Comparison of endothelium-dependent vasoactivity of internal mammary arteries from hypertensive, hypercholesterolemic, and diabetic patients

BACKGROUND

Endothelium-dependent relaxation is abnormal in a variety of diseased states. Despite the widespread use of the internal mammary artery (IMA) in coronary artery bypass grafting, there is a lack of comparative studies on IMA endothelial-dependent function in patients with major cardiovascular risk factors.

METHODS

An IMA segment from 48 selected patients undergoing coronary artery bypass grafting was harvested intraoperatively and assigned to one of four groups (n = 12): diabetics requiring therapy, hypertensives, hypercholesterolemic, and nondiabetic-normotensive-normocholesterolemic patients. Internal mammary artery specimens were cut into rings and suspended in organ bath chambers, and the isometric tension of vascular tissues was recorded. The IMA rings were (1) precontracted with norepinephrine, and the endothelium-derived relaxation was evaluated by cumulative addition of acetylcholine, (2) contracted with cumulative concentrations of endothelin-1, and (3) contracted with the nitric oxide synthase inhibitor, N(G)-monomethyl-L-arginine. Furthermore, the release of prostacyclin by the IMA rings was directly measured during basal tone conditions and at the end of the various pharmacologic interventions. Histology of IMA rings was randomly performed.

RESULTS

The results obtained in these experiments showed that IMA rings harvested from hypertensive patients have the greatest impairment of endothelium-dependent response to relaxant and contracting stimuli (p < 0.01 versus nondiabetic-normotensive-normocholesterolemic tissues; p < 0.05 versus hypercholesterolemic and diabetic tissues) and prostacyclin release in normal and stimulated conditions. To a lesser extent, hypercholesterolemic and diabetic tissues show similar depression (diabetic > hypercholesterolemic) both of relaxation and prostacyclin production, with respect to nondiabetic-normotensive-normocholesterolemic specimens (p < 0.05). Histology findings (scanning electron microscopy) did not differ in multiple sections from vessel studies.

CONCLUSIONS

Major cardiovascular risk factors affect the endothelium-dependent vasoactive homeostasis of human IMA differently. Depression of relaxation is highest in patients with a history of hypertension. These findings may be pertinent to early and long-term treatment of patients undergoing coronary artery bypass grafting.

Protectant activity of defibrotide in cardioplegia followed by ischemia/reperfusion injury in the isolated rat heart

BACKGROUND

Previous studies have shown that defibrotide, a polydeoxyribonucleotide obtained by depolymerization of DNA from porcine tissues, has important protective effects on myocardial ischemia, which may be associated with a prostacyclin-related mechanism. The purpose of this study was to investigate the direct effects of defibrotide (given in cardioplegia or after ischemia) on a model of rat heart recovery after cardioplegia followed by ischemia/reperfusion injury.

METHODS

Isolated rat hearts, undergoing 5 minutes of warm cardioplegic arrest followed by 20 minutes of global ischemia and 30 minutes of reperfusion, were studied using the modified Langendorff model. The cardioplegia consisted of St. Thomas' Hospital solution augmented with defibrotide (50, 100, and 200 microg/mL) or without defibrotide (controls). Left ventricular mechanical function and the levels of creatine kinase, lactate dehydrogenase, and 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha; the stable metabolite of prostacyclin) were measured during preischemic and reperfusion periods.

RESULTS

After global ischemia, hearts receiving defibrotide in the cardioplegic solution (n = 8) manifested in a concentration-dependent fashion lower left ventricular end-diastolic pressure (p < 0.001), higher left ventricular developed pressure (p < 0.01), and lower coronary perfusion pressure (p < 0.001) compared to the control group. After reperfusion, hearts receiving defibrotide in the cardioplegic solution also had, in a dose-dependent way, lower levels of creatine-kinase (p < 0.01), lactate dehydrogenase (p < 0.001), and higher levels of 6-keto-PGF1alpha (p < 0.001) compared to the control group. Furthermore, when defibrotide was given alone to the hearts at the beginning of reperfusion (n = 7), the recovery of postischemic left ventricular function was inferior (p < 0.05) to that obtained when defibrotide was given in cardioplegia.

CONCLUSIONS

Defibrotide confers to conventional crystalloid cardioplegia a potent concentration-dependent protective effect on the recovery of isolated rat heart undergoing ischemia/reperfusion injury. The low cost and the absence of contraindications (cardiac toxicity and hemodynamic effects) make defibrotide a promising augmentation to cardioplegia.

[Coronary surgery without extracorporeal circulation: the short-term results in high-risk patients]

BACKGROUND

This study was conducted to assess the impact of coronary bypass surgery (CABG) without cardiopulmonary bypass (CPB) on high-risk patients.

METHODS

From February 1997 to July 1998, 71 patients considered at high-risk underwent a CABG off-pump. Using the "Higgins score", eleven preoperative risk factors were identified and stratified in this group of patients. Among 1271 patients who underwent CABG with CPB in the same period, using a computer-based matched comparison, a second identical group of patients was selected according to the 11 risk variables and the number with coronary disease, so that complete preoperative matching included the year of operation, score index and coronary target. Moreover, among seven other preoperative variables that were not included in the matching comparison, the two groups differed only in mean age (64 +/- 10.9 vs 61.6 +/- 7.3 in groups off and on-pump, respectively, p < 0.05). Postoperative outcome and complications and blood requirement were compared. Myocardial cell injury and left ventricular performance were also assessed in the two groups.

RESULTS

The global incidence of neurologic complications in the off-pump group was significantly lower (9.8 vs 0%, in on and off-pump groups, respectively; p = 0.02). Patients undergoing CABG off-pump required blood far less often (% of transfused patients: 26.7% for the patients with CPB and 11.2% for the patients without CPB; p = 0.032). Three patients from the on-pump group (4.2%) had a perioperative myocardial infarction (AMI), versus 0% of the off-pump cases (p = ns). Postoperative atrial fibrillation accounted for 14.1% in off-pump patients and 30.9% in on-pump patients (p = 0.027). One patient in both groups (1.4%) suffered from postoperative heart failure. Mean ventilation time and ICU stay did not differ significantly between the two groups. However, hospital discharge occurred earlier in the off-pump group (9.3 +/- 3 vs 12.6 +/- 8, p = 0.007). In-hospital death occurred in one case from the on-pump group (1.4%) versus 0% of patients operated off-pump. CPK-MB release in patients without perioperative AMI was significantly lower in off-pump patients 6 and 12 hours after the operation (36.6 +/- 17 IU/l vs 69.8 +/- 23 IU/l after 6 hours, p < 0.05; and 36.7 +/- 19 IU/l vs 67.3 +/- 26 IU/l after 12 hours, p < 0.05, in off and on-pump groups, respectively) and LVSWI turned out to be better in off-pump patients 6 hours postoperatively (34.2 +/- 2 g*m/m2 vs 27.2 +/- 3 g*m/m2, p < 0.01).

CONCLUSIONS

CABG without CPB seems to be a promising technique for high-risk patients. It offers better neurologic and cardiac protection, shortens postoperative hospital stay and reduces the need for blood transfusion.