Is early anticoagulation with warfarin necessary after bioprosthetic aortic valve replacement?

OBJECTIVES

Freedom from anticoagulation is the principal advantage of bioprosthesis; however, the American Heart Association/American College of Cardiology and the American College of Chest Physicians guidelines recommend early anticoagulation with heparin, followed by warfarin for 3 months after bioprosthetic aortic valve replacement. We examined neurologic events within 90 days of bioprosthetic aortic valve replacement at our institution.

METHODS

Between 1993 and 2000, 1151 patients underwent bioprosthetic aortic valve replacement with (641) or without (510) associated coronary artery bypass. By surgeon preference, 624 had early postoperative anticoagulation (AC+) and 527 did not (AC-). In the AC- group, 410 patients (78%) received antiplatelet therapy. Groups were similar with respect to gender (female, 36% AC+ vs 40% AC-, P = .21), hypertension (64% AC+ vs 61%, P = .27), and prior stroke (7.6% AC+ vs 8.5% AC-, P = .54). The AC+ group was slightly younger than the AC- group (median, 76 years vs 78 years, P = .006).

RESULTS

Operative mortality was 4.1% with 43 (3.7%) cerebrovascular events within 90 days. Excluding 18 deficits apparent upon emergence from anesthesia, we found that postoperative cerebrovascular accident occurred in 2.4% of AC+ and 1.9% AC- patients. By multivariable analysis, the only predictor of operative mortality was hypertension ( P < .0001). Postoperative cerebrovascular accident was unrelated to warfarin use ( P = .32). The incidence of mediastinal bleeding requiring reexploration was similar (5.0% vs 7.4%), as were other bleeding complications in the first 90 days (1.1% vs 0.8%). No variables were predictive of bleeding by multivariate analysis.

CONCLUSIONS

Although these data do not address the role of antiplatelet agents, early anticoagulation with warfarin after bioprosthetic aortic valve replacement did not appear to protect against neurologic events.

Effectiveness of the Cobra aortic catheter for dual-temperature management during adult cardiac surgery

OBJECTIVES

In animals the Cardeon Cobra catheter (Cardeon Corp, Cupertino, Calif) allows independent control of aortic arch and descending aortic temperatures and profoundly reduces cerebral embolization during bypass. This investigation describes the first clinical use of the device during adult cardiac surgery. The purpose of the study was to confirm that the Cobra catheter delivers adequate cerebral and systemic perfusion while providing simultaneous cerebral hypothermia and systemic normothermia during cardiopulmonary bypass.

METHODS

In a prospective multicenter study the Cobra aortic catheter was placed in 20 adults undergoing cardiopulmonary bypass. Arch and corporeal temperatures, bypass flows, and arterial blood pressures were recorded intraoperatively. Jugular bulb and mixed venous oxygen saturation was used to assess the adequacy of cerebral and systemic perfusion.

RESULTS

Surgeons at 3 institutions placed the Cobra catheter in patients undergoing coronary artery bypass grafting (n = 13), valve (n = 3), and combined valve-bypass (n = 4) operations. Mean total bypass flows of 2.1 +/- 0.2 L x min(-1) x m(-2) maintained mean arterial pressures in arch and descending aortic circulations of greater than 55 mm Hg. A mean differential of 4.3 degrees C between arch and descending aortic temperatures was established before crossclamp application, and a mean maximum temperature differential of 7 degrees C was established during bypass. A 2.4 degrees C temperature differential was maintained at crossclamp removal. Cerebral and systemic venous oxygen saturation remained greater than 65% during bypass.

CONCLUSIONS

The Cobra device met all expectations for an arterial cannula with adequate perfusion to the arch and corporeal circulations. Dual perfusion with the Cobra catheter allows for independent temperature control during cardiopulmonary bypass with simultaneous cerebral hypothermia and systemic normothermia.

Cell proliferation in carcinoid valve disease: a mechanism for serotonin effects

BACKGROUND AND AIM OF THE STUDY

Elevated serum serotonin is associated with carcinoid heart disease, the hallmark of which is valvular thickening. Yet, the mechanistic role of serotonin in carcinoid heart disease is poorly understood. We postulated that serotonin has a direct mitogenic effect on cardiac valvular subendocardial cells, and that this effect is mediated by serotonin receptors.

METHODS

The dose-dependent proliferative effects of serotonin (10(-8) to 10(-4)M) on cultured porcine aortic valve cells via a [3H]thymidine assay were determined in vitro. Serotonin receptor antagonist studies in culture were also performed using methiotepin, a 5HT1b antagonist, and ketanserin, a 5HT2 receptor antagonist, to determine the mechanism of serotonin action. The ex-vivo proliferation level in human carcinoid (n = 26) and normal valves (n = 10) was compared using proliferating cell nuclear antigen (PCNA) staining, a marker for proliferation. Identification and localization of specific 5HT receptor was assessed by immunostaining for serotonin receptors in the valves.

RESULTS

Serotonin increased valvular proliferation in vitro in a dose-dependent manner (10-fold increase) (p <0.001), and this mitogenic effect was inhibited by methiotepin but not ketanserin. In human carcinoid heart valves the level of proliferation was 35-fold higher than in normal human valves (p <0.001). 5HT1b receptors were found only in the carcinoid valves, and not in the normal valves.

CONCLUSION

Serotonin is a powerful mitogen for valvular subendocardial cells. The mitogenic effect is at least partly mediated via 5HT1b receptors. Subendothelial cell proliferation is significantly elevated in human carcinoid valves in vivo. The data suggest a mechanism whereby serotonin may contribute to valvular proliferation in carcinoid heart disease.

Operation for anorexigen-associated valvular heart disease

OBJECTIVES

Recently, valvular regurgitation has been observed in patients who have taken fenfluramine or dexfenfluramine with or without phentermine. This study describes the clinical, echocardiographic, and pathologic findings of anorexigen-associated valvular heart disease and the surgical interventions required to treat it.

METHODS

We reviewed clinical information on 14 patients with severe anorexigen-associated valvular disease who underwent cardiac operations.

RESULTS

Thirteen women (mean age 44.2 +/- 5.3 years) received fenfluramine, 58.5 +/- 22.3 mg/day, and phentermine, 32.1 +/- 11.4 mg/day, for an average of 12.1 +/- 7.3 months before presentation. One woman received dexfenfluramine, 30 mg/day for 13 months, and phentermine, 60 mg/day, concomitantly for 6 months. Presenting symptoms included dyspnea (12 cases), palpitations (3), and atypical chest pain (3). Six patients had heart failure, and 4 had a new murmur. Echocardiography demonstrated severe mitral valve regurgitation in all patients. Seven also had aortic regurgitation, and 4 had significant tricuspid regurgitation. Four patients had successful mitral valve repair, 1 with concomitant aortic valve repair. Ten additional patients eventually required mitral valve replacement, 5 with concomitant aortic valve replacement. Excised valves demonstrated a glistening white appearance with plaque-like encasement of leaflets and chordae. Focal surface proliferation and fibrosis with a "stuck-on" appearance was consistently found.

CONCLUSIONS

Anorexigen use may lead to severe multivalvular regurgitation with characteristic echocardiographic and pathologic findings. Recognition of drug-induced valvulopathy is important because of widespread use of these medications and the uncertain natural history of the disease. Early surgical experience suggests that valve repair is possible in these young patients.

Biocompatibility of Trillium Biopassive Surface-coated oxygenator versus uncoated oxygenator during cardiopulmonary bypass

OBJECTIVE

To determine if the Trillium Biopassive Surface (Medtronic Cardiopulmonary, Minneapolis, MN) coating added to the cardiopulmonary bypass oxygenator reduces inflammatory mediators, blood loss, and transfusion requirements.

DESIGN

Prospective, randomized, and blinded human trial.

SETTING

Tertiary care academic medical center.

PARTICIPANTS

Thirty adult patients undergoing elective coronary artery bypass graft surgery.

INTERVENTIONS

Patients received visually identical coated or uncoated oxygenators.

MEASUREMENTS AND MAIN RESULTS

Hemoglobin, hematocrit, leukocyte count, platelet count, terminal complement complex, complement activation, myeloperoxidase, beta-thromboglobulin, prothrombin fragment 1.2, plasmin-antiplasmin, heparin concentration, activated coagulation time, and fibrinogen concentration were measured. Blood loss and blood product usage were recorded. In both groups, there were significant inflammatory alterations with the initiation of cardiopulmonary bypass. In the postprotamine samples, the coated oxygenator group had small but significant increases in hemoglobin, hematocrit, and leukocyte count. There were no differences in inflammatory mediators, blood loss, or transfusion requirements between the coated and uncoated groups.

CONCLUSION

This human trial of Trillium Biopassive Surface-coated oxygenators did not show clinical benefits or clinically important biochemical results.

Carbon dioxide management and the cerebral response to hemodilution during hypothermic cardiopulmonary bypass in dogs

BACKGROUND

Increases in blood flow support oxygen (O2) delivery with hemodilution. However, with alpha-stat management, the cerebral response to hemodilution is blunted. We tested the hypothesis that carbon dioxide (CO2) management is a primary determinant of the cerebral blood flow (CBF) response to hemodilution during hypothermic bypass.

METHODS

Following Animal Care Committee approval, 15 dogs underwent bypass at 18 degrees C (pH-stat, n = 7 or alpha-stat, n = 8). Measurements were obtained after progressive hemodilution, and cerebral blood flow was determined by sagittal sinus outflow. Arterial pressure was maintained at 60 to 70 mm Hg. The CBF response to hemodilution and cerebral metabolic rate were compared in the two groups of animals.

RESULTS

In both groups, hemodilution increased CBF. At every hematocrit, CBF and O2 delivery in the pH-stat group exceeded that of alpha-stat group, although O2 demand did not differ between groups. While absolute CBF in the pH-stat group was greater at every hematocrit, the relative change in CBF from control and the slope of the CBF-Hct relationship did not differ between groups.

CONCLUSIONS

pH-stat management is associated with a greater absolute CBF and a greater ratio of cerebral O2 supply to demand for any degree of hemodilution. However, over the range of hematocrits common in practice, CO2 management per se does not determine the cerebral response to hemodilution.

Very long-term survival and durability of mitral valve repair for mitral valve prolapse

BACKGROUND

Mitral regurgitation (MR) due to mitral valve prolapse (MVP) is often treatable by surgical repair. However, the very long-term (>10-year) durability of repair in both anterior leaflet prolapse (AL-MVP) and posterior leaflet prolapse (PL-MVP) is unknown.

METHODS AND RESULTS

In 917 patients (aged 65+/-13 years, 68% male), surgical correction of severe isolated MR due to MVP (679 repairs and 238 replacements [MVRs]) was performed between 1980 and 1995. Survival after repair was better than survival after MVR for both PL-MVP (at 15 years, 41+/-5% versus 31+/-6%, respectively; P=0.0003) and AL-MVP (at 14 years, 42+/-8% versus 31+/-5%, respectively; P=0.003). In multivariate analysis adjusting for predictors of survival, repair was independently associated with lower mortality in PL-MVP (adjusted risk ratio [RR] 0.61, 95% CI 0.44 to 0.85; P=0.0034) and in AL-MVP (adjusted RR 0.67, 95% CI 0.47 to 0.96; P=0.028). The reoperation rate was not different after repair or MVR overall (at 19 years, 20+/-5% for repair versus 23+/-5% for MVR; P=0.4) or separately in PL-MVP (P=0.3) or AL-MVP (P=0.3). However, the reoperation rate was higher after repair of AL-MVP than after repair of PL-MVP (at 15 years, 28+/-7% versus 11+/-3%, respectively; P=0.0006). From the 1980s to the 1990s, the RR of reoperation after repair of AL-MVP versus PL-MVP did not change (RR 2.5 versus 2.7, respectively; P=0.58), but the absolute rate of reoperation decreased similarly in PL-MVP and AL-MVP (at 10 years, from 10+/-3% to 5+/-2% and from 24+/-6% to 10+/-2%, respectively; P=0.04).

CONCLUSIONS

In severe MR due to MVP, mitral valve repair compared with MVR provides improved very long-term survival after surgery for both AL-MVP and PL-MVP. Reoperation is similarly required after repair or replacement but is more frequent after repair of AL-MVP. Recent improvement in long-term durability of repair suggests that it should be the preferred mode of surgical correction of MVP whether it affects anterior or posterior leaflets and is an additional incentive for early surgery of severe MR due to MVP.

Posterior pericardial ascending-to-descending aortic bypass: an alternative surgical approach for complex coarctation of the aorta

BACKGROUND

Coarctation of the aorta is commonly associated with recoarctation or additional cardiovascular disorders that require intervention. The best surgical approach in such patients is uncertain. Ascending-to-descending aortic bypass graft via the posterior pericardium (CoA bypass) allows simultaneous intracardiac repair or an alternative approach for the patient with complex coarctation.

METHODS AND RESULTS

Between 1985 and 2000, 18 patients (13 males and 5 females, mean age 43+/-13 years) with coarctation of the aorta underwent CoA bypass through median sternotomy. Before operation, average New York Heart Association class was II (range I to IV), and 15 patients (83%) had systemic hypertension. One or more previous cardiovascular operations had been performed in 12 patients (67%); 10 patients had >/=1 prior coarctation repair. Two patients had prior noncoarctation cardiovascular surgery. Concomitant procedures performed in 14 patients (78%) included the following: aortic valve replacement in 9; coronary artery bypass surgery in 3; mitral valve repair in 2; and septal myectomy, mitral valve replacement, aortoplasty, subaortic stenosis resection, ventricular septal defect closure, and ascending aorta replacement in 1 patient each. All patients survived the operation and were alive with patent CoA bypass at a mean follow-up of 45 months. No graft-related complications occurred, and there were no instances of stroke or paraplegia. Systolic blood pressure fell from 159 mm Hg before surgery to 125 mm Hg after surgery.

CONCLUSIONS

CoA bypass via median sternotomy can be performed with low morbidity and mortality. Although management must be individualized, extra-anatomic CoA bypass via the posterior pericardium is an excellent single-stage approach for patients with complex coarctation or recoarctation and concomitant cardiovascular disorders.

Distribution and hierarchy of regional blood flow during hypothermic cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) may decrease oxygen delivery relative to the nonbypass state. We predicted that a hierarchy of regional blood flow could be characterized under hypothermic (27 degrees C) CPB.

METHODS

Ten pigs underwent bypass at 27 degrees C. Fluorescent microspheres were administered before and during CPB at four randomized flows: 1.9, 1.6, 1.3, and 1.0 L x min(-1) x m(-2). At completion, tissue samples were obtained from brain, renal cortex and medulla, pancreas, small bowel, and limb muscle for regional blood flow determination.

RESULTS

Cerebral blood flow remained unchanged between CPB flows of 1.9 and 1.3 L x min(-1) x m(-2). Renal perfusion was stable between flows of 1.9 and 1.6 L x min(-1) x m(-2), whereas perfusion of small bowel decreased linearly with pump flow. Pancreatic perfusion was unchanged over the range of flows studied; muscle blood flow was profoundly reduced at the highest CPB flow and further decreased if pump flow was reduced below 1.6 L x min(-1) x m(-2).

CONCLUSIONS

This study characterizes the organ-specific hierarchy of blood flow and oxygen distribution during hypothermic CPB. These dynamics are relevant to clinical decisions for perfusion management.

Valvular heart operation in patients with previous mediastinal radiation therapy

BACKGROUND

The outcome of valvular heart operations in patients with previous mediastinal radiation therapy was studied.

METHODS

This is a single center retrospective study of 60 patients (37 females, 23 males) with a mean age of 62 +/- 15 years (28 to 88 years old) operated on from January 1976 to December 1998. Valvular heart operations performed included aortic valve replacements (n = 26), mitral valve procedures (n = 16), tricuspid valve procedures (n = 6), and multiple valve procedures (n = 12). A total of 264 clinical, hemodynamic, electrocardiographic and echocardiographic variables were analyzed.

RESULTS

Total follow-up was 199 patient-years with a mean of 3.3 +/- 3.1 years and a range of 0 to 12.4 years old. Early mortality was 7 patients (12%). Early mortality in patients with constrictive pericarditis was 40% (4 of 10) compared with 6% (3 of 50) in patients without constrictive pericarditis. By univariate analysis, early mortality was associated with constrictive pericarditis (p = 0.011), reduced preoperative ejection fraction (p = 0.015), and longer cardiopulmonary bypass times (p = 0.037). A total of 14 patients (23%) required permanent pacemaker placement before (n = 7), during (n = 1), or early (n = 6) after valvular heart operations. There were 19 late deaths (malignancies, 7; heart failures, 5; other cardiac, 4; and other noncardiac, 3). Overall survival and freedom from late cardiac death and cardiac reoperation at 5 years for hospital survivors were 66% +/- 8%, 82% +/- 7%, and 93% +/- 4%, respectively. By univariate analysis, late cardiac death was associated with low ejection fraction (p = 0.002), New York Heart Association (NYHA) functional class IV (p = 0.004), preoperative congestive heart failure (p = 0.02), and preoperative atrial fibrillation (p = 0.038). Eighty-five percent of the discharged patients were in NYHA functional class I or II at follow-up.

CONCLUSIONS

Early results of valve replacement after mediastinal radiation therapy were good except in the presence of constrictive pericarditis. Long-term outcome was limited by malignancy and heart failure. Early surgical intervention is recommended before the development of risk factors for late death, namely, severe symptoms, left ventricular dysfunction, and atrial fibrillation.

Complicated mitral valve repairs

The standard of care for mitral regurgitation secondary to degenerative valvular disease is mitral valve repair whenever possible. Mitral valve repair is associated with better left ventricular function preservation, fewer complications, and improved survival as compared with mitral valve replacement. Most of the mitral valve pathology involves the posterior leaflet or annulus and usually can be repaired by using standard valve repair techniques. Difficulties may arise when trying to repair the somewhat uncommon anterior leaflet prolapse or calcified mitral annulus. This article reviews these more complex mitral valve repair techniques and their outcomes.

Reoperation for prosthetic aortic valve obstruction in the era of echocardiography: trends in diagnostic testing and comparison with surgical findings

OBJECTIVES

We sought to: 1) identify trends in the diagnostic testing of patients with prosthetic aortic valve (AVR) obstruction who undergo reoperation and 2) compare diagnostic test results with pathologic findings at surgery.

BACKGROUND

It is unclear whether Doppler transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) have reduced hemodynamic catheterization rates.

METHODS

We reviewed 92 consecutive cases ofAVR reoperation at a single center from 1989 to 1998, comparing 49 cases of mechanical AVR obstruction (group A) to 43 cases of bioprosthetic obstruction (group B). Preoperative Doppler TTE was performed in all cases.

RESULTS

In group A cases, there was a marginally significant trend towards lower catheterization rates for the Gorlin AVR area, from 36% in 1989 to 1990 to 10% in 1997 to 1998 (p = 0.07), but diagnostic TEE utilization (47% of cases) did not vary. The cause of mechanical AVR obstruction was pannus in 26 cases (53%), mismatch (P-PM) in 19 (39%) and thrombosis in 4 (8%). The mechanism (pannus/thrombus vs. mismatch) was identified in 10% by TTE and 49% by TEE (p < 0.001). In group B cases, hemodynamic catheterization rates (21%) and diagnostic TEE utilization (21%) did not vary with time. Obstruction was caused by structural degeneration in 37 cases (86%), thrombosis in 3 (7%), mismatch in 2 (5%) and pannus in 1 (2%). The mechanism was correctly identified in 63% by TTE and in 81% by TEE (p = 0.18).

CONCLUSIONS

Doppler TTE is the primary means to diagnose AVR obstruction; hemodynamic catheterization is not routinely needed. In unselected patients with mechanical AVR obstruction, TEE differentiation of pannus or thrombus from mismatch is challenging.

Outcome of reoperation for aortic valve prosthesis-patient mismatch

We report a single center's 10-year experience with 21 consecutive cases of repeat aortic valve replacement for prosthesis-patient mismatch (P-PM) in which there was no hospital mortality among 12 patients treated for isolated P-PM. With an overall survival of 92% at a median follow-up of 4.5 years and functional class I symptoms in most survivors (73%), we conclude that repeat surgery for isolated P-PM has a relatively low mortality and a good intermediate-term clinical outcome.

Hierarchy of regional oxygen delivery during cardiopulmonary bypass

BACKGROUND

Relative to the nonbypass state, cardiopulmonary bypass may decrease whole-body oxygen (O2) delivery. We predicted that during cardiopulmonary bypass, a hierarchy of regional blood flow and O2 delivery could be characterized.

METHODS

In 8 46.5 +/- 1.2-kg pigs, fluorescent microspheres were used to determine blood flow and O2 delivery to five organ beds before and during 37 degrees C cardiopulmonary bypass at four randomized bypass flows (1.4, 1.7, 2.0, and 2.3 L/min/m2). At completion, 18 tissue samples were obtained from the cerebral cortex (n = 4), renal cortex (n = 2), renal medulla (n = 2), pancreas (n = 3), small bowel (n = 3), and limb muscle (n = 4) for regional blood flow determination.

RESULTS

At conventional cardiopulmonary bypass flow (2.3 L/min/m2), whole-body O2 delivery was reduced by 44 +/- 6% relative to the pre-cardiopulmonary bypass state (p < 0.05). Over a range of cardiopulmonary bypass flows (2.3 to 1.7 L/min/m2), brain and kidney maintained their perfusion. Blood flow and O2 delivery to both regions were reduced when the cardiopulmonary bypass flow was reduced to 1.4 L/min/m2. However, perfusion and O2 delivery to other visceral organs (pancreas, small bowel) and skeletal muscle showed pump flow dependency over the range of flows tested.

CONCLUSIONS

This study characterizes the organ-specific hierarchy of blood flow and O2 distribution during cardiopulmonary bypass. These dynamics are relevant to clinical decisions for perfusion management.

Surgical treatment of valvular heart disease in patients with acromegaly

BACKGROUND AND AIM OF THE STUDY

Acromegaly is associated with heart disease in one-third of patients, and diastolic dysfunction may precede global systolic dysfunction. Patients with acromegalic heart disease may have valvular disease, but the role of surgery in such patients has not been established. The purpose of this study was to document the outcome of surgery in a series of these patients from one institution.

METHODS

Among 951 patients with the diagnosis of acromegaly seen at our institution since 1972, 10 (eight men, two women) have undergone operation for valvular heart disease. Average patient age was 62.2 +/- 11.5 years; average body weight was 84 +/- 13 kg; average height was 178 +/- 12 cm. The mean duration of acromegaly was 15.2 +/- 12.7 years. At the time of heart surgery, seven patients had active disease, defined by elevation of growth hormone levels, while three had inactive disease. Treatment of pituitary adenomas before valvular surgery included surgical resection in three patients and external-beam radiation treatment in four. The preoperative ejection fraction was 42 +/- 19% (range: 20% to 66%). Valve lesions included aortic stenosis in four patients, aortic regurgitation in four, and mitral regurgitation in three (one patient had double valve disease).

RESULTS

Valve replacement was performed in all patients with aortic disease (two bioprostheses, six mechanical), and three patients with mitral regurgitation had repair. Concomitant procedures performed in seven patients included coronary bypass (two), left ventricular aneurysmectomy (two), and ligation of the left atrial appendage, septal myectomy and defibrillator insertion (one each). Early complications included endocarditis, low cardiac output and arrhythmia in one patient each. There were no perioperative deaths. One patient underwent reoperation ten years later for a perivalvular leak.

CONCLUSION

Valvular surgery can be performed safely in acromegalic patients, even those with active endocrinopathy.

Posterior pericardial approach for ascending aorta-to-descending aorta bypass through a median sternotomy

BACKGROUND

Bypass grafting for repeat operation or complex forms of descending aortic disease is an alternative approach to decrease potential complications of anatomic repair.

METHODS

Between December 1985 and February 1998, 17 patients (13 men, 4 women; mean age, 47.6 +/- 18.5 years) underwent ascending aorta-to-descending aorta bypass through a median sternotomy and posterior pericardial approach. Indications for operation were coarctation or recoarctation of aorta in 8 patients, Takayasu's aortitis in 2, prosthetic aortic valve stenosis associated with coarctation of aorta, complex descending aortic arch aneurysm, reoperation for chronic descending aortic dissection, long-segment stenosis of descending aorta, acquired coarctation after repair of traumatic transection of descending aorta, severe aortic atherosclerosis, and false aneurysm of descending aorta after repair of coarctation in 1 patient each. Concomitant procedures were performed in 12 patients.

RESULTS

No early or late mortality has occurred. Follow-up was 100% complete and extended to 12 years (mean, 2.7 +/- 3.3 years). No late graft-related complications have occurred; 1 patient had successful repair of perivalvular leak after mitral valve replacement, and 1 patient had replacement of lower descending and abdominal aorta.

CONCLUSIONS

Exposure of the descending aorta through the posterior pericardium for ascending aorta-descending aorta bypass is a safe alternative and particularly useful when simultaneous intracardiac repair is necessary.

Predictors of mortality and mortality from cardiac causes in the bypass angioplasty revascularization investigation (BARI) randomized trial and registry. For the BARI Investigators

BACKGROUND

The impact of percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG) on long-term mortality rates in the presence of various demographic, clinical, and angiographic factors is uncertain in the population of patients suitable for both procedures.

METHODS AND RESULTS

In the Bypass Angioplasty Revascularization Investigation (BARI) randomized trial and registry, 3610 patients who were eligible to receive PTCA and CABG were revascularized between 1989 and 1992. Multivariate Cox models were used to identify factors associated with 5-year mortality and cardiac mortality, with particular attention to factors that interact with treatment. Diabetic patients receiving insulin had higher mortality and cardiac mortality rates with PTCA compared with CABG (relative risk [RR] 1.78 and 2.63, respectively, P<0.001), and patients with ST elevation had higher cardiac mortality rates with CABG than with PTCA (RR 4.08, P<0.001). Factors most strongly associated with high overall mortality rates were insulin-treated diabetes, congestive heart failure, kidney failure, and older age. Black race was also associated with higher mortality rates (RR 1.49, P=0.019).

CONCLUSIONS

A set of variables was identified that could be used to help select a revascularization procedure and to evaluate risk of long-term mortality in the population of patients considering revascularization.

Blood loss from coronary angiography increases transfusion requirements for coronary artery bypass graft surgery

OBJECTIVE

To determine the blood loss associated with coronary angiography and its impact on hemoglobin and transfusion requirements for subsequent coronary artery bypass graft (CABG) surgery.

DESIGN

Retrospective chart review.

SETTING

Tertiary-care, academic medical center.

PARTICIPANTS

A total of 506 adult patients undergoing coronary angiography and CABG surgery.

INTERVENTIONS

None (observational study).

MEASUREMENTS AND MAIN RESULTS

Coronary angiography was associated with a reduction in hemoglobin of 1.8 g/dL. This reduction in hemoglobin was a significant predictor of allogeneic red blood cell transfusion.

CONCLUSION

Coronary angiography contributes to a 1.8 g/dL reduction in hemoglobin concentration before CABG surgery and was associated with increased transfusion of allogeneic blood products. Measures aimed at maintaining red cell volume during coronary angiography, increasing erythropoiesis, or delaying surgery beyond 2 weeks may result in a decrease in transfusion requirements for patients undergoing CABG surgery.

Effect of cerebral embolization on regional autoregulation during cardiopulmonary bypass in dogs

BACKGROUND

Embolization during cardiopulmonary bypass probably alters cerebral autoregulation. Therefore, using laser Doppler flowmetry we investigated the cerebral blood flow velocity changes in response to changes in arterial pressure, before and after embolization in a canine bypass model.

METHODS

After Institutional Animal Care and Use Committee approval, 8 anesthetized dogs had a laser Doppler flow probe positioned over the temporoparietal dura. During 37 degrees C cardiopulmonary bypass, the cerebral blood flow velocity response to changing mean arterial pressure (40 to 85 mm Hg in random order) was assessed before and after systemic embolization of 100 mg of 97-microm latex microspheres.

RESULTS

Before embolization, cerebral blood flow velocity increased 39% as mean arterial pressure increased from 40 to 85 mm Hg. Following embolization, a 94% increase in cerebral blood flow velocity was demonstrated over the same mean arterial pressure range. The slopes of the curves relating cerebral blood flow velocity to mean arterial pressure were 0.21+/-0.74 and 1.31+/-0.87, before and after embolization (p = 0.016) respectively.

CONCLUSIONS

Regional cerebral blood flow autoregulation may be impaired by microembolization known to occur during cardiopulmonary bypass, increasing the dependence of cerebral blood flow on mean arterial pressure.

Comparison of blood-conservation strategies in cardiac surgery patients at high risk for bleeding

BACKGROUND

Aprotinin and tranexamic acid are routinely used to reduce bleeding in cardiac surgery. There is a large difference in agent price and perhaps in efficacy.

METHODS

In a prospective, randomized, partially blinded study, 168 cardiac surgery patients at high risk for bleeding received either a full-dose aprotinin infusion, tranexamic acid (10-mg/kg load, 1-mg x kg(-1) x h(-1) infusion), tranexamic acid with pre-cardiopulmonary bypass autologous whole-blood collection (12.5% blood volume) and reinfusion after cardiopulmonary bypass (combined therapy), or saline infusion (placebo group).

RESULTS

There were complete data in 160 patients. The aprotinin (n = 40) and combined therapy (n = 32) groups (data are median [range]) had similar reductions in blood loss in the first 4 h in the intensive care unit (225 [40-761] and 163 [25-760] ml, respectively; P = 0.014), erythrocyte transfusion requirements in the first 24 h in the intensive care unit (0 [0-3] and 0 [0-3] U, respectively; P = 0.004), and durations of time from end of cardiopulmonary bypass to discharge from the operating room (92 [57-215] and 94 [37, 186] min, respectively; P = 0.01) compared with the placebo group (n = 43). Ten patients in the combined therapy group (30.3%) required transfusion of the autologous blood during cardiopulmonary bypass for anemia.

CONCLUSIONS

The combination therapy of tranexamic acid and intraoperative autologous blood collection provided similar reduction in blood loss and transfusion requirements as aprotinin. Cost analyses revealed that combined therapy and tranexamic acid therapy were the least costly therapies.

Effect of temperature and PaCO2 on cerebral embolization during cardiopulmonary bypass in swine

BACKGROUND

Patients experience cerebral embolization during cardiopulmonary bypass (CPB). This study determined if alterations in temperature and/or PaCO2 can reduce cerebral and ocular embolization.

METHODS AND RESULTS

Forty-four pigs underwent CPB: 24 animals at 28 degrees C, and 20 at 38 degrees C. The two temperature groups were randomized to undergo embolization (67-microm fluorescent microspheres) at either hypercarbia or hypocarbia. Before and after embolization, cerebral and ocular blood flow were determined at normocarbia. Reducing temperature or PaCO2 reduced cerebral and ocular embolization. Hypocarbia reduced cerebral embolization by 60% and 45% in normothermic and hypothermic groups, respectively (p < 0.0001 and p < 0.05). Relative to normothermic animals, hypothermia reduced cerebral embolization by 37% under an elevated CO2 condition (p < 0.05), but not under hypocarbic conditions. Similarly, regardless of temperature, fewer emboli were delivered to the eye in hypocarbic animals (p < 0.05), but hypothermia did not reduce ocular embolization.

CONCLUSIONS

Cerebral embolization is determined by both temperature and PaCO2 at the time of embolization. In CPB practice, reductions in temperature and/or PaCO2 during periods of embolic risk may reduce brain injury.

Cox-Maze procedure for atrial fibrillation: Mayo Clinic experience

The Cox-Maze procedure corrects atrial fibrillation in 90% of patients, and successful operation restores sinus rhythm, thereby reducing risks of thromboembolism and anticoagulant-associated hemorrhage. Symptoms such as palpitation and fatigability also improve with restoration of atrioventricular synchrony. At the Mayo Clinic, 221 Cox-Maze procedures were performed from March 1993 through March 1999. Over 75% of patients had associated cardiac disease and concomitant operations. Overall, early mortality was 1.4%, and the incidence of postoperative pacemaker implantation was 3.2%. Limiting incisions to the right atrium simplifies the operation for patients who primarily have tricuspid valve disease, and in early follow-up, outcome appeared to be as good as that achieved with biatrial incisions. The Cox-Maze procedure has proved particularly useful for patients with preoperative atrial fibrillation who require valvuloplasty for acquired mitral valve regurgitation; 87 patients have had this combined procedure, and there have been no early deaths. Further, our experience indicates that ventricular dysfunction is not a contraindication for operation and that restoration of sinus rhythm after the Cox-Maze procedure improves left ventricular ejection fraction in most patients.

Repair of anterior leaflet mitral valve prolapse: chordal replacement versus chordal shortening

BACKGROUND

To determine the optimal method of repair for severe, segmental anterior leaflet prolapse, we analyzed outcome of 121 patients who underwent chordal shortening (n = 46) and chordal replacement (n = 75) from 1988 to 1996.

METHODS

Chordae were replaced with expanded polytetrafluoroethylene sutures. Patients had an annuloplasty with either chordal replacement or shortening. Follow-up was 100% complete (mean, 3.7 years).

RESULTS

Mean age was 62.1 years, 86 were men, and 60 patients had isolated valve repair. There was one hospital death and 14 late deaths for a 5-year actuarial survival of 86.4%+/-4.5%. Sixteen patients underwent reoperation, 5 in the replacement group and 11 in the shortening group. Mechanism of valve failure in the replacement group was native chordae rupture (n = 4) and neochordae dehiscence (n = 1). With chordal shortening, repair failure was attributed to rupture of shortened chordae (n = 8), leaflet prolapse with and without annuloplasty ring dehiscence (n = 2), and native chordae elongation (n = 1). Risk of reoperation because of repair failure at 3.5 years was 1.4% in the chordal replacement group and 14.8% in the chordal shortening group (p = 0.02).

CONCLUSIONS

Chordal replacement is superior to chordal shortening, providing a predictable method for correction of mitral regurgitation with a low incidence of reoperation.

Mitral valve replacement or repair after previous coronary artery bypass grafting

BACKGROUND

Patients who have had previous CABG may subsequently develop significant mitral valve (MV) dysfunction that requires surgical intervention.

METHODS AND RESULTS

We reviewed 80 consecutive patients who had had previous CABG and who underwent MV surgery between January 1972 and March 1997. Forty-seven (59%) had initial CABG elsewhere, and 5 had had previous CABG twice. The mean interval between the previous CABG and the MV surgery was 6.3 years (range, 4.4 months to -17 years). At least 15 patients had grade 1/4 to 2/4 mitral regurgitation at initial CABG. The study group included 59 men and 21 women, with a mean study group age of 65.5 years. Ninety-four percent had symptoms of congestive heart failure, 60% had angina, 96% were in NYHA class III to IV, and 37% had an ejection fraction (EF) <50%. Origin of the MV disease was ischemic in 33 patients, myxomatous in 19, combined ischemic and myxomatous in 16, rheumatic in 5, infective in 3, and unknown in 4. MV repair was performed in 46 patients (58%) and MV replacement (MVR) in 34. Concomitant repeat CABG was performed in 38 (48%) patients. In-hospital mortality was 7 of 80 (8.8%); no early death occurred among patients with myxomatous disease. EF <50% was the only significant predictor of early mortality. Overall 1-, 5-, and 10-year survival was 83.8%, 55.6%, and 34.4% respectively. Predictors of late cardiac death were preoperative NYHA class IV (P=0.0006), urgent or emergency operation (P<0.0001), use of intra-aortic balloon pump (P=0.002), and EF <50% (P=0.01). Seven patients had an additional reoperation: 4 received CABG, 2 MVR, and 2 MV repair.

CONCLUSIONS

Ischemic, myxomatous, rheumatic, or infective MV dysfunction may develop subsequently after CABG. MVR or MV repair after previous CABG is associated with an acceptably low operative risk and good relief of symptoms. Left ventricular function is strongly correlated with both hospital and late mortality. Surgery should be done before LV dysfunction develops.

The role of gene therapy for intimal hyperplasia of bypass grafts

BACKGROUND

Proliferation of the intima is an early lesion of saphenous vein graft disease. Early patency rates of radial artery grafts are acceptable, but little is known about their risk of intimal hyperplasia.

METHODS AND RESULTS

To develop a model of intimal hyperplasia, we incubated human saphenous veins, internal mammary arteries, and radial arteries (n=6, 8, and 10, respectively) in an organ culture with Roswell Park Memorial Institute 1640 (30% serum) for 0, 4, 7, 10, and 14 days. Quantitative histological studies were performed, and the average intimal-to-medial (I/M) ratio was calculated for each incubation interval. After 10 and 14 days of culture, the I/M ratio increased in the saphenous veins (P=0. 03, P=0.04 versus 0 day, respectively). No significant increase occurred in the I/M ratio in either the internal mammary or radial arteries. Next, the ability of adenoviral gene transfers to inhibit intimal hyperplasia in the saphenous veins was evaluated. Adenoviral-mediated gene transfer of nitric oxide synthase significantly reduced the I/M ratio at 14 days compared with vehicle (P=0.001) and virus (P=0.004) controls.

CONCLUSIONS

The human saphenous vein has a greater propensity for intimal hyperplasia than arterial grafts; the human radial artery behaves similarly to the internal mammary artery. In the future, gene therapy may augment nitric oxide synthase, limiting vein graft disease.

Surgical patent foramen ovale closure for prevention of paradoxical embolism-related cerebrovascular ischemic events

BACKGROUND

The role of surgical closure of patent foramen ovale (PFO) for cerebral infarction (CI) or transient ischemic attack (TIA) resulting from paradoxical embolism is unclear, and its effect on recurrence is unknown. Our objective was to determine the outcome of surgical closure of PFO in patients with a prior ischemic neurological event, define the rate of CI or TIA recurrence after PFO closure, and identify risk factors for these recurrences.

METHODS AND RESULTS

We retrospectively analyzed 91 patients (58 men, 33 women) with >/=1 previous cerebrovascular ischemic events who underwent surgical PFO closure between April 1982 and March 1998. The presence of a PFO with a right-to-left shunt was confirmed with transesophageal echocardiography. Mean age was 44.2+/-12.2 years. The index event was a CI in 59 and a TIA in 32; a Valsalva-like episode preceded the event in 15 patients. Deep venous thrombosis was documented in 9 patients, and a hypercoagulable state was identified in 10. Surgical closure was performed with extracorporeal circulation by either direct suture (n=82) or patch closure (n=9). Limited incisions were used in 18.7% of patients. There was no operative mortality. Morbidity included transient atrial fibrillation (n=11), pericardial drainage for effusion (n=4), exploration for bleeding (n=3), and superficial wound infection (n=1). Follow-up totaled 176.3 patient-years, and mean follow-up was 2.0 years. No one had a CI, and 8 had a TIA during follow-up, with 1 caused by temporal arteritis. Transesophageal echocardiography demonstrated all closures to be intact in these patients. The overall freedom from TIA recurrence during follow-up was 92.5+/-3.2% at 1 year and 83.4+/-6.0% at 4 years. Having multiple neurological events before PFO closure was the only significant risk factor for TIA or CI recurrence after closure by univariate analysis (P=0.05); the small number of post-PFO closure cerebral ischemic events precluded multivariate analysis.

CONCLUSIONS

Surgical closure of PFO can be performed with minimal morbidity and mortality. PFO closure may decrease the risk of recurrent stroke or TIA and may avoid lifelong anticoagulation in the young adult if there is no other indication. Recurrent cerebrovascular ischemic events after surgery should prompt further evaluation to identify causes other than paradoxical embolism.

Cerebral response to hemodilution during hypothermic cardiopulmonary bypass in adults

We examined the cerebral response to changing hematocrit during hypothermic cardiopulmonary bypass (CPB) in 18 adults. Cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), and cerebral oxygen delivery (CDO2) were determined using the nitrous oxide saturation technique. Measurements were obtained before CPB at 36 degrees C, and twice during 27 degrees C CPB: first with a hemoglobin (Hgb) of 6.2 +/- 1.2 g/dL and then with a Hgb of 8.5 +/- 1.2 g/dL. During hypothermia, appropriate reductions in CMRO2 were demonstrated, but hemodilution-associated increases in CBF offset the reduction in CBF seen with hypothermia. At 27 degrees C CPB, as the Hgb concentration was increased from 6.2 to 8.5 g/ dL, CBF decreased. CDO2 and CMRO2 were no different whether the Hgb was 6.2 or 8.5 g/dL. In eight patients in whom the Hgb was less than 6 g/dL, CDO2 remained more than twice CMRO2.

IMPLICATIONS

This study suggests that cerebral oxygen balance during cardiopulmonary bypass is well maintained at more pronounced levels of hemodilution than are typically practiced, because changes in cerebral blood flow compensate for changes in hemoglobin concentration.

Functional anatomy of mitral regurgitation: accuracy and outcome implications of transesophageal echocardiography

OBJECTIVES

This study was performed to determine the accuracy and outcome implications of mitral regurgitant lesions assessed by echocardiography.

BACKGROUND

In patients with mitral regurgitation (MR), valve repair is a major incentive to early surgery and is decided on the basis of the anatomic mitral lesions. These lesions can be observed easily with transesophageal echocardiography (TEE), but the accuracy and implications for outcome and clinical decision-making of these observations are unknown.

METHODS

In 248 consecutive patients operated on for MR, the anatomic lesions diagnosed with TEE were compared with those observed by the surgeon and those seen on 216 transthoracic echocardiographic (TTE) studies, and their relationship to postoperative outcome was determined.

RESULTS

Compared with surgical diagnosis, the accuracy of TEE was high: 99% for cause and mechanism, presence of vegetations and prolapsed or flail segment, and 88% for ruptured chordae. Diagnostic accuracy was higher for TEE than TTE for all end points (p < 0.001), but the difference was of low magnitude (<10%) except for mediocre TTE imaging or flail leaflets (both p < 0.001). The type of mitral lesions identified by TEE (floppy valve, restricted motion, functional lesion) were determinants of valve repairability and postoperative outcome (operative mortality and long-term survival; all p < 0.001) independent of age, gender, ejection fraction and presence of coronary artery disease.

CONCLUSIONS

Transesophageal echocardiography provides a highly accurate anatomic assessment of all types of MR lesions and has incremental diagnostic value if TTE is inconclusive. The functional anatomy of MR defined by TEE is strongly and independently predictive of valve repairability and postoperative outcome. Therefore, the mitral lesions assessed by echocardiography represent essential information for clinical decision making, particularly for the indication of early surgery for MR.

Support of mean arterial pressure during tepid cardiopulmonary bypass: effects of phenylephrine and pump flow on systemic oxygen supply and demand

OBJECTIVE

To examine the effects of phenylephrine infusion and increases in pump flow on systemic oxygen supply and demand when they are used to support mean arterial pressure (MAP) during cardiopulmonary bypass (CPB).

DESIGN

Prospective, unblinded study.

SETTING

The animal cardiopulmonary laboratory at the Mayo Foundation (Rochester, MN).

PARTICIPANTS

Twelve pigs.

INTERVENTIONS

Twelve pigs had systemic oxygen delivery (DO2) and consumption (VO2) measured before CPB and then underwent CPB at 35 degrees C. During CPB, measurements of DO2 and VO2 were obtained at an MAP of approximately 50 mmHg and a pump flow of 2.2 L/min/m2. Thereafter, MAP was elevated to 70 mmHg either by increases in pump flow or by a phenylephrine infusion, and the balance between systemic oxygen supply and demand was reassessed.

MEASUREMENTS AND MAIN RESULTS

Before CPB, DO2 was 375 +/- 83 mL/min/m2 and decreased with the onset of CPB mainly because of the effects of hemodilution. During CPB, with a pump flow of 2.2 L/min/m2 and an MAP of 53 mmHg, DO2 was 218 +/- 40 mL/min/m2. Increasing perfusion pressure to an MAP of 72 mmHg with phenylephrine and maintaining pump flow constant (2.2 L/min/m2) did not change DO2 (222 +/- 37 mL/min/m2), and the oxygen extraction ratio (OER) was increased relative to pre-CPB levels. In contrast, increasing MAP to 71 mmHg by increasing pump flow to 3.2 L/min/m2 resulted in a significantly greater DO2, and the OER normalized to the pre-CPB value.

CONCLUSIONS

During CPB with conventional flow rates, DO2 is decreased. Supporting MAP with increases in pump flow better maintains DO2 than the administration of an alpha-agonist.

Coronary artery bypass grafting in patients with previous mediastinal radiation therapy

OBJECTIVES

Our objectives were to characterize the outcome of coronary artery bypass grafting in patients with previous mediastinal radiation therapy and to identify special features of this condition that relate to surgical management.

PATIENTS AND METHODS

We conducted a retrospective review of 47 patients (28 women, 19 men) with a mean age of 63.5 +/- 12.8 years (range 31.0-82. 9 years) from 1976 through December 1996 undergoing coronary artery bypass graft after mediastinal radiation therapy.

RESULTS

The mean interval between mediastinal radiation therapy and coronary artery bypass grafting was 15.1 +/- 9.8 years (range 1.1-37.8 years). In the 44 patients with isolated coronary surgery, operative mortality was 3 patients (6.8%). Sternal wound infection occurred in 3 patients (6.8%). Actuarial survival at 1 and 5 years was 87.2% +/- 4. 9% and 71.6% +/- 7.1%, respectively. Total follow-up was 293.7 patient-years (mean 6.2 +/- 5.1 years). There were 17 late deaths (malignancy, n = 7; heart failure, n = 6; stroke, n = 1; other noncardiac causes, n = 2; and sudden death, n = 1). Twelve of 43 discharged patients had the development of valvular disease demonstrated by follow-up echocardiography.

CONCLUSIONS

The early results of coronary artery bypass grafting for the treatment of ischemic heart disease after mediastinal radiation therapy are good. Late survival, however, is limited by malignancy, either recurrent or new, and the development of heart failure. Inasmuch as 25 other patients after radiation therapy required concomitant valve surgery and 12 of 43 (28%) discharged patients had later development of valvular disease, with 2 requiring reoperation, careful assessment of any valvular lesion is important during the initial coronary artery bypass grafting. Careful follow-up, including regular echocardiographic screening, is recommended in this patient population.

Endothelial regulation of vascular contraction in radial and internal mammary arteries

BACKGROUND

The extent to which the endothelium regulates radial artery (RA) contractions is unknown. The goals of this study were to characterize endothelium-dependent relaxations in the RA, compare these responses with those in the internal mammary artery (IMA), and, subsequently, manipulate nitric oxide production in the RA with adenovirus-mediated gene transfer.

METHODS

Segments of RA and IMA from 43 patients were studied initially in organ chambers. Endothelial function was evaluated and gene transfer, was examined.

RESULTS

After precontraction to 80% maximum tension with prostaglandin F2alpha, acetylcholine produced lesser relaxations in the RA (21.5%+/-5.8%) than in the IMA (66.7%+/-10.6%); human thrombin and adenosine 5'-diphosphate yielded similar results. Reduced relaxations in the RA (16.8%+/-4.2%) compared with those in the IMA (71.6%+/-11.9%) were noted with calcium ionophore. Superfusion bioassay demonstrated a similar baseline release in both arteries but a reduced stimulated production of vasoactive substances in the RA, results confirmed by cyclic guanosine monophosphate level determination. The RA produced less 6-keto-prostaglandin F1alpha than the IMA. Light microscopy demonstrated an intact endothelium in both arteries. Adenovirus-mediated gene transfer of nitric oxide synthase augmented relaxations of the RA to acetylcholine.

CONCLUSIONS

Reduced production of endothelium-derived relaxing factors suggests diminished endothelial regulation of vascular smooth muscle in the RA compared with the IMA. This finding may explain, in part, the predisposition to vasoconstriction in RA grafts.

Cerebral response to haemodilution during cardiopulmonary bypass in dogs: the role of nitric oxide synthase

During cardiopulmonary bypass, haemodilution is standard practice and is accompanied by increases in cerebral blood flow (CBF). We investigated if changes in cerebral vascular resistance (CVR) during cardiopulmonary bypass-haemodilution are dependent on nitric oxide synthase. The cerebral response to haemodilution in nine dogs treated with the nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME), was compared with a control group (n = 8). Both groups underwent serial isovolaemic haemodilution (target packed cell volumes 0.39, 0.26, 0.19 and 0.14) using 6% dextran 70. CBF, CVR and cerebral metabolic rate for oxygen (CMRO2) were measured. While initial CVR was different in the two groups, haemodilution-dependent reductions in CVR were equivalent and the curves describing the packed cell volume-CVR relationship were parallel in control and nitric oxide synthase inhibition groups. Our data indicate that nitric oxide synthase does not play a primary role in the cerebral response to haemodilution.

Impact of preoperative symptoms on survival after surgical correction of organic mitral regurgitation: rationale for optimizing surgical indications

BACKGROUND

Surgical correction of mitral regurgitation in patients with no or mild symptoms remains controversial, particularly because the impact of preoperative symptoms on postoperative outcome is unknown.

METHODS AND RESULTS

The long-term outcome of 478 patients with organic mitral regurgitation (199 in NYHA functional class I/II and 279 in class III/IV before surgery) operated on between 1984 and 1991 was analyzed. In patients in NYHA class I/II before surgery compared with those in class III/IV, postoperative long-term survival was higher (at 10 years, 76+/-5% versus 48+/-4%, P<0.0001), with lower operative mortality (0.5% versus 5.4%, P=0.003) and better late survival (P<0.0001). Comparison of observed and expected survival showed identical curves in patients in class I/II before surgery (P=0.18), whereas excess mortality was observed in patients in class III/IV before surgery (P<0.0001). Excess mortality associated with severe symptoms was also confirmed in all subgroups (all P<0.003) and in multivariate analysis (P=0.0036; adjusted hazard ratio [95% CI], 1.81 [1.21 to 2.70]).

CONCLUSIONS

In patients with organic mitral regurgitation, preoperative functional class III/IV symptoms are associated with excess short- and long-term postoperative mortality independently of all baseline characteristics. These data should lead to consideration of surgical correction of severe organic mitral regurgitation when no or minimal symptoms are present in patients at low operative risk, especially if repair is feasible.

Excess mortality due to coronary artery disease after valve surgery. Secular trends in valvular regurgitation and effect of internal mammary artery bypass

BACKGROUND

During the 1980s, mortality from coronary artery disease (CAD) decreased markedly in the United States. This raises the question of whether a parallel decrease occurred in excess mortality due to CAD in patients undergoing surgical correction of valvular regurgitation.

METHODS AND RESULTS

Survival of 752 patients (age, 64 +/- 13 years) with isolated left-sided valvular regurgitation operated on from 1980 to 1991 was analyzed. Of 242 patients with CAD (stenosis > or = 70%), 208 had coronary artery bypass grafting. Multivariate analysis identified CAD as an independent predictor of operative mortality (odds ratio [OR] = 2.35, P = 0.012), overall (hazard ratio [HR] = 1.65, P < 0.0001) and late mortality (HR = 1.57, P = 0.0006), and postoperative congestive heart failure (HR = 2.35, P = 0.0001). Comparison of patients operated on in 1980 to 1985 with those operated on in 1986 to 1991, excess of operative, overall, and late mortality and postoperative congestive heart failure (adjusted for age and gender) related to associated CAD did not decrease significantly (P = 0.23, P = 0.64, P = 0.90, and P = 0.61, respectively). Overall survival was better for patients receiving an internal mammary artery graft than those receiving vein grafts only (HR = 0.57, P = 0.011).

CONCLUSIONS

In contrast to the secular trend for decreased mortality from CAD, excess mortality related to associated CAD after surgery for valvular regurgitation has not decreased. Internal mammary artery grafts were associated with improved outcome. In patients with valvular regurgitations, these results support continued active search of associated CAD, wide use of internal mammary artery graft, and vigorous efforts for secondary prevention of complications of CAD.

Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs

BACKGROUND

The purpose of this study was to determine the minimum hematocrit (Hct) supporting cerebral oxygenation over the range clinically relevant cardiopulmonary bypass (CPB) temperatures in dogs. The effect of hemodilution on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), and cerebral oxygen delivery (CDO2) was determined over a range of Hcts during CPB at 38 degrees C, 28 degrees C, and 18 degrees C.

METHODS AND RESULTS

Measurements were obtained at target CPB temperature and after progressive normovolemic hemodilution in 3 groups of 8 anesthetized animals. Dextran 70 (6%) was used as a diluent. CBF was measured by use of the sagittal sinus outflow technique. CMRO2 and CDO2 were calculated by the use of standard formulae. In each temperature group, hemodilution was associated with a reciprocal rise in CBF. As Hct was reduced to 0.10 +/- 0.02 at 38 degrees C, 28 degrees C, and 18 degrees C, CBF increased 260%, 220%, and 160% of the control nonhemodiluted value. Increases in CBF helped compensate for decreased arterial oxygen content and maintain CDO2. With progressive temperature reduction, these compensatory flow increases were reduced and CDO2 was decreased at lesser degrees of hemodilution. Statistical analysis indicated that cerebral oxygen demand was maintained to an Hct of 0.14, 0.11, and < or = 0.10 in the 38 degrees C, 28 degrees C, and 18 degrees C groups; however, physiologically important changes in cerebral oxygen supply occur at Hcts of approximately 0.18, 0.15, and 0.12, respectively, at those temperatures.

CONCLUSIONS

This investigation systematically characterizes the critical Hct supporting cerebral oxygenation at differing CPB temperatures. Over a range of CPB temperatures, the curve describing the relationship between Hct and cerebral oxygen balance has a broad plateau, indicating cerebral tolerance for a wide range of Hcts. The minimum Hct that supports cerebral oxygenation is shifted leftward as temperature is reduced, but the reduction in critical Hct is not proportional to the reduction in CMRO2. Although we do not advocate hemodilution to these extreme values, we find that these data provide a physiological foundation for our hemodilution practice and provide some guidance for management of Hct as body temperature changes during CPB.

New approaches to prevention and treatment of radial artery graft vasospasm

BACKGROUND

There has been renewed interest in radial artery (RA) conduits for coronary artery bypass because of the relative resistance of arterial grafts to atherosclerosis compared with autogenous vein grafts. Although improved drug therapy for arterial spasm is now available, vasospasm still occurs in at least 5% to 10% of RA grafts. We systematically evaluated the effectiveness of calcium channel blockers and organic nitrates for inhibition or reversal of RA contraction in vitro. Additionally, we investigated the efficacy of novel gene therapy with endothelial nitric oxide synthase (eNOS) to inhibit RA contractions.

METHODS AND RESULTS

Segments of RA from 28 patients undergoing coronary artery bypass grafting were mounted in organ chambers. In control experiments, KCl (5 to 50 mmol/L) produced dose-dependent increases in tension (maximum tension, 14.3 +/- 3.0 g, n = 7). Addition of diltiazem or verapamil had no significant effect on KCl contraction (128 +/- 36% and 88 +/- 24% control, respectively); however, nifedipine markedly inhibited KCl contraction (27 +/- 4% control, P = 0.005). Norepinephrine (NE, 10(-9) to 10(-4) M) produced dose-dependent increases in tension (maximum tension, 15.7 +/- 2.7 g in control rings, n = 8). Diltiazem and verapamil pretreatment had no significant effect on NE contraction (103 +/- 14% and 90 +/- 14% control, respectively); nifedipine significantly inhibited NE contraction (70 +/- 11% control, P = 0.02). Isosorbide dinitrate and nitroglycerin markedly inhibited KCl contractions (47 +/- 9% and 30 +/- 8% of controls, n = 6) and NE contractions (42 +/- 10% and 31 +/- 9% of controls, n = 6). Nifedipine, isosorbide, and nitroglycerin were further evaluated for the ability to reverse an established contraction (KCl 40 mmol/L); nitroglycerin was most effective in reversing RA contraction. In separate experiments, RA underwent adenoviral-mediated gene transfer with vehicle, Escherichia coli beta-galactosidase, or eNOS (eNOS, 10(10) PFU/mL x 1 hour). Transgene expression was confirmed by beta-galactosidase activity and eNOS immunohistochemistry after 40 hours of ex vivo incubation. Immunohistochemistry demonstrated recombinant NOS in adenovirus encoding bovine eNOS (Ad.CMVeNOS) RA only. Ad.CMVeNOS arteries contracted only 46.6 +/- 13.7% of controls to KCl (n = 5) and 48.2 +/- 11.4% of controls to prostaglandin F2 alpha a (10(-9) to 10(-6) M, n = 5).

CONCLUSIONS

Diltiazem, which is used empirically to prevent RA vasospasm, had little effect on human RA contractions (receptor-independent and receptor-dependent). Organic nitrates inhibited and reversed RA contractions. Adenoviral transfer of NOS suggests that future clinical application of gene therapy may play an important role in prevention of RA vasospasm.

Role of emergency intraoperative transesophageal echocardiography

Transesophageal echocardiography (TEE) has a definitive role in the diagnosis and management of critically ill patients with cardiovascular disease and patients undergoing cardiac operations. The diagnostic role of emergency intraoperative TEE and the impact on clinical outcome have not been evaluated. We reviewed the indications, findings, and impact of emergency intraoperative TEE in 66 patients over a 4-year period. The indications for emergency TEE were unexplained hemodynamic instability (36 patients), preoperative evaluation of patients having emergency surgery (19 patients), cardiac evaluation of trauma cases (6 patients), and unexplained intraoperative hypoxemia (5 patients). New findings were disclosed in 53 (80%) patients, with an alteration of the planned surgical procedure in 15 (23%). Despite the therapeutic impact, 24 patients (36%) did not survive to hospital dismissal. We recommend that TEE be considered as the diagnostic tool of choice when surgical patients have unexplained hemodynamic instability, when time does not permit complete preoperative evaluation, when cardiovascular injury is suspected in a trauma patient, and to evaluate unexplained hypoxemia.

Mechanisms of hemolysis after mitral valve repair: assessment by serial echocardiography

OBJECTIVES

We sought to determine, using serial echocardiography, the hydrodynamic mechanisms involved in the occurrence of hemolysis after mitral valve repair.

BACKGROUND

Recently, fluid dynamic simulation models have identified distinct patterns of mitral regurgitant flow disturbances in patients with mitral prosthetic hemolysis that were associated with high shear stress and may therefore produce clinical hemolysis. Rapid acceleration, fragmentation, and collision jets were associated with high shear stress and hemolysis whereas slow deceleration and free jets were not.

METHODS

We reviewed serial echocardiographic studies of 13 consecutive patients with hemolytic anemia after mitral valve repair who were referred for mitral reoperation between January 1985 and December 1996 (group 1). Thirteen patients undergoing reoperation for mitral regurgitation after mitral valve repair but without hemolysis served as controls (group 2).

RESULTS

The mitral regurgitant jet was central in origin in 12 group 1 patients and 9 group 2 patients (Fisher exact test, p= 0.3). The other patients had para-ring regurgitation. Group 1 patients had collision (n=11), rapid acceleration (n=2) or fragmentation (n=1) jets whereas group 2 patients had slow deceleration (n=11) or free jets (n=2) (Fisher exact test, p < 0.0001). One patient with hemolysis had both collision and rapid acceleration jets. The "culprit" jet could be identified on the postbypass transesophageal echocardiography (TEE) study in only 1 patient at the time of initial mitral repair. Twelve group 1 patients underwent reoperation, with subsequent resolution of hemolysis in all patients. At reoperation, the initial repair was found to be intact in 8 (67%) patients.

CONCLUSION

Distinct patterns of flow disturbance associated with high shear stress were identified by color Doppler imaging in patients with hemolysis after mitral valve repair. The majority (92%) of these color flow disturbances were not present during intraoperative postbypass TEE study after initial mitral repair and subsequently developed in the early postoperative period.

Normothermic cardiopulmonary bypass increases heparin requirements necessary to maintain anticoagulation

OBJECTIVE

With the practice of warm cardiopulmonary bypass (CPB) at our institution we have observed an apparent increase in heparin requirements. CPB temperature predictability affects pharmacokinetics and differences in drug metabolism can be expected. We hypothesized that heparin requirements would increase with increasing CPB temperature.

METHODS

Following Institutional Review Board approval, we reviewed the charts of 354 patients undergoing primary coronary artery bypass graft surgery. We recorded patient demographic data, CPB duration, heparin requirements, and temperature during CPB. CPB was conducted between 24 degrees C and 37 degrees C. The Spearman's correlation coefficient, Pearson chi-square, and rank-sum tests were used for data analysis.

RESULTS

Core temperature during CPB correlated with heparin requirements (r = 0.13, p < 0.02). However, CPB duration was shorter in warm patients than in cold patients (r = -0.455, p < 0.0001). Additional heparin requirements adjusted for duration of CPB (units/minute) were also significantly greater in the warm group (p = 0.018).

CONCLUSIONS

Maintenance of adequate heparin anticoagulation during CPB is clinically important. Warm CPB patients required more heparin per minute than those undergoing cold CPB. More frequent assessment of anticoagulation and administration of additional heparin should be considered in patients undergoing warm CPB.

Modern management of prosthetic valve anticoagulation

Prosthetic heart valves have been effectively used for many years. Nonetheless, they are associated with risks of thrombosis and thromboembolic events, as well as anticoagulation-induced bleeding. Substantial changes in anticoagulation measurement and dosing have occurred during the past several years. In this review, the rationale for anticoagulation in patients with prosthetic heart valves, the changes in monitoring and dosing, and the comparison of relevant anticoagulation trials are discussed. On the basis of the existing data, new recommendations regarding lower anticoagulation levels are offered, utilizing a single value goal rather than the traditional therapeutic range. Perioperative management of anticoagulation is discussed in light of the available literature, and major drug interactions are reviewed.

Critical cerebral perfusion pressure during tepid heart operations in dogs

BACKGROUND

The management of blood pressure during cardiopulmonary bypass varies widely. This may be particularly relevant with the trend to warmer bypass temperatures and an older patient population. Therefore, we examined the minimal perfusion pressure that maintains cerebral oxygen delivery during cardiopulmonary bypass at 33 degrees C.

METHODS

Ten dogs were placed on bypass and body temperature was reduced to 33 degrees C (alpha-stat pH management). At six randomly ordered mean arterial blood pressures (35, 40, 45, 50, 60, and 70 mm Hg), cerebral blood flow, oxygen delivery, and metabolic rate were determined.

RESULTS

Cerebral oxygen delivery was stable if the mean arterial pressure was greater than or equal to 60 mm Hg. If mean arterial pressure was less than or equal to 50 mm Hg, cerebral oxygen delivery decreased, and at less than 45 mm Hg cerebral ischemia was seen.

CONCLUSIONS

In a dog without vascular disease, the brain becomes perfusion pressure-dependent at a mean arterial pressure of approximately 50 mm Hg. There is no leftward shift of the cerebral autoregulatory curve during bypass at 33 degrees C. Greater support of mean arterial pressure during "tepid" cardiopulmonary bypass is indicated in the current adult surgical population that is older and has vascular comorbidity.

Role of intraoperative transesophageal echocardiography in determining aortic annulus diameter in homograft insertion

The sizing of aortic valve (AV) homografts for optimum function requires an accurate measurement of the aortic annulus. Typically, this measurement is obtained directly with sizers in the open aorta. We describe the use of intraoperative transesophageal echocardiography (IOTEE) to measure the aortic annulus and select the appropriate AV homograft before cardiopulmonary bypass and aortic cross-clamping. Thirty-two patients underwent AV homograft insertion between March 1993 and March 1996 and had IOTEE. There were 13 women and 19 men. Mean age was 58 +/- 14 years. IOTEE measurements were satisfactory in sizing in all patients, and no extraordinary surgical measures were necessary to insert the AV homografts. Early postoperative follow-up showed trivial or mild regurgitation of all homografts. Prebypass IOTEE is reliable in guiding the selection of optimal AV homografts.

Hemodilution and whole body oxygen balance during normothermic cardiopulmonary bypass in dogs

OBJECTIVE

The purpose of this study was to determine the minimum hematocrit value that can support whole body oxygen consumption during normothermic cardiopulmonary bypass. The effect of hemodilution on peripheral resistance, whole body oxygen delivery, and oxygen consumption was determined over a range of hematocrit values.

METHODS

Measurements were obtained during 38 degrees C cardiopulmonary bypass with progressive normovolemic hemodilution (hematocrit value 40% to 9%) in nine dogs. Dextran 70 (6%) was used as a diluent. Anesthesia consisted of high-dose fentanyl and midazolam. A mean arterial pressure of 60 mm Hg was maintained throughout cardiopulmonary bypass via increases in pump flow.

RESULTS

Progressive hemodilution was associated with a decreasing total peripheral resistance. During normothermic cardiopulmonary bypass with a whole blood prime, the whole body oxygen consumption approximated values previously reported in dogs under nonbypass conditions. Oxygen delivery and whole body oxygen uptake were maintained between a hematocrit value of 39% and 25%. Significant decreases for both were seen when the hematocrit value was reduced to 18% and below.

CONCLUSIONS

A hematocrit level greater than 18% was needed to maintain systemic oxygen delivery and consumption during warm cardiopulmonary bypass. The critical hematocrit value may be higher under bypass than nonbypass conditions because the flow increases that are practical during cardiopulmonary bypass do not approximate those seen in response to hemodilution of the intact circulation. Finally, the critical hematocrit value for the body may be higher than that required for the brain during warm cardiopulmonary bypass.

Aortic valve homografts in adults: a clinical perspective

Aortic valve replacement is a lifesaving measure in patients with severe aortic valve disease. In the United States, the most commonly used prostheses are the mechanical and bioprosthetic valves. With mechanical valves, long-term anticoagulation is necessary because of high thrombogenic potential. Bioprosthetic valves have a relatively high incidence of structural failure, especially in younger patients. Aortic valve homografts, derived from human heart donors or autopsy material, provide an alternative to mechanical or animal valves. The advantages of the homograft in comparison with the mechanical prostheses are the low incidence of thromboembolism without anticoagulation and lower valvular gradients in smaller sizes. Homografts are relatively resistant to endocarditis and are the valve of choice during active endocarditis. Their major mode of failure has been aortic regurgitation; however, recent advances in preservation and operative techniques have decreased this problem. Whether implantation of an aortic valve homograft should be the procedure of choice in subsets of patients remains controversial. Herein we review the history, techniques, results, complications, and current indications for aortic valve homografts.

Minimum hematocrit for normothermic cardiopulmonary bypass in dogs

BACKGROUND

The purpose of this study was to determine the minimum hematocrit supporting cerebral oxygenation during normothermic cardiopulmonary bypass (CPB) in dogs. The effect of hemodilution on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), and cerebral oxygen delivery (CDO2) was determined over a range of hematocrits.

METHODS AND RESULTS

Measurements were obtained during 37.5 degrees C CPB with progressive normovolemic hemodilution (hematocrit 0.39 to 0.9) in eight anesthetized animals. Dextran 70 (6%) was used as a diluent. CBF was measured using the sagittal sinus outflow technique. CMRO2 and CDO2 were calculated using standard formula. Hemodilution was associated with a reciprocal rise in CBF. CBF at a hematocrit of 0.09 was 240% of the CBF when the hematocrit was 0.39. Increases in CBF compensated for decreased arterial oxygen content and CDO2 was maintained to a mean hematocrit of 0.14+/-0.02. At a hematocrit of 0.09+/-0.02, CDO2 and CMRO2 declined. Intracranial pressure remained stable throughout. Thus, the critical hematocrit for brain (the hematocrit at which metabolism becomes delivery-dependent) was between 0.09 and 0.14 during normothermic CPB in dogs.

CONCLUSIONS

This is the first systematic attempt to determine the critical hematocrit supporting cerebral oxygenation during warm CPB. The curve describing the relationship between hematocrit and cerebral oxygen balance has a broad plateau and a genu near a hematocrit value of 0.15. While we do not advocate hemodilution to a hematocrit of 15% during "warm" CPB, these data provide a physiological foundation for our hemodilution practice and offer an explanation why low hematocrits are tolerated in certain patient populations.

Third and fourth operations for myocardial ischemia: short-term results and long-term survival

BACKGROUND

An increasing number of patients having at least two operations for myocardial ischemia are now presenting for a third or fourth procedure. We report the Mayo Clinic experience with repeated reoperative surgery for coronary artery disease.

METHODS AND RESULTS

We have evaluated 67 consecutive patients (54 men, 13 women) during a 14-year period (1978 to 1992). The mean age at the third procedure (n=63) was 63.4 years and at the fourth procedure (n=4) was 70.6 years. Clinical indications for surgery were unstable angina in 29 patients (43%), New York Heart Association class III angina in 36 (54%), non-Q wave acute myocardial infarction in 1, and acute pulmonary edema in 1. Urgent or emergency surgery was undertaken in 17 patients (25%). All patients had triple-vessel disease, and 20 (30%) had left main coronary artery stenosis >50%. The mean ejection fraction in 56 patients was 0.56+/-0.11. Occlusion or significant stenoses of preexisting saphenous grafts were thought to be the major cause of recurrent ischemia in 64 patients (96%). Only 14 patients (21%) had received previous arterial grafts. An average of 2.4 grafts was placed, and a new internal mammary artery was used on 47 occasions. Eight patients (11.9%) died. Three patients required a left ventricular assist device, and one of them survived. There were 21 late deaths: 8 were cardiac and 5 were likely to be cardiac. Five-year and 10-year survival in all patients was 75.6%+/-5.3% and 47.9%+/-7.7%, respectively. Freedom from further intervention for hospital survivors at 5 and 10 years was 88.4+/-4.5 and 72.3+/-8.5%, respectively. Of the 38 patients still alive at last follow-up, 29 (76%) were considered to be in New York Heart Association functional class I or II. On univariate analysis, use of an intra-aortic balloon pump, prolonged bypass time, left main coronary artery stenosis >50%, and a surgeon's impression of angiographic inoperability correlated with increased risk of early mortality.

CONCLUSION

We conclude that in a select group of patients, repeated reoperative surgery, despite an increased mortality, can result in good long-term survival and significant improvement in clinical status.

Establishing and using a local/regional cardiac surgery database

BACKGROUND

In 1993, the Minnesota Society of Thoracic Surgeons and the Minnesota Cardiac Surgery Database were organized in response to a third-party payer demand for data about practice protocols and patient outcomes. It has matured to an active organization of 46 cardiothoracic surgeons, 14 institutions, and more than 7,000 patients who have undergone coronary artery bypass grafting.

METHODS

Data are validated for completeness and accuracy through a statewide auditing process. They are coded by hospital, analyzed using the standard Society of Thoracic Surgeons National Cardiac Surgery Database format and definitions, and reviewed quarterly in a continuous quality improvement process.

RESULTS

Through data review and exchange site visits, variations in practice protocols and outcomes have been identified. For example, our statewide data review and continuous quality improvement process identified prolonged ventilation (more than 24 hours) as one variation. Multidisciplinary teams were defined, and statewide exchange site visits led by cardiovascular surgeons were implemented. An example of the improvement in the accuracy and completeness of the data used to study procedure outcomes is represented by the improved reporting of ejection fraction values that has resulted from this process.

CONCLUSIONS

Using the standardized Society of Thoracic Surgeons National Cardiac Surgery Database and the Minnesota Society of Thoracic Surgeons organizational structure to establish a high-quality database will allow for statewide peer review, exchange of practice guidelines, and promotion of standardization, which eventually can improve outcomes and reduce costs. This organization or model can be replicated at any local, state, or regional level. Thoracic surgeons faced with similar challenges for public disclosure of surgical results can learn much from the successful development of the Minnesota Cardiac Surgery Database.