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Biomedical subjects

N G Dewhurst

Publications and source records attributed to N G Dewhurst.

22 records · Page 2Linked to original sources
PubMed1980

The influence of ectopic heart beats in gated ventricular blood-pool studies.

Direct data collection from ventricular blood-pool studies were stored in frame mode in a computer and by means of a modified tape recorder, the blood-pool image and ECG were recorded on tape. At the end of the study the tape data were replayed into the computer. The ECG signal was passed through a trigger circuit that detected the R wave which was sampled by the computer once every msec. Contractions outside of the desired range could be rejected along with the subsequent contraction. Of seven patients whose calculated ejection fractions were changed by more than 0.03, all had frequent (one in 20) ectopic contractions. The distorted ventricular volume curves were effectively restructured by the constraining procedure, changing the end-systolic volume and EF. Computer modeling showed a linear relationship between the percent of ectopic contractions and the underestimate of ejection fraction. One ectopic beat in ten led to a 5% underestimate of EF.

Cardiac Complexes, Premature↗
PubMed1980

Prognostic value of radionuclide ventriculography after myocardial infarction.

We have studied 50 consecutive patients who had sustained their first myocardial infarction. Using the noninvasive technique of radionuclide ventriculography, ventricular performance, as assessed by left ventricular ejection fraction (EF), was measured at rest just before discharge from hospital when patients were well and free from cardiac failure and then at one and four months after infarction, at rest and during submaximal supine exercise. Left ventricular ejection fraction was below normal in 42 patients (normal range 0.43-0.71). Mean EF for those patients recovering from inferior infarction was 0.43 +/- 0.09 (mean +/- 1 S.D.), whereas for those who had sustained anterior infarction mean EF was significantly lower, 0.33 +/- 0.13 (p less than 0.01). EF was significantly reduced (p less than 0.01) in those patients whose early progress was complicated either by serious arrhythmia or left ventricular failure. There was only poor correlation between EF and radiographically determined heart size but global left ventricular performance correlated well with the presence of abnormalities of regional wall movement. Over the first four months low EF failed to improve in seven patients with areas of dyskinesis (EF less tha 0.30) and despite diuretic therapy five suffered further episodes of cardiac failure. Excluding those with dyskinesis there were 18 patients who were unable to increase EF on exercise on month after infarction. Of these four already had symptoms of angina but a further 10 patients developed angina in the subsequent three months. Poor left ventricular performance is common after anterior myocardial infarction, complicated in the acute phase by serious arrhythmia or left ventricular failure. Patients with persistently low EF had an increased risk of further episodes of cardiac failure, whereas a fall in EF on exercise was associated with subsequent angina.

Adult↗