Internal Mammary Artery Group Research Articles

Left or bilateral internal mammary artery employment in coronary artery bypass grafting: midterm results.

The gold standard for coronary artery bypass grafting to the left anterior descending artery is use of the left internal mammary artery. Better long-term survival has been reported using bilateral internal mammary arteries compared to left internal mammary artery only, but many surgeons are reluctant to employ bilateral internal mammary arteries in coronary artery bypass grafting. This study aimed to evaluate the effectiveness and safety of bilateral internal mammary artery use. From 2014 to 2017, 1703 patients underwent coronary artery bypass grafting in our institute. Of these, 772 met the inclusion criteria and were randomly assigned to receive bilateral (n = 387) or left (n = 385) internal mammary artery grafts. The mean age was 67.1 ± 6.0 years (range 48-85 years) and 474 (61.4%) were male. The mean number of diseased vessels was 3.1 ± 0.9, and mean EuroSCORE II was 3.4% ± 1.1%. Hospital mortality was 1.2% in the left internal mammary artery group vs. 1.8% in the bilateral internal mammary artery group (p = 0.55). There was no difference in procedure-related complications between groups. Mean follow-up was 65.9 months. Survival in the bilateral internal mammary artery group at 1, 3, and 5 years was 98.7%, 98.7%, and 94.8% vs. 98.1%, 98.1%, and 90.9%, respectively, in the left internal mammary artery group (p = 0.63). Application of bilateral internal mammary arteries in coronary artery bypass grafting is safe and effective, with comparable midterm results to those with the left internal mammary artery only.

Graft failure and recurrence of symptoms after coronary artery bypass grafting

Objectives. Saphenous vein grafts (SVGs) most often used in coronary artery bypass grafting (CABG) are subject to graft disease and have poor long-term patency, however the clinical implication of this is not completely known. We aim to assess the influence of graft failure on the postoperative recurrence of coronary artery disease (CAD) symptoms in relation to the contribution from progression of atherosclerosis in the native coronary vessels. Design. Within the SWEDEHEART registry we identified 46,663 CABG cases between 2001 and 2015 with patient age 40–80 years where single internal mammary artery (IMA) anastomosis (IMA), single IMA with one (1SVG) or multiple SVG anastomoses (2+ SVG) had been performed. Clinical characteristics as well as mortality and postoperative incidence of coronary angiography were recorded and multivariable adjusted hazard ratios were calculated. Indications for the angiographies and occurrence of graft failure were also registered. Results. The adjusted hazard ratio for death was similar for the three groups. The adjusted hazard ratio for being submitted to angiography as compared to 2+ SVG was (95% CI) 1.24 (1.06–1.46) for IMA and 1.21 (1.15–1.28) for 1SVG. Failed grafts were found at the first postoperative angiography with preceding CAD symptoms in 21.4% of patients in the IMA group, 41.6% in the 1SVG group and 61.1% in the 2+ SVG group. Conclusions. A substantial amount of angiographies occur in patients without any graft failure and a large part of postoperative recurrence of CAD symptoms and are likely attributed to IMA failure or progression of atherosclerosis in the native coronary arteries.

Histologic comparison between the internal mammary artery and the deep inferior epigastric artery and clinical implications for microsurgical breast reconstruction

Background. The internal mammary artery (IMA) is one of the most popular recipients for microsurgical breast reconstruction. However, it is often separated into sleeve-like layers when it is handled. This study tried to explain this unique behaviour of the IMA through histologic observation. Methods. Nine pairs of IMAs and DIEAs were harvested and subject for haematoxylin-eosin and Verhoeff’s elastic staining. Thickness of the tunica media and the number of elastic lamellae were compared. Samples of the IMA, the DIEA, and the thoracodorsal artery from another patient were observed through the transmission electron microscope to further show the structural differences. Results. The most notable difference was presence of multiple elastic lamellae in tunica media in the IMAs, which was barely present in the DIEAs. The mean number of elastic lamellae was 9.2 in the IMA group and 1.0 in the DIEA group (p < 10−9). A transmission electron microscope showed that the tunica media of the DIEA and the TDA was densely packed with smooth muscle cells, while the muscle cells distributed sparsely in the IMA. Conclusions. The IMA is an elastic artery which is characterised by multiple layers of elastic lamellae while relatively lacking in smooth muscle cells. The wall of the IMA is easily dissected between the tunica media and the adventitia, or at the outer 1/3 of the tunica media. The inner structure is easily torn if microsutures do not engage the tunica adventitia.

Comparing the prevalence of chronic pain after sternotomy in patients undergoing coronary artery bypass grafting using the internal mammary artery and other open heart surgeries.

Background:The prevalence of chronic postoperative pain after cardiac surgery has been reported from 17% to 56%.Objectives:We aimed to compare the prevalence of postoperative pain between patients who had undergone CABG using the internal mammary artery (IMA) and those who had undergone other cardiac surgeries including CABG using the saphenous vein or cardiac valvular surgeries.Patients and Methods:In this cohort study, medical records of 188 patients were evaluated and divided into two equal groups (94 in each group); patients who had undergone CABG using the IMA (IMA group) and those who had undergone other cardiac surgeries using the saphenous vein or other cardiac valvular surgeries (non-IMA group). The patients' data were recorded in a self-structured questionnaire and then phone interviews were performed 3 months after the operations regarding the rate of postoperative pain. The severity of chronic pain was rated based on the numerical rating pain scale.Results:The two groups differed significantly regarding the prevalence of pain (P = 0.023). In the IMA group, 83 (88.3%) patients experienced pain lasting for more than three months compared to 71 (75.5%) patients in non-IMA group. The two groups differed significantly with respect to the severity of chronic pain after cardiac surgery via sternotomy (P = 0.001). The groups did not differ significantly regarding the effects of chronic pain on their sleep, referral to a physician, and drug consumption to alleviate their pain. The IMA group experienced more complications at work and during their occupational activity.Conclusions:The rate and severity of chronic pain after cardiac surgery via sternotomy was higher in patients undergoing CABG with separation of IMA for revascularization.

Skeletonized versus pedicled internal mammary artery: impact of surgical technique on post CABG surgery pain

Recent evidence suggests that coronary artery bypass graft (CABG) surgery often results in chronic chest wall pain, termed: 'post CABG pain syndrome' (PCP). Direct injury to intercostal nerves during the surgical procedure was presumed to underlie this syndrome. The aim of this study was to investigate the effect of two harvesting techniques of the internal mammary artery (IMA)-skeletonization (S-LIMA) and pedicle (P-LIMA) on the occurrence and incidence of PCP. A mailed questionnaire enquiring about the presence and characteristics of PCP was sent to all 482 patients who had undergone CABG in our institution in the years 1999-2000. A randomly chosen subgroup of IMA patients reporting PCP were summoned for evaluations of pain localization and intensity, thermal and tactile sensitivity, and disability assessment using recognized tests and indices. Of the 380 responders (S-LIMA: 221, P-LIMA: 125, veins only V-34) 169 (44%) reported having PCP. Its prevalence was similar between the two IMA groups (S-LIMA: 45%, P-LIMA: 50%) but significantly lower in the V group (18%, P=0.003). Physical assessment in the subgroup of 43 IMA patients (S-LIMA: 22, P-LIMA: 21) performed 40.2+/-8.7 months after surgery confirmed equal occurrence of mostly left and midline chest wall neuropathic pain in both IMA groups. No significant differences were found between the two groups in respect to indices of pain intensity, thermal and tactile sensitivity and disability. PCP is a prevalent finding in post CABG patients. The skeletonization technique of IMA harvesting although causing significantly less inner chest wall trauma does not appear to reduce the occurrence of PCP. This finding may imply that ischemic injury rather than direct mechanical injury to the intercostal nerves is the putative mechanism underlying PCP.

Acute pleuropulmonary complications detected by computed tomography following myocardial revascularization.

Pleuropulmonary changes are common following coronary artery bypass grafting surgery performed with a saphenous vein graft, with or without an internal mammary artery. The presence of atelectasis or pleural effusions reflects the thoracic trauma. To define the postoperative incidence of changes in the lung and in the pleural space and to evaluate the influence of the trauma. Thirty patients underwent elective coronary artery bypass grafting surgery (8 saphenous vein grafts and 22 saphenous vein grafts and internal mammary artery grafts with pleurotomy). Chest tubes in the left pleural space were used in all internal mammary artery patients. On the second (day 2) and seventh (day 7) postoperative day, patients underwent a computed tomography, and pleural effusions were rated as follows: grade 0 = no fluid to grade 4 = fluid in more than 75% of the hemithorax. Atelectasis was rated as follows: laminar = 1, segmental = 3, and lobar = 10 points. All patients had pleural effusion or atelectasis. Between day 2 and day 7, the number of patients with effusions or atelectasis on the right side decreased (P < 0.05). The incidence of effusions on day 2 in the saphenous vein graft group (87.5%) was higher (P < 0.05) than in the internal mammary artery group (52.3%). The incidence of atelectasis in the lower right lobe decreased (P < 0.05) from 86.7% (day 2) to 26.7% (day 7). The degree of atelectasis in both sides did not differ on day 2 (P = 0.42) but did on day 7 (P < 0.0001). There was a decrease in the atelectasis from day 2 to day 7 on the right side (P < 0.001), but not on the left (P = 0.21). On day 2 there was a relationship between atelectasis and effusion on the right (P = 0.04), but not on the left (P = 0.113). The present series demonstrates that there is a high incidence of both minimal pleural effusion and atelectasis after coronary artery bypass grafting surgery, which drops on the right side from day 2 to day 7 post surgery. Factors that contribute to the persistence of changes on the left side include the thoracic trauma and the presence of chest tubes and pericardial effusion.

Pain pattern and left internal mammary artery grafting

Background. This study was designed to determine whether the pain pattern in patients with an internal mammary artery (IMA) harvest differs from that in other cardiac operations and whether these patients present specific characteristics with clinical implications. Methods. One hundred patients with left IMA grafting (IMA group) were compared prospectively with 100 patients who had a heart operation without IMA harvest (non-IMA group). Pain assessment was performed on postoperative days (POD) 1, 2, 3, and 7, and included pain intensity (10-point scale) and pain localization. Results. In the IMA group, pain intensity was higher on POD 2 (4.2 ± 2.4 versus 3.2 ± 2.3, p < 0.01), and there were more patients without pain on POD 7 (32 versus 19, p = 0.03). In the IMA group, more patients had left basal thoracic pain throughout the entire study period and had sternal pain on POD 7, whereas more patients in the non-IMA group complained about back pain during the early postoperative period. Conclusions. The impact of IMA harvest on pain intensity is moderate, but the pain localization pattern of each group exhibits specific features that could help to better target pain management.

Minimally invasive direct coronary artery bypass grafting: intermediate-term results

Background. Intermediate- and long-term clinical outcome and graft patency in minimally invasive direct coronary artery bypass grafting (MIDCABG) procedures remain a concern. Methods. Over a 13-month period, 66 MIDCABG procedures were performed utilizing robotic-assisted internal mammary artery (IMA) harvesting and direct CABG through a 5-cm thoracotomy without cardiopulmonary bypass. Clinical follow-up was obtained on all patients. Graft patency was assessed in 61 of 66 consecutive patients 6 months (range 2 to 15 months) postoperatively. Group I consisted of 45 patients who underwent IMA angiography and group II consisted of 16 patients who underwent both a nuclear stress test and transthoracic Doppler examination. All group II patients had abnormal preoperative nuclear stress tests for comparison. Results. To date, all 66 patients are alive. Graft patency rates in the two groups were 97.8% (45 of 46 grafts in 45 patients) in group I and 100% (15 of 15 grafts), with one indeterminate study, in group II. The overall patency rate for the entire study group was 98.3% (60 of 61 grafts). Sixty-two of 66 (93.9%) patients were able to return to their normal level of activity within 3 weeks. Conclusions. This study demonstrates that the MIDCABG with thoracoscopic IMA harvesting can achieve effective intermediate-term revascularization and an acceptable clinical outcome.

Respiratory dysfunction after cardiac surgery: effects of avoiding cardiopulmonary bypass and the use of bilateral internal mammary arteries.

The quantitative contribution of cardiopulmonary bypass (CPB) to respiratory dysfunction after cardiac surgery is not documented and the effect of the use of bilateral internal mammary artery (IMA) grafts is not clear. One hundred and seventy-five patients undergoing CABG with (CPB, n=150) and without (NOCPB, n=25) CPB were studied. PMN elastase (as a marker of the systemic inflammatory response) and serial arterial oxygen (paO(2)) and carbon dioxide (paCO(2)) tension, alveolar arterial oxygen (AaO(2)) gradient and percent saturation were measured. The CPB group was subdivided into three groups by the number of IMA grafts used: 0IMA (n=12), 1IMA (n=82) and 2IMA (n=51). The NOCPB group was younger, had significantly better preoperative blood gases, received fewer grafts and had lower PMN elastase levels than the CPB group. In both groups maximum respiratory dysfunction occurred at 48 h (paO(2), percentage saturation and Aa gradient all P<0.001 versus baseline) with partial recovery by 5 days. The percentage decline and subsequent recovery in all blood gas parameters was near identical in the CPB and NOCPB groups. Amongst the three IMA groups the percentage changes in all blood gas parameters were similar, as was the duration of postoperative ventilation and time to discharge. There was no correlation between blood gas parameters at 48 h with age, CPB time, blood loss, duration of ventilation or peak PMN elastase level. Changes in postoperative gas exchange are similar in patients undergoing CABG with and without CPB even although PMN elastase levels indicate that CPB produces a more marked inflammatory response. The use of 2IMA compared with 1IMA does not increase respiratory dysfunction.

Valve surgery combined with coronary artery operation: is the use of internal mammary artery a predictor for early complications?

The internal mammary artery (IMA) provides better early and long-term patency than venous grafts do. Although IMA is the conduit of choice in isolated coronary artery bypass grafting (CABG), its use in combined procedures is not routine in some cardiovascular units. During a 16-month period, 188 patients underwent valve surgery combined with CABG. Internal mammary grafts were used in 68/188 (36%) patients (group 1) and vein grafts without arterial grafts (group 2) in 120/188 (64%). Left IMA was implanted in 67/68 (99%) and right IMA in 1/68 1%) cases. Surgeon A used IMA in 28/44 (64%), surgeon B in 20/32 (63%), surgeon C in 18/44 (41%), surgeon D in 1/4 (25%) and surgeon E in 1/63 (2%) patients. The final decision to use IMA in a combined procedure was left up to the surgeon. Statistically, the preoperative- and perioperative data were identical in the two groups, although the frequency of IMA grafting in patients with double valve replacement and reoperation was lower (1/68 vs 11/120, ns, and 3/68 vs 9/120, ns). Ten of 188 (5.3%) patients died within 30 days after operation. Longer cross-clamp time (P = 0.008) and mitral valve replacement (P = 0.05) were independent risk factors for early death. The use of IMA did not increase the risk of early mortality. The postoperative variables were similar in the IMA and vein groups, in particular data suggesting perioperative myocardial infarction (CK-MB, catecholamine support). Postoperative mechanical ventilation was longer in the IMA group, although not significantly (P = 0.06). Early mortality and morbidity were identical in the two groups in combined procedures. We did not find any hints for an increased risk of using IMA in this type of surgery. Internal mammary artery implantation is safe in selected patients undergoing combined valve and CABG surgery. Beside the better long-term patency of IMA, its use may have several technical advantages.

Surgical treatment of isolated left anterior descending coronary stenosis: Comparison of left internal mammary artery and venous autograft at 18 to 20 years of follow-up

To assess the long-term results of the surgical treatment of isolated left anterior descending coronary artery stenosis and compare surgical strategies for graft selection, we reviewed 100 consecutive patients receiving left internal mammary artery–to–left anterior descending artery grafts and 100 consecutive patients who received a saphenous vein autograft to the left anterior descending artery. All patients underwent operation from 1971 through 1973. The internal mammary artery and saphenous vein graft groups were equivalent with regard to preoperative clinical and angiographic variables, except that patients receiving left internal mammary artery grafts had a higher prevalence of noncritical disease (less than 50% stenosis) in the circumflex and right coronary arteries than did the saphenous vein graft group. Mean follow-up for the internal mammary artery and saphenous vein graft groups was 18.7 years and 20.7 years, respectively. The 18-year outcome was superior for the internal mammary artery group. Cox regression analysis confirmed that patients with left internal mammary artery grafts had superior survival, intervention-free survival, and event-free survival (all p < 0.01). The presence of noncritical disease in other vessels adversely affected intervention-free survival and event-free survival for both groups (all p < 0.03) and decreased survival for the saphenous vein graft group ( p = 0.01) but not for the internal mammary artery group ( p = 0.24). We conclude that in long-term follow-up of surgically treated isolated left anterior descending artery stenosis (1) the left internal mammary artery consistently yields better overall and intervention-free survival than does the saphenous vein graft, (2) outcome is influenced by the presence of noncritical disease in other vessels at the initial operation, and (3) deployment of the left internal mammary artery in the treatment of isolated left anterior descending artery stenosis yielded 18 years of intervention-free survival of 60.5% and provides a standard for comparison with other forms of therapeutic intervention. (J THORAC C ARDIOVASC S URG 1994;107:657-62)

Impact of mammary grafts on coronary bypass operative mortality and morbidity

The internal mammary artery is frequently used as a coronary artery bypass graft conduit because of superior long-term patency. The purpose of this study was to determine if there was also an advantage to the internal mammary artery in terms of operative mortality and morbidity. The Department of Veterans Affairs Cardiac Surgery Database was reviewed for two separate time periods, April 1987 through March 1989 and October 1990 through September 1991. During these periods, 14,172 patients underwent coronary artery bypass grafting. Univariate and multivariate logistic regression analyses were used to determine preopetative variables predictive of operative mortality and morbidity, with the independent variable of use of the internal mammary artery added to previously determined indicators. The total group was analyzed in risk quartiles according to expected mortality. Univariate analysis revealed an operative mortality of 6.8% in the early period and 6.5% in the latter period for the saphenous vein groups compared with 3.7% and 3.2%, respectively, for the internal mammary artery groups ( p = 0.000). Multivariate analysis revealed an odds ratio of operative death with use of the internal mammary artery graft versus use of vein grafts of 0.78 during the first period and 0.72 during the second period, reductions of 22% and 28%, respectively. There were 29% and 37% reductions in the odds of operative mortality in the highest-risk quartile group of patients using the internal mammary artery graft. The odds ratio of developing mediastinitis with one internal mammary artery graft was 1.84 ( p < 0.01) in the first time period and 1.11 in the second time period ( p = not significant). However, with multiple mammary bypass grafts, the odds ratios were 3.70 ( p < 0.01) and 2.96 ( p < 0.01) in the respective time periods. On the basis of this study, it is concluded that internal mammary artery grafts in addition to providing superior long-term patency also decreased operative mortality after adjustment for patient risk factors. Use of the mammary artery does not consistently increase operative complications with the exception of mediastinitis when both internal mammary arteries are employed.

Pleural and Pulmonary Complications After Bilateral Internal Mamary Artery Grafting

The long-term patency of internal mammary artery (IMA) grafts in coronary bypass surgery is superior to that of saphenous vein grafts. To investigate if bilateral IMA grafting increases the complication rate, especially pleural problems, 100 patients with bilateral and 100 with unilateral IMA grafts were retrospectively studied. Preoperatively the groups did not differ in age, previous myocardial infarction, ejection fraction, NYHA classification or previous respiratory disease, but the coronary artery status was poorer in the bilateral IMA group. Postoperative pleural drainage was greater after bilateral IMA grafting (1074 vs. 497 ml, p less than 0.0001). Reoperation was required for bleeding in 10% of the patients with unilateral, and 20% of those with bilateral IMA grafting (p less than 0.05), and more blood was transfused in the latter group (5.9 vs. 4.7 units, p less than 0.01). Pleural effusion at discharge from hospital or 3 months postoperatively, pain in the sternotomy wound, pain on breathing and postoperative use of nitroglycerin did not differ significantly between the groups. Bilateral IMA grafting thus led to more bleeding and reoperations than single IMA grafting, but did not cause excessive pulmonary complications.

Cardiothoracic Surgery

The internal mammary artery (IMA) remains firmly established as the conduit of choice for coronary artery revascularization procedures. Internal mammary artery grafts have better long-term patency than vein grafts and are associated with longer patient survival and a lower rate of reoperation. Furthermore, the IMA performs as well when used as a sequential or free graft as when it is grafted to a single coronary artery as an in situ graft. These excellent results have encouraged surgeons to perform bilateral IMA grafts. Recent studies have defined limitations on this technique and have demonstrated an increased frequency of complications when it is performed. Fiore et al¹studied patients who were undergoing coronary revascularization with either single or double IMA grafts. At a mean follow-up of 14.4 years, the double IMA group had a significantly better freedom from recurrent angina and myocardial infarction. Reoperation rates were not different, and survival benefits

Effect of omental, intercostal, and internal mammary artery pedicle wraps on bronchial healing

Bronchial transection and devascularization is necessary in the course of sleeve resection or lung transplantation, leaving distal bronchial segments ischemic and subject to stricture or dehiscence. Thirty mongrel dogs underwent left lung autotransplantation. The bronnchial anastomosis was wrapped with omentum (n = 9), intercostal muscle pedicle (n = 9), or internal mammary artery pedicle grafts (n = 6). Six control animals underwent bronchial anastomosis without an external wrep. Bronchial revascurlarization by capillary ingrowth from the pedicle to the bronchial submucosal plexus was demonstrated with all three types of vascular pedicle grafts; however, more consistent and confluent vascular ingrowth was provided by internal mammary artery pedicle grafts. Additionally, the bronchial anastomotic cross-sectional area was significantly better in the internal mammary artery group (84.5 ± 3.3) as compared with that of the omental (68.4 ± 8.3), intercostal muscle (66.9 ± 10.9), or contral groups (70.2 ± 7.6). An internal mammary artery pedicle graft and the presence of dense confluent submucosal vascular ingrowth from any pedicle graft were independently predictive ( p < 0.05) of minimizing bronchial anastomotic narrowing. These data are consistent with previous findings suggesting that omental and intercostal muscle pedicle grafts promote early bronchiai revascuiarization; moreover, the data demonstrate the superiority of an internal mammary artery pedicle graft to provide submucosal vascular ingrowth and to minimize anastomotic stenosis.

Risks of bilateral internal mammary artery bypass grafting

Although use of one internal mammary artery (IMA) for coronary artery bypass grafting does not appear to be associated with increased risk, the results with both IMAs are less certain; the potential for a higher incidence of sternal wound infection as a result of devascularization of the sternum is a major concern. During a 42-month interval ending July 1988, 1,566 patients had coronary artery bypass grafting alone or in combination with other procedures: 633 received only vein grafts, 687 had unilateral IMA grafting, and 246 had bilateral IMA grafting. The IMA patients were younger, were more often male, had better cardiac function, and underwent fewer emergent, urgent, or combined procedures than the patients receiving vein grafts ( p < 0.05). Thirty-day mortality was lower among the IMA patients (unilateral IMA group, 2.8%; bilateral IMA group, 3.7%; and vein graft group, 7.9%; p = 0.001). With the exception of sternal wound problems, occurrence rates for postoperative complications among the IMA patients did not differ significantly from or were lower ( p < 0.05) than those among the patients with vein grafts. Sternal infections occurred with greater frequency among the bilateral IMA patients (6.9%) than among the unilateral IMA (1.9%) or vein graft (1.3%) patients ( p = 0.001). By univariate analysis, obesity, diabetee, bilateral IMA grafting, and need for prolonged (>48 hours) mechanical ventilation were associated with a significantly higher incidence of sternal infection ( p < 0.05). Multivariate logistic regression analysis identified use of bilateral IMA grafts ( p = 0.0001), obesity ( p = 0.0014), and prolonged mechanical ventilation ( p = 0.0018) as significant risk factors for the development of sternal infection. We conclude that bilateral IMA grafting is an important predictor of sternal infection. It should be used selectively in obese or diabetic patients and in patients who are likely to require prolonged mechanical ventilation postoperatively.

Histologic comparison of experimental coronary artery bypass grafts: Similarity of in situ and free internal mammary artery grafts

This study compares patency and histologic structure of in situ internal mammary artery grafts, free internal mammary artery grafts, stripped, free internal mammary artery grafts, and stripped, free superficial femoral artery grafts (a muscular artery model) in a canine model of coronary artery bypass. Twenty-four adult mongrel dogs underwent bypass of the circumflex coronary artery with one of the above grafts. Three months postoperatively, graft patency was assessed by angiogram, and postmortem specimens were studied by intraluminal injection of a dilute barium solution proximal to the graft. Proximal, mid, and distal segments of each graft were examined microscopically. In situ internal mammary artery grafts and free internal mammary artery grafts were not significantly different in regard to patency, vascular wall cellular structure, or perfusion of the vasa vasorum. The stripped, free internal mammary artery group had a higher incidence of thrombosis, intimal thickening, and medial injury than the pedicled (in situ and free internal mammary artery) grafts. This difference may be due to early vascular wall ischemia as a result of poor early perfusion of the vasa vasorum. The stripped, free superficial femoral artery grafts were all patent, but all had adventitial injury.

Comparative study of the postoperative flow in the saphenous vein and internal mammary artery bypass grafts

Postoperative coronary bypass flow was evaluated in two groups of randomly selected patients with grafts to the left anterior descending artery (LAD). Saphenous vein bypass grafts were placed in 27 patients and internal mammary artery grafts in 25 patients. Postoperative flow studies were performed in both groups with roentgendensitometric methods based on the transit time of radiopaque media along the graft plus the mean graft diameter. There was no significant difference between the two groups of patients for age, duration of symptoms, or the frequency of hypertension, diabetes mellitus, prior myocardial infarction, or cardiomegaly. Intraoperative bypass flows were 75+/-27 and 77+/-24 ml. per minute for the saphenous vein group (SVG) and internal mammary artery group (IMAG), respectively. There was no significant difference in the heart rate or mean aortic pressure at the time of the roentgendensitometric flow study. The mean graft diameters were 3.0+/-0.5 and 1.9+/-0.3 mm. for the SVG and IMAG, respectively (p less than 0.001). The ratios of graft diameter to LAD diameter were 1.9+/-0.3 and 1.2+/-0.2 for the SVG and IMAG, respectively (p less than 0.001). The roentgendensitometric postoperative flows were 68+/-27 ml. per minute in the SVG and 46+/-16 ml. per minute in the IMAG (p less than 0.01). The present study indicates that flow in significantly higher in saphenous vein than in internal mammary artery bypasses and that the difference in flow may in part be explained on the basis of the graft diameter.