The contracting and relaxing responses of human internal mammary artery grafts harvested by two different methods

Antispastic Management in Arterial Grafts in Coronary Artery Bypass Grafting Surgery

Arterial grafts have long-term patency superior to vein grafts but have a tendency to develop spasm that can lead to potentially life-threatening complications. A perfect antispastic protocol should include advanced surgical technique and adequate pharmacologic methods. All pharmacologic vasodilator drugs relax the vessel through specific mechanisms, and therefore, there is no perfect, single best vasodilator to prevent or treat spasm of the arterial graft against all mechanisms of contraction. One of the choices is to use a combination of pharmacologic vasodilators targeting different mechanisms of spasm to obtain the reliable and best effect.

Effects of levosimendan on isolated human internal mammary artery and saphenous vein: concurrent use with conventional vasodilators

Graft spasm is a common problem in coronary artery bypass grafting (CABG). In this study, we aimed to investigate the interaction of levosimendan, a novel inodilator, with vasodilator agents that are clinically used for the treatment of graft spasm and with endogenous vasoconstrictors that are thought to play a role in graft vasospasm, in human internal mammary artery (IMA) and saphenous vein (SV). Isolated human IMA and SV segments derived from patients undergoing CABG were suspended in an organ bath. Responses to cumulative concentrations of noradrenaline (NA), serotonin (5-HT), papaverine, nitroglycerin (NG), and diltiazem were recorded before and after 10(-5) m levosimendan incubation (30 min). In addition, cumulative levosimendan responses were taken in vessels precontracted with NA or 5-HT. 10(-5) m levosimendan reduced NA Emax and sensitivity in IMA and SV, and 5-HT Emax responses in IMA. Moreover, levosimendan caused concentration-dependent relaxation in both grafts. Papaverine Emax or sensitivity was not altered by levosimendan neither in IMA nor in SV. Levosimendan diminished NG sensitivity in IMA and Emax responses in SV and decreased diltiazem Emax responses both in IMA and SV. Our results suggest that levosimendan may be used alone for prevention or treatment of graft spasm in IMA or in combination with papaverine in IMA and SV grafts. However, as concurrent administration with diltiazem or NG causes a reduction in relaxation in vitro, we suggest caution should be exercised when using levosimendan in combination with these agents.

A new antispastic solution for arterial grafting: nicardipine and nitroglycerin cocktail in preparation of internal thoracic and radial arteries for coronary surgery

OBJECTIVE

Antispastic protocols for arterial grafts are important in arterial grafting for coronary artery bypass grafting surgery. We designed a new nicardipine and nitroglycerin cocktail that is composed of a second-generation dihydropyridine calcium antagonist, nicardipine and nitroglycerin (30 micromol/L), and examined its effect in human internal thoracic and radial arteries.

METHODS

Human internal thoracic (n = 86) and radial (n = 74) artery segments from 72 patients undergoing coronary artery bypass grafting were studied. Relaxation against 3 classic vasoconstrictors (potassium chloride, thromboxane A(2) mimetic U46619, and alpha-adrenoceptor agonist norepinephrine) and prophylactic effect on contraction against these vasoconstrictors were examined. The effect of the nicardipine and nitroglycerin cocktail on the endothelial function in internal thoracic and radial arteries was studied in response to acetylcholine.

RESULTS

Nicardipine and nitroglycerin induced almost full relaxation (92.2% +/- 4.7% to 97.9% +/- 1.0%, P < .001 in internal thoracic arteries and 95.4% +/- 1.9% to 96.7% +/- 3.3%, P < .001 in radial arteries, n = 6-8) against 3 vasoconstrictors with significant prophylactic effect on contraction (maximal contraction was depressed to 32.5% to 76.4%, P < .05 or P < .001, and EC50s were increased to 5 to 42-fold more, P < .01). After treatment with the nicardipine and nitroglycerin cocktail, the acetylcholine-induced relaxation was unchanged (P > .05).

CONCLUSION

The use of the nicardipine and nitroglycerin cocktail provides a new antispastic protocol that has rapid onset, full relaxation, and excellent prophylactic effect against all known mechanisms of vasospasm and maximally protects the endothelial and smooth muscle function of the internal thoracic and radial arteries. The cocktail is therefore expected to provide a new method in treating grafts in coronary artery bypass grafting with the best antispastic effect and protection of the graft.

Effects of papaverine and carbon dioxide alone or in combination on the blood flow of internal thoracic artery

OBJECTIVE

The internal thoracic artery is frequently used as an arterial graft for coronary bypass. Spasms of internal thoracic artery may contribute to early myocardial ischemia. To prevent vasospasm and increase the blood flow, some vasodilatory agents (such as carbon dioxide or papaverine) are used. The aim of the study was to evaluate the combined effects of carbon dioxide and papaverine versus either alone on the blood flow of the internal thoracic artery.

METHODS

One hundred patients undergoing coronary artery bypass grafting (28 women and 72 men) with similar characteristics were randomly divided into four groups. We used the classic technique without any vasodilatory management before surgery in group 1, papaverine injection into the endothoracic fascia in group 2, and carbodissection technique in groups 3 and 4. Initial free flows of the internal thoracic arteries were measured after cutting of the vessel. After the first measurement, the ITA pedicles were washed with papaverine solution and wrapped with gauze in the first and fourth groups. Blood flow measurements were repeated 15 minutes later in all groups.

RESULTS

When vasodilatory management was applied during excision, the blood flows were significantly increased relative to group 1. The mean blood flows reached a significantly higher level in groups 1, 2, 3, and 4 at the second measurements. In groups 2 and 3, the increase at the first measurements compared to the first group's level was continuously high, but no additional increase was observed between the first and second measurements. In groups 1 and 4, regardless of whether a previous vasodilatory management was present, the increases measured at repeated measurements were significant versus each group's first measurements (P < .05).

CONCLUSIONS

Vasodilatory management, such as injection of papaverine into endothoracic fascia or carbon dioxide insufflation applied during excision, increased the free blood flows of internal thoracic artery pedicles. Exogenously applied papaverine produces an additional and continuous vasodilatation regardless of whether a vasodilatory intervention was previously applied.