Noninvasive evaluation of internal thoracic artery and left anterior descending coronary artery anastomotic sites using transthoracic Doppler echocardiography: comparison with coronary arteriography

Assessment of the Graft Quality and Patency during and after Coronary Artery Bypass Grafting

Coronary artery bypass grafting (CABG) is the gold standard procedure for multi vessels and left main coronary artery disease. The prognosis and survival outcomes of CABG surgery are highly dependent on the patency of the bypass graft. Early graft failure which can occur during or soon after CABG remains a significant issue, with reported incidences of 3-10%. Graft failure can lead to refractory angina, myocardial ischemia, arrhythmias, low cardiac output, and fatal cardiac failure, emphasizing the importance of ensuring graft patency during and after surgery to prevent such complications. Technical errors during anastomosis are among the leading causes of early graft failure. To address this issue, various modalities and techniques have been developed to evaluate graft patency during and after CABG surgery. These modalities aim to assess the quality and integrity of the graft, thus enabling surgeons to identify and address any issues before they lead to significant complications. In this review article, we aim to discuss the strengths and limitations of all available techniques and modalities, with the goal to identify the best modality for evaluating graft patency during and after CABG surgery.

Use of the right internal mammary artery and the great saphenous vein for left anterior descending artery revascularization in patients whose left internal mammal artery cannot be used: a study based on transit-time flow measurement

Background

Owing to the high patency, the use of the left internal mammary artery (LIMA) for left anterior descending artery (LAD) grafting has been a cornerstone of coronary artery bypass grafting surgery (CABG). However, for some patients whose LIMA cannot be used, surgeons have to choose other conduit materials to revascularize the LAD. The purpose of this study was to explore the differences in different conduit materials used for LAD in terms of parameters measured by transit-time flow measurement (TTFM) and the early graft patency detected by computed tomography angiography.

Methods

We retrospectively collected the data of 410 patients who underwent isolated primary OPCAB with intraoperative TTFM data. According to the strategy of the LAD revascularization, 410 patients were assigned to three groups: a left internal mammal artery (LIMA) group (n = 333), a right IMA (RIMA) group (n = 34) and a great saphenous vein (SVG) group (n = 43). The baseline and perioperative blood parameters were compared for the three groups, as well as the early graft patency rates.

Results

Compared with the LIMA-LAD group, the SVG-LAD group had a significantly higher mean graft flow volume (MGF) (37.15 ± 23.29 vs 29.71 ± 20.94 ml/min, P = 0.036), however, had a lower value of pulse index (PI) (2.07 ± 0.62 vs 2.65 ± 1.01, P<0.001). There was no significant difference between the two groups in terms of DF (P>0.05). Compared with the RIMA-LAD group, the SVG-LAD group just had a lower value of PI (2.07 ± 0.62 vs 2.56 ± 0.96, P = 0.029). However, there was no significant difference between the two groups in terms of MGF and DF (P>0.05). Compared with the LIMA-LAD group, the RIMA-LAD group had a slightly lower value of DF (70.76 ± 11.87 vs 74.06 ± 7.09, P = 0.018), while there was no difference in terms of MGF and PI between the two groups (P>0.05). The patency rate of the LIMA-LAD group was 98.72% (309/313), that of RIMA-LAD group was 97.06% (33/34), and that of SVG-LAD group was 100%. There was no difference among the three groups in patency rate (P = 0.405).

Conclusions

SVG-LAD has a higher intraoperative MGF and a lower value of the PI than both LIMA-LAD and RIMA-LAD. RIMA has a higher preoperative blood flow and a lower value of the PI than LIMA; however, there were no significant difference between RIMA grafted to LAD and LIMA grafted to LAD in terms of MGF, PI and DF. In situ skeletonized RIMA did not increase blood flow compared to pedicled LIMA.

Serial evaluation of flow in single or arterial Y-grafts to the left coronary artery

BACKGROUND

It is unclear whether composite Y-grafts can withstand the flow demand of the coronary system at rest and under stress. This study compared the graft flow and flow reserve of the left internal mammary artery (LIMA) intraoperatively and over a 2-year follow-up in single or composite Y-graft configurations using the radial artery (RA).

METHODS

One hundred patients who underwent off-pump myocardial revascularization with a composite Y-graft (group 2) were compared with a homogeneous group of 100 patients treated with a single independent LIMA graft on the left anterior descending artery (LAD) (group 1). Intraoperative baseline flow and flow after adenosine infusion into the left ventricle were analyzed. Over a 2-year follow-up, noninvasive longitudinal evaluation of flow was carried out at rest and during maximal hyperemic response by transthoracic Doppler ultrasonography. Final functional evaluation was obtained through a 2-day stress/rest 99mTc-sestamibi myocardial perfusion single-photon emission computed tomographic scan.

RESULTS

The proximal LIMA in a Y-graft configuration showed adaptability to flow dynamics. It had a greater average peak velocity (p = 0.02), flow volume (p < 0.01), and diameter (p < 0.01) than independent single LIMA grafts. Distal flow at rest and during adenosine recruitment was similar between groups both intraoperatively and at all time points of the follow-up. No steal phenomenon occurred at rest, nor was it induced by adenosine in the Y-graft group. Exercise nuclear scintigraphy showed satisfactory exercise tolerance and no inducible significant perfusion defects in both groups.

CONCLUSIONS

Left internal mammary artery Y-grafting with the RA is adequate for flow requirements of distal branches at rest and during maximal hyperemia and is able to adapt its dimension to flow demand. Optimal results for RA anastomoses are possible only in arteries with critical stenosis and of good size and quality.

Different flow patterns between left and right internal thoracic artery grafts influence the evaluation of severe graft stenosis by transthoracic Doppler echocardiography

OBJECTIVE

An increase in the diastolic to systolic flow velocity ratio (D/S) in the proximal left internal thoracic artery (ITA) after coronary artery bypass grafting (CABG) enables noninvasive assessment of graft patency by transthoracic Doppler echocardiography (TTDE). The increase in the D/S can be less pronounced at a site distant from the anastomosis. We postulated that proximal ITA flow patterns differ between the left and right ITAs and that the increase in D/S is less pronounced in the right than in the left proximal ITA.

METHODS

Proximal ITA flow was examined by TTDE in 129 consecutive patients after CABG of the left (75) or right (69) ITA to the left coronary artery. The mean D/S of the ITAs was compared with coronary angiography.

RESULTS

The D/S was lower in the group with a patent right ITA than in the group with a patent left ITA (P < .05). The D/S of both the left and right ITAs negatively correlated with angiographic stenosis (r = 0.56 or 0.67, P < .001, respectively). The regression line was significantly shifted downward in the right ITA compared with the left ITA, according to analysis of covariance (P = .01). Graft stenosis was predicted by a D/S of <0.57 and <0.28 with an accuracy of 91% and 97% in the left and right ITAs, respectively.

CONCLUSION

The patency of both left and right ITA grafts to the left coronary artery can be assessed using TTDE, but different cutoff values of D/S are required to diagnose severe ITA stenosis.

Assessment of internal thoracic artery patency with transesophageal echocardiography during coronary artery bypass graft surgery

OBJECTIVE

The purpose of this study was to evaluate intraoperative transesophageal echocardiography (TEE) for assessing patency of internal thoracic artery grafts.

DESIGN

A retrospective study.

SETTING

A university hospital.

PARTICIPANTS

Fifty-one consecutive patients who underwent coronary artery bypass graft (CABG) surgery using the left internal thoracic artery (LITA)-to-left coronary artery were examined postoperatively with coronary angiography (CAG).

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

The authors measured blood flow velocity using TEE after anastomosis of a LITA graft. Intraoperative TEE findings and routine CAG results were compared to evaluate the quality of TEE assessment. The LITA was detected in 45 of 51 patients (88%) intraoperatively with TEE. Peak and mean velocities and velocity time integral ratios were determined by dividing each diastolic value by its corresponding systolic value. The peak velocity ratio was 0.51 +/- 0.04 (range, 0.40-0.59) in the presence of stenosis and 1.14 +/- 0.10 (range, 0.58-3.87) in its absence (p = 0.0289), whereas mean velocity ratios were 0.62 +/- 0.05 (range, 0.45-0.72) and 1.27 +/- 0.10 (range, 0.66-4.08) (p = 0.0223), respectively, and velocity time integral ratios were 0.83 +/- 0.09 (range, 0.64-1.05) and 2.69 +/- 0.29 (range, 0.91-8.35) (p = 0.0224), respectively. The critical values for peak and mean velocities and velocity time integral ratios were 0.60, 0.73, and 1.06, respectively, whereas the sensitivity for each was 100% and the specificity was 92%, 94%, and 89%, respectively.

CONCLUSIONS

The authors concluded that the intraoperative assessment of LITA patency with TEE was a markedly useful and powerful tool for anesthesiologists during CABG surgery.

Development of severe string sign in internal thoracic arterial graft during first month

In the present case, development of the string sign in an internal thoracic arterial graft was observed using transthoracic Doppler echocardiography. Following surgery, the diameter of the internal thoracic graft decreased; however, the diameter of the left anterior descending coronary artery did not change from 1.9 mm. Further, the flow velocity in the internal thoracic artery during the systolic phase became greater than that in the early phase and then decreased on postoperative day 19, and it was not detected on postoperative day 31. Coronary arteriography performed on postoperative day 31 revealed a severely stringed internal thoracic artery.

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.