title: Ischemic intervals during warm blood cardioplegia in the canine heart evaluated by phosphorus 31-magnetic resonance spectroscopy.
abstract: OBJECTIVE
  Warm blood cardioplegia requires interruption by ischemic intervals to aid visualization. We evaluated the safety of repeated interruption of warm blood cardioplegia by normothermic ischemic periods of varying durations.
  
  
  METHODS
  In three groups of isolated cross-perfused canine hearts, left ventricular function was measured before and for 2 hours of recovery after arrest, which comprised four 15-minute periods of cardioplegia alternating with three ischemic intervals of 15, 20, or 30 minutes (I15, I20, and I30). Metabolism was continuously measured by phosphorus 31-magnetic resonance spectroscopy.
  
  
  RESULTS
  Adenosine triphosphate level fell progressively as ischemia was prolonged; after recovery, adenosine triphosphate was 99% +/- 6%, 90% +/- 1% (p = 0.0004 vs control), and 68% +/- 3% (p = 0.0002) of control levels in I15, I20, and I30, respectively. Intracellular acidosis with ischemia was most marked in I30. After recovery, left ventricular maximal systolic elastance at constant heart rate and coronary perfusion pressure was maintained in I15 but fell to 85% +/- 3% in I20, (p = 0.003) and to 65% +/- 6% (p = 0.003) of control values in I30, while relaxation (tau) was prolonged only in I30 (p = 0.007).
  
  
  CONCLUSIONS
  Hearts recover fully after three 15-minutes periods of ischemia during warm blood cardioplegia, but deterioration, significant with 20-minute periods, is profound when the ischemic periods are lengthened to 30 minutes. This suggests that in the clinical setting warm cardioplegia can be safely interrupted for short intervals, but longer interruptions require caution.
authors.affiliation: Department of Surgery, Massachusetts General Hospital, Boston 02114, USA.
authors.forename: N C
authors.initials: NC
authors.lastname: de Oliveira
authors.forename: T J
authors.initials: TJ
authors.lastname: Boeve
authors.forename: D F
authors.initials: DF
authors.lastname: Torchiana
authors.forename: H L
authors.initials: HL
authors.lastname: Kantor
authors.forename: J S
authors.initials: JS
authors.lastname: Titus
authors.forename: C J
authors.initials: CJ
authors.lastname: Schmidt
authors.forename: C Z
authors.initials: CZ
authors.lastname: Lu
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.forename: W M
authors.initials: WM
authors.lastname: Daggett
authors.forename: G A
authors.initials: GA
authors.lastname: Geffin
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001769:Blood; D002314:Cardioplegic Solutions; D004285:Dogs; D006324:Heart Arrest, Induced / Q000009:adverse effects / Q000379:methods; D006439:Hemodynamics / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D015428:Myocardial Reperfusion Injury / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D013997:Time Factors; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D002314:Cardioplegic Solutions; D010725:Phosphocreatine; D000255:Adenosine Triphosphate