Termination of atrial flutter by directed transesophageal atrial pacing during transesophageal echocardiography.

INTRODUCTION: The purpose of this study was to evaluate termination of atrial flutter (AFL) by directed rapid transesophageal atrial pacing (TAP) with and without simultaneous transesophageal echocardiography (TEE) performed using a novel TEE tube electrode. MATERIALS AND METHODS, AND RESULTS: A total of 16 AFL patients (age 63+/-12 years; 13 males) with mean AFL cycle length of 224+/-24 ms (n=12) and mean ventricular cycle length of 448+/-47 ms (n=12) were analyzed using either an esophageal TO electrode (n=10) or a novel TEE tube electrode consisting of a tube with four hemispherical electrodes that is pulled over the echo probe (n=6). AFL could be terminated by directed rapid TAP using an esophageal TO electrode, leading to induction of atrial fibrillation (AF) (n=6), induction of AF and spontaneous conversion to sinus rhythm (SR) (n=3), and with conversion to SR (n=1). AFL could also be terminated by directed rapid TAP using the TEE tube electrode, with induction of AF (n=3) or induction of AF and spontaneous conversion to SR (n=3). CONCLUSION: AFL can be terminated by directed rapid TAP with hemispherical electrodes with and without simultaneous TEE. TAP with the directed TEE tube electrode is a safe, simple, and useful method for terminating AFL.     

Percutaneous transcatheter repositioning of displaced permanent pacemaker atrial lead with a simple system

A 48-year-old man who was implanted with a DDD-R pacemaker because of sick sinus syndrome eight days ago presented to our institute with a syncopal attack. Fluoroscopy showed a dislodged active fixation atrial pacemaker lead. With a snare system simply improvised from a 0.014 inch guidewire and a NIH catheter, the lead was repositioned via percutaneous transfemoral approach. The procedure was easy and completed without any complication. Follow-up controls after two weeks and three months showed stability of the lead position with normal pacing and sensing functions.     

Diagnosis of left atrial myxoma by echocardiography

The diagnostic use of ultrasound was demonstrated in two patients with left atrial myxoma. In both cases the decision to proceed with confirmatory angiography and ultimate removal of the tumour was initiated by the echocardiographic findings. The echocardiogram proved to be a simple non-invasive technique for the diagnosis of left atrial mass.     

实时三维超声心动图评价房间隔缺损患者手术前后心室收缩功能

目的 应用实时三维超声心动图(RT-3DE)研究房间隔缺损(ASD)患者行内科介入手术前后左、右室心肌收缩变化的相关关系.方法 应用RT-3DE技术对34例ASD患者术前、术后1周以及35例正常受检者(对照组)的左、右室舒张末期容量(LVEDV/RVEDV),左、右室收缩末期容量(LVESV/RVESV),左、右室每搏量(LVSV/RVSV)及左、右室射血分数(LVEF/RVEF)进行统计分析.结果 术前,ASD患者LVEDV、LVSV、LVEF均小于对照组(均P＜0.05),RVEDV、RVESV、RVSV、RVEF均大于对照组(均P＜0.05);术后1周内,ASD患者LVEDV、LVSV、LVEF均较术前增大(均P＜0.05),RVEDV、RVSV、RVEF均较术前减小(均P＜0.05);ASD患者术后的LVEDV、LVESV、LVSV、LVEF与对照组比较均无统计学意义(均P＞0.05),而RVEDV、RVESV、RVSV均大于对照组(P＜0.05);ASD患者术后左、右室的射血分数变化之间均无相关性.结论 行内科介入的ASD患者术后初期左、右室收缩功能即恢复到正常水平,术后左、右室射血分数的变化之间均无相关性.     

S-ICD oversensing detected by remote monitoring using a new atrial fibrillation diagnostic algorithm

A 64-year-old male with a high body mass index, and subcutaneous implantable cardioverter defibrillator, (S-ICD) presented with a remote transmission of inappropriately diagnosed AF episodes, due to oversensing of P and T waves. The AF monitor can be an early warning for inappropriate sensing. Oversensing, due to small amplitude signals, can be caused by the lead position not being adequately opposed to the sternum.     

The effects of noradrenaline, applied by microelectrophoresis on different cells of the rabbit's atrial pacemaker

Noradrenaline has been applied by microelectrophoresis to a small portion of the atrial pacemaker area in the rabbit's heart in order to study the local effects of this chemical transmitter separately from the ones deriving from other parts of the pacemaker area. In a first group of cells, whose action potential and location assimilate them to true pacemaker cells, noradrenaline caused a reduction in cycle length and an increase in the steepness of slow diastolic depolarization. In a second group of cells similar to latent pacemaker cells, noradrenaline caused no change in cycle length, the outstanding effect being an increase in the steepness of the slow diastolic depolarization which afterwards changed into a subthreshold oscillation. A third type of cells showed intermediate characteristics between the two previous groups. These results suggest that: a) the chronotropic effect of noradrenaline on the heart atrial pacemaker seems to be due to changes in the steepness of slow diastolic depolarization which can assume, in some instances, the shape of subthreshold oscillations; the effects on the other parameters in our preparation seem to be either less constant or less significant; b) the different effects which are obtained on various kinds of cells seem to be the result of a different degree of sensitivity to noradrenaline and to the more or less premature activation of mechanisms antagonizing the action of noradrenaline. The results are discussed on the basis of a model of spontaneous atrial pacemaking which has been recently proposed.     

微电极阵列芯片技术研究48h房颤犬左、右心耳电生理特性

目的应用微电极阵列芯片（microelectrode arrays chip,MEA）技术评价48 h房颤（atrial fibrillation,AF）犬左、右心耳（LAA、RAA）的电生理特性。方法随意来源犬12只,以600次/分起搏右心房建立AF模型,分为48 h AF组（n=6）和对照组（n=6）。造模成功后迅速开胸剪取LAA、RAA,置于盛有台式液的MEA中,分别记录AF组及对照组LAA、RAA场电位（field action potential,FAP）形态、振幅、放电频率及激动传导情况。结果 AF组LAA、RAA组织FAP节律绝对不齐,LAA（185.22±25.62）次/分,较对照组（156.44±8.88）次/分增加15.67%（P〈0.01）,RAA（102.39±16）次/分,较对照组（156.44±8.88）次/分减慢34.62%（P〈0.01）。48 h AF组LAA组织电压（458.33±26.73）μV较对照组（740.55±18.93）μV降低38.11%（P〈0.01）,RAA（504.83±39.93）μV较对照组（840.56±18.93）μV明显降低（P〈0.01）,48 h房颤组LAA组织FAP时程（45.28±8.59）ms较对照组（70.77±6.98）ms缩短15 ms（P〈0.01）。RAA（61.78±7.1）ms较对照组（75.83±7.63）ms缩短14 ms（P〈0.01）。48 h AF组LAA、RAA FAP传导异质性增加。结论应用MEA技术可反映心肌组织片场电位电生理特性,48 h AF后LAA放电频率增加,频率绝对不齐,LAA、RAA电压降低,场电位时程延长。     

Dual chamber pacemaker implantation in woman with twin pregnancy and Chagas cardiomyopathy guided by 2D transthoracic echocardiography

We present a case of 36-year-old woman with twin pregnancy, Chagas cardiomyopathy and history of multiple episodes of dizziness and syncope. The patient's Holter study revealed sinus pauses of up to 5.3 seconds, frequent premature ventricular contractions (PVC) and some episodes of non-sustained ventricular tachycardia at 110 bpm. To avoid teratogenic radiation, dual chamber pacemaker implantation was performed guided by transthoracic echocardiography. The patient was treated with metoprolol succinate 100 mg once a day to reduce PVC and nonsustained ventricular tachycardia. During follow up, the patient reported complete resolution of syncope and dizziness. She went on to have a normal delivery without complications. PCRs for Chagas in both twins were negative.     

Right atrial dimension-pressure relation during volume expansion is unaltered by pregnancy in the rat

Blood volume expands significantly during pregnancy, but afferent signals from cardiac receptors are reduced. In addition, during exogenous volume expansion, right atrial pressure (RAP) increases more for equivalent volumes in pregnant animals, implying reduced atrial compliance. To examine possible gestational alterations in atrial dimension during volume expansion, we compared the effects of volume expansion on RAP and right atrial dimension (RAD) in pregnant vs. virgin rats. Anesthetized animals were ventilated and catheterized for measurement of arterial pressure and RAP and for drug infusion. Through a parasternal incision, ultrasonic crystals were glued to the medial and lateral surfaces of the right atrium for measurement of RAD. Plasma volume and hematocrit were determined before experimentation. RAP, RAD, and arterial pressure were recorded at baseline and during progressive volume expansion (6% dextran, 60% of initial blood volume). Baseline RAP was similar in the two groups: 2.82 +/- 0.40 and 2.72 +/- 0.47 mmHg in pregnant and virgin rats, respectively. Basal RAD was significantly larger in pregnant than in virgin rats: 4.36 +/- 0.66 vs. 3.36 +/- 0.48 mm. Despite increased basal RAD in pregnant rats, the slope of the RAD-RAP relation during volume expansion was similar in the two groups. Results indicate that resting RAD is increased in pregnant rats and that the change in dimension during volume loads is similar to that in virgin rats. Thus, during pregnancy, the right atrium appears to accommodate the increased blood volume, and reduced afferent signaling most likely is due to mechanisms other than mechanical alterations of the atrium by expanded volume.     

Inhibition of a dual chamber pacemaker by oversensing of far-field atrial depolarisation in a patient after His-bundle ablation

After His-bundle ablation, a 54-year-old pacemaker-dependent patient suffered from severe presyncopal attacks one year after pacemaker replacement. The attacks were caused by ventricular inhibition due to atrial far-field sensing during paroxysmal atrial flutter.     

Simulation of atrial activity by a phase response curve based model of a two-dimensional pacemaker cells array: the transition from a normal activation pattern to atrial fibrillation

In this paper, we present an original model of the atria, based on our hypothesis that atrial cells have features of pacemaker cells, characterized by their normally longer intrinsic cycle lengths and different type of connection (stronger) than the, sino-atrial (SA) node pacemaker cells. The atrium is simulated by a two-dimensional array of pacemaker cells (25 × 25), composed of a region of SA node pacemaker cells (11 × 11) surrounded by atrial pacemaker cells. All pacemakers cells are characterized by only the most relevant functional properties, those which play the most direct role in the determination of the cardiac rate and in the mechanism of arrhythmias. These properties are: the intrinsic cycle length, τ, an `internal' feature of each pacemaker cell, and the phase-response curve (PRC), an `overall collective' function. The PRC embodies the interactions of each pacemaker cell with its neighboring cells, and thus represents the type of connection (strong, weak, etc.) of the pacemaker cell with its surroundings. In our model, the SA node region differs from the atrial region by cycle length distribution and PRCs. We studied the spatial interaction between SA node pacemaker cells and atrial pacemaker cells as a function of the regional variation of cells properties and as a function of the “electrical” coupling between cells (the PRC), in the SA node region, in the atrial region, and in a border zone between them. We investigated the influence of those parameters on the activation pattern, on the conduction time of the array, and on a pseudo-ECG signal. This study demonstrates that by representing the atrial cells as a population of `pacemaker-like' cells, similar to the SA node pacemaker cells, but differing markedly in their cycle lengths and cell-to-cell interaction (PRC), we can create a global picture of the atrial system by applying a simple physical-mathematical model. This approach enables us to explore physiological phenomena related to the genesis and maintenance of atrial activity. It also reveals the conditions which predispose to atrial arrhythmias and conduction disturbances (e.g. tachycardia, pacemaker shift, re-entry, fibrillation). In particular, it yields insight into the mechanism of transition from normal atrial activity to the disordered state of atrial fibrillation. Therefore, this study suggests a new way of looking at the development of cardiac arrhythmias of atrial origin. Received: 8 September 1997 / Accepted in revised form: 6 October 1998     

Assessment of atrial regional and global electromechanical function by tissue velocity echocardiography: a feasibility study on healthy individuals

Background

Myocardial contrast echocardiography and coronary flow velocity pattern with a rapid diastolic deceleration time after percutaneous coronary intervention has been reported to be useful in assessing microvascular damage in patients with acute myocardial infarction.

Aim

To evaluate myocardial contrast echocardiography with harmonic power Doppler imaging, coronary flow velocity reserve and coronary artery flow pattern in predicting functional recovery by using transthoracic echocardiography.

Methods

Thirty patients with anterior acute myocardial infarction underwent myocardial contrast echocardiography at rest and during hyperemia and were quantitatively analyzed by the peak color pixel intensity ratio of the risk area to the control area (PIR). Coronary flow pattern was measured using transthoracic echocardiography in the distal portion of left anterior descending artery within 24 hours after recanalization and we assessed deceleration time of diastolic flow velocity. Coronary flow velocity reserve was calculated two weeks after acute myocardial infarction. Left ventricular end-diastolic volumes and ejection fraction by angiography were computed.

Results

Pts were divided into 2 groups according to the deceleration time of coronary artery flow pattern (Group A; 20 pts with deceleration time ≧ 600 msec, Group B; 10 pts with deceleration time < 600 msec). In acute phase, there were no significant differences in left ventricular end-diastolic volume and ejection fraction (Left ventricular end-diastolic volume 112 ± 33 vs. 146 ± 38 ml, ejection fraction 50 ± 7 vs. 45 ± 9 %; group A vs. B). However, left ventricular end-diastolic volume in Group B was significantly larger than that in Group A (192 ± 39 vs. 114 ± 30 ml, p < 0.01), and ejection fraction in Group B was significantly lower than that in Group A (39 ± 9 vs. 52 ± 7%, p < 0.01) at 6 months. PIR and coronary flow velocity reserve of Group A were higher than Group B (PIR, at rest: 0.668 ± 0.178 vs. 0.248 ± 0.015, p < 0.0001: during hyperemia 0.725 ± 0.194 vs. 0.295 ± 0.107, p < 0.0001; coronary flow velocity reserve, 2.60 ± 0.80 vs. 1.31 ± 0.29, p = 0.0002, respectively).

Conclusion

The preserved microvasculature detecting by myocardial contrast echocardiography and coronary flow velocity reserve is related to functional recovery after acute myocardial infarction.     

Early impairment of myocardial deformation assessed by regional speckle-tracking echocardiography in the indeterminate form of Chagas disease without fibrosis detected by cardiac magnetic resonance

Chagas disease (CD) will account for 200,000 cardiovascular deaths worldwide over the next 5 years. Early detection of chronic Chagas cardiomyopathy (CCC) is a challenge. We aimed to test if speckle-tracking echocardiography (STE) can detect incipient myocardial damage in CD. METHODS: Among 325 individuals with positive serological tests, 25 (age 55±12yrs) were selected to compose the group with indeterminate form of Chagas disease (IFCD), based on stringent criteria of being asymptomatic and with normal EKG/X-ray studies. This group was compared with a group of 20 patients with CCC (55±11yrs) and a group of 20 non-infected matched control (NC) subjects (48±10yrs). CD patients and NC were submitted to STE and CD patients were submitted to cardiac magnetic resonance (CMR) with late gadolinium administration to detect cardiac fibrosis by the late enhancement technique. Global longitudinal strain (GLS), circumferential (GCS) and radial strain (GRS) were defined as the average of segments measured from three apical view (GLS) and short axis views (GRS and GCS). Regional left ventricular (LV) longitudinal strain (Reg LS) was measured from each of the 17 segments. Twist was measured as systolic peak difference between basal and apical rotation and indexed to LV length to express torsion. RESULTS: STE global indices (GLS, GCS, twist and torsion) were reduced in CCC vs NC (GLS: -14±6.3% vs -19.3±1.6%, p = 0.001; GCS: -13.6±5.2% vs -17.3 ±2.8%; p = 0.008; twist: 8±7° vs 14±7°, p = 0.01 and torsion: 0.96±1°/cm vs 1.9±1°/cm, p = 0.005), but showed no differences in IFCD vs NC. RegLS was reduced in IFCD vs NC in four LV segments: basal-inferior (-16.3±3.3% vs -18.6±2.2%, p = 0.013), basal inferoseptal (-13.1±3.4 vs -15.2±2.7, p = 0.019), mid-inferoseptal (-17.7±3.2 vs -19.4±2, p = 0.032) and mid-inferolateral (-15.2±3.5 vs -17.8±2.8, p = 0.014). These abnormalities in RegLS occurred in the absence of myocardial fibrosis detectable with CMR in nearly 92% of subjects with IFCD, while myocardial fibrosis was present in 65% with CCC. CONCLUSION: RegLS detects early regional impairment of myocardial strain that is independent from fibrosis in IFCD subjects.     

Right ventricular lead implantation facilitated by a guiding sheath in a patient with severe chamber dilatation with tricuspid regurgitation

Implantation of pacemakers can be challenging in the context of dilated cardiac chambers and valvular regurgitation. We report a difficult case of single chamber pacemaker implantation in a patient with restrictrive cardiomyopathy resulting in grossly enlarged atria and severe tricuspid regurgitation. In this situation, use of a slittable guiding sheath, more typically used for coronary sinus lead implantation, greatly facilitated rapid and stable deployment of the right ventricular lead.     

Covalent structural changes in unfolded GroES that lead to amyloid fibril formation detected by NMR: insight into intrinsically disordered proteins

Co-chaperonin GroES from Escherichia coli works with chaperonin GroEL to mediate the folding reactions of various proteins. However, under specific conditions, i.e. the completely disordered state in guanidine hydrochloride, this molecular chaperone forms amyloid fibrils similar to those observed in various neurodegenerative diseases. Thus, this is a good model system to understand the amyloid fibril formation mechanism of intrinsically disordered proteins. Here, we identified a critical intermediate of GroES in the early stages of this fibril formation using NMR and mass spectroscopy measurements. A covalent rearrangement of the polypeptide bond at Asn(45)-Gly(46) and/or Asn(51)-Gly(52) that eventually yield β-aspartic acids via deamidation of asparagine was observed to precede fibril formation. Mutation of these asparagines to alanines resulted in delayed nucleus formation. Our results indicate that peptide bond rearrangement at Asn-Gly enhances the formation of GroES amyloid fibrils. The finding provides a novel insight into the structural process of amyloid fibril formation from a disordered state, which may be applicable to intrinsically disordered proteins in general.