Coronary-Coronary Bypass Grafting

Abstract

This work is devoted to the original method of myocardial revascularization—coronary-coronary bypass grafting. Coronary artery bypass grafting can be considered as an independent method in an exceptional case or as an addition to the standard coronary artery bypass grafting technique. This paper presents the technique for performing CCBG, as well as the early and long-term results of the main studies. Attention is also paid to the advantages and disadvantages of this method from the standpoint of physiology and physics.

1. Introduction

“Difficulties are meant to rouse, not discourage.”

William Ellery Channing

Coronary artery bypass grafting (CABG) with the use of saphenous vein grafts (SVG) and the left internal thoracic artery (ITA) is the standard of myocardial revascularization for many cardiac surgeons. But in everyday practice, the course of the surgery can change dramatically. Calcification of aortic root and ascending aorta, grafts limitation and lesion of subclavian artery are leading to a search for alternative sources of blood supply. One of those alternatives is the coronary artery itself. In coronary-coronary bypass grafting (CCBG), proximal and distal anastomoses are performed between one or more coronary arteries with the use of different conduits.

2. History of coronary-coronary bypass grafting and its reported outcomes

In the case of coronary-coronary bypass grafting, proximal and distal anastomoses are formed between different coronary arteries or segments of the same coronary artery. This technique requires a native proximal coronary artery to provide adequate distal flow. The idea of using the proximal portion of the coronary artery as an alternative source of blood supply came to several researchers almost simultaneously. In 1987, CCBG was described by Biglioli and colleagues [1]. The authors present their experience with coronary-coronary bypass grafting. The most usual site of proximal implantation for CCBG in this series was the origin of the RCA. According to Biglioli et al., this technique takes advantage of physiological position of the right coronary artery ostium: the filling of the graft and of the coronary circulation is assisted by several factors promoting the physiological diastolic coronary artery blood flow.

In the same 1987 Nishida et al. in a 62-year-old man used the proximal part of coronary artery to bypass distal vessels when other conventional grafting techniques are not possible [2]. In this patient, a saphenous vein graft was not possible to use, for this reason, the free right internal thoracic artery was used for grafting the right coronary artery. The proximal anastomosis was performed to RCA and distal one to posterior descending artery. The postoperative period of the patient and recovery progressed without any complications. Patient was discharged with no angina. Three months after bypass surgery, the coronary angiography was performed and that revealed patency of the coronary-coronary bypass graft.

Rowland et al, in 1987 also reported on the possibility of coronary-coronary bypass grafting in an emergency situation [3]. In one case this technique was performed on a 75-year-old man with significant chronic obstructive pulmonary disease (COPD), diabetes mellitus and left below-knee amputation. This patient was admitted with unstable angina. The coronary angiography revealed the circumflex artery with 99% proximal stenosis and two large, nondiseased distal obtuse marginal branches (OM). The left anterior descending (LAD) had a 70% proximal stenosis, and the right coronary artery showed a 50% lesion at the middle part. Distal runoff was unaffected. Intraoperatively the aortic arch and ascending aorta were found calcified for cannulation or proximal anastomosis excluding the small area of aorta, next to the ostium of right coronary artery, that was found to be suitable for cross-clamping. The cardiopulmonary bypass was established via peripheral cannulation. The proximal part of right coronary artery was separated and was found intact. CCBG was performed between proximal part of right coronary artery, obtuse marginal arteries and left anterior descending artery. The postoperative period was complicated by development of the left hemispheric stroke, kidney and hepatic failure, arrhythmias and prolonged ventilation and pneumonia as a result. The patient died two months postoperatively of noncardiac complications.

In the second case, CCBG was performed on a 59-year-old woman who had phlebectomy in anamnesis. Patient was admitted with an inferior myocardial infarction. The coronary angiography showed the right coronary artery with 40% proximal stenosis with a good distal runoff, and the 99% proximal of circumflex artery with good distal runoff. LAD had 85% stenosis located between the first and second diagonal arteries with a good distal runoff. Intraoperatively, only a short saphenous vein was available for harvesting. The left internal thoracic artery was not long enough for grafting the circumflex system. For complete revascularization bifurcated saphenous vein was used for coronary-coronary bypass grafting. Anastomoses were performed between the first diagonal artery, circumflex artery, left anterior descending artery and intact second diagonal branch. The postoperative course was uneventful, and four months later, the patient completed treadmill testing with no chest pain and no ischemic changes in ECG.

Thus, three independent researchers at almost the same time proposed a solution to one of the most difficult problems in coronary surgery. Further references to coronary-coronary bypass surgery were episodic. Basically, these are case descriptions using different conduits, as well as different observation periods.

Erdil N. et al. reported a CCBG in a 74-year-old man with a calcified ascending aorta [4]. Anastomoses were performed between proximal and distal parts of right coronary artery with a saphenous vein graft, while the left internal thoracic artery was anastomosed to the left anterior descending artery. Surgery was performed without cardiopulmonary bypass. The patient survived without negative evidence. Angiography showed graft patency one year after revascularization. Possibility of coronary-coronary bypasses grafting off-pump in patients with extensive atherosclerotic aorta was also described by Yalcikaya A. et al. and Wan L.F. et al [5].

Marisalco G. described the case of functioning of a coronary-coronary graft for 19 years. CCBG was performed to minimize manipulation of a porcelain ascending aorta. Sequential coronary-coronary bypass grafts had been performed using a saphenous vein graft from the proximal right coronary artery to the left anterior descending artery and the obtuse marginal branch [6].

Denis B. in 1995 used the radial artery for coronary-coronary bypass grafting. He performed anastomosis between proximal and terminal parts of the RCA. The postoperative course was uneventful. A control coronary angiogram performed on day 6 showed an excellent result with a good match of the RA graft and the distal RCA [7].

However, among the description of single cases, some researchers analyzed a series of such surgeries. Nottin R. et al. reported about 143 patients underwent myocardial revascularization with one (138 patients) or two (5 patients) coronary-coronary bypass grafts in addition to other bypass grafts, for a total of 463 distal anastomoses (mean 3.2 ± 0.6 per patient) [8]. In this study the coronary-coronary bypass grafts were chosen for the following reasons: arterial conduit-sparing procedure, inadequate length for in situ graft, calcified ascending aorta and stenosed or occluded subclavian arteries. For complete revascularization, the authors used both arterial and venous conduits. Coronary-coronary bypass grafts were performed for right, circumflex and anterior descending coronary arteries. Three patients (2%) died of myocardial infarction. Early postoperative angiography showed a patency rate of 98.6% (72/73). During the mean follow-up of 34.6–20.8 months, two patients died and two underwent reoperation. In this study, the authors did not provide long-term angiographic data. However, researchers of Federal Center for Cardiovascular Surgery (Penza) carried out an angiographic controlled study of the long-term results of CCBG. This study enrolled 95 patients. All patients underwent angiographic assessment of the coronary bypass grafts in the long-term follow-up period. The observation period was up to 123 months (mean 64.5 ± 24.4 months) [9].

Angiography in different types of CCBG is presented above. Figure 1A shows coronary-coronary bypass grafting of the distal left anterior descending artery with a left ITA segment, while the left ITA in situ was used to bypass obtuse marginal branch. In Figure 1B, the proximal part of the left anterior descending artery was grafted with a T-graft and the distal part was revascularized by CCBG. In a number of cases, CCBG was performed when the lesion of coronary artery was too distal for using internal thoracic artery in situ. To avoid the tension of the conduits CCBGs were used for grafting the distal parts of coronary arteries.

Figure 1.

Angiography of coronary-coronary bypasses graft. (a) Isolated CCBG of the left anterior descending artery. (b) Simultaneous CCBG and composite arterial grafting.

CCBG also allowed multiple arterial revascularizations while it was possible to save the ITA. Sometimes, the proximity of an occluded or stenosed coronary artery to a native patent coronary artery is predisposed to CCBG (Figure 2A and B).

Figure 2.

Angiography of coronary-coronary bypasses graft. (a) Saphenous vein for the circumflex/branches of the circumflex. (b) Internal thoracic artery for right coronary–posterior descending/right posterolateral artery.

In most cases, linear grafting was performed. However, there were 6 cases of sequential shunting: 3 cases of double (Figure 3B) and 3 cases of triple-sequential grafting (Figure 3A).

Figure 3.

Angiography of coronary-coronary bypasses graft. (a) Internal thoracic artery for right coronary–posterior descending/right posterolateral artery. (b) Saphenous vein for right coronary–right coronary/posterior descending/right posterolateral artery.

In a number of cases, CCBG was performed when it was impossible to form a proximal anastomosis with the aorta (limited length of conduit, calcification of the ascending aorta, etc.).

The early postoperative period was uneventful for all patients. In none of the cases, ischemic electrocardiogram changes or an increase in cardiac biomarkers were observed. No operative or hospital mortality occurred. The mean intensive care unit stay was 2±1.5 days and hospital stay was 9±4.5 days.

Researchers assessed the efficacy and safety of CCBG added to the conventional technique of myocardial revascularization. In total 156 arterial, 67 venous and 109 coronary-coronary grafts were assessed. Coronary angiography was performed after recurrence of clinic of chest pain. According to the results, 12 (7.6%) arterial and 11 (19.3%) venous conduits were occluded, as well as 8 (10.3%) arterial and 10 (31.3%) venous coronary-coronary grafts. Kaplan-Meier analysis demonstrated differences in the occlusion of conduit (Figure 4).

Figure 4.

Cumulative freedom from coronary bypass graft occlusion (Kaplan-Meier analysis). CABG: coronary artery bypass grafting; CCBG: coronary-coronary bypass grafting; ITA: internal thoracic artery; and SVG: saphenous vein graft.

According to results of research, the probability of occlusion of venous CCBG was significantly higher than that of arterial coronary-coronary grafts and ITA (log rank p ¼ 0.001 and 0.008, respectively) [9].

3. Operative technique of CCBG

In all described cases, revascularization was performed via median sternotomy. There are 3 techniques for the arterial grafts harvesting:

• pedicled, including internal thoracic veins, perivascular adipose, muscle and fascia;

• semiskeletonized, including only internal thoracic veins;

• skeletonized, only the internal thoracic artery.

It should be noted that pedicled and semiskeletonized harvesting of ITAs significantly reduces the length of the arterial conduit. In the case of a lack of transplants, the situation will worsen much. Systemic hypo-coagulation was achieved by infusion of unfractionated heparin (calculated dose 3 mg/kg⁻¹).

The most usual site of proximal implantation for CCBG was the proximal part of the RCA [7, 10]. According to many authors, the initial segment of the RCA was often free of atherosclerosis and adequate diameter and thickness of this vessel also allowed a satisfactory congruence of the anastomosis with the graft. Other sites of proximal implantation are also possible. Bazylev V. and Nottin R. reported about using of branches of circumflex artery and LAD. CCBG was performed either between two segments of the same coronary artery or between its branches, generally the RCA or Cx. The Figure 5 shows the scheme of complete myocardial revascularization with the use of CCBG technique.

Figure 5.

The scheme of revascularization for the left and right coronary artery.

4. Potential advantages and disadvantages of CCBG

Initially, coronary-coronary bypass grafts were described as an alternative method of myocardial revascularization in patients with a limited number of conduits suitable for grafting and/or severe calcification of the ascending aorta and its branches. In most cases, the use of this technique has been accidental and forced. Nevertheless, available data demonstrate the possibility of using coronary-coronary bypass grafting as an isolated intervention or as an addition to the standard CABG [11]. Information on the use of CCBG is limited, but the accumulated experience indicates patency of these grafts for decades.

Such long-term efficiency has its own physiological preconditions. Many authors have shown the hemodynamic advantages of coronary-coronary bypass grafts over saphenous vein grafted to the ascending aorta [12]. Proximal anastomoses formed with the coronary artery itself provide a diastolic character to the blood flow and a less pronounced Venturi effect. According to the law of Bernoulli-Venturi, the difference in diameter is accompanied by a change in speed and pressure in places of vessel recalibration. Thus, the velocity of the blood passing through a constricted area will increase and its static pressure will decrease. Exactly in the place of diameter change the generated turbulent flow affects the state of the endothelium.

Similar conclusions can be reached if we consider the hemodynamic changes in the grafts from the viewpoint of wall share stress alteration. The pathophysiological significance of wall shear stress has been described not so long ago. Wall share stress is directly proportional to the average velocity of blood flow and inversely proportional to the inner radius of the vessel. Low values of these parameters allow accelerating the development of atherosclerotic plaques with thickening of the intima and fibromuscular dysplasia and platelet aggregation [13]. For example, in the study of Bazylev V. et al. the frequency of occluded venous coronary-coronary bypass grafts was higher than arterial ones: 8 (10.3%) vs. 10 (31.3%). One of the indirect reasons for the failure of venous coronary-coronary bypass grafts in the long-term period could be a larger diameter of the venous transplants, and as a result, a more pronounced hemodynamic effect on the vascular wall.

One of the problems of coronary-coronary bypass grafting can be the blood flow discreditation of the donor artery. Nottin and colleagues described their early postoperative results where 3 patients died from recurrent myocardial infarction. However, the mean aortic crossclamp time and the average number of distal anastomoses in this study were 83±27 min and 3.23±0.67, respectively. Results of Bazylev and colleagues show the uneventful early postoperative period in both groups of patients. In no case, ischemic electrocardiogram changes or an increase in cardiac biomarkers were observed. The reason for this may lie in the shorter period of myocardial ischemia but comparable number of distal anastomoses (61±42 min and 3,4±1,19, respectively).

Another problem of CCBG could be the progression of atherosclerosis in the region of proximal anastomosis. Bruschke and colleagues explored the progression of atherosclerosis in the RCA in 256 patients who were not operated on. Researchers found that the proximal and middle parts of the right coronary artery were most addicted to the progression of atherosclerosis, while no progression of atherosclerosis in the ostium and first segment (before the conus branch) was observed [14].

The choice of conduit for CCBG also remains controversial. Many studies have shown that the patency of CABG mostly depends on the type of conduit used. This statement is true for CCBG also. Patency of coronary-coronary bypass grafts does not depend on the progression of atherosclerosis in the donor coronary artery but depends on the type of conduit used. Extrapolating the results of using the ITA in situ, many researchers believe that the ITA is the best conduit for this procedure. Korkmaz et al. and Nishida et al. believed that even as a coronary-coronary graft, the internal thoracic artery has a number of advantages such as resistance to atherosclerosis due to prostacyclin secretion, and a low tendency to vasospasm compared to radial artery [2, 15]. Nevertheless, the effectiveness of SVG has also been described. Bazylev V. and collogues used both arterial and venous transplants, but it is difficult to confirm the superiority or disadvantages of any graft because this study was a retrospective and single-centre based on a relatively small number of observations. The authors were not taking into account the quality of the grafts (diameter, possible damage, etc.). The overall patency rates may be overestimated because some patients did not have angiograms for several reasons also. However, it was found that the patency of venous CCBG was lower than that of arterial CCBG. It can be assumed that venous coronary-coronary bypass grafts, as well as CABG, obey the same laws. Thus, neointimal hyperplasia, appearance and progression of atherosclerosis in the venous transplants may be manifestations of the hemodynamic qualities described earlier.

Further study of CCBG is warranted and will improve the results of coronary bypass surgery.

5. Conclusion

Arterial CCBG represents an alternative technique that allows complete myocardial revascularization.

Conflict of interest

The authors declare no conflict of interest.