The effect of the number of electrocardiograms analyzed on cardiovascular disease surveillance: the Minnesota Heart Survey (MHS)

Patient characteristics and outcomes of acute myocardial infarction presenting without ischemic pain: Insights from the Atherosclerosis Risk in Communities Study

Background

Our objective was to describe characteristics of patients presenting with and without ischemic pain among those diagnosed with acute myocardial infarction (MI) using individual-level data from the Atherosclerosis Risk in Communities Study from 2005 to 2019.

Methods

Acute MI included events deemed definite or probable MI by a physician panel based on ischemic pain, cardiac biomarkers, and ECG evidence. Patient characteristics included age at hospitalization, sex, race/ethnicity, comorbidities (smoking status, diabetes, hypertension, history of previous stroke, MI, or cardiovascular procedure, and history of valvular disease or cardiomyopathy) and in-hospital complications occurring during the event of interest (pulmonary edema, pulmonary embolism, in-hospital stroke, pneumonia, cardiogenic shock, ventricular fibrillation). Analyses were stratified by MI subtype (STEMI, NSTEMI, Unclassified) and patient characteristics and 28-day case fatality was compared between MI presenting with or without ischemic pain.

Results

Between 2005 and 2019, there were 1711 hospitalized definite/probable MI events (47 % female, 26 % black, and age of 78 [6.7 years]). A smaller proportion of STEMI patients presented without ischemic pain compared to NSTEMI patients (20 % vs 32 %). Race, sex, age, and comorbidity profiles did not differ significantly across ischemic pain presentations. Patients presenting without ischemic pain had a higher 28-day all-cause case fatality after adjusting for age, race, sex, and comorbidities. However, after further adjustment, time from symptom onset to hospital arrival, time to treatment, and in-hospital complications explained the difference in 28-day case fatality between ischemic pain presentations.

Conclusions

Future research should focus on differences in treatment delay across ischemic pain presentations rather than sex differences in acute coronary syndrome presentation.

Differences in incident and recurrent myocardial infarction among White and Black individuals aged 35 to 84: Findings from the ARIC community surveillance study

BACKGROUND

No previous study has examined racial differences in recurrent acute myocardial infarction (AMI) in a community population. We aimed to examine racial differences in recurrent AMI risk, along with first AMI risk in a community population.

METHODS

The community surveillance of the Atherosclerosis Risk in Communities Study (2005-2014) included 470,000 people 35 to 84 years old in 4 U.S. communities. Hospitalizations for recurrent and first AMI were identified from ICD-9-CM discharge codes. Poisson regression models were used to compare recurrent and first AMI risk ratios between Black and White residents.

RESULTS

Recurrent and first AMI risk per 1,000 persons were 8.8 (95% CI, 8.3-9.2) and 20.7 (95% CI, 20.0-21.4) in Black men, 6.8 (95% CI, 6.5-7.0) and 14.1 (95% CI, 13.8-14.5) in White men, 5.3 (95% CI, 5.0-5.7) and 16.2 (95% CI, 15.6-16.8) in Black women, and 3.1 (95% CI, 3.0-3.3) and 8.8 (95% CI, 8.6-9.0) in White women, respectively. The age-adjusted risk ratios (RR) of recurrent AMI were higher in Black men vs White men (RR, 1.58 95% CI, 1.30-1.92) and Black women vs White women (RR, 2.09 95% CI, 1.64-2.66). The corresponding RRs were slightly lower for first AMI: Black men vs White men, RR, 1.49 (95% CI, 1.30-1.71) and Black women vs White women, RR, 1.65 (95% CI, 1.42-1.92) CONCLUSIONS: Large disparities exist by race for recurrent AMI risk in the community. The magnitude of disparities is stronger for recurrent events than for first events, and particularly among women.

Trends in myocardial infarction rates and case fatality by anatomical location in four United States communities, 1987 to 2008 (from the Atherosclerosis Risk in Communities Study)

Although the incidence of and mortality after ST-segment elevation myocardial infarction (STEMI) is decreasing, time trends in anatomical location of STEMI and associated short-term prognosis have not been examined in a population-based community study. We determined 22-year trends in age- and race-adjusted gender-specific incidences and 28-day case fatality of hospitalized STEMI by anatomic infarct location among a stratified random sample of 35- to 74-year-old residents of 4 communities in the Atherosclerosis Risk in Communities study. STEMI infarct location was assessed by 12-lead electrocardiograms from the hospital record and was coded as anterior, inferior, lateral, and multilocation STEMIs using the Minnesota code. From 1987 to 2008, a total of 4,845 patients had an incident STEMI; 37.2% were inferior STEMI, 32.8% were anterior, 16.8% occurred in multiple infarct locations, and 13.2% were lateral STEMI. For inferior, anterior, and lateral STEMIs in both men and women, significant decreases were observed in the age-adjusted annual incidence and the associated 28-day case fatality. In contrast, for STEMI in multiple infarct locations, neither the annual incidence nor the 28-day case fatality changed over time. The age- and race-adjusted annual incidence and associated 28-day case fatality of STEMI in anterior, inferior, and lateral infarct locations decreased during 22 years of surveillance; however, no decrease was observed for STEMI in multiple infarct locations. In conclusion, our findings suggest that there is room for improvement in the care of patients with multilocation STEMI.

Twenty-two-year trends in incidence of myocardial infarction, coronary heart disease mortality, and case fatality in 4 US communities, 1987-2008

BACKGROUND

Knowledge of trends in the incidence of and survival after myocardial infarction (MI) in a community setting is important to understanding trends in coronary heart disease (CHD) mortality rates.

METHODS AND RESULTS

We estimated race- and gender-specific trends in the incidence of hospitalized MI, case fatality, and CHD mortality from community-wide surveillance and validation of hospital discharges and of in- and out-of-hospital deaths among 35- to 74-year-old residents of 4 communities in the Atherosclerosis Risk in Communities (ARIC) Study. Biomarker adjustment accounted for change from reliance on cardiac enzymes to widespread use of troponin measurements over time. During 1987-2008, a total of 30 985 fatal or nonfatal hospitalized acute MI events occurred. Rates of CHD death among persons without a history of MI fell an average 4.7%/y among men and 4.3%/y among women. Rates of both in- and out-of-hospital CHD death declined significantly throughout the period. Age- and biomarker-adjusted average annual rate of incident MI decreased 4.3% among white men, 3.8% among white women, 3.4% among black women, and 1.5% among black men. Declines in CHD mortality and MI incidence were greater in the second decade (1997-2008). Failure to account for biomarker shift would have masked declines in incidence, particularly among blacks. Age-adjusted 28-day case fatality after hospitalized MI declined 3.5%/y among white men, 3.6%/y among black men, 3.0%/y among white women, and 2.6%/y among black women.

CONCLUSIONS

Although these findings from 4 communities may not be directly generalizable to blacks and whites in the entire United States, we observed significant declines in MI incidence, primarily as a result of downward trends in rates between 1997 and 2008.

Declining severity of myocardial infarction from 1987 to 2002: the Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Death rates for coronary heart disease have been declining in the United States, but the reasons for this decline are not clear. One factor that could contribute to this decline is a reduction in the severity of acute myocardial infarction (MI). We hypothesized that for those patients hospitalized in the Atherosclerosis Risk in Communities (ARIC) Study with acute incident MI, there was a decline in MI severity from 1987 to 2002.

METHODS AND RESULTS

The community surveillance component of the ARIC Study consisted of tracking residents 35 to 74 years of age with hospitalized MI or fatal coronary heart disease in 4 diverse communities. For incident, hospitalized MI, a probability sample of hospital discharges was validated and an MI classification was assigned according to an algorithm consisting of chest pain, ECG evidence, and cardiac biomarkers. Severity indicators were chosen from abstracted hospital charts validated as a definite or probable MI. With few exceptions, the MI severity indicators suggested a significant decline in the severity of MI during the period of 1987 to 2002. The percent of MI cases with major ECG abnormalities decreased as evidenced by a 1.9%/y (P=0.002) decline in the proportion of those with initial ST-segment elevation, a 3.9%/y (P<0.001) decline in those with subsequent Q-waves, and a 4.5%/y (P<0.001) decline in those with any major Q wave. Maximum creatine kinase and creatine kinase-MB values declined (5.2% and 7.6%; P<0.001, P<0.001 per year, respectively), although in the later years, maximum troponin I values remained stable (1.1%/y decline; P=0.66). The percent with shock declined (5.7%/y; P<0.001), although those with congestive heart failure remained stable. A combined severity score, the Predicting Risk of Death in Cardiac Disease Tool (PREDICT) score, also declined (0.2%/y; P<0.001). Results for blacks paralleled those of the entire group, as did results for women.

CONCLUSIONS

Evidence from ARIC community surveillance suggests that the severity of acute MI has declined among community residents hospitalized for incident MI. This reduction in severity may have contributed, along with other factors, to the decline in death rates for coronary heart disease.

Contribution of congestive heart failure and ischemic heart disease to excess mortality in rheumatoid arthritis

OBJECTIVE

Although mortality among patients with rheumatoid arthritis (RA) is higher than in the general population, the relative contribution of comorbid diseases to this mortality difference is not known. This study was undertaken to evaluate the contribution of congestive heart failure (CHF) and ischemic heart disease (IHD), including myocardial infarction, to the excess mortality in patients with RA, compared with that in individuals without RA.

METHODS

We assembled a population-based inception cohort of individuals living in Rochester, Minnesota, in whom RA (defined according to the criteria of the American College of Rheumatology [formerly, the American Rheumatism Association]) first developed between 1955 and 1995, and an age- and sex-matched non-RA cohort. All subjects were followed up until either death, migration from the county, or until 2001. Detailed information from the complete medical records was collected. Statistical analyses included the person-years method, cumulative incidence, and Cox regression modeling. Attributable risk analysis techniques were used to estimate the number of RA deaths that would be prevented if the incidence of CHF was the same in patients with RA and non-RA subjects.

RESULTS

The study population included 603 patients with RA and 603 subjects without RA. During followup, there was an excess of 123 deaths among patients with RA (345 RA deaths occurred, although only 222 such deaths were expected). The mortality rates among patients with RA and non-RA subjects were 39.0 and 29.2 per 1,000 person-years, respectively. There was a significantly higher cumulative incidence of CHF (but not IHD) in patients with RA compared with non-RA subjects (37.1% versus 27.7% at 30 years of followup, respectively; P < 0.001). The risk of death associated with either CHF or IHD was not significantly different between patients with RA and non-RA subjects. If the risk of developing CHF was the same in patients with RA and individuals without RA, the overall mortality rate difference between RA and non-RA hypothetically would be reduced from 9.8 to 8.0 excess deaths per 1,000 person-years; that is, 16 (13%) of the 123 excess deaths could be prevented.

CONCLUSION

CHF, rather than IHD, appears to be an important contributor to the excess overall mortality among patients with RA. CHF contributes to this excess mortality primarily through the increased incidence of CHF in RA, rather than increased mortality associated with CHF in patients with RA compared with non-RA subjects. Eliminating the excess risk of CHF in patients with RA could significantly improve their survival.

Increased unrecognized coronary heart disease and sudden deaths in rheumatoid arthritis: a population-based cohort study

OBJECTIVE

To examine the risk of clinical coronary heart disease (CHD) in patients with rheumatoid arthritis (RA) compared with age- and sex-matched non-RA subjects, and to determine whether RA is a risk factor for CHD after accounting for traditional CHD risk factors.

METHODS

We assembled a population-based incidence cohort of 603 Rochester, Minnesota residents ages >or=18 years who first fulfilled the American College of Rheumatology (ACR) 1987 criteria for RA between January 1, 1955 and January 1, 1995, and 603 age- and sex-matched non-RA subjects. All subjects were followed up through their complete inpatient and outpatient medical records, beginning at age 18 years until death, migration, or January 1, 2001. Data were collected on CHD events and traditional CHD risk factors (diabetes mellitus, hypertension, dyslipidemia, body mass index, smoking) using established diagnostic criteria. CHD events included hospitalized myocardial infarction (MI), unrecognized MI, coronary revascularization procedures, angina pectoris, and sudden CHD deaths. Conditional logistic regression and Cox regression models were used to estimate the risk of CHD associated with RA, both prior to and following RA diagnosis, after adjusting for CHD risk factors.

RESULTS

During the 2-year period immediately prior to fulfillment of the ACR criteria, RA patients were significantly more likely to have been hospitalized for acute MI (odds ratio [OR] 3.17, 95% confidence interval [95% CI] 1.16-8.68) or to have experienced unrecognized MIs (OR 5.86, 95% CI 1.29-26.64), and less likely to have a history of angina pectoris (OR 0.58, 95% CI 0.34-0.99) compared with non-RA subjects. After the RA incidence date, RA patients were twice as likely to experience unrecognized MIs (hazard ratio [HR] 2.13, 95% CI 1.13-4.03) and sudden deaths (HR 1.94, 95% CI 1.06-3.55) and less likely to undergo coronary artery bypass grafting (HR 0.36, 95% CI 0.16-0.80) compared with non-RA subjects. Adjustment for the CHD risk factors did not substantially change the risk estimates.

CONCLUSION

Patients with RA have a significantly higher risk of CHD when compared with non-RA subjects. RA patients are less likely to report symptoms of angina and more likely to experience unrecognized MI and sudden cardiac death. The risk of CHD in RA patients precedes the ACR criteria-based diagnosis of RA, and the risk cannot be explained by an increased incidence of traditional CHD risk factors in RA patients.

Trends in the sensitivity, positive predictive value, false-positive rate, and comparability ratio of hospital discharge diagnosis codes for acute myocardial infarction in four US communities, 1987-2000

Variations in the validity of hospital discharge diagnoses can complicate the assessment of trends in incidence of acute myocardial infarction (AMI). To clarify trends in the validity of discharge codes, the authors compared event classification based on published Atherosclerosis Risk in Communities (ARIC) Study criteria with the presence or absence of an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) hospital discharge code for AMI (code 410). Between 1987 and 2000, 154,836 coronary heart disease events involving hospitalization in the four ARIC communities had ICD-9-CM codes screened for AMI. The sensitivity of ICD-9-CM code 410 for classifying AMI in men (sensitivity = 0.65, 95% confidence interval (CI): 0.63, 0.66) was statistically significantly greater than that found for women (sensitivity = 0.60, 95% CI: 0.58, 0.62) and was greater in Whites (sensitivity = 0.67, 95% CI: 0.65, 0.68) than in Blacks (sensitivity = 0.50, 95% CI: 0.47, 0.53). The ethnic difference was related to a greater frequency of hypertensive heart disease and congestive heart failure codes encompassing AMI among Blacks as compared with Whites. The authors found that although the validity of ICD-9-CM code 410 to identify AMI was generally stable from 1987 through 2000, differences between Blacks and Whites and across geographic locations support investment in validation efforts in ongoing surveillance studies.

Trends in acute coronary heart disease mortality, morbidity, and medical care from 1985 through 1997: the Minnesota heart survey

BACKGROUND

Coronary heart disease (CHD) mortality continued to decline from 1985 to 1997.

METHODS AND RESULTS

We tabulated CHD deaths (ICD-9 codes 410 through 414) in the Minneapolis/St Paul, Minnesota, area. For 1985, 1990, and 1995, trained nurses abstracted the hospital records of patients 30 to 74 years old with a discharge diagnosis of acute CHD (ICD-9 codes 410 or 411). Acute myocardial infarction (AMI) events were validated and followed for 3-year all-cause mortality. Between 1985 and 1997, age-adjusted CHD mortality rates in Minneapolis/St Paul fell 47% and 51% in men and women, respectively; the comparable declines in US whites were 34% and 29%. In-hospital mortality declined faster than out-of-hospital mortality. The rate of AMI (ICD-9 code 410) hospital discharges declined almost 20% between 1985 and 1995, whereas the discharge rate for unstable angina (ICD-9 code 411) increased substantially. The incidence of hospitalized definite AMI declined approximately 10%, whereas recurrence rates fell 20% to 30%. Three-year case fatality rates after hospitalized AMI decreased consistently by 31% and 41% in men and women, respectively. In-hospital administration of thrombolytic therapy, emergency angioplasty, ACE inhibitors, beta-blockers, heparin, and aspirin increased greatly.

CONCLUSIONS

Declining out-of-hospital death rates, declining incidence and recurrence of AMI in the population, and marked improvements in the survival of AMI patients all contributed to the 1985 to 1997 decline of CHD mortality in the Minneapolis/St Paul metropolitan area. The effects of early and late medical care seem to have had the greatest contribution to rates during this time period.

Sex and race differences in short-term prognosis after acute coronary heart disease events: the Atherosclerosis Risk In Communities (ARIC) study

BACKGROUND

Case fatality after myocardial infarction (MI) among patients admitted to the hospital may differ between men and women and blacks and whites. Furthermore, a different pattern of sex and race differences in case fatality may occur when coronary deaths outside the hospital are included in the analysis. The ARIC study provides community-based data to examine 28-day case fatality rates after coronary heart disease (CHD) events.

METHOD AND RESULTS

Surveillance of out-of-hospital CHD deaths and hospitalized MI was conducted in 4 U.S. communities from 1987 to 1993. Hospital discharges and death certificates were sampled, medical records abstracted, and interviews conducted with witnesses of out-of-hospital deaths. MI and out-of-hospital death classifications followed a standard algorithm. Linkage of hospitalized MIs to fatality within 28 days ensured complete ascertainment of case fatality rate. Comorbidities and complications during hospital stay were compared to assess possible explanatory factors for differences in case fatality. Overall, age-adjusted 28-day case fatality (MI plus CHD) was higher in black men compared with white men (odds ratio 1.78, 95% confidence interval 1.4-2.2) and in black women compared with white women (odds ratio 1.5, 95% confidence interval 1. 2-2.0). Although men had higher overall case fatality rates than did women, this difference was not statistically significant. After a hospitalized MI, 28-day case fatality rate was not statistically significantly different between men compared with women or blacks compared with whites.

CONCLUSION

Race and sex differences in case fatality after hospitalized MI were not evident in these data, although when out-of-hospital deaths were included, men and blacks were more likely than women and whites to die within 28 days of an acute cardiac event. A majority of deaths occurred before hospital admission, and additional study of possible reasons for these differences should be a priority.

Agreement and coding reliability of the Minnesota and Mayo electrocardiographic coding systems

PROBLEM

To determine whether diagnoses of myocardial infarction assigned by a system that uses Marquette 12SL electrocardiographic (ECG) codes with manual over-reading agree with diagnoses assigned by Minnesota ECG codes.

STUDIES UNDERTAKEN

Agreement and recode reliability of Minnesota and Mayo coding systems based on 768 ECGs plus chest pain history and serum enzyme values were analyzed for a stratified random sample of 141 patients with an event in 1990 or 1991 coded as HICDA 410.x, 411, 413 or 796.9. The population was reconstructed from the stratified random sample so that population-based inferences could be made from the analysis.

RESULTS

For the stratified random sample, exact agreement on 4 categories (evolving diagnostic, diagnostic, equivocal, or other ECG) between Mayo and Minnesota ECG coding was 53.9% (kappa = 0.37 +/- 0.05). Code-recode agreement was higher for Minnesota coding (83.0%; kappa = 0.74 +/- 0.05) compared with Mayo coding (73.8%; kappa = 0.64 +/- 0.05). The same pattern was present for the reconstructed population. For coding myocardial infarction based on the ECG, serum enzyme levels, and the presence or absence of ischemic chest pain, agreement between Mayo and Minnesota coding was 84.4% (kappa = 0.72 +/- 0.05) based on the stratified random sample and 81.7% (kappa = 0.67 +/- 0.06) based on the reconstructed population. For the stratified random sample, reliability of diagnosis of myocardial infarction was 93.6% (kappa = 0.88 +/- 0.04) for the Minnesota system and 94.3% (kappa = 0.90 +/- 0.03) for the Mayo system.

CONCLUSION

ECG interpretation by the Mayo and Minnesota coding systems differs significantly, and Mayo ECG coding is less reliable than Minnesota ECG coding. Coding of myocardial infarction on the basis of ECGs, serum enzymes, and ischemic chest pain, however, is equally reliable for both systems.

Trends in the incidence of myocardial infarction and in mortality due to coronary heart disease, 1987 to 1994

BACKGROUND AND METHODS

To clarify the determinants of contemporary trends in mortality from coronary heart disease (CHD), we conducted surveillance of hospital admissions for myocardial infarction and of in-hospital and out-of-hospital deaths due to CHD among 35-to-74-year-old residents of four communities of varying size in the United States (a total of 352,481 persons in 1994). Between 1987 and 1994, we estimate that there were 11,869 hospitalizations for myocardial infarction (on the basis of 8572 hospitalizations sampled) and 3407 fatal coronary events (3023 sampled).

RESULTS

The largest average annual decrease in mortality due to CHD occurred among white men (change in mortality, -4.7 percent; 95 percent confidence interval, -2.2 to -7.1 percent), followed by white women (-4.5 percent; 95 percent confidence interval, -0.7 to -8.2 percent), black women (-4.1 percent; 95 percent confidence interval, -10.3 to +2.5 percent), and black men (-2.5 percent; 95 percent confidence interval, -6.9 to +2.2 percent). Overall, in-hospital mortality from CHD fell by 5.1 percent per year, whereas out-of-hospital mortality declined by 3.6 percent per year. There was no evidence of a decline in the incidence of hospitalization for a first myocardial infarction among either men or women; in fact, such hospital admissions increased by 7.4 percent per year (95 percent confidence interval for the change, +0.5 to +14.8 percent) among black women and 2.9 percent per year (95 percent confidence interval, -3.6 to +9.9 percent) among black men. Rates of recurrent myocardial infarction decreased, and survival after myocardial infarction improved.

CONCLUSIONS

From 1987 to 1994, we observed a stable or slightly increasing incidence of hospitalization for myocardial infarction. Nevertheless, there were significant annual decreases in mortality from CHD. The decline in mortality in the four communities we studied may be due largely to improvements in the treatment and secondary prevention of myocardial infarction.

Recent trends in acute coronary heart disease--mortality, morbidity, medical care, and risk factors. The Minnesota Heart Survey Investigators

BACKGROUND

Mortality from coronary heart disease (CHD) has declined in the United States since the late 1960s. To understand the reasons for the decline during the period form 1985 to 1990, we examined trends in mortality and morbidity due to CHD, medical care, and risk factors for CHD in a large metropolitan population.

METHODS

We identified all deaths from CHD in residents of the Minneapolis-St. Paul, Minnesota, metropolitan area who were 30 to 74 years old and classified the deaths according to whether they occurred in or out of the hospital. For 1985 and 1990, we obtained lists of patients in this age range who were discharged with a diagnosis of acute CHD from all area hospitals, and we selected the medical records of 50 percent of these patients for abstraction. Definite myocardial infarctions were identified with standardized diagnostic algorithm. The 1985 and 1990 cohorts of patients hospitalized for myocardial infarction were followed for at least three years to identify those who died from any cause. Trends in risk factors for CHD were investigated through surveys of 25-to-74-year-olds that were conducted in 1985 through 1987 and 1990 through 1992.

RESULTS

Between 1985 and 1990, mortality from CHD fell by 25 percent for both men and women, and the decline in in-hospital mortality (41 percent) exceeded the decline in out-of-hospital mortality (17 percent) among men. The rates of hospitalization for acute myocardial infarction declined slightly, by 5 to 10 percent, between 1985 and 1990. Survival among patients hospitalized for acute myocardial infarction increased substantially during that period. After adjustment for age and previous myocardial infarction, the relative risk of dying within three years of hospitalization for a myocardial infarction (for the 1990 cohort as compared with the 1985 cohort) was 0.76 for men (95 percent confidence interval, 0.65 to 0.89) and 0.84 for women (95 percent confidence interval, 0.71 to 1.00). Substantial increases in the use of thrombolytic therapy, heparin, aspirin, and coronary angioplasty paralleled the survival trends. In general, the risk-factor profile of the area population with respect to CHD also improved considerably during that time.

CONCLUSIONS

The recent decline in mortality due to CHD in the Minneapolis-St. Paul metropolitan area can be explained by both the declining incidence of myocardial infarction in the population and the improved survival of patients with myocardial infarction.

Surveillance and ascertainment of cardiovascular events. The Cardiovascular Health Study

While previous prospective multicenter studies have conducted cardiovascular disease surveillance, few have detailed the techniques relating to the ascertainment of and data collection for events. The Cardiovascular Health Study (CHS) is a population-based study of coronary heart disease and stroke in older adults. This article summarizes the CHS events protocol and describes the methods of surveillance and ascertainment of hospitalized and nonhospitalized events, the use of medical records and other support documents, organizational issues at the field center level, and the classification of events through an adjudication process. We present data on incidence and mortality, the classification of adjudicated events, and the agreement between classification by the Events Subcommittee and the medical records diagnostic codes. The CHS techniques are a successful model for complete ascertainment, investigation, and documentation of events in an older cohort.