Ventilatory support in the intensive care unit

This article focuses on the functional features of positive-pressure ventilators, the modes of invasive and non-invasive mechanical ventilation, and the main ventilator settings. It also highlights the potential complications of mechanical ventilation, the basic principles of weaning, and the pathophysiological basis of patient-ventilator dyssynchrony.     

高血压患者左室舒张功能与左室肥厚的关系及随龄改变

为探讨原发性高血压 (以下简称高血压 )患者的左室舒张功能和左室肥厚的关系及其随龄改变 ,抽取 1995年 2月至 2 0 0 2年 7月间门诊高血压患者 4 81例为高血压组 ,以同期体检健康者 2 54 3例为对照组 ,年龄 10～ 80岁 ,并将原发性高血压患者分为 3级 ,每级中按性别分 2组。采用惠普 2 50 0彩色多普勒超声诊断系统检测 2组的室间隔厚度、左室后壁厚度、E/A等指标。使用SPSS软件进行统计学处理分析。结果 :高血压和正常对照组相比E/A显著下降 ,室间隔和左室后壁显著增厚 (P <0 .0 1)。 2个组的E/A均随年龄下降 ,而室间隔厚度随年龄增厚 ,且室间隔厚度和E/A呈显著负偏相关 (P <0 .0 1)。在高血压分级组中 ,Ⅰ～Ⅲ级高血压组中男性的室间隔厚度均厚于女性 (均P <0 .0 1) ,Ⅰ、Ⅱ级高血压组中男性的左室后壁厚度厚于女性 (P <0 .0 5,P <0 .0 1) ,Ⅰ级高血压组中女性的E/A低于男性 (P <0 .0 5)。提示 :左室舒张功能随着年龄的增加而降低 ,而且和高血压左室肥厚呈负偏相关关系 ,性别对其也有一定的影响     

哺乳期营养对室间隔心肌细胞发育的影响——游离心肌细胞的形态测量

在心肌细胞分化性生长时期,改变新生鼠的哺乳期营养条件对这些鼠的空间隔心肌细胞将会产生暂时性作用和持久性影响。哺乳期高营养的暂时性作用是增加空间隔心肌细胞的大小和数量;而低营养的暂时性作用则是减慢室间隔心肌细胞的生长。哺乳期高营养的持久性作用是限制室间隔心肌细胞的过度肥大;而低营养则促进成熟鼠的室间隔心肌细胞的过度肥大。     

经皮穿刺封堵室间隔膜部缺损的应用解剖

目的:为经皮穿刺室间隔膜部缺损的封堵术提供应用解剖学基础。方法:解剖测量38例(男25.女13)正常成年人的心标本的室间隔膜部及周围结构。结果:室间隔膜部的形态可分为三角型、圆型和椭圆型;各型的出现率分别为58％(22例)、23.7％(9例)和18.3％(7例)。室间隔膜部在左室面的高度为(8.79±2.27)mm。右室面高度为(6.43±1.43)mm。室间隔膜部的长度为(9.37±2.52)mm。室间隔膜部上、下、前、后方和中点的厚度分别为(0.80±0.19)mm、(0.70±0.16)mm、(0.78±0.28)mm、(0.75±0.1 5)mm和(0.52±0.13)mm。结论:室间隔膜部以三角型为主,多位于室上嵴的后缘,膜部的左室面高于右室而和靠近右室面,建议封堵器的左室面的面积应大于右室面。     

Correlation between Electrocardiographic Features and Mechanical Dyssynchrony in Heart Failure Patients with Left Bundle Branch Block

Background: Few electrocardiographic parameters beyond the QRS duration were studied with regard to the correlation with mechanical dyssynchrony. This study aims to analyze the correlation between electrocardiographic parameters and mechanical dyssynchrony in patients with symptomatic heart failure (HF) and left bundle branch block (LBBB). Methods: Patients with HF, ejection fraction ≤ 35%, and QRS interval ≥ 120 ms with a LBBB were prospectively studied. We analyzed the correlation between electrocardiographic parameters (QRS duration, R voltage in limb leads, S voltage in precordial leads, Sokolow and Cornell indexes, QRS axis deviation, and QRS notches in lateral and inferior leads) and mechanical dyssynchrony measured by tissue Doppler imaging (TDI). Results: A group of 50 patients were studied, 60% male, 78% with nonischemic cardiomyopathy, NYHA Class III–IV (86%), and ejection fraction of 0.22 ± 0.6. Intra‐ and interventricular dyssynchrony occurred in 68% and 74% of patients, respectively. The S amplitude in precordial leads and the Sokolow and Cornel indexes show a weak correlation with the degree of dyssynchrony. In the patients with QRS notching in the lateral and inferior leads, we observed significantly greater prevalence of intraventricular dyssynchrony, with sensitivity and specificity of 85% and 56%, respectively, for notches in lateral leads. The QRS duration presents moderate correlation with the degree of both intraventricular (r = 0.48) and interventricular dyssynchrony (r = 0.46). Conclusion: The following electrocardiographic parameters were related to the degree of mechanical dyssynchrony: QRS duration and notches in QRS. In addition, the patients tend to have highest S amplitude in precordial leads. Ann Noninvasive Electrocardiol 2011;16(1):41–48     

Three-dimensional echocardiographic evaluation of mechanical dyssynchrony in systolic heart failure with narrow QRS complex

ObjectivesTo investigate the role of three-dimensional echocardiography (3DE) in evaluation of left ventricular mechanical dyssynchrony (LVMD) in heart failure (HF) patients with narrow QRS.Methods143 subjects (70 with HF and narrow QRS, 23 with HF and LBBB and 50 controls) were subjected to 3DE, evaluating global and regional dyssynchrony using systolic dyssynchrony index, maximum segmental dyssynchrony and opposite segment dyssynchrony. Spatial distribution of LVMD was studied in each patient using 3DE derived regional time volume curves. Extent of LVMD in HF patients with narrow QRS was compared to those with left bundle branch block (LBBB).ResultsFrequency of LVMD was similar in HF patients with narrow QRS or LBBB (55.7% vs. 47.8%, p = NS). There was no difference in the severity of LVMD between these two groups (10.7 ± 6.7% vs. 12.1 ± 7.4%, p = NS). Both HF groups had significantly more dyssynchrony than controls. A scattered pattern of distribution of asynchronous segments was seen in narrow QRS patients; 33.96% of them had their earliest contracting segment, instead of delayed segment, located in areas conventionally targeted for LV pacing i.e. anterolateral, inferolateral or inferior segments.Conclusions3DE confirmed significant dyssynchrony in  > 50% HF patients with narrow QRS as demonstrated by other imaging methods. 3D distribution patterns of asynchronous segments indicate possibility of left ventricular mechanics related reasons responsible for lack of CRT responsiveness, an observation that generates hypothesis on possible reasons of CRT non-responsiveness.     

Left Ventricular Dyssynchrony and Its Effects on Cardiac Function in Patients with Newly Diagnosed Hypertension

Objectives: Left ventricular (LV) systolic synchrony, defined as simultaneous peak contractions of corresponding cardiac segments, is well documented to be impaired in hypertension but its effect on LV function is not clear. The aim of this study was to assess the impacts of LV systolic dyssynchrony on LV function in newly diagnosed hypertensives. Methods: Forty-eight newly diagnosed hypertensive patients and 33 controls were enrolled. All study population underwent a comprehensive echocardiographic evaluation including tissue synchrony imaging. The time to regional peak systolic tissue velocity (Ts) in LV by 12 segmental models was measured and two parameters of systolic dyssynchrony were computed. Results: Baseline demographic characteristics were similar in both study groups. Dyssynchrony parameters prolonged in newly diagnosed hypertensive patients compared to controls: the standard deviation (SD) of 12 LV segments Ts (40.2 ± 21 vs. 26.2 ± 13.4, P = 0.003); the maximal difference in Ts between any 2 of 12 LV segments (123.3 ± 61.5 vs. 79.8 ± 37.9, P = 0.001). In multivariable analysis, Ts-SD-12 was found to be an independent predictor for systolic function (β=-0.29, P = 0.008). But, both diastolic and global functions were not independently related to Ts-SD-12. Conclusion: LV synchronization is impaired in newly diagnosed hypertensive patients. LV dyssynchrony is one of the independent predictors of systolic function in hypertensive patients.