Future cardioprotective considerations

Ultra-short-acting cardioselective beta-blockade attenuates postischemic cardiac dysfunction in the isolated rat heart

OBJECTIVES

We sought to test the effectiveness of ultra-short-acting cardioselective beta-blockade, landiolol hydrochloride, for warm heart surgery.

METHODS

The isolated perfused rat heart preparation was used. After preischemic measurement of cardiac function, 3 min of coronary infusion of crystalloid cardioplegic solution (37 degrees C) with landiolol hydrochloride of various concentrations (1, 2.5, 5, and 10 mmol/l) or without it (control group) was performed, followed by 30 min of warm ischemic arrest. Finally, postischemic function was measured.

RESULTS

The percentage recoveries of heart rate in hearts receiving 0, 1, 2.5, 5, and 10 mmol/l landiolol hydrochloride were 89.4+/-3.4%, 90.9+/-1.7%, 89.6+/-1.8%, 83.4+/-3.3%, and 74.3+/-1.9% (P<0.05 vs. 0, 1, and 2.5 mmol/l groups), respectively. The percentage recoveries of aortic flow were 55.6+/-3.1%, 62.8+/-3.3%, 75.0+/-4.2% (P<0.05 vs. 0 and 10 mmol/l groups), 65.3+/-5.3%, and 51.6+/-4.0%, respectively. Similar recovery profiles were observed with the first derivative of the rise in aortic pressure, stroke volume and stroke work. The total amount of coronary effluent in the hearts receiving 5 or 10 mmol/l was lower than in the other groups.

CONCLUSIONS

Landiolol hydrochloride has the potential to enhance postischemic cardiac function after the warm cardioplegic arrest. The optimal concentration for maximum postischemic functional recovery was 2.5 mmol/l, and recoveries of aortic flow and heart rate decreased in hearts receiving 5 mmol/l or more.

Risk factors of incomplete distribution of cardioplegic solution during coronary artery grafting

Myocardial distribution of cardioplegic solution infused by combined antegrade/retrograde routes was assessed with myocardial contrast echocardiography in 18 patients with chronic stable angina and three-vessel disease undergoing elective coronary artery bypass grafting. Overall myocardial opacification was significantly greater in retrograde than in antegrade cardioplegia (77.7% +/- 13.4% versus 59.1% +/- 15.7%; p = 0.0009). The difference was affected by collateral circulation, as pointed out by the significant interaction between coronary collateral circulation and percent of myocardial opacification after antegrade and retrograde cardioplegia (p = 0.002). When we performed multiple comparisons, in patients with good collaterals the opacification difference between antegrade and retrograde cardioplegia was not statistically significant (66.4% +/- 10.2% versus 76.0% +/- 15.2%; p = not significant), whereas in patients with poor collaterals myocardial opacification during retrograde cardioplegia was significantly greater (44.3% +/- 15.0% versus 81.2% +/- 9.0%; p < 0.02). During antegrade cardioplegia, patients with poor collaterals showed a lower degree of myocardial opacification than patients with good collaterals (44.3% +/- 15.0% versus 66.4% +/- 10.2%; p < 0.01). Our results show that retrograde cardioplegia in patients undergoing elective coronary artery bypass grafting offers no advantage over antegrade cardioplegia when collateral circulation is well developed. On the other hand, conventional aortic root infusion may not provide adequate myocardial protection in the subset of patients with significantly narrowed or occluded coronary arteries and poor collaterals.