Non-invasive estimation of the diastolic elastic and viscoelastic properties of the left ventricle

The present study applies a non-invasive method to the quantitative evaluation of left ventricular stiffness in normal subjects and in patients with ischaemic heart disease (IHD). We have studied 20 patients with IHD and 25 healthy subjects. The third heart sound (S3) was detectable in all patients. We have correlated the energy spectrum of S3, divided into 15 Hz bands, with a series of echocardiographic parameters. The existence of a significant correlation between the spectrum energy and the diameter and thickness of the left ventricle at the moment of S3 allowed us to explore the possibility of interpreting the origin of S3 based on a mathematical model. Our hypothesis has been that, once the left ventricle starts vibrating, it behaves as a simple physical model composed of a mass and an elastic element. To this purely elastic model one can add a factor accounting for viscosity, with a damping effect, to obtain a more complex viscoelastic model. The stiffness coefficient 'k' was computed in both models from the peak frequency of S3 and the left ventricular mass at the moment of S3. Furthermore, in the viscoelastic model, the damping element 'c' was also computed. Both parameters--k and c--were significantly increased in the group with IHD compared with the control group. Although a simplification of the vibrating system, these models make it possible to obtain non-invasively information on the characteristics of the left ventricle through the combined use of echocardiography and spectral analysis of S3.     

Stability of the Defibrillation Probability Curve with the Development of Ventricular Dysfunction in the Canine Rapid Paced Model

Most patients with implantable defibrillators have diminished cardiac function. Progressive heart failure might impair defibrillation efficacy, leading to interpreted device, failure. This study sought to determine the effect of ventricular dysfunction on defibrillation energy using a biphasic endocardial system. Eleven dogs were ventricularly paced at 225 pulses/min for 2 weeks to induce ventricular dysfunction, and five control dogs remained unpaced. Dose response defibrillation probability curves were generated for each animal at baseline, after 2 weeks (at which time the pacemakers were turned off in the paced group), and then 1 week later. The defibrillation thresholds, ED₂₀, ED₅₀, and ED₈₀ (the 20%, 50%, and 80% effective defibrillation energies, respectively) were determined for each dog at each study. In the paced dogs, the mean ejection fraction fell from 55% to 25% after pacing (P < 0.0001), and rose to 46% after its discontinuation (P = 0.0002). The defibrillation threshold, ED20, ED₅₀, and ED80 remained unchanged in both the control and paced groups for all three studies, even after adjustment for dog weight or left ventricular mass. Rapid pacing produced no change in left ventricular mass. It induced ventricular cavity dilatation and wall thinning, which had opposing effects on defibrillation energy requirements, resulting in no net change of the ED₅₀ in heart failure. In conclusion, the defibrillation efficacy of a biphasic transvenous system is not changed by the development of heart failure using the rapid paced canine model.     

人左、右心室阻抗微分心动图的比较研究

作者利用Ⅱ导心电图、心音图、颈动脉搏动图、右（或左）心室阻抗微分心动图同步描记的方法。对人左、右心室阻抗微分心动图进行了比较分析。结果显示:人的左、右心室阻抗微分心动图图形相似，波形稳定，转折明显，均有清晰的生理标志点。两种图形各相应生理标志点在时相上存在着区别．且人的左、右心室阻抗微分心动图能分别反映人的左、右心室收缩和舒张过程，说明利用人的左、右心室阻抗微分心动图能分别测定人的左、右心室收缩时间间期与舒张时间间期值，鉴别和评定左、右心室的功能。     

Low-Dose Doxapram Therapy in Premature Infants and Its CSF and Serum Concentrations

ABSTRACT. The efficacy of low-dose doxapram therapy (0.2 mg/kg/h) in combination with methylxanthines was evaluated in 20 premature infants with idiopathic apnea unresponsive to methylxanthines alone, and in 13 premature infants with secondary apnea. The serum concentrations of doxapram and, in some infants, the simultaneous cerebrospinal fluid and serum concentrations were measured, and the correlation between cerebrospinal fluid and serum concentrations in the postnatal period was determined. The following results were obtained: 1) In idiopathic apnea of prematurity, low-dose doxapram therapy was as effective as a dose of 1.0-2.5 mg/kg/h and the side effects were few, mild, and reversible. 2) In premature infants over seven days of age, serum concentrations of doxapram were almost stable but were significantly lower than in infants within the first six days of life. 3) The ratio of the cerebrospinal fluid to serum doxapram concentration was 0.48 ± 0.13 (mean ± SD). There was a good correlation between cerebrospinal fluid and serum concentrations ( r = 0.933, p < 0.001). The initial doxapram dose can be set as low as 0.2 mg/kg/h in very young premature infants with idiopathic apnea of prematurity unresponsive to methylxanthines.     

模拟高原和返回平原后大鼠心肌血流量的变化

目的：观察缺氧及停止缺氧后对大鼠心肌血流量的影响。方法：３４只Ｗｉｓｔａｒ大鼠，随机分为４组：①平原对照组；②急性缺氧组；③慢性缺氧组；④返回平原组。以放射性生物微球法测定心肌血流量。结果：急性缺氧引起ＰａＯ２、心输出量及氧运送量降低，但左、右心室心肌血流量明显增加；慢性缺氧时右心室收缩压、血球压积、血液粘滞性及右心室生理指数明显增加，而心肌血流量接近正常。停止缺氧３０ｄ后，上述所有指标均与平原以     

Prenatal lead exposure in relation to gestational age and birth weight: A review of epidemiologic studies

Although the adverse effect on pregnancy outcomes at high levels of lead exposure in the workplace has been recognized for years, there is uncertainty regarding the impact of exposure at the lower community exposure levels commonly encountered today. This review summarizes the epidemiologic literature and discusses pertinent methodologic issues and possible sources of interstudy variation. The authors conclude that prenatal lead exposure is unlikely to increase the risk of premature membrane rupture but does appear to increase the risk of preterm delivery. Whether prenatal lead exposure decreases gestational age in terms of infants is unclear. Prenatal lead exposure also appears to be associated with reduced birth weight, but results vary in relation to study design and degree of control for confounding. Adjustment for gestational age, a possible confounder of the birth weight-lead exposure association, did not yield clearer results.     

Myocardial cooling and right ventricular function in patients with right coronary artery disease: antegrade vs. retrograde cardioplegia

Background: Protection of the right ventricular (RV) myocardium during ischaemia in cardiac surgery is difficult, especially in patients with severe right coronary artery (RCA) disease. Retrograde coronary sinus cardioplegia is thought to distribute uniformly, but doubts still remain as to its adequacy in RV preservation. This study evaluated distribution of antegrade vs. exclusively retrograde coronary sinus cold blood cardioplegia by assessing myocardial cooling and compared the effects on RV function. Methods: Fifty-eight patients scheduled for elective coronary artery surgery - 29 patients with significant RCA disease and another 29 with no significant RCA stenosis (controls) - were randomised to receive either antegrade or retrograde cold blood cardioplegia through either aortic root or conventional self-inflating coronary sinus catheter (RCA-ante, RCA-retro, C-ante and C-retro groups). RV function was assessed by fast-response thermodilution. Myocardial temperatures were measured in the anterior and posterior wall of the right and left ventricle. Results: Cooling of the posterior wall of the RV was effective only in the control patients given antegrade cardioplegia (14.7°C), whereas in the other groups the lowest myocardial temperatures there remained above 20°C (RO.001). In patients with obstructed RCA both antegrade and retrograde cold cardioplegia led to uneven cooling of the myocardium. After cardiopulmonary bypass the RV ejection fraction (RVEF), RV stroke work index (RVSWI) and cardiac index (CI) were significantly reduced in the RCA-retro group, and RVSWI and CI in the C-retro group, too. Regression analysis showed an inverse relationship between the temperatures of the posterior walls of the ventricles and changes in the RVEF and CI. Conclusions: Retrograde and antegrade cardioplegia alone were not effective in reducing the temperature of the posterior wall of the RV in the patients with obstructed RCA, in whom with retrograde cardioplegia RV haemodynamics were impaired for 1 hour following bypass. Neither retrograde nor antegrade cardioplegia alone can be relied on to protect the posterior wall of the RV in the patients with obstructed RCA.     

早产胎膜早破65例妊娠结局分析

目的　探讨早产胎膜早破 (pretermprematureruptureofmembranes ,PPROM)的妊娠结局。方法　对 6 5例PPROM进行回顾性分析。结果　 6 5例PPROM中以流产引产史、感染及胎位不正多见。孕 2 8～ 34+ 6w 与孕35～ 36 + 6wPPROM比较 ,前者剖官产率明显低于后者 (P <0 .0 1) ,而新生儿发病率明显高于后者 (P <0 .0 1)。结论　对孕 2 8～ 34+ 6w 的PPROM宜采用期待疗法 ,以减少新生儿的并发症 ,降低新生儿的发病率及死亡率     

Acrometageria: A spectrum of “premature aging” syndromes

A child with manifestations of acrogeria and metageria, two “premature aging” syndromes, is presented. Because of his indistinct phenotype and because the question has been previously raised as to whether these conditions are separate, we propose the designation of acrometageria to describe this phenotypic continuum. As there is much in common clinically between acrometageria and the syndrome of type III procollagen deficiency (Ehlers-Danlos type IV), it might be presumed that a similar pathogenesis for acrometageria exists. This possibility has been tested previously, without demonstrating specific quantitative or qualitative deficits, but with some indirect evidence that collagen metabolism is deranged in these patients. One such crude indicator is the elevation of urinary hyaluronic acid levels, demonstrated in our patient and also observed in the phenotypically distinct Werner and Hutchinson-Gilford premature aging syndromes. On one hand, it could be argued that this supports the concept that premature aging syndromes exist as a biological continuum. On the other hand, it is equally valid to argue that syndromes of premature aging are so described merely because they include recognizable changes of normal aging and that the demonstration of an underlying mutation in a collagen gene, for example, invalidates their study as models of accelerated normal aging. © Wiley-Liss, Inc.