Microbubbles during radiofrequency catheter ablation: Composition and formation

OBJECTIVES: The purpose of this study was to measure tissue temperatures associated with microbubble formation during radiofrequency (RF) ablation. BACKGROUND: Microbubble formation visualized by echocardiography has been used to indicate excessive tissue heating during RF pulmonary vein isolation. However, little is known about the tissue temperatures associated with microbubble formation. METHODS: Optical fluorometric thermometry probes were used to record tissue temperatures in isolated porcine atrium overlying either lung or esophageal tissue in a saline bath. RF energy was delivered through an irrigated ablation electrode during echocardiographic monitoring for microbubble formation. RESULTS: The maximal recorded tissue temperatures were 81.0 +/- 5.0 degrees C and 88.3 +/- 8.1 degrees C at the time of intermittent (type 1) microbubble formation for lung and esophageal preparations, respectively. During continuous (type 2) microbubble formation, the temperatures were 91.4 +/- 8.2 degrees C and 99.2 +/- 7.8 degrees C, respectively (both P < .001 vs type 1). Tissue temperatures averaged >100 degrees C at the time of "pops." The maximal recorded temperature occurred up to 4 mm deep in the tissues and frequently occurred external to the atrial tissue. The total RF lesion volumes for lung and esophageal preparations were related to the pattern of microbubble formation but not to total power delivered. After generation of type 1 bubbles, up to 60% reductions in RF energy were needed to restore target tissue temperatures of 65 degrees C. Gas chromatographic analysis of the microbubbles was consistent with steam formation. CONCLUSIONS: Microbubble formation during RF ablation represents excessive tissue heating to the point of steam formation. Maximal tissue heating may occur in the adjacent lung and esophagus during cooled ablation.     

Dedifferentiation of atrial cardiomyocytes in cardiac valve disease: unrelated to atrial fibrillation

BACKGROUND: Valvular heart disease has become an important public health concern. The increased wall stress and underlying disease entity associated with mitral valve disease provide unfavorable circumstances for atrial cardiomyocytes. The expression of the alpha-smooth muscle actin isoform is considered characteristic of cardiomyocyte dedifferentiation (embryonic cardiomyocyte), and cardiomyocyte dedifferentiation may indicate an adaptive state, enabling cardiomyocytes to survive despite unfavorable circumstances. METHODS: This study comprised 20 adult patients with symptomatic severe mitral valve disease and moderate to severe tricuspid valve disease and without coronary artery disease undergoing valve operations for congestive heart failure. Ten patients had persistent atrial fibrillation and 10 patients had never been in atrial fibrillation by history and electrocardiograms before surgery. Atrial tissues of the right atrial appendage were obtained during surgery. RESULTS: Immunohistochemical study demonstrated that alpha-smooth muscle actin protein expression was not altered by atrial fibrillation, and alpha-smooth muscle actin protein expression in atrial tissues was higher in patients with sinus rhythm than in those with atrial fibrillation (the percentage of cells that were alpha-smooth muscle actin-positive was 51.5+/-34.9% for right atria from patients in sinus rhythm vs. 16.2+/-15.0% for right atria from patients with atrial fibrillation) (P<.03). Semiquantitation of alpha-smooth muscle actin by immunoblotting of extracts from atrial tissues showed similar findings as in the immunohistochemical observations: that is, atrial fibrillation did not influence the expression of alpha-smooth muscle actin protein. Interstitial fibrosis represented 43.2+/-13.9% of the right atrial tissue in the sinus group, whereas interstitial fibrosis comprised 49.8+/-8.2% of the right atrial tissue in the atrial fibrillation group (P=.320). CONCLUSIONS: Dedifferentiation of atrial cardiomyocytes occurs in patients with cardiac valve disease, even without atrial fibrillation.     

Alterations in contractile protein composition and function in human atrial dilatation and atrial fibrillation

The cellular mechanisms responsible for contractile dysfunction associated with atrial fibrillation (AF) are still poorly understood. Atrial fibrillation is often preceded by atrial dilatation. This study aimed to explain contractile alterations associated with AF and their relation to atrial dilatation, by studying the relationships between atrial dimensions, contractile protein composition, force production and Ca(2+)-sensitivity. Force development was determined in mechanically isolated single skinned cardiomyocytes from right atrial appendages from patients with sinus rhythm without (SR;n=9), or with atrial dilation (SR+AD;n=11) or atrial fibrillation (AF;n=16). Echocardiography showed that, compared to the SR group, mean right atrial dimensions were increased by 18% and 35% in the SR+AD and AF group, respectively (P<0.05). Protein composition was determined by 1- and 2-dimensional gel electrophoresis. Compared to the SR group, the AF group exhibited: a reduction in the kinetics of force redevelopment (K(tr)) in isolated atrial cardiomyocytes, enhanced protein expression of the slow myosin heavy chain isoform (beta-MHC), an increase in troponin T (TnT) phosphorylation and a marked increase (70%) of the cytoskeletal protein desmin. Significant correlations were observed between the right atrial major axis (RA(major)) and beta-MHC expression as well as the desmin/actin ratio. Our findings indicate that dilatation may influence cardiomyocyte stability through altered desmin expression, but that it does not predispose to the alterations in contractile function observed in AF.     

围术期房颤合并心功能不全的治疗

心房颤动（Af）是临床上常见的心律失常之一，Af患者围术期的治疗特别是房颤合并心功能不全的治疗不仅关系到患者术后的恢复而且直接威胁到患者的生命。我们以随机对照方法研究静脉注射胺碘酮与毛花甙C控制心功能（Killip）分级Ⅰ级、Ⅱ级、Ⅲ级患者快速心房纤维颤动，降低心室率及转复窦性心律的有效性。     

Sustained High Quality of Life in a 5-Year Long Term Follow-up after Successful Ablation for Supra-Ventricular Tachycardia. Results from a large Retrospective Patient Cohort

Introduction: The ablation of supraventricular tachycardias (SVT) using radiofrequency energy (RF) is a procedure with a high primary success rate. However, there is a scarcity of data regarding the long term outcome, particularly with respect to quality of life (QoL).     

Left atrial ball thrombus

We report a case of left atrial ball thrombus managed successfully by surgery. This is a rare clinical entity and has been reported quite infrequently in Indian literature despite the high incidence of Rheumatic mitral stenosis. The relevant literature is reviewed.     

心房超常传导与房性心律失常相关性探讨

目的：探讨心房超常传导（ＳＮＣ）与房性心律失常发生之间的关系。方法：按常规行心内电生理检查，观察有无ＳＮＣ发生及心房超常传导带与传导时间最大减少值。结果：有自发或诱发房性心律失常者（Ⅰ、Ⅱ组），ＳＮＣ检出率较无自发或无诱发房性心律失常者（Ⅲ组）明显增加（Ｐ＜０．０５）；３６例有ＳＮＣ者中２０例（５５．５６％）有自发或诱发的房性心律失常，而３９例无ＳＮＣ者中仅８例（２０．５１％）有自发或诱发的房性心律失常，两者比较相差非常显著（Ｐ＜０．００５）。结论：ＳＮＣ与房性心律失常的发生密切相关。     

Anomalous High Insertion of the Inferior Vena Cava into the Right Atrium: A Case Report with Review of Literature

Objective. Anomalous high insertion of the inferior vena cava into the right atrium is probably the most infrequent anomaly among the anomalies of the inferior vena cava. Patients. We present a case of anomalous high insertion of the inferior vena cava into the posterior wall of the right atrium in a 20‐year‐old asymptomatic man. Conclusions. This anomaly has unique characteristic because of presenting with an isolated anomaly different from earlier reported cases.     

Left atrial remodelling in mitral regurgitation--methodologic approach, physiological determinants, and outcome implications: a prospective quantitative Doppler-echocardiographic and electron beam-computed tomographic study.

AIMS: To define accurate and normal range of echocardiographic left atrial (LA) volume measurement and to assess the prevalence, determinants, and outcome implications of LA enlargement in mitral regurgitation (MR). METHODS AND RESULTS: We prospectively compared LA volume obtained simultaneously by electron beam-computed tomography (EBCT) and by four echocardiographic methods in 33 test patients. Accurate echocardiographic LA volume measurements were obtained only by biplane area-length method with vertical longitudinal-length (r = 0.95, P < 0.0001; 145 +/- 57 vs. 143 +/- 55 mL, P = 0.57). Using this method, the normal range in 100 normal subjects, the physiological determinants and outcome implications of LA enlargement in 320 patients with organic MR were analysed. In normal subjects, indexed to body surface area, LA index (27 +/- 6 mL/m(2)) was not influenced by age or gender and values > or = 40 mL/m(2) were beyond the upper limit of normal. In MR, the most powerful determinants of LA enlargement were higher regurgitant volume (RVol) and atrial fibrillation (AF) (P < 0.0001), followed by older age, female gender, higher left ventricular end-systolic volume, and mass (all P < 0.001). After diagnosis in sinus rhythm, LA index > or = 40 mL/m(2) predicted superiorly and independently to LA diameter the occurrence of AF [adjusted RR 1.48 (1.06-2.16), P < 0.01] and the combined endpoint of death or need for mitral surgery [adjusted RR 1.61 (1.3-2.0), P < 0.0001]. CONCLUSION: LA remodelling can be accurately assessed by echocardiography and LA index > or = 40 mL/m(2) is beyond the normal range. In organic MR, higher LA index is the combined result of multiple physiological effects, provides independent prognostic information, and therefore should be part of a comprehensive echocardiographic examination.