Brian F. Buxton

Patencies of 2,127 arterial to coronary conduits over 15 years

Abstract Background Use of arterial grafts in coronary surgery is based on the excellent patency of the left internal thoracic artery (LITA) and an expectation that other arterial grafts—right internal thoracic artery (RITA) and radial artery (RA)—will give similar patencies, superior to saphenous vein. We examined patencies of arterial grafts in a practice with extensive use for more than 15 years. Methods Consecutive postoperative angiograms of 2,127 arterial/coronary conduits were evaluated. Angiograms were performed for cardiac symptoms. Assessment was by two observers. String signs were considered as occlusions. Results There were 2,127 arterial conduits. Overall patencies were as follows: LITA, 96.4% (1,296 of 1,345); RITA, 88.3% (534 of 605); aortocoronary RA, 89.3% (158 of 177). The LITA patency to the left anterior descending artery was 97.1% (1,131 of 1,165); to the obtuse marginal artery it was 91.7% (165 of 180; p 0.01). The RITA pedicled graft patency was 86% (275 of 321) compared with free RITA, 91% (259 of 284; p = not significant). For RITA there was a hierarchy of patency for coronary territory grafted (left anterior descending artery best, right coronary/posterior descending artery worst) and for degree of coronary stenosis: if stenosis was less than 60%, patency was 65% (47 of 72); if stenosis was more than 60%, patency was 90.9% (485 of 533; p = 0.0001). Similarly for the radial artery there was higher patency with greater coronary stenosis. The LITA patency at 5 years was 98%, at 10 years it was 95%, and at 15 years it was 88%. The RITA patency at 5 years was 96%, at 10 years it was 81%, and at 15 years it was 65%. The radial artery patency at 1 year was 96% and at 4 years it was 89%. For 3,714 vein grafts also studied overall patency was 61% (2,266 of 3,214) with patencies of 95% at 5 years, 71% at 10 years, and 32% at 15 years. Conclusions Excellent long-term patencies of arterial grafts are noted, superior to those of vein grafts. Patencies were influenced by conduit, by distribution, and by coronary artery stenosis.

Sodium bicarbonate to prevent increases in serum creatinine after cardiac surgery: a pilot double-blind, randomized controlled trial

Objective:To test whether perioperative sodium bicarbonate infusion can attenuate postoperative increases in serum creatinine in cardiac surgical patients. Design:Double-blind, randomized controlled trial. Setting:Operating rooms and intensive care unit at a tertiary hospital. Patients:Cohort of 100 cardiac surgical patients at increased risk of postoperative acute renal dysfunction. Intervention:Patients were randomized to either 24 hrs of intravenous infusion of sodium bicarbonate (4 mmol/kg) or sodium chloride (4 mmol/kg). Measurements and Main Results:The primary outcome measure was the proportion of patients developing acute renal dysfunction defined as a postoperative increase in plasma creatinine concentration >25% of baseline within the first five postoperative days. Secondary outcomes included changes in plasma creatinine, plasma urea, urinary neutrophil gelatinase-associated lipocalin, and urinary neutrophil gelatinase-associated lipocalin/urinary creatinine ratio. Patients were well balanced for baseline characteristics. Sodium bicarbonate infusion increased plasma bicarbonate concentration (p < 0.001), base excess (p < 0.001), plasma pH (p < 0.001), and urine pH (p < 0.001). Fewer patients in the sodium bicarbonate group (16 of 50) developed a postoperative increase in serum creatinine compared with control (26 of 50) (odds ratio 0.43 [95% confidence interval 0.19–0.98]), (p = 0.043). The increase in plasma creatinine, plasma urea, urinary neutrophil gelatinase-associated lipocalin, and urinary neutrophil gelatinase-associated lipocalin/urinary creatinine ratio was less in patients receiving sodium bicarbonate, (p = 0.014; p = 0.047; p = 0.009; p = 0.004). There were no significant side effects. Conclusions:Sodium bicarbonate loading and continuous infusion was associated with a lower incidence of acute renal dysfunction in cardiac surgical patients undergoing cardiopulmonary bypass. The findings of this pilot study justify further investigation. (ClinicalTrials.gov, NCT00334191).

Radial artery patency and clinical outcomes: Five-year interim results of a randomized trial

OBJECTIVE This study was undertaken to compare elective angiographic patency and cardiac event-free survival of the radial artery graft with that of the free right internal thoracic artery or saphenous vein during a 10-year period after primary coronary artery bypass surgery. METHODS This prospective, randomized, single-center trial was conducted on two groups of patients undergoing primary coronary artery bypass surgery. In a younger group (group 1, n = 285, <70 years), the radial artery was compared with the free right internal thoracic artery. In an older group (group 2, n = 153, >/=70 years), the radial artery was compared with the saphenous vein. The trial conduit was grafted to the largest available coronary artery other than the left anterior descending coronary artery. Angiography was scheduled at intervals between 0 and 10 years according to a second random assignment. Patients were followed up at yearly intervals to assess clinical outcomes. Clinical outcomes were analyzed on an intent-to-treat basis during the 10-year follow-up with time-related analyses. This interim study reports angiographic and clinical outcome results during the first 5 years. RESULTS Graft patency estimates were as follows: 0.95 (95% confidence interval 0.85-0.99) in 39 radial arteries versus 1.0 in 29 right internal thoracic arteries (P =.4) in group 1, and 0.86 (95% confidence interval 0.67-0.99) in 24 radial arteries versus 0.95 (95% confidence interval 0.83-0.99) in 22 saphenous veins (P =.5) in group 2. Cardiac event-free survival estimates were as follows: 0.91 (95% confidence interval 0.76-0.99) for the radial artery versus 0.82 (95% confidence interval 0.63-0.99) for the right internal thoracic artery (P =.7) in group 1, and 0.84 (95% confidence interval 0.64-0.99) for the radial artery versus 0.89 (95% confidence interval 0.72-0.99) for the saphenous vein (P =.9) in group 2. CONCLUSION The 5-year interim results do not support the hypothesis that the radial artery has superior patency to or is associated with fewer clinical events than free right internal thoracic artery or saphenous vein grafts.

Long-Term Patency of 1108 Radial Arterial-Coronary Angiograms Over 10 Years

BACKGROUND To avoid late vein graft atheroma and failure, we have used arterial grafts extensively in coronary operations. The radial artery (RA) is the conduit of second choice. This study determined the long-term patency of the RA as a coronary graft. METHODS Two independent observers evaluated 1108 consecutive postoperative RA conduit angiograms performed between January 1997 and June 2007 for cardiac symptoms. Mean time to postoperative angiography was 48.3 months (range, 1 to 132 months). An RA graft was considered failed (nonpatent) if there was stenosis exceeding 60%, string sign, or occlusion. Patency was determined over time, by coronary territory grafted and by the degree of native coronary artery stenosis (NCAS). RESULTS At a mean of 48.3 months, 982 of the 1108 RA grafts (89%) were patent. RA patencies for the left anterior descending were 96% (24 of 25), diagonal/intermediate, 90% (121 of 135); circumflex marginal, 89% (499 of 561); right coronary, 83% (38 of 46); posterior descending, 89% (253 of 286); and left ventricular branch/posterolateral, 86% (47 of 55). Patency was 87.5% (56 of 64) for NCAS of less than 60% compared with 89% (926 of 1044; p = 0.89) for NCAS exceeding 60%. Of 318 RAs in place more than 5 years, 294 (92.5%) were patent, and for 107 RAs in place for more than 7 years, 99 were patent (92.5%). Patency was consistent through each year of the decade. Mechanisms of failure did not involve development of atherosclerosis. Patent RA grafts were smooth, with no angiographic evidence of atheroma. CONCLUSIONS Late patencies of RA grafts are excellent and justify continuing use of the RA in coronary operations.

The right internal thoracic artery: the forgotten conduit--5,766 patients and 991 angiograms.

BACKGROUND The right internal thoracic artery (RITA) is biologically identical to the left ITA, yet is rarely used in coronary artery bypass graft surgery (CABG). We examined the results and long-term patency of RITA grafts. METHODS Between 1986 and 2008, 991 consecutive RITA graft angiograms for postoperative cardiac symptoms were evaluated by two independent observers. Grafts were considered nonpatent if they had a greater than 80% stenosis, string sign, or total occlusion. Patency was examined over time by coronary territory, whether in situ or free RITA, and compared with other conduits. Clinical results were collected prospectively and by the National Death Index. RESULTS A total of 5,766 patients had a RITA graft as part of a bilateral ITA CABG procedure. Operative mortality was 1.1%; deep sternal infection 1.5%. Of 7,780 coronary conduits studied, 991 RITA conduits were examined; a mean of 100±60 months postoperatively (1 to 288 months). Overall ten-year RITA patency was 90%. The RITA graft patency to the left anterior descending artery (LAD; n=149) was 95% at 10 years and 90% at 15 years. Ten-year RITA patency to the circumflex marginal (Cx; n=436) was 91%, right coronary artery (n=199) was 84% (p<0.001), and posterior descending artery (n=207) was 86%. Ten-year RITA and LITA patencies to the LAD were identical (95% vs 96%) and to the Cx (91% vs 89%), respectively. In situ RITA (n=450) and free RITA (n=541) had similar ten-year patencies (89% vs 91%; p=0.44). The RITA patency was always better than the radial artery (p<0.01) and saphenous vein grafts (p<0.001). Atheromatous changes were not seen in the RITA angiograms. Ten-year survival of patients with RITA and LITA for triple-vessel coronary disease was 89%. CONCLUSIONS Late patencies of RITA are excellent, equivalent to the LITA for identical territories, always better than radial arteries and saphenous vein grafts, and remain free of atheroma. Use of RITA in addition to LITA is associated with excellent survival in triple-vessel coronary disease. More extensive use of the RITA in CABG is recommended.

Pharmacology of Coronary Artery Bypass Grafts

Spasm of arterial and venous graft conduits can occur both during harvesting and after the graft is connected. Attempts to overcome spasm during harvesting by probing or hydraulic distension can cause structural damage to the graft, which may impair short- and long-term patency. After a coronary artery bypass graft is connected, spasm can cause major problems with myocardial perfusion. To select the best pharmacologic agent to prevent or reverse vasoconstriction in a graft requires an understanding of the reactivity of that particular type of graft to vasoconstrictor and vasodilator agents. The pharmacologic reactivity of venous and arterial graft conduits has been documented through extensive studies of isolated vessels in the organ bath and of in situ grafts in the body. In this review we summarize the current state of knowledge of the reactivity of arterial and venous grafts to vasoconstrictor and vasodilator agents and describe the practical application of this knowledge in the operating room and in the postoperative period.

Pattern and significance of cerebral microemboli during coronary artery bypass grafting

BACKGROUND Strokes that occur during coronary artery bypass grafting are often caused by embolism. Intraoperative transcranial Doppler monitoring can detect cerebral microemboli. The aims of this study were to identify the pattern of microembolic phenomena during various stages of coronary artery bypass grafting, to verify whether numbers of high-intensity transient signals correlated with early neuropsychologic deficits, and to identify, using magnetic resonance imaging scans, whether radiologic evidence of cerebral infarction correlated with microembolic numbers during the bypass period. METHODS Forty-one consecutive patients undergoing coronary bypass grafting with transcranial Doppler monitoring were enrolled in this study. All had preoperative and postoperative magnetic resonance imaging brain scans. A subgroup of 32 patients were studied by comparing microembolic load and early neuropsychological outcomes. RESULTS Transcranial Doppler monitoring confirmed that most microemboli occurred during cardiopulmonary bypass. A significant early neuropsychological deficit after coronary artery bypass grafting did correspond to the total microembolic load during bypass (p = 0.008). However, patients with cerebral infarction on magnetic resonance imaging had significantly more microembolic signal during the preincision phases and not during the bypass period. CONCLUSIONS Microembolic load during bypass is associated with early neuropsychologic deficits. In contrast, patients who show evidence of strokes during coronary artery bypass grafting have a higher microembolic load during the preincision phase than those without cerebral infarction. Differing mechanisms may be responsible for these different outcomes.

Factors affecting saphenous vein graft patency: clinical and angiographic study in 1402 symptomatic patients operated on between 1977 and 1999

BACKGROUND The purpose of this study was to find the preoperative and intraoperative factors that affect vein graft patency. METHODS A total of 3715 graft angiograms in 1607 patients were studied for recurrence of angina. The preoperative patient characteristics and intraoperative variables were prospectively collected from patients who had primary coronary artery bypass grafting during the period from 1977 to 1999. A total of 1339 (83%) patients were male, with a mean age of 59 years. The mean period from operation to reangiogram was 99 months. The saphenous vein was grafted to the left anterior descending artery in 557 (15%), to the diagonal artery in 669 (18%), to the obtuse marginal artery in 1300 (35%), to the right coronary artery in 409 (11%), and to the posterior descending artery in 780 (21%) cases. Graft failure was defined as >or=80% stenosis. RESULTS During the course of the study, 2266 (61%) grafts were patent, and 1449 (39%) had failed. The patient variables that significantly reduced graft patency were a younger age (P <.001) and an ejection fraction <30% (P =.047). Operative variables associated with reduced graft patency were small coronary artery diameter (P <.001), large conduit diameter (P =.001), and the coronary artery grafted (lowest patency in the right coronary artery and maximum patency in the left anterior descending artery territory; P =.002). The interval from operation to repeat angiogram (P <.001, with 78% patent at 1 year, 78% at 5 years, 60% at 10 years, and 50% at 15 years) and the year in which the operation was performed (more recent operations had better patency; P <.001) significantly affected graft patency. CONCLUSIONS Saphenous vein graft patency improved over the course of the study. The best results were obtained in older patients with good left ventricular function. Large-caliber arteries on the left system, when grafted with a small-diameter vein, were associated with the best outcome.

Phase II, randomized, controlled trial of high-dose N-acetylcysteine in high-risk cardiac surgery patients

Objective:To assess the effect of high-dose N-acetylcysteine on renal function in cardiac surgery patients at higher risk of postoperative renal failure. Design:Multiblind, placebo-controlled, randomized, phase II clinical trial. Setting:Operating rooms and intensive care units of two tertiary referral hospitals. Patients:A total of 60 cardiac surgery patients at higher risk of postoperative renal failure. Interventions:Patients were allocated to either 24 hrs of high-dose N-acetylcysteine infusion (300 mg/kg body weight in 5% glucose, 1.7 L) or placebo (5% glucose, 1.7 L). Measurements and Main Results:The primary outcome measure was the absolute change in serum creatinine from baseline to peak value within the first five postoperative days. Secondary outcomes included the relative change in serum creatinine, peak serum creatinine level, serum cystatin C, and in urinary output. Further outcomes were needed for renal replacement therapy, length of ventilation, and length of stay in the intensive care unit and hospital. Randomization was successful and patients were well balanced for preoperative and intraoperative characteristics. There was no significant attenuation in the increase in serum creatinine from baseline to peak when comparing N-acetylcysteine with placebo (64.5 ± 91.2 and 38.0 ± 42.4 &mgr;mol/L, respectively; p = .15). Also, there was no attenuation in the increase in serum cystatin C from baseline to peak for N-acetylcysteine compared with placebo (0.45 ± 0.43 and 0.30 ± 0.33 mg/L, respectively; p = .40). Likewise, there was no evidence for differences in any other clinical outcome. Conclusions:In this phase II, randomized, controlled trial, high-dose N-acetylcysteine was no more effective than placebo in attenuating cardiopulmonary bypass–related acute renal failure in high-risk cardiac surgery patients.

Comparable patencies of the radial artery and right internal thoracic artery or saphenous vein beyond 5 years: results from the Radial Artery Patency and Clinical Outcomes trial.

OBJECTIVE To investigate the optimum conduit for coronary targets other than the left anterior descending artery, we evaluated long-term patencies and clinical outcomes of the radial artery, right internal thoracic artery, and saphenous vein through the Radial Artery Patency and Clinical Outcomes trial. METHODS As part of a 10-year prospective, randomized, single-center trial, patients undergoing primary coronary surgery were allocated to the radial artery (n = 198) or free right internal thoracic artery (n = 196) if aged less than 70 years (group 1), or radial artery (n = 113) or saphenous vein (n = 112) if aged at least 70 years (group 2). All patients received a left internal thoracic artery to the left anterior descending, and the randomized conduit was used to graft the second largest target. Protocol-directed angiography has been performed at randomly assigned intervals, weighted toward the end of the study period. Grafts are defined as failed if there was occlusion, string sign, or greater than 80% stenosis, independently reported by 3 assessors. Analysis is by intention to treat. RESULTS At mean follow up of 5.5 years, protocol angiography has been performed in groups 1 and 2 in 237 and 113 patients, respectively. There are no significant differences within each group in preoperative comorbidity, age, or urgency. Patencies were similar for either of the 2 conduits in each group (log rank analysis, P = .06 and P = .54, respectively). The differences in estimated 5-year patencies were 6.6% (radial minus right internal thoracic artery) in group 1 and 2.9% (radial minus saphenous vein graft) in group 2. CONCLUSION At mean 5-year angiography in largely asymptomatic patients, the selection of arterial or venous conduit for the second graft has not significantly affected patency. This finding offers surgeons, for now, enhanced flexibility in planning revascularization.