PubMed Health⌕ Search

Biomedical subjects

M R Cattell

Publications and source records attributed to M R Cattell.

7 recordsLinked to original sources
PubMed1980

Observations on exercise testing and coronary arteriography.

Exercise tests were performed on 551 patients with a clinical diagnosis of coronary artery disease during their admission for angiography. A computer-generated index (CI, 0-100%) was used to describe the coronary anatomy, and additional data on left ventricular contraction abnormalities were recorded. Significant correlations exist between exercise performance and angina grade, coronary pathology, left ventricular function, and prognosis.

Angina Pectoris↗
PubMed1978

A computer generated index for the assessment of coronary angiography.

Mortality in patients with coronary artery disease is related to its severity. The commonly used classification of 1, 2 or 3 vessel disease is relatively insensitive. We have designed a new classification which takes into account site, severity and effect of multiple lesions in the coronary circulation. Data is recorded on Mark Sense computer cards and a coronary index (CI) obtained. We have collected data from 1100 patients and shown correlations of the index with clinical variables, ventricular function and in particular, mortality.

Angina Pectoris↗
PubMed1976

Length-induced changes in activation during contraction. A study of mechanical oscillations in strontium-mediated contractions of cat and frog heart muscle.

The plateau phase of prolonged Sr-mediated contractions of preparations of cat and frog heart muscle was used to study the transient response to abrupt changes in load or length. An oscillatory response (total amplitude equal to or less than 5% Lmax) was obtained. Isotonic oscillations were less damped than their isometric counterparts, implying positive feedback and thus a causal role of the perturbation in length. Oscillation frequency was 2-3 HZ at 29 degrees C (Q 10, 2-3); it could be increased by epinephrine or caffeine, independently of their effects on extent of shortening; it otherwise changed as a generally constant function of the length at which the oscillation occurred, whether this was altered by changes in extracellular [Sr], frequency of contraction, or load (independent of the direction and magnitude of the preceding load step). Similar oscillatory responses were induced during Sr- or Ca-mediated contractures. Cat muscles showed an additional slower component to the oscillatory response. Transient augmentation of the velocity-length relationship after abrupt reduction in load, previously described for twitch contractions under certain conditions, appears to be analogous to the first phase of the oscillatory response studied here. Our findings indicate that the oscillation is not attributable to any mechanism intrinsic to myofilament interaction, but rather that it involves length-induced changes in the level of activation, probably mediated by Ca2+ or Sr2+. We conclude that length influences the level of activation during contraction of heart muscle.

Action Potentials↗
PubMed1976

Length as a factor in excitation-contraction coupling in heart muscle: an investigation of mechanical transients in strontium-mediated contractions.

Sr-mediated contractions have been used to provide an analogue of the normal twitch contraction but with a plateau phase of steady-state activity. An abrupt change of load during the plateau induced an isotonic oscillatory response whose frequency was generally related to the length at which it occurred but could be independently increased by adrenaline or caffeine. The response was not specific for Sr, being seen also in Sr- or Ca-activated K-contractures. The isotonic oscillatory response was less damped than the corresponding isometric transient, and spontaneous isotonic oscillation often occurred following the initial shortening phase, suggesting that the change in length rather than the change in load was the causal perturbation. In cat but not frog preparations a second slower oscillation, also influenced by adrenaline, could be induced. Analysis of velocity--length relations indicates that the isotonic oscillations observed during the plateau phase are analogous to the velocity transients previously described in twitch contractions, but then only in three states characterized implicitly by a relatively poor capacity for internal sequestration. These findings provide evidence that length influences the level of activation of the contractile proteins during shortening in heart muscle, probably through changing Sr/Ca availability.

Animals↗