Minimal operative mortality in patients undergoing coronary artery bypass with significant left ventricular dysfunction by maximization of metabolic and mechanical support

Cardioprotective Effects of Glucose-Insulin-Potassium Infusion in Patients Undergoing Cardiac Surgery: A Systematic Review and Meta-Analysis

The infusion of glucose-insulin-potassium (GIK) has yielded conflicting results in terms of cardioprotective effects. We conducted a meta-analysis to examine the impact of perioperative GIK infusion in early outcome after cardiac surgery. Randomized controlled trials (RCTs) were eligible if they examined the efficacy of GIK infusion in adults undergoing cardiac surgery. The main study endpoint was postoperative myocardial infarction (MI) and secondary outcomes were hemodynamics, any complications and hospital resources utilization. Subgroup analyses explored the impact of the type of surgery, GIK composition and timing of administration. Odds ratio (OR) or mean difference (MD) with 95% confidence interval (CI) were calculated with a random-effects model. Fifty-three studies (n=6129) met the inclusion criteria. Perioperative GIK infusion was effective in reducing MI (k=32 OR 0.66[0.48, 0.89] P=0.0069), acute kidney injury (k=7 OR 0.57[0.4, 0.82] P=0.0023) and hospital length of stay (k=19 MD -0.89[-1.63, -0.16] days P=0.0175). Postoperatively, the GIK-treated group presented higher cardiac index (k=14 MD 0.43[0.29, 0.57] L/min P<0.0001) and lesser hyperglycemia (k=20 MD -30[-47, -13] mg/dL P=0.0005) than in the usual care group. The GIK-associated protection for MI was effective when insulin infusion rate exceeded 2 mUI/kg/min and after coronary artery bypass surgery. Certainty of evidence was low given imprecision of the effect estimate, heterogeneity in outcome definition and risk of bias. Perioperative GIK infusion is associated with improved early outcome and reduced hospital resource utilization after cardiac surgery. Supporting evidence is heterogenous and further research is needed to standardize the optimal timing and composition of GIK solutions.

Outcomes of Coronary Artery Bypass Grafting in Patients With Poor Myocardial Viability: A Systematic Review and Meta-Analysis of the Last Decade

OBJECTIVES

Our objective is to assess whether the presence of myocardial viability is a predictor of mortality among patients undergoing coronary artery bypasss grafting (CABG) through a systematic review meta-analysis.

METHODS

Comprehensive review of EMBASE and PubMed in accordance with PRISMA guidelines, including studies of patients undergoing CABG with assessment of myocardial viability and recorded long-term mortality, age and sex. Studies were restricted to the last decade, and data were stratified by imaging modality (magnetic resonance imaging [MRI] or nuclear medicine). Random-effects model for assessing pooled effect, heterogeneity assessment using Chi-square and I² statistics, publication bias assessed by funnel plots and Egger's test.

RESULTS

Meta-analysis of contemporary data (January 2010 to October 2020) yielded 3,621 manuscripts of which 92 were relevant, and 6 appropriate for inclusion with 993 patients. Pooled analysis showed that patients with non-viable myocardium undergoing CABG are at 1.34 times the risk of mortality compared to those with viable myocardium (95% CI 1.01-1.79, p=0.05). Subgroup analysis of the MRI or nuclear medicine modalities was not statistically significant and there was no confounding by age or sex in meta-regression. There was significant heterogeneity in imaging modality and diagnostic criteria, but heterogeneity between study findings was low with an I² statistic of 29%. The risk of publication bias was moderate on the Newcastle-Ottawa Scale), but not statistically significant (Egger's Test coefficient=1.3, 95%CI -0.35-2.61, p=0.10).

CONCLUSIONS

There is a multitude of methods for assessing cardiac viability for coronary revascularisation surgery, making meta-analyses fraught with limitations. Our meta-analysis demonstrates that the finding of non-viable myocardium can not be used draw conclusions for risk assessment in coronary surgery.

Effects of myocardial viability and left ventricular remodeling on survival of patients with heart failure and reduced ejection fraction after coronary artery bypass grafting

Background

Heart failure with reduced ejection fraction (HFrEF) caused by coronary heart disease (CHD) accounts for the largest proportion of patients with heart failure and is associated with the poorest prognosis. However, date on the perioperative risk and long-term survival of patients with HFrEF are limited. The present study aimed at exploring the effects of the left ventricular end-systolic volume index (LVESVI) and myocardial viability on perioperative risk and long-term survival after coronary artery bypass grafting (CABG) in patients with HFrEF.

Methods

This is a single center, prospective, observational study. CHD patients with symptoms and signs of heart failure and a left ventricular ejection fraction (LVEF) <40% were enrolled consecutively from January 2014 to February 2018. Operative mortality, perioperative complications and long-term survival were compared in the patients with various LVESVIs and myocardial viabilities. The primary outcomes were cardiac death, myocardial infarction, heart failure, stroke and revascularization [percutaneous coronary intervention (PCI) or redo CABG] with a median follow-up of 30±12 months.

Results

Perioperative mortality was 6.8% in the 118 patients in this study. Perioperative mortality was significantly higher in the low myocardial viability (LMV) group than in the high myocardial viability (HMV) group (12.5% vs. 3.8%, P=0.034). The 12-, 24-, 36-month major adverse cardiac event (MACE)-free survival rate of patients with HMV was significantly higher than that of patients with LMV (HMV vs. LMV: 96.9% vs. 88.6%, 93.4% vs. 85.5%, 79.4% vs. 68.2%, P=0.004). There was no difference in MACE-free survival among patients with different degrees of left ventricular remodeling within each group.

Conclusions

Myocardial viability is an important factor that affects the perioperative mortality and long-term survival of patients with ischemic HFrEF after CABG. Left ventricular remodeling increases perioperative mortality but has no effect on long-term survival.

Methodological approach in adopting off-pump coronary artery bypass surgery in a British cardiothoracic unit: Harefield experience

The theoretical and practical disadvantages of coronary artery bypass graft surgery using cardiopulmonary bypass with cardioplegic arrest are well reported in the literature. Encouraged by our work and others, we adopted a systematic approach to the application of off-pump coronary artery bypass surgery. We aimed to validate the non-selective use of the off-pump technique in all patients and assess the outcome in specific patient groups including: patients with ischaemic left ventricular dysfunction, female and high-risk patients. We investigated specific technical details related to off-pump surgery including: the potential effect of the distortion of the mitral valve on haemodynamic stability intraoperatively and the feasibility of sequential coronary artery bypass grafting using the off-pump technique. We also compared the outcome to the national United Kingdom performance in a risk-stratified manner. An extensive retrospective data review for comparative analysis of outcome was carried out at both local and multi-centre levels. This showed that off-pump surgery was feasible for all patients, and provided a better outcome in patients with ischaemic left ventricular dysfunction, female and high-risk patients. The distortion of the mitral valve contributed to the haemodynamic instability. In conclusion, off-pump surgery is safe and provides better outcome in specific patient groups.

[Results of coronary artery bypass grafting with left ventricular dysfunction (comparison of off-pump versus on-pump)]

BACKGROUND

The aim of this study was to compare the results of myocardial revascularisation with or without cardiopulmonary bypass in patients with impaired left ventricular function.

PATIENTS AND METHODS

Five hundred and sixteen consecutive patients who underwent coronary artery bypass grafting from January 2000 through December 2007 were analyzed retrospectively. One hundred and eight cases had a left ventricular EF (ejection fraction) of 45% or less. Of these patients, 78 underwent conventional coronary artery bypass (CCABG) and 30 underwent off-pump procedure (OCABG). The CCABG group received 300IU/kg of heparin while the OCABG received 100IU/kg. The off-pump coronary surgery was carried out using a tissue stabilizer Octopus II. Different pre-, per- and postoperative variables were evaluated among both groups. Statistical analysis was performed by SPSS 11.5. The variables were compared between these two groups using univariate analysis (Chi(2) test, Fisher's test exact) for qualitative variable and (Student's t test, Mann-Whitney's test) for quantitative variable.

RESULTS

Patients profiles and risk factors were similar among both groups except for age (CCABG: 57.8±9.2 year vs OCABG: 52±9.9 year; P=0.004) and left ventricular EF (CCABG: 37.4±6.3% vs OCABG: 34±7.8%; P=0.02). The number of grafts performed per patient was significantly more among patients who underwent extracorporeal circulation (CCABG: 2.53±0.7 graft/patient vs OCABG: 1.77±0.8 graft/patient; P<0.0001). The hospital mortality was more among CCABG group 9% vs 3.3% in OCABG but the difference was not significant (P=0.3). However, the operative time and the operative room stay were long in CCABG (252±61min vs 175±38min; P<0.0001 - 389±70min vs 298±54min; P<0.0001). The ventilation time was also long in CCABG (32.3±67hour vs 10.4±5.9hour; P=0.15). There was more postoperative myocardial infarction in CCABG (P=0.008), but the EF increased and was better in CCABG.

CONCLUSION

Off-pump coronary artery bypass surgery provides satisfactory operative results for most patients with reduced left ventricular function. Prospective and randomly study will be necessary before concluding.

Stabilizing endothelium of donor hearts with fusogenic liposomes reduces myocardial injury and dysfunction

BACKGROUND

Myocardial injury after heart transplantation is a consequence of pathophysiologic events initiated by local ischemia/reperfusion injury that is further aggravated by the inflammatory response due to blood exposure to the pump's artificial surfaces during cardiopulmonary bypass. The purpose of the present study was to determine the effectiveness of fusogenic lipid vesicles (FLVs) in enhancing the cardioprotective effect of St. Thomas organ preservation solution (ST). We hypothesized that donor hearts preserved with ST+FLVs will stabilize the endothelium during reperfusion, which, in turn, will reduce both endothelial barrier dysfunction and myocardial damage.

METHODS

To examine the effect of ST+FLVs therapy in vitro, C3b deposition and adhesion molecule expression studies were performed on human umbilical vein endothelial cells challenged with plastic contact-activated plasma. To assess the therapy in vivo, a cervical heterotopic working heart transplantation model in rats was used. Donor hearts were preserved for 1 h at 27°C (15 min) and 4°C (45 min) and, after transplantation, were followed up for 2 h. Left ventricular function and the blood cardiac troponin I levels were quantified.

RESULTS

Human umbilical vein endothelial cells treated with ST+FLVs had reduced C3b deposition and expression of adhesion molecules compared with ST alone (P < 0.05). Donor hearts receiving ST+FLVs therapy had reduced left ventricular dysfunction and cardiac troponin I compared with ST alone.

CONCLUSIONS

We concluded that FLVs enhanced the cardioprotective effect of ST and reduced postischemic left ventricular dysfunction and myocardial damage. The mechanism of protection appears to be associated with the stabilization of endothelial cell membranes owing to incorporation of FLV-derived lipids.

Off-pump coronary artery bypass grafting in left ventricular dysfunction

Between August 2004 and May 2006, 124 patients undergoing coronary artery bypass grafting with ejection fractions <or= 35% were randomly assigned to off-pump or conventional procedures. Preoperative characteristics were the same in both groups, except for age and degree of mitral regurgitation. Off-pump coronary artery grafting was carried out using a tissue stabilizer and a single-suture technique; conventional coronary bypass employed cardiopulmonary bypass, moderate hypothermia, and antegrade-retrograde cold blood cardioplegic arrest. There were significantly fewer vessels grafted (3.09 +/- 0.41) in the off-pump group than in those who had a conventional procedure (3.42 +/- 0.86). The rates of mortality, morbidity, balloon pump support, inotropic usage, gastrointestinal bleeding, renal dysfunction, reintubation, as well as intensive care and hospital stay, were significantly lower in the off-pump group. The incidence of perioperative myocardial infarction did not differ significantly between groups. The results of this study indicate that beating-heart coronary bypass is safe and effective in patients with left ventricular dysfunction.

Long-term results of coronary artery bypass grafting in patients with left ventricular dysfunction

BACKGROUND

In this prospective study, we investigated the determinants of long-term outcome, symptoms, and left ventricular function after coronary artery bypass grafting in patients with a moderate to severely decreased left ventricular ejection fraction.

METHODS

Between 1997 and 1998, 75 consecutive patients with moderate to severe left ventricular dysfunction underwent coronary artery bypass grafting procedures. The operative mortality rate was 4.0%, and the 72 survivors were monitored for 8 years. The end points were mortality, symptomatic status (New York Heart Association [NYHA] functional class), and left ventricular function.

RESULTS

The total survival rate after 8 years was 89.3%. During follow-up, 8 patients died. Death was attributed to a cardiac cause in 5 patients and to a noncardiac cause in 3. There was no statistically significant difference between preoperative and late postoperative NYHA functional class, despite a statistically significant improvement that persisted for up to 4 years after CABG. The results of echocardiography showed a statistically significant improvement in the left ventricular ejection fraction (from 0.322 +/- 0.06 preoperatively to 0.463 +/- 0.02 at follow-up, p < 0.001). Multivariate analysis revealed that the left ventricular end-systolic volume index, the presence of angina pectoris, and absence of symptoms of congestive heart failure were preoperative indicators of freedom from heart failure after coronary operations (p < 0.05).

CONCLUSIONS

Coronary artery bypass grafting for patients with moderate-to-severe left ventricular dysfunction is associated with acceptable long-term results. The left ventricular end-systolic volume index is a simple noninvasive method to aid in the preoperative decision making in such patients.

Oral triiodothyronine for the prevention of thyroid hormone reduction in adult valvular cardiac surgery

Treatment of non-thyroidal illness by intravenous triiodothyronine (T3) after cardiac surgery causes a disproportional elevation of hormone levels. The administration of oral T3, which has never been studied in this context, could cause physiological hormone levels. The aim of this study was to test oral T3 for the prevention of T3 reduction during the postoperative period of valvular cardiac surgery in adults. Eighteen patients who underwent cardiac surgery for valvular disease with invasive hemodynamic monitoring were randomly assigned to 2 groups: the T group received oral T3 (N = 8), 25 microg three times/day, initiated 24 h before surgery and maintained for 48 h and the NT group (N = 10) received placebo. Serum T3, thyroxine and thyrotropin were determined at baseline, 1 h before surgery, within 30 min of cardiopulmonary bypass and 6, 12, 24, and 48 h after removal of the aortic cross-clamp. Baseline T3 was similar in both groups (T: 119 +/- 13; NT: 131 +/- 9 ng/dL). Serum T3 increased during the first 24 h in the T group compared to the NT group (232 +/- 18 vs 151 +/- 13 ng/dL; P < 0.001). In the NT group, T3 was reduced by 24% (P = 0.007) 6 h after removal of the aortic cross-clamp, confirming the non-thyroidal illness syndrome. There were no differences in clinical or hemodynamic parameters between groups. Administration of oral T3 prevented its serum reduction after valvular cardiac surgery in adults, with normal serum levels for 48 h without disproportional elevations.

Coronary artery bypass grafting in patients with left ventricular dysfunction

BACKGROUND

Coronary artery bypass grafting surgery (CABG) remains a challenge for patients with coronary artery disease and left ventricular (LV) dysfunction. The aim of this study was to evaluate the result of CABG in patients with LV dysfunction.

METHODS

Medical records of 1,847 patients who underwent primary, isolated CABG at Taipei Veterans General Hospital from January 1, 1991 to December 31, 2002, were reviewed. The mortality rate associated with clinical and operative variables was compared between patients with LV ejection fraction (LVEF) > or = 35% and patients with LVEF < 35%.

RESULTS

Patients with LVEF < 35% had more episodes of myocardial infarction (57.5% vs 28.9%, p < 0.001) and history of congestive heart failure (18.1% vs 3.2%, p < 0.001), higher New York Heart Association (NYHA) class, and higher angina class. Longer cardiopulmonary bypass time (147 +/- 44 minutes vs 137 +/- 40 minutes, p < 0.001) but fewer left internal mammary artery (LIMA) grafts (46.8% vs 65.7%, p < 0.001) were used in patients with LVEF < 35%. Patients with LVEF < 35% had significantly higher hospital mortality (6.6% vs 2.2%, p < 0.001), higher major morbidity (23.3% vs 16.1%, p < 0.01), and longer hospital stay (25 +/- 23 days vs 21 +/- 16 days, p < 0.01).

CONCLUSION

Although patients with LV dysfunction had higher mortality and morbidity, CABG could be done in these high-risk patients with acceptable results.

Coronary Artery Bypass Grafting in Patients with Severe Left Ventricular Dysfunction-Early and Mid-Term Outcomes

BACKGROUND

The prevalence of patients with severe left ventricular dysfunction (LVD) referred for coronary artery bypass grafting (CABG) is increasing. The aim of the present study was to assess the outcomes of patients with severe LVD undergoing CABG.

METHODS

Outcomes of 115 consecutive patients with severe LVD (left ventricular ejection fraction [LVEF]</= 30%, mean 22 +/- 6%) undergoing isolated CABG between 1995 and 2000 were compared to 2335 patients with LVEF >30% (HEF). To further evaluate the LVD patients, they were divided into three subgroups base on LVEF: 0% to 10%, 11% to 20%, and 21% to 30%. Data were collected prospectively and entered into the departmental database of the Society of Thoracic Surgeons.

RESULTS

Patients in the LVD group had increased incidence of diabetes, chronic obstructive pulmonary disease (COPD), peripheral vascular disease, prior myocardial infarction (MI), congestive heart failure, and less elective procedures compared to the HEF group. Despite this greater risk profile, operative mortality (LVD 2.6% vs. HEF 1.2%, p = 0.19), the incidence of stroke (2.6% vs. 1.0%, p = 0.13), and perioperative MI (0.9% vs. 0.7%) were not statistically different between the groups. The incidence of respiratory (14.8% vs. 1.9%, p < 0.001), renal (5.2% vs. 1.0%, p < 0.001), and vascular (5.2% vs. 0.5%, p < 0.001) complications was significantly higher in the LVD group, resulting in a longer hospital length of stay (8 +/- 8 vs. 6 +/- 4 days, p < 0.0001). In a multivariate analysis, advanced age was as an independent predictor of hospital mortality. Average follow-up in 108 (94%) LVD patients was 36 +/- 22 months (range 2 to 78 months). Twenty-one patients expired during the follow-up, for nine the causes were cardiac-related. Three- and 5-year survival rates were 91 +/- 3% and 76 +/- 6%, respectively. Independent predictors of mid-term mortality in the LVD group by a multivariate analysis included female gender, renal failure, respiratory complications, and grade I/II mitral regurgitation (MR). At the time of follow-up, 72% of LVD patients were in functional class I/II. There were no statistically significant differences in short- and mid-term outcomes among the LVD subgroups.

CONCLUSION

CABG in patients with severe LVD can be performed with a low mortality, albeit with higher morbidity and longer length of hospital stay, than patients with LVEF >30%. Low ejection fraction per se was not a predictor of hospital mortality. CABG should be considered a safe and effective therapy for low ejection fraction patients with ischemic heart disease. Mitral valve repair/replacement in the presence of moderate degree of MR should be considered at the time of the initial operation.

Coronary Bypass Surgery for Patients with Chronic Poor Preoperative Left Ventricular Function (EF<30%): 5-year Follow-up

BACKGROUND

Optimal therapy for patients with coronary artery disease and chronic poor left ventricular function, given the absence of randomized trials, is unclear. Although coronary surgery has been performed in such patients for 25 years, it is perceived as high risk and unproven long-term benefit, especially if thallium scanning fails to demonstrate large areas of viability. We report the results of coronary surgery in these patients.

METHODS

Retrospective analysis by a standardized patient questionnaire, of 107 such consecutive patients offered coronary surgery.

RESULTS

Mean follow-up was 3.3 years (range, 0.5-5.5); average patient age was 64.4+/-1 years. Preoperative thallium scans were performed solely on 31 patients with none or mild angina, of which 10 (32%) demonstrated large areas of viable myocardium. Perioperative mortality was 1.9%. On multivariate analysis, factors predictive of increased perioperative death were recent myocardial infarction (p<0.001) and nonelective surgery (p<0.001). Kaplan-Meier 5-year survival and freedom from major adverse cardiac events were 72.3 and 82.3%, respectively. In 21 patients, with preoperative nil-to-mild angina and nil-to-small areas of myocardial viability, thallium scanning failed to predict a successful outcome.

CONCLUSION

Offering coronary surgery to these patients irrespective of thallium testing is safe and effective in the medium term. Early surgery is recommended.

Heart failure after myocardial revascularization: risk markers

We investigated the prognostic weight of several risk factors for heart failure in patients undergoing CABG. We followed 351 consecutive patients for 18+/-12 months after surgery to assess clinical outcome, presence and degree of heart failure. The risk of developing heart failure >class 2 at 1 year was investigated by logistic regression on the following preoperative variables: sex, age, left ventricular EF, QRS duration, previous MI, history of heart failure, atrial fibrillation (AF), hypertension, hypercholesterolemia, diabetes, previous stroke. Age was 70+/-8 years and EF was 54+/-12% at the time of surgery. Heart failure >class 2 occurred in 95/351 patients (27%) at follow up. Logistic regression identified QRS duration (OR=1.02), a history of stroke (OR=3.94), and diabetes (OR=1.98) as predictors of CHF at follow up. All the other variables were not risk markers for heart failure at logistic regression. Thirty five patients (10%) had QRS> or =140 ms before surgery; 51% of them had CHF at follow up compared to 24% of patients with QRS<140 ms (p<0.05). In the current surgical era, candidates to CABG (50% of patients older than 70 years) have a relevant likelihood of heart failure at follow up, despite myocardial revascularization. Risk stratification may rely upon inexpensive variables as previous stroke, diabetes, and QRS duration. A minority of patients (5%) could benefit from LV-based pacing, which should be considered at the same surgical time via an epicardial implantation.

Low triiodothyronine (T3) or reverse triiodothyronine (rT3) syndrome modifies gene expression in rats with congestive heart failure

Heart failure (HF) is frequently associated with euthyroid "sick" syndrome (low T3 and elevated rT3). We investigated if altered thyroid hormone in HF could affect expression of the TH receptor (TRalpha1), and alpha and beta myosin heavy chains (alpha-MHC, beta-MHC). HF was provoked in rats by aortic stenosis. We showed that rT3 generated from liver and kidney deiodination significantly increased and T3 decreased in HF; there was significantly higher TRalpha1 expression, no alpha-MHC expression, but beta-MHC expression. Changes in TRalpha could be compensating for low T3 from HF.

Operative results of coronary artery bypass grafting in women

BACKGROUND

The relative mortality of coronary artery bypass grafting (CABG) surgery in women is not certain. The purpose of this study was to examine the results of primary, isolated CABG in a series of Taiwanese female patients.

METHODS

Medical records of 2055 patients (188 women and 1867 men), who underwent primary, isolated CABG at Taipei Veterans General Hospital from January 1, 1991 to December 31, 1999, were reviewed. The mortality rate, associated with clinical and operative variables, was compared between female and male patients.

RESULTS

The female patients had more diabetes (51.6% vs. 29.9%, P<0.01), more hypertension (77.1% vs. 65.0%, P<0.01), and more hypercholesterolemia (39.4% vs. 29.6%, P<0.01), as compared with men. Fewer women consumed cigarette smoking (17.0% vs. 52.1%, P<0.001). Fewer internal mammary artery grafts were used in women (43.1% vs. 57.3%, P<0.001). Nine female (4.8%) and 93 male patients (5.0%) died. There was no significant difference in hospital mortality between women and men. Other variables, including age, angina class, NYHA class, incidence of peripheral arterial occlusive disease, stenosis of left main coronary artery, number of stenotic coronary arteries, incidence of emergent operations, anastomosis number, aortic cross-clamping time, cardiopulmonary bypass time, and left ventricular ejection fraction, were not significantly different between female and male patients.

CONCLUSIONS

Although the female patients were more frequently diabetic, hypertensive, and hypercholesterolemic, the hospital mortality of CABG in women was not significantly different from that in men. This result supports an aggressive surgical treatment for women with coronary artery disease.

Why do patients with ischemic cardiomyopathy and a substantial amount of viable myocardium not always recover in function after revascularization?

OBJECTIVE

In patients with ischemic cardiomyopathy and a substantial amount of dysfunctional but viable myocardium, myocardial revascularization may improve left ventricular ejection fraction. The aim of this study was to evaluate why not all patients with a substantial amount of viable tissue recover in function after revascularization.

METHODS

A total of 118 consecutive patients with a depressed left ventricular ejection fraction (on average 29% +/- 6%) due to chronic coronary artery disease underwent myocardial revascularization. Before revascularization all patients underwent dobutamine stress echocardiography to assess regional dysfunction, left ventricular volumes, and myocardial viability as well as radionuclide ventriculography to determine the left ventricular ejection fraction. Next, 3 to 6 months after revascularization, the left ventricular ejection fraction and regional contractile function were reassessed. Improvement of left ventricular ejection fraction > or = 5% following revascularization was considered clinically significant.

RESULTS

Dobutamine stress echocardiography revealed that 489 (37%) of the 1329 dysfunctional segments were viable. A total of 61 (52%) patients had a substantial amount of viable myocardium (> or = 4 viable segments). In these 61 patients the global function was expected to recover > or = 5% after revascularization. However, left ventricular ejection fraction did not improve in 20 (33%) of 61 patients despite the presence of substantial viability. Clinical characteristics and echocardiographic data were comparable between patients with and without improvement. However, patients without improvement had considerably larger end systolic volumes (153 +/- 41 mL vs 133 +/- 46 mL, P =.007). The likelihood of recovery of global function decreased proportionally with the increase of end systolic volume (P <.001, R = 0.43, n = 61). Receiver operating characteristic curve analysis demonstrated that an end systolic volume > or = 140 mL had the highest sensitivity/specificity to predict the absence of global recovery.

CONCLUSIONS

In patients with ischemic cardiomyopathy not only the amount of dysfunctional but viable myocardium but also the extent of left ventricular remodeling determines the improvement in function following myocardial revascularization. Patients with a high end systolic volume due to left ventricular remodeling have a decreased likelihood of improvement of global function.

Relationship Between Processes of Care and Coronary Bypass Operative Mortality and Morbidity

BACKGROUND

Information is limited regarding the effects of processes of care on cardiac surgical outcomes. Correspondingly, many recommended cardiac surgical processes of care are derived from animal experiments or clinical judgment. This report from the VA Cooperative Study in Health Services, "Processes, Structures, and Outcomes of Cardiac Surgery," focuses on the relationships between 3 process groups (preoperative evaluation, intraoperative care, and supervision by senior physicians) and a composite outcome, perioperative mortality and morbidity.

METHODS

Data on 734 risk, process, and structure variables were collected prospectively on 3,988 patients who underwent coronary artery bypass grafting at 14 VA medical centers between 1992 and 1996. Data reduction was accomplished by examining data completeness and variation across sites and surgeon, using previously published data and clinical judgment. We then applied multivariable logistic regression to the 39 remaining processes of care to determine which were related to the composite outcome after adjusting for 17 patient-related risk factors and controlling for intraoperative complications.

RESULTS

Our first analysis showed several measures of operative duration, the use of inotropic agents, transesophageal echo, lowest systemic temperature, and hemoconcentration/ultrafiltration, to be powerful predictors of the composite outcome. Because the use of inotropic agents and operative duration may be related to an intermediate outcome (eg, intraoperative complications), we performed a second analysis omitting these processes. The use of intraoperative transesophageal echo and hemoconcentration/ultrafiltration remained significantly associated with an increased risk of an event (odds ratios 1.60 and 1.36, respectively).

CONCLUSIONS

Our results viewed in the context of past studies suggest the possibility that inotropic use, TEE, and hemoconcentration/ultrafiltration may have adverse effects on operative outcome. Further evaluation of these processes of care using observational data, as well as randomized trials when feasible, would be of interest.

Is the use of cardiopulmonary bypass for multivessel coronary artery bypass surgery an independent predictor of operative mortality in patients with ischemic left ventricular dysfunction?

BACKGROUND

l Coronary artery bypass grafting for patients with ischemic left ventricular dysfunction (ILVD) remains superior to medical therapy in terms of long-term survival. Recently, off-pump coronary artery bypass surgery has been shown to be very promising in achieving functional improvements with favorable operative mortality in this challenging group of patients. The aim of this study was to assess the risk factors responsible for operative mortality in this group of patients.

METHODS

The records of 305 consecutive ILVD patients, who underwent primary isolated coronary artery bypass grafting for multivessel disease at The National Heart and Lung Institute, Imperial College, University of London, between January 1999 and January 2002, were reviewed retrospectively. Patients were considered to have ILVD if they had a left ventricular ejection fraction of 0.30 or less on preoperative coronary angiography. One hundred six patients were operated on using the off-pump coronary artery bypass surgery technique, and 199 patients were operated on using the conventional coronary artery bypass grafting technique with cardiopulmonary bypass. RESU;TS: Seven (6.6%) patients died in the off-pump coronary artery bypass surgery group, whereas 28 (14.1%) patients died in the cardiopulmonary bypass group (p = 0.05). Univariate analysis of all the preoperative characteristics was performed to identify the potential predictors of mortality in the whole group of ILVD patients. Potential predictors of mortality included symptom status (stable/unstable), chronic obstructive airway disease, dyspnea grade III and IV on the New York Heart Association classification, intravenous nitrates, preoperative use of intraaortic balloon pump, ventricular tachycardia or ventricular fibrillation, body surface area less than 2, and cardiopulmonary bypass. Only ventricular tachycardia or ventricular fibrillation was proved to act as an independent predictor of operative mortality in this group of ILVD patients, with an odds ratio of 29.6 (95% confidence interval, 8.9 to 98).

CONCLUSIONS

This study showed that using cardiopulmonary bypass for multivessel coronary artery bypass grafting in patients with ILVD was not proved to act as an independent predictor of operative mortality.

Protecting the damaged heart during coronary surgery

In coronary surgery, protective strategies that offer adequate safety for patients with healthy ventricles may not be adequate for those with severe impairment of ventricular function.

Predictors of early outcome after coronary artery surgery in patients with severe left ventricular dysfunction

BACKGROUND

The surgical survival in patients with severe myocardial dysfunction is critically dependent on the selection of patients. The present study was undertaken to identify the prognostic factors in such patients.

METHODS

We analyzed the data of 176 consecutive patients (161 men, 15 women), aged 29 to 88 years (mean 58.43), with a left ventricular ejection fraction (LVEF) < 30% who underwent isolated coronary artery bypass grafting. The LVEF ranged from 15% to 30% (mean 27.18%). Preoperatively, 33% had angina, 19.9% had recent myocardial infarction, and 21.6% had congestive heart failure. The mean number of grafts was 2.5/patient. The intra-aortic balloon was used prophylactically in 20.5% of patients and therapeutically in 4.0% of patients.

RESULTS

The hospital mortality was 2.3%. The complications occurred as follows: perioperative myocardial infarction in two (1.1%), intractable ventricular arrhythmias in two (1.1%), prolonged ventilation in four (2.3%) and peritoneal dialysis in 1 (0.6%). The mean ICU and hospital stay were 2.46 +/- 0.76 and 7.57 +/- 2.24 days, respectively. The predictors of survival on univariate analysis were New York Heart Association (NYHA) class (x2 = 14.458, p < 0.001), recent myocardial infarction (x2 = 5.852, p = 0.016), congestive heart failure (CHF) (x2 = 5.526, p = 0.019), and left ventricular end-systolic volume index (LVESVI) (x2 = 25.833, p < 0.001). However, on multivariate analysis, left ventricular end-systolic volume index was the only independent left ventricular function measurement predictive of survival (x2 = 10.228, p = 0.001).

CONCLUSION

Left ventricular end-systolic volume index is the most important predictor of survival after coronary artery bypass surgery in patients with severe myocardial dysfunction.

Nonthyroidal illness syndrome in off-pump coronary artery bypass grafting

BACKGROUND

Cardiopulmonary bypass (CPB) is an established cause of nonthyroidal illness syndrome (NTIS). Off-pump coronary artery bypass (OPCAB) has been reported to be less invasive than coronary artery bypass grafting (CABG) with CPB. We prospectively evaluated thyroid metabolism in OPCAB patients.

METHODS

We analyzed free thyroid hormones (FT3 and FT4), thyroid-stimulating hormone (TSH), and reverse T3 (rT3) in 20 consecutive patients undergoing CABG surgery. Nine patients underwent CABG with CPB, and 11 underwent OPCAB. Blood samples were taken on admission, on the day of surgery (7:30 AM), after sternotomy, at the end of the operation, and at 2, 6, 12, 24, 36, 48, 72, 96, 120, and 144 hours postoperatively. The concentrations of FT3, FT4, and TSH were determined on each sample. Reverse T3 concentration was measured in 10 patients up to 48 hours and at 144 hours postoperatively.

RESULTS

Baseline, operative, and postoperative variables were similar in the two groups. FT3 concentration dropped significantly (p < 0.0001), reaching its lowest value 12 hours postoperatively. There were no significant differences between CPB and OPCAB patients. FT4 varied significantly in both groups (p < 0.0001), but remained in the normal range. TSH variation was not significant. rT3 concentration rose significantly (p = 0.0002) in both groups, peaking 24 hours after surgery. CONCLUSIONS. OPCAB induces a NTIS similar to that observed after CPB, probably due to the inhibition of T4 conversion to T3. This finding suggests that NTIS is a nonspecific response to stress. CPB should not be considered as the sole trigger of NTIS in cardiac surgical patients.

Thyroid hormone and cardiac surgery

Thyroid hormone has important effects on the heart and peripheral vascular system. The relationship between thyroid disease states and cardiovascular hemodynamics is well recognized. Diverse clinical situations are associated with low serum triiodothyronine (T3) levels including a number of cardiovascular illnesses. In particular, cardiopulmonary bypass and open heart operations result in a low T3 state and are often complicated by significant cardiovascular dysfunction similar to that observed in clinical hypothyroidism. Multiple lines of evidence have suggested that T3 can act acutely as a positive inotrope and vasodilator agent. This recognition has prompted a number of investigators to study the effects of T3 administration to patients in the perioperative period. This paper reviews the experimental background that supported such clinical trials as well as outlines the results that have been documented in both adult and pediatric patients undergoing cardiac surgery. Low serum T3 levels resulting from cardiopulmonary bypass can be safely reversed with pharmacologic T3 supplementation. Data have suggested that T3 repletion may improve postoperative hemodynamic performance and lower the incidence of arrythmias. However, beneficial effects on major clinical outcome variables have not yet been conclusively demonstrated, and require future large-scale clinical trials.

Thyroid hormone metabolism in patients with congestive heart failure: the low triiodothyronine state

Thyroid hormone has multiple effects on the cardiovascular system, ranging from molecular and cellular effects to the consequent hemodynamic alterations. Consequently, thyroid function has been evaluated in small cohorts of patients with advanced heart failure that indicate a significant prevalence of morphologic or functional thyroid disorders. We sought to determine the prevalence of altered thyroid hormone metabolism in a broad spectrum of ambulatory heart failure patients. Thyroid function tests were evaluated in 132 ambulatory patients (98 males, 32 females, mean age, 67 years) with left ventricular systolic dysfunction (EF < 35%) and New York Heart Association (NYHA) class I-IV symptoms. Hypothyroidism was defined as serum thyroid-stimulating hormone (TSH) > 4.25 U/mL and low triiodothyronine (T3) state was defined as T3 levels < 80 ng/dL, with normal thyroxine (T4) and TSH level. Seven percent of patients were found to have primary hypothyroidism and 34% have a low T3 state. Of patients receiving amiodarone, 21% had elevated TSH levels and 76% had low T3 levels. The prevalence of abnormal thyroid function correlated with NYHA class. There is an unexpectedly high risk of hypothyroidism and low T3 syndrome in patients regardless of treatment with amiodarone, which appears to correlate with disease severity that requires further investigation.

Surgical treatments for heart failure

The surgical options for CHF are a part of a larger paradigm shift in management. Viable and effective surgical options other than cardiac transplant and ventricular assist devices clearly exist and are applicable to a large portion of patients with CHF. These surgical therapies are of acceptable risk before decompensated CHF develops. The rapidly evolving therapies for altering LV remodeling, which underlies CHF progression, are an exciting area that may be joined in the future by molecular advances in myoblast transfer and gene therapy. These therapies are the basis of the discipline of CHF surgery within cardiovascular surgery.

Myocardial revascularization as a therapeutic strategy in the patient with advanced ventricular dysfunction

The number of patients with severe ventricular dysfunction from coronary artery disease is constantly increasing. Although the medical management of these patients with angiotensin-converting enzyme inhibitors and beta-blockers has favorable impact on the morbidity and mortality the overall prognosis is still poor. Historically many of these patients have been referred for transplantation. In the past few years there has been an increasing amount of information about the utility of surgical revascularization in patients with low ejection fraction. Careful patient selection and optimal perioperative management is of critical importance for good outcome. Coronary artery bypass grafting (CABG) can be performed relatively safely despite the advanced level of left ventricular dysfunction. Quality of life is improved by CABG with elimination of angina and enhanced functional capacity. Improvement in the ejection fraction and increased survival after the operation has been objectively demonstrated. However patients with advanced right ventricular dysfunction, pulmonary hypertension, redo bypass and ungraftable coronaries should be considered for heart transplantation. In this review we describe our experience and focus on pertinent issues in patient selection, perioperative management and long term outcome after coronary artery bypass grafting.

Predictors of operative risk for coronary bypass operations in patients with left ventricular dysfunction

OBJECTIVES

The prevalence of ventricular dysfunction in patients undergoing coronary operations, as well as the prevalence of other risk factors in these patients, has been increasing. We identified the predictors of mortality and morbidity in patients with ventricular dysfunction to permit more accurate evaluation of risk and to direct future strategies to improve outcomes.

METHODS

Demographic, intraoperative, and outcome data were collected prospectively on 20,614 patients undergoing isolated coronary operations at our institution from 1982-1997. Multivariable regression analyses were used to identify the independent predictors of mortality and low-output syndrome.

RESULTS

Moderate ventricular dysfunction (ejection fraction, 20%-40%) was noted in 4107 (19.9%) patients, and severe dysfunction (ejection fraction, <20%) was noted in 680 (3.3%) patients. Patients with worse ventricular function had an increasing prevalence of other risk factors with time. Mortality decreased between the 1982-1986 and 1987-1991 cohorts but did not decrease further. Low-output syndrome was less common in the 1992-1997 cohort than in previous years. The predictors of mortality were ventricular dysfunction, age, reoperation, year of operation, urgency, female sex, and left main stenosis. Low-output syndrome was predicted by ventricular dysfunction, reoperation, year of operation, female sex, urgency, extensive coronary disease, age, left main stenosis, and symptom class.

CONCLUSIONS

Despite the increasing prevalence and risk profile of patients with ventricular dysfunction, mortality rates and incidence of low-output syndrome declined with time. Patients with severe dysfunction were at greatest risk when facing reoperation or urgent operation. Earlier intervention and more aggressive preoperative optimization may improve outcomes in these high-risk patients.

Protection in the failing heart

Myocardial protection for surgical procedures on the failing heart can be broken down into three areas. The first area involves selection of the appropriate patient with enough myocardial viability and contractile reserve to permit a substantial cross-clamp time. Secondly, there should be adequate targets to revascularize or adequate tissue for reparative surgery. Thirdly, and most importantly, antegrade and retrograde blood cardioplegia given in sufficient amounts to satisfy myocardial oxygen needs is of prime importance.

Comparison of results and risk factors of cardiac surgery in two 3-year time periods in the 1990s

With the increasing number of treatment options for heart disease, decision-making requires profiles of risk for conventional cardiac surgery. Refinements in techniques and clinical practices seem to have reduced surgical risk. This study was performed to determine current risk factors. From July 1, 1990, to June 30, 1996, 1,036 consecutive patients underwent 1,042 heart operations using standard incisions and cardiopulmonary bypass with cardioplegia. Univariate and multivariate analyses using a logistic regression model were performed to determine factors significant for combined 30-day and hospital mortality. To determine if there were trends in the results and the risk factors, the last 500 consecutive cases in the series were analyzed separately. Overall, 30-day mortality was 17 of 1,042 (1.6%) and combined 30-day and hospital mortality was 27 of 1,042 (2.6%). Significant risk factors for combined 30-day and hospital mortality by multivariate analyses were: emergent/resuscitative status, preoperative dialysis, left ventricular ejection fraction < or = 30%, valve operation, and creatinine > or = 1.5 mg/dl. Comparison with baseline characteristics of the patients undergoing the last 500 consecutive operations to the earlier 542 operations in the study group showed that risk factors had a very similar profile for the 2 groups. The overall 30-day mortality for the last 500 consecutive operations was 5 of 500 (1.0%) and combined 30-day and hospital mortality was 8 of 500 (1.6%). The significant risk factors by multivariate analyses were reduced to left ventricular ejection fraction < or = 30% and creatinine > or = 1.5 mg/dl. These results indicate that modern techniques and clinical practices have mitigated well-recognized risk factors in conventional cardiac surgery and this trend is ongoing.

The direct vasomotor effect of thyroid hormones on rat skeletal muscle resistance arteries

The present study examines the hypothesis that the hormones have direct vasodilatory effects and attempts to determine whether the effects are endothelium-dependent. Rat skeletal muscle resistance arteries of approximately 100 microns were dissected, and vessel diameter changes were monitored using a videodetection system. After equilibration at 37 degrees C, each vessel was preconstricted with the thromboxane analog U46619 1 microM, and the percentage of dilation was measured after exposure to increasing concentrations of triiodothyronine (T3) or levothyroxine (T4) (10(-10) to 10(-7) M). Dilation in response to T3 was also measured after endothelial denudation and pretreatment with the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine (L-NNA) 10 microM, the cyclooxygenase inhibitor indomethacin 10 microM, the adenosine triphosphate-sensitive K+ channel blocker glibenclamide 1 microM, or the beta-adrenergic antagonist propranolol 1 microM. Both T3 and T4 demonstrated concentration-dependent dilation of the U46619-preconstricted vessels (P < 0.001 each), with T3 having a greater effect than T4 (P < 0.05) (36% +/- 9% [mean +/- SD] dilation at 10(-7) M T3 vs 24% +/- 6% dilation at 10(-7) M T4). In comparison, isoproterenol 10(-7) M produced 56% +/- 6% dilation. T3-mediated vasodilation was attenuated but not abolished by endothelial denudation (18% +/- 3% dilation at 10(-7) M T3) (P < 0.01), L-NNA (15% +/- 7% dilation at 10(-7) M T3) (P < 0.01), indomethacin (20% +/- 9% dilation at 10(-7) M T3) (P < 0.05), and glibenclamide (22% +/- 7% dilation at 10(-7) M T3) (P < 0.01), but it was not affected by propranolol (37% +/- 20% dilation at 10(-7) M T3) (P = 0.99). We conclude that thyroid hormones possess direct vasodilatory effects with both endothelium-independent and endothelium-dependent components.

IMPLICATIONS

Thyroid hormones may have modest direct vasodilatory effects. This may partially account for the cardiovascular actions of the hormones in hyperthyroidism or when administered pharmacologically in cardiac surgery.