Current challenges and future directions for liver transplantation

Liver transplantation is an effective and widely used therapy for several patients with acute and chronic liver diseases. The discrepancy between the number of patients on the waiting list and available donors remains the key issue and is responsible for the high rate of waiting list mortality. The recent news is that the majority of patients with hepatitis C virus related liver disease will be cured by new antivirals therefore we should expect soon a reduction in the need of liver transplantation for these recipients. This review aims to highlight, in two different sections, the main open issues of liver transplantation concerning the current and future strategies to the best use of limited number of organs. The first section cover the strategies to increase the donor pool, discussing the use of older donors, split grafts, living donation and donation after cardiac death and mechanical perfusion systems to improve the preservation of organs before liver transplantation. Challenges in immunosuppressive therapy and operational tolerance induction will be evaluated as potential tools to increase the survival in liver transplant recipients and to reducing the need of re‐transplantation. The second section is devoted to the evaluation of possible new indications to liver transplantation, where the availability of organs by implementing the strategies mentioned in the first section and the reduction in the number of waiting transplants for HCV disease is realized. Among these new potential indications for transplantation, the expansion of the Milan criteria for hepatocellular cancer is certainly the most open to question.     

Current challenges and future directions in cardiac imaging

Imaging is one of the most important accomplishments of medicine during the last 1000 years. The contribution of modern imaging to progress in the delivery of health care is unquestioned. However, we need to refine our use of imaging, limiting its use to those occasions when it can contribute directly or indirectly to improving and lengthening the lives of patients. Technology prowess in imaging alone is not sufficient to deliver value to individuals or to society. Continued investment in imaging technology requires critical appraisal of its use in clinical decision making and patient outcomes.KEYWORDS: Medical imaging, Multimodality imaging, Comparative effectiveness, Cost-effective care, Outcomes researchAt the beginning of the 21st century, the editors of the New England Journal named medical imaging as one of the 10 most important developments in all of medicine during the preceding 1000 years (Anon., 2000). Imaging of the cardiovascular system is barely a century old, beginning with the discovery of X-rays in the early 20th century. Mason Sones’ pursuit of coronary arteriography in the 1960s (Sones and Shirey, 1962) led directly to the development of coronary bypass surgery and percutaneous coronary intervention and thrombolytic therapy, fundamentally impacting the practice of cardiology around the world. Echocardiography (Edler, 1966; Feigenbaum et al., 1965) and nuclear cardiology (Wagner, 1974), also introduced to clinical cardiology in the 1960s, revolutionized the evaluation of structural heart disease and myocardial ischemia. As these methods continue to be refined and popularized additional imaging methods including cardiac magnetic resonance imaging¹ and cardiovascular computed tomographic angiography (Min et al., 2010) have vastly improved our ability to image various manifestations of cardiovascular disease with ever increasing sophistication.Cardiovascular disease is the most common cause of death worldwide, and an important focus for medical imaging. Our understanding of the fundamental pathophysiologic mechanisms underlying acute coronary syndrome and myocardial infarction continues to evolve in concert with the development of new and better means for assessing these abnormalities. Imaging has had a central role in improving our ability to recognize, characterize and successfully treat coronary artery disease. Cardiac catheterization with coronary arteriography and adjunctive techniques including intravascular ultrasound, ocular coherence tomography, and measurement of local temperature and PH within the heart have not only allowed development of the entire field of surgical and percutaneous coronary revascularization and thrombolytic therapy, but is leading to an improved understanding of the mechanisms of ischemic heart disease and development of better preventive and pharmacologic strategies.The diagnostic and prognostic accuracy of ECG stress testing was vastly improved by the addition of concomitant nuclear or ultrasound imaging. The use of metabolically active tracers allowed better understanding of coronary artery disease at the cellular level, just as sophisticated ultrasound and magnetic resonance tools have revealed many of the mechanical, structural and hemodynamic alterations resulting from acute and chronic macro- as well as micro-vascular coronary syndromes. Imaging techniques can be used to study coronary arterial plaques. These plaques have thrombogenic potential and are manifestations of atherosclerosis, a systemic disease affecting the vessel wall which is generally believed to be the primary cause of many of the other myriad manifestations of coronary artery disease (Fayad et al., 2002; Ambrose, 2008). Non-invasive imaging holds the promise to not only identify flow limiting coronary stenosis (Meijboom et al., 2008), but to also detect calcified and non-calcified plaque, measure atherosclerotic plaque burden and its response to treatment, and to differentiate stable plaques from those which are prone to rupture (Kitagawa et al., 2009; Takumi et al., 2007). These expectations have not yet been met (Nissen, 2008).Technologic progress in computed tomography has led to the ability to non-invasively visualize the epicardial coronary arteries with spatial and temporal resolution approaching that of invasive angiography. However, we know that high resolution angiography alone is often insufficient to differentiate flow limiting from non-flow limiting stenosis (Tonino et al., 2009; Joshi et al., 2009). Indeed, current cardiovascular nuclear and echocardiographic imaging techniques affect outcomes due to their ties with medical, percutaneous or surgical interventions. Thus, considerable attention is being focused on using CT to provide physiologic myocardial perfusion information downstream from a stenosis, much like fractional flow reserve is used in the catheterization laboratory or stress perfusion imaging in the nuclear, echocardiography or cardiovascular MR laboratories (Ambrose, 2008). We need functional as well as anatomic data to guide therapy. In a different direction, CT (Cheng et al., 2009) CMR, and other methods are being developed to better characterize the nature of atherothrombotic plaque, the cause of both flow limiting stable coronary stenosis, and, when a plaque ruptures or erodes, acute coronary occlusion and myocardial infarction.Crucial to this work is validation of the ability of non-invasive imaging to delineate physiologically relevant structural features of atherothrombotic plaque. Histology, the a priori gold standard, is limited in its ability to characterize the evanescent nature of the atherothrombotic process; post-mortem examination of histologic sections represents only a limited snapshot of the overall pathologic process. Nevertheless, these ex vivo histologic observations do serve to remind us of the resolution of both 40 MHz ultrasound and 64-slice CT in failing to depict the microstructure of plaque.Several other methods for in vivo interrogation of atherothrombotic plaque promise new insights into the pathophysiology of acute coronary syndromes, and could be superior not only to intravascular ultrasound and 64-detector CT, but also to conventional histologic analysis. Thermography, fluorescence imaging, nuclear imaging, magnetic resonance imaging, optical coherence tomography and near-infrared spectroscopy all have unique applications in detecting and characterizing plaque (Cheng et al., 2009; Waxman et al., 2009). In these efforts to detect and characterize plaque, it will be important to integrate morphologic and rheologic information with a patient’s overall state of coagulation and inflammation. Imaging will continue to play a central role in the investigation of the atherothrombotic process and development of new treatments for patients with coronary arterial disease. Adoption of any of these techniques for clinical use in individual patients awaits clinical trials in which plaque imaging is shown to lead to better risk stratification, identification of manifest disease and application or alteration of effective therapy (Matter and Stuber, 2009).Similar progress has also been made in applying new imaging technology to valvular, myocardial and congenital heart diseases. Ultrasound, nuclear imaging, magnetic resonance and computed tomography have all grown enormously, both in their contribution to our understanding of cardiovascular disease and in their cost to the health care system. In many regards, we have become victims of our own success. Patients and referring physicians alike have come to expect that imaging will be performed in nearly any circumstance, and many of us have been seduced by spectacular cardiovascular images to believe that imaging is an endpoint, in and of itself, rather than a means to a more meaningful end – making patients feel better, function better and live longer.As cardiac imaging has become more complex and more widely utilized, the costs of medical health care have risen dramatically. The costs of imaging have grown faster than other areas of health care, faster than costs of non-medical services, and faster than the economy has expanded, threatening our ability as a society to pay for these wondrous imaging procedures. While a picture may still be worth a thousand words, there is now widespread recognition that unbridled expansion of imaging services does not lead to better health. We have entered an era when a beneficial outcome must be documented for nearly everything we do, so that we may make informed decisions on how to spend our limited resources on health care (Douglas et al., 2009).We clinical imagers are now challenged not only to continue pursuing creative technical and engineering advances in our imaging procedures, but to also steer these developments toward improving patient outcomes. It is necessary but not sufficient to produce excellent quality images of the highest technical quality; reporting the results accurately and efficiently. We must also produce clinically actionable answers to clinically actionable and relevant questions in fiscally responsible and cost effective manner. We clinicians must lead the charge to use imaging discriminately, using the right procedure at the right time, for the right reason – the patients’ benefit (Shaw et al., 2010; Bove, 2009; Hackbarth et al., 2008).Imaging has obvious value in detecting and identifying disease early in its course, and in directing appropriate and effective prevention and treatment. Imaging can help measure the progression of disease, identifying ineffective treatments and helping to identify newer and better treatments. Imaging is increasingly an inseparable part of interventional cardiology and cardiovascular surgery, helping plan and monitor treatment, avoiding complications and defining “success”. Echocardiographic equipment is no longer restricted to the echocardiography laboratory, but is seamlessly integrated into the cardiac interventional laboratory and operating theater. Computed tomography is no longer restricted to the radiology department, but is integrated into the cath and nuclear labs, the electrophysiology lab and the emergency room.In this era of evidence-based medicine with emphasis on “real life” outcomes, we must show that an imaging procedure produces new, non-redundant information which clinicians can confidently use to make meaningful decisions regarding patient care, care that actually improves the patients well being, functional status and longevity. The ideal imaging procedure would help improve patients’ quality of life by affecting therapeutic choices and would be robust in diverse clinical environments, not limited to highly specialized units. The test should be definitive, not leading to further testing to resolve uncertainty, nor to pursuit of unrelated, incidental findings of uncertain clinical importance. The imaging procedure itself should also have a better benefit to risk ratio for a particular patient. Radiation exposure, if any, should be monitored and minimized. And having achieved all these lofty goals, an imaging procedure should also be cost-effective, delivering value to the individual and to society comparable to the value of other goods and services.We need to train new imaging physicians who are knowledgeable in applying multiple imaging modalities to a given patient’s problem and to think critically in evaluating the resulting information correctly into clinical decision making (Kosiborod and Spertus, 2009). Not all new modalities and new applications work as well in widespread clinical practice as they do in small numbers of patients in specialized luminary sites. To wit, use of tissue Doppler to select patients for cardiac resynchronization and use of proximal isovelocity area measurements to quantify the degree of mitral regurgitation turn out to be poorly reproducible in the clinical setting and not as useful in practice as was originally thought based on technical considerations and logic alone (Popovic and Thomas, 2008; Biner et al., 2010). We also need to recognize that existing “gold standards” are not good enough, and not be satisfied simply inventing new methods that produce results that resemble existing data. For instance, intra-arterial coronary angiography may be the existing gold standard for diagnosing coronary artery disease, but assessing the degree of obstruction by visual or even quantitative evaluation of angiograms, either intra-arterial or by CTA, does not compare well with a better gold standard – assessment of fractional flow reserve (Tonino et al., 2009; Schoepf et al., 2007).Both we and our patients are enamored with technology. Our expectations of advanced imaging technology do not always match the real value delivered. If we are to be able to afford to offer truly useful imaging to our patients, we must be willing to look at our offerings critically, eliminating waste, duplication and unneeded testing. Cardiovascular imaging is robust. We can withstand critical appraisal of our field, and will be strengthened by refocusing our efforts to use technology in a more thoughtful manner. We have enjoyed almost unbridled access to technologic improvements in cardiovascular imaging over the past 50 years. Future developments in imaging need not be constrained by emphasis on evidence of beneficial outcomes if we stay focused on the patient. In the words of Helen Keller, blind and deaf author, lecturer and social activist, “The only thing worse than being blind is having sight but no vision”.     

Estimation performance of a reduced lead system during continuous 12-lead ECG ST-segment monitoring

Background

Reduced lead systems utilizing patient-specific transformation weights have been reported to achieve superior estimates than those utilizing population-based transformation weights. We report upon the effects of ischemic-type electrocardiographic changes on the estimation performance of a reduced lead system when utilizing patient-specific transformation weights and population-based transformation weights.

Method

A reduced lead system that used leads I, II, V2 and V5 to estimate leads V1, V3, V4, and V6 was investigated. Patient-specific transformation weights were developed on electrocardiograms containing no ischemic-type changes. Patient-specific and population-based transformations weights were assessed on 45 electrocardiograms with ischemic-type changes and 59 electrocardiograms without ischemic-type changes.

Results

For patient-specific transformation weights the estimation performance measured as median root mean squared error values (no ischemic-type changes vs. ischemic-type changes) was found to be (V1, 27.5 μV vs. 95.8 μV, P<.001; V3, 33.9 µV vs. 65.2 µV, P<.001; V4, 24.8 μV vs. 62.0 μV, P<.001; V6, 11.7 μV vs. 51.5 μV, P<.001). The median magnitude of ST-amplitude difference 60 ms after the J-point between patient-specific estimated leads and actual recorded leads (no ischemic-type changes vs. ischemic-type changes) was found to be (V1, 18.9 μV vs. 61.4 μV, P<.001; V3, 14.3 μV vs. 61.1 μV, P<.001; V4, 9.7 μV vs. 61.3 μV, P<.001; V6, 5.9 μV vs. 46.0 μV, P<.001).

Conclusion

The estimation performance of patient-specific transformations weights can deteriorate when ischemic-type changes develop. Performance assessment of patient-specific transformation weights should be performed using electrocardiographic data that represent the monitoring situation for which the reduced lead system is targeted.     

Significance of lead aVR in acute coronary syndrome

The 12-lead electrocardiogram(ECG)is a crucial tool in the diagnosis and risk stratification of acute coronary syndrome(ACS).Unlike other 11 leads,lead aVR has been long neglected until recent years.However,recent investigations have shown that an analysis of ST-segment shift in lead aVR provides useful information on the coronary angiographic anatomy and risk stratification in ACS.ST-segment elevation in lead aVR can be caused by(1)transmural ischemia in the basal part of the interventricular septum caused by impaired coronary blood flow of the first major branch originating from the left anterior descending coronary artery;(2)transmural ischemia in the right ventricular outflow tract caused by impaired coronary blood flow of the large conal branch originating from the right coronary artery;and(3)reciprocal changes opposite to ischemic or non-ischemic ST-segment depression in the lateral limb and precordial leads.On the other hand,ST-segment depression in lead aVR can be caused by transmural ischemia in the inferolateral and apical regions.It has been recently shown that an analysis of T wave in lead aVR also provides useful prognostic information in the general population and patients with prior myocardial infarction.Cardiologists should pay more attention to the tracing of lead aVR when interpreting the12-lead ECG in clinical practice.     

Reconstruction of the 12-lead electrocardiogram from reduced lead sets

In clinical practice, continuous recording of all leads of the 12-lead electrocardiogram (ECG) is often not possible. We wanted to assess how well absent, noisy, or defective leads can be reconstructed from different lead subsets and how well lead reconstruction performs over time. A data set of 234 24-hour ECG recordings was divided into an equally sized training and test set. Precordial leads were systematically removed, and for all lead subsets including both limb leads and at least one precordial lead, the absent leads were reconstructed using general and patient-specific reconstruction templates. Reconstruction performance was measured by correlation between the original and reconstructed leads over the QRS and T waves, by average and maximum absolute ST differences, and by agreement when a clinical decision rule was applied. Reconstruction performance over time was evaluated at baseline, at 20 minutes, and 1, 6, 12 and 24 hours after the start of each recording. Reconstruction accuracy was high (correlation > or =0.932, average ST difference < or =30 microV, agreement > or =94.9%) with general reconstruction for lead sets with 1 or 2 precordial leads removed but was less satisfactory when more leads were missing. Patient-specific reconstruction performed well when up to 4 precordial leads were removed (correlation > or =0.967, average ST difference < or =26 microV, agreement > or =95.7%). Patient-specific reconstruction performance initially slightly decreased and then stabilized over time but remained much better than general reconstruction after 24 hours. Accurate reconstruction of the 12-lead ECG from lead subsets is possible over time. General reconstruction allows reconstruction of 1 or 2 precordial leads, whereas up to 4 leads can be reconstructed well using patient-specific reconstruction.     

Determinants of ST-segment level in lead aVR in anterior wall acute myocardial infarction with ST-segment elevation

Background

This study aimed to clarify the determinants of ST-segment level in lead aVR in anterior wall acute myocardial infarction (AAMI).

Methods

We analyzed ST-segment levels in all 12 leads on admission and emergency coronary angiographic findings in 261 patients with a first AAMI with ST-segment elevation. The length of the left anterior descending coronary artery (LAD) was classified as follows: short = not reaching the apex; medium = perfusing less than 25% of the inferior wall; long = perfusing 25% or more of the inferior wall.

Results

The ST-segment level in lead aVR correlated significantly with the ST-segment levels in leads I, II, III, aVF, V₁, and V_3-6, especially with those in leads II and V₆ (r = −0.63, P < .001; r = −0.61, P < .001; respectively). Patients with a proximal LAD occlusion had a greater ST-segment level in lead aVR than those with a distal LAD occlusion (P < .001). Patients with a long LAD had a lower ST-segment level than those with a short or medium LAD (P < .05).

Conclusions

The ST-segment levels, especially in leads II and V₆, the site of the LAD occlusion, and the length of the LAD affect the ST-segment level in lead aVR in ST-segment elevation AAMI.     

Evaluation of lead selection methods for optimal reconstruction of body surface potentials

In this study, several methods for optimal lead selection from multilead electrocardiographic recordings are analyzed. Two different lead selection methods have been implemented. For their evaluation, a linear transformation that reconstructs nonselected leads from selected leads is computed according to the least squares optimization, and the performance is evaluated in terms of the mean square error of the derived potentials and correlation. The algorithms were tested on a database of 72 body surface potential recordings: 18 controls, 18 bundle-branch block, 18 myocardial infarction, and 18 ventricular hypertrophy. Each data set was divided into a study and test subsets. Two experiments were carried out: (1) The lead selection, transformation matrix, and performance evaluation is carried out over the test data set (ideal case), and (2) the lead selection and transformation matrix is carried out over the study data set, but the performance is evaluated over the test data set (real case).Our results show important reconstruction errors with either lead selection methods, and only increasing the number of leads reduces the error in reconstruction. However, if a reduced number of leads are to be selected outside the standard 12-lead electrocardiogram, the method proposed by Lux has been shown to be the best option.     

Current status, challenges and future directions of drug-eluting balloons

For the past 30 years, contemporary coronary and endovascular interventions utilized balloon catheters, bare metal- and drug-eluting stents (DES) to recanalize narrowed vessels. Despite this, the quest for outcome optimization is ongoing for specific lesions and patients. Drug-eluting balloons (DEBs) are among the latest technologies proposed to overcome the limitations of DES, such as stent thrombosis and the dependency on long-term dual antiplatelet therapy. In the large part, DEBs were introduced as a substitute for DES in the treatment of in-stent restenosis and perhaps in certain de novo lesion subsets. DEBs have been tested in several clinical scenarios with encouraging preliminary results. This article will discuss the rationale for developing DEBs, basic concepts and available DEB platforms, along with preclinical studies and clinical experience to support the use of this new technology for endovascular interventions.     

Vaccination against hepatitis B: current challenges for Asian countries and future directions

AIMS: To review the current status of hepatitis B immunization programmes as well as future issues concerning hepatitis B immunization in Asian countries. METHODS: Pertinent literature was identified via in-house and MEDLINE (1980-99) searches and references cited in published articles. Articles within the Proceedings of the IX Triennial International Symposium on Viral Hepatitis and Liver Disease provided valuable state-of-the-art resource data. RESULTS: Chronic hepatitis B infection is responsible for 75-90% of primary hepatocellular carcinoma, one of the 10 most common cancers worldwide. Hepatitis B and its chronic sequelae can potentially be eradicated through vaccines that have been shown to be 95-99% efficacious in preventing development of the disease or the carrier state in immunized infants. Approximately 75% of the world's hepatitis B carriers live in Asian countries wherein wide variations in immunization strategies exist. Vaccination programmes in hyperendemic Asian countries have elicited decreases in the incidence of acute and chronic infections as well as a decrease in chronic carriers in the unvaccinated population. Decreases in the incidence of hepatocellular carcinoma have been recorded in Taiwan and Singapore after at least 10 years of universal hepatitis B immunization programmes. CONCLUSIONS: In Asian countries currently without nationwide hepatitis B programmes, utilization of the existing vaccination infrastructure for administration of other World Health Organization Expanded Programme on Immunization vaccines will provide the most economical and efficient means of administration of the hepatitis B vaccine.     

Significance of a prominent Q wave in lead negative aVR (−aVR) in acute anterior myocardial infarction

Purpose

The aim of this study was to clarify the significance of a Q wave in lead negative aVR (−aVR) in anterior wall acute myocardial infarction (AMI).

Methods

Eighty-seven patients with a first anterior wall AMI were classified into 2 groups according to the presence (n = 17, group A) or absence (n = 70, group B) of a prominent Q wave (duration ≥20 milliseconds) in lead −aVR at predischarge. Group A had a higher prevalence of a long left anterior descending coronary artery (LAD), a lower left ventricular ejection fraction, and more reduced regional wall motion in the apical and inferior regions than group B. None of group A patients had an LAD that did not reach the apex.

Conclusion

A prominent Q wave in lead −aVR in anterior wall AMI is related to severe regional wall motion abnormality in the apical and inferior regions, with an LAD wrapping around the apex.     

Mechanical circulatory support in children: Strategies,challenges and future directions

IntroductionThe use of mechanical circulatory support (MCS) in the pediatric population has evolved significantly in the past 20 years, but its management still poses several challenges. We aim to describe patient characteristics, outcomes, and morbidity associated with different modalities of MCS, in a tertiary center.MethodsRetrospective analysis of data from all the children who underwent MCS between 2002 and 2018 at a pediatric cardiology unit.ResultsBetween 2002 and 2018, 22 devices were implanted in 20 patients. Patients were divided into three groups: Group A (n=11) extracorporeal membrane oxygenator (ECMO); Group B (n=8) pulsatile paracorporeal ventricular assist device (VAD) and group C (n=3) paracorporeal continuous flow VAD.The median age was similar in groups A and B (18 and 23 months, respectively), and higher in group C (13 years). ECMO patients were cannulated mainly as a bridge to recovery (post cardiotomy- 8) while group B and C patients were bridged to transplantation. The most frequent complications were bleeding (group A - 36%, group C - 66.6%) and thromboembolic events (group B - 50%, group C - 33.3%).As for outcomes, in group A the majority of patients (54.5%) were weaned and 27.3% died. Half of group B and all of group C patients underwent transplantation.ConclusionBleeding and thromboembolic events were the main complications observed. Group B showed the highest mortality, probably related to the low weight of the patients. Overall, outcomes and complications are related to the type of device and patient status and characteristics.     

Pharmacotherapy for the management of achalasia: Current status,challenges and future directions

This article reviews currently available pharmacological options available for the treatment of achalasia, with a special focus on the role of botulinum toxin(BT) injection due to its superior therapeutic effect and side effect profile. The discussion on BT includes the role of different BT serotypes, better pharmacological formulations, improved BT injection techniques, the use of sprouting inhibitors, designer recombinant BT formulations and alternative substances used in endoscopic injections. The large body of ongoing research into achalasia and BT may provide a stronger role for BT injection as a form of minimally invasive, cost effective and efficacious form of therapy for patients with achalasia. The article also explores current issues and future research avenues that may prove beneficial in improving the efficacy of pharmacological treatment approaches in patients with achalasia.     

Interpreting device diagnostics for lead failure

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将AVR导联作为常规多导心电图的节律导联在心律失常诊断中意义的探讨

目的探讨将aVR导联作为常规多导联心电图的节律导联在心律失常诊断中的价值。方法收集我院自2007年1月至2009年7月间收治心律失常患者1874例,均设置aVR导联为节律导联之一进行常规多导心电图检查,结合心内电生理检查结果进行对比分析,观察aVR导联在基本心律起源的诊断及各型心律失常的鉴别诊断中的作用。结果各型心律失常(各类早搏1119例,房颤并宽QRS波87例,室上速59例,宽QRS心动过速29例,各类逸搏273例,其他307例)均可由aVR导联记录并准确定位。结论将aVR导联替代II导联作为常规多导联心电图的节律导联用于分析基本心律起源和心律失常起源更合理。     

aVR导联在急性肺栓塞中的意义

目的探讨aVR导联在急性肺栓塞中的意义。方法入选的42名患者，入院就诊时的发病时间为3h～1周，查心肌酶、肌钙蛋白定量等排除急性心肌梗死。根据其临床表现、心电图、超声心动图、肺灌注扫描等确诊为肺动脉栓塞的患者。观察溶栓前（入院时）、溶栓后2周内心电图的动态改变，做超声心动图（是否存在肺动脉高压）、肺灌注扫描（溶栓前后对比），观察疗效及12导联心电图的改变。结果（1）入院时情况：心动过速37例（88，1％），aVR ST段抬高26例（61．9％），肺动脉高压39例（92．9％），SⅠQⅢTⅢ13例（31．0％），V1～V3T波倒置23例（54．8％），行肺灌注扫描可见到肺动脉血栓形成42例；（2）溶栓后2周：心动过速3例（7，3％），aVRST段抬高5例（12．2％），SⅠQⅢTⅢ3例（7．3％），V1～V3T波倒置2例（4．9％），肺动脉高压6例（14．6％），肺灌注扫描可见到肺动脉血栓9例（22.0％）。结论心电图改变有些虽然是非特异性的，但其能特异性地反映肺动脉高压的改变，尤其aVR导联，可以观察溶栓效果，心电图对于肺动脉栓塞评价疗效与预后的价值也许更重于诊断价值。     

Patient Alert to detect ICD lead failure: efficacy, limitations, and implications for future algorithms.

AIMS: An algorithm that alerts implantable cardioverter-defibrillator (ICD) patients, in case of abnormal lead impedance (Patient Alerttrade mark, Medtronic), may help to recognize lead dysfunction. We aimed to determine the utility of Patient Alert for ICD lead-failure detection in a prospective study. METHODS AND RESULTS: Three hundred and sixty ICD patients were followed for 22+/-14 months. Patient Alert was active for pacing impedance <200 and >2000-3000 Omega, and high-voltage conductor impedance <10-20 and >200 Omega. Ten alert events and a total of 29 severe system complications occurred. Patient Alert detected three of 10 ICD lead failures, with a positive predictive value (PPV) of 77.8% for any severe system complication. Retrospective analysis identified 23 patients with a sensing integrity counter (SIC) >300 and revealed an additional four prior undetected lead defects. SIC detected ICD lead failure with 92.9% sensitivity and a PPV of 59.1%. Eight of nine patients with a false-positive SIC had an integrated bipolar lead. Patient Alert combined with SIC detected all ICD lead failures and 71.4% of all severe lead complications. CONCLUSIONS: Patient Alert, based on daily lead-impedance measurement, detected one-third of all ICD lead failures. Combined use with continuous lead integrity monitoring (SIC) increased sensitivity to 100%. Integrated bipolar leads may yield a false-positive SIC. Incorporating SIC and automated pace/sense threshold measurement may improve Patient Alert sensitivity for severe lead complications.     

On designing and testing transformations for derivation of standard 12-lead/18-lead electrocardiograms and vectorcardiograms from reduced sets of predictor leads

The aim of this study was to develop and evaluate transformation coefficients for deriving the standard 12-lead electrocardiogram (ECG), 18-lead ECG (with additional leads V7, V8, V9, V3R, V4R, V5R), and Frank vectorcardiogram (VCG) from reduced lead sets using 3 “limb” electrodes at Mason-Likar torso sites combined with 2 chest electrodes at precordial sites V1 to V6; 15 such lead sets exist and each can be recorded with 6-wire cable. As a study population, we used Dalhousie Superset (n = 892) that includes healthy subjects, postinfarction patients, and patients with a history of ventricular tachycardia. For each subject, 120-lead ECG recordings of 15-second duration were averaged, and all samples of the QRST complex for leads of interest were extracted; these data were used to derive—by regression analysis—general and patient-specific coefficients for lead transformations. These coefficients were then used to predict 12-lead/18-lead ECG sets and 3-lead VCG from 15 reduced lead sets, and the success of these predictions was assessed by 3 goodness-of-fit measures applied to the entire QRST waveform and to the ST deviation at J point; these 3 measures were similarity coefficient (SC in percentage), relative error (in percentage), and RMS error (in microvolts). Our results show that the best pair for predicting the standard 12-lead ECG by either general coefficients (mean SC = 95.56) or patient-specific coefficients (mean SC = 99.11) is V2 and V4; the best pair for deriving the 18-lead set by general coefficients (mean SC = 93.74) or by patient-specific coefficients (mean SC = 98.71) is V1 and V4; the best pair for deriving the Frank X, Y, Z leads is V1 and V3 for general coefficients (mean SC = 95.76) and V3 and V6 for patient-specific coefficients (mean SC = 99.05). The differences in mean SC among the first 8 to 10 predictor sets in each ranking table are within 1% of the highest SC value. Thus, in conclusion, there are several near-equivalent choices of reduced lead set using 6-wire cable that offer a good prediction of 12-lead/18-lead ECG and VCG; a pair most appropriate for the clinical application can be selected.