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Ann Thorac Surg 2001;72:1275-1281
© 2001 The Society of Thoracic Surgeons
graft with the radial artery or free left internal mammary artery anastomosed to the right internal mammary artery: flow dynamics
a Division of Cardiac Surgery, University of Carreggi, Firenze, Italy
b Division of Cardiovascular Surgery, "Maggiore della Carità," Novara, Italy
c IRCCS NEUROMED, Pozzilli, Italy
Accepted for publication April 13, 2001.
Address reprint requests to Dr Bonacchi, Divisione di Cardiochirurgia, Policlinico di Careggi, Viale Morgagni, 85, 50134 Careggi Firenze, Italy
e-mail: edvinprifti{at}hotmail.com
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Abstract |
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graft configuration, relative to a second arterial graft.
Methods. From 1998 to 2000, 47 patients (mean age 55.5 ± 4.7 years) with triple-vessel disease underwent arterial revascularization using the graft. The in situ left internal mammary artery (LIMA) and right internal mammary artery (RIMA) were anastomosed to the left anterior descending (LAD) and obtuse marginal arteries, respectively. In 21 patients (group I) presenting proximal or middle-third LAD or right coronary (RC) arterial stenoses, the graft was constructed by anastomosing the distal LIMA, as a free LIMA graft, to the RC and proximally to the in situ RIMA. In the other 26 patients (group II) presenting with middle-distal third LAD or RC arterial stenoses, the radial artery (RA) was used to construct the graft. All patients underwent transthoracic echo color Doppler before and after an adenosine test at 1 week and 3 months after operation.
Results. There were no hospital deaths. Overall, 47 grafts were constructed. There was no difference between baseline and maximal flows and coronary flow reserve (CFR) between groups. CFR at IMA stems increased in both groups within 3 months versus 1 week [LIMACFR = 2 ± 0.3 vs 2.3 ± 0.3 (p = 0.002) and RIMACFR = 2.2 ± 0.4 vs 2.5 ± 0.3 (p = 0.009) in group I, and LIMACFR = 2.12 ± 0.33 vs 2.4 ± 0.35 (p = 0.005) and RIMACFR = 2.17 ± 0.32 vs 2.52 ± 0.26 (p = 0.001) in group II]. At 3 months versus 1 week, the RIMAdiameteri (mm) at rest was 1.69 ± 0.32 versus 1.48 ± 0.2 (p = 0.015) in group I and 1.66 ± 0.3 versus 1.47 ± 0.2 (p = 0.01) in group II. At 6 ± 2.4 months, all patients were free of angina.
Conclusions. These data, almost identical for free LIMA and RA to RIMA using the graft, demonstrate that RIMA flow reserve is adequate for multiple coronary anastomoses irrespective of the second arterial graft.
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Introduction |
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-graft configuration, which permits TAMR using both IMAs only [12]. Later, we introduced a modified right Y-graft or -graft configuration employing both IMAs and RA [13]. In both variants of this configuration, the circumflex and right coronary (RCA) arteries bypass flow is dependent on the flow of the right internal mammary artery (RIMA). This has led to concern whether flow reserve in the RIMA main stem is sufficient for supplying the left and right coronary systems simultaneously. The aims of this study were to evaluate the early and short-term outcome of this new surgical configuration, and to compare baseline flow and maximum flow in the early postoperative period with the flow dynamics at follow-up relatively to the second arterial graft employed for constructing the graft configuration. |
Patients and methods |
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graft configuration. The graft configuration, using both IMAs only, was performed in 21 patients (group I) presenting proximal-middle third stenosis of the left anterior descending artery (LAD) and RCA. The modified graft configuration using both IMAs and RA was performed in 26 patients (group II) presenting middle-distal third stenosis of the LAD and distal stenosis of the RCA or posterior descending artery stenosis.
Patient selection
Both techniques were employed in young patients presenting triple-vessel disease with stenotic coronary lesions greater than 75%, right dominance, non-myocardial infarction, or diabetes. The decision for TAMR was based on prognostic reasons (age < 65 years) in 42 patients (89.4%), lack of vein grafts in 2 (4.3%) patients, and porcelain aorta in 3 (6.4%) patients. The preoperative variables between groups are given in Table 1.
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graft configuration, the RA was harvested simultaneously with IMA preparation at the nondominant arm. Preoperative assessment of the palmar arch was done with an Allen test. Digital plethysmography was done in questionable cases. The RA was cannulated with a 1-mm elastic needle, through which 10 mL of a solution containing dilzene (5 mg/mL Ringer’s solution) was injected gently.
Cardiopulmonary bypass
The right atrium was cannulated in the usual fashion using a double-stage cannula. In 3 patients with porcelain aorta, the axillary artery was cannulated. Intermittent anterograde or retrograde cold blood cardioplegia and mild systemic hypothermia (32°C to 34°C) were employed.
Surgical technique ( graft configuration)
In both sides of the superior mediastinum, the pleurae-pericardial tissues were dissected and the IMA "beds" were created. Routing of the RIMA behind the superior caval vein and further into transverse sinus allows additional length [14], facilitating the grafting of the obtuse marginal coronary arteries via a less circuitous and more protected route. Then, in both groups, as previously described [12, 13], the in situ RIMA and LIMA were anastomosed to the obtuse marginal artery and LAD, respectively, in end-to-side fashion. The free LIMA graft in group I and RA in group II patients were LAD, respectively, in end-to-side fashion. The free LIMA graft in group I and RA in group II patients were anastomosed distally to the mid-third and distal-third segments (or posterior descending artery) of the RCA, respectively. On-pump/beating-heart, the mid-proximal RIMA was clamped in proximally and distally and the free-LIMA graft in group I and RA in group II were anastomosed to the RIMA side, retrolaterally to the superior caval vein in a fashion (Fig 1A) [12, 13]. Unclamping the aorta, the intravenous nitro-derivates therapy was initiated and continued during the postoperative course in the intensive care unit, eventually associated with calcium channel-blocking agents followed by oral therapy for 4 weeks.
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/kg/min) for 3 minutes. The mean systemic arterial pressure and mean heart rate were maintained at 85 + 12 mm Hg and 82 + 7 bpm during the examination.
Follow-up
At 6 months after operation, the treadmill test was performed in 36 of 47 patients and TL201 scintigraphy under stress in 11 other patients. At 3-month follow-up, all patients underwent TTECD at rest and after adenosine provocative test. Twelve (26%) patients underwent postoperative angiographic control.
Definitions
Perioperative myocardial infarction was defined as the appearance of new Q-waves or significant loss of R-wave forces peak creatine phosphokinase MB fractions greater than 10% of total CK. Low cardiac output syndrome was defined as a cardiac index less than 2.01/min/m2, requiring pharmacological support, or intraaortic balloon pump. Postoperative bleeding was defined as rethoracotomy for hemorrhage.
Statistical analysis
Group statistics were expressed as mean ± 1 SD. The generalized Wilcoxon test was performed for the statistical analysis between groups. Fisher’s exact test was used for the noncontinuous variables. The relationship between preoperative and postoperative variables within the same group was assessed by the McNemar test. Significance between data was considered achieved when p was less than 0.05.
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Results |
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grafts were constructed. One hundred twenty arterial conduits were employed Twenty-one free LIMA grafts and 26 RA conduits were employed in groups I and II, respectively, for constructing the graft. There were no hospital deaths. The mean intensive care unit stay was 1.4 ± 0.5 days in group I and 1.6 ± 0.6 days in group II (p = 0.23). Postoperatively, 1 patient (group II) developed perioperative myocardial infarction and low cardiac output necessitating postoperative pharmacological support (dopamine 8 /kg/min and dobutamine 5 /kg/min); postoperatively, the coronary angiography revealed good graft patency. Another patient (group I) underwent mediastinal revision due to significant bleeding (> 1,500 mL). Deep sternal wound infection due to Staphylococcus aureus was identified in another patient (group I). This patient underwent successful surgical revision and was discharged 1 month later. In another patient, paresthesia of the left forearm was identified in the second postoperative day. At 1 week after the operation, after the adenosine provocative test, the CFR at the LIMA and RIMA main stems were 2 ± 0.3 and 2.2 ± 0.4, respectively, in group I (Table 2), and 2.12 ± 0.33 and 2.17 ± 0.32, respectively, in group II (Table 3) (p > 0.1). There were no differences between groups I and II regarding these IMA diameters, mean velocities, and mean flows. In only 1 patient (group I) did we find anomalous RIMA flow pattern, suggesting a partial graft closure. The peak systolic-to-diastolic velocity resulted to be 0.35. The postoperative angiography revealed a nonfunctioning free LIMA graft.
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At 3-month follow-up, after the adenosine provocative test, the CFR at the LIMA and RIMA main stems was 2.3 ± 0.3 and 2.5 ± 0.3, respectively, in group I (Table 2), and 2.4 ± 0.35 and 2.52 ± 0.26, respectively, in group II (p > 0.1) (Table 3). The CFRs at LIMA main stem were significantly higher at 3 months when compared with the values at 1 week after the surgical procedure within the same group: LIMACFR (3 months) = 2.3 ± 0.3 versus LIMACFR (1 week) = 2 ± 0.3 (p < 0.002) in group I, and LIMACFR (3 months) = 2.4 ± 0.35 versus LIMACFR (1 week) = 2.12 ± 0.33 (p = 0.005) in group II. Similarly, the CFRs at the RIMA main stem were significantly higher at 3 months when compared with the values at 1 week after the surgical procedure: RIMACFR (3 months) = 2.5 ± 0.3 versus RIMACFR (1 week) = 2.2±0.4 (p = 0.009) in group I, and RIMACFR (3 months) = 2.5 ± 0.26 versus RIMACFR (1 week) = 2.17 ± 0.32 (p = 0.001) in group II (Fig 2). The CFRs at the RIMA main stem were higher in all measurements within the same group, compared with the LIMA main stem, but the difference was not significant. Only in group I, at 3 months after surgery, was the CFR at the RIMA main stem (2.5 ± 0.3) significantly higher than the CFR at the LIMA main stem (2.3 ± 0.3, p = 0.035).
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The mean flowi (mL/min) at RIMA main stems was significantly higher versus the flow at the LIMA main stems at rest and after adenosine provocative test in all measurements (p < 0.001) (Tables 2 and 3). At 3 months, the mean velocity measured at LIMA and RIMA main stems before and after the adenosine provocative test (Tables 2 and 3) was similar versus the TTECD findings at 1 week after the surgical procedure. The ratio between systolic velocity and diastolic velocity for LIMA and RIMA was calculated at 3 months after the surgical procedure in all patients, which was 0.51 ± 0.13 at the LIMA main stem, demonstrating a predominantly diastolic waveform, and 0.97 ± 0.14 at the RIMA main stem (p < 0.001), demonstrating a continuous systolic-diastolic waveform (Fig 3A, 3B). The same patient with a nonfunctional free LIMA graft (at 1 week postoperatively) presented a peak systolic-to-diastolic velocity of 0.35 (Fig 4), similar to the early postoperative data. The postoperative angiography in 10 other patients from both groups demonstrated good graft patency rates (Fig 1B).
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Comment |
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grafts (the free arterial graft anastomosed to the side of the in situ LIMA) with good long-term composite graft patency [21]. Recently, we employed a new surgical configuration for TAMR using skeletonized IMAs [12, 13]. Different IMA harvesting techniques have been employed, such as pedunculated, semiskeletonized, and skeletonized techniques. Harvesting the IMAs according the skeletonized technique results in a longer arterial conduit [22]. The skeletonized technique is associated with lower infection incidence, probably due to reduced traumatic injuries of the mediastinal tissues during dissection [20]. Routing of the in situ RIMA behind the superior caval vein and further into the transverse sinus allows additional length [23], facilitating lateral coronary artery grafting via a less circuitous and more protected route.
The graft configuration is a potential benefit to selected CAD patients due to blood supply flow advantages related to grafting both in situ IMAs to the left ventricle coronary arteries. It has been demonstrated that the maximal long-term benefit of IMA employment is achieved by anastomosing both these conduits to the left ventricle coronary arteries [24]. Most of the reported TAMR techniques, employing composite grafts, provide left ventricle myocardial revascularization from the LIMA only [7, 25]. A potential disadvantage of these approaches may result from the fact that the coronary bypass flow is totally dependent on the flow in the proximal LIMA. Reduction of the LIMA flow, due to vasospasm or trauma, may result in a hypoperfusion syndrome with global ischemia and its catastrophic consequences [26].
The graft configuration avoids the difficulties of anastomosing a thin wall and small-caliber vessel like IMAs with the thick wall ascending aorta [7]. There are no grafts crossing the mid-line behind the sternum; the RIMA and LIMA are in a safe position, which decreases the operative risks in case of mediastinal revision or reintervention. This surgical configuration applies the "nontouch" principle, so it can be employed successfully in patients with heavily calcified aorta.
TAMR is not always feasible only using IMAs, and the employment of other arterial conduits is obligatory. Recently, the RA was reintroduced as a bypass graft by Acar and associates [27]. The composite T graft, constructed with the RA and LIMA, has had excellent results on postoperative flow dynamics [25]. The RA appears to have advantages over the other arterial conduits, such as the gastroepiploic artery, because it can be harvested while the LIMA is being dissected, surgical dissection is easier, and a laparotomy with its associated morbidity can be avoided. The main limitation of the right graft configuration or right Y-graft configuration using IMAs only appears in cases with distal stenosis of the LAD or RCA or posterior descending artery. In such occasions, we applied a modified graft configuration, constructing the composite graft by using the radial artery as a free graft anastomosed end-to-side to the RIMA.
Arterial grafts are known to be particularly prone to spasm, and patients undergoing TAMR procedure are at a high risk of the so-called hypoperfusion syndrome. In this pool of patients, we applied a simple protocol consisting of nitroderivates therapy (initiated intraoperatively), eventually associated with calcium channel-blocking agents. We encountered the hypoperfusion syndrome in only 1 patient undergoing modified graft configuration employing the radial artery.
For a full evaluation of this technique, we studied the flow dynamics of the graft configuration by employing the TTECD. The TTECD contrast enhanced before and after adenosine provocative test has been used successfully for evaluating flow dynamics of IMAs and its composite grafts [25, 28]. Caiati and associates [14] demonstrated a sensitivity of 86% and specificity of 90% using this technique versus angiography in detecting significant LAD stenosis. Other authors [29, 30] demonstrated a significant correlation between TTECD and postoperative angiography findings regarding the graft patency rates, reporting a sensitivity and specificity of 100% for this method regarding the graft stenosis identification and especially the LIMA patency. In our series of patients, we found a good correlation between the TTECD findings and angiography graft patency rates in 12 (26%) patients undergoing both examinations postoperatively.
In the present study, both groups showed an acceptable baseline flow at 1 week after the operation. A significant elevation of CFR at 3 months after the surgical procedure was observed, identified by a significantly increased CFR at IMAs stems in all patients from both groups. Different reports demonstrated that the construction of composite graft increases the flow through IMA main stems versus IMA simple grafts [14, 25]. The CFR measured at the RIMA stem was higher, although not significantly in most measurements, versus CFR measured at the LIMA stem due to higher runoff of RIMA related to the constructed composite graft. The increased RIMA flow reflects the greater supported myocardial area. For the same reason, the RIMA’s diameter increased more compared with the LIMA’s diameter after the adenosine provocative test. The significant increment of the IMA diameters at 3-month follow-up, versus the early postoperative data, is an adapting anatomic-functional mechanism versus blood flow requirements of the respective myocardium territory [31, 32]. It would appear that the substantially greater diameter of the RIMA stem explains the improved results offered by the composite grafts vis-à-vis the potential for hypoperfusion [25, 32]. On the other hand, the mean velocities at 1 week and 3 months after surgery were similar. These findings demonstrated that the increased IMA flow is closely related to the conduits’ dimensions and not to the blood velocity.
The Doppler waveform at the RIMA main stem ( graft configuration) demonstrated a continuous systolic-diastolic flow pattern mimicking a summarized right and left coronary artery hemodynamic pattern; however, the Doppler waveform at the LIMA main stem demonstrated a diastolic dominant circulation mimicking the left coronary arteries’ hemodynamic pattern. We found the peak systolic and diastolic velocities ratio to be a good variable for demonstrating the functional graft status. In 46 patients, the values of peak systolic and diastolic velocities were very similar, and the ratio value was greater than 0.85 in all patients, demonstrating a good flow through both distal sides of the graft. In only 1 patient did we find a reduced systolic flow and peak systolic-to-diastolic velocity ratio of 0.35. Indeed, the angiographic examination revealed a nonfunctioning free LIMA graft. The Doppler waveform of this type of configuration may identify which of the graft’s distal "legs" is nonfunctioning or occluded.
No significant modifications in mean velocity, mean flow, peak systolic-to-diastolic ratio, and diameters at rest and under stress at 1-week and 3-month follow-up were observed between groups, confirming the presence of a LIMA diastolic and RIMA systolic-diastolic circulation as indirect signs of good graft hemodynamics. We can hypothesize that the graft configuration guarantees adequate blood supply to the anastomosed myocardium with nearly normal CFR.
Study limitations
The number of patients included in the study is very small. Only 26% of them underwent postoperative coronary angiographic control due to the high cost of this examination. The follow-up period is very short.
These hemodynamic data, almost identical for free LIMA to RIMA versus RA to RIMA, using the graft configuration, demonstrate that this technique can be applied in selected CAD patients as a possible surgical TAMR alternative associated with better postoperative outcome. We found the TTECD contrast enhanced before and after adenosine provocative test a valuable procedure, which permits a good evaluation of the functional graft status. We conclude that the flow reserve of the proximal RIMA is adequate for multiple coronary anastomoses irrespective of the choice of the second arterial graft.
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grafts. J Thorac Cardiovasc Surg 2000;120:990-998.This article has been cited by other articles:
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L. R. Sajja, G. Mannam, N. R. Pantula, and S. Sompalli Role of Radial Artery Graft in Coronary Artery Bypass Grafting Ann. Thorac. Surg., June 1, 2005; 79(6): 2180 - 2188. [Abstract] [Full Text] [PDF]
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 M Bonacchi, F Battaglia, E Prifti, M Leacche, N S Nathan, G Sani, and G Popoff Early and late outcome of skeletonised bilateral internal mammary arteries anastomosed to the left coronary system Heart, February 1, 2005; 91(2): 195 - 202. [Abstract] [Full Text] [PDF]
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M. Bonacchi, E. Prifti, and G. Giunti The "{omega}-Anastomosis": a new revascularization technique for coronary bifurcations Ann. Thorac. Surg., September 1, 2003; 76(3): 954 - 955. [Abstract] [Full Text] [PDF]
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 M. Bonacchi, E. Prifti, G. Giunti, and G. Sani Retrocaval right internal mammary artery for left ventricular marginal arteries grafting Eur. J. Cardiothorac. Surg., May 1, 2002; 21(5): 952 - 952. [Full Text] [PDF]
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