[Radioisotopic tomography in the study of cardiac function]. / Apports de la tomographie radio-isotopique pour l'étude fonctionnelle cardiaque.

Dynamic tomographic images of the heart may be obtained by computerised treatment of a number of projections and planes recorded by a gamma camera rotating around a patient whose blood is labelled with radioactive technetium. This new technique of assessing cardiac function was tested in a group of 40 coronary patients and the results compared with standard contrast angiography. The following parameters were compared : LV volume, global and regional ejection fractions. The zones of interest were easily defined on the tomographic images and correction for background noise was negligible. Two different methods have been developed to measure volume. The first consists in counting the matrix units in three dimensions on serial planes through a given cavity. The second is based on the reconstruction of thick slices integrating all the ventricular radioactivity, the counting of which is calibrated with reference to an orthogonal plane. The correlations with angiography were excellent with both methods (R = 0,85 and 0,87 respectively). An equally good correlation was observed for ejection fraction (r = 0,85). A segmental model acceptable for both gamma line angiography, gamma tomography and contrast angiography comprises 6 segments : septal, apical, antero-lateral, postero-lateral, posterior, and inferior. The sensitivity and specificity of both isotopic methods of detection of major wall abnormalities (akinesia and dyskinesia) were assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

Negative lung thallium-201 uptake in right ventricular infarction.

In a case of right ventricular infarction, a negative lung image was observed on the resting thallium-201 scan, with a pulmonary activity much lower than the surrounding background. The myocardial image showed only a moderate inferior hypoactivity and the left ventricular ejection fraction was normal. This seems to be related to right ventricular failure with normal left ventricular function. It represents the opposite mechanism to the increased pulmonary thallium uptake commonly seen in severe left ventricular impairment.

Beat-to-beat assessment of left ventricular ejection in atrial fibrillation.

Beat-to-beat left ventricular ejection was evaluated in a group of 20 patients with chronic atrial fibrillation using a computerized single probe detector. The reference group consisted of 10 patients with sinus rhythm. For each patient 30 successive cardiac cycles were analyzed and the relative variations of four parameters were assessed: R-R interval, diastolic and systolic time intervals, and ejection amplitude, corresponding to the left ventricular stroke volume. The mean variations were respectively 3.4%, 10.4%, 8.4%, and 11.8% in patients with sinus rhythm, and 21.9%, 37.9%, 10.6% and 30.5% in patients with atrial fibrillation. This demonstrates that changes in ejection are mainly related to the duration of the filling phase, with nearly constant systolic times. Correlations between R-R intervals and systolic ejection amplitudes were highly significant (P less than 0.001) in patients with atrial fibrillation in 85% of cases. This information complements the average ejection fraction obtained from multiple cycle superimposition.