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Biomedical subjects

K M Kent

Publications and source records attributed to K M Kent.

At least 235 records · Page 13Linked to original sources
PubMed1984

Early and late morphologic changes in major epicardial coronary arteries after percutaneous transluminal coronary angioplasty.

Certain clinical and morphologic observations are described in 4 men who had PTCA of the left anterior descending coronary artery early (4 hours) or late (80, 90 and 150 days) before sudden death. Histologically, each of the 4 patients had the site of PTCA narrowed 76 to 95% in cross-sectional area by atherosclerotic plaque. The early PTCA patient had coronary artery dissection at the site of PTCA. Each of the 3 late PTCA patients had a decrease in the mean transstenotic coronary gradient (17, 38 and 43 mm Hg) and an angiographic increase in the left anterior descending coronary artery luminal diameter (55, 60 and 65%) at the time of PTCA. At necropsy, 80, 90 and 150 days later, the LAD coronary artery in the area of the PTCA in each patient was narrowed 76 to 95% in cross-sectional area by plaques. No cracks in plaques or other lesions that may have resulted from PTCA were identified histologically in the left anterior descending coronary artery in any late PTCA patient.

Adult↗
PubMed1984

Return to work after coronary angioplasty: a report from the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty Registry.

Employment status was analyzed in 2,250 patients enrolled at 65 clinical centers in the NHLBI PTCA Registry. Patients were classified into 3 groups depending on the outcome of PTCA. In 63.6%, PTCA was successful without MI or CABG (Group A); in 25.3%, PTCA was unsuccessful and was followed by CABG (Group B); and in 11.1%, PTCA was unsuccessful and was followed by medical therapy alone (Group C). At entry, 68.3% of all patients were employed full- or part-time. The clinical characteristics of the 3 groups were different. Patients in Group C had a higher incidence of previous MI and previous CABG. In addition, patients in Group C had a significantly decreased baseline employment rate compared with those in Group A. At a mean follow-up of 1.5 years, there was a small but similar decrease in the percentage employed full- or part-time in all groups. Employment status also was analyzed in a subset of 1,150 patients working full- or part-time at baseline and aged 60 years or younger, who would be expected to have the highest return to work rates. At a mean follow-up of 1.4 years, 81 to 86% of patients remained working irrespective of the outcome of PTCA. However, patients with successful PTCA returned to work significantly sooner. The occurrence of chest pain during follow-up in these patients was an important predictor of return to work, irrespective of the outcome of dilatation. In patients with chest pain during follow-up, only 77% were working, compared with 90% of patients who had not had chest pain.

Angioplasty, Balloon↗
PubMed1984

Relative cost of coronary angioplasty and bypass surgery in a one-vessel disease model.

A national study was carried out to determine the relative costs of PTCA and CABG. Baseline clinical criteria for the 2 groups were similar. Data were collected in 186 sets for the PTCA group and 175 sets for the CABG group. Male patients make up 81% of the PTCA group and 80% of the CABG group. Mean hospital stay was 12 +/- 5 days in the CABG group, compared with 4 +/- 2 days in the PTCA group (p less than 0.001). The base charges for hospital and professional components of the CABG procedure were $15,580 +/- $2,159, whereas the same charges for the PTCA procedure were $5,315 +/- $2,159 (p less than 0.001). With an 80% primary success rate, which was the group mean success rate, the average dollar savings per PTCA procedure would be $7,149, or $7,149,000 per 1,000 cases. Thus, PTCA for revascularization in 1-vessel CAD is significantly more cost-effective than CABG in the short term.

Aged↗
PubMed1984

Effect of investigator experience on percutaneous transluminal coronary angioplasty.

The NHLBI PTCA Registry collected clinical data on 3,101 PTCA procedures performed at 105 clinical centers between September 1977 and September 1981. To investigate the "learning curve" from introduction through the early application of this new therapy for revascularization, success rates and complication rates were examined by calendar year and according to investigator experience. Success rates improved by calendar year, from 54% in 1979 to 66% in 1981. Investigators with fewer than 50 cases had a success rate of 55%. After an investigator had performed 150 procedures, the success rate was 77%. The increase in success rate was largely the result of a dramatic increase in the ability to cross the narrowing with the catheter, and was accounted for by experience and improved equipment. Patient selection for PTCA was characterized by sex, age, previous CABG, number of diseased coronary arteries and stable Canadian Heart classification over time. Reflecting the increase in the success rate was the decrease in the need to perform elective CABG. Emergency CABG, death and MI rates were low (1% mortality, 5% nonfatal MI) and did not change significantly with time or with investigator experience.

Angina Pectoris↗
PubMed1984

Restenosis after percutaneous transluminal coronary angioplasty (PTCA): a report from the PTCA Registry of the National Heart, Lung, and Blood Institute.

The results of follow-up angiography in patients from 27 clinical centers enrolled in the PTCA Registry were analyzed to evaluate restenosis after PTCA. Of 665 patients with successful PTCA, 557 (84%) had follow-up angiography (median follow-up 188 days). Restenosis, defined as an increase of at least 30% from the immediate post-PTCA stenosis to the follow-up stenosis or a loss of at least 50% of the gain achieved at PTCA, was seen in 187 patients (33.6%). The incidence of restenosis in patients who underwent follow-up angiography was highest within the first 5 months after PTCA. Restenosis was found in 56% of patients with definite or probable angina after PTCA and in 14% of patients without angina after PTCA. Twenty-four percent of patients with restenosis did not have either definite or probable angina. Multivariate analysis selected 4 factors associated with increased rate of restenosis: male sex, PTCA of bypass graft stenosis, severity of angina before PTCA and no history of MI before PTCA.

Angioplasty, Balloon↗
PubMed1984

Percutaneous angioplasty of stenoses of bypass grafts or of bypass graft anastomotic sites.

Forty patients who had stenoses of coronary artery bypass grafts or stenoses of the proximal or distal coronary insertion sites were treated with percutaneous transluminal angioplasty (PTA). PTA was successful in 78% of the patients. Mean stenoses were diminished from 86% to 34% in luminal diameter. One patient needed emergency coronary artery bypass grafting. There were no deaths associated with PTA. Follow-up angiography showed continued patency in asymptomatic patients, whereas in all but 1 patient with recurrent symptoms restenosis had developed at the PTA site. In 38% of patients restenosis developed after successful PTA; the highest restenosis rate was after PTA of aorta/graft anastomoses or proximal graft stenoses. In conclusion, PTA is a successful, low risk alternative to repeat coronary artery bypass grafting, although the restenosis rates at some PTA sites are high.

Adult↗
PubMed1983

Employment and recreation patterns in patients treated by percutaneous transluminal coronary angioplasty: a multicenter study.

Employment and recreational patterns were analyzed in 279 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) for treatment of symptomatic coronary artery disease. PTCA was successful in 180 patients (65%). When it was unsuccessful, coronary artery bypass graft surgery was usually performed (80%). Return-to-work rates were high irrespective of the outcome of PTCA. Of patients employed full-time or part-time before treatment, 98.5% of those who had successful PTCA alone and 97% of those whose PTCA was unsuccessful but who underwent uncomplicated coronary artery bypass surgery maintained or improved their work status. In a subgroup of men who had been employed in occupations requiring physical labor, 85% of the men whose PTCA was successful returned to work, compared with 68% of those whose PTCA was unsuccessful. The interval from attempted PTCA to return to work was significantly shorter in the successfully treated group; in patients with successful PTCA, the median time to return to work was 14 days, compared with 60 days in patients in whom PTCA was unsuccessful (p less than 0.001). During follow-up, patients with successful PTCA had less angina and were more active in recreational activities than patients who required alternative treatments.

Angioplasty, Balloon↗
PubMed1983

Status of the major epicardial coronary arteries 80 to 150 days after percutaneous transluminal coronary angioplasty. Analysis of 3 necropsy patients.

Certain clinical and necropsy cardiac findings are described in 3 men who had percutaneous transluminal coronary angioplasty (PTCA) of the left anterior descending (LAD) coronary artery 80, 90, and 150 days before sudden death. Each patient had a decrease in the mean transstenotic coronary gradient (17, 38, and 43 mm Hg) and an angiographic increase in the LAD luminal diameter (55, 60, and 65%). At necropsy, the LAD coronary artery in the area of the PTCA in each patient was narrowed 76 to 95% in cross-sectional area by atherosclerotic plaques. No cracks in plaques or other lesions which may have resulted from the PTCA procedure were identified histologically in the LAD coronary artery of any patient.

Adult↗
PubMed1983

Percutaneous transluminal coronary angioplasty: report of complications from the National Heart, Lung, and Blood Institute PTCA Registry.

The complications reported in the first 1500 patients enrolled in the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty (PTCA) Registry are analyzed. Data were contributed from 73 centers between September 1977 and April 1981. PTCA was successful in 63% of attempts. Five hundred forty-three in-hospital complications occurred in 314 patients (21%). The most frequent complications were prolonged angina in 121, myocardial infarction (MI) in 72, and coronary occlusion in 70. One hundred thirty-eight patients (9.2%) had major complications (MI, emergency surgery or in-hospital death). One hundred two patients (6.8%) required emergency surgery, usually for coronary dissection or coronary occlusion. Sixteen patients (1.1%) died in-hospital; the mortality rate was 0.85% in patients with one-vessel disease and 1.9% in those with multivessel disease. The mortality rate was significantly higher in patients who had had bypass surgery (p less than 0.001). Nonfatal complications were significantly influenced by the presence of unstable angina (p less than 0.001) and initial lesion severity greater than 90% diameter stenosis (p less than 0.001). This report delineates and assesses the complications encountered with PTCA during its initial 3 1/2-year clinical experience. These results support the relative safety of PTCA as a method of nonsurgical myocardial revascularization in carefully selected patients.

Adult↗
PubMed1983

Effects of verapamil on left ventricular systolic and diastolic function in patients with hypertrophic cardiomyopathy: pressure-volume analysis with a nonimaging scintillation probe.

To investigate the effects of verapamil on left ventricular systolic and diastolic function in patients with hypertrophic cardiomyopathy, we studied 14 patients at catheterization with a nonimaging scintillation probe before and after serial intravenous infusions of low-, medium-, and high-dose verapamil (total dose 0.17 to 0.72 mg/kg). Percent change in radionuclide stroke counts after verapamil correlated well with percent change in thermodilution stroke volume (r = .87), and changes in diastolic and systolic counts were used to assess relative changes in left ventricular volumes after verapamil. Verapamil produced dose-related increases in end-diastolic counts (19 +/- 9% increase; p less than .001), end-systolic counts (91 +/- 54% increase; p less than .001), and stroke counts (7 +/- 10% increase; p less than .02). This was associated with a decrease in ejection fraction (83 +/- 8% control, 73 +/- 10% verapamil; p less than .001) and, in the 10 patients with left ventricular outflow tract gradients, a reduction in gradient (62 +/- 27 mm Hg control, 32 +/- 35 mm Hg verapamil; p less than .01). The end-systolic pressure-volume relation was shifted downward and rightward in all patients, suggesting a negative inotropic effect. In 10 patients, left ventricular pressure-volume loops were constructed with simultaneous micromanometer pressure recordings and the radionuclide time-activity curve. In five patients, verapamil shifted the diastolic pressure-volume curve downward and rightward, demonstrating improved pressure-volume relations despite the negative inotropic effect, and also increased the peak rate of rapid diastolic filling. In the other five patients, the diastolic pressure-volume relation was unaltered by verapamil, and increased end-diastolic volumes occurred at higher end-diastolic pressures; in these patients, the peak rate of left ventricular diastolic filling was not changed by verapamil. The negative inotropic effects of intravenous verapamil are potentially beneficial in patients with hypertrophic cardiomyopathy by decreasing left ventricular contractile function and increasing left ventricular volume. Verapamil also enhances left ventricular diastolic filling and improves diastolic pressure-volume relations in some patients despite its negative inotropic effect.

Adult↗
PubMed1982

Improved myocardial function during exercise after successful percutaneous transluminal coronary angioplasty.

Fifty-nine consecutive patients with coronary-artery disease undergoing percutaneous transluminal coronary angioplasty were evaluated with radionuclide ventriculography at rest and during exercise before angioplasty (when possible) and afterward when it was successful. Thirty-eight patients (64 per cent) had an angiographically successful procedure. Three (5 per cent) had coronary occlusion as a complication. Arterial stenosis was reduced from 74 +/- 2 per cent to 31 +/- 3 per cent (mean +/- S.E.M.). The mean ejection fraction was 55 +/- 2 per cent at rest and 51 +/- 3 per cent during exercise before the procedure. After successful angioplasty, the ejection fraction was unchanged at rest but increased to 62 +/- 2 per cent (P less than 0.001) during exercise. Regional dysfunction was present during exercise in 94 per cent of the patients before the procedure and in only 8 per cent after successful angioplasty. Of the 38 patients in whom the procedure was successful, 19 had sustained improvement for over six months, and eight for three to six months. Eleven patients had recurrence of symptoms; the second angioplasty was initially successful in nine. In 24 patients remaining asymptomatic for six months (19 after the first procedure and five after the second), the left ventricular ejection fraction during exercise remained stable or improved.

Adult↗
PubMed1982

Randomized withdrawal from nifedipine: placebo-controlled study in patients with coronary artery spasm.

A multicenter randomized double-blind withdrawal study was conducted to compare the efficacy of nifedipine to that of placebo in vasospastic angina. Following a 2-week single-blind nifedipine baseline period, during which nifedipine was maintained at prestudy levels, 38 patients, 19 taking placebo and 19 continuing nifedipine therapy, either completed a 4-week randomized phase or were prematurely withdrawn because of therapeutic failure. During the randomized phase, an increase in median anginal frequency (2.8 attacks/wk, p less than 0.003) and nitroglycerin usage (0.5 tablets/wk, p less than 0.03) occurred only in the placebo group. The randomized phase was prematurely terminated because of anginal exacerbation in 7 of 19 placebo patients (37%) (only 1 patient receiving nifedipine [p = 0.02] experienced anginal exacerbation). Double-blind therapy was judged effective in 16 patients (84%) receiving nifedipine and in 3 patients (16%) receiving placebo (p less than 0.001). Nifedipine was well tolerated. This study establishes the efficacy of nifedipine in the treatment of variant and validates previous clinical experience.

Adult↗
PubMed1982

Timing of operation for chronic aortic regurgitation.

Left ventricular systolic function is an important determinant of long-term prognosis in patients with chronic aortic regurgitation. Data from several centers, using invasive and noninvasive assessment of left ventricular function, indicate that long-term postoperative survival is excellent, even in symptomatic patients, if preoperative left ventricular systolic function is normal. The long-term postoperative results are significantly worse in symptomatic patients with preoperative left ventricular systolic dysfunction, many of whom appear to have irreversible left ventricular failure before the onset of symptoms and are at a risk of late postoperative death from congestive heart failure. However, within this high risk subgroup long-term prognosis is excellent for patients, despite left ventricular dysfunction, if preoperative exercise capacity is preserved. In these patients, left ventricular dysfunction is likely to be reversible after operation. Hence, all patients with left ventricular dysfunction at rest should undergo aortic valve replacement, even if severe symptoms and deterioration in exercise tolerance have not developed. Once exercise tolerance becomes limited in such patients, the likelihood of irreversible left ventricular dysfunction is increased, and long-term postoperative survival is threatened.

Aortic Valve↗
PubMed1982

Prognosis of asymptomatic or mildly symptomatic patients with coronary artery disease.

One hundred forty-seven asymptomatic or mildly symptomatic patients with coronary artery disease, who did not have significant left main coronary occlusion and had an ejection fraction greater than 20 percent, were followed up prospectively for 6 to 67 months (average 25). Significant obstruction of one coronary artery was present in 28 percent of patients, of two coronary arteries in 31 percent and of three coronary arteries in 41 percent. Ejection fraction was 55 percent or greater in 69 percent of patients. During the follow-up there were eight deaths (annual mortality rate 3 percent for the entire group, 1.5 percent for patients with single and double vessel disease but 6 percent for those with triple vessel disease). Better definition of high and low risk subgroups of patients with three vessel disease was accomplished with exercise testing. Despite a history of mild symptoms, 25 percent of the patients with triple vessel disease exhibited poor exercise capacity on exercise testing after administration of beta adrenoceptor blocking agents and nitrates was discontinued; of these, 40 percent either died (20 percent) or had progressive symptoms requiring operation (20 percent) (annual mortality rate 9 percent). Of the patients with good exercise capacity, only 22 percent either died (7 percent) or had progressive symptoms (15 percent) (annual mortality rate 4 percent). Thus, prognosis is excellent in patients with no or mild symptoms who have one or two vessel coronary disease. Patients with three vessel disease who have good exercise capacity documented by objective testing have an annual mortality rate of 4 percent. However, because patients with three vessel disease and poor exercise capacity have an extremely grave prognosis, it would appear reasonable to recommend coronary bypass surgery for this subgroup, even in the absence of supporting data derived from a definitive randomized study.

Adult↗
PubMed1982

Percutaneous transluminal coronary angioplasty: report from the Registry of the National Heart, Lung, and Blood Institute.

Data have been collected from 34 centers in the United States and Europe performing percutaneous transluminal coronary angioplasty since September 1977. The procedure was carried out in 631 patients, with an average age of 51 years (range 23 to 76), of whom 80 percent had single vessel coronary disease, 17 percent had double or triple vessel disease and 3 percent had stenosis of the left main coronary artery. Coronary angioplasty was successful (greater than 20 percent decrease of coronary stenosis) in 59 percent of the stenosed arteries. The mean degree of stenosis was reduced from 83 to 31 percent. Emergency coronary bypass operation was required in 40 patients (6 percent). Myocardial infarction occurred in 29 patients (4 percent). In-hospital death occurred in six patients (1 percent), three with single vessel and three with multivessel disease. Ninety-one patients have been followed up for at least 1 year after coronary angioplasty. Of the 65 patients with an initially successful angioplasty, 83 percent were in improved condition compared with their status before angioplasty. Thus, the initial satisfactory results obtained in a few centers have now been confirmed in many centers using transluminal coronary angioplasty.

Adult↗
PubMed1982

Effects of verapamil and propranolol on left ventricular systolic function and diastolic filling in patients with coronary artery disease: radionuclide angiographic studies at rest and during exercise.

To determine the effects of verapamil on left ventricular (LV) systolic function and diastolic filling in patients with coronary artery disease (CAD), we performed gated radionuclide angiography at rest and during exercise in 16 symptomatic patients before and during oral verapamil therapy (480 mg/day). Twelve patients were also studied during oral propranolol (160--320 mg/day). LV ejection fraction at rest was normal in 13 patients, but abnormal diastolic filling at rest, defined as peak filling rate (PFR) less than 2.5 end-diastolic volumes (EDV)/sec or time to PFR greater than 180 msec, was present in 15. During verapamil, resting ejection fraction decreased (control 50 +/- 10% [+/- SD), verapamil 45 +/- 12%, p less than 0.005), but resting diastolic filling improved: PFR increased (control 1.9 +/- 0.6 EDV/sec, verapamil 2.3 +/- 0.9 ECV/sec, p less than 0.005) and time to PFR decreased (control 185 +/- 38 msec, verapamil 161 +/- 27 msec, p less than 0.05). Exercise ejection fraction did not change during verapamil (control 42 +/- 13%, verapamil 43 +/- 12%, NS), but exercise PFR increased (control 3.1 +/- 0.9 EDV/sec, verapamil 3.6 +/- 1.1 EDV/sec, p less than 0.05) and exercise time to PFR decreased (control 108 +/- 30 msec, verapamil 91 +/- 17 msec, p less than 0.05). In contrast, propranolol did not alter ejection fraction, PFR, or time to PFR at rest or during exercise. Thus, LV ejection fraction is decreased by verapamil at rest but is unchanged during exercise. While LV systolic function is not improved by verapamil, LV diastolic filling is enhanced by verapamil, both at rest and during exercise. These mechanisms may account in part for the symptomatic improvement in many patients during verapamil therapy.

Adult↗