An update on radiopharmaceuticals for myocardial perfusion imaging.
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Heart↗
Biomedical subjects
E G De Puey
Publications and source records attributed to E G De Puey.
The QS2/QT ratio as an index of appropriate left ventricular response to autonomic and inotropic stimuli.
Dissociation between duration of electrical and mechanical systole has been seen with increase of myocardial shortening velocity or adrenergic activity. We found a decrease of the QS2/QT ratio after exercise in 10 pts with semisitting bicycle maximal exercise test and a normal radionuclide angiogram. No change was seen in 9 patients with a normal study with beta blockade, and in pts with a abnormal radionuclide test, without beta blockade (11 pts). In 19 normal active individuals, a significant QS2/QT decrease (p less than 0.001) was seen after a submaximal exercise treadmill test, which was inhibited by beta blockade. We believe that QS2/QT diminution is suggestive of an increase of the inotropic state of the left ventricle with exercise, produced through adrenergic stimulation. It is not seen either when an ischemic left ventricle cannot adequately respond to exercise or after beta blockade.
Adult↗
Left ventricular performance during exercise in patients with left bundle branch block: evaluation by gated radionuclide ventriculography.
To investigate changes in left ventricular (LV) function during exercise in patients with left bundle branch block (LBBB), 22 patients without a history or physical findings of previous myocardial infarction or LV dysfunction were studied by gated radionuclide ventriculography (GRNV) at rest and during bicycle exercise. Coronary arteriography demonstrated greater than 75% diameter narrowing of at least one coronary artery in nine patients. Of the remaining 13 patients, GRNV demonstrated wall motion abnormalities in seven patients either at rest or with exercise. During exercise, mean ejection fraction (EF) did not increase in patients without coronary artery disease (CAD). Patients with CAD had a 12-point fall in mean EF with exercise. We conclude that LV reserve, as demonstrated by ability to increase EF with exercise, is impaired in patients with LBBB even in the absence of CAD or other underlying cardiac disease and that standard GRNV criteria to exclude the presence of CAD (a greater than five-point increase in EF with exercise and normal wall motion) are not strictly applicable in screening patients with LBBB.
Adult↗
Radionuclide kymography for the assessment of regional myocardial wall motion.
Regional myocardial wall motion is usually evaluated qualitatively from ECG-gated end-systolic and end-diastolic blood-pool images. Radionuclide kymography, which displays a one-dimensional scintigraphic image in time, synchronized with the electrocardiogram, provides a method to quantitate this motion. The technique is analogous to M-mode ultrasound in that one dimension is displayed as a function of time, but the activity distribution is displayed in place of acoustic interfaces. The motion of regional myocardial segments can be measured from multiple kymographic projections across the cardiac blood pool, after equilibration of a radioactive tracer. Radionuclide kymography is potentially better quantitatively than gated blood-pool imaging and is not hindered by viewing windows as are single- and multiple-transducer ultrasonography. Regional wall motion determined from radionuclide kymography correlated well with that determined from contrast left ventriculography in a series of patients. Since the kymographic sweep is initiated by the R wave of the ECG and proceeds continuously throughout the cardiac cycle, the temporal sequence of regional myocardial contraction can be directly assessed and related to corresponding portions of the ECG.
Computers↗