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Biomedical subjects

D W Hunter

Publications and source records attributed to D W Hunter.

At least 55 records · Page 3Linked to original sources
PubMed1993

Anatomical mechanisms explaining damage to pacemaker leads, defibrillator leads, and failure of central venous catheters adjacent to the sternoclavicular joint.

The literature suggests that approximately 93% of all pacemaker lead fractures occur in the segment of the lead lateral to the venous entry, and costoclavicular compression has been implicated. While blood vessels can be compressed by movements of the clavicle, our research suggests that lead and catheter damage in that region is caused by soft tissue entrapment rather than bony contact. Dissection of eight cadavers with ten leads revealed that two entered the cephalic vein, and were not included in the study. Of the other eight leads, four passed through the subclavius muscle, two through the costoclavicular ligament, and two through both these structures before entering the subclavian, internal jugular, or brachiocephalic vein. Anatomical studies demonstrated that entrapment by the subclavius muscle or the costoclavicular ligament could cause repeated flexing of leads during movements of the pectoral girdle. Cineradiology of patients with position dependent catheter occlusion confirmed entrapment by the subclavius muscle. Soft tissue entrapment imposes a static load upon leads and catheters, and repeated flexure about the point of entrapment may be responsible for damage previously attributed to cyclic costoclavicular compression.

Arm↗
PubMed1993

Refractory ascites: early experience in treatment with transjugular intrahepatic portosystemic shunt.

PURPOSE: To evaluate the transjugular intrahepatic portosystemic shunt (TIPS) in treatment of refractory ascites. MATERIALS AND METHODS: Fourteen patients with chronic liver disease and portal hypertension were included in a prospective study. Six patients had Child-Pugh class B disease; eight had class C disease. Indications for TIPS were three previous hospital admissions over 9 months for treatment of tense ascites, no response to diuretic therapy, or an occluded peritoneovenous shunt with tense ascites. The volume of ascitic fluid was sonographically evaluated before and after TIPS placement. RESULTS: The technical success rate for TIPS creation was 93%. Mean portosystemic gradient decreased from 22.8 mm Hg +/- 7.2 before TIPS placement to 11.3 mm Hg +/- 3.6 after TIPS (P = .005). Complete resolution of ascites was achieved in seven (50%) patients. Treatment failed in seven; five had Child-Pugh class C disease, and four of these had a Child-Pugh score greater than 11. CONCLUSION: These results are comparable to those for other forms of treatment of ascites. The authors do not, however, recommend TIPS in patients with a Child-Pugh score greater than 11.

Ascites↗
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↗