Intracardiac Probe Research Articles

Migration intracardiaque de la sonde urétérale mono J : à propos d'un cas et techniques de retrait

The techniques of derivation of the high urinary tract are indispensable in common practice for the management of ureteral obstructions. Like any surgical gesture, its techniques are not without complications; Among those common are hematuria, urinary incontinence, migration in the bladder and rupture of the probe. However, intracardiac probe migration has rarely been described. We report the case of a 68-year-old patient treated for cervical cancer who benefited from the rise of a bilateral single-J probe, admitted for accidental migration of the left probe into the heart. The diagnosis was made by plain abdominal X-ray and confirmed by thoraco-abdominal CT angiography. The patient benefited, in the catheterization room, from a withdrawal of the probe by endoscopic way and under radioscopic control successfully and without any incident.

Spectral Analysis of Tissue Displacement for Cardiac Activation Mapping: Ex Vivo Working Heart and In Vivo Study.

Characterizing myocardial activation is of major interest for understanding the underlying mechanism of cardiac arrhythmias. Electromechanical wave imaging (EWI) is an ultrafast ultrasound-based method used to map the propagation of the local contraction triggered by electrical activation of the heart. This study introduces a novel way to characterize cardiac activation based on the time evolution of the instantaneous frequency content of the cardiac tissue displacement curves. The first validation of this method was performed on an ex vivo dataset of 36 acquisitions acquired from two working heart models in paced rhythms. It was shown that the activation mapping described by spectral analysis of interframe displacement is similar to the standard EWI method based on zero-crossing of interframe strain. An average median error of 3.3 ms was found in the ex vivo dataset between the activation maps obtained with the two methods. The feasibility of mapping cardiac activation by EWI was then investigated on two open-chest pigs during sinus and paced rhythms in a pilot trial of cardiac mapping with an intracardiac probe. Seventy-five acquisitions were performed with reasonable stability and analyzed with the novel algorithm to map cardiac contraction propagation in the left ventricle (LV). Sixty-one qualitatively continuous isochrones were successfully computed based on this method. The region of contraction onset was coherently described while pacing in the imaging plane. These findings highlight the potential of implementing EWI acquisition on intracardiac probes and emphasize the benefit of performing short time-frequency analysis of displacement data to characterize cardiac activation in vivo.

Temperature monitoring by channel data delays: Feasibility based on estimated delays magnitude for cardiac ablation

Ultrasound thermometry is based on measuring tissue temperature by its impact on ultrasound wave propagation. This study focuses on the use of transducer array channel data (not beamformed) and examines how a layer of increased velocity (heat induced) affects the travel-times of the ultrasound backscatter signal. Based on geometric considerations, a new equation was derived for the change in time delay as a function of temperature change. The resulting expression provides insight into the key factors that link change in temperature to change in travel time. It shows that velocity enters in combination with heating geometry: complementary information is needed to compute velocity from the changes in travel time. Using the bio-heat equation as a second source of information in the derived expressions, the feasibility of monitoring the temperature increase during cardiac ablation therapy using channel data was investigated. For an intra-cardiac (ICE) probe, using this “time delay error approach” would not be feasible, while for a trans-esophageal array transducer (TEE) transducer it might be feasible.

Intracardiac Echocardiography Guided Transeptal Catheter Injection of Microspheres for Assessment of Cerebral Microcirculation in Experimental Models

The use of microspheres for the determination of regional microvascular blood flow (RMBF) has previously used different approaches. This study presents for the first time the intracardiac injection of microspheres using transeptal puncture under intracardiac echocardiography guidance. Five Merino sheep were instrumented and cardiovascularly supported according to local guidelines. Two catheter sheaths into the internal jugular vein facilitated the introduction of an intracardiac probe and transeptal catheter, respectively. Five million colour coded microspheres were injected into the left atrium via this catheter. After euthanasia the brain was used as proof of principle and the endpoint for determination of microcirculation at different time points. Homogeneous allocation of microspheres to different regions of the brain was found over time. Alternate slices from both hemispheres showed the following flow ranges: for slice 02; 0.57–1.02 mL/min/g, slice 04; 0.45–1.42 mL/min/g, slice 06; 0.35–1.87 mL/min/g, slice 08; 0.46–1.77 mL/min/g, slice 10; 0.34–1.28 mL/min/g. A mixed effect regression model demonstrated that the confidence interval did include zero suggesting that the apparent variability intra- and intersubject was not statistically significant, supporting the stability and reproducibility of the injection technique. This study demonstrates the feasibility of the transeptal injection of microspheres, showing a homogeneous distribution of blood flow through the brain unchanged over time and has established a new interventional model for the measurement of RMBF in ovine models.

Ultrasound-Guided Placement of a Renal Artery Stent Using an Intracardiac Probe for Transvascular Imaging

In this set of images obtained during an experimental study using a porcine animal model, we introduce ultrasound guidance of percutaneous transluminal renal angioplasty and renal stenting. A state-of-the-art intracardiac ultrasound catheter is used here for transvascular scanning from within the lumen of the abdominal aorta, thus providing a field of view for navigation of a balloon catheter and a wire coil (“stent”) into each renal artery of a pig. This study is intended as a contribution to the growing field of minimally invasive interventions and their navigation by non-ionizing ultrasound imaging.

Transseptal puncture using minimally invasive echocardiography during atrial fibrillation ablation

To assess the usefulness of miniature transoesophageal echocardiography using a 10 F intracardiac probe (ICE-TEE) for transseptal catheterization during atrial fibrillation (AF) ablation. Intracardiac echocardiography probe was used transoesophageally in 79 consecutive patients (56 ± 11 years, 73% male) referred for AF ablation (60% paroxysmal and 38% persistent) to guide transseptal puncture. Transseptal catheterization monitored by ICE-TEE was well tolerated and successfully performed in all patients without any sedation. No mechanical oesophageal complication was noted. Moreover, the mean duration between ICE-TEE probe insertion and successful transseptal puncture was 4.5 min and the mean time of ICE-TEE was 10 min. Finally, no tamponade occurred during the AF ablation procedure. Intracardiac echocardiography-TEE is safe and well tolerated for the guidance of transseptal catheterization during AF ablation. Moreover, this technique was performed without requiring any anaesthesia.

Use of the Monoplane Intracardiac Imaging Probe in High‐Risk Infants during Congenital Heart Surgery

Imaging options are limited in high-risk infants with small or abnormal oropharyngeal anatomy during congenital heart surgery. All cases in which the monoplane intracardiac echo probe was used for transesophageal intraoperative imaging over a 15-month period at a single institution were reviewed. Eleven patients underwent intraoperative imaging using the intracardiac probe. Patient weight ranged from 1.96 kg to 4 kg. Adequate images of the anatomy relevant to the surgical repair were obtained in all cases. No adverse events related to probe use occurred. Transesophageal echocardiography using the monoplane intracardiac echo probe provides safe and effective imaging in patients who are not candidates for standard transesophageal echocardiography.

Intracardiac Echocardiography and Acoustic Radiation Force Impulse Imaging of a Dynamic Ex Vivo Ovine Heart Model

Intracardiac echocardiography (ICE) has demonstrated utility in providing high-resolution cardiac ultrasound images for guidance of numerous catheter-based interventions, including radiofrequency ablations (RFA). However, the training of interventionalists and refinement of procedures involving intracardiac catheters is costly and time consuming due to necessary clinical and animal studies. As a result, research and development of ICE for other purposes is gradual and deliberate. Intracardiac acoustic radiation force impulse (ARFI) imaging has been demonstrated to be a suitable modality to monitor the progress of RFA procedures; however, a clinical protocol has been slow to develop due to the expense and demands of clinical experiments. We report on the development and use of an ex vivo heart model to evaluate ICE and intracardiac ARFI imaging. The ability of this model to provide clinically-relevant intracardiac imaging angles was investigated by inserting an intracardiac probe into the heart and imaging it from various positions and orientations. ARFI images of all four chambers also were formed. RFAs were also performed to create stiffer lesions within the right and left ventricles. Upon completion of the ablation, ARFI imaging was used to visualize the lesion and compared with images taken from pathology.The results show the ovine heart model to be a suitable apparatus for recreating several clinically-relevant intracardiac viewing angles of the heart. Also, the results indicate the potential of the heart model to be a valuable tool in the future development and refinement of a clinical protocol for intracardiac ARFI imaging based guidance and assessment of cardiac radiofrequency ablations.

Abstract 2242: Very High Resolution Near Field Imaging of Ablation with a Newly-Developed Forward-Looking Catheter Mounted Microlinear Intracardiac Imaging Array

Background: We have developed the first forward-looking highly steerable intracardiac echo probe developed for ultrasound visualization of ablation. It is a 24-element forward-looking microlinear array on a 9 Fr catheter that has additional electrodes so it can be localized compared to separate ablation catheters through electrofield navigation by NavX. Methods: In 4 studies of closed-chest pigs, we have imaged ablation locations in the right atrium and the isthmus and on the right side of the septum and at the right ventricular apex, and also imaged across the septum at ablations in the left ventricle along the septum with this device. Results: Images at 150–170 frames/sec at 12–15 MHz give very high detail of the changes occurring during ablation, including liquefaction, heating changes, brightening and thickening of tissue, and thrombus formation in the adjacent region in unheparinized pigs. The devices are well enough shielded from RF energy that there is little interference, and yet an ablation is being performed. A catheter tip artifact makes it easy to see the actual location of the ablation catheter tip with the microlinear array. Tissue Doppler/strain rate imaging also yields the possibility of determining mechanical changes occurring in ablation where brightening of tissue associated with stiffening diminished mechanical strain deformations in ablated lesions, especially in the ventricles. Conclusions: This new technology provides a new method for guidance and, more importantly, a method for understanding the changes that occur with RF ablations in experimental animals and, eventually, in patients.

Challenges and implementation of radiation-force imaging with an intracardiac ultrasound transducer

Intracardiac echocardiography (ICE) has been demonstrated to be an effective imaging modality for the guidance of several cardiac procedures, including radiofrequency ablation (RFA). However, assessing lesion size during the ablation with conventional ultrasound has been limited, as the associated changes within the B-mode images often are subtle. Acoustic radiation force impulse (ARFI) imaging is a promising modality to monitor RFAs as it is capable of visualizing variations in local stiffnesses within the myocardium. We demonstrate ARFI imaging with an intracardiac probe that creates higher quality images of the developing lesion. We evaluated the performance of an ICE probe with ARFI imaging in monitoring RFAs. The intracardiac probe was used to create high contrast, high resolution ARFI images of a tissue-mimicking phantom containing stiffer spherical inclusions. The probe also was used to examine an excised segment of an ovine right ventricle with a RFA-created surface lesion. Although the lesion was not visible in conventional B-mode images, the ARFI images were able to show the boundaries between the lesion and the surrounding tissue. ARFI imaging with an intracardiac probe then was used to monitor cardiac ablations in vivo. RFAs were performed within the right atrium of an ovine heart, and B-mode and ARFI imaging with the intracardiac probe was used to monitor the developing lesions. Although there was little indication of a developing lesion within the B-mode images, the corresponding ARFI images displayed regions around the ablation site that displaced less.

The history of echocardiography

Following a brief review of the development of medical ultrasonics from the mid-1930s to the mid-1950s, the collaboration between Edler and Hertz that began in Lund in 1953 is described. Using an industrial ultrasonic flaw detector, they obtained time-varying echoes transcutaneously from within the heart. The first clinical applications of M-mode echocardiography were concerned with the assessment of the mitral valve from the shapes of the corresponding waveforms. Subsequently, the various M-mode recordings were related to their anatomical origins. The method then became established as a diagnostic tool and was taken up by investigators outside Lund, initially in China, Germany, Japan and the USA and, subsequently, world-wide. The diffusion of echocardiography into clinical practice depended on the timely commercial availability of suitable equipment. The discovery of contrast echocardiography in the late 1960s further validated the technique and extended the range of applications. Two-dimensional echocardiography was first demonstrated in the late 1950s, with real-time mechanical systems and, in the early 1960s, with intracardiac probes. Transesophageal echocardiography followed, in the late 1960s. Stop-action two-dimensional echocardiography enjoyed a brief vogue in the early 1970s. It was, however, the demonstration by Bom in Rotterdam of real-time two-dimensional echocardiography using a linear transducer array that revolutionized and popularized the subject. Then, the phased array sector scanner, which had been demonstrated in the late 1960s by Somer in Utrecht, was applied to cardiac studies from the mid-1970s onwards. Satomura had demonstrated the use of the ultrasonic Doppler effect to detect tissue motion in Osaka in the mid-1950s and the technique was soon afterwards applied in the heart, often in combination with M-mode recording. The development of the pulsed Doppler method in the late 1960s opened up new opportunities for clinical innovation. The review ends with a mention of color Doppler echocardiography. (E-mail: kjell.lindstrom@elmat.lth.se