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Biomedical subjects

T Meinertz

Publications and source records attributed to T Meinertz.

At least 343 records · Page 19Linked to original sources
PubMed1983

The suprasternal approach to recording aortic valve prostheses: a comparison with the precordial and subxiphoid approaches.

We evaluated 56 consecutive patients echocardiographically 9 days to 104 months after aortic valve replacement by the precordial, subxiphoid and suprasternal approach. In 11 patients, the mitral valve had also been replaced. For comparison, a subjective grading system (score 1 up to 3) was applied to the records obtained from each approach. Disc valves (n = 41) were equally scored from the precordial and suprasternal approach (score 2.6). Ball prostheses (n = 6) were best imaged from the suprasternal approach (score 3.0), whereas bioprostheses (n = 9) were best visualized from the precordial (1.8). Simultaneous imaging of both valves was possible in 6 out of 11 patients with a double prosthesis using the suprasternal approach but not from precordial and subxiphoid approaches. Six patients presented prosthetic valve dysfunction. Five patients had paravalvular insufficiency; 4 of these patients had a Björk-Shiley valve and one patient a Lillehei-Kaster valve. The echograms of 4 out of 5 patients with a paravalvular leak were normal from each approach. In another patient an obstructed Björk-Shiley prosthesis was found. The pre- and postoperative echograms demonstrated that the suprasternal approach was best to visualize the obstructed valve. The study shows that the suprasternal technique is superior for evaluation of most patients with aortic valve prostheses.

Adult↗
PubMed1983

Isosorbide dinitrate kinetics and dynamics after intravenous, sublingual, and percutaneous dosing in angina.

Isosorbide dinitrate (ISDN) kinetics and dynamics were examined after various routes of administration for angina. Given intravenously, ISDN kinetics were apparently linear over the range of infusion rate (0.083 and 0.133 mg/min) and duration (15 min and 1 and 2 hr) studied. Mean +/- SD systemic clearance of ISDN was 3.4 +/- 1.4 l/min and volume of distribution (VdSS or Vdarea) about 100 l. These data are consistent with the presence of extensive extrahepatic metabolism. In six patients, sublingual ISDN (5 mg) was also given and mean bioavailability of 59% (19% to 93%) for this route was determined. For this group, sublingual absorption of intact ISDN was incomplete and variable. The presence of a longer disappearance t 1/2 after sublingual dosing suggested that the input process may be rate limiting. After percutaneous application of a topical formulation (100 mg over an area of 400 cm2), steady-state plasma concentrations at about 7 ng/ml were maintained from 6 to 24 hr. The bioavailability of the topical application was estimated at 30%. At the doses given, intravenous ISDN had no apparent effect on heart rate but induced significant reduction in standing systolic blood pressure. The effect vs the ISDN concentration profile was described by a hysteresis loop, indicating that changes in blood pressure response lag behind changes in plasma ISDN concentration. After intravenous dosing, peak plasma ISDN concentration and peak effect (maximum change in standing systolic blood pressure). At the doses used, both sublingual and percutaneous ISDN induced less distinct circulatory changes than the intravenous infusion.

Absorption↗
PubMed1983

Hepatic extraction of isosorbide dinitrate in cardiac patients.

Hepatic extraction of organic nitrates, including that of isosorbide dinitrate (ISDN), has been thought to be nearly complete in man but has never been directly measured. We examined the time course of plasma ISDN and metabolite concentrations in arterial and hepatic venous blood in four cardiac patients receiving an intravenous ISDN infusion. Apparent hepatic extraction of ISDN was high (90%) at the beginning of infusion but fell to about 44% 1 hr after termination of infusion. The decrease in ISDN concentration gradient across the liver correlates with an increase in plasma isosorbide-5-mononitrate concentration, but a cause-and-effect relationship resulting from metabolite inhibition cannot be established. The time-averaged hepatic extraction of ISDN, at about 70%, agreed with its oral bioavailability in patients.

Biological Availability↗
PubMed1983

Alinidine in angina.

Alinidine--N-allyl-clonidine--reduces heart rate without blocking beta adrenoreceptors. It may be used in patients with angina without inducing the adverse effects of beta-adrenergic blockers. We therefore evaluated alinidine efficacy in patients with angiographically proven coronary artery disease and stable angina during a 10-wk placebo-controlled randomized double-blind trial. Alinidine (40 mg three times a day) reduced the number of anginal attacks and the average number of nitroglycerine capsules consumed. The double product was slightly lowered during rest but more pronounced during exercise. This effect was mainly due to decreased heart rate. The ischemic S-T segment depression was diminished. Exercise tolerance was clearly improved in six, slightly improved in two, and unchanged in four subjects.

Adult↗
PubMed1983

Cyclic interconversion of vitamin K1 and vitamin K1 2,3-epoxide in man.

The disposition of a single intravenous bolus dose of 10 mg vitamin K1 and vitamin K1-2,3-epoxide were studied in two healthy subjects without and with 12 h pretreatment dose of phenprocoumon (0.4 mg/kg). For each compound administered alone the plasma concentration-time profile was adequately fitted by a biexponential equation, with an average terminal half-life of 2.0 and 1.15 h for the administered vitamin K and its 2,3-epoxide respectively. While vitamin K1 was measurable in plasma following administration of vitamin K1-2,3-epoxide, the epoxide was not detectable following administration of vitamin K1. Following pretreatment with phenprocoumon and after intravenous administration of vitamin K1, both the average half-life and area under the plasma concentration-time profile of vitamin K1 were marginally reduced to 1.5 h and 1.76 mg l-1 h respectively, while the plasma concentration of vitamin K1-2,3-epoxide was readily measurable and its half-life markedly prolonged to 14.7 h. Following pretreatment with phenprocoumon and after oral administration of vitamin K1-2,3-epoxide, no vitamin K1 was detectable in plasma and the half-life of the epoxide was 13.8 h. Based on area considerations the data suggest that either phenprocoumon does more than just inhibit the reduction of vitamin K1-2,3-epoxide to vitamin K1, or that the simple model describing the interconversion between vitamin K1 and its epoxide is inadequate. The same conclusion is drawn from the analysis of comparable data in dogs, obtained by Carlisle & Blaschke (1981).

Adult↗
PubMed1983

[Beta-adrenergic stimulation with prenalterol in sick sinus syndrome].

The effect of beta-adrenergic receptor stimulation on sinus node function in patients with sick-sinus syndrome was investigated. Electrophysiological studies were performed in 14 patients (5 males and 9 females) aged 18-81 years before and after intravenous administration of 50 micrograms Prenalterol per kilogram body wt. Prenalterol decreased spontaneous cycle length by 26% (p less than 0.01), which corresponded to an increase in heart rate of 21 beats/min. The corrected sinus node recovery time was shortened by 23% (n.s.) in 10 patients, and was abnormal in 12 patients before and in 10 patients after Prenalterol. Secondary pauses occurred in 8 patients at control and in 9 patients after drug administration, in 2 of them for the first time after Prenalterol. In the sick-sinus syndrome the pronounced chronotropic response to beta-adrenergic receptor stimulation with Prenalterol doses not indicate improvement of impaired sinus node function.

Adolescent↗
PubMed1983

[Effect of nifedipine on sinus node and atrioventricular node function following autonomic blockade in the human].

The effect of intravenously administered nifedipine (7.5 micrograms/kg) on sinus node and atrioventricular (AV) node function was evaluated in 17 patients, 9 of whom had sinus node disease after autonomic blockade (propranolol 0.2 mg/kg and atropine 0.04 mg/kg i.v.). The patients' ages ranged from 18 to 77 years. After nifedipine there was a nonsignificant increase in the median values for sinus cycle length from 750 ms to 760 ms, for sinus node recovery time from 1150 ms to 1240 ms, for corrected sinus node recovery time from 440 ms to 460 ms, and for sinoatrial conduction time from 63 ms to 75 ms. Nevertheless, nifedipine produced a significant increase in the AV node refractory periods (median values): the effective refractory period lengthened from 300 ms to 305 ms (rate 100/min) and from 290 ms to 300 ms (rate 120/min) respectively. The functional refractory period increased from 380 ms to 400 ms (rate 100/min) and from 385 ms to 410 ms (rate 120/min) respectively. The Wenckebach period was significantly prolonged from 370 ms to 390 ms. We conclude, therefore, that in the absence of autonomic control intravenous administration of nifedipine exerts a mild depressive effect on AV node but not on sinus node function.

Adolescent↗
PubMed1983

[Repetitive ventricular response and left ventricular wall motion in patients with coronary heart disease].

As the first results of a prospective study on the value of programmed ventricular stimulation, the incidence of repetitive ventricular response with 3 or more consecutive beats (RVR3) in 136 patients (122 males, 14 females, age 51 +/- 8 years) with coronary artery disease is reported. 38 patients (group A) had no evidence of previous myocardial infarction, 31 patients (group B) had myocardial infarction less than 3 months and 67 patients (group C) more than 3 months before entry into the study. Programmed electrical stimulation included single (S2) and double (S2 S3) ventricular premature beats following ventricular drive at 3 cycle lengths (500, 600 and 430 msec) and was defined as positive (+PES) when RVR3 was induced. +PES was related to the extent and the degree of abnormal left ventricular wall motion, determined by left ventricular angiography (30 degrees RAO view) and quantified by a wall motion score. After single premature stimuli no RVR3 was observed in group A, but in 7% of group B and in 19% of group C (p less than 0.01). After double premature stimuli RVR3 occurred in 17% of group A, 42% of group B and 34% of group C (p less than 0.1). All 3 groups differed with respect to mean wall motion score and number of akinetic wall segments (p less than 0.001). Patients with positive (+PES) or negative (-PES) results could not be separated when the extent of wall motion abnormalities (wall motion score, number of akinetic segments) was considered. However, a relation (p less than 0.01) to the degree of abnormal wall motion classified according to the presence of normokinesis, hypokinesis, akinesis or dyskinesis could be demonstrated for +PES after single but not after double premature stimuli.

Coronary Disease↗
PubMed1983

[Separation of the left atrium from the right pulmonary artery in the suprasternal echocardiogram: a parameter of left atrial pressure].

A separation of the left atrium from the right pulmonary artery during atrial contraction may be observed in the suprasternal echocardiogram. In 280 catheterized patients with sinus rhythm, we investigated whether left atrial separation is a parameter from which an estimate of the left atrial pressure can be obtained. In 239 of the 280 patients, the suprasternal echograms were of a quality such that it could be seen whether there was, a left atrial separation. In 182 patients, a normal left atrial pressure (greater than or equal to 12 mm Hg) was found; in 57 patients, the left atrial pressure was elevated. An atrial separation was observed in 183 patients, and in 56 patients it was lacking. Lack of left atrial separation indicates a left atrial pressure elevation with a sensitivity of 73.7% and a specificity of 92.3%. If a left atrial pressure above 18 mm Hg was considered elevated, the sensitivity of this echoparameter amounted to 90.3%, and the specificity was 86.5%. The study shows that the left atrial separation from the right pulmonary artery separation from the right pulmonary artery in the suprasternal echocardiogram is a parameter valuable in providing a rough estimate of the left atrial pressure.

Blood Pressure↗
PubMed1982

[Importance of echocardiography for the assessment of left-ventricular function and cardiac complications in dilative cardiomyopathy].

One- and two-dimensional echocardiographic findings in 17 patients with dilated cardiomyopathy were compared with haemodynamic and angiographic results of cardiac catheterization. In a further 52 unselected patients with dilated cardiomyopathy, who had been seen as out- or in-patients over a period of two years, the frequency of intracardiac thrombi was investigated echocardiographically. A significant correlation (r = 0.66 and r = 0.68) was found between echocardiographically determined left-ventricular end-diastolic and end-systolic volumes on the one hand and volumes determined angiographically on the other. However, ventricular volumes were clearly underestimated by echocardiography. In contrast, both methods showed good agreement for the magnitude of the ejection fraction (r = 0.79). The aortic valve opening surface estimated with one-dimensional echocardiography correlated with left-ventricular ejection volume (r = 0.93). Thrombi were demonstrated in 7 out of 52 patients: 5 were located in the left, one in the right and a further one in the central pulmonary vascular system. Considering the aforementioned limitations, echocardiography is a useful method for evaluation of left-ventricular function and for demonstration of intracardiac thrombi in dilated cardiomyopathy.

Adolescent↗
PubMed1982

Estimation of pulmonary arterial pressure by measuring the size of the right pulmonary artery in the suprasternal echocardiogram.

We studied 175 patients within 24 hr before cardiac catheterization with suprasternal echocardiography to evaluate whether pulmonary arterial hypertension can be derived by measuring the size of the right pulmonary artery. Group I consisted of 103 patients without pulmonary arterial hypertension (enddiastolic less than or equal to 12 mm Hg; mean pressure less than 20 mm Hg) and group II consisted of 72 patients with pulmonary arterial hypertension. The right pulmonary artery could be imaged in 91.2% of the patients studied. The size of the right pulmonary artery at the end of diastole in group I measured 17.9 +/- 0.2 mm (mean +/- SEM) and correlated best to the body surface area in this group (r = 0.63; p less than 0.001). The respective index size amounted to 9.9 +/- 0.1 mm/m2, and was different from that in group II with 14.1 +/- 0.4 mm/m2 (p less than 0.001). The systolic percent expansion of the right pulmonary artery in group I was 21.2 +/- 0.8% and in group II 9.2 +/- 0.8% (p less than 0.001). The index size of the right pulmonary artery for both groups correlated best to the pulmonary enddiastolic pressure (r = 0.82; p less than 0.001). The systolic per cent expansion showed a negative log linear relationship to the pulmonary enddiastolic pressure (r = 0.67; p less than 0.001). Thus, pulmonary arterial pressure can be derived by measuring the size of right pulmonary artery with suprasternal echocardiography.

Adult↗
PubMed1982

Comparison of the antiarrhythmic activity of mexiletine and lorcainide on ventricular arrhythmias.

In a blind cross-over study, 12 patients with ventricular arrhythmias (VPC's; Lown Grades II-IVB) resistant to a daily dose of quinidine 1.2 g, disopyramide 0.8 g, N-propyl-ajmaline 0.1 g were randomly given, each dose for one week, placebo (PL), mexiletine (MEX; 400, 600, 800 mg daily) and lorcainide (LOR; 200, 300, 400 mg daily). On the last day of each treatment period, patients were evaluated by 24-h continuous ambulatory monitoring, 6-channel surface ECG, plasma concentrations and side-effects. During PL I (before) and PL II (after drug treatment), the mean number of VPCs per hour was 670 and 701. VPCs were reduced in 5 of the 12 patients with MEX by 43% (400 mg), 74% (600 mg) and 91% (800 mg). VPCs were reduced in 10 patients with LOR by 60% (200 mg), 78% (300 mg) and 93% (400 mg). Log. lin. plasma conc. effect relationships were constructed for MEX and LOR. Vomiting, nausea, and abdominal pain were seen in 2 patients with MEX; insomnia and feeling heat in 10 patients with LOR. At the end of the LOR-treatment, these side-effects were less in 5 and absent in 5 patients. In this study, LOR seems superior to MEX in refractory ventricular arrhythmias.

Adult↗
PubMed1982

[Transient sinus node arrest-a dysregulation of the autonomic nervous system (author's transl)].

Electrophysiologic studies had been performed before and after pharmacologic autonomic blockade (propranolol 0.2 mg/kg and atropine 0.04 mg/kg body weight) in a 23-year-old female patient with documented sinus arrest of 27 sec duration. Normal electrophysiologic findings before and after autonomic blockade excluded intrinsic sinus node dysfunction. Sinus arrest is therefore though to be due to an intermittent dysregulation of the autonomic nervous system.

Adult↗
PubMed1982

[Suprasternal M-mode echocardiography in the diagnosis of cardiovascular diseases in adults].

The study describes the technique and standardized evaluation of suprasternal M-mode echocardiography. The day-to-day variability of suprasternal echoparameters was tested in 7 subjects studied on five consecutive days. The variation coefficient found ranged from 3.5 to 6%. The interobserver variability were tested by evaluation of 127 suprasternal echocardiograms from two investigators independently. Absolute values differed slightly in only 2 out of 8 parameters between both investigators by about 0.8 and 6.3%. 349 consecutive patients were subsequently studied with the suprasternal notch technique. The clinical diagnosis of these patients were as follows: 35 normal subjects, 122 patients with coronary heart disease, 155 patients with valvular heart disease, 33 patients with dilative and 4 with hypertrophic cardiomyopathy. The feasibility to record the aortic arch amounted to 68%, the right pulmonary artery was visualized in 85%, and the left atrium was seen in 75% of the patients studied. The echographic parameters correlated to body size, weight and body surface area. It could be demonstrated that also hemodynamic changes caused variations of these echographic parameters. The different clinical entities did not differ from each other with respect to these suprasternal echoparameters for those in whom the pulmonary artery pressure was within normal range. The size of the pulmonary artery and of the left atrium was found increased in those patients with an elevated pulmonary artery pressure. The suprasternal approach seems to be a useful completion of the echocardiographic technique and should be applied routinely.

Aorta↗