Effects of intravenous verapamil on the haemodynamic response to exercise in patients with angina pectoris

The effects of intravenous Verapamil (V) on exercise haemodynamics and ventricular function were compared in 13 patients with stable effort angina. Intravascular pressures, thermodilution cardiac output and radionuclide ejection fraction were measured simultaneously at rest and during exercise. At rest Verapamil produced systemic vasodilation. During exercise at identical workloads compared to control, Verapamil increased cardiac index (CI) and decreased AVO2 difference. Pulmonary artery wedge pressure was lower. Ejection fraction was higher (control-55 +/- 11% vs V-64 +/- 11%) as the disproportionate increase in end systolic volume relative to the end diastolic volume was prevented. Verapamil is effective in exercise induced angina and alters haemodynamics primarily through its vasodilating properties associated with an increased CI.

SPET of a computerised model of diffuse lung disease

Emphysema is a common and debilitating disease that is the commonest cause of end-stage respiratory failure. Treatment is either by lung transplantation or by lung volume reduction surgery (LVRS) that improves the biomechanics of respiration. Patient selection for LVRS hinges on the demonstration of heterogeneous disease, predominantly involving the upper lobes, as a good surgical outcome is most likely in these patients. We used a virtual model of lung scintigraphy to compare planar with tomographic scintigraphy for the detection of diffuse lung disease. Lesions of the magnitude of the lung acinus, as well as larger and smaller lesions, were distributed throughout the lungs in volumes from 2% to 50%. Single-photon emission tomography does not add incremental value to planar images for the detection of diffuse lung disease.

Single-photon emission tomography of a computerised model of pulmonary embolism

Planar pulmonary scintigraphy is currently the standard investigation for the diagnosis of pulmonary embolism. There are a number of problems with the technique, particularly in patients with an intermediate scan report under the PIOPED criteria. The technique is also under threat from the increasing use of spiral CT angiography. A putative improvement may be gained by use of tomography. The incremental value of tomography over planar studies was therefore evaluated in a virtual model of pulmonary scintigraphy. A model of the segmental anatomy of the lungs was developed from computed tomography, cadaveric human lungs and available anatomical texts. Counts were generated within the phantom by Monte Carlo simulation of photon emission. Eighteen single segmental lesions were interspersed with 47 subsegmental defects and displayed on an Icon reporting station. These were presented in the transaxial, sagittal and coronal planes to four experienced reporters to obtain assessment of defect size. Planar studies of the same defects were displayed to the same observers in the standard eight views with a normal study for comparison. With planar studies, the accuracy of estimation of defect size was 51% compared with 97% using tomographic studies. Defects in the medial basal segment of the right lower lobe were not identified in planar studies but were easily seen by all observers in the tomographic study. It is concluded that there is marked improvement in the accuracy of determination of defect size for tomographic studies over the planar equivalents. This is especially important in the lung bases, the most common reported site of pulmonary emboli. Tomography permits visualisation of defects in the medial basal segment of the right lung, which are not seen in planar studies.

Inhalation of dry powder mannitol improves clearance of mucus in patients with bronchiectasis

Bronchiectasis is a disease characterized by hypersecretion and retention of mucus requiring physical and pharmacologic treatment. Recently we reported that inhalation of dry powder mannitol markedly increases mucociliary clearance (MCC) in asthmatic and in healthy subjects (Daviskas, E., S. D. Anderson, J. D. Brannan, H. K. Chan, S. Eberl, and G. Bautovich. 1997. Inhalation of dry-powder mannitol increases mucociliary clearance. Eur. Respir. J. 10:2449-2454). In this study we investigated the effect of mannitol on MCC in patients with bronchiectasis. Eleven patients 40 to 62 yr of age inhaled mannitol (approximately 300 mg) from a Dinkihaler. MCC was measured over 90 min, in the supine position, on three occasions involving: mannitol or control or baseline, using a radioaerosol technique. On the control day patients reproduced the breathing maneuvers and the number of coughs induced by the mannitol. Mannitol significantly increased MCC over the 75 min from the start of the intervention compared with control and baseline in the whole right lung, central, and intermediate region. Mean (+/- SEM) clearance with mannitol was 34.0 +/- 5.0% versus 17.4 +/- 3.8% with control and 11.7 +/- 4.4% with baseline in the whole right lung (p < 0.0001). The mean number of coughs induced by mannitol was 49 +/- 11. In conclusion, inhalation of dry powder mannitol increased clearance of mucus and thus has the potential to benefit patients with bronchiectasis.

Deposition of aqueous aerosol of technetium-99m diethylene triamine penta-acetic acid generated and delivered by a novel system (AERx) in healthy subjects

Deposition of technetium-99m diethylene triamine penta-acetic acid aqueous radioaerosols generated by a novel aerosol delivery system (AERx) was studied in six healthy subjects using both planar and single-photon emission tomography (SPET) imaging. AERx is a microprocessor-controlled, bolus inhalation device that is actuated at pre-programmed values of inspiratory flow rate and volume. The aims of the study were to determine the effects of posture and inhaled volume upon deposition of the aerosol in the lungs. Each subject inhaled the radioaerosol in two positions (supine vs sitting) and with two inspiratory manoeuvres [vital capacity (VC) vs "fixed volume" of 1 l above functional residual capacity]. Simultaneous transmission-emission planar and tomographic images were acquired. The results showed diffuse deposition of the aerosol in the lung. Neither the breathing manoeuvre nor the posture was found to affect the distribution of the aerosol as measured by the ratio of the activity (counts per pixel) in the peripheral:central (penetration index, PI) or in the apex:base regions of the planar lung images (P>0.1). A small, albeit statistically significant, difference in PI (P<0.03) was found between VC and fixed volume sitting manoeuvres with SPET only. The PI values themselves indicate that the radioaerosol was well distributed in the lung, with the periphery having 45%-64% of the activity of the central region. Superposition of transmission SPET lung outline on emission SPET visually confirmed the excellent peripheral deposition of the aerosol. The AERx system showed high efficiency of delivery, with approximately 50% of the extruded dose in the device depositing in the lung. The uniformity of radioactivity distributed throughout the lung is attributed to the fine particle size (mass median aerodynamic diameter of 2 microm) of the aerosol and the electronic control of aerosol inhalation by the device. In conclusion, the AERx system can be ideal for diffuse aerosol deposition of therapeutic or diagnostic agents and is largely unaffected by inhaled volume and posture. The efficiency of the device device can limit the total radiation exposure of patients and staff administering the radioaerosols, and can make it suitable for delivery of expensive drugs.

Enhanced accuracy and reproducibility in reporting of lung scintigrams by a segmental reference chart

The diagnostic probability of pulmonary embolic disease is based on the recognition of unmatched segmental perfusion defects. Although interobserver and intraobserver reproducibility have been studied, accuracy has been an elusive goal due to the lack of a gold standard. We investigated the accuracy and reproducibility of reporting in a virtual scintigraphic model of the lungs, with and without the use of a lung segmental reference chart.

METHODS

A Monte Carlo package was used to model lung scintigraphy from a digital phantom of the human lungs. An ideal lung segmental reference chart was created from the phantom. Five experienced nuclear medicine physicians reported a set of all possible defects involving 100% of a segment, without and with the chart. A further set of defects involving 45%-55% of a segment in the lower lobes was investigated using the chart.

RESULTS

There was a significant improvement in accuracy (from 48% to 72%) and intraobserver agreement (from 61% to 77%) with the chart. The accuracy of reporting defects in the upper and middle lobes was consistently better than that in the lower lobes. There was no significant difference between the accuracy of reporting large defects and that of reporting moderate defects in the lower lobes.

CONCLUSION

The lung segmental reference chart significantly improves both the accuracy and reproducibility of reporting lung scintigrams; however, although reporting in the lung bases is improved, absolute accuracy is substantially less than that in the upper and middle lobes. This emphasizes the need for caution because the lung bases are the most common site of embolic disease.

Variability of perceived defect size in virtual lung scintigraphy

The diagnosis of pulmonary embolism is based on the presence of mismatched segmental or subsegmental defects. An important axiom is the classification of defect sizes into small, moderate and large. Little information about the recognition and classification of such defects has been published. We undertook a study of the perception of defect size using a model of the virtual scintigraphic anatomy of the lungs to address this issue.

METHODS

Segmental anatomy of the lungs was modeled with CT, cadaveric lungs and standard anatomical tests. The emission, scatter and attenuation of photons were modeled within these virtual lungs and the surrounding tissues. Single segmental lesions, each 100% of a segment, were created in eight projections and submitted for blinded reporting by four experienced nuclear medicine physicians to obtain their assessment of the size of each defect on two occasions.

RESULTS

Of the 144 defects submitted for reporting, 15% were reported as <25% of a segment, 35% were reported as 25%-75% and 50% were reported as 75%-100%. The accuracy of each reporter and the intraobserver agreement were calculated; the weighted kappa value ranged from 0.34 to 0.60. The segmental defects that were most likely to be underestimated in size were in the right lower lobe.

CONCLUSION

It is clear that segmental defect sizes were underestimated, particularly in the right lower lobe. Although the intraobserver agreement in reporting was fair, the accuracy of estimation was only 50%. The variability and inaccuracy might be reduced by the use of a guide to segmental anatomy.

Optimization of the scintigraphic segmental anatomy of the lungs

Accurate and reproducible reporting of lung scintigraphy is predicated on a sound knowledge of the segmental anatomy of the lungs. A limited amount of hard data exists about the true segmental anatomy of the lungs. A virtual model of human lungs was created using a CT-based dataset and a Monte Carlo simulation technique to examine the optimal projections for the visualization of each segment in the lungs.

METHODS

Segmental anatomy of the lungs was modeled using CT, cadaveric lungs and standard anatomical texts. The emission, scatter and attenuation of photons was modeled within these virtual lungs and the surrounding tissues. Single segmental lesions were created in eight projections and submitted for blinded reporting to four experienced nuclear medicine physicians to obtain the best views for each segment.

RESULTS

The anterior and posterior oblique projections yielded the best views for 10 of 18 segments, with the laterals contributing four views, the anterior contributing two views and the posterior contributing one view. The majority of basal segments (six of nine) were best seen in the anterior and posterior oblique projections.

CONCLUSION

This model overcomes the major problems associated with experimentation in the normal human and has the potential to provide answers to the major problems of scatter, attenuation and "shine-through" in lung scintigraphy.

Inhalation of dry-powder mannitol increases mucociliary clearance

Inhalation of hypertonic saline stimulates mucociliary clearance (MCC) in healthy subjects and those with obstructive lung disease. We investigated the effect of inhaling the osmotic agent mannitol on MCC. We used a dry-powder preparation of mannitol British Pharmacopea (BP) which was encapsulated and delivered using a Dinkihaler. MCC was measured for 75 min in six asthmatic and six healthy subjects on two occasions before and after the mannitol inhalation or its control, using 99mTc-sulphur colloid and a gamma camera. The inhaled dose of mannitol was 267+/-171 mg (mean+/-SD) and 400 mg and the percentage fall in forced expiratory volume in one second (FEV1) was 22+/-3 and 4+/-2% in the asthmatic and healthy subjects, respectively. The total clearance in the whole right lung for the 60 min from the start of inhalation of mannitol was greater by 263+/-11.9% in the asthmatic and 18.1+/-4.9% in the healthy subjects compared to the control. The total clearance over 75 min was 54.7+/-9.6% and 33.6+/-9.4% on the mannitol and control day (p<0.002), respectively, in the asthmatic subjects and 40.5+/-7.1% and 24.8+/-7.8% (p<0.002) in the healthy subjects. In conclusion, inhalation of dry-powder mannitol increases mucociliary clearance in asthmatic and healthy subjects and may benefit patients with abnormal mucociliary clearance.

Monte Carlo and experimental evaluation of accuracy and noise properties of two scatter correction methods for SPECT

Scatter correction is a prerequisite for quantitative SPECT, but potentially increases noise. Monte Carlo simulations (EGS4) and physical phantom measurements were used to compare accuracy and noise properties of two scatter correction techniques: the triple-energy window (TEW), and the transmission dependent convolution subtraction (TDCS) techniques. Two scatter functions were investigated for TDCS: (i) the originally proposed mono-exponential function (TDCSmono) and (ii) an exponential plus Gaussian scatter function (TDCSGauss) demonstrated to be superior from our Monte Carlo simulations. Signal to noise ratio (S/N) and accuracy were investigated in cylindrical phantoms and a chest phantom. Results from each method were compared to the true primary counts (simulations), or known activity concentrations (phantom studies). 99mTc was used in all cases. The optimized TDCS(Gauss) method overall performed best, with an accuracy of better than 4% for all simulations and physical phantom studies. Maximum errors for TEW and TDCS(mono) of -30 and -22%, respectively, were observed in the heart chamber of the simulated chest phantom. TEW had the worst S/N ratio of the three techniques. The S/N ratios of the two TDCS methods were similar and only slightly lower than those of simulated true primary data. Thus, accurate quantitation can be obtained with TDCS(Gauss), with a relatively small reduction in S/N ratio.

Correlation between post-ejection shortening and improvement in regional wall motion after revascularization in patients with coronary artery disease

This study investigates the relationship between regional post-ejection shortening and improvement in wall motion after revascularization in patients with severe regional left ventricular contractile dysfunction. Canine studies have documented the phenomenon of post-systolic shortening during acute ischemia, and this predicted recovery of contractile function when ischemia was relieved. This delayed shortening from the ischemic segment would cause regional emptying while the other normal portion of the left ventricle starts to have diastolic relaxation. This was detectable by standard phase analysis of the radionuclide ventriculogram, the abnormal region with delayed emptying being distinguished from the normal portion of left ventricle as an area with a homogeneous phase delay. Twelve patients with successful revascularization and a pre-operative study demonstrating a single homogeneous area of phase delay were identified. The area was demarcated and the regional volume-time curve constructed. The volume-time curve of the abnormal region is analogous to the myocardial segment length versus time relationship in the canine model. We quantitated the amount of delayed (post-systolic) emptying in the demarcated region as the difference between end-systole counts and post-systolic nadir counts, and this was normalised to left ventricular stroke count. After revascularization, regional ejection fraction improved from 44 +/- 10% to 62 +/- 14% (P < 0.001), representing a 47 +/- 50% improvement over baseline. The percentage improvement in regional ejection fraction correlated with post-systolic emptying (r = 0.74, P < 0.05) but not with initial regional ejection fraction. In conclusion, post-ejection shortening causes regional post-systolic emptying and this correlates with post-revascularization improvement in regional wall motion.

Mucociliary clearance during and after isocapnic hyperventilation with dry air in the presence of frusemide

We have previously shown that mucociliary clearance (MCC) decreased during and increased after isocapnic hyperventilation (ISH) with dry air, both in asthmatic and healthy subjects. Inhaled frusemide, an inhibitor of the Na+/K+/2Cl- and NaCl co-transporters on the basolateral membrane of the epithelial cell, prevents the airway narrowing provoked by ISH with dry air. The co-transport system controls epithelial cell volume and chloride secretion and, thus, frusemide has the potential to modify the rate of recovery of periciliary fluid volume during and after ISH with dry air, and hence affect MCC. Frusemide also blocks mediator release from mast cells, which may also modify the increase in MCC after ISH. Eleven asthmatic and 11 healthy subjects inhaled frusemide (35.7 +/- 0.44 mg) or its vehicle, from a Fisoneb ultrasonic nebulizer 30 min before ISH with dry air, on two separate occasions. MCC was measured using 99mTc-sulphur colloid and a gamma camera. Frusemide, compared to its vehicle, did not affect MCC during or 45 min after ISH. However, in the presence of frusemide, the onset of the increase of MCC after ISH was significantly delayed for approximately 10 min in the whole right lung (p < 0.002) and central region (p < 0.01) in the asthmatic but not in the healthy subjects. These findings could be explained by frusemide delaying the recovery of the periciliary fluid volume after ISH with dry air and/or interfering with the stimulus that causes the increase in MCC in the asthmatic subjects after ISH.

Inhalation of hypertonic saline aerosol enhances mucociliary clearance in asthmatic and healthy subjects

Hyperosmolarity of the airway surface liquid (ASL) has been proposed as the stimulus for hyperpnoea-induced asthma. We found previously that mucociliary clearance (MCC) was increased after isocapnic hyperventilation (ISH) with dry air, and we proposed that the increase related to transient hyperosmolarity of the ASL. We investigated the effect of increasing the osmolarity of the ASL on MCC, by administering an aerosol of concentrated salt solution. MCC was measured using 99mTc-sulphur colloid, gamma camera and computer analysis in 12 asthmatic and 10 healthy subjects on three separate days, involving administration of each of the following: 1) ultrasonically nebulized 14.4% saline; 2) ultrasonically nebulized 0.9% saline; and 3) no aerosol intervention (control). The (mean +/- SD) volume of nebulized 14.4% saline was 2.2 +/- 1.2 mL for asthmatics and 3.2 +/- 0.7 mL for healthy subjects. This volume was delivered over a period of 5.4 +/- 1.3 and 6.4 +/- 0.7 min for asthmatic and healthy subjects, respectively. The airway response to 14.4% saline was assessed on a separate visit and the fall in forced expiratory volume in one second (FEV1) was 22 +/- 4% in the asthmatic and 3 +/- 2% in the healthy subjects. Compared to the MCC with the 0.9% saline and control, the hypertonic aerosol increased MCC in both groups. In asthmatic subjects, MCC of the whole right lung in 1 h was 68 +/- 10% with 14.4% saline vs 44 +/- 14% with 0.9% saline and 39 +/- 13% with control. In healthy subjects, MCC of the whole right lung in 1 h was 53 +/- 12% with 14.4% saline vs 41 +/- 15% with 0.9% saline and 36 +/- 13% with control. We conclude that an increase in osmolarity of the airway surface liquid increases mucociliary clearance both in asthmatic and healthy subjects. These findings are in keeping with our previous suggestion that the increase in mucociliary clearance after isotonic hyperventilation with dry air is due to a transient hyperosmolarity of the airway surface liquid.

Electrocardiographic measurement of infarct size after thrombolytic therapy

OBJECTIVES

We examined the utility of the 32-point QRS score from the 12-lead electrocardiogram (ECG) for measurement of the ischemic risk region and infarct size in patients receiving thrombolytic therapy.

BACKGROUND

The QRS score offers a means of evaluating the therapeutic benefit of thrombolytic therapy by comparing final infarct size with the initial extent of ischemic myocardium.

METHODS

The study included 38 patients (34 men, 4 women; mean [+/-SD] age 54 +/- 10 years) with a first infarction (18 anterior, 20 inferior). The maximal potential QRS score (QRS0) was assigned to all leads with >/= 100-microV ST elevation on the initial ECG. The QRS scores were calculated at 7 and 30 days after infarction. Left ventricular ejection fraction was measured by radionuclide ventriculography at 1 month. Twenty-eight patients had thallium (Tl)-201 and technetium (Tc)-99m pyrophosphate tomographic measurement of the ischemic region and infarct size.

RESULTS

The QRS0 was 10.3 +/- 3.1 (mean +/- SD) for anterior and 10.4 +/- 3.5 for inferior infarcts. The QRS scores were similar at 7 and 30 days for both anterior (5.6 +/- 3.4 vs. 5.5 +/- 3.4) and inferior infarcts (3.7 +/- 2.6 vs. 2.9 +/- 2.2). The day 7 QRS score and ejection fraction at 1 month were inversely correlated (r = -0.74, p < 0.01). The Tl-201 perfusion defect was 34 +/- 11% of the left ventricle for anterior and 32 +/- 7% for inferior infarcts. Subsequent Tc-99m pyrophosphate infarct size was 15 +/- 9% of the left ventricle for anterior and 17 +/- 9% for inferior infarcts. The QRS0 was correlated with the extent of the Tl-201 perfusion defect (r = 0.79, p < 0.001), and the day 7 QRS score was correlated with Tc-99m pyrophosphate infarct size (r = 0.79, p < 0.005).

CONCLUSIONS

The 32-point QRS score can provide useful immediate measurements of the ischemic risk region and subsequent infarct size.

Regional deposition of saline aerosols of different tonicities in normal and asthmatic subjects

Nonisotonic aerosols are frequently used in the diagnosis and therapy of lung disease. The purpose of this work was to study the difference in the pattern of deposition of aerosols containing aqueous solutions of different tonicities. 99mTechnetium-diethyltriaminepentaacetic acid (99mTc-DTPA)-labelled saline aerosols, with mass median aerodynamic diameter 3.7-3.8 microns and geometric standard deviation 1.4, were inhaled under reproducible breathing conditions on two occasions. Hypotonic and hypertonic solutions were used in 11 normals subjects, isotonic and hypertonic solutions in 9 asthmatics. The regional deposition was quantified by a penetration index measured with the help of a tomographic technique. There was a small but significant increase (6.7%) in the penetration index of the hypotonic as compared to the hypertonic aerosols in the normal subjects. The region that was markedly affected was the trachea. The differences in the penetration of the isotonic and hypertonic aerosols in the asthmatics appeared to be strongly dependent on the state of the airways at the time of the study. These findings can be interpreted in terms of effects of growth or shrinkage of nonisotonic aerosols, as well as of airway narrowing, on regional deposition of aerosols. Tonicity of aerosols appears to affect their deposition both through physical and physiological mechanisms. This should be taken into account when interpreting the effects of inhaled aqueous solutions of various tonicities in patients in vivo.

Regional deposition of nebulized hypodense nonisotonic solutions in the human respiratory tract

Deposition of nonisotonic therapeutic and diagnosis aerosols can cause changes in airway fluid composition and bronchoconstriction in sensitive subjects. "Hypodense" aerosols containing a relatively low concentration of droplets in the carrier air were used in the studies of regional deposition of radiolabelled nebulized solutions of hypo- and hypertonic saline, in order to investigate whether the number of droplets per volume of carrier can affect deposition. Solutions with and without 0.5% nedocromil sodium were nebulized in order to examine the effects of a potential modifier of the rates of heat and mass transfer. The deposition was quantified using penetration index (PI) calculated from images obtained by single photon emission computerized tomography (SPECT) in 11 healthy volunteers per study. There was an increase in the penetration index (10.9%, for the saline only; 15.5%, for the nedocromil study) of the hypotonic compared to the hypertonic aerosol, although the initial size distribution of both types of aerosols was very similar (mass median aerodynamic diameter (MMAD) 3.7 and 3.8 microns; geometric standard deviation (GSD) 1.8 and 1.5 for the hypo- and hypertonic aerosols, respectively). The present results confirm the effects of tonicity on deposition of aerosols found in a parallel study reported in this issue of the Journal. They also give support to the theory that, in addition to the concentration of the nebulized solutions, the number of droplets per volume of the carrier air is a factor affecting deposition of aqueous aerosols. The presence of 0.5% nedocromil sodium in the solutions did not appear to interfere with the processes of heat and water transfer in the airways.

Mucociliary clearance in patients with cystic fibrosis and in normal subjects

The aim of this study was to examine baseline mucociliary clearance (MCC) in patients with cystic fibrosis (n = 30; mean +/- SEM age, 23 +/- 1 yr; FEV1, 68 +/- 5% pred; range, 14 to 126%) and a group of normal subjects (n = 12; mean age, 27 +/- 1 yr) after an aerosol deposition of 99mTc-sulphur colloid (mass median diameter, 4.8 microns; geometric standard deviation, 1.6). Dynamic geometric mean images were formed from gamma camera data, and the percent clearance of activity after 60 min (%C60) was calculated for the whole right lung. Initial deposition of the aerosol was determined in terms of the penetration index, the ratio of peripheral to central activity. For normal subjects, an increase in mean inspiratory flow rate (MIFR) (49 +/- 5 versus 21 +/- 3 L/min, p < 0.05) resulted in an increase in whole right lung MCC (%C60, 31 +/- 4 versus 18 +/- 2%; p < 0.05). When aerosol delivery was controlled (MIFR, 34 +/- 5 versus 36 +/- 5 L/min), there was excellent reproducibility between studies (whole lung %C60, 34 +/- 8 versus 31 +/- 7; NS). The measurement of MCC was highly reproducible in six patients studied on four occasions with a mean coefficient of variation of 3.3 +/- 1%. A breathing pattern to accentuate central deposition was utilized in the patient studies (MIFR, 49 +/- 4 L/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of deep venous thrombi and pulmonary embolus with technetium-99m-DD-3B6/22 anti-fibrin monoclonal antibody Fab' fragment

Technetium-99m-labeled anti-fibrin DD-3B6/22 Fab' monoclonal antibody fragments, which specifically target human cross-linked fibrin with high affinity, were evaluated in humans for safety and their capacity to detect deep vein thrombi and pulmonary embolism.

METHODS

Twenty patients with proven deep-vein thrombosis, documented by contrast venography, or venous duplex scan, were injected with a 600 MBq (0.5 mg) dose of antibody. Planar images of the lower limbs were recorded at 0, 2, 6 and 24 hr and chest scintigrams were recorded at 6 and 24 hr.

RESULTS

All venography documented thrombus sites, calves, popliteal and femoral, were detected with the radioimmunoconjugate. For the venous duplex scan-proven thrombus sites, all except two calf thrombi in two patients with bilateral disease and other positive sites were detected. Five patients had bilateral deep-vein thrombosis with multiple sites being visualized with the radioimmunoconjugate in the calf, popliteal and femoral regions. One case of pulmonary embolus was also definitively demonstrated. Documented thrombus sites were detected at 2 and 6 hr postinjection. Nineteen patients were on heparin. No adverse reactions to the injected dose were observed and one low titer human anti-mouse antibody response may have occurred.

CONCLUSION

The results indicate that 99mTc-DD-3B6/22 Fab' has potential for noninvasive detection of deep-vein thrombosis and pulmonary embolism.

Mechanism and significance of precordial ST-segment depression during inferior wall acute myocardial infarction associated with severe narrowing of the dominant right coronary artery

The mechanism and significance of precordial ST depression during inferior wall acute myocardial infarction (AMI) is debated. This study assessed the location and extent of arterial perfusion distribution responsible for this electrocardiographic finding. Intracoronary thallium-201 was injected in 11 patients with 1-vessel right coronary disease to delineate perfusion distribution that was quantitated by a new angiographic distribution score. The angiographic score correlated with posterior (r = 0.84), posterolateral (r = 0.88) and total (r = 0.73) extent of intracoronary thallium distribution. The angiographic distribution score was related to electrocardiographic changes in 16 patients showing an inferior ST-segment elevation during angioplasty (7 with and 9 without precordial ST depression), of which 6 received intracoronary thallium injection. None had thallium distribution in the anterior or septal segment, but there was a trend toward a greater angiographic distribution score and posterior segment thallium score in patients with precordial ST depression. In another 77 patients with inferior wall AMI due to right coronary occlusion (24 with concomitant left anterior descending narrowing), precordial ST depression was present in 16 with and 31 without left anterior descending narrowing (p = NS). The angiographic distribution score was higher in those with than without precordial ST depression (0.59 +/- 0.10 vs 0.44 +/- 0.11, p < 0.001) in both patients with and without left anterior descending disease. The magnitude of both inferior ST elevation and precordial ST depression correlated with the angiographic distribution score, but only precordial ST depression was independently related in multivariate analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Derivation and validation of a new angiographic score of right coronary artery perfusion

A semi-quantitative right coronary artery score (RCA score) was derived from the ratio of the number of the major left ventricular branches of the right coronary artery to the total of the right coronary and left circumflex arteries, to stratify the extent of perfusion in patients with right coronary artery dominance. Thirty-seven patients with one-vessel coronary disease involving a dominant right coronary artery proximal to the left ventricular branches were selected for study. Thallium scintigraphy was performed after right intracoronary injection in 11 patients, and 26 patients underwent conventional stress thallium scintigraphy (24 exercise thallium and two dipyridamole thallium scintigraphy). Thallium scores of perfusion region size after right intracoronary thallium injection and perfusion defect size in stress thallium studies were quantitated from planar thallium images. Both the RCA score and the regional thallium scores spanned over a wide range. The RCA score (range 0.23-0.85) correlated best with the posterior (70 degrees left anterior oblique view) plus lateral segment (40 degrees left anterior oblique view) thallium score (r = 0.88 and 0.53 for intracoronary and stress thallium studies respectively). It also correlated with the summed thallium scores in the posterior, lateral, apical and inferior segments (r = 0.73 and 0.54 respectively) but not with thallium scores in the apex or inferior segment alone. The proposed RCA score quantitates the variable posterolateral perfusion territory of the right coronary artery, and could stratify the area of myocardium at risk from coronary stenosis in the majority of patients with right coronary dominance.

Comparisons of planar and tomographic gamma scintigraphy to measure the penetration index of inhaled aerosols

The quantitative measurement of regional aerosol deposition in human lungs using two-dimensional (2D) gamma scintigraphy has proven to be useful in therapeutic and diagnostic aerosol studies. The penetration index (PI) has been defined as the ratio of activity in a peripheral lung zone to a central lung zone, but the ability to discriminate between aerosol deposition in the large airways and lung parenchyma is reduced by the fact that the latter overlies the former in the central zone. To overcome this, we used a three-dimensional (3D) technique. Seven healthy subjects inhaled isotonic saline aerosols containing 99mTc-DTPA on two occasions. The droplets had a mass median aerodynamic diameter (MMAD) of either 2.6 or 5.5 microns (with geometric standard deviations [sigma g] of 1.4 and 1.7, respectively). Transmission tomography was performed on each subject to delineate lung boundaries in 2D and 3D. After inhalation, anterior (A) and posterior (P) images were collected and a tomographic study performed. Mid-lung slices were taken from coronal (CC) and transverse (TC) sections. PI was calculated on the 2D images (AP and P) and the 3D slices (CC and TC) using exactly defined regions. The PI values were smaller for the large droplet aerosol (5.5 microns) in all subjects and methods. The relative differences in PI between large and small (2.6 microns) droplet studies (d values) were greater and less variable for the 3D methods (TC, 56.5 +/- 11.4% and CC, 52.4 +/- 12.3%) compared to the 2D methods (P, 25.4 +/- 17.1% and AP, 38.3 +/- 15%; p less than 0.005). We found the 3D methods to be more sensitive for discriminating between aerosol deposition in large and small airways than were the conventional 2D methods.

A rapid method for the evaluation of diagnostic radioaerosol delivery systems

The effective delivery (ED) in MBq/min of a 100 MBq/ml nebuliser solution was defined as the rate of delivery of droplets in the respirable size range (aerodynamic diameter below 3.3 micron) to the mouthpiece of the aerosol delivery system (ADS). Wasted delivery (WD) was defined as the rate of delivery of droplets above 3.3 microns. ED and WD were measured on four types of commercially available ADS. The aerosols were sampled at the mouthpiece of each system and droplet size distribution measured with a seven stage cascade impactor. The effect of ambient air humidity on the droplet size produced by the Cadema delivery system was also evaluated. The ED values ranged from 6 to 15 MBq/min and WD values from 0.01 to 15 MBq/min. Two ADS produced low ED and WD values (6.1-9.0 and 0.01-0.07 MBq/min, respectively) due to a low output, while another produced higher ED and WD values [11.3 +/- 0.2 (SD) and 15.4 +/- 0.5 (SD) MBq/min, respectively] due to a larger droplet size. The Cadema delivery system gave the optimum characteristic of high ED [13.9 +/- 0.8 (SD) MBq/min] and low WD [1.24 +/- 0.61 (SD) MBq/min] values. The mass median aerodynamic diameter (MMAD) of the Cadema ADS fell by 22% (P less than 0.01) as the ambient dilution air was dried from a high relative humidity (RH) (88%-100%) to a low RH (12%-17%). The variability of both MMAD and geometric standard deviation (sigma g) was increased with dry dilution air (P less than 0.01).

Infarct artery perfusion and changes in left ventricular volume in the month after acute myocardial infarction

The relation between perfusion of the infarct-related artery and changes in left ventricular volume and function during the month after a first myocardial infarction was examined in 40 patients who did not receive thrombolytic therapy. Infarct artery perfusion was documented at predischarge coronary angiography, and left ventricular volume was measured by nongeometric analysis of radionuclide angiograms performed within 48 hours of infarction and at 1 month. Left ventricular dilation (greater than or equal to 20% increase in volume) developed in 16 patients, whereas 5 patients had a decrease in left ventricular volume of greater than or equal to 20% by 1 month. Left ventricular dilation occurred in all 14 patients without perfusion of the infarct-related artery, compared with only 2 of 26 patients with perfusion of this artery due to subtotal occlusion or collateral vessels. All five patients whose left ventricular volume decreased by greater than or equal to 20% had a perfused infarct artery. Multiple linear regression analysis confirmed that the degree of perfusion of the infarct artery (partial r = 0.58, p = 0.001) was a more important predictor of volume change than was infarct size measured by peak creatine kinase (partial r = 0.30, p = 0.009) or QRS score (partial r = 0.20, p = 0.087). Left ventricular ejection fraction decreased from 0.38 +/- 0.10 to 0.30 +/- 0.16 (p = 0.05) in 11 patients with an anterior infarct and ventricular dilation; it increased from 0.45 +/- 0.10 to 0.62 +/- 0.07 (p = 0.02) in the 5 patients with a greater than or equal to 20% decrease in volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of splenectomy failures in chronic immune thrombocytopenic purpura: role of accessory splenectomy

Accessory splenic tissue was demonstrated in four of eight patients with chronic immune thrombocytopenic purpura investigated following post-splenectomy relapses. Time from initial splenectomy to relapse of thrombocytopenia ranged from immediately to eight years and post-splenectomy changes were present on the peripheral blood films of all patients at time of relapse. Three scanning techniques were employed to demonstrate and localise residual splenic tissue. Conventional 99mTc scans were positive in three of the four patients whilst 99mTc-heat damaged red cell scans and computerised tomographic scans were each positive in three out of three patients including the one patient in whom a conventional 99mTc scan was negative. Histological confirmation of splenic tissue was obtained in all cases with the weights of the accessory spleens ranging from 0.6 g to 2 g. Two patients responded to accessory splenectomy and, without immunosuppressive therapy, have remained well with normal platelet counts for over four years. There was no correlation between length of initial remission and the response to removal of the accessory spleen. The presence of a functioning accessory spleen should be considered in all patients with chronic ITP who fail to respond to, or relapse following, initial splenectomy.

The reproducibility of nongeometric analysis of cardiac output and left ventricular volume by radionuclide angiography

This study examines the reproducibility of individual radionuclide attenuation factors used in the calculation of cardiac output and left ventricular volume by the nongeometric radionuclide method. Twenty male patients were studied at rest with thermodilution measurements of cardiac output on two separate days. Simultaneous equilibrium radionuclide angiograms were performed and left ventricular stroke volume and cardiac output were determined by the nongeometric method. Individual patient attenuation factors were calculated as the ratio of thermodilution and radionuclide cardiac output measurements at each study. There was a close linear relationship between radionuclide and thermodilution measurements of cardiac output in each study (r = 0.88 study 1, r = 0.97 study 2). A similar relationship was found for measurements of left ventricular stroke volume (r = 0.86, study 1, r = 0.97 study 2). Individual radionuclide attenuation factors ranged from 2.49 to 3.46 in study 1 and from 2.77 to 3.29 in study 2. The individual attenuation factors were reproducible to within 10% in 13 patients and to within 15% in 19 patients. When cardiac output was calculated from the radionuclide data of study 2, by means of individual attenuation factors previously determined in study 1, there was a good correlation with the simultaneous thermodilution measurements of cardiac output (r = 0.92, SEE = 0.38 L/min). Individual radionuclide attenuation factors show little variation in serial studies. Thus the nongeometric radionuclide technique can be used to make accurate serial measurements of cardiac output and left ventricular volume.

Comparison of thallium-201 scanning in idiopathic dilated cardiomyopathy and severe coronary artery disease

To determine whether cardiomyopathy could be distinguished from coronary artery disease, we used thallium scanning to study 25 patients with severe left ventricular dysfunction and chronic heart failure. Ten patients had normal coronary arteries and idiopathic cardiomyopathy (ejection fraction 20 +/- 5%), and 15 patients had multivessel coronary disease and left ventricular dysfunction (ejection fraction 25 +/- 6%). The exercise time and maximal heart rate were similar in the two groups. Two patients with cardiomyopathy and 11 with coronary artery disease had a positive exercise ECG (p less than 0.05). Thallium scans showed perfusion defects in all 25 patients. The perfusion defects were complete in nine coronary artery disease patients (60%) and in one patient (10%) with cardiomyopathy (p less than 0.05). Extensive defects involving more than 40% of the left ventricular circumference, the number of segments involved, redistribution on the 4-hour scan, lung uptake and ventricular size were similar in the two groups. Perfusion defects on thallium scanning can occur in patients with idiopathic dilated cardiomyopathy and chronic heart failure. Thallium scanning cannot be reliably used in patients with chronic heart failure to distinguish coronary artery disease from cardiomyopathy unless complete defects are present.

Verapamil in stable effort angina: effects on left ventricular function evaluated with exercise radionuclide ventriculography

A double blind placebo-controlled study was performed in 12 patients with stable angina pectoris to evaluate the effects of oral verapamil (320 mg/day) on left ventricular function, as measured at rest and during exercise with gated equilibrium radionuclide ventriculography. On verapamil, patients had a lower heart rate-blood pressure product at each work load than with placebo. Anginal threshold increased by 28 +/- 19 watts (p less than 0.005), and maximal exercise capacity increased by 20 +/- 14 watts (p less than 0.001) with verapamil, but the rate-pressure product at the onset of angina and at maximal exercise was unchanged. Left ventricular ejection fraction at rest during verapamil therapy was the same as with placebo therapy. On exercise during placebo therapy, the ejection fraction decreased from 40 +/- 9 to 35 +/- 11 percent (p less than 0.025) because end-systolic volume increased disproportionately compared with end-diastolic volume. On exercise during verapamil therapy, the ejection fraction did not decrease (44 +/- 8 versus 45 +/- 12 percent) and was significantly higher at identical work loads than on placebo because of a smaller increase in end-systolic volume. Oral verapamil is effective treatment for effort angina and may prevent the decrease in left ventricular ejection fraction due to exercise-induced ischemia.

The diagnosis of renal osteodystrophy: a comparison of Technetium-99m-pyrophosphate bone scintigraphy with other techniques

In order to determine the place of Technetium-99m-pyrophosphate bone scintigraphy in the assessment of renal osteodystrophy, 17 patients with chronic renal failure requiring hemodialysis underwent bone scans and these were compared to results of biochemical, radiological and histologic studies. Bone histology was abnormal in all patients with most having evidence of osteomalacia and hyperparathyroid bone disease. Using semi-quantitative scan scores and regional bone-standard ratios, isotope uptake was increased in 16 patients, while 15 had elevated alkaline phosphatase levels and 7 had X-ray changes. An osteoid-osteoclast index combining histological osteomalacia and hyperparathyroid disease was derived and was found to correlate more closely with alkaline phosphatase and parathyroid hormone levels than with scan parameters. It was concluded that bone scans did not provide therapeutically useful information that could not be obtained from biochemical and radiological studies. It appeared that only bone histology could differentiate osteomalacia and hyperparathyroid bone disease.

Improvement of left ventricular function in alcoholic cardiomyopathy documented by serial gated cardiac pool scanning

Serial gated cardiac blood pool scans showed a gradual return to normal left ventricular function over ten months in a 44-year-old patient who presented initially with severe alcoholic congestive cardiomyopathy. The clinical signs of left ventricular failure abated considerably before myocardial function improved objectively on gated blood pool scanning.

Myocardial perfusion scanning with thallium--201 for the non-invasive diagnosis of coronary artery disease

Thallium--201 myocardial perfusion scanning has been evaluated in Australia in patients with coronary artery disease. Myocardial scans reliably detect both acute myocardial infarction and the transient myocardial ischaemia of angina pectoris. The non-invasive nature, ease of study, and the ability to scan patients with conventional cameras makes thallium--201 an attractive additional diagnostic agent for patients with suspected coronary artery disease. Although thallium--201 reliably indicates perfusion defects in the myocardium, its diagnostic use at the moment should be reserved to clarify such diagnostic problems in patients with coronary artery disease which cannot be satisfactorily explained by conventional investigation.

Radionuclide imaging to assess myocardial damage during open heart surgery

Technetium 99m Pyrophosphate imaging before and after open heart surgery was performed in 38 patients to estimate the incidence of peri-operative infarction. Positive images were present pre-operatively in 11 of 30 patients with coronary artery disease. In three patients the images changed from negative to positive and in two this was thought to be due to infarction produced at operation. The high incidence of positive pre-operative images emphasises that many patients with evolving myocardial infarction, unstable angina or severe heart failure are now operated upon without delay. Because many patients have positive images before surgery pre-operative and post-operative images must be compared to assess myocardial damage due to surgery.

"Hot spot" myocardial scanning: experiences with a mobile nuclear camera in a coronary care unit

Twenty-nine patients with suspected or actual myocardial infarction have had myocardial "hot spot" scans with technietium 99m pyrophosphate, using a mobile nuclear camera in a coronary care unit. Nine patients with transmural infarcts had positive scans. Nine out of 12 patients thought to have had endocardial infarction had positive scans. Two patients who had had intramuscular injections presented with chest pain and abnormally high serum enzyme levels, but had negative scans. Myocardial radionuclide scanning with a mobile nuclear camera is a rapid, easy, repeatable, non-invasive method of helping to confirm or exclude the diagnosis of myocardial infarction and, used together with other available tests, is a valuable additional diagnostic aid.