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Biomedical subjects

N L Mills

Publications and source records attributed to N L Mills.

At least 19 recordsLinked to original sources
PubMed1996

"Legs" technique for management of widely separated coronary arteries during ascending aortic repair.

BACKGROUND: Widely separated coronary arteries with significantly diseased tissue continues to challenge surgeons repairing ascending aortic aneurysms. METHODS: Occasional troublesome leaks around coronary ostial anastomoses and Cabrol graft thrombosis prompted a change of our operative management of this condition. Collagen-impregnated 8-mm "legs" grafts are used to connect the coronary arteries to the composite graft. Ten patients, aged 14 to 70 years, underwent the operation. RESULTS: The first patient is 15 years after the operation and is symptom free. One patient died of an arrhythmia 1 month after discharge. Eight patients are living and well 11/2 to 4 years postoperatively. CONCLUSIONS: Advantages of direct interposition (legs) grafts are as follows: the coronary arteries are separately perfused and the risk of catastrophic thrombosis from a longer high-volume graft is eliminated. Problems with coronary ostial mobilization are avoided. The technique allows full visualization and hemostatic suture line testing with cardioplegia before aortic declamping. Space constraints with reoperations are easily managed, whereas other techniques may result in graft compression on refilling of the heart and termination of bypass. The technique is carried out with ease and reproducibility, and the availability of new graft material has made it our treatment of choice for ascending aortic composite graft replacement.

Adolescent↗
PubMed1996

North American experience with the Perma-Flow prosthetic coronary graft.

BACKGROUND: The Perma-Flow prosthetic coronary graft is a 5-mm polytetrafluoroethylene tube into which is incorporated a Venturi flow restrictor. An aorto-superior vena caval fistula is created and coronary anastomoses are constructed proximal to the resistor in side-to-side fashion, where arterial pressure is maintained. From November 1992 through December 1995, eight investigational centers in North America have implanted this graft in 40 patients with inadequate autologous alternatives. METHODS: Patients were selected for inclusion in this study if coronary artery bypass grafting was required and adequate autologous conduit to complete revascularization was not available. Operative data were completed by the implantating surgeon and referred to a central center, the Minneapolis Heart Institute, for correlation. Follow-up was conducted by data coordinators at each institution, and follow-up data were obtained directly from these coordinators for inclusion in the study. RESULTS: Patient age ranged from 53 to 82 years, and 15 patients were undergoing reoperations (38%). On each Perma-Flow graft one to four coronary side-to-side anastomoses were constructed. In addition, left internal mammary artery (n = 26), greater saphenous vein (8), right internal mammary artery (4), and gastroepiploic artery (4) were used to complete revascularization. Aortic (2) or mitral valve replacement (1) was also carried out. There were seven operative deaths (18%) and two late deaths (4 and 6 months). After 1 to 37 months (mean, 13 +/- 9 months) of follow-up, 29 of 31 surviving patients are asymptomatic. Echocardiographic heart size has not increased from the postoperative value, indicating limited volume load has not affected heart size. Protocol catheterization (n = 32) in 28 patients 1 week to 1 year postoperatively revealed 7 of 73 studied coronary anastomoses (9.5%) and two distal extensions and resistors were occluded (7%). In 1 patient during sternal debridement at 1 year, no flow was found in the graft. CONCLUSIONS: The Perma-Flow graft is a useful adjunct to complete revascularization in patients with deficient autologous conduit.

Aged↗
PubMed1995

Vein graft failure.

Saphenous vein graft failure is one of the primary reasons for coronary artery bypass reoperation. The economic impact alone in this country is staggering in an era of intensive cost cutting. The fact that some vein grafts remain free of disease for years while the sibling vein develops extensive atherosclerosis remains an enigma. Saphenous vein valves have recently attracted interest. Repeated angiograms show that vein graft disease invariably is accentuated around valves. Studies show that the segment of saphenous vein distal to the valves have more accelerated and intense atherosclerosis. Early results of saphenous vein bypass grafting may be predicted with some degree of certainty by saphenous vein graft biopsy. Attention is now being turned to the hypercoagulable state as a cause of graft failure, as this has not been previously addressed. Research into pharmacologic agents for maintaining open grafts has had disappointing results and aspirin alone is still the single drug of choice to promote patency. Preparation of the graft continues to be important because there is direct evidence that surgical injury during preparation leads to neointimal thickening and vascular smooth muscle proliferation. Although there are some exciting new modalities for preventing graft disease, the difficulty in transposing animal data to humans and the uncertainty of the biologic similarities of in vitro and in vivo endothelial cell biochemistry makes any immediate solution unlikely. Therefore an even greater increase in the use of arterial grafts in the near future seems likely, even with their associated problems.

Animals↗
PubMed1994

Reoperative coronary artery bypass grafting.

In recent years reoperative coronary artery bypass surgery has become increasingly more commonplace. This article reviews the current status of this procedure with regard to patient population, risk factors, and long-term follow-up. Important aspects of the specific technical considerations involved in reoperative surgery are also reviewed and evaluated.

Coronary Artery Bypass↗
PubMed1993

1985: left thoracotomy for reoperative coronary artery bypass procedures. 1993 update.

This paper describes our experience in performing saphenous vein bypass grafts to the circumflex coronary artery system with a left thoracotomy in 9 patients. Illustrative case reports demonstrate the spectrum of patients for whom this approach has been useful. The advantage of this technique is that it allows the surgeon to avoid the adhesions that make a redo sternotomy time-consuming and potentially dangerous when previously patent saphenous vein or internal mammary grafts are present. It is particularly useful for patients requiring grafting to the circumflex coronary artery system, especially if the patient is in relatively unstable condition and would benefit from rapid institution of cardiopulmonary bypass. The technique generally employs cannulation of the descending thoracic aorta for arterial inflow and of the main pulmonary artery for venous return. Usually the proximal end of the graft is easily placed to the left subclavian artery. Coronary anastomosis is performed on the cold (15 degrees C), fibrillating heart, and aortic cross-clamping and cardioplegic arrest have not been necessary. Venting is possible through the left atrial appendage should any rise in filling pressures occur. Saphenous vein or internal mammary artery may be used. All patients undergoing this technique have had expeditious discharge from the hospital and excellent relief of symptoms. The technique is an alternative to median sternotomy for properly selected patients.

Coronary Artery Bypass↗
PubMed1993

Technical advances in the treatment of left ventricular aneurysm.

The resulting abnormal geometry after surgical treatment of left ventricular aneurysm has concerned a number of surgeons since the first successful repair in 1958, but little attention was placed on the altered geometry until attempts were made to effect a more physiologic aneurysmorrhaphy in 1973. Substantial attention was focused on a concept of geometric reconstruction from within the left ventricle in 1985. A prosthetic patch was employed with the concept to redirect normal muscle bundles to their original orientation and position. Further refinements include use of improved materials for the repair, preservation and bypass of the left anterior descending coronary artery, ablation of ventricular arrhythmias when indicated, and the absence of prosthetic material used in contact with the pericardial surface. Our experience with repair of 61 left ventricular aneurysms at West Jefferson Medical Center over a 4 1/2-year period with a 3.3% mortality rate has prompted a change from the standard linear repair to routine use of a modified endoventricular repair. Currently, the low surgical risk due to advances in left ventricular aneurysmorrhaphy combined with the knowledge that contractile areas will progressively deteriorate in ventricles stressed by poor hemodynamics and with data showing improved left ventricular function postoperatively have led to more liberal recommendations for early left ventricular aneurysm repair.

Heart Aneurysm↗
PubMed1993

The subscapular artery: an alternative conduit for coronary bypass.

The search for an alternative conduit for coronary bypass has prompted our use of the subscapular artery for coronary bypass via a left thoracotomy in three patients. Historically, this artery in conjunction with muscle flaps has been used successfully as a free graft. Its size and length have proved feasible for coronary bypass to the circumflex coronary artery system. All three patients have had excellent clinical results lasting from 6 to 21 months.

Angina Pectoris↗
PubMed1993

Right gastroepiploic artery used for coronary artery bypass grafting. Evaluation of flow characteristics and size.

Questions remain concerning the physiologic capabilities of the right gastroepiploic artery as a bypass graft in the clinical setting. Our last 90 consecutive pedicle right gastroepiploic artery grafts were prepared with intraluminal papaverine and verapamil. Our series comprised 81 male and 9 female patients with average body surface areas of 1.92 m2. Ages ranged from 11 to 79 years (mean 57.2 years). A second to fourth revascularization was undertaken in 32 patients (35.5%). The following arteries were bypassed: posterior descending artery, 63; right coronary artery, 23; distal right, 4; circumflex, 2; left anterior descending, 1; and diagonal, 1. Free flow rates ranged from 42 to 660 ml/min (mean 179.96 ml/min). Internal diameters measured 1.5 to 4.0 mm (mean 2.20 mm) at the anastomotic sites. Pedicle lengths ranged from 16 to 26 cm (mean 19.2 cm). Inotropic support was required in 11 patients (12%) and had no adverse effects on right gastroepiploic artery grafts. There were 2 hospital deaths (2.2%). Angina has recurred in 6 patients. One patient with cardiomyopathy required transplantation 2 years after coronary bypass grafting. Repeat angiography showed widely patent grafts in 18 patients and generalized narrowing in 4 grafts. In only 2 patients of our total experience has right gastroepiploic artery grafting been aborted because of inadequate conduit size. One right gastroepiploic artery had visible atherosclerosis. This study shows that distal right gastroepiploic artery sizes are comparable with sizes of target coronary arteries. However, neither flow nor size is as consistent when compared with internal thoracic artery grafts. Higher flow rates are related to graft anatomic characteristics and larger body surface areas. Spasm, secondary to harvest in these vasoreactive grafts, can be managed appropriately by intraluminal vasodilating drugs. However, use of the right gastroepiploic artery should be avoided in a setting with possible competition of flow.

Adolescent↗
PubMed1992

Comparative effects of endothelin (ET-1) and U46619 on human saphenous vein and gastroepiploic artery, sources of human autologous grafts.

The effects of endothelin (ET-1) on smooth muscle contractile activity were investigated and compared in human saphenous vein and gastroepiploic artery, vessels frequently used in revascularization procedures. ET-1 contracted saphenous vein and gastroepiploic artery in a concentration-dependent manner. The peptide produced a greater maximal effect in the vein than in the artery and, in both preparations, ET-1 was less efficacious than U46619, an agent which mimics the actions of thromboxane A2 at the thromboxane A2/prostaglandin H2 receptor. The contractile response to ET-1 declined spontaneously at a more rapid rate in the artery than in the vein. The present data indicate that ET-1 has significant contractile activity in both vessels which are used for coronary arterial bypass surgery and suggest that although, a weaker vasoconstrictor than U46619, the peptide could induce vasospasm in both graft vessels.

Arteries↗
PubMed1991

Technique for use of the inferior epigastric artery as a coronary bypass graft.

A search for a coronary bypass conduit with increased longevity has resulted in harvest of the inferior epigastric artery. The artery is dissected through a paramedian incision with retraction of the rectus muscle to the lateral side. As the inferior epigastric artery courses superiorly, it may lie in one of three positions in relation to the rectus muscle. Distal coronary anastomoses using this conduit are conventional, and the proximal anastomosis may be made to the aorta or end-to-side to an internal mammary artery or venous conduit. After preparation with dilute papaverine-Plasmalyte solution proximal sizes have ranged from 2.5 to 3.25 mm (internal diameter), and distal inferior epigastric artery sizes measured 1.5 to 2.5 mm (internal diameter). The lengths of the conduit ranged from 11.5 to 17.0 cm. Eighteen patients aged 41 to 74 years had inferior epigastric artery grafts to 19 coronary arteries. The indications for use were absent or poor-quality vein, young age with an attempt to limit vein graft, and avoidance of use of bilateral internal mammary artery grafts in insulin-dependent diabetic patients. There was one sterile wound hematoma and one late wound infection. There were no other infections and no deaths. Three patients studied postoperatively revealed widely patent inferior epigastric artery grafts.

Adult↗
PubMed1991

Preparation of the internal mammary artery graft with intraluminal papaverine.

Harvest of arterial grafts causes varying degrees of vascular spasm. Preparation of the internal mammary graft by intraluminal injection of diluted papaverine solution (60 mg of papaverine in 40 mL of normal saline) allows graft dilation to occur while pericardiotomy, cannulation, etc., is performed. Advantages are an increased mammary graft size with less chance of technical error, elimination of spasm with improved flow rates, and the identification of unclipped or uncauterized branches that may require reexploration. Newer vasodilating agents may prove even more effective in the future.

Coronary Artery Bypass↗
PubMed1991

Technical considerations for myocardial protection during the course of coronary artery bypass reoperation: the impact of functioning saphenous vein and internal mammary artery grafts.

New technical challenges involving the delivery of cardioplegia during the course of coronary artery bypass operation continue to be presented to the surgeon. Functioning saphenous grafts at reoperation that are at risk for distal embolization, are managed by altering the standard cardioplegia delivery techniques. Management of patent internal mammary artery (IMA) grafts depends upon the status of the native circulation and coronary collateral. The reoperation may be performed with a fibrillating heart, standard cardioplegia with a clamped mammary graft, or cardioplegia delivered during simultaneous circulatory arrest. Myocardial temperature measurements, during the course of more complex operations, are useful in choosing the appropriate technique for myocardial protection.

Collateral Circulation↗
PubMed1991

Atherosclerosis of the ascending aorta and coronary artery bypass. Pathology, clinical correlates, and operative management.

Analysis of 1735 patients who underwent coronary artery bypass grafting from January 1981 through December 1988 revealed 152 (8.8%) patients with mild (4.5%), moderate (2.2%), or severe (2.0%) atherosclerosis of the ascending aorta. Three distinct pathologic patterns were found. The prevalence of stroke in patients with the severe type of aortic disease prompted development of a new operative technique that has been used in 16 patients. It involves a "no-touch" technique of the ascending aorta whereupon the proximal saphenous vein anastomoses are performed end to side to internal mammary artery grafts. Ages ranged from 49 to 80 years (mean 68.9). The 16 patients had 62 distal artery and vein anastomoses and 26 proximal saphenous vein-internal mammary end-to-side anastomoses. Internal mammary artery free flows ranged from 130 to 420 ml/min. Two hospital deaths were unrelated to the technique. There have been no strokes or recurrences of angina. An inordinately high incidence of main left coronary disease (50%), significant carotid disease (79%), and abdominal aortic occlusive or aneurysm disease (93%) was discovered. Ascending aortic atherosclerosis must be suspected in all coronary bypass patients with associated significant carotid, abdominal aortic, and main left coronary artery disease, aortic wall irregularity on ascending aortic angiography, adhesions between the ascending aorta and its adventitia, pale appearance of the ascending aorta, and minimal bleeding of an aortic cannulation stab wound. A "no-touch" technique that avoids any manipulation of the ascending aorta and that uses the internal mammary arteries as the sole source of blood supply for coronary bypass is an effective method to prevent aortic clamp injury, "trash heart," or stroke from severe ascending aortic disease. Preoperative angiographic visualization of the ascending aorta of all patients undergoing coronary artery bypass is mandatory.

Aged↗
PubMed1990

Newer surgical techniques in myocardial revascularization.

Recent trends in the patient population coming for surgical treatment of coronary artery disease have prompted alterations in the type of coronary artery bypass surgery performed. Emphasis is placed on the more widespread use of arterial grafts and revascularization of vessels with extensive distal disease, utilizing endarterectomy techniques, in an attempt to provide a more complete and long-lasting revascularization.

Coronary Artery Bypass↗
PubMed1989

Right gastroepiploic artery: a third arterial conduit for coronary artery bypass.

Experience with 39 patients (32 men, 7 women) undergoing coronary artery bypass grafting with the right gastroepiploic artery (RGEA) is reported. Indications initially included poor-quality or absent saphenous vein, ascending aortic atherosclerosis, and repeat coronary artery bypass grafting. The average number of grafts per patient was 4.10. Arteries bypassed were the posterior descending (22 patients), right coronary (12), diagonal (5), and marginal (4). Distal RGEA internal diameters of all grafts measured 1.5 to 3.25 mm (average diameter, 2.14 mm). Pedicled graft lengths measured 18 to 30 cm (average length, 23.7 cm), and free grafts, 8 to 24 cm (average length, 17.7 cm). In 6 patients, no vein grafts were used, and in all patients, at least one internal mammary artery graft was placed. Early postoperative cardiac catheterization (19 pedicled and ten free grafts) in 29 patients revealed all grafts to be patent without a kink or twist, but three of these free RGEA grafts had vasospasm. Advantages of RGEA grafts are as follows: (1) it is a third arterial conduit with artery-artery anastomoses of comparable sizes; (2) a shorter leg incision or no leg incision is necessary; (3) it can be harvested simultaneously with the internal mammary artery and the saphenous vein; (4) the proximal anastomosis (free grafts) is easy; (5) its use avoids bilateral internal mammary artery grafts in patients at high risk for sternal infection; and (6) atherosclerotic ascending aortas are not clamped. Subintimal hyperplasia and atherosclerosis of RGEA grafts are unlikely.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗