|Year : 2015 | Volume
| Issue : 1 | Page : 121-124
Assessment of left internal mammary artery to left anterior descending flow in composite arterial bypass grafting
Ahmed Labib Dokhan, Yahia Balbaa Anwar Balbaa, Mostafa Farouk Abo olo, Mohamed Sabry Abd Elmotellib Hussien
Cardiothoracic Surgery Department, Faculty of Medicine, Menufiya University, Menufiya, Egypt
|Date of Submission||05-Jun-2014|
|Date of Acceptance||15-Aug-2014|
|Date of Web Publication||29-Apr-2015|
Mohamed Sabry Abd Elmotellib Hussien
4, El sok street, Quesna
Source of Support: None, Conflict of Interest: None
The aim of the study was to achieve arterial myocardial revascularization using the 'Y-graft or T-graft' techniques and to measure intraoperative graft flow by transit-time flowmetry.
Composite grafting techniques for coronary artery bypass grafts have been widely used. However, it remains unclear whether this technique provides similar blood flow to the left coronary artery. In this study, we evaluated composite grafting techniques by intraoperative measurement graft flow by transit-time flowmetry.
Materials and methods
Fifty patients who underwent coronary artery bypass grafting during a time period of 24 months were enrolled in this prospective study. All patients received sequential grafting using both internal thoracic arteries and left radial artery joined as a composite Y or T graft. Intraoperative left internal mammary artery (LIMA) flow was measured by transit-time flowmetry.
This study provided evidence that the LIMA limb of a composite Y or T graft had intraoperative increase in mean flow, and there was statistical significance (P < 0.01) between mean flow with clamping Y or T graft (41.72 ± 15.59 ml/min) and with patent Y or T graft (78.60 ± 29.58 ml/min).
LIMA has the potential to provide sufficient blood flow to revascularize left coronary system.
Keywords: Composite arterial grafts, coronary artery bypass grafting, transit-time flowmetry
|How to cite this article:|
Dokhan AL, Balbaa YB, Abo olo MF, Hussien MS. Assessment of left internal mammary artery to left anterior descending flow in composite arterial bypass grafting. Menoufia Med J 2015;28:121-4
|How to cite this URL:|
Dokhan AL, Balbaa YB, Abo olo MF, Hussien MS. Assessment of left internal mammary artery to left anterior descending flow in composite arterial bypass grafting. Menoufia Med J [serial online] 2015 [cited 2020 Aug 3];28:121-4. Available from: http://www.mmj.eg.net/text.asp?2015/28/1/121/155966
| Introduction|| |
In the last few years, the superior results of coronary revascularization with the internal mammary artery (IMA) have led to a significant development in techniques to extend arterial revascularization procedures .
The Y-graft and T-graft techniques have developed, with different free arterial conduits anastomosed off the side of an in-situ left internal mammary artery (LIMA) to reach distal coronary segments. The midterm follow-up of patients operated on composite coronary artery bypass grafting (CABG) showed excellent graft patency rate .
The right internal mammary artery (RIMA) and radial artery (RA) were used to fashion an 'arterial Y or T' off the side of an in-situ ITA graft. As usually more than two anastomoses are required, Y-composite or T-composite grafting uses a sequential grafting technique .
However, the hypothesis that the flow reserve of pedicled IMA may not provide sufficient blood flow for extended left ventricular revascularization has so far not been investigated .
| Materials and methods|| |
This was a prospective study of 50 patients who underwent CABG using total arterial revascularization technique for left coronary system at a private hospital from October 2011 to October 2013. The Ethics Committee of the Faculty of Medicine, Menoufiya University approved the data collection within the project and patients' consent was written. Patients with single vessel disease, with ejection fraction less than 40%, who underwent redo CABG, who underwent CABG associated with other cardiac operative interference (e.g. valve repair or replacement), and who underwent CABG associated with other vascular operative interference (e.g. aortic root surgery) were excluded.
LIMA was anastomosed end-to-side to left anterior descending (LAD). Other vessels of left coronary system [Ramus, obtuse marginal (OM), and diagonals] were revascularized using arterial conduits (RIMA and RA) in Y or T manner to the LIMA. Assessment of flow was performed using transit-time flowmetry twice for each patient: first, LIMA flow to LAD with clamping of the Y or T graft and then LIMA flow to LAD with patent Y or T anastomosis.
| Results|| |
The age of patients ranged from 39 to 73 years with a mean age of 56.72 ± 7.99 years, and male sex (49/50) constituted most of them (98%), whereas female sex (1/50) was 2%.
There were 39/50 patients (78%) with hypertension, 40/50 patients (80%) with diabetes, and 25/50 patients (50%) were smokers.
In our study, total number of grafts was 140 with a mean of 2.80 ± 0.80 and a range of 2-5. LIMA and RIMA were used in 38/50 patients (76%); LIMA and RA were used in 10/50 patients (20%); and LIMA, RIMA, and RA were used in 2/50 patients (4%). Of the 140 grafts, there were 50 grafts LIMA to LAD (35.7%), 43 grafts RIMA to OM (30.7%), 18 grafts RA to OM (12.9%), 16 grafts RIMA to diagonals (11.4%), three grafts RIMA to Ramus (2.1%), and 10 grafts RA to diagonals (7.2%).
In our study, there was statistical significance (P < 0.01) between mean flow with clamping Y or T graft (41.72 ± 15.59 ml/min) and with patent Y or T graft (78.60 ± 29.58 ml/min), and there was statistical significance (P < 0.01) between pulsatility index (PI) with clamping Y or T graft (2.39 ± 0.82) and with patent Y or T graft (1.89 ± 0.65), but no statistical significance was found regarding diastolic flow.
In our study, 1/50 patient (2%) developed atrial fibrillation, and 1/50 patient (2%) explored for bleeding. There was no postoperative sternal wound infection or mortality.
| Discussion|| |
In the last few years, the superior results of coronary revascularization IMA have led to a significant development in techniques to extend arterial revascularization procedures. The Y-graft and T-graft techniques have developed, with different free arterial conduits anastomosed off the side of an in-situ IMA to reach distal coronary segment .
Transit-time flowmetry was widely accepted for use in intraoperative graft assessment because it is noninvasive, technically simple, reproducible, fast, and inexpensive. It provided important and accurate intraoperative information on the status and patency of each individual graft. The ideal PI value should be between 1 and 5 after bypass grafts finished. Sometimes, the technical error in the anastomosis may increase higher PI value. A problem was thought to be present when the mean flow of the graft was less than 15 ml/min .
The use of composite grafts of LIMA and RA or RIMA appeared to try to utilize arterial grafts more widely in myocardial revascularization. Thus, the proximal aortic anastomosis, originally to RA, was changed to the LIMA solving the problem of disproportion size between the graft and aortic walls. However, concern about the technically more difficult anastomosis between the two arterial grafts continued .
One disadvantage of the use of composite arterial grafts is the dependence on the LIMA for all the blood supply to the revascularized arteries. Thus, the capacity and reserve of the LIMA to supply a quantity of blood sufficient for the revascularized area should be questioned .
This study provides evidence that the LIMA limb of a composite Y or T graft has intraoperative statistically significant increase in mean flow comparable with that of the independent LIMA graft with P-value less than 0.001. The mean flow in LIMA graft was 41.72 ± 15.59 ml/min during clamping of the Y or T graft, and the mean flow in LIMA graft was 78.60 ± 29.58 ml/min during patent Y or T graft.
Regarding PI, there was statistically significant decrease in PI with P-value less than 0.001. PI in LIMA graft was 2.39 ± 0.82 during clamping of the Y or T graft and PI in LIMA graft was 1.89 ± 0.65 during patent Y or T graft.
Tagusari and colleagues examined 42 patients who underwent off-pump CABG using LIMA and Y-composite RA grafting. In these patients, the LIMA was used as a blood source of the Y-composite RA graft. The average number of distal anastomoses was 3.2 ± 0.7. Flow measurements of the proximal LIMA were achieved intraoperatively with a transit-time flowmeter. The mean flow rate of the LIMA was 61 ± 35 ml/min (range, 9-196 ml/min). These results demonstrate the early adaptation of the LIMA as a blood source of the Y-composite RA graft in off-pump CABG and the rationale for using the LIMA as a single blood source for total coronary artery revascularization .
Lemma and colleagues compared phasic blood flow velocity patterns and wall shear stress (WSS) of LIMA used as a composite Y graft (27 patients, Y group) and as a single graft (24 patients, S group) on LAD coronary artery. An intravascular Doppler-tipped guide wire was used for postoperative analysis of phasic blood flow velocity. Flow velocities were recorded proximally and distally into the LIMA in both groups. Digitalized spectral velocities were acquired to compute systolic peak velocity, diastolic peak velocity, and average peak velocity. The ratio of diastolic to systolic peak velocity was computed. WSS was calculated from graft flow velocity and vessel diameter. Results showed that proximal LIMA in the Y group had greater average peak velocity (P = 0.000), diastolic to systolic peak velocity ratio (P = 0.026), flow volume (P = 0.000), WSS (P = 0.02), and diameter (P = 0.019) than the S group. There were no significant differences for the distal LIMA between the two groups. Conclusions were that the LIMA shows marked adaptability to flow dynamics. The proximal tract of the LIMA in the Y group is able to match increased flow requirements, probably through the release of endothelial vasoactive mediators. Flow velocity spectra acquired in the proximal LITA in the Y group resemble the biphasic coronary artery pattern with a clear diastolic predominance. This pattern is probably consequence of the increase in blood flow due to the lower vascular resistance of the Y-graft system and due to the active dilatation of the LITA  [Table 1],[Table 2] and [Table 3].
|Table 1: Distribution of the studied patients regarding their age, sex, and risk factors|
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|Table 2: Distribution of the studied patients regarding coronary artery bypass grafts (number and type)|
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|Table 3: Distribution of the studied patients regarding left internal mammary flow by transit-time flowmetry|
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| Conclusion|| |
This study provides evidence that the LIMA limb of a composite Y or T graft has intraoperative increase in mean flow comparable with that of the independent LIMA graft. Regarding PI, there was decrease in PI in LITA graft during patent Y or T graft compared with during clamping of the Y or T graft.
| Acknowledgements|| |
Conflicts of interest
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[Table 1], [Table 2], [Table 3]