizing blood cardioplegia.
authors: Department of Heart Disease, Haukeland University Hospital, Bergen, Norway Faculty of Medicine and Dentistry, Department of Clinical Science, University of Bergen, Bergen, Norway terje.aass@helse-bergen.no.
authors: Terje
authors: T
authors: Aass
authors: Faculty of Medicine and Dentistry, Department of Clinical Science, University of Bergen, Bergen, Norway.
authors: Lodve
authors: L
authors: Stangeland
authors: Department of Heart Disease, Haukeland University Hospital, Bergen, Norway.
authors: Christian Arvei
authors: CA
authors: Moen
authors: Department of Heart Disease, Haukeland University Hospital, Bergen, Norway Faculty of Medicine and Dentistry, Department of Clinical Science, University of Bergen, Bergen, Norway.
authors: Pirjo-Riitta
authors: PR
authors: Salminen
authors: Department of Heart Disease, Haukeland University Hospital, Bergen, Norway Faculty of Medicine and Dentistry, Department of Clinical Science, University of Bergen, Bergen, Norway.
authors: Geir Olav
authors: GO
authors: Dahle
authors: Cardiac Surgical Research, The Rayne Institute (King's College London), Guy's and St Thomas' NHS Foundation Trust, St Thomas' Hospital, London, UK.
authors: David J
authors: DJ
authors: Chambers
authors: Cardiac Surgical Research, The Rayne Institute (King's College London), Guy's and St Thomas' NHS Foundation Trust, St Thomas' Hospital, London, UK.
authors: Thomais
authors: T
authors: Markou
authors: Department of Heart Disease, Haukeland University Hospital, Bergen, Norway.
authors: Finn
authors: F
authors: Eliassen
authors: Department of Heart Disease, Haukeland University Hospital, Bergen, Norway.
authors: Malte
authors: M
authors: Urban
authors: Department of Heart Disease, Haukeland University Hospital, Bergen, Norway Faculty of Medicine and Dentistry, Department of Clinical Science, University of Bergen, Bergen, Norway.
authors: Rune
authors: R
authors: Haaverstad
authors: Faculty of Medicine and Dentistry, Department of Clinical Science, University of Bergen, Bergen, Norway.
authors: Knut
authors: K
authors: Matre
authors: Faculty of Medicine and Dentistry, Department of Clinical Science, University of Bergen, Bergen, Norway.
authors: Ketil
authors: K
authors: Grong
mesh_terms: D000818:Animals; D002315:Cardiopulmonary Bypass / Q000379:methods*; D004195:Disease Models, Animal; D006323:Heart Arrest / Q000601:surgery*; D006324:Heart Arrest, Induced / Q000379:methods*; D013552:Swine
keywords: Animal model; Cardiac function; Cardioplegia; Myocardial protection