多普勒超声心动图（PDE）评价不同起搏方式对右心功能的影响

对17例安装永久性起搏器者应用脉冲多普勒记录肺动脉血流频谱,对比分析不同方式起搏器植入前后其右心功能的变化。结果显示:DDD起搏较VVI起搏的右室每搏量(SV)、心输出量(CO)增加(P<0.05、P<0.02),肺动脉峰值流速(PPFV)显著增加(P<0.01)。两组舒张早、晚期右室充盈指标均增加,DDD组舒张早期峰值流速(PFVE)显著增加(P<0.01)。表明:房室同步起搏较单纯心室起搏有更好的血液动力学效应,肺动脉血流参数可用于估价右室功能。     

心腔内超声评价希氏束起搏心脏血流动力学和解剖结构重构

目的采用单一的心腔内超声心动图和组织多普勒显像技术检测和评价直接希氏束起搏诱导的心室激动顺序、心脏解剖结构和血流动力学重构.方法六只急性闭胸直接希氏束起搏狗模型.采用美国Medtronic导向引导鞘管和主动螺旋电极,在心腔内超声心动图和组织多普勒显像技术引导下将起搏电极分别置放于希氏束(n=6)和右室心尖(n=6).所有部位的起搏频率均控制为120次/min.采用二维灰阶、血流频谱多普勒和组织多普勒技术,分别测量和计算心脏不同部位起搏时心室各房室和相连大血管解剖结构内径和容量、心肌的激动顺序和相关血流动力学参数,并进行不同起搏状态上述测量参数的配对统计比较.结果希氏束起搏状态下,左心室壁内心肌的激动顺序、心脏主要解剖结构和血流动力学参数与窦性心律状态下相同参数比较无显著性差异;与右心室心尖起搏状态下相同参数比较有显著性差异.结论单一的心腔内超声和组织多普勒技术能够有效地量化评价心脏起搏状态下的心脏解剖结构和血流动力学改变.与右心室心尖部起搏相比较,希氏束起搏能够明显地改善心脏解剖和血流动力学重构.     

不同起搏方式对血流动力学的急性影响

目的：探讨不同起搏方式对病窦综合征患者血流动力学的急性影响。方法：Swan-Ganz漂浮导管测量14例病窦综合征患者起搏前及VVI、AAI、DDD起搏时血流动力学参数；并根据VVI起搏时室房传导的情况分组对比。结果：起搏前及起搏时，平均动脉压(MAP)无明显差异。AAI、DDD起搏时，右房压(RAP)、平均肺动脉压(PAP)、肺毛细血管楔嵌压(PCWP)与起搏前对比无明显改变，但较VVI起搏明显下降(P＜0．01)；心输出量(CO)较起搏前及VVI起搏时显著增加(P＜0．01)。AAI、DDD起搏间对比无显著性差异。VVI起搏时，RAP、PAP、PCWP较起搏前显著增加，室房传导组更为明显；无室房传导组较起搏前CO略有增加(P＜0．05)，而室房传导组CO改变不明显；室房传导组较无室房传导组RAP、PCWP显著增加(P＜0．05)。结论：AAI、DDD起搏可以显著增加CO，对血流动力学影响较小；VVI起搏特别存有室房传导时，可导致血流动力学明显异常；AAI、DDD起搏明显优于VVI起搏。     

心室不同部位起搏的急性血流动力学效应

目的 在无束支阻滞、心功能Ⅰ～Ⅱ级患者中,比较5种不同起搏模式的血流动力学效应及其对QRS宽度的影响。方法 在安置永久起搏器前分别行右室心尖部、右室流出道、右室双部位、左室基底部、双室同步起搏(ⅤⅥ,60～80次/min)5min,测定心脏指数(CI)、平均肺动脉压(mPAP)、肺毛细血管嵌顿压(PCWP)以及QRS宽度。结果(1)与右室心尖部起搏相比,右室流出道、左室基底部、右室双部位、双室同步起搏CI显著增加、PCWP明显降低(P均<0.01);(2)右室双部位、双室同步起搏较右室流出道、左室基底部起搏的CI增高而PCWP降低(P均<0.05);(3)右室双部位与双室同步起搏、右室流出道与左室基底部起搏间CI和PCWP无显著差异;(4)右室流出道、右室双部位、双室同步起搏的QRS宽度较右室心尖部起搏时显著缩短(P<0.01),而左室基底部起搏与右室心尖部起搏时无显著差异。结论 在无束支阻滞、心功能Ⅰ～Ⅱ级患者中,双部位起搏的效果明显优于单部位起搏;双部位起搏的QRS宽度也比单部位起搏明显缩短。在单部位起搏中,右室流出道和左室基底部起搏优于右室心尖部起搏,但左室基底部起搏的QRS宽度无明显缩短。     

医学名词介绍(7) 心血管病学(上)

汉文名英文名心房同步心室起搏　atrialsynchronousventricularpacing ,VAT心房非同步起搏atrialasynchronouspacing,AOO心室非同步起搏ventricularasynchronouspacing,VOO非同步型房室顺序起搏asynchronousatrioventricularsequentialpacing ,DOO触发型起搏triggeredpacing心房触发型起搏atrialtriggeredpacing,AAT心室触发型起搏ventriculartriggeredpacing ,VVT抑制型起搏inhibitedpacing心房抑制型起搏atrialinhibitedpacing ,AAI心室抑制型起搏ventricularinhibitedpacing,VVI心房同步心室抑制型起搏atrialsynchronousventri…     

心律失常致心脏舒张期房室瓣返流的彩色M-型血流图研究

目的：探讨心律失常对心脏舒张期房室瓣返流的影响。方法：选择房室分离、心房扑动、心房颤动及对照患者各1例，采用数字化超声心动图技术观察上述心律失常与心脏舒张期房室瓣返流的关系。结果：1．在房室分离的情况下，舒张期房室瓣返流间断出现，返流仅见于PR间期明显延长的心动周期，引起返流的临界PR间期在房室分离伴心衰的患者为0．27s。在心房扑动的情况下，于舒张中晚期可见伴随扑动波规律出现的房室瓣返流，当房室传导为4：1时，舒张期返流为双相。在心房颤动的情况下，于舒张中晚期粗f波后可见不规则出现的房室瓣返流。比较上述几种心律失常，以PR间期明显延长及心房扑动所引起的舒张期返流较为显著；2．舒张期房室瓣返流出现在心房舒张期；3．舒张期房室瓣返流出现在有病变或有起搏导线通过侧瓣膜。结论：在瓣膜存在病变或有起搏导线跨瓣的基础上，房室分离、PR间期延长、心房扑动、心房颤动均可引起舒张期房室瓣返流。     

人造心脏瓣膜的血流动力学特点

人造心脏瓣膜的血流动力学特点将影响瓣膜在宿主体内的使用寿命,也与其生物相容性密切相关.文章介绍了测量人造心脏瓣膜血流动力学的方法及指标,以及影响人造心脏瓣膜血流动力学改变的相关因素,分析并提出了目前人造心脏瓣膜存在的问题,以便选择与患者相适应的人造心脏瓣膜.     

单导线心房同步心室按需型起搏器的临床应用——附11例报告

目的：探讨单导线心房同步心室按需型起搏器（ＶＤＤ）起搏系统的心房电极的感知功能特点和房室同步起搏率。方法：为１１例窦房结功能正常的完全性房室传导阻滞患者植入单导线ＶＤＤ,并随访观察。结果：术中心房感知电极位于心房中、上部的Ａ波振幅高于位于下部者,深吸气、深呼气、咳嗽对Ａ波振幅略有影响,但无显著性差异（Ｐ〉０．０５）。中位随访时间１１个月,心房感知电极的阀值稳定,无显著性变化。房室同步起搏率９例为１００％,１例为８０％,１例为７０％。无发生肌电干扰和快速性心律失常。结论：单导线ＶＤＤ起搏系统具有简便、心房感知功能稳定、房室同步起搏率高的特点,适用于窦房结功能正常的完全性房室传导阻滞患者。     

病窦综合征患者起搏器术后房室传导方式对Tei指数的影响

目的:评估固定的长AV间期下的DDD起搏模式对病态窦房结综合征(SSS)患者在减少心室起搏方面的效果;比较应用固定的长AV间期保留自身房室传导与最适AV间期下房室顺序起搏两种模式的优劣性,为此类患者选择具有最佳血流动力学效应的起搏参数设置提供临床依据。方法:连续选取2009年5月至2011年4月在我院因SSS而安置双腔心脏永久起搏器进行治疗的55位患者作为研究对象,分3次随访进行,每次随访时间间隔为2个月,将起搏器程控与超声测量相结合,进行两种不同AV间期下房室顺序起搏模式的血流动力学效应评估与对比。结果:与临床经验性AV间期相比,固定的长AV间期下的房室顺序起搏使心室起搏百分比由在31.8%降低至1.18%(P=0.00017);由最适AV间期下转为固定的长AV间期(350ms)下的房室顺序起搏模式后,心脏总体舒张和收缩功能指标(Tei指数)存在差异,且以左室Tei指数下降更为显著(0.67±0.17比0.45±0.09,P<0.0001)。结论:固定的长AV间期(350ms)下的房室顺序起搏能够有效减少心室起搏,且在血流动力学方面优于最适AV间期下的房室顺序起搏。     

起搏器治疗适应证新进展

随着心脏起搏技术的发展 ,起搏器治疗的适应证已不局限于缓慢性心律失常和传导系统疾病的狭小范围内 ,新的治疗作用、新的适应证不断拓宽。用起搏技术优化房内、房室、室内激动的协调 ,增进血流动力学的效果 ,使缓慢及非缓慢性心律失常的起搏适应证均有了进展 ,ＣＨＦ(ｃｏｎｇ     

Adverse Pacemaker Hemodynamics Evaluated by Pulmonary Venous Flow Monitoring

The pacemaker syndrome refers to symptoms and signs in the pacemaker patient caused by an inadequate timing of atrial and ventricular contractions. The lack of normal atrioventricular synchrony may result in a decreased cardiac output and venous cannon A waves. The objective of this study was to define the left atrial and pulmonary venous flow response to ventricular pacing in a group of 14 unselected consecutive patients with total heart block and sinus rhythm. Pulmonary venous flow was assessed by transesophageal pulsed Doppier echocardiography in the VVI and ODD pacing modes. An inappropriate atrial timing caused a marked augmentation of the normally small pulmonary venous z wave in all patients ("negative atrial kick" peak z wave in DDD pacing 14.5 ± 4.6 cm/s, VVI pacing 51.8 ± 15.0 cm/s). Restoration of AV synchrony (DDD pacing, AV interval 100 ms) abolished these "cannon z waves" in all patients, and a normal pattern of pulmonary venous flow was achieved. Abnormal pulmonary venous flow characteristics were observed in 2 of 14 patients during DDD pacing with short AV intervals (100 ms). The Doppier pattern was similar to the findings seen in VVI pacing. Assessment of pulmonary venous flow by transesophageal pulsed Doppier echocardiography may provide a simple, sensitive, and relatively noninvasive technique to evaluate patients with suspected pacing induced adverse hemodynamics.     

Single versus dual chamber pacing in the young: noninvasive comparative evaluation of cardiac function

The advantages of atrial synchrony over asynchronous ventricular pacing remain unclear in the young, chronically right ventricular (RV) - paced patient. This is in contrast to the older patient with inherent diastolic dysfunction who has been shown to benefit from atrial synchrony with dual chamber (DDD,R/VDD), over single chamber rate response (VVI,R) ventricular pacing. The goal of this study was to noninvasively assess cardiac function in a group of young, RV-paced patients before and after establishment of atrial synchrony. Echocardiographic data were retrospectively analyzed from 10 patients with congenital or acquired complete AV block, who were VVI,R paced for 10.2 +/- 2 years (mean age at study 19.2 +/- 8.9 years), and were subsequently converted to DDD,R/VDD pacing (mean age at study 20.7 +/- 9.5 years). Paired t-test analysis of left ventricular (LV) systolic and diastolic function during VVI,R versus DDD,R/VDD pacing did not result in any short-term difference in LV short axis fractional area of change or FAC (53% +/- 7.5% vs 56.8% +/- 8.7%) or mitral maximal velocity (E) normalized to mitral flow velocity time integral (VTI) (5.2/s +/- 1.5 vs 4.4/s +/- 1.5). A decrease in mitral flow E/A ratio was observed after short-term DDD,R/VDD pacing (2.2 +/- 0.5 vs 1.9 +/- 0.3). Atrial synchronous dual chamber pacing in young patients with complete AV block does not lead to any appreciable early change in global LV function over single-site RV pacing. Therefore, early establishment of atrial synchrony in the young asymptomatic VVI,R-paced patient with normal intrinsic ventricular function may not be warranted.     

Importance of Heart Rate Response During Exercise in Patients Using Atrioventricular Synchronous and Ventricular Pacemakers

Atrioventricular synchronous pacing offers advantages over fixed-rate ventricular (VVI) pacing both at rest and during exercise. This study compared the hemodynamic effects at rest and exercise of ventricular pacing at a rate of 70 beats/min, ventricular pacing where the rate was increased during exercise and dual chamber pacing. Ten patients, age 63 +/- 8 years, with multiprogrammable DDD pacemakers were studied using supine bicycle radionuclide ventriculography. Radionuclide data during dual chamber pacing was acquired at rest and during a submaximal workload of 200-400 kpm/min. The pacemakers were then programmed to VVI pacing at a rate of 70 beats/min, and 1 week later, studies were repeated in the VVI mode at rest, during exercise at a rate of 70 beats/min, and during exercise with the VVI pacemaker programmed to a rate adapted to the DDD pacing exercise rate. At rest, the cardiac output was lower in the VVI compared with the AV sequential mode (4.1 +/- 1.1 vs 5.7 +/- 1.1 1/min, P less than 0.01). During exercise, the cardiac output increased from resting values in the DDD and VVI pacing modes, however cardiac output in the rate-adapted VVI mode was higher than in the VVI mode with the rate maintained at 70 beats/min (8.1 +/- 1.5 vs 6.3 +/- 1.1 1/min, P = 0.02). Three patients completed lower workloads with VVI pacing at 70 beats/min compared with AV synchronous pacing. At rest, AV sequential pacing was superior to VVI pacing, suggesting the importance of the atrial contribution to ventricular filling. With VVI pacing during exercise, cardiac output was improved with an increased pacemaker rate, suggesting that the heart rate response during exercise was the major determinant of the higher cardiac output.     

A Double-Blind Study of Submaximal Exercise Tolerance and Variation in Paced Rate in Atrial Synchronous Compared to Activity Sensor Modulated Ventricular Pacing

To assess the variation in paced rate during everyday activity and the importance of atrioventricular synchronization (AV synchrony) for submaximal exercise tolerance, atrial synchronous (DDD) and activity rate modulated ventricular (VVI,R) pacing were compared in 17 patients with high degree AV block. The patients were randomly assigned to either mode and evaluated by treadmill exercise to moderate exertion and by 24-hour Holter monitoring after 2 months in the DDD and VVI,R modes, respectively. At the end of the study, the patients were programmed to the pacing mode corresponding to the preferred study period. During the treadmill test, the mean exercise time to submaximal exertion (Borg 5/10), exertion ratings and respiratory rate did not differ between pacing modes despite a significantly lower ventricular rate in the VVI,R mode. The atrial rate during VVI,R pacing was significantly higher than the ventricular rate, but did not differ from the ventricular rate during DDD pacing. There was a diurnal variation in paced rate in both pacing modes. Paced ventricular rate was, however, higher and variation in paced rate greater in DDD compared to VVI,R pacing. Nine patients preferred the DDD mode, three patients preferred the VVI,R mode, while five subjects did not express any preference. The results from this study indicate that the variation in paced rate during activity sensor-driven VVI,R pacing does not match that during DDD pacing neither during everyday activities nor during submaximal treadmill exercise. Nevertheless, no differences in exercise time, Borg ratings, and respiratory rate during submaximal exercise were found. Thus, for most patients with high degree AV block, DDD and VVI,R pacing seem equally satisfactory for submaximal exercise.     

Lack of Influence of Atrioventricular Delay on Stroke Volume at Rest in Patients with Complete Atrioventricular Block and Dual Chamber Pacing

Dual chamber pacing (DDD) maintains atrioventricular (AV) sequence; AV delay programmability modifies the relationship between atrial and ventricular contraction. To evaluate the hemodynamic effects of such a modification, ten patients with a DDD unit for complete AV block were studied by time-motion (M-mode) and Doppler echocardiography during inhibited ventricular pacing (VVI), atrial-triggered ventricular pacing (VDD) and atrioventricular sequential pacing (DVI) at different AV delay (90, 140, 190, 240 msec). A significant improvement in stroke volume (SV) (15%-20%, P less than 0.05) was seen during DDD versus VVI pacing; no changes, however, were observed in the same patient with different AV delay or during DVI versus VDD pacing. These data suggest that programming of AV delay does not affect systolic performance at rest; longer diastolic filling times recorded during DDD pacing with "short" AV delay (90-140 msec) do not seem to be a hemodynamically relevant epi-phenomenon of PM programming.     

Is DDD Pacing Superior to VVI,R? A Study on Cardiac Sympathetic Nerve Activity and Myocardial Oxygen Consumption at Rest and During Exercise

Rate responsive ventricular pacing (VVI,R) has been demonstrated to equal atrial synchronous ventricular pacing (DDD) with regard to hemodynamics and exercise tolerance. Whether the two modes are also comparable, with regard to cardiac metabolic effects, is not yet dear. We assessed central hemodynamics, cardiac sympathetic nerve activity fcardiac norepinephrine overflow), and myocardial oxygen consumption in 16 patients treated with rate responsive atrial synchronous ventricular pacemakers (DDD,R), due to high degree AV block. The study was performed at rest and during supine exercise at two workloads (30 ± 12 and 68 ± 24 watts, respectively) during VDD and rate matched VVI pacing (VVI_m). Ventricular rates at rest and during both workloads were almost identical. Cardiac output at rest tended to be higher in the VDD mode, due to a slightly higher stroke volume. Central pressures including right atrial pressure and pulmonary capillary wedge pressure were similar in the pacing modes. The coronary sinus blood flow, the coronary sinus arteriovenous oxygen difference, and the myocardial oxygen consumption did not differ between the two pacing modes. Cardiac norepinephrine overflow was similar in the two pacing modes, at rest or during exercise. Thus, we found no significant differences between VDD and VVI_m pacing with regard to central hemodynamics, cardiac sympathetic nerve activity (cardiac norepinephrine overflow), or myocardial oxygen consumption either at rest or during moderate exercise.     

Hemodynamically optimized temporary cardiac pacing after surgery for congenital heart defects

Disturbance of normal AV synchrony and dyssynchronous ventricular contraction may be deleterious in patients with otherwise compromised hemodynamics. This study evaluated the effect of hemodynamically optimized temporary dual chamber pacing in patients after surgery for congenital heart disease. Pacing was performed in 23 children aged 5 days to 7.7 years (median 7.3 months) with various postoperative dysrhythmias, low cardiac output, and/or high inotropic support and optimized to achieve the highest systolic and mean arterial pressures. The following four pacing modes were used: (1) AV synchronous or AV sequential pacing with individually optimized AV delay in 11 patients with first- to third-degree AV block; (2) AV sequential pacing using transesophageal atrial pacing in combination with a temporary DDD pacemaker for atrial tracking and ventricular pacing in three patients with third-degree AV block and junctional ectopic tachycardia, respectively, who had poor signal and exit block on atrial epicardial pacing wires; (3) R wave synchronized atrial pacing in eight patients with junctional ectopic tachycardia and impaired antegrade AV conduction precluding the use of atrial overdrive pacing; (4) Atrio-biventricular sequential pacing in two patients. Pressures measured during optimized pacing were compared to baseline values at underlying rhythm (13 patients with first-degree AV block or junctional ectopic tachycardia) or during pacing modes commonly used in the given clinical situation: AAI pacing (1 patient with slow junctional rhythm and first-degree AV block during atrial pacing), VVI pacing (2 patients with third-degree AV block and exit block and poor sensing on epicardial atrial pacing wires) and dual-chamber pacing with AV delays set to 100 ms (atrial tracking) or 150 ms (AV sequential pacing) in 7 patients with second- to third-degree AV block and functional atrial pacing wires. Optimized pacing led to a significant increase in arterial systolic (mean) pressure from 71.5 +/- 12.5 (52.3 +/- 9.0) to 80.5 +/- 12.2 (59.7 +/- 9.1) mmHg (P < 0.001 for both) and a decrease in central venous (left atrial) pressure from 12.3 +/- 3.4 (10.5 +/- 3.2) to 11.0 +/- 3.0 (9.2 +/- 2.7) mmHg (P < 0.001 and < 0.005, respectively). In conclusion, several techniques of individually optimized temporary dual chamber pacing leading to optimal AV synchrony and/or synchronous ventricular contraction were successfully used to improve hemodynamics in patients with heart failure and selected dysrhythmias after congenital heart surgery.     

Importance of AV synchronous pacing during low intensity exercise evaluated by oxygen kinetics

It has been shown that dual chamber pacing with preservation of AV synchrony (DDD) is superior to fixed rate ventricular (VVI) or rate responsive ventricular (VVIR) pacing modes, as evaluated by ventilatory response to exercise. Previous studies have focused on the benefits of maintained AV synchrony at maximal exercise. However, there are limited data comparing O2 kinetics in different pacing modes during low intensity exercise, representing the majority of daily activities. This study aimed to provide an evaluation of different pacing modes using O2 kinetics during low intensity exercise. Nineteen patients (age 61 +/- 18 years) with complete AV block underwent low intensity treadmill exercise (35 W) with simultaneous evaluation of symptoms and O2 kinetics in three pacing modes. The first test was performed in DDD mode followed by a second test in VVIR mode with a programmed heart rate corresponding to the sinus rate during the first test. After 6 minutes of each test, the mode was switched from DDD to VVIR and vice versa. The third test was performed in VVI mode at 70 beats/min. O2 kinetics were defined as O2 deficit (time [rest to steady state] x delta VO2-sigma VO2 [rest to steady state]) and mean response time (MRT) of oxygen consumption (O2 deficit/delta VO2). The O2 deficit was 551 +/- 134 mL in DDD pacing, 634 +/- 139 mL in VVIR pacing, and 648 +/- 179 mL in VVI pacing (P = 0.001). MRT was 49 +/- 7.8 seconds in DDD pacing, 54.7 +/- 9.5 seconds in VVIR pacing, and 57.4 +/- 11.0 seconds in VVI pacing (P = 0.002). Ten (53%) patients developed symptoms during switch from DDD to VVIR mode whereas the switch from VVIR to DDD mode was not perceived by any patient (P < 0.001). In conclusion, our study shows an impact of AV synchronous pacing and heart rate adaptation on O2 kinetics during low intensity exercise that correspond to casual daily life activities. Our observations may have clinical implications for the management of patients with complete AV block.     

Quality-of-Life in Patients Treated with Atrioventricular Synchronous Pacing Compared to Rate Modulated Ventricular Pacing: A Long-Term, Double-Blind, Crossover Study

To investigate whether the preservation of afrioventricular (AV) synchronization matters for quality-of-life during pacemaker treatment we assessed 17 consecutive patients with high degree AV block and preserved sinus node function in a double-blind, long-term crossover study. A questionnaire with regard to cardiovascular symptoms, sleep disturbances, cognitive functioning, physical ability, social interaction, emotional functioning, and self-perceived health was completed after 2 months of atrial synchronous (DDD) and rate modulated ventricular pacing (VVI,R), respectively. A significant improvement in shortness of breath, dizziness and palpitations as well as an improvement of cognitive functioning was observed during DDD pacing. Nine patients preferred the DDD mode and three the VVI,R mode. The remaining five patients did not express any preference. The preference for the DDD mode was explained by a significant reduction of cardiovascular symptoms and an improved self-perceived health, physical ability, and psychological well-being during DDD pacing. All differences in quality-of-life parameters between the two modes of pacing favored the DDD mode and no adverse effects of this mode were found. Thus, the maintenance of AV synchrony adds further symptomatic relief compared to rate increase alone. The results indicate that DDD pacing is the preferred mode of pacing in patients with high degree AV block and preserved sinus node function.