Noninvasive beat-by-beat registration of ventricular late potentials using high resolution electrocardiography.

We have developed a new high resolution ECG equipment for recording cardiac microvolt potentials from the body surface. Noise reduction has been achieved by specially designed suction electrodes, by spatial averaging of the electrocardiograms from four electrode pairs, using extremely low noise amplifiers, by performing registrations within a Faraday cage, and by teaching the patient to relax during end expiratory breath holding. Fourteen young males (controls) and 30 patients with various cardiac diseases (27 with CHD) were studied. In normals ventricular late potentials were not seen, but in 12/30 patients clearcut diastolic potentials were found. In 7/12 patients with positive findings, late potentials appeared beat-by-beat, in 5/12 patients those signals occurred intermittently, in 11/30 patients questionably, and in the remaining 5/30 patients no late potentials were recorded. One patient with the Romano-Ward syndrome revealed phases with stable beat-by-beat and intermittently occurring ventricular late potentials. These results demonstrate the feasibility of continuous non-invasive recording of ventricular late potentials, whose clinical and prognostic significance remains to be established.

Recovery of ventricular late potentials from body surface using the signal averaging and high resolution ECG techniques.

In 70 patients (3 females and 67 males), aged 16-72 years (mean: 51 +/- 9 years), the low noise ECG was recorded from body surface by the signal averaging and the high resolution beat-to-beat techniques. We found 61 patients were suffering from coronary heart disease, 4 had atypical coronary heart disease (syndrome X), 4 had dilatative cardiomyopathy, and one had the long QT syndrome (Romano-Ward syndrome). We found the following recovery rates for ventricular late potentials within the ST segment with the averaging technique: clearcut in 13/53 patients, doubtful in 16/53 patients, and late potentials absent in 26/53 patients. With the beat-to-beat technique the following recovery rates were found: clearcut late potentials in 27/70 patients, doubtful in 23/70 patients, none in 20/70 patients, and intermittently occurring late potentials in 18/70 patients (categorized as doubtful late potentials). When comparing the detection of late potentials with both methods in individual patients, we found concordant results in 39/53 patients studied (positive with both methods in 24/53 patients, negative with both methods in 15/53 patients), and discordant results in 14/53 patients (positive with the beat-to-beat technique and negative with the averaging technique in 12 individuals, negative with the beat-to-beat technique and positive with the averaging technique in the remaining 2 patients). The correlation between the incidence of late potentials and the presence of exercise-induced myocardial ischemia (submaximal bicycle exercise) was higher when using the high resolution beat-to-beat technique, as holds also true for the correlation to complex ventricular arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)

An electromagnetic distance measuring system.

A new accurate method to determine the myocardial deformation during the cardiac cycle in vivo is described. The system is based upon the mutual inductance principle, yet with transducers which consist of three perpendicular coils, yielding a spherical radiation and sensing characteristic. Thus the system is invariant with regard to rotational movements of the transducers. Residual angle dependences of the transducers can cause deviations of the recorded distance up to 4%. The output voltage is linear with the distance, with an accuracy better than 1%. The frequency response is set to 100 Hz (-3 dB). Zero drift doesn't exceed 0.5% after 24 hours. Measurements are not restricted to radiation propagating media, thus they can be performed in air, inside or outside of any biological object. For studies of regional myocardial performance in the left ventricle spherical transducers were designed with a diameter of 1.5 mm and a measuring range between 5 and 25 mm and flat surface transducers (5 mm diameter, 1.5 mm height) with a measuring range between 15 and 200 mm.

Changes of extracellular Na+, K+, Ca2+ and H+ of the ischemic myocardium in pigs.

In open-chest pigs during severe myocardial ischemia [K+]e, [Ca2+]e and [H+]e increase, [Na+]e increases transiently reaching control values after 30 min. Extracellular osmolality of the ischemic area increases due to an H2O-shift from the ECS to the ICS. The increase of [Na+]e and [Ca2+]e must b explained by the shrinkage of the ECS due to the H2O-shift. The increase of [Ca2+]e is additionally caused by the decrease of pHe. The increase of [K+]e is mainly caused by the release of K+ from the ICS. The changes of [K+]e and [K+]i cause a decrease of the membrane potential to a range in which slow response potentials and re-entry excitations can occur. The increase of [K+]e therefore seems to be a major factor to cause early post-ischemic arrhythmias.

[Continuous registration of micropotentials of the human heart. Initial experiences with a new high resolution ECG amplifier system]. / Fortlaufende Registrierung von Mikropotentialen des menschlichen Herzens. Erste Erfahrungen mit einem neuen, hochauflösenden EKG-Verstärkersystem.

A new ECG-amplifier system for recording cardiac microvolt potentials from the body surface is described. The improvement in signal-to-noise ratio was achieved by using specially designed suction electrodes, which were isolated from each other; by applying parallel signal averaging from four electrode pairs via four low-noise amplifiers; and by conducting the registration in Faraday cage. in 14 normal subjects, 12 patients with coronary heart disease and one patient with surgically corrected ventricular septal defect and pulmonary stenosis, pre-P-potentials (possible sinus node activity), His bundle potentials and ventricular late potentials were recorded with differing degrees of success. Variations of the time intervals to the preceding QRS complex were observed within the S-T segment in six of nine patients with demonstrable ventricular late ventricular late potentials. The advantage of such continuously recording ECG system lies in the highly accurate registration of cardiac micropotentials, particularly with ventricular late potentials that are changing in time, whereas the signal-averaging technique does not provide such possibilities.