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J Thorac Cardiovasc Surg 2006;132:1314-1320
© 2006 The American Association for Thoracic Surgery

Cardiopulmonary Support and Physiology

Keeping the heart empty and beating improves preservation of hypertrophied hearts for valve surgery

^a Institute for Biodiagnostics, National Research Council, Winnipeg, Manitoba, Canada
^b Department of Cardiothoracic Surgery, the Fourth Affiliated Hospital, Harbin Medical University, Harbin, People’s Republic of China
^c Division of Cardiothoracic Surgery, University of Miami, Miller School of Medicine, and Jackson Memorial Hospital, Miami, Fla.

Received for publication March 22, 2006; revisions received July 6, 2006; accepted for publication July 13, 2006.

^_* Address for reprints: Ganghong Tian, MD, PhD, Institute for Biodiagnostics, 435 Ellice Ave, Winnipeg, MB R3B 1Y6, Canada. (Email: Hong.Tian{at}nrc-cnrc.gc.ca).

OBJECTIVE: This study was designed to determine whether keeping the heart empty and beating improved myocardial fluid homeostasis and energy metabolism of hypertrophied pig hearts in comparison with cardioplegic arrest.

METHODS: Twenty piglets underwent a 12-week ascending aortic banding to induce left ventricular hypertrophy. Isolated hypertrophied hearts were divided into 4 groups (n = 5 in each group). Two groups underwent normothermic normokalemic simultaneous perfusion. The other 2 groups were subjected to normothermic hyperkalemic simultaneous perfusion and used as controls. Intramyocardial hydrostatic pressure was monitored with a microtip pressure transducer. Volumes of intracellular and extracellular compartments and myocardial energy metabolism were monitored by using phosphorus 31 magnetic resonance spectroscopy.

RESULTS: Normothermic normokalemic simultaneous perfusion (NNSP) maintained intramyocardial hydrostatic pressure at a significantly lower level (13.0 ± 0.6 mm Hg) compared with normothermic hyperkalemic simultaneous perfusion (NHSP) (23.3 ± 1.2 mm Hg) during a 90-minute preservation. NNSP maintained the normal volume of the intracellular compartment throughout the preservation period, whereas NHSP caused significant enlargement (to 123% ± 6% of its normal volume) of the intracellular compartment. Expansion of the extracellular compartment during preservation was significantly less in the NNSP group (124% ± 6%) than in the NHSP group (152% ± 7%). NNSP maintained normal levels of phosphocreatine and adenosine triphosphate until coronary perfusion flow was reduced to 50% of the initial control level. No decrease in energy metabolites was observed in the NHSP group even when coronary perfusion flow was reduced to 10% of the initial control level.

CONCLUSIONS: Keeping the heart empty and beating improves myocardial fluid homeostasis for hypertrophied hearts relative to cardioplegic arrest. Its ability to maintain energy metabolism depends on the degree of coronary stenosis. This technique may be a promising protective strategy for hypertrophied hearts.