The need to enhance the echocardiographic determination of left ventricular ejection fraction is greatest in patients with suboptimal images. Intravenous contrast (CON) and tissue harmonic imaging (THI) are 2 important methods for enhancing endocardial border definition. However, the comparative feasibility and accuracy of THI and contrast-enhanced power harmonic imaging in difficult-to-image patients have not been examined. We assessed the comparative accuracy of THI and CON in determining EF and ventricular volumes in patients with suboptimal fundamental images. We demonstrated that CON is feasible and exhibits a greater correlation with ejection fraction and ventricular volumes determined by radionuclide angiography (standard of comparison) than THI in this difficult-to-image population, with no reported side effects. For both ejection fraction and ventricular volumes, the observer variability was least for CON, intermediate with THI, and greatest for fundamental imaging. (J Am Soc Echocardiogr 2000;13:216-24.)

Feasibility and accuracy of left ventricular volumes and ejection fraction determination by fundamental, tissue harmonic, and intravenous contrast imaging in difficult-to-image patients.

Right Ventricular function in aortic and mitral valve disease.

To evaluate ventricular function late after atrial repair of transposition of the great arteries (TGA), 26 asymptomatic patients had rest and exercise radionuclide ventriculography performed a mean of 9 years (range 5 to 15) after undergoing the Mustard operation. The mean resting right (systemic) ventricular (RV) ejection fraction (EF) was 0.50 ± 0.10 (±1 standard deviation); the RVEF was The mean resting left (pulmonary) ventricular (LV) EF was 0.58 ± 0.09; the LVEF was The patient's age, operative age, postoperative interval, residual arterial desaturation, preoperative large ventricular septal defect or pulmonary stenosis, postoperative pulmonary stenosis or superior vena caval obstruction, or performance of a second open-heart procedure was predictive of the rest or exercise EF of either ventricle.

Rest and exercise right and left ventricular function late after the Mustard operation: assessment by radionuclide ventriculography.

Exercise generally aggravates ischemic myocardial dysfunction, presumably by increasing tissue oxygen demand out of proportion to the increase in supply. Nevertheless, resting left ventricular (LV) wall motion abnormalities can improve dramatically after upright exercise. To investigate this "paradoxical" phenomenon, we performed upright bicycle exercise equilibrium radionuclide ventriculography in 93 patients with angiographic coronary artery disease. Immediately after exercise, LV end-diastolic volume was similar to the resting level (1 +/- 22% of rest value), but end-systolic volume (ESV) was significantly below (p less than 0.05) that at rest (-11 +/- 32%) and LV ejection fraction increased significantly compared with rest (0.57 +/- 0.16 vs 0.51 +/- 0.13, p less than 0.05). Improvement in resting myocardial asynergy was frequent (115 of 330 abnormal segments), and was observed more commonly in patients without pathologic Q waves and in segments manifesting mild rather than severe asynergy. In 60 additional patients with resting asynergy who were also studied after nitroglycerin (NTG), there was 89% concordance of wall motion response in asynergic segments after exercise and NTG: 71 of 85 segments manifesting improvement with NTG also improved after exercise, and 157 of 172 segments without improvement with NTG also failed to improve after exercise. Despite the similar wall motion response, the mechanism of improvement is probably different from that produced by NTG. With NTG, preload (end-diastolic volume) and afterload (systolic blood pressure) were significantly lower than their resting control levels (p less than 0.05). These changes did not occur after exercise. Instead, an isolated, significant reduction in ESV was noted. These data support the hypothesis that catecholamine stimulation is responsible for paradoxical wall motion improvement after upright exercise.

Improvement of resting myocardial asynergy with cessation of upright bicycle exercise.

To assess the prognostic value of radionuclide ventriculography we followed 100 consecutive patients for two years after their first myocardial infarction. Ventricular performance as assessed by left ventricular ejection fraction was measured at rest one day before hospital discharge and again one, four, and 12 months later at rest and during submaximal exercise. Left ventricular ejection fraction at discharge was below normal (<0.47) in 74 patients and correlated well with abnormality of regional wall motion. Low left ventricular ejection fraction (<0.30) observed in 25 patients was poorly predicted either clinically, radiologically, or electrocardiographically. Peak serum creatine kinase correlated well with left ventricular ejection fraction but there was a significant difference between anterior (n=46) and inferior (n=54) infarction with relative sparing of left ventricular function after inferior infarction. Left ventricular ejection fraction after inferior infarction was significantly higher both for transmural and subendocardial infarction, reflecting a variable degree of right ventricular necrosis. Within two years of first infarction, angina had developed in 32 patients, left ventricular failure in 17, ventricular tachycardia or fibrillation in four patients, reinfarction in seven, and 17 died suddenly. Low resting left ventricular ejection fraction before discharge was associated with left ventricular failure, ventricular arrhythmia, and sudden death (10 patients). Of the remaining patients exercised one month after infarction 27 showed a significant fall (>5%) in left ventricular ejection fraction and 23 of these developed postinfarction angina, four suffered non-fatal reinfarction and five patients died. Radionuclide ventriculography with exercise testing thus identified 88% of patients who died suddenly in the first two years after infarction. This was superior to any of the coronary prognostic indices currently in use and more predictive than the conventional end points of exercise testing (chest pain or ST segment depression) used either separately or in combination.

https://heart.bmj.com/content/heartjnl/49/2/111.full.pdf

Comparative prognostic value of radionuclide ventriculography at rest and during exercise in 100 patients after first myocardial infarction.

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.

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

https://iopscience.iop.org/article/10.1088/0143-0815/1/3/305/pdf

Reconstruction of ventricular volume curves distorted by variations in heart rate

We have measured regional lung tidal volumes and functional residual capacities by accumulating and framing iso-volumic images while the patient rebreathes 127Xe. As the lung changes shape during ventilation corrections for changes in geometry were obtained by simultaneous collection of 99Tcm counts from the gated perfusion scan. Regions of interest were made to vary throughout the respiratory cycle so that a region had always the same value of 99Tcm counts. From the corrected 127Xe counts regional tidal volumes (TVr) and functional residual capacities (FRCr) were derived. In patients with established chronic bronchitis and emphysema FRCr were greater and the ratio TVr/FRCr decreased compared with patients with relatively normal static and dynamic lung volumes. Preliminary studies suggest that this ratio was a better discriminator between normal and abnormal regional function than estimates of regional xenon washout. Studies with xenon-133 have contributed to our understanding of the physiology of ventilation but have contributed somewhat less to routine clinical practice. This results in part from the unsatisfactory physical properties of xenon-133. Its relatively low gamma ray energy of 80 keV results in significant self-absorption losses and the activity which may be administered is limited by the radiation dose from the associated beta particles so that relatively poor counting statistics are obtained. With inhaled technetium-99m (99Tcm) microspheres imaging conditions are greatly improved but the distribution of these particles may not equate with the distribution of ventilation particularly if wet particles are used. Moreover, simultaneous microsphere perfusion scans with technetium-99m as a label are impossible. Krypton-81m gas has a suitable energy but the short half-life of the rubidium-81m generator (4.7 h) makes supply difficult and the ultrashort half-life of the krypton-81m gas (13 s) leads to problems in calculating the indices of ventilation. Xenon-127 (127Xe) gas has a more favourable dosimetry profile than xenon-133 because it does not have associated beta particles. Further it has an energy (203 keV) suitable for modern gamma cameras and may be used in the presence of injected 99Tcm microspheres to provide simultaneous ventilation/perfusion imaging. Conventional techniques have assumed that a static image of a dynamic process is adequate. As the lungs move during imaging, some account of this respiratory movement should be made.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional tidal volume assessed by gated lung imaging.

We have studied changes in left ventricular function with non-invasive nuclear angiography, at rest, during graded infusions of isoprenaline (0.75, 1 0, and 2-0 jig/min), and 10 minutes after a single intravenous injection of propranolol (0-25 mg/kg). To test the adequacy of beta-adrenoreceptor antagonism, isoprenaline (2.0 vg/min) was reinfused after propranolol. Eight healthy subjects have been studied. Ventricular volume-time curves were obtained by electrocardiogram-gated accumulation of count rates in sequential 20 ms time bins (over 500 cardiac cycles) from a selected region of interest corresponding to the left ventricular blood pool. 99mTc-HSA was used as the radiopharmaceutical. In addition to the ejection fraction, the mean ejection rate, peak rate of change of volume in systole and diastole, and the mean ejection and filling times were calculated from these volume-time curves. A linear dose dependance has been shown in the changes in ejection fraction, mean ejection rate, peak

https://heart.bmj.com/content/heartjnl/44/1/75.full.pdf

H.M. Brash

Papers

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

Reconstruction of ventricular volume curves distorted by variations in heart rate

Regional tidal volume assessed by gated lung imaging.

Effect of isoprenaline and propranolol on left ventricular function as determined by nuclear angiography.