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PubMed2000

Effects of TAK-044, a nonselective endothelin receptor antagonist, on the spontaneous and indomethacin- or methylene blue-induced constriction of the ductus arteriosus in rats.

We studied the effects of TAK-044, a nonselective endothelin (ET) receptor antagonist, on the indomethacin- or methylene blue-induced constriction of the ductus arteriosus (DA) in rats and compared them with the effects on spontaneous DA constriction. Injection of TAK-044 into 21-day-old fetuses in utero was performed through the uterine wall of laparotomized mother rats under light ether anesthesia. The fetuses were autopsied 3 hr after treatment with TAK-044 (10 mg/kg) in utero and simultaneous administration to the laparotomized mother rats of indomethacin (3 mg/kg, p.o.) or methylene blue (100 mg/kg, i.p.). In the second experiment, pregnant rats were decapitated on day 21 of gestation to obtain newborn rats by cesarean delivery. Newborn rats which were given TAK-044 (2, 10 mg/kg) immediately after or 1 hr before cesarean delivery were autopsied at various times after birth. In both experiments, pups were rapidly frozen in an acetone-dry ice mixture at autopsy to evaluate the DA constriction by the whole-body freezing and shaving method. TAK-044 injection into the fetus 3 hr before autopsy completely inhibited the DA constriction induced by maternal treatment with indomethacin or methylene blue. TAK-044 caused dose-dependent inhibition of the spontaneous closure of the DA after birth. The inhibitory effect was more pronounced in pups which were given TAK-044 in utero 1 hr before birth; however, the inhibitory effect was incomplete in newborn pups. These results, together with the previous finding that BQ-123, an ETA-specific receptor antagonist, inhibits the ductal constriction induced by oxygen in vitro [Coceani et al., 1992], indicate that the ETA receptor plays a significant role in the indomethacin- or methylene blue-induced DA constriction as well as in the spontaneous DA constriction after birth, and also indicate that the inhibition of ETA receptor by TAK-044 was more easily achieved in fetuses than in neonates.

Animals↗

PubMedDate not supplied

Detecting the apical constriction in curved mandibular molar roots--preflared versus nonflared canals.

BACKGROUND: Achieving and maintaining correct working length is critical to success in endodontic therapy. This involves placing the file in to the canal to feel the apical constriction, preparing the canal upto that extent and then filling the entire canal upto the apical constriction with gutta percha points. Detection of the apical constriction is affected if the coronal part of the canal is narrow or obstructed due to dentine deposition. This usually happens in curved canals and gives the operator a false feeling of the apical constriction. The aim of this study was to compare the effect on tactile detection of apical constriction in mandibular molars with curved roots, between the preflared and non-flared root canals. METHODS: This study was carried out at Armed Forces Institute of Dentistry, Rawalpindi, Pakistan, from February to April 2002. Seventy patients coming for the endodontic treatment of their mandibular first molars were selected. The study included only mandibular molars with curved mesial canals. The total no of patients were divided equally into the preflared and non-flared groups. In both groups a No. 15 K file was used to detect or feel the apical constriction but in the preflared group the coronal portion of the canal was flared/prepared using Hedstrom files (No. 25-55) and Gates Glidden Drills No. 02 to No. 05 before inserting the No. 15 file. The tooth was radiographed at this moment and the distance between the tip of the file and the radiographic apex was measured. The location of the tip was classified as: a) Within 1 mm of the radiographic apex, b) Under extended, more than 1 mm of radiographic apex, and c) Over extended, beyond the radiographic apex. RESULTS: In the non-flared group 31.4% belonged to group 'a', 40% to group 'b', and 28.57% to group 'c'. In the flared group 80% belonged to group 'a', 5.7% to group 'b', and 14.28% to group 'c'. CONCLUSIONS: Results of this study suggest that preflaring greatly improves the tactile sense to feel the apical constriction in curved canals.

Case-Control Studies↗

PubMed1994

Sequential agonist activation and site-specific mediation of acute cyclosporine constriction in rat renal arterioles.

Evidence suggests that acute and chronic cyclosporine (CsA) nephropathy may be related to its renal vasoconstrictor effects. While the mechanism of CsA-induced renal vasoconstriction is uncertain, several studies indicate that endogenous constrictor agonists including endothelins (ET), platelet activating factor (PAF), and thromboxane A2 (TXA2) play a mediating role. In this study, two possible mechanisms explaining the participation of multiple constrictor agonists in CsA vasoconstriction were investigated: sequential activation of agonists initiated by CsA and site-specific mediation of CsA constriction by different agonists. The acute constrictor effects of CsA were examined in isolated rat renal afferent (AA) and efferent arterioles (EA) without and with specific receptor antagonists of ETA (BQ123, 10(-7) M), PAF (L-659,989, 10(-7) M), and TXA2/PGH2 (SQ29,548, 10(-7) M) in the bathing media. Both BQ123 and L-659,989 completely inhibited CsA, constriction in AA, but had no significant inhibiting effect in EA. Constriction to ET-1 was also blocked by the PAF antagonist L-659,989 in AA, but not EA. There was no effect of SQ29,548 on CsA constriction in AA--however, there was partial attenuation of CsA constriction in EA. Based on these results in isolated rat renal arterioles, it is suggested that CsA-induced constriction in AA is likely mediated by sequential activation of ET and PAF. However, CsA constriction of EA involves a different mechanism or mediator that, in part, may involve TXA2/PGH2 stimulation.

Animals↗

PubMed1993

Inhibitory effects of dopamine on noradrenaline-induced constriction of arterioles in vivo in the striated cremaster muscle.

The effect of dopamine on the arterioles (50.8-95.2 microns) in the cremaster muscle was examined to determine its effect on microcirculation. Anesthetized rats were used under a light microscope connected to a videocamera. Drugs were applied using small round filter paper (370 microns in diameter) containing the drug and placed in the immediate vicinity of the arteriole on the cremaster with a micromanipulator. The dose of the drug applied was represented by concentration of the drug solution in which the filter paper was immersed. Dopamine (10(-6)-10(-4)M) induced neither constriction nor dilation of the arteriole in the cremaster. Papaverine (10(-2)M) did not dilate the arteriole. However, the arterioles were constricted by noradrenaline (10(-6)-10(-4)M) and vasopressin (10(-7)M) in a dose-dependent manner. Noradrenaline (10(-4)M)-induced constriction was blocked by concomitant application of dopamine (10(-4)M). This effect of dopamine was antagonized by SCH23390 (10(-3)M). However, isoproterenol (10(-3)M) did not affect the arteriole, nor inhibit noradrenaline (10(-4)M)-induced constriction of the arterioles. While forskolin (10(-2)M) alone did not produce constriction or dilation of the arterioles, it inhibited noradrenaline (10(-4)M)-induced constriction of the arteriole. These results suggest that dopamine prevents the constriction of the arteriole induced by noradrenaline, by activation of DA1 receptors, which activates adenylate cyclase.

Abdominal Muscles↗

PubMed1998

A method of scoring automated visual fields to determine field constriction causing blindness.

Blindness is usually defined by visual acuity criteria. Patients with markedly constricted visual fields are visually impaired even if they have good visual acuity. To our knowledge, no standardised criteria exist to determine the extent of constriction for fields done with the currently used automated static perimetry. The purpose of this study was to suggest a simple method to do so which would help in determining blindness due to field constriction. We reviewed a number of constricted visual fields obtained with Humphrey automated static perimetry. The central 30 degrees field was divided into six concentric zones. By trial and error, we devised criteria for defining visual field constriction based on absolute loss of sensitivity (< or = 0 dB) and relative loss of sensitivity (< or = 5 dB). We suggest that if a zone has at least 75% test points < or = 0 dB and no point > 10 dB, it be considered to have absolute loss of sensitivity for the purpose of defining visual field blindness. Two exceptions to this are also suggested to prevent this criterion from becoming too rigid. Examples are shown to demonstrate application of these criteria in defining blindness due to visual field constriction to < 10 degrees as suggested by the World Health Organization. Standardised determination of visual field constriction with automated perimetry could be useful in more accurate estimation of blindness in surveys, as well as in assessing eligibility for being classified as blind for legal benefits.

Blindness↗

PubMed1988

Conduction studies in peripheral cat nerve using implanted electrodes: II. The effects of prolonged constriction on regeneration of crushed nerve fibers.

Arrays of chronically implanted electrodes were used to examine the time course of elongation and maturation of peripheral nerve fibers in the cat after crush of the tibial nerve in the proximal calf. Regeneration after crush alone was compared with crush 5 mm proximal to a tight constriction of the nerve. Regeneration was monitored by the progression of excitability along the electrode arrays on the tibial and plantar nerves. The sensitivity was sufficient to record the averaged activity in single nerve fibers allowing detection of the earliest regeneration. The diameters of the fastest regenerating fibers were estimated from the conduction velocity proximal to the site of crush. Both after crush alone, and after crush constriction, small myelinated fibers regenerated in front of large fibers. The rate of elongation after crush alone was 3.2 mm/day, whereas it was slower (P less than 0.02) distal to crush + constriction (2.2 mm/day). In both lesions, the extrapolated delay to onset of regeneration was 8 days. In observations up to 300 days after crush, maturation was delayed or impaired by the constriction, and the compound nerve action potential had a smaller amplitude and a dispersed shape. Transverse sections of nerves after crush + constriction showed a diminished number of large and an increased number of small fibers compared with crush alone, possibly due to persistent branching of regenerated fibers. After both crush alone and crush + constriction, regenerated fibers had similar g ratios, suggesting that myelination developed fully in fibers of diminished diameters.

Action Potentials↗

PubMed2006

Umbilical vein constriction at the umbilical ring: a longitudinal study.

OBJECTIVE: It has been suggested that constriction of the umbilical vein (UV) at the umbilical ring has hemodynamic effects. We aimed to determine the occurrence and extent of such constriction in serial observations. METHODS: This was a prospective longitudinal study of UV velocities at the umbilicus measured at approximately 4-week intervals between 19 and 42 weeks' gestation in 129 low-risk singleton pregnancies. Each participant was examined three to five times. Multilevel modeling was used to construct the reference ranges and to test associations between variables. RESULTS: Gestational age-specific reference percentiles of UV velocities at the umbilicus were established based on 469 observations. Fetuses were able to alter the UV velocities considerably during the second half of pregnancy, signifying a varying degree of UV constriction. Of a total of 129 fetuses, 56 (43.4%) never had high UV blood velocity (i.e. > 46 cm/s, the highest quartile), 42 (32.6%) fetuses had high UV blood velocity on one occasion and 31 (24.0%) fetuses on two or more occasions. In 36 (27.9%) fetuses the UV velocity at the umbilical ring was > 300% of the mean gestational age-specific reference value at the intra-abdominal section on at least one occasion. Constriction of the UV at the umbilical ring did not affect the pulsatility of the umbilical artery, and was not associated with adverse perinatal outcome in this study. CONCLUSIONS: Low-risk fetuses may well constrict the UV at the abdominal wall with velocities extending over wide ranges on one or more occasions during the second half of pregnancy. Rather than being a risk for complications, the constriction seems to be part of physiological development and possibly a regulatory mechanism.

Adult↗

PubMed1975

Variation of proximal tubular reabsorptive capacity by volume expansion and aortic constriction during constancy of peritubular capillary protein concentration in rat kidney.

The present study was undertaken in anesthetized rats to examine the effect of aortic constriction and volume expansion on proximal tubular sodium reabsorption during constancy of flow and fluid composition in the peritubular circulation of the kidney. Efferent arterioles and branch capillaries were perfused at 625 nl/min with an artificial perfusate containing 9 g per oiter of albumin both before and during either aortic constriction or saline infusion. Results of recollection micropuncture studies in those tubules surrounded by artificially perfused capillaries were compared with results in control tubules in which the peritubular capillary flow and fluid composition were allowed to change during aortic constriction or volume expansion following saline infusion. Changes in single nephron filtration rate, fractional and absolute reabsorption induced by both aortic constriction and saline infusion were found to be qualitatively and quantitatively comparable in tubules with constant peritubular capillary microperfusion and in the control tubules with changing peritubular capillary environment due to the experimental maneuvers. Taken together, therefore, the present results indicate that with the use of the peritubular microperfusion technique no evidence is found to support a role of alteration in the peritubular environment in modulating the effect of aortic constriction or saline infusion on tubular sodium reabsorption in the rat nephron. Rather, these results provide indirect evidence in support of intraluminal factors as mediating these responses in tubular reabsorption to volume expansion and aortic constriction.

Animals↗

PubMed1983

Cardiac hypertrophy in rats after supravalvular aortic constriction. I. Size and number of cardiomyocytes, endothelial and interstitial cells.

The ascending aorta of 22 adult male Sprague-Dawley rats was constricted with a silver ring, and 25 animals were subjected to a sham-operation. The hearts, including the main arteries, were fixed by retrograde perfusion 3, 7, 14, 21 and 35 days after the operation. The cross-sectional area of the aorta was reduced by the constriction to an average of 20% of the values found after sham-operation. Twenty-one days after the constriction the weight of the left ventricular myocardium including the septum was increased 1.7-fold compared with controls. No further increase in weight was observed 35 days after the operation. The relative volumes of the tissue components remained largely constant in the subepicardial myocardium. In the subendocardial myocardium, however, the volume fraction of interstitial and, to a lesser extent, of endothelial tissue was significantly increased. Twenty-one days after constriction the estimated total volumes of the different myocardial components per left ventricle were increased 1.7-fold for heart muscle parenchyma, 1.8-fold for endothelial tissue, 2.9-fold for interstitial tissue, and 1.3-fold for capillary lumina compared with controls. At 35 days, only the interstitial tissue showed a further increase to 4.8-fold of control values. The mean cardiomyocyte volume was increased after aortic constriction in proportion to the increase in left ventricular weight, i.e. 1.7-fold over controls at 21 days. After 35 days its value was 29,500 +/- 790 micron 3 in rats subjected to aortic constriction compared with 16,800 +/- 640 micron 3 in controls. At this time the estimated number of cardiomyocytes per left ventricle showed no significant differences between experimental animals (2.9 X 10(7)) and controls (3.1 X 10(7)). Endothelial and interstitial cells were not only increased in average single cell volume (1.3-fold and 2.0-fold, respectively), but also in number per left ventricle (1.4-fold and 2.7-fold, respectively). Two-dimensional parameters indicated that during hypertrophy the capillary supply lagged behind the overall mass increase but achieved control levels on termination of hypertrophic growth at 35 days. These results show that even in pronounced hypertrophy the increase in mass of the myocardial parenchyma in the rat is due exclusively to an enlargement of cardiomyocytes (hypertrophy), whereas in endothelial and interstitial tissues enlargement of cells as well as increase in cell number (hyperplasia) also plays a role.

Animals↗

PubMed1987

The etiologic spectrum of constrictive pericarditis.

Ninety-five consecutive patients with constrictive pericarditis that was documented at the time of surgery during 1970 to 1985 were reviewed. The etiologies included idiopathic (42%), postradiotherapy (31%), post-cardiac surgery (11%), postinfective (6%), connective tissue disease-related (4%), neoplastic (3%) uremic (2%), and sarcoidosis (1%). Post-cardiac surgery etiology was seen only after 1980, but constituted 29% of cases during 1980-1985. Postradiotherapy etiology occurred with equal incidence in 1980-1985 and in 1970-1980, but the interval from radiotherapy to presentation with constrictive pericarditis was longer in the more recent period (11 vs 4.75 years). Effusive constrictive pericarditis occurred in 24% overall with similar prevalence in all of the etiologic groups except the postsurgical cases, which were caused by noneffusive fibrous constrictive pericarditis in all instances. Operative mortality was 12% overall: It was lower in the idiopathic group (8%) and higher in the postradiotherapy group (21%). Thus postradiotherapy constrictive pericarditis continues to occur despite technical changes aimed at reducing its likelihood, but recent cases have a longer latent period: and postsurgical constrictive pericarditis has emerged as an important etiology.

Adult↗

PubMed1989

Abnormal left ventricular-left atrial posterior wall contour: a new two-dimensional echocardiographic sign in constrictive pericarditis.

We measured the angle P formed by the junction of the left ventricular and left atrial posterior walls, and also the distances from the ultrasound transducer to the left ventricular posterior wall and left atrial posterior wall (DV and DA), respectively, in the parasternal long-axis two-dimensional echocardiographic view. We studied 23 normal adults and four patient groups with conditions commonly associated with left atrial dilatation: mitral regurgitation (14), mitral stenosis (16), hypertrophic cardiomyopathy (13), and constrictive pericarditis (7). Statistically significant differences were found between the constrictive pericarditis group and each of the other groups. Angle P was less than 150 degrees in 0 of 23 normal individuals, in 0 of 14 with mitral regurgitation, in 1 of 16 with mitral stenosis, in 0 of 13 with hypertrophic cardiomyopathy, and in five of seven with constrictive pericarditis. DA minus DV exceeded 20 mm in 0 of 23 normal individuals, one of four with mitral regurgitation, in 6 of 16 with mitral stenosis, in 0 of 13 with hypertrophic cardiomyopathy, and in five of seven patients with constrictive pericarditis; We conclude that angle P greater than 150 degrees suggests constrictive pericarditis; DA minus DV greater than 20 mm suggests constrictive pericarditis if mitral stenosis can be excluded.

Echocardiography↗

PubMed1994

Left atrial dilatation in constrictive pericarditis: a pre and post-operative echocardiographic study.

Thirty-three surgically proven cases of constrictive pericarditis were studied pre-operatively by echocardiography for left atrial dilatation and 18 of them underwent post-operative study at a mean follow-up period of 229 +/- 105 days. The degree of left atrial dilatation in these patients was compared with patients of restrictive cardiomyopathy (n = 8) and sex matched controls of similar age (n = 33). Significant left atrial dilatation was present in patients of constrictive pericarditis compared to controls and it was of a similar or greater degree compared to patients of restrictive cardiomyopathy (the left atrium to aorta ratio was 1.7 +/- 0.31, 1.53 +/- 0.18 and 1.07 +/- 0.1, in constrictive pericarditis, restrictive cardiomyopathy and controls, respectively, P = NS for constrictive pericarditis vs. restrictive cardiomyopathy and P < 0.001 for constrictive pericarditis vs. controls). There was no correlation of degree of left atrial dilatation with clinical and hemodynamic variables. Postoperatively, there was regression of left atrial size in patients with normal hemodynamics (n = 12, pre- vs. post-operative left atrium to aorta ratio 1.65 +/- 0.23 vs. 1.32 +/- 0.14, P < or = 0.001) and persisting or increasing left atrial dilatation in patients with persisting hemodynamic abnormality (n = 6, left atrium to aorta ratio 1.66 +/- 0.23 vs. 1.82 +/- 0.15, P = NS). We conclude that significant left atrial dilatation is a consistent echocardiographic feature of constrictive pericarditis. Hemodynamic normalization following successful pericardiectomy is associated with regression of atrial size.

Adolescent↗

PubMed1996

Differentiation of constrictive pericarditis from restrictive cardiomyopathy: assessment of left ventricular diastolic velocities in longitudinal axis by Doppler tissue imaging.

OBJECTIVES: We sought to determine the utility of left ventricular expansion velocities in differentiating constrictive pericarditis from restrictive cardiomyopathy. BACKGROUND: Several studies have shown that left ventricular diastolic expansion is influenced by the elastic recoil forces of the myocardium. These forces are affected by intrinsic myocardial disease but should be preserved when diastole is impaired as a result of extrinsic causes. METHODS: Using Doppler tissue imaging, we measured peak early velocity of longitudinal axis expansion (Ea) in 8 patients with constrictive pericarditis, 7 patients with restriction and 15 normal volunteers. Transmitral early (E) and late (A) Doppler flow velocities, left ventricular systolic and diastolic volumes, ejection fraction and mitral annular M-mode displacement were also compared between the groups. RESULTS: The Ea value was significantly higher in normal subjects (14.5 +/- 4.7 cm/s [mean +/- SD]) and in patients with constriction (14.8 +/- 4.8 cm/s) than in those with restriction (5.1 +/- 1.4 cm/s, p < 0.001 constriction vs. restriction). There was weak correlation between Ea and the extent of annular displacement (r = 0.55, p = 0.004) and the E/A ratio (r = 0.44, p = 0.03). There was no correlation between Ea and E (r = 0.33, p = 0.07) or ejection fraction (r = 0.21, p = 0.26). By multivariate analysis, Ea was the best variable for differentiating constriction from restriction. CONCLUSIONS: Our study indicates that longitudinal axis expansion velocities are markedly reduced in patients with restrictive cardiomyopathy. The poor correlation found with transvalvular flow velocities suggests that Ea may be relatively preload independent. The measurement of longitudinal axis expansion velocities provides a clinically useful distinction between constrictive pericarditis and restrictive cardiomyopathy and may prove to be valuable in the study of diastolic function.

Adult↗

PubMed2004

Differentiation of constrictive pericarditis from restrictive cardiomyopathy using mitral annular velocity by tissue Doppler echocardiography.

This study evaluated the diagnostic role of early diastolic mitral annular velocity (E') by tissue Doppler echocardiography for differentiating constrictive pericarditis from restrictive cardiomyopathy (primary restrictive cardiomyopathy and cardiac amyloidosis). The study group consisted of 75 patients (53 men, 22 women; mean age 62 years, range 27 to 87). Of these, 23 patients had surgically confirmed constrictive pericarditis, 38 had biopsy-proved systemic amyloidosis and typical echocardiographic features of cardiac involvement, and 14 had primary restrictive cardiomyopathy. Standard mitral inflow characteristics were measured. Tissue Doppler echocardiography was used to measure E' at the septal annulus. E' was significantly higher in patients with constrictive pericarditis than in those with primary restrictive cardiomyopathy or cardiac amyloidosis (12.3 vs 5.1 cm/second, p <0.001). An E' cut-off value > or =8 cm/second resulted in 95% sensitivity and 96% specificity for the diagnosis of constrictive pericarditis. There was no overlap of E' between patients who had constrictive pericarditis and those who had cardiac amyloidosis. In a subgroup analysis of restrictive cardiomyopathy, E' of patients who had cardiac amyloidosis was significantly lower than that of patients who had primary restrictive cardiomyopathy (4.6 vs 6.3 cm/second, p <0.001). Thus, E' velocity can distinguish between constrictive pericarditis and restrictive cardiomyopathy with a specific cut-off value in patients with clinical and echocardiographic evidence of diastolic heart failure.

Aged↗

PubMed1999

Nerve constriction in the rat: model of neuropathic, surgical and central pain.

In preparation for a series of electrophysiological experiments in a model of neuropathic pain, the present spinal reflex study was done to determine the optimal time after sciatic nerve constriction in the rat for tactile allodynia and to determine also the appropriate 'control' for the nerve constriction model. Therefore, this study focused on the magnitude and time course of change in paw withdrawal threshold following unilateral sciatic nerve constriction in the rat. Male Sprague-Dawley rats (375-425g) were used. Nerve constriction was done by placing a 2 mm polyethylene cuff (PE-90) around the left sciatic nerve (n=8). A second group of rats (n=8) received unilateral sham surgery and a third group (n=8) was unoperated. The ipsi- and contralateral hind paw withdrawal thresholds in each of the 3 groups were measured using von Frey hairs. In unoperated rats, the withdrawal threshold of each of the hind paws remained unchanged at approximately 50 g throughout the entire time course of the study, which lasted 145 days. However, in cuff-implanted rats, the withdrawal threshold of the nerve-injured hind paw decreased as soon as 1 day after surgery, reached as low as 1 to 2 g by 5 days and remained low throughout the test period. Threshold in sham-operated rats showed a bilateral decrease starting on days 1-3, which stabilised at about 30 g until about day 40, after which values returned gradually toward the unoperated withdrawal thresholds. In nerve-constricted rats the withdrawal threshold of the hind paw contralateral to the cuff followed the same change seen in sham-operated rats until about day 37, after which the withdrawal threshold matched that of the cuff-implanted hind paw. The data show that the cuff-induced sciatic nerve constriction produces a sustained hypersensitivity to normally innocuous tactile sensory input and that a relatively constant ipsilateral mechanical hyperalgesia can be found from days 5-27. It is also demonstrated that the contralateral hind paw and either hind paw in sham-operated rats are inappropriate as 'controls'. The data in this study suggest that three distinct types of allodynia are expressed. Ipsilateral allodynia may be representative of a model of neuropathic pain. The contralateral allodynia may be a model of central pain, as it likely arises from changes in central sensory processing. Allodynia in sham-operated rats was also expressed bilaterally and may be a model of long-term postoperative pain.

Analysis of Variance↗

PubMed1973

The maintenance of arterial constriction at different transmural pressures.

1. Distensibility characteristics of the isolated, perfused rabbit ear artery were measured in the presence and absence of different concentrations of adrenaline.2. The major effect of varying the adrenaline concentration was to vary the radius at which active tension first developed. This radius was inversely related to the adrenaline concentration.3. Increases in radius of the constricted artery produced by pressures rising from 40 to 150 mm Hg were small relative to the increase in wall stress. Distension was opposed largely by increases in active tension. With some arteries (60%) an increase in pressure between 30 and 80 mm Hg was associated with a decrease in radius when low concentrations of adrenaline were present.4. The ability of the constricted ear artery to resist distension at transmural pressures of 100 mm Hg was uninfluenced by the adrenaline concentration provided constriction exceeded 28% of maximal. The static, incremental, circumferential modulus of the artery wall varied little from a value of 6.5 x 10(6) dyn/cm(2).5. The maximum active tension required to maintain constriction was inversely related to the degree of constriction and hence to the adrenaline concentration. The modulus for fully or near-fully activated muscle was 18.5 x 10(6) dyn/cm(2) of media.6. Muscle function deteriorated following exposure of constricted arteries to pressures sufficient to overwhelm the constriction.7. These observations may be explained by a negative feedback system where the contractile elements are arranged in parallel with a length sensor element whose setting is determined by the concentration of adrenaline. The length sensor may be the cell membrane. It is concluded that a radius increase may be a primary stimulus for blood flow auto-regulation.

Animals↗

PubMed1995

Predictors of constrictive pericarditis after tuberculous pericarditis.

OBJECTIVE: To identify features which predict the subsequent development of constrictive pericarditis from acute or subacute tuberculous (TB) pericarditis. SETTING: Tertiary referral centre, chest hospital. PATIENTS: The records of 16 consecutive patients in whom acute or subacute TB pericarditis was diagnosed between 1988 and 1990 at a chest hospital were reviewed. These records included a follow up of at least 12 months. RESULTS: During a follow up of 14.2 (12-30) months, 8 patients had constrictive pericarditis diagnosed by cardiac catheterisation or by inspection at the time of operation (group A). There was no evidence of constriction in the other eight patients (group B). There was no significant difference between the two groups in the type or duration of symptoms of TB pericarditis before admission or the volume and characteristics of pericardial fluid obtained at hospital admission. Clinical features of cardiac tamponade on admission correlated closely with the subsequent development of constrictive pericarditis requiring pericardectomy (7/8 v 2/8; P = 0.01), despite the fact that the signs of tamponade resolved completely after pericardiocentesis. CONCLUSION: The findings suggest that cardiac tamponade in the early clinical stage of TB pericarditis is the most predictive factor of subsequent constrictive pericarditis. The degree of fibrosis of pericardium when treatment starts may be the most important determinant of whether or not constriction develops.

Adult↗

PubMed2003

Constrictive pericarditis in 26 patients with histologically normal pericardial thickness.

BACKGROUND: Traditionally, increased pericardial thickness has been considered an essential diagnostic feature of constrictive pericarditis. Although constriction with a normal-thickness pericardium has been demonstrated clinically by noninvasive imaging, the details of clinicopathological correlates have not been described. METHODS AND RESULTS: A total of 143 patients with proven constriction underwent pericardiectomy at Mayo Clinic between 1993 and 1999. Their baseline characteristics, operative data, and pathological specimens were reviewed retrospectively. The pericardium was of normal thickness (< or =2 mm) in 26 patients (18%; group 1) and was thickened (>2 mm) in 117 (82%; group 2). The most common causes of constriction in group 1 included previous cardiac surgery, chest irradiation, previous infarction, and idiopathic disease. There was little difference in symptoms and findings on physical examination between the 2 groups. Microscopically, no patient had an entirely normal pericardium. Histopathological abnormalities in group 1 were mild and focal, including fibrosis, inflammation, calcification, fibrin deposition, and focal noncaseating granulomas. Pericardiectomy was equally effective in relieving symptoms regardless of the presence or absence of increased thickness. CONCLUSIONS: Pericardial thickness was not increased in 18% of patients with surgically proven constrictive pericarditis, although the histopathological appearance was focally abnormal in all cases. When clinical, echocardiographic, or invasive hemodynamic features indicate constriction in patients with heart failure, pericardiectomy should not be denied on the basis of normal thickness as demonstrated by noninvasive imaging.

Adult↗