Upward creep of the heart in exercise thallium 201 single photon emission tomography: clinical relevance and a simple correction method.

The upward creep of the heart during myocardial single photon emission tomography (SPET) acquisition has been reported as a frequent source of false-positive results. The aim of this study was to simplify the detection and correction of this upward creep and to estimate its clinical relevance during routine patient care. To recognize the upward heart motion a straight line was fitted to the upper and lower border of consecutively displayed tomographic projection images. In this way, vertical translation of at least 1 pixel in size could be detected easily. On the assumption of a slow but continuous upward motion a fast interpolation correction method was developed. From 100 consecutive, supine, ergometric exercise studies, 1, 2 or 3 pixels of upward creep were found in 16, 4 or 3 patients, respectively. It was found that an upward creep of at least 2 pixels (7/100 cases) led to evident, mostly antero-septal defects on quantitative bull's-eyes, whereas only upward creeps of 3 pixels or more (3/100 cases) produced false-positive diagnostic results. The simple correction method offered a sufficient compensation of image and/or bull's-eye artefacts. These clinical findings could be reproduced in a computer model. Thus, it can be stated that clinically significant upward creep of the heart during stress SPET acquisition is relatively rare; it may have been overestimated in the past, and its artificial effects can be corrected by a quick and simple algorithm.

Reconstruction of Fourier coefficients: a fast method to get polar amplitude and phase images of gated SPECT.

Gated SPECT (GASPECT) during radionuclide ventriculography (RNV) is a time-consuming procedure requiring extended hard- and software. Furthermore, the procedure suffers from poor count statistics. Our method tries to overcome these difficulties by exploiting the count summation effect of Fourier analysis. The sine and cosine coefficients of the first harmonic are extracted from the gated views and reconstructed. This, in fact, results in an improvement of the count statistics by a factor of four combined with a tremendous reduction of disc space requirements. Using short-axis slices, bull's-eye plots of the amplitude and phase of the left ventricle are calculated. Cardiac functions and localization and extent of any malfunction are documented three-dimensionally without superposition.

[The role of radionuclide ventriculograms in determining the indications for valve replacement in chronic aortic valve insufficiency]. / Die Rolle des Radionuklid-ventrikulogramms für die Indikationsstellung zum Klappenersatz bei der chronischen Aortenklappeninsuffizienz.

Timing of aortic valve replacement (AVR) in chronic aortic regurgitation (AR) remains a difficult problem in clinical practice. Radionuclide ventriculography (RNV) yields information on the extent of valvular regurgitation, the enlargement and the systolic function of the left ventricle. A "well-timed" AVR is defined by 1) postoperative improvement of clinical symptoms, decrease in left ventricular end-diastolic volume (EDV) and normalization of ejection fraction (EF) as well as by 2) greater improvement under surgical therapy as compared to conservative management. In "too early" AVR the latter condition is not fulfilled, while in "too late" AVR the first condition is not accomplished. In this study 54 patients with chronic aortic incompetence were evaluated by RNV to see whether these three groups ("too early", "well timed", "too late" AVR, resp.) can be separated by the relation between EDV and regurgitant volume (RV), the level of the EDV and the clinical status. The examination was based on pre- and postoperative RNV studies as well as on follow-up studies. A good postoperative result can be expected in cases with a preoperative EDV/RV-ratio similar to that observed in 30 patients with AR in whom AVR was not indicated. In contrast, in the majority of those cases with an EDV/RV-ratio exceeding this normal range the postoperative outcome will be unsatisfactory. If the EDV/RV-ratio is normal, AVR should be performed in cases with an EDV exceeding 400 ml, while in cases with an EDV between 300-400 ml AVR is only indicated in the presence of additional symptoms (NYHA greater than or equal to II).(ABSTRACT TRUNCATED AT 250 WORDS)

[Radionuclide ventriculography. The significance of global and regional ejection fractions and Fourier amplitude and phase in the diagnosis of exertion-dependent ischemia]. / Radionuklidventrikulographie. Bedeutung der globalen und regionalen Auswurffraktion, Fourier-Amplitude und Phase bei der Diagnostik einer belastungsabhängigen Ischämie.

Electrocardiograms and radionuclide ventriculograms were obtained at rest and on exercise in 23 patients (20 men and 3 women, mean age 53.4 years) with exercise-dependent myocardial ischaemia after infarction, as well as in 22 persons (17 men and 5 women, mean age 43 years) without clinical, electrocardiographic and biochemical evidence of coronary heart disease. Among the ischaemia patients exercise-dependent loss of motility, as measured by regional ejection fraction and Fourier amplitude, occurred in 95% (50% of controls) in one sector, in 78% (4.5% of controls) in the two sectors with the highest contractility at rest, and in 74% (0% of controls) in three sectors. On exercise, phase shifts occurred in 87% (27% of controls). When combining the exercise-ECG, global ejection fraction as well as regional motility loss in one sector, in the two sectors with the highest contractility at rest and in three sectors, at least two of the five criteria of abnormality were present in 91.3% of the ischaemia patients, compared with at most one criterion in 90.9% of controls. The results indicate the greater diagnostic value of regional than global measures of ventricular function and emphasize the importance of radionuclide ventriculography as an addition to exercise electrocardiography in the pre-invasive diagnosis of coronary heart disease.

The contraction fraction (CF) in myocardial studies with technetium-99m-isonitrile (MIBI)--correlations with radionuclide ventriculography and infarct size measured by SPECT.

Criteria for the detection of coronary artery disease in nuclear cardiology include visualization of perfusion defects and functional impairment of contraction. The purpose of this study is to combine both methods in one procedure with the new myocardial perfusion tracer, 99mTc-methoxy-isobutyl-isonitril (MIBI), reducing time and radiation burden to the patient. Following an uncomplicated recovery, ten patients with first myocardial infarction participated in this study. Radionuclide ventriculography (RNV) was performed at rest and during exercise. Within 2-3 days, 370 MBq 99mTc-MIBI were injected and SPECT acquisition commenced 1 h later. Data processing included a scar image in polar coordinates. Areas of significantly reduced tracer uptake were expressed as a percentage of the total myocardial area. Directly following SPECT, resting and maximum exercise gated planar LAO images were recorded and the contraction was quantified. The concept of the contraction fraction (CF) rested on the end systolic change in count distribution: their increase in density and their centripetal concentration. For comparison, geometrical inner edge detection techniques were also applied. All algorithms for describing an EF equivalent were verified by computer simulations, showing a perfect correlation over a wide range of preset EFs. When applied to the patient studies only the non geometric methods revealed a good correlation with the ejection fraction (EF) obtained by RNV, and with the infarct size measured by SPECT.(ABSTRACT TRUNCATED AT 250 WORDS)

Radionuclide ventriculography (equilibrium gated blood pool scanning)--its present clinical position and recent developments.

Myocardial scanning (MS) and radionuclide ventriculography (RNV) are the foundation of nuclear cardiology. These procedures aim in two completely different directions: RNV tries to image heart motion, that is, mechanical (pump) function, and therefore belongs to the group of first-order functional imaging (FI, imaging mechanical function), whereas MS is based on myocardial metabolism, and therefore can be attributed to third-order functional imaging (metabolism). This statement is relevant for the assessment of the clinical position of RNV: Third-order (metabolism) functional imaging is the domain of nuclear medicine (NM), whereas first-order FI has to face the competition of alternative noninvasive procedures such as ultrasound (US), digital subtraction angiography (DSA), computer tomography (CT), and nuclear magnetic resonance (NMR). The domain of RNV includes stages two (acute infarction) and three (postinfarction period) of coronary arterial disease (CAD). The advantageous combination of quantitative data on global, left ventricular (LV) function and imaging of regional motion ensures the superiority of RNV over US. However, RNV is inferior to MS in physical examinations in the preinfarction stage of CAD, whereas US is clearly inferior to both NM procedures. Recent progress could be attained by gated SPECT (GASPECT). A proposal is presented for simplification of this time-consuming procedure. Technetium-labeled isonitriles offer the chance for the combination of "perfusion-motion" imaging of the myocardium. However, even standard RNV offers new possibilities. The multitude of parameters produced by quantitation has not yet been exploited completely. This can be done by discriminant analysis. The computer finds out an optimal subset from the whole set of parameters for the solution of a significant clinical problem. The software "learns" to find the "label" of a special pathognomonic entity. This computer work is supported by a relational data bank (Oracle) and an optical disk. Two examples for the effectiveness of the computer in problem solving are presented. It is concluded that RNV, even in the very competitive class of first-order functional imaging, enjoys a preferred position. The future indeed seems brighter because labeled isonitriles offer the chance for the combination of perfusion-motion imaging of the myocardium.

Differentiation between infarction and cardiomyopathy in left bundle branch block by parametric radionuclide imaging.

In LBBB the diagnosis of the underlying disease, i.e. infarction (MI) or cardiomyopathy (CMP), is still a challenge. In this study, the usefulness of radionuclide ventriculography (RNV) for solving this problem noninvasively was tested. The hypothesis was that quantitation of the space-time sequence of left ventricular (LV) contraction by Fourier analysis may differentiate among MI, CMP, and LBBB-specific wall motion abnormalities (WMA). Forty-seven patients (pts) with LBBB were divided into 3 groups: 1) 20 pts with MI, 2) 7 pts with CMP, 3) 20 pts without MI or CMP. Regional parametric amplitude and phase data of eight LV sectors were calculated and expressed in standard deviation units (SDU) of normal. Out of the many regional data only the values of the mean amplitude and the standard deviation of the mean phase shift showed high discriminative power for separating the three groups, with an average squared canonic correlation of 0.5 and a Wilks lambda of 0.22, respectively. In other words, 17 of 20 pts in group 1, 6 of 7 pts in group 2, and 19 of 20 pts in group 3 were truly diagnosed by RNV alone. Such a separation also seems reasonable physiologically, since the mean amplitude reflects global left ventricular function and standard deviation of phase is a measure of time homogeneity of contraction. Furthermore, there was a significant septal phase delay of -4.92 +/- 5.3 SDU in 15 pts with septal MI compared to group 3 pts, who had a subtle premature septal motion of +0.75 +/- 2.64 SDU, whereas the septal amplitude was not different and slightly decreased in both.(ABSTRACT TRUNCATED AT 250 WORDS)

[Radionuclide ventriculography--a noninvasive method of diagnosis and quantification of tricuspid valve insufficiency]. / Die Radionuklidventrikulographie--eine nichtinvasive Methode zur Diagnose und Quantifizierung der Trikuspidalklappeninsuffizienz.

The diagnosis of tricuspid regurgitation (TR) is difficult to make by simple clinical methods or by invasive techniques. Contrast echocardiography and Doppler echocardiography have improved diagnostic results, but a golden standard is still not available. Radionuclide ventriculography (RNV) is a well-established method for the detection and quantification of a volume load on the left ventricle: the regurgitation fraction can simply be derived from the regurgitant index as the ratio of enddiastolic-endsystolic count-rate differences between the left and right ventricle. In left heart valvular regurgitation a regurgitant index exceeding the upper normal limit can be expected. This study was performed to evaluate the diagnostic accuracy of an abnormally low regurgitant index in detecting TR, which is accompanied by an isolated volume load on the right ventricle. A series of 33 patients with TR on physical examination and cardiac catheterization underwent RNV and was compared with 48 patients with right ventricular enlargement or pressure load on the right ventricle. In addition, the specificity of the method was evaluated in 470 consecutive patients with various forms of heart disease. In 18 out of 20 subjects with isolated TR a regurgitant index below the lower normal limit was found. The remaining 2 cases with minor TR had a regurgitant index within the normal range, which is 0.89 to 1.97 in this laboratory. In patients with additional volume load on the left ventricle, the sensitivity of the method was found to be low, as could be expected from the principle of the method. The time-activity curve over the liver was usually in phase with that recorded over the atria in subjects with TR. Therefore, the additional examination of a region of interest over the liver was particularly useful in these patients with concomitant aortic or mitral valve regurgitation. None of the 48 patients with right ventricular enlargement or pressure load on the right ventricle had a falsely positive result. A total of 17 out of 470 consecutive patients had a regurgitant index below the normal range; left ventricular function was severely impaired in 9 of these patients. The remaining subjects had a regurgitant index slightly below the lower normal limit. In conclusion, RNV has a high sensitivity in the diagnosis of TR in patients without left heart valvular regurgitation and a high specificity in patients without severely impaired left ventricular function and without left-to-right shunt through an atrial septal defect.(ABSTRACT TRUNCATED AT 400 WORDS)

Haemodynamic response to exercise in patients with chest pain and normal coronary angiograms.

A series of 42 patients with chest pain but normal coronary angiograms and normal haemodynamics at rest were prospectively classified as typical angina (group 1, N = 9) or atypical angina (group 2, N = 16) or non-anginal chest pain (group 3, N = 17). All patients underwent radionuclide ventriculography and measurement of pulmonary artery pressure at rest and during maximum exercise. Comparison of data during exercise revealed significantly higher (P less than 0.025) left ventricular filing pressures as reflected by the diastolic pulmonary artery pressure in group 1 (29 +/- 5 mmHg) than in both group 2 (22 +/- 6 mmHg) and group 3 (22 +/- 5 mmHg). The rest-to-exercise change in left ventricular ejection fraction was variable and not significant in group 1 (62 +/- 6% vs 63 +/- 14%). By contrast, both group 2 and group 3 had significant increases (63 +/- 6% vs 69 +/- 10%, P less than 0.02 and 63 +/- 5% vs 68 +/- 5%, P less than 0.01). The classification as 'typical angina' was predictive of an abnormal (greater than 25 mmHg) filling-pressure response to stress. The positive and negative predictive values were 78% and 70%, respectively. The clinical classification was not a predictor of an abnormal (delta less than 5%) ejection-fraction response. No correlation between radionuclide and filling-pressure data could be established. The data suggest that the majority of patients assigned to group 1 manifested an impaired left ventricular function with exercise. This was primarily related to abnormalities in diastolic filling while the systolic performance was not consistently depressed.

Specification of regional wall motion abnormalities by phase analysis of radionuclide angiograms in coronary artery disease and non-coronary artery disease patients.

Fourier transform of gated radionuclide ventriculograms (RNV) permits the quantitative evaluation of regional wall motion abnormalities (RWMA) regarding both regional magnitude (amplitude display) and regional time sequence of contraction (phase display). In this study, an attempt was made to further specify coronary artery disease (CAD) and non-CAD RWMA detected on consecutive exercise RNV in 17 patients (pts) with proven severe CAD; or on resting RNV in 24 pts with transmural myocardial infarction (MI) compared with 27 pts after treatment with daunorubicin (DAU). RWMA were defined objectively from parametric images by a decrease of the sectorial amplitude by more than 2 s.d.s of normal as determined by quantification of RNV studies of 20 normal individuals. In 15 out of 17 CAD pts (88%) and in 19 out of 24 MI pts (79%), a significantly decreased regional amplitude was found. Importantly, in all abnormal CAD and MI amplitude scans (100%), a significantly abnormal phase delay in the same region could be noted. In five out of 27 pts on DAU (18%) an apical hypokinesis could be verified. In comparison with CAD pts, however, the phase distribution was normal in all these DAU pts. Thus, standardized phase analysis of RNV data provides a powerful tool for specifying RWMA. It allows a highly specific separation of RWMA caused by exercise-induced ischemia, MI, or DAU.

Parametric imaging of experimentally simulated Wolff-Parkinson-White syndrome conduction abnormalities in dogs: a concise communication.

In order to test the diagnostic potential of phase analysis of radionuclide ventriculography (RNV) for localizing accessory bundles in Wolff-Parkinson-White (WPW) syndrome, 24 experimental runs were performed in three open chest instrumented dogs. After a baseline study, WPW syndrome was simulated by stimulation at seven different sites around the base of the ventricles, and RNV's were obtained. Subsequent data processing including Fourier transformation allowed the localization of the site of the first inward motion of the ventricles by an isophasic wave display. In sinus rhythm, the septum contracted first. During ectopic premature ventricular stimulation by triggering the atrial signal, the phase scan was altered only when the stimulus was applied earlier than 20 ms before the expected QRS complex during sinus rhythm. During stimulation with fixed frequency, only the left lateral positions of the premature stimulation were detected by phase analysis with a sensitivity of 86%. Neither the antero- or posteroseptal nor the right ventricular premature contraction pattern could be exactly localized.

Limitations of radionuclide ventriculography in the non-invasive diagnosis of coronary artery disease. A correlation with right heart haemodynamic values during exercise.

A consecutive series of 56 patients with chest pain but no evidence of previous myocardial infarction was prospectively studied by radionuclide ventriculography to determine the value of global and regional radionuclide indices in detecting coronary artery disease. The results were correlated with the clinical judgment of chest pain, the results of the exercise electrocardiogram, and the right heart haemodynamic measurements during exercise. As a result of the criteria for entry, the study group was representative of the population seen in such a clinical setting. Only 25% of patients had coronary artery disease. The predictive power of radionuclide ventriculography was limited. The conventionally used criterion that normal subjects have an increase in left ventricular ejection fraction of at least 5% with exercise provided only 78% sensitivity and 57% specificity. Fourier analysis and visual interpretation of radionuclide studies wrongly diagnosed three out of 10 patients with extensive disease requiring surgery. These results suggest that radionuclide ventriculography is of limited value in the non-invasive diagnosis of coronary artery disease.

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.

Investigation of intrapartum clearance of the upper airway in the presence of meconium contaminated amniotic fluid using an animal model.

In order to define as effective a procedure as possible for the intra- and post-partum clearance of the upper airways of meconium contaminated infants, three methods of suction clearance, nasal, oral and combined nasal and oral, were carried out on each of five kittens aged between 17 to 19 weeks. There was an interval of at least one week between each investigation. The animals were anaesthetized with ketamine intramuscularly. The pressure changes during delivery were simulated using a compressed blood pressure cuff around the kittens thorax. During the first minute of thoracic compression Tc 99 labeled synthetic sputum was introduced into both the oro- and nasopharynx, then during the 2nd minute the instilled fluid was removed using a conventional extractor with mucus trap. Solely oral or solely nasal routes were used, suction was carried out for 60 secs, whereas when the combined technique was applied the oral and nasal cavities were cleared for only 30 secs each. At the end at the 2nd minute thoracic compression was released and a deep inspiration occurred. After five minutes the radioactivity remaining after suction was documented using a gamma-camera. We attempted to answer the following questions: How much mucus could be extracted with each different method, and where the remaining amount was later distributed? Nasal suction alone was found to be inefficient; using this route an average of 13% (only an eight of the amount instilled) could be removed. Oral suction led to the recovery of an average of 52% of the material instilled, the combined technique much as 56%. After re-establishment of spontaneous respiration, it could be clearly seen that, independent of the efficacy of the technique used, the majority of the remaining radioactivity (55 relative percent) is localized in the head and neck area. Absolute values are 45% for nasal suction, 26% for oral, and 24% for the combined oro-nasal route. The other part of the remaining radioactivity was found in the lung or in the stomach. It must be pointed out that the aspirate need not be disturbed in both of the parts, both the stomach and the lungs can be solely involved. Five minutes after spontaneous respiration had been resumed the lungs revealed only a centrally distributed radioactivity. This corresponds anatomically to the trachea and major bronchi. The peripheral area of the lungs was free of aspirate at this point in time.(ABSTRACT TRUNCATED AT 400 WORDS)

Radionuclide ventriculography: a noninvasive method for the detection and quantification of left-to-right shunts in atrial septal defect.

The present investigation was undertaken to assess a new scintigraphic method for the diagnosis of left-to-right shunts due to atrial septal defect based on the differing stroke volumes of left and right ventricles and to compare it with oxymetric data. Radionuclide ventriculography was carried out after injection of 20 mCi 99mtechnetium-labeled red blood cells. Time-activity curves were obtained from the left and right ventricular regions, and the ratio (A) of end-diastolic-end-systolic count rate differences for the left and right ventricles was calculated. The left-to-right shunt (in percent of the pulmonary flow rate) is then given as 100 X (1 - A/1.43; 1.43 being the previously determined mean value of A in 66 normal patients. In 16 patients with an atrial septal defect and/or partial anomalous pulmonary venous connection a correlation of r = 0.81 was found between those shunts determined by the scintigraphic method and those calculated by oxymetric data. The specificity of the method and the sensitivity in detecting left-to-right shunts exceeding 30% are high. The method is practical and already widely used for determination of ejection fraction end-diastolic volume and other factors. The combination of this technique with other methods for shunt diagnosis such as gamma-fit analysis may prove of special value.

Regional evaluation of the left ventricular wall motion by radionuclide ventriculography.

ECG gated radionuclide ventriculography was performed in 85 patients with heart disease. From the analysis of time activity curves of each pixel, sets of parametric scans were displayed. Of 496 parametric scans, 192 were normal and 304 showed wall motion abnormalities. There was good correlation between the individual parametric scans (r greater than or equal to 0.815) and between parametric scans and contrast ventriculograms (r greater than or equal to 0.631) in the occurrence and extent of regional wall motion abnormalities. The highest sensitivity was revealed by the peak filling rate (relaxation velocity) scan. The best specificity was shown by scans using the amplitude and phase of the first Fourier element. Good results were obtained by a combination of four parametric images. The ability of the phase scan to detect local dyskinesis may be better than that of the contrast ventriculogram. Changes in parametric scans were related to, but preceded, impairment of left ventricular function (r greater than or equal to 0.513), It is concluded that parametric scans provide a reliable, objective and non-invasive method for regional evaluation of left ventricular function, of great use in the diagnosis of local wall motion abnormalities and their effect on the heart performance.