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Biomedical subjects

W Bleifeld

Publications and source records attributed to W Bleifeld.

At least 37 records · Page 2Linked to original sources
PubMed1991

[Results of emergency bypass operation following percutaneous transluminal coronary angioplasty].

Between 1980 and 1988, percutaneous transluminal coronary angioplasty (PTCA) was performed in 1,514 patients. Fifty-five patients (3.6%) underwent emergency coronary bypass surgery because of an acute occlusion of the vessel or a dissection with sustained angina and signs of ischemia on the electrocardiogram. Twenty-five of these 55 patients had a myocardial infarction and 5 patients died, 3 perioperatively, 2 after hospital discharge. The degree of stenosis of the dilated vessel significantly influenced the incidence of infarction, while left ventricular ejection fraction prior to PTCA significantly influenced mortality. Patients who underwent surgery with an occluded vessel experienced myocardial infarction significantly more often (87%) than patients with a patent vessel (24%). The incidence of infarction was 27% when reperfusion of the vessel occluded during PTCA was achieved with a reperfusion catheter, repeated PTCA or intracoronary lysis. The patients' age, presence of unstable angina, left ventricular ejection fraction prior to PTCA, the dilated vessel, the extent of coronary artery disease, collateralization of the dilated vessel, and the time between the onset of the event necessitating bypass surgery and the beginning of extracorporeal circulation were found to have no influence on the incidence of infarction. Patients who died had a significantly lower ejection fraction before PTCA than survivors and all patients who died had experienced a large perioperative myocardial infarction.

Adult↗
PubMed1991

[Low-dose fish oil in primary hypertriglyceridemia. A randomized placebo-controlled study].

In a double-blind, randomized, placebo-controlled trial, we prospectively investigated the effects of two low doses of fish oil (10.5 and 5.25 g daily) in capsule form in patients with primary hypertriglyceridemia. During a 6 weeks' therapy with 10.5 g fish oil, serum triglycerides decreased by a mean of 38% from 578 +/- 167 to 358 +/- 66 mg/dl (p less than 0.05). With 5.25 g daily, triglyceride levels fell by 20% from 538 +/- 100 to 431 +/- 64 mg/dl (n.s.). With placebo, triglycerides increased by 8% from 835 +/- 176 to 900 +/- 228 mg/dl (n.s.). Total and HLD-cholesterol levels remained uninfluenced in all groups. Serum alkaline phosphatase decreased by a mean of 12% from 86 +/- 7 to 76 +/- 6 units/l in the patients treated with 10.5 g fish oil (p less than 0.01). Platelet aggregation after induction with collagen was slightly, but significantly inhibited in the patients treated with the higher dose of fish oil. Thus, in patients with primary hypertriglyceridemia, fish oil at a daily dose of 10.5, but not at 5.25 g, led to a significant reduction of serum triglyceride levels and to an inhibition of platelet aggregation.

Cholesterol↗
PubMed1990

Recanalization of chronic, totally occluded coronary arteries by new angioplasty systems.

The benefit and safety of new angioplasty equipment as compared with the conventional guidewire approach was evaluated in 154 consecutive patients. with chronic, totally occluded coronary arteries. The protocol followed a stepwise design: first, conventional guidewires and low-profile balloons were used, followed by "balloon-on-the-wire" systems (Probe, Ace) or by a shaft-enforced, tip-deflecting catheter (Omniflex). In 97 patients with occlusions of 2 to 12 weeks' duration, recanalization was achieved in 51 patients (53%) with the conventional approach and in 29 patients with the new devices (balloon-on-the-wire [n = 5], Omniflex [n = 24]), thereby raising the success rate to 82%. In 57 occlusions of greater than 12 weeks' duration, the recanalization attempt was successful in 58%, mediated in 16 patients (28%) by the Omniflex catheter and in 5 patients by balloon-on-the-wire systems. There were no life-threatening complications and only 1 (0.6%) emergency bypass operation was necessary. New angioplasty devices are therefore of considerable value in the attempt to improve the results of coronary angioplasty in chronic total occlusions.

Angioplasty, Balloon, Coronary↗
PubMed1990

Detection of human collateral circulation by vasodilation-thallium-201 tomography.

Coronary arteriolar vasodilation may provoke redistribution of flow to collateral-dependent jeopardized myocardium. To assess the physiologic significance of collaterals, 80 consecutive post-infarction patients (age 58 +/- 8 years) underwent vasodilation-redistribution thallium-201 tomographic imaging after administration of 0.56 mg of intravenous dipyridamole/kg body weight. Circumferential profile analysis of thallium-201 uptake and redistribution in representative left ventricular tomograms provided quantitative assessment of transient and fixed defects and separation between periinfarctional and distant inducible hypoperfusion. Tomographic perfusion data were correlated to wall motion and collateral circulation between distinct anatomic perfusion territories. Patients were grouped according to presence (59%) or absence (41%) of angiographically visible collateral channels to jeopardized myocardium. In the presence of collaterals, distant reversible defects were larger than in absence of collaterals (p less than 0.05); the extent of combined periinfarctional and distant redistribution was also larger in collateralized patients (p less than 0.025), whereas the size of the persistent perfusion defect was similar in both groups. By prospective analysis the tomographic perfusion pattern of combined periinfarctional and distant redistribution revealed a sensitivity of 85% and a specificity of 78% for the detection of significant collateral circulation in this group of patients. Thus, using the exhausted flow reserve as a diagnostic tool, vasodilation-thallium-201 tomography has the potential to identify and quantitate collateralized myocardium in post-infarction patients and may guide diagnostic and therapeutic decision-making.

Cardiac Catheterization↗
PubMed1990

Role of transmitral blood flow velocity by Doppler echocardiography in the evaluation of coronary artery disease.

To determine the relation between presence and severity of coronary artery disease and diastolic filling abnormalities by Doppler echocardiography, recordings of transmitral inflow velocity were made at rest in 90 patients with coronary artery disease and 28 normals. At the time of the Doppler examination, 81 patients with coronary artery disease (90%) and 10 normals (36%) were treated with antianginal medications. No difference was found in the ratio between early (E) and late (A) diastolic filling velocity (E/A ratio) when comparing patients with greater than 70% obstruction of at least one coronary artery to age-matched normals, regardless of the presence or absence of wall motion abnormalities. The E/A ratio was 1.3 +/- 0.46 in coronary patients with normal wall motion, 1.2 +/- 0.47 in coronary patients with abnormal wall motion, and 1.3 +/- 0.53 in both samples of age-matched normals. Multivariate analysis of the relation between E/A ratio and other variables showed that heart rate (F = 24.46, p less than 0.00001) and age (F = 19.51, p less than 0.00001) were significant independent determinants of the E/A ratio, while the presence or severity of coronary artery disease, the presence of hypertension, the magnitude of wall motion abnormalities, and end-diastolic dimension by echocardiography were not. These data suggest that transmitral inflow velocity recordings by Doppler have limited value for the recognition of coronary artery disease, since the E/A ratio is profoundly influenced by other factors, such as heart rate and age.

Adult↗
PubMed1990

Acute haemodynamic and neurohumoral effects of intravenous nisoldipine in patients with severe congestive heart failure.

Twenty patients (5 females, 15 males) with severe heart failure (NYHA IV), due to coronary artery disease in 14, and congestive cardiomyopathy in 6, received an intravenous bolus of the calcium blocker nisoldipine 0.2 mg followed by a continuous infusion of 0.2 micrograms.kg-1.min-1. Haemodynamic measurements were performed at baseline and after 30 min. The mean arterial pressure fell from 91 to 73 mmHg, pulmonary capillary wedge pressure from 31 to 26 mm Hg and systemic vascular resistance from 1695 to 1040 dyn.s.cm-5. The cardiac index (2.2 to 2.71.min-1.m-2, and stroke volume index (25 to 33 ml.m-2) were markedly increased. There was no reflex tachycardia as the heart rate dropped from 92 to 85 beats.min-1. Plasma renin activity and norepinephrine concentration did not change significantly. The findings indicate that nisoldipine acts as a strong vasodilator and that it has a beneficial acute haemodynamic effect in patients with severe left heart failure irrespective of its aetiology.

Adult↗
PubMed1990

Unstable angina: pathophysiology and drug therapy.

Unstable angina is a clinical syndrome characterized by increased rate and severity of angina pectoris attacks and, sometimes but not always, accompanied by ECG changes similar to those seen in coronary insufficiency. According to the present conception of the pathogenesis, ruptures at points of high-grade stenosis in the epicardial coronary arteries with simultaneous apposition of thrombi and vasoconstriction cause critical narrowing of the vascular lumen, which means that with the same level of oxygen consumption, coronary blood flow might be inadequate even at rest. In this way the development of severe ischemia, sudden cardiac death or myocardial infarction is programmed. Therapy must accordingly aim at avoiding or eliminating the progression of thrombosis and at increasing the reduced coronary blood flow. The prognosis is unequivocally improved by aspirin. In addition, heparin, 400 units/kg body weight, should be given. Thrombolysis may be possible after mechanical recanalization, depending on the individual results of coronary angiography. Providing the adverse reactions are monitored, nitroglycerin given intravenously is the basic drug therapy, although comparative studies against other drugs are not available and some data show the development of tolerance during prolonged use. Therefore, an early change to sustained-release nitrates or mononitrates can be justified. beta-receptor blockers reduce the frequency of silent ischemia and of myocardial infarction. By these means, in 80% of the patients affected, unstable angina will be converted to the stable form of the disease. If symptoms persist coronary angiography is urgently indicated, to allow the selection of PTCA or aortocoronary bypass surgery according to the findings.

Adrenergic beta-Antagonists↗
PubMed1990

Exercise capacity, arrhythmias, humoral and chemical parameters during long-term therapy with xamoterol.

In order to assess potential harmful effects of the partial beta-1 agonist xamoterol during long-term therapy, we randomly assigned 30 patients with coronary arterial disease and heart failure in classes II and III of the classification of the New York Heart Association to 200 mg of xamoterol twice daily or placebo during a treatment period of 3 months. A supine bicycle exercise test was performed at baseline and after three months in order to assess changes of exercise capacity. Blood samples for determination of creatinine, electrolytes, renin and norepinephrine were withdrawn simultaneously. Twenty-four hour ambulatory Holter electrocardiograms were performed before study, at the end of the study and 72 hours after withdrawal of study medication. On xamoterol, exercise capacity increased from 21.9 +/- 9.7 to 27.8 +/- 14.8 kilojoule (P = 0.032) compared to baseline levels. Exercise duration increased from 340 +/- 115 to 400 +/- 144 seconds (P = 0.043). Heart rate decreased by 10% (P = 0.05) at the 50 watt level and by 10% (P = 0.024) on maximum exercise compared to the baseline values. The rate pressure product was unchanged at rest and dropped by 11% (P = 0.038) on maximum exercise. In contrast, on placebo no significant changes occurred. During xamoterol therapy no changes of blood pressure, electrolytes, renal function and the time-intervals of electrocardiogram were observed. Xamoterol did not enhance arrhythmias during 24-hour ambulatory Holter monitoring. No serious side effects were observed. Xamoterol would appear to be a suitable and safe drug in the therapy of mild to moderate heart failure.

Adrenergic beta-Agonists↗
PubMed1990

Effects of streptokinase, urokinase, and recombinant tissue plasminogen activator on platelet aggregability and stability of platelet aggregates.

STUDY OBJECTIVE: The aim of the study was to evaluate the effects of streptokinase, urokinase and recombinant tissue plasminogen activator (TPA) on platelet aggregability and metabolism and the stability of preformed platelet aggregates. DESIGN: The experiments (n = 15 for each condition) were performed on citrated plasma or on platelet suspensions in phosphate buffered saline, both with a standardised platelet count of 250 x 10(9).litre-1. SUBJECTS: were healthy volunteers. MEASUREMENTS AND MAIN RESULTS: With both ADP (1 mumol.litre-1) and collagen (1 mg.litre-1) as aggregating agents, streptokinase at greater than or equal to 10(5) units.litre-1 led to reduction in the rate of platelet aggregation. With collagen and in most instances with ADP, this was associated with a decreased extent of aggregation, though in five out of 30 cases with ADP as aggregating agent, a conversion from reversible to irreversible aggregation occurred with streptokinase. Urokinase inhibited platelet aggregation at greater than or equal to 3 x 10(5) units.litre-1 with both aggregating agents. TPA inhibited aggregation at greater than or equal to 1 mg.litre-1 with ADP and at greater than or equal to 3.3 mg.litre-1 with collagen as aggregating agent. The inhibitory effect was still present when the platelets were suspended in saline. Platelet synthesis of thromboxane on stimulation with collagen, and of c-AMP on stimulation with prostaglandin E1, was markedly reduced by either agent. The stability of platelet aggregates, as assessed photometrically during a 90 min exposure to stirring stress, increased when streptokinase or urokinase was added to platelet rich plasma, but remained uninfluenced with TPA. CONCLUSIONS: Urokinase and TPA inhibited platelet aggregability uniformly and in a dose dependent manner. Streptokinase inhibited platelet aggregation in most instances, but led to a stimulation of aggregation in a minority of cases. These effects of the thrombolytic agents on platelets might have an influence on the occurrence of bleeding and of reocclusion after thrombolytic therapy.

Adenosine Diphosphate↗
PubMed1990

Sympathetic modulation in practice: the German clinical experience.

Xamoterol is a beta 1-selective adrenoceptor partial agonist. The acute effects of xamoterol were studied in 30 patients with ischaemic heart failure. Haemodynamic data were assessed at baseline, at rest and after supine bicycle exercise (50 W for 3 min), and repeated 15 min after xamoterol (0.2 mg kg-1) given by infusion over 5 min. At rest, xamoterol increased heart rate, mean blood pressure and cardiac index, and reduced pulmonary wedge pressure. On exercise, heart rate fell while cardiac index was maintained and pulmonary wedge pressure fell slightly but significantly. There was a tendency for plasma renin activity and plasma noradrenaline to fall both at rest and on exercise. The clinical relevance of these haemodynamic and neurohumoral changes were examined in conjunction with the German-Austrian Xamoterol Group's study, screening 443 patients with mild to moderate heart failure and giving xamoterol or placebo for 3 months as part of a randomized, double-blind study. The German experience was then placed in context of the pooled world-wide database of efficacy and safety in three other large (greater than 100 patients) studies with xamoterol in mild to moderate heart failure. In brief, this overview demonstrated a 2.98 +/- 0.68 kJ improvement in work done over placebo, equivalent to 14% (xamoterol) and 6% (placebo) improvements over baseline (P less than 0.0001). Xamoterol is thus a promising new approach to the treatment of mild to moderate heart failure.

Adrenergic beta-Agonists↗
PubMed1990

Assessment of post-infarction jeopardized myocardium by vasodilation--thallium-201 tomography: impact on risk stratification.

For the purpose of risk stratification 80 consecutive patients (mean age 58 +/- 7 years) with a chest pain syndrome after documented myocardial infarction underwent tomographic vasodilation-redistribution thallium-201 perfusion imaging, using 0.56 mg kg-1 intravenous dipyridamole. Tomograms were analysed for size and location of reversible and fixed perfusion defects and correlated to angiographic characteristics, left ventricular ejection fraction and wall motion, collateral status and 1-year prognosis, as measured by cardiac events within 12 months. No serious side-effects were noted with the diagnostic use of intravenous dipyridamole. According to the perfusion pattern three subgroups of post-infarction patients were identified: (1) by ischaemia at a distance with redistribution in non-infarct related territories (n = 48); (2) by peri-infarctional ischaemia with redistribution in the territory of the 'infarct artery' (n = 9); and (3) by exclusively fixed defects without redistribution (n = 23). Ischaemia at a distance was associated with a larger reversible defect than peri-infarctional ischaemia (P less than 0.05) and the pattern without redistribution (P less than 0.005); the fixed defect size, however, was similar in all three subgroups. In addition, the severity of coronary artery disease (Gensini score and number of diseased vessels) and the degree of collateralization was higher in the presence of a redistribution pattern (P less than 0.05), although no significant differences in global and regional function were noted as a function of thallium-201 redistribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

A prospective study of the diagnostic value of urinary thromboxane in patients presenting with acute chest pain.

In chance single-case observations thromboxane excretion has been reported to increase several days prior to myocardial infarction. To test its frequency and potential diagnostic value we prospectively measured thromboxane excretion in 166 consecutive patients who had presented to the emergency unit with acute chest pain indicative of ischaemia. Thromboxane excretion at presentation was increased, sometimes dramatically, in 17 of 33 (52%) patients with unstable angina, in 42 of 73 (57%) patients with definite myocardial infarction, but in only two of 14 (14%) patients with stable angina. Nineteen of 29 patients undergoing early angiography had detectable intracoronary thrombi, and these patients excreted significantly more thromboxane than patients without thrombi. Ongoing platelet activation may be detected by increased thromboxane excretion in more than 50% of the patients presenting with unstable angina and myocardial infarction, particularly in those with intracoronary thrombi, but it is not a general phenomenon that can be used in diagnosis.

Aged↗
PubMed1990

Stability of pacing threshold, impedance, and R wave amplitude at rest and during exercise.

The pacing threshold of the human heart may be altered by physiological factors such as physical exercise. These changes may influence the individual programming of a pacemaker, since pacemakers can be programmed at pulse amplitudes of 2.5 volts and less. We investigated 22 patients with a multiprogrammable ventricular demand pacemaker 3 months after implantation; 16 patients had received a steroid-eluting lead and six patients had an Elgiloy lead. Parameters measured at rest and immediately after exercise were: Voltage threshold at pulse durations between 0.05 and 0.6 ms, impedance, R wave amplitude and energy consumption for the pacing threshold at 0.5 ms pulse duration. All patients performed a symptom limited supine bicycle exercise test. None of the investigated parameters showed a significant difference between rest and exercise, neither for the steroid eluting lead nor for the Elgiloy lead. The data suggest that the individual programming of a pacemaker adapted to the measurements at rest is also reliable and safe during exercise.

Aged↗
PubMed1990

Chronic ventricular electrograms: do steroid-eluting leads differ from conventional leads?

The aim of steroid-eluting leads is to reduce chronic pacing thresholds. Whether steroid-eluting leads also modify acute and chronic R wave amplitudes as well as R wave sensing of the pulse generator was investigated in 31 patients with a unipolar ventricular pacemaker. Four different leads were implanted: Two steroid-eluting leads with different electrode surface areas (8 mm2 and 5.8 mm2) and two conventional leads (Target Tip, Elgiloy lead). At implantation filtered R wave amplitudes, peak-to-peak values, and slew rates were measured by a pacing system analyzer. One year after implantation R wave amplitudes were directly determined from intracardiac electrograms and compared to the peak-to-peak data at implantation. Additionally, R wave inhibition was evaluated at a sensitivity setting of 5 mV. There were no differences among the four leads in respect to any of the parameters studied at implantation. At follow-up, no differences in R wave amplitudes were found leading to an appropriate sensing in all leads. Steroid-eluting leads did not differ from conventional leads and a smaller electrode surface area of 5.8 mm2 had no influence on ventricular electrogram. Together with a pacemaker with an input impedance of 37 kohms R wave sensing was a correct setting of 5 mV.

Aged↗
PubMed1990

Lack of tolerance development after long-term administration of the partial beta-adrenoceptor agonist xamoterol.

Xamoterol is a selective partial beta-adrenoceptor agonist. In a double-blind randomized placebo-controlled study, 30 patients (1 female, 29 male) with mild to moderate heart failure were treated with 200 mg of xamoterol twice daily or placebo during 3 months. At baseline and 72 h after the last tablet intake, the hemodynamic and humoral effects of a single intravenous dose of xamoterol (0.2 mg/kg) were assessed by right heart catheterization. At baseline, intravenous xamoterol raised resting heart rate by 3% (NS) in the placebo and by 6% (NS) in the xamoterol group. On exercise, heart rate was reduced by 10% (p = 0.015) and 7% (p = 0.016), respectively. Pulmonary capillary wedge pressure (PCWP) dropped in both groups: at rest by 4 mm Hg (p = 0.0004) in the placebo group and by 6 mm Hg (p = 0.0002) in the xamoterol group; on exercise by 1 mm Hg (NS) in the placebo and by 6 mm Hg (p = 0.0001) in the xamoterol group. Similar changes of all variables were obtained after long-term therapy in both groups. Mean arterial blood pressure, cardiac index and systemic vascular resistance did not change importantly. Norepinephrine levels did not change, but plasma renin activity decreased at baseline as well as after long-term therapy in both groups by similar amounts. Thus, no signs of tolerance development were observed after an oral treatment with 200 mg of xamoterol twice daily during 3 months. However, xamoterol as a partial agonist exerted only weak changes of cardiac index and PCWP compared to full beta-adrenoceptor agonists. The drug was well tolerated, and serious side effects were absent.

Administration, Oral↗
PubMed1990

[Hemodynamic and humoral changes following intravenous administration of xamoterol in patients with heart failure and coronary heart disease].

Xamoterol is a beta-1 selective partial adrenoceptor agonist. Thirty patients (one female, 29 male, mean age 56 +/- 8 years) with coronary artery disease and mild to moderate heart failure, according to NYHA classes II and III, were studied before and 15 min after intravenous administration of 0.2 mg/kg xamoterol, at rest and during standard, supine bicycle exercise. At rest, the pulmonary capillary wedge pressure fell by 39% (p = 0.0001) and the cardiac index increased by 7% (p = 0.0084); heart rate increased only slightly. With exercise, cardiac index did not change and the pulmonary capillary wedge pressure decreased by 11% (p = 0.0003). In addition, the heart rate dropped from 115 to 105 bt/min (p = 0.0001) which resulted in a decrease of the rate pressure product by 9% (p = 0.0041). Arterial blood pressure remained unchanged. Norepinephrine plasma levels did not change at rest or during exercise, whereas at rest plasma renin activity dropped by 18% (p less than 0.05) and by 20% (p less than 0.05) during exercise. No untoward side effects were observed and the drug was well tolerated. In conclusion, xamoterol, given acutely to patients with heart failure NYHA classes II or III exerted advantageous hemodynamic effects at rest and during exercise.

Adrenergic beta-Agonists↗
PubMed1990

[Sympathetic activity in patients with heart failure due to idiopathic dilated cardiomyopathy: effect of ACE inhibitors and other vasodilators].

A decrease in cardiac output in patients with congestive heart failure due to dilated cardiomyopathy is compensated by stimulation of the sympathetic nervous system and the renin-angiotensin-aldosterone system. The increase in plasma norepinephrine and depletion of norepinephrine in the myocardium as well as the disturbance of beta-adrenal and baroreceptor function reflect the limits of the sympathetic nervous stimulation. Together with augmented levels of angiotensin II and vasopressin, this stimulation leads to a significant increase in systemic vascular resistance. Sustained stimulation of at least one of these mechanisms can cause further impairment of the left ventricular function. The severity and prognosis of congestive heart failure due to dilated cardiomyopathy is expressed by the plasma norepinephrine concentration and by its myocardial depletion. Ultimately, activation of the compensatory mechanisms provides the basis for therapeutic approaches: 1. reduction of afterload and systemic vascular resistance and/or 2. diminution of the sympathetic nervous activity. For about the last ten years, ACE inhibitors have been used as pharmacological treatment in addition to positive inotropic and vasodilating substances. Captopril, one of the first orally applicable drugs, reduces left ventricular filling pressure, pulmonary capillary pressure, systemic vascular resistance and increases the cardiac output. Beside the hemodynamic improvement, a decrease in plasma norepinephrine and aldosterone can be observed. Vasodilators and alpha-blocking agents can also reduce afterload and systemic vascular resistance in patients with congestive heart failure due to dilated cardiomyopathy, and may lead to hemodynamic improvement. The main limitations of their long-term application are relatively short duration of action, reflex activation of the renin-angiotensin system due to vasodilation and induction of tolerance.

Angiotensin-Converting Enzyme Inhibitors↗