Isoprostanes constrict human radial artery by stimulation of thromboxane receptors, Ca2+ release, and RhoA activation.

OBJECTIVES: Radial artery vasospasm remains a potential cause of early graft failure after coronary bypass graft surgery, despite pretreatment with alpha-adrenergic or calcium channel blockers. We examined the roles of isoprostanes and prostanoid receptors selective for thromboxane A2 in the vasoconstriction of human radial arteries. METHODS: Human radial arterial segments were pretreated intraoperatively with verapamil/papaverine or nitroglycerine/phenoxybenzamine, or not treated. In the laboratory, we measured isometric contractions in ring segments, vasoconstriction in pressurized segments, and changes in [Ca2+] and K+ currents in single cells. RESULTS: Although phenoxybenzamine eliminated adrenergic responses, the isoprostane 15-F(2t)-IsoP and 2 closely related E-ring molecules (15-E(1t)-IsoP and 15-E(2t)-IsoP) still evoked powerful contractions; 15-E(2t)-IsoP was approximately 10-fold more potent than the other 2 agents. Responses were mediated through thromboxane receptors because they were sensitive to ICI-192605. Furthermore, they were sensitive to the Rho-kinase inhibitors Y-27632 or H-1152 (both 10(-5) mol/L) or to cyclopiazonic acid (which depletes the internal Ca2+ pool), but not to nifedipine. In single cells, 15-E(2t)-IsoP elevated [Ca2+]i and suppressed K+ current. CONCLUSIONS: Isoprostanes accumulate after coronary artery bypass graft surgery, yet none of the currently available antispasm treatments for radial artery grafts is effective against isoprostane-induced vasoconstriction. It is imperative that more specific treatment strategies be developed. We found that isoprostane responses in radial arteries are mediated by prostanoid receptors selective for thromboxane A2 with activation of Rho-kinase and release of Ca2+. Pretreatment of radial artery grafts with Rho-associated kinase inhibitors may potentially reduce postoperative graft spasm. Clinical studies to test this are indicated.

Does the number of grafts influence surgeon choice and patient benefit of off-pump over conventional on-pump coronary artery revascularization in multivessel coronary artery disease?

BACKGROUND: It is not known whether surgeons preferentially assign patients requiring fewer grafts (1 to 3) to off-pump coronary artery bypass graft surgery (OPCABG) and those requiring many grafts (4 to 7) to conventional on-pump coronary artery bypass graft surgery (ONCABG), nor whether risk-adjusted outcomes are similar for OPCABG and ONCABG among patients receiving 1 to 3 and 4 to 7 grafts. METHODS: Emory Hospitals' prospective database was retrospectively reviewed for 11,413 consecutive, isolated, primary coronary revascularization procedures between January 1997 and May 2005. Patients were divided into four groups: OPCABG 1 to 3 grafts (n = 3,187), OPCABG 4 to 7 grafts (n = 1,305), ONCABG 1 to 3 grafts (n = 3,279), and ONCABG 4 to 7 grafts (n = 3,642). A propensity score for surgery type was estimated from 39 risk factors. Multivariable logistic regression examined independent impact of surgery type and number of vessels grafted on outcomes. Computed interactions determined whether the effect of surgery type on risk-adjusted outcomes was consistent across groups. RESULTS: Patients requiring 4 to 7 grafts had adjusted odds of receiving ONCABG 2.92 times higher than patients requiring 1 to 3 grafts (p < 0.001). The OPCABG patients had adjusted odds ratios of 0.53 for death (p = 0.007), 0.42 for stroke (p < 0.001), 0.51 for major adverse cardiac events (p < 0.001), and 0.71 for renal failure (p = 0.05) as compared with ONCABG patients. The interaction between OPCABG and number of vessels grafted was not statistically significant. CONCLUSIONS: This study demonstrates that surgeons tend to perform OPCABG for patients requiring 1 to 3 grafts and ONCABG for those requiring 4 to 7 grafts. Off-pump CABG is associated with reduced adjusted risk of adverse outcomes compared with ONCABG. This benefit is consistent for patients requiring 1 to 3 or 4 to 7 grafts.

Off-pump coronary artery bypass grafting through sternotomy: for whom?

PURPOSE OF REVIEW: Off-pump coronary artery bypass grafting hopes to avoid morbidity associated with cardiopulmonary bypass, improving clinical outcomes. Yet its technical difficulty and unfamiliarity raise concern that adoption of off-pump coronary artery bypass might be associated with poorer outcomes. Both surgeon-specific and patient-related factors are believed to play roles in the success of off-pump coronary artery bypass. This review sought to elucidate these factors. RECENT FINDINGS: Current prospective data suggest that both techniques have similar rates of mortality but off-pump coronary artery bypass does provide patients with a lower morbidity. Multiple prospective studies suggest a decrease in stroke rates for off-pump coronary artery bypass grafting. There is a consensus that certain patients will have better outcomes if done off-pump. Surgeon experience with the procedure does impact patient outcome. SUMMARY: Though every patient must be dealt with on an individual basis, it would appear that almost any patient is a candidate for off-pump coronary artery bypass and that, given time and an appropriate desire, most any surgeon can perform the procedure.

Determination of troponin I release after CABG surgery.

BACKGROUND: Troponin I is used to diagnose myocardial infarction (MI). Its use and pattern of elevation is not well defined in coronary artery bypass graft (CABG) surgery. This study assessed the timing of troponin I elevation in patients undergoing urgent CABG. METHOD: Patients undergoing urgent isolated-CABG with cardiopulmonary bypass were studied prospectively. Blood samples were taken to measure CK, CK-MB, and troponin I: preoperatively, 7 hours postoperatively, 14 to 18 hours postoperatively, 30 to 48 hours postoperatively, and on postoperative day 4. Electrocardiograms and in-hospital course were recorded. Perioperative MI (PMI) was defined by either (i) ECG criteria of new Q-waves in the presence of CK-MB elevation >50 microg/L or (ii) CK-MB > 100 microg/L. RESULTS: Of the 50 patients studied, 6 met the criteria for PMI (12%); 2 by criteria (i) and 4 by criteria (ii). In patients not meeting the criteria for MI the troponin I level peaked at 7 hour post-op with a mean of 20.97 microg/L (95% CI, 17.11 to 24.83). At this time, patients who met the criteria for MI had a mean troponin I level of 46.85 microg/L (95% CI, 36.40 to 57.30). Of variables investigated for the 44 patients who did not meet MI criteria, only preoperative troponin I level impacted peak postoperative troponin I. CONCLUSIONS: CABG elevates troponin I far beyond current diagnostic benchmarks without the clinical occurrence of a MI and appears to peak during the second postoperative day. An elevated preoperative troponin I may predict an elevated peak postoperative troponin I in patients who do not have a PMI.

The effect of oxygenator membranes on blood: a comparison of two oxygenators in open-heart surgery.

Open-heart surgery (OHS) requires cardiopulmonary bypass (CPB) in most patients. Membrane oxygenators are a critical component of the CPB system. Despite advancements in CPB technology, injury to blood components during CPB still occurs and may result in complications after surgery. The purpose of the present study was to evaluate the performance of the Medtronic Affinity NT with Trillium coating and the Cobe Optima XP oxygenators and compare their influence on blood components. Two hundred and fifty-six male and female patients scheduled for urgent or elective cardiac surgery with CPB were randomly assigned to either the Affinity NT or the Optima XP oxygenators. Outcomes included platelets, hemoglobin, leukocyte counts, and O2 transfer, measured preoperatively and at 15, 45 and 75 min of CPB time. Blood loss was measured at six and 12 hours postoperatively. A modified intention-to-treat analysis was conducted. The two groups were similar for age, sex, height, weight, body surface area, and blood components at baseline. There were no differences between the Affinity NT and Optima XP for any outcome measure, although a significant change with time was seen in platelets, hemoglobin, hematocrit and leukocytes, as well as O2 transfer for both groups (p < 0.001). The Affinity NT oxygenator had a significantly lower difference in pressure across the membrane (p < 0.001) compared with the Optima XP. In conclusion, the two oxygenators performed similarly with respect to their impact on blood components, O2 transfer, and blood loss postoperatively during OHS with CPB. The Affinity NT had the smaller transmembrane pressure drop of the two.