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Biomedical subjects

M H Friedman

Publications and source records attributed to M H Friedman.

At least 37 records · Page 2Linked to original sources
PubMed1997

Influence of the geometry of the left main coronary artery bifurcation on the distribution of sudanophilia in the daughter vessels.

The proximal portions of the left anterior descending (LAD) and left circumflex (LCx) coronary arteries are among the sites most predisposed to atherosclerotic disease. This predisposition might be a consequence of their location immediately distal to the left main (LM) coronary artery bifurcation, which may increase the susceptibility of these segments by promoting an adverse fluid dynamic environment within them. The detailed geometry of the bifurcation influences this environment and would therefore affect the susceptibility of the proximal daughter vessels to disease. This hypothesis was tested by examination of the relationship between the geometry of the LM bifurcation and the distribution of sudanophilia in the proximal portions of the LAD and LCx. The geometric parameters at the LM bifurcation, including all three angles and LM length, were obtained from multiangle photographs of 17 vascular casts by use of objective computer-based algorithms. A robust index, the relative proximal involvement (RPI), was developed to measure the localization of disease to the proximal portions of the daughter vessels. The RPI of the LAD segment correlated best with an interaction term that included the planarity of the LM bifurcation and the LCx-LAD branch angle (P = .013). In addition to supporting the concept of geometric risk factors, these observations also suggest that interactions between the hemodynamic influences of multiple geometric variables may play a role in the mediation of tissue susceptibility by geometric factors.

Adolescent↗
PubMed1996

Relationship between the geometry and quantitative morphology of the left anterior descending coronary artery.

The well established 'systemic' risk factors for atherosclerosis can explain only half of the variability in its occurrence. To account for some of the remaining variability, it was suggested that certain geometric features of atherosclerosis-prone segments ('geometric risk factors') can increase the likelihood of disease locally through their influence on the hemodynamic environment of the vessel wall. Since this mediation might elicit early morphological changes in the artery, relationships were sought between the histomorphometry and axial geometry of the left anterior descending (LAD) coronary arteries of 15 angiographically lesion-free human hearts obtained at autopsy. Geometric variables were quantified by image processing of multiplane angiograms of the hearts, and morphometry was obtained from transverse histologic sections at 91 sites. The results show that: (1) total intimal and medial area are negatively correlated with the distance from the site to the origin of the LAD; (2) the angle of the branch immediately proximal to the site is positively correlated with most of the intimal and medial variables, and appears to have a major influence on the intima; (3) the area ratio of the immediately proximal branch is correlated primarily with medial variables; and (4) local curvature is correlated only with the maximum thickness of the intima and media. These observations suggest that there are significant relationships between arterial geometry and vascular morphology prior to the development of frank disease.

Adolescent↗
PubMed1996

Head and neck pain review: traditional and new perspectives.

A variety of conditions are frequently associated with the occurrence of head and neck pain. The purposes of this review are: to describe the characteristics of several musculoskeletal, neurological, and systemic conditions frequently cited as possible causes of head and neck pain and to suggest a new technique for treating head and neck pain. The characteristics of musculoskeletal conditions, such as muscle spasm, tendinitis, trigger points, and joint inflammation, and their relationship to head and neck pain are considered. The features and clinical implications of neurologic conditions, such as atypical facial pain, trigeminal and glossopharyngeal neuralgia, reflex sympathetic dystrophy, and neurogenic inflammation, are also described. The distinguishing characteristics of headaches, including cluster, tension, chronic daily, rebound, posttraumatic, and postlumbar puncture, are detailed. This review also addresses the contributions of systemic disorders, such as osteoarthritis, rheumatoid arthritis and the variants, and rheumatoid-related conditions, like dermatomyositis, temporal arteritis, Lyme's disease, and fibromyalgia, to head and neck pain. The results of a recent pilot study of the effectiveness of intraoral circulating ice water for resolving symptoms related to head and neck pain secondary to neurogenic inflammation are presented in this work. Ice water circulating through hollow metal tubes was placed intraorally for 15 minutes in the posterior maxillary area on 12 individuals with cervical pain and muscle spasm. In nine of these individuals, reduced cervical pain perception, upper trapezius electromyography signal reduction, and increased cervical range of motion was produced. Six out of 12 individuals had accompanying headache, which was reduced or eliminated in four cases. These findings suggest a strong trigemino-cervical relationship to neck pain and headache.

Headache↗
PubMed1995

Fabrication of vascular replicas from magnetic resonance images.

Image processing and Computer Numerical Controlled (CNC) machining techniques have been used to prepare a large-than-life investment cast of an aortic bifurcation from magnetic resonance images of a replica of the vessel. The technique will facilitate experimental studies of vascular fluid dynamics and permit the in vitro reproduction of flows in living subjects.

Animals↗
PubMed1995

The effect of pulsatile frequency on wall shear in a compliant cast of a human aortic bifurcation.

A realistically compliant flow-through cast of a human aortic bifurcation was perfused with two almost identical physiological flow waves differing in pulsatile frequency. Near-wall fluid velocities were measured with a laser Doppler velocimeter at 14 sites along the flow divider and the lateral walls of the aorta and iliac arteries. The wall position at each site was tracked using a linescan camera. The temporal wall shear rate at each site was then calculated from the near-wall velocity profile and the instantaneous wall position. Increasing the frequency reduced the oscillatory component of shear rate at sites where it was greater than average, and increased it at sites where it was less, effectively reducing its site to site variability. Pulsatile frequency had no significant effect on mean shear rate at most sites. The phase shift between wall shear and radial strain was governed by the phase of the shear, and was linearly related to the extent of site dependent shear reversal. The mean shear rate was inversely related to the extent of shear reversal. If atherosclerotic development depends chiefly on mean shear rate, heart rate would not be expected to affect susceptibility, however, if only the wall sites experiencing the lowest maximum shears are vulnerable, then the effect of increasing the heart rate would seem to be beneficial.

Adult↗
PubMed1995

Atypical facial pain: the consistency of ipsilateral. Maxillary area tenderness and elevated temperature.

A consistent zone of ipsilateral tenderness adjacent to the maxillary molar root apices often is present in patients with atypical facial pain. The author performed bilateral palpation and recorded the temperature of this area on 18 consecutive patients with facial pain. He found tenderness and increased temperature on the involved side of the face in 15 and 17 patients, respectively. In two control groups of 10 patients without pain and 10 TMD patients, he observed no significant association between maxillary tenderness and increased temperature.

Body Temperature↗
PubMed1993

Relation between coronary artery geometry and the distribution of early sudanophilic lesions.

The relationship between the angle formed by the left circumflex (LCX) and left anterior descending (LAD) coronary arteries at the bifurcation of the left main coronary artery (LM) and the location of sudanophilia in the proximal portions of the LCX and LAD, was investigated, using a normalized index of disease severity (relative proximal involvement, RPI) to isolate the local effect of geometry on the predisposition to disease from that of other risk factors. Multiplane angiograms of the left coronary artery system of 15 hearts were digitized and processed to form a three-dimensional representation of the centerline of the lumen (termed the 'axis') of each coronary segment; the LM branch angle was objectively computed from the reconstruction. The coronary vessels were fixed in situ, removed from the hearts, opened longitudinally and stained with Sudan IV. The RPIs of the LAD and LCX were obtained by dividing the percentage sudanophilia seen en face in the first 1 cm of each vessel by the percentage sudanophilia in the first 5 cm. RPI was correlated negatively with LM branch angle, suggesting that a small LM branch angle may be a 'geometric risk factor' for proximal atherosclerotic disease in the daughter vessels. The correlation was stronger for the LCX than the LAD. These results would appear to be consistent with the notion that atherosclerosis is favored where a larger extent of the vessel experiences fluid dynamic wall shears near zero for an appreciable part of the pulsatile cycle.

Adolescent↗
PubMed1993

Arterial permeability dynamics and vascular disease.

There is a growing consensus that regional susceptibility to atherosclerosis correlates topographically with an increased endothelial permeability to macromolecules such as low-density lipoprotein. Earlier research suggested that increases in arterial macromolecular permeability accompany the adaptation of the endothelial lining to changes in fluid dynamic shear stress, and that permeability might therefore be chronically increased where the endothelium is exposed to a shear stress environment that changes throughout the day. Thus the temporal variability of hemodynamic stresses at the vessel wall, with time constants of many minutes or a few hours, may affect local susceptibility to disease. Changes in the hemodynamic stresses on the endothelial surface ('local' stress) result from the normal variations in more 'global' hemodynamic variables such as blood flow rate, heart rate, and flow partition at branches, that occur throughout the day in response to changes in peripheral metabolic demand. Thus, at any given time, the permeability at a site is determined by: (1) the steady-state relationship between the local permeability and local shear stress; (2) the dynamics of the permeability change induced by changes in local shear; and (3) the extent to which the shear stress at the site is affected by changes in the global variables. Regional variations in any or all of these three factors can lead to corresponding variations in endothelial permeability, macromolecular uptake and, apparently, atherosclerotic risk. Among the three factors, the first may be relatively unimportant if most transport takes place while the endothelium is responding to hemodynamic changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Closed lock. A survey of 400 cases.

Four hundred consecutive classic closed lock cases were examined. Of these, 301 were treated. Mandibular range of motion was restored by condylar distraction during jaw opening, anterior, and lateral movements. Mandibular appliances were used to prevent complete closure during healing. Of the 45 males and 355 females examined, almost all reported jaw restrictions, but 38% reported little or no pain. Secondary disorders of temporomandibular joint inflammation, muscle spasm, trigger points, and cervical dysfunction were seen on patients with temporomandibular joint pain. Of the 301 conservatively treated patients, 209 were successfully treated, 55 were moderately successful, and 37 failed. Occlusal factors did not appear as primary etiologic factors. Because all locks were preceded by clicking, treatment is recommended for clicking temporomandibular joint's that lock, however briefly, to prevent future locking. Conservative closed lock treatment is successful in many cases.

Adolescent↗
PubMed1993

Postsurgical temporomandibular joint hypomobility. Rehabilitation technique.

Specific techniques to treat temboromandibular joint (TMJ) hypomobility caused by capsular restriction are explained. Initially inflammation must be controlled. TMJ manipulation by condylar distraction during opening, protrusion, and lateral movements, and a simple stretching exercise to maintain increased mandibular range of motion, are described. Resistive opening and closing exercises at full opening to relax the lateral pterygoid muscles are prescribed. For all exercises five repetitions, repeated five times per day, are prescribed. These techniques are demonstrated in the successful treatment of a child with a presurgically and postsurgically hypomobile right TMJ.

Child↗
PubMed1993

Arteriosclerosis research using vascular flow models: from 2-D branches to compliant replicas.

A large body of evidence implicates fluid dynamic forces in the genesis and progression of atherosclerosis, the leading cause of death in the United States. To understand the mechanism by which hemodynamics influences the disease process, and to identify the specific flow variable(s) responsible for its localization, it is essential to know the distribution of hemodynamic variables in susceptible regions of the vasculature. Vascular flow models have been used more than any other means to gain insight into the details of arterial hemodynamics. The first flow models were not very realistic. Our first attempt, reported at an early Biomechanics Symposium, was probably the most unrealistic of all: a "2-D branch" that was constructed to validate a 2-D computed flow field. Most of the first models were made of cylindrical tubes, and their geometry too only approximated that of real arteries. Much was learned about the fluid dynamics in branches and bends using such models, but measurements in them could be related only generally to the fluid dynamics in living vessels. Accordingly, we began to make flow field measurements in replicas prepared from human arteries. Others challenged their glassblowers and shops to make models more representative of real vessels. These flow-through casts and fabricated models were initially rigid and perfused with Newtonian fluids. Using these more realistic systems, we and others were able to demonstrate relationships between specific hemodynamic variables and localized arterial pathology. The fidelity of flow simulations today exceeds that of only a few years ago. We now perfuse compliant replicas as small as coronary diagonal branches with fluids whose rheology mimics blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriosclerosis↗
PubMed1992

Effects of arterial compliance and non-Newtonian rheology on correlations between intimal thickness and wall shear.

A minimally diseased (mean intimal thickness = 56 microns) human aortic bifurcation was replicated in rigid and compliant flow-through casts. Both casts were perfused with physiological flow waves having the same Reynolds and unsteadiness numbers; the pulse pressure in the compliant cast produced radial strains similar to those expected from post-mortem measurements of the compliance of the original tissue. The compliant cast was perfused with a Newtonian fluid and one whose rheology was closer to that of blood. Wall shear rate histories were estimated from near-wall velocities obtained by laser Doppler velocimetry at identical sites in both casts. Intimal thickness was measured at corresponding sites in the original vessel and linear regressions were performed between these thicknesses and several normalized shear rate measures obtained from the histories. The correlations showed a positive slope--that is, the intima was thicker at sites exposed to higher shear rates--consistent with earlier results for relatively healthy vessels, but their significance was often poor. There was no significant effect of either model compliance or fluid rheology on the slopes of the correlations of intimal thickness against any normalized shear rate measure.

Aorta↗
PubMed1990

Some atherosclerosis may be a consequence of the normal adaptive vascular response to shear.

Estimates and measurements of fluid dynamic shear at the arterial wall suggest the presence of mechanisms to regulate this quantity. Arterial wall thickening prompted by chronic reductions in wall shear is one mechanism by which that regulation might be accomplished. Reduced wall shears that are a direct consequence of arterial geometry would be less susceptible to this mechanism, leading to exaggerated and focal intimal thickening, possibly leading to atherosclerosis, at affected sites. Thus some foci of vascular disease can be a natural, if undesirable, consequence of fluid shear regulation.

Adaptation, Physiological↗