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Biomedical subjects

T Behrenbeck

Publications and source records attributed to T Behrenbeck.

31 records · Page 2Linked to original sources
PubMed1990

Measurement of myocardium at risk and salvage in myocardial infarction with ST-segment depression.

A patient with symptoms of acute myocardial infarction but ST-segment depression rather than elevation constitutes a clinical dilemma for which few guidelines exist. Herein we describe such a patient, in whom serial tomographic imaging with a new radiopharmaceutical agent, technetium-99m sestamibi, was useful in demonstrating a large area of myocardium at risk and subsequent substantial benefit from acute reperfusion therapy. Because this perfusion agent washes out slowly from the myocardium, imaging can be delayed for several hours; thus, acute reperfusion therapy can be performed without delay. Subsequent imaging, however, will reflect myocardial perfusion at the time of administration of the radionuclide. Additional studies with this agent may be valuable in identifying those patients with ST-segment depression who will benefit from acute reperfusion therapy.

Aged↗
PubMed1990

Serial changes in myocardial perfusion using tomographic technetium-99m-hexakis-2-methoxy-2-methylpropyl-isonitrile imaging following reperfusion therapy of myocardial infarction.

Resting tomographic myocardial perfusion images using technetium-99m-hexakis-2-methoxy-2-methylpropyl-isonitrile (Tc-Sestamibi) were obtained in 25 patients during their first myocardial infarction. Tc-Sestamibi was injected intravenously before acute reperfusion therapy, and repeated twice, at 18-48 hr, and at 6 to 14 days. Reperfusion was successful in 19 patients. In the patients with successful reperfusion, there was a mean decrease in the amount of hypoperfused myocardium between the initial and second studies (-9% +/- 12%, p = 0.004) and a further decrease between the second and final studies (-10% +/- 12%, p = 0.002). Nine of these 19 patients (47%) had evidence of significant improvement at the time of the second study. In six patients, significant improvement was not evident until the final study. Although tomographic imaging with Tc-Sestamibi following reperfusion therapy may show improvement in perfusion at 18-48 hr, the full extent of improvement is usually not evident until later.

Adult↗
PubMed1989

Serial quantitative planar technetium-99m isonitrile imaging in acute myocardial infarction: efficacy for noninvasive assessment of thrombolytic therapy.

Technetium-99m isonitrile is a new myocardial perfusion imaging agent that accumulates according to the distribution of myocardial blood flow. However, unlike thallium-201, it does not redistribute over time. This imaging agent was used with serial quantitative planar imaging to assess the initial risk area of infarction, its change over time and the relation to infarct-related artery patency in 30 patients with a first acute myocardial infarction. Twenty-three of 30 patients were treated with recombinant tissue-type plasminogen activator (rt-PA) within 4 h after the onset of chest pain. Seven patients were treated in the conventional manner without thrombolytic therapy. Technetium-99m isonitrile was injected before or at the initiation of thrombolytic therapy, and imaging was performed several hours later. These initial images demonstrated the area at risk. Repeat imaging was performed 18 to 48 h later and at 6 to 14 days after the onset of myocardial infarction to visualize the ultimate extent of infarction. The initial area at risk varied greatly (range defect integral 2 to 61) both in patients treated with rt-PA and in those who received conventional treatment. For the total group, the initial imaging defect decreased in size in 20 patients and was unchanged or larger in 10 patients. Patients with a patent infarct-related artery had a significantly greater decrease in defect size than did patients with persistent coronary occlusion (-51 +/- 38% versus -1 +/- 26%, p = 0.0001). All patients with a decrease in defect size greater than 30% had a patent infarct-related artery. In 12 patients who also had predischarge quantitative exercise thallium-201 imaging, good agreement existed between the extent and severity of myocardial perfusion defect on the last technetium-99m isonitrile study before discharge and that noted on delayed thallium-201 imaging. It is concluded that serial planar technetium-99m isonitrile myocardial imaging in patients with acute myocardial infarction undergoing thrombolytic therapy offers a new quantitative noninvasive approach for assessment of the initial risk zone as well as the success of reperfusion.

Contrast Media↗
PubMed1989

Feasibility of tomographic 99mTc-hexakis-2-methoxy-2-methylpropyl-isonitrile imaging for the assessment of myocardial area at risk and the effect of treatment in acute myocardial infarction.

99mTc-hexakis-2-methoxy-2-methylpropyl-isonitrile (Tc-Sestamibi), a new myocardial perfusion radiopharmaceutical, was injected intravenously in 11 patients within 4 hours of the onset of acute myocardial infarction before treatment with intravenous tissue-type plasminogen activator and 6-14 days later. Five patients with acute myocardial infarction who did not receive intravenous thrombolytic therapy underwent a similar injection of radiopharmaceutical. The absence of redistribution of Tc-Sestamibi permitted imaging with single-photon emission computed tomography up to 6 hours after intravenous injection to assess the distribution of myocardial perfusion at the time of administration. The region of hypoperfused myocardium on the initial images varied widely from 9% to 68% of the left ventricle and was significantly greater in anterior than in inferior infarcts (p less than 0.01). The region of hypoperfused myocardium on the final images varied widely from 0% to 63% of the left ventricle and was also greater in anterior infarcts (p less than 0.01). The final hypoperfused region correlated (r = -0.82) with the late resting ejection fraction and with the late regional wall motion score in the infarct segment for both anterior (r = -0.74) and inferior (r = -0.97) infarcts. There was a significant decrease (-13 +/- 11%, p less than 0.003) in the extent of hypoperfused myocardium between the initial and final studies in the patients who received thrombolytic therapy compared with an insignificant increase (4 +/- 6%, p greater than 0.5) in the patients who did not receive thrombolytic therapy. Tomographic imaging with Tc-Sestamibi permits determination of the amount of hypoperfused myocardium "at risk" in acute myocardial infarction. The change in myocardial perfusion determined by Tc-Sestamibi before and after therapy in acute myocardial infarction is a promising tool for assessing treatment.

Aged↗
PubMed1989

[Combination therapy with slow release isosorbide nitrate and diltiazem in silent myocardial ischemia].

In 11 patients (2 female, 9 male) suffering from angiographically proven CHD (age 45-60 years; 54.3 years on an average) the efficacy of a once-daily oral medication with 120 mg ISDN/50 mg ISMN and diltiazem (D) each in a long-acting preparation was examined in a placebo-controlled study. Each period lasted for 3 days; 2 capsules were given at 0700 a.m. one capsule at 5 p.m. Long-term ECG-recordings for 24 hrs (Tracker recorder, Pathfinder III) were performed twice under placebo and once during the third day of ISDN or ISMN, ISDN/ISMN + D in the morning and JSDN or ISMN in the morning and D in the afternoon. The rate of ischemic events declined from 10.4 to 4.7, 3.3 and 2.2; the duration of ischemia in 24 hours declined from 128 min to 43 min, 44 min and 34 min. The product of ST-depression (mV) and time of duration (min) showed an equivalent course. A more than 80% reduction of ischemia (duration and frequency) was achieved by a combination therapy in 72% of the patients. Minimal increase of heart rate at the beginning of ST-depression increased significantly during all periods of therapy, maximal increase of heart rate at that time showed a decrease only during combination therapy with D, the mean value did not change significantly. The once-daily application of ISDN/ISMN (50 mg) in a long-acting preparation (120 mg) led to a significant reduction of silent myocardial ischemia. The efficacy of ISDN/ISMN can be improved by D (120 mg, long acting preparation) up to a greater than 80% reduction in frequency and duration of ischemic events.

Adult↗
PubMed1987

Prophylaxis of exercise-induced ventricular arrhythmias by verapamil.

In this study prophylactic antiarrhythmic effects of verapamil on exercise-induced ventricular arrhythmias are evaluated. Investigations were carried out on a total of 22 patients. All patients showed frequent and/or complex ventricular arrhythmias during repeated exercise tests under control conditions. After two control exercise tests all patients were treated with verapamil 120 mg given every 8 hours orally over 4 days. On the 3rd and 4th day of treatment the exercise tests were repeated. Verapamil caused a significant reduction in the incidence and severity of exercise-induced ventricular arrhythmias in 13 out of 22 patients. In patients with exercise-induced ST-segment depression a prophylactic action could be demonstrated in 9 out of 10 cases. The antiarrhythmic effect was independent of changes in heart rate. A reduction in myocardial oxygen consumption and direct electrophysiological effects (suppression of the 'slow response' and/or an increase in the resting potential of the 'depressed fast response') can be considered, as well as a suppression of 'triggered activity' or a direct inhibition of adrenergic effects. Calcium antagonists (type verapamil) prove to be suitable drugs for the treatment of exercise-induced ventricular arrhythmias in patients with myocardial ischaemia.

Adult↗
PubMed1987

[Prevention of effort-induced ventricular arrhythmia using verapamil].

In this study prophylactic antiarrhythmic effects of verapamil on exercise-induced ventricular arrhythmias were evaluated in a total of 22 patients. All patients displayed frequent and/or complex ventricular arrhythmias during repeated exercise tests under control conditions. After two control exercise tests, all patients were treated with 120 mg verapamil given every 8 h orally for 4 days. On the 3rd and 4th day of treatment the exercise tests were repeated. The results were that verapamil caused a significant reduction in the incidence and severity of exercise-induced ventricular arrhythmias in 13 out of 22 patients. In patients with concomitant significant ST-segment depression, a prophylactic action could be demonstrated in nine out of ten cases. The antiarrhythmic effect was independent of changes in heart rate. In patients with myocardial ischaemia, a reduction in myocardial oxygen consumption and direct electrophysiological effects (suppression of the "slow response" and/or an increase in the resting potential of the "depressed fast response") can be discussed as mechanisms of action. Also, a suppression of "triggered activity" or a direct inhibition of adrenergic effects must be considered. According to our results and the literature, calcium antagonists (verapamil type) proved to be suitable drugs for the treatment of exercise-induced ventricular arrhythmias, particularly in patients with concomitant myocardial ischaemia.

Arrhythmias, Cardiac↗
PubMed1987

[Electrophysiologic and hemodynamic effects of the new anti-arrhythmia agent diprafenone].

Diprafenone is a new antiarrhythmic agent currently under clinical investigation, with close chemical similarity to propafenone. In this study, the electrophysiological and haemodynamic effects of the compound were investigated both in animals, by experiment, and in man. Diprafenone produces a dose-dependent prolongation of conduction in all parts of the conducting system. Lengthening of PQ-time is more pronounced than prolongation of QRS. The atrial and ventricular refractory periods are also significantly prolonged. There are no significant changes in the QT-time. Heart rate and aortic pressure are slightly decreased. The electrophysiological and haemodynamic profile of Diprafenone is similar to propafenone with respect to a dominant local anaesthetic activity and an additional beta-sympatholytic effect. However, with respect to the dose needed, the efficacy of the new drug appears to be significantly stronger. Diprafenone can be considered an effective antiarrhythmic drug for the treatment of supraventricular and ventricular tachyarrhythmias.

Animals↗
PubMed1987

[Treatment of chronic ventricular arrhythmias with the new class Ic anti-arrhythmia agent diprafenon--results of long-term therapy].

Diprafenone is a new antiarrhythmic drug with a dominant local anaesthetic action and an additional beta-sympathicolytic activity. In this study, the results of long-term treatment (8 months on average) obtained from 27 patients with chronic ventricular arrhythmias are reported. Before diprafenone, all patients were treated unsuccessfully with flecainide, propafenone, sotalol, combined sotalol/flecainide and sotalol/propafenone, and another two to six antiarrhythmic agents. Following diprafenone (300-600 mg/24 h), a substantial reduction in arrhythmic activity (greater than or equal to 80%; Lown classification less than or equal to II) was achieved in 21 cases. In 12 patients, side effects (fatigue, headache, blurred vision, dizziness and heartburn) were apparent. Diprafenone had to be discontinued in five patients, because of these side effects. At dosages greater than or equal to 450 mg/24 h, the PQ interval was significantly lengthened, and QRS duration prolonged. In one patient, an AV block III degree developed. In another case, SGOT and SGPT increased significantly; this increase was reversed after the drug was discontinued. Despite these side effects, further clinical evaluation of the compound seems promising, as the antiarrhythmic potency of diprafenone is very strong and superior to that of propafenone with respect to the required doses.

Adult↗
PubMed1983

Estimation of regional pleural surface expansile forces in intact dogs.

Distances between percutaneously inserted apical and basal lung markers determined by biplane X-ray, computer-based videometry (J. Appl. Physiol. 34: 544, 1973) were calibrated against dependent percutaneously recorded pleural liquid pressures (J. Appl. Physiol. 31: 277, 1971) in five 10-12 kg mongrel dogs under morphine-pentobarbital anesthesia studied without thoracotomy. At the same apical pleural-liquid pressure values, the apical intermarker distances were uniformly greater when in the head-up rather than head-down position. This finding suggests that the expansile forces acting on the apical regions of the lung, in the head-up position, are greater (-30 +/- 2 cmH2O) than would be predicted from "pleural liquid" pressures (-15 +/- 1 cmH2O) measured at this nondependent site in the thorax, and much greater than the "pleural surface" pressures measured by the generally accepted balloon and counter-pressure techniques. In contrast, in the head-down body position, expansile forces acting on the nondependent basal regions of the lung estimated by the intermarker distance technique were variable to either side of the pressures measured by open-ended liquid-filled catheters, and thus were not significantly different. Mean values measured by the catheters and predicted by the markers were -14 +/- 1 and -10 +/- 3 cmH2O, respectively.

Animals↗
PubMed1982

Three-dimensional spatial, density, and temporal resolution of the dynamic spatial reconstructor.

Spatial, density, and temporal resolution of the dynamic spatial reconstructor (DSR), a multiple X-ray source, high speed, computed tomography scanning system, are evaluated. Hole-pair resolution was evaluated in a stationary phantom surrounded with air, 15 cm of water, or 20 cm of water. Temporal resolution was evaluated by rotation of one of the resolution phantoms during the scan, and with a balloon inflated to a known volume and at a known rate to approximate a typical left ventricular chamber volume and filling rate. These studies confirmed that the spatial resolution is essentially the same in the transverse and axial directions, and that retrospective manipulation of the image data is important for maximization of spatial and density resolution in any structure under examination by obtaining a tradeoff with partial-volume and motion-blurring effects. Maximum spatial resolution in the scanned volume was shown, under ideal conditions, to be greater than five hole pairs per centimeter. Under conditions of intravenous injection of contrast agent, the resolution of blood vessels in an experimental animal approximately 25 kg in weight is expected to be on the order of three hole pairs per centimeter; and in an adult human weighting approximately 60 kg, a resolution of about two hole pairs per centimeter is to be expected.

Angiography↗