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.

Phase alterations of spin echoes by motion along magnetic field gradients.

Using a Taylor series expansion of the phase shift of a moving isochromatic spin group in the presence of a magnetic field gradient, the refocusing effects of the Carr-Purcell-Meiboom-Gill pulse sequence on stationary nuclei and those with constant, rectilinear velocity are readily demonstrated. Continuing the analysis to higher orders of motion reveals that nuclei with a constant, rectilinear acceleration have a phase shift at the spin echoes which increases linearly with echo number. Constant, rectilinear jerk (the time rate of change of acceleration) leads to an increase in phase shift from echo to echo which is quadratic in nature with an overlying reduction of the odd-numbered echoes by a constant amount. Motion parameters may be measured by parameter identification techniques. These principles may be applied to phase-sensitive NMR imaging.

Integration of database capabilities into a patient reporting system.

A database design is described which automatically archives computer-generated patient imaging and radioassay reports. Selected phrases are condensed so that data storage will be efficient without sacrificing a prose style of report. An indexed file structure has been used to facilitate rapid record retrieval even when several hundred thousand records are stored. Personnel time is considerably reduced for recalling patient records, preparing periodic summaries of studies completed, and performing administrative functions such as billing and keeping track of checked out images. Complex queries, such as "list all the patients between the ages of 50 and 60 on digitalis referred for a stress cardiac study, with left ventricular ejection fraction less than 40% and apical dyskinesis," become feasible. A system for data backup is described to protect against catastrophic data loss.

Correlations of systolic time intervals and radionuclide angiography at rest and during exercise.

Systolic time intervals (STI) were correlated with radionuclide angiography studies (RAS) in 57 patients at rest, during maximal semisitting bicycle exercise, and at 4 minutes following the cessation of exercise. Eleven were judged as being free of coronary artery disease (group 1), while 14 had coronary artery disease without (group 2A), and 27 (group 2B) with a previous transmural myocardial infarction. For RAS, resting radionuclide ejection fraction (REF), the changes in REF and end-systolic volume, and the development of a wall motion abnormality at peak exercise were each highly correlated with the presence of coronary disease (p less than 0.001). The accuracy of STI parameters in predicting the presence of coronary disease was poor (less than 60%). Changes in end-diastolic volume (EDV) correlated significantly with PEP/LVET and LVET1 changes following exercise. Moreover, patients with an abnormal (greater than 25%) increase in EDV at peak exercise had a greater increase in LVET1 in the postexercise period (p less than 0.01). We conclude that STI is not accurate enough a predictor of coronary disease or left ventricular function to serve as a useful screening test. Changes in STI parameters appear to be more related to changes in ventricular volume than to ventricular function.

Restenosis after transluminal coronary angioplasty detected with exercise-gated radionuclide ventriculography.

Forty-one patients were evaluated with exercise-gated radionuclide ventriculography before and within 4 days after successful transluminal coronary angioplasty and 4 to 12 months later. Patients were subgrouped according to the degree of restenosis demonstrated angiographically at 4 to 12 months (Group I [n = 23]: less than or equal to 20%; Group II [n = 10]: greater than 20% but less than 50%; Group III [n = 8]: greater than or equal to 50%). Patients with abnormal findings on gated radionuclide ventriculography (less than 5 point increase in ejection fraction or wall motion deterioration) early after angioplasty were eventually found to have a greater degree of restenosis than were patients with normal findings (41.2 +/- 30.3 versus 19.0 +/- 25.4% restenosis, p less than 0.0001). The accuracy of abnormal radionuclide ventriculography in predicting 50% or greater restenosis was 73% immediately after angioplasty and 77% at the time of follow-up angiography. Gated radionuclide ventriculographic results were abnormal in 5% of Group I patients compared with 75% of Group III patients (p less than 0.01) early after angioplasty; at late follow-up, they were abnormal in 27% of Group I patients compared with 88% of Group III patients (p less than 0.01). Group I patients had a greater increase in ejection fraction than did Group III patients at early (+11.3 +/- 7.5 versus + 3.5 +/- 6.5 points, p less than 0.01) and late (+11.8 +/- 7.8 versus -1.9 +/- 8.7 points, p less than 0.0005) follow-up. It is concluded that gated radionuclide ventriculography is useful in predicting coronary restenosis after transluminal coronary angioplasty.

Advantages of list-mode data acquisition in gated blood-pool studies.

Because of physiologic R-R interval variability and arrhythmia, frame-mode acquisition of gated images may produce erroneous left ventricular volume curves, particularly in the diastolic filling phase. Eighteen patients in sinus rhythm underwent gated imaging in which both frame-mode and list-mode acquisitions were used. The systolic portions of the volume curves were similar in both studies, and the ejection fractions correlated well (R = 0.97). "Dropout" of data in the late diastolic phase, noted in 15 patients in whom frame mode was used, was not present in list mode, in which the atrial kick was clearly delineated. In additional patients with various arrhythmias, separate volume curves were obtained with list mode for premature, post-premature, and sinus beats. In patients with atrial fibrillation, a prominent peak mid-range on the R-R histogram was selected, and a complete volume curve was obtained. It was concluded that list-mode acquisition provided improved volume curves, with particular applicability in arrhythmic patients.

Automated patient report-generation in nuclear medicine.

The proliferation of computer-based office-management systems in the past few years has involved the private physician's office as well as the hospital laboratory. Many radiology departments have already adopted this approach for patient report generation and data storage. Due to the absence of commercially available software, some nuclear medicine departments will be interested in writing their own, but may not have enough experience in nonimaging computer applications to determine the performance needed for a practical system. A report-generation system for scintigraphic studies has been developed in our department over the past 2 yr. During this time an essential hardware/software performance level was established. Ideas for design of program flow that enhance staff acceptance of this concept are presented. Significant reduction of errors in report transcription and billing, together with reduced requirements for secretarial and clerical staff, make a general system like this cost effective.

Left ventricular functional assessment by radionuclide ventriculography during isometric handgrip and bicycle exercise in patients with aortic insufficiency.

Twelve patients with chronic aortic insufficiency underwent radionuclide ventriculography performed in conjunction with dynamic bicycle and isometric handgrip exercise. Changes in left ventricular ejection fraction (LVEF) during exercise were measured. In all patients, the degree of regurgitation was determined by catheterization, and in eight patients, left ventricular end-diastolic pressure (LVEDP) was measured. The change in LVEF during either form of exercise was inversely related to the LVEDP. This correlation was somewhat better and more linear for bicycle exercise (R=0.84, p <.005) than for handgrip (R = 0.71, p<.025). By either exercise technique, a decrease in LVEF by >4 points occurred only in patients with 3 to 4 + regurgitation. We conclude that although radionuclide ventriculography with either bicycle or handgrip exercise is useful in determining the effect of aortic insufficiency on left ventricular functional reserve, bicycle exercise correlates better with other criteria of ventricular dysfunction.

Tc-99m glucoheptonate estimation of glomerular filtration rate. Correlation with endogenous creatinine clearance.

Estimation of GFR using radioisotope techniques has been successfully accomplished with I-125 iothalamate, Cr-51 EDTA, and Tc-99m DTPA. However, the techniques have required up to several hours to complete with blood and/or urine sampling. A method introduced by Schlegel and modified by Gates provides a simple and rapid technique of GFR quantitation that obviates the need for blood and urine sampling. In the present study an evaluation of Tc-99m GHA was undertaken to assess its ability to reflect GRF using a modification of Gates' technique. When the GFR determinations were compared with a current 24-hour CrC1, a correlation coefficient of 0.91 was obtained. Tc-99m GHA-derived GFR appears to closely correlate with endogenous CrC1 over a wide range of renal function.

Clinical utility of a two-site immunoradiometric assay for creatine kinase-MB in the detection of perioperative myocardial infarction.

In 144 patients, creatine kinase MB was measured serially at 0, 8, 16, 24, 48, and 72 hr using a two-site immunoradiometric assay (IRMA). Cardiac enzymes were also measured, including SGOT, LDH, total CPK, and CK-MB by electrophoresis. The presence of perioperative myocardial infarction (poMI) was established in 24 patients by the appearance of new electrocardiographic Q waves and/or new wall motion abnormalities detected by radionuclide ventriculography. In patients without poMI, CK-MB (IRMA) was elevated (6.4 +/- 4.9 equivalent units per liter) at 0-8 hr but decreased to 3.4 +/- 1.3 EU/l by 16 hr. In patients with poMI, peak values occurred at 16-24 hr (21.0 +/- 19.8 EU/l). Using a threshold value of 8.5 EU/l, patients with poMI could be distinguished from those without with 97% accuracy (sensitivity = 88%, specificity = 99%). The CK-MB (IRMA) was more reliable than the other enzyme assays, for which we used both empirically elevated threshold values based upon previous experience, and also threshold values retrospectively optimized for the study population. We conclude that the CK-MB (IRMA) can serve as a valuable postoperative screening test for poMI.

Determination of cardiac output and ejection fraction with the dual cardiac probe.

Cardiac output and left ventricular ejection fraction were determined noninvasively at the bedside in 26 patients by using a dual scintillation probe. The probe is a nonimaging detector that records a high frequency time-activity curve of the passage of an intravenously injected radioactive bolus through the heart. Results were correlated with ejection fraction measured by biplane cineangiography (r = 0.80) and cardiac output determined by green dye dilution (R = 0.86). It is concluded that the dual probe provides an accurate noninvasive means of measuring these parameters, and that it may be particularly applicable to serial measurements in patients in the intensive care unit.

Cardiac imaging by nuclear magnetic resonance.

Proton nuclear magnetic resonance (NMR) imaging has been developed and improved over the past few years to the state that images of static structures have recently shown spatial resolution equivalent or superior to other techniques such as X rays, ultrasound, or gamma ray-emitting radionuclides. The current state of NMR development is described; however, use of this exciting new diagnostic modality depends on the results of extensive clinical trials.

Exercise radionuclide ventriculography in evaluating successful transluminal coronary angioplasty.

To evaluate the ability of transluminal coronary angioplasty (TCA) to relieve myocardial ischemia, 44 patients with single vessel disease underwent exercise gated radionuclide ventriculography (GRNV) before and 2.8 +/- 1.3 days following angiographically successful TCA. Pre-TCA GRNV was abnormal in 11 of 14 patients with right coronary artery (RCA) stenosis and 24 of 30 with left anterior descending (LAD) stenosis. Following TCA there was an increase in exercise duration from 500 +/- 288 sec to 625 +/- 273 sec (P less than 0.001), and in maximum double product from (209 +/- 69) x 10(2) to (263 +/- 70) x 10(2) (P less than 0.001). The number of patients with stress-induced ST-T abnormalities decreased from 13 to 4 (P less than 0.05), and the number with chest pain during exercise decreased from 18 to one (P less than 0.001). Whereas resting ejection fraction was unchanged (0.58 +/- 0.10 vs 0.59 +/- 0.11) following TCA, the ejection fraction at peak exercise increased from 0.61 +/- 0.13 to 0.66 +/- 0.12 (P less than 0.001). Of 24 patients with resting abnormalities, regional wall motion improved in 13. In 22 of 31 patients with stress-induced asynergy, the wall motion response to exercise improved (P less than 0.001). Of 19 patients restudied angiographically and with exercise GRNV at 6-12 months, restenosis of greater than or equal to 50% had occurred in six, four of whom had abnormal studies. In six of whom the degree of stenosis of the dilated artery had remained less than or equal to 20% the exercise GRNV study remained normal. It is concluded that GRNV is helpful in documenting the improvement in resting left ventricular function and functional reserve in patients with angiographically successful TCA. In the limited number of patients with late follow-up studies, data suggest that GRNV may be a valuable test to detect restenosis.

Effects of stress management training and dietary changes in treating ischemic heart disease.

To evaluate the short-term effects of an intervention that consists of stress management training and dietary changes in patients with ischemic heart disease (IHD), we compared the cardiovascular status of 23 patients who received this intervention with a randomized control group of 23 patient who did not. After 24 days, patients in the experimental group demonstrated a 44% mean increase in duration of exercise, a 55% mean increase in total work performed, somewhat improved left ventricular regional wall motion during peak exercise, and a net change in the left ventricular ejection fraction from rest to maximum exercise of +6.4%. Also, we measured a 20.5% mean decrease in plasma cholesterol levels and a 91.0% mean reduction in frequency of anginal episodes. In this selected sample, short-term improvements in cardiovascular status seem to result from these adjuncts to conventional treatments of IHD.

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.

The noninvasive diagnosis of coronary artery disease in patients with left bundle-branch block.

The prognosis in patients with left bundle-branch block (LBBB) is related primarily to the presence or absence of underlying cardiac disease. Because coronary artery disease (CAD) is the most common underlying disease found in these patients, it would be desirable, in the presence of LBBB, to have a noninvasive method of differentiating between patients with and without CAD. We reviewed our experience in patients with LBBB who had undergone coronary arteriography with regard to electrocardiographic (ECG) stress testing, exercise radionuclide ventriculography (RNV), and exercise thallium scintigraphy; we also reviewed their clinical histories. A clinical history of typical angina pectoris was specific for CAD, a false-positive history being present in only one of 12 patients without CAD. The frequency of a positive ECG ST response to exercise was equal in patients with and without CAD. False-positive ejection fraction and wall-motion responses to exercise were frequent by RNV. A modification of the usual RNV criteria for positivity improved specificity but resulted in poor sensitivity for CAD. False-positive thallium study results also were. frequent in these patients. The perfusion defects usually involved the ventricular septum; the inferior and posterior walls were involved only in patients with CAD. We conclude that the usual noninvasive diagnostic tests for CAD are of limited value in patients with LBBB.

Interpretation of multigated Fourier functional images.

First-harmonic Fourier analysis is currently used to aid in the interpretation of multigated cardiac studies. Its intrinsic inaccuracies are not generally appreciated. This study investigates the characteristics and magnitudes of the errors of this technique. The study analyzes computer-generated phantoms that isolate the various motions of the ventricles (contraction, translation, and rotation) with the first-harmonic approach. The first-harmonic output is compared with a more accurate fitting scheme using multiple terms of the Fourier expansion. Significant artifacts of the inaccuracy of the first harmonic appear in the phantom studies and are observed in patient examples. We conclude that caution is needed in interpreting first-harmonic phase and amplitude images, and particularly in associating them with parameters like the onset of contraction and the stroke volume.

Post-exercise potentiation of wall motion to identify myocardial viability.

Resting left ventricular wall motion abnormalities may represent myocardial scars or areas of viable muscle which are ischemic and may thus benefit from revascularization surgery. Improvement in wall motion in the 3-6 minute post-exercise recovery period as compared to the resting state was investigated as a possible criterion to predict myocardial viability in 168 patients with coronary artery disease. Of 125 patients with abnormal resting wall motion, 14 of 14 who improved regional function post-exercise also improved following coronary bypass surgery. However, wall motion improved postoperatively in an additional 55 patients who had not demonstrated post-exercise improvement. An increase in ejection fraction post-exercise occurred in patients with coronary disease as well as an additional group of 24 normal subjects. Thus in the post-exercise period, improvement in resting wall motion is a highly specific but insensitive predictor of myocardial viability.