Heart Care Info - Heart Disease Prevention & Treatment

Favorable Changes in Cardiac Geometry and Function Following Gastric Bypass Surgery:: 2-Year Follow-Up in the Utah Obesity Study

T Owan, E Avelar, K Morley, R Jiji, N Hall... - Journal of the American ..., 2011 - Elsevier At a 2-year follow up, GBS subjects had a large reduction in body mass index compared with the reference group (−15.4 7.2 kg/m 2 vs. −0.03 4.0 kg/m 2 ; p < 0.0001), as well as significant reductions in waist circumference, systolic blood pressure, heart rate, triglycerides, low- ...

Left ventricular dimensions and volumes were determined from 2-dimensional or M-mode images according to established criteria ( [26] and [27]). These measurements were used to calculate LV mass using the modified cube formula (28) and the area-length method (26). Global LV systolic function was assessed using LV endocardial fractional shortening and ejection fraction, and myocardial function was assessed with midwall fractional shortening (MWFS) ( [26] and [29]). Left ventricular hypertrophy was defined using LV mass/height2.7 with sex-specific cut-offs (30). The LA volume was measured in the apical 4-chamber view at end-systole using the method of discs. The LA volume was not indexed to body surface area because this causes underestimation of the relative chamber size in severely obese subjects. Right ventricular (RV) major and minor axis dimensions and systolic and diastolic cavity areas were measured in the apical 4-chamber view. Pulsed-wave Doppler measurements were recorded at the medial portion of the mitral annulus to assess the early diastolic myocardial velocity (E ). The ratio of the early diastolic mitral flow velocity (E) to E was used as an index of LV filling pressure (31). Interobserver and intraobserver variability for the main measurements have been reported previously (16).

Continuous variables are reported as means SD. For normally distributed variables, within-group changes from baseline to 2 years were compared using a paired t test, and differences between the groups at each time point (baseline or 2 years) were compared using an unpaired t test. The nonparametric Kruskal-Wallis test was used for between-group comparison, and the Wilcoxon signed-rank sum test was used to examine within-group change for variables that were not normally distributed. To account for incomplete follow-up and missing data, imputation and carry-forward methods were used. Categoric variables are reported as proportions, and differences were compared using the chi-square test. Univariate linear regression was performed using the Pearson correlation. Collinearity between selected variables (body mass index [BMI] and surgical status) was assessed using tolerance and variance inflation factor. Multiple linear regression analysis was used to determine the factors that were associated with each of the 4 main outcome variables (LV mass index, LA volume, LV MWFS, and RV fractional area change) at the 2-year follow-up. For all 3 analyses, the variables used in the initial and final models were chosen based on clinical relevance or a plausible role in a causal pathway that might affect these outcome variables. Two sets of models were constructed. The first (model 1) used changes in clinical parameters between visits 1 and 2 as the input variables, with the absolute value of LV mass index, LA volume, and LV MWFS at visit 2 as the outcome variable. This approach was employed in an effort to minimize the effects of baseline differences between the groups while maintaining the clinical meaning of absolute measures of LV mass, LA volume, and MWFS. The second (model 2) used changes between visit 1 and visit 2 for both input and outcome variables (Online Appendix Tables 2 to 4). The initial variables were the same for both models. In each case, after the initial model was run, backward stepwise regression analysis was used to successively remove variables from the model that were not statistically significant. For analyses in which the mean values of 3 groups were compared, p ≤ 0.01 was considered significant. When only 2 groups were compared, p < 0.05 was considered to be significant.

The clinical characteristics of the study subjects are shown in Table 1. Systolic and diastolic blood pressures, fasting glucose, and glycosylated hemoglobin levels were all at the upper end of the normal range at visit 1. Serum insulin levels were markedly elevated. Patients in the GBS group lost an average of 44 kg (98 lbs) and decreased their BMI by 15.4 kg/m2 (Table 1). In conjunction with this marked degree of weight loss, those in the GBS group had improvements in systolic blood pressure, heart rate, glucose level, insulin level, and homeostasis model assessment of insulin resistance (HOMA IR) at visit 2 compared with baseline and compared with the reference groups (Table 1). At the 2-year follow-up, there were 2 deaths in the GBS group and 2 deaths in the reference group.