Reproducibility of thermodilution cardiac output measurements

The findings of this study provide preliminary evidence to suggest that the first in a series of three thermodilution cardiac output measurements is statistically significantly higher than the second and third measurements when 10 ml of iced 5% dextrose is used as the injectate. The repeated measures analysis of variance was highly significant (p = 0.00001) for the sample (N = 61) and for a subset of patients (N = 34) with concurrent central infusions of 1 to 25 ml/hr (p = 0.004). The first measurement was the highest reading in the series more frequently than expected (54% of the sample). However 23% of the subjects had the second measurement as the highest reading and 22% had the third reading as the highest measurement in the series. The effect of the concurrent central infusions on this set of data is not known. The mean difference between sequential measurements was smallest between the second and third measurements (0.33 L/min) but the mean difference between the first and second measurement (0.38 L/min) and the first and third measurement (0.44 L/min) was of similar magnitude. The first measurement differed from the average of the second and third measurements by more than 10% or by greater than 0.5 L/min in 26% (N = 16) of the readings for the entire sample; this figure was 38% (N = 13) in the subset of patients with concurrent central infusions of 1 to 25 ml/hr. It is important that the measurement protocol be consistent and that triplicate measurements be done so that trends in a patient's hemodynamics can be accurately assessed and the effects of therapeutic interventions evaluated. Data should be cautiously interpreted if the first measurement is significantly higher than the second and third measurements because hemodynamically compromised patients could be adversely affected by this type of technical error.     

Echography after regularization of atrial fibrillation]

An echographic study was carried out on 17 patients before and after conversion of atrial fibrillation to normal rhythm. It showed up the moment of return of atrial contraction as a movement of the posterior wall of the left auricle and a reappearance of the 'a' wave or the anterior cusp of the mitral valve. The contraction can appear immediately after the electric shock, or may be delayed.     

Noninvasive cardiac output monitoring during exercise before and after coronary artery bypass surgery

A computerized continuous wave Doppler instrument was used to monitor changes in cardiac output and stroke volume during supine symptom limited graded bicycle exercise in 30 subjects. Eight patients were studied before and after coronary artery bypass graft (CABG) and were found to have patent grafts (group 1). Six patients were symptomatic after CABG and had at least one graft occluded (group 2). Sixteen age matched asymptomatic subjects served as controls (group 3). In group 1 patients before CABG, the duration of exercise was 5 +/- 2 mins (mean +/- standard deviation), the double product was 162 +/- 25, the percentage change in cardiac output with exercise was 33 +/- 7 and the percentage change in stroke volume was 1 +/- 5. Following CABG in group 1 patients, the duration of exercise increased to 9 +/- 2 mins, the double product to 186 +/- 16, the percentage change in cardiac output to 74 +/- 14 and the stroke volume to 13 +/- 12% (P less than 0.05). These results were not significantly different from those obtained in the group 3 patients (controls) in whom the duration of exercise was 10 +/- 3 mins, double product 211 +/- 24, percentage change in cardiac output 95 +/- 30 and the percentage change in stroke volume was 13 +/- 5.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thermodilution cardiac output measurements during conventional and high-frequency ventilation

The thermodilution method for cardiac output determinations correlates well with Fick and dye dilution methods. Experimental work with thermodilution techniques has shown that individual measurements of right heart cardiac output during conventional ventilation vary throughout the respiratory cycle. The aims of this study were to compare thermodilution cardiac output determinations made at a fixed point (zero end-expiratory pressure [ZEEP]) with those made randomly throughout the respiratory cycle during conventional controlled positive pressure ventilation (CPPV) and high-frequency jet ventilation (HFJV) with up to 10cm H₂O positive end-expiratory pressure (PEEP). There were no statistically significant differences between the cardiac output determinations made at ZEEP and randomly in the ventilation cycle in any group and all correlations were significant. The clinical implications of these results are discussed, and it is concluded that it is not necessary to time the measurements of thermodilution cardiac output determinations during CPPV or HFJV with up to 10 cm H₂O of PEEP.     

继发孔型房间隔缺损介入治疗前后超声心动图心功能的对比研究

目的:使用组织多普勒技术,对房间隔缺损(atrial septal defect,ASD)介入治疗术前、后的心功能和血流动力学情况,进行对比和随访研究,了解介入治疗及封堵器植入对ASD患者心功能的影响。方法:44例单纯继发孔型ASD患者,24例为封堵术近期组,20例为封堵术中远期组,按照封堵器与左心房面,房间隔面积比的中位值分别将近期组和中远期组,分为大伞组和小伞组。所有患者,进行经胸常规及组织多普勒超声心动图检查。对所获得的组织多普勒(tissue doppler image,TDI)信息,进行图像后处理。观察封堵术前后心室肌和心房肌运动速度,应变和应变率的变化。结果:1.近期大伞组和小伞组,术前右心室游离壁基底段,各时期峰值速度均较相应对照组增高(P<0.05);各组右心房侧壁收缩速度较对照组增高(P<0.05);封堵术后1 d,各组右心室游离壁基底段,各时期峰值速度迅速下降。同期大伞组与小伞组相比较,术前二者间收缩期运动速度差异有统计学意义(P<0.05)。2.近期大伞组和小伞组术前右心室游离壁基底段收缩期、舒张期的峰值,应变及应变率均较对照组增高(P<0.05),右心房侧壁舒张期峰值,应变及应变率较对照组增高(P<0.05)。封堵术后1 d右心室游离壁基底段收缩期、舒张期和右心房侧壁的峰值应变及应变率即显著下降;同期大伞组与小伞组测定值比较,大伞组术前右心室游离壁收缩期和舒张期,应变及应变率较小伞组增高(P<0.05),术后1 d大伞组右心室游离壁舒张期应变率较小伞组增高(P<0.05)。结论:1.本组ASD患者的右心系统处于高动力状态,封堵术使这种高动力状态恢复,封堵术后1 d可见明显恢复,至术后6个月左右,右心功能恢复至正常对照组水平。2.本研究未见左心和右心功能受封堵器大小和植入时间长短的影响,提示ASD封堵术安全有效。3.组织多普勒技术能够更为早期、细致地评价心功能。     

Simple and efficient identification of conduction gaps in post-ablation recurring atrial flutters.

AIMS: Cavo-tricuspid isthmus (CTI) radiofrequency (RF) ablation is a curative therapy for common atrial flutter (AFl), but is associated with a recurrence rate of 5-26%. Although complete bidirectional conduction block is usually achieved, the recurrence of AF is due to recovered conducting isthmus tissue through which activation wavefronts pass. We evaluated a simple and efficient electrophysiological strategy, which pinpoints the ablation target. METHODS AND RESULTS: Twenty-five patients (19 men), mean age 61 +/- 6, with recurrent AFl required a repeat ablation, 250 +/- 160 days after a successful RF CTI procedure. Transverse CTI conduction was monitored during AFl or coronary sinus (CS) pacing by a 24-pole mapping catheter positioned in the right atrium (RA), with the distal poles in the CS, proximal poles on the lateral RA, and intermediate poles on the CTI. A slow conduction area traversing the CTI (velocity, 37 +/- 22 vs. 98 +/- 26 cm/s on either side, P < 0.05) and a lower potential amplitude than at both sides (0.2 +/- 0.15 vs. 0.5 +/- 0.5 mV, P < 0.05), defined by a bayonet-shaped depolarization sequence, were considered to represent the incomplete line of block (InLOB). An ablation catheter was progressively dragged up to this InLOB, from the tricuspid annulus to the inferior vena cava, analysing the widely separated double potentials (DPs) until these coalesced. In nine patients (35%), the target conduction gap was a coalesced fractionated atrial potential within the InLOB (duration, 77 +/- 12 ms), and in 16 patients (65%), a narrow DP toward the healthy margins of this InLOB (duration, 28 +/- 15 ms). Adopting this strategy yields 100% successful re-ablation of recurring AFl leading to bidirectional block, with a mean 2.7 +/- 1.4 RF applications. CONCLUSION: Transverse CTI mapping precisely locates the InLOB and helps find conduction gaps along the CTI in re-ablation procedures for common AFl.     

心脏瓣膜置换术后低心排血量综合征的临床研究

目的:分析心脏瓣膜置换术后发生低心排血量综合征(LCOS)的临床危险因素及潜在病因,为临床防治提供依据。方法:回顾性分析行瓣膜置换并有Swan-Ganz导管监测的386例患者,将其分为LCOS组和无LCOS组,对发生LCOS的相关危险因素进行多因素logistic回归分析。结果:术后发生LCOS共108例(28.0%),无LCOS278例(72.0%);年龄、术前是否有高血压、糖尿病、心律失常病史、瓣膜置换方式在2组间无明显差异(P>0.05);LCOS组术前体重指数小于非LCOS组,而心胸比、脑钠肽(BNP)、肺动脉压力(PAP)、欧洲心血管手术危险因素评分系统高于后者,术中的体外循环(CPB)时间、主动脉阻断时间长于非LCOS组,术后的出血量、二次手术例数也多于非LCOS组(均P<0.05);多因素logistic回归分析表明术前BNP>600pg/mL、体重指数<18kg/m2、心胸比>0.7、PAP>65mmHg、CPB时间>120min、主动脉阻断时间>60min和术后出血量>20%总血容量是心脏瓣膜病术后发生LCOS的独立危险因素。结合Swan-Ganz导管监测数据和床边心脏超声等辅助检查分析发现,有62例(57.4%)因前负荷不足、36例(33.3%)因泵功能衰竭、6例(5.6%)因心脏压塞、4例(3.7%)因心律失常导致术后的LCOS。结论:术前心功能差、低体重、心胸比>0.7、肺动脉高压、体外循环时间及主动脉阻断时间长,术后出血量多是心脏瓣膜病术后发生LCOS的危险因素;导致LCOS的主要原因有前负荷不足、泵功能衰竭、心脏压塞和心律失常。     

Morphologic study of cardiac cells in sheep before and after electric shock

A combined electrophysiological and histopathological study was conducted on sheep myocardium fragments rich in easily identifiable conduction cells subjected to electric shocks of varying intensity. Tissue fragments were immersed in a thermostatically-controlled bath at 37 degrees C, perfused with a carbonated standard tyrode solution at the rate of 30 ml/min and stimulated at a constant bipolar 1 C/sec tension twice as high as the threshold of diastolic excitability. After measurement of reference values, electric shocks of 2 to 80 joules were delivered between two electrodes placed on both sides of the tissue fragment. The electrophysiological part of the study showed disorders of conduction which, depending on the energy delivered, were more or less complete and reversible. The histopathological part of the study showed that conduction tissue was extremely fragile, even to low-energy shocks. This fragility was in glaring contrast with the relatively modest damage suffered by myocytes. Liquefaction and/or coagulation of Purkinje's cells was also striking, as it extended over an area much wider than that subjected to the shock. Thus, with medium intensity shocks destroyed conduction bundles were seen to creep between myocytes that often were perfectly normal or showed rare hypercontraction bands. Some myocytes were in the process of degeneration or even eosinophilic necrosis, but except in case of violent shock these were more or less isolated elements in the vicinity of the stimulated area. The fragility of conduction tissue and its selective damage by low-intensity shocks may be explained partly by its low impedance which allows preferential passage of the electric current.(ABSTRACT TRUNCATED AT 250 WORDS)     

ANP and BNP in atrial fibrillation before and after cardioversion--and their relationship to cardiac volume and function

The role of atrial (ANP) and B-type (BNP) natriuretic peptide in atrial fibrillation (AF) is not clear. Our aim was to describe ANP and BNP in AF, and their changes following cardioversion in persistent AF. Furthermore, we wanted to assess the association between ANP and BNP and cardiac volume and function evaluated by magnetic resonance imaging. ANP and BNP decreased significantly following cardioversion. After 180 days of sinus rhythm, ANP and BNP were still significantly elevated. Same results were seen in patients with lone AF. Left and right atrial volumes correlated positively with ANP and BNP. Changes in left atrial volume were predictive of changes in ANP and BNP following cardioversion. AF may cause enduringly elevated ANP and BNP and atrial volume seems to be an important determinant of ANP and BNP in AF.     

Functional capacity before and after cardioversion of atrial fibrillation: a controlled study.

OBJECTIVE--To evaluate the effect of cardioversion on peak oxygen consumption (peak VO2) in patients with long-standing atrial fibrillation, to assess the importance of underlying heart disease with respect to the response to exercise, and to relate functional capacity to long-term arrhythmia outcome. DESIGN--Prospective controlled clinical trial. SETTING--Tertiary referral centre. PATIENTS--63 consecutive patients with chronic atrial fibrillation accepted for treatment with electrical cardioversion. Before cardioversion all patients were treated with digoxin, verapamil, or a combination of both to attain a resting heart rate < or = 100 beats per minute. INTERVENTIONS--Electrical cardioversion. MAIN OUTCOME MEASURES--Peak VO2 measured before and 1 month after electrical cardioversion to compare patients who were in sinus rhythm and those in atrial fibrillation at these times. Maintenance of sinus rhythm for a mean follow up of 19 (7) months. RESULTS--Mean (1SD) peak VO2 in patients in sinus rhythm after 1 month (n = 37) increased from 21.4 (5.8) to 23.7 (6.4) ml/min/kg (+11%, P < 0.05), whereas in patients with a recurrence of atrial fibrillation 1 month after cardioversion (n = 26) peak VO2 was unchanged. In patients who were in sinus rhythm both those with and without underlying heart disease improved, and improvement was not related to functional capacity or left ventricular function before cardioversion. Baseline peak VO2 was not a predictive factor for long-term arrhythmia outcome. CONCLUSION--Restoration of sinus rhythm improved peak VO2 in patients with atrial fibrillation, irrespective of the presence of underlying heart disease. Peak VO2 was not a predictive factor for long-term arrhythmia outcome after cardioversion of atrial fibrillation. These findings suggest that cardioversion is the best method of improving functional capacity in patients with atrial fibrillation, whether or not they have underlying heart disease and whatever their functional state.     

冠状动脉旁路移植术后低心排的危险因素

目的探讨冠状动脉旁路移植（CABG）术后低心排的危险因素。方法：采用病例对照研究,以宜昌市第一人民医院重症医学科2008年1月-2012年9月CABG术后临床资料完整的全部病例（92例）患者为研究对象,低心排[诊断标准：多巴胺用量〉10μg／（kg·min）]者为病例组（n=13）,以无低心排患者对照组（n=79）。对两组患者潜在的危险因素进行对比分析,并采用非条件logistic多元回归分析判断影响CABG术后低心排的独立危险因素。结果：单因素分析结果显示：年龄、性别、术前近期心肌梗死（MI）、心律失常、术后呼吸衰竭、术前贫血为CABG术后低心排的危险因素。logistic多因素回归分析显示,CABG术后低心排的独立的危险因素是：术前近期MI OR18．149,95．O％CI[1．949-169．011];心律失常OR 30．509,95．0％CI[2．607-357．028];女性OR 10．743,95．0％CI[1．347-85．659]（P〈0．05,P〈0．01）。结论：术前近期MI;心律失常是CABG术后低心排的独立的危险因素。