Biomedical subjects

M Groh

Publications and source records attributed to M Groh.

16 recordsLinked to original sources

PubMed2005

[Telemedical-supported screening of retinal vessels ("talking eyes")].

BACKGROUND: Cerebral and retinal vessels behave similarly under the influence of vascular risk factors. Several groups have shown that retinal microvascular abnormalities represent an independent risk factor with regard to strokes and heart attacks. AIM OF THE STUDY: The aim of this study was to perform a prospective screening examination with regard to retinal microvascular abnormalities as well as an extended vessel diagnosis in a subgroup of patients with lower arteriovenous risk values. METHODS: In the course of a prospective cross-sectional study ("Talking Eyes") between 1.9.2001 and 1.8.2002 a telemedical-supported screening of the retina (study I) was carried out in 7,163 subjects. The patients were selected without any inclusion or exclusion criteria. The mean age was 48.2 +/- 8 years (18 - 83 years) with a sex distribution of 39.2 % females to 60.8 % males. Digital fundus photos of the right and left eyes were taken for all patients. The pictures were taken without pupil dilation using a CANON-NM camera. The pictures and case histories were stored in a central server using web-based software (MedStage, Siemens). In a central reading centre, the arteriovenous ratio of both eyes was determined telemedically using the Parr-Hubbard formula and the retinas subjected to a standardised examination by an ophthalmologist. The retinal risk factor was calculated on the basis of the arteriovenous ration, the presence of microvascular abnormalities and the case history. The reproducibility of measurement of the arteriovenous ratio (Kronbach alpha coefficient) was evaluated by double measurements on 1,332 images. In a subgroup of study I with arteriovenous ratio values < 0.76 (N = 107), an extended vessel diagnosis with measurement of 24-h blood pressure and vessel-relevant blood values (homocysteine, cholesterol, LDL, HDL, CRP, TG, HbA1c) was carried out (study II). RESULTS: Study I: The Kronbach alpha coefficient as a measure of reproducibility amounted to 0.77. The mean arteriovenous ratio of the retinal vessels was 0.83 +/- 0.09 and showed a pronounced age dependence (R = 0.9, p < 0.0001). On multivariate testing the arteriovenous ratio correlated significantly (R = 0.33, p < 0.001) with the factors age, systolic blood pressure, diastolic blood pressure and body mass index. Diastolic blood pressure followed by age had the largest influence. The prevalence of microvascular abnormalities in the right (RE) and left (LE) eyes, respectively were: cotton wool foci RE 0.0015 %, LE 0.003 %, retinal haemorrhage RE 0.1 %, LE 0.1 %, focal stenoses RE 3.4 %, LE 3.4 %, tortuositas vasorum RE 4.1 %, LE 4.0 %, arteriovenous crossing signs RE 11.2 %, LE 11.2 %. On multivariate testing the occurrence of microvascular abnormalities correlated significantly (R = 0.38, p < 0.001) with the factors high blood pressure known from case history, body mass index, and gender. Arterial hypertension had the strongest influence followed by diastolic blood pressure. The calculated retinal risk factor correlated with the prevalence of angina pectoris. Study II: 2/3 of the subjects with arteriovenous risk factor values < 0.76 exhibited pathologically high 24-h blood pressure values. For these patients there were significant correlations between the arteriovenous ratio and the low-density lipoprotein concentration as well as the Framingham risk score. CONCLUSION: In the course of a prospective, telemedical-supported screening examination of the retinal vessels of more than 7,000 subjects the arteriovenous ratio exhibited a strong dependence on age and blood pressure. Among the subjects with lowered arteriovenous ratio values, 2/3 exhibited arterial hypertension in the 24-h blood pressure determination.

Adolescent↗

PubMed1999

[Changes in retinal blood flow by topical administration of 0.1% dipivefrin].

PURPOSE: Most of the antiglaucomatous drugs affect ocular blood flow. Blood flow of the anterior uvea under the effect of glaucoma medication has been described in the literature, but measurement of microcirculation at the posterior pole correlated to glaucoma medication is rarely found. We present a placebo-controlled study in which we focused on the short and long-term effects of topical dipivefrine 0.1% on the microcirculation of the retina and optic nerve head. PATIENTS AND METHODS: In a randomized, placebo-controlled double-masked study we examined 40 healthy persons (21 male and 19 female) with a mean age of 35 +/- 4.6 years. Two groups of volunteers (n = 20) were treated either with placebo or dipivefrine 0.1% for 5 days twice a day. Measurement of microcirculation was done at baseline, 30 min after the first application and on days 3 and 5. Microcirculation was evaluated by scanning-laser Doppler flowmetry (SLDF, Heidelberg Engineering; Heidelberg, Germany) [retinal and optic nerve head capillary blood flow (ONH)]. Systemic parameters were checked at all times of blood flow measurement (blood pressure, pulse); intraocular pressure (IOP) was also measured at baseline, 30 min after and on days 3 and 5. RESULTS: Systemic parameters: None of serum medications affected blood pressure or pulse. Dipivefrine 0.1% lowered the IOP significantly (P = 0.01). Microcirculation: dipivefrine 0.1% leads to a significant reduction of retinal capillary blood flow (P = 0.01). ONH blood flow was not significantly affected by dipivefrine 0.1%. CONCLUSION: Retinal capillary perfusion is affected by dipivefrine 0.1% medication. In neuroprotection, it is of interest that glaucoma medication did not alter the microcirculation in a way that leads to an increase of hypoxemia. Therefore, we consider dipivefrine 0.1% not to be useful for long-term glaucoma treatment.

Adult↗

PubMed1999

Multivessel coronary bypass grafting with minimal access using cardiopulmonary bypass.

The port-access approach for coronary artery bypass grafting is an excellent technique for minimal access, multivessel coronary revascularization. Patient selection criteria, technical aspects, and clinical results are reviewed.

Cardiopulmonary Bypass↗

PubMed1995

[2-dimensional mapping and retinal and papillary microcirculation using scanning laser Doppler flowmetry].

PURPOSE: To present clinical applications of a new non-invasive method imaging in a high-definition the topography of perfused retinal vessels. METHOD: By a combination of a laser Doppler flowmeter with a scanning laser system the perfusion of the retina and the optic nerve head is visualized and quantified. The principles of measuring blood flow by Laser Doppler Flowmetry are based on the optical Doppler effect: laser light scattered by a moving particle is shifted in frequency by an amount delta f. Our data acquisition and evaluation system is a modified laser scanning tomograph. The technical data are: retinal area of measurement 2.7 mm x 0.7 mm, 10 degree-field with 256 points x 64 lines, measurement accuracy 10 microns, wavelength 670 nm and 790 nm, light power 100 microW, data acquisition time 2,048 s. Every line is scanned 128 times by a line-sampling rate of 4,000 Hz. By performing a discrete Fast Fourier Transformation over 128 intensities of each retinal point the laser Doppler-shift is calculated for each retinal point. With these data a 2-D map with 256 x 64 points of the retinal perfusion is created. The brightness of the picture-point is coded by the value of the Doppler shift. We estimated the reliability and the validity of the method. Perfusion-pictures of the superficial retinal layer and in the optic nerve head were presented. RESULTS: The reliability-coefficients r1 of "Flow", "Volume" and "Velocity" were 0.85, 0.83, and 0.85 respectively. The blood flow measurements by the presented method ("Scanning Laser Doppler Flowmetry") in an artificial capillary gave a linear relationship (r-value 0.973, p < 0.00001) between defined blood velocities and the measured blood flow. By the confocal technique, dependent on the focus, capillaries of the retinal superficial vasculature of the optic nerve head became visible with a high resolution. Off line the blood flow of areas of 110 microns x 110 microns were calculated in terms of laser Doppler flowmetry. CONCLUSION: "Scanning Laser Doppler Flowmetry" facilitates the visualisation of perfused retinal capillaries and vessels in high resolution. The representation of the function of the retinal circulation by SLDF leads to an image similar to the anatomical situation. The 2-dimensional mapping of local blood flow leads to a physiological picture of the retinal perfusion with visible vessels and capillaries.

Adult↗

PubMed1994

Regulation of ocular blood flow during increases of arterial blood pressure.

The blood flow in the uvea in cats and monkeys during acute increases of arterial blood pressure is well controlled by a sympathetic mechanism protecting the eye from overperfusion. Ocular macrocirculation (ophthalmic artery) and ocular microcirculation (iris) were examined in 22 healthy subjects during acute increases of arterial blood pressure induced by physical exercise (125 W). With a data acquisition and storage software in real time mode several parameters of ocular perfusion and systemic functions were measured simultaneously. Blood flow parameters were measured in the ophthalmic artery by pulsed Doppler sonography and in the iris by laser Doppler flowmetry. Systolic, diastolic, and mean velocities of the ophthalmic artery peak velocity pulse curve, the ophthalmic artery mean velocity pulse curve, and the iris velocity pulse curve were estimated off line. The ophthalmic artery mean velocity pulse curve resembles the integrated velocity of all erythrocytes in the vessel including the slowly running cells near the vessel wall. The iris velocity pulse curve was calculated by a special statistic procedure (ALDF). After exercise there was a significant increase in systolic and diastolic blood pressure and heart rate. The pulse curve of the ophthalmic artery showed significantly increased systolic and decreased diastolic velocities. The vascular resistance of the branches of the ophthalmic artery increased significantly. The iridal vasculature showed no significant change in blood cell velocity but an increased vascular resistance. It was observed that the elevated perfusion pressure was associated with an increased vascular resistance and a constant mean blood velocity in the ophthalmic artery and iridal vessels. The parallel elevation of vascular resistance and blood pressure during exercise may be the reason for a constant blood flow in the ophthalmic artery and the iris. This may be accounted for by a sympathetic mechanism for protecting the eye from overperfusion.

Adult↗

PubMed1988

Radiology and pathology in canine acalculous cholecystitis.

Although the value of hepatobiliary scan and ultrasonography are well established in calculous cholecystitis, their role in acute acalculous cholecystitis (AAC) is less certain. This study assesses the diagnostic reliability of these tests in AAC chemically induced in 10 dogs with rutin, a compound known to induce AAC. Ultrasonography demonstrated pericholecystic fluid or wall thickening in 8 of 10 dogs. Hepatobiliary scans were abnormal in only 2 of 9 dogs. Pathologic evaluation showed significant abnormalities in all gallbladders. Our studies confirm the usefulness of ultrasonography in diagnosing AAC and suggest caution in using a normal hepatobiliary scan to exclude the diagnosis of AAC.

Animals↗

PubMed1987