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Biomedical subjects

W Merx

Publications and source records attributed to W Merx.

At least 37 records · Page 2Linked to original sources
PubMed1977

[Clinical value of multiple praecordial chest leads for evaluating the course of acute anterior myocardial infarction (author's transl)].

Percordial ST-segment mapping using an improved 48-lead system was evaluated 2-to-3-hourly in 322 single measurements on 24 patients with acute anterior myocardial infarction. Changes in the sum of ST-elevation (capital sigma ST) or in the number of leads with ST-elevation (NST) could be distinguished in two different phases: an initial rapid increase and decrease in capital sigmaST and NST was followed after 6 to 12 hours, by a more plateau-like course, which exhibited, especially in uncomplicated cases, only slight further changes. During the initial phase, marked differences in the maximal rate of decrease were observed for capital sigma ST and NST. In this phase, interpretation of therapeutical interventions using changes of capital sigma ST or NST as reference is therefore very critical. However, during the second plateau-like phase, extension of myocardial necroses is significantly associated with a new steep increase in capital sigma ST. Thus precordial mapping is suitable for rapid and sensitive detection of infarct extension in patients with anterior myocardial infarction. The development of pericarditis or bundle-branch block, which principally can disturb the evaluation of capital sigma ST and NST, occurred only sporadically in a few patients and therefore caused no major problems.

Acute Disease↗
PubMed1977

[Multiple chest leads to evaluate the course of acute myocardial infarction (author's transl)].

At present, precordial mapping is the only reliable method to define the course of myocardial ischemia in patients with acute myocardial infarction. To improve registration technique and evaluation an elastic synthetic plate with 48 electrodes and a computer program for calculation of the different ecg-changes have been developed. Registration and evaluation require an average period of 15 minutes (+/-3 minutes) thus allowing repeated application within time intervals.

Acute Disease↗
PubMed1975

Effects of unipolar cathodal and bipolar stimulation on vulnerability of ischemic ventricles to fibrillation.

The effects of unipolar and bipolar stimulation on ventricular fibrillation threshold were studied during acute occlusion of the left anterior descending coronary artery in 13 anesthetized dogs. Values for ventricular fibrillation threshold were determined by delivering trains of rapid bipolar or unipolar pulses (100/sec) during the vulnerable period. The mean threshold value was found to be 13.0 ma for bipolar, 13.9 ma for unipolar anodal and 21.0 ma for unipolar cathodal stimulation. Ventricular fibrillation threshold was significantly lower (P less than 0.01) with both unipolar anodal and bipolar stimulation than with unipolar cathodal stimulation. In these animals, the first premature beats induced by the rapid stimuli occurred significantly earlier with unipolar anodal and bipolar stimulation than with unipolar cathodal stimulation. The effect of competition of unipolar or bipolar pacing stimuli with normally conducted ventricular beats was also studied in a group of 16 dogs. Repeated trials of competitive pacing during coronary occlusion showed that the incidence of ventricular fibrillation was significantly greater (P less 0.05) with bipolar pacing (36 percent) than with unipolar cathodal pacing (15 percent). These results indicate that bipolar pacing is potentially more dangerous than unipolar cathodal pacing and suggest that the incidence of pacemaker-induced ventricular fibrillation might be further reduced by the use of unipolar cathodal stimulation during acute myocardial infarction.

Animals↗
PubMed1975

Experiences with different computerprograms for the ECG-analysis.

As the use of computers for ECG-analysis has left the stage of laboratory investigation, and different systems are offered by industrial firms with high grade promises concerning their reliability, it seemed about time to perform an evaluation of the programs available. Each ECG of 252 adult patients was recorded in one session from adhesive electrodes within 10 minutes on the magnetic tapes of the data-acquisition-units of four different manufacturers. The computer-analysis of each of these ECGs was done by six programs of Pordy (Mt. Sinai-Hospital, New York), Caceres, Smith (Mayo Clinic, Rochester), Arvedson, Riedl with modified criteria of the USPHS and Riedl with criteria of the Minnesota-code. Besides this each ECG was also analysed in the conventional way by each of the three cardiologists involved in this study. The results of the computers' and the physicians' analysis concerning rhythm, extrasystoles, infarctions and ST-T-segment-variations are demonstrated and discussed.

Diagnosis, Computer-Assisted↗