High-density Mapping Guided Pulmonary Vein Isolation for Treatment of Atrial Fibrillation-Two-year clinical outcome of a single center experience

Pulmonary vein isolation (PVI) as interventional treatment for atrial fibrillation (AF) aims to eliminate arrhythmogenic triggers from the PVs. Improved signal detection facilitating a more robust electrical isolation might be associated with a better outcome. This retrospective cohort study compared PVI procedures using a novel high-density mapping system (HDM) with improved signal detection vs. age-and sex-matched PVIs using a conventional 3D mapping system (COM). Endpoints comprised freedom from AF and procedural parameters. In total, 108 patients (mean age 63.9 +/- 11.2 years, 56.5% male, 50.9% paroxysmal AF) were included (n = 54 patients/group). Our analysis revealed that HDM was not superior regarding freedom from AF (mean follow-up of 494.7 +/- 26.2 days), with one- and two-year AF recurrence rates of 38.9%/46.5% (HDM) and 38.9%/42.2% (COM), respectively. HDM was associated with reduction in fluoroscopy times (18.8 +/- 10.6 vs. 29.8 +/- 13.4 min;p < 0.01) and total radiation dose (866.0 +/- 1003.3 vs. 1731.2 +/- 1978.4 cGy;p < 0.01) compared to the COM group. HDM was equivalent but not superior to COM with respect to clinical outcome after PVI and resulted in reduced fluoroscopy time and radiation exposure. These results suggest that HDM-guided PVI is effective and safe for AF ablation. Potential benefits in comparison to conventional mapping systems, e.g. arrhythmia recurrence rates, have to be addressed in randomized trials

Fast catheter segmentation from echocardiographic sequences based on segmentation from corresponding X-ray fluoroscopy for cardiac catheterization interventions

© 2014 IEEE. Echocardiography is a potential alternative to X-ray fluoroscopy in cardiac catheterization given its richness in soft tissue information and its lack of ionizing radiation. However, its small field of view and acoustic artifacts make direct automatic segmentation of the catheters very challenging. In this study, a fast catheter segmentation framework for echocardiographic imaging guided by the segmentation of corresponding X-ray fluoroscopic imaging is proposed. The complete framework consists of: 1) catheter initialization in the first X-ray frame; 2) catheter tracking in the rest of the X-ray sequence; 3) fast registration of corresponding X-ray and ultrasound frames; and 4) catheter segmentation in ultrasound images guided by the results of both X-ray tracking and fast registration. The main contributions include: 1) a Kalman filter-based growing strategy with more clinical data evalution; 2) a SURF detector applied in a constrained search space for catheter segmentation in ultrasound images; 3) a two layer hierarchical graph model to integrate and smooth catheter fragments into a complete catheter; and 4) the integration of these components into a system for clinical applications. This framework is evaluated on five sequences of porcine data and four sequences of patient data comprising more than 3000 X-ray frames and more than 1000 ultrasound frames. The results show that our algorithm is able to track the catheter in ultrasound images at 1.3 s per frame, with an error of less than 2 mm. However, although this may satisfy the accuracy for visualization purposes and is also fast, the algorithm still needs to be further accelerated for real-time clinical applications

Exploiting Temporal Image Information in Minimally Invasive Surgery

Minimally invasive procedures rely on medical imaging instead of the surgeons direct vision. While preoperative images can be used for surgical planning and navigation, once the surgeon arrives at the target site real-time intraoperative imaging is needed. However, acquiring and interpreting these images can be challenging and much of the rich temporal information present in these images is not visible. The goal of this thesis is to improve image guidance for minimally invasive surgery in two main areas. First, by showing how high-quality ultrasound video can be obtained by integrating an ultrasound transducer directly into delivery devices for beating heart valve surgery. Secondly, by extracting hidden temporal information through video processing methods to help the surgeon localize important anatomical structures. Prototypes of delivery tools, with integrated ultrasound imaging, were developed for both transcatheter aortic valve implantation and mitral valve repair. These tools provided an on-site view that shows the tool-tissue interactions during valve repair. Additionally, augmented reality environments were used to add more anatomical context that aids in navigation and in interpreting the on-site video. Other procedures can be improved by extracting hidden temporal information from the intraoperative video. In ultrasound guided epidural injections, dural pulsation provides a cue in finding a clear trajectory to the epidural space. By processing the video using extended Kalman filtering, subtle pulsations were automatically detected and visualized in real-time. A statistical framework for analyzing periodicity was developed based on dynamic linear modelling. In addition to detecting dural pulsation in lumbar spine ultrasound, this approach was used to image tissue perfusion in natural video and generate ventilation maps from free-breathing magnetic resonance imaging. A second statistical method, based on spectral analysis of pixel intensity values, allowed blood flow to be detected directly from high-frequency B-mode ultrasound video. Finally, pulsatile cues in endoscopic video were enhanced through Eulerian video magnification to help localize critical vasculature. This approach shows particular promise in identifying the basilar artery in endoscopic third ventriculostomy and the prostatic artery in nerve-sparing prostatectomy. A real-time implementation was developed which processed full-resolution stereoscopic video on the da Vinci Surgical System

Translation of Intravascular Optical Ultrasound Imaging

ances in the field of intravascular imaging have provided clinicians with power ful tools to aid in the assessment and treatment of vascular pathology. Optical Ultra sound (OpUS) is an emerging modality with the potential to offer significant bene fits over existing commercial technologies such as intravascular ultrasound (IVUS) or optical coherence tomography (OCT). With this paradigm ultrasound (US) is generated using pulsed or modulated light and received by a miniaturised fibre-optic hydrophone (FOH). The US generation is facilitated through the use of engineered optically-absorbing nanocomposite materials. To date pre-clinical benchtop stud ies of OpUS have shown significant promise however further study is needed to facilitate clinical translation. The overall aim of this PhD was to develop a pathway to clinical translation of OpUS, enabled by the development of a catheter-based device capable of high resolution vascular tissue imaging during an in-vivo setting. A forward-viewing OpUS imaging probe was developed using a 400 µm mul timode optical fibre, dip-coated in a multi-walled carbon nanotube-PDMS com posite, paired with a FOH comprising a 125 µm single mode fibre tipped with a Fabry-Perot cavity. With this high US pressures were generated (21.5 MPa at the transducer surface) and broad corresponding bandwidths were achieved (−6 dB of 39.8MHz). Using this probe, OpUS imaging was performed of an ex-vivo human coronary artery. The results demonstrated excellent correspondence, in the detec tion of calcification and lipid infiltration, with IVUS, OCT and histological analysis. A side-viewing OpUS imaging probe, employing a reflective 45 °angle at the dis tal fibre surface, was used to demonstrate rotational B-mode imaging of a vascular structure for the first time. This provided high-resolution imaging (54 µm axial resolution) with deep depth penetration (>10.5 mm). Finally the clinical utility of this technology was demonstrated during an in-vivo endovascular procedure. An OpUS imaging probe, incorporated into an interventional device, allowed guidance of in-situ fenestration of an endograft during a complex abdominal aortic aneurysm repair. Through this work the potential clinical utility of OpUS, to assess pathology and guide vascular intervention, has been demonstrated. These results pave the way for translation of this technology and a first in man study

A Review of the Impella Devices

The use of mechanical circulatory support (MCS) to provide acute haemodynamic support for cardiogenic shock or to support high-risk percutaneous coronary intervention (HRPCI) has grown over the past decade. There is currently no consensus on best practice regarding its use in these two distinct indications. Impella heart pumps (Abiomed) are intravascular microaxial blood pumps that provide temporary MCS during HRPCI or in the treatment of cardiogenic shock. The authors outline technical specifications of the individual Impella heart pumps and their accompanying technology, the Automated Impella Controller and SmartAssist, their indications for use and patient selection, implantation techniques, device weaning and escalation, closure strategies, anticoagulation regimens, complications, future directions and upcoming trials

Mechanical assist in cardiac arrest: Optimising circulatory support. Experimental studies.

Introduction: Mechanical circulatory support (MCS) may be useful in cardiac arrest (CA), both in- and out- of hospital. However, efficacy and survival benefit has been difficult to evaluate compared to standard cardiopulmonary resuscitation. In three experimental studies we aimed to assess different modes of MCS during CA in providing adequate organ perfusion and systemic circulation and identify predictors of sustainable post-CA heart function. Different theoretical assumptions were the background for analysis in the three study protocols performed as acute experiments in anaesthetized pigs: Paper I: A major limitation to the effectiveness of a LVAD alone during CA is the lack of left ventricular (LV) filling due to minimal pulmonary circulation. We therefore wanted to assess if the combination of a left- and right ventricular assist device (BIVAD/BiPella) was beneficial as circulatory support versus a LVAD alone. Paper II: ECMO has the potential to replace systemic circulation during CA. However, concerns have been voiced regarding retrograde flow-delivery and effect on the myocardium during circulatory collapse. Based on results from Paper I we optimized BiPella support aiming to improve and maintain acceptable coronary perfusion pressure, believing this could potentially rectify the poor outcome of BIVAD/BiPella in Paper I if successful. Thus, in Paper II we compared the efficacy of balanced biventricular circulatory assist with extracorporeal membrane oxygenation (ECMO). Paper III: Pressure build-up in the left ventricle during cardiac arrest may be detrimental during extracorporeal cardiopulmonary resuscitation (ECPR) as indicated in Paper II. Therefore, we wished to investigate if unloading (venting) the left ventricle using add-on LVAD could be of benefit. However, the ideal flow-contributions of each assist device when combining LVAD and ECMO during ECPR in is not known. We therefore wanted to compare ECMO with standard or reduced flow and add-on LVAD versus ECMO alone. Finally, we wished to assess the contribution of add-on LVAD regarding pulmonary flow. Materials and methods: The animal experiments were performed at the Vivarium, University of Bergen, and protocols were approved by the Norwegian Animal Research Authority or by the Norwegian Food Safety Authority. Paper I and II were performed with percutaneous techniques. The final experiment was an open chest model. All protocols followed a similar timeline: 1. Anaesthesia and instrumentation of the pig. 2. Baseline evaluation. 3. Induction of CA by application of a 9V DC battery to the myocardium. 4. Immediate initiation of mechanical circulatory support (MCS). 5. Three attempts of cardioversion at the end of the CA period. 6. If successful return of spontaneous circulation (ROSC) was achieved, unsupported observation (Paper II and Paper III). Comparisons between intervention groups: 1. Haemodynamics (during and after CA). 2. Organ tissue blood flow rate (organ perfusion) and device output as calculated from fluorescent microspheres. 3. Arterial blood gases and biomarkers. 4. ROSC. 5. Sustained cardiac function post-ROSC (Paper II and Paper III). In Paper I, twenty animals were randomized in two groups receiving circulatory support either by the Impella CP alone (LVAD) or in combination with the Impella RP (BIVAD/BiPella) during 30 minutes of CA. In Paper II, twenty pigs were randomized to receive MCS either by BiPella or by extracorporeal membrane oxygenation (ECMO) during 40 minutes of CA. If ROSC was successful, animals were observed for 60 minutes unsupported. In Paper III, twenty-four animals were randomized in three groups. Extracorporeal cardiopulmonary resuscitation (ECPR) in Group 1 was provided by ECMO with standard-flow and add-on Impella CP. In Group 2: ECMO with reduced flow combined with Impella CP. In Group 3, animals were supported by standard-flow ECMO alone. ECPR lasted for 60 minutes. If ROSC was successful, 180 minutes unsupported observation followed. Results: Paper I demonstrated that BIVAD/BiPella provides superior circulatory support and perfusion for peripheral organs (including the brain) related to higher LVAD output and increased central aortic pressure compared to LVAD alone. However, myocardial perfusion was related to the pressure difference between mean aortic pressure and mean left ventricular pressure during cardiac arrest. Myocardial perfusion was inferior with BiPella resulting in significantly fewer ROSC (5/10 vs 10/10, p = 0.033) despite significantly higher etCO2 (p = 0.029). Paper II showed that balancing RVAD and LVAD to ensure acceptable coronary perfusion pressure and concomitant LVAD output was feasible, also sustaining vital organ perfusion. However, ECMO provided a more optimal systemic circulatory support. Device output and mean aortic pressure were increased with subsequent improved peripheral tissue perfusion reflected by reduction of s-lactate. In animals where sufficient myocardial perfusion pressure (mean aortic pressure – mean LV pressure > 10-15 mmHg) could not be achieved, perfusion (ml/min/g) was reduced in the subendo- and midmyocardium, averaging 0.59 ± 0.05 vs. 0.31 ± 0.07, (p = 0.005) and 0.91 ± 0.06 vs 0.65 ± 0.15 (p = 0.085), but not in the subepicardium (1.02 ± 0.07 vs 0.86 ± 0.17, p = 0.30) irrespective of group. These subjects also had inferior post-ROSC cardiac function. Paper III showed that add-on LVAD improved haemodynamics compared with ECMO alone during refractory CA. Add-on LVAD could not substitute a reduced ECMO-flow. Three animals with reduced ECMO flow and adjunctive Impella support did not achieve ROSC. With ECMO alone, ROSC was obtained in all animals. However, 4/8 died post-ROSC due to development of cardiogenic shock. In the remaining 21 animals, 17 animals had sustained cardiac function at study termination 3 h after ROSC. Animals without sustained cardiac function (7/24) had reduced mAP (p < 0.001), CPP (p = 0.002) and mPAf (p = 0.004) during CA and ECPR. Conclusions: Paper I: Biventricular support during cardiac arrest was associated with high intraventricular pressure in the left ventricle resulting in decreased myocardial perfusion pressure, reduced myocardial tissue blood flow rate and subsequent reduction in ROSC. Paper II: Myocardial perfusion and sustained cardiac function were related to myocardial perfusion pressure during VF irrespective of MCS (ECMO and balanced biventricular support). Balanced biventricular support maintained lower intraventricular pressure compared to ECMO. Paper III: Add-on LVAD improved haemodynamics compared to ECMO alone. An add-on Impella could not substitute a reduction in ECMO flow. Increased mean aortic pressure, myocardial perfusion pressure and mean pulmonary artery flow were related to sustained cardiac function and ROSC.Doktorgradsavhandlin

Three Dimensional Color Doppler Sonographic Assessment of changes in Volume and Vascularity of Fibroids - Before and After Uterine Artery Embolization.

Menorrhagia is defined as bleeding that originates from the uterus. In developing countries, the majority of cases are due to fibroid uterus. Massive menorrhagia is a major clinical and surgical problem with a mortality of 80%, which is most often related to hemodynamic instability. Uterine fibroids are the most frequent tumors of the female genital tract, occurring in 20 –50% of women who are older than 40 years. Uterine fibroid, the most common cause of nonacute abnormal uterine bleeding, is also the most common solid uterine neoplasm occurring in 20–40% of all women during their reproductive period. Uterine artery embolization (UAE) was introduced in the 1970s to treat postpartum hemorrhage. In the 1990s, this technique was successfully used preoperatively 3–10 days before myomectomy to reduce bleeding during the surgical phase. In 1995, Ravina et al. proposed embolization of uterine arteries as an alternative to surgical treatment of uterine leiomyoma. Menorrhagia is defined as heavy or prolonged uterine bleeding that occurs at regular intervals. Some sources define menorrhagia further as the loss of ≥ 80 mL blood per cycle or bleeding > 7 days. Conservative management of massive menorrhagia carries a mortality rate of 50%–100% and the mortality is up to 35% even in patients undergoing operation. Surgery remains the procedure of choice in the treatment of massive menorrhagia caused by specific conditions, such as dysfunctional uterine bleeding, hypertension, and endocrine etiology, that is resistant to other therapies. Embolization has become a first-line treatment for symptomatic uterine fibroid . Therapeutic uterine artery embolization is a good treatment adjunct to control uterine bleeding and reduces the need for high -risk hysterectomy.UAE may help to avoid surgery in patients who are not good surgical candidates. Should menorrhagia recur in these patients, repeat embolization can be performed safely. Even in surgical candidates, UAE is effective in preparing the patient for elective rather than high-risk surgery. The goal of uterine fibroid embolisation is to stop blood flow to the uterus through the uterine arteries, thus depriving myomas of their blood supply to produce ischemic infarction . AIM OF THE STUDY: The purpose of the present study is to prospectively evaluate the accuracy of three-dimensional color doppler sonography in depicting changes in fibroid volume and vascularity of pre and post uterine artery embolisation in patients undergoing treatment of fibroid. CONCLUSION: From this study we have found that Uterine Artery Embolisation for the patients having symptomatic uterine fibroid is an effective and safe alternate treatment with significant reduction in volume and vascularity of fibroid particularly in less than 7 cm fibroids. Three dimensional color Doppler sonography assists in assessing the vascularity within the fibroid before and after embolisation. Single trans femoral approach with bilateral uterine arteries embolisation technique was used successfully in most of our patients. Combined PVA - Gelfoam is one of the ideal embolic agents effective in causing volume and vascularity reduction along with relief of the symptoms in patients with fibroid. Hypervascular fibroid respond well to embolisation . It has less failure rates in long term follow up. This procedure has good patient’s tolerance, short recovery time, quick and sustained symptomatic improvement. This procedure may reduce the need for invasive surgery in many patients. From this study we conclude that Three Dimensional Color Doppler Imaging can be a tool for pre and post UAE evaluation in assessing reduction in fibroid vascularity and volume. It is less expensive, more extensively available and provides an estimate of completeness of embolisation

Current Issues and Recent Advances in Pacemaker Therapy

Patients with implanted pacemakers or defibrillators are frequently encountered in various healthcare settings. As these devices may be responsible for, or contribute to a variety of clinically significant issues, familiarity with their function and potential complications facilitates patient management. This book reviews several clinically relevant issues and recent advances of pacemaker therapy: implantation, device follow-up and management of complications. Innovations and research on the frontiers of this technology are also discussed as they may have wider utilization in the future. The book should provide useful information for clinicians involved in the management of patients with implanted antiarrhythmia devices and researchers working in the field of cardiac implants