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Biomedical subjects

B I Lee

Publications and source records attributed to B I Lee.

At least 73 records · Page 4Linked to original sources
PubMed1990

Potential of radio-frequency balloon angioplasty: weld strengths, dose-response relationship, and correlative histology.

Previous studies have established the feasibility of combining tissue heat generated by radio-frequency (RF) current and mechanical pressure to manage problems of percutaneous transluminal angioplasty (PTA) that are thought to cause postangioplasty restenosis (PARS). In the current in vitro study of normal and atherosclerotic human aortic layers (intima-media and media-adventitia) separated artificially, the purposes were to identify a dose-response relationship between the total RF energy delivered and the resultant weld strength between vascular tissues and to study the histologic correlates. Twenty-eight control and 100 experimental specimens were evaluated. The mean weld strength for all specimens with no RF current (at 0 J) was 4.1 g +/- 2.0; at 100 J, 5.9 g +/- 2.8; at 200 J, 28.5 g +/- 3.3; at 300 J, 50.0 g +/- 5.5; and at 500 J, 82.0 g +/- 8.2. Inspection of treated specimens revealed vascular molding (depression in the surface corresponding in dimensions to those of the electrode gap in the treatment chamber). Histologic examination revealed necrosis in the region underlying the electrode gap, a hypocellular fusion zone, indistinct boundaries between welded specimen parts, and transition zones to normal histologic characteristics at either end of each specimen. RF energy combined with mechanical pressure produces dose-dependent thermal welds in artificially dissected vascular tissues, molding of vascular tissue, and cellular destruction in the media. These findings may have clinical application in the management or prevention of all forms of PARS in humans and in the treatment of spontaneous aortic dissection.

Angioplasty, Balloon↗
PubMed1990

Effect of capsular infarct size on clinical presentation of stroke.

We reviewed the medical records and cranial computed tomograms of 74 patients with acute capsular infarcts to investigate the correlation between infarct size and clinical symptoms. Average infarct size varied significantly by clinical syndrome; patients with sensorimotor stroke had the largest infarcts, patients with pure motor hemiparesis had middle-sized infarcts, and patients with ataxic hemiparesis or the dysarthria-clumsy hand syndrome had the smallest infarcts. Although it has been proposed that the type of lacunar syndrome is determined entirely by the infarct location, our results suggest that infarct size is another important factor influencing the clinical presentation of lacunar syndromes.

Adult↗
PubMed1990

HIPDM-SPECT brain imaging in the presurgical evaluation of patients with intractable seizures.

We report the results of interictal and ictal HIPDM-SPECT brain imaging in 34 patients who eventually underwent temporal lobectomy for treatment of medically intractable complex partial seizures. Interictal studies revealed decreased regional cerebral perfusion (rCP) in the temporal lobe corresponding to the eventual site of surgery in 73% of the patients. Similarly, ictal study demonstrated increased rCP in 93% of the patients. In 69% of the patients, the SPECT studies were able to demonstrate both increased rCP on the ictal scan and decreased rCP on the interictal scan in the same location, corresponding to the eventual site of surgery. These results suggest that interictal and ictal SPECT brain imaging can be easily obtained and provide reliable localizing information in the presurgical evaluation of patients with medically intractable epilepsy.

Adolescent↗
PubMed1989

The effect of radiofrequency-generated thermal energy on the mechanical and histologic characteristics of the arterial wall in vivo: implications for radiofrequency angioplasty.

Abrupt reclosure of atherosclerotic vessels after percutaneous transluminal balloon angioplasty has been blamed on traumatic dissections and elastic recoil of the vessel wall. Thermal energy with compression produces fusion of separated arterial wall layers, and heat appears to alter the elastic recoil of the vessel wall. Radiofrequency (RF) thermal energy has been used to perform vascular anastomoses and thermal angioplasty. A simple in vivo experiment was designed to describe and quantitate vascular tissue weld strength produced by a range of RF thermal energy levels. Canine carotid arteries were compressed between a pair of modified bipolar forceps that applied RF energy, causing occlusive tissue welds between the apposed intimal surfaces. The strength of the welds was evaluated by measuring the perfusion pressure required to reopen the vessel lumen. A dosimetry range of 0 to 205 joules showed a typical dose-response curve for the relationship between energy applied and bond strength, plateauing at approximately 300 mm Hg. Light microscopy showed fusion of the inner surfaces of the vessel with preservation of vessel wall architecture. Additionally inflation of a bipolar RF balloon catheter in the normal canine carotid lumen produced an alteration of vessel profile angiographically and histologically. Results of these preliminary experiments suggest that balloon angioplasty with adjunctive RF thermal energy may have benefits in reducing the factors causing acute failure of conventional percutaneous transluminal balloon angioplasty.

Angiography↗
PubMed1989

Thermal compression and molding of atherosclerotic vascular tissue with use of radiofrequency energy: implications for radiofrequency balloon angioplasty.

The combined delivery of pressure and thermal energy may effectively remodel intraluminal atherosclerotic plaque and fuse intimal tears. To test these hypotheses with use of a non-laser thermal energy source, radiofrequency energy was delivered to postmortem human atherosclerotic vessels from a metal "hot-tip" catheter, block-mounted bipolar electrodes and from a prototype radiofrequency balloon catheter. Sixty-two radiofrequency doses delivered from a metal electrode tip produced dose-dependent ablation of atherosclerotic plaque, ranging from clean and shallow craters with histologic evidence of thermal compression at doses less than 40 J to tissue charring and vaporization at higher (greater than 80 J) doses. Lesion dimensions ranged between 3.14 and 3.79 mm in diameter and 0.20 and 0.47 mm in depth. Tissue perforation was not observed. To test the potential for radiofrequency fusion of intimal tears, 5 atm of pressure and 200 J radiofrequency energy were delivered from block-mounted bipolar electrodes to 48 segments of human atherosclerotic aorta, which had been manually separated into intima-media and media-adventitial layers. Significantly stronger tissue fusion resulted (28.5 +/- 3.3 g) with radiofrequency compared with that with pressure alone (4.8 +/- 0.26 g; p less than 0.0001). A prototype radiofrequency balloon catheter was used to deliver 3 atm of balloon pressure with or without 200 J radiofrequency energy to 20 postmortem human atherosclerotic arterial segments. In 10 of 10 radiofrequency-treated vessels, thermal "molding" of both normal and atherosclerotic vessel wall segments resulted with increased luminal diameter and histologic evidence of medial myocyte damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1989

Aortic valvuloplasty: medical and critical care nursing perspectives.

Aortic valvuloplasty, an investigational alternative to valve replacement, is explained from the perspectives of a nurse in a cardiac catheterization laboratory, a nurse in a coronary care unit, and a cardiologist. A case study is presented along with a plan of care developed around three nursing diagnoses. A prevalvuloplasty nursing diagnosis includes a teaching plan to assist nurses in preparing patients for aortic valvuloplasty.

Aged↗
PubMed1988

HIPDM-SPECT in patients with medically intractable complex partial seizures. Ictal study.

Both interictal and ictal N,N,N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3,propanediamine -single photon emission computed tomography (HIPDM-SPECT) were performed in 16 patients with medically intractable complex partial seizures. Ictal HIPDM-SPECT localized epileptic foci in 13 of 14 patients with unilateral temporal focus and provided confirmative evidence of epileptic focus in 11 patients by demonstrating maximally increased regional cerebral perfusion (rCP) in epileptic foci that had shown decreased rCP in a previous interictal study. Ictal HIPDM-SPECT in two patients with bitemporal foci showed more complicated patterns consisting of slightly increased rCP in bilateral multifocal regions. Ictal HIPDM-SPECT was particularly useful for investigating epileptic foci, and correlation with simultaneously recorded ictal electroencephalograms provided further insight for localizing epileptic foci.

Brain↗
PubMed1988

Radiofrequency balloon angioplasty. Rationale and proof of principle.

Post-angioplasty restenosis (PARS) in atherosclerotic lesions of medium and small arteries occurs in about one-third of cases in the first year following percutaneous transluminal angioplasty (PTA) (early PARS). PARS includes acute spasm, dissection with reclosure, elastic recoil, fibrocellular proliferative response, and progressive atheromatous disease. Fibrocellular proliferation (possibly initiated by platelet derived growth factor) is felt to be culpable in many cases of early PARS (months). Pharmacologic regimens, stents, and thermal welding of the intimal-medial cracks of PTA are among the interventions being developed to deal with PARS. Radiofrequency (RF) current as a source of thermal energy may be useful in combination with balloon angioplasty to reduce PARS. Ideally, this combination would (1) weld intimal-medial cracks of PTA; (2) mold plaque and normal vessel to increase lumen diameters without creating intimal-medial cracks; and (3) destroy medial smooth muscle cells and multipotential cells (cellular substrate of PARS). Canine in vivo studies have established the feasibility of RF-mediated vascular tissue welding. Human aortic specimens (N = 28) were manually dissected into intima-media and media-adventitia layers. Bipolar RF energy (650 KHz, total 300 J) and mechanical pressure (1 atm) (experimental group, N = 24) or mechanical pressure alone (control group, N = 4) were applied to the reapposed specimen layers in a special chamber. The chamber was modified with a bipolar electrode designed to reproduce that planned for an RF balloon angioplasty catheter. Welding was demonstrated in normal and atherosclerotic treated specimens (23/24 or 96%) but not controls (0/4).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1987

Effects of hypothermia on brainstem auditory evoked potentials in humans.

Ten adult patients who underwent open heart surgery under induced hypothermia had brainstem auditory evoked potentials (BAEPs) recorded at 1 degree- to 2 degrees C-steps as body temperature was lowered from 36 degrees C to 20 degrees C to determine temperature-dependent changes. Hypothermia produced increased latencies of BAEP waves I, III, and V; the prolongation was more severe for the later components with the result that interpeak latencies I-III, III-V, and I-V were also prolonged. The temperature-latency relationship was nonlinear and best expressed by exponential curve. The latencies of waves I, III, V and the interpeak latency I-V increased roughly 7% for each 1 degree C drop; they doubled at a temperature around 26 degrees C. The amplitude of the BAEP components had a quasiparabolic relationship to temperature; the amplitude rose with hypothermia to 28 degrees or 27 degrees C, but decreased linearly with further cooling. All BAEP components were present at temperatures above 23 degrees C and absent below 20 degrees C. With rewarming, the changes reversed and BAEPs returned to initial prehypothermia status.

Acoustic Stimulation↗
PubMed1986

Cortical potentials related to voluntary and passive finger movements recorded from subdural electrodes in humans.

Movement-related potentials were recorded from subdural electrodes placed on the precentral and postcentral cortex in 3 patients undergoing operation for intractable epilepsy. With self-initiated index finger movement, a negative potential of 25 to 50 microvolts in amplitude, preceding onset of the electromyographic activity by 60 to 95 ms (or onset of movement by 150 to 230 ms), was recorded from the hand somatosensory postrolandic area in all 3 patients. A similar potential preceding the movement was recorded from the precentral hand motor area in one subject who was the only patient in whom the precentral electrodes were placed on the hand motor area. Following active and passive movements, a clearly defined positivity (18 to 32 ms after a photometer trigger) that reversed phase across the central fissure was recorded. The premovement potentials are most probably generated by pyramidal tract neurons and motor-function-related neurons located in the post- and prerolandic areas. The postmovement positivity is most probably due to short-latency kinesthetic reafferent activation of the posterior bank of the central fissure (equivalent to P2 of the somatosensory evoked potentials).

Brain Mapping↗
PubMed1986

Thermal effects of laser and electrical discharge on cardiovascular tissue: implications for coronary artery recanalization and endocardial ablation.

To determine the thermal responses of cardiovascular tissues to laser and electrical ablation, and to characterize the effects of different superfusing media and temperatures on target tissue temperatures and resulting extent of tissue injury, 184 laser and 15 electrical discharges were delivered to segments of human and canine aorta and canine ventricular endocardium. Tissue temperatures were measured 2 mm from the point of contact of laser fiber tip and tissue. When superfusing media consisted of whole blood or plasma at room temperature, a standard 40 J laser discharge caused peak arterial temperatures to rise 29.2 +/- 1.6 degrees C and 30 +/- 1.4 degrees C, respectively; however, tissue cooling was significantly slower in blood than in plasma. When saline solution was superfused, tissue temperatures rose by 11.4 +/- 2.2 degrees C, and tissue cooling occurred significantly faster than with either plasma or blood. The dimensions of the resulting aortic lesions were larger when blood (1.69 +/- 0.26 mm) was superfused than when plasma (1.39 +/- 0.04 mm) or saline (0.77 +/- 0.13 mm) was superfused (p less than 0.0001). Similar findings were observed with ventricular endocardium using blood or saline as the superfusing medium. In arterial tissue, superfusion with cold blood or saline solution resulted in lower peak temperature elevations (22 +/- 3.8 degrees C and 13.5 +/- 1.3 degrees C, respectively) and faster tissue cooling after laser discharge. Corresponding aortic lesion sizes were significantly smaller (1.4 +/- 0.03 and 0.5 +/- 0.02 mm, respectively) than when blood or saline medium was superfused at room temperature (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Single photon emission computed tomography (SPECT) brain imaging using N,N,N'-trimethyl-N'-(2 hydroxy-3-methyl-5-123I-iodobenzyl)-1,3-propanediamine 2 HCl (HIPDM): intractable complex partial seizures.

HIPDM-SPECT brain imaging was performed in four patients with intractable complex partial seizures (CPS). Three patients had an epileptogenic focus in one temporal lobe and underwent anterior temporal lobectomy. Interictal HIPDM-SPECT demonstrated decreased regional cerebral perfusion (rCP) in the epileptogenic area in only one patient, but ictal studies showed increased rCP in the epileptic foci of all three patients. In the fourth patient, interictal HIPDM-SPECT showed increased rCP in the area of epileptogenic focus; when antiepileptic medication was taken, rCP decreased. HIPDM-SPECT brain imaging is useful for localizing epileptogenic foci in CPS.

Adolescent↗
PubMed1985

Elevated CK-MB and CK-BB in serum and tumor homogenate of a patient with lung cancer.

Elevated serum levels of creatine kinase (CK) were found in a patient with small-(oat) cell carcinoma of the lung. Fractionation of the enzyme showed markedly elevated CK-MB and CK-BB isoenzymes. Clinical and subsequent pathological examination showed no evidence of infarction, inflammation, or tumor involvement of the heart; however, analysis of tumor tissue for CK showed predominance of CK-MB and CK-BB isoenzymes, thus implicating tumor as the source of the circulating levels of CK-MB and CK-BB. Our case is the first to document CK-MB from neoplastic tissue homogenates, and illustrates that markedly elevated circulating levels of CK-MB, or increased levels of CK-MB in combination with CK-BB may point away from a myocardial source, and toward the existence of a malignancy.

Aged↗
PubMed1985

Transcatheter ablation: comparison between laser photoablation and electrode shock ablation in the dog.

To characterize and compare the effects of transcatheter laser and electrical energy on endocardium, 35 laser pulses were delivered to the endocardial surfaces of isolated canine hearts, and 33 endocardial lesions were produced by the transarterial delivery of either transcatheter laser irradiation or electrical shock in closed-chest anesthetized dogs. Laser-induced lesion dimensions in vitro and in vivo increased with increased total dose of energy; however, the lesions produced in vivo were different in morphology and were significantly larger than lesions produced by equivalent doses of energy delivered in vitro (p less than .05). Endocardial lesions produced in vivo by laser at 40 and 80 J (7.9 X 5.4 X 6.6 and 7.9 X 5.1 X 7.5 mm) were comparable in gross morphology and size to those produced by electrical shock at 100 and 200 J (8.5 X 6.6 X 6.6 and 10.0 X 8.5 X 8.2 mm, respectively; p = NS), but transcatheter electrode shock produced significantly more ventricular tachycardia (p less than .003), premature ventricular beats in the 7 min after energy discharge (p less than .05), and wall motion abnormality (p less than .005). Transcatheter laser photoablation can create controlled endocardial lesions with less energy and fewer deleterious effects than transcatheter electrode shock.

Animals↗