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Biomedical subjects

G Härtel

Publications and source records attributed to G Härtel.

At least 19 recordsLinked to original sources
PubMed2001

Photochemical oxidation of p-chlorophenol by UV/H2O2 and photo-Fenton process. A comparative study.

In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV/H2O2 and the photo-Fenton reaction (UV + classical Fenton reaction) were investigated in lab-scale experiments for the degradation of p-chlorophenol. The study showed that the photo-Fenton process, (a mixture of hydrogen peroxide and ferrous or ferric ion), was the most effective treatment process under acidic conditions and produced a higher rate of degradation of p-chlorophenol at a very short radiation time. It accelerated the oxidation rate by 5-9 times the rate for the UV/H2O2 process. The reaction was found to follow the first order, the reaction was influenced by the pH, the input concentration of H2O2 and the amount of the iron catalyst and the type of iron salt. The experimental results showed that the optimum conditions were obtained at a pH value of 3, with 0.03 mol/l H2O2, and 1 mmol/l Fe(II) for the UV/H2O2/Fe(II) system and 0.01 mol/l H2O2 and, 0.4 mmol/l Fe(III) for the UV/H2O2/Fe(III) system. The reactions were accompanied by the generation of Cl- which reached its maximum value at a short reaction time when using the photo-Fenton process. Finally a rough comparison of the specific energy consumption shows that photo-Fenton process reduced the energy consumption by at least 73 to 83% compared with the UV/H2O2 process.

Chlorophenols↗
PubMed1987

Value of combined cross sectional and Doppler echocardiography in the detection of left ventricular pseudoaneurysm after mitral valve replacement.

The development of a left ventricular pseudoaneurysm is a rare complication of heart surgery. Until recently it has been impossible to detect without an angiographic study of the left ventricle. A combination of cross sectional and Doppler ultrasound studies led to the correct diagnosis in two patients with left ventricular pseudoaneurysms after mitral valve replacement. Cross sectional echocardiography showed a posterolateral echo-free space confined only by the pericardium and communicating with the left ventricle through a defect in the ventricular wall, and Doppler echocardiography confirmed the presence of blood flow in this cavity. This Doppler finding is critical if the perforation is too small to be identified reliably by cross sectional imaging. Surgical repair of the pseudoaneurysm can be undertaken without invasive studies if the echocardiographic findings are unequivocal and there is no reason to suspect the integrity of the circumflex coronary artery.

Adult↗
PubMed1987

Psychological factors in cardiac arrhythmias.

Autonomic nervous control of the heart and the blood vessels is essential for optimal physical performance. Afferent nerves conduct impulses to the vasomotor and cardioaccelerator and cardioinhibitor centres resulting in efferent sympathetic and vagus output. Information inputs also from the environment and the person's thought processes are mediated from the cortex by the hypothalamus, the limbic system, and the autonomic nervous system to the heart and blood vessels. Emotional factors like anger, anxiety, and fear increase sympathetic output and influence heart rate. On the other hand, fear and the feeling of being in a helpless situation causes intensive vagal activation with ensuing severe bradycardia or asystole and vasovagal syncope. Although psychologic factors can cause extreme grades of tachy- or bradycardia they usually have no acute deleterious effects in the normal heart. In the diseased heart, however, consequences may be hazardous. Emotional factors are known to increase ventricular arrhythmias either directly or indirectly by increasing heart rate and causing ischaemia as in coronary heart disease. In animal experiments ventricular fibrillation threshold is lowered by aversive conditions. In heart diseases with sudden death as a well known complication increased sympathetic activity may give rise to fatal arrhythmias. In man the evidence of psychologic factors as the cause of life-threatening arrhythmias and sudden death is mostly anecdotal or circumstantial. Well designed studies are needed to evaluate the role of psychologic factors in arrhythmias.

Animals↗
PubMed1985

Efficacy of oral propafenone in chronic ventricular arrhythmias: a placebo controlled cross-over exercise study.

The efficacy of propafenone, a new class I C antiarrhythmic drug, on ventricular premature contractions (VPCs) during rest and exercise was assessed during a two-phase protocol: phase 1, an initial two week placebo controlled double blind cross-over assessment; phase 2, an open 3 month follow-up. Twelve consecutive patients with symptomatic chronic ventricular arrhythmias and fulfilling other inclusion criteria underwent an exercise test and were allocated to either propafenone or placebo. During the double blind phase, oral propafenone significantly reduced the number of VPCs at rest with the patient supine or sitting, during the bicycle ergometer test, and after the exercise test. After 3 months of treatment a 90 to 100% reduction of VPCs was achieved in 11 patients continuing on 600 to 900 mg of propafenone daily. Treatment was stopped in one patient during the double blind phase because of drug induced LBBB. A prolongation of the PR interval and QRS duration occurred in all patients with propafenone doses exceeding 450 mg day-1. Subjective side effects were slight and consisted of abnormal taste sensations and minor central nervous symptoms. The results suggest that propafenone is an effective drug for the treatment of ventricular arrhythmias in selected patients. A-V or intraventricular conduction disturbances contraindicate its use.

Administration, Oral↗
PubMed1985

Removal of monofilamental and multifilamental temporary pacing leads following open-heart surgery: occurrence of arrhythmias.

This study compared multifilamental and monofilamental temporary pacing leads in a clinical series of 83 patients who underwent valve replacement or coronary artery bypass grafting. The leads were used in the bipolar mode and were implanted into the outer layers of the right ventricular myocardium. The force required for wire removal (newtons), and the arrhythmias which occurred during removal were monitored. During electrode removal, 48% of the patients had transient arrhythmias (46% with monofilamental and 51% with multifilamental leads). The most common was a single ventricular premature contraction. In one case, wire removal caused non-sustained ventricular tachycardia. All the arrhythmias subsided spontaneously. There was no statistical difference between results of the two leads. The force needed for removal was monitored directly by applying force via a graduated spring; they were equal in both groups (2.6 newtons). Both electrode types behaved similarly during wire removal, and the spiral tail of the monofilamental lead did not provoke arrhythmias.

Adult↗
PubMed1982

Neurogenic and psychological factors in coronary heart disease: an introductory overview.

Some of the major nervous and psychological factors affecting the functioning of the heart are briefly reviewed. Emphasis is placed on the autonomic nervous system and its response to stressful situations. Possible pathways by which mental processes and behaviour might influence cardiovascular pathology and sudden death are outlined. Differences observed in the pattern of response are emphasized, as are the factors upon which these differences depend. The Type A behaviour pattern is considered and the importance of marital and social support is also discussed.

Autonomic Nervous System↗
PubMed1982

Surgical intervention in cases of Ebstein's anomaly. Abnormal origin and structure of the tricuspid valve.

During the ten-year period 1972-81 four patients, two men and two women, with Ebstein's disease underwent operation at our institution. Their average age was 34. Central cyanosis at rest, clubbing and polycythaemia were the most common clinical features of the patients. Enlarged heart, a small pulmonary arterial arch and transluminal lung fields were seen in chest X-ray. Operative findings were a grossly enlarged right atrium and ventricle, the latter having a segment that was typically atrialized and thin-walled but was contracting synchronously with the true right ventricle, and a wide variation in the leaflets of the tricuspid valve and their origins. The atrial septal defect was small in all cases. Artificial heart valves (1 Cutter-Smeloff, 2 Björk-Shiley, 1 St. Jude) were used in the tricuspid reconstruction in addition to closure of the ASDs. One of the patients died postoperatively, the other three are doing well.

Adult↗
PubMed1976

Human serum and myocardium digoxin.

Linear correlation was demonstrated between serum digoxin and papillary muscle digoxin concentrations in patients undergoing mitral valve surgery. The mean ratio of myocardial tissue to serum digoxin concentrations was 6711. This result supports the use of serum digoxin as a guide for assessing the degree of digitalization under steady-state conditions.

Adult↗