Association of low-grade urinary albumin excretion with left ventricular hypertrophy in the general population: the MONICA/KORA Augsburg Echocardiographic Substudy

Association of leukocyte telomere length with echocardiographic left ventricular mass: the Framingham heart study

BACKGROUND

Leukocyte telomere length (LTL) decreases over the adult life course owing to the cumulative burden of oxidative stress, inflammation, and exposure to vascular risk factors. Left ventricular (LV) mass is a biomarker of long-standing exposure to cardiovascular disease risk factors. We hypothesized that LTL is related inversely to LV mass.

METHODS AND RESULTS

We related LTL (measured by Southern blot analysis) to echocardiographic LV mass and its components (LV diastolic dimension and LV wall thickness) in 850 Framingham Heart Study participants (mean age 58 years, 58% women) using multivariable linear regression with adjustment for age, sex, height, weight, systolic blood pressure, hypertension treatment, and smoking. Overall, multivariable-adjusted LTL was positively related to LV mass (beta-coefficient per SD increase 0.072; P=0.001), LV wall thickness (beta=0.053; P=0.01), and LV diastolic dimension (beta=0.035; P=0.09). We observed effect modification by hypertension status (P for interaction=0.02 for LV mass); LTL was more strongly associated with LV mass and LV wall thickness in individuals with hypertension (beta-coefficient per SD increment of 0.10 and 0.08, respectively; P<0.01 for both). Participants with hypertension who were in the top quartile of LV mass had LTL that was 250 base pairs longer than those in the lowest quartile (P for trend across quartiles=0.009).

CONCLUSIONS

In contrast to our expectation, in the present community-based sample, LTL was positively associated with LV mass and wall thickness, especially so in participants with hypertension. These data are consistent with the hypothesis that longer LTL may be a marker of propensity to LV hypertrophy.

Importance of low-grade albuminuria

The well-described association between chronic kidney disease and cardiovascular disease is typically thought to originate from loss of renal function, as estimated by the glomerular filtration rate. However, recent data suggest that urinary albumin excretion has an important role in this association. Albuminuria is a marker of underlying vascular dysfunction and has been correlated with structural and functional integrity of the vasculature. Although the traditional upper limit of normal daily albumin excretion has been 30 mg/d, recent epidemiologic data suggest that levels in the general population are actually much lower. Further, within this range of low-grade albuminuria (LGA), increasing excretion rates are associated with increasing risk of cardiovascular disease. This association is independent of renal function, and in the earliest stages of chronic kidney disease, LGA seems to be a more important determinant than the glomerular filtration rate. This emerging association underscores the complexity of albumin excretion, in which subtle changes in albumin excretion reflect widespread vascular processes. Using the key words albuminuria, low-grade albuminuria, and microalbuminuria in a PubMed search of literature from January 1, 1995, to February 29, 2008, this review summarizes the most recent data on LGA and its association with cardiovascular and renal disease.

Electrocardiographic criteria of left ventricular hypertrophy in general population

The question on whether the electrocardiographic criteria are reliable for detection of left ventricular hypertrophy (LVH) and play a role in predicting outcome is open. Answer can only proceed from population-based studies over unselected people followed up for years. In this study, 1,699 subjects from general population underwent echocardiogram and standard electrocardiogram (ECG) codified for LVH with Minnesota code and with other five methods. Other items were also recorded and used as covariables. Left ventricular mass index (LVMI) was 127.6 +/- 44.9 g m(-2) in men and 120.8 +/- 41.2 g m(-2 )in women, and correlated directly with age in both genders. Prevalence of echocardiographic LVH was 36.6% in men and 53.4% in women. LVMI correlated directly with the Sokolow-Lyon score in both genders at any age, with the Romhilt-Estes, Cornell and R(aVL) scores in all subjects but elderly men, and with the Lewis score in men and women aged < or =69 years. Sensitivity and the predictive value of electrocardiographic tests, as well as the prevalence of LVH diagnosed with electrocardiographic criteria, were always low. Specificity was high for all the tests, and in particular for the Cornell index. Only when diagnosed with echocardiogram or with the Sokolow-Lyon criterion, LVH was an independent predictor of mortality. We conclude that electrocardiographic tests cannot be used as a surrogate of echocardiogram in detecting LVH in the general population because their positive predictive value (PPV) is unacceptably low. On the contrary, they could replace echocardiography in the follow up and for prediction of outcome, when LVH has previously been correctly diagnosed with other methods.

[Kidney insufficiency and cardiovascular disease]

Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in patients with chronic renal disease. Severe cardiac and arterial disorders such as left ventricular hypertrophy, coronary artery disease, and arteriosclerosis of the large vessels are already evident in early renal disease, even in young patients. Despite major advances in dialysis therapy and treatment options for acute coronary syndromes, mortality remains high--up to 10-30 times higher than in the general population. The increased risk for cardiovascular disorders results from the additive effect of traditional risk factors, volume overload, and endocrine and metabolic abnormalities in uremia. During the course of the renal disease, the progression of CVD disease manifestations significantly influences outcome. Thus, preventive measures and optimal treatment are mandatory and should be among the main targets of early management of patients with chronic renal disease.

Relation of left ventricular hypertrophy with systemic inflammation and endothelial damage in resistant hypertension

The relation between left ventricular hypertrophy (LVH) and unfavorable cardiovascular prognosis may involve systemic inflammation and endothelial dysfunction/damage. The aim of this study was to investigate in a cross-sectional design the relationships of LVH with C-reactive protein (CRP) levels (a marker of systemic low-grade inflammation) and with microalbuminuria (a marker of glomerular endothelial damage) in 705 patients with resistant hypertension. At baseline, all were submitted to a laboratory evaluation including 24-hour urinary albumin excretion, 2D echocardiogram, and 24-hour ambulatory blood pressure monitoring. A total of 463 patients also had high-sensitivity CRP levels determined. LVH was defined as an indexed left ventricular mass >110 g/m(2) in women and >125 g/m(2) in men. Microalbuminuria was evaluated in 3 categories: low normal (<15 mg/24 hours), high normal (between 15 and 29 mg/24 hours), and abnormal (between 30 and 299 mg/24 hours). CRP was dichotomized at the median value (3.7 mg/L). Associations with LVH were examined after adjustment for all of the potential confounders by multivariate logistic regression. A total of 534 patients (75.7%) had LVH. After full adjustment, both abnormal microalbuminuria (odds ratio: 1.97; 95% CI: 1.04 to 3.73) and high CRP (OR: 1.76; 95% CI: 1.06 to 2.93) were independently associated with LVH occurrence. The high-normal albuminuria was associated with a borderline significant 46% increased chance of having LVH. Furthermore, the association between high CRP and LVH was observed exclusively in the subgroup with normal albuminuria. In conclusion, both systemic inflammation and endothelial damage were associated with LVH occurrence. These relationships offer insight into the pathophysiological mechanisms linking LVH to atherosclerosis and to increased cardiovascular morbidity and mortality.