Ablation of atrial fibrillation with the Epicor system: a prospective observational trial to evaluate safety and efficacy and predictors of success

Mid-Term Results of Surgical Treatment of Atrial Fibrillation in Valvular Heart Disease Assesed by Speckle Tracking Echocardiography

Background

Atrial fibrillation frequently affects patients with valvular heart disease. Ablation of atrial fibrillation during valvular surgery is an alternative for restoring sinus rhythm.

Objectives

This study aimed to evaluate mid-term results of successful atrial fibrillation surgical ablation during valvular heart disease surgery, to explore left atrium post-ablation mechanics and to identify predictors of recurrence.

Methods

Fifty-three consecutive candidates were included. Eligibility criteria for ablation included persistent atrial fibrillation <10 years and left atrium diameter < 6.0 cm. Three months after surgery, echocardiogram, 24-hour Holter monitoring and electrocardiograms were performed in all candidates who maintained sinus rhythm (44 patients). Echo-study included left atrial deformation parameters (strain and strain rate), using 2-dimensional speckle-tracking echocardiography. Simultaneously, 30 healthy individuals (controls) were analyzed with the same protocol for left atrial performance. Significance was considered with a P value of < 0.05.

Results

After a mean follow up of 17 ± 2 months, 13 new post-operative cases of recurrent atrial fibrillation were identified. A total of 1,245 left atrial segments were analysed. Left atrium was severely dilated in the post-surgery group and, mechanical properties of left atrium did not recover after surgery when compared with normal values. Left atrial volume (≥ 64 mL/m²) was the only independent predictor of atrial fibrillation recurrence (p = 0.03).

Conclusions

Left atrial volume was larger in patients with atrial fibrillation recurrence and emerges as the main predictor of recurrences, thereby improving the selection of candidates for this therapy; however, no differences were found regarding myocardial deformation parameters. Despite electrical maintenance of sinus rhythm, left atrium mechanics did not recover after atrial fibrillation ablation performed during valvular heart disease surgery.

Ultrasound-Guided Transesophageal High-Intensity Focused Ultrasound Cardiac Ablation in a Beating Heart: A Pilot Feasibility Study in Pigs

Catheter ablation for the treatment of arrhythmia is associated with significant complications and often-repeated procedures. Consequently, a less invasive and more efficient technique is required. Because high-intensity focused ultrasound (HIFU) enables the generation of precise thermal ablations in deep-seated tissues without harming the tissues in the propagation path, it has the potential to be used as a new ablation technique. A system capable of delivering HIFU into the heart by a transesophageal route using ultrasound (US) imaging guidance was developed and tested in vivo in six male pigs. HIFU exposures were performed on atria and ventricles. At the time of autopsy, visual inspection identified thermal lesions in the targeted areas in three of the animals. These lesions were confirmed by histologic analysis (mean size: 5.5 mm(2) × 11 mm(2)). No esophageal thermal injury was observed. One animal presented with bradycardia due to an atrio-ventricular block, which provides real-time confirmation of an interaction between HIFU and the electrical circuits of the heart. Thus, US-guided HIFU has the potential to minimally invasively create myocardial lesions without an intra-cardiac device.

Epicardial Catheter Ablation Using High-Intensity Ultrasound: Validation in a Swine Model

BACKGROUND

Epicardial radiofrequency catheter ablation of ventricular tachycardia remains challenging because of the presence of deep myocardial scar and adjacent cardiac structures, such as the coronary arteries, phrenic nerve, and epicardial fat that limit delivery of radiofrequency energy. High-intensity ultrasound (HIU) is an acoustic energy source able to deliver deep lesions through fat, while sparing superficial structures. We developed and tested an epicardial HIU ablation catheter in a closed chest, in vivo swine model.

METHODS AND RESULTS

The HIU catheter is an internally cooled, 14-French, side-facing catheter, integrated with A-mode ultrasound guidance. Swine underwent percutaneous subxyphoid epicardial access and ablation with HIU (n=10 swine) at 15, 20, and 30 W. Compared with irrigated radiofrequency lesions in control swine (n = 5), HIU demonstrated increased lesion depth (HIU 11.6±3.2 mm versus radiofrequency 4.7±1.6 mm; mean±SD) and epicardial sparing (HIU 2.9±2.1 mm versus radiofrequency 0.1±0.2 mm) at all HIU powers, and increased lesion volume at HIU 20 and 30 W (P<0.0001 for all comparisons). HIU ablation over coronary arteries and surrounding epicardial fat resulted in deep lesions with normal angiographic flow. Histological disruption of coronary adventitia, but not media or intima, was noted in 44% of lesions.

CONCLUSIONS

Compared with radiofrequency, HIU ablation in vivo demonstrates significantly deeper and larger lesions with greater epicardial sparing in a dose-dependent manner. Further development of this catheter may lead to a promising alternative to epicardial radiofrequency ablation.

Cardiovascular complications in newly diagnosed rheumatic heart disease patients at Mulago Hospital, Uganda

BACKGROUND

Complications of rheumatic heart disease are associated with severe morbidity and mortality in developing countries where the disease prevalence remains high. Due to lack of screening services, many patients present late, with severe valve disease. In Uganda, the disease and its complications are still not well studied.

OBJECTIVE

To profile and describe cardiovascular complications in newly diagnosed rheumatic heart disease patients attending the Mulago National Referral Hospital in Uganda.

METHODS

This was a cross-sectional study where consecutive, newly diagnosed rheumatic heart disease patients were assessed and followed up for complications, such as heart failure, pulmonary hypertension, atrial fibrillation, recurrence of acute rheumatic fever, and stroke.

RESULTS

A total of 309 (115 males and 196 females) definite rheumatic heart disease patients aged 15-60 years were enrolled in the study and analysed. Complications occurred in 49% (152/309) of the newly diagnosed rheumatic heart disease cases, with heart failure (46.9%) the most common complication, followed by pulmonary arterial hypertension (32.7%), atrial fibrillation (13.9%), recurrence of acute rheumatic fever (11.4%), infective endocarditis (4.5%) and stroke (1.3%). Atrial fibrillation and acute rheumatic fever were the most common complications associated with heart failure.

CONCLUSION

In this study we found that about 50% of newly diagnosed rheumatic heart disease patients in Uganda presented with complications. Heart failure and pulmonary arterial hypertension were the most commonly observed complications.

Cardiovascular applications of therapeutic ultrasound

Ultrasound (US) has gained widespread use in diagnostic cardiovascular applications. At amplitudes and frequencies typical of diagnostic use, its biomechanical effects on tissue are largely negligible. However, these parameters can be altered to harness US's thermal and non-thermal effects for therapeutic indications. High-intensity focused ultrasound (HIFU) and extracorporeal shock wave therapy (ECWT) are two therapeutic US modalities which have been investigated for treating cardiac arrhythmias and ischemic heart disease, respectively. Here, we review the biomechanical effects of HIFU and ECWT, their potential therapeutic mechanisms, and pre-clinical and clinical studies demonstrating their efficacy and safety limitations. Furthermore, we discuss other potential clinical applications of therapeutic US and areas in which future research is needed.

Impact of epicardial ablation of concomitant atrial fibrillation on atrial natriuretic peptide levels and atrial function in 6 months follow-up: does preoperative ANP level predict outcome of ablation?

Background

Epicardial ablation concomitant to cardiac surgery is an easy and safe approach to treat atrial fibrillation (AF), but its efficacy in longstanding persistent (LsPe) AF remains intermediate. Although larger left atrial size has been associated with worse outcome after ablation, biochemical predictors of success are not well established. The aim of this study was to evaluate relationship between biochemical marker, echo-characteristic and cardiac rhythm in 6 months follow-up after epicardial ultrasound (HIFU) ablation.

Methods

We included 78 consecutive patients, who underwent elective cardiac surgery. 42 patients with AF (11.9% paroxysmal, 23.8% persistent, 64.3% LsPeAF) underwent concomitant HIFU ablation (AF ablation group), 16 with AF underwent cardiac surgery without ablation (AF control) and 20 had preoperatively normal sinus rhythm (SR control). We measured plasma ANP secretion before, on postoperative day (POD) 1, POD 7 as well as 3 and 6 months after surgery. Moreover, we estimated cardiac rhythm and atrial mechanical function by Atrial Filling Fraction (AFF) and A-wave velocity in follow-up.

Results

Baseline ANP levels were higher in patients with LsPeAF, as compared to the paroxysmal and permanent AF and to the SR control group. Patients with LsPeAF (n = 27) who converted to SR had preoperatively smaller left atrial diameter (LAD) and LA area (p < 0.05) and higher ANP level (p = 0.009) than those who remained in AF at 6 months after ablation. Multivariate regression analysis revealed that only preoperative ANP level was an independent predictor of cardiac rhythm after ablation. Patients with LsPeAF and preoperative ANP >7.5 nmol/l presented with SR in 80%, in contrast to those with ANP <7.5 nmol/l who converted to SR in 20%. We detected gradual increase of AFF and A-velocity at 6 months after ablation (p < 0.05) solely in AF ablation group. ANP levels were increased on POD 1 in ablation group (p < 0.05), without changes in further follow-up.

Conclusion

Our results indicate that preoperative ANP levels may be a new biochemical predictor of successful epicardial ablation in patients with concomitant LsPeAF. HIFU ablation caused a significant improvement of atrial mechanical function and gradual increase of AFF and did not associate with alteration of atrial endocrine secretion at 6 months follow-up.

Evaluation of Early and Intermediate Outcomes of Cryo-MazeProcedure for Atrial Fibrillation

INTRODUCTION

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in patients with mitral valve disease affecting 50% of patients undergoing mitral valve surgery, contributing to increased risks of systemic embolization, anticoagulant- related hemorrhage and mortality. The maze procedure is an effective way to treat AF. Over the last several years, cryoablation was substituted for atrial incision in many reports to simplify the maze procedure. However, few studies have been carried out to evaluate the results of cryoablation surgery. In the present study we evaluated the results of this procedure.

METHODS

In this cross sectional study, 47 AF patients were treated with Cryo-Maze surgery method. Rhythm assessment using electrocardiographic and echocardiographic survey was performed in all patients before surgery, during the patients' hospital stay, on discharge and after six months.

RESULTS

Survival rate of the studied patients at six months was 93.6%. Sinus rhythm restoration rate in Cryo-Maze patients was 72.1% on discharge and 76.7% six months after their operation.

CONCLUSION

The present study revealed that Cryo-Maze procedure is an effective and safe therapeutic modality in AF while normal sinus rhythm can be achieved in patients following this intervention.

Long-term outcomes following high intensity focused ultrasound ablation for atrial fibrillation

BACKGROUND AND OBJECTIVE

The aim of this study is to assess the safety and efficacy of the Epicor high intensity focused ultrasound (St. Jude, Inc.®, Minneapolis, MN, USA) system using seven-day ambulatory electrocardiogram (ECG) monitoring over a two-year follow-up period.

METHODS

One hundred and ten patients undergoing ablation were included from a single center between January 2006 and December 2009. Rhythm was assessed using seven-day ambulatory ECG or permanent pacemaker interrogation. Seventeen patients were lost to follow-up, seven through death. Results were reported according to atrial fibrillation (AF) class preoperatively: paroxysmal, persistent, and long-standing persistent (LSP).

RESULTS

Forty-nine percent of patients remained in sinus rhythm at greater than two years. The percentage of patients in sinus rhythm according to preoperative AF class were 81% (paroxysmal AF), 56% (persistent AF), and 18% (long-standing AF). The class of AF prior to surgery, left atrium size, and body mass index determined the long-term outcome. There were no procedure-related complications.

CONCLUSIONS

We conclude that high intensity focused ultrasound ablation for atrial fibrillation using the Epicor system is safe and effective for surgical patients with paroxysmal AF. The persistent and LSP AF results suggest that alternative ablation strategies should be considered for these patients.

Design and evaluation of a transesophageal HIFU probe for ultrasound-guided cardiac ablation: simulation of a HIFU mini-maze procedure and preliminary ex vivo trials

Atrial fibrillation (AF) is the most frequent cardiac arrhythmia. Left atrial catheter ablation is currently performed to treat this disease. Several energy sources are used, such as radio-frequency or cryotherapy. The main target of this procedure is to isolate the pulmonary veins. However, significant complications caused by the invasive procedure are described, such as stroke, tamponade, and atrioesophageal fistula, and a second intervention is often needed to avoid atrial fibrillation recurrence. For these reasons, a minimally-invasive device allowing performance of more complex treatments is still needed. High-intensity focused ultrasound (HIFU) can cause deep tissue lesions without damaging intervening tissues. Left atrial ultrasound-guided transesophageal HIFU ablation could have the potential to become a new ablation technique. The goal of this study was to design and test a minimally-invasive ultrasound-guided transesophageal HIFU probe under realistic treatment conditions. First, numerical simulations were conducted to determine the probe geometry, and to validate the feasibility of performing an AF treatment using a HIFU mini-maze (HIFUMM) procedure. Then, a prototype was manufactured and characterized. The 18-mm-diameter probe head housing contained a 3-MHz spherical truncated HIFU transducer divided into 8 rings, with a 5-MHz commercial transesophageal echocardiography (TEE) transducer integrated in the center. Finally, ex vivo experiments were performed to test the impact of the esophagus layer between the probe and the tissue to treat, and also the influence of the lungs and the vascularization on lesion formation. First results show that this prototype successfully created ex vivo transmural myocardial lesions under ultrasound guidance, while preserving intervening tissues (such as the esophagus). Ultrasound-guided transesophageal HIFU can be a good candidate for treatment of AF in the future.

Impact of medical treatment on long-term results after surgical ablation of atrial fibrillation in cardiac surgical patients

BACKGROUND

The aim of this study was to evaluate the long-term outcome (4 years) of high-intensity-focused-ultrasound (HIFU) cardiac ablation, the significance of postablation antiarrhythmic drugs (AADs) and predictors of successful sinus rhythm (SR) restoration.

METHODS

103 patients were prospectively enrolled in a single-center study. The preoperative atrial fibrillation (AF) type was paroxysmal in 36%, permanent in 53%, persistent in 5% and flutter in 6% patients. The left atrial diameter was <50 mm in 78 patients and >50 mm in 25. Long-term results, up to 4 years, and postablation antiarrhythmics were evaluated. Follow-up studies including 12-lead electrocardiogram (ECG) and 24-h Holter ECG obtained at 3 and 6 months in our institute, and 12, 24, and 48 months during outpatient visits.

RESULTS

No device- or procedure-related complications or deaths were observed. A pacemaker was implanted in 5% patients. Freedom from AF and flutter at 6-/12-/and 48-month visit were 66%/63%/68% for the entire population, 84%/77%/90% in patients with paroxysmal AF, 50%/46%/40% in patients with permanent AF and at any time in all 6 patients with flutter. No significant changes were noted at 2 years.Postablation results were not statistically different in patients on or not on antiarrhythmic therapy. At discharge, 53% of patients on antiarrhythmics and 55%, not on AADs were free of AF. At the 6-month visit, 66% of patients on AADs versus 69% of patients, not on AADs presented with SR, an improved outcome by 13 percentage points with AADs versus 14 percentage points without AADs (p = 0.65). Patients taking a β-blocker showed better results in restoration/maintenance of SR after 6 months. No significant difference was noted regarding the use of UltraWand.Sixty-seven percent with a left atrium (LA) diameter <50 mm were successfully converted into SR, vs. 48% with an LA diameter >50 mm. Best results were achieved in patients with paroxysmal AF and LA <50 mm with 81% freedom of AF.

CONCLUSION

AF treatment with HIFU ablation during concomitant cardiac surgery is a safe and effective procedure for restoring SR, especially in patients with AF and especially in patients with a smaller left atrial diameter. No significant difference was noted between the antiarrhythmic and non drug groups regarding restoration and maintaining SR; however, better results were achieved by those taking a β-blocker.

Radiofrequency ablation for atrial fibrillation during concomitant cardiac surgery. Mid-term results

BACKGROUND

Atrial fibrillation is found in an increasing number of patients undergoing open heart surgery. It is associated with higher mortality rates, risk of stroke and left ventricular dysfunction. Surgical ablation for atrial fibrillation has evolved from the complex"cut and sew" Maze procedure to less invasive techniques, utilizing alternative energy sources. We present our experience with left atrial radiofrequency ablation during cardiac surgery, outlining the technical aspects of the procedure and postoperative outcomes, with emphasis on mid-term freedom from atrial fibrillation.

METHODS

The study included 93 consecutive patients with history of atrial fibrillation scheduled for cardiac surgery between January 2008 and December 2011. Concomitant left atrial radiofrequency ablation was performed using monopolar (endocardial) or bipolar (epicardial) systems, depending on the type of underlying cardiac pathology. Duration of the atrial fibrillation, re-do surgery, low ejection fraction, advanced age, or giant left atria were not considered as contraindications.

RESULTS

Of the included patients, 73.1 % were discharged in stable sinus rhythm. Overall freedom from atrial fibrillation was 69.6 % at late follow-up, which ranged from 12 to 48 months (median, 22 months) and did not differ for the two approaches (epicardial vs. endocardial). The presence of early atrial tachyarrhythmia was a predictor of atrial fibrillation recurrence (p = 0.026). Age was also associated with higher recurrence rates during hospital stay (p = 0.04), but not for late atrial fibrillation.

CONCLUSION

Concomitant left atrial radiofrequency ablation conveyed satisfactory early and mid-term rhythm control, with acceptable postoperative outcomes, given the risk profile of our patient cohort.

Heart ablation using a planar rectangular high intensity ultrasound transducer and MRI guidance

The aim of this study was to evaluate a flat rectangular (3×10mm(2)) MRI compatible transducer operating at 5MHz. The main task was to explore the feasibility of creating deep lesions in heart at a depth of at least 15mm. The size of thermal necrosis in heart tissue was estimated as a function of power and time using a simulation model. The system was then tested in an excised lamb heart. In this study, we were able to create lesions of 15mm deep with acoustic power of 6W for an exposure of approximately 1min. The contrast to noise ratio (CNR) between lesion and heart tissue was evaluated using fast spin echo (FSE). The CNR value was approximately 22 using T1W FSE. Maximum CNR was achieved with repetition time (TR) between 300 and 800ms. Using T2W FSE, the corresponding CNR was approximately 13 for the 14 in vivo experiments. The average lesion depth was 11.93mm with a standard deviation of 0.62mm. In vivo irradiation conditions were 6W for 60s. The size of the lesion in the other two dimensions was close to 3×10mm(2) (size of the transducer element).

High-frequency ultrasound m-mode imaging for identifying lesion and bubble activity during high-intensity focused ultrasound ablation

Effective real-time monitoring of high-intensity focused ultrasound (HIFU) ablation is important for application of HIFU technology in interventional electrophysiology. This study investigated rapid, high-frequency M-mode ultrasound imaging for monitoring spatiotemporal changes during HIFU application. HIFU (4.33 MHz, 1 kHz PRF, 50% duty cycle, 1 s, 2600‒6100 W/cm²) was applied to ex vivo porcine cardiac tissue specimens with a confocally and perpendicularly aligned high-frequency imaging system (Visualsonics Vevo 770, 55 MHz center frequency). Radio-frequency (RF) data from M-mode imaging (1 kHz PRF, 2 s × 7 mm) was acquired before, during and after HIFU treatment (n = 12). Among several strategies, the temporal maximum integrated backscatter with a threshold of +12 dB change showed the best results for identifying final lesion width (receiver-operating characteristic curve area 0.91 ± 0.04, accuracy 85 ± 8%, compared with macroscopic images of lesions). A criterion based on a line-to-line decorrelation coefficient is proposed for identification of transient gas bodies.