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Biomedical subjects

H Krönert

Publications and source records attributed to H Krönert.

13 recordsLinked to original sources
PubMed1980

Vasodilatory response of arteriovenous anastomoses to local cold stimuli in the dog's tongue.

In anesthetized dogs total tongue blood flow and its distribution to mucosa and muscle capillaries and to arteriovenous anastomoses (AVA) was determined by combining venous outflow measurements with the radioactive microsphere technique. Local temperature changes of the tongue surface in the physiological range revealed an inverse relationship between lingual blood flow (8.6--30.4 ml . min-1) and tongue surface temperature (40.5 to 27.7 degrees C). The temperature dependent changes of tongue blood flow were exclusively due to changes of AVA blood flow (6.3--21.4 ml . min-1).

Animals↗
PubMed1980

[Hemodynamic effects of medical and surgical therapy of hypertrophic obstructive cardiomyopathy (author's transl)].

In order to assess the hemodynamic effects of medical (propranolol) and surgical (transaortal subvalvular myectomy) therapy, we determined in 20 patients with hypertrophic obstructive cardiomyopathy the following circulatory parameters at rest and during maximal exercise before and after therapy: heart rate, stroke volume, cardiac output, and pulmonary artery pressure. 9 patients were re-investigated after medical therapy of 3.5 weeks to 7 months (averaging 3 months) with a daily dose of 120 to 360 mg (mean 198 +/- 80 mg) propranolol, 11 patients 1 week to 28 months (averaging 7.5 months) after operation. Propranolol induced a significant reduction of heart rate and cardiac output averaging 20.9% and 20.3%, respectively (p in both cases < 0.0001) at equal exercise levels, no change in stroke volume, and a slight increase in the pathologically elevated exercise mean pulmonary artery pressure, with the pulmonary vascular resistance remaining unchanged. Although 3 of the 9 patients reported a slight subjective improvement, exercise capacity did not change significantly from a mean of 66.7 to 69.4 watts. Myectomy, on the other hand, induced no change in heart rate, but a significant increase in exercise stroke volume by 14.9% (p < 0.025) and a distinct increase in cardiac output by an average of 11.2% (not significant), whereas the pathologically elevated exercise mean pulmonary artery pressure fell significantly by 23.8% from a mean of 45.0 to 34.3 mm Hg (p < 0.025). 10 of the 11 surgically treated patients reported a usually marked subjective improvement, and the exercise capacity increased from an average of 61.4 to 81.8 watts (p < 0.01). Thus, the clinical and functional result of surgical therapy was significantly better than that of medical therapy and included, in contrast to medical therapy, a significant hemodynamic improvement and increase in exercise capacity.

Adult↗
PubMed1980

[Thallium-201 myocardial scintigraphy in patients with normal coronary arteries and normal left ventriculogram - comparison with hemodynamics, metabolic and morphologic findings (author's transl)].

36 consecutive patients with chest pain and/or severe ventricular dysrhythmias, but normal coronary arteries and normal left ventriculogram, underwent thallium-201 myocardial imaging at rest and during exercise. The myocardial scintigram was abnormal in 27 patients (group A) and normal in only 9 patients patients (group B). To answer the question, whether the scintigram was false positive or a correct expression of a myocardial disorder not detectable with angiocardiographic methods, we compared the scintigraphic results with the findings of resting and exercise ECG (n = 36), mean pulmonary artery pressure during exercise (n = 27), myocardial lactate extraction during highrate atrial pacing (n = 14) and light- and electronmicropic examination of right ventricular endomyocardial biopsies (n = 14). The resting ECG was abnormal in 7 of 27 patients of group A and 1 of 9 patients of group B, the exercise ECG in 20 of 27 patients of group A and 1 of 9 patient B. An abnormally elevated exercise pulmonary artery pressure was measured in 10 of 21 patients of group A and 1 of 6 patients of group B. High rate atrial pacing induced an abnormal myocardial lactate extraction in 3 of 13 patients of group A, but not in the single investigated patient of group B. All 12 examined patients of group A and 1 of 2 patients of group B had abnormal biopsy findings. The high incidence of abnormal findings in group A compared to the rare incidence in group B suggests, that the abnormal myocardial scintigrams in patients with chest pain and normal coronary arteries is likely not false positive but reflects a myocardial disorder not being recognized on angiography.

Adult↗
PubMed1976

Lingual blood flow and its hypothalamic control in the dog during panting.

1. The effects of increased ambient temperature (Ta) on blood-flow and -temperatures of the tongue were studied in the unanaesthetized dog. At Ta of 20 degrees C and a relative humidity (rh) of 30% the mean lingual blood flow was 11 ml-min-1 (0.15 ml-g-1-min-1) and the temperature difference between the lingual artery and vein (deltaTLAV) was 1.0 degrees C. Accordingly, a heat loss of 48.6 J-min-1 was calculated even for the dog breathing with the mouth closed. When Ta was elevated to 38 degrees C at constant rh, panting ensued. In parallel fashion lingual blood flow increased to 60.4 ml-min-1 (0.81 ml-g-1-min-1) in mean and to 74.7 ml-min-1 (0.99 ml-g-1-min-1) at peak rate of thermal tachypnoea (272 breaths-min-1). This flow increase resulted from a decrease in the local vascular resistance since the driving systemic pressure remained constant. It was accompanied by an increase in TLAV to 1.5 degrees C equivalent to a heat loss of 400.7J-min-1 in mean and 496.2J-min-1 at maximum respiratory rate. 2. The preoptic/anterior hypothalamic (PO/AH) region was heated with a water perfused thermode in urethane anaesthetized dogs at constant body temperature in order to study the relationship in time between the increase in lingual blood flow and the onset of thermal panting. Lingual blood flow was found to be 20 ml-min-1 at a respiratory rate of 60 breaths/min. During hypothalamic heating both respiratory rate and lingual blood flow increased markedly. At maximum respiratory rates (244 breaths-min-1) lingual blood flow reached a level of 60 ml-min-1. When perfusion of the thermode was stopped, both respiratory rate and lingual blood flow synchronously returned to control values within 5 min. Similar changes did not occur in dogs in which a ventilatory response failed to be elicited during hypothalamic heating. 3. The results suggest that the tongue contributes to the evaporative heat loss mechanism and they confirm the concept that panting, associated with increased lingual blood flow, is induced by a common autonomic outflow pattern which is mediated by the central mechanism controlling thermal homeostasis.

Animals↗