The relationship of myocardial stroke work to coronary flow velocity immediately after aortic valve replacement

Background. The interrelations between myocardial stroke work and coronary flow velocity have not been fully defined during aortic valve replacement o r with different cardioplegias. Methods. Twenty-six patients (15 men age 63 +/- 13 years) who had elective isolated aortic valve replacement were studied by transesophageal Doppler e chocardiography with simultaneous high fidelity left ventricular pressure. Fifteen patients received cold blood cardioplegia and 11 had warm blood car dioplegia. Myocardial stroke work and flow velocities in proximal left ante rior descending coronary artery were quantified simultaneously before cardi opulmonary bypass and at 1, 6, 12, and 20 hours afterwards. Results. Myocardial stroke work decreased postoperatively in both groups (1 60 +/- 19 versus 228 +/- 19 mJ/cm(3) per minute, with cold blood cardiopleg ia; 135 +/- 22 versus 227 +/- 22 mJ/cm(3) per minute with warm blood cardio plegia; both p < 0.001 versus time, but p > 0.05 versus cardioplegia, by tw o-way analysis of variance). Left anterior descending artery now velocity-t ime integral per minute increased significantly in both groups (26.1 +/- 2. 1 versus 15.0 +/- 2.1 m/min with cold blood cardioplegia; 32.8 +/- 2.5 vers us 14.4 +/- 2.5 m/min with warm blood cardioplegia; both p < 0.001 versus t ime, but p > 0.05 versus cardioplegia). Thus, at 1 hour postoperatively the mJ . cm(-3) . m(-1). min ratio of myocardial stroke work to left anterior descending artery now velocity-time integral decreased significantly in bot h groups (4.3 +/- 1.6 versus 16.3 +/- 1.7 mJ . cm(-3) . m(-1) . min with wa rm blood cardioplegia, and 7.4 +/- 1.4 versus 17.9 +/- 1.4 J . cm(-3) . m(- 1) . min with cold blood cardioplegia; both p < 0.001 m versus time). Warm blood cardioplegia was also associated with a lower mean ratio perioperativ ely than that with cold blood cardioplegia (7.8 +/- 0.9 versus 10.9 +/- 0.7 mJ . cm(-3) . m(-1) . min, p = 0.014). Conclusions. Coronary hyperemia occurs for at least 20 hours postoperativel y when myocardial stoke work has decreased. The ratio of myocardial stroke work to coronary now velocity appears to be more sensitive than either alon e in differentiating the effect of warm versus cold blood cardioplegia. (An n Thorac Surg 1999;67:705-10) (C) 1999 by The Society of Thoracic Surgeons.