In vitro and in vivo mechanical evaluations of plasma-sprayed hydroxyapatite coatings on titanium implants: the effect of coating characteristics

This study was undertaken to evaluate the effect of coating characteristics on the mechanical strengths of the plasma-sprayed HA-coated Ti-6Al-4V implant system both in vitro and in vivo. Two types of HA coatings (HACs) with quite different microstructures, concentrations of impurity-phases, and indices-of-crystallinity were used. In vitro testings were done by measuring the bonding-strength at the Ti-6Al-4V-HAC interface, with HACs that had and had not been immersed in a pH-buffered, serum-added simulated body fluid (SBF). The shear-strength at the HAC-bone interface was investigated in a canine transcortical femoral model after 12 and 24 weeks of implantation. The results showed a bonding degradation of approximately 32% or higher of the original strength after 4 weeks of immersion in SBF, and this predominantly depended on the constructed microstructure of the HACs. After the push-out measurements, it was demonstrated that the HACs with higher bonding-strength in vitro would correspondingly result in significantly higher shear-strength at each implant period in vivo. Nevertheless, there were no substantial histological variations between the two types of HACs evaluated. The most important point elucidated in this study was that, among coating characteristics, the microstructure was the key factor in influencing the mechanical stability of the HACs both in vitro and in vivo. As a consequence, a denser HAC was needed to ensure mechanical stability at both interfaces.

Relation of systemic arterial pulse pressure to coronary atherosclerosis in patients with mitral stenosis

The relation of a wide systemic arterial pulse pressure to coronary atherosclerosis has not been fully defined. One hundred fifty-nine patients > 40 years old with symptomatic mitral stenosis (MS) who received routine coronary angiography were classified into 2 groups according to the presence of > or = 50% diameter narrowing of > or = 1 coronary artery (n = 48) or no significant disease (n = 111). Pulse pressure was determined both by noninvasive sphygmomanometer and invasive catheterization methods. There were no significant differences in risk factors of coronary artery disease (CAD) or the severity of MS between the 2 groups. From multivariate logistic regression analysis, independent predictors of development of CAD in MS were age (standardized coefficient beta = 1.3437, p = 0.0025), gender (beta = 0.0107, p = 0.0105), mean blood pressure (beta = 1.1839, p = 0.0105), and pulse pressure (beta = 1.3157, p = 0.0008). A wide pulse pressure (> or = 60 mm Hg) correlated with the presence of angiographically significant CAD with a sensitivity and specificity of 88% and 77%. The negative predictive value was 93%. Pulse pressure assessed by sphygmomanometry provided important clinical information. A wide pulse pressure in patients with MS was associated with a high incidence of CAD.

The induction of Fos-like proteins in the suprachiasmatic nuclei and intergeniculate leaflet by light pulses in degus (Octodon degus) and rats

In nocturnal rodents, exposure to light results in an increase in Fos expression in two regions that receive direct retinal input: the suprachiasmatic nuclei (SCN) of the hypothalamus and the intergeniculate leaflet (IGL) of the thalamus. The induction of Fos within the SCN of nocturnal rodents is phase dependent, with light presented during the subjective night increasing Fos expression and light presented during the subjective day having little effect. By contrast, Fos expression increases in the IGL when light is presented during the subjective day or night. It is unclear whether Fos is part of the pathway mediating light-induced phase shifts in diurnal rodents. In the present study, the ability of light to induce immunostaining for Fos in the SCN and IGL was compared in diurnal rodents, Octodon degus (degus), and nocturnal rats. Degus and rats were either maintained in constant darkness or exposed to a 1-h light pulse at circadian time (CT) 4 or 16. Degus exhibit robust phase shifts at each of those circadian hours, whereas rats demonstrate phase shifts only at CT 16. In degus, exposure to a 1-h light pulse at CT 16 resulted in an increase in the number of Fos-immunopositive (Fos+) cells in the ventrolateral SCN. By contrast, a 1-h light pulse at CT 4 resulted in a decrease in the number of Fos+ cells in the dorsomedial portion of the SCN. In rats, a light pulse presented at CT 16 resulted in an increase in Fos+ cells throughout the SCN, and a pulse at CT 4 had no effect on Fos staining. Both degus and rats showed increases in Fos expression in the IGL after light exposure at CTs 4 and 16. The authors conclude that light pulses presented at times that produce phase shifts in activity rhythms also alter Fos expression in the SCN and IGL of degus. Although these effects of light exposure on Fos expression are not identical in diurnal and nocturnal rodents, it is likely that Fos and other immediate early genes are part of the pathway mediating the effects of light in both diurnal and nocturnal rodents.

Pathophysiological mechanism of seasonal affective disorder

Despite the long history in medicine, the pathophysiological mechanism(s) of seasonal affective disorder (SAD) remain largely unknown. By employing a meta-analytic methodology, the authors of this study attempted to verify the validity of different pathophysiological mechanism(s) proposed for SAD. The findings showed that for phototherapy of medium light intensity, a combination of morning-evening therapy regime yielded the best therapeutic effect, and the antidepressant effect of the morning-evening light regime was superior to a single pulse of light administered at other times of day. Furthermore, the data showed that the antidepressant effect of a single pulse of light was similar for morning, midday, and evening light. These findings supported the photon-count hypothesis and refuted the proposed photoperiod, melatonin, and phase-shifting models of SAD.

Rhythm chronotypes in a diurnal rodent, Octodon degus

Interindividual variations in entrained human circadian rhythms and their relationship to differences in ease of adjustment to phase shifts have been well described. Humans classified as morning type (MT) display phase-advanced temperature minimum, onset of daily activity, and onset of sleep, whereas evening type (ET) individuals demonstrate the opposite pattern with a later phase angle of entrainment for these measures. We examined 15 variables of circadian activity and temperature for diurnal Octodon degus (n = 49; 28 male, 21 female), and noted similar chronotype variations as described for humans. Individuals with extreme MT and ET chronotypes were identified as those who differed from the entire population mean by one or more standard deviations. Compared with MTs (n = 5) and intermediate chronotypes (ITs, n = 34), ETs (n = 10) displayed a significant delay in the phase of temperature minimum, rise in temperature above the daily mean, and decline in activity and temperature below the daily mean, and had longer elevated activity and temperature durations and higher levels of mean daily activity and activity amplitude. MTs also displayed a significant phase advance in the morning temperature rise compared with ITs and ETs. This is the first description of variation in entrained circadian rhythms similar to that described for humans in both an outbred animal population and a diurnal rodent.

Left atrial spontaneous echo contrast in patients with permanent pacemakers

OBJECTIVE

To determine the relations between left atrial appendage function, spontaneous echo contrast, and thromboembolism in patients with different modes of permanent pacemakers.

PATIENTS AND METHODS

88 patients with pacemaker implantation and 25 healthy controls in sinus rhythm had transoesophageal echocardiographic examination of the left atrial appendage. Left atrial size, appendage area, peak filling and emptying velocities of the atrial appendage, and the presence or absence of spontaneous echo contrast and thromboembolism were determined. The results in 63 patients with ventricular pacing (group 1, subdivided into subgroup 1A: 42 patients with sinus rhythm, and subgroup 1B: 21 patients with atrial fibrillation) were compared with those in 25 patients with synchronous pacing (group 2), and 25 normal control subjects (group 3).

RESULTS

Patients with ventricular pacing had two distinct appendage flow patterns: well defined biphasic filling and emptying waves in subgroup 1A, and irregular very low filling and emptying waves in subgroup 1B. The ejection fraction of the left atrial appendage in subgroup 1A was significantly better than that in subgroup 1B (mean (SD) 40.6 (12.0)% v 7.6 (5.0)%, P < 0.0001). The spontaneous echo contrast was observed in 90% of subgroup 1B patients but in only 19% in subgroup 1A (P < 0.05) and was not found in groups 2 and 3 (P < 0.0001). There was a trend for increased prevalence of spontaneous echo contrast in subgroup 1A v group 2 (P = 0.053). Thrombi were detected in two cases, and cardiogenic embolism occurred in one case in subgroup 1B. All patients with spontaneous echo contrast had ventricular pacing. Multivariate analysis showed that atrial fibrillation was associated with occurrence of spontaneous echo contrast in patients with ventricular pacing (P = 0.005).

CONCLUSIONS

The left atrial appendage ejection fraction was lower with ventricular pacing than with synchronous pacing. With ventricular pacing there was a trend towards increased prevalence of left atrial spontaneous echo contrast in patients in sinus rhythm, and a significantly increased prevalence in patients with atrial fibrillation.

Spectral properties of phototherapy for seasonal affective disorder: a meta-analysis

The general therapeutic effect of light on seasonal affective disorder (SAD) has been widely acknowledged. However, the antidepressant effect of light does not seem to be the same for different spectra of light. In this study, the authors attempted to study the spectral properties of phototherapy for SAD using a meta-analytical procedure. The findings suggested that light of short to medium wavelengths (blue/green/yellow) seem to be essential for the therapeutic effect of light on SAD. Red wavelengths were relatively ineffective. It was then postulated that SAD may be predisposed and/or precipitated by the inefficiency of the S and M cones in the retina. Furthermore, ultraviolet (UV) waves did not seem to be essential for SAD symptom alleviation by artificial light. Therefore, these potentially harmful UV waves should be blocked in any clinical application of phototherapy for SAD.

Olfactory bulbectomy impedes social but not photic reentrainment of circadian rhythms in female Octodon degus

Recent studies demonstrated that nonphotic (social) cues markedly accelerate reentrainment to large phase shifts of the light-dark (LD) cycles in female Octodon degus and that such changes are likely effected by chemosensory stimuli. This experiment investigated the effects of olfactory bulbectomies on (1) socially facilitated reentrainment rates of circadian rhythms following a 6-h phase advance of the LD cycle, (2) photic reentrainment rates of circadian rhythms following a 6-h advance of the LD cycle, (3) photic entrainment, and (4) the circadian period (tau) of activity rhythms in constant darkness (DD). olfactory bulbectomies (BX) blocked socially facilitated reentrainment rates but did not alter reentrainment rates of circadian rhythms to photic cues alone. In addition, BX lowered mean daily locomotor activity levels and decreased the amplitude of the activity rhythm in degus housed in entrained (LD 12:12) conditions but did not alter the phase of activity onset or offset, duration (alpha) of activity, or mean daily core body temperature. Bulbectomies also failed to modify tau of free-running activity rhythms. This experiment confirms that the olfactory bulbs and chemosensory cues are necessary for socially facilitated reentrainment. In contrast to their effects in nocturnal rodents, BX do not produce significant circadian photic changes in diurnal degus. This is the first experiment to determine that chemosensory stimuli modulate the circadian system in a diurnal rodent.

Individual variation in reentrainment after phase shifts of light-dark cycle in a diurnal rodent Octodon degus

The rate and pattern of activity and temperature reentrainment was determined after 3-, 6-, and 9-h phase advances and phase delays in two groups of Octodon degus for whom phase response curves (PRCs) to light and dark pulses and free-running periods (tau) in constant darkness and constant light had previously been determined [T.M. Lee and S. E. Labyak. Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol. 42): R278-R286, 1997.]. We predicted that individuals with light-pulse PRCs containing both significant phase delay and phase advance regions would phase delay more rapidly than individuals lacking significant phase delays after light pulses. We also expected that animals without a phase delay region in the light-pulse PRC would demonstrate more temporary circadian abnormalities during the period of reentrainment (periods of masking, bimodal patterns of activity, and abnormal phase relationships between activity and temperature). Degus with light-pulse PRCs containing both a significant phase-delay and -advance region reentrained significantly faster and with fewer disrupted patterns of entrainment after 6- and 9-h phase delays than degus without phase-delay regions in the PRC. The rate of reentrainment after phase advances did not differ between animals with the two types of PRC except for temperature after a 6-h phase shift. Because animals with and without phase-delay regions in the light-pulse PRC had equivalent tau s, the interindividual variation in reentrainment is best explained by the fundamental differences in the light-pulse PRCs. The variation of rate and pattern of reentrainment for both groups of animals were reasonably predicted or explained by knowledge of the light-pulse and dark-pulse PRCs.

Social cues modulate free-running circadian activity rhythms in the diurnal rodent, Octodon degus

Two experiments assessed the effects of social cues and daily disturbance on the circadian locomotor activity rhythms of Octodon degus housed in constant darkness. In experiment 1, females in free-running conditions were housed alone or with entrained female partners ("donors") in cages on either side of a mesh barrier. Donors were removed daily and entrained to 1 h of light, and as a control, the cages of singly housed animals were rustled daily coincident with donor removal and replacement. None of the animals housed alone entrained to daily disturbances presented during the active phase, and seven of eight degus failed to show changes in the circadian period (tau) or phase of their rhythms. In contrast, although the presence of entrained donors did not elicit full entrainment of free-running rhythms, five of six animals demonstrated partial entrainment for 5-12 days (of 30 days), four of six altered phase of activity onset, and six of six lengthened tau of circadian rhythms. In experiment 2, females whose free-running circadian activity rhythms were at least 10 h out of phase were housed together in pairs. None of the pairs demonstrated mutual synchronization of their activity rhythms, although 8 of 12 degus modified phase of activity onset and 9 of 12 animals altered tau. We conclude social information in the absence of light, is sufficient for partial entrainment and for changes in tau and phase of free-running rhythms in this diurnal rodent.

Intramedullary implant of plasma-sprayed hydroxyapatite coating: an interface study

An intramedullary implant model in the canine femora was developed to evaluate the mechanical and histological responses between cancellous bone and plasma-sprayed hydroxyapatite coatings (HACs) on ti-6A1-4V implants, with 12- and 24-week follow-ups. HACs of different thicknesses were investigated. Results of the mechanical testings revealed that after 24 weeks of implantation, the mean shear strength (2.49 +/- 0.12 MPa) of the 50 microns HACs was significantly higher (p < 0.05) than that of the 200 microns HACs (1.44 +/- 0.19 MPa). However, using backscattered electron images (BEIs) throughout all the implant periods, no substantial histological variations in the extent of new bone apposition between the two HACs were observed. Occasionally, solution-mediated disintegration of the 50 microns HAC was found 24 weeks postimplantation. Histomorphometric studies from the BEIs demonstrated that for both HACs the percentage of the direct HAC-cancellous bone contact was approximately 50% at 12 weeks and 75% at 24 weeks. After the mechanical tests, the 200 microns HACs had fracture sites either inside the coating layers or at the HAC-titanium interfaces, which might explain why the mechanical performance of the 200 microns HACs was inferior to that of the 50 microns HACs even though both HACs had the same histological behaviors.

Free-running rhythms and light- and dark-pulse phase response curves for diurnal Octodon degus (Rodentia)

Only rarely have precise, short-duration light pulses been used to generate phase response curves (PRCs) in diurnal mammals as done for nocturnal mammals, and a dark-pulse PRC has never been generated for a diurnal mammal. In addition, the relationship between free-running rhythms in different light intensities and PRCs has not been explored in diurnal mammals. We examined these relationships in Octodon degus, a diurnal hystricomorph rodent. Male degus lengthened the circadian period (tau) and duration of daily activity (alpha) after an increase in light intensity from 0 (DD) to 250 lx, and tau was furthered lengthened when light intensity increased from 580 to 5,800 lx. To generate a light-pulse PRC, degus were housed in DD and exposed to 20-min light pulses (250 lx) and phase shifts recorded across the circadian day. Two different PRCs were generated in response to 20-min light pulses. The majority of animals produced significant phase delays between circadian time (CT) 0 and CT 6, phase advances between CT 13 and CT 22, and a nonsignificant response period between CT 8 and CT 13. Two animals produced a PRC devoid of significant phase delays, producing only significant phase advances between CT 17 and CT 24. To generate a dark-pulse PRC, animals were moved to LL (580 lx) and exposed to 1-h dark pulses. After dark pulses degus produced significant phase delays between CT 20 and CT 8, advances from CT 10 to CT 17, and nonsignificant responses between CT 18 and CT 20. This is the first report of a PRC to dark-pulse stimuli for a diurnal mammal. Thus light- and dark-pulse PRCs can be generated in a comparable way to those of nocturnal rodents, and we conclude that nocturnal and diurnal rodents use similar photic signals to produce somewhat different PRCs.

Effects of dobutamine on aortic valve indexes in asymptomatic patients with bileaflet mechanical prostheses in the aortic valve position

We investigated the effects of alternating transvalvular flow rate on Doppler-derived aortic valve resistance and valve area in asymptomatic patients with mechanical aortic valve replacement under dobutamine infusion. The Gorlin-derived aortic valve area and continuity equation-derived aortic valve area seem to be less flow dependent; valve resistance tends to be flow dependent.

Exaggerated luminal loss a few minutes after successful percutaneous transluminal coronary angioplasty in patients with recent myocardial infarction compared with stable angina: an intracoronary ultrasound study

This study investigates the mechanisms of exaggerated acute luminal loss after successful coronary angioplasty in patients with recent myocardial infarction compared with stable angina by angiography and intracoronary ultrasound (ICUS). We studied 15 consecutive patients (group 1) who, after a successful thrombolysis for myocardial infarction, underwent delayed (8 +/- 2 days after the myocardial infarction) successful balloon coronary angioplasty. Group 1 patients were individually matched with 15 stable angina patients (group 2). The percentage of stenosis and acute luminal loss were measured by quantitative coronary analysis. The ultrasound characteristics of lumen pathology were described as soft, hard, calcified, eccentric, concentric, thrombotic, and dissection lesions. Matching by stenosis location, reference diameter, sex, and age resulted in 2 comparable groups of 15 lesions with identical baseline characteristics. Immediately after percutaneous transluminal coronary angioplasty (PTCA), the minimal luminal diameter increased from 0.5 +/- 0.3 mm to 2.4 +/- 0.3 mm and from 0.5 +/- 0.2 mm to 2.4 +/- 0.3 mm in groups 1 and 2, respectively. Similar balloon sizes were used in both groups. The acute luminal loss (the difference between the maximal dilated balloon diameter and the minimal luminal diameter) immediately after PTCA was 0.4 +/- 0.2 mm and 0.3 +/- 0.3 mm (14 +/- 8% and 10 +/- 11% of balloon size) (P = not significant [NS]) in groups 1 and 2, respectively. After ICUS (mean 24 min after the last balloon deflation), the acute luminal loss was 0.9 +/- 0.3 mm and 0.5 +/- 0.4 mm (29 +/- 11% and 17 +/- 8% of balloon size) (P = 0.01) in groups 1 and 2, respectively. There was a significantly higher prevalence of intracoronary thrombus formation as detected by ICUS in group 1 compared with group 2 (80% vs. 20%; P < 0.001). In matched groups of successfully treated coronary angioplasty, patients with recent myocardial infarction had a similar magnitude of acute gained luminal loss immediately after the procedure. However, an exaggerated luminal loss a few minutes after the last balloon deflation in patients with recent myocardial infarction was noted because of mural thrombus formation compared with patients with stable angina.

Percutaneous transvenous mitral balloon valvuloplasty alone in patients with combined aortic and mitral stenosis

To investigate the feasibility of percutaneous transvenous balloon dilatation of the mitral valve in patients with combined aortic and mitral stenosis, 12 patients were studied by echocardiography and catheterization before and after mitral valvuloplasty. Aortic stenosis was defined from prevalvuloplasty catheterization study as a transaortic pressure gradient of more than 25 mm Hg. All 12 patients underwent transvenous balloon mitral valvuloplasty successfully. Immediately after the procedure, all patients experienced improvement in clinical symptoms and in hemodynamic variables. Mitral valve areas were significantly increased from 0.78 +/- 0.18 to 1.73 +/- 0.21 cm2 (P < 0.0001) by planimetry method. Cardiac output was significantly increased from 3.6 +/- 0.1 to 4.2 +/- 0.5 L/min (P = 0.01). Mean transaortic flow rate increased 33% (from 198 +/- 68 to 254 +/- 41 mL/s, P = 0.002). Mean pressure gradient across the aortic valve after mitral valvuloplasty was not significantly increased, from 34 +/- 7 to 37 +/- 13 mm Hg. Aortic valve areas, derived from the Gorlin formula, were significantly increased from 0.57 +/- 0.12 to 0.73 +/- 0.14 cm2 (P = 0.006) after mitral valvuloplasty. However, continuity equation-derived aortic valve area was independent of increasing flow rate after mitral valvuloplasty from 1.29 +/- 0.35 to 1.30 +/- 0.29 cm2. During follow-up with a mean of twenty four +/- fourteen months, 8 patients were in New York Heart association functional class I, 3 in class II, and 1 in class IV who received pericardiotomy owing to constrictive pericarditis without aortic valve replacement. In conclusion, mitral valvuloplasty alone may be safe and effective in alleviating symptoms in mitral stenosis patients with transaortic pressure gradient > 25 mm Hg. Continuity equation-derived aortic valve areas seem to be flow independent in evaluation of aortic stenosis and are important for decision making.

Role of transesophageal echocardiography in the management of metastatic tumors invading the left atrium

Two patients with metastatic tumors invading the left atrium are described. One is a 52-year-old woman with osteosarcoma; the other is a 77-year-old man with lung cancer. The first patient presented with severe dyspnea 1 year after treatment for a primary tumor. Cardiac metastasis was suspected, then documented by transesophageal echocardiography. The study of pulmonary vein flow showed decreased systolic forward and increased diastolic components of pulmonary venous flow. The second patient presented with chronic cough without dyspnea. Although a huge tumor invaded the left atrium, as in the first patient, a normal pattern of pulmonary vein flow with higher systolic than diastolic velocities was shown by transesophageal echocardiography. Thus, transesophageal echocardiography is not only a useful tool to diagnose left atrial metastatic tumors, but also the study of pulmonary venous flow patterns can delineate causes of dyspnea in patients with metastatic tumors invading the left atrium.

Effects of increasing flow rate on aortic stenotic indices: evidence from percutaneous transvenous balloon dilatation of the mitral valve in patients with combined aortic and mitral stenosis

OBJECTIVES

To investigate the effects of transvalvar flow rate on aortic valve resistance and valve area after percutaneous transvenous balloon dilatation of the mitral valve in a homogeneous group of patients with rheumatic heart disease.

DESIGN

Retrospective analysis of 12 patients with combined aortic and mitral stenosis who had undergone balloon dilatation of the mitral valve over a period of 9 years.

SETTING

Tertiary referral centre.

PATIENTS

Twelve (8 women, 4 men; mean (SD) age 37 (9) of 227 consecutive patients with critical mitral stenosis undergoing transvenous balloon dilation of the mitral valve in the centre also had aortic stenosis, defined as a transaortic pressure gradient of more than 25 mm Hg measured at a catheterisation study before valvuloplasty.

INTERVENTIONS

Echocardiographic variables (mitral valve area measured by the pressure half-time method and planimetry, and the aortic valve area derived from the continuity equation) and haemodynamic measurements (cardiac output, left ventricular mean systolic pressure, aortic mean pressure, transaortic valve pressure gradient, mitral valve and aortic valve areas derived from the Gorlin formula, and aortic valve resistance) were assessed before and after transvenous balloon dilatation of the mitral valve. Follow up catheterisation to measure haemodynamic variables was performed one week after mitral valvuloplasty.

RESULTS

Mean transaortic flow rate increased 33% after mitral valvuloplasty (from 198 (68) to 254 (41) ml/s, P = 0.002). Aortic valve areas derived from the Gorlin formula were significantly increased from 0.57 (0.12) to 0.73 (0.14) cm2 (P = 0.006) after mitral valvuloplasty. However, aortic valve area and valve resistance derived from the continuity equation were independent of the increase in flow rate after mitral valvuloplasty (from 1.29 (0.35) to 1.30 (0.29) cm2 and from 317 (65) to 259 (75) dyn.s.cm-5, both P = NS).

CONCLUSION

The Gorlin-derived aortic valve area tends to be flow-dependent, and continuity equation-derived aortic valve area and catheterisation-derived valve resistance seem to be less flow-dependent. In patients with combined mitral and aortic stenosis, these flow-independent indices are important for decision-making.

Left atrial spontaneous echo contrast in asymptomatic patients with a mechanical valve prosthesis

BACKGROUND

Valve thromboembolism may be a fatal complication of mechanical valve prosthesis if detected late. Spontaneous echo contrast (SEC) is a well-documented prothrombotic phenomenon; here we report it in asymptomatic patients with a mechanical valve prosthesis.

METHODS

Ninety-two asymptomatic patients with a mechanical valve prosthesis for underlying rheumatic heart disease underwent transesophageal echocardiography. Appendage area, peak filling and emptying velocities of the left atrial appendage, and the presence or absence of SEC and thrombi were determined. The results of 56 patients without SEC or thrombi (group I) were compared with those of 24 patients with SEC and no thrombi (group II) and 12 patients with thrombi (group III).

RESULTS

Spontaneous echo contrast was present in 39% of the asymptomatic patients with a mechanical valve prosthesis. Although 12 patients had cardiac thrombi, including valve thrombi in 4, no patients presented symptoms. Anticoagulant therapy had no significant association with SEC and atrial thrombi. There was a significantly greater prevalence of atrial fibrillation and mitral prosthesis in groups II and III than in group I. Two patterns of left atrial appendage flow were identified: one was organized biphasic flow with peak filling velocities of 41.2 +/- 17.2 cm/s and emptying velocities of 40.5 +/- 17.5 cm/s. The other showed irregular, very low peak filling velocities (104 +/- 11.5 cm/s) and emptying velocities (12.3 +/- 13.1 cm/s). The former flow pattern was associated with sinus rhythm and the latter form was associated with atrial fibrillation.

CONCLUSIONS

There was a relatively high prevalence of SEC and thrombi in patients with a mechanical valve prosthesis. Patients with a valve prosthesis may not have clinical symptoms. Anticoagulation intensity was not associated with the occurrence of SEC and thrombi. Patients with the mitral valve prosthesis and atrial fibrillation were identified as a high-risk of subgroup for the development of SEC and thrombi.

Case report: reversible systolic heart failure and deep jaundice in hyperthyroidism

Systolic heart failure because of hyperthyroidism in patients without preexisting heart disease is not common. Thyrotoxic systolic heart failure is rarely diagnosed during life. Reports about thyrotoxicosis-related systolic heart failure have been diagnosed postmortem. However, antemortem diagnosis of this fatal disease has important clinical implications because if detected early, thyrotoxicosis-related systolic heart failure is reversible. Here is a report a patient with Graves' disease, systolic heart failure, and deep jaundice, which resolved after the treatment of antithyroid drugs.

Changes of left ventricular function after percutaneous balloon mitral valvuloplasty in mitral stenosis with impaired left ventricular performance

The pathophysiological role of mechanical and myocardial factors for impairment of left ventricular performance in mitral stenosis is still not clear. To investigate this controversy, 27 patients of mitral stenosis with left ventricular ejection fraction < 50% were studied. Patients were divided into two groups: Group 1: 20 patients, left ventricular ejection fraction improved to > 50% after valvuloplasty, and Group 2: 7 patients, left ventricular ejection fraction still < 50% after valvuloplasty. The clinical and hemodynamic characteristics were comparable for the two groups before valvuloplasty. Follow-up catheterization done one week later showed similar changes in mitral valve area, cardiac index, pulmonary pressure, left ventricular end-diastolic volume index and systemic vascular resistance between the two groups. However, left ventricular end-systolic volume was significantly decreased after valvuloplasty in Group 1 but not in Group 2, resulting in significantly higher ejection fraction in Group 1 than in Group 2. Postoperatively, regional wall motion scores were lower in Group 1 than in Group 2 (2.0 +/- 0.6 vs. 2.7 +/- 0.5 at the anterolateral wall, P = 0.002; 1.9 +/- 0.6 vs. 2.9 +/- 0.4 at the posterobasal wall, P = 0.0003). Most of our mitral stenosis patients with impaired left ventricular ejection fraction showed improvement after mitral valvuloplasty had released the mechanical obstruction. However, in some patients, impaired ejection fraction persisted after valvuloplasty, suggesting the mechanism of myocardial failure. Thus, both myocardial and mechanical factors play important roles in the pathogenesis of left ventricular ejection performance impairment.

Excessive papillary muscle traction and dilated mitral annulus in mitral valve prolapse without mitral regurgitation

This study demonstrated excessive papillary muscle displacement during peak systole but normal mitral annulus function during the cardiac cycle in patients with mitral valve prolapse and no mitral regurgitation. The excessive papillary muscle displacement may play an important role in the pathogenesis of the superior displacement of mitral leaflets in patients with mitral valve prolapse.

Usefulness of transdermal scopolamine for vasovagal syncope

We studied short-term effectiveness of transdermal scopolamine in a group of patients with unexplained syncope provoked during head-up tilt testing. This double-blind randomized trial of transdermal scopolamine demonstrated no significant effect of preventing vasovagal syncope.

Relationship of circadian activity and social behaviors to reentrainment rates in diurnal Octodon degus (Rodentia)

Previous experiments with female Octodon degus showed that entrained males (donors) inhibited and entrained females accelerated female phase-shifters' teentrainment rates of temperature and activity rhythms following 6-h advances. In this experiment, entrained males were housed with other entrained males or with phase-shifting females (experiencing a phase advance of the light-dark (LD) cycle) and entrained females were housed with other entrained females or with phase-shifting females. Pairs separated by a barrier were videotaped for 66 h to identify the behavioral interactions that underlie the opposite effects of donor social cues on reentrainment rates in females. As reported previously, female phase-shifters housed with entrained females reentrained faster than those "housed with entrained males following 6-h advances. Despite accelerated reentrainment, the timing or total durations of general activity, sleep, cage investigation, barrier investigation, and scent marking did not differ between female phase-shifters housed with male or female donors, although all phase-shifters increased investigatory behaviors compared to entrained animals. In contrast, male and female donors housed with female phase-shifters increased the frequency of scent marking and the duration of cage and barrier investigation compared with those housed with entrained same-sex conspecifics. Changes in scent marking and sniffing investigation suggest olfactory cues, not alterations in sleep or other daily rhythms, supply the critical social influence necessary to alter reentrainment rates in females. Daily and/or specific phase increases in motor activity did not correlate with accelerated reentrainment. We suggest that the salience of social cues perceived by female phase-shifters, female phase-shifters' sensitivity to cues and/or the strength of emitted donor cues may contribute to differential responses of the circadian system in females housed with male vs. female donors.

Excessive myocardial contraction in vasovagal syncope demonstrated by echocardiography during head-up tilt test

The purpose of this study was to gain insight into the mechanism of vasovagal syncope and to test the efficacy of theophylline to prevent syncope. Twenty-six patients with vasovagal syncope underwent two-dimensional echocardiography and theophylline test during head-up tilt test. A standard parasternal short-axis view of echocardiography at the level of the papillary muscle was recorded to measure fraction shorting of the left ventricle, and left ventricular end-diastolic and end-systolic dimensions. Heart rate, blood pressure, and symptoms were recorded. There were three groups; Group 1: no syncope with and without isoproterenol (n = 5); Group 2: syncope only after the infusion of isoproterenol (n = 16); Group 3: syncope without isoproterenol (n = 5). Groups 2 and 3 proceeded to theophylline injection (250 mg). The study showed that the 80 degrees tilt induced an increase in heart rate of 6.6 +/- 4.0, 12.4 +/- 6.6, and 25.4 +/- 4.5 beats/min in Groups 1, 2, and 3, respectively (p < 0.05 in Groups 1 and 2, p < 0.05 in Groups 1 and 3). The addition of isoproterenol during posture change from supine to an 80 degrees tilt made the significant change of fractional shortening from 0.4 +/- 5% to 6 +/- 13% in Group 2 (p = 0.05), compared with no significant change in Group 1. There were no significant differences in left ventricular end-diastolic dimension and end-systolic dimension in each group between baseline and isoproterenol infusion during posture change. Vasovagal syncope was associated with vigorous myocardial contraction, rather than with contraction against an empty left ventricle. The acute loading of theophylline was not effective in preventing vasovagal syncope.

Changes in phases and crystallinity of plasma-sprayed hydroxyapatite coatings under heat treatment: a quantitative study

With three kinds of plasma-sprayed hydroxyapatite coatings (HACs) prepared, the objectives of this study were (1) to establish the calibration methods for quantitatively measuring the concentration of impurity phases and the degree of crystallinity of the HACs, and (2) to explore the effects of postheat treatments at various temperatures in vacuo on the changes of phases and crystallinity of the HACs. By the internal standard method used, the concentrations of impurity phases, such as alpha-TCP, beta-TCP, and TP, of the assprayed HACs were significantly higher than those measured by the direct intensity-ratio method, and the CaO phase was lower than the direct intensity-ratio method. When the HACs were heat treated in the temperature interval 630-850 degrees C, the concentrations of impurity phases obviously decreased, and the coating crystallinity apparently increased. After annealing at 850 degrees C, an HAC consisting of at least 95% crystallinity with few impurity phases was obtained. As the annealing temperatures in the interval 850-1000 degrees C were applied, however, the HA phase seriously decomposed, resulting in the appearance of a large number (higher than 20 wt%) of impurity phases in the HACs. This work suggests that the optimum heat treatment conditions in vacuo for maximizing crystallinity and minimizing impurity phases of the HACs do not occur at the same temperature.