Bedside diagnosis of silent aspiration using mobile dynamic digital radiography: a preliminary study.

PURPOSE: This study aimed to assess reliable options for bedside diagnosis of silent aspiration in the intensive care unit by examining the use of default grayscale images (DGI) obtained using a mobile, general-purpose, radiography system capable of dynamic digital radiography (M-DDR) and inverted grayscale images (IGI) of DGI. METHODS: This cohort study (exploratory and preliminary) involved 18 adult patients (mean age, 89.0 years) for whom a swallowing assessment request was received from their primary physicians. Fifty-six IGI videoclips were evaluated by three specialists using the penetration-aspiration scale (PAS), with the gold standard being the consensus reading of all three specialists. Another three speech-language pathologists (SLPs) assessed 56 DGI and IGI videoclips using the PAS. PAS scores 1 and 2 were classified as normal range, PAS scores 3-5 as pathological laryngeal penetration, and PAS scores 6-8 as aspiration. The correct rates with IGI and DGI were then determined, and the level of agreement of IGI and DGI evaluations was evaluated. RESULTS: The correct rate of all evaluators was 100% for normal range, 80-100% for pathological laryngeal penetration, and 83-100% for aspiration with IGI and 100% for normal range, 90% for pathological laryngeal penetration, and 83% for aspiration with DGI. The kappa coefficient for IGI and DGI showed almost complete agreement for abnormal conditions. CONCLUSION: Dynamic imaging of swallowing 2-5 ml of liquid using M-DDR performed for elderly patients at the bedside showed that aspiration assessments by SLPs obtained from DGI videos immediately after imaging are acceptable.

Endoscopic papillectomy could be rewarding to patients with early stage duodenal ampullary carcinoma?

BACKGROUND/PURPOSE: There is currently no consensus on the use of endoscopic papillectomy (EP) for early stage duodenal ampullary adenocarcinoma. This study aimed to evaluate the feasibility of EP for patients with early stage duodenal ampullary adenocarcinoma. METHODS: Patients who underwent EP for ampullary adenocarcinomas were investigated. Complete and clinical complete resection rates were evaluated. Clinical complete resection was defined as either complete resection or resection with positive or unknown margins but no cancer in the surgically resected specimen, or no recurrence on endoscopy after at least a 1-year follow-up. RESULTS: Adenocarcinoma developed in 30 patients (carcinoma in situ [Tis]: 21, mucosal tumors [T1a(M)]: 4, tumors in the sphincter of Oddi [T1a(OD)]: 5). The complete resection rate was 60.0% (18/30) (Tis: 66.7% [14/21], T1a[M]: 50.0% [2/4], and T1a[OD]: 40.0% [2/5]). The mean follow-up period was 46.8 months. The recurrence rate for all patients was 6.7% (2/30). The clinical complete resection rates of adenocarcinoma were 89.2% (25/28); rates for Tis, T1a(M), and T1a(OD) were 89.4% (17/19), 100% (4/4), and 80% (4/5), respectively. CONCLUSIONS: EP may potentially achieve clinical complete resection of early stage (Tis and T1a) duodenal ampullary adenocarcinomas.

The Efficacy and Safety of EUS-Guided Gallbladder Drainage as a Bridge to Surgery for Patients with Acute Cholecystitis.

BACKGROUND AND AIM: This study aimed to compare the efficacy and safety of endoscopic ultrasound-guided gallbladder drainage and percutaneous transhepatic gallbladder drainage as a bridge to surgery in patients with acute cholecystitis unfit for urgent cholecystectomy. METHODS: This retrospective study included 46 patients who underwent cholecystectomy following endoscopic ultrasound-guided gallbladder drainage (EUS-GBD) or percutaneous transhepatic gallbladder drainage (PTGBD) for acute cholecystitis in NTT Tokyo Medical Center. We surveyed 35 patients as the EUS-GBD group and 11 patients as the PTGBD group, and compared the rate of technical success of the cholecystectomy and periprocedural adverse events. A 7-F, 10-cm double pigtail plastic stent was used for ultrasound-guided gallbladder drainage. RESULTS: The rate of technical success of cholecystectomy was 100% in both groups. Regarding postsurgical adverse events, no significant difference was noted between the two groups (EUS-GBD group, 11.4%, vs. PTGBD group, 9.0%; p = 0.472). CONCLUSIONS: EUS-GBD as a BTS seems to be an alternative for patients with AC because it can ensure lower adverse events. On the other hand, there are two major limitations in this study--the sample size is small and there is a risk of selection bias.

Clinical outcomes of permanent stenting with endoscopic ultrasound gallbladder drainage.

BACKGROUND/AIMS: Endoscopic ultrasound gallbladder drainage (EUS-GBD) is gaining attention as a treatment method for cholecystitis. However, only a few studies have assessed the outcomes of permanent stenting with EUS-GBD. Therefore, we evaluated the clinical outcomes of permanent stenting using EUS-GBD. METHODS: This was a retrospective, single-center cohort study. The criteria for EUS-GBD at our institution are a high risk for surgery, inability to perform surgery owing to poor performance status, and inability to obtain consent for emergency surgery. EUS-GBD was performed using a 7-Fr double-pigtail plastic stent with a dilating device. The primary outcomes were the recurrence-free rate of cholecystitis and the late-stage complication-avoidance rate. Secondary outcomes were technical success, clinical success, and procedural adverse events. RESULTS: A total of 41 patients were included in the analysis. The median follow-up period was 168 (range, 10-1,238) days. The recurrence-free and late-stage complication-avoidance rates during the follow-up period were 95% (38 cases) and 90% (36 cases), respectively. There were only two cases of cholecystitis recurrence during the study period. CONCLUSION: EUS-GBD using double-pigtail plastic stent was safe and effective with few complications, even in the long term, in patients with acute cholecystitis.

Large Palatal Pleomorphic Adenoma Complicated by Dysphagia: A Case Report.

A 60-year-old Japanese woman presented with a palatal pleomorphic adenoma measuring 5 cm in size. In addition to impairments during the oral preparatory and oral transport phases, dysphagia with nasopharyngeal closure disorder was observed in the pharyngeal phase. After resection of the tumor, dysphagia resolved, and the patient was immediately able to eat a standard meal. A videofluoroscopic swallowing study confirmed improvement in the movement of the soft palate compared with the pre-operative condition.

A single-sided trans-nasal catheter for smooth and efficient oxygen delivery can improve the safety in patients undergoing pancreato-biliary endoscopy under intravenous sedation: A randomized trial.

Background: Pancreato-biliary endoscopic procedures often need to be performed under deep intravenous sedation. The patients are at an increased risk of respiratory depression influenced by the anatomical dead space of the upper respiratory system. We aimed to evaluate the benefit of oxygen delivery through a single-sided trans-nasal catheter (TC) for patients undergoing pancreato-biliary endoscopy. Methods: Oxygen supplementation during the procedure was provided either by insertion of a single-sided TC or insertion of a conventional nasal catheter (NC). A prospective, single-blind, randomized controlled study was conducted in two groups. Results: The number of patients who indicated a decrease in the peripheral transcutaneous oxygen saturation (SpO2; desaturation) was significantly lower in the TC group than in the counterpart (8/58; 13.8% vs. 26/58; 44.8% p < 0.001). The efficient oxygen delivery in the safe range was better conserved in the TC group than in the NC one. There was no adverse effect on both groups. The maximum SpO2 while the endoscopic procedure was significantly higher in the TC group (99.7% vs. 99.3% p = 0.016) and the minimum SpO2 was also significantly higher in the same group (97.7% vs. 94.1% p < 0.0001), which meant that the efficient oxygen delivery was better maintained in TC group than the NC group. Conclusions: A single-sided TC placed in the pharynx in patients undergoing pancreato-biliary endoscopy prepares a superior condition of the patients for venous sedation, maintained hyper-oxygen saturation and a relatively higher SpO2 level to be maintained in limited conditions to reduce the dead space with acceptable tolerance, as compared to the placement of a conventional NC.

Microscopic origin of thermal droop in blue-emitting InGaN/GaN quantum wells studied by temperature-dependent microphotoluminescence spectroscopy.

To elucidate the microscopic origin of the thermal droop, a blue-emitting indium gallium nitride (InGaN) quantum well grown on epitaxially laterally overgrown gallium nitride was investigated using temperature-dependent microphotoluminescence spectroscopy. Below 300 K, the sample exhibited a well-known dislocation-tolerant luminescence behavior. However, as temperature increases from 300 K to 500 K, the near band-edge emission at the wing region (with lower threading dislocation densities) was stronger than that at the seed region (with higher threading dislocation densities), indicating that threading dislocations are the microscopic origin of the thermal droop. Considering the carrier diffusion length, edge-type threading dislocations should play a major role in the thermal droop of heteroepitaxially grown InGaN-based LEDs.

Successful Treatment with the Chin-down Maneuver of Dysphagia Secondary to Descending Necrotizing Mediastinitis: A Case Study.

BACKGROUND: Descending necrotizing mediastinitis is a potentially fatal polymicrobial infection that often leads to dysphagia after treatment. Such dysphagia is likely the result of fibrosis and scarring from inflammatory changes in the fascial space. A case is presented in which the mechanism of dysphagia was verified using two-dimensional analysis of the muscle lengths of the suprahyoid and infrahyoid muscles. CASE: A 57-year-old woman presented with a hyoid and laryngeal movement disorder with pharyngeal residue secondary to descending necrotizing mediastinitis. To treat this disorder, the chin-down maneuver was performed, and it immediately improved hyoid and laryngeal elevation and reduced pharyngeal residue at the epiglottic valleculae and pyriform sinus. Analysis of the mechanism of these improvements revealed that combined head and neck flexion, compared with neck flexion, decreased the distance between the origin and insertion (DOI) of the sternohyoid muscle (SM) and increased the muscle contraction rate and the maximum contraction duration of the geniohyoid muscle (GM) during swallowing. DISCUSSION: In the present case, the patient had restrictions in extension of the SM that applied resistance to GM contraction. Compensation of this condition was achieved by combined head and neck flexion, which decreased the DOI of the SM, thereby improving the contractile function of the GM.

The Clinical Efficacy of Botulinum Toxin Injections to the Upper Lumbrical Muscles for Clenched Fist Deformity in Chronic Stroke Patients.

OBJECTIVE: Post-stroke hemiplegic patients with a spastic clenched fist deformity that was caused by upper motor neuron syndrome often have problems with hygiene and nursing. Botulinum toxin-A (BTX-A) had been given for treatment of such patients to relieve spasticity by targeting finger joint muscles, such as the flexor digitorum superficialis and flexor digitorum profundus. However, some of these patients do not have satisfactory outcomes. Therefore, we aimed to examine the clinical efficacy and outcome of BTX-A treatment that targeted the upper lumbrical muscles (ULM) in patients with spastic clenched fist deformity caused by stoke. METHODS: Chronic stroke patients with spastic clenched fist deformity who received BTX-A treatment were evaluated retrospectively. We obtained data from medical records before and at 4 weeks after BTX-A injection to the ULM. The clinical data and outcome measures analyzed included range of motion, the Modified Ashworth Scale, the numeric graphic rating scale for pain, and 2 items from the disability assessment scale (ease of cleaning palm and trimming nail). RESULTS: Wilcoxon signed rank test showed that BTX-A treatment significantly improved all measures. CONCLUSION: BTX-A therapy to the ULM provided satisfactory outcomes in improving spastic clenched fist.

Efficacy of Tape Feedback Therapy on Synkinesis Following Severe Peripheral Facial Nerve Palsy.

BACKGROUND: Mirror feedback rehabilitation is effective in preventing the development of oro-ocular synkinesis following severe facial palsy. However, we do not have effective maneuvers to prevent the deterioration of oculo-oral synkinesis. We developed a new method of biofeedback rehabilitation using tape for the prevention of oculo-oral synkinesis. OBJECTIVE: The aim of the present study was to investigate the efficacy of taping feedback rehabilitation. METHODS: Twelve consecutive patients with peripheral facial nerve palsy who developed synkinesis were divided into 2 groups. Six patients were treated with the new training method, and the remaining 6 patients were treated with conventional therapy as controls. In the experiment group, tape was placed around the mouth, and the patient was instructed to close the eyes so that no movements of the mouth would be perceived from sensations of the taped skin. After 4 weeks of training, facial movements were recorded and movie images were graded for mouth synkinesis using the revised Sunnybrook facial grading system by examiners blinded to patient grouping. RESULTS: Mouth corner contraction during eye closure was significantly weaker in the experimental group than in the control group. CONCLUSIONS: Our new feedback method could help prevent the deterioration of oculo-oral synkinesis.

Proposal for a Modified Jaw Opening Exercise for Dysphagia: A Randomized, Controlled Trial.

OBJECTIVE: To verify the feasibility and effectiveness of a newly developed modified jaw opening exercise (MJOE) in post-stroke patients with pharyngeal residue who completed a sixweek exercise regimen. DESIGN: Double-blind, randomized, controlled trial. PARTICIPANTS: 16 patients with stroke-related dysphagia. INTERVENTIONS: Participants were allocated to an intervention group (MJOE: one set of five repetitions at 80% maximum voluntary contraction (MVC) for 6 seconds) or a control group (isometric jaw closing exercise: one set of five repetitions at 20% MVC for 6 seconds). Each group performed four sets a day, five times a week, for a total of six weeks. MAIN OUTCOME MEASURES: A videofluorographic swallowing study was performed before and after exercise. The distance between the mental spine and the hyoid bone (DMH) and hyoid displacement (HD) were measured. RESULTS: Twelve participants completed the study. No pain in the temporomandibular joint and/or anterior region of the neck occurred during the exercise period. In the intervention group (N=6), a decrease in DMH where anterior HD ended and an increase in anterior HD were seen. In the control group (N=6), no changes were seen. CONCLUSIONS: MJOE is feasible without any adverse events in poststroke patients, and it promotes anterior HD during swallowing.

Proposal for a New Exercise Method for Dysphagia with Velopharyngeal Inadequacy: A Case of Bickerstaff's Brainstem Encephalitis.

Bickerstaff's brainstem encephalitis is an autoimmune disease with the primary lesion situated in the brainstem and three cardinal signs: ophthalmoplegia; ataxia; and impaired consciousness. A 68-year-old man was started on rehabilitation exercise 3 months after onset of Bickerstaff's brainstem encephalitis, due to remnant dysarthria and dysphagia (Functional Oral Intake Scale, level 5) after the cardinal signs of Bickerstaff's brainstem encephalitis resolved. Exercise involved using a straw in the anterior midline between the dorsal tongue and hard palate. While the patient was inhaling through the straw, the straw was blocked. After strengthening suction as much as possible, the patient was asked to immediately dry swallow at the same time that suction was stopped. Effects of exercise were examined using videofluorographic swallowing studies before and after 6 weeks of training to compare posterior and superior velar displacements and the presence of nasopharyngeal reflux. No adverse effects of exercise were encountered, and Functional Oral Intake Scale improved to level 7, with significant increases in posterior and superior velar displacement during swallowing compared with before training. In addition, nasopharyngeal reflux that had consistently been seen on swallowing before training was absent after 6 weeks of exercise. This exercise method may prove useful.

What is the most sensitive test for diagnosing carpal tunnel syndrome?

OBJECTIVE: To compare sensitivities between 7 principal nerve conduction studies (NCS) for diagnosing carpal tunnel syndrome (CTS). METHOD: In 104 CTS and 64 control hands, following "Standard" NCSs were examined simultaneously: (1) Median sensory NCS; (2) segmental wrist-palm sensory NCS; (3) 4th digit latency difference; (4) 1st digit latency difference and (5) palmar mixed nerve latency difference. As "Guideline" and "Option" NCSs, we also examined: (6) Median motor distal latency and (7) second lumbrical-interossei latency difference (2LILD). Forty-nine CTS hands were divided into a milder subgroup only if action potentials could be recorded using all tests applied; that is, those with any absent potentials were excluded from the subgroup. Sensitivities and specificities were compared to each other. RESULTS: In all CTS hands, the sensitivity of test (1), (2), (3), (4), (5), (6) and (7) was 83, 87, 92, 90, 90, 70 and 92%, respectively. In the milder subgroup, it was 67, 78, 84, 82, 84, 43, and 84% in the same order. There was no statistical difference between Standard tests and 2LILD. Specificities of all tests were over 95%. CONCLUSIONS: All "Standard" tests and 2LILD have high comparable sensitivities. Therefore, 2LILD should be recommended as "Standard" NCS detecting CTS.

Swallowing appliance: intraoral reshaping prosthesis for dysphagia secondary to oral floor cancer: a pilot study.

Patients with oral floor cancer often have difficulty swallowing solid foods. The aim of this study was to improve the propulsion of solid foods using a swallowing appliance (SW-A). Subjects comprised three patients with oral floor cancer who had undergone curative surgery. Each participant was asked to swallow gelatin under three conditions: without an SW-A, with a maxillary SW-A, and with both maxillary and mandibular SW-As. This procedure was repeated thrice with three volumes of gelatin (2.5, 5, and 7.5 ml), with videofluorographic swallowing study. Swallowing was assessed on the basis of whether the participant could propel the gelatin from the oral cavity to the pharynx. No subject could propel 2.5 ml of gelatin to the pharynx without an SW-A or with only a maxillary SW-A in place. When both SW-As were used, all subjects could propel all three volumes of gelatin. The mandibular SW-A complemented the compensatory effects of the maxillary SW-A.

Premotor potential study in carpal tunnel syndrome.

INTRODUCTION: Premotor potentials (PMPs) precede compound muscle action potentials evoked from the second lumbrical muscle after median nerve stimulation. Although PMP has been identified as a median sensory nerve action potential, few reports have documented the significance of PMP parameters for diagnosing carpal tunnel syndrome (CTS). METHODS: We investigated the relationships between PMP parameters and results of 6 standard median nerve conduction studies in 74 CTS hands. RESULTS: Significant correlations were noted in all comparisons. PMP conduction velocity was strongly correlated with the sensory conduction velocity between wrist and digit 2 (r(2) = 0.91). Moreover, PMP parameters were significantly correlated with neurophysiological severity of CTS. CONCLUSION: Measuring PMP parameters with a second lumbrical-interosseous study may be useful for diagnosing CTS.

Effect of low-frequency repetitive transcranial magnetic stimulation combined with physical therapy on L-dopa-induced painful off-period dystonia in Parkinson's disease.

Previous research has shown that low-frequency repetitive transcranial magnetic stimulation over the primary motor area and supplementary motor area can reduce L-dopa-induced dyskinesias in Parkinson's disease; however, it involved only patients with peak-dose or diphasic dyskinesia. We report a case of a patient with severely painful off-period dystonia in the unilateral lower limb who underwent 0.9-Hz subthreshold repetitive transcranial magnetic stimulation over contralateral primary motor area and supplementary motor area. Repetitive transcranial magnetic stimulation over the primary motor area significantly reduced the painful dystonia and walking disturbances but repetitive transcranial magnetic stimulation over the supplementary motor area did not. The cortical silent period also prolonged after repetitive transcranial magnetic stimulation over the primary motor area. At 5 mos of approximately once a week repetitive transcranial magnetic stimulation over the primary motor area, the Unified Parkinson's Disease Rating Scale motor score also improved. This report shows that repetitive transcranial magnetic stimulation over the inhibitory primary motor area can be useful for rehabilitating patients with Parkinson's disease with off-period dystonia and suggests that this treatment should be further verified in such patients.

Suprahyoid muscles motor evoked potentials in response to transcranial magnetic stimulation.

OBJECTIVE: The objective of this study was to reveal whether corticobulbar projection to the suprahyoid muscles (SHM) is contralateral or bilateral. METHODS: Thirty-nine healthy subjects between 27 and 77 years of age participated. All subjects underwent transcranial magnetic stimulation (TMS) in both cerebral hemispheres using surface EMG recording in bilateral SHM. One subject underwent TMS in cerebral hemisphere at the same time using needle and surface EMG recording in the contralateral and ipsilateral SHM. Eight subjects underwent TMS in both cerebral hemispheres using surface EMG recording in bilateral SHM, within 6 months of the first day. RESULTS: We obtained larger response in contralateral SHM than in ipsilateral SHM in the surface EMG recording. However, in the needle EMG recording, only contralateral SHM responses were evoked. TMS of either hemisphere evoked contralateral SHM motor-evoked potentials (MEPs) in all subjects [SHM latency: (left) 8.5 ± 0.9 ms, (right) 8.6 ± 1.1 ms]. There was no significant difference in latency between the first and second tests. In a case of right medullary infarction with left cortical stimulation, MEPs of right SMH were absent. CONCLUSION: Corticobulbar projections to the SHM appear to be dominated by contralateral projections in healthy adults.

The relationship between coronary plaque characteristics and small embolic particles during coronary stent implantation.

OBJECTIVES: We investigated the relationship between coronary plaque components and small embolic particles during stenting and examined the influence on the coronary microcirculation. BACKGROUND: In vivo tissue characterization of atherosclerotic plaques was introduced by the Virtual Histology intravascular ultrasound (VH-IVUS) system (Volcano Therapeutics, Inc., Rancho Cordova, California). METHODS: The study consisted of 44 patients who underwent elective coronary stenting. Plaque characteristics were identified with VH-IVUS, and small embolic particles liberated during stenting were detected as high-intensity transient signals (HITS) with a Doppler guidewire. Coronary flow velocity reserve (CFVR) was also measured before and after stenting. RESULTS: Patients were divided into the tertiles according to the HITS counts: the lowest, HITS <5 (n = 16); the middle, 5 to 12 (n = 15); and the highest, >12 (n = 13). Dense calcium and necrotic core area identified with VH-IVUS were significantly larger in the highest tertile (lowest vs. middle vs. highest; dense calcium: 0.2 +/- 0.3 mm2 vs. 0.3 +/- 0.6 mm2 vs. 0.8 +/- 0.7 mm2, p = 0.007; necrotic core: 0.5 +/- 0.4 mm2 vs. 0.9 +/- 0.9 mm2 vs. 1.8 +/- 1.0 mm2, p < 0.001, respectively). Multivariate logistic regression analysis revealed only necrotic core area was an independent predictor of high HITS counts (odds ratio 4.41, p = 0.045). Furthermore, there was a significant negative correlation between the HITS count and CFVR after stenting (r = -0.35, p = 0.017). CONCLUSIONS: The necrotic core component identified with VH-IVUS is related to liberation of small embolic particles during coronary stenting, which results in the poorer recovery of CFVR.

Effects of intra-aortic balloon counterpulsation on coronary pressure in patients with stenotic coronary arteries.

BACKGROUND: The benefits of intra-aortic balloon pumping (IABP) usage reportedly occur through systolic unloading of the left ventricle and the augmentation of diastolic coronary flow. The aim of this study was to assess the change in intracoronary pressure distal to the coronary stenosis after the IABP by using an intracoronary pressure wire. METHODS: Hemodynamic variables and intracoronary pressure data were measured in 16 patients requiring IABP for clinical indication (11 vessels with coronary stenosis and 5 normal vessels were enrolled). Coronary pressure was measured directly in each vessel with and without IABP support. RESULTS: The diastolic aortic pressure during IABP increased compared with that without the IABP (97.9 +/- 11.7 vs 80.3 +/- 10.7 mm Hg, P < .01). The systolic aortic and intracoronary pressure during the IABP decreased (aortic pressure: 83.8 +/- 10.4 vs 95.9 +/- 11.3 mm Hg, P < .01, intracoronary pressure: 67.6 +/- 16.5 vs 76.2 +/- 20.4 mm Hg, P < .01). The diastolic distal coronary pressure (Pd) increased during the IABP in healthy coronary arteries (87.3 +/- 4.8 vs 72.1 +/- 10.3 mm Hg, P < .05). However, Pd in stenotic coronary arteries with the IABP did not increase statistically compared with those without the IABP (44.0 +/- 21.3 vs 42.8 +/- 17.9 mm Hg). There was a significant correlation between the change in Pd after IABP insertion and percent diameter stenosis calculated by quantitative coronary angiography (r2 = 0.51, P < .001). CONCLUSIONS: In the presence of a critical coronary stenosis, the IABP does not increase the diastolic coronary pressure distal to the stenosis. Thus, the major effect of IABP on high-risk patients with severe coronary stenosis may relate to the reduction of oxygen demand by systolic unloading more than diastolic augmentation of the coronary flow.

Heterogeneity of myocardial perfusion in distal coronary embolism with different particle sizes.

BACKGROUND: We hypothesized that altered myocardial perfusion distribution patterns could be seen with coronary distal emboli of different particle sizes using myocardial contrast echocardiography. METHODS: In 16 open-chest anesthetized dogs, microsphere suspensions of 9 or 500 microm in diameter were injected into the left anterior descending coronary artery until the mean left anterior descending coronary artery flow rate was reduced to less than 30% of baseline flow. During baseline conditions and after maximal embolization, real-time myocardial contrast echocardiography was performed by intravenous infusion of an echocontrast agent. RESULTS: In animals infused with 9-microm microspheres, a transmural perfusion defect was seen at the time of maximal embolization. In contrast, in animals infused with 500-microm microspheres, a subendocardial perfusion defect was observed. CONCLUSIONS: The particle size of coronary distal emboli affects myocardial perfusion distribution.