Left atrial chamber and appendage function after internal atrial defibrillation: a prospective and serial transesophageal echocardiographic study

Proteolytic degradation of atrial sarcomere proteins underlies contractile defects in atrial fibrillation

Atrial fibrillation (AFib) is the most common cardiac rhythm disturbance, often treated via electrical cardioversion. Following rhythm restoration, a period of depressed mechanical function known as atrial stunning occurs, suggesting that defects in contractility occur in AFib and are revealed upon restoration of rhythm. This project aims to define the contractile remodeling that occurs in AFib. To assess contractile function, we used a canine atrial tachypacing model of induced AFib. Mass spectrometry analysis showed dysregulation of contractile proteins in samples from AFib compared with sinus rhythm atria. Atrial cardiomyocytes show reduced force of contraction, decreased resting tension, and increased calcium sensitivity in skinned single cardiomyocyte studies. These alterations correlated with degradation of myofilament proteins including myosin heavy chain altering force of contraction, titin altering resting tension, and troponin I altering calcium sensitivity. We measured degradation of other myofilament proteins, including cardiac myosin binding protein C and actinin, that show degradation products in the AFib samples that are absent in the sinus rhythm atria. Many of the degradation products appeared as discrete cleavage products that are generated by calpain proteolysis. We assessed calpain activity and found it to be significantly increased. These results provide an understanding of the contractile remodeling that occurs in AFib and provide insight into the molecular explanation for atrial stunning and the increased risk of atrial thrombus and stroke in AFib.NEW & NOTEWORTHY Atrial fibrillation is the most common cardiac rhythm disorder, and remodeling during atrial fibrillation is highly variable between patients. This study has defined the biophysical changes in contractility that occur in atrial fibrillation along with identifying potential molecular mechanisms that may drive this remodeling. This includes proteolysis of several myofilament proteins including titin, troponin I, myosin heavy chain, myosin binding protein C, and actinin, which is consistent with the observed contractile deficits.

Does Sinus Rhythm Restoration in Patients With Atrial Fibrillation Undergoing Pulmonary Vein Isolation Have Acute Hemodynamic Benefits?

Background

Although the restoration and maintenance of sinus rhythm (SR) in patients with atrial fibrillation (AF) have long-term benefits, few studies have investigated the acute hemodynamic benefits immediately after SR restoration. Therefore, we investigated whether hemodynamic changes occurred in the first few minutes after cardioversion from AF to SR.

Methods

We retrospectively enrolled 145 patients with AF and divided them into a pre-AF group comprising patients in whom SR was restored by electrical cardioversion during pulmonary vein isolation (PVI; n = 74) and a control group comprising patients who were in SR throughout the procedure (n = 71). The pre-AF group was subdivided into subgroups according to AF classification (paroxysmal AF (PAF), persistent AF (PerAF), and long-standing persistent AF (LSPAF)) and into quartiles based on the AF-heart rate (HR). The mean arterial pressure (MAP) and left atrial pressure (LAP) were measured immediately after transseptal puncture (pre-measurement) and before withdrawal from the left atrium after PVI (post-measurement). The changes in MAP and LAP between the pre- and post-measurement (ΔMAP and ΔLAP) were calculated by subtracting the pre-measurements (MAPpre and LAPpre) from the post-measurements (MAPpost and LAPpost).

Results

In the pre-AF group, the time from cardioversion to post-measurement was 19 ± 16 min. When ΔMAP and ΔLAP were compared with the control group, ΔMAP was significantly smaller (4.9 ± 17.8 vs. 11.0 ± 14.2 mm Hg, respectively; P = 0.025), and ΔLAP was not significantly different between the groups. In the subgroup analyses, although ΔLAP was not significantly different among AF types, ΔMAP was significantly increased in the PAF group compared to the PerAF and LSPAF groups (24.0 ± 18.5 vs. 3.1 ± 16.8 and 4.5 ± 18.1 mm Hg, respectively; P = 0.042). The HRpre in the quartiles with the lowest, second, third, and highest AF-HR were approximately 58, 74, 86, and 109 beats per minute (bpm), respectively. The ΔLAP and ΔMAP were not significantly different among the AF-HR quartile groups.

Conclusions

In patients with PAF, atrial contractions may resume quickly, which leads to hemodynamic improvement immediately after SR restoration. As for AF-HR, there was no significant impairment of ventricular diastolic filling at approximately < 109 bpm.

Proteolytic degradation of atrial sarcomere proteins underlies contractile defects in atrial fibrillation

Aims

Atrial fibrillation (AFib) is the most common cardiac rhythm disturbance. Treatment of AFib involves restoration of the atrial electrical rhythm. Following rhythm restoration, a period of depressed mechanical function known as atrial stunning occurs that involves decreased blood flow velocity and reduced atrial contractility. This suggests that defects in contractility occur in AFib and are revealed upon restoration of rhythm. The aim of this project is to define the contractile remodeling that occurs in AFib.

Methods and Results

To assess contractile function, we used a canine atrial tachypacing model of induced AFib. Mass spectrometry analysis showed dysregulation of contractile proteins in samples from AFib compared to sinus rhythm atria. Atrial cardiomyocytes showed reduced force of contraction in skinned single cardiomyocyte calcium-force studies. There were no significant differences in myosin heavy chain isoform expression. Resting tension is decreased in the AFib samples correlating with reduced full-length titin in the sarcomere. We measured degradation of other myofilament proteins including cMyBP-C, actinin, and cTnI, showing significant degradation in the AFib samples compared to sinus rhythm atria. Many of the protein degradation products appeared as discrete cleavage products that are generated by calpain proteolysis. We assessed calpain activity and found it to be significantly increased. Skinned cardiomyocytes from AFib atria showed decreased troponin I phosphorylation, consistent with the increased calcium sensitivity that was found within these cardiomyocytes.

Conclusions

With these results it can be concluded that AFib causes alterations in contraction that can be explained by both molecular changes occurring in myofilament proteins and overall myofilament protein degradation. These results provide an understanding of the contractile remodeling that occurs in AFib and provides insight into the molecular explanation for atrial stunning and the increased risk of atrial thrombus and stroke in AFib.

Assessment of left atrial appendage function by echocardiography

The left atrial appendage (LAA) is considered not only to be the most frequent site of thrombus formation, but also to play a pivotal role in maintaining normal cardiac function. Transesophageal echocardiography (TEE) is widely used to assess LAA function. The LAA flow velocity has been used as a surrogate for LAA function, and it varies with multiple interrelated factors including age, hemodynamics, type of arrhythmia, and antiarrhythmic interventions. Relatively great importance of LAA function is involved with intraatrial thrombus formation and subsequent thromboembolism, and thus, understanding of characteristics and behaviors of the LAA under various clinical conditions may help determine strategies against atrial thrombosis. Also, techniques other than TEE-derived Doppler to assess LAA function, such as tissue Doppler imaging, have been proposed. In this review, we introduce clinical and echocardiographic correlates of LAA function, the LAA flow velocity in particular, its significance, and how to interpret functional patterns of the LAA each relevant to specific clinical settings.

Intra- and Postprocedural Multimodality Imaging in Atrial Fibrillation

Multi-modality imaging plays critical roles during and after procedures associated with atrial fibrillation. Transesophageal echocardiography is an invaluable tool for left atrial appendage occlusion during the procedure and at follow-up. Both cardiac computed tomography and cardiac magnetic resonance contribute to postprocedural evaluation of pulmonary vein isolation ablation. The present review is the second of a 2-part series where we discuss the roles of cardiac imaging in the evaluation and management of patients with atrial fibrillation, focusing on intraprocedural and postprocedural assessment, including the clinical evidence and outcomes data supporting this future applications.

Association of Structure and Function of left atrial Appendage with Left atrial appendage Thrombus formation in patients with Rheumatic Heart Disease

Context:

In patients with rheumatic heart disease (RHD), left atrial appendage (LAA) dilation and thrombus formation is widely known. LAA thrombus formation is a risk factor for stroke even in patients with sinus rhythm. The aim of this study was to determine an association between LAA structure and function with respect to thrombus formation and differences in LAA size and velocity between patients with sinus rhythm and those with atrial fibrillation (AF).

Materials and Methods:

We prospectively studied LAA structure and function in 120 patients with RHD by transthoracic echocardiography and/or transesophageal echocardiography by measuring left atrial (LA) dimension, LA area, LAAmax/min, LAA ejection fraction (EF), and LAA emptying velocity.

Results:

Four out of 48 patients with sinus rhythm had LAA thrombus. In 72 patients with AF, 32 had LAA thrombus. Patients with LAA thrombus had lower mean LAA EF and emptying velocity both variables P-value is same (P<0.0001 and P<0.0001) Patients with LAA thrombus had increased mean LAA max and LAA min as compared to LAA max and LAA min in patients without LAA thrombus (P 0.008 for mean LAA max and P<0.0001 for LAA min respectively). Patients with AF with LAA thrombus had greater LAAmax compared to that in patients with AF without LAA thrombus (P < 0.0001). Doppler demonstrated a recognizable sawtooth LAA outflow velocity pattern in 32 of 36 (88.9%) patients with LAA thrombus versus 32 of 84 (38.1%) patients without LAA thrombus.

Conclusions:

We conclude that LAA contractility is reduced in RHD with LAA thrombus, and loss of both contractility and LAA dilation is associated with increased risk of thrombus formation and hence the risk of stroke.

Mechanical atrial recovery after cardioversion in persistent atrial fibrillation evaluated by bidimensional speckle tracking echocardiography

BACKGROUND

Atrial fibrillation induces reversible electrical and mechanical modifications (atrial remodeling). Atrial stunning is a mechanical dysfunction with preserved bioelectrical function, occurring after successful atrial fibrillation electrical cardioversion (ECV). Two-dimensional speckle tracking echocardiography is a new technology for evaluating atrial mechanical function. We assessed atrial mechanical function after ECV with serial two-dimensional speckle tracking echocardiography evaluations. The investigated outcome was left atrium mechanical recovery within 3 months.

METHODS

A total of 36 patients [mean age 73 (7.9) years, 23 males] with persistent atrial fibrillation underwent conventional transthoracic and transesophageal echocardiography before ECV. Positive global atrial strain (GSA+) was assessed at 3 h, 1, 2, 3, 4 weeks and 3 months after ECV. Mechanical recovery was defined as the achievement of a GSA+ value of 21%.

RESULTS

Independent predictors of GSA+ immediately after ECV (basal GSA+) were E/e' ratio and left atrial appendage anterograde flow velocity. During the follow-up, 25% of patients suffered atrial fibrillation recurrence. In 12/36 patients (33%) left atrium mechanical recovery was detected (mechanical recovery group), while in 15/36 (42%) recovery did not occur (no atrial mechanical recovery group). At univariate analysis, the variables associated with recovery, were basal GSA+ (P = 0.015) and maximal velocity left atrial appendage (P = 0.022). Female sex (P = 0.038), N-terminal pro-B type natriuretic peptide (P = 0.013), E/e' (P = 0.042) and the indexed left atrium volume (P = 0.019) were associated with the lack of left atrium mechanical recovery.

CONCLUSION

In almost half of the patients, the left atrium did not resume mechanical activity within the 3 months after ECV, despite sinus rhythm recovery. The left atrium of these patients was larger, stiffer and their E/E' was higher, suggesting a higher endocavitary pressure compared with mechanical recovery patients. These findings might suggest an increased thromboembolic risk.

Atrial electromechanical delay assessment in early phase after catheter ablation for patients with atrial fibrillation

BACKGROUND

Variation of atrial electromechanical delay (AED) in early phase after catheter ablation in patients with atrial fibrillation (AF) is lacking.

METHODS

Fifty-five consecutive patients restored sinus rhythm after ablation was included. Echocardiography was performed at 4 h, 1 day, and 3 days after radiofrequency catheter ablation, and AED was measured simultaneously by echocardiography with pulse Doppler imaging and pulse wave tissue Doppler imaging.

RESULTS

AED parameters were significantly longer in the nonparoxysmal atrial fibrillation (NPAF) group than in the paroxysmal atrial fibrillation (PAF) group at each checking point after ablation (P < 0.05). Compared with other checking points, AED parameters were significantly longer 4 h postablation in the NPAF group, while no significant difference was found between different checking points in the PAF group. AED-leap, representing the variation of AED in NPAF patients, was significantly positively correlated with the duration of NPAF (r = 0.5291, P = 0.0113).

CONCLUSIONS

Compared with PAF, NPAF patients have a longer AED postablation, and an abrupt decrease in the initial-h postablation. Such phenomenon gives rise to the different clinical features of PAF and NPAF, and could guide different assessment and treatment strategies for different types of AF.

The Evolving Role and Use of Echocardiography in the Evaluation of Cardiac Source of Embolism

This report will review the role of echocardiography in the diagnosis of cardiac sources of embolism. Embolism of cardiac origin accounts for around 15%–30% of ischemic strokes. The diagnosis of a cardioembolic source of stroke is frequently uncertain and relies on the identification of a potential cardiac source of embolism in the absence of significant autochthonous cerebrovascular occlusive disease. Transthoracic and/or transesophageal echocardiography serves as a cornerstone in the evaluation, diagnosis, and management of these patients. This article reviews potential cardiac sources of embolism and discusses the role of echocardiography in clinical practice. Recommendations for the use of echocardiography in the diagnosis of cardiac sources of embolism are given including major and minor conditions associated with the risk of embolism.

Atrial Strain and Strain Rate: A Novel Method for the Evaluation of Atrial Stunning

Background

Atrial fibrillation (AF) is the most common arrhythmia seen in adults. Atrial stunning is defined as the temporary mechanical dysfunction of the atrial appendage developing after AF has returned to sinus rhythm (SR).

Objectives

We aimed to evaluate atrial contractile functions by strain and strain rate in patients with AF, following pharmacological and electrical cardioversion and to compare it with conventional methods.

Methods

This study included 41 patients with persistent AF and 35 age-matched control cases with SR. All the AF patients included in the study had transthoracic and transesophageal echocardiography performed before and after. Septum (SEPsSR), left atrium (LAsSR) and right atrium peak systolic strain rate (RAsSR) were defined as the maximum negative value during atrial contraction and septum (SEPε), left atrium (LAε) and right atrium peak systolic strain (RAε) was defined as the percentage of change. Parameters of two groups were compared.

Results

In the AF group, 1st hour and 24th hour LAε, RAε, SEPε, LAsSR, RAsSR, SEPsSR found to be significantly lower than in the control group (LAε: 2.61%±0.13, 3.06%±0.19 vs 6.45%±0.27, p<0.0001; RAε: 4.03%±0.38, 4.50%±0.47 vs 10.12%±0.64, p<0.0001; SEPε: 3.0%±0.22, 3.19%±0.15 vs 6.23%±0.49, p<0.0001; LAsSR: 0.61±0.04s-¹, 0.75±0.04s-¹ vs 1.35±0.04s-¹, p<0.0001; RAsSR: 1.13±0.06s-¹, 1.23±0.07s-¹ vs 2.10±0.08s- ¹, p<0.0001; SEPsSR: 0.76±0.04s- ¹, 0.78±0.04s- ¹ vs 1.42±0.06 s- ¹, p<0.0001).

Conclusion

Atrial strain and strain rate parameters are superior to conventional echocardiographic parameters for the evaluation of atrial stunning in AF cases where SR has been achieved.

The left atrial appendage: anatomy, function, and noninvasive evaluation

The left atrial appendage (LAA) is a finger-like extension originating from the main body of the left atrium. Atrial fibrillation (AF) is the most common clinically important cardiac arrhythmia, occurring in approximately 0.4% to 1% of the general population and increasing with age to >8% in those >80 years of age. In the presence of AF thrombus, formation often occurs within the LAA because of reduced contractility and stasis; thus, attention should be given to the LAA when evaluating and assessing patients with AF to determine the risk for cardioembolic complications. It is clinically important to understand LAA anatomy and function. It is also critical to choose the optimal imaging techniques to identify or exclude LAA thrombi in the setting of AF, before cardioversion, and with current and emerging transcatheter therapies, which include mitral balloon valvuloplasty, pulmonary vein isolation, MitraClip (Abbott Laboratories, Abbott Park, Illinois) valve repair, and the implantation of LAA occlusion and exclusion devices. In this review, we present the current data regarding LAA anatomy, LAA function, and LAA imaging using the currently available noninvasive imaging modalities.

Left atrial appendage flow velocity after successful ablation of persistent atrial fibrillation: clinical perspective from transesophageal echocardiographic assessment during sinus rhythm

BACKGROUND

Left atrial appendage flow velocity (LAAFV) is a predictor of thromboembolism in atrial fibrillation (AF) patients, as well as CHA2DS2-VASc score. However, little is known about LAAFV in sinus rhythm (SR) after catheter ablation. The aim of this study was to determine clinical predictors of low LAAFV in patients in whom stable SR had been maintained after catheter ablation for persistent AF.

METHODS

The study comprised 104 patients with persistent AF (median AF duration 24 months) in whom SR had been achieved and maintained for at least 6 months after the final ablation procedure. Transesophageal echocardiography was performed to assess LAAFV during SR after ablation. Lower LAAFV was defined as ≤40 cm/s.

RESULTS

Mean LAAFV before ablation was 29 ± 11 cm/s (range 10-67 cm/s). In 23 (22%) patients, LAAFV remained low even after being in SR for at least 6 months. Multiple logistic regression analysis showed that CHA2DS2-VASc scores of ≥2 (odds ratio 2.18, 95% CI 1.19-3.99, P = .012) was an independent predictor of lower LAAFV after successful ablation. Seventeen (74%) of the 23 patients with low LAAFV during SR presented CHA2DS2-VASc scores of ≥2 complicated by spontaneous echo contrast during AF.

CONCLUSIONS

Long-term maintenance of SR after catheter ablation for persistent AF does not guarantee LAAFV recovery. The CHA2DS2-VASc score appears to predict poor recovery of LAAFV. Further studies are necessary to confirm the usefulness of LAAFV during SR as a surrogate marker predicting thromboembolism in patients after AF ablation.

Low stroke risk after elective cardioversion of atrial fibrillation: an analysis of the Flec-SL trial

BACKGROUND

Current recommendations for anticoagulation management during cardioversion are largely based on historical data and expert consensus.

METHODS AND RESULTS

To characterize current practice of anticoagulation during and after elective cardioversion for AF and the risk of stroke and bleeding events, all patients enrolled into the Flec-SL trial were analyzed for stroke/transient ischemic attack and major bleeds after cardioversion. Flec-SL (ISRCTN62728743, NCT00215774) enrolled 635 patients (mean age 63.7 ± 10.9, 66% male). 629 (99.1%) patients received periprocedural anticoagulation, 556 (87.6%) were adequately anticoagulated following current recommendations. 202 (31.8%) patients underwent transesophageal echocardiography-guided cardioversion. Electrical cardioversion was used in 508 patients (80.0%), pharmacological cardioversion in 127 (20%). Six patients suffered from stroke (n = 5) or transient ischemic attack (3 TIAs in 1 patient, event rate 0.9%, 95% CI 0.4-2.1), five others from major bleeds (event rate 0.8%, 95% CI 0.3-1.9), consistent with the low reported event rates in prior studies. Three strokes occurred in the first 5 days after cardioversion. Events were independent of type of cardioversion or the use of TEE to exclude thrombi.

CONCLUSION

Strokes are rare in this large, prospectively followed cohort of patients undergoing cardioversion for AF and receiving antithrombotic therapy following local routine. These results support adherence to current recommendations for anticoagulation during cardioversion of AF.

Natriuretic peptides for the detection of paroxysmal atrial fibrillation in patients with cerebral ischemia--the Find-AF study

Background and Purpose

Diagnosis of paroxysmal atrial fibrillation (AF) can be challenging, but it is highly relevant in patients presenting with sinus rhythm and acute cerebral ischemia. We aimed to evaluate prospectively whether natriuretic peptide levels and kinetics identify patients with paroxysmal AF.

Methods

Patients with acute cerebral ischemia were included into the prospective observational Find-AF study. N-terminal pro brain-type natriuretic peptide (NT-proBNP), brain-type natriuretic peptide (BNP) and N-terminal pro atrial-type natriuretic peptide (NT-proANP) plasma levels were measured on admission, after 6 and 24 hours. Patients free from AF at presentation received 7 day Holter monitoring. We prospectively hypothesized that patients presenting in sinus rhythm with NT-proBNP>median were more likely to have paroxysmal AF than patients with NT-proBNP<median.

Results

281 patients were included, of whom 237 (84.3%) presented in sinus rhythm. 220 patients naïve to AF with an evaluable prolonged Holter ECG were analysed. In patients with NT-proBNP>median (239 pg/ml), 17.9% had paroxysmal AF in contrast to 7.4% with NT-proBNP<239 pg/ml (p = 0.025). The ratio of early (0 h) to late (24 h) plasma levels of NT-proBNP showed no difference between both groups. For the detection of paroxysmal atrial fibrillation, BNP, NT-proBNP and NT-proANP at admission had an area under the curve in ROC analysis of 0.747 (0.663–0.831), 0.638 (0.531–0.744) and 0.663 (0.566–0.761), respectively. In multivariate analysis, BNP was the only biomarker to be independently predictive for paroxysmal atrial fibrillation.

Conclusions

BNP is independently predictive of paroxysmal AF detected by prolonged ECG monitoring in patients with cerebral ischemia and may be used to effectively select patients for prolonged Holter monitoring.

Cardioembolic stroke in atrial fibrillation-rationale for preventive closure of the left atrial appendage

Atrial fibrillation is the most common cardiac arrhythmias, and a major cause of morbidity and mortality due to cardioembolic stroke. The left atrial appendage is the major site of thrombus formation in non-valvular atrial fibrillation. Loss of atrial systole in atrial fibrillation and increased relative risk of associated stroke point strongly toward a role for stasis of blood in left atrial thrombosis, although thrombus formation is multifactorial, and much more than blood flow irregularities are implicated. Oral anticoagulation with vitamin-K-antagonists is currently the most effective prophylaxis for stroke in atrial fibrillation. Unfortunately, this treatment is often contraindicated, particularly in the elderly, in whom risk of stroke is high. Moreover, given the risk of major bleeding, there is reason to be skeptical of the net benefit when warfarin is used in those patients. This work reviews the pathophysiology of cardioembolic stroke and critically spotlights the current status of preventive anticoagulation therapy. Various techniques to exclude the left atrial appendage from circulation were discussed as a considerable alternative for stroke prophylaxis.

TEE screening in Atrial flutter: A single-centre experience with retrospective validation of a new risk score for the presence of atrial thrombi

Transesophageal echocardiography (TEE) has been proposed as a screening tool to exclude the presence of atrial thrombi and left atrial spontaneous echocontrast before cardioverting persistent atrial flutter (AFl) and atrial fibrillation (AF). However in pure AFl a very low prevalence of atrial thrombi has been observed by many investigators: a confirmation of this finding would make TEE screening redundant. We review our database of patients with AFl who underwent TEE screening before cardioversion in the last 5 years. A new risk score for the presence of left atrial thrombus (AFLAT score) is here proposed, as a potential tool to avoid unnecessary TEE exams. Out of the 106 patients examined, in fourteen left atrial thrombi were diagnosed (13%). Only two cases belonged to the pure AFl subgroup (prevalence=3%), while twelve cases were detected in the subgroup of AFl patients with previous AF episodes (prevalence=32%, p<0.001). All of the fourteen patients with a positive TEE for thrombus were identified by a AFLAT score >2. The validation of this index in a larger and prospective setting would lead to a 85% reduction in unnecessary TEE exams in patients with pure AFl undergoing cardioversion.

Pulmonary venous flow assessed by Doppler echocardiography in the management of atrial fibrillation

Pulmonary venous blood flow (PVF) visualized by Doppler echocardiography exhibits a pulsatile behavior, which is related to left atrial pressure and function, mitral valve function, and left ventricular compliance. In atrial fibrillation (AF), the disappearance of atrial reverse flow, a decrease in systolic flow with a greater diastolic than systolic flow, a prolonged onset of systolic flow and the appearance of an early systolic reverse flow are characteristic findings. A reduction in systolic PVF expressed by reduced peak velocity, reduced velocity-time integral of systolic flow, and reduced systolic fraction of PVF has been found to be associated with reduced left atrial appendage flow, left atrial spontaneous echo contrast formation, frequency of AF paroxysms and propensity for AF recurrence following restoration of sinus rhythm. Ablation techniques targeting pulmonary vein ostia and adjacent left atrium are promising treatment options to cure AF. Monitoring the PVF response to and adjusting of ablation procedures has been suggested to optimize outcome and prevent complications such as pulmonary vein stenosis. In conclusion, assessment of PVF variables and patterns by Doppler echocardiography seems useful in the management of AF patients. Especially the reduction in systolic PVF may be used as marker for left atrial dysfunction which favors thrombus formation and AF reinitiation. Finally, PVF monitoring has the potential to an increasing role in AF ablation procedures.

Severe stunned myocardium after lightning strike

OBJECTIVE

To report the development of myocardial stunning and severe heart failure after lightning strike with total recovery of function.

DESIGN

Case report.

SETTING

Coronary care unit at Medica Sur Clinic, Mexico.

PATIENT

A 42-yr-old woman who was hit by lightning developed rapid and progressive hemodynamic deterioration manifested by cardiogenic shock that required invasive monitoring. Twenty-four hours after the strike, intravenous levosimendan and intra-aortic balloon pump were initiated because the patient demonstrated no significant response to management with conventional inotropic agents. Two days later, echocardiographic signs of systolic and diastolic dysfunction improved markedly. Dual-isotope-imaging myocardial perfusion testing with technetium-99m-sestamibi and thallium-201, performed 9 days after admission, showed normal perfusion and normal left ventricular systolic function. The patient exhibited complete recovery of function. The exact mechanism of abnormal contractility in the absence of direct electrofulguration is unknown but may be explained by release of oxygen free radicals, proteolysis of the contractile apparatus, and cytosolic overload of intracellular calcium, followed by reduced myofilament sensitivity to calcium. These abnormalities are consistent with stunned myocardium.

CONCLUSIONS

Lightning strike may cause serious contractile dysfunction in the absence of irreversible myocardial injury, but the exact mechanism of this phenomenon remains unknown. We propose that lighting strike can cause myocardial stunning resulting in severe but reversible left ventricular dysfunction. The patient's recovery was facilitated by support treatment including administration of levosimendan, which increases the intracellular sensitivity to calcium, a mechanism disturbed in patients with myocardial stunning.

[TEE-guided cardioversion in patients with atrial fibrillation without previous anticoagulation]

A total of 332 patients (mean age 65+/-10 years, 86 female) with nonvalvular atrial fibrillation (AF) of more than 48 hours duration and lack of a sufficient anticoagulation were included. After exclusion of thrombotic material in the left atrium using transesophageal echocardiography (TEE) cardioversion (CV) was performed within 24 hours. At the same time oral anticoagulation (AC) (overlapping with PTT-affecting heparinisation) was started. If thrombi were found by TEE, the examination was repeated after at least four weeks of anticoagulation. If thrombi were absent at this time, CV was performed. Periprocedural embolism was defined as primary endpoint, whereas the detection of atrial thrombi before CV was defined as secondary endpoint. In 33 of the 332 Patients (9.9%) the TEE showed a thrombus in the left atrium respectively the left atrial appendage (n=22) or thrombi could not be excluded (n=11). 383 TEEs were performed without complications in an overall of 332 patients.A total of 305 CV were performed (electrical n=300, pharmacological n=5) and during periprocedural monitoring and in the time of four weeks after CV no thromboembolic complications were observed.TEE-guided CV in patients with AF persisting for more than 48 hours and without previous AC can be considered as a method that is both safe and effective.

Acute anticoagulation adjustment in patients with atrial fibrillation at risk for stroke: approaches, strategies, risks and benefits

The acute management of anticoagulation in patients with atrial fibrillation to prevent stroke and other thromboembolic complications includes the use of individualized strategies tailored to the patient and based on the situation (cardioversion, surgeries, dental procedures, cardiac interventions, other invasive procedures and initiation of, or adjustment to, warfarin dosing). The vast range of choices can cause confusion and few randomized controlled clinical trials in this area provide adequate guidance. Chronic anticoagulation management is more straightforward since clinical evidence is ample, randomized clinical trial data provides cogent informaiton and guidelines have been established. Acute management of anticoagulation in patients with atrial fibrillation to prevent thromboembolic complications is often unrecognized but is emerging as a crucial, but challenging, and increasingly complex aspect of the care of patients with atrial fibrillation. This review addresses issues regarding such patients who may be at risk for stroke and require acute adjustments of anticoagulation (in light of, or in lieu of, chronic anticoagulation). Several promising new strategies are considered in light of established medical care. This analysis provides practical recommendations based on available data and presents results from recent investigations that may provide insight into future strategies.

Antithrombotic therapy in atrial fibrillation: beyond the AFFIRM study

In the last few decades several clinical studies evaluated the efficacy and safety of different strategies for antithrombotic prophylaxis to prevent thromboembolic events in patients with atrial fibrillation (AF). Nowadays, a frequently debated point is related to the high embolic risk deriving from the asymptomatic and symptomatic AF recurrence after cardioversion or in paroxysmal AF, especially in patients with a large number of prolonged episodes of AF. In fact, after the recent AFFIRM and RACE trials, patients after successful cardioversion at risk for thromboembolism could also need lifelong anticoagulation. Considering this, should we anticoagulate all patients with clinical risk factors for thromboembolism with a single episode of AF, without considering the hemorrhagic risk? Based on recent trials, it is reasonable to hypothesize that long AF recurrences (> 48 h), both symptomatic and asymptomatic, are present mostly (if not exclusively) in patients with structural left atrial appendage (LAA) dysfunction and remodeling. Conversely, AF recurrences in patients without LAA dysfunction and remodeling, could be too short to allow thrombi formation in the LAA, and the anticoagulation could also be avoided. Once other clinical and echocardiographic determinants of stroke have been excluded, the LAA velocity could select patients with a normal appendage function at low embolic risk who could benefit from anti-aggregation and patients with irreversible appendage dysfunction, at high embolic risk, who need lifelong anticoagulation.

Atrial Thrombi-A Prospective Follow-up Study over 3 Years with Transesophageal Echocardiography and Cranial Magnetic Resonance Imaging

BACKGROUND

Patients with atrial fibrillation (AF) and atrial thrombi have an increased risk for cerebral embolism. However, there is little knowledge about the long-term fate of atrial thrombi and the incidence of cerebral embolism in patients under oral anticoagulation.

METHODS

Consecutive patients with persistent or permanent AF and left atrial (LA) thrombi were included in the study. We performed serial and prospective transesophageal echocardiography, cranial magnetic resonance imaging, and clinical examinations during a period of 3 years. Oral anticoagulation was continued or initiated in all patients. A target INR of 2.5 was intended in all patients.

RESULTS

Forty-three patients with LA thrombi and persistent or permanent AF were included. During the follow-up period 31(72%) of the thrombi disappeared. Patients with disappearance of thrombi had significantly smaller thrombi (P < 0.01), a lower echogenicity of thrombi (P < 0.01), and a lower LA volume (P = 0.02). Twenty-two (51%) patients suffered from cerebral embolism and/or death during the observation period. Five patients died due to embolic events. The only independent predictors of cerebral embolism were an elevated peak emptying velocity of the LA appendage (P < 0.001) and a history of previous thromboembolism (P < 0.01).

CONCLUSIONS

Patients with persistent or permanent AF and atrial thrombi have a high long-term risk of cerebral embolism and/or death (51%) even despite the oral anticoagulation therapy. Thrombus size may predict thrombus resolution under continued anticoagulation.

Atrial fibrillation - patients at high risk for cerebral embolism

OBJECTIVE

Patients with atrial fibrillation (AF) have a risk of cerebral embolism. Echocardiographic parameters elevate this risk significantly. However, there is little knowledge about the long-term fate and the rate of clinically silent cerebral embolism under continued oral anticoagulation. The aims of our study were to assess prognosis of patients with AF and determine a high risk group with an increased risk of cerebral embolism under oral anticoagulation.

METHODS

Consecutive patients with persistent or permanent AF and left atrial (LA) thrombi, dense spontaneous echo contrast (SEC) and/or reduced LA appendage peak emptying velocities (LAAv) were included in the study (N = 128). Patients with AF and without echocardiographic risk factors (N = 114) served as controls. All patients were examined with transesophageal echocardiography, cranial magnetic resonance imaging and clinically during a period of three years.

RESULTS

During the three-year follow-up period 6 (5%) of the high risk patients had cerebral embolism with neurological deficits. 4 (3%) patients died due to embolic events and 17 (13%) patients had silent embolism as documented on MRI. In the control group 8 (7%) patients had embolic events (n = 1 clinically apparent and n = 7 silent embolism) documented on MRI, one was clinically apparent. Study patients with an event had more commonly previous thromboembolism (p < 0.0001).

CONCLUSIONS

Patients with peristent or permanent AF and LA thrombi, dense SEC or reduced LAAv have an explicitly increased risk of cerebral embolism (21%) despite oral anticoagulation. Previous thromboembolic event is another important predictor for an event.

Doppler echocardiographic prediction of recurrent atrial fibrillation following cardioversion

BACKGROUND

Cardioversion for atrial fibrillation (AF) is associated with impairment of left atrial mechanical function and increased risk of thrombus formation with subsequent embolisation. Measuring atrial mechanical function is of interest to determine the individual risk of thromboembolism and the risk of recurrent AF.

METHODS

We included 112 consecutive patients with AF and planned cardioversion. Serial echocardiographic measurements of left atrial size and Doppler measurement of mitral valve peak A wave velocities were obtained at days 0, 1, 2, 3, and 28 following cardioversion. These measurements and clinical parameters were related to clinical events and recurrent AF within 4 weeks following cardioversion. Cardioversion was achieved in 100 patients.

RESULTS

AF-recurrence within 4 weeks was 23.9% and 45.8% for patients with < or = and > 6 weeks AF-duration, respectively (p=0.04). Peak A wave velocities were significantly lower up to 2 days following cardioversion in patients with AF-recurrence. A peak A wave velocity < 52 cm/s at day 1 resulted in an odds ratio of 5.0 (95% CI: 1.4-18.6) for recurrence of AF. In multiple logistic regression analysis, peak A wave velocity at day 1 remained the only independent predictor of recurrent AF. Left atrial diameter did not correlate with recurrence of AF.

CONCLUSIONS

A single measurement of mitral peak A wave velocity 1 day following cardioversion is predictive of AF recurrence. This method is feasible for risk estimation with potential therapeutic implications.

Identification of good responders to rhythm control of paroxysmal and persistent atrial fibrillation by transthoracic and transesophageal echocardiography

BACKGROUND

Identification of good responders to rhythm control in the management of atrial fibrillation (AF) is worthwhile in terms of increasing hemodynamic benefit and decreasing the likelihood of unstable anticoagulation even after the Atrial Fibrillation Follow-Up Investigation of Rhythm Management.

METHODS

We tested the hypothesis that atrial substrate determines the risk of recurrence on rhythm control both in patients with paroxysmal AF (PAF) and in those with persistent or sustained AF (> or =1 week, SAF). There were 90 consecutive patients (mean age 63 +/- 12 years, 67 males and 23 females) with previous PAF (n = 66) or SAF (n = 24). They were maintained in sinus rhythm successfully for at least 1 month after conversion and then studied by transthoracic and transesophageal echocardiography. All of the patients were followed regularly by determination of symptoms, 12-lead ECG and intermittent Holter recording to determine recurrence of AF after echocardiographic study.

RESULTS

After 9.1 +/- 3.8 (range 3-12) months of follow-up, 23 of the 90 (26%) patients had documented recurrence of AF (67 without recurrence). Univariate analysis of demographic characteristics, medications, ECG and echocardiographic parameters revealed that, compared with the group of patients without recurrent AF, the group of those with it included more members of the SAF group (11/27 vs. 13/67, p = 0.039), included more male subjects (22/23 vs. 45/67, p = 0.045), had a larger left atrial volume index (LAVI; 27 +/- 9 vs. 22 +/- 9 ml/m2, p = 0.024) and had lower LA appendage peak emptying velocity (LAAPEV; 42 +/- 15 vs. 55 +/- 22 cm/s, p = 0.01). Multivariate Cox proportional hazards regression analysis adjusted for age, gender and AF group revealed that patients with LAVI <30 ml/m2 and LAAPEV >46 cm/s had the least recurrence of AF (relative risk 0.18, 95% confidence interval 0.06-0.55, vs. with LAVI >30 ml/m2 or LAAPEV <46 cm/s, p = 0.002). Kaplan-Meier probability of freedom from AF recurrence was significantly better when LAVI <30 ml/m2 (log-rank p = 0.02), LAAPEV > 46 cm/s (p = 0.013) or both (p = 0.004). The superiority to predict the rate of sinus rhythm maintenance was the same in the PAF and SAF groups.

CONCLUSIONS

Good responders to rhythm control in the PAF and SAF groups share the characteristics of smaller LA volume and better LAA contractile function, emphasizing the critical role of atrial substrate remodeling in recurrence of AF.

Patients at High Risk with Atrial Fibrillation: A Prospective and Serial Follow-up During 12 Months with Transesophageal Echocardiography and Cerebral Magnetic Resonance Imaging

OBJECTIVE

Patients with atrial fibrillation and echocardiographic risk factors have a relevant risk of cerebral embolism. However, there is little knowledge about the long-term fate and the rate of clinical silent cerebral embolism under continued oral anticoagulation. Our aims were to assess the prognosis of patients with atrial fibrillation and determine a high-risk group with an increased risk of cerebral embolism under oral anticoagulation.

METHODS

A total of 173 consecutive patients with persistent or permanent atrial fibrillation and left atrial (LA) thrombi, dense spontaneous echocontrast, reduced LA appendage peak emptying velocities, or a combination of these were included in the study. In all, 169 patients with atrial fibrillation and without echocardiographic risk factors served as control patients. We performed serial and prospective transesophageal echocardiography, cranial magnetic resonance imaging, and clinical examinations during a period of 12 months.

RESULTS

During the follow-up period 7 (4%) of the patients at high risk had cerebral embolism with neurologic deficits. A total of 4 (2%) patients died because of embolic events and 19 (11%) patients had silent embolism as documented on magnetic resonance imaging. In the control group, 10 (6%) patients had embolic events documented on magnetic resonance imaging; one was clinically apparent. Study patients with an event had more often previous thromboembolism (P < .0001).

CONCLUSIONS

Patients with persistent or permanent atrial fibrillation and LA thrombi, dense spontaneous echocontrast, or reduced LA appendage peak emptying velocities have an explicitly increased risk of cerebral embolism (17%) despite oral anticoagulation. Previous thromboembolic event is another important predictor for an event.

Pre- and post-cardioversion transesophageal echocardiography for brief anticoagulation therapy with enoxaparin in atrial fibrillation patients: a prospective study with a 1-year follow-up

BACKGROUND

In patients with atrial fibrillation (AF) eligible for electrical cardioversion (C), the guided approach with transesophageal echocardiography (TEE) allows to avoid the 3 weeks of recommended precardioversion anticoagulation therapy. However, after sinus rhythm restoration, at least other 4 weeks of oral anticoagulation therapy are indicated, due to the postcardioversion thromboembolic risk related to left atrial (LA) and left atrial appendage (LAA) stunning. The aim of this study was to prospectively assess the effectiveness and the safety of anticoagulation therapy discontinuation 7 days after C using low-molecular-weight heparins (LMWH) in a selected group of patients who underwent a pre-C and 7 days post-C TEE evaluation.

METHODS

One hundred one patients (74 patients with nonvalvular AF and 27 patients with atrial flutter lasting >48 h and history of AF) were enrolled into the study. Two patients refused the TEE, therefore, in 99/101, we performed a first TEE and, within 24 h, a C if there were no LAA thrombi, complex aortic plaques or severe spontaneous echocontrast. After C and 7 days of home-administered enoxaparin, a second TEE was carried out. In the absence of any new thrombi, severe spontaneous echocontrast and/or low emptying velocity of LAA, the therapy with enoxaparin was stopped; otherwise, anticoagulation therapy with enoxaparin was overlapped with oral anticoagulation and continued for at least 3 weeks. All patients were clinically followed at 1, 6 and 12 months after C.

RESULTS

Sinus rhythm was restored in 68/99 patients after successful C. The second TEE was carried out in 53 patients. At 1 month follow-up, no thromboembolic events were recorded either in patients at risk who had continued the oral anticoagulant therapy for at least 3 weeks or in those who suspended LMWH after 7 days post-C TEE. Between the 2nd and 12th month, three ischemic strokes occurred, all in the group of patients who had anticoagulation therapy for at least 3 weeks and had shown LAA velocity <25 cm/s at first or second TEE. No thromboembolic events were recorded in patients with normal LAA velocity; conversely, among the patients who had shown low LAA velocity at either TEE, three suffered from ischemic stroke. In two of these three patients, low LAA velocity was detected only at post-C TEE.

CONCLUSIONS

A brief anticoagulation therapy using LMWH appears to be safe and feasible. The 7 days post-C TEE can well-define patients without LAA stunning at low thromboembolic risk, who may take advantage of an early interruption of enoxaparin as an alternative to long oral anticoagulation. The LAA stunning, even in the absence of other thromboembolic risk factors, could select a group of patients at high risk who should continue oral anticoagulation indefinitely or until signs of LAA dysfunction disappear.

Incidence of Cerebral Embolism after Cardioversion of Atrial Fibrillation: A Prospective Study with Transesophageal Echocardiography and Cerebral Magnetic Resonance Imaging

BACKGROUND

After cardioversion of atrial fibrillation the risk for cerebral embolism is increased. There is little knowledge about the incidence of cerebral embolism for patients with transesophageal echocardiography (TEE)-guided cardioversion under oral anticoagulation.

METHODS

Consecutive patients with atrial fibrillation and TEE-guided cardioversion were included in the study. We performed serial TEE studies, Holter electrocardiography, cranial magnetic resonance imaging, and clinical examinations during a period of 4 weeks before and after cardioversion. Oral anticoagulation was continued or initiated in all patients.

RESULTS

During the observation period 6 of 127 (4.7%) patients had new embolic lesions after cardioversion documented on cerebral magnetic resonance imaging. Patients with an event were significantly older (P = .04) and had a larger left atrium (P = .04) than patients without event.

CONCLUSION

Patients with atrial fibrillation and oral anticoagulation have a low rate of clinical apparent cerebral embolism after TEE and anticoagulation-guided cardioversion. The rate of silent cerebral embolism is almost 5%. Age and left atrial size are predictors for an event.

Patients With Atrial Fibrillation and Dense Spontaneous Echo Contrast at High Risk

OBJECTIVES

We sought to assess the prognosis of patients with atrial fibrillation (AF) and dense spontaneous echo contrast (SEC) and to determine the incidence of cerebral embolism under continued oral anticoagulation.

BACKGROUND

Patients with AF and dense SEC have an increased risk of cerebral embolism. However, there is little knowledge about the long-term fate and the rate of clinical silent cerebral embolism under continued oral anticoagulation.

METHODS

Between 1998 and 2001, all consecutive patients with AF and dense SEC were included in the study. We performed serial and prospective transesophageal echocardiography, cranial magnetic resonance imaging, and clinical examinations during a period of 12 months.

RESULTS

A total of 128 patients with dense SEC and AF were included. The control group consisted of 143 patients with faint SEC and AF. During the follow-up period, three patients (2%) had cerebral embolism with neurologic deficits. A total of eight patients (6%) died due to embolic events, and 19 (15%) patients had silent embolism, as documented on cerebral magnetic resonance imaging. Patients with an event had significantly lower left atrial appendage peak emptying velocities and more commonly had a history of previous thromboembolism and denser SEC, as compared with patients without an event.

CONCLUSIONS

Patients with AF and dense SEC have a high likelihood of cerebral embolism (22%) and/or death, despite oral anticoagulation. Low peak emptying velocities of the left atrial appendage and dense SEC are independent predictors of an event.

Stunning of the Left Atrium after Conversion of Atrial Fibrillation: Predictor for Maintenance of Sinus Rhythm?

Recurrence of atrial fibrillation (AF) after cardioversion (CV) to sinus rhythm (SR) is determined by various clinical and echocardiographic parameters. The aim of this study was to determine the value of mitral inflow A-wave velocity, performed at 24 hours after CV in estimation of AF recurrence. The study group consisted of 187 consecutive patients with nonvalvular atrial fibrillation, who had been cardioverted to SR from 1998 to 2000. Transthoracic echocardiography was performed in all cases recruited for the study 24 hours after CV. Left atrial (LA) diameter, left ventricular ejection fraction, and mitral inflow A-wave velocity were measured. The patients were evaluated in five groups according to their recurrence time (<30 days, 31-90 days, 91-180 days, 181-365 days, and >365 days). Maintenance of SR was determined to have a negative linear correlation with age (r =-0.97, P = 0.006), LA diameter (r =-0.93, P = 0.02), and AF duration (r =-0.93, P = 0.02), while having a positive linear correlation with mitral inflow A-wave velocity (r = 0.96, P = 0.008). In the maintenance of sinus rhythm, age, LA diameter, and AF duration were not affected from the method of CV, while mitral inflow A-wave velocity was found to be affected with the method of CV. No relationship was determined between mitral inflow A-wave velocity and the maintenance of sinus rhythm in those performed electrical cardioversion, while frequency of recurrence was found to be higher in those with slow mitral inflow A-wave velocity who were performed pharmacological cardioversion (r = 0.89, P = 0.004). In conclusion, age, duration of AF, LA diameter, and the mitral inflow A-wave velocity can be used to predict the maintenance of SR after CV.

Usefulness of Doppler assessment of pulmonary vein and left atrial appendage flow following pulmonary vein isolation of chronic atrial fibrillation in predicting recovery of left atrial function

Atrial fibrillation (AF) is a widespread condition that causes significant morbidity and mortality. Recently, pulmonary venous (PV) isolation using radiofrequency ablation has been used successfully to exclude the pulmonary venous ostia, resulting in correction of AF. Further, miniaturized high-frequency ultrasound phased-array transducers currently provide Doppler and 2-dimensional imaging during the ablation procedure. We examined atrial function and its determinants using intracardiac echocardiography before and after PV isolation in 45 patients who had chronic AF (56 +/- 11 years old). PV, left atrial (LA) appendage, and mitral and tricuspid flows were recorded. Recovery of booster pump function (defined by the presence of mitral inflow A wave, LA appendage a-wave, and PV A-reversal wave velocities >10 cm/s) was observed in 39 of 45 patients (86.6%). PV flow systolic wave before and after ablation correlated with the degree of LA booster pump function after PV isolation. An early systolic PV flow peak velocity >57.47 cm/s predicted "good" LA booster pump function recovery with 96% specificity. Diastolic LA appendage emptying in AF correlated (p <0.001) and predicted good LA booster pump function with 92% specificity for velocities >46.4 cm/s. Thus, monitoring LA function during PV isolation for chronic AF is feasible. Most patients recovered LA booster pump function immediately after PV isolation, and the degree of recovery correlated with LA reservoir function. Preserved reservoir function during AF is predictive of satisfactory recovery of booster pump function after PV isolation.

Acute improvement of atrial mechanical stunning after electrical cardioversion of persistent atrial fibrillation: comparison between biatrial and single atrial pacing

OBJECTIVE

To evaluate the acute effects of atrial pacing at different pacing sites on mechanical stunning after cardioversion of atrial fibrillation (AF).

SETTING

Tertiary referral centre.

PATIENTS

20 patients with persistent AF were studied.

INTERVENTIONS

Spontaneous echo contrast (SEC), left atrial appendage emptying velocity (LAAEV), and left atrial appendage emptying fraction (LAAEF) were assessed by transoesophageal echocardiography (TOE) during AF, after conversion to sinus rhythm, and during atrial pacing from the right atrial appendage, left lateral atrium, and both atria simultaneously. Transmitral inflow velocity of the atrial wave (TMIF-A) by TOE and the maximum P wave duration in 12 lead ECG were also measured during sinus rhythm and atrial pacing.

MAIN OUTCOME MEASURES

Comparison of atrial mechanical function and P wave duration in 12 lead ECG during atrial pacing from different sites after cardioversion of AF.

RESULTS

Compared with sinus rhythm, atrial pacing at 80 beats/min increased LAAEV from mean (SD) 14.6 (10.1) to 33.4 (19.8) cm/s (p = 0.001), LAAEF from 13.8 (8.5) to 32.1 (11.2)% (p < 0.001), and TMIF-A from 24.6 (11.9) to 45.6 (21.0) cm/s (p < 0.001) and reduced SEC grade from 2.6 (1.0) to 1.6 (0.9) (p < 0.001). These effects had a positive force-frequency relation. Biatrial pacing produced the shortest P wave duration and resulted in the most significant improvement in atrial function (LAAEV, 33.2 (19.3) v 53.7 (23.9) cm/s, p = 0.0001; LAAEF, 31.9 (11.1) v 46.2 (12.6)%, p < 0.0001; TMIF-A, 37.7 (18.3) v 54.1 (21.2) cm/s, p < 0.001; SEC grade, 1.4 (1.1) v 0.8 (0.9), p = 0.001, right atrial appendage versus biatrial pacing).

CONCLUSIONS

Atrial pacing at increased rates can improve atrial mechanical function after cardioversion of persistent AF. Biatrial pacing may be the most effective technique to reverse atrial mechanical stunning.

Plasma von Willebrand factor, soluble thrombomodulin, and fibrin D-dimer concentrations in acute onset non-rheumatic atrial fibrillation

OBJECTIVE

To investigate whether new onset acute atrial fibrillation (AF) of < 48 hours' duration creates a prothrombotic state in the absence of anticoagulation and to assess the evolution in research indices after spontaneous or pharmacological cardioversion.

METHODS

24 patients were recruited with first onset acute non-rheumatic AF, in whom sinus rhythm was restored within 48 hours of arrhythmia onset, without anticoagulant treatment. Atrial mechanical function was assessed by transmitral inflow. Soluble thrombomodulin and von Willebrand factor concentrations (both as indices of endothelial damage or dysfunction) and fibrin D-dimer concentrations (as an index of thrombogenesis) were measured. Blood samples were drawn and echocardiographic studies were performed at days 1, 3, 7, and 30 after cardioversion. Research indices were compared with those of 24 healthy participants, 24 patients with chronic AF, and 24 patients with ischaemic heart disease in sinus rhythm.

RESULTS

Patients with AF had higher concentrations of soluble thrombomodulin (acute AF 12.1 (4.1) ng/ml; chronic AF 11.8 (4.6) ng/ml), von Willebrand factor (acute AF 137.2 (36.9) ng/ml; chronic AF 133.1 (25.0) ng/ml), and fibrin D-dimer concentrations (acute AF 2.35 (2.68) microg/ml; chronic AF 1.12 (0.65) microg/ml) than did healthy controls (5.9 (2.7) ng/ml, 86.7 (33.2) ng/ml, and 0.39 (0.28) microg/ml, respectively) and patients with ischaemic heart disease (7.4 (3.7) ng/ml, 110.0 (29.0) ng/ml, and 0.99 (0.73) microg/ml, respectively) (all p < 0.05). Day 30 concentrations of fibrin D-dimer were higher in patients with acute AF than in patients with chronic AF (p = 0.038) but sTM and von Willebrand factor concentrations were not different (both not significant). There were no significant changes in research indices or echocardiographic parameters after cardioversion (all p > 0.05).

CONCLUSIONS

There was evidence among patients with acute onset AF of endothelial damage or dysfunction and increased thrombogenesis, which persisted up to 30 days after cardioversion.

Fate of left atrial thrombi in patients with atrial fibrillation determined by transesophageal echocardiography and cerebral magnetic resonance imaging

Patients with atrial fibrillation (AF) and atrial thrombi have an increased risk for cerebral embolism. However, there is little knowledge about the long-term fate of atrial thrombi and the incidence of cerebral embolism in patients receiving continued oral anticoagulation. Forty-three consecutive patients with AF and atrial thrombi were enrolled in the study. Serial and prospective transesophageal echocardiographic studies, cranial magnetic resonance imaging (MRI), and clinical examinations were performed during a period of 12 months. Oral anticoagulation was continued or initiated in all patients. An international normalized ratio of 2.0 to 3.0 was regarded as effective. During follow-up, 56% of the thrombi disappeared (7 [16%] at 1 month, 18 [42%] at 3 months, 21 [49%] at 6 months, and 24 [56%] at 12 months). Patients with the disappearance of thrombi had significantly smaller thrombi compared with patients with persistent thrombi (1.5 +/- 0.8 cm in length and 0.8 +/- 0.5 cm in width vs 1.9 +/- 0.6 cm in length and 1.3 +/- 0.4 cm in width, p = 0.04), reduced echogenicity of thrombi (46% vs 89%, p <0.01), and smaller left atrial (LA) volume (83 +/- 27 vs 116 +/- 55 cm(3)). Seven patients (16%) had embolic lesions during follow-up MRI. Six of these patients (86%) had clinically apparent embolisms, and 1 died from stroke. The only independent predictors of cerebral embolism were an elevated peak emptying velocity of the LA appendage (p <0.01) and previous thromboembolic events (p = 0.02). Patients with AF and atrial thrombi have a large likelihood of cerebral embolism (16%) and/or death despite oral anticoagulation therapy. Thrombus size may predict thrombus resolution under continued anticoagulation.

Antithrombotic Therapy in Atrial Fibrillation

This chapter about antithrombotic therapy in atrial fibrillation (AF) is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following (all vitamin K antagonist [VKA] recommendations have a target international normalized ratio [INR] of 2.5; range, 2.0 to 3.0): In patients with persistent or paroxysmal AF (PAF) [intermittent AF] at high risk of stroke (ie, having any of the following features: prior ischemic stroke, transient ischemic attack, or systemic embolism, age > 75 years, moderately or severely impaired left ventricular systolic function and/or congestive heart failure, history of hypertension, or diabetes mellitus), we recommend anticoagulation with an oral VKA, such as warfarin (Grade 1A). In patients with persistent AF or PAF, age 65 to 75 years, in the absence of other risk factors, we recommend antithrombotic therapy with either an oral VKA or aspirin, 325 mg/d, in this group of patients who are at intermediate risk of stroke (Grade 1A). In patients with persistent AF or PAF < 65 years old and with no other risk factors, we recommend aspirin, 325 mg/d (Grade 1B). For patients with AF and mitral stenosis, we recommend anticoagulation with an oral VKA (Grade 1C+). For patients with AF and prosthetic heart valves, we recommend anticoagulation with an oral VKA (Grade 1C+); the target INR may be increased and aspirin added depending on valve type and position, and on patient factors. For patients with AF of > or = 48 h or of unknown duration for whom pharmacologic or electrical cardioversion is planned, we recommend anticoagulation with an oral VKA for 3 weeks before and for at least 4 weeks after successful cardioversion (Grade 1C+). For patients with AF of > or = 48 h or of unknown duration undergoing pharmacologic or electrical cardioversion, an alternative strategy is anticoagulation and screening multiplane transesophageal echocardiography (Grade 1B). If no thrombus is seen and cardioversion is successful, we recommend anticoagulation for at least 4 weeks (Grade 1B). For patients with AF of known duration < 48 h, we suggest cardioversion without anticoagulation (Grade 2C). However, in patients without contraindications to anticoagulation, we suggest beginning IV heparin or low molecular weight heparin at presentation (Grade 2C).

D-Ribose improves diastolic function and quality of life in congestive heart failure patients: a prospective feasibility study

Patients with chronic coronary heart disease often suffer from congestive heart failure (CHF) despite multiple drug therapies. D-Ribose has been shown in animal models to improve cardiac energy metabolism and function following ischaemia. This was a prospective, double blind, randomized, crossover design study, to assess the effect of oral D-ribose supplementation on cardiac hemodynamics and quality of life in 15 patients with chronic coronary artery disease and CHF. The study consisted of two treatment periods of 3 weeks, during which either oral D-ribose or placebo was administered followed by a 1-week wash out period, and then administration of the other supplement. Assessment of myocardial functional parameters by echocardiography, quality of life using the SF-36 questionnaire and functional capacity using cycle ergometer testing was performed. The administration of D-ribose resulted in an enhancement of atrial contribution to left ventricular filling (40+/-11 vs. 45+/-9%, P=0.02), a smaller left atrial dimension (54+/-20 vs. 47+/-18 ml, P=0.02) and a shortened E wave deceleration (235+/-64 vs. 196+/-42, P=0.002) by echocardiography. Further, D-ribose also demonstrated a significant improvement of the patient's quality of life (417+/-118 vs. 467+/-128, P< or =0.01). In comparison, placebo did not result in any significant echocardiographic changes or in quality of life. This feasibility study in patients with coronary artery disease in CHF revealed the beneficial effects of D-ribose by improving diastolic functional parameters and enhancing quality of life.

Atrial stunning: basics and clinical considerations

Conversion of atrial fibrillation and flutter to sinus rhythm results in a transient mechanical dysfunction of atrium and atrial appendage, termed atrial stunning. Atrial stunning has been reported with all modes of conversion of atrial fibrillation and flutter to sinus rhythm including both transthoracic and low energy internal electrical, pharmacological, and spontaneous cardioversion, and conversion by overdrive pacing and by radiofrequency ablation. Atrial stunning is a function of the underlying arrhythmia becoming apparent at the restoration of sinus rhythm, not the function of the mode of conversion, and does not develop after the unsuccessful attempts of cardioversion or the delivery of electric current to the heart during rhythms other than atrial fibrillation or flutter. Tachycardia-induced atrial cardiomyopathy, cytosolic calcium accumulation, and atrial hibernation are the suggested mechanisms of atrial stunning. Atrial stunning is at maximum immediately after cardioversion and improves progressively with a complete resolution within a few minutes to 4-6 weeks depending on the duration of the preceding atrial fibrillation, atrial size, and structural heart disease. Atrial stunning causes postcardioversion thromboembolism despite restoration of sinus rhythm. Duration of anticoagulation therapy after successful cardioversion should depend on the duration of atrial stunning. Lack of improvement in cardiac output and functional recovery of patients immediately after cardioversion is attributed to the atrial stunning. Verapamil, acetylstrophenathidine, isoproterenol, and dofetilide have been reported to protect from atrial stunning in animal and small human studies. Right atrium stunning is less marked and improves earlier than that of left atrium, resulting in a differential atrial stunning explaining the rare occurrence of pulmonary edema after cardioversion.

Acute reductions in ventricular myocardial tissue velocities after direct current cardioversion of atrial fibrillation

BACKGROUND

Cardioversion by direct current (DC) and other methods can cause atrial "stunning." There are case reports of acute pulmonary edema after DC cardioversion, but whether acute ventricular dysfunction is a general consequence of DC cardioversion is unknown. We have investigated whether DC cardioversion acutely affects myocardial velocity assessed by Doppler tissue imaging.

METHODS

40 patients (30 with atrial fibrillation and 10 with atrial flutter) undergoing elective DC cardioversion underwent transthoracic echocardiography with Doppler tissue imaging before and immediately after cardioversion, and after follow-up. Peak systolic velocity was derived for 6 ventricular segments using Doppler tissue imaging.

RESULTS

Immediately after DC cardioversion of atrial fibrillation, peak systolic velocity decreased in basal lateral (4.3 +/- 2.0-3.3 +/- 1.7 cm/s, P <.001), mitral annulus-septal (3.8 +/- 1.0-3.5 +/- 0.9, P <.05), mitral annulus-lateral (4.9 +/- 1.6-4.1 +/- 1.7, P <.001), and tricuspid annular (7.8 +/- 2.0-7.0 +/- 1.2, P <.03) segments, even though left ventricular ejection fraction was unchanged. In contrast, for the atrial flutter group there were no significant changes in peak systolic velocity in any segment post-DC cardioversion. Follow up studies were performed after sustained in sinus rhythm in both atrial fibrillation and atrial flutter groups. For both groups, increased peak systolic velocity was found in all 6 segments on follow-up (all P <.05).

CONCLUSIONS

DC cardioversion causes subclinical, acute reversible reduction in left ventricular peak systolic velocity in patients with atrial fibrillation. The causes of this reduction in myocardial contractile velocity and the circumstances in which acute dysfunction become clinically significant warrant further investigation.

Late improvement in ventricular performance following internal cardioversion for persistent atrial fibrillation: an argument in support of concealed cardiomyopathy

The aim of the study was to evaluate the time course of atrial and ventricular function improvement following internal atrial cardioversion in patients with structural heart disease. Twenty-nine patients with chronic persistent atrial fibrillation (AF) and underlying structural heart disease were followed by serial echocardiograms performed at 1 and 6 hours, 1 day, 1, 2, and 3 weeks, and 1, 2, 3, and 6 months after successful cardioversion. Sinus rhythm was maintained at 6 months in 24 patients. Following cardioversion the time course of left atrial mechanical function (peak A wave, percent A wave filling) differed from that of left ventricular ejection fraction: peak A wave values (cm/s) increased significantly at 1 week (51 +/- 23 vs 35 +/- 15 at 1 hour, P < 0.05), percent A wave filling (%) increased significantly at 2 weeks (34 +/- 12 vs 22 +/- 9 at 1 hour, P < 0.05), whereas left ventricular ejection fraction (%) increased later (at 1 month 60 +/- 14 vs 55 +/- 14 at baseline, P < 0.05 and at 2 months 60 +/- 14 vs 56 +/- 14 at 1 hour, P < 0.05). In conclusion, restoration of sinus rhythm results in an improvement in left ventricular ejection fraction during follow-up, even in patients with structural heart disease without fast ventricular rates at baseline. The dissociation between the time course of atrial and ventricular function improvement suggests that the latter was partly due to regression of a concealed form of cardiomyopathy and/or of a ventricular dysfunction due to chronic AF.

Atrial stunning: determinants and cellular mechanisms

BACKGROUND

Atrial stunning is a transient depression of atrial and atrial-appendage mechanical function after successful cardioversion of atrial fibrillation compared with its precardioversion state.

METHOD

Atrial stunning associated with different methods of cardioversion of atrial fibrillation and the determinants and cellular mechanisms of atrial stunning were elaborated by thoroughly examining the studies on the subject identified through a comprehensive literature search.

RESULTS AND CONCLUSION

Atrial stunning has been reported with all methods of cardioversion of atrial fibrillation, including transthoracic electrical, low-energy internal electrical, pharmacological, and spontaneous. It is a function of the underlying atrial fibrillation becoming apparent at the restoration of sinus rhythm, regardless of the method used for conversion. Unsuccessful cardioversion does not result in atrial stunning. The duration of the preceding atrial fibrillation, atrial size, and underlying structural heart disease are the determinants of atrial stunning. A shorter duration of atrial fibrillation and smaller atrial diameters are associated with a relatively less severe stunning, lasting for a shorter duration. Atrial stunning after cardioversion of atrial fibrillation of <1 week usually resolves within 24 hours, and atrial stunning after cardioversion of chronic atrial fibrillation usually resolves within 4 weeks. Tachycardia-induced atrial cardiomyopathy, atrial cytosolic calcium alterations with down-regulation of the L-type Ca2+ channels and up-regulation of the Na+/Ca2+ exchanger, atrial hibernation with myocyte dedifferentiation and myolysis, and atrial fibrosis are the suggested mechanisms underlying atrial stunning. Atrial stunning determines the risk of postcardioversion thrombus formation in atria and atrial appendages, the duration of postcardioversion anticoagulation therapy, the recovery of the atrial contribution to the ventricular function, and the functional recovery of the patients after successful cardioversion of atrial fibrillation.