Atherosclerosis and the internal mammary arteries

Prevalence of left internal mammary artery disease in patients undergoing coronary angiography for suspected coronary artery disease: A meta-analysis and meta-regression study

Left internal mammary artery (LIMA) to bypass left anterior descending artery has demonstrated to improve survival in multivessel coronary artery disease, but its routine angiography during index coronary angiography is seldom performed as LIMA is rarely diseased. A systematic literature review and meta-analysis was conducted using PubMed and Cochrane databases selecting the studies reporting prevalence of LIMA disease among patients undergoing coronary angiography and considered for CABG. Meta-regression analysis was performed to evaluate the prevalence of LIMA disease and the relative predictive value of canonical risk factors. After scrimmage, 9 studies for a total of 1365 patients were included. LIMA disease prevalence was 1.8 % (95 % CI; 1.2 %-2.8 %) in the entire cohort, whereas we reported a rate of subclavian artery disease of 7.6 % (95 % CI, 6-9.9 %). At univariate meta-regression analysis, only age (p = 0.031) and smoking habit (p = 0.035) were directly correlated with LIMA disease. In conclusion, LIMA angiographic assessment might be considered in selected patients that could undergo CABG, during index coronary angiography. However, prospective studies are needed to better evaluate the safety of routine selective LIMA angiography prior to CABG and whether the practice is associated with improved clinical outcomes among those individuals.

Aortic Coarctation Effect on Atherosclerosis of the Left Internal Mammary Artery: A Case Presentation and Literature Review

Atherosclerosis of the internal mammary artery (IMA) is an uncommon disease. We present a case report of a patient with stable angina who had a history of coarctation repair. After meticulous investigation and discussion, a coronary artery bypass graft (CABG) was planned. During the surgery, we found that the left internal mammary artery (LIMA) was severely atherosclerotic without any blood flow, and a fragment of LIMA was taken for histopathological examination for further insight into pathogenesis. Vein grafts were alternatively used. Furthermore, relevant literature review and management were discussed for the use of LIMA in patients with a history of aortic coarctation.

Resilience of the Internal Mammary Artery to Atherogenesis: Shifting From Risk to Resistance to Address Unmet Needs

Fueled by the global surge in aging, atherosclerotic cardiovascular disease reached pandemic dimensions putting affected individuals at enhanced risk of myocardial infarction, stroke, and premature death. Atherosclerosis is a systemic disease driven by a wide spectrum of factors, including cholesterol, pressure, and disturbed flow. Although all arterial beds encounter a similar atherogenic milieu, the development of atheromatous lesions occurs discontinuously across the vascular system. Indeed, the internal mammary artery possesses unique biological properties that confer protection to intimal growth and atherosclerotic plaque formation, thus making it a conduit of choice for coronary artery bypass grafting. Its endothelium abundantly expresses nitric oxide synthase and shows accentuated nitric oxide release, while its vascular smooth muscle cells exhibit reduced tissue factor expression, high tPA (tissue-type plasminogen activator) production and blunted migration and proliferation, which may collectively mitigate intimal thickening and ultimately the evolution of atheromatous plaques. We aim here to provide insights into the anatomy, physiology, cellular, and molecular aspects of the internal mammary artery thereby elucidating its remarkable resistance to atherogenesis. We propose a change in perspective from risk to resilience to decipher mechanisms of atheroresistance and eventually identification of novel therapeutic targets presently not addressed by currently available remedies.

Aging-related carcinoembryonic antigen-related cell adhesion molecule 1 signaling promotes vascular dysfunction

Aging is an independent risk factor for cardiovascular diseases and therefore of particular interest for the prevention of cardiovascular events. However, the mechanisms underlying vascular aging are not well understood. Since carcinoembryonic antigen‐related cell adhesion molecule 1 (CEACAM1) is crucially involved in vascular homeostasis, we sought to identify the role of CEACAM1 in vascular aging. Using human internal thoracic artery and murine aorta, we show that CEACAM1 is upregulated in the course of vascular aging. Further analyses demonstrated that TNF‐α is CEACAM1‐dependently upregulated in the aging vasculature. Vice versa, TNF‐α induces CEACAM1 expression. This results in a feed‐forward loop in the aging vasculature that maintains a chronic pro‐inflammatory milieu. Furthermore, we demonstrate that age‐associated vascular alterations, that is, increased oxidative stress and vascular fibrosis, due to increased medial collagen deposition crucially depend on the presence of CEACAM1. Additionally, age‐dependent upregulation of vascular CEACAM1 expression contributes to endothelial barrier impairment, putatively via increased VEGF/VEGFR‐2 signaling. Consequently, aging‐related upregulation of vascular CEACAM1 expression results in endothelial dysfunction that may promote atherosclerotic plaque formation in the presence of additional risk factors. Our data suggest that CEACAM1 might represent an attractive target in order to delay physiological aging and therefore the transition to vascular disorders such as atherosclerosis.

Recurrent angina caused by coronary subclavian steal syndrome confirmed by positron emission tomography

Coronary subclavian steal syndrome is a rare cause of recurrent angina after coronary artery bypass grafting. Identification of the myocardial ischemic region is crucial because it guides revascularization interventions to improve symptoms and myocardial ischemia. Positron emission computed tomography (PET) with rubidium might be a helpful tool because it identifies ischemia, localizes more precisely the ischemic region, and evaluates coronary flow reserve. Here, we report a case of recurrence of angina after coronary artery bypass grafting caused by an obstruction in the left subclavian artery and consequently by coronary steal syndrome confirmed by PET.

Multislice Computed Tomography for Preoperative and Postoperative Assessment in Totally Endoscopic Coronary Artery Bypass Grafting

This article reviews the clinical value of noninvasive multi-slice computed tomography (MSCT) angiography before and after totally endoscopic coronary artery bypass surgery. The use of coronary and aorto-iliaco-femoral MSCT angiography in the preoperative assessment is addressed and the use of bypass MSCT angiography for postoperative control of bypass graft patency is discussed.

Vascular profile of patients with multivessel coronary artery disease

PURPOSE

Early and accurate diagnosis of peripheral atherosclerosis is of paramount importance for global management of patients with known coronary artery disease (CAD). We sought to retrospectively evaluate the clinical relevance of significant subclavian artery stenosis (SAS) and abdominal vessel stenosis or aneurysm (AVA) in patients undergoing coronary angiography.

SUBJECTS AND METHODS

Medical records of consecutive patients underwent coronary angiography at two public institutions over a 12-month period were evaluated. Angiographic results of patients underwent coincident diagnostic abdominal aorta angiography to evaluate abdominal vessels or subclavian angiography on the basis of clinical and angiographic criteria were analyzed.

RESULTS

During the study period, 724 consecutive patients (535 males, mean age 68.1+/-11 years) were enrolled (Table 2): a significant atherosclerotic disease of at least one arterial segments were observed in 198 patients (27.3%). Angiographically significant SAS was observed in 18/220 patients (8.1%) undergoing concomitant subclavian artery angiography and candidates to coronary surgery using the internal mammary artery. Ten patients with subclavian artery stenosis and upper limb ischemia underwent subclavian artery angioplasty and stenting and bypass surgery using LIMA. AVA were reported in 180 (35.7%) of 504 consecutive patients: renal artery stenosis was found in 13.1% of cases (66 patients), aortoiliac artery disease in 13.7 % (69 patients), and aortic aneurismal disease in 8.9% (45 patients). Logistic regression analyses revealed > or =3-vessel CAD (odds ratio [OR] 9.917, p=0.002), age>60 years old (OR 3.817, p=0.036), > or =3 risk factors (OR 2.8, p=0.048) as independent predictors of SAS and AVA.

CONCLUSION

Patients with multivessel CAD are frequently aged, have an high risk profile and multiple vascular atherosclerotic distributions, suggesting the usefulness of a more global and comprehensive cardiovascular approach.

Malpractice in Invasive Cardiology: Is Angiography of Abdominal Aorta or Subclavian Artery Appropriate in Patients Undergoing Coronary Angiography?

BACKGROUND

Identification of peripheral vascular disease by angiography in patients undergoing coronary angiography may be considered as malpractice but sometimes seems to be justified under clear entry criteria. The present mata-analysis is aimed to analyze the appropriateness and results of screening angiography of subclavian or abdominal aorta performed at the time of coronary angiography.

METHODS

A search of published literature for peripheral angiography in patients undergoing coronary angiography over the last 10 years was performed using the MEDLINE database. No language restriction was employed. Only studies enrolling more than 100 patients for abdominal aortography and 50 patients for subclavian/internal mammary artery angiography were considered. Reference lists from identified studies were also reviewed to identify other potentially relevant references.

RESULTS

Twenty-nine studies were retrieved: 8 articles about subclavian artery (SA) and internal mammary (IMA) angiography and 21 about renal (RA) and aortoiliac (AOI) angiography. The total number of patients enrolled was 27,936. Nine studies out of 29 were prospective. Defined entry criteria were reported in 24 out of 29 studies. Significant SA and IMA stenosis were reported in 5.5 and 9% of patients, respectively. RA stenosis >50% was present in 12.7% of patients with CAD. Finally, undetected AOI disease was reported in 35.5% of patients undergoing coronary angiography. Mean complication rate was 0.8 +/- 0.6%. Predictors of SA and IMA stenosis were unclear. Age, multi-risk profile, multi-vessel CAD, history of PVD or carotid disease, severe hypertension, unexplained renal dysfunction or decreased creatinine clearance have been reported most frequently as predictors of RA and AOI disease in patients undergoing coronary angiography.

CONCLUSIONS

Consistent evidence of appropriateness of renal angiography in selected patients undergoing coronary angiography have been produced in literature. IMA and AOI angiography seem to be not justified unless they are part of SA in patients scheduled for arterial conduit with brachial differential pressure, thoracic irradiation or surgery, or of abdominal angiography to detect RA stenosis in laboratories with radiological digital peripheral equipment.

Endovascular therapy in prevention and management of coronary-subclavian steal

BACKGROUND

The optimal management of patients undergoing coronary artery bypass grafting (CABG) who have proximal subclavian artery stenosis (SAS) is not well established. SAS may lead to flow reversal through a patent in situ internal mammary artery graft, resulting in myocardial ischemia (coronary-subclavian steal). We review our experience in prevention and management of coronary-subclavian steal.

METHODS

The medical records of patients who received treatment of symptomatic coronary-subclavian steal were reviewed. Patients who underwent subclavian artery revascularization before CABG were also included in our review. Patient demographic data, findings at presentation, imaging and treatment methods, and short-term and intermediate-term results were analyzed.

RESULTS

Over 4 years, 14 patients with combined subclavian and coronary artery disease were identified. Nine patients had angina (n = 8) and/or congestive heart failure (n = 2) after CABG (post-CABG group). Four patients underwent treatment of SAS and one underwent treatment of recurrent stenosis before or during CABG (pre-CABG group). Among this pre-CABG group, one patient had symptoms of left arm claudication; the other four patients had no symptoms. A blood pressure gradient was commonly noted between both arms. An angiogram confirmed the proximal location of SAS in all patients, and established the presence of flow reversal in a patent internal mammary artery graft in the post-CABG group. Operative management consisted of percutaneous transluminal angioplasty (PTA) and stenting of the subclavian lesion in 11 patients, PTA only in 2 patients, and carotid-subclavian bypass grafting in 1 patient. No known perioperative complications or morbidity was encountered in either group. Mean follow-up was 29 months, during which stenosis recurred in two patients, along with associated cardiac symptoms. In both patients repeat angioplasty was successful, for an assisted primary patency rate of 100%.

CONCLUSION

PTA and stenting to treat SAS appears to provide effective protection from and treatment of coronary-subclavian steal over the short and intermediate terms. A surveillance program is essential because of the risk for recurrent stenosis. Continued follow-up is necessary to determine long-term efficacy of this treatment compared with more conventional surgical approaches.

Percutaneous angioplasty and stenting of left subclavian artery stenosis in patients with left internal mammary-coronary bypass grafts: clinical experience and long-term follow-up

The authors report their experience with percutaneous transluminal angioplasty (PTA) and stenting of the left subclavian artery (LSA) in patients with recurrent angina and a left internal mammary (LIMA)-coronary bypass graft or in patients who will be undergoing LIMA-coronary artery bypass grafting. From November 1990 to February 2001, 21 patients (11 men and 10 women) with significant left subclavian artery stenosis were treated; 18 patients had a prior LIMA bypass graft, and 3 patients were treated before coronary artery bypass surgery. Angiographic follow-up was performed in 12 patients and clinical follow-up was obtained in all patients. All lesions were atherosclerotic in etiology and located in the proximal left subclavian artery. The mean stenosis was 81% (range 50-100%). All patients initially underwent PTA. Stents were placed in 7 patients for suboptimal PTA results. Technical success was achieved in all patients. Pressure gradient measurements were available in 6 patients. Mean pretreatment gradient was 29 mm Hg (range, 10-50 mm Hg) and fell to 3 mm Hg (0-8 mm Hg) posttreatment. There were 2 minor and 2 major complications. The 30-day mortality rate was 9.5% (2 patients). The remaining 19 patients had clinical or angiographic follow-up of 4-68 months (mean, 27 months). Three patients were found to have recurrent stenoses by angiography 8-43 months after PTA and 3 more had clinical signs of recurrent stenosis. Therefore, the long-term clinical patency rate of LSA PTA and stent was 15 of 19 (79%). One was managed with bypass surgery, 1 with repeat PTA and stent placement, and 1 was managed conservatively. Therefore, the assisted patency was 15 of 19 (79%). Eleven of 19 (58%) of the patients in long-term follow-up had cardiac symptoms, but repeat angiography excluded recurrent LSA stenosis as the cause of their symptoms in 7 cases. Only 4/19 (21%) had cardiac symptoms potentially attributable to LSA restenosis. Four patients expired during follow-up, but 3 had no evidence of subclavian stenosis. PTA and stenting is an effective treatment of proximal left subclavian artery stenosis in patients who develop angina after a LIMA-coronary artery bypass, or in patients before a LIMA-CABG. Cardiac symptoms after LSA PTA and stent are most often due to progressive coronary artery disease rather than to recurrent LSA stenosis.

The in vitro reversal of histamine-induced vasodilation in the human internal mammary artery

Anaphylactic shock therapy includes the use of catecholamines but they may not always be effective. Because vasodilation during anaphylaxis is a result of the endothelial release of multiple mediators, we investigated the effects of epinephrine, vasopressin, and inhibitors of nitric oxide and prostanoid pathways on histamine-induced relaxation in human internal mammary artery. The vessel segments were obtained intraoperatively and were suspended in organ chambers to record isometric tension. Norepinephrine (10(-6) M) was used to precontract the rings followed by histamine (10(-6.5) M) to relax the vessels and mimic vascular collapse. Epinephrine, vasopressin, methylene blue, N(G)-monomethyl-L-arginine (L-NMA) and indomethacin were added in a cumulative fashion to reverse the histamine-induced vasodilation. The internal mammary artery segments exhibited greater contraction in the presence of the epinephrine (4.9 +/- 0.7 g) compared with vasopressin (2.6 +/- 0.7 g). Vasopressin (10(-11) to 10(-7) M), methylene blue (10(-7) to 10(-5) M), L-NMA (10(-6) to 10(-4) M), and indomethacin (10(-7) to 10(-5) M) were only partially effective. These findings suggest that vasopressin and methylene blue may offer a potential therapeutic option in the treatment of histamine-induced vasodilatory shock.

IMPLICATIONS

Epinephrine only partially reverses histamine-induced vasodilation in human internal mammary arteries, whereas vasopressin, methylene blue, and drugs involved in the inhibition of nitric oxide and prostaglandin generation lead to a complete reversal of the vascular relaxation.

Histomorphological studies of the distal internal thoracic artery which support its use for coronary artery bypass grafting

The use of the internal thoracic artery (ITA) for myocardial revascularization in coronary artery disease increased because of its relative immunity to atherosclerotic obstruction. This study investigated the distal part of the vessel, the region of anastomosis by means of histology to focus the visualization of this region of interest. The histological examination of arterial segments showed minor intimal thickening in 48 out of 100 patients. Twelve patients demonstrated a severe intimal thickening, the residual patients were without any changes. In 52% the elastic type dominated in the distal part. Hybrid and muscular patterns were found in 22 and 26%, respectively. The media could be classified into three different types: muscular, hybrid and elastic type. There was no correlation concerning the different histological type and the incidence of intimal thickening. No evidence whatsoever of atherosclerotic lesion was encountered in any of the investigated vessels. There is no limitation in the use of the distal part of the ITA for coronary artery revascularization.

Angiographic prevalence and clinical predictors of left subclavian stenosis in patients undergoing diagnostic cardiac catheterization

The angiographic prevalence, clinical predictors, and sensitivity and specificity of a bilateral arm blood pressure differential for predicting proximal left subclavian artery stenosis were established in 492 patients undergoing cardiac catheterization. Seventeen subjects (3.5%) in the overall population and nine subjects (5.3%) with potential surgical coronary disease had proximal left subclavian stenosis. Precatheterization evidence of peripheral vascular disease (PVD) was the only predictor of subclavian stenosis in the overall population (P < 0.001; OR = 7.9; 95% CI = 2.6-24.3) and in patients with potential surgical coronary disease (P = 0.04; OR = 5.4; 95% CI = 1.1-27.2). Both a bilateral blood pressure differential of > 10 mm Hg and of > or =20 mm Hg had a good specificity but a poor sensitivity for predicting left subclavian stenosis. Thus, left subclavian angiography should be performed in patients with surgical coronary disease with either an arm blood pressure differential of > 10 mm Hg or with other precatheterization evidence of PVD. Cathet Cardiovasc Intervent 2001;54:8-11.

Transcatheter interventions for the treatment of peripheral atherosclerotic lesions: part I

Transcatheter endovascular procedures are increasingly used to treat symptomatic peripheral atherosclerosis. This two-part review identifies the existing evidence supportive of the application of transcatheter treatments for peripheral atherosclerotic lesions. The first part addresses the treatment of obstructive lesions that cause limb claudication and critical ischemia, renovascular hypertension and azotemia, and mesenteric ischemia. Studies were identified via a search of MEDLINE (January 1993 through April 1999) and reference lists of identified articles. When multicenter prospective randomized trials or other high-quality studies were unavailable, a preference was given to studies with at least 50 patients per treated group and a minimum mean follow-up duration of 6 months. Data presented in tables are proportionally weighted averages from included studies. For each application, the authors assessed the quality of evidence (QOE; efficacy, safety, and, where available, cost-effectiveness) and made recommendations with appropriate caveats. There is higher QOE supporting the more established treatments such as lower limb percutaneous transluminal angioplasty (PTA) with stent placement and thrombolysis. Treatments such as renal artery PTA and stent placement and mesenteric and brachiocephalic PTA are in wide use, but high QOE supporting general application is lacking. Blanket recommendations based on established efficacy and cost-effectiveness cannot be made. However, the use of transcatheter therapies can be supported in specific circumstances based on an expected reduction in procedure-related morbidity and/or mortality rates. It is hoped that the identification of deficiencies in the literature will inform and inspire critically needed research in this area.

Percutaneous revascularization of atherosclerotic obstruction of aortic arch vessels

OBJECTIVES

To compare stenting of aortic arch vessel obstruction with surgical therapy and to establish recommendations for treatment.

BACKGROUND

Though surgery has been considered to be the procedure of choice for subclavian and brachiocephalic obstruction, little work has been done to compare it with stenting.

METHODS

Eighteen patients with symptomatic aortic arch vessel stenosis or occlusion were treated with stenting, followed by periodic clinical follow-up and noninvasive arterial Doppler studies. Data were compared with the results as shown in a systematic review of a published series of surgery and stenting procedures which included comparison of technical success, complications, mortality and patency.

RESULTS

Primary success in our series was 100% with improvement in mean stenosis from 84+/-11% to 1+/-5% and mean arm systolic blood pressure difference from 44+/-16 mm Hg to 3+/-3 mm Hg. There were no major complications (death, stroke, TIA, stent thrombosis or myocardial infarction). At follow-up (mean 17 months), all patients were asymptomatic with 100% primary patency. Literature review demonstrates equivalent patency and complications in the other published series of stenting. In contrast, there was a similar patency but overall incidence of stroke of 3+/-4% and death of 2+/-2% in the published surgical series.

CONCLUSIONS

Subclavian or brachiocephalic artery obstruction can be effectively treated by primary stenting or surgery. Comparison of stenting and the surgical experience demonstrates equal effectiveness but fewer complications and suggests that stenting should be considered as first line therapy for subclavian or brachiocephalic obstruction.

The vasodilator effects of clevidipine on human internal mammary artery

Endothelial dysfunction and platelet activation with thromboxane release may contribute to spasm or alterations in internal mammary artery (IMA) graft flow during coronary artery surgery. Clevidipine, an ultrashort-acting dihydropyridine calcium channel blocker, is undergoing clinical development, but there are little data regarding its effects on human vasculature. We investigated the effects of clevidipine on human IMA obtained during surgery. After precontracting IMA segments with an analog of thromboxane (U46619, 10(-8) mol/L), acetylcholine and nitroglycerin were added cumulatively to examine endothelial function. Concentration-response curves to clevidipine were cumulatively obtained during submaximal contraction to the U46619 (10(-8) mol/L) in rings with and without endothelium. In the IMA samples with endothelium, acetylcholine did not completely reverse the U46619-mediated contraction, which implies impaired endothelial function (40% +/- 6% maximal response). Both clevidipine and nitroglycerin completely reversed U46619-induced contraction (clevidipine (50% effective concentration [EC50] = 3.88 +/- 0.84 x 10(-6) mol/L, nitroglycerin EC50 = 4.84 +/- 2.76 x 10(-8) mol/L). The responses to clevidipine were similar in preparations with or without intact endothelium. Clevidipine is an endothelium-independent arterial vasodilator that offers a potential therapeutic option in the treatment of perioperative arterial graft vasospasm and/or hypertension.

IMPLICATIONS

Clevidipine is a new ultrashort-acting dihydropyridine calcium antagonist. In human internal mammary arteries precontracted with a thromboxane A2 analog, clevidipine was an effective vasodilator on vessel segments in the presence and in the absence of endothelium.

Different effects of thrombin receptor activation on endothelium and smooth muscle cells of human coronary bypass vessels. Implications for venous bypass graft failure

BACKGROUND

Thrombin is implicated in coronary bypass graft disease; it cleaves its receptor's extracellular N-terminal domain and unmasks a new N-terminus as a tethered ligand. We studied the effects of thrombin receptor activation in human internal mammary artery (IMA) and saphenous vein (SV).

METHODS AND RESULTS

To study the effects of thrombin receptor activation on vasomotion, isolated blood vessels were suspended for isometric tension recording, and the effects on cell proliferation were studied in cultured smooth muscle cells (SMCs) of IMA and SV. Thrombin receptor expression in IMA and SV was analyzed by reverse transcription polymerase chain reaction and immunohistology. Receptor function was studied by analyzing the activation of mitogen-activated protein kinase (p42MAPK). In IMA thrombin evoked endothelium-dependent relaxations (65 +/- 5%) that were mimicked by thrombin receptor agonist peptide (TRAP) and reduced by the thrombin inhibitors recombinant (r-) hirudin and D-Phe-Pro-Arg-chloromethyl ketone (PPACK) (P < .05). In SV thrombin caused contractions (36 +/- 5% of 100 mmol/L KCl) that were inhibited by r-hirudin or PPACK (P < .05) but not mimicked by TRAP. In SMCs thrombin induced more pronounced [3H]thymidine incorporation (inhibited by r-hirudin or PPACK) in SV than IMA (P < .05), but activation of p42MAPK was similar in both vessels. TRAP induced weaker activation of p42MAPK than thrombin and did not stimulate [3H]thymidine incorporation in SMCs of SV or IMA. Immunohistology and RT-PCR demonstrated that the endothelium and SMCs of IMA and SV express thrombin receptor.

CONCLUSIONS

Functional thrombin receptors are present on endothelium and SMCs of IMA and SV. Endothelial thrombin receptors mediate relaxation in IMA but not SV. Thrombin causes much more pronounced contraction and proliferation in SMCs of SV than IMA independent of tethered receptors, suggesting other thrombin receptors exist. These differences of thrombin receptor activation in IMA and SV may be important in the development of and therapy for graft disease.

Use of angioplasty in the prevention and treatment of coronary--subclavian steal syndrome

PURPOSE

The coronary-subclavian artery steal (CSS) syndrome is caused by critical stenosis in the subclavian artery proximal to a bypass graft from the internal mammary artery (IMA) to the coronary artery. The stenosis results in retrograde flow in the IMA and steal from the coronary artery.

PATIENTS AND METHODS

Percutaneous transluminal angioplasty (PTA) was performed in eight patients (five men, three women). In four patients (group 1), coronary ischemia had developed 0.5-70 months (mean, 31 months) after IMA-to-coronary artery bypass surgery. These four patients (mean age, 58 years; range, 44-68 years) underwent PTA of a single area of focal subclavian stenosis to treat CSS. In four other patients (group 2), atherosclerotic subclavian stenosis had developed proximal to a donor IMA before planned bypass surgery. These patients (mean age, 53 years; range, 50-57 years) underwent PTA of a single focal subclavian stenosis to prevent CSS.

RESULTS

Group 1 patients were free of myocardial ischemia at follow-up (mean follow-up, 39.0 months; range, 14-101 months). Three of four patients in group 2 underwent coronary artery bypass grafting with the ipsilateral IMA following PTA of the subclavian stenosis; they were free of angina at follow-up (mean follow-up, 14 months; range, 10-18 months).

CONCLUSION

PTA is a safe and efficacious short-term method for prevention and treatment of CSS syndrome.

Internal mammary artery collateral to the external iliac artery: an angiographic consideration prior to coronary bypass surgery

The role of routine selective angiography of the internal mammary artery prior to myocardial revascularization is controversial. We report a patient with coronary artery disease and peripheral vascular disease in whom the left internal mammary artery supplied blood flow to the left external iliac artery via a collateral network. Thus, selective angiography of the internal mammary artery did play a major role in the proper management of this patient who required coronary bypass surgery. A major potential postoperative complication of left lower extremity ischemia may have been prevented.

Calcium antagonists differently inhibit proliferation of human coronary smooth muscle cells in response to pulsatile stretch and platelet-derived growth factor

BACKGROUND

Vascular smooth muscle cell proliferation is the key event of coronary artery disease. Mechanical forces, in particular, pulsatile stretch and platelet-derived growth factor, may play an important role.

METHODS AND RESULTS

Vascular smooth muscle cells were cultured from the media of human left descending coronary arteries obtained from organ donors using the explant method. To study effects of pulsatile stretch on vascular smooth muscle cell proliferation, a computer-controlled in vitro pulsatile stretch device was used. Cells were seeded onto Flex I culture plates with deformable membranes and exposed to pulsatile stretch (60 cycles per minute) and/or growth factors. Proliferation of smooth muscle cells was determined by 3H-thymidine incorporation. Pulsatile stretch markedly stimulated 3H-thymidine incorporation of coronary smooth muscle cells (180 +/- 15 to 432 +/- 27 cpm/10(5) cells; P < .05) after 24 hours and increased cell number after 6 days (10.3 +/- 0.7 x 10(4)/mL; P < .05). Platelet-derived growth factor-AB (0.01 to 10 ng/mL) concentration-dependently stimulated 3H-thymidine incorporation in coronary smooth muscle cells (EC50, 0.1 ng/mL) and had additive effects with pulsatile stretch. The Ca2+ antagonist verapamil (10(-7) to 10(-5) M) concentration-dependently inhibited proliferation stimulated by platelet-derived growth factor back to control levels (P < .05 to .01) but not that induced by pulsatile stretch.

CONCLUSIONS

Pulsatile stretch and platelet-derived growth factor are potent stimuli for proliferation of coronary smooth muscle cells. The selective inhibitory effect of a Ca2+ antagonist on smooth muscle cell proliferation stimulated by platelet-derived growth factor but not by pulsatile stretch may explain why the drugs have only modest antiatherogenic effects in patients with coronary artery disease.

A pathohistological and biochemical study of arteriosclerosis in the internal thoracic artery, a vessel commonly used as a graft in coronary artery bypass surgery

Pathohistological and biochemical studies were conducted on the severity of arteriosclerosis in the internal thoracic artery (ITA), an artery commonly used for coronary artery bypass grafting (CABG). For the pathohistological examination, 26 bilateral ITAs and 13 left anterior descending coronary arteries (LADs) obtained in full length from 13 autopsy cases, none of which had died of arteriosclerotic heart disease, were used. The ratio of the thickness of the intima to that of the media (R) was used as the index for arteriosclerosis. ITAs and LADs were classified as grades I to IV according to the value of R. The R of the ITAs was approximately 1/10 that of the LADs (P < 0.01). Most ITAs showed a low arteriosclerotic grade, with no variation in arteriosclerosis along their length and a low R in all segments. No difference was found between right and left ITAs. Biochemical examination was conducted on 12 ITAs and 11 LADs, obtained from 12 different and unselected autopsy cases. The lipid content in the vascular wall was determined to evaluate the severity of arteriosclerosis, with the following results: Total cholesterol, 5.5 +/- 1.8 and 17.8 +/- 13.6 micrograms/mg wet weight (P < 0.05); triglyceride, 90.4 +/- 90.3 and 114.4 +/- 117.2 micrograms/mg wet weight (n.s.); and phospholipid, 7.4 +/- 3.9 and 11.2 +/- 3.9 micrograms/mg wet weight (P < 0.05), respectively, for the ITAs and LADs. These findings thus demonstrate that arteriosclerosis of the ITA in Japanese people is very mild, compared to that of the LAD in the same individuals.

Internal mammary artery angiography should be a routine component of diagnostic coronary angiography

Left internal mammary artery (LIMA) angiography was performed with diagnostic coronary angiography in 130 cases for which the coronary findings made use of the LIMA as a bypass graft a consideration. In 98% of the cases the approach to LIMA angiography was femoral with a 5F LIMA catheter first directed into the proximal subclavian and then advanced over a guidewire placed into the distal subclavian well beyond the origin of the LIMA. After withdrawing the wire the catheter was brought proximally to selectively cannulate and visualize the LIMA with nonionic contrast media. The only complication was a single transient occipital visual field loss. LIMA caliber too narrow to permit use as a graft was found twice, LIMA occlusion unrelated to prior surgery was found once, and LIMA occlusion related to prior surgery was found twice. Subclavian and/or vertebral stenosis was present five times. Large proximal branches of the LIMA best identified prior to surgery were present 12 times. Based on this experience, LIMA angiography 1) can be performed safely with a high degree of success, 2) demonstrates significant findings in 15% of cases, and 3) should therefore be performed whenever coronary angiographic findings make it appropriate to consider LIMA to coronary artery bypass grafting.

Subclavian artery angioplasty proximal to a left internal mammary-coronary artery bypass graft: case report

Subclavian artery angioplasty is an established treatment for subclavian steal syndrome and arm ischemia caused by subclavian stenosis. We report a case of angina pectoris caused by a subclavian artery stenosis proximal to a left internal mammary-coronary artery bypass graft. Angioplasty was performed without complication and with complete relief of symptoms. Reactive hyperemia was induced in the forearm and hand with a blood pressure cuff prior to angioplasty to increase blood flow to the arm, and to reduce the chance of graft embolization. Repeat angiography 6 months later confirmed continued patency of the subclavian artery and the graft and reversal of the steal physiology. The patient remains symptom free 15 months after angioplasty.

Grafting with the internal mammary artery: correlation between preoperative angiography and intraoperative findings

No data exist on the relation between angiography of the internal mammary artery and intraoperative findings during bypass surgery. We studied 47 consecutive patients and found no atherosclerotic changes. Intraoperatively, however, 4 left internal mammary arteries were judged unsuitable for grafting. No relation could be found to the diameter of the vessel as judged angiographically. Possible causes of unsuitability are discussed.

Different interactions of platelets with arterial and venous coronary bypass vessels

We studied the interaction of platelets with the wall of human internal mammary arteries and saphenous veins, suspended in organ chambers for measurement of isometric tension. Vessels were obtained during coronary bypass surgery and cut into 5 mm rings; in some the endothelium was chemically removed. Rings from several patients were randomly chosen for each experiment, and in each ring six concentrations of platelets (from healthy blood donors; 1-75 x 10(3)/microliters) were tested consecutively and concentration-response curves constructed; the areas under these curves were used for statistical comparisons. In rings of internal mammary artery contracted in response to noradrenaline, aggregating platelets induced endothelium-dependent relaxation which was prevented by apyrase (0.67 U/ml ADPase activity) and L-NG-monomethylarginine (1 mmol/l). By contrast, in saphenous vein rings contracted in response to noradrenaline, aggregating platelets induced only a further increase in tension. In quiescent vessels, the platelet-induced contraction did not occur in arteries with endothelium but that in veins was greater and facilitated by endothelium. Preincubation of platelets with aspirin (10 mumol/l) reduced the contraction in both vessels, but contraction was abolished only in the presence of both the thromboxane receptor antagonist SQ-30741 and the serotoninergic (5HT2) receptor antagonist ketanserin. These findings show that platelet-derived ADP causes release of nitric oxide by the endothelium of internal mammary artery but not of saphenous vein; thromboxane A2 and serotonin mediate contraction in vein but not artery with endothelium. These differences may contribute to differences in graft function and the clinical efficacy of antiplatelet drugs.

Different activation of the endothelial L-arginine and cyclooxygenase pathway in the human internal mammary artery and saphenous vein

The endothelium releases substances controlling vascular tone and platelet function. We investigated mediators of endothelium-dependent responses in human internal mammary arteries and saphenous veins. The inhibitor of nitric oxide formation, NG-monomethyl L-arginine, enhanced the sensitivity to norepinephrine (fivefold) and evoked more pronounced endothelium-dependent contractions in internal mammary arteries (19 +/- 6% of 100 mM KCl) than in saphenous veins (2 +/- 1%; p less than 0.005). In internal mammary arteries, NG-monomethyl L-arginine, but not indomethacin, markedly reduced endothelium-dependent relaxations to acetylcholine (from 95 +/- 2% to 39 +/- 7%; p less than 0.005) and prevented those to histamine (78 +/- 6% to 4 +/- 3%; p less than 0.005). In saphenous veins, endothelium-dependent relaxations to acetylcholine were weak (24 +/- 11%), while nitric oxide caused comparable relaxations (85 +/- 3%) as in internal mammary arteries (80 +/- 5%; NS). NG-Monomethyl L-arginine prevented the relaxations to acetylcholine and unmasked endothelium-dependent contractions (30 +/- 10%). Indomethacin and the thromboxane synthetase inhibitor CGS-13080 augmented relaxations of saphenous veins to acetylcholine from 24 +/- 11% to 46 +/- 9% (p less than 0.05). Histamine-evoked contractions were converted to endothelium-dependent relaxations by indomethacin and the thromboxane A2/endoperoxide receptor antagonist SQ-30741 (38 +/- 3% and 40 +/- 6%; p less than 0.05) but not CGS-13080. Thus, 1) nitric oxide mediates endothelium-dependent relaxations in human arteries and veins; 2) internal mammary arteries release more nitric oxide than do saphenous veins, and 3) in saphenous veins, the effects of nitric oxide are reduced by endothelium-derived contracting factors originating from the cyclooxygenase pathway.

Interaction between endothelin-1 and endothelium-derived relaxing factor in human arteries and veins

Endothelin-1 is a 21-amino acid endothelial vasoconstrictor peptide that may be the physiological antagonist of endothelium-derived relaxing factor (EDRF). Endothelin-1 (10(-11)-3 x 10(-7) M) evoked potent contractions of isolated internal mammary arteries, internal mammary veins, and saphenous veins, which were enhanced in internal mammary veins as compared with internal mammary arteries (concentration shift, 6.3-fold; p less than 0.05) but not in the saphenous veins. Endothelial removal augmented the response to the peptide (at 3 x 10(-7) M) in internal mammary arteries (p less than 0.05) but not in veins. In the artery, EDRF released by acetylcholine or bradykinin reversed endothelin-1-induced contractions; in saphenous veins, both agonists were much less effective compared with the artery and veins contracted with norepinephrine (p less than 0.005-0.01). This inhibition of endothelium-dependent relaxations in veins occurred at half-maximal contractions but was most prominent at maximal contractions to the peptide. Nitric oxide similarly inhibited contractions to endothelin-1 and norepinephrine in internal mammary arteries, whereas in veins that were contracted with endothelin-1 but not with norepinephrine, the relaxations were blunted (p less than 0.005). The nitric oxide donor SIN-1 and sodium nitroprusside induced complete relaxations of internal mammary arteries but were less effective in veins contracted with endothelin-1 (p less than 0.005). Thus, in normal human arteries, EDRF inhibits endothelin-1-induced contractions, whereas the peptide specifically attenuates the effects of EDRF and nitrovasodilators in veins. This may be important in pathological conditions associated with increased levels of endothelin-1 and in veins used as coronary bypass grafts.

Endothelium-derived relaxing factor and protection against contractions induced by histamine and serotonin in the human internal mammary artery and in the saphenous vein

We investigated the release of endothelium-derived relaxing factor (EDRF) in response to serotonin and histamine in the human internal mammary artery and saphenous vein. The arteries and veins were obtained intraoperatively and were suspended in organ chambers to record isometric tension. In mammary arteries, histamine (10(-8) to 3 X 10(-6) M) induced relaxations in rings with (70 +/- 5%, IC50, 6.5 +/- 0.2) but not without endothelium (p less than 0.005 for rings with compared with those without endothelium, n = 7-10). The response was inhibited by methylene blue or hemoglobin, but not meclofenamate, and, therefore, EDRF was delineated as the mediator. Because chlorpheniramine but not cimetidine inhibited the response, EDRF was released by the H1-histaminergic receptor (n = 5-8). In contrast, in saphenous veins, histamine caused only weak or absent endothelium-dependent relaxations, but contractions were enhanced in rings with endothelium (p less than 0.05, n = 6). Serotonin did not induce endothelium-dependent relaxations, but contractions were markedly greater in veins compared with arteries (p less than 0.005, n = 6). The endothelium inhibited the maximal contraction to serotonin in arteries (p less than 0.034) but not in veins. Thus, EDRF protects against contractions induced by histamine and serotonin in the mammary artery but not in the saphenous vein. This may be important for improved graft function and patency of the artery compared with that of the vein.

A comparison of morphologic and angiographic findings in long-term internal mammary artery and saphenous vein bypass grafts

Internal mammary artery grafts are currently considered the conduits of choice for myocardial revascularization. Comparisons of long-term morphologic changes in internal mammary artery grafts and saphenous vein grafts and correlation with premortem angiography have not been reported. Eighteen internal mammary artery and 15 saphenous vein grafts that had been in place for 12 to 118 months (mean 56) in 18 patients were removed either surgically or at necropsy and examined histologically. Premortem angiograms were performed within 1 month of histologic study in 15 of these patients. Fibrointimal proliferation was more frequent in internal mammary artery than in saphenous vein grafts 8 [( 44%] of 18 versus 4 [27%] of 15; p = NS). In contrast, atherosclerosis was common in saphenous vein grafts but was extremely rare in internal mammary artery grafts (10 of 15 versus 1 of 18; p = 0.01). A good correlation was noted between the degree of narrowing estimated by angiographic and histologic measurements in both internal mammary artery grafts (d = 0.90) and saphenous vein grafts (d = 0.71). Accelerated atherosclerosis did not occur in internal mammary artery grafts, but was common in saphenous vein grafts. Fibrointimal proliferation was commonly associated with graft narrowing in internal mammary artery grafts and may be an important factor in late graft closure. This study also confirms that internal mammary artery grafts have greater longevity compared with saphenous vein grafts.

Percutaneous angioplasty of internal mammary artery graft stenosis: case report and discussion

Percutaneous transluminal coronary angioplasty (PTCA) was successfully used for the first time in 1977. With experience, its application broadened to include multiple lesions, complex anatomical stenoses, multiple vessels, and saphenous vein aorto-coronary bypass grafts. This case demonstrates successful internal mammary graft angioplasty with continued long-term (eight months) success, documented angiographically.

Progression of coronary atherosclerosis. Clues to pathogenesis from serial coronary arteriography

Fifty two patients with coronary artery disease underwent repeat coronary arteriographic studies separated by 2-108 (mean 51) months of medical treatment. The results were compared and correlated with symptoms to determine the nature of the progression of coronary atherosclerosis. The condition appeared to progress episodically in the proximal segments of the coronary arteries and in relation to the abrupt development of new symptoms or acute coronary events such as unstable angina or myocardial infarction. Thirty four of 105 (33%) of the pre-existing stenoses showed evidence of progression. Progression to total occlusion was uncommon (13) except for stenoses greater than 90% (six out of 18). New lesions frequently occurred (37) in previously normal segments of the arteries; most of these were stenoses greater than 90% (13) or total occlusions (12). Rapid progression of a mild lesion and new lesions occurred in the form of smooth intimal protrusions into the arterial lumen. Intimal haemorrhages are the likely explanation for these intimal encroachments and also for the episodic nature of the progression of coronary artery disease. Coronary atherosclerosis does not progress gradually in a linear fashion, and local anatomical factors appear to play a dominant role in the natural history.