Peter B. Mansfield

Histologic fate and endothelial changes of distended and nondistended vein grafts.

Sixty-two autogenous cephalic vein segments were grafted into the femoral arteries of 31 mongrel dog: the left side receiving non-distended (control) grafts and the right side distended (experimental) grafts. Distending media were heparinized blood and saline. Veins were distended at 600 mm Hg for 2 minutes. Specimens were taken at intervals from 15 minutes to 3 months, and were studied by gross inspection, surface observations (light scanning stereoscope to X 70 scanning electron microscope to x 6,000) and routine histologic techniques (light microscope to X 1000). In general, grafting of veins in the arterial system was followed by progressive degenerative changes in all layers of the vein, including endothelial cell involution, desquamation and re-endothelialization. Often a variable degree of subendothelial fibrous and/or myoepithelial proliferation occurred which might compromise even a lumen lined by healthy endothelium. Distention caused these changes to occur earlier (2–4 weeks) and to be more pronounced. Distention with saline caused more damage to the endothelium than did distention with blood. We conclude that preimplant distention of vein grafts (to overcome spasm) should be employed sparingly, as it adversely affects the endothelial covering of the flow surface, accelerates the development of degenerative changes, and may predispose the graft to early thrombotic complications.

Healing Basis and Surgical Techniques for Complete Revascularization of the Left Ventricle Using Only the Internal Mammary Arteries

Long-term follow-up data from several leading centers concerning patients undergoing coronary artery bypass clearly demonstrate the superiority of the internal mammary artery (IMA) with patency rates of 83 to 94% at 7 to 12 years compared with the saphenous vein and its patency rates of 41 to 53%. Our experimental studies provide a biological basis for understanding this difference. Thin-walled arterial autografts undergo no histological change after being implanted in the arterial system, while venous autografts undergo major changes with an initial scattered loss of endothelium and marked thickening due to a proliferative reaction. The challenge to the cardiac surgeon is to revascularize the entire left ventricle with the IMAs. We have found this possible in most patients with advanced three-vessel disease by using both IMAs either as in situ grafts or free grafts with as many sequential anastomoses as necessary to achieve full revascularization. Our use of the term in situ refers to the grafts origin from the subclavian artery as opposed to a free IMA graft arising from another site.

Future Directions in the Development of Arterial Prostheses for Small and Medium Caliber Arteries

Discussion of the problems and developmental possibilities of prostheses is based upon the search either for a truly satisfactory artificial flow surface or for means to accelerate healing by aiding the ingrowth of perigraft tissues and also, if possible, by using a healable, nonthrombogenic substance as the initial flow surface.

Effect of pH and Pco2 on pulmonary and systemic hemodynamics after surgery in children with congenital heart disease and pulmonary hypertension

Fourteen children with congenital heart disease and associated pulmonary hypertension (preoperative mean pulmonary artery pressure (MPAP) 48 mm Hg +/- 1 SEM were examined to determine the effect of arterial carbon dioxide tension (PaCO2) and pH on pulmonary and systemic hemodynamics after surgical repair. Baseline measurements were obtained with hyperventilation to PaCO2 20 to 30 mm Hg (pH 7.56 +/- 0.01 mm Hg). The addition of carbon dioxide to inspired gas to achieve a PaCO2 40 to 45 mm Hg (pH 7.35 +/- 0.01) resulted in a significant increase in MPAP, from 32 +/- 5 mm Hg to 47 +/- 8 mm Hg (p less than 0.05). An increase in mean cardiac index (CI) from 2.7 +/- 0.3 L/min/m2 to 3.3 +/- 0.3 L/min/m2 (p less than 0.05) explained in part the associated increase in MPAP. For a subgroup of eight patients with postoperative MPAP greater than 30 mm Hg (at pH 7.35 to 7.40), pulmonary vascular resistance index (PVRI) also significantly increased (p less than 0.05) as PaCO2 was increased, implying a direct pulmonary vasodilating effect of alkalosis. Removal of carbon dioxide from inspired gas returned hemodynamic values to baseline. The higher the MPAP at physiologic pH the greater the absolute amount of MPAP reduction and PVRI reduction (p less than 0.05) with alkalosis. No complications from alkalosis were seen. We suggest that a trial of hypocarbic alkalosis in the child with severe residual pulmonary hypertension after surgical repair of congenital heart disease is warranted to reduce right ventricular afterload.

Presence of endothelium in an axillary femoral graft of knitted Dacron with an external velour surface

An axillary-bilateral common femoral graft of knitted Dacron with an external velour surface was examined within one hour after the patients death from non-graft-related causes. The prothesis, implanted for 20 months, was patent and was completely healed over 32% of the flow surface—that is, full wall fibrous tissue encapsulation of the graft had occurred, and 32% of the flow surface was endothelialized. The remaining flow surface was formed of fibrin, but fibrous tissue healing had reached the inner surface of the graft material, and the fibrin overlay was very thin. The healed portions of the graft included not only the areas adjacent to the anastomoses, but were scattered throughout the 45 cm length of the prosthesis. To our knowledge, this is the first report of complete healing (fibrous tissue encapsulation and endothelialization) documented at points beyond the pannus ingrowth at the prosthesis-artery anastomosis.

Axillofemoral bypass: A critical reappraisal of its role in the management of aortoiliac occlusive disease

Two hundred twenty-four consecutive patients (361 graft limbs) who underwent bypass grafting with the USCI Sauvage filamentous velour Dacron arterial prosthesis for aortoiliac occlusive disease over the 9 year period 1970 to 1979 are reviewed. Eighty-four axillofemoral (23 percent of patients), 210 aortofemoral (47 percent of patients), and 67 femorofemoral grafts (30 percent of patients) had cumulative patency rates of 72.1, 91.1, and 86.4 percent, respectively. Experimental and clinical factors influencing the patency of axillofemoral grafts are discussed, and the concept of an improved porous Dacron prosthesis specific for the axillofemoral site is presented.

Pneumopericardium and pneumomediastinum in infants and children

Abstract The increasing use of continuous positive airway pressure (CPAP), and positive end-expiratory pressure (PEEP) in the treatment of pulmonary insufficiency is associated with an increased frequency of pneumothorax, pneumomediastinum, and pneumopericardium in children. While the clinical implications and treatment of pneumothorax are well documented, the treatment of pneumomediastinum and pneumopericardium in the presence of continuing elevated airway pressures is not. In the presence of continuing positive-pressure ventilation in the newborn compression of the heart and great veins, sudden bradycardia, and loss of blood pressure lead to a fatal outcome unless the pericardium is decompressed. In older patients, routine palpation for subcutaneous emphysema aids in early diagnosis. When positive-pressure ventilation is needed to sustain life, early measures to decompress the trapped air are necessary.

A Five-to Seven-Year Experience with Externally-Supported Dacron Prostheses in Axillofemoral and Femoropopliteal Bypass

We have examined the clinical results of 56 externally-supported (EXS) Dacron grafts in the axillofemoral position and 117 in the femoropopliteal position. Results have been analyzed from two perspectives: primary patency concerns only those grafts that had never occluded; extended patency refers to all open grafts including those whose continued patency is the result of thrombectomy. The 5-to 7-year life-table patency rates are: axillofemoral 8 mm and 6 mm bypass: primary 75% and extended 97%; above-knee femoropopliteal 6 mm bypass: primary 78% and extended 93%; below-knee 6 mm femoropopliteal bypass: primary 41% and extended 91%. In contrast, the results for the 5 mm grafts used for femoropopliteal bypass were inferior to the 6 mm grafts: femoropopliteal 5 mm bypasses had an above-knee primary patency rate of 44% and an extended rate of 55%, with a below-knee primary patency rate of 15% and an extended rate of 32%. Rendering the noncrimped porous Dacron prosthesis kink and compression resistant by an external support coil appears to increase its potential for successful use, especially in 8 mm axillofemoral and 6 mm femoropopliteal bypasses.

Platelet Adherence in Endothelial Cell Cultures

Platelet adherence in bovine endothelial cultures was studied by scanning and transmission electron microscopy. Following incubation with platelet-rich plasma (PRP), platelet adherence to endothelial cell surfaces was rare as compared to similarly-tested fibroblasts which displayed numerous adherent platelets. When endothelial cells were induced to retract from their substrate by exposure to cold or versene and then incubated with PRP, platelets were observed adhering to endothelial cell processes and to an extracellular microfilamentous network, located beneath the cell. Platelets were attached singly, retained their discoidal shape, and showed no evidence of granule release. In contrast, microfilaments and adherent platelets were conspicuously absent in endothelial cultures which were retracted with trypsin or collagenase and incubated with PRP. These preliminary results suggest that the observed interaction between platelets and the subcellular surface of cultured endothelial cells is specific for an extracellular network of microfilaments produced by the cells.

A healable filamentous Dacron surgical fabric. Experimental studies and clinical experience.

A strong, lightweight, highly compliant Dacron surgical fabric of warp-knit, velour construction has been developed as an outgrowth of research on filamentous tubular vascular prostheses. This material has excellent suturability and conformability, high preclotting efficiency, and is imprinted with calibration marks at 2 cm intervals. Experimentally, iliac artery and descending thoracic aorta patch grafts of this material were completely healed 28 days after implantation in dogs. Light and electron microscopy showed excellent healing. This paper reports clinical results of 119 patches implanted in 109 patients who have been followed for a mean of 26.4 months (range: 16--34 months). Of these, 20 patches were used in arterial reconstructions, and 99 were used in the heart for repair of 95 congenital and four acquired defects. The 20 patch angioplasties were performed in the carotid artery (four patches), subclavian artery, (one patch), common femoral artery, profunda femoris artery, or superficial femoral artery (10 patches), and in the popliteal artery (five patches). This new surgical fabric is easily adaptable to complex angioplasties and for repair of intracardiac abnormalities. No complications intrinsic to the surgical fabric have been observed in clinical use of this material in 109 patients.