Left ventricular (LV) geometry is an independent predictor of cardiovascular morbidity and mortality. Although obesity is a known risk factor for cardiovascular diseases, studies have suggested a paradoxical relation between obesity and prognosis. We retrospectively assessed 26,126 female patients with normal LV ejection fraction to determine the impact of LV geometry, including normal structure, concentric remodeling, and eccentric or concentric LV hypertrophy, and obesity on mortality during an average follow-up of 1.7 years. Abnormal LV geometry occurred more commonly in obese (body mass index ≥30 kg/m 2 , n = 10,465) compared with nonobese (body mass index <30 kg/m 2 , n = 15,661) patients (56% vs 47%, respectively, p <0.0001). Overall mortality, however, was considerably less in obese compared with nonobese patients (5.6% vs 8.7%, respectively, p <0.0001). In both groups, progressive increases in mortality were observed from normal structure to concentric remodeling and then to eccentric and concentric LV hypertrophy (obese patients 2.9%, 6.5%, 6.7%, and 11.1%, respectively, and nonobese patients 5.3%, 10.6%, 11.4%, and 16.8%, respectively, p <0.0001 for trend). In conclusion, although an obesity paradox exists, in that obesity in women is associated with abnormal LV geometry but less mortality, our data demonstrate that abnormal LV geometric patterns are highly prevalent in both obese and nonobese female patients with normal ejection fraction and are associated with greater mortality.
Obesity is a strong risk factor for the development of left ventricular (LV) hypertrophy. Both obesity and LV hypertrophy has been independently shown to predict adverse cardiovascular (CV) outcomes. However, obese patients with known CV diseases such as heart failure have been shown to have better prognosis compared with leaner patients with similar disease processes, highlighting an “obesity paradox.” In the present study, in 26,216 female patients with normal systolic function, we assessed the prevalence of abnormal LV geometric patterns in both obese and nonobese female patients, the impact of obesity on these individual geometric patterns, and the independent effects of LV geometry and obesity on all-cause mortality.
Methods
We obtained relevant clinical and echocardiographic data from Ochsner clinical echocardiography database (CVIS) of 26,126 studies that were recorded at Ochsner Clinic Foundation (New Orleans, Louisiana) from January 2004 to December 2006. Patients who were selected had normal LV ejection fraction (LVEF, defined as LVEF ≥50%) and absence of moderate or severe valvular heart disease. Patients with missing clinical or echocardiographic information were also excluded from the study. Survival status for the entire cohort was obtained from the National Death Index during a mean follow-up of 1.7 ± 1.0 years. The end point was death due to all causes. This study was approved by the Institutional Review Board of the Ochsner Clinic Foundation.
Height and weight were measured to calculate body mass index (BMI = weight in kilograms divided by the square of the height in meters). Obesity was defined as BMI ≥30 kg/m 2 . Echocardiographic examinations were performed using a standard protocol. The LV dimensions and wall thickness were measured and LV mass was calculated as recommended by the American Society of Echocardiography. Using LV mass indexed to body surface area (LV mass index), LV hypertrophy was considered present in women when the LV mass index was >95 g/m 2 . Relative wall thickness (RWT) was calculated as 2 × (posterior wall thickness in diastole)/(LV internal diameter). Increased RWT was present when this ratio was >0.42. Using the gender-specific criteria recommended by the American Society of Echocardiography, the normal geometry was present when both LV mass index and RWT were normal (LV mass index ≤95 g/m 2 and RWT ≤0.42); increased RWT (>0.42) and normal LV mass index (≤95 g/m 2 ) was classified as concentric remodeling, increased LV mass index (>95 g/m 2 ) but normal RWT (≤0.42) identified eccentric LV hypertrophy, and increase in both RWT (>0.42) and LV mass index (>95 g/m 2 ) represented concentric LV hypertrophy.
All statistical analyses were performed with SAS, version 9.1 (SAS Institute, Cary, North Carolina). Two-tailed p <0.05 was considered statistically significant. Clinical data, echocardiographic data, and mortality prevalence were compared between obese and nonobese as well as among patients classified according to the different types of LV geometric patterns. Mortality prevalence by different BMI categories in total population and by LV geometric patterns in obese and nonobese patients was also assessed. Continuous variables are reported as mean ± SD, and comparison was performed by the Student t test. Categorical variables are reported as percentages, and comparison was performed using the chi-square test. Comparison among multiple groups and trend assessment were performed using analysis of variance and Mantel-Haenszel statistics. Univariate and multivariate associations of clinical (age and BMI) and echocardiographic variables (LVEF, RWT, and LV mass index) with the all-cause mortality were assessed using Cox proportional hazards regression models in the total population. Similar multivariate analysis was also performed in subgroups of obese and nonobese patients. Hazard ratios and their associated 95% confidence intervals are reported.
Results
Compared with nonobese ( Table 1 ), the obese women had significantly greater RWT and LV mass index. Within the obese group, abnormal LV geometry was present in 56%, with concentric remodeling being by far the most common abnormal geometric pattern, present in 30% of this cohort. Definite LV hypertrophy was present in 25% of the obese group (eccentric LV hypertrophy 11% and concentric LV hypertrophy 14%), whereas in the nonobese group, abnormal LV geometry was present in 47% (concentric remodeling 26%, eccentric hypertrophy 9%, and concentric LV hypertrophy 11%). Despite having greater RWT and LV mass index and a greater prevalence of abnormal LV geometric patterns, the obese women had significantly less mortality (5.6% vs 8.7%, p <0.0001) compared with nonobese. Furthermore, when examined by different BMI categories, the mortality prevalence showed significant inverse relation with BMI ( Figure 1 ). Compared with normal LV geometry ( Table 2 ), the mortality prevalence increased from 4.2% in normal to 8.7% in concentric remodeling and then 9.3% in eccentric LV hypertrophy to 14.2% in concentric LV hypertrophy groups. Compared with normal LV geometry, abnormal LV geometric patterns were associated with increased mortality in both obese and nonobese women ( Figure 2 ). Among abnormal LV geometry categories, concentric hypertrophy had the highest mortality, both in obese (11.1%) and nonobese patients (16.8%). Importantly, within each LV geometric category, the mortality prevalence was significantly less in obese compared with nonobese patients. During the follow-up, 1,947 women (7.5%) died. As listed in Table 3 , compared with surviving women, deceased women had significantly lower BMI and obesity prevalence but greater RWT, LV mass index, and prevalence of abnormal LV geometry. In univariate analysis ( Table 3 ), the mortality risk increased with changes from concentric remodeling to eccentric LV hypertrophy and then to concentric LV hypertrophy. Similarly, obesity was associated with lower mortality. Using multivariate analysis, although in the total cohort, higher BMI was an independent predictor of lower mortality; within the obese group, higher BMI is a strong independent predictor of higher mortality ( Table 4 ).
| Parameter | Nonobese (n = 15,661) | Obese (n = 10,465) | p Value |
|---|---|---|---|
| Age (yrs) | 63.2 ± 16.9 | 58.4 ± 14.1 | <0.0001 |
| BMI (kg/m 2 ) | 24.7 ± 3.3 | 37.0 ± 6.5 | <0.0001 |
| Ejection fraction (%) | 61.3 ± 4.5 | 61.6 ± 4.4 | <0.0001 |
| LV end-diastolic diameter (cm) | 4.3 ± 0.5 | 4.5 ± 0.5 | <0.0001 |
| Septal thickness (cm) | 0.88 ± 0.18 | 0.95 ± 0.17 | <0.0001 |
| Posterior wall thickness (cm) | 0.87 ± 0.16 | 0.94 ± 0.15 | <0.0001 |
| RWT | 0.41 ± 0.10 | 0.42 ± 0.08 | <0.0001 |
| LV mass (g) | 134.0 ± 46.2 | 167.3 ± 52.7 | <0.0001 |
| LV mass index (g/m 2 ) | 78.8 ± 26.0 | 83.1 ± 24.8 | <0.0001 |
| LV geometry (%) | |||
| Normal | 53.2 | 44.4 | <0.0001 |
| Concentric remodeling | 26.4 | 30.0 | <0.0001 |
| Eccentric hypertrophy | 9.1 | 11.3 | <0.0001 |
| Concentric hypertrophy | 11.3 | 14.3 | <0.0001 |
| Mortality (%) | 8.7 | 5.6 | <0.0001 |
| Variable | Normal (12,987) | Concentric Remodeling (7,272) | Eccentric Hypertrophy (2,600) | Concentric Hypertrophy (3,267) | p Value | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| N vs CR | N vs EH | N vs CH | CR vs EH | CR vs CH | EH vs CH | |||||
| Age (yrs) | 57.3 ± 16.1 | 64.2 ± 15.1 | 64.1 ± 15.3 | 68.2 ± 13.9 | <0.0001 | <0.0001 | <0.0001 | 0.77 | <0.0001 | <0.0001 |
| BMI (kg/m 2 ) | 28.8 ± 7.3 | 30.1 ± 7.8 | 30.7 ± 8.3 | 30.7 ± 8.2 | <0.001 | <0.001 | <0.001 | 0.001 | 0.0005 | 0.97 |
| Obesity (BMI ≥30 kg/m 2 ), % | 35.8 | 43.2 | 45.3 | 45.8 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| Ejection fraction (%) | 61.3 ± 4.1 | 62.1 ± 4.4 | 59.7 ± 5.0 | 61.9 ± 5.2 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | 0.04 | <0.0001 |
| LV end-diastolic diameter (cm) | 4.45 ± 0.39 | 3.93 ± 0.40 | 5.11 ± 0.38 | 4.5 ± 0.43 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| Posterior wall thickness (cm) | 0.79 ± 0.10 | 0.96 ± 0.10 | 0.94 ± 0.08 | 1.15 ± 0.16 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| Septal wall thickness (cm) | 0.81 ± 0.11 | 0.94 ± 0.13 | 0.98 ± 0.14 | 1.16 ± 0.19 | <0.0001 | <0.0001 | <0.0001 | <0.001 | <0.001 | <0.001 |
| RWT (cm) | 0.36 ± 0.04 | 0.49 ± 0.07 | 0.37 ± 0.04 | 0.52 ± 0.12 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| LV mass (g) | 126.4 ± 31.6 | 129.9 ± 33.1 | 209.1 ± 42.9 | 220.4 ± 50.7 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| LV mass index (g/m 2 ) | 69.5 ± 14.1 | 70.7 ± 14.9 | 112.7 ± 18.2 | 120.2 ± 24.8 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| Mortality, % | 4.2 | 8.7 | 9.3 | 14.2 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
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