Prokinetic therapy: what can be measured by gastric scintigraphy?

OBJECTIVE: To evaluate whether gastric scintigraphy with quantitative analysis of gastric peristalsis may be a useful tool for documenting the effects of prokinetic therapy. METHODS: Gastric emptying was determined in eight patients with insulin dependent diabetes mellitus (IDDM) and nine patients with progressive systemic sclerosis (PSS) after ingestion of a semi-solid test meal. Fourier analysis of condensed images was used to evaluate contraction amplitudes of the entire stomach, as well as frequency and velocity of gastric contractions. Patients were studied twice, first under baseline conditions and then after 4 weeks of continuous oral prokinetic therapy with cisapride (10 mg t.i.d.). Findings were compared with data derived from 15 healthy controls. RESULTS: At baseline conditions IDDM and PSS patients exhibited reduced gastric peristalsis and delayed emptying compared to controls. After 4 weeks of prokinetic treatment, gastric contraction amplitudes increased significantly, especially in the gastric corpus and the proximal stomach, associated with a slight improvement of gastric emptying. Changes in frequency and velocity of gastric contractions during prokinetic treatment correlated with the improvement of gastric motility and emptying. CONCLUSIONS: Prokinetic therapy with cisapride stimulates gastric motility, and could be non-invasively monitored by scintigraphy. This radionuclide technique provides a number of relevant parameters of gastric function, such as gastric emptying, contraction amplitudes, frequency and velocity of gastric contractions, which give crucial insights into the mechanisms of action of prokinetic drugs.     

Factor analysis of gated cardiac blood-pool data: application to patients with congenital heart disease.

Ventricular emptying was evaluated in patients with congenital heart disease (CHD) with left-to-right (L-R) shunt by factor analysis of gated equilibrium radionuclide angiography. In 36 (95%) of 38 ventricular septal defect patients and 20 (95%) of 21 atrial septal defect patients with small L-R shunt (pulmonary to systemic blood flow, Qp/Qs less than or equal to 2.5), as well as all patent ductus arteriosus patients, two significant cardiac factors corresponding to the ventricles (ventricular factor) and the atria plus large vessels (atrial factor) were extracted. However, in all of nine ventricular septal defect patients with large L-R shunt (Qp/Qs greater than 2.5), two different ventricular factors were determined which corresponded to the right and left ventricles (RV and LV). The RV factor showed a delay of ejection phase compared with the LV factor, and the delay was correlated with the value of Qp/Qs (r = 0.82, P less than 0.01). In eight (80%) of 10 ASD patients with large L-R shunt (Qp/Qs greater than 2.5), RV was described by the two different ventricular factors located in the septal and free-wall regions. The LV was extracted in the same factor as that located in the septal region of RV. This study demonstrates the capability of factor analysis in the pathophysiological investigation of CDH with L-R shunt.     

Value of combined assessment of global and segmental ventricular contraction with right anterior oblique ECG-gated first-pass and left anterior oblique equilibrium radionuclide ventriculography

A semi-automated, variable-region-of-interest method of analysis was used to measure both global and segmental left ventricular (LV) and global right ventricular (RV) contraction with ECG-gated first-pass and equilibrium radionuclide ventriculography. Normal values were defined in 20 healthy volunteers, and in 24 symptomatic patients, the results were compared with right anterior oblique (RAO) contrast left ventriculography. The global LV ejection fraction (LVEF) obtained by equilibrium imaging in the left anterior oblique (LAO) projection correlated closely with the results obtained by the gated first-pass method in the RAO projection (r = 0.95) and those obtained with contrast left ventriculography (r = 0.94); furthermore, the interobserver variability was small (r = 0.985). The normal values for LVEF obtained using radionuclide techniques and contrast ventriculography did not differ, but with the equilibrium radionuclide method, the RV ejection fraction (RVEF) values were underestimated in comparison to those obtained by the RAO gated first-pass technique. In five patients with localised inferior segmental akinesis at contrast angiography, the RAO first-pass cine display demonstrated a corresponding wall-motion abnormality in all cases, but LAO equilibrium cine displays did so in only one out of five patients. For segmental quantitation of LV contraction, a computer programme defined the ventricular edge, divided the RAO LV images into five segments and determined both the segmental area contraction (SAC) and the counts-based segmental ejection fraction (SEF). Radionuclide SAC measurements correlated very strongly with SEF measurements (r = 0.94-0.99). Both radionuclide SAC and radionuclide SEF correlated well with contrast angiographic SAC, except in the inferobasal segment.(ABSTRACT TRUNCATED AT 250 WORDS)     

A study of ventricular contraction sequence in complete right bundle branch block by phase analysis

Twenty-four patients with complete right bundle branch block (CRBBB) combined with and without left axis deviation (LAD) on ECG, were compared with 17 normal subjects to evaluate the right ventricular contraction sequence and pattern in detail. Blood pool scintigrams were obtained in the left anterior oblique projection, and these images were analyzed by first component Fourier harmonics. In the normal subjects, the phase value distribution representing the pattern of ventricular contraction was almost homogeneous in both the right and left ventricles (RV & LV). In the CRBBB patients without LAD, the phase images showed apparent phase delay in the right ventricle. In the CRBBB patients with LAD, the phase images showed many different contraction patterns varying from normal to RV phase delay, owing to the effects of the hemi-block. Quantitative analysis of the absolute values, showed that the mean (RV-LV) value was 6.6 +/- 8.4 msec in the normal subjects. In the CRBBB patients without LAD, the duration of the QRS complex correlated with the mean (RV-LV) value, whereas no difference was observed between the duration of the QRS complex and the standard deviation of the right ventricle. Using phase analysis the degree of the RBBB can be determined from the phase images, and can be quantitatively analyzed as in electrical studies.     

Value of combined assessment of global and segmental ventricular contraction with right anterior oblique ECG-gated first-pass and left anterior oblique equilibrium radionuclide ventriculography

A semi-automated, variable-region-of-interest method of analysis was used to measure both global and segmental left ventricular (LV) and global right ventricular (RV) contraction with ECG-gated first-pass and equilibrium radionuclide ventriculography. Normal values were defined in 20 healthy volunteers, and in 24 symptomatic patients, the results were compared with right anterior oblique (RAO) contrast left ventriculography. The global LV ejection fraction (LVEF) obtained by equilibrium imaging in the left anterior oblique (LAO) projection correlated closely with the results obtained by the gated first-pass method in the RAO projection (r=0.95) and those obtained with contrast left ventriculography (r=0.94); furthermore, the interobserver variability was small (r=0.985). The normal values for LVEF obtained using radionuclide techniques and contrast ventriculography did not differ, but with the equilibrium radionuclide method, the RV ejection fraction (RVEF) values were underestimated in comparison to those obtained by the RAO gated first-pass technique. In five patients with localised inferior segmental akinesis at contrast angiography, the RAO first-pass cine display demonstrated a corresponding wall-motion abnormality in all cases, but LAO equilibrium cine displays did so in only one out of five patients. For segmental quantitation of LV contraction, a computer programme defined the ventricular edge, divided the RAO LV images into five segments and determined both the segmental area contraction (SAC) and the counts-based segmental ejection fraction (SEF). Radionuclide SAC measurements correlated very strongly with SEF measurements (r=0.94–0.99). Both radionuclide SAC and radionuclide SEF correlated well with contrast angiographic SAC, except in the inferobasal segment. Mean radionuclide SAC (29%) for the five segments did not differ from mean contrast SAC (29%). This combined protocol enables rapid and accurate biventricular assessment of global and segmental contraction. Significant diagnostic value exists in combining these two acquisition protocols in specific clinical situations.     

Scintigraphic quantitation of gastrointestinal motor activity and transport: oesophagus and stomach.

For the recognition and characterisation of oesophageal motor disorders, manometry represents the most reliable tool but yields no information on bolus transport. The transport can be quantitated by radionuclide techniques. The patient is positioned supine beneath a gamma-camera and instructed to swallow a radiolabelled bolus in a single gulp. Using a marker over the cricoid and the activity in the stomach as landmarks, regions of interest are drawn representing the upper, middle and lower third of the oesophagus and the gastric fundus. Activity-time curves enable one to recognise the clearance patterns in these regions. In combination, manometric and radionuclide transit studies recognise a higher number of motor disorders than either procedure alone. Radionuclide methods also are the most reliable and sensitive to quantitate gastric emptying. Procedure, meal size and composition as well as patient position must be standardised and correction techniques applied. The emptying of solid and liquid meal constituents can be evaluated concomitantly. Solids start to empty only after a lag phase of varying extent. With semi-solid meals, which are emptied at the same rate as solid meals of identical composition in the postlag phase, the recording time can be considerably shorter. Besides gastric emptying, the amplitude, frequency and propagation velocity of antral contractions can be recorded using serial images of short frame time and specially devised analytic techniques.     

Fourier phase parameters with possible diagnostic importance as obtained from the radionuclide ventriculograms of normal baboons with and without cardiac catheterization and under prolonged anaesthesia

The possible diagnostic importance of parameters defined from radionuclide ventriculograms and Fourier phase analysis was investigated for data from normal baboons (Papio ursinus) under prolonged anaesthesia (7 hours). Of the 14 animals, 7 were studied using indwelling cardiac catheters. Phase angle differences between the electromechanical activation of the septum and left lateral wall (LLW), and again between the activation of the septum and the apex indicated no significant differences (p greater than 0.05) for the consecutive hourly values for both catheterized and non-catheterized baboons. Consequently, average values and their ranges (mean +/- 1 S.D.) were obtained for these parameters in each group, and they did not differ significantly between the two groups. As could be expected, the activation delays between the septum and LLW, and the septum and apex differed with the latter being significantly longer. The phase angle histogram parameters of atrial peak width, left ventricular plus right ventricular peak width, (LV + RV), LV-to-RV peak separation and LV-to-atrial peak separation were similarly analysed and found not to change significantly between hourly measurements or because of catheterization. Therefore mean normal values and ranges were also obtained for these parameters, possibly to serve as baselines in the diagnosis of subtle conduction pathology.     

Fourier phase analysis of SPECT equilibrium radionuclide angiography in symptomatic patients with mitral valve prolapse without significant mitral regurgitation: Assessment of biventricular functional abnormalities suggesting a cardiomyopathy

BACKGROUND: Ventricular premature beats are common in patients with mitral valve prolapse (MVP). The purpose of this study was to determine whether symptomatic patients with MVP had certain functional characteristics and if ventricular arrhythmia (VA) could be explained by functional extravalvular abnormalities. Single photon emission computed tomography equilibrium radionuclide angiography with Fourier phase analysis was preferred to the planar radionuclide method. Only patients without significant mitral regurgitation were studied. METHODS AND RESULTS: A total of 23 symptomatic patients with MVP (13 men, 10 women, mean age, 47+/-14 years) without mitral regurgitation underwent single photon emission computed tomography equilibrium radionuclide angiography. Symptoms were present in 20 patients, and VA was present in 14 patients. Ejection fraction, regional wall motion, and Fourier phase analysis were examined in both ventricles and compared with results for normal subjects. Ventricular abnormalities were observed in 20 (87%) patients: decreased left ventricular and right ventricular ejection fractions, increased standard deviations of the mean phase and focal wall motion, and/or delayed phase abnormalities. Abnormalities were less frequent but more marked in the right ventricular free wall, the infundibulum, or the septum compared with left ventricular delayed abnormalities, which were more frequent but limited. In 12 of 14 patients with VA, phase-delayed areas were observed in the ventricle where the origin of ventricular premature beats was suspected on the basis of their electrocardiographic morphologic features. A relation was found between late potentials and delayed-phase areas (right ventricle or septum) and left bundle branch block morphologic features of VA. CONCLUSIONS: Symptomatic patients with MVP frequently have ventricular dysfunction in 1 or both ventricles, sometimes limited but more marked in the presence of severe VA even without significant mitral regurgitation, suggesting structural modification. The use of a sensitive, accurate, and 3-dimensional method such as single photon emission computed tomography equilibrium radionuclide angiography may be of interest for a noninvasive investigation, especially in young symptomatic patients with MVP and VA.     

Scintigraphic quantitation of gastrointestinal motor activity and transport: oesophagus and stomach

For the recognition and characterisation of oesophageal motor disorders, manometry represents the most reliable tool but yields no information on bolus transport. The transport can be quantitated by radionuclide techniques. The patient is positioned supine beneath a gamma-camera and instructed to swallow a radiolabelled bolus in a single gulp. Using a marker over the cricoid and the activity in the stomach as landmarks, regions of interest are drawn representing the upper, middle and lower third of the oesophagus and the gastric fundus. Activity-time curves enable one to recognise the clearance patterns in these regions. In combination, manometric and radionuclide transit studies recognise a higher number of motor disorders than either procedure alone. Radionuclide methods also are the most reliable and sensitive to quantitate gastric emptying. Procedure, meal size and composition as well as patient position must be standardised and correction techniques applied. The emptying of solid and liquid meal constituents can be evaluated concomitantly. Solids start to empty only after a lag phase of varying extent. With semi-solid meals, which are emptied at the same rate as solid meals of identical composition in the postlag phase, the recording time can be considerably shorter. Besides gastric emptying, the amplitude, frequency and propagation velocity of antral contractions can be recorded using serial images of short frame time and specially devised analytic techniques. Offprint requests to: G. Stacher     

Diagnosis of exercise-induced left bundle branch block at rest by scintigraphic phase analysis

Accurate diagnosis of diseases of the ventricular conducting system is essential for their appropriate therapy. Some conduction abnormalities, such as exercise-induced left bundle branch block (EX-LBBB), are not apparent on resting electrocardiograms. Phase analysis of rest and exercise radionuclide ventriculograms (RVG's) was used to compare four EX-LBBB patients with six normal controls. All patients had normal resting electrocardiograms, ejection fractions, and visually normal wall motion. First harmonic phase images were generated reflecting the timing of ventricular contraction. Dynamic phase displays were reviewed and graded in a blinded fashion by three independent experienced observers. Phase angle histograms of the right and left ventricle were determined for both resting and exercise images. The mean phase angle and standard deviation were also calculated for each ventricle. Visual grading of the resting phase images failed to show a significant difference between normal patients and patients with EX-LBBB. Quantitative analysis, however, revealed a significant difference in mean phase angle differences (LV-RV) in resting studies: 0.8 degrees (+/- 1.9 degrees SEM) in normals versus 9.3 degrees (+/- 2.3 degrees SEM) in EX-LBBB patients (P less than 0.03). Exercise accentuated the phase angle differences: 1.8 degrees in normals vs. 31.2 degrees in EX-LBBB patients (P less than 0.001). Quantitative phase analysis of resting RVG's permits the diagnosis of cardiac conduction disease that is not apparent on the resting EKG and may result in better monitoring and treatment.     

Radionuclide angiography of the heart in coronary heart disease: Where do we stand?

Regional systolic left ventricular performance after myocardial infarction was assessed from 216 radionuclide angiograms performed in 170 patients. Recording of first transit of an intravenously injected bolus of technetium-99m pertechnetate was made by a multicrystal scintillation camera at a framing rate of 20 per second. The RAO view was used and a simultaneous ECG was employed. Statistics adequate for resolving regional events were obtained by a compact bolus input and phasic summation into one representative cycle of data obtained during left ventricular passage. Emphasis was given to imaging of regional systolic left ventricular function: perimeter images of end-systole and end-diastole, regional stroke volume images and ejection fraction images were processed. New trend images are presented that reflect total systolic contraction and improve image quality: regional rate of decrease and increase images, wall motion trend images and regional mean transit time images. In 96% of the cases, correspondence was found between the electrocardiographic location of the infarct and the region of major wall motion and ejection disorder. Akinesia and/or dyskinesia were seen in 77% of the cases; a ventricular aneurysm was found in 11%. Additional areas of wall motion anomalies were shown by 70%. Image analysis, nuclear image signs and their diagnostic meaning, as well as the indications for this nontraumatic examination in coronary heart disease are discussed. Relevant information for medical or surgical therapy can be obtained from early and follow-up studies in patients with unstable, progressive angina, ischemic electrocardiographic signs and those who have had myocardial infarctions.     

A unique method by which to quantitate synchrony with equilibrium radionuclide angiography

Background

Cardiac resynchronization therapy (CRT) improves symptoms and the survival rate in patients with advanced heart failure by improving synchrony. However, CRT is not always successful, is costly, and is applied without individualization. There is no specific measure of synchrony. The goal of this study was to analyze new quantitative parameters of synchrony and compare them with established measures.

Methods and Results

Equilibrium radionuclide angiography, phase angle (Ø), and amplitude quantitate regional contraction timing and magnitude and are the basis for new synchrony (S) and entropy (E) parameters. S is the vector sum of all amplitudes based on the angular distribution of Ø divided by the scalar sum of the length of all vectors. Complete S equals 1, and its absence equals 0. E measures the disorder in the region of interest, is 1 with random contraction and 0 with full synchrony, and differentiates among differing contraction patterns. Left ventricular S and E were measured in 22 normal equilibrium radionuclide angiography studies, where regions of interest were drawn from the left ventricle, left atrium, and background to analyze model ventricles with normal wall motion (N), ventricles with aneurysm (An), ventricles with severe diffuse dysfunction (Diff), and ventricles with severe regional dysfunction (Reg). The new S and E parameters were highly reproducible and well differentiated among N, An, Diff, and Reg, which were not separated by SD Ø (SD of ventricular phase), which has gained popularity as a measure of synchrony.

Conclusion

Unique scintigraphic parameters for the evaluation of ventricular synchrony were derived, and their added value was determine compared with established measures.Indications for pacemaker therapy now include the treatment of severe congestive heart failure (CHF). Atrial triggered biventricular pacemakers reduce CHF symptoms¹ and prolong life² in patients with cardiomyopathy, severe CHF, left ventricular (LV) ejection fraction (EF) lower than 35%, and QRS greater than 120 milliseconds. Such pacing, or cardiac resynchronization therapy (CRT), seeks to reduce the heterogeneity and increase the synchrony of ventricular activation, conduction, and contraction. CRT has improved hemodynamics, increased exercise tolerance, reduced symptoms and the need for hospitalization,^1,32 reversed ventricular remodeling, and^4,5 reduced the all-cause mortality rate² in CHF. However, CRT is costly, fails to improve symptoms or activity level in more than 30% of patients,^2,3,6 and is applied blindly without individualization or consideration of lead placement sight.⁷A variety of echocardiographic methods have sought to measure synchrony and its serial changes with CRT.^4,8-16 A recent study presented evidence of the poor reproducibility of several widely applied echocardiographic measurements by which to determine ventricular synchrony.¹⁷ Magnetic resonance imaging has excellent resolution of regional wall motion and has been applied to assess ventricular synchrony and its response to pacing therapy.¹⁸ However, these methods are complex and are not well established or widely available, and magnetic resonance imaging has not been widely applied after pacing. An accurate and reproducible method is needed by which to objectively measure regional ventricular synchrony.¹⁹Phase image analysis, a functional method based on the first Fourier harmonic fit of the gated blood pool time versus radioactivity curve, generates the parameters of amplitude (A), which parallels the extent of regional ventricular contraction or stroke volume, and phase angle (Ø), which represents the timing of regional contraction. It was applied early with demonstrated reproducibility²⁰ to show the linkage between electrical and mechanical dyssynchrony21 and to characterize the contraction pattern in heart failure and its alteration with CRT.^22,23 The SD of ventricular Ø, applied as a marker of synchrony, has been shown to demonstrate the beneficial effects of biventricular pacing,²⁴ and its strong prognostic value has been shown in patients with congestive cardiomyopathy and CHF, superior to LVEF.²⁵ The SD Ø may not be optimal for synchrony evaluation.We sought improved, more sensitive parameters to better differentiate synchrony among the spectrum of possible patterns of dyssynergy. We derived, initially evaluated, and here present new synchrony (S) and entropy (E) parameters, based on the phase method, to quantitate regional and global ventricular synchrony and applied them in simulation and clinical protocols.

     

Gated first pass radionuclide ventriculography. Methods, validation, and applications

Electrocardiographic gating provides an alternative method of acquiring first pass radionuclide ventriculograms from both ventricles. This report details the methods of acquisition and analysis, provides validation and reproducibility data, and describes applications of gated first pass radionuclide ventriculography using a count-based method. Left ventricular ejection fractions measured by gated first pass were correlated quite closely with gated blood pool ventriculography (n = 43; r = 0.95) but less well with contrast angiography (n = 23; r = 0.72). The right ventricular ejection fractions measured by gated first pass compared favorably with gated blood pool ventriculography (n = 32; r = 0.93). When one observer processed the images two times, the reproducibilities of RVEF (n = 10; r = 0.99) and LVEF (n = 10; r = 0.88) were excellent. Similarly, when two observers processed the images independently, the reproducibilities of RVEF (n = 11; r = 0.99) and LVEF (n = 11; r = 0.98) were excellent. The first pass studies were obtained in a right anterior obliquity, which provided the best atrioventricular chamber separation and provided a different view of global ventricular function and segmental wall motion from that provided by the standard blood pool views.     

An evaluation of the diagnostic efficacy of phase analysis of data from radionuclide ventriculograms in patients with Wolff-Parkinson-White syndrome

It has been suggested that phase analysis of radionuclide ventriculograms may be of value for detecting and localising the abnormal sequence of ventricular contraction secondary to Wolff-Parkinson-White (WPW) syndrome. The present study was undertaken to test this hypothesis. The space-time sequences of right- and left-ventricular action obtained from radionuclide ventriculograms obtained during rest studies were evaluated in 8 patients with WPW syndrome (confirmed by 12-lead surface electrocardiography) and compared to those of 14 normal subjects. All of the latter showed a consistent ventricular activation pattern, i.e. the first site of ventricular activity in the upper septal region followed by a second site either at the base of the left ventricle or located apically. It was possible to diagnose 11 of the 14 normal subjects (specificity, 79%) and 7 of the 8 patients (sensitivity, 88%). The 4 patients who had been classified as having a left-sided accessory bundle by surface electrocardiography were likewise diagnosed by phase analysis, as were the 2 patients with a confirmed right-sided bypass tract. Two patients with septal posterior accessory pathways could not be identified by phase analysis. Furthermore, cases with an activation pattern which closely resembled that of the 2 patients with right-sided accessory bundles were found to be normal from their ECGs. It is now necessary to evaluate phase analysis against invasive electrophysiological methods in such patients.This work was made possible by an award by the Alexander von Humboldt Stiftung     

Scintigraphic assessment of atrial function in patients with longstanding hypertension

Right and left atrial function were assessed using Fourier analysis of gated radionuclide images in 14 normal subjects and 50 patients with long-standing essential hypertension. Slopes representing filling and early diastolic emptying were similar for both atria; however, early diastolic emptying of the left atrium was slowed markedly in the hypertensive group (42.6 +/- 18.6 counts/sec., vs. 79 +/- 16 in normal persons; p less than 0.001), implying a reduction in left ventricular compliance. The right ventricular ejection fraction was depressed in hypertensive patients compared with normal subjects (37.1 +/- 6% vs. 43.4 +/- 8.1%; p less than 0.01). These findings may be helpful in understanding the effect of hypertension on the left and right heart and could have prognostic and therapeutic implications as well.     

Scintigraphic phase analysis of left anterior hemiblock

Left anterior hemiblock (LAHB) is a relatively common disturbance of ventricular conduction which can be an indicator of early conduction system disease. In an effort to better understand this condition, phase analysis of resting radionuclide ventriculograms (RVG) was used to evaluate five patients with LAHB and six normal patients with particular reference to the phase angle difference between the septum and the postero-lateral wall. All patients had normal ejection fractions and visually normal wall motion on RVG. Visual analysis of phase images showed significant differences between the LAHB and normal patients' LV contraction synergy (p less than 0.03) with a delay in septal contraction versus the postero-lateral wall. Four of five patients with LAHB were outside 2 standard deviations of the normal range. Regional quantitative analysis of phase angle differences between posterolateral and septal walls tended to show this difference between normals and LAHB (p = 0.08) as well. Three of five patients with LAHB were outside 2 standard deviations from the normals' mean. There were no significant differences between the standard deviations, skewness, or kurtoses of phase angle histograms of LAHB versus normal patients. Phase analysis can identify some patients with LAHB by both visual and quantitative analysis. The ability to detect and possibly quantitate subtle conduction abnormalities such as LAHB may result in a better understanding of such conduction system diseases.     

Diagnosis of exercise-induced left bundle branch block at rest by scintigraphic phase analysis

Accurate diagnosis of diseases of the ventricular conducting system is essential for their appropriate therapy. some conduction abnormalities, such as exercise-induced left bundle branch block (EX-LBBB), are not apparent on resting electrocardiograms. Phase analysis of rest and exercise radionuclide ventriculograms (RVG's) was used to compare four EX-LBBB patients with six normal controls. All patients had normal resting electrocardiograms, ejection fractions, and visually normal wall motion. First harmonic phase images were generated reflecting the timing of ventricular contraction. Dynamic phase displays were reviewed and graded in a blinded fashion by three independent experienced observers. Phase angle histograms of the right and left ventricle were determined for both resting and exercise images. The mean phase angle and standard deviation were also calculated for each ventricle. Visual grading of the resting phase images failed to show a significant difference between normal patients and patients with EX-LBBB. Quantitative analysis, however, revealed a significant difference in mean phase angle differences (LV-RV) in resting studies: 0.8° (±1.9° SEM) in normals versus 9.3° (±2.3° SEM) in EX-LBBB patients (P<0.03). Exercise accentuated the phase angle differences: 1.8° in normals vs. 31.2° in EX-LBBB patients (P<0.001). Quantitative phase analysis of resting RVG's permits the diagnosis of cardiac conduction disease that is not apparent on the resting EKG and may result in better monitoring and treatment.     

Functional mapping of ventricular contraction and phase using single-photon emission computed tomography (SPECT)

A method for functional mapping of ventricular contraction and phase was developed using gated blood-pool SPECT. Parameters of contraction and phase were calculated using length-based and count-based Fourier analyses. In length-based Fourier analysis (LFA), percentage-shortening and length-based phase were calculated based on the changes of lengths from a ventricular centre to edges. In count-based Fourier analysis (CFA), phase and amplitude were also calculated using serial tomographic phase images. Two-dimensional polar display format was employed to summarize the SPECT data of whole cardiac surface. This program was applied to evaluate coronary artery disease and conduction anomalies. The polar functional map using gated blood-pool SPECT can be an effective method to integrate three-dimensional cardiac information in conjunction with myocardial SPECT studies.     

Fully automated data acquisition,processing, and display in equilibrium radioventriculography

A fully automated data acquisition, processing, and display procedure was developed for equilibrium radioventriculography. After a standardized acquisition, the study is automatically analzyed to yield both right and left ventricular time-activity curves. The program first creates a series of edge-enhanced images (difference between squared images and scaled original images). A marker point within each ventricle is then identified as that pixel with maximum counts to the patient's right and left of the count center of gravity of a stroke volume image. Regions of interest are selected on each frame as the first contour of local maxima of the two-dimensional second derivative (pseudo-Laplacian) which encloses the appropriate marker point, using a method developed by Goris. After shifting the left ventricular end-systolic region of interest four pixels to the patient's left, a background region of interest is generated as the crescent-shaped area of the shifted region of interest not intersected by the end systolic region. The average counts/pixel in this background region in the end systolic frame of the origina study are subtracted from each pixel in all frames of the gated study. Right and left ventricular time-activity curves are then obtained by applying each region of interest to its corresponding background-subtracted frame, and the ejection fraction, end diastolic, end systolic, and stroke counts determined for both ventricles. In fourteen consecutive patients, in addition to the automatic ejection fractions, manually drawn regions of interest were used to obtain ejection fractions for both ventricles. The manual regions of interest were drawn twice, and the average obtained. For the right ventricle, the correlation between auto and average manual ejection fraction was 0.52; the correlation between the two manual ejection fractions was 0.88. For the left ventricle, the correlation between auto and average manual ejection fraction was 0.96; the correlation between the two manual ejection fractions was 0.91. Automated processing is essential for the accurate and reproducible assessment of left ventricular ejection fraction.This work was supported in part by USPHS Grant Nos. HL 20674 and GM 10548     

Verification of Fourier phase and amplitude values from simulated heart motion using a hydrodynamic cardiac model

Using pusher-plate-type artificial hearts, changes in the degree of synchrony and stroke volume were compared to phase and amplitude calculations from the first Fourier component of individual-pixel time-activity curves generated from gated radionuclide images (RNA) of these hearts. In addition, the ability of Fourier analysis to quantify paradoxical volume shifts was tested using a ventricular aneurysm model by which the Fourier amplitude was correlated to known increments of paradoxical volume. Predetermined phase-angle differences (incremental increases in asynchrony) and the mean phase-angle difference calculated from RNAs showed an agreement of -7 degrees +/- 4.4 degrees (mean +/- SD). A strong correlation was noted between stroke volume and Fourier amplitude (r = 0.98; P less than 0.0001) as well as between the paradoxical volume accepted by the 'aneurysm' and the Fourier amplitude (r = 0.97; P less than 0.0001). The degree of asynchrony and changes in stroke volume were accurately reflected by the Fourier phase and amplitude values, respectively. In the specific case of ventricular aneurysms, the data demonstrate that using this method, the paradoxically moving areas may be localized, and the expansile volume within these regions can be quantified.