Anatomic Narrowing Research Articles

Acoustic pharyngometry patterns of snoring and obstructive sleep apnea patients

Objective Anatomic narrowing of the pharyngeal airway increases the relative negative pressure generated during inspiration, thus affecting the dynamic behavior of the upper airway. The aim of this work was to measure pharyngeal area in snoring patients with and without obstructive sleep apnea (OSA), as categorized by polysomnography and by acoustic pharyngometry, and to analyze the different curve patterns obtained from patients of both groups. Methods We examined 50 snorers who were divided into 2 groups matched for age, gender, and body mass index. Results Mean Apnea Index (AI) in nonapneic snorers (group 1) was 4, and mean pharyngeal area was 2.41 cm 2. In snoring patients with OSA (group 2), mean AI was 25.9 with a mean pharyngeal area of 1.589 cm 2 ( P < 0.001). In both groups, the dependent variable (AI) can be predicted from a linear relation with the independent variable (pharyngeal area) with normality and constant variance tests passed. In group 1, the resulting curve can be 1 of 2 types depending on the relative area of the pharyngeal segment to the velopharyngeal area. In group 2, the curve pattern can be categorized into 3 patterns depending on the possible pathology of pharyngeal obstruction. Conclusion The acoustic reflection technique is reproducible, noninvasive, and free from potential side effects. The good correlation between AI and pharyngeal area adds to the potential of acoustic pharyngometry. Careful study of the pharyngeal cross-sectional area and curve topography may give a good idea about the site of upper airway obstruction.

Techniques of foreign body removal in infants and children

Foreign body ingestions are common in pediatric patients and represent a challenge for the pediatric endoscopist. The most common objects ingested by children in the United States are coins, although toys and batteries account for a significant fraction of ingestions. The timing of and requirement for endoscopy is based on the type of foreign body ingested, its location, and the presence or absence of symptoms. In some cases, ingested foreign bodies require urgent removal even in asymptomatic patients. This is the case for example, with esophageal batteries. In smaller pediatric patients, the size of the foreign body is an important factor in determining the timing and requirement for endoscopy and the management may differ as compared to adults. Areas of anatomic narrowing or disease may be an underlying reason why a foreign body becomes lodged and endoscopists are cautioned against blindly advancing a foreign body or meat impaction distally. Various techniques and endoscopic equipment are used to remove ingested foreign bodies in children including specialized forceps, baskets, snares, and friction fit adaptors and these are discussed.

Canalicular stenosis secondary to weekly versus every-3-weeks docetaxel in patients with metastatic breast cancer

Purpose To compare the frequency of canalicular stenosis as a side effect of weekly versus every-3-weeks docetaxel in patients with metastatic breast cancer. Design Retrospective nonrandomized comparative trial. Patients and methods Eighteen patients enrolled in a phase II study of weekly docetaxel plus trastuzumab and 18 patients enrolled in a phase II study of every-3-weeks docetaxel plus doxorubicin were evaluated. Each patient underwent a comprehensive ophthalmologic examination, probing and irrigation of the nasolacrimal duct, and, in some instances, a nuclear lacrimal scan. Main outcome measures If epiphora (excessive tearing) was reported by the patient, its time of onset was documented. In patients with epiphora, presence or absence of canalicular stenosis was evaluated on the basis of the findings on probing and irrigation. The duration of treatment with docetaxel, the dose frequency, and the cumulative dose of docetaxel were recorded in each case. Results Fourteen patients (77%) receiving weekly docetaxel plus trastuzumab had epiphora. Nine of these patients had significant anatomic narrowing of the canaliculi. Bicanalicular silicone intubation or dacryocystorhinostomy was recommended in all nine patients. Eight patients underwent surgery and experienced complete or near complete resolution of epiphora. Although two patients (11%) receiving every-3-weeks docetaxel plus doxorubicin reported transient symptoms of epiphora, neither patient was found to have narrowing of the canaliculi, and the epiphora was not severe enough to justify surgical intervention. The mean duration of docetaxel therapy for the patients in this study was 19 weeks. The mean cumulative dose of docetaxel was higher in patients with canalicular stenosis than in patients without this side effect. Conclusions Canalicular stenosis was more common in patients receiving weekly docetaxel than in those receiving every-3-weeks docetaxel for metastatic breast cancer. Bicanalicular silicone intubation early in the course of weekly docetaxel therapy should be considered, because this intervention can prevent complete closure of the canaliculi. Once complete or near complete stenosis of the canaliculi occurs, placement of a permanent Pyrex glass tube may become necessary to overcome the blockage of tear outflow.

Canalicular stenosis secondary to weekly docetaxel: a potentially preventable side effect

BackgroundThe purpose of this study was to describe canalicular stenosis as a mechanism for epiphora (excessive tearing) secondary to weekly docetaxel. Patients and methodsFourteen patients with metastatic breast cancer who developed epiphora during weekly docetaxel therapy underwent an ophthalmologic examination, and probing and irrigation of the nasolacrimal ducts. The total duration of docetaxel therapy, the duration of treatment at the time of onset of epiphora, the number of infusions, the cumulative dose of docetaxel and the severity of canalicular stenosis were recorded. ResultsAll 14 patients had anatomic narrowing of the canaliculi as the underlying mechanism for epiphora. Bicanalicular silicone intubation or dacryocystorhinostomy (DCR) was recommended for all 14 patients. Eleven patients underwent surgery and experienced resolution of their symptoms. The three patients who declined surgery continue to have epiphora at the time of this report. ConclusionsCanalicular stenosis is an underlying mechanism for epiphora in patients receiving weekly docetaxel. Bicanalicular silicone intubation should be considered early in the course of weekly docetaxel therapy to prevent complete closure of the canaliculi. Once complete or near complete stenosis of the canaliculi occurs, DCR with a permanent pyrex glass tube placement may become necessary to overcome the blockage of tear outflow.

Decompression of Multiple Peripheral Nerves in the Treatment of Diabetic Neuropathy: a Prospective, Blinded Study

Background: Diabetic neuropathy traditionally is considered progressive and irreversible, and will result in lower extremity ulceration and amputation in a segment of the diabetic population despite the best efforts to control serum glucose levels. Restoration of sensation to the diabetic may prevent these complications of neuropathy. The present study was designed to evaluate whether decompression of a peripheral nerve at a known site of anatomic narrowing can restore sensibility to that nerve in the diabetic.

Limitations of Doppler echocardiography for the post-operative evaluation of aortic coarctation

Doppler blood flow measurements and derived pressure differences, through the Bernoulli equation, are used in the diagnosis of aortic coarctation, a congenital stenosis distal to the left subclavian artery. Doppler velocities remain elevated at the coarctation site after successful repair of coarctation, leading to high Doppler derived pressure differences without significant arm–leg pressure differences. We studied this apparent contradiction of two diagnostic methods, in vivo using patient and control data, and in vitro using a hydraulic model. Clinical and echocardiographic data from 31 patients, aged 13.0±4.0, 10.5±4.7 yr after coarctectomy by end-to-end anastomosis, and 18 age-matched healthy subjects were reviewed. Doppler peak velocities at the aortic isthmus were elevated in patients (2.2±0.4 vs. 1.2±0.2 m/s, P<0.001), corresponding to significant Doppler differences (20±7 mmHg), however, without significant arm–leg pressure differences. In all patients, a mild anatomic stenosis could still be observed. Local stiffness was increased. The hypothesis that the less distensible surgical scar in post-coarctectomy patients leads to a significant dynamic obstruction in systole was validated in a latex model of the aorta. Rigid rings (0.5–1.5 cm), matching the unloaded aortic diameter, were mounted around the aorta. Under loading conditions, Doppler peak velocities increased by 40±7%, yielding Doppler differences of 21±3 mmHg, without a significant pressure drop. An alternative expression to calculate pressure differences, using both velocity and geometric information, was validated in the model. In conclusion, post-operatively, Doppler velocities remain elevated due to a mild anatomical and significant dynamic narrowing, but the specific geometry, resembling a tubular hypoplasia rather than an abrupt stenosis, permits an almost complete pressure recovery explaining the occurrence of Doppler differences in disagreement with the negligible arm–leg pressure difference.

Fixed region of nondistensibility after coarctation repair: In vitro validation of its influence on Doppler peak velocities

After coarctectomy, local loss of distensibility is noted in addition to mild anatomic narrowing. We hypothesize that the increased Doppler peak velocities measured at the aortic isthmus in these patients partly reflect obstruction secondary to the stiff surgical scar. The hypothesis was studied in a pulsatile hydraulic model. Thirty-one patients (13.0 ± 4.0 years of age), 10.5 ± 4.7 years after coarctectomy by end-to-end anastomosis, were studied clinically and echocardiographically. Indexes of distensibility were calculated. The effect of isolated increased stiffness was studied in vitro with a stiff and a compliant 1:1 scale latex model of the aorta mounted in a pulsatile full-scale circulation loop. Local stiffening was obtained by a rigid ring mounted around the aorta, fitted to the dimension of the unloaded aorta. For different pressure and flow regimens, pressures and Doppler velocities were measured across the ring. Mean peak velocities at the surgical scar were 2.2 ± 0.4 m/s. Mild anatomic stenosis was present. All distensibility indexes indicated locally increased stiffness (P <.001). In the stiff latex model, Doppler peak velocities increased from 1.89 ± 0.04 m/s to 2.32 ± 0.06 m/s (P <.03); in the compliant model, from 1.15 ± 0.03 m/s to 1.79 ± 0.05 m/s (P <.001). The increase of Doppler peak velocities depends on model compliance only and is independent of flow rate, length of the noncompliant segment, and viscosity of the perfusion fluid. Velocities do not change when semicircular stiffening is applied. We have demonstrated in vitro that isolated local nondistensibility leads to vessel narrowing during vascular distension. The relative contribution of local scar stiffness in the increase of Doppler peak velocities after coarctectomy was hereby assessed. (J Am Soc Echocardiogr 2001;14:580-7.)

Results of Decompression of Peripheral Nerves in Diabetics: A Prospective, Blinded Study

Diabetic neuropathy traditionally is considered progressive and irreversible and will result in lower extremity ulceration and amputation in a segment of the diabetic population, despite the best efforts to control serum glucose levels. Restoration of sensation to the diabetic may prevent these complications of neuropathy. The present study was designed to evaluate whether decompression of a peripheral nerve at a known site of anatomic narrowing can restore sensibility to that nerve in the diabetic. Twenty diabetic patients (14 type I, 6 type II, with a mean duration of diabetes of 14.8 years) had surgical decompression of a median nerve at the wrist and an ulnar nerve at the elbow, or a decompression of the posterior tibial nerve at the ankle (total of 31 nerves). A therapist, in a manner blind to the operative site, evaluated two-point discrimination in the pulp of the appropriate digit. The postoperative sensibility was compared with that of the nontreated, contralateral extremity. At a mean of 23.3 months, 69 percent of the lower-extremity nerves and 88 percent of the upper-extremity nerves (79 percent overall) had improvement in sensibility. In comparison, 32 percent of the control (not decompressed) contralateral nerves had measurable progression of neuropathy. The hypothesis that decompression of a peripheral nerve in the diabetic will improve sensibility was confirmed at the p < 0.001 level. (Plast. Reconstr. Surg. 106: 816, 2000.)

From simple snoring to sleep apnea syndrome--clinical spectrum

About 40% of adults are habitual snorers. 2% of women and 4% of men between 30 and 60 years of age present additional sleep disordered breathing. There is a continuous spectrum from simple to disease-causing snoring ranging from merely disturbing noises to pharyngeal obstructions and breathing pauses. Repetitive episodes of upper airway obstructions lead to frequent arousals from sleep. Sleep fragmentation is responsible for non-refreshing sleep and subsequent excessive daytime sleepiness resulting in reduced performance at work, social problems and a higher risk for accidents. Furthermore there is a correlation between arousals and cardiovascular abnormalities. Anatomic narrowing of the upper airway or hypotonia of the orpharyngeal dilator muscles favour collapse of the oropharyngeal walls. Obstructive sleep apnea syndrome is characterized by repetitive oxyhemoglobin desaturations during sleep recorded by pulseoximetry. Polygraphy quantifies the average number of apneas and hypopneas which occur during one hour of sleep (apnea-hypopnea index = AHI). In upper airway resistance syndrome (= UARS), upper airway resistance is increased, but pharyngeal obstruction is not complete. Saturation doesn't decrease significantly, but arousals with consecutive sleep disruption still occur. Polysomnography is a comprehensive study including EEG-, EOG- and EMG-recordings. Sleep stages and events can be scored to evaluate sleep architecture, sleep efficiency and sleep fragmentation.

Diagnosis of sleep apnea syndrome--role of family practitioner

The obstructive sleep apnea syndrome is a highly prevalent and underdiagnosed disease. Repetitive arousals due to upper airway obstruction lead to hypersomnia. Due to the insidious onset, patients often underestimate the severity of their symptoms. Relatives can give helpful additional informations and should be involved in history taking and motivation for treatment. In general, GP's are confronted with the problem of fatigue and hypersomnia in the first line. They play the most important role in selecting patients for further investigations. The patient history helps to separate hypersomnia from fatigue. Hypersomnia indicates falling asleep at daytime in unappropriate situations, especially when the subject is passive. Often, a multidisciplinary approach including respiratory physicians, ENT specialists, orthopedic dentists and neurologists is warranted. Anatomic narrowing of the upper airway must be ruled out by clinical investigation. Overnight sleep studies detect apneas/hypopneas and repetitive arousals. Continuous positive airway pressure, applied by a nose mask and a flow generator remains the mainstay of therapy. Motivation, counseling and troubleshooting especially in the beginning of this therapy are of outmost importance. Ongoing research aims to improve comfort of nose masks and optimize function of flow generators.

Upper airway collapsibility and cephalometric variables in patients with obstructive sleep apnea.

Increased pharyngeal collapsibility and abnormal anatomic structures have been postulated to contribute to the pathophysiology of obstructive sleep apnea (OSA) syndrome. It is unclear whether the abnormal craniofacial and soft tissue features may affect the pharyngeal collapsibility and contribute to the apnea density. In the present study we examine the relationship between pharyngeal collapsibility and cephalometric variables in a group of 57 male OSA patients. Pharyngeal collapsibility was measured during the night of nasal continuous positive airway pressure (nCPAP) titration by analyzing the pressure-flow relationship. Pharyngeal critical pressure (Pcrit) was calculated as the extrapolated pressure at zero flow. The patients, age 52.0 +/- 9.0 yr, had an average apnea-hypopnea index (AHI) of 72.6 +/- 31.8 and a mean Pcrit of 2.4 +/- 1.0 cm H(2)O. A significant correlation was found between Pcrit and the soft palate length (SPl) (r = 0.27, p = 0.04), the distance from the hyoid bone to the posterior pharyngeal wall (H-Ph) (r = 0. 29, p = 0.03), and the distance from the hyoid bone to posterior nasal space (H-Pns) (r = 0.32, p = 0.02). While in obese patients Pcrit was related to SPl and neck circumference, the distance of the hyoid bone to the mandibular plane (H-MP) affected Pcrit in nonobese patients. Our results show that both pharyngeal soft tissue abnormalities and the lower position of the hyoid bone affect Pcrit in OSA patients, suggesting that an anatomic narrowing contributes to the upper airway collapsibility.

Jugular foramen syndrome caused by varicella zoster virus infection in a patient with ipsilateral hypoplasia of the jugular foramen

We report a patient with acute cranial polyneuropathy with unilateral involvement of the ninth, tenth, and eleventh cranial nerves. Although this patient lacked a typical cutaneous herpetic manifestation, elevated levels of IgM and IgG antibodies to varicella zoster virus (VZV) in both the serum and cerebrospinal fluid confirmed the clinical diagnosis of VZV infection and zoster sine herpete. Coexisting hypoplasia of the ipsilateral jugular foramen was detected using three-dimensional, surface-rendering displays reconstructed from the cranial helical CT scan. The patient recovered almost completely following treatment with an anti-inflammatory corticosteroid. Anatomical narrowing of the jugular foramen in this patient may have contributed to entrapment of the affected nerves at their passage through the foramen.

BLOOD FLOW IN RAT CAROTID ARTERY AFTER MECHANICAL INJURY

Introduction. Reactive neointimal proliferation following mechanical injury in rat carotid artery is a commonly used animal model for postangioplasty restenosis. The majority of studies dealing with prevention of restenosis use the anatomical index of neointimal area as the only indicator for success of intervention. The goal of our study is to characterize blood flow in injured carotid arteries. Such information will provide an essential data to be used in studies of the effects of vasoactive anesthetic drugs given to patients with carotid artery stenosis. Methods. The left common carotid artery of 24 Sprague-Dawley rats weighting 350-450 g was injured by three passages of inflated 2F Fogarty catheter under general anesthesia. Blood flow was assessed in the common carotid artery before injury and 30 min after injury. The rats were recovered and a second operation was performed at different time points to study flow in the injured artery. Measurements were performed at 4, 7, 14 and 21 days after injury. For flow measurements an Ultrasonic Blood Flowmeter (Transonic Systems Inc., USA) with microcirculation probe 1RB was used. We also measured flow in other 8 rats at 14 days after injury and compared the flow in the injured artery to the right, uninjured, common carotid artery. Degree of anatomical narrowing was determined by ratio of neointima area to media area (I/M), measured by morfometric computerized planimetry. Results. (Table 1)Table 1Reduction in flow was found immediately after injury and was followed by slow rise in flow to up to 80% of baseline. In the 8 rats studied at 14 days flow in the left common carotid artery was 62% of the flow value in the right uninjured common carotid artery. Neointimal proliferation was not found at the 4th day and only in two rats at 7th day. Significant proliferation was observed at the 14th and 21st day, I/M ratio was 1,28 +/- 0.6 and 1,17 +/- 0.1 accordingly. Discussion. Blood flow in rat carotid artery continued to rise progressively up to 21st day after mechanical injury despite progressive neointimal proliferation and lumen narrowing. Characterization of blood flow in the narrowed rat carotid arteries may serve as a potent research tool for the study of vasoactive anesthetics.

Mechanical properties of the upper airway

Abnormalities of upper airway mechanical properties are a well-recognized and important feature of the pathophysiology of the obstructive sleep apnea hypopnea syndrome (OSAHS). Recently, investigations enhanced our understanding of the factors that promote upper airway obstruction. In patients with OSAHS, anatomic narrowing of the pharyngeal airway, particularly in the lateral dimension with thickening of the lateral pharyngeal walls, is present. In addition, the passive upper airway (absent muscle activity) demonstrates increased collapsibility, which is modulated by caudal tracheal traction, mucosal surface forces, route of breathing, and the balance of intraluminal airway and extraluminal tissue pressures. In patients with OSAHS, pharyngeal dilator muscles (including the genioglossus and soft palate muscles) demonstrate a coordinated pattern of increased muscle activity while awake compared with normals. This is thought to represent a neuromuscular compensatory mechanism for the anatomically narrow, more collapsible upper airway. With the onset of sleep, the reflexes that drive this muscular compensation are diminished, leading to reduced muscle activity and predisposing the OSAHS patient to pharyngeal collapse. Better understanding of the mechanical properties of the upper airway in normals and patients with OSAHS should help in the development of new therapeutic strategies.

Why should we enlarge the pharynx in obstructive sleep apnea?

Patency of the collapsible segment of the pharynx is dependent upon the interplay of anatomic and physiologic factors. The upper airway of the typical patient with obstructive sleep apnea (OSA) is structurally narrowed by fat deposits in the lateral pharyngeal walls. During wakefulness, the upper airway dilator muscles compensate for the structurally reduced pharyngeal size by increasing their activity, thereby pulling the tongue and soft palate forward. As a consequence, the cross-sectional area is relatively preserved, but the shape of the pharynx becomes elliptical along the anteroposterior axis. In the awake patient with OSA, patency of the pharynx is largely dependent upon increased dilator muscle activity. During sleep, the activity of the muscular apparatus of the pharynx decreases causing a critical narrowing. Because anatomic narrowing appears to be a basic feature, enlarging the pharynx should be beneficial, particularly if its lateral diameter can be increased. Whereas facial advancement surgery structurally increases the anteroposterior diameter of the pharynx, thereby accounting for the good results reported with this technique, it is doubtful that uvulopalatopharyngoplasty has a similar effect on either the anter-oposterior or lateral diameters of the pharynx.

Arm-leg pressure gradients on late follow-up after coarctation repair. Possible causes and implications.

Seventeen years after coarctation repair, 36 patients were studied by magnetic resonance imaging and exercise testing to measure residual anatomical stenosis and hormonal response to exercise, and to evaluate their effect on arm-leg gradients and on exercise hypertension. The systolic arm pressure, leg pressure and arm-leg gradient were measured at rest and during exercise. Active renin and catecholamines were measured in the plasma at rest and after peak exercise. On magnetic resonance imaging 18 patients had residual stenosis of less than 30% (group I) and 18 had residual stenosis of equal to or more than 30% (group II). At peak exercise, the arm pressure was 235 (133-296) mmHg in group I and 241 (157-286) mmHg in group II (ns), the leg pressure was 138 (111-173) mmHg in group I and 114 (75-154) mmHg in group II (P = 0.002). The adrenalin increase from rest to exercise was 32.7 +/- 9.1 pg.ml-1 in the patients with exercise hypertension and 3.1 +/- 4.7 pg.ml-1 in the patients who remained normotensive during exercise (P = 0.02). In conclusion, residual anatomical stenosis leads to a pressure drop in the legs, which influences the arm-leg gradient. Arm hypertension is not related to anatomical narrowing but to interaction of enhanced sympathetic nerve activity and structural and functional abnormality of the precoarctation vessels.

Preferential flow to the right pulmonary artery after an early arterial switch procedure

AbstractDespite early arterial switch repair of complete transposition of the great vessels, significant physiologic aberrations may still occur. Two cases of vascular disease in the left pulmonary arterial system are described and potential mechanisms are discussed. We conclude a small number of children with simple transpostion may develop asymmetric patterns of pulmonary blood flow without evidence of anatomic narrowing of either arterial vessel.

Correlation of symptoms, myocardial perfusion imaging, and anatomic narrowing of the left anterior descending artery

The use of myocardial perfusion imaging in assisting clinical decisions in patients with known coronary artery disease is well documented. Occasionally myocardial perfusion imaging may be also useful in patients with other causes of chest pain syndromes.

Upper Airway Patency and Nocturnal Desaturation in Habitual Snoring and Obstructive Sleep Apnea: Pathogenesis of Sleep-Related Breathing Disorders

Sixty patients, 53 men and 7 women, referred for excessive snoring or suspected sleep apnea syndrome were analyzed by polysomnography, Mueller maneuver, cephalometric roentgenography, and pulmonary function testing, to evaluate the contribution of static and dynamic upper airway obstruction in the pathogenesis of sleep-related breathing disorders and OSAS. Desaturation index and maximal desaturation were used in the analysis as indicators of severity of sleep-related breathing disorders. Body Mass Index, increased collapsibility at the base of the tongue by the Mueller maneuver, increased distance between hyoid and mandibular plane, and increased soft palate diameters by cephalometry as well as a decreased peak inspiratory flow by pulmonary function testing were found to be related to increased oxygen desaturation parameters. In a multivariate analysis the significant obstruction parameters could explain only 37% of the variability of maximum desaturation and 31% of the variability of desaturation index, 63 and 69%, respectively, must therefore be explained by other mechanisms. We conclude that instability of respiratory and muscular control, possibly enhanced by sleep-phase-related changes, is more important in the pathogenesis of sleep-related breathing disorders than pure anatomic narrowing of the airway.

Quantification of collateral blood flow in coarctation of the aorta by velocity encoded cine magnetic resonance imaging.

Knowledge about the volume of collateral flow provides insight into the severity of coarctation of the aorta and may be critical in planning the operative approach. There is currently no method for the quantification of collateral flow in coarctation of the aorta. In this study, we applied velocity encoded cine magnetic resonance imaging (VENC-MR) to establish the flow pattern and volume of collateral flow in the descending thoracic aorta in normal subjects and patients with coarctation, introducing a new possibility to quantify the severity of the coarctation by determining the amount of collateral flow. VENC-MR was used to measure flow in the proximal and distal descending thoracic aorta in 10 normal subjects. In 23 patients with coarctation, flow was measured near the coarctation site and above the diaphragm. Patients were divided into a group with moderate to severe coarctation and a group with mild coarctation on the basis of clinical gradient between upper and lower extremities and the estimation of the gradient across the coarctation by Doppler echocardiography. The gradient across the coarctation and the degree of anatomic narrowing were also assessed by MR imaging. In normal volunteers, VENC-MR showed a 7 +/- 6% decrease in total flow, from proximal to distal aorta. The interobserver reproducibility was 3.9% to 4.9% (mean, 4.4%). In patients with moderate to severe coarctation, VENC-MR demonstrated an 83 +/- 50% increase in total flow from proximal to distal aorta, yielding a significant change compared with normal subjects (P < .01). Patients with mild coarctation showed a normal flow pattern and no significant change in total flow. There was a significant relation between the amount of flow increase in the distal aorta and the reduction in luminal diameter at the coarctation site (r = .94) as well as the clinical gradient (r = .84). This study shows the normal flow pattern in the descending thoracic aorta and its reversal in coarctation due to collateral flow. Thus, VENC-MR can measure collateral flow in coarctation and serves as a unique method for providing this important measurement of the severity of coarctation of the aorta.