In BITA Grafting, RITA Patency Depends on Coronary Targets More Than Configuration

Among coronary artery bypass grafts (CABG) using bilateral internal thoracic arteries (BITAs), right ITA (RITA) grafting achieves high long-term patency independent of its inflow configuration. That’s a key finding from the largest series reported to date of BITA grafts with evaluable angiograms, recently published online in the Annals of Thoracic Surgery.

“When conducting BITA, priority for RITA should be to achieve a configuration that optimizes its reach to important coronary targets without tension and to maximize supply to the myocardium,” says the study’s first author, Cleveland Clinic cardiothoracic surgeon Faisal Bakaeen, MD. “We found that inflow conduit configuration has less of an effect on outcomes than the outflow target.”

Is there a best RITA configuration?

Venous grafting has a standard inflow configuration from the ascending aorta, but surgeons use multiple configurations for arterial grafts. That CABG using BITA improves long-term survival over single ITA grafting was established by a large Cleveland Clinic series published more than 20 years ago (J Thorac Cardiovasc Surg 1999;117:855-872). More recently, Cleveland Clinic researchers reported that using BITA to bypass multiple important targets to maximize myocardium perfusion optimizes outcomes (JACC. 2020;75:269-272).

However, little is known about how various RITA inflow configurations affect graft patency. To address this knowledge gap, this study was designed to compare outcomes of various RITA inflow configurations while adjusting for outflow coronary target location.

Cohort characteristics and findings

The study cohort consisted of patients who underwent primary CABG at Cleveland Clinic from 1972 to 2016 and received BITA grafting with available postoperative coronary angiography to assess graft patency (N = 1,331).

Among the LITA grafts, 1,311 (98.5%) were in situ (with 59% of these having an LAD target) and 20 (1.5%) were free graft.

The RITA grafts had more varied configurations. There were 835 in situ inflow grafts (63%), with the LAD as a target in 49% of these. The 496 free grafts (37%) had the following origins:

• Aorta, 311 (63%)
• LITA Y-graft, 98 (20%)
• Vein graft, 76 (15%; 64 hood, 12 mid-segment)
• Radial artery, 11 (2%)

Overall, RITA patency was 90% at 1 year, 87% at 5 years and 86% at 10 and 15 years. At 15 years, patency rates for various inflow configurations were as follows:

• In-situ RITA, 91%
• Free RITA off the aorta, 91%
• Free RITA off LITA as Y-graft, 89%
• Free RITA off hood of a saphenous vein graft, 77%

Patency was similar for all these configurations after adjusting for coronary target location and degree of stenosis. However, RITAs grafted to the LAD as the target had fewer occlusions, with patency similar to LITA grafts.

Target choice more important than conduit configuration

Dr. Bakaeen and his co-authors highlight the following conclusions from this study:

• Long-term RITA graft patency is high and independent of inflow configuration. RITA patency was found to be excellent after 15 years regardless of inflow configuration. A surgeon’s priority should be to use RITA for any inflow configuration that achieves the goal of maximizing myocardial coverage without tension.
• RITA may be used for LAD targets. Although a RITA graft is usually (and preferably — see below) used to bypass non-LAD targets as a supplement to a LITA-LAD graft, patency rates for LAD targets are similar whether RITA or LITA is used.

Tips from the operating room

After more than 7,000 cases of BITA grafting at Cleveland Clinic during the study period, the authors recommend the following practices.

1. Avoid anastomosing ITAs or radial arteries to an ascending aorta with a thick wall (use epi-aortic ultrasonography to screen for this).
2. A friable or small ITA is best anastomosed to a vein graft (at the hood of the proximal anastomosis, not distal along the vein) or used as a free graft from the LITA.
3. Use in situ LITA-LAD as the pillar for most BITA configurations. When an in situ RITA crosses the midline to bypass the LAD, technical problems can arise, such as graft tension or kinking, as well as compression by chest tubes after closure. Similarly, in situ LITA to a non-LAD target to supplement a RITA-LAD configuration may be awkward; acute turns should be avoided, especially where LITA crosses the pericardial edge.
4. Consider future risk. Avoid having an ITA cross the midline close to the sternum or chest wall, putting it at risk for injury during a subsequent cardiac surgery. “If the situation dictates an in situ RITA-LAD configuration, cover the graft with mediastinal fat tissue before sternal closure to allow for safer reentry, if necessary,” advises Cleveland Clinic cardiothoracic surgeon Kenneth McCurry, MD, a study co-author.
5. In general, avoid using multiarterial grafting if there is a large myocardial territory at risk in the setting of ongoing acute ischemia and critical native coronary stenosis. “Arterial flow may not be immediately sufficient,” Dr. Bakaeen explains, “particularly for small-caliber arterial conduits that have not had the chance to mature and increase in size and associated blood flow to match myocardial demand.”
6. Ensure balanced flow between grafts to avoid competitive flow.

“Our findings inform and support flexibility in decision-making in BITA grafting while using best practices,” observes co-author Hiba Ghandour, MD, research fellow in thoracic and cardiovascular surgery at Cleveland Clinic. “They remind us all that the reach of a RITA graft should not determine its target, but the intended target should shape the ITA configuration.”