Growth potential of left internal thoracic artery grafts: analysis of angiographic findings

Coronary artery bypass grafting for an anomalous origin of the right coronary artery: is it a valid surgical procedure?

The right internal thoracic artery to the right coronary artery bypass with ligation of the proximal native vessel is a simple and reliable option for the treatment of an anomalous aortic origin of the right coronary artery arising from the left sinus of Valsalva without an intramural course. Coronary artery bypass grafting is an uncomplicated option for elderly patients, those with connective tissue diseases, and those for whom combined aortic valve procedures are planned. Herein, we present four cases of this anomaly that underwent right internal thoracic artery anastomosis to the distal right coronary artery along with proximal right coronary artery ligation using a surgical clip. There was no occurrence of complications such as hypoperfusion syndrome, graft occlusion, recurrent symptoms, or late cardiac events.

Computational fluid dynamics of internal mammary artery-left anterior descending artery anastomoses

OBJECTIVES

The aim of this study was to elucidate the remodelling of the internal mammary artery (IMA)-left anterior descending artery anastomosis and compare 2 different anastomosis techniques (end-to-side versus side-to-side) using computational fluid dynamics.

METHODS

This study included 9 patients. Computed tomography (CT) angiography was performed immediately after coronary artery bypass grafting (CABG) and at 3-6 months later. The computational fluid dynamics models were made using the CT data. The pulsatile 3-dimensional blood flow was achieved with the finite volume method to evaluate the postoperative morphological and haemodynamic changes at the anastomosis in each patient. Flow velocity distribution, wall shear stress (WSS) and its fluctuation oscillatory shear index were measured.

RESULTS

No early or mid-term graft occlusion was observed in the study series. In the side-to-side anastomosis, pouch formation at the distal end of IMA caused a vortex flow with low WSS immediately after CABG. However, at 3-6 months after surgery, this pouch disappeared. As a result, the laminar straight flow with uniform WSS distribution was achieved inside the anastomosis. In the end-to-side anastomosis, the anastomosis shape was remodelled, resulting in a laminar flow pattern with uniform WSS distribution. A patchy high oscillatory shear index was detected at the IMA wall on the top of anastomosis in either anastomosis techniques immediately after the surgery, but it disappeared at 3-6 months after surgery.

CONCLUSIONS

Regardless of the anastomosis technique used, a successful remodelling of the IMA-left anterior descending artery anastomosis shape was achieved a few months after surgery, resulting in a straightforward flow streamline, with uniform WSS distribution and minimal oscillatory shear index.

Change in luminal diameter of the left internal thoracic artery anastomosed to the totally occluded left anterior descending coronary artery

Background

Coronary artery bypass grafting (CABG) with a composite Y-graft made of the left internal thoracic artery (LITA) and another arterial graft has a risk for hypoperfusion. Changes over time in the diameter of the LITA anastomosed to the left anterior descending coronary artery (LAD) are not known.

Methods

Data were collected for 71 patients who had undergone coronary angiography (CAG) immediately and at 1 year following off-pump CABG with a composite Y-graft made of the LITA and either the radial artery or the right gastroepiploic artery. These patients were divided into 2 groups depending on the degree of LAD stenosis. Group 1 (n = 28) consisted of patients with complete occlusion of the LAD. Group 2 (n = 43) consisted of patients with <90% stenosis of the LAD. The clinical state and luminal diameter of the LITA on immediate postoperative and postoperative 1-year CAG were compared and analyzed.

Results

On the immediate postoperative CAG, mean LITA diameter of Group 1 was larger than that of Group 2 (2.09 ± 0.53 vs. 1.61 ± 0.33 mm, P = 0.01). Mean LITA diameter 1 year following CABG was also larger in Group 1 than in Group 2 (2.49 ± 0.31 vs. 2.10 ± 0.45 mm, P = 0.005). Both groups showed significant increases in the LITA diameters at postoperative 1 year.

Conclusions

The LITA used as a composite Y-graft underwent remodeling, resulting in a larger diameter, to supply adequate myocardial blood. The degree of change in luminal diameter varied according to the severity of the LAD stenosis.

Off-pump coronary artery bypass grafting using a bilateral internal mammary artery Y graft

Objective

To evaluate the outcome of off-pump coronary artery bypass grafting (OPCABG) using a bilateral internal mammary artery (BIMA) Y configuration graft to achieve total arterial myocardial revascularization.

Methods

From October 2002 to December 2008, 208 patients (196 males and 12 females) underwent OPCABG using a BIMA Y configuration graft. The average age of the patients was 56.5 ± 11.3 years, with an age range of 33–78 years. A total of 167 (80.2%) cases had triple-vessel disease. Left main stem disease was found in 33 (15.9%) cases, and double-vessel disease was found in 8 (3.9%) cases. The semi-skeletonization technique was used to harvest the two internal mammary arteries (IMAs), and then the free right internal mammary artery was connected end-to-side to the left internal mammary artery (LIMA) in situ to complete the Y configuration graft. Off-pump and sequential anastomosis methods were used to perform coronary artery bypass surgery in all patients. Graft patency was assessed intra-operatively with the HT311 transit time flowmeter.

Results

A total of 728 distal anastomoses were performed in 208 patients, with the average being 3.5 ± 1.3 per person. No one died or experienced recurrent angina within 30 days after the operation.

Conclusions

OPCABG using the BIMA Y graft was safe and effective to achieve total arterial revascularization. This method avoids surgical operation on the ascending aorta and other incisions.

Total Arterial Off-pump Coronary Revascularization with a Bilateral Internal Mammary Artery Y Graft (208 cases)

Objective:

The aim was to evaluate the early outcome of off-pump coronary artery bypass grafting (OPCABG) with a bilateral internal mammary artery (BIMA) Y configuration graft to achieve total arterial myocardial revascularization.

Materials and Methods:

From October 2002 to December 2008, 208 patients (196 male and 12 female patients) underwent OPCABG by only using a BIMA Y configuration graft. The average age of the patients was 56.5±11.3 years, with the age range being 33–78 years. A total of 167 (80.2%) cases had triple-vessel disease. Left main stem disease was found in 33 (15.9%) cases, and double-vessel disease was found in 8 (3.9%) cases. The semiskeletonization skill was used to harvest the two IMAs, and then the free right internal mammary artery was anastomosed end-to-side to the in situ left internal mammary artery to composite a Y configuration graft. Off-pump and sequential anastomosis methods were used to perform coronary artery bypass surgery for the patients. Graft patency was assessed by using the HT311 transit time flowmeter (USA Transonic Systems Inc.), intraoperatively.

Results:

We performed distal anastomoses of the grafts in 728 patients, the average being 3.5±1.3 per person. No one died and got recurrent angina within 30 days after operation.

Conclusion:

OPCABG by using the BIMA Y graft was safe and effective to achieve total arterial revascularization, and avoid surgical operation on the ascending aorta, and other incisions.

Surgical patch angioplasty of the left main coronary artery

Isolated ostial stenosis of the left main coronary artery (LMCA) is rare, occurring in <1% of the patients undergoing coronary angiography. Surgical patch angioplasty (SPA) offers an alternative to conventional coronary artery bypass grafting (CABG) in such cases and is advantageous in restoring more physiological myocardial perfusion, maintaining ostial patency and preserving conduit material. However, a number of early technical failures and high perioperative mortality have limited the generalized uptake of this procedure, and only recently have advances in myocardial protection and novel surgical approaches to the LMCA resulted in a resurgence of the technique. A systematic literature search identified 45 studies incorporating 478 patients undergoing SPA. A variety of patch materials were used, including the pericardium, saphenous vein and internal mammary and pulmonary arteries. Patients were followed up for a mean of 54.4 months. The 30-day mortality was 1.7% and cardiac specific mortality 3.3% at last follow-up. Encouragingly, 92.4% of reported cases (n = 182) showed complete angiographic patency at last follow-up. Our results indicate that SPA may be a viable alternative to CABG in the surgical management of isolated ostial LMCA stenosis. However, no randomized trials have been performed, and it is clear that careful patient selection is essential in minimizing morbidity and mortality in the short- and long-term. Further research is required to allow a direct comparison of SPA to techniques with a more substantial evidence base such as CABG and percutaneous coronary intervention, and to define the optimal patch graft material, elucidating that any beneficial effects arterial patches may have on long-term patency.

Non-invasive evaluation of internal thoracic artery anastomosed to the left anterior descending artery with 320-detector row computed tomography and adenosine thallium-201 myocardial perfusion scintigraphy

PURPOSE

We evaluated the relationship between internal thoracic artery (ITA) stenosis anastomosed to the left anterior descending artery (LAD) and the degree of LAD stenosis using 320-detector row computed tomography (320-ADCT) and adenosine thallium-201 myocardial perfusion scintigraphy (Tl-201-MPS).

METHODS

We included 101 patients who underwent coronary artery bypass grafting (CABG) using ITA grafts; 320-ADCT and adenosine Tl-201-MPS were performed 2-3 months after CABG. Clinical parameters, degree of LAD stenosis, and regional myocardial ischemia of the LAD territory were compared between patients without ITA stenosis (Group A) and with ITA stenosis (Group B).

RESULTS

Thirty patients (30%) had ≤75% LAD stenosis, and 9 patients (30%) showed significant ITA stenosis. Regional ischemia was noted in 23 patients (23%). There were no differences in clinical parameters between the 2 groups. Twenty-two patients (24%) in Group A and 8 patients (89%) in Group B had ≤75% LAD stenosis (P <0.002). No Group B patients had regional myocardial ischemia of the LAD territory.

CONCLUSION

We concluded that ≤75% LAD stenosis significantly influences ITA stenosis, without associated regional myocardial ischemia of the LAD territory. Non-invasive 320-ADCT and adenosine Tl-201-MPS for ITA evaluation may be useful for long-term follow-up of patients after CABG.

Improvement of flow capacity of the left internal thoracic artery graft assessed by using a pressure wire

OBJECTIVE

We sought to evaluate improvement of flow capacity in a left internal thoracic artery graft by means of pressure measurement.

METHODS

Eighteen patients who received a left internal thoracic artery graft to the left anterior descending coronary artery were studied. Angiography and pressure measurement at the proximal and distal portions of the left internal thoracic artery graft during maximal hyperemia with a pressure guide wire were performed at 1 month (early study) and 6 months (late study) after surgical intervention.

RESULTS

There are no significant differences between the early and late studies in resting mean aortic pressure, left ventricular end-diastolic pressure, left ventricular ejection fraction, and percentage diameter stenosis of the recipient left anterior descending coronary artery. There was no stenosis in the anastomosis site of the left internal thoracic artery graft and the distal left anterior descending coronary artery, as determined by means of angiography, in the early and late studies. The mean diameter of the distal left internal thoracic artery graft was significantly increased in the late study (1.6 +/- 0.2 vs. 1.8 +/- 0.2 mm, P = .011). There was a significant difference between the early and late studies in the pressure gradient through the graft (15 +/- 4 vs 13 +/- 3 mm Hg, P = .036). The ratio of distal to proximal pressure within the left internal thoracic artery graft in the late study was significantly increased from that in the early study (0.80 +/- 0.04 to 0.84 +/- 0.03, P = .0003).

CONCLUSIONS

The pressure ratio within the left internal thoracic artery graft became higher as the left internal thoracic artery graft adapted itself to the myocardial circulation. This finding might relate to decreasing the resistance of the left internal thoracic artery graft.

Late regression of left internal thoracic artery graft stenosis at the anastomotic site without intervention therapy

OBJECTIVE

Intervention therapy has been recently performed on the left internal thoracic artery graft stenosis. The purpose of this study was to evaluate the natural course of the left internal thoracic artery graft stenosis at the anastomotic site and clarify whether intervention therapy should be performed early after surgery.

METHODS

We investigated early angiographic results of the left internal thoracic artery graft in 343 consecutive patients who underwent coronary bypass surgery. In 100 of 343 patients who underwent follow-up angiography, the graft diameter and percentage diameter stenosis at the anastomotic site were compared between early postoperative and follow-up angiography. None of these patients underwent intervention therapy on the left internal thoracic artery graft.

RESULTS

Of 343 patients, 46 showed 50% or greater diameter stenosis, and 20 showed 70% or greater diameter stenosis at the anastomotic site. In the 100 patients with follow-up angiography, the graft diameter significantly increased (1.8 +/- 0.4 vs 2.1 +/- 0.5 mm, P < .0001) at follow-up angiography. The percentage diameter stenosis significantly decreased (69% +/- 13% vs 35% +/- 20%, P < .0001) at follow-up angiography in the patients with 50% or greater diameter stenosis at early postoperative angiography. Regression of left internal thoracic artery graft stenosis was detected in most patients with 70% or greater diameter stenosis.

CONCLUSIONS

Our study demonstrated that left internal thoracic artery graft stenosis at the anastomotic site at early postoperative angiography might improve without intervention therapy. We should consider the natural course of the left internal thoracic artery graft stenosis in determining the indication of intervention therapy early after surgery.

Noninvasive Dynamic Assessment With Transthoracic Echocardiography of a Composite Arterial Y-Graft Achieving Complete Myocardial Revascularization

BACKGROUND

Composite arterial grafts are increasingly used in coronary artery bypass surgery. We assessed with transthoracic echocardiography the composite radial artery and in situ left internal thoracic artery Y-graft.

METHODS

In 53 of 60 consecutive patients who underwent complete myocardial revascularization using only this composite arterial graft, good transthoracic echocardiographic images and pulsed Doppler signals of the Y-graft main stem were obtained at rest and early after standard exercise. Stress/rest 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT) was the gold standard for residual myocardial ischemia. The patients with negative SPECT were divided into groups according to the number of coronary artery systems grafted, and history of preoperative myocardial infarction.

RESULTS

Diastolic peak velocity, diastolic velocity-time integral, the diastolic-to-systolic ratio of the peak velocities and velocity-time integrals, and the stress-to-rest ratio of the diastolic peak velocities and diastolic velocity-time integrals in the negative-SPECT patients were significantly greater than in the 6 positive-SPECT patients. Sensitivity and specificity for ischemia of the stress-to-rest ratio of the diastolic peak velocities less than 1.5 were 100%. The stress-to-rest ratio of the diastolic velocity-time integrals in the patients with three coronary systems grafted, and in those without preoperative myocardial infarction, were respectively greater than in the patients with two systems grafted (p < 0.0001), and in those with preoperative myocardial infarction (p = 0.0048).

CONCLUSIONS

Noninvasive dynamic assessment with transthoracic echocardiography of a composite arterial graft, including in situ left internal thoracic artery, is feasible and correlates with myocardial perfusion SPECT. The Y-graft used was able to regulate its flow capacity to myocardial demand.

Total Arterial Revascularization with a Single Y-Composite Graft for Triple-Vessel Disease: Comparison of 2- and 3-Artery Grafts

BACKGROUND

Treating triple-vessel disease by grafting a single Y-composite graft with 1 arterial conduit attached to the side of the internal thoracic artery is sometimes not used because of the possibility of hypoperfusion.

METHODS

Between March 2001 and June 2003, 271 patients who underwent total arterial revascularization for triple-vessel disease were divided into 2 groups. Group I (n = 188) received a Y-composite graft with 2 arterial conduits, and group II (n = 83) received a Y-composite graft and 1 additional arterial conduit. We retrospectively reviewed the data and compared the clinical results of the 2 groups.

RESULTS

The numbers of distal anastomoses were 3.9 +/- 0.7 (mean +/- SD) per patient in group I and 4.1 +/- 0.8 in group II (P = .021). There were 2 in-hospital deaths in group I and none in group II (difference not statistically significant). Perioperative myocardial infarction occurred in 2 patients in group I and none in group II (not statistically significant). No patient in either group needed a new intra-aortic balloon pump postoperatively, and no patients experienced hypoperfusion syndrome. A cerebrovascular accident occurred in 1 patient of each group. During the follow-up period (15.9 +/- 6.7 months in group I, 25.2 +/- 8.3 months in group II), 5 patients died (4 in group I, 1 in group II). Two patients in group I and 1 patient in group II needed an intervention on the right coronary artery, but the other patients required no additional procedures and had no symptoms of angina. There were no statistically significant differences in survival and reintervention-free survival between the 2 groups.

CONCLUSION

Single Y-composite grafts with 2 arterial conduits may be a safe and effective strategy for treating triple-vessel disease.

Coronary revascularization in the 21st century. Emphasis on contributions by Japanese surgeons

The first three decades of coronary artery surgery have provided the foundation for the next century of this evolution. It is apparent that a multitude of events including the development of cardioplegia, improving surgical instrumentation, technological advances including endoscopic approaches and computer assisted robotics and biologic discoveries such as the role of the endothelium have provided the underpinnings for improved surgical outcomes. However, the single most important determinant of late results is the type of bypass conduit used for grafting. Thus, use of the left internal thoracic artery (ITA) grafted to the left anterior descending coronary is a more important determinant of survival than is any other factor (progression of coronary artery disease, increased age, poor left ventricular function, diabetes, female gender and off-pump operations). Use of two ITAs provides further benefit and it is likely that three or more arterial conduits will be shown to be advantageous in this regard in due time. Japanese cardiothoracic surgeons have made significant contributions to the continuing evolution of coronary bypass surgery and particularly to the advance of arterial conduits. This report will address those contributions to this evolution.

Composite arterial Y graft has less coronary flow reserve than independent grafts

BACKGROUND

It is not known whether a composite Y graft of the left internal thoracic artery can provide sufficient blood flow to the whole left coronary system. The aim of this study was to compare regional myocardial blood flow (MBF) and coronary flow reserve after coronary artery bypass grafting using arterial composite Y graft or independent arterial grafts.

METHODS

Positron emission tomography was performed at rest and after dipyridamole infusion using oxygen-15-labeled water 2 weeks after coronary artery bypass grafting. Regional MBF was calculated in seven segments of the left ventricle. Coronary flow reserve was defined as the ratio of MBF after dipyridamole infusion to MBF at rest. In the Y graft group (n = 22), a free arterial graft to obtuse marginal arteries was anastomosed to the proximal side of in situ left internal thoracic artery, which was anastomosed to the left anterior descending artery. In the independent graft group (n = 13), left anterior descending and obtuse marginal arteries were independently revascularized using in situ left internal thoracic artery and a free arterial graft.

RESULTS

There was no difference between the groups in MBF at rest. Coronary flow reserve in the Y graft group was lower than that in the independent group in the anterobasal (1.43 +/- 0.07 versus 1.90 +/- 0.13, p = 0.038), apical (1.24 +/- 0.06 versus 1.64 +/- 0.12, p = 0.003), septal (1.34 +/- 0.05 versus 1.75 +/- 0.13, p = 0.023), and lateral regions (1.19 +/- 0.04 versus 1.66 +/- 0.09, p = 0.001).

CONCLUSIONS

Although arterial composite Y graft improved MBF at rest, it was not as effective as independent grafts for improving coronary flow reserve soon after coronary artery bypass grafting.