Role of Coronary Collaterals in Off-Pump and On-Pump Coronary Bypass Surgery

Vieussens' Arterial Ring: Historical Background, Medical Review and Novel Anatomical Classification

In coronary artery disease, the presence of Vieussens' arterial ring (VAR), a ring-shaped anastomosis between the conus branch of the right coronary artery with the left anterior descending artery (LAD), will allow blood flow to return to the obstructed coronary system. We have conducted a literature review, aiming to collect all the existing information about the documented VAR cases and any related pathological conditions. A total of 54 studies entered the review, including 56 patients. The mean age of the patients was 56.12 ± 16.2 years. Angina was present in 53.6% of the patients, with 7.2% of the cases being asymptomatic. Coronary artery disease outweighed (58.9%) as the patients' most frequent diagnosis. We propose a novel VAR anatomical classification, based on the sites of origin and termination of its course, with six distinct types, for a better understanding and surgical management of VAR. Type IA, originating from the conus branch and terminating in the proximal segment of the LAD was most frequently reported (51.8%). The recognition and the subsequent evaluation of the ring's anatomy and course are crucial for a customized clinical intervention. When right and left coronary angiographies fail to reveal any collateral circulation, selective conus artery catheterization should be in order. The proposed classification offers a manageable and comprehensive context for the assessment, evaluation and planning of therapeutic strategies of VAR and sets a new terminology frame for treatment guidelines.

The Role of Angiogenesis and Arteriogenesisin Myocardial Infarction and Coronary Revascularization

Surgical myocardial revascularization is associated with long-term survival benefit in patients with multivessel coronary artery disease. However, the exact biological mechanisms underlying the clinical benefits of myocardial revascularization have not been elucidated yet. Angiogenesis and arteriogenesis biologically leading to vascular collateralization are considered one of the endogenous mechanisms to preserve myocardial viability during ischemia, and the presence of coronary collateralization has been regarded as one of the predictors of long-term survival in patients with coronary artery disease (CAD). Some experimental studies and indirect clinical evidence on chronic CAD confirmed an angiogenetic response induced by myocardial revascularization and suggested that revascularization procedures could constitute an angiogenetic trigger per se. In this review, the clinical and basic science evidence regarding arteriogenesis and angiogenesis in both CAD and coronary revascularization is analyzed with the aim to better elucidate their significance in the clinical arena and potential therapeutic use.

Non-invasive Ischaemia Testing in Patients With Prior Coronary Artery Bypass Graft Surgery: Technical Challenges, Limitations, and Future Directions

Coronary artery bypass graft (CABG) surgery effectively relieves symptoms and improves outcomes. However, patients undergoing CABG surgery typically have advanced coronary atherosclerotic disease and remain at high risk for symptom recurrence and adverse events. Functional non-invasive testing for ischaemia is commonly used as a gatekeeper for invasive coronary and graft angiography, and for guiding subsequent revascularisation decisions. However, performing and interpreting non-invasive ischaemia testing in patients post CABG is challenging, irrespective of the imaging modality used. Multiple factors including advanced multi-vessel native vessel disease, variability in coronary hemodynamics post-surgery, differences in graft lengths and vasomotor properties, and complex myocardial scar morphology are only some of the pathophysiological mechanisms that complicate ischaemia evaluation in this patient population. Systematic assessment of the impact of these challenges in relation to each imaging modality may help optimize diagnostic test selection by incorporating clinical information and individual patient characteristics. At the same time, recent technological advances in cardiac imaging including improvements in image quality, wider availability of quantitative techniques for measuring myocardial blood flow and the introduction of artificial intelligence-based approaches for image analysis offer the opportunity to re-evaluate the value of ischaemia testing, providing new insights into the pathophysiological processes that determine outcomes in this patient population.

The Effects of Preoperative Coronary Collateral Circulation on Cardiac-Related Events after Coronary Artery Bypass Graft Surgery

Introduction

This study aimed to evaluate the effects of coronary collateral circulation (CCC) in patients who had undergone coronary artery bypass grafting (CABG).

Methods

A total of 127 patients who had undergone CABG (2011-2013) were enrolled into this study and follow-up was obtained by phone contact. Patients were categorized into two groups according to preoperative CCC using the Rentrop method. Percutaneous coronary intervention (PCI), recurrent myocardial infarction (MI), stroke, heart failure (HF), and mortality rates were compared between groups. Clinical outcome was defined as combined end point including death, PCI, recurrent MI, stroke, and HF.

Results

Sixty-two of 127 patients had poor CCC and 65 had good CCC. There were no differences in terms of PCI, recurrent MI, and HF between the groups. Stroke (seven of 62 [11.3%] and one of 65 [1.5%], P=0.026) and mortality (19 of 62 [30.6%] and 10 of 65 [15.4%], P=0.033) rates were significantly higher in poor CCC group than in good CCC group. In Kaplan-Meier analysis, survival time was not statistically different between the groups. Presence of poor CCC resulted in a significantly higher combined end point incidence (P=0.011).

Conclusion

Stroke, mortality rates, and combined end point incidence were significantly higher in poor CCC patients than in the good CCC group.

Mid-term outcomes of coronary endarterectomy combined with coronary artery bypass grafting

OBJECTIVES

The aim of this study was to evaluate the mid-term outcome of coronary endarterectomy (CE) combined with coronary artery bypass grafting (CABG) and explore the potential risk factors for adverse events.

METHODS

A total of 208 consecutive patients underwent CE between 2008 and 2018 in our centre, of which 198 were included in this retrospective cohort study. The primary end point was major adverse cardiovascular and cerebrovascular events (MACCEs). Kaplan-Meier analysis was performed to evaluate event-free survival, whereas subgroup analysis and Cox regression were used to explore risk factors for the outcomes.

RESULTS

The median follow-up time was 34.7 months. CE + CABG was performed mainly on the left anterior descending artery (42.3%) or right coronary artery (42.3%). Both operative mortality and incidence of perioperative myocardial infarction were 1.5%. The overall survival at 3 and 5 years was 98.0% and 95.9%, whereas the MACCE-free survival was 93.7% and 89.4%, respectively. No significant difference in the incidence of MACCE was observed between on-pump and off-pump CE (P = 0.256) or between left anterior descending artery and non-left anterior descending artery endarterectomy (P = 0.540). Advanced age (>65 years) was associated with a higher risk of MACCE both in univariate [hazard ratio (HR) 3.62, 95% confidence interval (CI) 1.37-9.62; P = 0.010] and multivariate analysis (HR 3.59, 95% CI 1.32-9.77; P = 0.013).

CONCLUSIONS

When performed by experienced surgeons, CE + CABG could be an acceptable approach to achieve complete revascularization of diffusely diseased coronary arteries with satisfactory outcomes, although advanced age might increase the risk of MACCE.

Does the site of coronary endarterectomy have an impact on the clinical outcomes and graft patency?

OBJECTIVES

To explore whether coronary endarterectomy (CE) sites have obvious impacts on the clinical outcomes and graft patency in off-pump coronary artery bypass (OPCAB).

METHODS

The patients who underwent OPCAB with CE in our unit between January 2009 and December 2016 were included. The patients and the grafts were grouped according to the CE sites. The primary end points were mid-term main adverse cardiovascular and cerebrovascular events.

RESULTS

In total, 290 patients who underwent OPCAB with CE were included. CE of the left anterior descending artery (LAD), left circumflex artery and the right coronary artery was performed in 46, 30 and 194 patients, respectively. There were 60, 42 and 217 grafts anastomosed to LAD-CE, left circumflex artery-CE and right coronary artery-CE sites in 290 patients. CE was not performed in the 20 patients requiring multivessel CE. There was no significant difference in perioperative outcomes. The average follow-up time was 51 months (12-103 months). There was no significant difference in mid-term death, main adverse cardiovascular and cerebrovascular events, myocardial infarction (MI), stroke, Canadian Cardiovascular Classification for angina class and 1-year graft patency among the 3 groups. However, the rate of New York Heart Association (NYHA) class III or IV (LAD vs left circumflex artery: 59% vs 25%, P = 0.011; LAD vs right coronary artery: 59% vs 27%, P < 0.001) was higher in the LAD group than in the other groups. These results were consistent with the Kaplan-Meier curves of freedom from the adverse events.

CONCLUSIONS

CE sites had no obvious impact on mid-term death, main adverse cardiovascular and cerebrovascular events, MI, stroke, Canadian Cardiovascular Classification for angina class and 1-year graft patency in patients who underwent OPCAB with CE. The patients undergoing LAD-CE had higher rates of NYHA class III or IV.

Efficacy and effectiveness of on- versus off-pump coronary artery bypass grafting: A meta-analysis of mortality and survival

BACKGROUND

Despite many studies comparing on- versus off-pump coronary artery bypass graft (CABG), there is no consensus as to whether one of these techniques offers patients better outcomes.

METHODS

We searched PubMed from inception to June 30, 2015, and identified additional studies from bibliographies of meta-analyses and reviews. We identified 42 randomized controlled trials (RCTs) and 31 rigorously adjusted observational studies (controlling for the Society of Thoracic Surgeons-recognized risk factors for mortality) reporting mortality for off-pump versus on-pump CABG at specified time points. Trial data were extracted independently by 2 researchers using a standardized form. Differences in probability of mortality (DPM) were estimated for the RCTs and observational studies separately and combined, for time points ranging from 30 days to 10 years.

RESULTS

RCT-only data showed no significant differences at any time point, whereas observational-only data and the combined analysis showed short-term mortality favored off-pump CABG (n = 1.2 million patients; 36 RCTs, 26 observational studies; DPM [95% confidence interval (CI)], -44.8% [-45.4%, -43.8%]) but that at 5 years it was associated with significantly greater mortality (n = 60,405 patients; 3 RCTs, 5 observational studies; DPM [95% CI], 10.0% [5.0%, 15.0%]). At 10 years, only observational data were available, and off-pump CABG showed significantly greater mortality (DPM [95% CI], 14.0% [11.0%, 17.0%]).

CONCLUSIONS

Evidence from RCTs showed no differences between the techniques, whereas rigorously adjusted observational studies (with >1.1 million patients) and the combined analysis indicated that off-pump CABG offers lower short-term mortality but poorer long-term survival. These results suggest that, in real-world settings, greater operative safety with off-pump CABG comes at the expense of lasting survival gains.

ISMICS Consensus Conference and Statements of Randomized Controlled Trials of Off-Pump versus Conventional Coronary Artery Bypass Surgery

Objective

At this consensus conference, we developed evidence-informed consensus statements and recommendations on the practice of off-pump coronary artery bypass graft (OPCAB) by systematically reviewing and performing meta-analysis of the randomized controlled trials (RCTs) comparing OPCAB and conventional coronary artery bypass (CCAB).

Methods

All RCTs of OPCAB versus CCAB through April 2013 were screened, and 102 relevant RCTs (19,101 patients) were included in a systematic review and meta-analysis (15 RCTs of 9551 high-risk patients; and 87 RCTs of 9550 low-risk patients) in accordance with the Cochrane Collaboration and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology. Consensus statements for the risks and benefits of OPCAB surgery in mortality, morbidity, and resource use were developed based on best available evidence.

Results

Compared to CCAB, it is reasonable to perform OPCAB to reduce risks of stroke [class IIa, level of evidence (LOE) A], renal dysfunction/failure (class IIa, LOE A), blood transfusion (class I, LOE A), respiratory failure (class I, LOE A), atrial fibrillation (class I, LOE A), wound infection (class I, LOE A), ventilation time, and ICU and hospital length of stay (class I, LOE A). However, OPCAB may be associated with a reduced number of grafts performed (class I, LOE A) and with diminished graft patency (class IIa, LOE A, with increased coronary reintervention at 1 year and beyond (class IIa, LOE A), as well as increased mortality at a median follow-up of 5 years (class IIb, LOE A).

Conclusions

OPCAB compared with CCAB may improve outcomes in the short-term (stroke, renal dysfunction, blood transfusion, respiratory failure, atrial fibrillation, wound infection, ventilation time, and length of stay). However, over the longer-term, OPCAB may be associated with reduced graft patency, and increased risk of cardiac re-intervention and death.

Effects of the coronary collateral circulation on the Tp-e interval and Tp-e/QT ratio in patients with stable coronary artery disease

BACKGROUND

The clinical utility of the Tp-e interval and Tp-e/QT ratio in the risk stratification of ventricular arrhythmic events is controversial. Therefore, we investigated the impact of CCC on these electrocardiographic indexes in the course of stable CAD.

METHODS

Two hundred three consecutive patients with stable CAD who underwent coronary angiography and had documented total occlusion of one of the major coronary arteries were enrolled in this prospective cross-sectional study. The Tp-e interval and Tp-e/QT ratio were measured by 12-lead electrocardiogram.

RESULTS

The Tp-e interval, cTp-e interval, Tp-e/QT ratio, and cTp-e/QT ratio were lower in the grade 3 CCC group compared with the others in all leads. Multivariate linear regression analyses was performed to identify the clinical factors affecting the cTp-e interval and was indicated that age (β = 0.261, P < 0.001), male sex (β = 0.334, P < 0.001), poor Rentrop grade (β = -0.228, P < 0.001), and NLR (β = 0.137, P = 0.027) were independent predictors of a prolonged cTp-e interval.

CONCLUSION

It could be concluded that the decreased dispersion of ventricular repolarization might contribute to the lower incidence of ventricular arrhythmias and SCD in CAD patients with a good CCC.

Fractional flow reserve-guided coronary bypass surgery: should surgeons use it?

PURPOSE OF REVIEW

Physiology-based evaluation in stable ischemic heart disease is transforming percutaneous cardiovascular intervention (PCI). Fractional flow reserve (FFR)-guided PCI is associated with more appropriate and beneficial outcomes at lower costs. The surgical community can no longer ignore this development. We review evidence for the rationale, practicality and appropriateness of FFR-guided coronary artery bypass grafting (CABG), as compared with the current conventional, anatomy-based strategy for surgical revascularization.

RECENT FINDINGS

Physiologic evaluation links the nature (anatomic or functional) of coronary stenoses to the perfused myocardium supplied by the target vessel and challenges the use of anatomy as the sole criterion for revascularization intervention. In CABG, a functional perfusion deficit/ischemia identifies myocardial territories that would physiologically benefit from revascularization by grafting beyond the functional stenosis. Conversely, deliberately not grafting beyond an anatomic stenosis would dramatically change the procedure of CABG. Recent studies of functionally guided revascularization (PCI or CABG) support this approach, while recent trials of PCI vs. CABG demonstrated a late survival advantage with anatomy-based CABG. Finally, new intraoperative imaging technologies are elucidating the physiologic consequences of surgical revascularization in real time, yielding insights into resolving this dilemma.

SUMMARY

Physiologic-based revascularization is challenging our thinking about the historic strategy for CABG. Understanding better the physiologic consequences of revascularization will drive the evolution of CABG in the future.

Historical aspects and relevance of the human coronary collateral circulation

In 1669, anastomoses between the right and left coronary artery were first documented by Richard Lower of Amsterdam. Using post-mortem imaging, a debate followed on the existence of structural inter-coronary anastomoses, which was not resolved before the first half of the 20 ieth century in case of the presence of coronary artery disease (CAD), and not before the early 1960 ies in case of the normal human coronary circulation by William Fulton. Functional coronary collateral measurements during coronary interventions were first performed only in the 1970 ies, respectively in the early 1980 ies. In humans, the existence of functional coronary collaterals in the absence of CAD has not been documented before 2003. Though the coronary collateral circulation has been recognized as an alternative source of blood supply to ischemic myocardium, its prognostic significance for the CAD population as a whole has been controversial until recently. The debate was due to different populations examined (acute versus chronic CAD, varying severity of CAD), to variable definitions of the term "prognosis", to insufficient statistical power of the investigation with rare occurrence of prognostic endpoints, to short duration of follow-up and to blunt instruments employed for collateral assessment. Individually, it has been acknowledged that a well functioning collateral supply to a myocardial area at risk for necrosis reduces infarct size, preserves ventricular function, prevents ventricular remodelling and aneurysm formation. Collectively, evidence has accumulated only recently that an extensive coronary collateral circulation is a beneficial prognosticator quoad vitam. In a recent meta-analysis on the topic, the risk ratio to die from any cause for high vs low or absent collateralization in patients with subacute myocardial infarction was 0.53 (95% confidence interval 0.15-1.92; p=0.335), and for patients with acute myocardial infarction, it was 0.63 (95% confidence interval 0.29-1.39; p=0.257)¸ the relative risk to die from any cause for well vs poorly developed collaterals in patients with stable CAD was 0.59 (95% confidence interval 0.39-0.89), p=0.012.

FREEDOM, SYNTAX, FAME and FUNCTIONALITY: the future of surgical revascularization in stable ischemic heart disease

ABSTRACT: At the age of nearly 50 years, the procedure of coronary artery bypass grafting (CABG) now has the most solid evidence supporting its role in revascularization for stable ischemic heart disease in its history. In what is a relatively infrequent occurrence in medicine, the results from large-scale observational database analyses are now aligned with and supported by data from recent randomized trials, providing important contemporary evidence in support of CABG. However, even with strong evidence, the changing landscape of revascularization for stable ischemic heart disease threatens to make this evidence irrelevant in deciding which patients should be referred for CABG in the future. How the procedure of CABG could be modified and optimized for incorporation into this new landscape is discussed in this article.

The human coronary collateral circulation: development and clinical importance

Coronary collaterals are an alternative source of blood supply to myocardium jeopardized by ischaemia. In comparison with other species, the human coronary collateral circulation is very well developed. Among individuals without coronary artery disease (CAD), there are preformed collateral arteries preventing myocardial ischaemia during a brief vascular occlusion in 20-25%. Determinants of such anastomoses are low heart rate and the absence of systemic arterial hypertension. In patients with CAD, collateral arteries preventing myocardial ischaemia during a brief occlusion are present in every third individual. Collateral flow sufficient to prevent myocardial ischaemia during coronary occlusion amounts to one-fifth to one-fourth the normal flow through the open vessel. Myocardial infarct size, the most important prognostic determinant after such an event, is the product of coronary artery occlusion time, area at risk for infarction, and the inverse of collateral supply. Well-developed coronary collateral arteries in patients with CAD mitigate myocardial infarcts and improve survival. Approximately one-fifth of patients with CAD cannot be revascularized by percutaneous coronary intervention or coronary artery bypass grafting. Therapeutic promotion of collateral growth is a valuable treatment strategy in those patients. It should aim at growth of large conductive collateral arteries (arteriogenesis). Potential arteriogenic approaches include the treatment with granulocyte colony-stimulating factor, physical exercise training, and external counterpulsation.

Off-pump versus on-pump coronary artery bypass grafting for ischaemic heart disease

BACKGROUND

Coronary artery bypass grafting (CABG) is performed both without and with cardiopulmonary bypass, referred to as off-pump and on-pump CABG respectively. However, the preferable technique is unclear.

OBJECTIVES

To assess the benefits and harms of off-pump versus on-pump CABG in patients with ischaemic heart disease.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (Issue 1, 2011), MEDLINE (OVID, 1950 to February 2011), EMBASE (OVID, 1980 to February 2011), Science Citation Index Expanded on ISI Web of Science (1970 to February 2011) and CINAHL (EBSCOhost, 1981 to February 2011) on 2 February 2011. No language restrictions were applied.

SELECTION CRITERIA

Randomised clinical trials of off-pump versus on-pump CABG irrespective of language, publication status and blinding were selected for inclusion.

DATA COLLECTION AND ANALYSIS

For statistical analysis of dichotomous data risk ratio (RR) and for continuous data mean difference (MD) with 95% confidence intervals (CI) were used. Trial sequential analysis (TSA) was used for analysis to assess the risk of random error due to sparse data and to multiple updating of accumulating data.

MAIN RESULTS

Eighty-six trials (10,716 participants) were included. Ten trials (4,950 participants) were considered to be low risk of bias. Pooled analysis of all trials showed that off-pump CABG increased all-cause mortality compared with on-pump CABG (189/5,180 (3.7%) versus 160/5144 (3.1%); RR 1.24, 95% CI 1.01 to 1.53; P =.04). In the trials at low risk of bias the effect was more pronounced (154/2,485 (6.2%) versus 113/2,465 (4.6%), RR 1.35,95% CI 1.07 to 1.70; P =.01). TSA showed that the risk of random error on the result was unlikely. Off-pump CABG resulted in fewer distal anastomoses (MD -0.28; 95% CI -0.40 to -0.16, P <.00001). No significant differences in myocardial infarction, stroke, renal insufficiency, or coronary re-intervention were observed. Off-pump CABG reduced post-operative atrial fibrillation compared with on-pump CABG, however, in trials at low risk of bias, the estimated effect was not significantly different.

AUTHORS' CONCLUSIONS

Our systematic review did not demonstrate any significant benefit of off-pump compared with on-pump CABG regarding mortality, stroke, or myocardial infarction. In contrast, we observed better long-term survival in the group of patients undergoing on-pump CABG with the use of cardiopulmonary bypass and cardioplegic arrest. Based on the current evidence, on-pump CABG should continue to be the standard surgical treatment. However, off-pump CABG may be acceptable when there are contraindications for cannulation of the aorta and cardiopulmonary bypass. Further randomised clinical trials should address the optimal treatment in such patients.

Effects of remote ischemic preconditioning with postconditioning in patients undergoing off-pump coronary artery bypass surgery--randomized controlled trial

BACKGROUND

Myocardial injury is associated with an adverse outcome after off-pump coronary artery bypass graft surgery (OPCAB). The authors conducted a randomized controlled trial to evaluate whether remote ischemic preconditioning (RIPC) with remote ischemic postconditioning (RIPostC) reduces myocardial injury in patients undergoing OPCAB.

METHODS AND RESULTS

Seventy patients scheduled for OPCAB were randomly assigned to an RIPC+RIPostC group (n=35) or a control group (n=35). In the RIPC+RIPostC group, 4 cycles of 5-min ischemia and 5-min reperfusion were done on a lower limb before anastomoses (RIPC) and after anastomoses (RIPostC). RIPC+RIPostC significantly reduced postoperative serum troponin I levels (P=0.001). The area under the curve for postoperative troponin I was 48.7% lower in the RIPC+RIPostC group (median [interquartile range], 21.3 h·ng⁻¹·ml⁻¹, 16.5-53.1 h·ng⁻¹·ml⁻¹ vs. 41.5 h·ng⁻¹·ml⁻¹, 24.6-90.2 h·ng⁻¹·ml⁻¹, P=0.020). There was no significant difference in creatinine levels and PaO₂/F(i)O₂ ratios between the 2 groups.

CONCLUSIONS

RIPC+RIPostC by lower limb ischemia decreased postoperative myocardial enzyme elevation by almost half postoperatively in patients undergoing OPCAB.

Outcomes after conversion in the Veterans Affairs randomized on versus off bypass trial

BACKGROUND

The Randomized On versus Off Bypass trial reported conversion of 12.4% (n = 137) off-pump coronary artery bypass (OPCAB) patients and 3.6% (n = 40) on-pump cardiopulmonary bypass (CPB) patients. This paper explored outcomes after conversions.

METHODS

Elective and urgent CABG patients (n = 2,203) at 18 sites were studied. Randomization within 54 participating surgeons occurred preoperatively, after which conversion occurred if clinically indicated. Conversion reasons and outcomes were captured prospectively with additional details retrospectively extracted from patient records by a core clinical group.

RESULTS

Conversion rates varied considerably across participating surgeons. Converted OPCAB patients had more right coronary disease and coronary targets less than 1.5 mm. Conversions were elective in 49.3% of cases, urgent in 27.2%, or emergent in 23.5%. Elective conversions were mainly for poor exposure-intramyocardial vessel (35.8%). Urgent and emergent conversions were usually for hemodynamic instability (89.2% and 75.0%, respectively). Compared with CPB and OPCAB patients, OPCAB-converted patients had more 30-day complications and deaths (composite outcome rate of 5.7% and 5.5% vs 17.5% respectively, p < 0.001). Thirty-day outcomes for OPCAB-converted patients trended worse for emergent versus elective conversions (31.3% vs 13.4%, respectively, p = 0.05). One-year composite outcome rate (death, nonfatal myocardial infarction or revascularization) in OPCAB-converted patients was worse than in CPB patients (13.5% vs 7.1%, p = 0.02), but similar to OPCAB-nonconverted (9.4%).

CONCLUSIONS

The OPCAB patients requiring conversion had worse 30-day and 1-year outcomes. The OPCAB patients with right coronary artery disease or small targets were more often converted. The 30-day composite outcome trended worst for emergent OPCAB conversions.

Plasma chemokine levels are associated with the presence and extent of angiographic coronary collaterals in chronic ischemic heart disease

BACKGROUND

In patients with chronic ischemic heart disease (IHD), the presence and extent of spontaneously visible coronary collaterals are powerful determinants of clinical outcome. There is marked heterogeneity in the recruitment of coronary collaterals amongst patients with similar degrees of coronary artery stenoses, but the biological basis of this heterogeneity is not known. Chemokines are potent mediators of vascular remodeling in diverse biological settings. Their role in coronary collateralization has not been investigated. We sought to determine whether plasma levels of angiogenic and angiostatic chemokines are associated with of the presence and extent of coronary collaterals in patients with chronic IHD.

METHODOLOGY/PRINCIPAL FINDINGS

We measured plasma concentrations of angiogenic and angiostatic chemokine ligands in 156 consecutive subjects undergoing coronary angiography with at least one ≥90% coronary stenosis and determined the presence and extent of spontaneously visible coronary collaterals using the Rentrop scoring system. Eighty-eight subjects (56%) had evidence of coronary collaterals. In a multivariable regression model, the concentration of the angiogenic ligands CXCL5, CXCL8 and CXCL12, hyperlipidemia, and an occluded artery were associated with the presence of collaterals; conversely, the concentration of the angiostatic ligand CXCL11, interferon-γ, hypertension and diabetes were associated with the absence of collaterals (ROC area 0.91). When analyzed according to extent of collateralization, higher Rentrop scores were significantly associated with increased concentration of the angiogenic ligand CXCL1 (p<0.0001), and decreased concentrations of angiostatic ligands CXCL9 (p<0.0001), CXCL10 (p = 0.002), and CXCL11 (p = 0.0002), and interferon-γ (p = 0.0004).

CONCLUSIONS/SIGNIFICANCE

Plasma chemokine concentrations are associated with the presence and extent of spontaneously visible coronary artery collaterals and may be mechanistically involved in their recruitment.

The effect of remote ischaemic preconditioning on myocardial injury in patients undergoing off-pump coronary artery bypass graft surgery

In several recent clinical trials on cardiac surgery patients, remote ischaemic preconditioning (RIPC) showed a powerful myocardial protective effect. However the effect of RIPC has not been studied in patients undergoing off-pump coronary artery bypass graft surgery. We evaluated whether RIPC could induce myocardial protection in off-pump coronary artery bypass graft surgery patients. Patients undergoing elective off-pump coronary artery bypass graft surgery were randomly allocated to the RIPC (n = 65) or control group (n = 65). After induction of anaesthesia, RIPC was induced by four cycles of five-minute ischaemia and reperfusion on the upper limb using a pneumatic cuff. Anaesthesia was maintained with sevoflurane, remifentanil and vecuronium. Myocardial injury was assessed by troponin I before surgery and 1, 6, 12, 24, 48 and 72 hours after surgery. There were no statistical differences in troponin I levels between RIPC and control groups (P = 0.172). Although RIPC reduced the total amount of troponin I (area under the curve of troponin increase) by 26%, it did not reach statistical significance (RIPC group 53.2 +/- 72.9 hours x ng/ml vs control group 67.4 +/- 97.7 hours x ng/ml, P = 0.281). In this study, RIPC by upper limb ischaemia reduced the postoperative myocardial enzyme elevation in off-pump coronary artery bypass graft surgery patients, but this did not reach statistical significance. Further study with a larger number of patients may be needed to fully evaluate the clinical effect of RIPC in off-pump coronary artery bypass graft surgery patients.

Clinical outcomes in randomized trials of off- vs. on-pump coronary artery bypass surgery: systematic review with meta-analyses and trial sequential analyses

AIMS

To assess the clinical outcomes of off- vs. on-pump coronary artery bypass surgery in randomized trials.

METHODS AND RESULTS

We searched electronic databases and bibliographies until June 2007. Trials were assessed for risk of bias. Outcome measures were all-cause mortality, myocardial infarction, stroke, atrial fibrillation, and renewed coronary revascularization at maximum follow-up. We applied trial sequential analysis to estimate the strength of evidence. We found 66 randomized trials. There was no statistically significant differences regarding mortality [relative risk (RR) 0.98; 95% confidence interval (CI) 0.66-1.44], myocardial infarction (RR 0.95; 95% CI 0.65-1.37), or renewed coronary revascularization (RR 1.34; 95% CI 0.83-2.18). We found a significant reduced risk of atrial fibrillation (RR 0.69; 95% CI 0.57-0.83) and stroke (RR 0.53; 95% CI 0.31-0.91) in off-pump patients. However, when continuity correction for zero-event trials was included, the reduction in stroke became insignificant (RR 0.62; 95% CI 0.32-1.19). Trial sequential analysis demonstrated overwhelming evidence supporting that off-pump bypass surgery reduces atrial fibrillation.

CONCLUSION

Off-pump surgery reduces the risks of postoperative atrial fibrillation compared with on-pump surgery. For death, myocardial infarction, stroke, and renewed coronary revascularization, the evidence is still weak and more low-bias risk trials are needed.

Warm ischemia provokes inflammation and regional hypercoagulability within the heart during off-pump coronary artery bypass: a possible target for serine protease inhibition

OBJECTIVE

Accumulating evidence suggests that a hypercoagulable state influences early graft failure after off-pump coronary artery bypass (OPCAB). We hypothesized that regional myocardial ischemia caused by obligatory periods of coronary occlusion during OPCAB is an important trigger for this prothrombotic state.

METHODS

Using a series of biomarkers, 60 consecutive patients undergoing OPCAB were monitored for myocardial injury (myoglobin), inflammation (TNF-alpha, IL-8) and thrombosis (thrombin generation-F1.2, contact activation pathway-FXII-a, platelet derived microparticles-via flow cytometry). The transcardiac gradients of these markers were determined by assaying both arterial and coronary sinus blood just after protamine administration. Intramyocardial pH was monitored continuously during coronary occlusion in a subset (N=30 grafts, 11 patients). The influence of management strategies affecting hemostasis (e.g. antiplatelet therapy, anti-fibrinolytics, peak activated clotting time (ACT) during heparinization) was analyzed.

RESULTS

Ischemic injury, depicted by the transcardiac myoglobin gradient, significantly correlated with intramyocardial acidosis during coronary occlusion (R=0.96, p<0.0001) and predicted the transcardiac gradients of TNF-alpha (R=0.83, p<0.001) and F1.2 (R=0.72, p<0.0001). Transcardiac F1.2 strongly correlated with TNF-alpha (R=0.73, p=0.01) and IL-8 (R=0.51, p=0.02). Patients receiving aprotinin (N=20) showed significantly lower transcardiac gradients for myoglobin (4.1+/-7.5% vs 72.9+/-108.8% change, p=0.002), F1.2 (31+/-37% vs 89+/-149%, p=0.03), FXII-a (2.6+/-4.1% vs 19.2+/-34%, p=0.04) and microparticles (7+/-3.9% vs 12.9+/-8%, p=0.01).

CONCLUSIONS

Strong correlations between myocardial ischemia and the transcardiac gradients of markers for inflammation and thrombosis suggest that even brief episodes of coronary occlusion in the beating heart may have pathophysiologic consequences. Aprotinin, but not other factors that influence the coagulation system, appears to mitigate this process during OPCAB.

Coronary collaterals improve prognosis in patients with ischemic heart disease

BACKGROUND

The recruitment of coronary collateral vessels results from an endogenous adaptation to ischemic heart disease (IHD). Presence of collaterals may exert protection at the time of acute or chronic obstructive coronary disease. The protective role of collaterals in patients with extensive coronary artery disease however, has been disputed. We examined the effects of coronary collateral circulation on cardiovascular outcomes, with an emphasis on clinical prognostic value and on a putative role of IHD burden.

METHODS

Data analyzed were obtained in the REGRESS study, involving 879 male participants undergoing coronary angiography and being followed for 24 months. Presence of coronary collaterals spontaneously visible on angiography was assessed. Events included: myocardial infarction (MI), coronary heart disease death and percutaneous or surgical coronary intervention. Estimates of relative risks of outcome events were calculated using proportional hazard analysis, with adjustments for confounding factors and stratification for initial revascularization strategy and factors reflecting extent of IHD burden.

RESULTS

Event-free survival after two years was 84% in patients without collaterals, and 92% in patients with collaterals (p=0.0020). The crude HR was 0.48 (95% CI: 0.30-0.77), and 0.38 (0.23-0.65) after adjustment for confounders and cardiovascular risk factors. The protective effect of coronary collaterals was not modified by the extent of IHD burden (interaction p=0.99).

CONCLUSION

The angiographical presence of coronary collaterals is a clinical predictor of cardiovascular prognosis. Collaterals exert a protective effect on outcome in a broad spectrum of patients. Our data suggest that this protective effect is independent of disease burden, and remains present in patients with extensive IHD.

Beneficial effect of recruitable collaterals: a 10-year follow-up study in patients with stable coronary artery disease undergoing quantitative collateral measurements

BACKGROUND

The prognostic relevance of the collateral circulation is still controversial. The goal of this study was to assess the impact on survival of quantitatively obtained, recruitable coronary collateral flow in patients with stable coronary artery disease during 10 years of follow-up.

METHODS AND RESULTS

Eight-hundred forty-five individuals (age, 62+/-11 years), 106 patients without coronary artery disease and 739 patients with chronic stable coronary artery disease, underwent a total of 1053 quantitative, coronary pressure-derived collateral measurements between March 1996 and April 2006. All patients were prospectively included in a collateral flow index (CFI) database containing information on recruitable collateral flow parameters obtained during a 1-minute coronary balloon occlusion. CFI was calculated as follows: CFI = (P(occl) - CVP)/(P(ao) - CVP) where P(occl) is mean coronary occlusive pressure, P(ao) is mean aortic pressure, and CVP is central venous pressure. Patients were divided into groups with poorly developed (CFI < 0.25) or well-grown collateral vessels (CFI > or = 0.25). Follow-up information on the occurrence of all-cause mortality and major adverse cardiac events after study inclusion was collected. Cumulative 10-year survival rates in relation to all-cause deaths and cardiac deaths were 71% and 88%, respectively, in patients with low CFI and 89% and 97% in the group with high CFI (P=0.0395, P=0.0109). Through the use of Cox proportional hazards analysis, the following variables independently predicted elevated cardiac mortality: age, low CFI (as a continuous variable), and current smoking.

CONCLUSIONS

A well-functioning coronary collateral circulation saves lives in patients with chronic stable coronary artery disease. Depending on the exact amount of collateral flow recruitable during a brief coronary occlusion, long-term cardiac mortality is reduced to one fourth compared with the situation without collateral supply.

Coronary collaterals—insights in molecular determinants and prognostic relevance

In the field of molecular cardiology, recently several determinants of coronary collateral circulation have been identified. Knowing these factors may aid risk-stratification and put forward targets for intervention by stimulating development of collateral blood vessels (arteriogenesis). However, prognostic importance of coronary collaterals is not yet beyond debate, and seems to be modified by the extent of atherosclerotic burden. Combining these insights is essential to increase our understanding of these mechanisms and to proceed with developing strategies for risk-stratification and therapeutic stimulation of arteriogenesis.

Angiographic Fate of Collateral Vessels After Surgical Revascularization of the Totally Occluded Left Anterior Descending Artery

BACKGROUND

Coronary artery bypass grafting (CABG) is best indicated for chronic total occlusion of the left anterior descending artery (LAD) with collaterals. We investigated angiographic changes in the collateral circulation after CABG.

METHODS

Preoperative and postoperative angiograms were reviewed in 42 patients who underwent grafting onto occluded LADs. We described the type, location, and size of collaterals, the Rentrop grading, and collateral frame count (CFC). Regional wall motion of the LAD area was also evaluated with the centerline method. Postoperatively, we measured the lengths of LAD proximal (Lp) and distal (Ld) to the graft anastomotic site.

RESULTS

Preoperative collaterals comprised 78 pathways (septal 42%, branch-branch 20%, atrial 19%, bridging 18%). After CABG, residual collaterals were identified, mainly through the septal pathways, in 6 patients (14%), most of whom were diabetic. The residual collaterals were a part of those which had been opacified in earlier phases of the preoperative angiograms (CFC: 17 +/- 3 vs 25 +/- 15, p = 0.01). Also, the Ld was shorter in these patients so that Lp/Ld was greater than in patients without residual collaterals (0.80 +/- 0.24 vs 0.53 +/- 0.28, p = 0.04). We found no association of residual collaterals with the improvement of LAD regional wall motion after CABG.

CONCLUSIONS

Even after successful CABG, some collaterals with earlier filling of the LAD remain, mainly through the septum. Although the clinical significance remains to be clarified, complex and diffuse atherosclerosis associated with more distal graft anastomoses may contribute to maintaining collaterals after CABG to the occluded LAD, especially in diabetic patients.

Transesophageal Doppler echocardiographic detection of intramyocardial collateral flow to the right coronary artery and changes in the flow to the inferior left ventricular wall immediately after coronary artery bypass grafting

This study examined the feasibility of Doppler transesophageal echocardiography (TEE) to detect collateral flow to the myocardium supplied by the right coronary artery (RCA) in the inferior left ventricular wall. Forty-four patients who underwent elective coronary artery bypass grafting (CABG) were prospectively studied. Presence of collateral flow to the RCA was diagnosed on preoperative angiography using the Rentrop score and by intraoperative Doppler TEE. Agreement of the 2 methods was analyzed by calculating the kappa coefficient. Collateral flow was present on preoperative angiography in 19 patients and absent in 25 patients. Intraoperative TEE detected collateral flow in the inferior wall in 15 patients (79%) with and 3 patients (12%) without angiographic collaterals, resulting in a kappa coefficient for agreement of 0.67 (95% confidence interval 0.45 to 0.90). Baseline collateral flow disappeared after CABG in 12 of 14 patients with grafting of the RCA but persisted in all patients without such grafting. Physiologic flow in the inferior wall was detected by TEE in a total of 27 patients at baseline and in 38 patients after CABG (p = 0.0018); its peak velocity increased after surgery only in the subgroup of patients with grafting of the RCA. In conclusion, these findings indicate that Doppler TEE may detect collateral flow in the inferior left ventricular wall, and that there are typical changes in collateral and physiologic flow after CABG.

Determinants and prognostic significance of collaterals in patients undergoing coronary revascularization

There is evidence that coronary collaterals improve the prognosis in patients with acute myocardial infarction (MI). However, there is limited clinical information on the protective role of collaterals in patients with stable coronary artery disease. This information may help risk stratification and the development of novel therapies, such as arteriogenesis and angiogenesis. The relation between collaterals and cardiac death or MI at 1 year after coronary revascularization was studied in 561 patients who were enrolled in a randomized study that compared stent implantation with bypass grafting. Collaterals were assessed on an angiogram using Rentrop's classification and considered present with a Rentrop grade >1. Unadjusted and adjusted odds ratios for cardiac death or MI at 1 year were calculated using univariate and multivariate regression analyses. In addition, determinants of collaterals were assessed using univariate and multivariate analyses. Collaterals were present in 176 patients (31%). The adjusted odds ratio of cardiac death or infarction was 0.18 (95% confidence interval 0.04 to 0.78) in the presence of collaterals. Independent determinants of collaterals were age (odds ratio 0.97, 95% confidence interval 0.95 to 0.99), multivessel disease (odds ratio 1.60, 95% confidence interval 1.02 to 2.51), impaired ventricular function (odds ratio 1.85, 95% confidence interval 1.04 to 3.29), type C lesion (odds ratio 3.72, 95% confidence interval 2.33 to 5.95), and stenosis severity >90% (odds ratio 9.08, 95% confidence interval 4.65 to 17.73). In conclusion, in patients with a low risk profile, the presence of collaterals protects against cardiac death and MI at 1 year after coronary revascularization. Variables that reflect the duration and severity of the atherosclerotic and ischemic burden determine their presence.

Long Segmental Reconstruction of Diffusely Diseased Left Anterior Descending Coronary Artery With Left Internal Thoracic Artery With or Without Endarterectomy

BACKGROUND

The diffusely diseased left anterior descending coronary artery (LAD) remains a challenge for both interventional cardiologists and cardiac surgeons. In this study we assessed the surgical outcomes obtained from coronary artery reconstruction, with or without endarterectomy, for a diffusely diseased LAD.

METHODS

Two hundred and fifty patients were treated with an extended LAD reconstruction, with or without endarterectomy, as part of coronary artery bypass grafting to achieve complete revascularization. The left internal thoracic artery (LITA) was used to reconstruct the LAD in all patients. There were 197 men and 53 women. The mean age was 65.1 +/- 9.0 years. Coronary artery reconstruction was performed without endarterectomy in 183 patients (73.2%) and with endarterectomy in 67 patients (26.8%). The off-pump technique was used in 204 patients (81.6%).

RESULTS

The operative mortality was 1.6%. Perioperative myocardial infarction was observed in 6.4% of the patients. The mean LAD incision length was 4.3 +/- 1.7 cm. The patency rate of the LITA to LAD was 98.6% by early angiographic examination (mean, 7.5 +/- 2.6 postoperative days). There were 3 late cardiac-related deaths at a mean follow-up of 21.2 +/- 10.7 months. The actuarial survival was 92.0% at 45 months. Freedom from death or cardiac events was 88.1% at 45 months.

CONCLUSIONS

Coronary artery reconstruction, with or without endarterectomy, using the left internal thoracic artery for a diffusely diseased LAD can be performed with acceptable early and midterm results.