The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting an estimated 6 million people in the United States ¹. Since AF affects primarily elderly people, its prevalence increases parallel with age. As such, it is expected that 15.9 million Americans will be affected by the year 2050 ². Ischemic stroke occurs in 5% of non-anticoagulated AF patients each year. Current treatments for AF include rate control, rhythm control and prevention of stroke ³.The American College of Cardiology, American Heart Association, and European Society of Cardiology currently recommended rate control as the first course of therapy for AF ³. Rate control is achieved by administration of pharmacological agents, such as β-blockers, that lower the heart rate until it reaches a less symptomatic state ³. Rhythm control aims to return the heart to its normal sinus rhythm and is typically achieved through administration of antiarrhythmic drugs such as amiodarone, electrical cardioversion or ablation therapy. Rhythm control methods, however, have not been demonstrated to be superior to rate-control methods ^4-6. In fact, certain antiarrhythmic drugs have been shown to be associated with higher hospitalization rates, serious adverse effects ³, or even increases in mortality in patients with structural heart defects ⁷. Thus, treatment with antiarrhythmics is more often used when rate-control drugs are ineffective or contraindicated. Rate-control and antiarrhythmic agents relieve the symptoms of AF, including palpitations, shortness of breath, and fatigue ⁸, but don''t reliably prevent thromboembolic events ⁶.Treatment with the anticoagulant drug warfarin significantly reduces the rate of stroke or embolism ^9,10. However, because of problems associated with its use, fewer than 50% of patients are treated with it. The therapeutic dose is affected by drug, dietary, and metabolic interactions, and thus requires detailed monitoring. In addition, warfarin has the potential to cause severe, sometimes lethal, bleeding ². As an alternative, aspirin is commonly prescribed. While aspirin is typically well tolerated, it is far less effective at preventing stroke ¹⁰. Other alternatives to warfarin, such as dabigatran ¹¹ or rivaroxaban ¹² demonstrate non-inferiority to warfarin with respect to thromboembolic events (in fact, dabigatran given as a high dose of 150 mg twice a day has shown superiority). While these drugs have the advantage of eliminating dietary concerns and eliminating the need for regular blood monitoring, major bleeding and associated complications, while somewhat less so than with warfarin, remain an issue ^13-15.Since 90% of AF-associated strokes result from emboli that arise from the left atrial appendage (LAA) ², one alternative approach to warfarin therapy has been to exclude the LAA using an implanted device to trap blood clots before they exit. Here, we demonstrate a procedure for implanting the WATCHMAN Left Atrial Appendage Closure Device. A transseptal cannula is inserted through the femoral vein, and under fluoroscopic guidance, inter-atrial septum is crossed. Once access to the left atrium has been achieved, a guidewire is placed in the upper pulmonary vein and the WATCHMAN Access Sheath and dilator are advanced over the wire into the left atrium. The guidewire is removed, and the access sheath is carefully advanced into the distal portion of the LAA over a pigtail catheter. The WATCHMAN Delivery System is prepped, inserted into the access sheath, and slowly advanced. The WATCHMAN device is then deployed into the LAA. The device release criteria are confirmed via fluoroscopy and transesophageal echocardiography (TEE) and the device is released.     

Catheter Ablation in Combination With Left Atrial Appendage Closure for Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting millions of individuals worldwide ^1-3. The rapid, irregular, and disordered electrical activity in the atria gives rise to palpitations, fatigue, dyspnea, chest pain and dizziness with or without syncope ^{4, 5}. Patients with AF have a five-fold higher risk of stroke ⁶.Oral anticoagulation (OAC) with warfarin is commonly used for stroke prevention in patients with AF and has been shown to reduce the risk of stroke by 64% ⁷. Warfarin therapy has several major disadvantages, however, including bleeding, non-tolerance, interactions with other medications and foods, non-compliance and a narrow therapeutic range ^8-11. These issues, together with poor appreciation of the risk-benefit ratio, unawareness of guidelines, or absence of an OAC monitoring outpatient clinic may explain why only 30-60% of patients with AF are prescribed this drug ⁸.The problems associated with warfarin, combined with the limited efficacy and/or serious side effects associated with other medications used for AF ^12,13, highlight the need for effective non-pharmacological approaches to treatment. One such approach is catheter ablation (CA), a procedure in which a radiofrequency electrical current is applied to regions of the heart to create small ablation lesions that electrically isolate potential AF triggers ⁴. CA is a well-established treatment for AF symptoms ^{14, 15}, that may also decrease the risk of stroke. Recent data showed a significant decrease in the relative risk of stroke and transient ischemic attack events among patients who underwent ablation compared with those undergoing antiarrhythmic drug therapy ¹⁶.Since the left atrial appendage (LAA) is the source of thrombi in more than 90% of patients with non-valvular atrial fibrillation ¹⁷, another approach to stroke prevention is to physically block clots from exiting the LAA. One method for occluding the LAA is via percutaneous placement of the WATCHMAN LAA closure device. The WATCHMAN device resembles a small parachute. It consists of a nitinol frame covered by fabric polyethyl terephthalate that prevents emboli, but not blood, from exiting during the healing process. Fixation anchors around the perimeter secure the device in the LAA (Figure 1). To date, the WATCHMAN is the only implanted percutaneous device for which a randomized clinical trial has been reported. In this study, implantation of the WATCHMAN was found to be at least as effective as warfarin in preventing stroke (all-causes) and death (all-causes) ¹⁸. This device received the Conformité Européenne (CE) mark for use in the European Union for warfarin eligible patients and in those who have a contraindication to anticoagulation therapy ¹⁹.Given the proven effectiveness of CA to alleviate AF symptoms and the promising data with regard to reduction of thromboembolic events with both CA and WATCHMAN implantation, combining the two procedures is hoped to further reduce the incidence of stroke in high-risk patients while simultaneously relieving symptoms. The combined procedure may eventually enable patients to undergo implantation of the WATCHMAN device without subsequent warfarin treatment, since the CA procedure itself reduces thromboembolic events. This would present an avenue of treatment previously unavailable to patients ineligible for warfarin treatment because of recurrent bleeding ²⁰ or other warfarin-associated problems.The combined procedure is performed under general anesthesia with biplane fluoroscopy and TEE guidance. Catheter ablation is followed by implantation of the WATCHMAN LAA closure device. Data from a non-randomized trial with 10 patients demonstrates that this procedure can be safely performed in patients with a CHADS₂ score of greater than 1 ²¹. Further studies to examine the effectiveness of the combined procedure in reducing symptoms from AF and associated stroke are therefore warranted.     

经食道超声心动图评估特发性房颤左心房左心耳的价值

目的:研究经食道超声心动图(TEE)评估特发性房颤左心房左心耳的临床价值。方法:选择自2015年1月到2016年8月在医院接受诊治的特发性房颤患者100例纳入本次研究,阵发性房颤92例,记为阵发性房颤组;持续性房颤8例,记为持续性房颤组。另选同期在医院进行健康体检的心功能正常志愿者90例作为对照组。利用TEE对受试者进行检查,对比房颤组与对照组的左心房及左心耳参数,是否含有自发性显影(LASEC)的房颤患者的左心房及左心耳参数,利用TEE分析对房颤患者的预后情况。结果:阵发性房颤组左心房的前后径和左右径,左心耳血流最大的排空速度(Lev)均明显小于对照组,左心耳的面积变化率及最大的充盈速度(Lfv)均明显大于对照组,差异有统计学意义(P0.05)。持续性房颤组左心房的前后径和左右径均明显大于对照组,左心耳的面积变化率、Lev及Lfv均明显小于对照组,差异有统计学意义(P0.05)。阵发性房颤组左心房的前后径和左右径均明显小于持续性房颤组,左心耳的面积变化率、Lev及Lfv均明显大于持续性房颤组,差异有统计学意义(P0.05)。有LASEC者左心房的前后径和左右径均明显大于无LASEC者,左心耳的面积变化率、Lev及Lfv均明显小于无LASEC者,差异有统计学意义(P0.05)。100例房颤患者中发现34例LASEC,占34.00%,其中有18例患者合并有左心耳血栓,占18.00%。总计有66例患者接受导管射频消融疗法,占66.00%,均未在术中及术后7d内出现血栓及栓塞并发症。结论:利用TEE对特发性房颤的患者左心房及左心耳进行评估,有利于更好的辅助患者的临床治疗,值得重视。     

术前使用左心耳3D模型及左心耳封堵体外模拟治疗心房颤动患者的疗效

摘要 目的：探讨术前使用左心耳3D模型及左心耳封堵体外模拟治疗心房颤动患者的疗效。方法：回顾性选择2021年1月至2022年10月来我院诊治的心房颤动患者,对照组行经食管超声心动图检查、心脏CT造影检查及左心耳封堵术。观察组行经食管超声心动图检查、心脏CT造影检查、基于心脏CT造影数据打印左心耳3D模型、应用3D打印模型进行左心耳封堵体外模拟演练及左心耳封堵术,对比两组相关指标。结果：两组经食管超声心动图检查左心耳各径线对比无差异（P>0.05）。两组经CT检查左心耳各径线对比无差异（P>0.05）。两组封堵器固定大小对比有差异（P<0.05）。术后经食管超声心动图检查发现,观察组术后3个月及12个月血流通过封堵器几率高于对照组,但组间对比无差异（P>0.05）。术后3个月及12个月时,两组的左心房内径降低,且同时间点观察组较对照组（P<0.05）;两组术后3个月及12个月时左心室内径对比无差异（P>0.05）。观察组的封堵器型号匹配率较对照组高,手术操作时间、X线曝光量、造影剂使用量、封堵器术中释放次数较对照组低（P<0.05）,观察组的残余分流及手术并发症较对照组低,但组间对比无差异（P>0.05）。观察组术后3个月封堵器位置、有无残腔及不良心血管事件与对照组相比无差异（P>0.05）,术后12个月,封堵器位置良好率较对照组低（P<0.05）,其余两组间对比无差异（P>0.05）。结论：术前使用左心耳3D模型及左心耳封堵体外模拟可提高心房颤动患者的疗效。     

Morphological and Volumetric Analysis of Left Atrial Appendage and Left Atrium: Cardiac Computed Tomography-Based Reproducibility Assessment

Objectives

Left atrial appendage (LAA) dilatation and morphology may influence an individual''s risk for intracardiac thrombi and ischemic stroke. LAA size and morphology can be evaluated using cardiac computed tomography (cCT). The present study evaluated the reproducibility of LAA volume and morphology assessments.

Methods

A total of 149 patients (47 females; mean age 60.9±10.6 years) with suspected cardioembolic stroke/transient ischemic attack underwent cCT. Image quality was rated based on four categories. Ten patients were selected from each image quality category (N = 40) for volumetric reproducibility analysis by two individual readers. LAA and left atrium (LA) volume were measured in both two-chamber (2CV) and transversal view (TV) orientation. Intertechnique reproducibility was assessed between 2CV and TV (200 measurement pairs). LAA morphology (A = Cactus, B = ChickenWing, C = WindSock, D = CauliFlower), LAA opening height, number of LAA lobes, trabeculation, and orientation of the LAA tip was analysed in all study subjects by three individual readers (447 interobserver measurement pairs). The reproducibility of volume measurements was assessed by intra-class correlation (ICC) and the reproducibility of LAA morphology assessments by Cohen''s kappa.

Results

The intra-observer and interobserver reproducibility of LAA and LA volume measurements was excellent (ICCs>0.9). The LAA (ICC = 0.954) and LA (ICC = 0.945) volume measurements were comparable between 2CV and TV. Morphological classification (ĸ = 0.24) and assessments of LAA opening height (ĸ = 0.1), number of LAA lobes (ĸ = 0.16), trabeculation (ĸ = 0.15), and orientation of the LAA tip (ĸ = 0.37) was only slightly to fairly reproducible.

Conclusions

LA and LAA volume measurements on cCT provide excellent reproducibility, whereas visual assessment of LAA morphological features is challenging and results in unsatisfactory agreement between readers.     

Reversible Changes of Left Atrial Function during Pregnancy Assessed by Two-Dimensional Speckle Tracking Echocardiography

Background

Left ventricular diastolic function is impaired during pregnancy. However, changes in left atrial (LA) function remain unclear. We aimed to evaluate changes in LA function during pregnancy using two-dimensional speckle tracking echocardiography (2DSTE).

Methods and Results

50 pregnant and 50 healthy nulliparous (control group) women were enrolled in this study. All pregnant women were followed up postpartum in sixth-month. The LA maximum volume, LA minimal volume and LA preatrial contraction volume were obtained using biplane modified Simpson’s method. LA filling volume, LA expansion index, LA ejection fraction, passive volume, passive emptying index, active volume, and active emptying index were calculated. LA longitudinal systolic strain (SS), systolic strain rate (s-SR), early diastolic strain rate (e-SR), and late diastolic strain rate (a-SR) were obtained by 2DSTE. Compared to the control group, the reservoir function was increased in pregnant patients (P<0.05); conduit function was decreased in pregnant patients (P<0.05); booster pump function was increased in pregnant patients (P<0.05). There was no statistically significant difference between the control group and postpartum group.

Conclusions

LA reservoir and booster pump function were increased, while conduit function was decreased during pregnancy using 2DSTE. The changes were reversible. 2DSTE can easily assess LA function during pregnancy with good repeatability.     

超声心动图评价左房形态和功能的临床应用进展

左房形态和功能既可反映机体的生理状态,也可反映其病理状态,左房形态和功能异常改变是冠心病、高血压、心血管硬化、中风等诸多心血管疾病的早期表现之一,是心血管死亡、心肌梗死、卒中、心力衰竭等不良心血管事件的危险因素之一,与这类疾病的预后密切相关,因而准确、有效评估左房形态和功能在不良心血管事件的诊疗及预后评估中意义重大。采用超声心动图评价左房形态和功能具有无创、实时高效、价格低廉及可重复性高等优点,临床上应用非常广泛。随着超声技术的进步,除二维超声心动图、彩色多普勒超声心动图等常规超声技术外,组织多普勒显像(TDI)技术、由TDI派生出来的应变及应率显像技术、实时三维超声心动图(RT-3DE)、二维斑点追踪成像(2D-STI)技术、三维斑点追踪成像(3D-STI)技术等新型超声技术也逐渐应用于左房形态、功能的评价中,然而不同的超声技术评价左房形态和功能仍有一定的不足之处,本研究就不同超声心动图评价左房形态和功能的临床应用及研究进展进行综述。     

Multivariate Analysis of Correspondence between Left Atrial Volumes Assessed by Echocardiography and 3-Dimensional Electroanatomic Mapping in Patients with Atrial Fibrillation

Background

Left atrial (LA) enlargement is a predictor of worse outcome after catheter ablation for atrial fibrillation (AF). Widely used two-dimensional (2D)-echocardiography is inaccurate and underestimates real LA volume (LAV). We hypothesized that baseline clinical characteristics of patients can be used to adjust 2D-ECHO indices of LAV in order to minimize this disagreement.

Methods

The study enrolled 535 patients (59 ± 9 years; 67% males; 43% paroxysmal AF) who underwent catheter ablation for AF in three specialized centers. We investigated multivariately the relationship between 2D-echocardiographic indices of LA size, specifically LA diameter in M-mode in the parasternal long-axis view (LAD), LAV assessed by the prolate-ellipsoid method (LAV_Ellipsoid), LAV by the planimetric method (LAV_Planimetry), and LAV derived from 3D-electroanatomic mapping (LAV_CARTO).

Results

Cubed LAD of 106 ± 45 ml, LAV_Ellipsoid of 72 ± 24 ml and LAV_Planimetry of 88 ± 30 ml correlated only modestly (r = 0.60, 0.69, and 0.53, respectively) with LAV_CARTO of 137 ± 46 ml, which was significantly underestimated with a bias (±1.96 standard deviation) of -31 (-111; +49) ml, -64 (-132; +2) ml, and -49 (-125; +27) ml, respectively; p < 0.0001 for their mutual difference. LA enlargement itself, age, gender, type of AF, and the presence of structural heart disease were independent confounders of measurement error of 2D-echocardiographic LAV.

Conclusion

Accuracy and precision of all 2D-echocardiographic LAV indices are poor. Their agreement with true LAV can be significantly improved by multivariate adjustment to clinical characteristics of patients.     

左心耳封堵术后房颤患者生活质量评价及其影响因素研究

摘要 目的：探讨左心耳封堵术（LAAC）术后对房颤（AF）患者的生活质量的影响,并分析其影响因素。方法：回顾性分析兰州大学第二医院2019年3月至2022年3月期间接受LAAC治疗的213例AF患者的临床资料。根据简明健康调查量表（SF-36）将213例LAAC术后AF患者分为低生活质量组（总分≤50分,n=107）和高生活质量组（总分＞50分,n=106）。收集并比较AF患者术前基线资料、实验室资料和影像学资料。采用多因素Logistic回归模型分析LAAC术后AF患者生活质量的影响因素。结果：低生活质量组心房颤动血栓发生危险度（CHA2DS2-VASc）评分高于高生活质量组（P<0.05）。低生活质量组的凝血酶原时间百分比高于高生活质量组（P<0.05）。高生活质量组红细胞水平高于低生活质量组（P<0.05）。高生活质量组的左心室射血分数（LVEF）高于低生活质量组（P<0.05）。多因素Logistic回归分析结果显示：CHA2DS2-VASc评分偏高、LVEF偏低是影响LAAC术后AF患者生活质量的危险因素（P<0.05）。结论：CHA2DS2-VASc评分偏高、LVEF偏低是影响LAAC术后AF患者生活质量的危险因素,可降低LAAC术后AF患者的生活质量。     

Diffusion Tensor Imaging of Brain Abnormalities Induced by Prenatal Exposure to Radiation in Rodents

We assessed brain abnormalities in rats exposed prenatally to radiation (X-rays) using magnetic resonance imaging (MRI) and histological experiments. Pregnant rats were divided into 4 groups: the control group (n = 3) and 3 groups that were exposed to different radiation doses (0.5, 1.0, or 1.5 Gy; n = 3 each). Brain abnormalities were assessed in 32 neonatal male rats (8 per group). Ex vivo T₂-weighted imaging and diffusion tensor imaging (DTI) were performed using 11.7-T MRI. The expression of markers of myelin production (Kluver–Barrera staining, KB), nonpyramidal cells (calbindin-D28k staining, CaBP), and pyramidal cells (staining of the nonphosphorylated heavy-chain neurofilament SMI-32) were histologically evaluated. Decreased brain volume, increased ventricle volume, and thinner cortices were observed by MRI in irradiated rats. However, no abnormalities in the cortical 6-layered structure were observed via KB staining in radiation-exposed rats. The DTI color-coded map revealed a dose-dependent reduction in the anisotropic signal (vertical direction), which did not represent reduced numbers of pyramidal cells; rather, it indicated a signal reduction relative to the vertical direction because of low nerve cell density in the entire cortex. We conclude that DTI and histological experiments are useful tools for assessing cortical and hippocampal abnormalities after prenatal exposure to radiation in rats.     

实时三平面定量组织速度成像技术评价正常人左房机械功能的研究

目的:应用实时三平面(real-time tri-plane)定量组织速度成像技术(quantitative tissue velocity imaging,QTVI)分析正常人不同年龄左心房局部心肌舒缩功能特点,并探讨正常值区间。方法:选取202例健康志愿者,按年龄分为青年组A组≤44岁(63例),中年组B组45~59岁(87例),老年组C组≥60岁(52例),应用实时三平面组织多普勒成像(tissue Doppler imaging,TDI)软件中的QTVI技术,同步测量左心房基底段六个壁(房间隔、外侧壁、前壁、下壁、前间隔、后壁)收缩期心肌组织运动速度(Vs)、舒张早期心肌组织运动速度(Ve)、舒张晚期心肌组织运动速度(Va)的测量值,并计算出各壁不同时相的测量值95%可信区间,分析不同年龄组各房壁在各时相心肌运动速度特点。结果:各年龄组不同房壁在相同时相的心肌运动速度测量值比较差异无统计学意义(P均0.05);同一房壁Vs、Ve值在A组、B组与C组差异无统计学意义(P0.05),Va值在A组与B组差异无统计学意义(P0.05),Va在A组与C组、B组与C组差异有统计学意义(P0.05)。将A组与B组整合D组后,D组与C组左心房六个壁(房间隔、外侧壁、前壁、下壁、前间隔、后壁)心肌组织运动速度(Vs、Ve、Va)的95%可信区间分别为:D组(4.73~5.17、-7.49~-5.83、-5.57~-4.62)cm/s、(5.93~6.82、-8.75~-6.93、-6.31~-5.26)cm/s、(5.31~6.22、-7.89~-6.23、-6.03~-4.91)cm/s、(4.24~5.18、-6.98~-5.42、-6.01~-4.87)cm/s、(4.94~5.13、-7.23~-6.11、-5.76~-4.71)cm/s、(5.15~6.17、-7.15~-5.44、-6.05~-4.88)cm/s;C组(4.83~5.48、-7.23~-5.95、-5.63~-4.67)cm/s、(5.97~6.99、-8.70~-7.03cm/s、-6.36~-5.28)cm/s、(5.53~6.31、-7.99~-6.29、-6.09~-4.99)cm/s、(4.86~5.21、-6.94~-5.48、-6.04~-4.91)cm/s、(5.53~6.31、-7.99~-6.29、-6.09~-4.99)cm/s、(5.23~6.25、-7.08~-5.47、-6.08~-4.90)cm/s。结论:实时三平面QTVI技术在定量评价正常人左房机械功能方面具有一定可行性。     

Relationship of CHA2DS2-VASc and CHADS2 Score to Left Atrial Remodeling Detected by Velocity Vector Imaging in Patients with Atrial Fibrillation

Background

The CHADS₂/CHA₂DS₂-VASc scores are used to predict thrombo-embolic/stroke in patients with nonvalvular atrial fibrillation (AF). Nevertheless, limited data are available regarding the association between these risk stratification for stroke and left atrial (LA) remodeling status of AF patients. The purpose of this study was to explore the association between these scores and LA remodeling status assessed quantificationally by echocardiography in AF patients.

Methods

One hundred AF patients were divided into 3 groups based on the CHA₂DS₂-VASc/CHADS₂ score: the score of 0 (low stroke risk), the score of 1 (moderate stroke risk) and the score of ≥2 (high stroke risk). All patients were performed through conventional and velocity vector imaging echocardiography. Echocardiographic parameters: maximum LA volume index (LAVImax), LA total emptying fraction (LAEFt) and LA mean strain were obtained to assess quantificationally LA remodeling status.

Results

On categorizing with CHA₂DS₂-VASc, the score of 1 group showed augment in LAVImax and attenuation in LA mean strain derived from VVI, compared with the score of 0 group (LAVImax: 40.27±21.91 vs. 26.79±7.87, p=0.002; LA mean strain: 15.18±6.36 vs. 22±8.54, p=0.001). On categorizing with the CHADS₂ score, similar trends were seen between the score of ≥2 and 1 groups (LAVImax: 43.72±13.77 vs. 31.41±9.50, p<0.001; LA mean strain: 11.01±5.31 vs. 18.63±7.00, p<0.001). With multivariate logistic regression, LAVImax (odds ratio: 0.92 , 95% C=I: 0.85 to 0.98, p= 0.01) and LA mean strain reflecting LA remodeling (odds ratio: 1.10, 95% CI: 1.02 to 1.19, p=0.01) were strongly predictive of the CHA₂DS₂-VASc score of 0.

Conclusions

The superiority of the CHADS₂ score may lay in identifying LA remodeling of AF patients with high stroke risk. Whereas, the CHA₂DS₂-VASc score was better than the CHADS₂ score at identifying LA remodeling of AF patients presenting low stroke risk.     

Left Atrial Systolic and Diastolic Dysfunction in Patients with Chronic Constrictive Pericarditis: A Study Using Speckle Tracking and Conventional Echocardiography

Background

Left atrial (LA) function plays an important role in the maintenance of cardiac output, however, in patients with constrictive pericarditis (CP), whether pericardial restriction and adhesion can lead to LA dysfunction, and the characteristics of LA function remain unclear. The aim of the study is to compare the left atrial (LA) function of patients with CP to that of healthy study participants using speckle tracking echocardiography (STE) and conventional echocardiography.

Methods and Results

Thirty patients with CP and 30 healthy volunteers (controls) were enrolled in the study. The underlying cause of CP was viral pericarditis in 24 (80%) patients and unknown in 6 (20%) patients. The LA maximum volume (Vmax), LA minimal volume (Vmin), and LA volume before atrial contraction (Vpre-a) were measured using biplane modified Simpson’s method. The LA expansion index (LA reservoir function) was determined as follows: ([LAVmax - LAVmin]/LAVmin) ×100. The passive emptying index (LA conduit function) was calculated as follows: ([LAVmax - LAVpre-a]/LAVmax) ×100, and the active emptying index (booster pump function) was calculated as follows: ([LAVpre-a - LAVmin]/LAVpre-a) ×100. All the patients underwent two-dimensional STE. The LA global systolic strain (S), systolic strain rate (SrS), early diastolic strain rate (SrE) and late diastolic strain rate (SrA) were measured. The LA expansion index, passive emptying index, the active emptying index and the LA global S, SrS, SrE, SrA were found to be significantly lower in patients with CP than in the control participants (P <0.001). LA function was correlated with the early diastolic velocity of the lateral mitral annulus (P <0.05).

Conclusions

Although left ventricular systolic function was preserved in patients with CP, the LA reservoir, conduit, and booster functions were impaired. Pericardial restriction and impairment of the LA myocardium may play an important role in the reduction of LA function in patients with CP.     

Non-Invasive Determination of Left Ventricular Workload in Patients with Aortic Stenosis Using Magnetic Resonance Imaging and Doppler Echocardiography

Early detection and accurate estimation of aortic stenosis (AS) severity are the most important predictors of successful long-term outcomes in patients. Current clinical parameters used for evaluation of the AS severity have several limitations including flow dependency. Estimation of AS severity is specifically challenging in patients with low-flow and low transvalvular pressure gradient conditions. A proper diagnosis in these patients needs a comprehensive evaluation of the left ventricle (LV) hemodynamic loads. This study has two objectives: (1) developing a lumped-parameter model to describe the ventricular-valvular-arterial interaction and to estimate the LV stroke work (SW); (2) introducing and validating a new index, the normalized stroke work (N-SW), to assess the global hemodynamic load imposed on the LV. N-SW represents the global hemodynamic load that the LV faces for each unit volume of blood ejected. The model uses a limited number of parameters which all can be measured non-invasively using current clinical imaging modalities. The model was first validated by comparing its calculated flow waveforms with the ones measured using Cardiovascular Magnetic Resonance (CMR) in 49 patients and 8 controls. A very good correlation and concordance were found throughout the cycle (median root mean square: 12.21 mL/s) and between the peak values (r = 0.98; SEE = 0.001, p<0.001). The model was then used to determine SW using the parameters measured with transthoracic Doppler-echocardiography (TTE) and CMR. N-SW showed very good correlations with a previously-validated index of global hemodynamic load, the valvular arterial impedance (), using data from both imaging modalities (TTE: r = 0.82, SEE = 0.01, p<0.001; CMR: r = 0.74, SEE = 0.01, p<0.001). Furthermore, unlike , N-SW was almost independent from variations in the flow rate. This study suggests that considering N-SW may provide incremental diagnostic and prognostic information, beyond what standard indices of stenosis severity and provide, particularly in patients with low LV outflow.     

Adaptive Iterative Dose Reduction Using Three Dimensional Processing (AIDR3D) Improves Chest CT Image Quality and Reduces Radiation Exposure

Objective

To assess the advantages of Adaptive Iterative Dose Reduction using Three Dimensional Processing (AIDR3D) for image quality improvement and dose reduction for chest computed tomography (CT).

Methods

Institutional Review Boards approved this study and informed consent was obtained. Eighty-eight subjects underwent chest CT at five institutions using identical scanners and protocols. During a single visit, each subject was scanned using different tube currents: 240, 120, and 60 mA. Scan data were converted to images using AIDR3D and a conventional reconstruction mode (without AIDR3D). Using a 5-point scale from 1 (non-diagnostic) to 5 (excellent), three blinded observers independently evaluated image quality for three lung zones, four patterns of lung disease (nodule/mass, emphysema, bronchiolitis, and diffuse lung disease), and three mediastinal measurements (small structure visibility, streak artifacts, and shoulder artifacts). Differences in these scores were assessed by Scheffe''s test.

Results

At each tube current, scans using AIDR3D had higher scores than those without AIDR3D, which were significant for lung zones (p<0.0001) and all mediastinal measurements (p<0.01). For lung diseases, significant improvements with AIDR3D were frequently observed at 120 and 60 mA. Scans with AIDR3D at 120 mA had significantly higher scores than those without AIDR3D at 240 mA for lung zones and mediastinal streak artifacts (p<0.0001), and slightly higher or equal scores for all other measurements. Scans with AIDR3D at 60 mA were also judged superior or equivalent to those without AIDR3D at 120 mA.

Conclusion

For chest CT, AIDR3D provides better image quality and can reduce radiation exposure by 50%.     

Catheter-Based Renal Sympathetic Denervation Significantly Inhibits Atrial Fibrillation Induced by Electrical Stimulation of the Left Stellate Ganglion and Rapid Atrial Pacing

Background

Sympathetic activity involves the pathogenesis of atrial fibrillation (AF). Renal sympathetic denervation (RSD) decreases sympathetic renal afferent nerve activity, leading to decreased central sympathetic drive. The aim of this study was to identify the effects of RSD on AF inducibility induced by hyper-sympathetic activity in a canine model.

Methods

To establish a hyper-sympathetic tone canine model of AF, sixteen dogs were subjected to stimulation of left stellate ganglion (LSG) and rapid atrial pacing (RAP) for 3 hours. Then animals in the RSD group (n = 8) underwent radiofrequency ablation of the renal sympathetic nerve. The control group (n = 8) underwent the same procedure except for ablation. AF inducibility, effective refractory period (ERP), ERP dispersion, heart rate variability and plasma norepinephrine levels were measured at baseline, after stimulation and after ablation.

Results

LSG stimulation combined RAP significantly induced higher AF induction rate, shorter ERP, larger ERP dispersion at all sites examined and higher plasma norepinephrine levels (P<0.05 in all values), compared to baseline. The increased AF induction rate, shortened ERP, increased ERP dispersion and elevated plasma norepinephrine levels can be almost reversed by RSD, compared to the control group (P<0.05). LSG stimulation combined RAP markedly shortened RR-interval and standard deviation of all RR-intervals (SDNN), Low-frequency (LF), high-frequency (HF) and LF/HF ratio (P<0.05). These changes can be reversed by RSD, compared to the control group (P<0.05).

Conclusions

RSD significantly reduced AF inducibility and reversed the atrial electrophysiological changes induced by hyper-sympathetic activity.