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Biomedical subjects

K M Kent

Publications and source records attributed to K M Kent.

At least 217 records · Page 12Linked to original sources
PubMed1987

Computer-assisted ST-segment monitoring: experience during and after brief coronary occlusion.

As the technology of computer-assisted ECG analysis continues to advance the frontier of multi-lead acquisition and real time analysis, conceptual approaches to the research applications as well as to the electrical and clinical validity of changes in the ECG signal amongst heterogeneous patient groups need to be continually reassessed. Comparisons between different devices, lead configurations, rates of acquisition, approaches to analysis, and patient populations may have large gaps that will require cautious extrapolation and careful investigation.

Coronary Disease↗
PubMed1986

Noninvasive detection of coronary artery patency using continuous ST-segment monitoring.

Continuous ST-segment Holter recordings were analyzed from 46 patients with acute myocardial infarction (AMI) receiving intracoronary streptokinase (SK) during the first 48 hours of hospitalization. Changes in ST deviation and the time periods of these changes were quantitated and correlated with angiographic evidence of reperfusion. Thirty-six patients had total occlusion of the infarct vessel and 10 had subtotal occlusion. Of the 36 vessels that were totally occluded, 19 were reperfused and 17 were not. In patients in whom reperfusion was successful, an ST steady state was achieved 55 +/- 32 minutes after SK administration. In patients in whom it was not successful, a steady state was achieved in 219 +/- 141 minutes (p less than 0.001). Achievement of steady state within 100 minutes after SK reperfusion indicated successful reperfusion with 89% sensitivity and 82% specificity. All patients with subtotal occlusion achieved an ST steady state before SK infusion. No patient with total occlusion achieved a steady state before SK. Achievement of ST steady state before SK infusion was 100% sensitive and 100% specific for subtotal occlusion at initial angiography. Continuous, quantitative ST-segment analysis is a sensitive and specific noninvasive technique for following coronary artery patency during AMI.

Coronary Vessels↗
PubMed1986

Ventricular arrhythmias during reperfusion.

Accelerated idioventricular rhythm has been used as a marker for coronary reperfusion. The incidence of accelerated idioventricular rhythm and ventricular tachycardia was evaluated in 52 consecutive patients undergoing thrombolysis with intracoronary streptokinase during acute myocardial infarction. Complete 12-hour Holter recordings during and after intracoronary streptokinase were obtained in 39 patients. Reperfusion was documented in 17 patients (44%), no reperfusion in 14 (36%), and subtotal occlusion in eight (20%). Accelerated idioventricular rhythm occurred in 83%, 57%, and 63% of patients by group, respectively (p greater than 0.05). Ventricular tachycardia occurred in 100%, 71%, and 100% of patients by group, respectively (p less than 0.05). These data demonstrate that accelerated idioventricular rhythm is not specific for reperfusion and cannot be used as a marker for this event, and that ventricular tachycardia is more common with reperfusion and subtotal occlusion.

Cardiac Catheterization↗
PubMed1986

The assessment of contractile reserve after thrombolytic therapy for acute myocardial infarction.

"Stunned" myocardium prevents the assessment of myocardial salvage after streptokinase. In order to unmask "stunning," we sought to evaluate left ventricular inotropic contractile reserve of patients after streptokinase. Radionuclide ventriculograms were obtained in 75 consecutive patients 2 weeks after myocardial infarction, at rest and during intravenous isoproterenol infusion. Resting and isoproterenol-stressed ejection fractions were compared in the patent and closed-infarct vessel groups. Although there was no difference in the resting ejection fractions between the patent group (0.48 +/- 0.02) and the closed group (0.48 +/- 0.02), isoproterenol increased the ejection fractions in the patent group (increase 0.14 +/- 0.01) significantly more than in the closed group (increase 0.06 +/- 0.01) (p less than 0.0001). Thus, despite identical resting ventricular function, the greater inotropic contractile reserve in the patent infarct vessel group suggests that restoration of blood flow in acute myocardial infarction salvages myocardium.

Adult↗
PubMed1986

Thrombolysis in acute myocardial infarction.

Emergency cardiac catheterization and angiography in patients have resulted in an appreciation of the pathogenesis of AMI and the efficacy of thrombolytic therapy. Simple reperfusion of the infarcted myocardium, however, does not necessarily guarantee myocardial salvage, and preliminary studies have been somewhat confusing as to its beneficial effects. Metabolic support of the ventricle during early reperfusion may enhance left ventricular performance. Although the potential effects of thrombolytic therapy are still unclear, the routine administration of these agents has resulted in more frequent performance of early coronary angiography, with the result that appropriate therapeutic decisions can be made immediately regarding medical treatment, coronary angioplasty, or complete myocardial revascularization. In fact, in prolonged chest pain syndromes, emergency angiography may play a very important role in establishing appropriate initial therapy early in the course of hospitalization, potentially lowering mortality, morbidity, and cost. These issues will be answered ultimately only by carefully designed long-term randomized trials.

Fibrinolytic Agents↗
PubMed1986

Use of hemodynamic measurements for management of acute myocardial infarction.

The modern coronary care unit now can provide hemodynamic measurements that characterize the determinants of myocardial oxygen consumption and mechanical performance. These determinants of preload, afterload, contractile state, and heart rate can be obtained from measurements with the Swan-Ganz catheter, systemic blood pressure, assessment of ventricular function, and heart rate. With the hemodynamic characterization of the determinants of left ventricular function, drugs can be selected that either decrease or increase the specific determinants in order to optimize left ventricular performance. Thus, a physiologic approach can be taken to the pharmacologic management of patients with acute myocardial infarction based on hemodynamic measurements and appropriate therapeutic strategies.

Blood Pressure↗
PubMed1985

Ischemia during angioplasty after streptokinase: a marker of myocardial salvage.

Although thrombolytic therapy can result in lysis of a coronary artery thrombus, salvage of myocardium as measured by enzymatic, electrocardiographic and regional wall motion evaluation has not been clearly documented. Many patients after successful reperfusion continue to experience recurrent chest pain. The presence of recurrent chest pain suggests salvaged myocardium. Controlled reocclusion of the infarct vessel with the use of coronary angioplasty may support evidence for myocardial salvage. Experience in 50 patients who underwent angioplasty was reviewed retrospectively. Sixteen of the 50 patients had electrocardiographic or clinical evidence of ischemia at the time of balloon inflation. Prospectively, all patients who underwent angioplasty after they had received streptokinase were evaluated, and 5 of 5 patients had chest pain and ST-segment elevation during balloon inflation. The development of ischemic changes during balloon catheter inflation suggests the presence of persistently viable, salvaged myocardium after successful thrombolysis.

Angioplasty, Balloon↗
PubMed1985

Coronary angioplasty: clinical and angiographic follow-up.

To evaluate the clinical status and restenosis rate after percutaneous transluminal coronary angiography (PTCA), 251 consecutive patients who had undergone a successful procedure from February 1979 to May 1983 were studied. Angiography was done routinely in 92 of the initial 100 consecutive patients in whom the procedure was successful (group I), 1 to 11 months (mean 6) after PTCA. Restenosis occurred in 37 of 92 patients (40%); all but 2 (who had collateral flow to the restenosed vessel) had symptoms. Conversely, 44 of 46 asymptomatic patients had no restenosis. The other 159 patients (group II) were followed up clinically, with angiography performed only if signs or symptoms of ischemia recurred. Restenosis suspected clinically and confirmed angiographically occurred in 35 of 92 patients (38%) in group I and 36 of 154 patients (23%) in group II. Of 251 patients with follow-up of at least 6 months, 109 patients (43%) became symptomatic. Of 109 symptomatic patients, 104 consented to coronary angiography; restenosis was found in 67%, progression of narrowing in other arteries occurred in 13%, and the remaining patients were presumed to have large or small vessel vasospasm. The mortality rate for the entire group was 0.8%. When repeat angioplasty was applied to patients with restenosis, over 80% of the group improved at an average follow-up time of 21 months. Symptomatic restenosis may occur less often when higher balloon inflation pressures are used during PTCA.

Angioplasty, Balloon↗
PubMed1985

Sex differences in early and long-term results of coronary angioplasty in the NHLBI PTCA Registry.

To assess whether gender influenced the outcome of percutaneous transluminal coronary angioplasty (PTCA), we analyzed data from the NHLBI PTCA Registry. Early results were compared in 705 women and 2374 men. Women were older (p less than .01) and had more unstable angina (p less than .01), and class 3 or 4 angina (p less than .01). Men had more multivessel disease (p less than .01), prior bypass surgery (p less than .01), and abnormal left ventricular function (p less than .05). Women had a lower angiographic success rate (60.3 vs 66.2%; p less than .01) and had a lower clinical success rate (56.6% vs 62.2%; p less than .01). More women had complications (27.2% vs 19.4%; p less than .01), but overall frequency of major complications (death, myocardial infarction, emergency surgery) was not different (9.8% vs 9.3%). Women had a higher incidence of coronary dissection (p less than .05) and higher in-hospital mortality (1.8% vs 0.7%; p less than .01). PTCA-related mortality was nearly six times higher in women (1.7% vs 0.3%; p less than .001) and mortality with emergency surgery was more than five time higher (17.4% vs 3.2%; p less than .001). Multivariate analysis indicated that female gender was an independent predictor for lower success (p less than .05) and early mortality (p less than .05) and was the only baseline predictor for PTCA-related mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1985

Asynchronous left ventricular regional function and impaired global diastolic filling in patients with coronary artery disease: reversal after coronary angioplasty.

Left ventricular diastolic filling is impaired in many patients with coronary artery disease and normal left ventricular systolic function, and is improved in many patients after coronary angioplasty (PTCA). To investigate the mechanisms for this improvement, we studied regional asynchrony by radionuclide angiography in 26 patients with single-vessel coronary artery disease before and after successful PTCA. Before PTCA, all patients had normal ejection fractions at rest and normal qualitative left ventricular regional wall motion, as determined by radionuclide and contrast angiography. Quantitative left ventricular regional function was assessed by dividing the left ventricular region of interest into 20 sectors. Phase analysis was performed on each sector's time-activity curve, and the average intersector phase difference was used as an index of left ventricular regional synchrony. Before PTCA, average intersector phase difference was increased compared with normal (6.0 +/- 2.2 vs 4.0 +/- 1.7 degrees, p less than .005), indicating asynchronous regional function. After PTCA, ejection fraction at rest was unchanged, but peak left ventricular filling rate at rest increased from 2.5 +/- 0.6 to 3.0 +/- 0.6 end-diastolic volume/sec (p less than .001) and was associated with a decrease in average intersector phase difference from 6.0 +/- 2.2 to 5.1 +/- 2.3 degrees (p less than .05). Average intersector phase difference decreased in 16 of 21 patients in whom peak filling rate increased after PTCA (p less than .005), compared with one of five patients in whom peak filling rate was unchanged or decreased. Hence, improved global left ventricular filling after PTCA was associated with more synchronous left ventricular regional behavior. To identify the cause of regional asynchrony before PTCA, we then generated time-activity curves from each of four left ventricular quadrants. These data indicated that the asynchrony was caused by regional variation in timing of diastolic rather than systolic events and that PTCA resulted in reduction in regional diastolic asynchrony. These data suggest that in many patients with coronary artery disease and normal left ventricular systolic function, impaired global diastolic filling may result from asynchronous left ventricular regional diastolic function, which is a reversible manifestation of myocardial ischemia or reduced coronary flow.

Adult↗
PubMed1985

Indications for transluminal coronary angioplasty.

During the 7 years that have followed the introduction of transluminal coronary angioplasty, the indications for this therapeutic, nonoperative procedure have changed from very strict angiographic and clinical criteria to much broader ones. This evolution has occurred because of the technical capabilities of the equipment that is currently available and because of the attractiveness of this nonoperative procedure, which is effective in reducing coronary arterial obstructions. Although there are current studies that demonstrate the effectiveness of the improved techniques for dealing with a larger range of angiographic obstruction, few, if any, clinical studies are currently available that support the widespread use of this technique in patients with clinical syndromes such as new-onset angina, asymptomatic exercise test abnormalities, high-grade stenosis after thrombolysis, etc. As the current indications increase, clinical studies establishing the efficacy of this therapeutic procedure are indicated.

Angioplasty, Balloon↗
PubMed1984

Exercise-induced ischemia in mildly symptomatic patients with coronary-artery disease and preserved left ventricular function. Identification of subgroups at risk of death during medical therapy.

To determine prospectively whether the severity of reversible left ventricular ischemia provides prognostic information in mildly symptomatic patients with coronary-artery disease and preserved left ventricular function at rest (ejection fraction greater than 40 per cent), we studied 117 patients by means of exercise electrocardiography and radionuclide angiography. No patient had stenosis of the left main coronary artery. Mortality during subsequent medical therapy was significantly associated (by univariate life-table analysis) with three-vessel coronary-artery disease and the magnitude of the ejection fraction during exercise. In patients with three-vessel disease who had both ST-segment depression of 1 mm or more and a decrease in ejection fraction during exercise, in association with an exercise tolerance of 120 W or less, the probability of survival at four years was only 71 +/- 11 per cent (S.E.). All deaths occurred in this subgroup. Thus, objective evidence of left ventricular ischemia during exercise and exercise capacity identify one subgroup of minimally symptomatic patients with three-vessel disease with an excellent prognosis and another subgroup at relatively high risk of dying during subsequent medical therapy.

Adult↗
PubMed1984

Cardiovascular features of homozygous familial hypercholesterolemia: analysis of 16 patients.

Familial hypercholesterolemia (FH) is characterized by an autosomal codominant inheritance, an abnormality in low-density lipoprotein (LDL) receptor function, elevated plasma cholesterol levels and premature atherosclerosis. Sixteen patients with homozygous FH were studied to correlate the extent of their atherosclerotic disease with their lipid levels and receptor function. The age range at initial presentation was 3 to 38 years (mean 12), and at the last examination, 6 to 43 years (mean 20). The mean pretreatment total plasma cholesterol concentration for all patients was 729 +/- 58 mg/dl (+/- standard error of the mean), and the mean LDL cholesterol level was 672 +/- 58 mg/dl (normal 60 to 176). High-density lipoprotein cholesterol was 28 +/- 3 mg/dl (normal 30 to 74). In the 7 patients with FH who had symptoms of myocardial ischemia (Group I), the mean pretreatment LDL cholesterol value (817 +/- 62 mg/dl) was higher than that of the 9 asymptomatic patients (Group II) (560 +/- 74 mg/dl). In Group I, 5 of 7 patients had left or right coronary ostial narrowing and 3 had significant left ventricular outflow obstruction. Most coronary arterial narrowing occurred in the right coronary and left anterior descending arteries and the least amount in the left circumflex coronary artery. A femoral bruit was the physical finding that correlated best with the Group I population; brother:sister pairs revealed a milder clinical course for the female. Seven of the 16 patients have survived into their third decade without symptoms. Comparison of these persons with those in whom angina developed reveals a marked heterogeneity in their clinical course, which appears to be associated with receptor negative/defective status.

Adolescent↗
PubMed1984

Long-term efficacy of percutaneous transluminal coronary angioplasty (PTCA): report from the National Heart, Lung, and Blood Institute PTCA Registry.

The NHLBI PTCA Registry has collected data from 3,079 patients who underwent PTCA at 105 centers from September 1977 through September 1981 that document the initial risks and benefits of PTCA. A subgroup of 2,272 patients at 65 centers was chosen to examine the long-term effects of PTCA (97% follow-up). All patients were followed for 1 year, 191 for 3 years and 57 for 4 years. Initial success occurred in 1,397 (61%), and 72% remained improved at 1 year with no further procedures; during the first year of follow-up, 14% had repeat PTCA, 12% had CABG, 3% had MI and 1.6% died. After 1 year, 67% were asymptomatic; of these, 52% had no other procedure, 7% had a second PTCA and 8% had CABG. Follow-up at 2 to 4 years was similar except that there were few repeat PTCA or CABG procedures after 1 year. The annual mortality rate after PTCA in patients with 1-vessel diseases was less than 1% per year and with multivessel CAD, 3% per year. Thus, successful PTCA alone results in sustained improvement in 84% of patients; 59% were asymptomatic (12% had repeat PTCA). PTCA offers extended effective therapy in selected patients with CAD.

Angioplasty, Balloon↗
PubMed1984

Efficacy of repeat percutaneous transluminal coronary angioplasty for coronary restenosis.

The short- and long-term outcome of patients within the NHLBI PTCA Registry who underwent repeat PTCA for coronary restenosis were analyzed. Of 1,880 patients in whom an initial PTCA was successful, 203 had a repeat PTCA attempted after restenosis developed. Repeat PTCA was usually performed within 6 months of the first procedure. The success rate of repeat PTCA was 85.2%. As a direct result of repeat PTCA, 1.5% of patients had an MI and 2% required emergency CABG. No patient died as a result of the attempted second procedure. One to 3 years of follow-up information was available in 94% of eligible patients. Most patients (75.9%) did not have a subsequent (third) PTCA, CABG or an MI. The late mortality rate was 0.8%. Angiographic follow-up information was available in 62 patients. Sustained enhancement of the diameter of the redilated lesion was observed in 66%. Thus, repeat PTCA has a high success and a low complication rate. Most patients did not have subsequent restenosis and are free of angina. Hence, repeat PTCA should be recommended for patients who have restenosis and should be considered as an integral component of PTCA therapy.

Angina Pectoris↗
PubMed1984

Exercise, electrocardiographic and functional responses after percutaneous transluminal coronary angioplasty.

Exercise testing after successful PTCA showed improved cardiac functional status on examination of electrocardiographic and symptomatic responses, myocardial perfusion and global and regional left ventricular function. Sixty-six patients were studied before and after persistently successful PTCA. Follow-up studies an average of 8 months after the successful procedure showed an incidence of abnormal testing of only 7% using both electrocardiographic and subjective symptomatic criteria during treadmill studies and no abnormal studies with thallium scintigraphy. Radionuclide cineangiography demonstrated similar left ventricular ejection fractions at rest before and after PTCA, but an improvement of 9 +/- 10% (p less than 0.001) in the exercise ejection fraction at follow-up. However, 52% of patients with paired data still had an abnormal radionuclide cineangiographic study after successful PTCA, raising the question of the presence of subclinical ischemia or a false-positive result.

Angioplasty, Balloon↗