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Biomedical subjects

D W Hunter

Publications and source records attributed to D W Hunter.

At least 19 recordsLinked to original sources
PubMed1992

Changes in sequential coronary arteriograms and subsequent coronary events. Surgical Control of the Hyperlipidemias (POSCH) Group.

OBJECTIVE: Assessment of the relationship between changes in sequential coronary arteriograms and subsequent clinical coronary events. DESIGN: The Program on the Surgical Control of the Hyperlipidemias, a randomized secondary atherosclerosis intervention trial, obtained coronary arteriograms at baseline, 3, 5, and 7 or 10 years of follow-up. Assessments of changes between pairs of coronary arteriograms were made by two-member panels blinded to the patients' assigned treatment and to the temporal sequence of the films. The relationship of changes between the baseline and the 3-year follow-up arteriograms and subsequent clinical coronary events was examined. SETTING: Three university hospitals and one private primary care facility. PATIENTS: A total of 838 patients, with 417 patients randomized to the control group and 421 to the intervention group. Of all patients, 695 had baseline and 3-year arteriograms. INTERVENTION: The control group received American Heart Association Phase II diet instruction and the intervention group received identical dietary instruction plus a partial ileal bypass operation. MAIN OUTCOME MEASURE: The use of arteriographic changes as a predictor of subsequent clinical coronary events. RESULTS: Changes between the baseline and the 3-year coronary arteriographic overall disease assessment were significantly associated with subsequent overall and atherosclerotic coronary heart disease mortality (P less than .01). For the combined end point of atherosclerotic coronary heart disease mortality or confirmed nonfatal myocardial infarction, a significant relationship between the overall disease assessment and subsequent clinical events was found in the control group (P less than .0001) and in the surgery group (P = .04). For this combined end point, however, the control and the surgery groups were different with respect to clinical coronary events after 3 years, stratified by the baseline to 3-year overall disease assessment (P less than .001, unadjusted; P = .06, adjusted for 3-year clinical covariates). CONCLUSIONS: Coronary arteriographic changes can be used in atherosclerosis intervention trials as a limited surrogate end point for certain clinical coronary events. This relationship is statistically compelling for overall mortality and atherosclerotic coronary heart disease mortality. For an individual patient, changes in the severity of coronary atherosclerosis seen on sequential coronary arteriograms can serve as prognostic indicators for subsequent overall or atherosclerotic coronary heart disease mortality.

Adult↗
PubMed1992

Thrombolytic therapy for postoperative pulmonary embolism.

The use of thrombolytic agents in the treatment of postoperative pulmonary embolism presents a dilemma to the surgeon. On one hand, postoperative pulmonary embolism usually occurs within 2 weeks of surgery. On the other hand, recent surgery is considered a contraindication for the use of thrombolytics. We developed a protocol for treating pulmonary embolism patients who have recently undergone surgery. Urokinase, at a dose of 2,200 U/kg wt, is injected directly into the clot via a catheter positioned in the pulmonary artery. This is followed by continuous infusions of urokinase at 2,200 U/kg wt/hr until the clot is lysed (up to 24 hrs). Simultaneously, heparin is administered peripherally at 500 U/hr. The level of serum fibrinogen is monitored every 6 hours and maintained at no less than 0.2 g/dL to prevent bleeding. Thirteen patients were treated for angiographically proven pulmonary embolism within 14 days of surgery. Complete lysis of every embolus was achieved, and no deaths or bleeding complications occurred. Two patients received inferior vena cava filters, and nine patients no longer needed chronic anticoagulants within 3 months after the embolic event.

Adult↗
PubMed1992

Hemodynamic, left ventricular structural and hormonal changes after discrete myocardial damage in the dog.

Transmyocardial direct-current (DC) shock produces localized left ventricular myocardial necrosis without obstruction to coronary blood flow. In 43 dogs sequential measurements of hemodynamic, neuroendocrine and myocardial structural changes were made at baseline and for 16 weeks after DC shock. Six dogs (14%) died in the peri-shock period. By 1 week after shock, left ventricular mass, as measured by nuclear magnetic resonance imaging, had increased from a mean value +/- SD of 67.9 +/- 10.1 to 82.5 +/- 12.9 g (p = 0.0001). Left ventricular end-diastolic volume was unchanged at 1 week but increased at 16 weeks from 56.1 +/- 10.3 to 70.3 +/- 10.7 ml (p = 0.0003). Left ventricular mass demonstrated a further increase at 12 months (107.8 +/- 14.8 g). Rest cardiac output was significantly decreased at 4 months (3.67 +/- 1.23 to 3.18 +/- 0.81 liters/min, p less than 0.01) as was stroke volume (43 +/- 9 to 37 +/- 7 ml, p less than or equal to 0.01). Left ventricular ejection fraction decreased progressively from 73% to 38% at 1 year. At 4 months there were increases in mean pulmonary artery pressure (18 +/- 4 to 23 +/- 4 mm Hg, p less than 0.01), pulmonary capillary wedge pressure (9 +/- 3 to 15 +/- 3 mm Hg, p less than 0.01) and right atrial pressure (5 +/- 4 to 9 +/- 3 mm Hg, p less than 0.01). Plasma norepinephrine was increased at 4 months (318 +/- 190 to 523 +/- 221 pg/ml, p = 0.0003), whereas plasma renin activity was not significantly changed (4.3 +/- 2.6 vs. 5.2 +/- 3.4 ng/ml per h). Microsphere regional blood flow studies demonstrated a 50% reduction in skeletal muscle blood flow at 4 months (0.06 +/- 0.06 ml/min per g compared with 0.12 +/- 0.09 in normal dogs, p = 0.05), and a reduction in the endocardial/epicardial blood flow ratio (1.11 +/- 0.13 compared with 1.24 +/- 0.13 in normal dogs, p = 0.02). Therefore, in this model of acute left ventricular damage, left ventricular hypertrophy precedes progressive left ventricular dilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Pneumothorax after lung biopsy: prevention with transpleural placement of compressed collagen foam plugs.

The effectiveness of pleural sealing with a compressed collagen foam plug in preventing the development of pneumothorax was evaluated in a prospective, comparative study of 50 patients undergoing transthoracic needle biopsies. The 4-cm-long plug was deposited through the thin-walled guidance needle at the end of the procedure in a position where it would cross both the visceral and the parietal pleura. The prevalence of postbiopsy pneumothorax was 28% (seven of 25 patients) in the control group and 8% (two of 25 patients) in the plug group. In each study group, two patients with pneumothoraces required chest tubes. Although further experience is necessary, the authors conclude that transpleural collagen foam plug placement may be an effective supplement for transthoracic needle biopsies.

Biopsy, Needle↗
PubMed1992

Thoracic outlet syndrome: evaluation of the subclavian vessels by color duplex sonography.

Changes in flow in the subclavian artery and vein resulting from the use of a hyperabduction maneuver during Doppler sonography in 20 volunteers were compared with retrospective findings in 16 patients clinically suspected of having thoracic outlet syndrome. Significant compression of the subclavian artery showed in the Doppler waveform as at least a doubling of peak systolic velocity or complete cessation of flow with hyperabduction; significant compression of the subclavian vein was diagnosed by complete cessation of blood flow or loss of atrial and respiratory dynamics in the waveform of the subclavian vein with hyperabduction. In volunteers, asymptomatic compression of the subclavian vein with arm abduction was seen in two (10%) and asymptomatic compression of the subclavian artery was seen in four (20%). Of the 16 patients, thrombosis of the subclavian vein was found in seven, compression of the subclavian vein with hyperabduction was found in six, and diagnoses other than thoracic outlet syndrome were established as the cause of pain in three. When duplex sonography was compared with venography, which was performed in 10 patients, one false-negative case was found because a subclavian vein thrombus had not been detected. The subclavian artery was examined in five of the six patients with positional compression of the subclavian vein; compression of the subclavian artery was found in three. The clinical significance of compression of the subclavian artery cannot be determined from our data because of the small number of patients involved. When the sonographic criteria of subclavian vein clot or compression resulting in a complete loss of normal venous phasicity with arm abduction and the clinical criterion of subsequent improvement in symptoms after curative surgery are used, color Doppler sonography is 92% sensitive and 95% specific for the diagnosis of thoracic outlet syndrome. This preliminary study shows that Doppler sonography has potential in the evaluation of thoracic outlet syndrome.

Adult↗
PubMed1991

Spermatic vein occlusion with hot contrast material: angiographic results.

Spermatic vein occlusion by means of selective injection of boiling contrast material into the spermatic vein was attempted in 175 men with symptomatic varicoceles or infertility. Seventy-six patients (43%) returned for follow-up venography. Of 115 veins injected, 96 (83%) were totally occluded on the follow-up venogram obtained at 6 weeks to 2 years after injection. In the latter portion of the study, the technique was changed slightly, with injection of larger volumes of hot contrast material, resulting in a 91% occlusion rate. Each vein that was found patent on the follow-up venogram (19 of 115 [16%]) was assessed radiographically, and results were categorized as grade 1, a complete failure in which there was no change from the presclerotherapy appearance (nine of 19 [47%]); grade 2, a failure in which the treated vein was smaller but patent (five of 19 [26%]); or grade 3, a failure in which the treated vein was occluded with newly developed collateral vessels (five of 19 [26%]). The pretreatment size of the spermatic vein and the quantity of hot contrast material injected were both statistically significant factors in the treatment outcome.

Adolescent↗
PubMed1991

Thrombectomy with the transluminal endarterectomy catheter (TEC) system: experimental study and case report.

The transluminal endarterectomy catheter (TEC) system was employed as a percutaneous rotational mechanical thrombectomy device in 1-week-old thrombi in five dogs (five thrombosed polytetrafluoroethylene grafts and four thrombosed native superficial femoral arteries). Luminal patency was restored in all vessels with no angiographic evidence of significant distal embolization. The TEC catheter was also successfully used for recanalization of the superior vena cava in a patient with superior vena cava syndrome.

Animals↗
PubMed1991

Urokinase-mediated thrombolysis: a dose-response relationship in cats. Work in progress.

A cat model was developed to study thrombolytic agents. The infrarenal aorta was surgically exposed, all side branches were ligated, and both ends of the segment were occluded. After preformed clot was injected into the segment, proximal flow was restored and a distal stenosis was created. Urokinase was infused at rates varying from 4,000 to 250,000 U/h. Amount of remaining clot was quantified every 15 minutes with cine angiography. Pre- and postinfusion measurements of prothrombin time, partial thromboplastin time, thrombin time, and levels of fibrinogen and fibrin degradation products were obtained. A graph of thrombolysis rate versus infusion rate was obtained yielding maximal thrombolytic activity at 126,000 U/h and 90% of maximal activity at an infusion rate of 70,000 U/h. Levels of fibrin degradation products did not change. Prothrombin, partial thromboplastin, and thrombin times increased with increasing infusion rates, leveling off at 100,000 U/h, while fibrinogen levels decreased, with a plateau at 50,000 U/h.

Animals↗
PubMed1991

Angiogenesis after hepatic arterial occlusion in liver transplant patients.

The authors describe 10 liver transplant recipients who developed occlusion of the hepatic artery or aortic conduit. Since all potential collateral arterial supply to the transplant is severed at hepatectomy, hepatic artery occlusion is usually a catastrophic event that necessitates repeat transplantation. Four patients died within 8 weeks of transplantation. The remaining six developed spontaneous arterial liver revascularization. This phenomenon is believed to be an example of neovascularization through angiogenesis. Radiologic studies, particularly duplex sonography and angiography, were helpful in the evaluation of transplant vascular integrity. The tissues of the omentum and the mesentery have known angiogenic ability. The authors postulate that in transplantation techniques in which these tissues are placed close to the transplanted liver (eg, Roux-en-Y choledochojejunostomy), the omental and mesenteric tissues may be the source of neovascularity.

Adult↗
PubMed1991

Nonselective and semiselective catheters for renal artery evaluation: experimental study.

Abdominal aortography is widely used for evaluation of potential renal donors and for patients with renal failure or hypertension in whom a renal artery ostial or polar branch stenosis is suspected. It would be desirable to use a catheter that consistently enables good bilateral renal artery and polar branch visualization without opacification of overlying mesenteric vessels. Existing and newly designed catheters were compared to determine the optimal design necessary for these studies. An in vitro model of the abdominal aorta and its branches was made, and dye dilution densitometry was employed for quantitative evaluation. Semiselective catheters demonstrated significantly increased renal artery opacification with decreased mesenteric opacification in this in vitro model.

Aorta, Abdominal↗
PubMed1991

LGM vena cava filter: objective evaluation of early results.

One hundred one LG-Medical (LGM) vena cava filters were placed in 97 patients at four institutions. Placement was a complete technical success in 90% (91 of 101). In 6% of attempts, LGM filter insertion was complicated by incomplete opening of the filter. Pulmonary embolism after filter placement was not definitely demonstrated in any patient. The probability of inferior vena cava patency was 92% at 6 months after filter insertion. Thrombosis at the insertion site was seen in eight of 35 patients (23%) evaluated with duplex ultrasound or venography. Thrombus was observed in 37% of filters at follow-up examination, with cephalic extension of thrombus above the filter in 20% of all patients examined. Filter migration (greater than 1 cm) was seen in 12%; significant angulation was observed in only one patient (2%). In vitro experimentation demonstrated that incomplete opening of the LGM filter during placement can be avoided, in part, by brisk retraction of the insertion cannula. The low-profile introducer system of the LGM filter allows increased alternatives in selecting the site for filter insertion. The low-profile system also makes outpatient filter placement a possibility. No significant difference in the prevalence of thrombosis at the insertion site following LGM filter insertion was noted compared with previous results reported for percutaneous transfemoral placement of the Greenfield filter. The nonopaque sheath does not permit careful localization prior to filter deposition. Modification of the LGM filter to include a radiopaque sheath is suggested.

Equipment Design↗
PubMed1991

Nitinol gooseneck snare for removal of foreign bodies: experimental study and clinical evaluation.

The authors describe their use of a new right-angle snare made of nickel-titanium (nitinol) cable for retrieval of foreign bodies and iatrogenically placed devices. The snare loop is at right angles to the cable and comes in five sizes (5, 10, 15, 25, and 35 mm); its radiographic visualization is enhanced by gold-plated tungsten coils. This snare was used to retrieve wire and catheter fragments introduced into the thoracic vasculature of four dogs. Eleven of 13 attempts were successful. Three attempts to retrieve intravascular foreign bodies were successful in two patients; in one of these patients, a 10-mm snare was used to remove a fractured end of a ventriculoatrial shunt tube from the left pulmonary artery. In three other patients, four ureteral stents were successfully removed under fluoroscopic guidance. All retrievals were performed through a vascular sheath and with standard techniques and angiographic equipment. No complications were seen in any of the patients or dogs.

Alloys↗
PubMed1991

Pancreatic transplantation: radiologic evaluation of vascular complications.

Transplantation of the pancreas is an increasingly common therapeutic option for preventing or delaying complications of type I diabetes mellitus. The authors studied the relative roles of various radiologic examinations in diagnosing vascular complications in these grafts including arterial and venous thrombosis, stenosis, and anastomotic leak (the most common vascular factors that necessitate pancreatectomy of the transplant), as defined with pathologic or arteriographic data. The results of 78 scintigraphic flow studies, 40 abdominal and pelvic computed tomographic (CT) scans, 27 sonograms, and eight color Doppler studies were evaluated in 52 patients who received a total of 27 cadaveric and 26 living-donor grafts over a 12-year period. These results were correlated with the data from 45 gross and microscopic pathologic studies and 37 arteriograms to determine their relative value in enabling detection of graft thrombosis and other vascular complications. Scintigraphy, CT, sonography, and color Doppler were all sensitive in detection of generalized graft abnormalities but lacked specificity in defining the underlying etiologic factors.

Adult↗
PubMed1991

Clot-trapper device for transjugular thrombectomy from the inferior vena cava.

The clot-trapper device for transjugular thrombectomy was used in 10 dogs with acute thrombosis and two dogs with chronic thrombosis. In eight of these animals, the clots were trapped with the clot-trapper device, then a mechanical thrombectomy device was used to destroy the clots. In 10 animals, including eight with in vitro thrombi and two with in situ thrombi, thrombi were efficiently trapped with the clot-trapper device. In two animals, pulmonary embolism occurred because of a discrepancy between the diameter of the inferior vena cava and the diameter of the bag opening. After increasing the size of the loop to match the diameter of the inferior vena cava, trapping of all thrombi was possible in both experiments (acute and chronic thrombosis). The clot-trapper device, in conjunction with an embolectomy balloon catheter and/or a mechanical thrombectomy device, facilitates the removal of thrombi from the inferior vena cava and iliac veins.

Animals↗