Impact of incomplete surgical revascularization on survival

Abstract

Complete revascularization is considered superior to incomplete revascularization (IR), with better long-term survival and a lower rate of reintervention. However, it has yet to be established whether this difference is due directly to IR as a surgical strategy or whether this approach is merely a marker of more severe coronary disease and more rapid progression. We believe that IR is a prognostic marker for a more complex coronary pathology, and adverse effects are probably due to the preoperative condition of the patient. In fact, although IR may negatively affect long-term outcomes, it may be, when wisely chosen, the ideal treatment strategy in selected high-risk patients. IR can derive from a surgical strategy of target vessel revascularization, where the impact of surgery is minimized to reduce perioperative mortality and morbidity, aiming to achieve the best feasible safe revascularization.

INTRODUCTION

Coronary artery bypass grafting (CABG) still remains the benchmark treatment for patients with multi-vessel coronary artery disease [1]. The indications are well documented [2] and the results relatively satisfying in terms of morbidity, mortality and ischaemic recurrence. However, the incidence of risk factors and preoperative comorbidities is increasing and many patients arrive for surgery at an advanced age, with severe left ventricular dysfunction, chronic renal disease, peripheral vascular disease and chronic bronchopulmonary disease. To improve the management of these patients, surgeons have had to adapt their operating techniques.

Complete revascularization (CR) approach is considered superior to incomplete revascularization (IR), with better long-term survival and a lower rate of reintervention [3]. This consensus among surgeons arose following the first long-term observational studies in young patients undergoing saphenous vein grafting [4]. However, it has yet to be established whether this difference is due directly to IR as a surgical strategy or whether this approach is merely a marker of more severe coronary disease and more rapid progression [5, 6]. In fact, it has been demonstrated that opting for on-pump CABG as part of an obsessive desire for CR in patients with comorbidities, particularly vascular disease and renal failure, confers no additional benefit and may even be harmful [1]. The tendency to operate on older patients with more preoperative comorbidities, higher surgical risk and with critical coronary anatomy unsuitable for complete percutaneous revascularization means that surgeons more frequently opt for a faster and more conservative approach. In those cases percutaneous or off-pump, less CR is accepted to limit the invasiveness of the procedure [7]. In fact, although CR is a desirable goal, the majority of the evidence suggests that as long as the left anterior descending coronary artery is grafted, the impact of CR versus IR on the hard end points of death, myocardial infarction or additional revascularization is small [8, 9].

In the present review, we will discuss the role of off-pump CABG and IR in selected patients. In fact, it remains unclear whether the decreased number of grafts seen in off-pump versus on-pump CABG is owing to patient selection. IR can derive from a surgical strategy of ‘target vessel revascularization’ in high-risk patients, where the impact of surgery is minimized to reduce perioperative mortality and morbidity, aiming to achieve the best feasible ‘safe’ revascularization.

COMPLETE MYOCARDIAL REVASCULARIZATION

Myocardial revascularization in patients with multi-vessel coronary artery disease may be accomplished, by percutaneous coronary interventions (PCI) or surgery, either on all diseased lesions or directed to selectively targeted coronary segments. The extent of planned revascularization is often a major determinant of treatment strategy. Revascularization of all diseased coronary segments has a potential long-term benefit, but is more complex and may increase in-hospital untoward events [10]. Revascularization may otherwise be incomplete, either because of the operator's inability to treat all diseased coronary segments or by choice of deciding to selectively revascularize only large areas of myocardium at risk. Although IR may negatively affect long-term outcomes, it may be, when wisely chosen, the ideal treatment strategy in selected patient categories because of its lower immediate risks [11]. The patient's clinical status, ventricular function and the presence of co-morbidities may orient clinical decisions in favour of IR versus unsafe CR.

The guidelines currently available for treatment of coronary artery disease [2] do not formally discuss the issue on adequacy of myocardial revascularization. For both PCI and CABG, there is still a substantial uncertainty on the definition and evaluation of the ‘adequacy’ of myocardial revascularization. Theoretically, complete anatomical revascularization should provide benefits in terms of recovery of myocardial function or protection from intervening events that should translate into a better survival. This comes, however, at the price of longer procedures and higher immediate risk [10]. Prior studies [6] have used different definitions for complete or adequate revascularization, which accounts for some controversies regarding mid- and long-term event-free survival. An ‘anatomically complete’ revascularization is accomplished when all vessels with clinically significant stenoses (>1.5 mm vessel diameter stenosis ≥50%) are treated, irrespective of the underlying myocardial function. A ‘functionally complete’ revascularization instead refers to cases in which only lesions supplying a viable myocardium are treated. Revascularization may, therefore, also be anatomically incomplete but still functionally adequate [10].

The advantages of CR emerge from long-term follow-up studies showing a direct relationship between the number of treated coronary segments and the reduction in cardiovascular events. The largest data set derives from the BARI trial [12] where an improved long-term event-free survival was documented when all stenoses >50% in diameter were bypassed. Similar results were obtained at the very beginning of PCI procedures [13]. However, patients with IR were generally older and with a higher prevalence of severe comorbidities. Thus, the higher perioperative risk of patients not allocated to CR could flaw conclusions on the adopted strategy, owing to the existence of a systematic bias. In the CABRI trial [14], IR was allowed in the PCI arm. After 1 year of follow-up, subjects showed a trend toward a higher mortality when compared with CABG, and a significantly worse event-free survival. The superiority of CABG over PCI was attributable to a greater probability of CR when surgery was used. IR, however, limits periprocedural risk, and can therefore be wisely used in high-risk patients, when the aim is to target vessels supplying large amounts of myocardium. In this case, attempts at treating small coronary arteries or occluded vessel supporting necrotic areas likely increase the duration of the intervention and procedure-related complications [15], and should be therefore deliberately avoided.

It has been our opinion that supplying at least one graft to each of the three major myocardial territories would be of far greater prognostic significance [11, 16]. Clinical features should influence the choice of a CR or IR strategy in selected patient categories [10]. Diabetics benefit from a more CR, better performed with CABG. In patients with left ventricular dysfunction, revascularization of all viable segments should also be accomplished in order to maximize benefit. Conversely, in subjects presenting with acute coronary syndromes, an IR with stent-PCI of the culprit lesion is extremely effective when performed in a timely fashion. In the elderly, or in patients with severe co-morbidities, every effort should be taken to reduce acute adverse events, and very often the additional perioperative risk entailed by attempts at CR appears to be unwarranted.

CABG VERSUS PCI

The analysis of patients with multiple vessel disease including the chronic occlusion of a major vessel in the CABRI trial [14] indicates that surgery gives a better outcome in these patients in terms of subsequent mortality and risk of acute myocardial infarction. A CR was obtained much more frequently in the surgical group than in the PCI group, principally due to the frequent failure of PCI in the revascularization of the occluded vessel [14]. Possible explanation of the clinical benefit of occluded vessel revascularization survival include improvement in left ventricular function in patients with viable myocardium, prevention or slowdown of ventricular remodelling, decrease in electrical instability and associated risk of fatal arrhythmic events and increased tolerance of future coronary occlusion events [17].

However, the extent of revascularization has not been unequivocally proven to be predictive of outcome in angioplasty patients [18]. In fact, compared with treatment with CABG, several randomized trials [19–22] have shown that treatment with PCI is associated with higher rates of angina and subsequent revascularization, but no significant differences in mortality or rates of acute myocardial infarction have been found. There may be several reasons for this discrepancy, including the definition and assessment of completeness of revascularization, the patients studied and the duration of follow-up. Generally, all bypass operations are considered by the surgeon to be complete, but early closure of a certain percentage of bypass grafts is well documented. Thus, revascularization by 30 days after the procedure may not be as complete as assumed by the surgeon at the time of the operation. Angioplasty, by its very nature, is easier to evaluate critically with respect to the completeness of revascularization. IR may be due to lesions that are not amenable to angioplasty, but it may also be due to a generous interpretation of the postprocedural angiogram by the operator.

Instead, MASS II data [23] demonstrated the better long-term prognosis of surgical patients, and it also confirmed the superiority of CABG over PCI with regard to the need for subsequent mechanical revascularization. That is understandable on the basis of both clinical and anatomic arguments. Atherosclerosis is a progressive and diffuse disease, whereas PCI is directed against a target or ‘culprit’ lesion or lesions, CABG bypasses most epicardial vessels and, as such, can provide protection at least in the intermediate term against disease progression involving ‘future’ culprits [24]. A functioning bypass graft will continue to protect a native coronary vessel, even if it is subject to disease progression or abrupt closure at any site proximal to the graft anastomosis.

Authors of SoS [19] trial also found that patients with multivessel disease managed with CABG rather than PCI had a lower mortality rate and more CR, particularly if native vessels are occluded at presentation. Observational studies [25] of PCI practice have suggested that failure to successfully reopen an occluded vessel at PCI is associated with an increased subsequent mortality. Besides, CABG may provide a more appropriate method of revascularization for patients with long-segment or diffuse disease, and significant but worrisome non-critical lesions. In angioplasty, such an aggressive approach usually entails increased risk of acute closure and restenosis and, therefore, it is not followed.

In conclusion, regardless of the mode of intervention (operation or angioplasty), the ultimate value of completeness of revascularization has been difficult to elucidate over the years. In patients with multivessel coronary disease, including the chronic occlusion of a major epicardial vessel, CABG can offer a higher probability of full revascularization and a higher probability of remaining alive and free of acute myocardial infarction in the long-term. If a percutaneous revascularization strategy is attempted, every effort must be made to reopen the occluded vessel and obtain CR. If this proves impossible, a surgical approach should be reconsidered.

OFF-PUMP CABG

During the last decades, the preoperative risk profile of patients referred for CABG surgery has changed [26]. Coronary disease is now a disease of the elderly. The 75-year-old patient with calcific tight left main stem, right coronary artery disease and impaired left ventricular function who presents with an acute coronary syndrome and pulmonary oedema and is found to have a porcelain aorta at surgery is becoming a dreaded phenotype many cardiac surgeons are becoming familiar with. These patients have a substantial risk of postoperative morbidity and mortality [27]. In several observational studies and registry data in which detailed statistical analyses were used, mortality and morbidity have been found to be significantly reduced after off-pump CABG compared with on-pump CABG, mainly, in high-risk patients [28, 29].

Cardiopulmonary bypass results in the activation of inflammatory mediators exacerbating myocardial damage in impaired ventricles [30]. In addition, other factors are known to contribute to myocardial injury, such as direct damage to myocardial cells during manipulation and cannulation, effect of potassium and hypothermia or fibrillation on cellular function and cell membrane and alteration of coronary blood flow. Furthermore, aortic cannulation and cross-clamping, which are used when CABG is performed with cardiopulmonary bypass, can result in micro- and macroembolization with subsequent neurological and other end-organ injury, including global myocardial ischaemia/reperfusion injury [31, 32].

However, the majority of evidence has been retrospective in nature, with many investigators reporting a variety of benefits when comparing CABG performed with and without cardiopulmonary bypass. These include cost benefits, reduced length of hospitalization and decreased incidence of mortality in patients undergoing off-pump CABG compared with those undergoing on-pump CABG [33]. More recent retrospective studies that used more sophisticated statistical tools, such as case matching and propensity scores analysis, have also suggested that off-pump CABG is associated with decreased morbidity, which manifests as a reduction in transfusion requirements, infection rates, length of hospitalization and incidence of renal failure and encephalopathy, but not mortality [7, 34]. The advantages of off-pump CABG have been observed, mainly, for high-risk cases [28].

Although completeness of revascularization was a major concern in the early era of beating heart surgery, most recent series have shown the absence of any such disparity between off-pump and conventional on-pump CABG [35]. An important long-term outcome of off-pump CABG is graft patency as it compares with the gold standard of on-pump CABG, particularly when considering that off-pump surgery is believed by many to be technically more demanding than conventional CABG. To date, there are limited conclusive data on graft patency [36–39]. Puskas et al. [37, 38] reported similar patency rates at 1 year, with no differences in the rates of death, stroke, myocardial infarction, angina or reintervention. However, ROOBY trial [39] presented outcomes quite controversial. It demonstrated higher mortality in the off-pump CABG group. This is against several other recently published studies [40–42], which showed benefit of off-pump CABG surgery over the on-pump technique, in several outcomes in specific subgroups such as elderly and patients with serious coexisting morbidities. ROOBY conclusions probably were the result of two aspects: (i) lower graft patency in the off-pump CABG group and (ii) increased number of IR in the off-pump CABG group. However, we expect the ROOBY study does not impair the use of a surgical procedure as important as the off-pump CABG surgery and thus hindering its use and benefits to our patients. In fact, it should be read and interpreted in the light of reality and faults committed by their authors.

Nevertheless, off-pump procedures have gained in popularity over the last decade. Unfortunately, substantial uncertainties remain about the long-term outcomes. There is suggestive evidence from observational studies [43] that off-pump may be associated with increased rates of repeat revascularization after hospital discharge, but its long-term effects on other major morbidities such as myocardial infarction, stoke and rehospitalization are not well characterized. To address some of these uncertainties, Hu et al. [44] reported a large observational study of both the short-term and long-term effects of off-pump compared with conventional CABG. There was no difference between the two groups in terms of in-hospital mortality, but there was a reduced risk of atrial fibrillation, blood transfusion and ventilation for 24 h in patients having off-pump. However, the rate of repeat revascularization was significantly higher in the off-pump group than in the on-pump group. Overall, the proportional excess risk of major vascular event associated with off-pump did not differ significantly in the different subcategories of patients studied. There was, however, a trend toward a higher relative risk of major vascular event among higher-risk patients presented with triple-vessel disease. In fact, that study also revealed a strong association between off-pump surgery and IR. This finding provides further supporting evidence for concerns about IR associated with off-pump technique [45]. Good evidence is available that IR at CABG can lead to poor long-term prognosis. In addition, although previous studies have consistently found that graft flow after anastomosis, which is another major concern related to off-pump techniques, is significantly lower after off-pump than on-pump [46], no information is available on the quality of anastomosis in that study. To what extent the reduced quality of anastomosis associated with off-pump procedures affects long-term prognosis remains to be established.

Use of the off-pump procedure appeared to be associated with a reduced risk of hospital complications, but this saving is not translated into long-term benefits. The choice between such procedures should be considered extremely carefully; in particular, any potential short-term gain should be balanced against the potential for the long-term hazard. With the use of improved cardiac stabilizers, refinements in the surgical technique, increasing surgical experience, and close collaboration from the anaesthesiology team, off-pump surgery becomes possible in almost all cases. We believe off-pump CABG is generally accepted as a safe alternative to conventional on-pump CABG in most patients. The benefit of off-pump CABG could be recognized even in mid-risk patients, but became more significant in high-risk patients [47]. Despite of the lower discriminative power observed in studies, off-pump reduces the incidences of major complications, especially postoperative heart failure, perioperative stroke, myocardial infarction and early mortality [48]. However, much larger randomized evidence is needed to compare the effects of off-pump procedures and conventional procedures reliably.

IMPACT OF OFF-PUMP IR

CR has been considered the standard approach in coronary artery disease. Nevertheless, data on this dogma remain very limited so far and therefore this issue is not precisely defined and highlighted in the contemporary guidelines for CABG [2]. However, even when CR is a major goal, there remain several reasons to perform reasonable surgical IR, based on preoperative assessment or more unexpected findings during the operation. Additionally, it is well known that in coronary artery disease, left main and proximal left anterior descending artery lesions have the highest prognostic relevance [49]. Thus, it can be speculated that bypass grafting of the left anterior descending artery with the left internal mammary artery may mainly compensate the prognostic impact of multivessel coronary artery disease. Moreover, CABG surgery has evolved in the past decade, allowing an individualized surgical concept, including total arterial bypass grafting and off-pump CABG. Over the last decade, off-pump CABG has become a widespread alternative to conventional on-pump CABG and several randomized trials have shown potential benefits in regard to myocardial protection and postoperative morbidity [50].

Recently, to provide concurrent clinical data, we studied (personal unpublished data) the early and mid-term outcomes of patients presenting with proximal left anterior descending artery or left main stem lesions receiving off-pump left internal mammary artery to left anterior descending artery grafting plus additional CR or reasonable IR. In this study, we analysed the impact of the choice of a surgical strategy of consecutive off-pump CABG, with special emphasis on completeness of revascularization, perioperative complications, angina recurrence and ischaemic events incidence, as well as operative and mid-term mortality.

Between January 2005 and December 2010, 195 consecutive and systematic off-pump procedures were performed at the Casa de Saúde da Boavista, a private small hospital, by a single surgeon (J.C.M.) representing 96% of all revascularization procedures (CABG alone) during the same time frame. CR was achieved only in 73 patients (37%). Patients receiving IR (122 patients, 63%) had similar demographic and preoperative characteristics except for a higher incidence of previous myocardial infarction (Table 1). CR was defined when at least one bypass was performed in a significantly diseased primary arterial territory. Patients who had more diseased coronary segments (i.e. >50% stenosis in the left anterior descending coronary artery, circumflex and right coronary artery systems) than distal anastomoses were classified as having IR. The reasons for adopting a strategy of IR were: (i) small target vessel (<1.25 mm) or highly calcified or with multiple stenoses; (ii) calcified ascending aorta; (iii) infarcted or fibrotic myocardium; (iv) non-dominant diseased right coronary artery; (v) lack of suitable conduits; and (vi) very high surgical risk (age over 75 years, severe pulmonary disease, acute renal failure, peripheral vascular disease, haemodynamic instability or emergency surgery). The most common reason for IR was the poor quality of the target coronary arteries judged by the surgeon to be unsuitable for grafting. IR was associated more frequently to right coronary territory (64.7%) than circumflex coronary territory (35.3%). The operative data and use of resources are reported in Table 2. Surgical strategy was to perform a left internal thoracic artery to left anterior descending coronary artery graft and safena saphenous vein grafts to other territories. More than one bypass per territory was an exception (n = 10; 5.1%), as well as, the use of both internal thoracic arteries (n = 5; 2.6%).

Table 1.

Patient characteristics

	Complete revascularization (n = 73)			Incomplete revascularization (n = 122)
	CAD 1 (CABGx1), n = 22	CAD 2 (CABGx2), n = 34	CAD 3 (CABGx3), n = 17	CAD 2 (CABGx1), n = 28	CAD 3 (CABGx1), n = 39	CAD 3 (CABGx2), n = 55
Demographic characteristics
Age, years (mean ± SD)	64.8 ± 9.1	63.9 ± 8.9	59.9 ± 7.6	64.2 ± 8.3	68.1 ± 8.6	62.8 ± 9.1
Male gender, n (%)	18 (81.8)	28 (82.4)	14 (82.4)	21 (75.0)	31 (79.5)	48 (87.3)
Weight, kg (mean ± SD)	77.8 ± 13.0	78.2 ± 10.7	79.5 ± 14.5	77.3 ± 9.1	74.7 ± 10.3	77.1 ± 10.9
BMI, kg/m2 (mean ± SD)	28.6 ± 4.2	28.2 ± 3.6	28.2 ± 5.7	28.7 ± 3.4	27.7 ± 4.0	27.6 ± 3.4
Obese BMI > 28, n (%)	9 (40.9)	14 (41.2)	9 (52.9)	16 (57.1)	15 (38.5)	20 (36.4)
Medical characteristics
CCS class pre-op (mean ± SD)	2.3 ± 0.8	2.4 ± 1.3	2.6 ± 1.0	2.4 ± 0.5	2.5 ± 0.8	2.5 ± 0.8
NYHA class pre-op (mean ± SD)	1.3 ± 0.7	1.3 ± 0.6	1.3 ± 0.5	1.4 ± 0.5	1.5 ± 0.6	1.4 ± 0.6
LVEF (%)	57.0 ± 6.9	59.5 ± 4.4	50.7 ± 11.7	54.0 ± 6.1	53.1 ± 9.9	56.2 ± 8.6
Old myocardial infarction, n (%)	8 (36.4)	11 (32.3)	5 (29.4)	13 (46.4)a	23 (59.0)a	24 (43.6)a
Smokers/previous smokers, n (%)	6 (27.3)	10 (29.4)	6 (35.3)	8 (28.6)	11 (28.2)	17 (30.9)
Hypertension, n (%)	16 (72.7)	24 (70.6)	12 (70.6)	20 (71.4)	28 (71.8)	42 (76.4)
Diabetes, n (%)	10 (45.5)	16 (47.1)	7 (41.2)	12 (42.9)	17 (43.6)	29 (52.7)
Pre-op creatinine > 1.5 mg/dl, n (%)	2 (9.1)	3 (8.8)	1 (5.8)	2 (7.1)	1 (2.6)	2 (3.6)
COPD, n (%)	3 (13.6)	4 (11.8)	2 (11.8)	5 (17.9)	5 (12.8)	9 (16.4)
Cerebrovascular disease, n (%)	2 (9.1)	4 (11.8)	2 (11.8)	2 (7.1)	5 (12.8)	6 (10.9)
Peripherial arterial disease, n (%)	5 (22.7)	3 (8.8)	3 (17.6)	2 (7.1)	4 (10.3)	10 (18.2)

CAD, coronary artery disease; CABG, coronary artery bypass graft; BMI, body mass index; CCS, Canadian Cardiovascular Society grading of angina pectoris; NYHA, stage of heart failure according to the New York Heart Association functional classification system; LVEF, left ventricular ejection fraction; COPD, chronic obstructive pulmonary disease.

CR Definition: when at least one bypass is performed in a significantly diseased primary arterial territory (anterior, descendent anterior coronary artery territory; lateral, circumflex coronary artery territory; inferior, right coronary artery territory).

^aIR versus CR (P < 0.05).

Table 2.

Surgical details

	Complete revascularization (n = 73)			Incomplete revascularization (n = 122)
	CAD 1 (CABGx1), n = 22	CAD 2 (CABGx2), n = 34	CAD 3 (CABGx3), n = 17	CAD 2 (CABGx1), n = 28	CAD 3 (CABGx1), n = 39	CAD 3 (CABGx2), n = 55
Use of resources
Operative time (min)	88 ± 19	129 ± 14	162 ± 29	105 ± 31	106 ± 39	133 ± 22
Postoperative ICU stay (days)	1.3 ± 0.4	1.1 ± 0.4	1.0 ± 0.3	1.1 ± 0.4	1.0 ± 0.3	1.0 ± 0.4
Postoperative hospital stay (days)	3.8 ± 0.6	4.2 ± 1.3	4.0 ± 0.0	4.1 ± 0.8	3.8 ± 0.7	4.2 ± 0.7
Operative room extubation, n (%)	22 (100)	31 (91.2)	16 (94.1)	23 (82.1)	36 (92.3)	54 (98.2)
Re-intubation, n (%)	0	0	0	1 (3.6%)	0	0
Post-op ventilation > 12 h, n (%)	0	0	0	3 (10.7)	0	1 (1.8)
Patients receiving red cells, n (%)	2 (9.1)	1 (2.9)	1 (5.9)	1 (3.6)	4 (10.3)	2 (3.6)

CAD, coronary artery disease; CABG, coronary artery bypass graft; ICU, intensive care unit.

Complete revascularization definition: when at least one bypass is performed in a significantly diseased primary arterial territory (anterior, left anterior descendent anterior coronary artery territory; lateral, circumflex coronary artery territory; inferior, right coronary artery territory).

No patients died during hospitalization or within 30 days. The incidence of acute myocardial infarction, stroke, atrial fibrillation and infection were 0.5, 1.0, 3.6 and 1.5%, respectively. No acute heart failure neither acute renal failure was observed. Surgical morbidity rate with reoperation needed was very low (1.5%). Univariate analysis did not show any difference in early outcome between the patients receiving CR and those having IR (Table 3). Discharge medication was aspirin (100%), clopidogrel (94.8%), β-blocker (97.4%), statin (92.3%) and angiotensin-converting enzyme inhibitor (87.2%). Follow-up was completed at 97% with an average follow-up period of 32.9 ± 15.6 months. The cumulative patient survival was 0.99. No mortality was observed in the CR group. Freedom from ischaemic events was 0.98 and 0.93 for complete and IR, respectively (P > 0.05, however a small sample).

Table 3.

Post-operative morbidity and mortality

	Complete revascularization (n = 73)			Incomplete revascularization (n = 122)
	CAD 1 (CABGx1), n = 22	CAD 2 (CABGx2), n = 34	CAD 3 (CABGx3), n = 17	CAD 2 (CABGx1), n = 28	CAD 3 (CABGx1), n = 39	CAD 3 (CABGx2), n = 55
Short-term morbidity
CPK elevation, n		1 (2.9%)
Stoke, n	1 (4.5%)			1 (3.6%)
Postoperative atrial fibrillation, n	1 (4.5%)	1 (2.9%)		1 (3.6%)		4 (7.3%)
Post-op fever, n		1 (2.9%)		1 (3.6%)
Sternal instability, n		1 (2.9%)
Surgical revision, n						1 (1.8%)
ICU readmission, n				1 (3.6%)		1 (1.8%)
Hospital readmission, n		1 (2.9%)
Long-term
Non-fatal myocardial infarction		1 (2.9%)		2 (7.1%)
Angina		2 (5.8%)		3 (10.7%)		3 (5.5%)
Re-revasculatization (stent)				1 (3.6%)		2 (3.6%)
Cerebrovascular event		1 (2.9%)			1 (2.6%)	1 (1.8%)
Death from cardiac cause					1 (2.6%)a
Death from other cause						1 (1.8%)b

Age: ^a84 years old; ^b81 years old.

CR definition: when at least one bypass is performed in a significantly diseased primary arterial territory (anterior, left anterior descendent anterior coronary artery territory; lateral, circumflex coronary artery territory; inferior, right coronary artery territory).

CAD, coronary artery disease; CABG, coronary artery bypass graft; CPK, creatine phosphokinase; ICU, intensive care unit.

That study was performed to analyse the outcome of off-pump CABG patients who received IR versus CR in others than left anterior descending coronary artery territories. The important finding of this study was that this subgroup of patients performed reasonably well. In fact, hospital and late survival were comparable for IR and CR patients. This finding implies that one should be cautious about interpreting the increased risk of morbidity and mortality from IR (shown in some studies) as truly due to the failure to graft all diseased coronary systems. One may be comparing ‘apples with oranges’ and inadequately characterizing factors associated with IR. We believe that IR is a prognostic marker for a more complex coronary pathology and adverse effects are probably due to the preoperative condition of the patient rather than IR itself. It can be supposed that a higher risk of death early after IR might be simply a surrogate for advanced coronary artery disease and more extra-cardiac morbidities. However, we found no impact of IR on early or late survival. It might be reasonable that secondary pharmacological treatment could compensate surgical IR in diffuse distal coronary artery disease of the non-left anterior descending coronary artery territories. A more aggressive pharmacological approach with statins and full antiplatelet therapy has ameliorated the outcome of candidates to IR. Its positive effects on cardiovascular event rate and protective pleiotropic effects may have considerably blurred differences between IR and CR.

Despite this positive finding, surgeons should not be misled to perform IR in patients with graftable vessels. It must also be stressed that reasonable surgical IR is strongly different from IR in PCI of multivessel disease when frequently good graftable vessels with large areas of viable myocardium remain untreated. Because of modern armamentarium, surgeons now more often than in former decades can adapt their surgical strategy based on the individual patient risks. For patients presenting with poor target vessel or at high risk for cardiopulmonary bypass, IR can be a good therapeutic option and the benefit of CR should be balanced against the risk.

CONCLUSION

IR may derive from a surgical strategy of ‘target vessel revascularization’ in high-risk patients, where the impact of surgery is minimized to reduce perioperative mortality and morbidity. The perception of higher technical difficulties and the fear of deleterious effects on patient health can lead some operators to reduce the extension of revascularization during off-pump CABG, aimed at achieving the best feasible ‘safe’ revascularization.

It has been difficult to define CR and to separate the effect of IR as a surgical strategy from the possibility that IR is a marker for worse coronary artery disease or, perhaps, a more rapid rate of progression of coronary artery disease. Among patients with a reduced life expectancy, however, aiming at a CR may certainly increase immediate risks, and this is hardly balanced by the hypothetical long-time survival benefit. The survival benefit of a complete surgical revascularization seems evident, in general, only for subjects having a predicted life expectancy of >10 years. Thus, whenever life expectancy is shorter, there is no solid ground for a choice of CR at all prices. For elderly patients, beating heart CABG is an attractive option, limiting untoward events related to extracorporeal circulation and aortic manipulation.

Several trials have tried to answer the question of what constitutes optimal surgical revascularization, showing only marginally lower event-free survival in patients after IR versus CR. In fact, recent evidence showed that IR in off-pump surgery did not affect early outcomes. However, with longer follow-up, IR may cause angina to recur more often requiring further revascularization.

Conflict of interest: none declared.