PubMed Health⌕ Search

Biomedical subjects

B Denef

Publications and source records attributed to B Denef.

26 records · Page 2Linked to original sources
PubMed1979

Comparability and reproducibility of apex cardiogram recorded with six different transducer systems.

A comparison was made in 7 dogs of the results obtained by 6 different apex cardiographic transducers applied before, during, and after controlled infusion of angiotensin and isoprenaline. The electrocardiogram, internal phonocardiogram, aortic and left ventricular pressure using a Telco micromanometer, and apex cardiogram were recorded simultaneously on magnetic tape and paper. Digital computer techniques were used to derive various measurements. The comparison of the 6 transducer systems was made expecially with respect to measurements derived from the normalised derivative, calculated using total as well as developed pressure or displacement. Measurements derived from left ventricular pressure were very reproducible. Differences in results of 'contractility' indices varied between 0.5 and 1.9 per cent. Indices from the apex cardiogram using 6 different transducer systems showed variations up to 20 per cent, with mean values varying between 3.2 and 8.1 per cent. There was a systematic deviation for one transducer system, which was responsible for a significant part of the observed variability. It may be concluded that in order to assure maximal reproducibility, technical characteristics of the apex cardiograph transducer should be taken into account and an optimal recording technique should be used.

Angiotensins↗
PubMed1976

Calibrated apexcardiography and assessment of left ventricular dynamics in man.

Using a calibrated displacement transducer, the total amplitude of the systolic wave of the left apexcardiogram (S), its first derivative (dS) and the normalized first derivative (nS), were evaluated as noninvasive indices of left ventricular function in human subjects. A strong correlation was present between peak dS and S in normal subjects (r=0.95, P less than 0.001). At an identical S, abnormal hearts had a lower peak dS, and this allowed a separation between groups with normal and abnormal ventricular dynamics. The index peak nS was significantly lower in patients with congestive cardiomyopathy (P less than 0.005) and ischemica heart disease in the presence of a low ejection fraction (P less than 0.001). It correlated significantly with LVEDP (r=-0.69, P less than 0.001), with ejection fraction (r=0.66, P less than 0.001) and with left ventricular contractility indices derived from isovolumic left ventricular pressure and its first derivative, recorded simultaneously by means of high fidelity micromanometers (peak VCE: r=0.76; Vmax total pressure: r=0.70; peak dP/dt: r = 0.69; P less than 0.001). The index peak nS was superior to S and peak dS, being less variable, independent of thorax circumference and better correlated with hemodynamic parameters. A close relationship was also present between the total amplitude of the atrial wave (A) and its peak first derivative (peak dA) in normal subjects (r = 0.98, P less than 0.001). For an identical A wave amplitude, patients with an increased left ventricular anddiastolic volume had lower values for peak dA (P less than 0.001).

Heart↗
PubMed1975

On the clinical value of calibrated displacement apexcardiography.

A new type of displacement transducer for recording the calibrated left apexcardiogram (QLAC) has been evaluated in 69 normal subjects and 99 cardiac patients. Total displacement of QLAC (TD), its peak first derviative (peak dD/dt (t-peak dD/dt). A strong corretation exists between peak dD/dt and TD in normal subjects (r=0.95) and the deviation from the normal relationship allows a separation between normal and abnormal ventricular function. In normal subjects (dD/dt/Dt) max averaged 34.2 plus or minus 5.7 sec-1; it was signigicantly lower in patients with congestive cardiomyopathy (26.5 plus or minus 6.3 sec-1 p greater than 0.005). This index correlates with left ventricular end-diastolic pressure (LVEDP) (R = - 0.69) and with ejection fraction (R - 0.66) and behaves as expected during positive and NEGATIVE INOTROPIC interventions. The index (dD/dt/Dt) max is superior to TD and peak dD/dt, being less variable independent of thorax circumference and better correlated with hemodynamic parameters. The index t-peak dD/dt was 53.9 plus or minus 9.5 msec in normal subjects and 81.6 plus or minus 18.9 msec in patients with congestive cardiomyopathy (p greater than 0.001). This time-interval correlates weakly with LVEDP (R = 0.04) and with ejection fraction (R = - 0.66). It is concluded that the normalized first derivative of QLAC provides useful information on left ventricular function.

Adolescent↗
PubMed1970

Value of reference tracings in diagnosis and assessment of constrictive epi- and pericarditis.

Reference tracings are of great value in the diagnosis and assessment of constrictive pericarditis. The Q-h interval in the jugular venous pulse tracing is strongly correlated with the mean right atrial pressure (r=0.91). The left ventricular ejection time, the Q-A2 interval, and the Q-h interval are independent during atrial fibrillation from the preceding diastolic filling interval. This differentiates constrictive pericarditis from valvular heart disease. Cases with haemodynamically significant constrictive epicarditis are characterized by a rapid evolution, absence of pericardial calcification and absence of an early diastolic filling sound, a dominant a wave in the jugular venous pulse tracing, and a high early diastolic ventricular pressure. The haemodynamic behaviour is similar to that found in cases with myocardial fibrosis.

Adolescent↗