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Biomedical subjects

D O Williams

Publications and source records attributed to D O Williams.

At least 109 records · Page 6Linked to original sources
PubMed1985

Adaptation to the stress of tachycardia in patients with coronary artery disease: insight into the mechanism of the warm-up phenomenon.

Adaptation to exercise or the "warm up phenomenon" has been observed in some patients with angina pectoris. To investigate adaptation, eleven patients with exertional angina pectoris and angiographic evidence of coronary artery disease underwent two identical bouts of sequential tachycardia stress separated by a brief recovery period. Manifestations of ischemia were less during the second stress, as evidenced by a reduction in the severity of angina pectoris, less ST segment depression, and improved lactate extraction. Peak coronary blood flow during the second stress (81 +/- 20 ml/min) was not significantly different from that during the first (95 +/- 32 ml/min). Regional myocardial oxygen consumption, however, was significantly (p = .03) lower during the second stress (8.8 +/- 2.4 ml O2/min) when compared with the first (11.4 +/- 3.0 ml O2/min). Thus, patients with coronary artery disease can develop anginal tolerance to the stress of tachycardia similar to that observed after repeated bouts of exercise. A relative reduction in myocardial oxygen consumption, rather than an increase in coronary blood flow, appears to account for this phenomenon.

Adaptation, Physiological↗
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

Follow-up assessment of St. Jude Medical prosthetic valve in the tricuspid position: clinical and hemodynamic results.

Seven patients underwent postoperative right heart catheterization implantation of the St. Jude Medical prosthetic valve in the tricuspid position. Six patients were in atrial fibrillation at catheterization, and 1 was in normal sinus rhythm. At postoperative catheterization, the mean right atrial pressure ranged between 4 and 16 mm Hg (mean, 9.7 mm Hg); right ventricular systolic pressure was normal in 1 patient, mildly elevated (less than 50 mm Hg) in 4 patients, and moderately elevated (65 and 70 mm Hg) in 2. The cardiac output ranged between 3.0 and 7.0 L/min (mean, 4.2 L/min). There was no end-diastolic gradient across the St. Jude Medical prosthesis in 6 patients. The other patient had a gradient of 2 mm Hg across the valve when cardiac output was 7.0 L/min. On fluoroscopy, both discs demonstrated full excursion in all patients. These data demonstrate that a normally functioning St. Jude Medical valve in the tricuspid position does not create obstruction to forward flow, and they support use of this prosthesis in patients with tricuspid valve disease.

Adult↗
PubMed1984

Recovery of myocardial function following brief versus prolonged atrial pacing stress in the presence of coronary artery stenosis.

The ability of myocardium distal to a severe coronary artery stenosis to recover from brief (5 min) versus prolonged (30 min) atrial pacing stress was compared in this study. Eight closed chest pigs were prepared with a coronary artery stenosis (82% lumenal diameter reduction) in the left anterior descending artery and ultrasonic length sensors in left anterior descending endocardium. Extent of recovery of systolic function 5 min following a brief (5 min) period of ischaemia induced by rapid (175 to 190 min-1) atrial pacing (AP-1) was compared with that following a prolonged (30 min) period of ischaemia induced by rapid atrial pacing (AP-2). Regional myocardial blood flow (ml X min-1 X g-1) was measured at control, during, and following atrial pacing. Regional shortening (%) distal to the stenosis declined versus control at both 5 min of AP-1 (10.0 +/- 7.3 (mean +/- 1 SD) to 0.6 +/- 0.9, p less than 0.01) and 30 min of AP-2 (6.8 +/- 3.3 to 2.1, +/- 3.5, p less than 0.01). However, within 5 min of discontinuing both brief as well as prolonged pacing, regional segmental shortening (5.7 +/- 3.9 and 7.0 +/- 6.9, respectively) returned to 50 to 70% of initial control levels (10.0 +/- 7.3). Regional shortening was similar 5 min following brief and prolonged stress. Distal left anterior descending zone epicardial regional myocardial blood flow increased (p less than 0.01) versus control at AP-1 (1.05 +/- 0.24 to 1.39 +/- 0.24) and 30 min of AP-2 (0.99 +/- 0.21 to 1.40 +/- 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Contrasting effects of nifedipine and adenosine on regional myocardial flow distribution and metabolism distal to a severe coronary arterial stenosis: observations in sedated, closed-chest, domestic swine.

This study tested the hypothesis that intrinsic negative inotropic effects of a drug used to induce coronary vasodilation distal to a severe coronary arterial stenosis may influence the extent of redistribution of transmural flow and its metabolic consequences. To test this hypothesis, studies were conducted in eight closed-chest, sedated swine with severe (82% reduction in luminal diameter) coronary arterial stenoses. Measurement of hemodynamic parameters, regional myocardial blood flow (microsphere technique), lactate metabolism, and oxygen consumption were made (1) under control conditions, (2) after 10 min of intracoronary infusion of a vasodilator distal to the stenosis, and (3) under repeat control conditions. Each animal received both intracoronary adenosine (400 micrograms/min) and nifedipine (50 micrograms/min). The order of drug infusion was chosen at random and a control period separated administration of each. In response to nifedipine there was no significant change in the group mean (+/- SD) value of endocardial flow (1.21 +/- 0.34 to 1.29 +/- 0.61 ml/min X g-1) distal to the stenosis. In contrast, epicardial flow increased in comparison with control in response to nifedipine (1.30 +/- 0.58 to 1.79 +/- 0.74 ml/min X g-1; p less than .05). Regional myocardial oxygen consumption (MVO2) declined in comparison with control in response to nifedipine (14.0 +/- 4.2 to 11.1 +/- 5.0 ml/min X 100 g-1; p less than .05). Regional lactate extraction did not change in comparison with control during infusion of nifedipine (18.2 +/- 22.4 vs 11.7 +/- 16.8). In response to adenosine, endocardial blood flow distal to the stenosis declined in comparison with control (1.25 +/- 0.53 to 1.07 +/- 0.38 ml/min X g-1; p less than .05), while epicardial flow increased (1.31 +/- 0.55 to 2.26 +/- 0.59 ml/min X g-1; p less than .01). Regional MVO2 also tended to decline in comparison with control in response to adenosine (13.4 +/- 4.9 to 11.7 +/- 2.9 ml/min X 100 g-1) and was significantly (p less than .05) reduced in comparison with postintervention control (14.6 +/- 4.2 ml/min X 100 g-1). In contrast to nifedipine, adenosine caused a significant decline in regional lactate extraction in comparison with control (12.7 +/- 23.2% to -40.6 +/- 55.0%; p less than .01). Thus, administration of nifedipine, a negative inotropic agent, resulted in (1) a decline in regional MVO2, (2) increased epicardial blood flow with variable effects on endocardial flow distal to the stenosis, and (3) no evidence of de novo or worsening ischemia, even in animals in which endocardial flow decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine↗
PubMed1984

Evidence against significant resting alpha-adrenergic coronary vasoconstrictor tone.

The importance of sympathetically mediated coronary vasoconstrictor tone as a determinant of resting coronary blood flow was assessed in the conscious dog by comparing blood flow and oxygen extraction in a normally innervated (I) and a previously sympathectomized (Sx) region of the same left ventricle. The regional ventricular sympathectomy was achieved by the topical application of phenol. The animals were well acclimated to the laboratory environment before regional myocardial blood flow was measured with microspheres or regional myocardial oxygen extraction was determined on blood sampled from chronically implanted coronary venous catheters. Results indicated that blood flow and oxygen extraction were not significantly different in I and Sx regions under these conditions. Regional blood flow data obtained after beta-adrenergic blockade or combined alpha- and beta-adrenergic blockade were not significantly different from control data. Thus we were unable to confirm previous evidence in the literature of significant resting sympathetic coronary vasoconstrictor tone in the conscious animal.

Animals↗
PubMed1983

Coronary circulatory dynamics before and after successful coronary angioplasty.

The hypothesis that successful percutaneous transluminal coronary angioplasty restores normal coronary circulatory dynamics was tested. Regional coronary blood flow, myocardial oxygen consumption and lactate extraction were measured at rest and during sustained pacing tachycardia. Before angioplasty, tachycardia stress was associated with an attenuated blood flow and oxygen consumption response and the induction of anaerobic metabolism. After successful angioplasty, blood flow and myocardial oxygen consumption increased during tachycardia stress and aerobic metabolism was sustained. The influence of basal alpha-adrenergic tone in modifying the time course of blood flow response to abrupt pacing was also assessed. Patients with normal coronary arteries demonstrated delayed increase in blood flow after alpha-adrenergic blockade. Alpha-adrenergic blockade did not affect the time course of blood flow response in patients with coronary artery disease, suggesting that alpha-adrenergic tone was chronically withdrawn. In patients undergoing coronary angioplasty, flow response before angioplasty was delayed, consistent with withdrawal of basal alpha-adrenergic tone. After coronary angioplasty, a brisk flow response was observed, indicating that basal alpha-adrenergic tone had been restored. Thus, successful coronary angioplasty restores the normal responsiveness of the coronary circulation.

Adrenergic alpha-Antagonists↗
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

Endobronchial polyposis following smoke inhalation.

A 50-year-old fireman was found to have multiple endobronchial polyps when investigated for hemoptysis two months after acute thermal inhalation injury. Biopsy was obtained and the histology demonstrated benign granulation tissue. The polyps spontaneously regressed, without specific treatment, six months after the accident. Tracheal bronchial polyposis appears to be another complication of heat and smoke inhalation.

Bronchial Neoplasms↗
PubMed1982

Percutaneous vs surgical placement of intra-aortic balloon assist.

Fifty-three patients required IABP over a one-year period. The type of insertion (percutaneous vs surgical) was used randomly. The hemodynamic effect, complication rate, and inability to insert the balloon were similar in both groups. Besides less trauma and cost-effectiveness, the most important advantage of percutaneous over surgical balloon insertion is shorter time interval between decision and insertion which thus allows faster stabilization of ischemic heart patients.

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

The effect of intraaortic balloon counterpulsation on regional myocardial blood flow and oxygen consumption in the presence of coronary artery stenosis in patients with unstable angina.

To determine whether a reduction in myocardial oxygen demand or an increase in coronary blood flow or both are responsible for the salutory effect of intraaortic balloon counterpulsation (IABP) in relieving medically refractory angina, we assessed these variables in six patients in whom IABP was required for relief of myocardial ischemia. IABP decreased the rate-pressure product and aortic end-diastolic pressure, and the peak systolic aortic pressure and regional myocardial oxygen consumption declined in all but one patient. Peak and mean aortic diastolic pressures increased. Changes in regional coronary blood flow paralleled changes in peak systolic aortic pressure (r = 0.92, p less than 0.007). Thus, relief of angina during IABP could not be ascribed to an increase in regional coronary blood flow. Reduction of myocardial oxygen consumption is the most likely mechanism by which IABP relieves myocardial ischemia in patients with unstable angina pectoris.

Aged↗