Racial differences in ambulatory blood pressure and echocardiographic left ventricular geometry

Effects of Race, Cardiac Mass, and Cardiac Load on Myocardial Function Trajectories from Childhood to Young Adulthood: The Augusta Heart Study

Background

The overall goal of this longitudinal study was to determine if the Black population has decreased myocardial function, which has the potential to lead to the early development of congestive heart failure, compared with the White population.

Methods and Results

A total of 673 subjects were evaluated over a period of 30 years including similar percentages of Black and White participants. Left ventricular systolic function was probed using the midwall fractional shortening (MFS). A longitudinal analysis of the MFS using a mixed effect growth curve model was performed. Black participants had greater body mass index, higher blood pressure readings, and greater left ventricular mass compared with White participants (all P<0.01). Black participants had a 0.54% decrease of MFS compared with White participants. As age increased by 1 year, MFS increased by 0.05%. As left ventricular mass increased by 1 g, MFS decreased by 0.01%. As circumferential end systolic stress increased by 1 unit, MFS decreased by 0.04%. The MFS trajectories for race differed from early age to young adulthood.

Conclusions

Changes in myocardial function mirror the race‐dependent variations in blood pressure, afterload, and cardiac mass, suggesting that myocardial function depression occurs early in childhood in populations at high cardiovascular risk such as Black participants.

Differential impact of race and risk factors on incidence of atrial fibrillation

Despite some common risk factors for atrial fibrillation (AF) being more prevalent among blacks, African Americans are increasingly being reported with lower prevalence and incidence of AF compared with whites. Contemporary studies have not provided a complete explanation for this apparent AF paradox in African Americans. Although many traditional and novel risk factors for AF have been identified, the role of ethnic-specific risk factors has not been examined. Whereas hypertension has been the most common risk factor associated with AF, coronary artery disease also plays an important role in AF pathophysiology in whites. Thereby, elucidating the role of ethnic-specific risk factors for AF may provide important insight into why African Americans are protected from AF or why whites are more prone to develop the arrhythmia. The link between AF susceptibility and genetic processes has only been recently uncovered. Polymorphisms in renin-angiotensin system genes have been characterized as predisposing to AF under certain environmental conditions. Several ion channel genes, signaling molecules, and several genetic loci have been linked with AF. Thereby, studies investigating genetic variants contributing to the differential AF risk in individuals of African American versus European ancestry may also provide important insight into the etiology of the AF paradox in blacks.

Racial and ethnic differences in subclinical myocardial function: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Racial/ethnic differences in the incidence and severity of heart failure (HF) are not well understood, but may be related to pre-existing variations in myocardial function.

OBJECTIVE

To examine racial/ethnic differences in regional myocardial function among asymptomatic individuals free of known cardiovascular disease.

DESIGN, SETTING AND PATIENTS

The Multi-Ethnic Study of Atherosclerosis is a prospective, observational study of individuals without baseline cardiovascular disease, representing four major racial/ethnic groups. A total of 1099 study participants underwent cardiac MRI with tissue tagging; for each study, peak systolic strain (Ecc) and strain rate (SRs) were determined in four left ventricular (LV) regions.

MAIN OUTCOME MEASURES

Multiple linear regression was used to analyse the relationship between race/ethnicity and regional strain (Ecc and SRs) while adjusting for cardiovascular risk factors.

RESULTS

Compared with other racial/ethnic groups, Chinese-Americans had the greatest magnitude of Ecc in a majority of LV regions (-19.60±3.78, p<0.05); Chinese-Americans also had the greatest absolute values for SRs in all regions, reflecting higher rate of systolic contraction (-2.01±0.76, p<0.05). Conversely, African-Americans had the lowest Ecc values (-17.50±4.00, p<0.05) in the majority of wall regions while Hispanics demonstrated the lowest rate of contractility in all wall regions (-1.44±0.50, p≤0.001) in comparison with the other racial/ethnic groups. These race-based differences remained significant in the majority of LV wall regions after adjusting for multiple variables, including hypertension and LV mass.

CONCLUSIONS

Important race-based differences in regional LV systolic function in a large cohort of asymptomatic individuals have been demonstrated. Further research is needed to investigate the possible mechanisms related to the race/ethnicity-based variations found in this study.

Low cardiovascular risk is associated with favorable left ventricular mass, left ventricular relative wall thickness, and left atrial size: the CARDIA study

BACKGROUND

Echocardiographic measures of left ventricular (LV) mass and relative wall thickness and left atrial (LA) size predict future cardiovascular morbidity and mortality. The aim of this study was to compare young adults with low cardiovascular risk (body mass index, 18.5-24.9 kg/m(2); blood pressure < 120/80 mmHg; no tobacco use, no diabetes, and physical fitness) with those without these characteristics with regard to LV mass and relative wall thickness and LA size, to determine the protective effect of a healthy lifestyle on the development of these characteristics.

METHODS

Cross-sectional assessment of 4059 black and white men and women aged 23 to 35 years in the Coronary Artery Risk Development in Young Adults (CARDIA) study at the year 5-examination, when risk factors were measured, and echocardiography to assess LV mass and relative wall thickness were performed. Physical fitness was measured at baseline using a symptom-limited maximal treadmill test. All other covariates were measured concurrently with echocardiography.

RESULTS

Gender, body mass index, and systolic blood pressure were associated with LV mass and relative wall thickness and LA size in multivariate models. Additional correlates of LV mass/height(2.7) ratio were tobacco use, resting heart rate (inverse), self-reported physical activity, gender (male higher), and age. Age was associated with LV relative wall thickness but not other measures of LV size. Additional correlates of LA diameter/height ratio were tobacco use, resting heart rate (inverse), serum glucose, and self-reported physical activity. Seven hundred ninety of 4059 subjects (19%) were classified as having low risk; black race was less likely in the low-risk group. Those with low risk had lower LV mass/height(2.7) ratios (32.0 vs 34.6 g/m(2.7), P < .0001), better LV relative wall thickness (0.33 vs 0.35, P < .0001), and lower LA diameter/height ratios (2.02 vs 2.08 cm/m, P < .01).

CONCLUSIONS

A low cardiovascular risk profile in young adulthood is associated with more favorable LV mass, LV relative wall thickness, and LA size. This may be one mechanism of lifestyle protection against cardiovascular morbidity and mortality.

Effect of ethnicity and hypertension on atrial conduction: evaluation with high-resolution P-wave signal averaging

BACKGROUND

Measurements by P-wave signal-averaged electrocardiogram (P-SAECG) of P-wave duration and P-wave voltage integral are higher in patients with atrial fibrillation (AF) than in those with sinus rhythm. Hypertension is perhaps the most common cardiovascular antecedent cause of AF, and particularly a disproportionate cause of morbidity and mortality among blacks. The purpose of this study was to examine the effect of hypertension and ethnicity on P-SAECG parameters in patients without AF.

HYPOTHESIS

It was hypothesized that P-SAECG parameters can identify hypertensives, and are disproportionately higher in hypertensive blacks.

METHODS

In all, 234 normotensives and 84 hypertensives underwent P-SAECG analysis. In an ancillary study group of 34 hypertensive black men, the relationship between severity of hypertension and measured parameters of P-SAECG was evaluated.

RESULTS

Mean filtered P-wave duration and total P-wave voltage integral for normotensives of both ethnic groups were similar. Hypertensive blacks had greater increase in P-wave duration (138 +/- 16 vs. 132 +/- 12ms;p < 0.01, N42:42) and total P-wave voltage integral (922 +/- 285 vs. 764 +/- 198 microV-ms; p < 0.001) than white hypertensives. Filtered P-wave duration and total P-wave voltage integral increased with severity of hypertension.

CONCLUSIONS

Patients at very early stages of hypertension have demonstrable evidence of prolonged atrial conduction by P-SAECG and, thus, cardiac electrical remodeling. P-wave duration and total P-wave voltage integral increase with severity of hypertension. Hypertensive blacks manifest a greater increase in P-SAECG parameters than whites. This may portend an increased cardiovascular risk for black patients with hypertension.

Left ventricular architecture and survival in African-Americans free of coronary heart disease (from the Atherosclerosis Risk in Communities [ARIC] study)

Published studies of the prognostic value of left ventricular (LV) hypertrophy and LV geometric pattern in African-Americans were based on referred or hospitalized patients with hypertension or coronary heart disease. All-cause mortality rates and survival associated with LV geometric pattern were determined using echocardiography in a population-based sample of middle-aged and elderly African-American men and women. During the third (1993 to 1995) visit of the ARIC Study, echocardiography was performed at the Jackson, Mississippi, field center on the cohort of 2,445 African-Americans aged 49 to 75 years. M-Mode LV echocardiographic measurements were available for 1,722 persons. Mortality data were available through December 31, 2003. During the follow-up period (median 8.8 years, maximum 10.4), 160 deaths were identified. In men, multivariable-adjusted hazard ratios for all-cause mortality (compared with men with normal LV geometry) were 1.75 (95% confidence interval [CI] 0.71 to 4.33) in those with concentric LV hypertrophy, 0.38 (95% CI 0.08 to 1.88) in those with eccentric LV hypertrophy, and 0.79 (95% CI 0.41 to 1.54) in those with concentric remodeling. In women, multivariable-adjusted hazard ratios for all-cause mortality (compared with women with normal LV geometry) were 1.17 (95% CI 0.48 to 2.84) in those with concentric LV hypertrophy, 1.23 (95% CI 0.46 to 3.28) in those with eccentric LV hypertrophy, and 1.17 (95% CI 0.60 to 2.28) in those with concentric remodeling. In conclusion, in this population-based cohort of middle-aged and elderly African-Americans free of coronary heart disease, adjustment for baseline differences in cardiovascular disease risk factors and LV mass greatly attenuated the strength of the association between LV pattern and all-cause mortality risk in women. In men, an association between concentric LV hypertrophy and mortality risk remained.

Improvement in hypertrophic cardiomyopathy after significant weight loss: case report

A 17-year-old obese boy found to have familial apical hypertrophic cardiomyopathy on routine screening was enrolled in a weight loss program on the basis of the hypothesis that significant weight loss would improve his cardiac status. He was followed with serial dual-energy x-ray absorptiometry, electrocardiography, echocardiography, and blood pressure and pulse rate measurements. Within 1 year, he lost 49 kg, with a body mass index reduction from 43.6 to 28.1 kg/m2 and associated reductions in systolic blood pressure, diastolic blood pressure, pulse pressure, mean heart rate, rate pressure product, and echocardiographic indices of left ventricular mass that resulted in a change from the initial geometric finding of eccentric left ventricular hypertrophy to a "normal" left ventricular mass with minimal asymmetric apical left ventricular thickening. Significant weight loss in an obese adolescent with presumed familial apical hypertrophic cardiomyopathy was associated with striking improvement in cardiac functional indices, which could have profound implications for long-term cardiovascular risk.

A longitudinal study of ethnic differences in ambulatory blood pressure patterns in youth

BACKGROUND

Many studies demonstrated an ethnic difference in ambulatory blood pressure (BP) patterns. We examined: 1) the stability of this difference; 2) demographic and anthropometric characteristics that predict the difference over 2 years; and 3) the clinical significance of the difference.

METHODS

Recordings were performed 2 years apart on 94 African American and 92 European American youths with a positive family history of hypertension, aged 14 +/- 2 years at initial testing.

RESULTS

African Americans had higher nighttime systolic BP (SBP) on the initial (109 +/- 9 v 105 +/- 8 mm Hg; P < .001) and follow-up (110 +/- 10 v 105 +/- 8 mm Hg; P < .0001) visits despite similar daytime SBP. This was associated with greater left ventricular mass/height2.7 (LVM/height2.7) during the initial (31 +/- 8 v 28 +/- 6 g/height2.7; P < .01) and follow-up (32 +/- 8 v 28 +/- 8 g/height2.7; P < .02) visits. Sex accounted for 17% (P < .0001) of the variance of follow-up daytime SBP in African Americans, and age for an additional 10% (P < .001). In comparison, initial height accounted for 11% (P < .001) of the variance in European Americans. Sex accounted for 18% (P < .0001) of the variance of follow-up nighttime SBP in African Americans, age for an additional 12% (P < .0001), and initial LVM/height2.7 an additional 6% (P < .02). In contrast, sex accounted for 13% of the variance of follow-up nighttime SBP in European Americans, and initial height accounted for an additional 8% (P < .004).

CONCLUSIONS

The pattern of higher nighttime BP despite similar daytime BP in African Americans is stable over time, with sex as the most important predictor of nighttime BP in both groups. This study provides confirmatory data on the clinical significance of the differences.

Hypertension-induced organ damage in African Americans: transforming growth factor-beta(1) excess as a mechanism for increased prevalence

Hypertension is prevalent world-wide, and it affects over 50 million individuals in the United States alone. African Americans (blacks) have a high prevalence of hypertension, develop it at an earlier age, and suffer excessively from severe or malignant hypertension. They also have a high prevalence of target organ damage attributable to hypertension, including left ventricular hypertrophy, stroke, end-stage renal disease (ESRD) and coronary artery disease. Hypertensive nephrosclerosis is particularly more prevalent in blacks compared to whites, and there is evidence that factors in addition to elevated blood pressure contribute to its pathogenesis. Transforming growth factor-beta 1 (TGF-beta1) is a fibrogenic cytokine that has been implicated in the development and progression of experimental and human renal diseases. We have demonstrated that blacks with ESRD have higher circulating levels of TGF-beta1 protein compared to whites with ESRD. We have also found that hyperexpression of TGF-beta1 is more frequent in blacks with hypertension than in whites. We propose that TGF-beta1 hyperexpression may be an important mediator of hypertension and hypertensive nephrosclerosis. We hypothesize also that the increased frequency of TGF-beta1 hyperexpression may contribute to the excess burden of ESRD in blacks. Based on our hypotheses, and the observations that angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists reduce angiotensin II-mediated stimulation of TGF-beta1 production, we propose that treatment with these agents might be efficacious in preventing or slowing the progression of target organ damage in hypertensive blacks.