Cardiorespiratory fitness, exercise haemodynamics and birth outcomes: the Coronary Artery Risk Development in Young Adults Study.

OBJECTIVE: Determine associations of cardiorespiratory fitness, exercise systolic blood pressure (SBP) and heart rate recovery (HRR) following a maximal exercise test performed years preceding pregnancy with odds of preterm birth (PTB; <37 weeks' gestation) and small for gestational age (SGA; birthweight <10th percentile) delivery. DESIGN: Prospective, longitudinal. SETTING: Multi-site, observational cohort study initially consisting of 2787 black and white women aged 18-30 at baseline (1985-86) and followed for 25 years (Y25; 2010-2011). POPULATION: 768 nulliparous women at baseline who reported ≥1 live birth by the Y25 exam. METHODS: We used Poisson regression to determine associations of exposures with PTB/SGA. MAIN OUTCOME MEASURES: PTB and/or SGA births. RESULTS: Women with PTB (n = 143) and/or SGA (n = 88) were younger, had completed fewer years of education and were more likely to be black versus women without PTB/SGA (n = 546). Women with PTB/SGA had lower fitness (501 ± 9 versus 535 ± 6 seconds, P < 0.002) and higher submaximal SBP than women without PTB/SGA (144 ± 1 versus 142 ± 1 mmHg, P < 0.04). After adjustment, no exercise test variables were associated with PTB/SGA, though the association with HRR and submaximal SBP approached significance in the subset of women who completed the exercise test <5 years before the index birth. CONCLUSIONS: Neither fitness nor haemodynamic responses to exercise a median of 5 years preceding pregnancy, were associated with PTB/SGA. These findings indicate excess likelihood of PTB/SGA is not detectable by low fitness or exercise haemodynamic responses 5 years preceding pregnancy, but exercise testing, especially HRR and submaximal SBP, may be more useful when conducted closer to the onset of pregnancy. TWEETABLE ABSTRACT: Exercise testing conducted >5 years before pregnancy may not detect women likely to have PTB/SGA.

Coherent control of Rydberg states in silicon.

Laser cooling and electromagnetic traps have led to a revolution in atomic physics, yielding dramatic discoveries ranging from Bose-Einstein condensation to the quantum control of single atoms. Of particular interest, because they can be used in the quantum control of one atom by another, are excited Rydberg states, where wavefunctions are expanded from their ground-state extents of less than 0.1 nm to several nanometres and even beyond; this allows atoms far enough apart to be non-interacting in their ground states to strongly interact in their excited states. For eventual application of such states, a solid-state implementation is very desirable. Here we demonstrate the coherent control of impurity wavefunctions in the most ubiquitous donor in a semiconductor, namely phosphorus-doped silicon. In our experiments, we use a free-electron laser to stimulate and observe photon echoes, the orbital analogue of the Hahn spin echo, and Rabi oscillations familiar from magnetic resonance spectroscopy. As well as extending atomic physicists' explorations of quantum phenomena to the solid state, our work adds coherent terahertz radiation, as a particularly precise regulator of orbitals in solids, to the list of controls, such as pressure and chemical composition, already familiar to materials scientists.

Sedentary behavior and blood pressure control among osteoarthritis initiative participants.

OBJECTIVE: To examine the association between sedentary behavior and blood pressure (BP) among Osteoarthritis Initiative (OAI) participants. DESIGN: We conducted a cross-sectional analysis of the OAI 48-month visit participants whose physical activity was measured using accelerometers. Participants were classified into four quartiles according to the percentage of wear time that was sedentary (<100 activity counts per min). Users of antihypertensive medications or non-steroidal anti-inflammatory drugs (NSAIDs) were excluded. Our main outcomes were systolic and diastolic blood pressures (SBP and DBP) and "elevated BP" defined as BP ≥ 130/85 mm Hg. RESULTS: For this study cohort (N = 707), mean BP was 121.4 ± 15.6/74.7 ± 9.5 mm Hg and 33% had elevated BP. SBP had a graded association with increased sedentary time (P for trend = 0.02). The most sedentary quartile had 4.26 mm Hg higher SBP (95% confidence interval (CI), 0.69-7.82; P = 0.02) than the least sedentary quartile, adjusting for age, moderate-to-vigorous (MV) physical activity, and other demographic and health factors. The probability of having elevated BP significantly increased in higher sedentary quartiles (P for trend = 0.046). There were no significant findings for DBP. CONCLUSION: A strong graded association was demonstrated between sedentary behavior and increased SBP and elevated BP, independent of time spent in MV physical activity. Reducing daily sedentary time may lead to improvement in BP and reduction in cardiovascular risk.

Cardiometabolic health after first pregnancy: Associations with social determinants of health. A nuMoM2b-HHS study.

Study objective: This study sought to evaluate the associations between social determinants of health (SDOH) at the time of first pregnancy and subsequent cardiometabolic health, defined as the development of metabolic syndrome. Design: nuMoM2b-HHS (Nulliparous Pregnancy Outcomes Study- Monitoring Mothers-to-Be-Heart Health Study) is an ongoing prospective cohort study. Setting: Eight academic medical centers enrolled and continue to follow participants. Participants: 4484 participants followed a mean of 3.2 years from the time of their first pregnancy. Interventions: N/a. Main outcome measure: Unadjusted and adjusted Poisson regression models with robust standard errors were used to obtain relative risks and 95% confidence intervals estimating the risk of metabolic syndrome for each baseline SDOH. In secondary analyses we examined the associations between SDOH and incident hypertension, obesity, and diabetes mellitus. Results: Metabolic syndrome developed in 13.6% of participants. Higher socioeconomic position at the time of pregnancy was associated with lower rates of metabolic syndrome [income > 200% poverty level aRR 0.55 (95% CI, 0.42-0.71), attainment of a bachelor's degree aRR 0.62 (0.46-0.84) or higher aRR 0.50 (0.35-0.71)], while being single [aRR 1.45 (95% CI, 1.18-1.77)] and having low health literacy were associated with a greater risk of metabolic syndrome [aRR 1.98 (95% CI, 1.28-3.07)]. Conclusions: Over a short interval following first pregnancy, participants accumulated high proportions of cardiovascular risk factors and metabolic syndrome, with some risk associated with SDOH. The impact of interventions addressing SDOH in pregnant people on cardiometabolic health should be tested as a means of reducing health inequities at the population level.

The initialization and manipulation of quantum information stored in silicon by bismuth dopants.

A prerequisite for exploiting spins for quantum data storage and processing is long spin coherence times. Phosphorus dopants in silicon (Si:P) have been favoured as hosts for such spins because of measured electron spin coherence times (T2) longer than any other electron spin in the solid state: 14 ms at 7 K with isotopically purified silicon. Heavier impurities such as bismuth in silicon (Si:Bi) could be used in conjunction with Si:P for quantum information proposals that require two separately addressable spin species. However, the question of whether the incorporation of the much less soluble Bi into Si leads to defect species that destroy coherence has not been addressed. Here we show that schemes involving Si:Bi are indeed feasible as the electron spin coherence time T2 is at least as long as for Si:P with non-isotopically purified silicon. We polarized the Si:Bi electrons and hyperpolarized the I=9/2 nuclear spin of (209)Bi, manipulating both with pulsed magnetic resonance. The larger nuclear spin means that a Si:Bi dopant provides a 20-dimensional Hilbert space rather than the four-dimensional Hilbert space of an I=1/2 Si:P dopant.

Coherent superpositions of three states for phosphorous donors in silicon prepared using THz radiation.

Superposition of orbital eigenstates is crucial to quantum technology utilizing atoms, such as atomic clocks and quantum computers, and control over the interaction between atoms and their neighbours is an essential ingredient for both gating and readout. The simplest coherent wavefunction control uses a two-eigenstate admixture, but more control over the spatial distribution of the wavefunction can be obtained by increasing the number of states in the wavepacket. Here we demonstrate THz laser pulse control of Si:P orbitals using multiple orbital state admixtures, observing beat patterns produced by Zeeman splitting. The beats are an observable signature of the ability to control the path of the electron, which implies we can now control the strength and duration of the interaction of the atom with different neighbours. This could simplify surface code networks which require spatially controlled interaction between atoms, and we propose an architecture that might take advantage of this.

Effects of exercise, dietary cholesterol, and dietary fat on blood lipids.

Exercise, a low fat diet, or a diet low in saturated fat content can each lower plasma total cholesterol and low-density lipoprotein (LDL) cholesterol. We investigated whether these factors together could prevent the lipid-raising effects of dietary cholesterol. Ten healthy, athletic, normolipidemic male volunteers were studied. Two diets of 4 weeks duration each were compared in a randomized, blind crossover design. Diets were identical except for cholesterol content: one contained 600 mg/d; the other 200 mg/d. Both diets contained 15% of calories as protein, 55% as carbohydrate, 30% as fat, and the polyunsaturated fat to saturated fat ratio was 1.5. Exercise level and body weight were kept constant in each subject. As compared with plasma values obtained following the 200-mg/d cholesterol diet, mean values following the 600-mg/d cholesterol diet significantly increased for LDL cholesterol and apolipoprotein B by 10% and 13%, respectively. Mean plasma triglycerides, high-density lipoprotein 2 and 3, and apolipoprotein A-1 levels did not change significantly. Individual responses, however, were highly variable. Three subjects increased LDL cholesterol by more than 25%; 2 subjects increased LDL cholesterol by 10% to 25%; and 5 subjects had 5% or less change in LDL cholesterol. A dietary cholesterol increase can significantly elevate plasma LDL cholesterol and apolipoprotein B in certain normolipidemic, healthy men even when they are exercising regularly and consuming a moderately fat restricted, low saturated fat diet. Dietary cholesterol restriction may therefore be justifiable even when other life-style and dietary measures to minimize blood cholesterol are undertaken.

Arrhythmic complications in the Guillain-Barré syndrome.

The occurrence of cardiac arrhythmia in Guillain-Barré syndrome (GBS) was examined in a retrospective study of 16 consecutive patients with GBS admitted to an intensive care unit primarily for respiratory insufficiency, Bradyarrhythmias, including sinus arrest or atrioventricular block rhythms, and/or tachyarrhythmias, supraventricular as well as ventricular, were observed in 13 patients. Two patients required pacemaker insertion because of recurrent asystolic episodes. Of the four fatalities, however, none were considered cardiac in origin. While clinically apparent autonomic nervous system dysfunction accompanied many of the observed arrhythmias and may be involved in arrhythmogenesis, these patients also suffered from pulmonary, infectious, and thromboembolic complications that could produce similar arrhythmic complications and must also be considered whenever such arrhythmias are seen.

Thyrotoxicosis in institutionalized elderly patients with atrial fibrillation.

We hypothesized that hyperthyroidism would be an infrequent cause of atrial fibrillation in older persons because atherosclerotic, hypertensive, and degenerative heart disorders are more prevalent with aging. We determined the cardiac rhythm and thyroid status of 316 patients older than 65 years of age residing in a nursing home. One (11%) of the nine elderly men and five (31%) of the 16 women with atrial fibrillation had laboratory evidence or a history of hyperthyroidism. The elderly patients with cardiac rhythms other than atrial fibrillation (n = 291) had only a 1.7% prevalence of hyperthyroidism. The analysis for elderly women demonstrated a statistically significant association between atrial fibrillation and hyperthyroidism, but the association was not statistically significant for men. These findings indicate that hyperthyroidism is common in institutionalized elderly women with atrial fibrillation.

Exertional leg symptoms other than intermittent claudication are common in peripheral arterial disease.

BACKGROUND: Epidemiological data show that most community-dwelling men and women with lower-extremity peripheral arterial disease (PAD) do not have typical symptoms of intermittent claudication. We compared the prevalence of intermittent claudication, leg symptoms other than intermittent claudication, and absence of exertional leg symptoms between patients with PAD identified from a blood flow laboratory (group 1), patients with PAD in a general medicine practice (group 2), and control patients without PAD (group 3). METHODS: Numbers of participants in groups 1, 2, and 3 were 137, 26, and 105, respectively. Patients with previously diagnosed PAD were excluded from groups 2 and 3. All participants underwent ankle-brachial index measurement and were administered the San Diego claudication questionnaire to assess leg symptoms. RESULTS: Within groups 1, 2, and 3, prevalences of intermittent claudication were 28.5% (n = 39), 3.8% (n = 1), and 3.8% (n= 4), respectively. Prevalences of exertional leg symptoms other than intermittent claudication were 56.2% (n= 77), 42.3% (n= 11), and 19.0% (n = 20), respectively. Absence of exertional leg symptoms was reported by 15.3% (n= 21), 53.8% (n= 14), and 77.1% (n=81), respectively. Among patients with PAD, older age, male sex, diabetes mellitus, and group 2 vs group 1 status were associated independently with absence of exertional leg symptoms in multivariable regression analysis. Lower ankle-brachial index levels and group 1 vs group 2 status were associated with intermittent claudication. CONCLUSIONS: Clinical manifestations of PAD are diverse, particularly among patients identified by ankle-brachial index screening. Exertional leg symptoms other than intermittent claudication are common in PAD. Patients with PAD who are older, male, diabetic, or identified with ankle-brachial index screening in a primary care setting are more likely to have asymptomatic PAD.

Impact of major cardiovascular disease risk factors, particularly in combination, on 22-year mortality in women and men.

BACKGROUND: The appropriateness of current cardiovascular disease (CVD) risk factor guidelines in women continues to be debated. OBJECTIVE: To present new data on the appropriateness of current CVD risk factor guidelines, for women and men, from long-term follow-up of a large population sample. METHODS: Cardiovascular disease risk factor status according to current clinical guidelines and long-term impact on mortality were determined in 8686 women and 10503 men aged 40 to 64 years at baseline from the Chicago Heart Association Detection Project in Industry; average follow-up was 22 years. RESULTS: At baseline, only 6.6% of women and 4.8% of men had desirable levels for all 3 major risk factors (cholesterol level, <5.20 mmol/L [<200 mg/dL]; systolic and diastolic blood pressure, <120 and <80 mm Hg, respectively; and nonsmoking). With control for age, race, and other risk factors, each major risk factor considered separately was associated with increased risk of death for women and men. In analyses of combinations of major risk factors, risk increased with number of risk factors. Relative risks (RRs) associated with any 2 or all 3 risk factors were similar: for coronary heart disease mortality in women, RR= 5.72 (95% confidence interval [CI], 2.35-13.93), and in men, RR = 5.51 (95% CI, 3.10-9.77); for CVD mortality in women, RR = 4.54 (95% CI, 2.33-8.84), and in men, RR = 4.12 (95% CI, 2.56-6.37); and for all-cause mortality in women, RR = 2.34 (95% CI, 1.73-3.15), and in men, RR = 3.20 (95% CI, 2.47-4.14). Absolute excess risks were high in women and men with any 2 or all 3 major risk factors. CONCLUSIONS: Combinations of major CVD risk factors place women and men at high relative, absolute, and absolute excess risk of coronary heart disease, CVD, and all-cause mortality. These findings support the value of (1) measurement of major CVD risk factors, especially in combination, for assessing long-term mortality risk and (2) current advice to match treatment intensity to the level of CVD risk in both women and men.

Relationship of blood pressure to 25-year mortality due to coronary heart disease, cardiovascular diseases, and all causes in young adult men: the Chicago Heart Association Detection Project in Industry.

BACKGROUND: Data are limited on blood pressure (BP) in young adults and long-term mortality. Moreover, screening and hypertension treatment guidelines have been based mainly on findings for middle-aged and older populations. This study assesses relationships of BP measured in young adult men to long-term mortality due to coronary heart disease (CHD), cardiovascular diseases (CVD), and all causes. METHODS: This cohort from the Chicago Heart Association Detection Project in Industry included 10 874 men aged 18 to 39 years at baseline (1967-1973), not receiving antihypertensive drugs, and without CHD or diabetes. Relationship of baseline BP to 25-year CHD, CVD, and all-cause mortality was assessed. RESULTS: Age-adjusted association of systolic BP to CHD mortality was continuous and graded. Multivariate-adjusted CHD hazard ratios (HRs) for 1 SD higher systolic BP (15 mm Hg) and diastolic BP (10 mm Hg) were 1.26 (95% confidence interval [CI], 1.11-1.44) and 1.17 (95% CI, 1.01-1.35), respectively. Compared with the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure stratum with normal BP (and lowest mortality rates), the large strata with high-normal BP and stage 1 hypertension had 25-year absolute risks for death of 63 and 72 per 1000, respectively, and absolute excess risks of 10 and 20 per 1000, respectively; accounted for 59.8% of all excess CHD, CVD, and all-cause mortality; and were estimated to have life expectancy shortened by 2.2 and 4.1 years, respectively. CONCLUSIONS: In young adult men, BP above normal was significantly related to increased long-term mortality due to CHD, CVD, and all causes. Population-wide primary prevention, early detection, and control of higher BP are indicated from young adulthood on.

Diabetes, asymptomatic hyperglycemia, and 22-year mortality in black and white men. The Chicago Heart Association Detection Project in Industry Study.

OBJECTIVE: To assess relationships of diabetes and asymptomatic hyperglycemia at baseline to the risk of cardiovascular disease (CVD) and all-cause (ALL) mortality in employed, white and black middle-aged men. RESEARCH DESIGN AND METHODS: A prospective cohort study of 11,554 white men and 666 black men between the ages 35 and 64 from 1967 to 1973 was conducted using data from the Chicago Heart Association (CHA) Detection Project in Industry 22-year mortality follow-up. cox proportional hazards models, adjusted fro age and other CVD risk factors, were used to estimate the relative risk (RR) and the 95% CI of mortality associated with baseline glycemic status. RESULTS: Age-adjusted baseline prevalence of clinical diabetes was similar in white (3.7%) and black (4.3%) men; asymptomatic hyperglycemia (glucose post-50-g load > or = 11.1 mmol/l) was present in 11.1% of whites and 7.8% of blacks. After controlling for age, lifestyle, and other CVD risk factors, mortality risk was increased among white men with clinical diabetes (CVD: RR 2.51, CI 2.08-3.02; ALL: RR 1.88, CI 1.63-2.17) and asymptomatic hyperglycemia (CVD: RR 1.18, CI 1.01-1.37; ALL: RR 1.24, CI 1.11-1.37), compared with men with postload glucose < 8.9 mmol/l. Risks were similarly, though nonsignificantly (owing to low statistical power), increased among black men with clinical diabetes (CVD: RR 1.60, CI 0.60-4.29; ALL: RR 1.78, CI 0.97-3.25) and asymptomatic hyperglycemia (CVD: RR 1.29, CI 0.61-2.72; ALL: RR 1.37, CI 0.85-2.20). CONCLUSIONS: Asymptomatic hyperglycemia and clinical diabetes appear to confer increased mortality risk in both white and black men. In addition, mortality risk is increased with increased severity of glycemia. These findings indicate the importance of applying efforts to reduce risk factors and prevent diabetes in both blacks and whites.

Coherent creation and destruction of orbital wavepackets in Si:P with electrical and optical read-out.

The ability to control dynamics of quantum states by optical interference, and subsequent electrical read-out, is crucial for solid state quantum technologies. Ramsey interference has been successfully observed for spins in silicon and nitrogen vacancy centres in diamond, and for orbital motion in InAs quantum dots. Here we demonstrate terahertz optical excitation, manipulation and destruction via Ramsey interference of orbital wavepackets in Si:P with electrical read-out. We show milliradian control over the wavefunction phase for the two-level system formed by the 1s and 2p states. The results have been verified by all-optical echo detection methods, sensitive only to coherent excitations in the sample. The experiments open a route to exploitation of donors in silicon for atom trap physics, with concomitant potential for quantum computing schemes, which rely on orbital superpositions to, for example, gate the magnetic exchange interactions between impurities.

Indications for echocardiography in patients with ischemic stroke.

The recent availability of two-dimensional echocardiography (2DE) has fostered the expectation that cardiac embolic sources could be identified or excluded with certitude in ischemic stroke patients. As a screening procedure, 2DE has had a low yield. In selected patients, 2DE holds promise as a useful diagnostic test. Stroke patients who may benefit from 2DE include patients under age 45, patients with suspected left atrial myxoma, and patients with known infective endocarditis, prosthetic heart valves, or rheumatic valvular heart disease. In patients with ischemic heart disease, the yield of useful information from 2DE will be low but may, on occasion, influence management.

Closing the treatment gap: in the community and at hospital discharge.

Although most physicians agree on the value of risk reduction in patients with cardiovascular disease, preventive strategies are not being implemented as widely as they should be in current practice. Several obstacles may account for this trend: Preventive medicine is not widely encouraged or expected; urgency takes precedence over long-term severity; physicians' time per patient is severely limited; preventive services can be considered the responsibility of other healthcare professionals; and positive feedback is generally absent. Strategies for overcoming these obstacles include the systematic identification of appropriate candidates for preventive care, adequate communication with patients to increase their understanding of the need for therapy, clarification of how to take action, assistance in doing so, and reinforcement of preventive behaviors already being practiced by patients. The case-manager approach provides one effective method for implementing these strategies: Nurses assume responsibility for preventive services, working in concert with a multidisciplinary team of physicians and other specialists. Such an approach redefines risk management as a primary treatment goal, rather than an afterthought.

Effectiveness of low-dose colestipol therapy in patients with moderate hypercholesterolemia.

Recommended doses of bile-acid binding resins have an established hypocholesterolemic effect, but data on responses to low doses, especially in women and subjects with moderate hypercholesterolemia, are sparse. A double-blind, placebo-controlled, randomized trial of 3 low doses of colestipol hydrochloride was conducted in women and men with moderate hypercholesterolemia. Men and women with plasma low-density lipoprotein (LDL) cholesterol concentrations greater than 4 mmol/liter (155 mg/dl) and triglyceride concentrations less than 2.82 mmol/liter (250 mg/dl) were recruited for the study. Eligible patients (54 women and 98 men) were placed on the American Heart Association step I diet 6 weeks before randomization. Participants were subsequently assigned to 1 of 4 drug treatment groups (placebo, and 5, 10 and 15 g/day of colestipol in 2 divided doses) for an additional 12 weeks. Of the 152 patients randomized, 141 completed all aspects of the study. For the treatment groups--placebo, and 5, 10 and 15 g of colestipol--LDL cholesterol reductions (mmol/liter) were observed respectively (n = 141): 0.10 +/- 0.49 (2.7%), 0.65 +/- 0.41 (16.3%), 0.98 +/- 0.36 (22.8%) and 1.17 +/- 0.47 (27.2%) (p less than 0.001). Similar changes were observed in total cholesterol and apolipoprotein B concentrations. The apolipoprotein B/LDL cholesterol ratio increased significantly with increasing colestipol dosage. Modest but insignificant changes in plasma triglyceride levels occurred, and high-density lipoprotein cholesterol levels remained unchanged. A dose of 5 g/day of colestipol achieved 51% of the LDL cholesterol reduction noted with 15 g/day. Low-dose colestipol therapy is effective in the treatment of patients with moderate hypercholesterolemia.(ABSTRACT TRUNCATED AT 250 WORDS)

One-hour postload plasma glucose and risks of fatal coronary heart disease and stroke among nondiabetic men and women: the Chicago Heart Association Detection Project in Industry (CHA) Study.

Associations of baseline one-hour postload plasma glucose with 22-year coronary heart disease, stroke, cardiovascular diseases, and all cause mortality were assessed in five age-specific cohorts of nondiabetic men and women from the Chicago Heart Association Detection Project in Industry: 10,269 men ages 18-39 years; 7993 men ages 40-59 years; 1240 men ages 60-74 years; 6319 women ages 40-59 years; and 932 women ages 60-74 years. Plasma glucose was determined one hour after a 50-gram oral glucose load. Cox regression analyses were used to control for age and other covariates. Generally, higher glucose was significantly associated with mortality from coronary heart disease, stroke, cardiovascular diseases, and all cause mortality in men and women. This large longitudinal study provides evidence that one-hour postload plasma glucose in the absence of clinical diabetes at baseline apparently is an independent risk factor for fatal coronary heart disease and stroke in middle-aged and older nondiabetic men and women, and also for cardiovascular diseases and for all cause mortality.

Acute valvular insufficiency complicating hypertrophic obstructive cardiomyopathy.

This report describes a patient with hypertrophic obstructive cardiomyopathy complicated by acute aortic and probably mitral valvular incompetence caused by endocarditis due to Staphylococcus aureus. Following the onset of valvular insufficiency, this patient developed hypotension and pulmonary edema and eventually underwent cardiac surgery in an attempt to control these complications. We review the unique pathophysiology of hypertrophic obstructive cardiomyopathy and its alterations in the presence of acute valvular incompetence and analyze the limitations of medical management of cardiac decompensation in patients with this combination of cardiac abnormalities. The possible need for early surgery in such patients is examined.

The ankle brachial index independently predicts walking velocity and walking endurance in peripheral arterial disease.

OBJECTIVES: Maintaining function among older men and women is an important public health goal as the population lives longer with chronic disease. We report the relationships between lower extremity peripheral arterial disease (PAD), PAD severity, and PAD-related symptoms with walking velocity and endurance among men and women aged 55 and older. DESIGN: A cross-sectional design. SETTING: An academic medical center. PARTICIPANTS: Participants with PAD were men and women aged 55 and older identified from a blood flow laboratory or a general medicine practice (n = 158). Randomly selected controls without PAD were identified from the general medicine practice (n = 70). MEASUREMENTS: PAD was diagnosed and quantified using the ankle brachial index (ABI). Subjects were categorized according to whether they had severe PAD (ABI <0.40), mild to moderate PAD (ABI 0.40 to <0.90), or no PAD (ABI 0.90 to <1.50). Walking endurance was assessed with the 6-minute walk. Usual walking velocity and maximal walking velocity were assessed with "usual" and "maximal" paced 4-meter walks, respectively. RESULTS: Average distances achieved in the 6-minute walk were 1569+/-390 feet for subjects with ABI 0.90-1.50, 1192+/-368 feet for subjects with ABI 0.40 to <0.90, and 942+/-334 feet for subjects with ABI < 0.40 (trend P value < .001). Walking velocities for both the usual and maximal paced 4-meter walks were slowest among subjects with ABI < 0.40 and fastest among subjects with ABI 0.90 to <1.50. Subjects with PAD who had pain at rest had slower walking velocity and poorer walking endurance than other subjects with PAD. In multiple linear regression analyses that included subjects with PAD only, ABI level was an independent predictor of 6-minute walk performance (regression coefficient = 159 ft/0.40 ABI units, P = .011), usual paced 4-meter walk (regression coefficient = .095 meters/sec/0.40 ABI units, P = .031), and maximal paced 4-meter walk (regression coefficient = .120 meters/sec/0.40 ABI units, P = .050) adjusting for age, sex, race, leg symptoms, and comorbid diseases known to affect functioning. Pain at rest was associated independently with the maximally paced 4-meter walk (-0.201 meters/sec, P = .024), but not with the other walks. CONCLUSION: ABI level has a measurable and independent association with walking endurance and both usual and maximal walking velocity. These data suggest that PAD may impair lower extremity function by diminishing function of both Type I ("slow twitch") and Type II ("fast twitch") muscle fibers. Because walking velocity has important prognostic implications for functioning, these data also suggest that ABI may be used to identify patients at increased risk of mobility loss.