Degenerative Stenosis Research Articles

VERTEBRAL BODY REPLACEMENT SYSTEMS WITH EXPANDABLE CAGES IN THE TREATMENT OF VARIOUS SPINAL PATHOLOGIES

Vertebral body reconstruction after corpectomy has become a common surgical procedure. The authors describe a prospectively followed case series of patients treated with expandable cages for various indications. Sixty patients underwent single or multilevel corpectomy for degenerative stenosis (13 patients), herniated disc (7 patients), deformity (14 patients), traumatic fracture (3 patients), infection (1 patient), or tumor (22 patients). Six different expandable vertebral body systems were used in the cervical spine (41 patients), thoracic spine (15 patients), and lumbar spine (4 patients). All patients were evaluated clinically and radiographically. Thirty-nine patients underwent single-level corpectomy, 18 patients underwent two-level corpectomy, and 3 patients underwent three-level corpectomy. Anterior reconstruction alone was performed in 30 patients; circumferential reconstruction was performed in 30 patients, 9 of whom underwent reconstruction through a posterior approach only. At the time of the final follow-up examination (mean, 9 mo), the Nurick grade improved significantly. Ninety-five percent of the patients maintained or improved their Frankel score and 67% had good clinical results. The regional angulation was corrected significantly (4.0 +/- 9.0 degrees, P = 0.002), and the segment height increased significantly (3.5 +/- 8.0 mm, P = 0.002). Bony fusion was achieved in 93% of the cases. Subsidence was documented in nearly half of the patients (1.4 +/- 2.0 mm) and was reduced after circumferential fusion (0.9 +/- 1.9 mm, P = 0.08). Eighteen patients (30%) had complications and 12 patients (20%) underwent revision surgery. Expandable vertebral body replacement systems can provide solid anterior column constructs with restoration of height and sagittal alignment. Favorable clinical outcome was shown in most patients, although the complication and reoperation rates are rather high.

Congenitally corrected transposition and degenerative severe aortic stenosis

Congenitally corrected transposition is a rare cardiac anomaly characterized by the combination of discordant atrioventricular and ventriculoarterial connections. Young patients with this lesion can present with congestive cardiac failure, usually secondary to a large ventricular septal defect or pulmonary stenosis. We report here our experience with a lady aged 79, admitted to our unit because of deterioration of her congestive cardiac failure as a consequence of uncorrected congenitally corrected transposition associated with degenerative severe aortic stenosis.

Answer to the Letter to the Editor concerning “4- and 5-level anterior fusions of the cervical spine”

Answer to the Letter to the Editor concerning “4- and 5-level anterior fusions of the cervical spine”

Étude à long terme du risque de réintervention après traitement chirurgical d’une sténose canalaire lombaire

The short- and mid-term symptom-relief of surgical treatment for lumbar stenosis is generally acknowledged, but the probability of a long-term reoperation remains to be studied. The purpose of this work was to determine the long-term risk of reoperation after surgical treatment of degenerative lumbar stenosis and to search for factors influencing this probability. All patients who underwent from 1989 to 1992 surgical treatment for degenerative lumbar spine stenosis were included in this work. At last follow-up, we noted functional outcome using a specific self-administered questionnaire, patient satisfaction, lumbalgia and radiculalgia using a visual analog scale, SF36 quality-of-life, reoperation or not with time since first operation if performed and the reasons and modalities of the reoperation. The probability of reoperation was determined with the acturarial method. A Cox model was used to search for factors linked with the probability of reoperation; variables studied were: age, comorbid factors, extent of the release, posterolateral arthrodesis or not, extent of the potential fusion, use or not of instrumentation for arthrodesis. The study included 262 patients. At last follow-up, 61 patients had died a mean 3.7+/-3 years after the operation; only one of these patients had a second operation 22 months after the first. Forty-four patients were lost to follow-up at mean 6.6+/-3 years. Among these 44 patients, four had a second operation during their initial follow-up at mean 47 months. One hundred fifty-seven patients were retained for this analysis at mean 15+/-1 years follow-up. Among these 157 patients, 29 had a second operation a mean 75 months after the first. There were four reasons for reoperating: insufficient release, destabilization within or above the zone of release, development or renewed zone of stenosis, development or renewed discal herniation. The risk of a second operation was 7.4% [95% CI 4.8-11.6], 15.4% [95% CI 10.7-21.1] and 16.5% [95% CI 11.7-219] at five, 10 and 15 years respectively after the first operation. Among the risk factors studied, only one had a significant impact on reoperation: extent of the zone of release (p=0.003). Compared with a release limited to one level, the risk of reoperation after release of three levels or more was five times greater [95% CI 1.8-12.7].

Suspended Laminoplasty

Cervical laminoplasty is a recognized technique commonly used for multilevel posterior cervical decompression, and it is favored over laminectomy for maintaining spinal stability. Traditional hinge techniques, however, limit lateral exposure on one side and can limit dural exposure. The authors present their experience with a modified laminoplasty technique incorporating complete laminectomy and placement of titanium miniplate instrumentation. This method allows wide bilateral posterior decompression and unobscured dural access. Twenty-eight patients (mean age 57 years) underwent cervical laminoplasty during a 4-year period. Twenty-seven patients presented with progressive cervical myelopathy. Seventeen patients (61%) had degenerative spondylotic stenosis; nine (32%) underwent resection of an intradural neoplasm. A mean of 3.5 levels were exposed and reconstructed. The follow-up period ranged from 4 months to 4 years (mean 15 months). The mean angular extension-flexion displacement measured between C-1 and C-7 was unchanged postoperatively, with preserved mobility across laminoplasty-treated segments in all patients. The anteroposterior diameter of the spinal canal increased 3.6 mm (27.2%) postoperatively (p = 0.004). In one patient an asymptomatic postoperative kyphosis developed. There were five cases of postoperative infection. One superficial infection resolved after intravenous antibiotic therapy alone, and four deep infections required surgical reexploration. The advantages of this technique over other laminoplasty methods include wide lateral spinal canal and intradural access, as well as preserved motion with partial restoration of the posterior tension band.

Foreword

Degenerative mitral stenosis (DMS) is characterized by decreased mitral valve (MV) orifice area and increased transmitral pressure gradient due to chronic noninflammatory degeneration and subsequent calcification of the fibrous mitral annulus and the MV leaflets. The “true” prevalence of DMS in the general population is unknown. DMS predominantly affects elderly individuals, many of whom have multiple other comorbidities. Transcatheter MV replacement techniques, although their long-term outcomes are yet to be tested, have been gaining popularity and may emerge as more effective and relatively safer treatment option for patients with DMS. Echocardiography is the primary imaging modality for evaluation of DMS and related hemodynamic abnormalities such as increased transmitral pressure gradient and pulmonary arterial pressure. Classic echocardiographic techniques used for evaluation of mitral stenosis (pressure half time, proximal isovelocity surface area, continuity equation, and MV area planimetry) lack validation for DMS. Direct planimetry with 3-dimensional echocardiography and color flow Doppler is a reasonable technique for determining MV area in DMS. Cardiac computed tomography is an essential tool for planning potential interventions or surgeries for DMS. This article reviews the current concepts on mitral annular calcification and its role in DMS. We then discuss the epidemiology, natural history, differential diagnosis, mechanisms, and echocardiographic assessment of DMS.

Review and retrospective analysis of degenerative lumbosacral stenosis in 156 dogs treated by dorsal laminectomy

The medical records of 156 dogs with degenerative lumbosacral stenosis (DLS) that underwent decompressive surgery were reviewed for signalment, history, clinical signs, imaging and surgical findings. The German Shepherd Dog (GSD) was most commonly affected (40/156, 25.6%). Pelvic limb lameness, caudal lumbar pain and pain evoked by lumbosacral pressure were the most frequent clinical findings. Radiography showed lumbosacral step formation in 78.8% (93/118) of the dogs which was associated with elongation of the sacral lamina in 18.6% (22/118). Compression of the cauda equina was diagnosed by imaging (epidurography, CT, or MRI) in 94.2% (147/156) of the dogs. Loss of the bright nucleus pulposus signal of the L7-S1 disc was found on T2-weighted MR images in 73.5% (25/34) of the dogs. The facet joint angle at L7-S1 was significantly smaller, and the tropism greater in GSD than in the other dog breeds. The smaller facet joint angle and higher incidence of tropism seen in the GSD may predispose this breed to DLS. Epidurography, CT, and MRI allow adequate visualization of cauda equina compression. During surgery, disc protrusion was found in 70.5% (110/156) of the dogs. Overall improvement after surgery was recorded in the medical records in 79.0% (83/105) of the dogs. Of the 38 owners that responded to questionnaires up to five years after surgery, 29 (76%) perceived an improvement.

Transiliac Approach for Exposure of Lumbosacral Intervertebral Disk and Foramen: Technique Description

To describe and evaluate a transiliac approach to the L7-S1 disk and intervertebral foramen in dogs. Cadaver study. Fresh canine cadavers (n=10). A craniolateral approach was made to each iliac wing of 10 fresh canine mixed breed cadavers. An 18 mm hole was drilled in a standardized position through the iliac wing. The musculature connected to the cranial aspects of the sacral wing was dissected and retracted cranially through this iliac window. Endoscopic exploration of the area was performed. The foramen and intervertebral disk were clearly observed in all specimens without iatrogenic injury of the L7 nerve branch. Access to the foramen was possible in 16 of 20 specimens without excision of the sacral wing; however, it was always partially excised to observe the intervertebral disk which lies more caudally and ventrally. Transiliac approach to the lumbosacral joint allows direct exposure of the intervertebral disk and foramen through an iliac window. Endoscopic exploration provided good observation of the intervertebral disk and/or foramen. Transiliac approach could be used for lateral corpectomy and foraminotomy in dogs with degenerative lumbosacral stenosis caused by ventral or ventrolateral disk protrusion, foramen stenosis, or OCD of the L7-S1 joint. Clinical study will be necessary to evaluate the efficacy of this approach.

Biomechanical Flexion–Extension Forces in Normal Canine Lumbosacral Cadaver Specimens Before and After Dorsal Laminectomy–Discectomy and Pedicle Screw–Rod Fixation

To determine biomechanical flexion-extension forces in cadaveric canine lumbosacral specimens, before and after dorsal laminectomy with partial discectomy, and after dorsal pedicle screw-rod fixation of L7 and S1. Biomechanical cadaver study. Cadaveric spine specimens without lumbosacral pathology from mature, intact Labrador retrievers (n=12). Lumbosacral spine segments were subjected to a constant bending moment from L6 to S1 in a hydraulic 4-point bending materials testing machine. Force and displacement were recorded during each loading cycle constituting 1 complete flexion-extension cycle of the spine. Each spine segment had 3 series of recordings of 5 loading cycles each: (1) intact spine, (2) after surgical destabilization by dorsal laminectomy and partial discectomy, and (3) after surgical stabilization using dorsal pedicle screw-rod fixation. After dorsal laminectomy and partial discectomy, the neutral zone and range of motion were not different from those in the native spine specimen. After pedicle screw-rod fixation, the neutral zone and range of motion of the instrumented specimen significantly (P<.0001) decreased compared with the native specimen and the specimen after dorsal laminectomy. Dorsal laminectomy and partial discectomy does not lead to significant spinal instability in flexion and extension whereas pedicle screw and rod fixation effectively stabilizes the lumbosacral spine. Dorsal laminectomy and partial discectomy does not lead to significant spinal instability. Pedicle screw-rod fixation of L7 and S1 may be used to stabilize an unstable L7-S1 junction in dogs with degenerative lumbosacral stenosis.

A follow-up study of neurologic and radiographic findings in working German Shepherd Dogs with and without degenerative lumbosacral stenosis

To identify radiographic abnormalities associated with degenerative lumbosacral stenosis (DLSS) in German Shepherd Dogs (GSDs) and determine whether specific radiographic abnormalities could be used to identify dogs at risk of developing DLSS. Cohort study. 33 GSDs working as police dogs. Results of physical, neurologic, and orthopedic examinations were used to identify dogs with DLSS. Survey radiography of the lumbosacral junction was performed, and radiographs were compared with radiographs obtained 3 years earlier. DLSS was diagnosed in 15 of the 33 (45%) dogs. Thirteen of the 15 dogs with DLSS and 14 of the 18 dogs without DLSS had radiographic abnormalities of the lumbosacral junction. Twenty-two (67%) dogs were able to perform unrestricted duties, including 3 dogs with suspected DLSS. Six (18%) dogs had been excluded from active duty during the period of surveillance because of DLSS. Significant progression in specific clinical and radiographic signs was detected, but multiple logistic regression analysis did not identify any radiographic signs that could be used to predict the development of DLSS. Results suggested that survey radiography cannot be used to predict development of DLSS in working GSDs.

Surgical Treatment of Lumbosacral Foraminal Stenosis Using a Lateral Approach in Twenty Dogs with Degenerative Lumbosacral Stenosis

To describe clinical signs, magnetic resonance imaging (MRI) and surgical findings using a lateral approach to the lumbosacral intervertebral foramen and to evaluate clinical outcomes in dogs with or without concurrent dorsal decompression and annulectomy. Retrospective study. Dogs (n=20) with degenerative lumbosacral stenosis (DLSS). Medical records (2002-2006) of dogs that had lumbosacral lateral foraminotomy alone or in combination with dorsal decompression were reviewed. Degree of dysfunction was assessed separately for each pelvic limb; dogs with unilateral signs were included in group A, those with bilateral signs in group B. Retrieved data were: signalment, history, neurologic status on admission, 3 days, 6 weeks, and 6 months postoperatively, duration of clinical signs, results of MRI, surgical site(s), intraoperative findings, and outcome. Based on the clinical and MRI findings unilateral foraminotomy was performed in 8 dogs, bilateral foraminotomy in 1 dog, unilateral foraminotomy with concurrent dorsal decompression in 7 dogs, and bilateral foraminotomy with concomitant dorsal decompression in 4 dogs. Surgery confirmed the presence of foraminal stenosis in all dogs, with osteophyte formation and soft tissue proliferations being the most common lesions. Outcome was good to excellent in 19 dogs and poor in 1 dog. Mean follow-up was 15.2 months (range, 6-42 months). Lateral foraminotomy addresses compressive lesions within exit and middle zones of the lumbosacral foramen. Successful surgical management of DLSS is dependent on recognition and correction of each of the compressive lesions within the lumbosacral junction.

Magnetic resonance imaging – unravelling the mystery

Magnetic resonance imaging – unravelling the mystery

Assessment of Decompressive Surgery in Dogs with Degenerative Lumbosacral Stenosis Using Force Plate Analysis and Questionnaires

To evaluate the long-term outcome after decompressive surgery in dogs with degenerative lumbosacral stenosis (DLS), using force plate analysis (FPA) and owner questionnaires. Prospective clinical study. Dogs with DLS (n=31) and 24 clinically normal Labrador Retrievers. FPA was performed before surgery (31 dogs) and at 3 days, 6 weeks, 6 months (each, 31 dogs) and >or=1.5 years (12 dogs) after surgery. Peak vertical forces (Fz(+)), braking (Fy(+)), and propulsive forces (Fy(-)), and the corresponding impulses were determined. Questionnaires were completed by the owners before and at 6 months and >or=1.5 years after surgery. Fy(-) of the pelvic limbs and the ratio pelvic/thoracic of Fy(-) (P/TFy(-)) were significantly smaller in dogs with DLS than controls. Fy(-) and P/TFy(-) decreased significantly 3 days after surgery, and increased during 6 months follow-up, but with long-term follow-up the values remained the same and were smaller than controls. From questionnaires there was a significant improvement after surgery compared with function before surgery. Most owners were satisfied with outcome after surgery. Propulsive forces of the pelvic limbs in dogs with DLS are impaired and are partially restored by decompressive surgery. Owner's questionnaires illustrate that decompressive surgery restores function as perceived by owners whereas FPA continues to show impaired propulsive forces for the pelvic limbs.

Prospective analysis of clinical evaluation and self-assessment by patients after decompression surgery for degenerative lumbar canal stenosis

Background context Objective measures including neurological findings, radiographic evaluation, and the Japanese Orthopaedic Association (JOA) score are commonly used for the evaluation of surgical outcomes. Because many surgeries are performed primarily to improve quality of life, a patient's subjective evaluations are also important for accurately assessing surgical outcomes. Currently available instruments for assessing quality of life include the Short-Form 36 (F-36), the Oswestry disability index (ODI), and the visual analog scale (VAS) clinical pain scale. Purpose The aims of this study were to measure surgical outcomes by using both objective measures and subjective measures including patient self-assessments and psychological changes; to assess the adequacy of the JOA alone for measuring outcome; and to determine which measures, the SF-36v2, ODI, VAS, or JOA correlate with the VAS pain scale score in lumbar canal stenosis. Study design We performed a prospective study to measure surgical outcomes for lumbar canal stenosis using traditional objective measures such as neurological findings and subjective measures such as performance of ADLs, patient self-assessments, and psychological changes. Patient sample Forty-two surgical patients with a mean age of 66.8±10.9 years at the time of surgery were included in the study. All cases were followed for more than 2 years. Surgical indications included no response to conservative treatment and neurological deterioration. Neurological symptoms were classified as nerve root type, cauda equine type, or combined type. We performed surgical decompression at the location of the dural or root indentation by myelography. The concomitant diagnosis causing the spinal stenosis was degenerative spondylolisthesis in 20 cases undergoing posterolateral fusion with pedicle screws. Outcome measures Surgical outcomes were assessed by comparing preoperative and 24-month postoperative JOA scores for low back pain, SF-36v2, ODI-v2, and VAS scores. Statistical analysis was performed by using the analysis of variance. A p value<0.05 was considered statistically significant. Methods Objective clinical measures, patient self-assessments, and psychological changes were measured before and at 24 months postoperatively. We also examined which measurements correlated with the VAS scale for pain evaluation, thereby relating patient satisfaction to surgery outcome. Results All JOA, SF-36v2, ODI-v2, and VAS scores significantly improved postoperatively. The physical component summary (PCS) of the SF-36 v2 showed significant improvement, although all scores remained less than the Japanese norm-based scores (NBSs). The mental component summary (MCS) exhibited such a significant improvement that all postoperative subscales were higher than the Japanese NBS. JOA scores significantly correlated only with postoperative lower-extremity VAS score. All PCS and two MCS scores significantly correlated with the VAS score for low back pain. Parts of the PCS and MCS significantly correlated with the lower-extremity VAS. The ODI significantly correlated with both the preoperative and postoperative VAS scores for low back pain as well as with the postoperative lower-extremity VAS score. Conclusions The JOA, SF-36, ODI, and VAS questionnaires are all useful instruments for measuring surgical outcomes. The VAS score is a better assessment of physical rather than mental health. The ODI is more reflective of patients' subjective symptoms. Finally, the SF-36 is particularly informative because it includes questions addressing both psychological and physical status. Therefore, when combined, the SF-36v2, VAS, and ODI scores are a valuable complement to the JOA scores in evaluating outcomes of surgery for lumbar canal stenosis.

Clinical outcomes of the Dynesys dynamic neutralization system: 1-year preliminary results

In this study the authors present the preliminary clinical outcomes of dynamic stabilization with the Dynesys spinal system as part of a multicenter randomized prospective Food and Drug Administration (FDA) investigational device exemption (IDE) clinical trial. This study included 101 patients from six IDE sites (no participants were omitted from the analysis) who underwent dynamic stabilization of the lumbar spine with the Dynesys construct. Patient participation was based on the presence of degenerative spondylolisthesis or retrolisthesis (Grade I), lateral or central spinal stenosis, and their physician's determination that the patient required decompression and instrumented fusion for one or two contiguous spinal levels between L-1 and S-1. Participants were evaluated preoperatively, postoperatively at 3 weeks, and then at 3-, 6-, and 12-month intervals. The 100-mm visual analog scale was used to score both lower-limb and back pain. Patient functioning was evaluated using the Oswestry Disability Index (ODI), and the participants' general health was assessed using the Short Form-12 questionnaire. Overall patient satisfaction was also reported. One hundred one patients (53 women and 48 men) with a mean age of 56.3 years (range 27-79 years) were included. The mean pain and function scores improved significantly from the baseline to 12-month follow-up evaluation, as follows: leg pain improved from 80.3 to 25.5, back pain from 54 to 29.4, and ODI score from 55.6 to 26.3%. The early clinical outcomes of treatment with Dynesys are promising, with lessening of pain and disability found at follow-up review. Dynesys may be preferable to fusion for surgical treatment of degenerative spondylolisthesis and stenosis because it decreases back and leg pain while avoiding the relatively greater tissue destruction and the morbidity of donor site problems encountered in fusion. However, long-term follow-up care is still recommended.

DIFFERENTIAL SURGICAL TREATMENT OF CERVICAL SPINE STENOSIS

Objectives. To determine the efficacy of various procedures of precise differentiated surgical decompression for elimination of prevailing clinical manifestations of degenerative stenosis depending on a character and localization of morphological changes (degenerative or posttraumatic) in the cervical spine, the expediency and necessity of application of various fixation and stabilization techniques. Material and Methods. Eighteen patients included in the study were examined for degenerative stenosis in the cervical spine. All of them underwent decompressive surgery. International representative scales were used to estimate results depending on basic clinical syndrome. Results. The increase in latency and central sensory conduction time (according to somatosensory evoked potentials data) indicates that ischemic compression lesion is mainly caused by dorsal compression. In this case a laminectomy according to Hirabayashi was performed. The increase in central motor latency time (according to central transcranial magnetic stimulation) greater by 30 % than a norm indicates that ischemic lesion is caused by anterior vertebral artery compression. In this case a corporectomy was performed. Conclusion. Compression lesions in cervical spine stenosis have local ischemic character and correspond to blood supply basin of compromised spinal or segmental artery. There is a correlation of ischemic compression focus localization with a character of electrophysiological conduction and responses. Differential character of surgical decompression provides observation of minimal invasive principles and better neurological restoration of patients.

Agreement between computed tomography, magnetic resonance imaging, and surgical findings in dogs with degenerative lumbosacral stenosis

To assess the extent of agreement between computed tomography (CT), magnetic resonance imaging (MRI), and surgical findings in dogs with degenerative lumbosacral stenosis. Observational study. 35 dogs with degenerative lumbosacral stenosis. Results of preoperative CT and MRI were compared with surgical findings with respect to degree and location of disk protrusion, position of the dural sac, amount of epidural fat, and swelling of spinal nerve roots. A lumbosacral step was seen on radiographic images from 22 of 32 (69%) dogs, on CT images from 23 of 35 (66%) dogs, and on MR images from 21 of 35 (60%) dogs. Most dogs had slight or moderate disk protrusion that was centrally located. There was substantial or near perfect agreement between CT and MRI findings in regard to degree of disk protrusion (kappa, 0.88), location of disk protrusion (0.63), position of the dural sac (0.89), amount of epidural fat (0.72), and swelling of spinal nerve roots (0.60). The degree of agreement between CT and surgical findings and between MRI and surgical findings was moderate in regard to degree and location of disk protrusion (kappa, 0.44 to 0.56) and swelling of spinal nerve roots (0.40 and 0.50). Results indicate that there is a high degree of agreement between CT and MRI findings in dogs with degenerative lumbosacral stenosis but that the degree of agreement between diagnostic imaging findings and surgical findings is lower.

X-ray measurement of cervical spinal canal in patients with degenerative lumbar spinal canal stenosis

To investigate the mechanism of high occurrence of cervical spondylotic myelopathy in the patients with degenerative lumbar spinal stenosis and the relationship between these two diseases. Lateral radiographic plain films were made on 68 cases with degenerative lumbar spine stenosis 23 males and 45 females, aged 50.0 (22 - 69). The sagittal diameter of the spinal canal (a) was obtained by measuring the shortest distance between the middle point of the posterior margin of the cervical spinal body to the connective cortex of spinal process and vertebral lamina, the distance between the middle points of anterior and posterior margins of vertebral body was measured as the sagittal diameter of vertebral body (b), and the ratio of these sagittal diameters was calculated for the vertebral bones C3 - C7. The data of sagittal diameters of cervical spinal canal and cervical vertebral body and relevant a/b ratio value obtained from 411 healthy subjects ware used as normal controls to be compared with those of the degenerative lumbar spine stenosis patients. In the group of degenerative lumbar spinal stenosis the average value of a/b ratio of C3 - C7 were 0.781 in the males and was 0.807 in females respectively, both significantly lower than those of the healthy control group (0.874 in the males and 0.968 in the females respectively, both P < 0.05). The incidence rate of developmental cervical spinal stenosis in the group of degenerative lumbar spine stenosis was 27.9%, and that in healthy objective was 10%. Compared to the healthy objectives, the patients with degenerative lumbar spinal stenosis is easier to be inclined to the developmental cervical spinal stenosis.

Fluid mechanical and physicochemical modeling interprets hypertension to be capable of inducing secondary complications

The relationship of hypertensives and many pathological syndromes still remains unclear. A mathematical model in terms of the fluid mechanics and physicochemical analyses is established to correlate the plasma viscosity, the shear stress and the rate of shear in blood stream with the ligand-receptor dissociation constant. This model has arrived at the conclusive results that high viscosity, high rate of shear created in the blood streams, and the peripheral resistance may act as important preceding factors to induce a serial subsequent pathological clinical manifestations. High viscosity may interfere with the ligand-receptor combination, in contrast, high rate of shear may knock the ligand (s) off the existing ligand-receptor complex, while elevation of peripheral resistance may slow down the blood flow rate, resulting in a diminished dissociation of ligand-receptor complex. This model has successfully interpreted the possible cause of some post-hypertensive abnormal outcome manifestations involving obstructive and degenerative stenosis (such as renal artery stenosis), growth retardation, blood vessel detriment, coarctation of aorta, coronary thrombotics, atherosclerosis, hyperinsulinemia, diabetes, obesity, hypothyroidism, infertility, and at the worst, carcinoma, etc.

Left Ventricular Outflow Obstruction

Left ventricular outflow tract obstructions (LVOTOs) encompass a series of stenotic lesions starting in the anatomic left ventricular outflow tract (LVOT) and stretching to the descending portion of the aortic arch (Figure 1). Obstruction may be subvalvar, valvar, or supravalvar. These obstructions to forward flow may present alone or in concert, as in the frequent association of a bicuspid aortic valve with coarctation of the aorta. All of these lesions impose increased afterload on the left ventricle and, if severe and untreated, result in hypertrophy and eventual dilatation and failure of the left ventricle. LVOTOs are congenital in the vast majority of individuals younger than 50 years in the United States; some variants of subaortic obstruction are the exception. It is imperative to consider all patients with LVOTO at a high risk for developing infective endocarditis, and one should always institute appropriate measures for prophylaxis. The present article is intended as a contemporary review of the causes, manifestations, treatments, and outcomes of LVOTO; it will not address LVOTO in the pediatric population or genetic hypertrophic cardiomyopathy but will focus strictly on congenital malformations in the adult. Figure 1. Artist’s rendering of the LVOTO lesions in sequence as viewed from a superolateral orientation. A, Gradient echo cardiac MR image as viewed from the frontal projection demonstrating flow acceleration at a site of supravalvar aortic stenosis (white arrow) in a patient with Williams syndrome. The black arrow identifies the level of the unrestricted aortic valve. B, Classic radiological signs of coarctation of the aorta: rib notching (white arrows) as seen on a posteroanterior chest x-ray in a patient with coarctation of the aorta. The rib notching is caused by erosion of the inferior rib margins by dilated pulsatile posterior intercostals collateral arteries. The black arrow points to the Figure 3 silhouette that …