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Biomedical subjects

S L Bacharach

Publications and source records attributed to S L Bacharach.

At least 109 records · Page 6Linked to original sources
PubMed1981

Measurement of ventricular function by ECG gating during atrial fibrillation.

The assumptions necessary to perform ECG-gated cardiac studies are seemingly not valid for patients in atrial fibrillation (AF). To evaluate the effect of AF on equilibrium gated scintigraphy, beat-by-beat measurements of left-ventricular function were made on seven subjects in AF (mean heart rate 64 bpm), using a high-efficiency nonimaging detector. The parameters evaluated were ejection fraction (EF), time to end-systole (TES), peak rates of ejection and filling (PER,PFR), and their times of occurrence (TPER,TPFR). By averaging together single-beat values of EF, PER, etc., it was possible to determine the true mean values of these parameters. The single-beat mean values were compared with the corresponding parameters calculated from one ECG-gated time-activity curve (TAC) obtained by superimposing all the single-beat TACs irrespective of their length. For this population with slow heart rates, we find that the values for EF, etc., produced from ECG-gated time-activity curves, are very similar to those obtained from the single-beat data. Thus use of ECG gating at low heart rates may allow reliable estimation of average cardiac function even in subjects with AF.

Atrial Fibrillation↗
PubMed1980

Beat-by-beat validation of ECG gating.

Ejection fraction, normalized peak ejection and filling rates, and the time of occurrence of these events relative to the R-wave were determined in each of 512 consecutive individual cardiac cycles in each of 30 patients using an ultra-high-efficiency nonimaging detector system. For a given patient the 512 measurements of each quantity were averaged and compared with the value of this same quantity as determined from an R-wave-gated left-ventricular (LV) time-activity curve (TAC) derived from the same 512 cycles. We conclude (a) that a small but detectable systematic underestimate occurs in some LV function parameters when they are derived from gated LV TACs; (b) that the magnitude of this underestimate is smaller and less variable for systolic than for diastolic measurements; (c) that the magnitude of the underestimate is not greater than 20% in any single patient for diastolic parameters, nor greater than 8% in any individual patient for systolic parameters, and is substantially less for most patients; and (d) that a small subset of patients may require beat-length windowing if the gated values of diastolic parameters are to fall within these limits. Thus LV function measurements obtained from gated TACs adequately reflect the true average of such values during the measurement interval.

Cardiac Output↗
PubMed1979

Detection of early cardiac dysfunction in patients with severe beta-thalassemia and chronic iron overload.

To detect early left ventricular dysfunction, we used radionuclide cineangiography to determine left ventricular ejection fraction during exercise in 24 patients with transfusion-dependent, congenital anemias, 21 of whom had severe beta thalassemia. Ejection fraction at rest was normal in 21 patients (greater than 45 per cent) and in all patients was 53 +/- 2 per cent (mean +/- S.E.M.)--not significantly different from the value in normal subjects. However, ejection fraction during exercise was normal in only 11 patients (53 +/- 3 per cent in all patients, P less than 0.001 as compared with the normal value). All eight patients who had received fewer than 100 transfusions but only three of 16 (19 per cent, P less than 0.001) who had received 100 or more transfusions had normal responses during exercise. Whereas echocardiographic fractional shortening at rest was normal in 16 of 19 patients studied, eight patients with normal fractional shortening had abnormal ejection-fraction responses to exercise. Thus, radionuclide cineangiography during exercise is a highly sensitive technique for detecting preclinical myocardial dysfunction in patients with systemic iron overload.

Adolescent↗
PubMed1979

Left ventricular function at rest and during exercise after aortic valve replacement in patients with aortic regurgitation.

To determine the effect of aortic valve replacement on reversing abnormalities of left ventricular function in patients with aortic regurgitation, radionuclide cineangiography was used to study 16 sympatomatic patients with aortic regurgitation before and 6 months after aortic valve replacement. Before operation, left ventricular ejection fraction was 46 +/- 3 percent at rest (normal mean +/- standard error of the mean 57 +/- 1 percent; P less than 0.001), and decreased to 37 +/- 4 percent during exercise (normal 71 +/- 2 percent; P less than 0.001). after operation, ejection fraction rose to 58 +/- 4 percent at rest, indistinguishable from the normal value, and during exercise was 53 +/- 4 percent, increased (P less than 0.001) from before operation but significantly (P less than 0.001) subnormal. Thus, aortic valve replacement can improve but usually does not normalize left ventricular function during exercise in symptomatic patients with aortic regurgitation.

Adult↗
PubMed1979

Instrumentation and data processing in cardiovascular nuclear medicine: evaluation of ventricular function.

Cardiovascular nuclear medicine encompasses a variety of clinical procedures. Some of these procedures place demands on the imaging and data processing equipment that far exceeds those associated with other nuclear medicine procedures. This paper is devoted to an evaluation of the imaging and data processing requirements for two of the more demanding studies in cardiovascular nuclear medicine--first transit and gated equilibrium measurement of ventricular function. Imaging instrumentation and collimation, computer system hardware, and computer acquisition and analysis software are each treated as they apply to these procedures.

Cardiovascular Diseases↗
PubMed1979

Effect of septal myotomy and myectomy on left ventricular systolic function at rest and during exercise in patients with IHSS.

Patients with idiopathic hypertrophic subaortic stenosis (IHSS) have supernormal left ventricular systolic function at rest. Septal myotomy/myectomy reduces outflow obstruction and symptoms. However, it has been proposed that operation causes myocardial damage, with consequent reduction in left ventricular function and potentially deleterious long-term consequences, despite relief of symptoms. To evaluate the effect of myotomy and mylectomy on left ventricular function, we employed noninvasive radionuclide cineangiography at rest and during maximal exercise in21 consecutive patients with IHSS, before and 6 months after operation. In 30 normal subjects, the ejection fraction (EF) was 57 +/- 2% at rest and 71 +/- 2% during exercise. Before operation in patients with IHSS, the EF was supernormal at rest (76 +/- 2%, p less than 0.001), and normal during exercise (71 +/- 3%, NS). All patients improved from NYHA functional class III-IV preoperatively to class I-II postoperatively; the maximal provocable gradient invariably diminished (average, 100 +/- , mm Hg preop, 33 +/- 9 mm Hg postop, p less than 0.001). Postoperatively, the EF at rest was 67 +/- 2%, still supernormal, but less than that noted preoperatively (p less than 0.001). During exercise, the EF was 66 +/- 4%, only mildly diminished (p less than 0.01) from that preoperatively. We conclude that muscle resection during myotomy and myectomy usually does not cause any important impairment of global left ventricular function at rest or during exercise stress.

Adolescent↗
PubMed1978

Effects of coronary-artery bypass on global and regional left ventricular function during exercise.

To determine the effect of coronary revascularization on exercise-induced abnormalities of left ventricular-ejection fraction and regional contraction, we obtained electrocardiograph-gated 99mTc radionuclide cineangiograms before and after operation in 23 consecutive patients. At rest, their average ejection fraction remained unchanged: 51 +/- 3 versus 54 +/- 4 per cent (+/- S.E.M.). However, 17 of the patients showed improvement of ejection fraction during postoperative exercise (increase of 51 per cent). The remaining six patients had no change or a decreased ejection fraction during exercise. All patients with improved ejection fractions during exercise were symptomatically improved. No improvement of regional function occurred at rest, but improvement did occur in regions of exercise-induced dysfunction. Although coronary revascularization has little effect on left ventricular function at rest, the ejection fraction during exercise and exercise-induced wall-motion abnormalities improve in most patients who experience symptomatic improvement.

Adult↗
PubMed1978

Exercise-induced left ventricular dysfunction in symptomatic and asymptomatic patients with aortic regurgitation: assessment with radionuclide cineangiography.

In patients with aortic regurgitation,, left ventricular dysfunction at rest, which is associated with a poor long-term prognosis, often develops before severe symptoms. To determine whether evidence of left ventricular dysfunction could be detected before it appeared at rest, 43 patients with severe aortic regurgitation were studied using radionuclide cineangiography during exercise. In 30 normal subjects, left ventricular ejection fraction increased during exercise (57 +/- 1 percent [mean +/- standard error] at rest, 71 +/- 2 percent during exercise, P less than 0.001). In contrast, among 21 symptomatic patients, ejection fraction was normal at rest in 14 patients (average 47 +/- 2 percent) but normal during exercise in only one patient (average 38 +/- 2 percent, P less than 0.001). Ejection fraction was normal at rest in 21 of 22 asymptomatic patients (average 62 +/- 2 percent) but was normal during exercise in only 13 (average 57 +/- 3 percent, P less than 0.001). Thus, exericse-induced left ventricular dysfunction can precede symptoms and dysfunction at rest. Radionuclide assessment of left ventricular function during exercise may prove valuable in sequentially following the state of left ventricular function in patients before the onset of symptoms or of irreversible left ventricular failure.

Adolescent↗
PubMed1978

Effect of nitroglycerin on exercise-induced abnormalities of left ventricular regional function and ejection fraction in coronary artery disease. Assessment by radionuclide clineagiography in symptomatic and asymptomatic patients.

The effects of nitroglycerin (TNG) on exercise-induced abnormalities of left ventricular wall motion and ejection fraction are unknown in symptomatic and asymptomatic patients with coronary artery disease (CAD). In the present investigation radionuclide cineangiographic studies were performed in 47 patients with CAD (14 without angina during exercise) and in 25 normal subjects. All CAD patients, including those without symptoms, demonstrated regional wall motion abnormalities during exercise. In all patients, ejection fraction (EF) also responded abnormally to exercise: EF decreased from 48% at rest to 36% during exercise (P less than 0.001). EF increased in all normal subjects from an average of 58% at rest to 71% during exercise (P less than 0.001). In all CAD patients TNG reduced exercise-induced regional wall abnormalities and increased EF attained during exercise from an average of 36 to 48% (P less than 0.001). EF in normal subjects was unchanged by TNG. Thus, exercise can cause abnormalities in left ventricular regional function and ejection fraction in patients with or without symptoms; these abnormalities can be mitigated by prophylactic TNG.

Adult↗
PubMed1978

Ejection fraction by count rate from gated images.

Left-ventricular (LV) ejection fraction (EF) was determined from ECG-gated images of the cardiac blood pool, by computing the relative change in net LV counts occurring in these images during systole. EFs obtained with this method gave satisfactory interobserver agreement in 20 studies reviewed by three independent observers (average r = 0.95) and also compared favorably with EFs obtained by contrast ventriculography in 39 patients (r = 0.92). The technique appears suitable for use in the evaluation of systolic function in patients with heart disease.

Coronary Circulation↗
PubMed1978

Radionuclide cineangiography during stress.

A "real-time" ECG-gated scintigraphic image system was developed at NIH, Bethesda. This system presents in real-time manner 1) an image sequence, that spans a complete heart cycle, 2) a regional time activity curve, in which later distolic phenomena are correctly portrayed, and 3) a beat length distribution function. This system is suitable especially for stress investigations. Normal subjects showed an increase of ejection fraction, whereas patients with CAD revealed a decrease of EF.

Cineangiography↗
PubMed1977

Real-time radionuclide cineangiography in the noninvasive evaluation of global and regional left ventricular function at rest and during exercise in patients with coronary-artery disease.

Although coronary angiography defines regions of potential ischemia in patients with coronary-artery disease, accurate assessment of the presence and functional importance of ischemia requires appraisal of regional and global left ventricular function during stress. To perform such assessment, we developed a noninvasive real-time radionuclide cineangiographic procedure permitting continuous monitoring and analysis of left ventricular function during exercise. In 11 patients with coronary disease who had normal regional and global ventricular function at rest, new regions of dysfunction developed during exercise (P less than 0.001), and in 10, global ejection fraction dropped 7 to 47 per cent. Fourteen age-matched normal subjects were studied; during exercise none had regional dysfunction, and each increased global ejection fraction (average increase, 23 +/- 3 per cent [+/-S.E.], P less than 0.001 as compared with patients with coronary disease). Radionuclide cineangiography during exercise permits accurate assessment of the presence and functional severity of ischemic heart disease.

Adult↗