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Biomedical subjects

J W Hammon

Publications and source records attributed to J W Hammon.

At least 73 records · Page 4Linked to original sources
PubMed1988

Surgical treatment of acute traumatic tear of the thoracic aorta.

Acute traumatic tear of the thoracic aorta is a severe injury with a high mortality rate. This condition requires expeditious evaluation and prompt surgical intervention in order to improve patient survival. The experience at the authors' institution from 1971 to 1987 includes 41 patients who sustained acute traumatic tear of the thoracic aorta and reached the hospital alive. The purpose of the study was to evaluate the surgical management of this injury with regards to mortality rate and the incidence of spinal cord injury. Five patients died from exsanguination before definitive repair could be undertaken. Thirty-six patients had repair of traumatic aortic tear in the area of the isthmus. Nine patients were operated upon with the clamp and sew technique, 20 patients had a heparin-bonded shunt placed, and seven patients were treated by repair with cardiopulmonary bypass. There were five operative deaths that were not related to the technique employed. Two patients without preoperative evidence of spinal cord injury developed paraparesis. No patient had postoperative paraplegia. Despite rapid transport, expeditious evaluation, and emergency thoracotomy, some patients die from exsanguination prior to definitive repair. Even with the provision of distal aortic perfusion during clamping, the risk of spinal cord injury is not eliminated.

Adolescent↗
PubMed1987

Intermittent reperfusion extends myocardial preservation for transplantation.

A protocol was developed to compare prolonged heart preservation by hypothermic storage with prolonged hypothermic storage interrupted by a period of reperfusion. Hearts from adult mongrel dogs were excised after administration of 4 degrees C crystalloid cardioplegia. Group A hearts (N = 7) underwent 7.5 hours of ischemia at 4 degrees C followed by 1.5 hours of reperfusion and rewarming (A0). Group B hearts (N = 8) underwent 3 hours of ischemia at 4 degrees C, 1.5 hours of reperfusion and rewarming (B1), 3 additional hours of ischemia at 4 degrees C following repeat cardioplegia, and finally 1.5 hours of reperfusion and rewarming (B2). During reperfusion, hearts were defibrillated and left ventricular (LV) function was assessed by measuring isovolumic peak systolic pressure and maximum positive rate of rise of LV pressure (+dP/dtmax) with an intraventricular balloon. LV biopsy samples for adenosine triphosphate (ATP) assay were obtained before ischemia and after each rewarming period. One Group A heart could not be defibrillated and studied. All Group B hearts completed the protocol. LV function, as assessed by peak pressure and +dP/dtmax, at B1 and B2 exceeded values obtained at A0, but the differences were not statistically significant. The mean ATP level was 63.4 +/- 7.7% of baseline at B1 and 79.7 +/- 4.3% of baseline at B2 (p less than .03). The mean ATP level was 57.9 +/- 5.9% of baseline at A0 (p less than .007, B2 vs. A0). It is presumed that intermittent reperfusion allows repletion of substrate stores, which results in improved myocardial protection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1987

Myocardial adenosine triphosphate content as a measure of metabolic and functional myocardial protection in children undergoing cardiac operation.

In an effort to quantitate the metabolic and functional response to global myocardial ischemia as a prelude to specific interventions to improve myocardial protection in children, the following data were collected. Twenty children (age, 1.16 +/- 0.3 years) underwent repair of congenital intracardiac malformations using aortic cross-clamping and cold potassium cardioplegia (ischemic time, 56.1 +/- 4.5 minutes). Metabolic protection was assessed by measuring the myocardial adenosine triphosphate (ATP) content by microbioluminescence. Before and after ischemia 10-mg myocardial samples were obtained from the left ventricular apex using a Tru-cut biopsy needle. In 15 patients, postoperative ventricular function was measured by radionuclide ventriculography at 72 to 96 hours following operation. Five of 6 patients with a postischemic ATP level less than 40% of control (26.3 +/- 2.8) had a left ventricular ejection fraction (EF) lower than 55% (50.3 +/- 2.3). Seven of 9 patients with an ATP level greater than 40% of the preischemic level (98.0 +/- 14.4) had a normal EF (61.8 +/- 2.9; p less than 0.04). Two other patients with postischemic ATP levels lower than 40% of control died of low cardiac output and had no postoperative ventricular function studies. Thus, of 7 patients with postischemic ATP levels lower than 40% of preischemic levels, 2 died and 5 had depressed left ventricular function. These data support the concept that low postischemic ATP levels correlate with death or poor postoperative ventricular function, and indicate that this variable will be useful to assess future improvements in myocardial protection during pediatric cardiac operations.

Adenosine Triphosphate↗
PubMed1987

Surgical treatment of pediatric cardiac arrhythmia.

The combination of improved diagnostic techniques, new and potent antiarrhythmia agents, and progress in antiarrhythmia surgical procedures has resulted in successful management of complex cardiac arrhythmia in children. The kinds of arrhythmia that can be considered for possible surgical intervention share several features. Each produces symptoms and usually is hemodynamically compromising. Each requires extensive preoperative and intraoperative electrophysiologic evaluation to establish the mechanism, response to drugs, and suitability for surgery. Although reports of surgical arrhythmia treatment have been limited in children, with increasing success the indications for such treatment may become less stringent. Our recommendations are shown in the Table. In general, patients intolerant of or unresponsive to medical treatment for symptomatic arrhythmia (tachycardia or bradycardia), should be considered candidates for surgical antiarrhythmia procedures. These patients should be referred for testing to cardiac centers staffed by pediatric cardiac electrophysiologists and surgeons experienced in arrhythmia diagnosis and ablation. Careful evaluation can identify those patients in whom surgical approaches are most appropriate. At present, surgical operations for selected, serious pediatric cardiac arrhythmias offer definitive and possibly curative treatment, and may be preferable to inadequate, poorly tolerated, or long-term medical therapy.

Adolescent↗
PubMed1987

Surgical intervention in neonates with critical pulmonary stenosis.

The surgical experience with 18 consecutive neonates with critical pulmonary stenosis (PS) and intact ventricular septum was reviewed. All patients had cardiac catheterization with calculation of right ventricular volume. Group A patients (N = 8) had a small right ventricular end-diastolic volume (RVEDV less than 72% of predicted). Group B patients (N = 10) had a normal or enlarged RVEDV. All patients had a closed pulmonary valvotomy. Five Group A patients required a systemic-pulmonary shunt or prostaglandin (PGE1) after operation; one patient died. Nine Group B patients did well after valvotomy; one moribund patient died after valvotomy and shunt. Six of 16 survivors required reoperation: valvectomy in four patients and shunt takedown in two patients. Four of the six patients who had reoperation also had a transannular patch. There was one unrelated late death. All long-term survivors are asymptomatic. Recatheterization in four patients with a small right ventricle (RV) documented significant RV growth. In conclusion, most neonates with critical PS can be managed with closed valvotomy. Patients with a small RV may require PGE1 or a shunt after operation for persistent hypoxemia. Some patients with a small RV will have significant RV growth after valvotomy.

Heart Defects, Congenital↗
PubMed1987

Excisional surgery for patients with ventricular tachyarrhythmias.

Thirty-eight patients with drug refractory ventricular tachycardia have been operated on since 1980. An attempt at preoperative localization of the site of arrhythmia was made in those patients who did not have severe ischemia or multifocal tachycardia. Operation consisted of intraoperative mapping, when feasible, subendocardial resection and cryolesions placed when sites of interest could not be resected. Patients averaged 56 +/- 44 years of age and 25 had associated coronary bypass. The operative mortality was 5/38 (13%) and two deaths were related to recurrent arrhythmia. Of 33 survivors, 21 (64%) were cured of their arrhythmia and an additional nine patients who had been drug refractory were controlled with medication alone. The best results were found in patients with anteroapical scar and unifocal tachycardia. Thus, direct operation for drug refractory ventricular tachycardia can be performed at a reasonable risk and with a high likelihood of successful arrhythmia control.

Aged↗
PubMed1986

Prostacyclin reduction of regional ischemic injury in the canine myocardium.

The effect of prostacyclin (PGI2) on the myocardium of the awake dog subjected to coronary artery occlusion was examined. Animals were randomly administered PGI2 200 ng/kg/min (n = 6), PGI2 100 ng/kg/min (n = 6), or the vehicle control (n = 6), beginning 30 min prior to coronary artery occlusion. Radiolabeled microspheres (15 microns) were used to measure myocardial blood flow. The myocardial region at risk was determined by fluorescein injection, and infarct size was assessed by triphenyl tetrazolium staining. Segmental myocardial function was evaluated from the systolic ejection shortening (SES) by subendocardial ultrasonic dimension crystals in normal, ischemic, and border zones. PGI2 200 ng/kg/min produced significant decreases in aortic pressure and systemic vascular resistance. PGI2 100 ng/kg/min, which achieves 95% platelet inhibition, had no significant hemodynamic effects. Animals receiving PGI2 200 ng/kg/min had significantly higher blood flow to the ischemic region, better border zones SES, and a smaller infarct. PGI2 ameliorates myocardial injury and reduces functional impairment produced by ischemia in doses that elicit vasodilation. This beneficial effect of PGI2 does not appear to be mediated solely by an antiplatelet mechanism.

Animals↗
PubMed1986

Cardiac surgery in patients with chronic renal disease.

The combination of chronic renal failure and cardiovascular disease is identified frequently and results in high morbidity and mortality without appropriate medical and surgical therapy. Experience during the last eighteen years has shown that cardiac operations can be undertaken in this high-risk group with acceptable morbidity and mortality and with reasonable expectation of symptomatic improvement. In a six-year period, 17 patients with chronic renal disease underwent cardiac procedures at the Vanderbilt University Affiliated Hospitals. Ten patients were on long-term hemodialysis, and 7 had a functioning renal transplant. Thirteen patients had a coronary artery bypass procedure alone, 1 had a bypass procedure plus aortic valve replacement, 1 had a bypass procedure plus repair of the mitral valve, 1 had a bypass procedure and resection of a left ventricular aneurysm, and 1 had aortic valve and mitral valve replacement for endocarditis. Sixteen patients survived and were discharged. The hospital stay was shorter for patients with a renal transplant than for those on hemodialysis (mean, 11 days versus 22 days, respectively), and perioperative complications were less frequent in the transplant group. There has been 1 late death unrelated to the operative procedure. Fifteen long-term survivors have been followed a mean of 26 months (range 7 to 108 months). All have achieved symptomatic improvement and are in New York Heart Association Functional Class I or II. These results in this high-risk patient group provide a basis for cautious optimism and for a continued aggressive approach in patients with chronic renal disease who require cardiac operation.

Adult↗
PubMed1986

Free radical scavengers and myocardial preservation during transplantation.

The efficacy of oxygen radical scavengers in preservation of left ventricular (LV) function after prolonged hypothermic global ischemia was investigated in a model of orthotopic cardiac transplantation in sheep. Group 1 hearts (N = 8) received hypothermic crystalloid cardioplegic solution, and were harvested and stored at 4 degrees C in balanced electrolyte solution for six hours prior to transplantation. Group 2 (N = 9) received identical treatment with the addition of 30,000 units of superoxide dismutase to the cardioplegic solution and the administration of 60,000 units of superoxide dismutase coincident with reperfusion. All animals were weaned from cardiopulmonary bypass. Preischemic and postischemic LV function was determined using sonomicrometry and a micromanometer-tipped LV catheter. Coronary blood flow was determined using standard microsphere techniques, and platelet deposition was assayed with autologous platelets labeled with indium 111. Lipid peroxidation products were measured using thiobarbituric acid assay. LV performance was significantly better (p less than .05) in Group 2 hearts when assessed by the slope of the end-systolic pressure-volume relationship and the stroke work versus end-diastolic volume relationship. There was better preservation of endocardial blood flow in the group receiving superoxide dismutase compared with controls (p less than .05). Platelet deposition, as determined by the tissue to blood ratio of scintigraphic counts, was greater (p less than .05) in controls compared with the group receiving superoxide dismutase. In addition, thiobarbituric acid reactive species were significantly less (p less than .05) in Group 2 versus Group 1 hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Repair of interrupted aortic arch and associated malformations in infancy: indications for complete or partial repair.

There is uncertainty regarding the best method of repair of interrupted aortic arch. The question is whether to perform primary definitive repair of this anomaly plus the associated defects versus arch repair only and palliation of the intracardiac defects, usually by pulmonary artery banding. Since 1976, 16 infants with interrupted aortic arch have been treated surgically. They were seen at 5.2 +/- 3 days of age and weighed 3.2 +/- 0.7 kg. The interruption occurred between the left carotid and left subclavian arteries (type B) in 9 and between the left subclavian artery and the descending aorta in 7 (type A). Isolated ventricular septal defect (VSD) was the only associated anomaly in 7 and aortopulmonary window, in 4. Two patients had truncus arteriosus type 1. Three had transposition of the great arteries: 1 with VSD and 2 with single ventricle. Prior to 1980, our policy was to palliate all patients. Between 1976 and 1980, 4 infants underwent left thoracotomy with arch repair plus pulmonary artery banding (3, VSD; 7, transposition of the great vessels and single ventricle) with only 1 (25%) survivor. Because of this high mortality, 8 patients with interrupted aortic arch and VSD or aortopulmonary window, seen since 1980, received complete repair with median sternotomy, end-to-end arch anastomosis, and closure of the VSD or aortopulmonary window utilizing profound hypothermia and circulatory arrest. All 8 survived.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta, Thoracic↗
PubMed1986

Surgical management of patients with pulmonary valve dysplasia.

Pulmonary valve dysplasia is a distinct pathological entity consisting of markedly thickened, deformed, and largely immobile pulmonary valve leaflets. The clinical features and surgical management of 21 consecutive patients operated upon between 1975 and 1985 were reviewed. Mean age at operation was 26.7 months (range: 1 month to 9.5 years). Initial surgical intervention in 3 patients consisted of closed valvotomy or systemic pulmonary artery shunt. One of these patients subsequently had a partial pulmonary valvectomy; the other 2 had total valvectomy and pulmonary annuloplasty. Two patients had partial valvectomy as a primary procedure, and 1 has subsequently required total valvectomy and annuloplasty. Sixteen patients initially had total pulmonary valvectomy, 4 with a simultaneous transannular outflow tract patch. One patient subsequently required a transannular outflow tract patch. Therefore, definitive repair consisted of partial valvectomy in 2 patients, total valvectomy in 19, and a transannular outflow tract patch in 9 patients with a hypoplastic pulmonary annulus. There were no operative deaths, and all patients are asymptomatic at a mean follow-up of 37.9 months. Five patients who underwent total valvectomy were catheterized postoperatively. The mean residual gradient was 25 mm Hg. Pulmonary valvectomy appears to provide both effective relief of stenosis and long-term asymptomatic status in patients with pulmonary valve dysplasia. Total excision of all valve leaflets is recommended. Careful consideration should be given to a simultaneous transannular outflow tract patch if the annulus is hypoplastic.

Child↗
PubMed1986

Indications for different modes of surgical therapy in medically refractory ventricular arrhythmias.

Fifty-one adult patients were referred for surgical treatment during the time period from July 1980 to November 1985. The average age was 59 +/- 6 years (19-70 years). All patients had symptomatic ventricular tachycardia that was refractory to standard or experimental drug therapy. On the basis of patient condition, site of arrhythmia, ventricular function, and extent of coronary disease, 21 patients were classed as good risk (GR) while 30 patients were thought to represent a poor surgical risk (PR). Thirty-two patients (15 GR, 17 PR) underwent electrophysiologic guided endocardial resection of arrhythmic foci. The hospital mortality was 12% (4/32), and two additional patients died late. All deaths were in poor risk patients. Recurrent arrhythmia was the primary cause of death in only one patient. Nineteen patients have required automatic internal cardioverter defibrillation (AICD) or chronic burst pacing (BP) with an implantable radiofrequency stimulator, with no operative mortality. AICD implantation was chosen for 13 drug refractory patients who were either poor surgical risk and/or had a tachycardia rate above 130 beats/minute with multiple scars or a multifocal tachycardia. Six additional patients who had tachycardia less than 130 beats/minute and whose arrhythmia could be safely terminated with BP had radiofrequency stimulator implantation. The one late death in this group was in a medically noncompliant patient. On the basis of this experience, we feel that map-guided endocardial resection should be offered to all good risk patients with a single scar and unifocal tachycardia who are refractory to medical treatment. This operation should be considered in all patients who have frequent, life-threatening attacks of tachycardia of any sort on maximum drug therapy. The remainder can be well managed with an AICD if their tachycardia rate is greater than 130 beats/minute or with BP using a radiofrequency stimulator.

Adult↗
PubMed1986

Interaction of platelets with the vessel wall in the pathophysiology of sudden cardiac death.

The occurrence of ventricular fibrillation after occlusion of the circumflex coronary artery in the conscious dog was examined as one preparation for sudden cardiac death arising from coronary artery disease. The incidence of ventricular fibrillation after after circumflex occlusion was reduced from 53% to 6% (p less than .01) by the infusion of prostacyclin in doses that do not alter cardiac output or peripheral resistance. This effect of prostacyclin led to the evaluation of two structurally different inhibitors of thromboxane synthase in this preparation; RO 22-4679 and U-63557A reduced ventricular fibrillation by 82% and 100%, respectively (p less than .05). The inhibition of ventricular fibrillation by U-63557A was abrogated by pretreatment with indomethacin, suggesting that a metabolite of the endoperoxide that accumulated during thromboxane synthase inhibition was responsible for the protection from ventricular fibrillation.

Animals↗
PubMed1985

Operative repair of coarctation of the aorta in infancy: results with and without ventricular septal defect.

Coarctation of the aorta (CA) presenting in infancy is a life-threatening condition, especially if associated with intracardiac left-to-right shunts. Between 1971 and 1980, 51 infants with symptomatic CA have been diagnosed and treated. Ventricular septal defect (VSD) was present in 18 patients and patent ductus arteriosus in 24. End-to-end repair was performed in 20 patients, 17 (85%) of whom were long-term survivors. Subclavian flap angioplasty repair was used in 28 patients, of whom 25 (89%) were long-term survivors. During long-term follow-up 6 patients (35%) who underwent end-to-end repair had recurrent CA, whereas only 3 patients (12%) who underwent subclavian flap angioplasty had recurrent CA (p less than 0.05). The mortality rate in patients with associated VSD was higher (4 of 18, 22%). Pulmonary trunk banding with subsequent VSD repair was associated with a better survival (13 of 14 patients, 90%) than when banding was not performed (2 of 5 patients) (p less than 0.05). These results suggest subclavian flap angioplasty is the preferred treatment for symptomatic CA occurring in infancy. Concomitant pulmonary trunk banding in patients with VSD can be performed with the expectation of a lower mortality at subsequent VSD repair.

Aortic Coarctation↗