Major electrocardiographic abnormalities among American Indians aged 45 to 74 years (the Strong Heart Study)

A large population-based study on the prevalence of electrocardiographic abnormalities: A result of Mashhad stroke and heart atherosclerotic disorder cohort study

BACKGROUND

Twelve-lead electrocardiogram (ECG) is a common and inexpensive tool for the diagnostic workup of patients with suspected cardiovascular disease, both in clinical and epidemiological settings. The present study was designed to evaluate ECG abnormalities in Mashhad population.

METHODS

ECGs were taken as part of MASHAD cohort study (phase1) and were coded according to the Minnesota coding criteria. Data were analyzed using SPSS.

RESULTS

Total 9035 ECGs were available for final analysis including 3615 (40.0%) male and 5420 (60.0%) female. Among ECG abnormalities precordial Q wave, major T-wave abnormalities, inferior Q wave, sinus bradycardia, and left axis deviation were the most prevalent abnormalities. The frequency of precordial and inferior Q wave, inferior QS pattern, major and minor ST abnormalities, major and minor T abnormalities, Wolff-Parkinson-White and Brugada pattern, sinus bradycardia, sinus tachycardia, left axis deviation, ST elevation, and tall T wave were significantly different between two genders. Moreover, the frequency of Q wave in precordial and aVL leads, QS pattern in precordial and inferior leads, major and minor T-wave abnormalities, Wolff-Parkinson-White, atrial fibrillation, sinus bradycardia, left axis deviation, and ST elevation were significantly different in different age groups. A comparison of the heart rate, P-wave duration, and QRS duration between men and women indicated that there was a significant difference.

CONCLUSIONS

Our finding indicated that the prevalence ECG abnormalities are different between men and women and also it varied in different age groups.

Very Low Prevalence and Incidence of Atrial Fibrillation among Bolivian Forager-Farmers

Background

Atrial fibrillation is the most common arrhythmia in post-industrialized populations. Older age, hypertension, obesity, chronic inflammation, and diabetes are significant atrial fibrillation risk factors, suggesting that modern urban environments may promote atrial fibrillation.

Objective

Here we assess atrial fibrillation prevalence and incidence among tropical horticulturalists of the Bolivian Amazon with high levels of physical activity, a lean diet, and minimal coronary atherosclerosis, but also high infectious disease burden and associated inflammation.

Methods

Between 2005-2019, 1314 Tsimane aged 40-94 years (52% female) and 534 Moseten Amerindians aged 40-89 years (50% female) underwent resting 12-lead electrocardiograms to assess atrial fibrillation prevalence. For atrial fibrillation incidence assessment, 1059 (81% of original sample) Tsimane and 310 Moseten (58%) underwent additional ECGs (mean time to follow up 7.0, 1.8 years, respectively).

Findings

Only one (male) of 1314 Tsimane (0.076%) and one (male) of 534 Moseten (0.187%) demonstrated atrial fibrillation at baseline. There was one new (female) Tsimane case in 7395 risk years for the 1059 participants with >1 ECG (incidence rate = 0.14 per 1,000 risk years). No new cases were detected among Moseten, based on 542 risk years.

Conclusion

Tsimane and Moseten show the lowest levels of atrial fibrillation ever reported, 1/20 to ~1/6 of rates in high-income countries. These findings provide additional evidence that a subsistence lifestyle with high levels of physical activity, and a diet low in processed carbohydrates and fat is cardioprotective, despite frequent infection-induced inflammation. Findings suggest that atrial fibrillation is a modifiable lifestyle disease rather than an inevitable feature of cardiovascular aging.

Reference interval determination of total plasma homocysteine in an Indian population

Hyperhomocysteinemia has been shown to be an independent risk factor for cardiovascular disease as well as retinal vascular occlusion. Because of the epidemiological, dietary, genetic and environmental diversity among the different countries, each country should establish the reference interval of homocysteine of their own population for recommending appropriate medical decision limits. Hence a total of 1,288 apparently healthy subjects including 636 male and 652 female were enrolled in the present study to determine the reference intervals of homocysteine in an Indian population. Results of the study were presented as mean, standard deviation, median and 2.5th and 97.5th percentile with the 0.90 confidence interval of each percentile values of homocysteine along with decade-wise changes.

Major and minor electrocardiographic abnormalities and their association with underlying cardiovascular disease and risk factors in Hispanics/Latinos (from the Hispanic Community Health Study/Study of Latinos)

The association of electrocardiographic (ECG) abnormalities with cardiovascular disease and risk factors has been extensively studied in whites and African-Americans. Comparable data have not been reported in Hispanics/Latinos. The Hispanic Community Health Study/Study of Latinos (HCHS/SOL) is a multicenter, community-based, prospective cohort study of men and women of diverse backgrounds aged 18 to 74 years who self-identified as Hispanic/Latinos. Participants (n = 16,415) enrolled from March 2008 to June 2011. We describe the prevalence of minor and major ECG abnormalities and examined their cross-sectional associations with cardiovascular disease and risk factors. The Minnesota code criteria were used to define minor and major ECG abnormalities. Previous cardiovascular disease and risk factors were based on data obtained at baseline examination. Significant differences in prevalent ECG findings were found between men and women. Major ECG abnormalities were present in 9.2% (95% confidence interval 8.3 to 10.1) of men and 6.6% (95% confidence interval 5.8 to 7.3) of women (p <0.0001). The odds of having major ECG abnormalities significantly increased with age, presence of ≥3 cardiovascular risk factors, and prevalent cardiovascular disease, in both men and women. Significant differences in major ECG abnormalities were found among the varying groups; Puerto Ricans and Dominicans had more major abnormalities compared with Mexican men and women. In conclusion, in a large cohort of Hispanic/Latino men and women, prevalence of major abnormalities was low, yet strong associations of major ECG abnormalities with cardiovascular disease and risk factors were observed in both men and women.

Reference intervals for serum total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, Lp (a), apolipoprotein A-I, A-II, B, C-II, C-III, and E in healthy South Indians from Andhra Pradesh

The incidence of cardiovascular and cerebrovascular disease is steadily increasing in South East Asian countries including Indian sub continent. Many lipids, apolipoproteins and Lp (a) except HDL-C and apo A-I, A-II are implicated as risk factors for coronary artery disease and cerebrovascular disease. There is great need to have national guidelines for each country like the ATP III guidelines recommended for U.S. population. For recommending appropriate medical decision limits, it is mandatory that each country establishes reference intervals pertaining to their population due to dietary, genetic and environmental diversity. In the present study, reference intervals for serum lipids, apolipoproteins and Lp (a) were established in a total of 1923 healthy Indian reference individuals comprising 1161 healthy men and 762 healthy women from Andhra Pradesh. For each analyte viz., serum total cholesterol, HDL-C, LDL-C, triglycerides, Lp (a), Apo A-I, Apo A-II, B, C-II, C-III and E, mean, two SD, median, confidence limits of mean, different percentile values are presented. The study also includes decade wise changes in each analyte and comparison of lipids, lipoproteins and Lp (a) among few populations covering U.S., India, Japan, Sweden, Finland and China. Reference Intervals for all lipid and lipoprotein parameters will immensely help in assessing associated risk for cardiovascular and cerebrovascular diseases in India. Additionally, the results will be beneficial in formulating our own guidelines pertaining to Indian population.

Asymptomatic myocardial ischaemia in HIV-infected adults

BACKGROUND

Asymptomatic ischaemic heart disease (IHD) in HIV-infected patients has not been studied.

METHODS

Resting, 12-lead electrocardiograms (ECG) were evaluated for asymptomatic IHD (Q-wave and/or ST segment depression) at baseline from HIV-infected participants with no known IHD enrolling in the SMART study. The ECG recordings were standardized and centrally analysed. Factors associated with asymptomatic IHD were identified by logistic regression, sequentially adjusted for demographics, clinical history, metabolic risk factors and type and duration of antiretroviral therapy (ART).

RESULTS

Of 4831 participants with an evaluable, baseline ECG and no prior IHD, mean age was 44 years (SD, 9.3); 28.4% were female; 6.6% had diabetes; 16.5% were receiving antihypertensive therapy; and 95.4% were ART experienced. ECG evidence of IHD was detected in 526 (10.9%) [Q-wave in 283 (5.9%), ST segment depression in 264 (5.5%)]; 16.7% in those 60 years or older. Variables independently associated with these abnormalities were older age [age > or= 60 versus < 40 years: odds ratio (OR), 2.2; 95% confidence interval (CI), 1.5-3.2; P < 0.001], current antihypertensive therapy (OR, 1.5; 95% CI, 1.1-1.9; P = 0.003) and recruitment in Europe (OR, 1.4; 95% CI, 1.1-1.7; P = 0.004) or Asia (OR, 1.6; 95% CI, 1.0-2.6; P = 0.05), both compared with North America. Diabetes was borderline significant (OR, 1.4; 95% CI, 1.0-2.0; P = 0.06).

CONCLUSIONS

ECG evidence of asymptomatic IHD was common in this large cohort of HIV-infected adults and more common than a history of symptomatic IHD. Traditional factors were the predominant determinants of risk. No clear association between ART type or duration and asymptomatic IHD was noted.

Prevalence and Prognostic Significance of Wall-Motion Abnormalities in Adults Without Clinically Recognized Cardiovascular Disease

Background— Left ventricular wall motion (WM) abnormalities have recognized prognostic significance in patients with coronary or other heart diseases; however, whether abnormal WM predicts adverse events in adults without overt cardiovascular disease has not been assessed. Our objective was to determine whether echocardiographic WM abnormalities predict subsequent cardiovascular events in a population-based sample.

Methods and Results— Participants (n=2864, mean age 60±8 years, 64% women) without clinically evident cardiovascular disease in the second Strong Heart Study examination who had complete echocardiographic WM assessment were studied. Echocardiographic assessment revealed that 5% of participants (n=140) had focal hypokinesia, and 1.5% (n=42) had WM abnormalities. Relationships between WM abnormalities and fatal and nonfatal cardiovascular events (including myocardial infarction, stroke, coronary artery disease, and heart failure; n=554) and cardiovascular death (n=182) during 8±2 years follow-up were examined. In Cox regression, after adjustment for age, gender, waist/hip ratio, systolic blood pressure, and diabetes mellitus, segmental WM abnormalities were associated with a 2.5-fold higher risk of cardiovascular events and a 2.6-fold higher risk of cardiovascular death (both P <0.0001). In similar multivariable models, global WM abnormalities were associated with a 2.4-fold higher risk of cardiovascular events ( P =0.001) and a 3.4-fold higher risk of cardiovascular death ( P =0.003).

Conclusions— Echocardiographic left ventricular WM abnormalities in adults without overt cardiovascular disease are associated with 2.4- to 3.4-fold higher risks of cardiovascular morbidity and mortality, independent of established risk factors.

Computerized ST depression analysis improves prediction of all-cause and cardiovascular mortality: the strong heart study

BACKGROUND

Nonspecific ST depression assessed by standard visual Minnesota coding (MC) has been demonstrated to predict risk. Although computer analysis has been applied to digital ECGs for MC, the prognostic value of computerized MC and computerized ST depression analyses have not been examined in relation to standard visual MC.

METHODS

The predictive value of nonspecific ST depression as determined by visual and computerized MC codes 4.2 or 4.3 was compared with computer-measured ST depression >or= 50 microV in 2,127 American Indian participants in the first Strong Heart Study examination. Computerized MC and ST depression were determined using separate computerized-ECG analysis programs and visual MC was performed by an experienced ECG core laboratory.

RESULTS

The prevalence of MC 4.2 or 4.3 by computer was higher than by visual analysis (6.4 vs 4.4%, P < 0.001). After mean follow-up of 3.7 +/- 0.9 years, there were 73 cardiovascular deaths and 227 deaths from all causes. In univariate Cox analyses, visual MC (relative risk [RR] 4.8, 95% confidence interval [CI] 2.6-9.1), computerized MC (RR 6.0, 95% CI 3.5-10.3), and computer-measured ST depression (RR 7.6, 95% CI 4.5-12.9) were all significant predictors of cardiovascular death. In separate multivariate Cox regression analyses that included age, sex, diabetes, HDL and LDL cholesterol, body mass index, systolic and diastolic blood pressure, microalbuminuria, smoking, and the presence of coronary heart disease, computerized MC (RR 3.0, 95% CI 1.6-5.6) and computer-measured ST depression (RR 3.1, 95% CI 1.7-5.7), but not visual MC, remained significant predictors of cardiovascular mortality. When both computerized MC and computer-measured ST depression were entered into the multivariate Cox regression, each variable provided independent risk stratification (RR 2.1, 95% CI 1.0-4.4, and RR 2.1, 95% CI 1.0-4.4, respectively). Similarly, computerized MC and computer-measured ST depression, but not visual MC, were independent predictors of all-cause mortality after controlling for standard risk factors.

CONCLUSIONS

Computer analysis of the ECG, using computerized MC and computer-measured ST depression, provides independent and additive risk stratification for cardiovascular and all-cause mortality, and improves risk stratification compared with visual MC. These findings support the use of routine computer analysis of ST depression on the rest ECG for assessment of risk and suggest that computerized MC can replace visual MC for this purpose.

Electrocardiographic abnormalities predict deaths from cardiovascular disease and ischemic heart disease in Pima Indians with type 2 diabetes

BACKGROUND

The association between electrocardiographic (ECG) abnormalities and deaths from cardiovascular diseases (CVD) and ischemic heart disease (IHD) has been reported in the general population, but there is little information regarding persons with type 2 diabetes.

METHODS

Minor and major ECG abnormalities were identified and classified according to the Minnesota Code in a longitudinal study of 1605 Pima Indians aged > or =35 years with type 2 diabetes. Underlying causes of death were determined by review of all available clinical records, autopsy reports, medical examiners' findings, and death certificates.

RESULTS

During a median follow-up of 14.1 years (range 0.1 to 33.8 years), there were 190 CVD deaths, 135 (71.1%) of which were attributable to IHD. The age-adjusted CVD death rates in men with none, minor, and major ischemic ECG abnormalities were 7.3, 12.2 and 27.8, and in women, 4.3, 4.8 and 12.5 per 1000 person-years, respectively. After adjustment for other co-variables in a multiple proportional hazards model, subjects with minor and major ischemic abnormalities on ECG had 1.22 (95% CI, 0.76-1.97) and 1.83 (95% CI, 1.21-2.76) times the CVD death rate, and 1.32 (95% CI, 0.70-2.50) and 2.12 (95% CI, 1.26-3.57) times the IHD death rate of those with no ischemic ECG abnormalities, respectively.

CONCLUSIONS

The CVD and IHD death rates were higher in men and in subjects with major ischemic ECG abnormalities. Major ischemic abnormalities on ECG predicted death after accounting for other cardiovascular risk factors, including proteinuria.

Prevalence of hypertrophic cardiomyopathy in a population-based sample of American Indians aged 51 to 77 years (the Strong Heart Study)

Recognition of the frequency with which hypertrophic cardiomyopathy (HC) occurs in the general population is critical to understanding its demographics and public health implications. However, few data are available for estimating HC prevalence in large populations of different age strata and ethnic or racial groups. The Strong Heart Study is a prospective, population-based epidemiologic survey of cardiovascular disease in residents of 13 geographically diverse American Indian communities. The study population was comprised of 3,501 subjects with echocardiograms performed in 1993 and 1995 to determine the prevalence of HC in middle-aged and older adult populations. Evidence of the HC phenotype was present in 8 previously undiagnosed patients (0.23%; 2 of 1,000) based on a left ventricular (LV) wall thickness >/=15 mm and a nondilated cavity that was not associated with another cardiac disease and was sufficient to produce the magnitude of hypertrophy evident. Ages were 51 to 77 years (mean 64 +/- 9). Four subjects were men and 4 were women, with prevalences by gender of 0.3% (3 of 1,000) and 0.18% (1.8 of 1,000), respectively. Maximum LV thicknesses were 19 to 29 mm (mean 21 +/- 3). Two subjects had mitral valve systolic anterior motion, which was sufficient to produce LV outflow obstruction at rest in 1 patient. Different electrocardiographic abnormalities were present in 5 subjects. In conclusion, clinically unrecognized HC was present in 1:500 of an aging American Indian cohort. This prevalence was similar to that reported in other general populations comprised of younger subjects of other races, offering evidence that HC is a relatively common genetic disease with widespread occurrence within the United States.

ECG abnormalities in the elderly: prevalence, time and generation trends and association with mortality

BACKGROUND AND AIMS

Electrocardiographic (ECG) abnormalities are often found in older patients but relatively few epidemiological studies have been performed. This study describes: a) cross-sectional differences in ECG abnormalities among three 70-year-old cohorts born over a period of 30 years; b) longitudinal changes in ECG abnormalities from the age of 70 to 85; and c) the relationship between ECG abnormalities at age 70 and subsequent 10- and 15-year mortality in men and women.

METHODS

Trends in the prevalence of ECG abnormalities were investigated among 2100 70-year olds (994 men, 1106 women) from three cohorts born in 1901/02 (I), 1911/12 (III) and 1930 (VI). Longitudinal changes and mortality risks were investigated among 973 70-year olds (449 men and 524 women) from cohort I, which was followed from 1971 until 2001.

RESULTS

In both sexes, the prevalence of ECG abnormalities was significantly lower in the later-born cohorts. From age 70 to 85, there was an increase in both men and women of large or intermediate Q-waves, left axis deviation, negative T-waves (0-5 mm), complete right bundle branch block (RBBB), and atrial fibrillation or flutter. Compared with those with no ECG abnormalities, the mortality risk was higher among individuals with large and intermediate Q-waves and negative T-waves (> or = 1 mm) in both sexes, and STJ depression > or = 0.5 mm and complete LBBB together with complete RBBB and intraventricular block; QRS > or = 0.12 sec in men only.

CONCLUSIONS

ECG abnormalities are frequent in the elderly, they increase with age, and are associated with increased mortality.

Diabetes mellitus and coronary heart disease

Diabetes mellitus, especially type 2 diabetes, is a growing concern in America. Longitudinal trends show that obesity is more prevalent than in the past, and the incidence of type 2 diabetes is also increasing. Type 2 diabetes typically doubles the CHD risk in men and triples the risk in women. Intervening to control lipid levels and blood pressure has been shown to be especially helpful in preventing CHD, but the impact of better glycemic control on CHD risk is less convincing, especially in clinical trials. Revascularization studies in diabetics show that coronary bypass surgery is related to better outcomes than angioplasty procedures.

Ethnic differences in the ST segment of the electrocardiogram: a comparative study among six ethnic groups

Deviation of the ST segment of the electrocardiogram (ECG) may signify infarction or ischemia. Prior studies suggest that normal ECG patterns may differ among ethnic groups. We retrospectively reviewed the first thousand medical files of a multiethnic community, where all individuals shared similar living conditions. Only healthy adults, aged 15 to 60 years, were included. Along with age, the most common causes for exclusion were diabetes, hypertension, and ischemic heart disease. A total of 597 subjects (349 men) were included: 350 Saudi Arabians, 39 Filipinos, 95 Indians, 17 Sri-Lankans, and 57 Caucasians. Twenty men and one woman had an ECG pattern of early repolarization (ST segment elevation with upward concavity, notching on QRS, and large symmetrical T wave), with no difference in incidence among ethnic groups. ST segment elevation (2 mm in any of the leads V1-V4, or 1 mm in any of the other leads) without criteria of early repolarization occurred in 11.58%, 13.46%, 3.57%, 4.35%, 11.76%, 7.32% of Saudi, Indian, Jordanian, Filipino, Sri-Lankan, and Caucasian men, respectively (P =.61). Only one Jordanian and 2 Indian women had this pattern. However, Filipino men had higher median ST segment levels than others in leads V1 and V3. Among women, the median ST segment level was iso-electric in all leads in all ethnic groups. Only 3 subjects had ST segment depression >1 mm. Significant ST segment elevation is common in normal healthy men but may not fulfill criteria for early repolarization; it has no ethnic predilection. ST segment elevation is uncommon in normal women. ST segment depression is a rare finding in healthy adults regardless of ethnic origin.

Spirometry reference values for American Indian adults: results from the Strong Heart Study

STUDY OBJECTIVE

To derive spirometry normative values from a large population of American Indian adults and compare them to reference values for white adults.

DESIGN

Pulmonary function was assessed using spirometry in participants of the Strong Heart Study, a multicenter, community-based, prospective study of cardiovascular risk factors and disease in American Indians, utilizing American Thoracic Society guidelines and a vigorous quality assurance program.

SETTING

Central Arizona, southwestern Oklahoma, central South Dakota, and northeastern North Dakota.

PARTICIPANTS

Acceptable spirometry results were obtained from 1,619 women and 1,005 men aged 45 to 74 years.

RESULTS

Internal reference values and normal ranges for FEV(1), FVC, and the FEV(1)/FVC ratio were derived from a healthy subgroup of 253 women and 190 men, identified by excluding participants with factors associated with a lower FEV(1). Ten percent of the entire cohort (269 of 2,624 subjects) had airways obstruction, as defined by an FEV(1)/FVC below the lower limit of the normal (LLN) using the internal reference equations. After allowing for measurement "noise," 31 participants were below the LLN using reference equations for white adults from the large National Health and Nutrition Examination Study (NHANES) III study but were normal using the internal reference equations (1.3% false-positive), while 27 participants were classified as normal using NHANES III equations but had airways obstruction using the internal reference equations (1.2% false-negative). Similarly low misclassification rates were seen for a low FVC (prevalence, 17.6%).

CONCLUSION

For clinical purposes, NHANES III spirometry reference equations for white adults may be used when testing American Indian women and men aged 45 to 74 years.

An evidence-based review of the resting electrocardiogram as a screening technique for heart disease

Given renewed interest in the primary prevention of cardiovascular disease, we comprehensively reviewed the utility of the electrocardiogram (ECG) for screening considering the seminal epidemiologic studies. It appears that conventional risk factors relate to long-term risk, while ECG abnormalities are better predictors of short-term risk. For individual ECG abnormalities as well as for pooled categories of ECG abnormalities, the sensitivity of the ECG for future events was too low for it to be practical as a screening tool. This almost certainly relates to the low prevalence of these abnormalities. However, all ECG abnormalities increase with age and pre-test risk. Also screening with the ECG is of minimal cost and likely to decrease further as stand-alone machines are replaced by integration into personal computers (PC). Another potential impact on performing screening ECGs would be distribution and availability of digitized ECG data via the World Wide Web. For clinical utility of ECG data, comparison with previous ECGs can be critical but is currently limited. PC based ECG systems could very easily replace many of the ECG machines in use that only have paper output. PC-ECG systems would also permit interaction with computerized medical information systems, facilitate emailing and faxing of ECGs as well as storage at a centralized web-server. Web-enabled ECG recorders similar to the new generation of home appliances could follow this quick PC solution. A serious goal for the medical industry should be to end the morass of proprietary ECG digital formats and follow a standardized format. This could lead to a network of web-servers from which every patient's ECGs would be available. Such a situation could have a dramatic effect on the advisability of performing screening ECGs.

Differences in echocardiographic findings and systemic hemodynamics among non-diabetic American Indians in different regions: The Strong Heart Study

PURPOSE

This study was undertaken to determine whether differences in left ventricular (LV) and systemic hemodynamic findings exist between American Indians in different regions that might contribute to known differences in cardiovascular morbidity rates among American Indians.

METHODS

We compared echocardiography results in 290 non-diabetic Strong Heart Study (SHS) participants in Arizona, 595 in Oklahoma and 572 in North/South Dakota (ND/SD).

RESULTS

Participants in the 3 regions were similar in age and gender but those in Arizona had the highest body mass indices and lowest heart rates while those in ND/SD had the lowest diastolic blood pressures (BP). In analyses that adjusted for significant covariates, ND/SD participants had larger aortic (Ao) anular, Ao root, and LV chamber size as well as higher cardiac output and lower peripheral resistance, whereas Arizona participants had increased LV wall thickness and mass and reduced LV myocardial contractility. These findings may contribute to the known high rates of cardiovascular events in ND/SD Indians and to the proportionately higher rate of cardiovascular death than of non-fatal cardiovascular events that has been recently documented in Arizona Indians.

CONCLUSIONS

Application of echocardiography to non-diabetic SHS participants reveals that LV chamber and arterial size are larger in ND/SD Indians and that LV wall thicknesses and mass are higher and LV myocardial contractility lower in Arizona Indians, possibly contributing to the higher than expected rates of cardiovascular morbidity and mortality among Indians in Arizona.

Assessment of QT interval and QT dispersion for prediction of all-cause and cardiovascular mortality in American Indians: The Strong Heart Study

BACKGROUND

Both a prolonged QT interval and increased QT interval dispersion (QTD) have been proposed as surface ECG markers of vulnerability to ventricular arrhythmias and potential predictors of mortality.

METHODS AND RESULTS

The predictive values of QT prolongation and QTD were assessed in 1839 participants in the Strong Heart Study, a prospective study of cardiovascular disease in American Indians. ECGs were acquired at 250 Hz; QT intervals were measured by computer in all 12 leads and corrected for heart rate (QTc) by use of Bazett's formula. QTD was calculated as the difference between the maximum and minimum QTc. After a mean follow-up of 3.7+/-0.9 years, there were 188 deaths from all causes, including 55 cardiovascular deaths. In univariate Cox analyses, prolonged QTc and increased QTD were significant predictors of all-cause mortality (chi(2)=53.0, P<0.0001; chi(2)=11.3, P=0.0008) and cardiovascular mortality (chi(2)=14.7, P=0.0001; chi(2)=26.5, P<0.0001). In multivariate Cox regression analyses controlling for risk factors, QTc remained a strong predictor of all-cause mortality (chi(2)=16.5, P<0.0001) and a weaker predictor of cardiovascular mortality (chi(2)=5.8, P=0.016); QTD remained a significant predictor of cardiovascular mortality only (chi(2)=12.5, P=0.0004).

CONCLUSIONS

These findings support the value of computerized measurements of QTc and QTD in noninvasive risk stratification and suggest that these surface ECG variables may reflect different underlying abnormalities of ventricular repolarization.

Rising tide of cardiovascular disease in American Indians. The Strong Heart Study

BACKGROUND

Although cardiovascular disease (CVD) used to be rare among American Indians, Indian Health Service data suggest that CVD mortality rates vary greatly among American Indian communities and appear to be increasing. The Strong Heart Study was initiated to investigate CVD and its risk factors in American Indians in 13 communities in Arizona, Oklahoma, and South/North Dakota.

METHODS AND RESULTS

A total of 4549 participants (1846 men and 2703 women 45 to 74 years old) who were seen at the baseline (1989 to 1991) examination were subjected to surveillance (average 4.2 years, 1991 to 1995), and 88% of those remaining alive underwent a second examination (1993 to 1995). The medical records of all participants were exhaustively reviewed to ascertain nonfatal cardiovascular events that occurred since the baseline examination or to definitively determine cause of death. CVD morbidity and mortality rates were higher in men than in women and were similar in the 3 geographic areas. Coronary heart disease (CHD) incidence rates among American Indian men and women were almost 2-fold higher than those in the Atherosclerosis Risk in Communities Study. Significant independent predictors of CVD in women were diabetes, age, obesity (inverse), LDL cholesterol, albuminuria, triglycerides, and hypertension. In men, diabetes, age, LDL cholesterol, albuminuria, and hypertension were independent predictors of CVD.

CONCLUSIONS

At present, CHD rates in American Indians exceed rates in other US populations and may more often be fatal. Unlike other ethnic groups, American Indians appear to have an increasing incidence of CHD, possibly related to the high prevalence of diabetes. In the general US population, the rising prevalence of obesity and diabetes may reverse the decline in CVD death rates. Therefore, aggressive programs to control diabetes and its risk factors are needed.