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Biomedical subjects

J W Hammon

Publications and source records attributed to J W Hammon.

At least 55 records · Page 3Linked to original sources
PubMed1994

Extrapulmonary thoracic disease caused by Blastomyces dermatitidis.

A case of blastomycosis is reported involving the mediastinum and compromising the plexus brachialis. The pathology, pathophysiology, and treatment of this patient and of a previously reported patient are discussed and compared with the characteristics of extrapulmonary thoracic disease caused by histoplasmosis. Because of the favorable response of these patients to prolonged antifungal therapy, blastomycosis should be considered in the differential diagnosis of invasive extrapulmonary thoracic disease.

Adult↗
PubMed1993

Total anomalous pulmonary connection: then and now.

In their classic article "Total anomalous pulmonary venous drainage. Correction with cardiopulmonary bypass in 62 patients," Denton A. Cooley, MD, and associates defined the proper course of therapy for most patients with this lesion. This article was published in 1966 in the Journal of Thoracic and Cardiovascular Surgery. The text and illustrations in this signal publication have served as one of the guiding features for surgeons attempting operations on patients with these lesions since that time. This article reviews that publication and points out the marked similarities between the treatment practices at that time and those in use today.

Cardiopulmonary Bypass↗
PubMed1992

Steroid-eluting epicardial pacing leads in pediatric patients: encouraging early results.

OBJECTIVES: This study evaluated the pacing and sensing characteristics of a new porous-tipped steroid-eluting epicardial lead in a group of pediatric patients. BACKGROUND: Pacing in children may be complicated by small patient size, patient growth and the prevalence of structural congenital heart disease in children requiring pacing. Epicardial pacing has been associated with a high incidence of problems with sensing and capture, prompting the use of transvenous endocardial pacing when possible. In some children, epicardial pacing may still be desirable because of small patient size, potential for caval obstruction, previous cardiac surgery limiting transvenous access to the heart, or the need to repair congenital heart disease at the time of pacemaker insertion. METHODS: Twelve patients aged 3 weeks to 18 years underwent placement of 23 epicardial pacing leads (8 atrial, 15 ventricular). Pulse width thresholds, sensing thresholds and lead impedance were measured weekly for 6 weeks, then at 3, 6, 12 and 18 months after pacemaker implantation. The median duration of follow-up was 12 months. RESULTS: Ventricular pulse width thresholds did not change over time, whereas atrial pulse width thresholds improved significantly. At 6 months, the mean pulse width threshold at 2.5 V for the atrial and ventricular leads was 0.10 +/- 0.03 and 0.19 +/- 0.09 ms, respectively. The thresholds were slightly lower at 12 and 18 months. At the most recent follow-up, all atrial leads sensed appropriately at 2.5 mV and all ventricular leads at 5 mV. CONCLUSIONS: These encouraging early results suggest that steroid-eluting epicardial pacing leads may be an attractive option for children needing epicardial pacing. Their excellent pacing and sensing characteristics may allow reliable dual-chamber pacing in infants who are too small for transvenous pacing.

Cardiac Pacing, Artificial↗
PubMed1992

Response of the hypertrophied left ventricle to global ischemia. Comparison of hyperkalemic cardioplegic solution with and without verapamil.

The hypertrophied left ventricle is at considerably greater risk for injury when subjected to global ischemia than is an otherwise normal heart. We evaluated the efficacy of verapamil, a calcium-channel blocking agent, as an adjunct to standard crystalloid cardioplegic solution in animals with left ventricular hypertrophy subjected to myocardial ischemia during cardiopulmonary bypass. Infracoronary aortic stenosis was produced in 15 mongrel puppies by plication of the noncoronary cusp of the aortic valve. Studies were conducted 3 to 4 months later. Left ventricular catheter-tip pressure transducers and major and minor axis ultrasonic dimension crystals were inserted, and the animals were then supported by cardiopulmonary bypass with 30 minutes of normothermic ischemia. Animals were randomized to receive either standard hyperkalemic crystalloid cardioplegic solution (n = 8) or the same solution with verapamil, 0.1 mg/kg (n = 7). After the 30 minutes of ischemia, the animals were supported on cardiopulmonary bypass for an additional 30 minutes and then separated from bypass. They were then studied for another 2 hours by measurement of myocardial adenosine triphosphate content, myocardial blood flow, systolic function with use of the end-systolic pressure/volume ratio, and compliance with use of the natural strain coefficient of the minor axis at 15 mm Hg end-diastolic pressure. There was a better recovery of systolic function in the animals treated with verapamil (89.2% versus 63.3%). The compliance as measured with use of the minor axis natural strain coefficient returned essentially to baseline in the group of animals treated with verapamil (0.236 +/- 0.038 before ischemia and 0.254 +/- 0.043 2 hours after ischemia), but it fell markedly in the control animals (0.219 +/- 0.027 before ischemia and 0.153 +/- 0.016 2 hours after ischemia). Myocardial adenosine triphosphate levels were not significantly different at any time during the study. Likewise, myocardial blood flow was not significantly different between groups. We conclude that the addition of verapamil to hyperkalemic cardioplegic solution improves recovery of both systolic and diastolic function after global ischemia in dogs with left ventricular hypertrophy resulting from aortic stenosis. The precise mechanism for this is unknown.

Adenosine Triphosphate↗
PubMed1992

Twenty years' experience with pulmonary metastasectomy.

From January 1969 through December 1989, 63 patients had 69 operations for pulmonary metastases. Patients ranged in age from 1 to 75 years; there were 36 men and 27 women. Metastasectomy was accomplished through a thoracotomy incision in 59 cases (5 staged, bilateral), and median sternotomy was used in 10 instances. Wedge resection was performed in 54 patients, with segmentectomy in 2, lobectomy in 12, and pneumonectomy in 1. There were no operative deaths. Multiple metastases were present in 29 patients, and a single metastasis in 34. Follow-up ranges from 2 to 204 months (mean = 42 months). Thirty-eight patients remain alive; thirty are free of disease and eight have developed other metastases. Actuarial survival at 5, 10, and 15 years is 40 (CL [confidence limits] 49,31), 36 (CL 44,26), and 24 (CL 35,13) per cent, respectively. Mean actuarial survival is 84 months, and median survival is 58 months. There is no difference in survival whether metastases were single or multiple. Survival is significantly less in groups with primary sarcoma and melanoma (P = .012). While pulmonary metastases may be a manifestation of terminal disease, metastasectomy has an important role in the multidisciplinary management of selected patients when metastatic disease is confined to the lung. Prolonged survival may be achieved in many patients.

Actuarial Analysis↗
PubMed1991

Complete repair of atrioventricular septal defect.

We report our experience with 103 consecutive children who underwent repair of complete atrioventricular septal defect between 1971 and 1990. Ninety-one patients were less than 18 months old (mean age, 6.2 months; mean weight, 5.8 kg) and were repaired using deep hypothermia and circulatory arrest. There were 15 perioperative deaths. Twelve patients were older (mean age, 40.2 months; mean weight, 18.9 kg) and were repaired using moderate hypothermia and cardiopulmonary bypass. There were two perioperative deaths. Repairs were performed with the single-patch technique. Four younger patients required repeat repair to control residual mitral regurgitation. Two of the older children required late reoperation to replace one or both atrioventricular valves. Three younger children underwent pulmonary artery banding initially; 1 died after complete repair. Three older children underwent initial pulmonary artery banding; 2 died at definitive repair, and the survivor required pulmonary artery reconstruction, which was repeated subsequently. Since 1977 our policy has been to perform primary definitive repair whenever possible. Two patients died late from unrelated causes. At the most recent follow-up the majority of patients had no or minimal symptoms. We continue to advocate primary definitive repair whenever possible using the single-patch technique in symptomatic patients with complete atrioventricular septal defect.

Cardiac Catheterization↗
PubMed1991

Attenuation of the pulmonary vascular response to endotoxin by a thromboxane synthesis inhibitor (UK-38485) in unanesthetized sheep.

Previous studies have documented the phasic pulmonary vascular response to infused Escherichia coli endotoxin in unanesthetized sheep. Cyclooxygenase inhibition attenuates the initial vasoconstrictive phase (phase I) but not the late phase of increased microvascular permeability (phase II). We undertook to selectively inhibit thromboxane A2 synthesis and assess the pulmonary microvascular response to endotoxin. Twelve paired studies were carried out in six sheep prepared with chronic lung lymph fistulas and pressure monitoring catheters. Each sheep received E. coli endotoxin (0.5 microgram/kg) at time 0, both alone (control group) and 1 hr after pretreatment with a thromboxane synthetase inhibitor (UK-38485, 2 mg/kg). The animals were monitored for 1-2 hr prior to and 5 hr following endotoxin infusion to ensure a steady-state baseline and a complete late response. The pairs of studies were done in random order. In the presence of UK-38485, endotoxin caused significantly less pulmonary hypertension and shorter duration of leukopenia and lower lung lymph flow and lymph protein clearance rates than did endotoxin alone. The differences in lymph protein clearance were more pronounced in phase II. These data suggest that both the vasoconstrictive and permeability phases of the pulmonary vascular response to endotoxin may be modified on endogenous thromboxane A2.

Animals↗
PubMed1991

Origin of cardiac-related thoracic electrical impedance variations in lambs.

Cardiac-related deflections in thoracic electrical impedance have been thought to correlate sufficiently well with cardiac stroke volume to be used as the basis for a noninvasive estimation of cardiac output. To determine more precisely the physiological origin of the impedance deflection (DZ), we regarded right ventricular stroke volume (SVa) as the sum of two components: 1) that part of SVa responsible for the transient increment in pulmonary blood volume within a cardiac cycle, SVa-v and 2) the remaining part of SVa, (SVa-SVa-v). SVa-v was measured in lambs by integration of the difference between pulmonary arterial and pulmonary venous flow. SVa and its components were varied experimentally by opening and closing an aorticocaval shunt or by inflating and deflating a cuff implanted around the pulmonary artery. DZ was measured using a tetrapolar disk electrode system. Multivariate linear regression analysis revealed that SVa-v had a significant positive effect on DZ, and, at the same time, (SVa-SVa-v) had a significant negative effect on DZ. In the pulmonary artery occluder model, the positive effect of SVa-v dominated the opposing negative effect of (SVa - SVa-v) so that the net effect of SVa on DZ was positive and significant. In the aorticocaval shunt model, these effects opposed each other to the extent that there was no significant correlation between SVa and DZ. These results shed new light on the physiological origin of DZ. They also demonstrate that use of DZ to measure acute changes in cardiac output may yield misleading results. Changes or the lack of changes in thoracic electrical impedance do not necessarily reflect cardiac output status.

Animals↗
PubMed1990

Reappraisal of localized resection for subvalvar aortic stenosis.

Between June 1972 and August 1989, we operated on 45 patients with fixed subaortic stenosis. Discrete membranous stenosis was present in 28 patients and tunnel stenosis, in 13. Four patients had subvalvar stenosis complicating double-outlet right ventricle. There were 33 male and 12 female patients. Mean age at operation was 7.1 +/- 4.3 years (range, 6 months to 21 years). Local resection of the fibrous membrane was performed in 26 patients. Local resection was combined with myectomy in 18 patients. Aortoventriculoplasty (modified Konno procedure) was required at operation in 3 patients. There were three perioperative deaths at initial operation and two deaths at the time of reoperation. Follow-up ranges from 1 month to 17 years (average follow-up, 47.0 months). Reoperation for recurrent obstruction has been required in 12 patients (27%), and 3 patients have required a second reoperation. Mild to moderate aortic regurgitation was present in 17 patients. Subaortic stenosis is a spectrum of anatomical derangements ranging from a discrete fibrous membrane to a long, tortuous fibrous tunnel with aortic annulus hypoplasia. Successful removal of a discrete fibrous membrane can be followed later by recurrent stenosis necessitating myectomy or aortoventriculoplasty. Correction of subvalvar aortic stenosis can be followed by recurrent stenosis necessitating reoperation as long as 17 years after the initial procedure.

Cardiomyopathy, Hypertrophic↗
PubMed1990

Cardiac surgery in patients age 80 years or older.

Between February 1978 and August 1989, forty patients aged 80 years or older underwent cardiac surgery at this institution. Patient age varied from 80 to 87 years (mean, 82.4 years). Operative indications were angina pectoris or congestive heart failure. Twenty-eight patients underwent coronary artery bypass (CAB) alone and 12 underwent valve replacement(s) with or without CAB. The operative mortality rate was 10%. Postoperative hospitalization averaged 14 days. There were three late cardiac deaths at 13, 36, and 48 months after operation and one late noncardiac death. Thirty-two survivors have been followed from 1 to 86 months (mean, 20 months). All experienced sustained improvement in functional status and minimal late morbidity. All survivors remained in NYHA class 1 or 2. Cardiac surgical procedures in patients older than 80 years can be performed with increased but acceptable mortality and morbidity rates. Most patients achieve sustained symptomatic improvement and excellent long-term survival.

Aged↗
PubMed1989

Absence of left ventricular volume loading in infants with coarctation of the aorta and a large ventricular septal defect.

Clinical characteristics and angiographic ventricular volume data were obtained in 25 infants aged 1 to 66 days who presented with coarctation of the aorta, ventricular septal defect and congestive heart failure to determine if left ventricular volume loading was present and if there were hemodynamic or volumetric variables that were predictive of operative mortality in this group. Pulmonary to systemic flow ratio averaged 2.8 +/- 0.8 and right ventricular/left ventricular peak pressure ratio was 0.96 +/- 0.12. Left ventricular end-diastolic volume averaged 116 +/- 49% of normal and was less than the investigators' lower limit of normal in 5 (20%) of 25 patients. In contrast, right ventricular end-diastolic volume, measured in eight patients, averaged 173 +/- 47% of normal and was greater than the investigators' upper limit of normal in seven (88%) of eight. Left ventricular ejection fraction averaged 0.47 +/- 0.17 and was below normal (less than 0.55) in 14 (58%) of 24 patients. Preoperative volume and ejection fraction data did not differ in infants with coarctation plus ventricular septal defect and a similar group of 19 infants with isolated coarctation. Abnormal left ventricular operative volume distensibility was inferred by normal or decreased left ventricular end-diastolic volume and increased left ventricular end-diastolic pressure (greater than 12 mm Hg) in 12 (55%) of 24 patients. Early plus late mortality was related to left ventricular size: 3 of 5 patients with a small left ventricular end-diastolic volume died, compared with only 4 of 20 with a normal or increased volume (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Multiple↗
PubMed1989

Ten years' experience with the Senning operation for transposition of the great arteries: physiological results and late follow-up.

We report our results in 93 consecutive infants and children who underwent atrial repair of simple transposition of the great arteries using the Senning operation between February 1978 and February 1988. Mean age at operation was 5.6 +/- 6.3 months (range, 1 week to 4 years); 60 were less than 6 months old. There were 65 boys and 28 girls. Operative mortality was 5.4%, and there has been 1 late death. Average follow-up is 45.1 months with 39 followed more than 3 years and 25 followed more than 5 years. Postoperative cardiac catheterization was performed in 43 patients. Right ventricular ejection fraction at rest averaged 0.50 +/- 0.09 and was normal in 26 patients. Response of right ventricular ejection fraction to afterload stress was abnormal in 12 of 14 patients tested. Right ventricular ejection fraction increased normally during exercise in 6 patients, but was abnormal in 15. Mild tricuspid regurgitation was noted in 10 patients. Mild obstruction of the superior vena cava was noted in 4 patients. Baffle leak requiring reoperation occurred in 1 patient. Seventy-two of 80 patients are in sinus rhythm by latest electrocardiogram. Postoperative electrophysiological studies were performed in 34 patients and Holter monitoring was performed in 22. A major arrhythmia occurred in 8 patients: 3 required a pacemaker for junctional rhythm or sinus node dysfunction, 2 have symptomatic or inducible supraventricular tachycardia, 2 have junctional rhythm, and 1 has sick sinus syndrome. Eight additional patients have delayed sinus node recovery time. At last follow-up, 78 children (97.5%) are in New York Heart Association functional class I, and 2 (2.5%) are in class II.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1989

Increased plasma oncotic pressure inhibits pulmonary fluid transport when pulmonary pressures are elevated.

Hydrostatic and oncotic pressures are the primary determinants of fluid movement across the pulmonary vascular membrane. The precise role of oncotic pressure in regulating transvascular fluid exchange especially when hydrostatic pressure is high is not known. Awake, adult sheep were instrumented for pressure monitoring and the collection of pulmonary lymph. A left atrial (LA) balloon catheter was utilized to control LA pressure. Statistically significant increases in lymph protein flux were seen with infusion of saline and elevated pulmonary microvascular pressure (Pmv) over elevated Pmv alone (15.3 +/- 1.23 versus 11.2 +/- 1.09 mg/min) concomitant with a decrease in plasma colloid oncotic pressure (COP) (14.9 +/- 0.5 versus 16.9 +/- 0.5 mm/Hg). The protein flux seen with elevated Pmv and saline infusion was blunted when plasma was infused (13.8 +/- 1.58 mg/min) and the plasma COP augmented (18.1 +/- 0.05 mg Hg) but was not statistically different. We conclude that under conditions of stable membrane permeability and elevated Pmv, the plasma COP appears to be an important mechanism for protection against pulmonary edema.

Animals↗
PubMed1989

Pharmacokinetics of superoxide dismutase during hypothermic cardiopulmonary bypass.

We evaluated the plasma elimination of recombinant human superoxide dismutase (rHSOD) when given before reperfusion in an experimental canine model of global hypothermic myocardial ischemia. Adult mongrel dogs were placed on cardiopulmonary bypass, and core temperature was reduced to 25 degrees C. Hypothermic global myocardial ischemia was maintained for 90 minutes with intermittent crystalloid cardioplegic solution. Five minutes before reperfusion, rHSOD was administered via the pump oxygenator as a bolus injection. Plasma rHSOD levels were measured at 0, 3, 5, 10, 20, 30, 60, and 120 minutes after injection. Animals were rewarmed and weaned from bypass. Three experimental groups received either 4, 8, or 16 mg/kg rHSOD. Based on previously reported dose-response data, we conclude that desirable peak serum concentrations are achieved with 16 mg/kg rHSOD. In the setting of hypothermic cardiopulmonary bypass and global myocardial ischemia, single bolus administration of rHSOD before reperfusion is an effective method due to the prolonged serum half-life.

Animals↗
PubMed1988

Predictors of operative mortality in critical valvular aortic stenosis presenting in infancy.

Congenital aortic stenosis presenting within the first 6 months of life is a highly lethal anomaly. Although aortic valvotomy has offered excellent palliation in many instances, the operative risk remains substantial. To better understand the factors associated with a poor operative result, the records of all patients less than 6 months of age undergoing aortic valvotomy at our institution from 1972 through 1986 were analyzed. Nineteen patients (58%) (Group I) survived operation; 14 (42%) (Group II) died. The following variables were analyzed in an attempt to define those with prognostic significance: mean pulmonary artery pressure (PAP), left ventricular (LV) peak systolic pressure, LV end-diastolic pressure, peak systolic aortic valve gradient, LV end-diastolic volume (LVEDV), LV ejection fraction, and age at operation. The only variables that were significantly different in the two groups were mean PA (Group I, 29 +/- 3 mm Hg, and Group II, 54 +/- 3 mm Hg; p less than 0.001) and LVEDV (Group I, 50 +/- 8 ml/m2, and Group II, 20 +/- 4 ml/m2; p less than 0.05). No patient with an LVEDV of 20 ml/m2 or less survived operation. We conclude that small LV dimension and elevation of PAP may be predictive of a poor surgical result in patients with severe aortic stenosis presenting in infancy.

Actuarial Analysis↗