Breastfeeding Duration and the Risk of Coronary Artery Disease.

BACKGROUND: Previous studies have suggested that prolonged breastfeeding has beneficial effects on the health of the mother including the reduction of long-term risk of coronary artery disease (CAD). The mechanism of this association remains unclear. METHODS: We surveyed 643 women aged 40-65 years receiving outpatient care at Stanford University Hospital on their reproductive/lactation history, including 137 women (cases) with clinically confirmed CAD. Survey data were supplemented with traditional risk factor data for CAD obtained from the participant's medical record. We then conducted logistic regression analyses to assess the relationship between breastfeeding duration and case-control status for each of the two separate definitions of duration. The first was based on the participant's single longest duration of breastfeeding considering all live births reported and the second was based on a participant's total duration of breastfeeding summed over all live births. For each of these two definitions, we ran three sequential models each with a different reference group-(1) nulliparous women, (2) parous women that never breastfed, and (3) parous women with a short duration of breastfeeding-successively excluding women in the reference group of the previous model(s). RESULTS: Just over one-half (51.6%) of the women surveyed reported a history of breastfeeding. We found nominally significant associations (p = 0.04-0.12) for our multivariate analyses that modeled maximum duration of breastfeeding. When compared with nulliparous women, parous women who either never breastfed or always breastfed for <5 months had approximately double the risk of CAD. Among parous women, women who breastfeed for ≥5 months at least once in their lifetime had a ∼30% decrease risk of CAD compared with those who did not initiate breastfeeding. Among parous women who breastfed ≥1 month, women who breastfed ≥5 months had ∼50% decreased risk of CAD. We found similar point estimates of effect for analogous analyses modeling maximum breastfeeding duration but p-values for these analyses were not significant. Unadjusted analyses demonstrated higher valued odds ratios and lower p-values suggesting the presence of some confounding by traditional risk factors. CONCLUSIONS: Parous women who breastfeed ≥5 months in at least one pregnancy seem to be at decreased risk of CAD later in their life, whereas parous women who either never breastfed or discontinued breastfeeding early seem to be at increased risk. More research is needed to more reliably quantify and determine the nature of the relationship between parity, breastfeeding duration, and risk of CAD.

Usefulness of a normal coronary angiogram in patients aged ≥65 years to foretell survival.

A normal coronary angiogram (CA) has been reported to confer a good prognosis. However, how this applies to patients aged ≥65 years is not well known. From 1986 to 1996, 11,625 patients aged ≥65 underwent coronary angiography. We identified 271 patients with either normal (NORM, n = 160) CA or <30% diameter stenosis disease (NEAR-NORM, n = 111). Using the Myocardial Infarction Data Acquisition System, we examined the probability of survival and the risk of developing an ischemic event or undergoing a revascularization procedure during an average of 15.1 ± 6.2 years (range 0.5 to 25.8 years). Matched actuarial subjects were used to compare survival to the general population. The incidence of an ischemic event was low (2.0 events per 100 persons/year for the NORM and 2.8 patients per 100 persons/year for the NEAR-NORM group, p = NS). Rates of revascularization were higher in the NEAR-NORM group compared to the NORM group (1 per 100 persons/year vs 0.5 per 100 persons/year, p = 0.04). During the 25.8-year follow-up, there were 77 deaths (48.4%) for the NORM and 64 (57.1%) for the NEAR-NORM group (χ2 = 1.7, NS). The NORM group survived 6,789 days, 1,517 more days than the actuarial subjects (95% confidence interval [CI] 1,072 to 1,956; p <0.0001) and the NEAR-NORM group survived 5,922 days, 875 more days (95% CI 368 to 1,376; p <0.005). In conclusion, patients with normal or near-normal CA at age ≥65 years have a low rate of myocardial ischemic events and have significantly longer survival than matched subjects from the general population.

Variation in use of echocardiography among veterans who use the Veterans Health Administration vs Medicare.

BACKGROUND: Rapid growth in the provision of cardiac imaging tests has led to concerns about overuse. Little is known about the degree to which health care delivery system characteristics influence use and variation in echocardiography. METHODS: We analyzed administrative claims of veterans with heart failure older than 65 years from 2007 to 2010 across 34 metropolitan service areas (MSAs). We compared overall rates and geographic variation in use of transthoracic echocardiography (TTE) between veterans who used the Veterans Health Administration (VA) and propensity-matched veterans who used Medicare. "Dual users" were excluded. RESULTS: There were no significant differences in clinical characteristics or mortality between the propensity-matched cohorts (overall n = 30,404 veterans, mean age 76 years, mortality rate 52%). The Medicare cohort had a significantly higher overall rate of TTE use compared with the VA cohort (1.25 vs 0.38 TTEs per person-year, incidence rate ratio 2.89 [95% CI 2.80-3.00], both P < .001), but a similar coefficient of variation across MSAs (0.36 [95% CI 0.27-0.45] vs 0.48 [95% CI 0.37-0.59]). There was a moderate to strong correlation in variation at the MSA level between cohorts (Spearman r = 0.58, P < .001). CONCLUSION: Overall rates of TTE use were significantly higher in a Medicare cohort compared with a propensity score-matched VA cohort of veterans with heart failure living in urban areas, with similar relative degrees of geographic variation and moderate to strong regional correlation. Rates of TTE use may be strongly influenced by health care system characteristics, but local practice styles influence echocardiography rates irrespective of health system.

Measurement of pulmonary partial pressure of oxygen and oxygen depletion rate with hyperpolarized helium-3 MRI: a preliminary reproducibility study on pig model.

RATIONAL AND OBJECTIVES: Pulmonary partial pressure of oxygen (pO(2)) and oxygen depletion rate (R) are two important parameters of lung function. The dependence of hyperpolarized (3)He (HP (3)He) T(1) on local oxygen concentration provides the basis for high-resolution mapping of the regional distributions of pO(2) and R in the lung. Although the oxygen-sensitive HP (3)He magnetic resonance imaging technique has been applied in human subjects and several animal species, reproducibility studies are rarely reported in the literature. This work presents a preliminary reproducibility study on a pig model. In this study, important scan parameters, such as measurement timing and flip angle, are optimized to minimize the noise-induced measurement uncertainty. MATERIALS AND METHODS: In the in vivo study, five normal pigs and one diseased pig with simulated pulmonary emboli were scanned with a small flip angle gradient echo sequence. The pulmonary oxygen measurement was repeated two to four times in each pig. In each measurement, a series of six images were acquired with optimal timing and flip angle. The parametric maps were generated using a bin-based data processing procedure that applied the multiple regression fitting method to extract the pO(2) and R. Variations of global mean, percentiles, and regions of interest were calculated from the maps to analyze reproducibility. RESULTS: The global statistical analyses show that average variation of global mean is 10.7% for pO(2) and 23.8% for R, and that the average variation of percentiles (10th, 25th, 50th, 75th, and 90th) and interquartile range is 14.8% for pO(2) and 30.4% for R. The region-of-interest analysis on the manually selected regions shows that the average variation of mean is 12.6% for pO(2) and 21.9% for R. CONCLUSION: In this work, a preliminary study on the reproducibility of measuring pO(2) and R with HP (3)He magnetic resonance imaging on a pig model is presented.

Multiple regression method for pulmonary apparent diffusion coefficient measurement by hyperpolarized 3He MRI.

PURPOSE: To develop and validate a new multiple regression technique for the separation of flip angle effect in pulmonary apparent diffusion coefficient (ADC) measurement. MATERIALS AND METHODS: Hyperpolarized (3)He MRI (HP (3)He MRI) ADC measurements were performed on phantom, pig, and human models. The diffusion-sensitization sequence is modified from a standard gradient echo (GRE) sequence with a nonlinear progression in the bipolar gradient amplitude with each image. In the self-diffusion phantom experiment, four images were acquired with base gradient factor b(0) = 0.15 second/cm(2); in the pig and human experiment, six images were acquired with base gradient factor b(0) = 1.4 second/cm(2). RESULTS: The self-diffusion coefficient measured in the phantom experiment was 1.98 +/- 0.16 cm(2)/second. The measured uncertainty curve was consistent with the theoretically predicted curve. The measured in vivo ADC values (three coronal slices in the supine direction) were 0.20/0.16/0.13 cm(2)/second and 0.20/0.18/0.16 cm(2)/second for pig and human experiments, respectively. CONCLUSION: With the introduction of a nonlinear progression in the diffusion-sensitization gradients, the multiple regression technique is capable of separating the flip angle effect in ADC measurement. In addition, this technique can perform a rigorous measurement uncertainty analysis and provide the optimal scan parameters that yield best noise performance.

Muscle metabolism with blood flow restriction in chronic fatigue syndrome.

The purpose of this study was to determine whether chronic fatigue syndrome (CFS) is associated with reduced blood flow and muscle oxidative metabolism. Patients with CFS according to Centers for Disease Control criteria (n = 19) were compared with normal sedentary subjects (n = 11). Muscle blood flow was measured in the femoral artery with Doppler ultrasound after exercise. Muscle metabolism was measured in the medial gastrocnemius muscle with (31)P-magnetic resonance spectroscopy. Muscle oxygen saturation and blood volume were measured using near-infrared spectroscopy. CFS and controls were not different in hyperemic blood flow or phosphocreatine recovery rate. Cuff pressures of 50, 60, 70, 80, and 90 mmHg were used to partially restrict blood flow during recovery. All pressures reduced blood flow and oxidative metabolism, with 90 mmHg reducing blood flow by 46% and oxidative metabolism by 30.7% in CFS patients. Hyperemic blood flow during partial cuff occlusion was significantly reduced in CFS patients (P < 0.01), and recovery of oxygen saturation was slower (P < 0.05). No differences were seen in the amount of reduction in metabolism with partially reduced blood flow. In conclusion, CFS patients showed evidence of reduced hyperemic flow and reduced oxygen delivery but no evidence that this impaired muscle metabolism. Thus CFS patients might have altered control of blood flow, but this is unlikely to influence muscle metabolism. Furthermore, abnormalities in muscle metabolism do not appear to be responsible for the CFS symptoms.

Blood flow and muscle metabolism in chronic fatigue syndrome.

The purpose of this study was to determine if chronic fatigue syndrome (CFS) is associated with reduced blood flow and oxidative delivery to skeletal muscle. Patients with CFS according to CDC (Center for Disease Control) criteria ( n =19) were compared with normal sedentary subjects ( n =11). Muscle blood flow was measured with Doppler ultrasound after cuff ischaemia and exercise. Muscle oxygen delivery was measured as the rate of post-exercise and post-ischaemic oxygen-haem resaturation. Oxygen-haem resaturation was measured in the medial gastrocnemius muscle using continuous wavelength near-IR spectroscopy. Muscle metabolism was measured using (31)P magnetic resonance spectroscopy. CFS patients and controls were not different in the peak blood flow after cuff ischaemia, the rate of recovery of phosphocreatine after submaximal exercise, and the rate of recovery of oxygen saturation after cuff ischaemia. In conclusion, CFS patients showed no deficit in blood flow or oxidative metabolism. This suggests that CFS symptoms do not require abnormal peripheral function.