Does the internal thoracic artery graft delay the recovery of myocardial metabolism?

BACKGROUND

The left internal thoracic artery (LITA) bypass graft to the left anterior descending artery has greater long-term patency than a saphenous vein graft. However, surgeons may be reluctant to use the LITA graft in some patients because they are unable to deliver cardioplegia to the left anterior descending artery territory.

METHODS

We compared the myocardial levels of high-energy phosphates and their metabolites in patients who received an LITA graft with those in patients who received a saphenous vein graft to the left anterior descending artery territory during elective coronary artery bypass grafting. Right and left ventricular biopsy specimens were obtained at three times: before aortic cross-clamping, after cross-clamp removal, and after 10 minutes of reperfusion.

RESULTS

No differences were found between the LITA graft group and the saphenous vein graft group in any right ventricular metabolites. There was an improvement in myocardial protection over time and a higher proportion of LITA graft patients in the late time period (early group, 63% versus late group, 80%; p < 0.01). Within each time period, there were no differences between the LITA and saphenous vein graft groups. Among patients receiving cold antegrade cardioplegia, the myocardial levels of high-energy phosphates were better preserved in those receiving an LITA graft.

CONCLUSIONS

Advances in myocardial protection have led to improved preservation of high-energy phosphate levels after cardioplegic arrest. In patients undergoing elective coronary artery bypass grafting, the use of an LITA graft does not adversely affect myocardial metabolism. Further investigations are required to determine the effects of the use of the LITA during urgent or emergent procedures.

Vitellogenin induction and reduced serum testosterone concentrations in feral male carp (Cyprinus carpio) captured near a major metropolitan sewage treatment plant

Endocrine disrupting chemicals can potentially alter the reproductive physiology of fishes. To test this hypothesis, serum was collected from common carp (Cyprinus carpio) at five riverine locations in Minnesota. Male fish collected from an effluent channel below the St. Paul metropolitan sewage treatment plant had significantly elevated serum egg protein (vitellogenin) concentrations and significantly decreased serum testosterone concentrations compared to male carp collected from the St. Croix River, classified as a National Wild and Scenic River. Carp collected from the Minnesota River, which receives significant agricultural runoff, also exhibited depressed serum testosterone concentrations, but no serum vitellogenin was apparent. These data suggest that North American rivers are receiving estrogenic chemicals that are biologically active, as has been reported in Great Britain.

Preconditioning to improve myocardial protection

Major advances in the composition and delivery of cardioplegia have helped to reduce the morbidity and mortality associated with coronary bypass surgery. The discovery of the preconditioning response should facilitate the development of more powerful myocardial protective agents. These new agents may act to directly stimulate the preconditioning response or may act in a supplementary fashion to either augment the response or provide protection from alternate pathways. As new techniques of myocardial protection continue to be developed, the risk-to-benefit ratio of coronary bypass surgery will continue to improve. As a result of these improvements, surgeons will be able to offer surgery to an increasingly high risk patient population without increasing the morbidity or mortality currently associated with coronary bypass.

Cardiomyocyte transplantation improves heart function

BACKGROUND

Transplantation of cultured cardiomyocytes into myocardial scar tissue may prevent heart failure.

METHODS

Scar tissue was produced in the left ventricular free wall of 15 rats (weight, 450 g) by cryoinjury. Seven animals had operation only and survived for 8 weeks (sham group). Four weeks after cryoinjury, cultured fetal rat cardiomyocytes or culture medium was injected into the scar tissue of transplantation (n = 5) and control (n = 5) animals, respectively. Five other rats were sacrificed for scar assessment. Eight weeks after cryoinjury heart function in the transplantation, control, and sham groups was measured using a Langendorff preparation. Histologic studies were performed to quantify the extent of the scar and the transplanted cells.

RESULTS

Four weeks after cryoinjury, 36% +/- 4% (mean +/- 1 standard error) of the left ventricular free wall surface area was scar tissue. At 8 weeks, the scar size had increased (p < 0.01) to 55% +/- 3% in the control group. Although the scar size (43% +/- 2%) in the transplantation group at 8 weeks was not significantly different from that at 4 weeks, it was less (p < 0.05) than that in the control group. Hearts in the sham group had no scar tissue. The transplanted cardiomyocytes had formed cardiac tissue within the myocardial scar. Systolic and developed pressures in the transplantation group hearts were greater (p = 0.0001) than in the control group hearts but less (p < 0.01) than those in the sham group hearts.

CONCLUSIONS

The transplanted cardiomyocytes formed cardiac tissue in the myocardial scar, limited scar expansion, and improved heart function compared with findings in the control hearts.

Primary malignant melanoma of the sinonasal cavity: MR imaging evaluation

To evaluate the magnetic resonance (MR) imaging characteristics of primary malignant melanoma of the sinonasal cavity, T1- and T2-weighted MR images of 12 patients with primary sinonasal melanoma were retrospectively reviewed. Gadolinium-enhanced imaging was performed in seven cases. The MR images were compared with histopathologic results. There were seven melanotic melanomas and five amelanotic melanomas; hemorrhage was present in three melanotic and two amelanotic melanomas. The seven melanotic melanomas were hyperintense to gray matter on T1-weighted images (whether hemorrhage was present or not), consistent with the paramagnetic effect of melanin. Four of the five amelanotic melanomas had intermediate signal intensity on T1-weighted images; one was not detected. On T2-weighted images, all of the melanomas detected had intermediate though variable signal intensity compared with that of gray matter. On gadolinium-enhanced images, all cases demonstrated mild to moderate enhancement. The signal intensity of sinonasal melanoma appears to vary according to the histopathologic components of the tumor. High signal intensity within the lesion on T1-weighted images suggests the presence of melanin.

Antegrade and retrograde cardioplegia: alternate or simultaneous?

Neither antegrade nor retrograde cardioplegic protection provides homogeneous distribution, and a combination may be required to avoid anaerobic metabolism and depressed postoperative ventricular function. Tepid cardioplegia (29 degrees C) avoids the delayed recovery of cardiac function and metabolism associated with cold cardioplegia (15 degrees C) and reduces the anaerobic metabolism seen with warm (37 degrees C) cardioplegia. We compared two techniques that combine antegrade and retrograde tepid cardioplegia: alternate and simultaneous.

METHODS

Sixty patients undergoing elective isolated coronary artery bypass grafting were randomized to receive near continuous tepid retrograde and either intermittent antegrade cardioplegia (the alternate technique) or antegrade cardioplegia with the solution delivered concurrently through each completed vein graft (the simultaneous technique).

RESULTS

Myocardial lactate extraction was greater after crossclamp release following simultaneous than alternate cardioplegia. Postoperative ventricular function was better after alternate than simultaneous cardioplegia.

CONCLUSION

Both techniques permitted rapid postoperative recovery of myocardial metabolism and ventricular function. However, simultaneous cardioplegia was simpler and did not require deairing the aortic root between antegrade infusions.

Results of combined pulmonary resection and cardiac operation

BACKGROUND

Concomitant lesions of the heart and lung are uncommon, but when present they pose a therapeutic challenge for thoracic surgeons. A combined procedure avoids the need for a second major thoracic procedure and may improve outcomes and provide economic benefit. However, cardiopulmonary bypass may adversely affect the natural history of pulmonary malignancies.

METHODS

The clinical records of 30 patients were reviewed who underwent simultaneous lung resection and cardiac operations between January 1982 and July 1995. Follow-up was obtained on all 30 patients (mean follow-up, 22 months; range, 1 to 100 months).

RESULTS

Twenty-four patients underwent coronary artery bypass grafting in conjunction with pulmonary resection. Six patients underwent aortic (n = 4) or mitral (n = 2) valve replacement. The pulmonary resections consisted of pneumonectomy (n = 3), lobectomy (n = 14), wedge excision (n = 12), and tracheal resection (n = 1). Twenty-one patients had pathologic findings that confirmed adenocarcinoma (n = 10), squamous cell carcinoma (n = 5), small cell carcinoma (n = 2), or other malignancy (n = 4). Tumor stage of primary lung cancers was stage I, n = 12; stage II, n = 3; and stage IIIa, n = 2. Pathologic examination revealed benign disease in 9 patients. There were two operative deaths, one due to aspiration and one due to stroke. There were three late deaths, two cardiac and one of metastatic disease. Overall late survival was 85% +/- 7% and 73% +/- 16% at 1 and 5 years, respectively. Actuarial survival for patients with malignant disease was 64% at 5 years.

CONCLUSIONS

Simultaneous cardiac operation and lung resection was not associated with increased early or late morbidity or mortality. Cardiopulmonary bypass does not adversely affect survival in patients with malignant disease. Cardiac valve replacement can be performed safely in conjunction with pulmonary resection.

Structure in Thin and Ultrathin Spin-Cast Polymer Films

The molecular organization in ultrathin polymer films (thicknesses less than 1000 angstroms) and thin polymer films (thicknesses between 1000 and 10,000 angstroms) may differ substantially from that of bulk polymers, which can lead to important differences in resulting thermophysical properties. Such constrained geometry films have been fabricated from amorphous poly(3-methyl-4-hydroxy styrene) (PMHS) and semicrystalline poly(di-n-hexyl silane) (PD6S) by means of spin-casting. The residual solvent content is substantially greater in ultrathin PMHS films, which suggests a higher glass transition temperature that results from a stronger hydrogen-bonded network as compared with that in thicker films. Crystallization of PD6S is substantially hindered in ultrathin films, in which a critical thickness of 150 angstroms is needed for crystalline morphology to exist and in which the rate of crystallization is initially slow but increases rapidly as the film approaches 500 angstroms in thickness.

Acute myocardial infarction, reperfusion injury, and intravenous magnesium therapy: basic concepts and clinical implications

The concept of reperfusion-induced injury has aroused special interest during the past decade as thrombolysis and direct angioplasty were introduced for early restoration of coronary blood flow in patients with acute myocardial infarction. There is experimental and clinical evidence that oxygen-derived free radicals (oxyradical hypothesis), activation of the complement system (complement hypothesis), and disturbance in calcium homeostasis (calcium hypothesis), may account for the development of reperfusion injury. Data from numerous animal experiments and clinical trials suggest that magnesium, a physiologic calcium blocker, may be efficacious for reduction of reperfusion injury. Despite encouraging results from previous clinical trials that revealed beneficial effects of intravenous magnesium therapy with respect to mortality, left ventricular function, and infarct size, a recently published large-scale trial (ISIS-4) provided conflicting data and caused major controversy. Further clinical trials, well-designed and carefully conducted, should elucidate the beneficial effects of magnesium in acute myocardial infarction, especially in conjunction with new and aggressive reperfusion techniques.

Results of combined pulmonary resection and cardiac operation

BACKGROUND

Concomitant lesions of the heart and lung are uncommon, but when present they pose a therapeutic challenge for thoracic surgeons. A combined procedure avoids the need for a second major thoracic procedure and may improve outcomes and provide economic benefit. However, cardiopulmonary bypass may adversely affect the natural history of pulmonary malignancies.

METHODS

The clinical records of 30 patients were reviewed who underwent simultaneous lung resection and cardiac operations between January 1982 and July 1995. Follow-up was obtained on all 30 patients (mean follow-up, 22 months; range, 1 to 100 months).

RESULTS

Twenty-four patients underwent coronary artery bypass grafting in conjunction with pulmonary resection. Six patients underwent aortic (n = 4) or mitral (n = 2) valve replacement. The pulmonary resections consisted of pneumonectomy (n = 3), lobectomy (n = 14), wedge excision (n = 12), and tracheal resection (n = 1). Twenty-one patients had pathologic findings that confirmed adenocarcinoma (n = 10), squamous cell carcinoma (n = 5), small cell carcinoma (n = 2), or other malignancy (n = 4). Tumor stage of primary lung cancers was stage I, n = 12; stage II, n = 3; and stage IIIa, n = 2. Pathologic examination revealed benign disease in 9 patients. There were two operative deaths, one due to aspiration and one due to stroke. There were three late deaths, two cardiac and one of metastatic disease. Overall late survival was 85% +/- 7% and 73% +/- 16% at 1 and 5 years, respectively. Actuarial survival for patients with malignant disease was 64% at 5 years.

CONCLUSIONS

Simultaneous cardiac operation and lung resection was not associated with increased early or late morbidity or mortality. Cardiopulmonary bypass does not adversely affect survival in patients with malignant disease. Cardiac valve replacement can be performed safely in conjunction with pulmonary resection.

Results of represervation of the chordae tendineae during redo mitral valve replacement

BACKGROUND

Previous studies have shown that preservation of the chordae tendineae improves early and late postoperative left ventricular function after mitral valve replacement. This report describes the results of represervation of the chordae tendineae during redo mitral valve replacement in patients who had their chordae tendineae preserved during their initial operation.

METHODS

Fifty-four patients undergoing reoperative mitral valve replacement with preservation of their chordal annular attachments (chordae group) were compared with 187 patients who had redo mitral valve replacement without preservation of the chordae (nonchordae group). The interval between the initial operation and the reoperation was 8.7 +/- 4.4 years in the chordae group and 8.6 +/- 4.9 years in the nonchordae group (p = 0.315). Seventy-three patients underwent aortic valve replacement during their redo mitral valve replacement compared with 168 patients who had mitral valve replacement alone. There were 15 patients who had their chordal attachments represerved during redo double-valve replacement.

RESULTS

In the chordae group, intraoperative assessment revealed excellent chordal connection between the preserved papillary muscles and the mitral annulus in all patients. One patient had adhesions between the preserved chordae and the stent of the tissue valve. The chordal attachments were preserved during insertion of the second valve in all patients. The incidence of low output syndrome and operative mortality in the chordae group was 16.7% and 7.4%, respectively. In the nonchordae group, the incidence of low output syndrome was 27.3% (p = 0.112 compared with the chordae group) and the operative mortality was 13.4% (p = 0.236 compared with the chordae group). In patients with double-valve replacement, represervation of the chordae was associated with a reduction in low output syndrome (0% versus 24%; p = 0.034) and mortality (6.7% versus 15.5%; p = 0.374).

CONCLUSIONS

Preservation of the chordal attachments between the papillary muscles and the mitral annulus can be accomplished during reoperative mitral valve replacement. Represervation of the chordae tendineae may reduce postoperative low output syndrome, especially in high-risk patients undergoing redo double-valve replacement.

Predictors of low cardiac output syndrome after coronary artery bypass

The purpose of this study was to identify patients at risk for the development of low cardiac output syndrome after coronary artery bypass. Low cardiac output syndrome was defined as the need for postoperative intraaortic balloon pump or inotropic support for longer than 30 minutes in the intensive care unit to maintain the systolic blood pressure greater than 90 mm Hg and the cardiac index greater than 2.2 L/min per square meter. The preoperative patient characteristics that were independent predictors of low cardiac output syndrome were identified among 4558 consecutive patients who underwent isolated coronary artery bypass at The Toronto Hospital between July 1, 1990, and December 31, 1993. The overall prevalence of low cardiac output syndrome was 9.1% (n = 412). The operative mortality rate was higher in patients in whom low cardiac output syndrome developed than in those in whom it did not develop (16.9% versus 0.9%, p < 0.001). Stepwise logistic regression analyses identified nine independent predictors of low output syndrome (percent frequency in parentheses) and calculated the factor-adjusted odds ratios associated with each predictor: (1) left ventricular ejection fraction less than 20% (27%, odds ratio 5.7); (2) repeat operation (25%, odds ratio 4.4); (3) emergency operation (27%, odds ratio 3.7); (4) female gender (16%, odds ratio 2.5); (5) diabetes (13%, odds ratio 1.6); (6) age older than 70 years (13%, odds ratio 1.5); (7) left main coronary artery stenosis (12%, odds ratio 1.4); (8) recent myocardial infarction (16%, odds ratio 1.4); and (9) triple-vessel disease (10%, odds ratio 1.3). Low cardiac output syndrome is a clinical outcome that may result from inadequate myocardial protection or perioperative ischemic injury. Patients at high risk for the development of low cardiac output syndrome should be the focus of trials of new techniques of myocardial protection to resuscitate the ischemic myocardium.

Intragraft TGF-beta 1 mRNA: a correlate of interstitial fibrosis and chronic allograft nephropathy

Chronic allograft nephropathy is a relentlessly progressive process and a major cause of long-term graft dysfunction and ultimate failure. Interstitial fibrosis, tubular atrophy, and glomerular and vascular lesions characterize this mechanistically unresolved disorder. Given the prominent role of TGF-beta 1 in tissue repair and in fibrosis, we have explored the hypothesis that fibrosis and chronic allograft nephropathy would be distinguished by intragraft TGF-beta 1 mRNA expression. This postulate was tested by mRNA phenotyping of RNA isolated from 127 human renal allograft biopsies. Reverse transcription assisted polymerase chain reaction was used to amplify and identify ingraft gene expression. Our investigation demonstrated a significant correlation between intragraft TGF-beta 1 mRNA display and renal allograft interstitial fibrosis and chronic allograft nephropathy. In contrast, intragraft expression of mRNA encoding immunoregulatory cytokines, IL-2, IFN-gamma, IL-4, IL-10, or cytotoxic attack molecules, granzyme B and perforin was not a correlate of interstitial fibrosis or chronic allograft nephropathy. Our studies identify, for the first time, a significant association between intragraft TGF-beta 1 mRNA expression and renal allograft interstitial fibrosis, and advance a candidate molecular mechanism for chronic allograft nephropathy.

Phenotypic changes and loss of melanoma-specific endogenous C-type retroviruses in BL6 melanoma cells transfected with the H-2Kb gene

The murine B16 melanoma and its sublines are low or totally deficient in expression of the H-2Kb class I major histocompatibility complex (MHC) gene. In clones derived from the B16F10BL6 subline, expression of the transfected or endogenous H-2Kb gene resulted in alterations of various phenotypic properties of these melanoma cells, among which was the loss of melanoma-associated antigen (MAA) expression. Because our previous immunoelectron microscopy studies showed that MAA was associated with a C-type ecotropic retrovirus specific for melanomas of C57BL/6 origin, we examined the effect of class I H-2Kb as well as class II H-2IAk gene expression on retrovirus production in subclones of BL6 melanoma cells. Here we have shown that expression of the transfected or endogenous H-2Kb gene resulted in the loss of production of budding, MAA-specific, C-type retrovirus particles. Northern blot analysis demonstrated expression of ecotropic retroviral mRNAs in both particle-producing and non-producing BL6 melanoma clones. Southern blot analysis of high-molecular-weight cellular DNAs using an ecotropic env-specific DNA probe indicated that the parental BL6-8 melanoma cells contained the C57BL/6 endogenous ecotropic MuLV (Emv-2) and at least three additional, novel ecotropic retroviral DNAs. Restriction enzyme analysis of the proviral DNA suggests that the loss of retrovirus production in the H-2Kb-expressing melanoma clones is the result of multiple rearrangements in the novel proviral DNAs. Thus, phenotypic changes observed in the H-2Kb gene-transfected BL6 melanoma cells were associated with loss of endogenous melanoma-specific ecotropic retrovirus production.

Impact of preoperative risk and perioperative morbidity on ICU stay following coronary bypass surgery

Prolonged intensive care unit treatment (> 3 days) contributes to increased health costs and resource utilization. In order to devise strategies to limit intensive care unit stay, and provide cost-effective medical care, it is necessary to identify the pre- and perioperative risk factors of prolonged treatment. Over 100 potential risk variables were collected prospectively in 889 consecutive patients undergoing isolated coronary bypass surgery between 1990 and 1992. The incidence of intensive care unit therapy lasting > 3 days was 6.8%. Univariate statistics identified 23 pre- and perioperative variables that were potential contributors to prolonged intensive care unit therapy. However, multivariate analysis of preoperative risk variables identified only recent myocardial infarction (within 30 days of surgery) and continued preoperative smoking (within 30 days of surgery) to be independent risk factors. Only 6.3% of patients without preoperative myocardial infarction and 6.1% of non-smokers required prolonged intensive care unit treatment, compared with 14.8% of patients with preoperative myocardial infarction (P = 0.01) and 10.1% of smokers (P = 0.07). When multivariate analysis was repeated with both pre- and perioperative variables, only ischemic morbidity (inotropes, myocardial infarction and low-output syndrome; 138 patients) and non-ischemic morbidity (infection, stroke or bleeding; 37 patients) predicted prolonged intensive care unit treatment. Intensive care unit treatment for > 3 days occurred in 26.8% of patients with ischemic morbidity compared with 3.2% of patients without ischemic morbidity (P = 0.001). Prolonged intensive care stay occurred in 32.4% of patients who suffered non-ischemic complications compared with 5.7% of patients who did not suffer these complications. The multiple logistic regression analysis odds ratio for ischemic morbidity was 7.4 (95% c.i. 4.0-13.4) compared with 4.8 (95% c.i. 1.9-10.1) for non-ischemic morbidity. Strategies designed to reduce the incidence of prolonged intensive care unit treatment should include prevention of stroke, infection and bleeding. However, the greatest reduction of intensive care unit utilization would be mediated by prevention of ventricular dysfunction secondary to myocardial ischemia or inadequate myocardial preservation.

Can patients with left main stenosis wait for coronary artery bypass grafting?

BACKGROUND

The economic impact of health care reforms may result in waiting lists for coronary artery bypass grafting. This study was designed to examine the clinical results of patients with left main stenosis who were placed on a triaged wait list for operation.

METHODS

Data were collected prospectively on 2,145 patients undergoing isolated coronary artery bypass grafting between 1989 and 1994. Critical left main stenosis (LMS, 50% or more stenosis) was present in 281 patients, and 1,864 patients had no left main disease, or a left main stenosis of less than 50% (no LMS).

RESULTS

The average time from angiography to operation was shorter in patients with LMS (LMS 38 +/- 46 days versus no LMS 84 +/- 71 days; p = 0.0001). Two patients in the LMS group died; they had declined operation. Four patients suffered non-Q wave myocardial infarctions, all of whom subsequently underwent operation with no perioperative complications. The presence of LMS did not influence operative mortality (LMS 2.8% versus no LMS 1.3%), the incidence of low output syndrome (LMS 8.3% versus no LMS 5.4%), or the incidence of perioperative myocardial infarction (LMS 3.8% versus no LMS 4.2%). To examine the effect of waiting time on outcomes, patients with LMS were divided into early (operation 10 days or less after angiography) and late revascularization groups (more than 10 days). Operative mortality, low output syndrome, and myocardial infarction were similar in the early and late groups. Patients in the early group were more likely to have New York Heart Association functional class IV symptoms (64% versus late 22%; p < 0.0001), unstable angina (87% versus late 65%; p < 0.0001), or a recent preoperative myocardial infarction (17% versus late 2%; p < 0.0001).

CONCLUSIONS

Carefully selected patients with significant left main stenosis can safely wait for operation with a low risk of complications. Early surgical intervention is allocated to patients with severe symptoms or recent preoperative myocardial infarction.

Activation of glycosylasparaginase. Formation of active N-terminal threonine by intramolecular autoproteolysis

The activation mechanism of glycosylasparaginase of Flavobacterium meningosepticum has been analyzed by site-directed mutagenesis and activation of purified precursors in vitro. Mutation of Thr-152 to Ser or Cys leads to gene products that are not activated in vivo but are activated in vitro because processing of the mutant precursors is inhibited by certain amino acids in the cell. Kinetic studies reveal that activation is an intramolecular autoproteolytic process. The involvement of His-150 and Thr/Ser/Cys-152 in activation suggests that autoproteolysis resembles proteolysis by serine/cysteine proteases. Multiple functions of the highly conserved active threonine residue are implicated.

Randomized study of right ventricular function with intermittent warm or cold cardioplegia

BACKGROUND

Transient right ventricular dysfunction has been previously documented after bypass operations despite adequate myocardial protection with intermittent antegrade cold blood cardioplegia. Recently warm blood cardioplegia has been interrupted during construction of distal anastomoses to improve visualization. The effects of intermittent antegrade warm blood cardioplegia, and the resultant periods of right ventricular normothermic ischemia, on postoperative right ventricular function are unknown.

METHODS

To assess the effects of cardioplegia on right ventricular protection, 52 patients undergoing isolated bypass grafting were randomized to intermittent warm or cold blood cardioplegia. The two groups were similar with respect to age, sex, ventricular function, and right coronary stenoses. Cross-clamp times were similar (warm, 64 +/- 22 minutes; cold, 63 +/- 15 minutes; not significant). The cumulative time of cardioplegia interruption was longer in the cold group (42 +/- 8 minutes) than in the warm group (31 +/- 14 minutes; p < 0.002). A rapid-response thermodilution catheter was employed to assess postoperative right ventricular ejection fraction and end-diastolic and end-systolic volume indices.

RESULTS

The right ventricular ejection fraction was greater in the warm group at 6 hours (warm, 0.46 +/- 0.06; cold, 0.37 +/- 0.08; p < 0.05) and 8 hours (warm, 0.43 +/- 0.08; cold, 0.37 +/- 0.08; p < 0.05) postoperatively. The right ventricular end-diastolic volume index was less in the warm group 8 hours postoperatively (warm, 83 +/- 11 mL/m2; cold, 94 +/- 16 mL/m2; p < 0.05). There were no differences in pulmonary arterial pressures or right ventricular stroke work index.

CONCLUSIONS

Despite intermittent normothermic ischemia of half the cross-clamp time, patients receiving warm cardioplegia maintained right ventricular hemodynamics after bypass grafting.

Trends in pediatric cardiac pacing

OBJECTIVE

To review retrospectively a 31-year experience with pediatric cardiac pacing at the University of Toronto, with an emphasis on the changing trends in pacemaker implantation in infants and children.

DATA SOURCE

Data were obtained from the pediatric pacemaker follow-up clinic at The Hospital for Sick Children, Toronto, Ontario or from the referring pediatric centre. Follow-up was normally continued until the death of the child or referral to an adult hospital at age 18 years.

PATIENT SELECTION

The study comprised 397 children (under 18 years of age) who underwent initial pacemaker implantation at The Hospital for Sick Children between January 1962 and December 31, 1992. Follow-up was 99% complete (five children lost) and ranged from one month to 32 years (mean 6.5 years).

DATA SYNTHESIS

The use of endocardial versus epicardial leads increased significantly over time (P < 0.001). In addition, significantly more children receiving pacemakers had sick sinus syndrome (P < 0.001). No difference in survival was found between children paced by endocardial versus epicardial leads or between children paced for sick sinus syndrome versus atrioventricular block. The frequency of exit block, by lifetable analysis, did not differ between children who received epicardial versus endocardial leads.

CONCLUSIONS

Guidelines for permanent pacemaker implantation in children continue to evolve as developments in lead technology alter trends in pediatric cardiac pacing.

Intragraft expression of IL-10 messenger RNA: a novel correlate of renal allograft rejection

A major conceptual advance is the formulation that type I cytokines (such as IL-2 and IFN-gamma) enhance cellular immunity and are host-protective, and that type II cytokines (such as IL-4 and IL-10) dampen cellular immunity and facilitate the progression of infection. We have explored the intragraft expression of type I and type II cytokines during human renal allograft rejection. RNA was isolated from 98 allograft biopsies, and reverse transcription-PCR was used to amplify and identify intragraft expression of mRNA encoding IL-2, IFN-gamma, IL-4, or IL-10. Intragraft expression of IL-7 mRNA and TGF-beta 1 mRNA was also investigated. Our investigation demonstrated that: (a) intragraft expression of IL-10 mRNA and IL-2 mRNA are significant correlates of acute rejection; (b) IL-4, IL-7, IFN-gamma and TGF-beta 1 mRNA expression do not correlate with acute rejection; and (c) IL-10 does not prevent in vivo expression of IFN-gamma, IL-2, IL-7, or TGF-beta 1. Our studies identify, for the first time, a significant association between intragraft IL-10 mRNA expression and acute rejection, and suggest that treatment strategies capable of constraining IL-10 expression might be of value in the prevention of acute rejection.

Is body size the cause for poor outcomes of coronary artery bypass operations in women?

Although small body size and coronary artery diameter are recognized as major contributors to the increased risk of coronary artery bypass grafting in women, few studies have established the independent influence of body size and gender on outcome. We studied 7025 consecutive patients (5694 men, 1331 women) undergoing isolated coronary artery bypass grafting between 1990 and 1994. Women were older, had higher preoperative prevalences of urgent operation because of unstable angina, diabetes, peripheral vascular disease, hypertension, and single-vessel coronary artery disease (p < 0.0001), and a lower prevalence of left ventricular ejection fraction 40% or less (p < 0.0001). The prevalences of operative mortality (men, 1.8%; women, 3.5%), low-output syndrome (men, 6.6%; women, 14.8%), and myocardial infarction (men, 2.8%; women, 5.5%) were higher in women (p < 0.0001). Patients were divided into quartiles for body surface area, weight, height, and body mass index. For both men and women, there was no difference in operative mortality between the highest and lowest quartiles of body size. Women, however, had a higher prevalence of operative mortality than men in the lower quartiles of body surface area, height, and weight and in the higher quartiles of body mass index. Among men, the prevalence of low-output syndrome increased (p < 0.0001) with decreasing body surface area, weight, and body mass index, suggesting that body size did influence the prevalence of low-output syndrome. However, women had a higher prevalence of low-output syndrome than men in every category and quartile of body size (p < 0.0001). Multivariable analysis identified gender as a significant determinant of operative mortality (odds ratio 1.83, 95% confidence interval 1.27 to 2.64) and low-output syndrome (odds ratio 2.52, 95% confidence interval 2.05 to 3.11). When multivariable adjustments were made for body size and preoperative risk factors, gender remained a predictor of both operative mortality and low-output syndrome. Multivariable assessment of risk for men and women separately identified that urgent operation was a predictor of operative mortality (odds ratio 2.52, 95% confidence interval 1.32 to 5.61) and low-output syndrome (odds ratio 1.57, 95% confidence interval 1.14 to 2.17) in women but not men. In conclusion, the increased risk of coronary artery bypass grafting in women may be explained in part by dramatic differences in preoperative risk factors between men and women. In both men and women, small body size did not increase the risk of operative mortality, but may have contributed to the risk of low-output syndrome.(ABSTRACT TRUNCATED AT 400 WORDS)

Myocardial protection for coronary bypass grafting: the Toronto Hospital perspective

BACKGROUND

The contemporary results of coronary artery bypass grafting using a variety of myocardial preservation techniques are excellent. In recent years, the number of "high-risk" patients referred for operation has increased, thus necessitating continued advances in surgical myocardial protection.

METHODS

In this article, we review recent advances in clinical myocardial protective techniques and emphasize studies conducted at The Toronto Hospital. Further, on the basis of promising current research, we speculate on future prospects for myocardial protection.

RESULTS

At The Toronto Hospital, we converted from crystalloid to intermittent cold blood cardioplegia in 1985. We demonstrated that "continuous" cardioplegic strategies may help resuscitate the ischemic myocardium and reduce operative complications in high-risk patients. Further improvements in myocardial protection will require refinements in cardioplegic solution temperature, direction of delivery, and additives to "precondition" the myocardium against ischemic damage.

CONCLUSIONS

Major advances that meet the requirements of an increasingly high risk patient population have been made in surgical myocardial protection in recent years. The future is bright for continued progress in this area.

Exercise oximetry versus spirometry in the assessment of risk prior to lung resection

BACKGROUND

Spirometry remains a standard method of assessing patient risk prior to lung resection despite its poor sensitivity and specificity. This study compares the relative ability of standardized exercise oximetry and spirometry--forced expiratory volume in the first second--to predict morbidity and mortality after lung resection.

METHODS

The study comprised a retrospective review of 396 consecutive patients of whom 299 underwent both oximetry and spirometry. Oximetry was undertaken during standard exercise under the supervision of a single physical therapist. Spirometry identified 46 patients with a forced expiratory volume in the first second of less than 1.5 L who were considered to be high risk. Exercise oximetry was used to identify patients with arterial oxygen desaturation at rest, while walking on level ground, or while climbing two flights of stairs (n = 65).

RESULTS

Compared with spirometry, exercise oximetry more reliably predicted home oxygen requirements (p < 0.001), need of admission to the intensive care unit (p < 0.05), prolonged hospital stay (p < 0.001), and respiratory failure (p < 0.05). Oximetry identified 50% of the patients who died, all of whom had a forced expiratory volume in the first second of greater than 1.5 L. Despite its superior predictive value, the sensitivity of oximetry remained low.

CONCLUSIONS

We conclude that standardized exercise oximetry is a superior screen of the high-risk patient than spirometry (forced expiratory volume in the first second) prior to pulmonary resection when there are no other risk factors noted on initial history and physical examination. A prospective, randomized trial is required to substantiate this conclusion.