ECG Coding Center Epidemiology.docx



Minnesota ECG Coding For over 40 years, Minnesota ECG Coding has been a major electrocardiographic computer and visual reading service for epidemiological studies and clinical trials nationally and internationally.The mission of the center was to document the prognostic and diagnostic value of electrocardiography for epidemiological studies and clinical trials. The Coding Center was at the fore front of developing and evaluating new criteria sets for incident cardiac events including silent myocardial infarction, ischemia, left ventricular hypertrophy, QT dispersion, and heart rate variability.The TeamDirectorDr. Richard Crow has had 25 years of experience in designing, implementing and executing electrocardiogram analysis in multicenter epidemiologic studies and clinincal trials.95250Dr. Crow has enlarged the Minnesota Code classsification procedures to include standardized serial ECG comparision to document incident or recurrent (silent) myocardial infarction, in-hospital Q wave myocardial infarction, progression or regression of LVH (See studies MRFIT, TOMHS and ALLHAT), and ECG quality control methodology.Director EmeritusDr. Ronald Prineas has served as director of the Minnesota Central ECG Laboratory and Miami ECG Coding Center in the past.He has 34 years of experience in the design, conduct and implementation of multicenter studies (epidemiologic and clinical) that make use of the ECG. He is also a consultant to the World Health Organization (WHO) on population electrocardiography.Founding FatherDr. Henry Blackburn is the founding father of The Minnesota Code. He developed the original standardized criteria in the late 1950s, to meet the needs for objective comparisions of heart disease rates amongst countries.95250In 1968, Dr. Blackburn and Geoffrey Rose of London first published the Minnesota Code with the World Health Organization in a book entitled, Cardiovascular Survey Methods. Dr. Blackburn is also responsible for developing the idea of training technicians to code ECG's in the laboratory setting. (See History of ECG Coding.)About UsFor more than 40 years, the Minnesota ECG Coding Center has been the major electrocardiographic visual reading service center for epidemiological studies and clinical trials, both nationally and internationally. The mission of the Center is to document the prognostic and diagnostic value of electrocardiography for epidemiological studies and clinical trials. The Center has been at the forefront of developing and evaluating new criteria sets for incident cardiac events, including silent or symptomatic myocardial infarction, ischemia, left ventricular hypertrophy, QT dispersion, and heart rate variability.The Minnesota Code is a classification system for the electrocardiogram that utilizes a defined set of measurement rules to assign specific numerical codes according to severity of ECG findings. The Minnesota Code, developed in the late 1950s by Dr. Henry Blackburn in response to the need for reporting ECG findings in uniform, clearly defined, and objective terms, is the most widely used ECG classification system in the world for clinical trials and epidemiologic studies. It incorporates ECG classification criteria that have been validated, widely employed, and accepted by clinicians. The Minnesota Code provides an objective ECG classification system free of impressionist physician bias, by which different studies can have a common standard to compare or pool ECG findings. It now includes objective procedures for defining significant pattern changes from serial ECG comparison, such as evidence of new MI, new ischemia, progression or regression of LVH and new conduction defect.Minnesota Code procedures have been incorporated into a computer program, the Minnesota Code Modular ECG Analysis System (MC-MEANS). MC-MEANS also includes logic for serial ECG comparison, developed and validated at the Center.EpiCH faculty, along with other researchers around the world, use these facilities for service and research activities. Active collaboration is ongoing between ECG Centers at Wake Forest University in North Carolina and Erasmus University in Rotterdam, Netherlands.The Center provides the following services: Visual or computer assigned standard Minnesota Codes; amplitude, axis and duration measurements; serial ECG comparisons for documenting evolving Q-waves, evolving ST-T waves, evolving bundle branch block and progression or regression of ECG LVH and visual or computer determination of left ventricular mass index; prolonged heart rate corrected QT or JT intervals; heart rate variability; QT dispersion; T-wave axis; and ECG prognostic score.The Center currently has eight active studies that send approximately 3,500 ECGs per month for analysis. The Minnesota ECG Coding Center also provides training and evaluation of technical staff for new studies and refresher training for ongoing studies. Researchers wishing to use the Minnesota Code to code their own ECGs can use the Minnesota Code interactive computer tutorial or can submit samples of their coded ECGs for evaluationHistory of ECG CodingIn the 1950s, when most systematic population studies of heart disease began, it became important to have standard and quantitative means to compare disease rates. Diagnoses from death certificates or by physicians having different training might very easily result in spurious differences.95250Even independent diagnoses by specially trained physicians may be highly variable. This problem of comparability in clinical assessment led to consideration of the electrocardiogram (ECG) as an objective measure for assessing heart disease. Why? Because its findings are strongly related to heart disease manifestations of greatest interest, that is, death of heart muscle (infarction), increased heart size (hypertrophy), and disturbances of rhythm or conduction.The ECG seemed particularly promising because it is a graphic record, amenable to standard procedures of collection, measurement, and classification. It also seemed ideal because it is so acceptable, painless, simple, and inexpensive to record.This was all very well until several facts quickly emerged. Differences between physicians’ “impressionistic” reading of ECGs were large; sizable differences were found by the same cardiographer at different times, and no objective criteria existed for abnormality or for specific cardiac findings, only a pattern recognition. Clearly, the challenge of standard criteria measurement had first to be met before endpoint cardiac “events” and population rates could be reliably assessed and compared.My first approach was to compile all existing ECG criteria and attempt to sort them into quantitative classes. Where this was not possible, “reasonable” criteria were devised and empirically tested for sensitivity and specificity in well-defined populations containing different proportions of normals versus patients having specific abnormalities, from both living and autopsy series.Finally, all these ECG criteria were assembled, unambiguously described, rank ordered by magnitude and amplitude according to a clinical impression of their importance and assigned code numbers. The resulting classes were quantitative, mutually exclusive, and generally relevant to important disease states. However, they were objectively described as Q-QS waves, negative T-waves, etc., rather than given clinically diagnostic labels. Finally, records from many different living populations were classified and evaluated for “reasonableness” of the population distributions obtained. Test-retest reliability improved among the collaborating physicians closely involved in development of the code: Pentti Rautaharju, Sven Punsar, Gunnar Blomqvist, and me.Early on, between 1958-59, other investigators in cardiovascular disease population studies received a version of the criteria and code.Someone, possibly Frederick Epstein at the University of Michigan or Geoffrey Rose in London, termed it “Minnesota Code.” They began to use the criteria and provide suggestions for minor revisions, and were enthusiastic about an increasing ability to classify prevalence and incidence data quantitatively.About this time we also shared records to assess variation between us in coding. We were a little surprised to find out how sizable was the coding variation, despite the unambiguous and quantitative criteria and awareness of standard laboratory procedures.The extent of observer variability, of course, should not have surprised us at all but should have been anticipated. Clear definitions and objective criteria do not guarantee, in themselves, their similar application by different observers. In consequence, more attention was given to the conditions of recording and measurement and to coding procedures and rules. Measuring devices were developed, particularly for assessing Q wave duration, to improve classifications at the borderlines between criteria. Rules were devised to account for pattern variation between beats. The system was generally shored up by quality control procedures for individual code and standardization by a system of duplicate independent readings and adjudication.By the early 1960s the burden of coding still lay mainly on me and a few visiting physicians in this laboratory, while the volume of ECGs increased from population studies. High interest in the developmental phases of Minnesota coding was replaced by a tedious chore. At about the same time, independently, Geoffrey Rose in London and I in Minnesota hit upon an idea to make coding by technicians practical.My resolution of the issue grew out of a special experience of ECG coding.In the summer of 1962 I was solicited by the National Health Examination Survey of the National Center for Health Statistics to classify electrocardiograms on 6000 individuals, a true sample of the United States population. Standard coding was designed in the only existing objective classification system. I agreed to do this as a summer undertaking. It offered only the princely reward of twenty-five cents a record, but seemed a worthwhile undertaking, that is, until I received the shipment of actual ECGs.They were unmounted strips stowed in tiny cardboard cubicles as tightly wrapped cylinders some 6 to 9 feet long. They required to be removed from the case, unrolled, held flat, read, measured, codified, tabulated, rerolled, and reinserted in the packing. The reading, classification, and tabulation involved approximately one-fifth of the total time required for handling. At the inducement of one cent per record per person, I was able to enlist the enthusiastic aid of two alert, though very young, non-technical persons who happened to be close at hand that summer. While one, aged 8, would extract and unroll the record, the other, aged 9, would hold it down while I coded and then rolled and refilec it. Their summer wage was thus 6000? each, and mine, 6000 x 23?. However, their work reduced mine substantially and allowed an increasingly pleasant relationship among these very close relatives.After only a few experiences, from normal curiosity, my assistants could soon identify P-, QRS-, and T-waves. After a little time, they were careful to point out to me when a P-wave or a T-wave was “upside down” or when a Q-wave was “big and fat” or an R-wave particularly tall, and so on. After a few more days, by which time they spontaneously associated the code numbers I was writing down with tall or flat or inverted or prolonged waves, it was clear that they were embryonic Minnesota Coders.With a little more incentive and a little more time and instruction they could become excellent ECG coders, even at ages 8 and 9. I resolved soon thereafter never to read numbers of ECGs from population studies, having read some 20,000 to 30,000 records a year for several years. I therefore proceeded in the fall of 1962 to recruit University students and instruct them in the Minnesota Coding procedures. This has been going on ever since, and several hundreds of student coder alumni have, over the decades, helped in this service to national and international studies, while helping themselves through the University with part-time employment.It had not been my intention to develop a coding system for export. It was my intention only to develop sound methodological procedures for assigning objective “events” related to cardiac disease for our extensive laboratory studies. However, the Minnesota Code became widely used because it met a need in the burgeoning new field of cardiovascular epidemiology. It became used internationally when it was included in the World Health Organization monograph series as Cardiovascular Survey Methods, published in 1968.Since, the code has been expanded and updated to classify endpoints of clinical trials and to better characterize arrhythmias and conduction defects.This manual provides standard procedure for its application. In a blinded, centrally standardized approach to the ascertainment of disease endpoints in clinical trials it complements clinical data from physicians who may inadvertently be biased by knowledge of the drugs being administered, or otherwise. The ECG has a different set of “errors” from clinical assessments, and thus is independent of them. Finally, it came to be used, and a new set of criteria were developed to estimate significant serial change in the ECG over time. Interestingly, the original 1960 publication in Circulation was recently cited by the Cumulative Index Medicus as one of the most extensively referenced articles in the scientific literature.This, then, is the story of the Minnesota Code up to the presentation of this new manual of procedure for training and testing. It has long been the intention that these observations, measurements, and classifications be made by machine rather than by humans.Drs. Prineas and Crow have collaborated with numerous computer centers to develop Minnesota Code logic and programs, most of which have succeeded more or less. But the differing natures of man and machine leave a problem in that the computer’s determination of wave onset and offset, and of baselines, though much more repeatable, are often systematically different from human-visual interpretation.The present strategy of the Minnesota group is to use the computerized Minnesota Code for things the computer does best, i.e., measurement repeatability, and to complement its classification by things that the human does best, judging baselines and resolving borderline situations. The group has demonstrated that combined human / machine adjudication obtains the more reliable and valid electrocardiographic classification.I have only a few words more about visual coding of ECGs by student technicians. First, there is no absolute “right or wrong” in classification. The job is to get as close to the truth and as repeatably as possible by the means taught in this manual. After an instruction period, learning occurs best by reading ECGs entirely independently and as rapidly as possible, by making a firm commitment to a code and then comparing that decision to a standard.As one becomes a more confident and productive senior coder, the most important thing to remember is to remain scrupulously honest, and to read sets of cardiograms independently of all others’ readings. Then, afterwards, it is important to be curious to compare your independently coded findings with the others. Independent coding helps us learn causes for differences, and as always, “two heads are better than one” in detecting codable findings in the first place.Few student coders at Minnesota go on to medical or health-related careers. However, this coding course allows one to become highly competent in a discipline which to this day remains a “medical mystique” (while it provides good fees to cardiological specialists to interpret electrocardiograms in the hospital setting). In a few months of on-the job training, student technicians often become superior to most interns or even medical residents in their ability to detect, differentiate, and classify repeatedly most ECG abnormalities. Keep in mind that this technical function you are learning should give no basis for the interpretation of those findings or the diagnosis of heart disease.Thus, we talk very little about the significance of these findings to the individuals learning them. Rather, we want you to take pride in your accomplishment and in the excellent research function you provide to the scientific community.Coders must never let themselves be put in the position to misuse their ECG reading skills outside the laboratory. Once we had a student who tried to “sell” her skills to record rooms in local hospitals as an “electrocardiographic coder.” They, of course, did not know what she was talking about and called us for fear she was mentally “unbalanced.”The Minnesota Code is not standard in any hospital practice. Rather, it is a system designed for rigorous population researches and clinical trials. Then, we had another student who once read her grandmother’s electrocardiogram saying, “Oh, what a nice big 7-1. You have a complete left bundle branch block, Grandma!” It took some hours of medical persuasion and sedation to calm the old lady down - she thought she’d had a heart attack!I am sure you won’t take your work (or skills) home with you!Coding ServicesThe Minnesota Code was created in response to the need for reporting ECG findings in uniform, clearly defined, and objective terms with the least risk of confusion regarding interpretation. As such, it provides an objective description of bio-electrical phenomena. It incorporates ECG criteria for classification which have been validated, widely employed and accepted by clinicians.The Minnesota Code provides an objective ECG classification system free of impresssionist physician bias, by which different studies throughout the world can have a common standard to compare or pool ECG findings. It includes objective procedures for defining significant pattern changes from serial ECG comparison. The Minnesota Code is the most widely used ECG classification system in the world for clinical trials and epidemiologic studies.Minnesota Code procedures have been incorporated into a computer program, the Minnesota Code Modular ECG Analysis System (MC-MEANS) which has been extensively validated. MC-MEANS also includes logic for serial ECG comparison which was developed and validated at the Minnesota Coding Laboratory.MN Central ECG Laboratory (CEL)The Minnesota Central ECG Laboratory offered:Visual or computer assigned standard Minnesota Codes.Visual or computer determined amplitude, axis and duration measurements.Visual or computer serial ECG comparsions for documenting evolving Q-waves, evolving ST-T waves, evolving bundle branch block and progression or regression of ECG-LVH.Visual or computer determination or prolonged heart rate corrected QT or JT intervals.Visual or computer determination of:- Left ventricular mass index. - Heart rate variability. - QT dispersion- T-wave axis- ECG prognostic score.Automatic logging, tracking and inventory of received ECGsComputerized billing based on the number of ECGs completedStandardized quality control procedures and transfer of data in computer compatible formCentral training of ECG technicians, certification and quality assurance monitoring of technical staff.Frequently Asked QuestionsThe Minnesota Central ECG is dedicated to informing medical specialists and average persons alike. The following list of questions represents a sampling from both populations.Q: What is an ECG?A: An ECG, or electrocardiogram, is a graphic display of the time-varying voltage of the electrical activity occurring in the muscle of the heart.Q: Can hardcopy paper records of ECG's be coded by computer?A: Yes, but only for specially designed and limited measurement programs, not the Minnesota Code or diagnostic codings.Q: Can ECG hardcopy records already recorded, but lacking a study protocol, be coded by the Minnesota ECG Coding Center?A: Yes, all paper records can be coded with standard measurement codes, despite varying or absent aquisition protocols.Q: Do extant ECG recordings need to be mounted in a particular manner before submission to the Service Center?A: Yes or No, the mounting can be done by either the client or the Service Center.Return to MN ECG Coding HomeMN ECG Coding ManualContents410527585725Download the Minnesota Code ClassificationWhat is the Electrocardiogram orECG?ECG LeadsMeasuring DevicesQ-QS Waves (1-Codes)Frontal Plane QRS Axis (2-Codes)High R Waves (3-Codes)ST Segment Depression (4-Codes)and Negative T-Waves (5-Codes)Atrioventricular (A-V) Conduction Defects (6-Codes)Intraventricular Conduction Defects (7-Codes)Arrhythmias (8-Codes)Miscellaneous Codes (9-Codes)Exact MeasurementsCoding the Whole ECGECG Data Acquisition ProceduresCriteria for Significant ECG Pattern ChangeQuality ControlAppendix- Minnesota Code 1982The Minnesota Code Manual presents a systematic, objective measuring system for electrocardiographic findings in clinincal trials and population studies of cardiovascular disease. The current edition published in 1982 classifies endpoints of clinical trials and characterizes arrhythmias and conduction defects. This edition also provides standard procedure for the codes application by trained medical or technical personnel. In addition, it is used by experienced investigators to teach measurement and coding of the ECG in the Core ECG Lab.The Minnesota Code Manual of Electrocardiographic Findings constitutes an essential source of reference for clinincal trials and population-based cardiovascular studies.New EditionIn the late 1990s work began on revision of the current Manual of Electrocardiographic Findings. The Second Edition will be updated and expanded to include Serial Change criterion, the use of Computer Analysis and a Tutorial Edition. The format media is also under review and expected to include hardcover as well as CD ROM.Download the Minnesota Code ClassificationStudies Using the MN ECGThe Minnesota Central ECG Laboratory was the core ECG center of numerous clinical trials and epidemiologic studies.These trials and studies ranged from international multicenter complex efforts (40,000 plus participants) to simple local trials.National/ InternationalALLHAT Atrial Fibrillation Studythe Anemia StudyAnti-Lipid Lowering Heart Attack Trial (ALLHAT)Australian National Blood Pressure Study (ANBPS)Atheroclerosis Risk in Communities Study (ARIC)Beta Blocker Heart Attack Trial (BHAT)Boston Health Care Project (BHC)Budapest WHO Test ECG CodingCardiovascular Disease among Seattles Japanese (NDP)Center for Disease Translation Study (CDT)the China 1990 StudyCommunity Diabetes Project (RTI)Comparison of ECG Algoritms for Ischemic Endpoints StudyCoronary Artery Risk Development in Young Adults (CARDIA)Coronary Drug Project (CDP)Coronary Risk in Seniors Program (CRISP)Chicago Western Electric (CHE)CVD Risk Factors and Brain Morphology in NHLBI Twins (TWINS)Diabetes Control and Complications Trial (DCCT)Diabetes Prevention in Yupik Eskimos (ESKIMO)Early Treatment of Diabetic Retinopathy Study (ETDRS)Enhancing Recovery in Coronary Heart Disease (ENRICH)Epidemiology of Diabetes Intervention and Complications (EDIC)Evans County and Charleston Heart StudiesGaurdian ECG Minnesota Code Analysis (GAURDIAN)HDL Intervention Trial (HIT)Healthy Heart Study (HHS)Heart Rate Variability and Survival after MI StudyHip Fracture Study (HIP)Hypertension Control Program (HCP)Hypertension Detection and Follow-up Program (HDFP)Indian Heart StudyInter-Tribal Heart Project (ITHP)the Kronhort StudyLipid Researech Centers Study (LIPID)Lorsartan Intervention for Endpoint Reduction in Hypertension Project (LIFE)Lorsartan NIDDM Endpoint StudyLorsartan Post MI StudyMeharry Cohort Study (MCS)Mexico City Diabetes StudyMiami Senior Health Trial (MSHT)Multiple Risk Factor Intervention Trial (MRFIT)Munich Transit Worker Cardiovascular Risk Factor Intervention Study (GERMANY)National Health and Nutrition Examination Study (NHANES)National Hypertension Study (NHP)Nicotine Patch Study (NPS)Normative Aging Study (NRM)New York Bridge and Tunnel Workers Study (BNT)New York State MI Validation StudyNIDDM Primary Prevention TrialOccupational Exposure StudyOtsego-Schoharie Healthy Heart Program (OSH)Pawtucket Heart Health ProgramPfizer/Parke-Davis TNT Program (GDXI)Poland Study- Warsaw and Cracowthe Precursors StudyPrevention of High Blood Pressure in Children Study (PHBPC)the Reaven StudyRenal and Cardiovascular Disease in Navajo Indians with Type II Diabetes (NAVAJO)Renal Protective Effects of Lorsartan StudySan Antonio Heart StudySan Luis Valley Diabetes Study (SLV)Scandinavian Simvastatin Survival Study (4S)Seven Countries Study, 9 Hypertension Control Program (HCP)the SHEPII StudyShould We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock (SHOCK)Sodium-Potassium Study in Children (NAKS)Solomon Island ECG Studythe Southeastern Kidney Council StudySpinal Cord Injury and Carsiovascular Disease StudyStanford Heart Disease Prevention Program (STANFORD)Strong Heart Study (SHS)Systolic Hypertension in Elderly Program (SHEP)Tamoxifen and Risk of Subsequent Thrombembolic Disease (TKP)Tiawan- case control study of myocardial ischemia and injury (TIAWAN)Treatment of Mild Hypertension Study (TOMHS)the Trichlorotrifluorethane StudyVA Collaborative Study on Insulin Dependent DiabetesVA Cooperative 344 StudyVascular Disease in Women StudyLocal/ RegionalMayo Clinic Study (MAYO)Minnesota Heart Health Program (MHHP)Minnesota Heart Survey (MHS)Stratis Health Acute MI Validation (STRATIS) ................
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