Biomedical subjects

Emily B Schroeder

Publications and source records attributed to Emily B Schroeder.

7 recordsLinked to original sources

PubMed2005

Impaired lung function and subclinical atherosclerosis. The ARIC Study.

An association between reduced pulmonary function and increased risk of atherosclerotic vascular events has been reported. The mechanisms underlying this association are unknown, but are unlikely to be entirely due to smoking given the presence of the association among non-smokers. Few studies have examined the cross-sectional association between subclinical atherosclerosis and pulmonary function. In 14,000 adults in the ARIC Study, we examined the cross-sectional relationship between lung function, measured by the forced expiratory volume at 1s (FEV(1)), and three markers of subclinical atherosclerosis: ankle-brachial index (ABI), carotid intimal-medial thickness (IMT), and presence of carotid plaques. Mean FEV(1) was computed by ABI category, IMT category, or plaque status, in the full cohort and after stratification by smoking status, adjusted for age, gender, race, study center, height, height-squared, smoking, and pack years. Decreased FEV(1) was associated with decreased ABI and increased IMT in the full cohort and in each smoking group. Further adjustment for CVD risk factors did not alter the ABI association, but attenuated the IMT association, eliminating it in never smokers. Plaque was not associated with FEV(1). These findings suggest a complex relationship between FEV(1) and atherosclerotic vascular disease that invites further study.

Arteriosclerosis↗

PubMed2005

Short-term repeatability of electrocardiographic spatial T-wave axis and QT interval.

Although ventricular repolarization abnormalities reflect arrhythmic susceptibility, few reliable tools exist to identify their presence. We investigated the repeatability of the spatial T-wave axis and QT interval from standard 12-lead electrocardiograms in 63 asymptomatic volunteers. Certified technicians used a standardized protocol to digitally record 2 electrocardiograms per participant at each of 2 visits separated by 1 to 2 weeks. Absolute paired differences within and between visits were 0.19 degrees and 0.90 degrees for the T-wave axis and 1.08 and 1.55 milliseconds for the QT interval, respectively. The intraclass correlation coefficients for the T-wave axis and QT interval were 0.87 and 0.86, respectively. The impact of repeated measurements on the precision of the QT-interval measurements was evaluated for a hypothetical clinical trial aimed at detecting a drug-induced QT prolongation. We conclude that the spatial T-wave axis is as repeatable a measure of ventricular repolarization as the QT interval.

Electrocardiography↗

PubMed2005

Diabetes, glucose, insulin, and heart rate variability: the Atherosclerosis Risk in Communities (ARIC) study.

OBJECTIVE: To describe the progression of autonomic impairment among individuals with diabetes and pre-diabetic metabolic impairments. RESEARCH DESIGN AND METHODS: We investigated the consequence of diabetes and pre-diabetic metabolic impairments on the 9-year change in heart rate variability (HRV) in a population-based cohort of 6,245 individuals aged 45-64 years at baseline and cross-sectional associations among 9,940 individuals. RESULTS: Diabetic subjects had a more rapid temporal decrease in HRV conditional on baseline HRV than nondiabetic subjects. Adjusted mean annual changes (95% CI) (ms/year) in the SD of all normal-to-normal R-R intervals were -0.65 (-0.69 to -0.61) for those with normal fasting glucose vs. -0.95 (-1.09 to -0.81) for diabetic subjects, in root mean square of successive differences in normal-to-normal R-R intervals -0.35 (-0.39 to -0.30) vs. -0.66 (-0.82 to -0.51), and in R-R interval 6.70 (6.37-7.04) vs. 3.89 (2.72-5.05). While we found cross-sectional associations between decreased HRV and diabetes and nondiabetic hyperinsulinemia and a weak inverse association with fasting glucose, neither impaired fasting glucose nor nondiabetic hyperinsulimenia was associated with a measurably more rapid decline in HRV than normal. CONCLUSIONS: Cardiac autonomic impairment appears to be present at early stages of diabetic metabolic impairment, and progressive worsening of autonomic cardiac function over 9 years was observed in diabetic subjects. The degree to which pre-diabetic metabolic impairments in insulin and glucose metabolism contribute to decreases in cardiac autonomic function remains to be determined.

Arteriosclerosis↗

PubMed2004

Repeatability of heart rate variability measures.

Due to the sparse data on the repeatability of short and ultra-short term heart rate variability (HRV) measures, we measured the repeatability of common HRV measures derived from 10-second, 2-minute, and 6-minute recordings in 63 healthy men and women, aged 45-64, in Chapel Hill, North Carolina. Three 10-second and 2 six-minute heart rate recordings were obtained during each of 2 visits, separated by 1 to 2 weeks. We partitioned the measurement error into components and computed intraclass correlation coefficients using nested, random effects models. Repeatability improved with the length of recording: intraclass correlation coefficients were greater than 0.7 for 6-minute measures and 2-minute time domain measures and greater than 0.5 for 2-minute frequency domain measures. Repeatability of measures from 10-second records was lower, but improved considerably when the mean from 2 or 3 records was used. Correlations between the same measures from different length recordings were quite high. Our findings support the use of records of at least 5 minutes in length in epidemiological studies, in accordance with previous guidelines. Researchers using 10-second records should consider taking the mean of several recordings, when possible, or using statistical methods to correct for measurement error.

Electrocardiography↗

PubMed2003

Lung function and incident coronary heart disease: the Atherosclerosis Risk in Communities Study.

The authors examined the association between lung function, as measured by forced expiratory volume in 1 second (FEV1) and forced vital capacity, and the 10-year incidence of coronary heart disease among 14,480 participants in the Atherosclerosis Risk in Communities Study (1987-1998). Separate proportional hazards models were used for FEV1 and forced vital capacity, with gender-specific lung function quartiles and lung function x gender interaction terms. An association between lung function and coronary heart disease was observed in both genders and was stronger among women. After adjustment for age, race, study center, height, height squared, smoking, and cardiovascular disease risk factors, the hazard ratios for the first (lowest), second, and third quartiles of FEV1 were 3.70 (95% confidence interval (CI): 2.19, 6.24), 2.54 (95% CI: 1.49, 4.32), and 2.25 (95% CI: 1.31, 3.87) for women and 1.51 (95% CI: 1.07, 2.13), 1.59 (95% CI: 1.15, 2.20), and 1.52 (95% CI: 1.10, 2.09) for men. After stratification by smoking status, associations were observed in each smoking group for women, while those in men were weaker and less consistent. Similar results were obtained for forced vital capacity. This analysis indicates an association between lung function and incident coronary heart disease that may be stronger in women than in men.

Black or African American↗

PubMed2003

Hypertension, blood pressure, and heart rate variability: the Atherosclerosis Risk in Communities (ARIC) study.

Dysregulation of the autonomic nervous system has been implicated in the development of hypertension. Heart rate variability is a noninvasive tool to quantitatively estimate cardiac autonomic activity and has been used to document decreased cardiac autonomic activity in hypertension. The ability of decreased heart rate variability to predict incident hypertension has not been well studied, and there are no studies of whether hypertension leads to changes in heart rate variability. We investigated the temporal sequence linking hypertension, blood pressure, and heart rate variability in a population-based cohort of 11 061 individuals aged 45 to 54 years at baseline. Individuals with hypertension had decreased heart rate variability at baseline, and this association was present across the full blood pressure range. Among 7099 individuals without hypertension at baseline, low heart rate variability predicted greater risk of incident hypertension over 9 years of follow-up. The hazard ratio (95% confidence interval [CI]) for the lowest compared with the highest quartile of the standard deviation of normal-to-normal R-R intervals was 1.24 (95% CI, 1.10-1.40), for the root mean square of successive differences in normal-to-normal R-R intervals was 1.36 (95% CI, 1.21-1.54), and for R-R interval was 1.44 (95% CI, 1.27-1.63). Over 9 years, there was no measurable difference in the rate of change in heart rate variability among those with and without hypertension, although the differences in heart rate variability at follow-up were smaller than those at baseline. These findings thus support the thesis that the autonomic nervous system is involved in the development of hypertension, yet suggest that differences in the autonomic profile of hypertensives and normotensives do not increase with time.

Blood Pressure↗

PubMedDate not supplied

Calling emergency medical services for acute stroke: a study of 9-1-1 tapes.

OBJECTIVE: To obtain a better understanding of how stroke events are communicated to 9-1-1 telecommunicators, and how telecommunicators and emergency medical services (EMS) personnel respond to such calls. METHODS: The authors identified 104 patients with a hospital discharge diagnosis of stroke or transient ischemic attack who were transported to hospital by ambulance in two North Carolina counties during 1999 and 2000. Ambulance call reports were abstracted and linked to 9-1-1 call center audiotapes, which were transcribed and verified. RESULTS: Of the 104 calls, 44 were made by medical personnel, 38 by a family member, eight by a bystander or neighbor, five undetermined, and three by other nonmedical personnel. In only six instances (6%) was the call placed by the patient. The most common symptoms reported were altered mental status (40%), trouble walking (32%), impaired speech (27%), and abnormal breathing (27%). Although the word "stroke" was often used (45%), 9-1-1 telecommunicators classified the calls as a stroke in only 31% of cases. However, in the majority of cases (79%), paramedics were dispatched at the highest priority. The median time from dispatch of EMS to patient arrival at the hospital was 41 minutes, approximately half of which was spent at the scene. CONCLUSION: Although typical stroke symptoms are commonly described, calls are often not classified as "strokes" by telecommunicators. Nevertheless, because of the symptoms reported during the calls, the majority of cases are treated as high priority by telecommunicators.

Aged↗