Endothelium-dependent vasoconstriction in isolated vessel grafts: a novel mechanism of vasospasm?

BACKGROUND

YC-1 (3-(5'-hydroxymethyl-2'furyl)-1-benzyl-indazole) is an allosteric activator of soluble guanylyl cyclase (sGC) and a vasodilator. This study describes a paradoxical action of YC-1 in isolated vessels of patients with coronary artery disease (CAD) that appears to trigger an endothelium-dependent vasoconstrictor pathway present in vessels with endothelial dysfunction.

METHODS

Effects of YC-1 on the tensions of isolated vessels were investigated in an organ bath. Vasoconstrictors released from the vessels were quantified through enzyme-linked immunosorbent assay.

RESULTS

YC-1 elicited long-lasting constriction in saphenous veins and radial arteries from patients with CAD, but not in human umbilical veins. The half-maximal effective dose was 1.0 μmol/L. Constriction was attenuated by nifedipine (an L-type Ca(2+)-channel blocker), bosentan (an endothelin [ET](A)/ET(B) inhibitor), BQ-788 (N-[(cis-2,6-Dimethyl-1-piperidinyl)carbonyl]-4-methyl-L-leucyl-1-(methoxycarbonyl)-D-tryptophyl-D-norleucine; an ET(B) inhibitor), and by denuding, but not by ODQ (1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one; an inhibitor of sGC), BQ-123 (cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu); an ET(A) inhibitor), or phosphoramidon (an endothelin converting enzyme inhibitor). Indomethacin (an inhibitor of cyclooxygenase-1 and -2) and SQ29,548 ([1S-[1α,2α(Z),3α,4α]]-7-[3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid; a thromboxane receptor antagonist) suppressed YC-1-induced constriction, whereas DFU (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanone; a cyclooxygenase-2 inhibitor) had no effect. Rings of saphenous vein released significantly more endothelin-1 in the presence than in the absence of YC-1.

CONCLUSIONS

YC-1-induced vasoconstriction demonstrates the existence of an endothelium-dependent vasoconstrictor pathway in the blood vessels of patients with CAD that to date has been described only in animal models of hypertension. Patients with CAD who have elevated plasma levels of endothelin-1 are thus prone to endothelium-dependent vasoconstriction, which may also play a role in vasospasm in vascular grafts.

Minimized extracorporeal circulation in coronary artery bypass surgery is equivalent to standard extracorporeal circulation in patients with reduced left ventricular function

BACKGROUND

Minimized extracorporeal circulation (MECC) is a promising alternative to standard extracorporeal circulation (ECC) and its use is increasing in routine coronary bypass surgery. We analyzed the clinical outcome of patients with reduced left ventricular function who underwent coronary artery bypass surgery with MECC or with standard ECC.

METHODS

From January 2003 to September 2008, 238 patients with a left ventricular function < 30 % underwent bypass surgery with ECC or MECC. The primary end point of our retrospective observational study was 30-day mortality. Secondary endpoints were the transfusion requirements, as well as intensive care and the in-hospital course.

RESULTS

Demographic data, comorbidities and left ventricular function were similar in the study groups. MECC patients had a tendency towards a lower 30-day mortality rate, a better postoperative renal function and reduced ventilation times. Extracorporeal circulation time and postoperative high-dose inotropic support were significantly lower in the MECC group, while the stays in the intensive care unit and in hospital were comparable between the two groups. In our study, age in the ECC group, and previous infarction and New York Heart Association grade IV in the MECC group were preoperative risk factors associated with a higher mortality.

CONCLUSION

Coronary bypass surgery using MECC is feasible and safe for patients with severely impaired left ventricular function. It is a promising alternative to ECC with a low mortality rate and a more favorable postoperative course.

Impact of normothermic perfusion and protein supplementation on human endothelial cell function during organ preservation

BACKGROUND

Hypothermia-induced changes in endothelial cell (EC) morphology and function after organ storage may influence the initial outcome and development of transplant-associated coronary artery disease.

METHODS

Human saphenous vein ECs were incubated with saline (NaCl), University of Wisconsin (UW), and histidine-tryptophan-ketoglutarate (HTK) solution, with and without protein additives, at 4 degrees C and 37 degrees C. After 6 hours, ECs were recultivated for 24 and 48 hours with culture medium (reperfusion). Mitochondrial activity, adenosine triphosphate concentration, cell count, and inflammatory responses were analyzed.

RESULTS

Cold preservation did not affect the mitochondrial activity of ECs and allowed a complete regeneration of the metabolic turnover after reperfusion. However, under normothermic conditions the metabolism of the cells was influenced by time and type of preservation solution. While both the mitochondrial activity and cell count did not change after treatment with NaCl and culture medium, the metabolic turnover of cells treated with HTK and UW solution significantly increased (twofold) and decreased (twofold, p < 0.05), respectively, after reperfusion. The endothelial reactivity remained unchanged after treatment with NaCl and HTK. The addition of serum proteins significantly improved mitochondrial activity of cells treated with warm NaCl and HTK (p < 0.05). The UW-treated cells burned out through a significant up-regulation of the ATP concentration resulting in a complete metabolic regression after reperfusion and induction of apoptosis.

CONCLUSIONS

Normothermic preservation in UW prevented regeneration of ECs, while treatment with HKT solution did not irreversibly affect mitochondrial activity of ECs and allowed complete regeneration of metabolism and function. Serum proteins improved the preservation effect of HTK and NaCl.