Digital echocardiographic laboratory: where do we stand?

Clinically Compressed Digital Echocardiography: A Patient-safe Alternative to Videotape Review

Introduction: Digital storage of echocardiographic data offers logistical advantages over videotape archival. However, limited information is available on the accuracy of clinically compressed digitised examinations, an important consideration for patient safety. Materials and Methods: Transthoracic echocardiograms of 520 consecutive patients were prospectively acquired digitally and on videotape. Two echocardiologists, in consensus, reported studies in both formats sequentially. Using the videotape as a reference, the significance of any reported differences was graded from both imaging and clinical standpoints, and the reasons for these differences identified. Results: From an imaging perspective, differences between digital and videotaped studies were absent or minor in 459 cases (88%), fairly significant in 55 (11%) and very significant in 6 (1%). The main reasons for the observed differences were inadequate acquisition of optimal views (59%), an insufficient number of acquired cardiac cycles (25%) and suboptimal image quality (9%). These differences were considered to be of possible or definite clinical importance in 21 (4%) and 8 (2%) cases, respectively. In multinominal logistic regression models, the only independent predictor of significant difference between digitised and videotaped images was study complexity. Regardless of case complexity, most diagnostic errors arising from digital review were attributable to technical failure rather than observer error. Conclusions: The potential for important errors arising from exclusive reporting of clinically compressed digital echocardiograms is small. Digital echocardiography, as practiced in a routine clinical setting, offers a patient-safe alternative to videotape review. Key words: Clinical implications, Digital echocardiography, Patient safety, Videotape

High-grade video compression of echocardiographic studies: a multicenter validation study of selected motion pictures expert groups (MPEG)-4 algorithms

BACKGROUND

Large files produced by standard compression algorithms slow down spread of digital and tele-echocardiography. We validated echocardiographic video high-grade compression with the new Motion Pictures Expert Groups (MPEG)-4 algorithms with a multicenter study.

METHODS

Seven expert cardiologists blindly scored (5-point scale) 165 uncompressed and compressed 2-dimensional and color Doppler video clips, based on combined diagnostic content and image quality (uncompressed files as references). One digital video and 3 MPEG-4 algorithms (WM9, MV2, and DivX) were used, the latter at 3 compression levels (0%, 35%, and 60%).

RESULTS

Compressed file sizes decreased from 12 to 83 MB to 0.03 to 2.3 MB (1:1051-1:26 reduction ratios). Mean SD of differences was 0.81 for intraobserver variability (uncompressed and digital video files). Compared with uncompressed files, only the DivX mean score at 35% (P = .04) and 60% (P = .001) compression was significantly reduced. At subcategory analysis, these differences were still significant for gray-scale and fundamental imaging but not for color or second harmonic tissue imaging. Original image quality, session sequence, compression grade, and bitrate were all independent determinants of mean score.

CONCLUSIONS

Our study supports use of MPEG-4 algorithms to greatly reduce echocardiographic file sizes, thus facilitating archiving and transmission. Quality evaluation studies should account for the many independent variables that affect image quality grading.

Digital echocardiography 2002: now is the time

The ability to acquire echocardiographic images digitally, store and transfer these data using the DICOM standard, and routinely analyze examinations exists today and allows the implementation of a digital echocardiography laboratory. The purpose of this review article is to outline the critical components of a digital echocardiography laboratory, discuss general strategies for implementation, and put forth some of the pitfalls that we have encountered in our own implementation. The major components of the digital laboratory include (1) digital echocardiography machines with network output, (2) a switched high-speed network, (3) a high throughput server with abundant local storage, (4) a reliable low-cost archive, (5) software to manage information, and (6) support mechanisms for software and hardware. Implementation strategies can vary from a complete vendor solution providing all components (hardware, software, support), to a strategy similar to our own where standard computer and networking hardware are used with specialized software for management of image and measurement information.

Impact of telemedicine on the practice of pediatric cardiology in community hospitals

BACKGROUND

Tele-echocardiography has the potential to bring real-time diagnoses to neonatal facilities without in-house pediatric cardiologists. Many neonates in rural areas, smaller cities, and community hospitals do not have immediate access to pediatric sonographers or echocardiogram interpretation by pediatric cardiologists. This can result in suboptimal echocardiogram quality, delay in initiation of medical intervention, unnecessary patient transport, and increased medical expenditures. Telemedicine has been used with increased frequency to improve efficiency of pediatric cardiology care in hospitals that are not served by pediatric cardiologists. Initial reports suggest that telecardiology is accurate, improves patient care, is cost-effective, enhances echocardiogram quality, and prevents unnecessary transports of neonates in locations that are not served by pediatric cardiologists.

OBJECTIVE

We report the largest series to evaluate the impact of telemedicine on delivery of pediatric cardiac care in community hospitals. We hypothesized that live telemedicine guidance and interpretation of neonatal echocardiograms from community hospitals is accurate, improves patient care, enhances sonographer proficiency, allows for more efficient physician time management, increases patient referrals, and does not result in increased utilization of echocardiography.

METHODS

Using desktop videoconferencing computers, pediatric cardiologists guided and interpreted pediatric echocardiograms from 2 community hospital nurseries 15 miles from a tertiary care center. Studies were transmitted in real-time using the H.320 videoconferencing protocol over 3 integrated services digital network lines (384 kilobits per second). This resulted in a frame rate of 23 to 30 frames per second. Sonographers who primarily scanned adult patients but had received additional training in echocardiography of infants performed the echocardiograms. Additional views were suggested as deemed necessary by the interpreting physician, and interpretations were made during the videoconference. The results of the echocardiogram and recommendations for patient care were communicated to the referring physician over the telemedicine system. Analyses of accuracy, patient treatment, echocardiogram quality, time to diagnosis, pediatric cardiologist practice time management, patient referral patterns, and echocardiography utilization were conducted prospectively.

RESULTS

A total of 500 studies in 364 patients were transmitted during a 30-month period. The most common indication for echocardiography was to rule out congenital heart disease (208 of 500 studies). Signs and symptoms that prompted this concern included cyanosis, murmur, tachypnea, genetic syndrome, arrhythmia, abnormal fetal echocardiogram, and maternal diabetes. Other indications included suspected patent ductus arteriosus (PDA; 182 of 500 studies), intracardiac clot or catheter position, persistent pulmonary hypertension, and hemodynamic instability. Cardiac diagnoses included complex congenital heart disease (n = 16), noncritical heart disease (n = 107), and PDA (n = 86). Additional diagnoses included persistent pulmonary hypertension (n = 12), septal hypertrophy (n = 18), right atrial mass/clot/vegetation (n = 11), and decreased cardiac function (n = 6). An umbilical venous catheter was visualized in the left atrium in 9% (45 of 500) of all studies. No significant abnormalities were found in 244 studies. Major diagnoses were confirmed by subsequent review of videotape in all studies. Comparison of final videotape interpretation to initial telemedicine diagnosis resulted in 1 minor diagnostic change (membranous versus inlet ventricular septal defect). Echocardiograms were performed in subsequent visits in 264 patients. The diagnosis was altered in 3 patients. Telemedicine had an immediate impact on patient care in 151 transmissions. The most common interventions were indomethacin treatment for PDA (n = 76), retraction of umbilical venous catheters from the left atrium (n = 45), inotropic or anticongestive therapy (n = 19), anticoagulation (n = 8), and prostaglandin infusion (n = 8). Nineteen patients were transported to our hospital because of the telemedicine diagnosis. Inpatient or outpatient cardiology follow-up was recommended in an additional 131 studies and did not result in any change in the initial management. The most common diagnoses in these patients were ventricular septal defect (n = 56), atrial septal defect (n = 21), septal hypertrophy (n = 9), intracardiac thrombosis (n = 8), and pulmonary valve stenosis (n = 4). We speculate that the immediate availability of an echocardiographic diagnosis likely prevented unnecessary transport in 14 cases. Recommendations for additional views or adjustment of echocardiography machine settings were made in 95% of transmissions. Real-time guidance was especially helpful in suprasternal notch and subcostal sagittal imaging. Depth, color Doppler sector size, and color Doppler scale were frequently adjusted from routine adult settings during the teleconference. The average time from request for echocardiogram to completion of the videoconference was 28 +/- 14 minutes. This was significantly shorter than the waiting time (12 +/- 16 hours) for the videotape to be delivered by courier. Telemedicine eliminated the need for consultation in 194 cases and allowed the cardiologist to delay the visit until the end of the day in an additional 26 cases. This resulted in average time savings of 4.2 person-hours/wk based on travel and consultation time. Utilization of echocardiography was similar before (35 of 1000 births) and after (33 of 1000 to 43 of 1000) telemedicine installation. The percentage of neonatal echocardiograms that were interpreted by our practice increased from 63% to 81% at 1 hospital and from 0% to 100% at the other hospital.

CONCLUSION

Real-time transmission of neonatal echocardiograms from community hospitals over 3 integrated services digital network lines is accurate and has the potential to improve patient care, enhance echocardiogram quality, aid sonographer education, and have a positive impact on referral patterns and time management without increasing the utilization of echocardiography.

Telecardiology: potential impact on acute care

Echocardiography is often used to diagnose and exclude important cardiac diagnoses in adults and children. Evolving telemedicine technology has the potential to improve access to echocardiography diagnoses in the intensive care unit, emergency room, and newborn nursery. The two primary modes of telemedicine practice are "store and forward" and "real-time" videoconferencing. A digital echocardiogram (often several one cardiac cycle loops) can be stored at one site and forwarded across a telemedicine network to a receiving station for review at a later time. Pediatric cardiologists often favor "real-time" telemedicine because of the ability to guide sonographers with limited experience in congenital heart disease. A complete telemedicine system requires a modified computer, a low- or high-speed connection, and telemedicine inputs. Several adult and pediatric clinical studies have shown telemedicine to be accurate and cost-effective, improve patient care, enhance echocardiogram quality and sonographer proficiency, and promote practice expansion. Obstacles to widespread implementation of telemedicine include lack of standardization of telemedicine components, confusing legal issues and licensure requirements, and poor reimbursement.

Digital echocardiography: its role in modern medical practice

Digital echocardiography has evolved rapidly during the last decade, and the all-digital echocardiographic laboratory has just reached the threshold of reality. This review article explains what this transition means for the modern medical practice and concisely presents what a digital echocardiogram is, the technical aspects of digital image acquisition and processing, and the advantages and limitations of digital echocardiography vs analog echocardiography. This review should serve as a useful source of information for the general cardiologist not working closely with digital echocardiography, as well as a resource for the noncardiologist.

Transition to an all-digital echocardiography laboratory: a large, multi-site private cardiology practice experience

Acquisition, interpretation, and storage of digital echocardiographic images has many advantages over the standard videotape-based method. Archival, transmission, and comparative interpretation are all optimized with digital echocardiography. A study performed at one site can be immediately available for viewing and analysis at another site by means of standard data transfer technology. Echocardiograms can be interpreted in the context of prior studies, which are readily available for side-by-side comparison. The transition to an all-digital laboratory involves the commitment of persons at multiple levels in the cardiology practice, including administrators, information technology specialists, sonographers, and physicians. Quality of patient care, use of physicians' and sonographers' time, and long-term financial benefit are all areas where improvement may be realized with the use of digital echocardiography. We present our experience in the development of an all-digital echocardiography laboratory, and we conclude that digital echo-cardiography is practical and can be implemented readily in a clinical setting. We performed several correlative analyses during this transition to validate the consistency and accuracy of digital interpretation compared with those of analog methods. The transition process from analog (videotape) to digital, including full wide area network exchange, took approximately 8 months. As technology advances, issues surrounding storage, comparison, and acquisition formats will continue to develop. We hope that our experience will help others make the transition to the digital environment and benefit from the ease of image access, the ability to comparatively interpret echocardiograms, and the superior image quality afforded by this advancement.

A comparison of the interpretation of digitized and videotape recorded echocardiograms

Conventional echocardiograms are typically recorded on videotape and later reviewed and interpreted by a physician. Although videotape recording is an excellent medium for this purpose, it does have several disadvantages, which may be overcome by digital storage. This study compared the diagnostic accuracy of digitized and videotape recorded echocardiograms. Echocardiographic examinations (n = 110) were recorded simulta-neously on videotape and were digitized with a commercially available frame grabber system. Images were transmitted by an Ethernet link to the network-based computer system and compressed with a nondestructive compression algorithm. Images were reviewed on a personal computer. Images were interpreted by 3 observers, and differences in interpretation were documented. There were 274 findings in 110 patients. Exact agreement in interpretation was found in 83%. A major discrepancy occurred in 2%, and a minor discrepancy occurred in 15%. Most discrepancies occurred in the setting of valvular heart disease. When compared with a consensus interpretation, no significant difference was seen in the number of errors between the digital and videotape interpretation. We conclude that the interpretation of a properly recorded digitized echocardiographic examination yields interpretations equivalent to those of videotape recordings.