Limitations of retrograde continuous tepid blood cardioplegia for myocardial remodeling

We assessed potential limitations of retrograde continuous tepid blood cardioplegia (RCTBC) for myocardial remodeling, represented by hypertrophied and/or dilated myocardium in patients with severe cardiomyopathy following single aortic valve replacement.

The study was conducted on 91 patients who underwent initial single aortic valve replacement with tepid cardiopulmonary bypass (CPB) and RCTBC. Based on the postoperative maximum creatine phosphokinase (max CPK)-MB level, the patients were allocated to Group H (>/=100 IU/mL) with severe cardiomyopathy or Group L (<100 IU/mL) to make intergroup comparisons of preoperative, intraoperative, and postoperative parameter values.

Preoperative measurements were as follows: pressure gradient between left ventricle and aorta (DeltaPG), 92.8+/-46.2 mmHg in Group H and 57.9+/-41.6 mmHg in Group L (p<0.01); implanted valve size, 21.0+/-2.2 mm in Group H and 22.8+/-2.2 mm in Group L (p<0.01); left ventricular end-diastolic volume (LVEDV), 155.7+/-73.3 mL in Group H and 224.3+/-101.5 mL in Group L (p<0.01). The rate of RCTBC flow rate increase did not differ between the groups (17.6% in Group H and 20.7% in Group L), while the rate of concomitant use of optional antegrade coronary perfusion was significantly lower in Group H (25%) than in Group L (37%) (p<0.05). Pre- and post-perfusion lactic acid levels in the myocardial protection solution measured every 30 min after aortic cross clamping were higher in Group H than in Group L.

The study suggests preoperative high DeltaPG, small aortic root diameter, and low LVEDV, namely, concentrically hypertrophied myocardium, as risk factors for severe cardiomyopathy after RCTBC. RCTBC in patients with any risk factor should be accompanied by an increase in initial continuous perfusion flow and/or aggressive use of intermittent antegrade coronary perfusion.