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Biomedical subjects

H Mayr

Publications and source records attributed to H Mayr.

At least 19 recordsLinked to original sources
PubMed2002

[Recanalization of chronic coronary occlusions].

Recanalization of occluded coronary arteries is the aim of percutaneous interventions with acute myocardial infarction. Moreover, chronic coronary occlusion is a common finding during diagnostic coronary angiography and is often a contributing factor in the choice of revascularisation by surgery rather than by percutaneous coronary interventions (PCI). An occluded coronary artery with some degree of collateral supply is functionally comparable to a severe coronary stenosis. Therefore, recanalization of chronic occluded coronary arteries results in less angina and often in improvement of left ventricular function. Success is limited in particular in longer lasting occlusions. Characterization of lesions, where recanalization can performed successfully is warranted. We correlated primary success rates of attempted coronary recanalizations with localisation of lesions and procedural characteristics. We analyzed records of 124 consecutive patients, who underwent attempted coronary recanalization of chronically occluded coronary arteries at our institution in 1998. Revascularisation was successful in 84 (64 male, 20 female) of 124 (92 male, 32 female) patients. Therefore, success rate was 67.7% (69.9% in men, 62.5% in women, p = 0.42). Target vessel was the left anterior descending artery (LAD) in 49 cases. Success rate in the LAD did not differ significantly from that in "non-LAD"-vessels (65.3% versus 69.3%; p = 0.35). Successful recanalizations were performed using only one guide-wire in 77.3%. More than one guide-wires were used during procedures without success in 44.5% and exceeded use in successful interventions (p < 0.05). Procedures, failing to be successful after an attempt with a first guide-wire, could be performed successfully using at least a second wire in 50%. Coronary stenting after recanalization has been performed in 84.4% in the LAD and in 59.7% in non-LAD vessels (p < 0.01). Success rate of attempted recanalizations of chronic occluded coronary arteries in unselected patients is high. Most procedures can be performed successfully using only one guidewire. Additional use of other wires can increase success rates in procedures with primary failure to pass the occlusion. Stenting has been performed in three out of four patients with successful recanalization of chronically occluded coronary arteries.

Aged↗
PubMed2001

Reference scales for the characterization of cationic electrophiles and neutral nucleophiles.

Twenty-three diarylcarbenium ions and 38 pi-systems (arenes, alkenes, allyl silanes and stannanes, silyl enol ethers, silyl ketene acetals, and enamines) have been defined as basis sets for establishing general reactivity scales for electrophiles and nucleophiles. The rate constants of 209 combinations of these benzhydrylium ions and pi-nucleophiles, 85 of which are first presented in this article, have been subjected to a correlation analysis to determine the electrophilicity parameters E and the nucleophilicity parameters N and s as defined by the equation log k(20 degrees C) = s(N + E) (Mayr, H.; Patz, M. Angew. Chem., Int. Ed. Engl. 1994, 33, 938-957). Though the reactivity scales thus obtained cover more than 16 orders of magnitude, the individual rate constants are reproduced with a standard deviation of a factor of 1.19 (Table 1). It is shown that the reactivity parameters thus derived from the reactions of diarylcarbenium ions with pi-nucleophiles (Figure 3) are also suitable for characterizing the nucleophilic reactivities of alkynes, metal-pi-complexes, and hydride donors (Table 2) and for characterizing the electrophilic reactivities of heterosubstituted and metal-coordinated carbenium ions (Table 3). The reactivity parameters in Figure 3 are, therefore, recommended for the characterization of any new electrophiles and nucleophiles in the reactivity range covered. The linear correlation between the electrophilicity parameters E of benzhydryl cations and the corresponding substituent constants sigma(+) provides Hammett sigma(+) constants for 10 substituents from -1.19 to -2.11, i.e., in a range with only very few previous entries.

Journal Article↗
PubMed2001

[Acute coronary syndromes: an update. II. Coronary revascularization and risk stratification].

UNLABELLED: CORONARY REVASCULARIZATION: PTCA in patients with refractory unstable angina is associated with a substantial risk of the following complications: death, myocardial infarction, need for emergency surgery, and restenosis. The introduction of intracoronary stents, however, has improved both short-term and long-term outcomes. The newer adjunctive pharmacologic therapies enhance even further the benefits associated with the use of stents. The decision regarding the specific revascularization procedure to be used (e.g., CABG, PTCA, stent placement, or atherectomy) is based on the coronary anatomy, the left ventricular function, the experience of the medical and surgical personnel, the presence or absence of coexisting illnesses, and the preferences of both the patient and the physician. RISK STRATIFICATION: Among patients with unstable angina or non-Q-wave myocardial infarction, there is an increased risk of death within 6 weeks in those with elevated troponin I levels and the risk of death continues to increase as the troponin level increases. Reversible ST segment depression is associated with an increase by a factor of 3-6 in the likelihood of death, myocardial infarction, ischemia at rest, or provocable ischemia during a test to stratify risk. Exercise or pharmacologic stress testing provides important information about a patient's risk. Although the conditions of the majority of patients with unstable angina will stabilize with effective antiischemic medications, approximately 50-60% of such patients will require coronary angiography and revascularization because of the "failure" of medical therapy. High-risk patients are those who have had angina at rest, prolonged angina, or persistent angina with dynamic ST segment changes or hemodynamic instability, and they urgently require simultaneous invasive evaluation and treatment. Medical therapy should be adjusted rapidly to relieve manifestations of ischemia and should include antiplatelet therapy (aspirin, or ticlopidine or clopidogrel if aspirin is contraindicated), antithrombotic therapy (unfractionated heparin or low-molecular-weight heparin), beta-blockers, nitrates, and possibly calcium-channel blockers. Early administration of glycoprotein IIb/IIIa inhibitors may be particularly important, especially in high-risk patients with positive troponin tests or those in whom implantation of coronary stents is anticipated.

Acute Disease↗
PubMed2001

[Acute coronary syndromes: an update. I. Pathogenesis and drug therapy].

BACKGROUND: Unstable angina accounts for more than one million hospital admissions annually. 6-8% of patients with this condition have non-fatal myocardial infarction or die within the first year after diagnosis. Recently, the term "acute coronary syndromes" has been used to describe the spectrum of conditions that includes unstable angina, non-Q-wave myocardial infarction (which generally presents without ST-segment elevation), and Q-wave myocardial infarction (which generally presents with ST-segment elevation). PATHOGENESIS: Disruption of a formed plaque is a complex pathologic process that is central to the initiation of the acute coronary syndromes. Local thrombosis occurring after plaque disruption results from complex interactions among the lipid core, smooth-muscle cells, macrophages, and collagen. TREATMENT: Multiple huge clinical trials confirmed that aspirin reduces the risk of death from cardiac causes and fatal and non-fatal myocardial infarction by about 50-70% in patients presenting with unstable angina. Ticlopidine may be substituted for aspirin in patients with hypersensitivity to aspirin or gastrointestinal intolerance. Clopidogrel acts similarly to ticlopidin but has fewer side effects than ticlopidine and has not been reported to cause neutropenia. High-risk patients with refractory unstable angina and elevated troponin levels may have substantial benefit of glycoptotein (GP) IIb/IIIa inhibition. Current practice guidelines support the use of the combination of unfractionated heparin and aspirin for the treatment of unstable angina. Clinical studies have demonstrated that the incidence of the composite end point of death, myocardial infarction, or recurrent angina was lower with enoxaparin than with unfractionated heparin. Beta-blockers, nitrates, and calcium-channel blockers are useful for antiischemic therapy in patients with acute coronary syndromes.

Acute Disease↗
PubMed2001

[Coronary artery bypass graft dysfunction--clinical presentation, laboratory and electrocardiographic parameters].

The recurrence of symptoms after coronary artery bypass surgery is often caused by bypass-dysfunction. In this study we tried to determine factors related to the long-term patency of arterial and venous bypass grafts. We evaluated all patients with bypass grafts undergoing coronary angiography in the year 1998 at our hospital (163 patients, mean age 67 years, mean interval since the operation 79 months, a total of 341 venous bypasses (VBP), 386 peripheral venous anastomoses and 85 arterial (LIMA = left internal mammarial artery) bypasses. The data were collected by a retrospective analysis of the hospital records. Statistics were performed using the Wilcoxon-Mann-Whitney-U test. After an interval of 53 months LIMA-bypasses were patent without stenosis in 92%. Symptoms were caused in only 2% by a dysfunction of the LIMA-graft. The patency of venous bypass grafts decreased with time (5 years after the operation 74% were patent without stenosis, 5-10 years 56%, more than 10 years 35%, p < 0.01). We found clear relations between the function of the venous grafts and the clinical presentation (patent grafts without stenosis in 43% with acute coronary syndromes, in 57% with stable angina [p = 0.08] and in 86% with atypical angina [p < 0.0001 for the difference between each of the first two and the last syndrome]), the resting-ECG (65% patent VBP without stenosis with normal ST-segments and 49% with abnormal ST-segments, p < 0.01), the body-mass-index (70% patent VBP without stenosis with a BMI < 25 and 56% with a BMI > 30, p = 0.05) and the erythrocyte sedimentation rate after 2 hours (79% patent VBP with an ESR < or = 20 mm vs. 64% with an ESR > 49 mm, p = 0.02). The function of VBP after coronary artery bypass graft (CABG)-procedure depends primarily upon the interval since the operation. In addition, we found correlations with clinical presentation, resting-ECG, body-mass-index and erythrocyte-sedimentation rate as a possible marker of inflammation in bypass-atherosclerosis. Therefore, inflammatory processes seem to play an important role in the development of venous graft dysfunction.

Aged↗
PubMed2001

[Pharmacologic interventions in primary prevention: lipid lowering drugs, aspirin, antiobesity drugs, and antihypertensive agents].

Heart disease, particularly coronary heart disease is a major cause of morbidity and mortality in developed countries. Cardiovascular disease accounts for more than 50% of deaths. Drug therapy is highly effective for treatment of patients after a first cardiovascular event (secondary prevention). In contrast, introduction of drug therapy for lowering cardiovascular risk before a first cardiovascular event (primary prevention) is discussed controversially. The number of persons who need to be treated for prevention of one cardiovascular event is high and drug therapy in more or less "healthy" people is justified only after accurate assessment of potential risks and possible beneficial effects. Drug therapy combined with non-pharmacological treatment strategies is considered to be appropriate in selected high-risk persons for primary prevention. The following article describes potential indications of several drugs, in particular cholesterol-lowering therapy, aspirin, drug therapy of obesity and hypertension, for use in primary prevention of cardiovascular disease.

Anti-Obesity Agents↗
PubMed2001

Virtual eye muscle surgery based upon biomechanical models.

Within our research project "SEE-KID", a Software Engineering Environment for Knowledge-based Interactive Eye Motility Diagnostics, we focus on virtual reality training for the surgery of human eye muscles of--mostly--children age 1 to 3. Our report gives details on the sound integration of biomechanical muscle data into our virtual reality models in order to evaluate the quality of specific techniques for eye motility surgery regarding real-world pathologies. We illustrate the usefulness of our software system describing some of the possible medical applications, like optimized transposition surgery of the musculus obliquus superior.

Artificial Intelligence↗
PubMed2001

Early investigation of silver-coated Silzone heart valves prosthesis in 126 patients.

BACKGROUND AND AIM OF THE STUDY: Permanent silver (Silzone) coating of the sewing cuff of St. Jude Medical prosthetic heart valves may reduce the rate of prosthetic valve endocarditis (PVE). However, the incidence of paravalvular leaks and stroke in patients after implantation of Silzone-coated heart valve prostheses is largely unknown. METHODS: Complications were analyzed among 126 consecutive patients (78 males, 48 females; mean age 64.7 years; range: 40-80 years) who received Silzone-coated prostheses at our institution between February 1998 and December 1999. Among patients, 94 had aortic valve replacement, 29 mitral valve replacement, and three had aortic and mitral valve replacement. Concomitant cardiac procedures (mainly coronary bypass) were performed in 47 patients (37.3%). RESULTS: Hospital mortality was 1.6% (2/126) and freedom from valve-related mortality 99.2+/-0.9%. Total follow up was 137.4 patient-years, and 98.4% complete. Strokes or transitory ischemic attacks (TIAs) occurred in four cases (two strokes, two TIAs; stroke rate 1.5%/year; 95% CI 0.4-2.6%/year; stroke+TIA rate 3%/year; 95% CI 0.4-5.25%/year). There was no case of prosthetic valve dysfunction or PVE. Freedom from reoperation due to procedure-associated complications was 97.6% (one aortic dissection, two major bleeds). Paravalvular leak was detected in 19 cases, and graded trivial or mild in 17 cases (11 grade 0-I, six grade I), and moderate in two cases (grade I-II in one, grade II in one). No patient needed reoperation due to paravalvular leak. Left ventricular (LV) function was normal in 80 cases, but was impaired mildly in 20 cases, moderately in 16, and severely in eight. Bicycle exercise testing in 92 patients (73%) showed median exercise performance (81.4+/-23.9% of normal) after correction for age and weight. Cerebral magnetic resonance imaging was performed in 64 patients (50.8%); median MRI score was 2.0+/-1.8 according to a 12-scaled score system. CONCLUSION: The overall incidence of echocardiographic paravalvular leak graded more than trivial or mild was low (1.6%) in patients followed for a mean of 1.1+/-0.5 years (range: 1-27 months) after valve replacement with Silzone-coated heart valve prostheses. No patient required reoperation due to paravalvular leak; moreover, the stroke rate (1.5%/year) was low in these patients. The present data indicated no significant disadvantages or higher rate of complications related to silver coating compared with other, non-silver-coated prostheses. Future investigation is needed to determine long-term outcome.

Adult↗
PubMed2000

[Rupture of a congenital right coronary sinus of Valsalva aneurysm as etiology of acute cardiac decompensation].

A 54 year old woman was admitted to a hospital because of acute thoracal pain, dyspnea, and clinical signs of overt right heart failure. Transthoracic and multiplane echocardiography established the diagnosis of a ruptured aneurysm of the right coronary sinus of valsalva into the right atrium which could be confirmed by cardiac catheterization. During heart surgery, which was done without complications, the defect was closed with a suture. Six months later echocardiography showed a normal right ventricle; the function of the aortic valve was regular. Acute heart failure may be due to a congenital structural cardiac anomaly in spite of the age of 54. In such conditions transthoracic and especially transesophageal echocardiography serve as noninvasive excellent tools to make an exact diagnosis.

Acute Disease↗
PubMed2000

[Physical activity and training in heart failure].

The main symptoms of chronic heart failure are dyspnea and exercise intolerance. The pathophysiological basis of these symptoms is not simply the dysfunction of the heart, but a complex interaction of the central circulation, the peripheral vessels, the skeletal muscles, the ventilatory, and the endocrine system. In contrast to acute heart failure, where bedrest is known to be beneficial, prolonged limitation of physical activity can be detrimental in the chronic stage of the disease. Therefore, since the 1980s there have been several reports about heart failure patients participating in exercise programs. The results were encouraging: the physiological gains were impressive, and contrary to prior fears, in the great majority of reports no deterioration of the cardiac function could be observed. The net result of training in this condition is an improvement in exercise capacity in the range of the best pharmacological treatment. In detail, blood flow into the working muscle is increased, the ventilation for each given workload is reduced, the skeletal muscle overall function (including biochemical and histological aspects) is improved, the increased neurohormonal activity--especially of the sympathico-adrenergic system--will be normalized, and the patient's quality of life is significantly improved. Whether all of these beneficial aspects will result in improved survival is not yet proven, although one recent study provides some evidence in this direction. But even if today no definite answer to this question from a large, multicenter trial is available, application of exercise training for selected heart failure patients can be recommended, if adequate supervision is provided.

Autonomic Nervous System↗
PubMed2000

[Anti-ischemia effect of estrogens].

Consideration of estrogen replacement therapy is well established in the treatment of postmenopausal syndrome and osteoporosis in menopause. Some observational epidemiologic studies on this topic have suggested beneficial effects on cardiovascular disease. A prospective, controlled, randomized clinical trial with respect to cardiovascular events and mortality in postmenopausal hormone users, the HERS (Heart and Estrogen/Progestin Replacement) study has recently been published. Anti-ischemic effects of estrogens are mediated by improvement of menopausal-associated endothelial dysfunction, calcium antagonism, and activation of endothelial synthesis of prostacyclin. Improvement in functional state and reduction of stress-induced myocardial ischemia with hormone replacement therapy (HRT) have been demonstrated in several clinical trials. Thus, because of available clinical data, introduction of HRT for cardiovascular reasons in patients with coronary artery disease is still considered ambiguous and cannot be generally recommended for secondary prevention in this group of patients.

Clinical Trials as Topic↗