Contemporary patterns of lipoprotein(a) testing and associated clinical care and outcomes.

Objective: Elevated lipoprotein(a) [Lp(a)] is associated with atherosclerotic cardiovascular disease, yet little is known about Lp(a) testing patterns in real-world practice. The objective of this analysis was to determine how Lp(a) testing is used in clinical practice in comparison with low density lipoprotein cholesterol (LDL-C) testing alone, and to determine whether elevated Lp(a) level is associated with subsequent initiation of lipid-lowering therapy (LLT) and incident cardiovascular (CV) events. Methods: This is an observational cohort study, based on lab tests administered between Jan 1, 2015 and Dec 31, 2019. We used electronic health record (EHR) data from 11 United States health systems participating in the National Patient-Centered Clinical Research Network (PCORnet). We created two cohorts for comparison: 1) the Lp(a) cohort, of adults with an Lp(a) test and 2) the LDL-C cohort, of 4:1 date- and site-matched adults with an LDL-C test, but no Lp(a) test. The primary exposure was the presence of an Lp(a) or LDL-C test result. In the Lp(a) cohort, we used logistic regression to assess the relationship between Lp(a) results in mass units (< 50, 50-100, and > 100mg/dL) and molar units (<125, 125-250, > 250nmol/L) and initiation of LLT within 3 months. We used multivariable adjusted Cox proportional hazards regression to evaluate these Lp(a) levels and time to composite CV hospitalization, including hospitalization for myocardial infarction, revascularization and ischemic stroke. Results: Overall, 20,551 patients had Lp(a) test results and 2,584,773 patients had LDL-C test results (82,204 included in the matched LDL-C cohort). Compared with the LDL-C cohort, the Lp(a) cohort more frequently had prevalent ASCVD (24.3% vs. 8.5%) and multiple prior CV events (8.6% vs. 2.6%). Elevated Lp(a) was associated with greater odds of subsequent LLT initiation. Elevated Lp(a) reported in mass units was also associated with subsequent composite CV hospitalization [aHR (95% CI): Lp(a) 50-100mg/dL 1.25 (1.02-1.53), p<0.03, Lp(a) > 100mg/dL 1.23 (1.08-1.40), p<0.01]. Conclusion: Lp(a) testing is relatively infrequent in health systems across the U.S. As new therapies for Lp(a) emerge, improved patient and provider education is needed to increase awareness of the utility of this risk marker.

Corneal Clouding in a Young Woman With Low HDL Cholesterol.

This report describes the early diagnosis of lecithin cholesterol acyl transferase deficiency in a young asymptomatic woman who initially presented to ophthalmology with bilateral corneal clouding. The diagnosis was suggested by characteristic slit-lamp findings, undetectable high-density lipoprotein, and proteinuria, and it was confirmed by cardiology consultation and genetic testing. (Level of Difficulty: Beginner.).

Association between low ankle-brachial index and accelerometer-derived sedentary and exercise time in the asymptomatic general population.

Sedentary behavior is an adverse health risk factor that is independent of physical activity. The relationship between sedentary behavior, exercise activity and the ankle-brachial index (ABI) is not well understood. We analyzed data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004. Accelerometer data were used to quantify exercise and sedentary time for each participant. A low ABI was defined as a value <1.0 (including borderline values). Multi-variable adjusted logistic regression analyses were performed with sedentary and exercise times as independent variables, adjusting for important confounders. There were 1443 asymptomatic participants (mean age 61 years, 49% female, 55% current/prior smokers) with mean daily sedentary and exercise times of 454 ± 144 and 18 ± 20 minutes, respectively. Of the participants, 23% had an ABI <1.0 (8.7% with ABI <0.9). Sedentary time was positively associated with a low ABI (odds ratio [OR] 1.22 per 1 standard deviation [SD], [95% confidence interval (CI), 1.03-1.43]; p=0.02) while exercise time was inversely associated with a low ABI (OR 0.71 per 1 SD, [95% CI, 0.57-0.89]; p=0.003). Sedentary time is associated with low ABI values in the asymptomatic population. This association appears to be independent of exercise time and warrants further investigation.

Association between cardiorespiratory fitness and accelerometer-derived physical activity and sedentary time in the general population.

OBJECTIVE: To determine the association between cardiorespiratory fitness and sedentary behavior, independent of exercise activity. PATIENTS AND METHODS: We included 2223 participants (aged 12-49 years; 1053 females [47%]) without known heart disease who had both cardiovascular fitness testing and at least 1 day of accelerometer data from the National Health and Nutrition Examination Survey 2003-2004. From accelerometer data, we quantified bouts of exercise as mean minutes per day for each participant. Sedentary time was defined as less than 100 counts per minute in mean minutes per day. Cardiorespiratory fitness was derived from a submaximal exercise treadmill test. Multivariable-adjusted linear regression analyses were performed with fitness as the dependent variable. Models were stratified by sex, adjusted for age, body mass index, and wear time, and included sedentary and exercise time. RESULTS: An additional hour of daily exercise activity time was associated with a 0.88 (0.37-1.39; P<.001) metabolic equivalent of task (MET) higher fitness for men and a 1.37 (0.43-2.31; P=.004) MET higher fitness for women. An additional hour of sedentary time was associated with a -0.12 (-0.02 to -0.22; P=.03) and a -0.24 (-0.10 to -0.38; P<.001) MET difference in fitness for men and women, respectively. CONCLUSION: After adjustment for exercise activity, sedentary behavior appears to have an inverse association with fitness. These findings suggest that the risk related to sedentary behavior might be mediated, in part, through lower fitness levels.

Benefit of low-fat over low-carbohydrate diet on endothelial health in obesity.

Obesity is associated with impaired endothelial-dependent flow-mediated dilation, a precursor to hypertension and atherosclerosis. Although dieting generally improves cardiovascular risk factors, the direct effect of different dietary strategies on vascular endothelial function is not known. The purpose of this study was to test the hypothesis that a low-fat (LF) diet improves endothelial function compared with an isocaloric low-carbohydrate (LC) diet. Obese (n=20; body mass index: 29 to 39; mean systolic blood pressure: 107 to 125 mm Hg) and otherwise healthy volunteers were randomly assigned to either the American Heart Association modeled LF (30% fat calories) diet or an isocaloric LC Atkins' style diet (20 g of carbohydrates) for 6 weeks (4-week weight loss and 2-week maintenance phase). Brachial flow-mediated dilation and dilation to nitroglycerin were measured with ultrasound using automated edge detection technology (baseline, week 2, and week 6). Blood pressure, weight loss, and cholesterol profiles were measured throughout the study. Weight loss was similar in LF (100+/-4 to 96.1+/-4 kg; P<0.001) and LC (95.4+/-4 to 89.7+/-4 kg; P<0.001) diets. Blood pressure decreased similarly in both groups (LF: 8/5 mm Hg; LC: 12/6 mm Hg) at 6 weeks. After 6 weeks, the percentage of flow-mediated dilation improved (1.9+/-0.8; P<0.05) in the LF diet but was reduced in the LC diet (-1.4+/-0.6; P<0.05) versus baseline. Dilation to nitroglycerin and lipid panels was similar at 0, 2, and 6 weeks. Despite similar degrees of weight loss and changes blood pressure, LF diets improved brachial artery flow-mediated dilation over LC diets. LF diets may confer greater cardiovascular protection than LC diets.