Computed Tomography of the Coronary Arteries

Non-invasive coronary computed tomography angiography (CCTA) has become an important tool for visualisation of coronary arteries since the introduction of 64-channel detector CCTA in 2004. It has been proved to be especially beneficial for ruling out coronary artery disease (CAD) in selected patient populations, due to the high negative predictive value (NPV). The aim of this thesis was to study some aspects of the introduction, establishment and development of a new method, retrospectively ECG-gated CCTA with 64-channel detector, to evaluate coronary arteries. In study I the diagnostic capacity and limitation of CCTA was compared to that of invasive coronary angiography (ICA) in a newly established CCTA team. CCTA had a very high NPV but the number of non-diagnostic scans was also high. The main limitations were motion artifacts and vessel calcifications, while short experience in reading CCTA did not affect image interpretation. Study II described the learning-curve effect of the interpretation of 100 CCTA and also compared the diagnostic accuracy of both radiologists and radiographers, after a common introduction. The review time for novices was approximately halved during the first 100 cases, with maintained diagnostic accuracy. There was a learning-curve effect in positive predictive value (PPV) for radiologists, but not for the radiographers. However, the diagnostic accuracy of dedicated radiographers indicated that they might be considered as part of the evaluation team. Study III compared the radiation exposure in retrospectively ECG-gated CCTA and ICA in the same population. Both mean estimated effective dose (ED) and organ doses (skin, breast, lung and oesophagus) were higher in CCTA when compared to ICA. The relatively high radiation dose to breast indicates that bismuth shielding should be used in women when performing CCTA. When using the updated tissue weighting factors provided in ICRP 103 the calculated ED from CCTA were significantly higher than those obtained using outdated ICRP 60. In study IV the image quality and radiation doses were compared when decreasing X-ray tube peak kilovoltage (kVp) from 120 to 100 kVp in patients undergoing CCTA. By reduction of tube voltage the radiation dose was almost halved while the diagnostic image quality was kept at a clinically acceptable level. In conclusion, CCTA is increasingly available throughout the world as an alternative to gold standard ICA, especially due to the excellent capability to rule out CAD. Still, retrospectively ECG-gated 64-channel detector CCTA has limitations such as motion artifacts and vessel calcifications. Another limitation is the high radiation doses required for CCTA compared to ICA. By lowering the kVp from traditionally 120 kVp to 100 kVp the radiation dose is halved while retaining diagnostic accuracy. There is a learning curve effect (regarded PPV and review time) of the interpretation of CCTA. However, more than 100 reviewed CCTA cases are necessary to reach a diagnostic accuracy that is acceptable

Late deflation study : hemodynamic effects of IAB timing in humans

Conventional IABP timing deflates 100% of the balloon volume before the onset of left ventricular ejection and has been well established in the literature as a safe and effective method. Yet, recent studies suggest that deflation of the IAB at or near the onset of systole improve myocardial efficiency (Kern, 1999, 1129). To test whether deflation of the JAB at a later deflation time reduces left ventricular workload and enhances coronary perfusion, four timing methods were evaluated in 20 patients: T1 (100% JAB volume deflated before onset of ejection), T2 (60% IAB volume deflated before and 40% volume during ejection), T3 (25% IAB volume deflated before and 75% volume during ejection) and T4 (100% deflation simultaneous with left ventricular ejection). To identify an optimal timing point for the deflation of the JAB, data was analyzed. Data analysis consisted of three main parts: elimination of files containing noise artifact, normalization of data for ease of analysis, and correction for variations in mean aortic pressure and heart rate which take into account the dynamic state of the heart. Late LAB deflation at 50% of the volume deflated prior to left ventricular ejection produced significantly greater percentage changes in systolic pressure time index (SPTI), diastolic pressure time index (DPTI), the SPTI/DPTI ratio, systemic vascular resistance (SVR) as compared to conventional timing, T1. No significant change in heart rate or cardiac output was established

Haemodynamic optimization of cardiac resynchronization therapy

Heart failure carries a very poor prognosis, unless treated with the appropriate pharmacological agents which, have been evaluated in large randomized clinical trials and have demonstrated improvements in morbidity and mortality of this cohort of patients. A significant proportion of these patients develop conduction abnormalities involving both the atrioventricular node and also the specialised conduction tissue (bundle of His and Purkinje fibers) of the ventricular myocardium which is most commonly evidenced by the presence of a wide QRS, typically left bundle branch block. The net effect of these conduction abnormalities is inefficient filling and contraction of the left ventricle. The presence of these conduction abnormalities is an additional strong marker of poor prognosis. Over the last 15 years pacing treatments have been developed aimed at mitigating the conduction disease. Large scale randomized multicentre trials have repeatedly demonstrated the effectiveness of cardiac pacing, officially recognized as cardiac resynchronization therapy (CRT). This mode of pacing therapy has undoubtedly had a positive impact on both the morbidity and mortality of these patients. Despite the large advancement in the management of heart failure patients by pacing therapies, a significant proportion of patients (30%) being offered CRT are classed as non-responders. Many explanations have been put forward for the lack of response. The presence of scar at the pacing site with failure to capture or delayed capture of myocardium, too much left ventricular scar therefore minimal contractile response, incorrect pacing site due to often limited anatomical options of lead placement and insufficient programming i.e optimization, of pacemaker settings such as the AV and VV delay are just some of the suggested areas perceived to be responsible for the lack of patients’ response to cardiac resynchronization therapy. The effect of optimization of pacemaker settings is a field that has been investigated extensively in the last decade. Disappointingly, current methods of assessing the effect of optimization of pacemaker settings on several haemodynamic parameters, such as cardiac output and blood pressure, are marred with very poor reproducibility, so measurement of any effect of optimization is close to being meaningless. Moreover, detailed understanding of the effects of CRT on coronary physiology and cardiac mechanoenergetics is equally, disappointingly, lacking. In this thesis, I investigated the acute effects of cardiac resynchronization therapy and AV optimization on coronary physiology and cardiac mechanoenergetics. This was accomplished using very detailed and demanding series of invasive catheterization studies. I used novel analytical mathematical techniques, such as wave intensity analysis, which have been developed locally and this provided a unique insight of the important physiological entities defining coronary physiology and cardiac mechanics. I explored in detail the application and reliability of photoplethysmography as a tool for non-invasive optimization of the AV delay. Photoplethysmography has the potential of miniaturization and therefore implantation alongside pacemaker devices. I compared current optimization techniques (Echocardiography and ECG) of VV delay against beat-to-beat blood pressure using the Finometer device and defined the criteria that a technique requires if such a technique can be used meaningfully for the optimization of pacemaker settings both in clinical practice and in clinical trials. Finally, I investigated the impact of atrial pacing and heart rate on the optimal AV delay and attempted to characterize the mechanisms underlying any changes of the optimal AV delay under these varying patient and pacing states. In this thesis I found that optimization of AV delay of cardiac resynchronization therapy not only improved cardiac contraction and external cardiac work, but also cardiac relaxation and coronary blood flow, when compared against LBBB. I found that most of the increase in coronary blood flow occurred during diastole and that the predominant drive for this was ventricular microcirculatory suction as evidenced by the increased intracoronary diastolic backward-travelling decompression wave. I showed that non-invasive haemodynamic optimization using the plethysmograph signal of an inexpensive pulse oximeter is as reliable as using the Finometer. Appropriate processing of the oximetric signal improved the reproducibility of the optimal AV delay. The advantage of this technology is that it might be miniaturized and implanted to provide automated optimization. In this thesis I found that other commonly used modalities of VV optimization such as echocardiography and ECG lack internal validity as opposed to non-invasive haemodynamic optimization using blood pressure. This finding will encourage avoidance of internally invalid modalities, which may cause more harm than good. In this thesis I found that the sensed and paced optimal AV delays have, on average, a bigger difference than the one assumed by the device manufacturers and clinicians. As a significant proportion of patients will be atrially paced, especially during exercise, optimization during this mode of pacing is equally crucial as it is during atrial sensing. Finally, I found that the optimal AV delay decreases with increasing heart rate, and the slope of this is within the range of existing pacemaker algorithms used for rate adaptation of AV delay, strengthening the argument for the rate adaptation to be programmed on.Imperial Users Onl

Preclinical Efficacy of an Epicardial Heart Assist Device

Of the millions of Americans with heart failure, a significant portion are end-stage and experience symptoms even at rest. Moreover, around half of people with heart failure die within 5 years of diagnosis. The ideal treatment option for these patients is a heart transplant. However, fewer than 3000 donor hearts are available for transplant in North America each year. Given the significant disparity in number of donor hearts and end-stage failure patients, there is great clinical need for heart assist technology that supports heart function, and for improved approaches that lead to heart recovery. The current leading device therapy for advanced heart failure patients is a Ventricular Assist Device (VAD). While these devices have been clinically available in the United States since 2003, they are associated with severe complications – including a high risk for stroke and gastrointestinal bleeding. As an alternative to mechanical blood pumps, direct cardiac compression (DCC) devices have been developed for heart assist. The investigation described herein includes the development, simulation, and preclinical testing of a novel DCC device – coined the EpicHeart™ (Epicardial Heart Assist Device). First, engineering design improvements were required to allow for synchronization between device activation and the native contraction of the heart. The methods to accomplish this goal are described with results of in vivo testing. Then, the hemodynamic effects of the device in an acute heart failure model were investigated. Finally, the results of the in vivo testing of the device were applied for technical specification verification of a simulation platform developed to model the clinical effects of the EpicHeart™ Device. The outcomes of this study have yielded an improved preclinical medical device that will proceed with future investigations over longer study durations as well as other heart failure etiologies – while continuing to explore potential for heart recovery. Additionally, the pilot study of simulating this technology is unique and has provided support for future validation of a clinical simulation tool. This simulation is anticipated for use in a clinical environment to predict patient outcomes of the EpicHeart™ Device for treatment of heart disease

Preclinical Efficacy of an Epicardial Heart Assist Device

Of the millions of Americans with heart failure, a significant portion are end-stage and experience symptoms even at rest. Moreover, around half of people with heart failure die within 5 years of diagnosis. The ideal treatment option for these patients is a heart transplant. However, fewer than 3000 donor hearts are available for transplant in North America each year. Given the significant disparity in number of donor hearts and end-stage failure patients, there is great clinical need for heart assist technology that supports heart function, and for improved approaches that lead to heart recovery. The current leading device therapy for advanced heart failure patients is a Ventricular Assist Device (VAD). While these devices have been clinically available in the United States since 2003, they are associated with severe complications – including a high risk for stroke and gastrointestinal bleeding. As an alternative to mechanical blood pumps, direct cardiac compression (DCC) devices have been developed for heart assist. The investigation described herein includes the development, simulation, and preclinical testing of a novel DCC device – coined the EpicHeart™ (Epicardial Heart Assist Device). First, engineering design improvements were required to allow for synchronization between device activation and the native contraction of the heart. The methods to accomplish this goal are described with results of in vivo testing. Then, the hemodynamic effects of the device in an acute heart failure model were investigated. Finally, the results of the in vivo testing of the device were applied for technical specification verification of a simulation platform developed to model the clinical effects of the EpicHeart™ Device. The outcomes of this study have yielded an improved preclinical medical device that will proceed with future investigations over longer study durations as well as other heart failure etiologies – while continuing to explore potential for heart recovery. Additionally, the pilot study of simulating this technology is unique and has provided support for future validation of a clinical simulation tool. This simulation is anticipated for use in a clinical environment to predict patient outcomes of the EpicHeart™ Device for treatment of heart disease

Review of journal of cardiovascular magnetic resonance 2010

There were 75 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2010, which is a 34% increase in the number of articles since 2009. The quality of the submissions continues to increase, and the editors were delighted with the recent announcement of the JCMR Impact Factor of 4.33 which showed a 90% increase since last year. Our acceptance rate is approximately 30%, but has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. Last year for the first time, the Editors summarized the papers for the readership into broad areas of interest or theme, which we felt would be useful to practitioners of cardiovascular magnetic resonance (CMR) so that you could review areas of interest from the previous year in a single article in relation to each other and other recent JCMR articles [1]. This experiment proved very popular with a very high rate of downloading, and therefore we intend to continue this review annually. The papers are presented in themes and comparison is drawn with previously published JCMR papers to identify the continuity of thought and publication in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication

Southwest Research Institute assistance to NASA in biomedical areas of the technology

Significant applications of aerospace technology were achieved. These applications include: a miniaturized, noninvasive system to telemeter electrocardiographic signals of heart transplant patients during their recuperative period as graded situations are introduced; and economical vital signs monitor for use in nursing homes and rehabilitation hospitals to indicate the onset of respiratory arrest; an implantable telemetry system to indicate the onset of the rejection phenomenon in animals undergoing cardiac transplants; an exceptionally accurate current proportional temperature controller for pollution studies; an automatic, atraumatic blood pressure measurement device; materials for protecting burned areas in contact with joint bender splints; a detector to signal the passage of animals by a given point during ecology studies; and special cushioning for use with below-knee amputees to protect the integrity of the skin at the stump/prosthesis interface

Multislice computed tomography coronary angiography

__Abstract__ Computed Tomography (CT) imaging is also known as "CAT scanning" (Computed Axia

Reversed septal curvature is associated with elevated troponin level in hypertrophic cardiomyopathy

The aim of study was to compare patients with hypertrophic cardiomyopathy divided according to septal configuration assessed in a 4-chamber apical window. The study group consisted of 56 consecutive patients. Reversed septal curvature (RSC) and non-RSC were diagnosed in 17 (30.4%) and 39 (69.6%) patients, respectively. Both RSC and non-RSC groups were compared in terms of the level of high-sensitivity troponin I (hs-TnI), NT-proBNP (absolute value), NT-proBNP/ULN (value normalized for sex and age), and echocardiographic parameters, including left ventricular outflow tract gradient (LVOTG). A higher level of hs-TnI was observed in RSC patients as compared to the non-RSC group (102 (29.2-214.7) vs. 8.7 (5.3-18) (ng/l), p=0.001). A trend toward increased NT-proBNP value was reported in RSC patients (1279 (367.3-1186) vs. 551.7 (273-969) (pg/ml), p=0.056). However, no difference in the NT-proBNP/ULN level between both groups was observed. Provocable LVOTG was higher in RSC as compared to non-RSC patients (51 (9.5-105) vs. 13.6 (7.5-31) (mmHg), p=0.04). Furthermore, more patients with RSC had prognostically unfavourable increased septal thickness to left LV diameter at the end diastole ratio. Patients with RSC were associated with an increased level of hs-TnI, and the only trend observed in this group was for the higher NT-proBNP levels. RSC seems to be an alerting factor for the risk of ischemic events. Not resting but only provocable LVOTG was higher in RSC as compared to non-RSC patients

3D Imaging for Planning of Minimally Invasive Surgical Procedures

Novel minimally invasive surgeries are used for treating cardiovascular diseases and are performed under 2D fluoroscopic guidance with a C-arm system. 3D multidetector row computed tomography (MDCT) images are routinely used for preprocedural planning and postprocedural follow-up. For preprocedural planning, the ability to integrate the MDCT with fluoroscopic images for intraprocedural guidance is of clinical interest. Registration may be facilitated by rotating the C-arm to acquire 3D C-arm CT images. This dissertation describes the development of optimal scan and contrast parameters for C-arm CT in 6 swine. A 5-s ungated C-arm CT acquisition during rapid ventricular pacing with aortic root injection using minimal contrast (36 mL), producing high attenuation (1226), few artifacts (2.0), and measurements similar to those from MDCT (p\u3e0.05) was determined optimal. 3D MDCT and C-arm CT images were registered to overlay the aortic structures from MDCT onto fluoroscopic images for guidance in placing the prosthesis. This work also describes the development of a methodology to develop power equation (R2\u3e0.998) for estimating dose with C-arm CT based on applied tube voltage. Application in 10 patients yielded 5.48┬▒177 2.02 mGy indicating minimal radiation burden. For postprocedural follow-up, combinations of non-contrast, arterial, venous single energy CT (SECT) scans are used to monitor patients at multiple time intervals resulting in high cumulative radiation dose. Employing a single dual-energy CT (DECT) scan to replace two SECT scans can reduce dose. This work focuses on evaluating the feasibility of DECT imaging in the arterial phase. The replacement of non-contrast and arterial SECT acquisitions with one arterial DECT acquisition in 30 patients allowed generation of virtual non-contrast (VNC) images with 31 dose savings. Aortic luminal attenuation in VNC (32┬▒177 2 HU) was similar to true non-contrast images (35┬▒177 4 HU) indicating presence of unattenuated blood. To improve discrimination between c