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Biomedical subjects

K M Kent

Publications and source records attributed to K M Kent.

At least 181 records · Page 10Linked to original sources
PubMed1992

Prolonged intravenous urokinase infusion: an alternative pharmacologic approach in the treatment of thrombus-containing saphenous vein graft stenoses.

A subtotally occlusive saphenous vein graft stenosis resolved after rapid intracoronary and prolonged intravenous urokinase infusion. Additional therapy was unnecessary, avoiding the attendant risks of saphenous vein graft angioplasty. Combined intracoronary and intravenous urokinase infusion should be considered prior to coronary angioplasty of saphenous vein graft stenoses, particularly when diffuse degeneration is present or the risk of underlying thrombus is high.

Angioplasty, Balloon, Coronary↗
PubMed1992

Failure or success of complex catheter-based interventional procedures assessed by intravascular ultrasound.

Intravascular ultrasound provides high resolution cross-sectional images of vessel walls and may help to characterize atherosclerotic plaque morphology subtypes. This new imaging modality may have an important role in assessing the results of standard and investigational interventional therapeutic procedures. Four case histories of patients with coronary artery disease treated with different catheter-based therapies are presented. In each case, intravascular ultrasound added diagnostic information unobtainable from standard radiographic imaging techniques. These cases, involving PTCA (balloon dilatation), directional coronary atherectomy, high-speed rotational ablation, and balloon-expandable stent implantation, each represent an interesting example of procedure success or failure that could not be fully discerned without the use of intravascular ultrasound. Specifically, the distribution of intramural dissection, the presence and magnitude of intracoronary calcification, and morphologic patterns of intimal hyperplasia leading to restenosis, were accurately identified by ultrasound images. Thus intracoronary ultrasound imaging significantly enhances the understanding of failure modes, success, and complications after therapeutic interventions in patients with complex coronary disease.

Aged↗
PubMed1992

Arterial responses to balloon coronary angioplasty: an intravascular ultrasound study.

OBJECTIVES: The purpose of this study was to examine the coronary artery response to percutaneous transluminal coronary angioplasty by using intravascular ultrasound. BACKGROUND: The immediate effects of coronary angioplasty on arterial wall geometry and surface appearance are understood poorly. Most of the available data are derived from small necropsy series, inferred from animal models or extrapolated from in vitro studies. High frequency intravascular ultrasound provides transmural images of coronary arteries in vivo. METHODS: We used intravascular ultrasound to study 29 patients before or after, or both, successful coronary angioplasty. RESULTS: The angiographic diameter narrowing was 72 +/- 13% before and improved to 19 +/- 11% after angioplasty. Calcium was visualized in 7 (24%) of the 29 angioplasty sites by fluoroscopy versus 15 (52%) of sites by intravascular ultrasound (p = 0.022). Arterial dissection after angioplasty was observed in 8 (27%) of cases by contrast angiography versus 24 (83%) by intravascular ultrasound (p less than 0.001). Intravascular ultrasound detected extensive dissection at the angioplasty site in 11 (73%) of the 15 calcified plaques and in only 3 (21%) of the 14 noncalcified plaques (p = 0.024). Arterial expansion (defined as the area within the external elastic membrane at the angioplasty site greater than that of the proximal reference segment) occurred in 29% of calcified plaques compared with 86% of noncalcified plaques (p = 0.007). CONCLUSIONS: Intravascular ultrasound is more sensitive than angiography for identifying arterial calcium and dissection at the site of angioplasty. At the site of angioplasty, arterial dissection occurred more frequently in calcified plaques whereas arterial expansion occurred more frequently in noncalcified plaques. Successful angioplasty causes a continuum of arterial responses that vary importantly with plaque composition.

Angioplasty, Balloon, Coronary↗
PubMed1992

Morphological predictors of acute complications after percutaneous excimer laser coronary angioplasty. Results of a comprehensive angiographic analysis: importance of the eccentricity index.

BACKGROUND: Percutaneous excimer laser coronary angioplasty (ELCA) is a new technique for recanalization of arteries obstructed by coronary atherosclerosis. This study was conducted to assess the complication rate and determine the influence of clinical and angiographic characteristics on complications after ELCA. METHODS AND RESULTS: A detailed, quantitative, angiographic core laboratory analysis of patients undergoing ELCA was performed by two experienced angiographers who were not the primary laser angioplasty operators. Two hundred patients underwent 203 separate procedures on 220 lesions at three medical centers. Laser success was achieved in 180 lesions (81.8%) and procedural success in 199 (90.5%). Emergency coronary artery bypass graft (CABG) was required in five patients (2.5%). One patient suffered a Q wave myocardial infarction; there were no deaths. Also, acute closure and perforation occurred in 10 (4.5%) and three (1.4%) vessels, respectively. Coronary dissections after laser treatment were seen in 36 vessels (16.4%). Multivariate analysis found two independent preprocedural factors related to complications: eccentricity index, which is the percent deviation of the lesion lumen from the center of the artery (p = 0.0007), and proximal vessel diameter (p = 0.033). In addition, an abrupt proximal face of the lesion was associated with angiographic complications by univariate analysis (p = 0.051). Multivariate analysis showed the eccentricity index (p = 0.032) to be the only independent predictor for the occurrence of any one or more of the important complications (emergency CABG, perforation, acute closure, or Q wave myocardial infarction), whereas lesion angle greater than 45 degrees was a significant univariate predictor (p = 0.029). Other predictors of complications with balloon percutaneous transluminal coronary angioplasty, such as increased lesion length, rough edges, calcification, ulceration, and branch point, were not predictive of complications with the excimer laser. CONCLUSIONS: The degree of lesion eccentricity is the most powerful predictor of complications after ELCA. This and other morphological predictors may be of benefit in the selection of patients for ELCA as well as directing future development of this new technology.

Aged↗
PubMed1992

Intravascular ultrasound evaluation of the effect of rotational atherectomy in obstructive atherosclerotic coronary artery disease.

BACKGROUND: High-speed rotational atherectomy uses a diamond-coated, elliptical burr to abrade occlusive atherosclerosis, especially noncompliant calcified plaque. METHODS AND RESULTS: Intravascular ultrasound (IVUS) was used to analyze 28 patients after atherectomy. Arteries treated and imaged were left main (three), left anterior descending (12), left circumflex (five), right coronary (seven), and saphenous vein graft (one). Twenty patients had adjunct balloon angioplasty. Twenty-two (79%) target lesions were calcified; the intimal arc of calcium was 160 +/- 126 degrees (range, 0-360 degrees). After atherectomy, the intima-lumen interface was unusually distinct and circular. The lumen was larger than the largest burr used for both stand-alone (1.19 +/- 0.19-fold the largest burr size) and adjunct balloon procedures (1.30 +/- 0.15-fold the largest burr). Three-dimensional reconstruction of the ultrasound images showed a smooth lumen, especially in calcified plaque. Deviations from cylindrical geometry occurred only in areas of soft plaque or superficial tissue disruption of calcified plaque. Five patients were studied before and after rotational atherectomy. IVUS showed an increase in lumen size, a decrease in plaque-plus-media area and in arc of target lesion calcification, and no change in target lesion external elastic membrane cross-sectional area. CONCLUSIONS: Rotational atherectomy causes atheroablation with only moderate evidence of barotrauma in heavily calcified arteries, even after adjunct balloon angioplasty. The lumen is cylindrical, especially in areas of calcified plaque, and somewhat larger than the largest burr tip used.

Angioplasty, Balloon, Coronary↗
PubMed1991

Quantification of ST-segment changes during coronary angioplasty in patients with left bundle branch block.

Electrocardiographic manifestations of ischemia are difficult to interpret in the presence of left bundle branch block (LBBB). Recently developed techniques allow continuous computerized digital analysis of ST segments that can be zeroed to the patient's own baseline electrocardiogram even if that baseline is abnormal conduction. With use of this technology, ST-segment changes during balloon coronary occlusion were compared in 10 patients with LBBB versus an age-, sex-, and coronary anatomy-matched population of 20 control subjects with normal baseline conduction. ST-segment deviation of greater than or equal to 1 mm from baseline was present in 80% of patients with LBBB and in 75% of control patients (difference not significant). There was no significant difference between patients with LBBB versus control patients in maximal ST-segment deviation (2.6 +/- 1.7 vs 2.0 +/- 1.0 mm) or in ST-segment deviation measured after 60 seconds of occlusion (2.4 +/- 1.3 vs 1.8 +/- 1.1 mm). ST-segment deviation reached 1 mm more quickly in patients with LBBB (33 +/- 11 seconds) than in control subjects (60 +/- 36 seconds) (p = 0.003). It is concluded that ST-segment analysis is feasible in patients with LBBB using digital self-referenced ST analysis and may provide important clinical information regarding the presence of myocardial ischemia.

Angioplasty, Balloon, Coronary↗
PubMed1991

Relation of stenosis resolution pressure to long-term clinical outcome after successful percutaneous transluminal coronary angioplasty.

Variables associated with a poor long-term prognosis after successful percutaneous transluminal coronary angioplasty (PTCA) include a short duration of symptoms before PTCA, unstable angina and the presence of thrombus at the PTCA site. These imply a component of transient or dynamic obstruction as opposed to a pure fixed obstruction. It is postulated that resolution pressure (i.e., the pressure at which complete balloon inflation occurs) may also correlate with prognosis after successful PTCA. In 173 consecutive patients undergoing successful, elective, single-lesion PTCA, 48 (28%) were found to have narrowings that resolved at less than or equal to 2 atm (group 1) and 125 (72%) were found to have narrowings resolved at greater than 2 atm (group 2). There were no significant differences in baseline, anatomic or procedural variables between the 2 groups, except that angiographic coronary dissection occurred in 17% of group 1 patients versus 40% of group 2 patients (p less than 0.007). During a mean follow-up of 12.0 +/- 6.1 months, the incidence of cardiac events (repeat PTCA, coronary artery bypass grafting or myocardial infarction) was 29% in group 1 versus 15% in group 2 (p less than 0.05). The overall incidence of angina was similar between the groups (25 vs 28%), but Canadian Cardiovascular Association class 4 angina occurred significantly more frequently in group 1 than group 2 (21 vs 8%) (p less than 0.04). These data suggest that a low resolution pressure is associated with a higher incidence of unstable angina and recurrent cardiac events during follow-up than higher resolution pressures.

Aged↗
PubMed1991

Reduction of myocardial infarction after emergency coronary artery bypass grafting for failed coronary angioplasty with use of a normothermic reperfusion cardioplegia protocol.

Emergency coronary artery bypass grafting is necessary in 2.7% to 13.5% of patients undergoing elective percutaneous transluminal coronary angioplasty. Myocardial infarction develops in 11% to 49% of these patients, with 18% to 46% of infarcts resulting in new Q waves. Since February 1987 a revised protocol for myocardial preservation has been used in 19 patients undergoing emergency bypass grafting for failed angioplasty. Cardioplegia is induced with a normothermic blood cardioplegic solution. Multiple maintenance doses of cold (4 degrees C) blood cardioplegic solution are then delivered through the aortic root and vein grafts. Before the aortic crossclamp is removed, normothermic reperfusion cardioplegic solution is delivered through the aortic root and vein grafts. This group was compared with all patients undergoing emergency bypass grafting for failed angioplasty before February 1987. These 45 patients received cold induction of cardioplegic solution, multiple maintenance doses of cold cardioplegic solution, and no reperfusion cardioplegic solution. The prevalence of myocardial infarction in the group receiving cold cardioplegic solution was 65% versus 26% in the group receiving normothermic cardioplegic solution (p less than 0.007). Multivariate analysis identified the use of the normothermic cardioplegia protocol (p less than 0.005), nontotal occlusion of the angioplasty vessel (p less than 0.03), and presence of collateral flow to the angioplasty vessel (p less than 0.04) as being independently associated with absence of myocardial infarction.

Angioplasty, Balloon, Coronary↗
PubMed1990

Reduction of myocardial ischemia during percutaneous transluminal coronary angioplasty with oxygenated Fluosol.

The effects of perfusion of an oxygen-carrying perfluorochemical emulsion (Fluosol) in alleviating symptoms of myocardial ischemia during balloon occlusion were examined in a multicenter trial of 245 patients. Severe anginal pain occurred less frequently in patients receiving Fluosol perfusion (21%) than in those receiving routine angioplasty (34%) (p less than 0.05). ST-segment changes at balloon deflation in routine angioplasty patients were significantly greater than in patients who received oxygenated Fluosol perfusion (2.2 +/- 1.2 vs 1.7 +/- 0.9 mm; p less than 0.03). Profound regional wall dysfunction (-561 +/- 224 U) was observed in routine angioplasty patients by 2-dimensional echocardiography. Patients receiving oxygenated Fluosol perfusion, however, maintained near baseline levels of ventricular function (-61 +/- 335 U) during occlusion (p less than 0.0001). Mean global left ventricular ejection fraction was preserved at baseline levels during balloon inflation in patients perfused with oxygenated Fluosol but decreased significantly (p less than 0.001) during occlusion in routine angioplasty patients. A total of 26 complications (19 routine group; 7 perfusion group) was reported. Adverse responses to the perfusate were infrequent, occurring in 1.6 and 2.0% of patients after the test dose and during perfusion, respectively. Thus, transcatheter perfusion with an oxygen-carrying perfluorochemical emulsion is effective in alleviating myocardial ischemia during angioplasty and can be safely administered in this patient population.

Aged↗
PubMed1990

The portable programmable microprocessor-driven real-time 12-lead electrocardiographic monitor: a preliminary report of a new device for the noninvasive detection of successful reperfusion or silent coronary reocclusion.

Successful intravenous thrombolytic therapy early in myocardial infraction has the potential to reduce patient mortality without the additional risk and cost of aggressive invasive therapy. Noninvasive detection of successful reperfusion using resolution of chest pain, ST-segment changes assessed on static electrocardiograms, arrhythmia evolution, early isoenzyme peaking or changes in ventricular perfusion or function has been hampered by poor sensitivity or specificity, or inability to provide timely information. A newly available portable programmable microprocessor-driven real-time 12-lead electrocardiographic monitor has been introduced that may address these limitations. A continuously updated precise digital record of ST-segment activity at the bedside provides valuable information both in monitoring patients during reperfusion therapy to determine the efficacy of such treatment and in the subsequent hours to signal threatened reocclusion. This report describes the salient features of the monitor and presents 4 distinct situations in which the monitor detected timely information regarding coronary patency after reperfusion.

Angioplasty, Balloon, Coronary↗
PubMed1990

Myocardial salvage after failed coronary angioplasty.

UNLABELLED: Patients undergoing coronary angioplasty have a 2% to 7% risk of requiring emergency coronary artery bypass graft surgery for impending infarction. These patients provide a unique model of early reperfusion because the exact time of compromise to blood flow and the composition of the reperfusion solution are known. However, the amount of myocardium salvaged is unknown. Between December 1981 and September 1985, 859 patients underwent coronary angioplasty. Forty-two patients had emergency surgery for objective evidence of impending infarction. Five patients died. Thirty-six patients were contacted for follow-up; 21 (58%) of 36 had a radionuclide ventriculogram performed at a mean of 39 +/- 13 months after surgery. These radionuclide studies were compared with the patient's preangioplasty contrast ventriculogram. One patient had a myocardial infarction 3 years after surgery. Eleven (55%) of the remaining 20 patients had a normal radionuclide ventriculogram at follow-up study (ejection fraction 65 +/- 9%). Five (25%) of the 20 patients had a depressed ejection fraction (46 +/- 4%) with wall motion abnormalities, but these were unchanged from the preangioplasty studies. Four patients (20%) had a significant decrease in ejection fraction over baseline (37 +/- 10%) with new wall motion abnormalities. IN CONCLUSION: 1) there is an 80% chance that left ventricular function will be unchanged at 3 year follow-up study in patients surviving emergency bypass grafting for failed angioplasty; 2) these data suggest that early revascularization for impending infarction in this setting is associated with a good late outcome; and 3) this patient group offers a unique opportunity to study the effects of early reperfusion in a human model.

Angioplasty, Balloon, Coronary↗
PubMed1990

Incidence and consequences of periprocedural occlusion. The 1985-1986 National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty Registry.

Of 1,801 patients in the 1985-1986 Percutaneous Transluminal Coronary Angioplasty (PTCA) Registry, 122 (6.8%) had periprocedural occlusion (4.9% in the catheterization laboratory, 1.9% outside the laboratory). Baseline patient factors independently associated with increased occlusion rates included triple-vessel disease, high risk status for surgery, and acute coronary insufficiency. Lesion characteristics showing significant positive association included severe stenosis before PTCA, diffuse or multiple discrete morphology, thrombus, and collateral flow from the lesion. Intimal tear and dissection were also very strongly associated with occlusion. Sixty patients (49%) had a transient occlusion that was reopened with PTCA, 43 (35%) were not redilated and managed with bypass surgery, and 19 (16%) were not redilated and managed medically. In-hospital mortality was 5% in each of these treatment groups, compared with 1% in occlusion-free patients. In-hospital infarction rates ranged from 27% in patients with transient occlusion to 56% in the patients managed with surgery, compared with 2% in patients without occlusion. During 2 years of follow-up, somewhat increased mortality continued in patients with occlusion, whereas follow-up infarction rates were comparable for all patients regardless of occlusion. Patients with an occlusion that was reopened or managed medically had increased rates of surgery during follow-up. Rates of repeat PTCA were comparable (about 23% by 2 years) in patients with transient occlusion and those without occlusion. Occlusion remains a serious complication of angioplasty and is associated most strongly with major events and surgical procedures that occur during the in-hospital period.

Aged↗
PubMed1990

Quantitative and qualitative ST segment monitoring during and after percutaneous transluminal coronary angioplasty.

Patients who undergo elective percutaneous transluminal coronary angioplasty (PTCA) provide a unique human model, with fully defined coronary anatomy and known sites and periods of coronary occlusion. High-resolution, quantitative ST segment monitoring during PTCA procedures allows characterization of the first moments of coronary occlusion, as well as the effect of interventions intended to reduce ischemia during occlusion. Data from more than 1,000 coronary occlusions are reviewed in this presentation. Intracoronary interventions during acute myocardial infarction (MI) and elective PTCA create a potentially unstable coronary nidus through their therapeutic effect. Angiographic evidence of the anatomic appearance remains the "gold standard" for real-time assessment of success although angiography has limited ability to identify the 2-4% of patients who suffer morbidity or mortality in the coronary care unit (CCU) after an apparently successful intervention. Standard CCU monitoring of patient symptoms and rhythms underestimates transient ischemic activity in 87% of patients who experience ischemia after interventions. The capabilities of real-time multilead ST segment monitoring are reviewed from 8,331 hours of monitoring in 338 patients after intracoronary interventions. The documentation of persistent ischemia after angiographically successful PTCA and the clinical potential of qualitative patient-specific, coronary site-specific, precordial "fingerprinting" for identification of high-risk patients before or in the absence of anginal symptoms are discussed.

Angina Pectoris↗