Influence of preoperative renal dysfunction on one-year bypass graft patency and two-year outcomes in patients undergoing coronary artery bypass surgery

Cardiac surgery-associated acute kidney injury

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a well-recognized complication resulting with the higher morbid-mortality after cardiac surgery. In its most severe form, it increases the odds ratio of operative mortality 3-8-fold, length of stay in the Intensive Care Unit and hospital, and costs of care. Early diagnosis is critical for an optimal treatment of this complication. Just as the identification and correction of preoperative risk factors, the use of prophylactic measures during and after surgery to optimize renal function is essential to improve postoperative morbidity and mortality of these patients. Cardiopulmonary bypass produces an increased in tubular damage markers. Their measurement may be the most sensitive means of early detection of AKI because serum creatinine changes occur 48 h to 7 days after the original insult. Tissue inhibitor of metalloproteinase-2 and insulin-like growth factor-binding protein 7 are most promising as an early diagnostic tool. However, the ideal noninvasive, specific, sensitive, reproducible biomarker for the detection of AKI within 24 h is still not found. This article provides a review of the different perspectives of the CSA-AKI, including pathogenesis, risk factors, diagnosis, biomarkers, classification, postoperative management, and treatment. We searched the electronic databases, MEDLINE, PubMed, EMBASE using search terms relevant including pathogenesis, risk factors, diagnosis, biomarkers, classification, postoperative management, and treatment, in order to provide an exhaustive review of the different perspectives of the CSA-AKI.

Impact of renal function in patients with multi-vessel coronary disease on long-term mortality following coronary artery bypass grafting compared with percutaneous coronary intervention

BACKGROUND

Comorbidities, such as diabetes, affect revascularization strategy for coronary disease. We sought to determine if the degree of renal impairment affected long-term mortality after percutaneous coronary intervention (PCI) compared to coronary artery bypass grafting (CABG) in patients with multi-vessel coronary disease (MVD).

METHODS AND RESULTS

8970 patients with MVD undergoing revascularization between 2004 and 2008, in two multi-center parallel PCI and CABG Australian registries were assigned to three groups based on their estimated glomerular filtration rate (eGFR)≥60 mL/min/1.73 m2 (n=1678:839), 30-59 mL/min/1.73 m2 (n=452:226) and <30 mL/min/1.73 m2 (n=74:37). We used 2:1 propensity matching to compare 3306 patients undergoing primary CABG versus PCI. Shock, myocardial infarction (MI)<24 h, previous CABG, valve surgery or PCI were exclusions. Long-term mortality (mean 3.1 years) was compared with Cox-proportional hazard-adjusted modeling. Observed long-term mortality rates (CABG vs. PCI) were 4.5% vs. 4.3% p=0.84, 12.8% vs. 17.3% p=0.12, and 23.0% vs. 40.5% p=0.05 in the three strata, respectively. In patients with eGFR≥60 mL/min/1.73 m2, long-term mortality between PCI and CABG (HR 0.99, 95% CI 0.65-1.49, p=0.95) was similar. However, amongst patients with eGFR 30-59 mL/min/1.73 m2, there was a significant mortality hazard with PCI (HR 2.00, 95% CI 1.32-3.04, p=0.001). In patients with eGFR<30 mL/min/1.73 m2, there was a trend for hazard with PCI (HR 1.66, 95% CI 0.80-3.46, p=0.17).

CONCLUSION

Long-term mortality in MVD patients with preserved renal function was very low and similar between PCI and CABG. However there was a long-term mortality hazard associated with PCI amongst patients with moderate renal impairment.

Duration and magnitude of blood pressure below cerebral autoregulation threshold during cardiopulmonary bypass is associated with major morbidity and operative mortality

OBJECTIVES

Optimizing blood pressure using near-infrared spectroscopy monitoring has been suggested to ensure organ perfusion during cardiac surgery. Near-infrared spectroscopy is a reliable surrogate for cerebral blood flow in clinical cerebral autoregulation monitoring and might provide an earlier warning of malperfusion than indicators of cerebral ischemia. We hypothesized that blood pressure below the limits of cerebral autoregulation during cardiopulmonary bypass would be associated with major morbidity and operative mortality after cardiac surgery.

METHODS

Autoregulation was monitored during cardiopulmonary bypass in 450 patients undergoing coronary artery bypass grafting and/or valve surgery. A continuous, moving Pearson's correlation coefficient was calculated between the arterial pressure and low-frequency near-infrared spectroscopy signals and displayed continuously during surgery using a laptop computer. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was compared between patients with and without major morbidity (eg, stroke, renal failure, mechanical lung ventilation >48 hours, inotrope use >24 hours, or intra-aortic balloon pump insertion) or operative mortality.

RESULTS

Of the 450 patients, 83 experienced major morbidity or operative mortality. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was independently associated with major morbidity or operative mortality after cardiac surgery (odds ratio, 1.36; 95% confidence interval, 1.08-1.71; P = .008).

CONCLUSIONS

Blood pressure management during cardiopulmonary bypass using physiologic endpoints such as cerebral autoregulation monitoring might provide a method of optimizing organ perfusion and improving patient outcomes from cardiac surgery.

Saphenous vein graft failure and clinical outcomes: toward a surrogate end point in patients following coronary artery bypass surgery?

Saphenous vein graft (SVG) failure is a common finding in patients following coronary artery bypass graft (CABG) surgery. In the literature SVG failure rates have been reported from 25 to over 50% within 10 years. Although common, it remains unclear to what extent SVG failure affects clinical outcome, due to differences in definition, patient selection and follow-up. Particularly the lack of agreement on a universal definition makes comparisons between studies, and therefore generalizability of associations with outcomes, challenging. We suggest using a definition of SVG failure that is based on imaging as well as clinical parameters, that includes reporting SVG failure on both graft and patient level. The use of non-invasive imaging may help improve follow-up rates, and provide a more accurate picture of the real incidence and clinical impact of SVG failure. Given the lack of supportive evidence showing a consistent association between SVG failure and major adverse cardiovascular events, SVG failure should not be considered a valid surrogate endpoint at this time.

Contribution of deletion in angiotensin-converting enzyme but not A1166C angiotensin II type-1 receptor gene polymorphisms to clinical outcomes in atherothrombotic disease

BACKGROUND AND AIMS

Angiotensin-converting enzyme insertion/deletion (rs4340) and angiotensin II type 1 receptor A1166C (rs5186) gene polymorphisms may be involved in coronary heart disease (CHD). This study was designed to evaluate potential relationships between these polymorphisms and the risk of long-term all-cause mortality and major adverse cardiovascular events (MACE) in patients requiring revascularization for atherothrombotic disease (ATD) lesions.

METHOD

This prospective observational study concerned patients referred for supra-aortic vessel disease (SVD), CHD, peripheral artery occlusive disease (PAOD) or visceral artery disease (VAD). Collected data included ATD referral site, ATD symptoms, personal and familial medical histories, ATD extent, vascular risk factors, biological values, medication use and rs4340 and rs5186 polymorphisms. The primary end point was all-cause mortality. The secondary end point, MACE, included cardiovascular death, clinical ischemic event related to SVD, CHD, PAOD or VAD.

RESULTS

The cohort comprised 956 patients of whom 872 (91.2%) were genotyped and followed for 21.1 ± 9.9 months. Patients were referred for SVD (25.9%), CHD (42.3%), PAOD (35.2%) or VAD (1.6%). All-cause mortality and MACE rates were 7.6 and 27.2%, respectively. When comparing I/D + D/D vs. I/I genotypes, rs4340 polymorphism was associated with higher all-cause mortality rates according to uni- and multivariate analyses (p=0.008 and 0.011, respectively). Other differences were not significant (rs4340 polymorphism and MACE, rs5186 polymorphism and all-cause mortality and MACE). No interaction was found between the polymorphisms. Other independent predictors of all-cause mortality included PAOD history, SVD history, body mass index <25 kg/m(2), HbA(1c) ≥6.5%, absence of dyslipidemia and no use of aspirin.

CONCLUSION

rs4340 polymorphism is associated with long-term all-cause mortality in advanced ATD patients requiring revascularization, whereas rs5186 polymorphism does not.

Impact of recovery of renal function on long-term mortality after coronary artery bypass grafting

Whether prognosis differs in acute renal failure (ARF) after coronary artery bypass grafting (CABG) in patients with and without recovery of renal function is not known. We studied patients who had CABG at Duke University Medical Center (1995 to 2008). ARF was defined as an increase in peak creatinine ≥50% after CABG or ≥0.7 mg/dl above baseline or need for new dialysis. Patients were categorized into 3 groups: (1) no ARF after CABG, (2) ARF after CABG and completely recovered renal function at day 7 (return of creatinine to no higher than baseline and no dialysis), or (3) ARF after CABG with no recovery of renal function at day 7 (creatinine no higher than baseline or new dialysis). Main outcome measurement was risk-adjusted long-term mortality (excluding death ≤7 days). ARF after CABG occurred in 2,083 of 10,415 patients (20%) and completely recovered in 703 (33.7%). Risk-adjusted mortality was highest in patients with ARF without recovery of renal function (hazard ratios 1.47, 95% confidence interval 1.34 to 1.62) and intermediate in those with ARF but completely recovered renal function (hazard ratios 1.21, 95% confidence interval 1.07 to 1.37, referent no-ARF group). Mortality was lower in patients with ARF compared to those without complete recovery of renal function (p = 0.0083). In conclusion, in patients with ARF after CABG, complete recovery of renal function was associated with significantly lower long-term mortality compared to those without such recovery, although this was significantly higher than in those without ARF. Thus, major emphasis should be on prevention of ARF in patients undergoing CABG.

Selective endothelin-1 receptor type A inhibition in subjects undergoing cardiac surgery with preexisting left ventricular dysfunction: Influence on early postoperative hemodynamics

OBJECTIVE

A robust release of endothelin-1 with subsequent endothelin-A subtype receptor activation occurs in patients after cardiac surgery requiring cardiopulmonary bypass. Increased endothelin-A subtype receptor activation has been identified in patients with poor left ventricular function (reduced ejection fraction). Accordingly, this study tested the hypothesis that a selective endothelin-A subtype receptor antagonist administered perioperatively would favorably affect post-cardiopulmonary bypass hemodynamic profiles in patients with a preexisting poor left ventricular ejection fraction.

METHODS

Patients (n = 29; 66 +/- 2 years) with a reduced left ventricular ejection fraction (37% +/- 2%) were prospectively randomized in a blinded fashion, at the time of elective coronary revascularization or valve replacement requiring cardiopulmonary bypass, to infusion of the highly selective and potent endothelin-A subtype receptor antagonist sitaxsentan at 1 or 2 mg/kg (intravenous bolus; n = 9, 10 respectively) or vehicle (saline; n = 10). Infusion of the endothelin-A subtype receptor antagonist/vehicle was performed immediately before separation from cardiopulmonary bypass and again at 12 hours after cardiopulmonary bypass. Endothelin and hemodynamic measurements were performed at baseline, at separation from cardiopulmonary bypass (time 0), and at 0.5, 6, 12, and 24 hours after cardiopulmonary bypass.

RESULTS

Baseline plasma endothelin (4.0 +/- 0.3 fmol/mL) was identical across all 3 groups, but when compared with preoperative values, baseline values obtained from age-matched subjects with a normal left ventricular ejection fraction (n = 37; left ventricular ejection fraction > 50%) were significantly increased (2.9 +/- 0.2 fmol/mL, P < .05). Baseline systemic (1358 +/- 83 dynes/sec/cm(-5)) and pulmonary (180 +/- 23 dynes/sec/cm(-5)) vascular resistance were equivalent in all 3 groups. As a function of time 0, systemic vascular resistance changed in an equivalent fashion in the post-cardiopulmonary bypass period, but a significant endothelin-A subtype receptor antagonist effect was observed for pulmonary vascular resistance (analysis of variance; P < .05). For example, at 24 hours post-cardiopulmonary bypass, pulmonary vascular resistance increased by 40 dynes/sec/cm(-5) in the vehicle group but directionally decreased by more than 40 dynes/sec/cm(-5) in the 2 mg/kg endothelin-A subtype receptor antagonist group (P < .05). Total adverse events were equivalently distributed across the endothelin-A subtype receptor antagonist/placebo groups.

CONCLUSION

These unique findings demonstrated that infusion of an endothelin-A subtype receptor antagonist in high-risk patients undergoing cardiac surgery was not associated with significant hemodynamic compromise. Moreover, the endothelin-A subtype receptor antagonist favorably affected pulmonary vascular resistance in the early postoperative period. Thus, the endothelin-A subtype receptor serves as a potential pharmacologic target for improving outcomes after cardiac surgery in patients with compromised left ventricular function.

Minimized extracorporeal circulation cannot prevent acute kidney injury but attenuates early renal dysfunction after coronary bypass grafting

We studied the impact of minimized extracorporeal circulation (MECC) on acute kidney injury (AKI) after coronary bypass grafting. A retrospective, observational study with 1,685 patients with MECC and 3,046 patients with conventional bypass was done. Primary outcome was AKI defined as a decline > or = 50% in estimated glomerular filtration rate (eGFR) within 48 hours after surgery. Secondary outcome was temporary dialysis. MECC exerts beneficial hemodynamic effects but does not prevent AKI. Fewer patients developed a decline in eGFR <60 mL/min/1.73 m(2) (MECC) compared with conventional extracorporeal circulation (ECC) (30.7% versus 45.5%, p < 0.001). The incidence of eGFR decrease by > or = 50% did not differ (1.8% versus 2.7%, p = 0.20). Temporary dialysis was required in 61 patients with ECC (2%) and in 16 patients with MECC (0.9%, p < 0.001). A preoperative eGFR <60 mL/min/1.73 m(2) increased in both groups the risk for mortality compared with patients with an eGFR >60 mL/min/1.73 m(2) (ECC: odds ratio 3.6, 95% confidence interval 2.6-4.9; MECC: odds ratio 4.9, 95% confidence interval 2.8-8.6). MECC is renoprotective in the early postoperative period but cannot prevent AKI. An impaired preoperative eGFR increases the risk for mortality irrespective of the cardiopulmonary bypass system used.