高原地区体外循环应用超滤对儿童术后右心室功能的影响

目的　探讨高原地区体外循环 (CPB)中应用血液超滤技术对心内直视手术后右心室功能的保护作用。方法　选择在海拔 370 0m开展的CPB心脏手术患者 12例 ,根据CPB过程中有无应用血液超滤技术 ,将患者分成血液超滤组和对照组 ,分别于CPB前、CPB结束时以及CPB后 1h、3h、6h、12h、2 4h ,测定肺动脉平均压 (MPAP)、右心房压 (RAP)、右心室舒张末容积指数 (RVEDVI)、右心室射血分数 (RVEF)、心脏指数 (CI)、右心室每搏容量指数 (RVSI)和肺血管阻力指数 (PVRI)。结果　CPB结束和CPB后 6h内 ,对照组MPAP、RVEDVI以及RAP均较CPB前明显升高 (P <0 0 5 ) ,而RVEF、CI和RVSI较CPB前降低 (P <0 0 5 ) ;CPB后 12h对照组MPAP、RVEDVI以及RAP均逐渐减低 ,但RVEF、CI和RVSI仍未高于CPB前 ;血液超滤组RVEF、CI和RVSI在CPB后各时间点均显著高于对照组 (P <0 0 5 )。结论　高原地区在CPB下施行心内直视手术后早期 ,右心室心肌收缩力显著降低 ,右心室的泵血功能受损 ;CPB中应用血液超滤技术有利于CPB后心脏泵血功能的恢复。     

Decreased right ventricular function after coronary artery bypass grafting

Decreased right ventricular function after coronary artery bypass grafting is a common and well-known (if not well-understood) phenomenon.We prospectively evaluated right ventricular function via echocardiographic tricuspid annular motion, tricuspid annular velocity, and right ventricular strain analysis before and after coronary artery bypass grafting. We also evaluated the effect of right coronary artery disease and revascularization on post-coronary artery bypass grafting, right ventricular function, and interventricular septal motion.We performed baseline echocardiography in 250 candidates for coronary artery bypass grafting, and we repeated echocardiography in 240 of those patients 1 year after coronary artery bypass grafting. We evaluated right ventricular function via tricuspid annular motion, tricuspid annular velocity, and right ventricular strain analysis, all measured at the right ventricular free wall.Right ventricular function as evaluated by tricuspid annular motion showed a significant reduction 1 year after coronary artery bypass grafting (21.7 vs 12.1 mm; P < 0.001) compared with preoperative measurements. Right ventricular tissue velocity (14.0 vs 7.0 cm/s; P < 0.001) and right ventricular strain (20.3% vs 11.6%; P < 0.001) were also significantly reduced after coronary artery bypass grafting. Interventricular septal motion was paradoxical in 97% of the patients 1 year after coronary bypass.Right ventricular function remained depressed for as long as 1 year after coronary artery bypass grafting. These findings were independent of the state of the right coronary artery and the graft. It is likely that the interventricular septum is recruited to maintain right ventricular stroke volume after coronary artery bypass grafting.     

Pulmonary artery occlusion pressure is not accurate immediately after cardiopulmonary bypass

Elevated pulmonary vascular resistance (PVR), differential cardiac dynamics, and increased lung water following cardiopulmonary bypass (CPB) have been proposed as limitations to the accuracy of the pulmonary artery occlusion pressure (PAOP) in estimating left ventricular preload. A prospective study of 22 patients undergoing elective myocardial revascularization is described wherein PAOP was compared with directly measured left atrial pressure (LAP). The reliability of PAOP to estimate LAP in the hour immediately following CPB and at 1, 4, 8, and 12 hoyrs post-CPB was examined with repeated measures analysis of variance. Relationships between the PAOP-LAP difference and PVR, core temperature, arterial CO₂ tension, and right and left ventricular stroke work indices (RVSWI, LVSWI) were tested by linear regression analysis. There was greater variability in measurements at 15, 30, and 45 minutes immediately after CPB, demonstrated by a pooled correlation coefficient of 0.73 versus 0.90 in the postoperative period. The degree of discrepancy between PAOP and LAP lessened with time. There was no determinable relationship of the PAOP-LAP gradient to PVR, level of PCO₂, temperature, RVSWI, or LVSWI. Potential sources of discrepancy include airway pressure effects, position of the measuring catheters, positive end-expiratory pressure, infusion of protamine sulfate, extremes of pulmonary artery pressures, and effects of an open pericardium. This study was designed to limit the contribution from these sources, but a consistent pattern of discrepancy was observed. A previously proposed cause of increased lung water following CPB was not supported by the present study. In conclusion, the use of a pulmonary artery catheter alone to estimate left heart filling pressure immediately following CPB may lead to inaccurate ventricular function curves and treatment; however, postoperative use offers acceptable reliability.     

Effects of mechanical ventilation on right and left ventricular function

We have discussed the complex hemodynamic changes that occur throughout the respiratory cycle during mechanical ventilation and have reviewed the physiologic changes associated with spontaneous respiration. In patients, many cumulative factors account for the total hemodynamic burden of mechanical inspiration and expiration. Thus, the change in pleural pressure, respiratory rate, mode of ventilation, amount of spontaneous ventilation, underlying lung and cardiac disease, and intravascular volume status all affect cardiocirculatory equilibrium during the respiratory cycle. Knowledge of the effects presented in this article will aid the physician in choosing the therapeutic options in instrumented, mechanically ventilated patients.     

Central nervous system function after cardiopulmonary bypass

In a prospective study, an elderly group of patients (n = 63,47 male, 16 female, age 40–65 years) was examined beforeand after open-heart surgery under cardiopulmonary bypass: postoperatively,19 patients (30%) showed no clinical neuropsychiatric symptoms,whereas in 35 patients (56%) mild or transient neurologicalsigns and in nine (14%) severe neurological complications werefound. The postoperative EEG changes were characterized by a slightdelta-theta increase, an alpha decrease and a significant cantslowing of the dominant frequency from 9.7 to 9.3 Hz. In brainstemauditory evoked potentials no changes were found, and in somatosensoryevoked potentials (median nerve) the latency of the early corticalcomponent, N20, increased. Cardiovascular reflexes showed increasedchanges, similar to those found in autonomic neuropathies. Inthe neuropsychological test battery, the Visual retention test(Benton) and the Rorschach test showed slight postoperativeimprovement, whereas other psychometric variables (flicker fusionfrequency, reaction time) did not change. Despite an improvedoperative technique some minor clinical and neurophysiologicaldisturbances of the central nervous system remain. However,specific pre- or peri-operative risk factors for these postoperativedisturbances or complications could not be identified.     

Influence of pericardiectomy on cat right ventricular function after pulmonary arterial constriction

Although the results of mitral valve replacement in patients with mitral valve disease and pulmonary arterial hypertension are usually gratifying, persistent right ventricular decompensation occasionally occurs despite successful insertion of a mitral prosthesis. It is possible that when pulmonary hypertension is slow to resolve, the loss of an intact pericardium incurred by the operative intervention allows right ventricular dilatation to occur acutely. In some cases, the latter might lead to chronic irreversible right ventricular failure. To test this hypothesis, right ventricular hypertension and failure were produced in 62 cats by pulmonary arterial banding. Thirty-two of these cats had a total pericardiectomy, and in 30 the pericardium was reconstituted. The mortality rates for each group were similar. Right heart catheterization was performed in the surviving animals 4 to 145 days later. There were no significant differences in the degree of right ventricular failure between cats with and without an intact pericardium. Isometric contractile function of papillary muscles was measured with each muscle at the peak of its length-tension curve (L_max). Active tension, rate of tension development, time to peak tension and the contractile response of the papillary muscles to norepinephrine were similar in each group. Thus, the absence of a pericardium does not seem to affect the degree of experimental right ventricular failure induced by a chronic pressure stress on the right ventricle.     

Influence of respiratory variations on right ventricular function

Respiratory effort during inspiration, expiration, and the Valsalva manoeuvre changes right ventricular preload and afterload. On inspiration these changes should improve systolic emptying of a larger end diastolic volume and so increase the ejection fraction, whereas on expiration the reverse should be true. The resting right ventricular ejection fraction was measured by first pass radionuclide angiography with gold-195m (half life 30.5 s) in 17 individuals at maximal inspiration and expiration and in eight at rest and during the strain phase (phase 2) of the Valsalva manoeuvre. The right ventricular ejection fraction was significantly lower during expiration than during inspiration. There were, however, no significant differences in bolus duration or right ventricular transit time. The Valsalva manoeuvre, in contrast, significantly increased the ejection fraction and also significantly prolonged both the bolus duration and right ventricular transit time. The conformation of the bolus curves during the Valsalva manoeuvre suggested the development of tricuspid regurgitation. These data suggest that relative influences of venous return, pulmonary arterial pressure, pulmonary vascular resistance, and possible functional tricuspid regurgitation vary during inspiration, expiration, and the Valsalva manoeuvre and can affect the right ventricular ejection fraction. Changes in right ventricular function on exercise assessed by first pass radionuclide angiography must be interpreted with caution because maximal respiratory effort may alter the right ventricular ejection fraction independently of ischaemia or other non-ischaemic factors.     

Impact of different pacing modes on left ventricular function following cardiopulmonary bypass

BACKGROUND: Patients with severely impaired left ventricular (LV) function often demonstrate prolonged inter- and intraventricular conduction. This prospective study investigates hemodynamic effects and outcomes of perioperative temporary biventricular pacing in patients with heart failure undergoing heart surgery. METHODS: 80 consecutive cardiac surgery patients with a LV ejection fraction below 35 % received biventricular stimulation via temporary myocardial electrodes. Group 1 consisted of 40 patients with LV dilatation (mean LVEDD 65 +/- 5 mm), Group 2 of 40 patients with normal or slightly dilated LV (mean LVEDD 52 +/- 4 mm). RESULTS: Hemodynamic parameters were measured immediately, 6 and 24 hours after operation. An increase of cardiac index (CI) and arterial blood pressure with biventricular pacing was observed in 27 patients (Group 1/67.5 %) versus 22 patients (Group 2/55 %) from 2.4 +/- 0.7 l/min/m2 to 3.5 +/- 0.5 l/min/m2 ( P < 0.01). This benefit persisted 6 and 24 hours postoperatively. The remaining patients already showed a higher cardiac index prior to pacing (3.7 +/- 0.9 l/min/m2). In Group 1, the duration of ventilation support and time in the intensive care unit of responding patients was shorter. QRS duration before surgery was not predictive for the response to biventricular pacing. CONCLUSIONS: In the majority of patients with reduced LV function, temporary biventricular pacing improves CO and arterial blood pressure after surgery, especially when LV dilatation is present.     

Effect of modified ultrafiltration on pulmonary function after cardiopulmonary bypass

BACKGROUND: Pulmonary dysfunction is one of the most common manifestations of inflammatory response after cardiopulmonary bypass (CPB). OBJECTIVE: This prospective randomized study was conducted to evaluate the effect of a modified ultrafiltration (MUF) technique on pulmonary function after CPB in children. METHODS: Forty patients weighing from 5 to 10 kg with congenital heart disease who required CPB for primary biventricular operative repair were prospectively randomized into two groups. The control group received conventional ultrafiltration (CUF) during CPB, and the study group received CUF and MUF. Pulmonary compliance (static and dynamic) and gas exchange capacity of the lung expressed as oxygen index, respiratory index, ventilation index, and alveolar-arterial oxygen pressure difference were measured after intubation (baseline), at the termination of CPB, at the end of MUF, on admission to the ICU, and 6 h postoperatively. RESULTS: There was no significant difference in lung compliance and gas exchange between the two groups before CPB. CPB produced a significant decrease in static and dynamic lung compliance in both groups. In the control group, static and dynamic lung compliance decreased from 1.0 +/- 0.3 to 0.90 +/- 0.3 mL/cm/kg and 0.87 +/- 0.2 to 0.71 +/- 0.1 mL/cm/kg (+/- SE) [p = 0.0002 and p = 0.002, respectively]. In the study group, static and dynamic lung compliance decreased from 1.0 +/- 0.2 to 0.89 +/- 0.03 mL/cm/kg and 0.94 +/- 0.2 to 0.77 +/- 0.1 mL/cm/kg (p = 0.002 and p = 0.002, respectively). There was no significant difference in the decrease in static (p = 0.9) or dynamic lung compliance (p = 0.3) between the two groups. MUF produced a significant immediate improvement in both static lung compliance (0.89 +/- 0.2 to 0.98 +/- 0.2 mL/cm/kg, p = 0.03) and dynamic lung compliance (0.77 +/- 0.1 to 0.93 +/- 0.2 mL/cm/kg, p = 0.007). The same was observed regarding the gas exchange capacity. CPB produced a significant decrease in lung gas exchange capacity, and MUF produced a significant immediate improvement in lung gas exchange capacity. The effect of MUF on lung compliance and gas exchange capacity was not sustained after admission to the ICU nor 6 h later postoperatively. There was no significant difference in the time of extubation between the two groups (12 +/- 3 h and 13 +/- 2 h, p = 0.4), the length of ICU stay, or the total hospital stay postoperatively. CONCLUSIONS: The use of MUF after CPB can produce an immediate improvement in lung compliance and gas exchange capacity, which may effectively minimize pulmonary dysfunction postbiventricular repair of congenital heart disease. However, these improvements are not sustained for the first 6 h postoperatively and do not reduce the duration of postoperative intubation, ICU stay, or total hospital stay.     

Influence of acute preoperative hemodilution on right ventricular function

In a randomized study, the effects of acute, preoperative hemodilution (HD) (12 mL/kg) on right ventricular function were investigated in coronary artery surgery patients with reduced left ventricular function (ejection fraction < 50%) and significant stenosis of the right coronary artery (RCA). Blood was replaced either by hydroxyethyl starch (HES) solution (ratio 1:1; HD-HES; n = 15) or by Ringer's lactate, (RL) (ratio 2.5:1; HD-RL; n = 15). Fifteen comparable patients without HD served as a control group. Besides commonly measured pressure parameters, right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV), and right ventricular ejection fraction (RVEF) were measured using a computerized thermodilution technique before and after HD, as well as after extracorporeal circulation (ECC). Right ventricular systolic function, expressed as RVEF, was not changed significantly by HD in any group. Furthermore, right ventricular function of the hemodiluted patients was not impaired by the subsequent ECC procedure. None of the traditionally measured parameters could be correlated significantly to the right ventricular thermodilution variables. It is concluded that moderate HD does not change right ventricular function even when the RCA is significantly stenosed.     

Influence of respiratory variations on right ventricular function.

Respiratory effort during inspiration, expiration, and the Valsalva manoeuvre changes right ventricular preload and afterload. On inspiration these changes should improve systolic emptying of a larger end diastolic volume and so increase the ejection fraction, whereas on expiration the reverse should be true. The resting right ventricular ejection fraction was measured by first pass radionuclide angiography with gold-195m (half life 30.5 s) in 17 individuals at maximal inspiration and expiration and in eight at rest and during the strain phase (phase 2) of the Valsalva manoeuvre. The right ventricular ejection fraction was significantly lower during expiration than during inspiration. There were, however, no significant differences in bolus duration or right ventricular transit time. The Valsalva manoeuvre, in contrast, significantly increased the ejection fraction and also significantly prolonged both the bolus duration and right ventricular transit time. The conformation of the bolus curves during the Valsalva manoeuvre suggested the development of tricuspid regurgitation. These data suggest that relative influences of venous return, pulmonary arterial pressure, pulmonary vascular resistance, and possible functional tricuspid regurgitation vary during inspiration, expiration, and the Valsalva manoeuvre and can affect the right ventricular ejection fraction. Changes in right ventricular function on exercise assessed by first pass radionuclide angiography must be interpreted with caution because maximal respiratory effort may alter the right ventricular ejection fraction independently of ischaemia or other non-ischaemic factors.     

右心室流出道间隔部起搏对左心室功能的影响

目的比较右心室流出道间隔部(RVOT)起搏与右心室心尖部(RVA)起搏的血流动力学差异;评估RVOT起搏技术的可行性与安全性。方法选择有永久起搏器置入适应证的患者75例。根据术者建议和患者意愿分为RVOT组(40例)和RVA组(35例)。所有房室传导阻滞及病窦综合征合并一度房室传导阻滞患者采用双腔起搏双腔感知触发抑制型起搏模式,心房颤动伴长间歇患者采用抑制型心室按需起搏模式。比较2组的血流动力学差异。结果 RVOT组的QRS波宽度较RVA组缩窄(23.2±28.7)ms,差异有统计学意义(P<0.01)。与RVA组比较,RVOT组LVEF、左心室短轴缩短率明显升高,左心室舒张末容积明显下降(P<0.05,P<0.01)。与术前比较,RVA组LVEF、左心室短轴缩短率明显下降,左心室舒张末容积明显升高,差异有统计学意义(P<0.01)。结论利用螺旋电极进行RVOT起搏可行且较为安全。RVOT起搏的血流动力学参数优于RVA。     

Left ventricular function immediately after exercise in elite cyclists.

To determine the response to exercise of the left ventricle of endurance-trained athletes, 6 elite (world class) cyclists were compared to 6 untrained healthy control subjects. In athletes the stroke volume increased with exercise. In untrained volunteers the stroke volume did not change with exercise. This difference of the response of the stroke volume to exercise reflected a difference of the left ventricular end-diastolic volume. In athletes the left ventricular end-diastolic volume tended to increase. In control subjects the end-diastolic volume decreased. In conclusion, athletes increased cardiac output by increasing stroke volume and heart rate, whereas control subjects increased their cardiac output only by increasing their heart rate.     

Lung function after deep hypothermic cardiopulmonary bypass in infants

There is increasing concern about neurologic injury due to deep hypothermia with low flow during repair of complex congenital heart defects in neonates and infants. Twenty infants with ventricular septal defect and pulmonary hypertension were randomly assigned to cardiac repair under deep hypothermia with circulatory arrest or deep hypothermia with low flow. Measurements of static pulmonary compliance, airway resistance, and respiratory index were performed before institution of cardiopulmonary bypass and at 5 minutes and 2 hours after cessation of cardiopulmonary bypass. Both groups had significant pulmonary dysfunction in terms of static pulmonary compliance, airway resistance, and respiratory index. There was greater impairment of pulmonary compliance and respiratory index after deep hypothermia with low flow, and this group required longer intensive care unit stay.     

Left ventricular function during and after right ventricular pacing

OBJECTIVES: The aim of this research was to evaluate right ventricular pacing effects on left ventricular function. BACKGROUND: Right ventricular pacing alters the ventricular activation sequence and reduces left ventricular ejection fraction (EF). It is unclear whether the observed reduction in EF can be completely attributed to the alteration in activation sequence. METHODS: Twelve subjects (eight women), mean age 68 +/- 12 years, with transvenous dual-chamber pacemakers, normal left ventricular function, and intact atrioventricular (AV) conduction were studied with serial-gated blood pool studies. Left ventricular EF was measured at a fixed rate after at least 1 week of atrial pacing only (baseline), during short-term (2 h) and mid-term (1 week) AV sequential pacing with a short AV delay, and after short- and mid-term AV pacing. RESULTS: Baseline EF was 66.5 +/- 4.5%. Short-term AV pacing resulted in a decrease in EF to 60.3 +/- 5.2% (p < 0.0002). After one week of AV pacing, there was a further decline in EF to 52.9 +/- 8.3% (p < 0.0001). After cessation of mid-term pacing, EF was 57.3 +/- 5.9% (p < 0.0001 vs. baseline). A total of 2, 5, 8, and 24 h later, EF remained depressed (59% to 60%, p < 0.007). At 32 h, EF was 62.9 +/- 7.6% (p < 0.11 compared with baseline). CONCLUSIONS: The abnormal activation sequence resulting from right ventricular pacing accounts for only part of the reduction in EF as mid-term pacing is associated with a lower EF than short-term pacing, and EF remains depressed after cessation of AV pacing. Changes in ventricular function induced by right ventricular pacing may account for some of its associated adverse effects.     

单纯急性下壁心肌梗死及其合并右心室心肌梗死对右心长轴功能的影响

目的应用心肌组织多普勒技术结合M型超声心动图,评价单纯急性下壁心肌梗死及其合并右心室心肌梗死对右心室长轴功能的影响。方法选择首次急性下壁心肌梗死患者28例,分为单纯急性下壁心肌梗死18例(Ⅰ组),急性下壁心肌梗死伴右心室心肌梗死10例(Ⅱ组),另选健康体检者20例(Ⅲ组)。在标准心尖四腔心切面二维图像指引下,应用M型超声记录右心房室环右心室游离壁及中心纤维支架处运动曲线,测量收缩期、舒张早期、舒张晚期最大运动幅度(SD,DED,DAD)及收缩期、舒张早期、舒张晚期平均运动速度(SMV,DEMV,DAMV),计算DED/DAD比值。心肌组织多普勒记录该处运动速度曲线,测量上述各期最大运动速度(Sm、Em、Am)及Em/Am比值。结果与Ⅲ组比较,Ⅰ组和Ⅱ组右心房室环右心室游离壁处SD、DED、DED/DAD、SMV、DEMV、Sm及Em均明显下降。DAD、DAMV、Am虽有下降,但差异无统计学意义。结论急性下壁心肌梗死无论是否合并右心室心肌梗死均可影响右心室长轴功能,导致右心室整体功能降低。     

Combined thermodilution and two-dimensional echocardiographic evaluation of right ventricular function during respiratory support with PEEP

In ten patients requiring respiratory support for an episode of acute respiratory failure (ARF), the best therapeutic level of PEEP was determined by measurement of changes in lung and chest wall compliance (CT) during a PEEP challenge from 0 to 20 cm H2O. During this challenge, hemodynamic monitoring combined with thermodilution measurement of right ventricular (RV) ejection fraction (EF) and two-dimensional echocardiographic measurement of RV size permitted assessment of the effects of increasing levels of PEEP on RV function. RV preload, as reflected by RV end-diastolic volume (EDV) and two-dimensional RV end-diastolic area (EDA), remained unchanged and RV diastolic compliance progressively decreased. On the other hand, RV systolic function, as assessed by RVEF and two-dimensional RV fractional area contraction (FAC), was progressively depressed. Substantial deleterious effects of PEEP were noted at high levels of PEEP including reduced CT and augmented pulmonary vascular resistance. Inadequate increase in RV preload to compensate for increased RV afterload resulted in depressed RV systolic function and contributed to the reduction in cardiac output. Finally, two-dimensional echocardiography proved to be more sensitive than fast-response thermodilution to evaluate change in RV function.     

体外循环心脏手术对机体免疫功能的影响

目的　探讨体外循环心脏直视手术病人围术期细胞和体液免疫功能的变化及其临床意义。方法　选择 45例心脏直视手术病人 ,检测术前、术后 1天、3天、7天和 14天的血清 T淋巴细胞亚群 ,CD3 ( T淋巴细胞总数 )、CD4(辅助 T淋巴细胞 )、CD8(抑制 T淋巴细胞 )、自然杀伤细胞 ( NK)活性和免疫球蛋白水平。结果　术后第 1、3天血清 CD3、CD4、CD8活性明显降低 ,CD4/ CD8比值下降 ,NK细胞活性增强 ;免疫球蛋白均较术前降低。术后 7至 14天逐步恢复至术前水平。结论　体外循环心脏直视手术对患者细胞和体液免疫均有不良影响 ,临床应采取相应措施 ,改善术后病人免疫机能 ,预防术后感染