Effects of a single administration of fibroblast growth factor on vascular wall reaction to injury.

Expansion of the vascular wall through formation of neointimal fibromuscular lesions is the basic mechanism underlying stenosis of vascular grafts, restenosis of arteries treated by balloon angioplasty, and other major cardiovascular problems. This study examined the effect of a single, systemic, low dose of basic fibroblast growth factor (bFGF) on formation of neointimal fibromuscular lesions in response to injury. New Zealand white rabbits (n = 76) were subjected to balloon injury of the abdominal aorta. Forty-five rabbits were given a single intravenous dose of bFGF (0.5 microgram/kg) immediately after injury, and 31 rabbits were given only the vehicle solution as controls. After 2 (n = 15), 5 (n = 21), 14 (n = 29), or 28 (n = 11) days the rabbits were sacrificed. Those rabbits receiving the single administration of bFGF exhibited significantly greater intimal thickening (intima/media ratio) than the control group at 5 days (mean +/- standard error of the mean, 0.091 +/- 0.009 versus 0.058 +/- 0.006; p < 0.002), but not at 14 or 28 days. These results were achieved without any significant differences in mitotic indices, as determined by a mitostatic method, between the two groups at any postinjury interval examined. The findings suggest that a single systemic dose of exogenous bFGF has a relatively long term effect on enhancing the neointimal response to vascular injury. Therefore, local control of endogenous bFGF may be useful in limiting formation of vascular neointimal fibromuscular lesions, thus improving the long-term results of vascular grafts, balloon angioplasty, and other cardiovascular procedures.

Resuscitative retrograde blood cardioplegia. Are amino acids or continuous warm techniques necessary?

This experiment was designed to determine the relative degree of cardiac functional recovery provided by various forms of resuscitative retrograde blood cardioplegia after global ischemic injury. Twenty-four dogs were subjected to 20 minutes of normothermic global myocardial ischemia followed by 60 minutes of cardioplegic arrest by one of three methods: group 1, standard cold blood cardioplegia with a cold terminal dose (n = 8); group 2, aspartate-glutamate-enhanced blood cardioplegia with warm induction and terminal enhancement (n = 8); and group 3, continuous warm blood cardioplegia (n = 8). Sonomicrometry was used to analyze left ventricular function for maximal elastance and preload recruitable stroke work area. Data were recorded at baseline and after 30 and 60 minutes of unloaded reperfusion. The results showed improved early recovery of preload recruitable stroke work area, but not of maximal elastance, after reperfusion of ischemic hearts with warm resuscitative blood cardioplegic solution enhanced with amino acids. The functional improvement provided by this technique was transient, however, and no significant differences were detectable among the groups after 60 minutes of unloaded reperfusion. Neither amino acid enhancement nor continuous warm cardioplegia offered a significant advantage in functional recovery over the standard method of cold blood cardioplegia reperfusion.

Direct-current injury from external pacemaker results in tissue electrolysis.

In two patients undergoing open heart operations, electrochemical burns developed at the sites of connection to an external pacing system. Investigation revealed that failure of the pacing generator caused a small, continuous, direct current to pass through the patients, resulting in electrolysis at the sites of contact with the pacing and grounding wires. This electrolytic reaction was recreated in a mock pacing system and resulted in tissue injury and disintegration of the pacing wire. Guidelines to help recognize and prevent this complication are presented.

Surgical repair of type A aortic dissection by the circulatory arrest-graft inclusion technique in sixty-six patients.

During an 8-year period (1984 to 1991) 66 patients (mean age 59 years, range 26 to 84 years) with type A aortic dissection (60 ascending aorta tears, 6 arch tears; 35 acute, 31 chronic) had surgical repair by a continuous suture-graft inclusion technique. Hypothermic circulatory arrest (16 degrees C) was used in 58 patients (35/35 acute, 23/31 chronic; mean arrest time 26 minutes, range 10 to 55 minutes). Fifty-two patients had hemiarch repair and 6 had total arch replacement. Aortic valve disease necessitated treatment in 38 patients (1 valved conduit, 20 valve replacements, 17 valve repairs). Recently 11 patients had valve repair by reconstruction of the native aortic root, by means of techniques similar to those used for homograft valve insertion. Operative mortality was 9% (14% acute, 3% chronic). Stroke occurred in 2 patients (3%) and was fatal in both. Variables suggestive of increased operative risk by univariate analysis were acuteness (p = 0.12), visceral ischemia (p = 0.12), and preoperative shock (p = 0.13). No variable was significant by multivariate analysis. Overall actuarial survival at 48 months was 77%, with 3 late deaths from a ruptured distal aneurysm. Late computed tomography or magnetic resonance imaging scan was done in 28 patients at a mean interval of 33 months. These studies identified 1 patient with a pseudoaneurysm requiring reoperation and 3 patients with contained flow between the graft and the wrap. Three patients required late operation: 1 for pseudoaneurysm, 1 for arch dissection, and 1 for repair of a distal aneurysm.

Differences in carotid shunt flow rates and implications for cerebral blood flow.

A wide variety of carotid shunts are available for use in extracranial carotid surgery. Since it is commonly assumed that when properly positioned all shunts are equal in ability to protect the brain from cerebral ischemia, the choice of shunt is usually based on handling characteristics. However, after an intraoperative stroke occurred in a patient, we compared shunt flow rates using a simple and reproducible method of measurement. A mock circuit was created using a saline-filled fluid reservoir connected to the particular shunt being tested via 1/2-inch tubing. Hydrostatic pressure across the shunt was varied by changing the height of the reservoir, and the flow was collected over 30-second intervals. Multiple flow rate measurements were performed for each shunt with pressure gradients varying from 25 to 150 cm H2O. The data show significant hemodynamic differences among commercially available carotid shunts. A pressure gradient of 75 cm H2O produced a 2.8-fold variation in the amount of fluid delivered by various shunts. Minimal cerebral blood flow requirements and the possibility of underperfusion require that the surgeon consider such data in choosing an appropriate carotid shunt.

The effects of different techniques of internal mammary artery harvesting on sternal blood flow.

We investigated chest wall blood flow in a canine model to determine if the technique used to harvest the mammary artery has a differential effect on residual chest wall blood flow. Eight dogs underwent bilateral internal mammary artery mobilization; one artery was harvested as a pedicle and the other was harvested as a skeletonized vessel. Residual blood flow to the chest wall distribution of each artery was measured with radioactive microspheres. Chest wall blood flow was significantly decreased from preharvest levels after internal mammary artery mobilization regardless of the technique used. Tissue blood flows decreased to 46.9%, 22.1%, and 41.2% of baseline values for the manubrium (p < 0.01), sternum (p < 0.001), and ribs (p < 0.05), respectively. Residual sternal blood flow on the side of the skeletonized vessel was significantly greater than on the side of the pedicle graft (2.60 +/- 0.68 versus 1.27 +/- 0.27 cm3/min/100 gm, p < 0.001). We conclude that minimization of tissue mobilization during internal mammary artery harvesting may reduce sternal devascularization. This finding may have clinical significance with respect to lowering the incidence of sternal wound complications in coronary bypass surgery using the internal mammary artery as a bypass conduit.

Experience with twenty-eight cases of systolic anterior motion after mitral valve reconstruction by the Carpentier technique.

Systolic anterior motion of the mitral valve with left ventricular outflow tract obstruction after Carpentier-type mitral reconstruction with ring annuloplasty has led some surgeons to abandon an otherwise successful repair or to avoid use of a rigid ring. To assess the long-term significance of such motion, we studied 439 patients undergoing Carpenter mitral reconstruction at our institution between March 1981 and June 1990. The hospital mortality rate was 4.8% (21/439) overall and 3.7% (9/243) for isolated mitral reconstruction. Systolic anterior motion was found in 6.4% (28/438) after the operation, and 2.3% (10/438) had a coexisting left ventricular outflow tract gradient (mean 53 mm Hg). Of the 28 patients with systolic anterior motion, 27 (96.4%) had leaflet prolapse, 17 (60.7%) had undergone more than a 3 cm resection of the posterior leaflet, and two (7.1%) had preexisting idiopathic hypertrophic subaortic stenosis. All patients were treated medically, 14 with negative inotropic agents. Follow-up echocardiograms at a mean of 32 months demonstrated the disappearance of systolic anterior motion in 13 of 28 patients (46.4%) and resolution of the outflow tract gradient in 10 of 10 (100%). At follow-up only one patient was in New York Heart Association class III or IV and required reoperation for rheumatic mitral insufficiency. These data demonstrate that systolic anterior motion after Carpentier mitral reconstruction with ring annuloplasty is not prevalent and should be managed medically in most cases. Associated left ventricular outflow tract obstruction resolves with medical treatment.