Biomedical subjects
Publications and source records attributed to H Mayr.
In a patient with the scimitar syndrome duplex Doppler sonography was used to show the point of entry of the abnormal pulmonary vein into the inferior vena cava to determine blood flow. Chest radiography and computed tomography also showed the vein descending to the diaphragm.
Twenty-four hour electrographic recordings were made on 36 grossly obese children and adolescents during a 3-week weight reduction regimen with a 525 kcal (2196 kj) mixed diet at weekly intervals. One hundred and ten Holter ECGs were analysed. Weight loss during the treatment was calculated to be 5.7 +/- 1.6 kg. Average and minimal heart rate decreased constantly throughout the study period from 83.9 +/- 9 to 75 +/- 9/min and 53 +/- 6 to 45 +/- 6/min, respectively (P less than 0.01, P less than 0.005). During the second week maximal heart rate increased significantly but returned to baseline values in the third week. Neither before nor during the period of therapy were any dysrhythmias monitored. Dietary regimens containing 500-700 kcal, based on a mixed composition of foods with sufficient amounts of minerals, can be regarded as a safe therapeutic tool in the treatment of obese children and adolescents.
Magnetic resonance imaging (MRI) of the thoracic aorta, including cine-MRI, was performed in 25 patients suspected of having dissection of the thoracic aorta. MRI was correlated with echocardiography, CT and angiography. The sensitivity of MRI (100%) was most closely followed by CT and angiography (83% and 77% respectively). The specificity of MRI and angiography was equally good, at 100% each. MRI was able to demonstrate the intimal flap in all 9 cases of aortic dissection, and there were no false-positive results. Differentiation of thrombosis and slow flow was possible on proton density images, gradient echo images permitted detection of the entry and re-entry sites. The nature of the dissection was determinated correctly in 8 out of 9 cases. MRI is capable of providing all the relevant parameters necessary to decide appropriate treatment of dissecting aneurysms of the thoracic aorta.
To assess the value of MRI in the diagnosis of aneurysm of the thoracic aorta with suspected or known dissection 23 patients were imaged with cardiac gating. Seven patients (group 1) had known dissection of the thoracic aorta; in 16 patients (group 2) an aneurysm was suspected by chest x-ray or 2D-echocardiography. Reference methods were: x-ray, 2D-echocardiography, angiography, and computered tomography. In the first group MRI clearly identified the intimal flap, could differentiate between true and false lumen, slow flow, and thrombus, respectively. In the second group MRI could exclude a dissection of the ectatic part of the thoracic aorta in 11 patients and demonstrate paracardiac or mediastinal mass in five patients. MRI can serve as an important diagnostic tool in known or suspected aneurysm of the thoracic aorta.
The first case of cyclophosphamide-induced myocardial ischaemia with electrocardiographically documented ST-segment elevation, T-wave inversion, arrhythmias, angina pectoris and cardiac decompensation is reported. The data suggest that cyclophosphamides induces myocardial ischaemia by eliciting coronary artery spasm.
The survival rate of 2256 patients with pacemakers was analyzed. Patients paced for Adams-Stokes equivalents (e.g. dizziness) showed a significantly better survival rate than did patients with pacemakers implanted for Adam-Stokes attacks or heart failure (P less than 0.0001). The estimated survival of the latter two groups did not differ significantly. Of the deceased patients who had received a pacemaker for the treatment of heart failure, 54% died due to this condition despite pacemaker implantation. The relative percentage of cases of sudden death after pacemaker implantation was high in the groups with Adams-Stokes attacks (12%) and Adams-Stokes equivalents (13%). In patients paced for Adams-Stokes attacks, sudden death occurred more frequently in the first year after pacemaker implantation (P less than 0.015) than during the following years. Therefore, increased efforts should be made to monitor patients carefully after pacemaker implantation to enable prompt detection of malignant tachyarrhythmias, probably the cause of sudden death in a substantial number of patients with pacemakers.
Quantitative 31P-NMR and enzymatic analysis of high-energy phosphates were used to characterize an isolated perfused working rabbit heart preparation. In this model, the left side of the heart works against a physiological after-load. Two perfusates, Krebs-Henseleit saline and the perfluorocarbon emulsion FC-43 (perfluorotributylamine), were evaluated in their ability to maintain cardiac function and high-energy phosphate metabolites over a period of 2-3 h. Adenine nucleotides ATP, ADP, phosphocreatine and inorganic phosphate (Pi) were measured by 31P-NMR while monitoring cardiac output and coronary flow. Intracellular pH was determined using the chemical shift of Pi. At the end of each experiment, hearts were freeze clamped and enzymatically assayed for adenine nucleotides, phosphocreatine and Pi. In every experiment, hearts perfused with FC-43 emulsion maintained the same rate of cardiac output as hearts perfused with Krebs-Henseleit saline, but with half the coronary flow rate: FC-43, 22 +/- 2.5 (n = 5), Krebs-Henseleit saline 42 +/- 2.7 (n = 6) ml/min, P less than 0.001. Hearts perfused with FC-43 emulsion showed higher [phosphocreatine] and [ATP] measured by 31P-NMR. For [phosphocreatine]: FC-43 3.2 +/- 0.7 (n = 5), Krebs-Henseleit saline 1.7 +/- 0.2 (n = 6) mumol/g wet wt., P less than 0.01. For [ATP]: FC-43 1.8 +/- 0.7 (n = 5), Krebs-Henseleit saline 0.9 +/- 0.2 (n = 6) mumol/g wet wt., P less than 0.02. [phosphocreatine] and [ATP] determined by 31P-NMR values were identical within experimental error to those values obtained by enzymatic analysis. Comparing [Pi] determined by both methods, 36% of Pi in FC-43-perfused hearts, and only 24% of Pi in Krebs-Henseleit saline-perfused hearts were visible by NMR, indicating that a large proportion of Pi is bound in the intact functioning heart. Similar results were obtained for [ADP]. Using the combined techniques of 31P-NMR and enzymatic assay, we have shown in this model of the isolated working rabbit heart preparation, that FC-43 emulsion maintains significantly better function and high-energy phosphate levels than Krebs-Henseleit saline.
Intrapulmonary percussion with a high-frequency jet system is a new method in the treatment of respiratory impairment. It imitates the conventional percussion massage of the thorax by introducing high-frequency gas oscillations (300 impulses per minute) into the tracheobronchial system. In 14 patients with abnormal alveolo-arterial oxygen differences due to bronchial mucostasis ventilation was satisfactorily improved by its application.
The effect of pressure-controlled intermittent coronary sinus (CS) occlusion on myocardial infarction (MI) size was evaluated. A device for this purpose was developed that consisted of a balloon catheter and pump system that produced controlled, intermittent occlusion of the CS and used CS pressure as a feedback to determine the duration of occlusion. It was hypothesized that proper selection of occlusion and non-occlusion times would both facilitate improved retrograde flow to ischemic areas and allow for more complete venous washout of metabolites. In 13 treated dogs and 12 control dogs before treatment, myocardium at risk of MI was estimated by injection of technetium-labeled microspheres. Intermittent CS occlusion was then begun, 15 minutes after coronary artery occlusion, and continued until termination of the experiment 6 hours later. Postmortem determination of infarct size was performed using the triphenyltetrazolium chloride staining technique. Intermittent CS occlusion begun 15 minutes after coronary artery occlusion and continued for 6 hours resulted in a 45% average reduction in MI size (p less than 0.001). During CS occlusion, the sinus systolic mean pressure increased from 10 to 44 mm Hg, while the distal coronary artery mean pressure increased by an average of 36% (from 22 to 30 mm Hg, p less than 0.05). These results suggest intermittent occlusion may be an effective treatment for evolving MI. This therapy, used alone or combined with other therapies (e.g., administration of pharmacologic agents), appears to have great clinical potential.
In several modern pacemakers, end-of-life (EOL) is indicated by a single-step rate drop, which is initiated by a voltage-sensitive electronic switch. This switch may also be activated by other causes, such as very short voltage drops, low temperatures, and electrocautery. We report a case in which a Cordis 233 F Sequicor II pulse generator was operating at 51.6 bpm in VOO mode at the time of implantation. As telemetry seemed to indicate that back-up pacing (the EOL indicator in this model) was "off," it was erroneously assumed that the pacemaker was not working properly. The unit was replaced by another impulse generator. At laboratory testing, the pacemaker was within specifications, when back-up pacing was separately programmed off. In conclusion, physicians should be aware of the new phenomenon of reversible EOL indicators, and that they may not rely on telemetry in this respect. Future pacemakers should incorporate a telemetry message which prevents similar misunderstandings.
The dexamethasone suppression test (DST) was administered shortly after admission to 102 consecutive in-patients with a Hamilton depression score greater than or equal to 16. Post-dexamethasone cortisol exceeded 6 micrograms/dl in 16 cases, and levels correlated significantly with Hamilton scores; with the AMP syndromes 'hypochondria', 'apathy' and 'catatonia'; and with the IMPS 'retarded depressive' syndrome. The criterion of suppression/non-suppression did not distinguish significantly between diagnostic categories (RDC or ICD), nor between endogenous and neurotic depression. (Newcastle scale). Both base-line and post-dexamethasone cortisol levels were reduced by prior treatment with minor tranquillisers, but not by major tranquillisers or antidepressants. DST results cannot be used as straightforward indicators of prognosis.
A case is presented in which a new cause for decrease in pacemaker rate was encountered: six months after implantation of a Medtronic 5967 pacemaker, the first routine check-up revealed a rate of 62.5 ppm instead of 70 ppm. After application of a magnet, all measurements returned to normal. The cause for this phenomenon, which could not be attributed to battery depletion or oversensing, was probably a change of state of the flip-flop which is responsible for the sudden rate drop of 10% which serves as the end-of-life (EOL)-indicator in this pacemaker. This change of state may result from a very short decrease of power supply voltage during shipment or at the time of implant, and is fully and permanently reversible by performance of the magnet test. In order to prevent unnecessary pacemaker explants, future pacemaker circuits should be redesigned to eliminate the effect of very short voltage changes. Meanwhile, a routine magnet test should be performed immediately after implantation.
The usefulness of contrast echocardiography for demonstration of myocardial perfusion was studied on six mongrel dogs. Two contrast agents tested were: (1) 0.9 percent saline solution, and (2) CO2-enriched saline solution (containing 0.2 ml CO2/10 ml). Only the latter solution produced an elucidation of the myocardium and allowed an estimation of the distribution and flow velocity of the contrast agent, which was characterized using the following three parameters: (1) transmural flow time (0.13 +/- 0.02 s x +/- SEM); (2) circumferential flow time (1.43 +/- 0.31 s); and (3) persistence time (42.0 +/- 4.3 s). There were no serious side effects on hemodynamics or heart rhythm. Thus, contrast echocardiography offers the possibility of detecting and quantitating myocardial perfusion.
202 patients with congestive cardiomyopathy have been classified according to their hemodynamic, angiographic, echocardiographic and scintigraphic findings: 72 patients were in the late stage (LS), 103 patients in an early stage (ES) and 17 patients showed a latent form of the disease. 48% of the hemodynamic ES were found to be clinically in stage IV NYHA and 53% of ES fell in class III. 40% of the patients with LS showed a stationary clinical course whereas 46% could improve their classification by one grade. The mortality in hemodynamic LS was 46% within an interval of 18 +/- 14 months after the diagnosis. In ES 64% showed a stable clinical course, where a 22% were deteriorating. Mortality in this group was 10%. Sensitivity and specificity of echocardiography (93 vs 80%) and radionuclide methods (80 vs 71%) were quite good in the late stage whereas in ES specificity was only 71% vs 80%. There was a discrepancy between the degree of myocardial impairment and clinical symptoms in the late stage whereas in the early stage there was no correlation between exercise capacity and LV-hemodynamics. Non-invasive methods allow the hemodynamic evaluation of the disease; invasive methods are required for clarification of diagnosis or establishing prognosis.
To determine the influence of interventions on infarct size numerous studies have attempted a comparison between treatment and control groups. This has been complicated by the great variability in the quantity of necrosis due to the differences in coronary bed size and collateral flow. An experimental model is presented in which it is possible to determine an "area at risk of infarction" at several time points during the evolution of the infarct. This model allows to estimate infarct size that may be expected under the present conditions, prior to interventions, early, in vivo and in the same experiment. It is possible to quantitate topographically changes in collateral flow and to investigate the effect of intervention in the same experiment. We found a correlation of life-threatening arrhythmias including ventricular fibrillation with the size of the "myocardium at risk of infarction" and with the size of the infarcts measured post mortem. Several beneficial interventions were studied.
Hemodynamic advantages led to an increasing number of implantations of so called "physiologic pacemakers", which preserve the natural sequence of atria and ventricles. The growing complexity of these systems renders ECG evaluation increasingly difficult. 85 patients had physiologic pacemakers implanted during the last 4 years and were controlled in our pacemaker outpatient clinic. Typical problems in ECG evaluation of the different pacemaking modes are discussed.
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