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Biomedical subjects

M K Hong

Publications and source records attributed to M K Hong.

At least 127 records · Page 7Linked to original sources
PubMed1996

Arterial remodeling after coronary angioplasty: a serial intravascular ultrasound study.

BACKGROUND: Restenosis occurs after 30% to 50% of transcatheter coronary procedures; however, the natural history and pathophysiology of restenosis are still incompletely understood. METHODS AND RESULTS: Serial (postintervention and follow-up) intravascular ultrasound imaging was used to study 212 native coronary lesions in 209 patients after percutaneous transluminal coronary angioplasty, directional coronary atherectomy, rotational atherectomy, or excimer laser angioplasty. The external elastic membrane (EEM) and lumen cross-sectional areas (CSA) were measured; plaque plus media (P+M) CSA was calculated as EEM minus lumen CSA. The anatomic slice selected for serial analysis had an axial location within the target lesion at the smallest follow-up lumen CSA. At follow-up, 73% of the decrease in lumen (from 6.6+/-2.5 to 4.0+/-3.7 mm2, P<.0001) was due to a decrease in EEM (from 20.1+/-6.4 to 18.2+/-6.4 mm2, P<.0001); 27% was due to an increase in P+M (from 13.5+/-5.5 to 14.2+/-5.4 mm2, P<.0001). Delta Lumen CSA correlated more strongly with delta EEM CSA (r=.751, P<.0001) than with delta P+M CSA (r=.284, P<.0001). Delta EEM was bidirectional; 47 lesions (22%) showed an increase in EEM. Despite a greater increase in P+M (1.5+/-2.5 versus 0.5+/-2.0 mm2, P=.0009), lesions exhibiting an increase in EEM had (1) no change in lumen (-0.1+/-3.3 versus 3.6+/-2.3 mm2, P<.0001), (2) a reduced restenosis rate (26% versus 62%, P<.0001), and (3) a 49% frequency of late lumen gain (versus 1%, P<.0001) compared with lesions with no increase in EEM. CONCLUSIONS: Restenosis appears to be determined primarily by the direction and magnitude of vessel wall remodeling (delta EEM). An increase in EEM is adaptive, whereas a decrease in EEM contributes to restenosis.

Aged↗
PubMed1996

Effects of endoluminal coronary stents on the frequency of coronary artery bypass grafting after unsuccessful percutaneous transluminal coronary vascularization.

Coronary artery stents have been rapidly incorporated into clinical practice so that they are currently deployed in nearly 50% of all patients undergoing angioplasty procedures in a busy laboratory. A decline in the frequency of coronary bypass surgery for unsuccessful angioplasty is associated with this change in practice-a decline in the use of atherectomy devices and no increase in length of stay for angioplasty patients.

Angioplasty, Balloon, Coronary↗
PubMed1996

Ergonovine echocardiography as a screening test for diagnosis of vasospastic angina before coronary angiography.

OBJECTIVES: In patients with chest pain suggestive of variant angina, we performed this prospective study to test the specificity and diagnostic validity of ergonovine echocardiography (detection of regional wall motion abnormality during bedside ergonovine challenge) as a screening procedure before coronary angiography. BACKGROUND: Spasm provocation test outside the catheterization room has generally not been accepted as a safe diagnostic method. METHODS: Ergonovine echocardiography was performed in 80 consecutive patients with chest pain syndrome after confirmation of negative treadmill or normal stress myocardial perfusion scan results using thallium-201. A bolus of ergonovine maleate was injected at 5-min intervals up to a total cumulative dosage of 0.35 mg with echocardiographic monitoring of left ventricular wall motion. A 12-lead electrocardiogram (ECG) was also recorded every 3 min after each ergonovine injection. Positive test results were development of regional wall motion abnormalities or transient ST segment elevation or depression >0.1 mV in any single lead of the 12-lead ECG. Coronary angiography was undertaken within 2 +/- 4 days (mean +/- SD) after ergonovine echocardiography, and the spasm provocation test with acetylcholine or ergonovine was performed in patients with normal angiographic findings or lumen diameter narrowing <70%. RESULTS: On the basis of angiographic criteria, 56 patients had coronary vasospasm; this finding was later ruled out in 19 patients with near-normal angiographic results by a negative response on the spasm provocation test. In the remaining five patients, coronary spasm provocation was not performed because they revealed a high degree of fixed stenosis (lumen diameter narrowing 97 +/- 4%). Ergonovine echocardiography could diagnose coronary vasospasm before angiography, with a sensitivity of 91% (51 of 56 patients, 95% confidence interval [CI] 84% TO 98%) and specificity of 88% (21 of 24 patients, 95% CI 75% to 100%). Of 53 patients showing regional wall motion abnormalities during ergonovine echocardiography, characteristic ST segment elevation in the simultaneously recorded ECG was observed in only 20 (38%). There were no complications, including myocardial infarction or fatal arrhythmia, during the test. CONCLUSIONS: Ergonovine echocardiography before coronary angiography is safe and can be used as a reliable diagnostic screening test for coronary vasospasm in patients with negative treadmill or normal stress myocardial perfusion scan results. These findings suggest that invasive coronary angiography can be avoided in selected patients for the diagnosis of vasospastic angina.

Adult↗
PubMed1996

Increased basal tone and hyperresponsiveness to acetylcholine and ergonovine in spasm related coronary arteries in patients with variant angina--basal coronary artery tone in patients with variant angina.

In patients with variant angina, previous data have been inconclusive as to whether basal coronary artery tone is elevated at the spastic and non-spastic sites. Thus, the purpose of this study was to assess the basal coronary artery tone and the responsiveness to acetylcholine (Ach) and ergonovine (Erg) in patients with variant angina. We compared the basal coronary artery tone and the constrictive responses to Ach and Erg between 31 patients (Group 1) with variant angina in whom spasm was provoked by the low doses of Ach (intracoronary 20 micrograms) or Erg(intravenous 50 micrograms) and 35 patients (Group 2) provoked by higher doses of Ach (intracoronary 100 micrograms) or Erg (intravenous cumulative dose of 350 micrograms), and 26 control subjects. Patients with variant angina in whom spasm was provoked by low doses of Ach or Erg, had a higher incidence of mixed disease, multi-vessel spasm and higher disease activity. The basal coronary artery tone at the spastic and nonspastic sites of spasm related artery was significantly more elevated in Group 1 than that in Group 2 (44 +/- 17 vs 14 +/- 11% and 26 +/- 14 vs 16 +/- 10% respectively, P < 0.05), but not in the nonspasm related artery, The magnitudes of vasoconstrictive responses to Ach and Erg at the nonspastic sites were also greater in Group 1 than those in Group 2 and the control groups (Ach; 40 +/- 20 vs 26 +/- 11, 27 +/- 12%: Erg; 37 +/- 18 vs 12 +/- 8, 13 +/- 10% respectively, P < 0.05). However, the basal coronary artery tone was not elevated at the spastic and nonspastic sites in Group 2 compared to the in control subjects. These findings suggest that the basal coronary artery tone is increased in patients with variant angina with higher disease activity at the spastic sites and nonspastic sites of the spasm-related artery, and this may be related to the occurrence of coronary artery spasm.

Acetylcholine↗
PubMed1996

Safety and efficacy of elective stent implantation following rotational atherectomy in large calcified coronary arteries.

Rotational atherectomy is an effective transcatheter therapy for calcified coronary lesions. In large (> 3-mm) calcified coronary arteries, stent implantation following rotational atherectomy may further improve acute and especially, long-term benefit. To determine the safety and efficacy of this device synergy approach, we studied 24 consecutive patients undergoing this procedure electively in native coronary arteries. Procedural success was achieved in 100% without any major ischemic complications. There was also no incidence of subacute thrombosis or cardiac event during 30-day follow-up period. Thus, we conclude that elective stent implantation following rotational atherectomy in large, calcified coronary arteries is safe and results in excellent clinical benefit up to 30 days.

Aged↗
PubMed1995

Expansion of the Ki-67 proliferative compartment correlates with degree of dysplasia in Barrett's esophagus.

BACKGROUND: Barrett's esophagus is a histologically defined premalignant lesion of the esophagus in which normal squamous epithelium is replaced by intestinalized columnar epithelium. In a multistep progression from Barrett's esophagus to fully developed carcinoma, accelerated proliferation may indicate or precede genomic instability and, therefore, may be an important factor in the pathogenesis and/or prediction of malignant transformation. Ki-67 is a nuclear antigen expressed in proliferating cells, (G1, S, G2, and M phases) but not in resting cells (G0 phase). This study was undertaken to determine if Ki-67 expression correlates with the degree of dysplasia and if Ki-67 expression can help to differentiate those patients with or without dysplasia. METHODS: The Ki-67 proliferation fraction in 87 paraffin embedded esophageal biopsies from 43 patients with the Ki-67 antibody (MIB-1) was analyzed using immunohistochemistry. Using a computerized proliferation index program (QNA v2.54, Becton Dickinson Cellular Imaging Systems, Inc., Elmhurst, IL), a Ki-67 score was derived for the luminal surface, upper esophageal crypt, lower crypt, and underlying glandular zone of the columnar-lined esophagus. RESULTS: Significant differences in Ki-67 scores were noted in each zone among different histologic categories: normal gastric ([NG] n = 17); Barrett's without dysplasia ([ND] n = 17); low grade dysplasia ([LG] n = 21); high grade dysplasia ([HG] n = 14); and adenocarcinoma ([CA] n = 5). The pattern of Ki-67 expression was associated strongly with each histologic category. The percentage of Ki-67 positive nuclei in each mucosal zone statistically separated high grade from low grade dysplasia (P < 0.001). In high grade dysplastic tissues, the Ki-67 positive nuclei were found predominantly on the surface epithelium and upper crypt zones, whereas in low grade dysplasia, the majority of Ki-67 positive nuclei were found in the lower crypt zone. The number of Ki-67 positive nuclei in each mucosal component also was significantly different in Barrett's esophagus without dysplasia when compared with Barrett's esophagus with low grade dysplastic tissues. (P < 0.001) Staining patterns of indefinite for dysplasia by H & E staining separated into several distinct patterns (five LG, seven ND, one NG) whereas six biopsies with low grade dysplasia had a Ki-67 expression pattern more consistent with that of high grade dysplasia. CONCLUSION: The Ki-67 staining pattern correlated with histologic findings in Barrett's esophagus and may represent an additional parameter for differentiating patients with or without dysplasia.

Adult↗
PubMed1995

Comparison of clinical and angiographic outcomes after saphenous vein graft angioplasty using coronary versus 'biliary' tubular slotted stents.

BACKGROUND: Saphenous vein graft (SVG) angioplasty using 15-mm articulated, tubular slotted stents results in low (0% to 20%) residual diameter stenoses and infrequent (< 5%) major complications. A "biliary" stent design with greater radial compressive strength, enhanced visibility, and more variable sizing (diameter and length) has been approved for noncoronary indications. A comparison of outcomes after coronary versus biliary stent placement in SVG stenoses has not been performed. The purpose of this study was to compare the angiographic and clinical results after SVG angioplasty using these two balloon-expandable, tubular slotted stent designs. METHODS AND RESULTS: During a 3-year period, 231 patients with 305 SVG lesions were treated using Palmaz-Schatz coronary (n = 108) or biliary (n = 123) stents. Cineangiograms were reviewed using qualitative morphological and quantitative angiographic methods. Time-dependent clinical outcome (freedom from death, Q-wave myocardial infarction, or the need for repeat coronary bypass surgery or SVG angioplasty) was assessed using Kaplan-Meier life-table methods. Unstable angina (P < .001) and recent myocardial infarction (P = .001) were present more often in patients undergoing biliary stent versus coronary stent placement. Biliary stent-treated SVG lesions were more frequently de novo (P = .001), ostial in location (P = .002), > or = 10 mm in length (P = .009), thrombus containing (P = .001), and ulcerated (P < .001) than coronary stent-treated SVG lesions. Angiographically, biliary stent-treated lesions had larger reference vessel diameter (3.43 +/- 0.59 mm versus 3.10 +/- 0.64 mm, P < .001), higher balloon-to-artery ratio (1.15 +/- 0.16 mm versus 1.07 +/- 0.19, P = .0001), and lower residual diameter stenosis (6 +/- 17% versus 14 +/- 11% in coronary stent-treated patients; P < .001). Procedural success rates were high (95%), in-hospital major complications were uncommon (< 3%), and follow-up clinical outcomes were favorable (6-month event-free survival approximately 80%) in both groups. CONCLUSIONS: Despite frequent short-term ischemic syndromes and unfavorable lesion characteristics, both biliary and coronary cohorts have similarly favorable short-term procedural results and long-term clinical outcomes. The increased strut thickness of the biliary stent confers greater fluoroscopic visibility and radial compressive strength in exchange for decreased stent flexibility and added technical demand in stent deployment. Extreme caution is recommended with biliary stent placement in the treatment of SVG lesions as clinical results are highly operator dependent.

Aged↗
PubMed1995

Localized drug delivery in atherosclerotic arteries via a new balloon angioplasty catheter with intramural channels for simultaneous local drug delivery.

A dual-purpose angioplasty catheter with intramural channels and exterior pores for local drug delivery ("channeled balloon") was studied in eight atherosclerotic human necropsy arteries and in 22 rabbits with atherosclerotic peripheral arteries, in which markers (0.005 microns to 15 microns) were infused locally at 2 atmospheres during simultaneous angioplasty at 6 atmospheres. Thirteen of the rabbits were sacrificed at 4 or 24 h after procedure to determine the intramural retention over time. Histology confirmed effective angioplasty and revealed presence of markers in the arterial wall in 29 of 43 treated arteries (67%), whereas all control segments without local delivery had no marker staining. majority of the ineffective local delivery (12/14) occurred when 15 micron particles were infused (12/13 arteries without intramural markers), especially when examined 4 or 24 h later. Thus, in atherosclerotic arteries, the channeled balloon enabled simultaneous local drug delivery at low pressure during effective angioplasty, although particle size may play a role in successful intramural impregnation and retention.

Angioplasty, Balloon↗
PubMed1995

Can coronary flow parameters after stent placement predict restenosis?

Intracoronary stent was used to treat a dissection resulting from balloon angioplasty. Coronary flow parameters measured with Doppler Flowire pre- and post-stenting suggested abnormal coronary flow even after stenting. The patient returned 4 months later with an instent restenosis. This case suggests the intriguing possibility of coronary flow parameters obtained immediately after new device angioplasty in predicting restenosis.

Aortic Dissection↗
PubMed1995

Vascular effects of diet-induced hypercalcemia after balloon artery injury in giant Flemish rabbits.

To determine whether metastatic calcification during neointima formation can result in neointimal calcification that simulates advanced human atherosclerosis, 32 giant Flemish rabbits (weight 5.5 +/- 0.6 kg) underwent overstretch balloon injury of bilateral iliac arteries and received diet therapy for 8 weeks: high cholesterol (2%) and low calcium-vitamin D2 regimen (250 mg of calcium carbonate orally 5 times weekly and 50,000 U of calciferol intramuscularly 3 times weekly; group 1; n = 5); low cholesterol (0.5%) and high calcium-vitamin D2 regimen (500 mg of calcium carbonate orally 5 times weekly and 100,000 U of calciferol intramuscularly three times weekly; group 2; n = 19); or 0% cholesterol and high calcium-vitamin D2 regimen (group 3; n = 8). The incidence of vascular calcification was highest (71.4%) in group 2. Eighty-one percent of calcification was medial. Residual strain measurements of 7 thoracic aortas from group 2 compared to normal thoracic aortas from 8 control rabbits showed that residual strain was significantly increased in the calcified atherosclerotic aortas (12.3% vs 5.2%; p = 0.001). We conclude that diet-induced hypercalcemia predominantly affects the media despite the presence of concomitant neointima formation from balloon artery injury with or without hypercholesterolemia and increases the residual strain more than twofold compared to normal thoracic aortas.

Animals↗
PubMed1995

A modified directional atherectomy catheter for resection of calcified atherosclerotic plaques.

BACKGROUND: The purpose of this study was to determine the feasibility of resecting calcified atherosclerotic plaques in human cadaveric vessels by using a modified directional coronary atherectomy catheter and to correlate these results with bench tests using an in-vitro sea coral model. METHODS: The conventional directional coronary atherectomy catheter was modified by changing the cutter blade to a tungsten carbide material and by increasing the torsional strength of the drive cable. The performance of the modified directional coronary atherectomy (DCA) catheter was compared with the conventional catheter using a sea coral model to simulate calcified material. Then, 10 human ex-vivo arteries (eight with calcification) were treated with both conventional and modified catheters, and the results studied with intravascular ultrasound and confirmed by histologic examination. RESULTS: Using the modified directional coronary atherectomy catheter it was possible to perform effective and consistent longitudinal cutting, and to resect a significantly larger amount of coral (1.0 +/- 0.1 mm2 versus 0.2 +/- 0.1 mm2 with conventional cutter, P < 0.0001). In heavily calcified ex-vivo arteries, the modified catheter was more effective in removing calcified plaques (13 +/- 11 mg versus 3.7 +/- 1.4 mg with conventional cutter, P = 0.07). Intravascular ultrasound confirmed the effective atherectomy (residual area stenosis 28 +/- 16% versus 47 +/- 10% with the conventional device, P < 0.05), and histologic examination showed calcified nodules in the atherectomy samples obtained with the modified cutter (area of calcium 1.43 +/- 0.89 mm2 versus 0.93 +/- 0.83 mm2 with the conventional cutter). CONCLUSIONS: The modified directional coronary atherectomy catheter effectively removed both non-calcified and calcified plaques in the ex-vivo human cadaveric arteries, thus demonstrating the feasibility of directional coronary atherectomy of calcified plaques. This modified device shows promise for treating calcified coronary lesions, especially in larger vessels.

Animals↗
PubMed1995

Evidence for apoptosis in human atherogenesis and in a rat vascular injury model.

Apoptosis is a physiological cell death process important for normal development and involved in many pathological conditions. In atherosclerosis, pathological accumulation of cells in the intima has been attributed to the migration and proliferation of smooth muscle cells, macrophages, and lymphocytes. In this report, we explored the possibility that apoptosis may also contribute to the pathogenesis of this disease. We examined 35 human atherosclerotic lesion samples and identified a substantial number of cells undergoing apoptosis in 25 of the samples. Furthermore, in a rat vascular injury model, apoptotic cells were specifically identified in the neointima. The presence of apoptotic cells was demonstrated by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling, nuclear staining with propidium iodide, and electron microscopy. Immunostaining with cell-type-specific markers and subsequent terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling analysis on the same sample revealed that the majority of the apoptotic cells were modulated smooth muscle cells as well as macrophages. These results indicate that apoptosis occurs in cells of the injured blood vessel as well as the advanced atherosclerotic lesion and that physiological cell death may have an important role in determining the course of atherogenesis.

Adult↗
PubMed1994

Limitations of angiography for analyzing coronary atherosclerosis progression or regression.

PURPOSE: To analyze the utility and limitations of serial coronary angiography for determining atherosclerosis progression and regression. DATA SOURCES: A MEDLINE search of the English-language literature (1966 to January 1994) using the keywords atherosclerosis regression, atherosclerosis progression, lipid reduction therapy, and coronary angiography. STUDY SELECTION: Selected articles on the effects of cholesterol reduction and lifestyle modification on angiographic coronary artery disease, on the animal models of atherosclerosis progression and regression, and on the limitations of coronary angiography. DATA EXTRACTION: Independent extraction by two authors. RESULTS: Although several studies have reported that the rate of atherosclerosis progression, defined by serial coronary angiography, can be reduced and that luminal diameter can be improved somewhat by aggressive lipid modification, the reported changes are small (0.3 mm or 10% change) and have required a prolonged study duration (range, 1 to 10 years). More importantly, angiography simply does not measure atherosclerosis and cannot assess lesion composition. Angiography also underestimates the extent of atherosclerosis, especially in angiographically normal segments. In addition, difficulties with data acquisition, such as substantial variabilities in serial measurements of percent diameter stenosis and minimal luminal diameters, require large sample sizes to show statistically significant regression, even with computerized quantification. CONCLUSIONS: Given its current limitations, serial coronary angiography is not a satisfactory means of detecting atherosclerosis progression or regression.

Anticholesteremic Agents↗
PubMed1994

A dual-purpose angioplasty-drug infusion catheter for the treatment of intragraft thrombus.

An investigational angioplasty-drug infusion catheter (Transport, CardioVascular Dynamics, Irvine, CA) was used to treat a saphenous vein graft stenosis associated with a thrombus. The catheter was successfully used both to infuse urokinase at the site of angioplasty and to perform effective angioplasty, demonstrating the feasibility and utility of a dual-purpose angioplasty catheter capable of angioplasty and/or local drug infusion with the same catheter.

Angioplasty, Balloon, Coronary↗