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Biomedical subjects

T G Pickering

Publications and source records attributed to T G Pickering.

At least 73 records · Page 4Linked to original sources
PubMed1998

Relation of age to left ventricular function in clinically normal adults.

The extent to which age, independent of cardiovascular diseases, influences left ventricular (LV) function in adults is uncertain. Echocardiograms and simultaneous arterial pressure in 464 clinically normal adults aged 16 to 88 years were used to measure LV dimensions, endocardial and midwall LV fractional shortening, stroke volume, cardiac output, and circumferential end-systolic stress. The ratios of observed endocardial and midwall shortening to values predicted for observed end-systolic stress were used as measures of chamber and myocardial function. LV endocardial shortening increased slightly with age, as did an index of LV chamber performance, the end-systolic stress/volume index ratio (r = 0.11, p = 0.019, and r = 0.20, p <0.001). However, when age-related increases in LV wall thickness and blood pressure were controlled for by examining afterload-corrected endocardial shortening, no age relation was detected. Weak age-related declines were observed in midwall shortening (r = -0.09, p = 0.043) and afterload-corrected midwall shortening (r = -0.12, p <0.01). Cardiac index decreased slightly with advancing age (r = -0.14, mean -6.7 ml/min/m2/ year, p = 0.003). Total peripheral resistance and the pulse pressure/stroke volume ratio, a measure of arterial stiffness, increased more strongly with age (r = 0.27 and 0.38, both p <0.001). Thus, LV pump performance at rest measured by cardiac index is slightly lower in older than in younger clinically normal adults. Endocardial fractional shortening was slightly higher in older subjects, but the physiologically more appropriate midwall measures of myocardial function decreased slightly. The observed change in LV pump performance was related to smaller LV chamber size and higher total peripheral resistance in older subjects.

Adolescent↗
PubMed1998

The generalizability of cardiovascular responses across settings.

The generalizability of cardiovascular reactivity change scores remains largely unsupported. In previous studies, several factors differed between laboratory and field, making poor lab-to-life correlations difficult to interpret. The present study varied only one parameter between the lab and field: setting. In this study, 24 females were studied on four occasions: twice in the lab (to provide test-retest reliability); once in a classroom; and once at home. After a baseline, subjects performed a math task, while blood pressure and heart rate were monitored. Procedures were identical in all sessions. Blood pressure changes were fairly reliable between the two lab sessions, with rs values 0.68 (systolic) and 0.62 (diastolic pressure); however, lab/nonlab correlations were lower (0.47 for SBP; 0.38 for DBP). This suggests that even a minor variation in procedure, such as a change in setting, can affect generalizability; other lab-field differences may have an even greater impact.

Adolescent↗
PubMed1998

Differential effects of angiotensin converting enzyme inhibition and diuretic therapy on reductions in ambulatory blood pressure, left ventricular mass, and vascular hypertrophy.

Diuretic-based therapy is less effective in reducing the cardiac complications of hypertension than the risk of stroke and may be less effective in reducing left ventricular (LV) mass than is therapy with angiotensin converting enzyme (ACE) inhibition. In view of the strong association of LV hypertrophy with cardiovascular risk, this study was designed to compare the impact of therapy with a diuretic and ACE inhibition on cardiac and vascular structure. Fifty essential hypertensives (74% male, 88% nonwhite) participated in a double-blind study for 6 months and were randomized to either ramipril or hydrochlorothiazide (HCTZ). Echocardiography, carotid ultrasonography, and ambulatory blood pressure (BP) monitoring were performed at baseline and 3 and 6 months after initiation of therapy. The 22 ramipril patients were comparable to the 28 HCTZ patients at baseline in age, race, and 24-h BP. Although HCTZ resulted in a greater reduction in 24-h BP, only treatment with ramipril resulted in a decrease in LV mass (193 to 179 g, P < .005, v 184 to 182 g, P = NS), attributable to a reduction in wall thicknesses but not in chamber diameter. In multivariate analysis, both change in BP and treatment group were independent predictors of change in LV mass. Importantly, although neither drug reduced carotid artery cross-sectional area, relative wall thickness increased due to a tendency for vessel diameter to decrease and wall thickness to increase, particularly in the diuretic group. Ramipril caused a sustained fall in plasma angiotensin II, whereas HCTZ increased angiotensin II levels. Although diuretic therapy was more effective in lowering ambulatory BP in this predominantly nonwhite population, only therapy with ACE inhibition was associated with regression of LV mass. Vascular geometry was altered consistent with the reduction in distending pressure resulting in vascular remodelling.

Adult↗
PubMed1998

Relation of left ventricular midwall function to cardiovascular risk factors and arterial structure and function.

Left ventricular (LV) midwall shortening (MWS) is subnormal in relation to LV circumferential end-systolic stress (ESS) (ESS-corrected MWS) in many hypertensive patients with normal LV chamber function and predicts subsequent morbidity and mortality. However, little is known of the relations of LV midwall function to demographic and metabolic variables or to arterial geometry. Asymptomatic, unmedicated normotensive (n=366) or hypertensive (n=282) adults were assessed with echocardiography and carotid ultrasound. In normal adults, lower LV MWS and ESS-corrected MWS, an index of LV contractility, were related independently to high total peripheral resistance, high heart rate, and male gender (all P<.00001), lower serum HDL cholesterol (P=.001) and diastolic pressure (P=.003), and for ESS-corrected MWS only, arterial relative wall thickness (RWT, P=.03). Among hypertensive patients, lower values for both midwall function indices were associated independently with higher peripheral resistance (P<.00001), heart rate (P<.00005), body mass index (P<.01), and arterial RWT (P=.04), as well as male gender (P<.0002). In the entire population, lower LV MWS was independently related to higher peripheral resistance, heart rate (both P<.00001), body mass index (P=.0006) and arterial RWT (P=.009); male gender (P<.00001); and lower age (P=.004), diastolic pressure (P=.042), and systolic carotid artery expansion (P=.032). Lower ESS-corrected MWS in the entire population was independently associated with higher peripheral resistance and heart rate (both P<.00001), body mass index (P=.0006), arterial RWT (P=.004); male gender; and lower diastolic pressure (both P<.00001), age (P<.00005), arterial expansion in systole (P=.006), and serum HDL cholesterol levels (P=.04). Among a subset (n=60), ESS-corrected MWS was positively related to apolipoprotein A1 (P=.004) and negatively to hemoglobin A1c (P<.01). Thus, higher LV midwall function is associated with female gender and more favorable profiles of hemodynamics, metabolic pattern, and arterial structure and function.

Apolipoproteins↗
PubMed1998

Time-voltage QRS area of the 12-lead electrocardiogram: detection of left ventricular hypertrophy.

Identification of left ventricular hypertrophy (LVH) using 12-lead ECG criteria based primarily on QRS amplitudes has been limited by poor sensitivity at acceptable levels of specificity. Because the product of QRS voltage and duration, as an approximation of the time-voltage area of the QRS complex, can improve accuracy of the 12-lead ECG for LVH, we examined the diagnostic value of true time-voltage area measurements of QRS complexes from the standard 12-lead ECG. Standard 12-lead ECGs and echocardiograms were obtained in 175 control subjects without LVH and in 74 patients with regurgitant valvular heart disease and LVH defined by echocardiographic criteria (indexed LV mass >110 g/m2 in women and >125 g/m2 in men). Standard voltage criteria, voltage-duration products (voltage multiplied by QRS duration), and true time-voltage areas of the QRS were calculated for Sokolow-Lyon criteria (SV1 +RV(5/6)) and the 12-lead sum of voltage criteria. Test sensitivities were compared using gender-specific partitions with matched specificity of 98% in the 175 subjects without LVH. Measurement of the time-voltage area significantly improved sensitivity for both criteria. The 76% sensitivity of the 12-lead sum area and 65% sensitivity of Sokolow-Lyon area were significantly greater than the 54% sensitivity of the approximation of QRS area provided by each voltage-duration product (P<.001 and P=.021) and than the 46% and 43% sensitivities of the respective simple voltage criteria (each P<.001). Comparison of receiver operating characteristic curves confirmed the superior overall performance of time-voltage area criteria compared with both voltage-duration products and simple voltage criteria. These results suggest that use of time-voltage areas can dramatically improve identification of LVH by 12-lead ECG. Further study of this approach is needed to identify optimal criteria for LVH based on the time-voltage area measurements from the 12-lead ECG.

Echocardiography↗
PubMed1998

Impact of shift work and race/ethnicity on the diurnal rhythm of blood pressure and catecholamines.

To evaluate the effects of shift work and race/ethnicity on the diurnal rhythm of blood pressure and urinary catecholamine excretion of healthy female nurses, 37 African American women and 62 women of other races underwent ambulatory blood pressure monitor and urine collection for 24 hours that included a full work shift: day shift (n=61), evening shift (n=11), and night shift (n=27). Awake and sleep times were evaluated from subjects' diaries. Of African Americans, 79% who were working evenings or nights and 32% working day shifts were nondippers (<10% drop in systolic pressure during sleep), whereas only 29% of others working evening+night and 8% working day shifts were nondippers. Regression analyses indicated that evening+night shift workers had a 5.4 mm Hg (P<0.001) smaller drop than day shift workers, and African Americans had a 4.0 mm Hg (P<0.01) smaller drop than others. The odds of an evening+night shift worker being a nondipper were 6.1 times that of a day shift worker (P<0.001), and the odds of an African American were 7.1 times that of others (P<0.001). Total sleep time was significantly greater in the non-African American day shift workers than in the other 3 groups. After controlling for work shift and race/ethnicity, we determined that longer sleep times predicted less dipping (absolute and relative) in blood pressure. Urinary norepinephrine and epinephrine were higher during work than nonwork in both racial groups of day shift workers, but in evening+night shift workers the difference was small and in the opposite direction. These results indicate that being African American and working evening or night shifts are independent predictors of nondipper status. Higher sleep blood pressure may contribute to the known adverse effects of shift work.

Adult↗
PubMed1998

Prospective study of simultaneous orthoiodohippurate and diethylenetriaminepentaacetic acid captopril renography. The Einstein/Cornell Collaborative Hypertension Group.

UNLABELLED: Captopril renography (CR) has been established in the past 10 yr as a useful diagnostic test for renovascular hypertension. However, direct comparison of tubular and glomerular tracers, quantitative criteria, comparison of quantitative and qualitative results and the reliability of the results in renal failure have not been described in a systematic, prospective fashion. METHODS: Same-day baseline and CR using 99mTc-labeled diethylenetriaminepentaacetic acid (DTPA) and [131I]orthoiodohippurate (OIH) were simultaneously performed in two groups of hypertensive subjects, one with demographically defined essential hypertension (n = 43) and the other (n = 60) with a high prevalence of renovascular disease, defined with angiograms. Quantitative criteria for abnormal CR were derived from results among the subjects with essential hypertension. Qualitative analysis was performed using widely established criteria. RESULTS: There were no statistically significant differences between quantitative and qualitative accuracy, between OIH and DTPA or among quantitative parameters. The best accuracies for quantitative CR were 56% with DTPA (n = 57) and 60% with OIH (n = 60), in both cases using the relative renal uptake parameter. Qualitative CR (n = 60) had accuracies of 43% (DTPA) and 50% (OIH), both hindered by 29 (DTPA) and 25 (OIH) abnormal but nondiagnostic studies. Two false-positive studies were detected. Twenty-seven of 29 nondiagnostic studies were associated with a glomerular filtration rate of <50 ml/min (n = 17), one small kidney (n = 17) and/or bilateral renal artery stenosis (n = 16). Supplemental measurement of in vitro stimulated plasma renin activity insignificantly (p > 0.10) and improved accuracies to 63% (DTPA) and 70% (OIH), without introducing additional false-positive tests. CONCLUSION: Orthoiodohippurate and DTPA have comparable accuracy in prospective simultaneous evaluation of CR. False-positive studies are fewer than 5%. The accuracies of quantitative and qualitative criteria do not differ significantly but may be improved by supplemental use of the in vitro stimulated plasma renin activity. In individuals with renal insufficiency, small kidneys and/or bilateral renal artery disease, up to 48% of CR studies are abnormal but nondiagnostic.

Antihypertensive Agents↗
PubMed1997

Relation of hemodynamic volume load to arterial and cardiac size.

OBJECTIVES: This study sought to assess the relation of Doppler stroke volume (SV) to cardiac and carotid artery size and to determine whether volume load accounts for the parallelism between the two. BACKGROUND: It has been suggested that altered hemodynamic volume load can modify the degree and pattern of left ventricular (LV) hypertrophy from that predicted from blood pressure (BP) alone. METHODS: We related Doppler echocardiographic SV in 342 normotensive or unmedicated asymptomatic hypertensive adults to echocardiographic LV mass, LV internal dimension (LVID), wall thickness, carotid ultrasound arterial lumen diameter, intimal-medial thickness (IMT) and cross-sectional area (CSA). RESULTS: SV was positively related to LV mass (r = 0.42), LVID (r = 0.45), ventricular wall thickness (r = 0.20 to 0.29) and carotid diameter (r = 0.23, all p < 0.0001); CSA (r = 0.17, p < 0.002); and IMT (r = 0.12, p = 0.03). In multivariate analyses controlling for awake ambulatory BP and the circumferential end-systolic stress/end-systolic volume index ratio, SV remained an independent predictor of LV mass and chamber size (both p < 0.0001) but not LV wall thickness. SV also predicted carotid diameter (p < 0.0002), CSA (p = 0.001) and, to a lesser degree, IMT (p = 0.02) after controlling for mean awake BP and age. In additional analyses, LV and carotid dimensions were significantly interrelated independent of SV. CONCLUSIONS: SV measured by invasively validated Doppler echocardiography is associated with LV and carotid artery enlargement and eccentric hypertrophy, independent of arterial pressure, LV contractility, age and body size; however, SV and other variables do not account for the previously documented parallelism between cardiac and arterial structure.

Age Factors↗
PubMed1997

Is the absence of a normal nocturnal fall in blood pressure (nondipping) associated with cardiovascular target organ damage?

OBJECTIVE: To determine whether the failure to decrease blood pressure normally during sleep is associated with more prominent target organ damage. METHODS: Cardiac and vascular structure and function were characterized in 183 asymptomatic, unmedicated hypertensive patients and compared with their ambulatory blood pressures. RESULTS: The 104 patients with a normal (> 10%) nocturnal fall in systolic blood pressure (dippers) were similar to the 79 patients with an abnormal fall (nondippers) in sex, race, body size, smoking history, and average awake ambulatory blood pressure. Nondippers tended to be older (57 versus 54 years, P = 0.06). The supine blood pressure upon completion of the ultrasound studies was higher in the nondippers (156/93 versus 146/89 mmHg, P < 0.005) as was the variability of the awake diastolic blood pressure. There were no differences between dippers and nondippers in left ventricular mass (170 versus 172 g), mass index (90 versus 91 gm/m2), prevalence of abnormal ventricular geometry, common carotid artery diameter (5.74 versus 5.75 mm), and vascular strain. Although nondippers were more likely to have carotid artery plaque (41 versus 27%, P = 0.053) and an increased intimal-medial thickness (0.84 versus 0.79 mm, P < 0.05), adjustment for age rendered the differences insignificant. There were no differences in the relation of awake and sleeping systolic pressures to the left ventricular mass (r = 0.36 and 0.35, respectively, both P < 0.005) or to the carotid wall thickness (r = 0.28 and 0.29, respectively, both P < 0.005). When the 114 men and 69 women were considered separately, similar findings were obtained. When the 109 whites and 56 blacks (African-Americans and Afro-Caribbeans) were considered separately, there were no differences in left ventricular structure in either group, and differences in vascular structure were confined to the white subgroup. CONCLUSION: The lack of a normal nocturnal fall in blood pressure is not associated with an increase in left ventricular mass or in arterial disease independently of age. Age-related changes in carotid artery wall thickness and plaque among nondippers may reflect a contribution of an altered baroreceptor function to the lack of normal nocturnal and supine blood pressure decreases.

Adult↗
PubMed1997

Relation of exercise-induced myocardial ischemia to cardiac and carotid structure.

There is a strong relation of carotid atherosclerosis to coronary artery disease and left ventricular hypertrophy. In addition, abnormalities of carotid structure are strongly associated with abnormal left ventricular geometry and structure. However, little is known regarding the relation of exercise-induced ST depression to carotid atherosclerosis, carotid, or left ventricular structure in the absence of apparent coronary disease. The relationship of exercise ECG myocardial ischemia to the presence of carotid atherosclerosis and to carotid and left ventricular structure was assessed in 204 asymptomatic subjects free of clinical evidence of cardiovascular disease. Myocardial ischemia on the exercise ECG, defined by a chronotropically adjusted ST/HR slope of >3.47 microV/bpm, was associated with a nearly threefold greater likelihood of discrete carotid atherosclerosis (50% [6 of 12] versus 17% [29 of 192], P=.007) and with older age, male sex, higher systolic and diastolic blood pressures, greater left ventricular mass and mass index, and greater common carotid artery intimal-medial thickness and cross-sectional area index. Stepwise logistic regression analyses, including standard risk factors, revealed that only carotid artery cross-sectional area index (P=.0007) and systolic blood pressure (P=.005) independently predicted an abnormal chronotropically adjusted ST/heart rate slope. Moreover, among 132 subjects with > or = 10 microV of ST-segment depression, only left ventricular mass index and carotid artery cross-sectional area index were significant predictors of the chronotropically adjusted ST/heart rate slope response. Subendocardial ischemia on the exercise ECG is strongly associated with the presence of carotid atherosclerosis and is related to systolic blood pressure, carotid artery cross-sectional area index, and left ventricular mass index, independent of age, sex, and other cardiac risk factors. These findings provide additional insights into the relation between coronary and carotid atherosclerosis and suggest that an association among ischemia and left ventricular and carotid structural abnormalities may contribute to the pathogenesis of coronary events.

Arteriosclerosis↗
PubMed1997

The effects of environmental and lifestyle factors on blood pressure and the intermediary role of the sympathetic nervous system.

Essential hypertension is thought to be caused by both genetic and environmental factors, with varying combinations in different individuals. Proposed environmental factors include exposure to chronic stress, obesity alcohol and salt intake, and physical inactivity. The prevalence of hypertension is related to social factors such as urbanization and education. Several studies, conducted both experimentally in animals and observationally in people, have suggested that chronic social conflict is associated with higher blood pressure. Ambulatory monitoring has shown that most people have their highest pressures during working hours. Occupational stress can be evaluated as job strain, which is a combination of high demands at work with low decision latitude or control. Job strain has been related to coronary heart disease, and a number of studies have shown that it is also associated with higher ambulatory blood pressures, both cross-sectionally and prospectively, in men but not in women. It is likely that environmental and lifestyle facts operate interactively rather than independently to promote hypertension. There is also extensive evidence that overactivity of the sympathetic nervous system plays a role in the development of hypertension, particularly in its early stages. So far it has not been established why this should occur. There are several possible environmental origins, however, and all of the lifestyle factors mentioned above have been shown in at least some studies to operate via the sympathetic nervous system.

Animals↗
PubMed1996

Association of the auscultatory gap with vascular disease in hypertensive patients.

OBJECTIVE: To assess the relation of the auscultatory gap during blood pressure measurement to cardiovascular structure and function. DESIGN: Cross-sectional study. SETTING: A hypertension center in a university hospital. PATIENTS: 168 persons with hypertension who were otherwise healthy and were not receiving medication. MEASUREMENTS: Wideband external pulse recordings and ultrasonographic examination of the left ventricle and extracranial carotid arteries. Vascular stiffness was evaluated using simultaneous carotid pressure waveforms obtained by applanation tonometry of the contralateral carotid artery. RESULTS: Classic auscultatory gaps were present in 21% of patients and were associated with older age (mean age SD, 64 11 years for patients with gaps and 55 13 years for patients without gaps; P < 0.001), female sex (67% of patients with gaps and 44% of patients without gaps were female; P < 0.05), and increased arterial stiffness (arterial stiffness index, 8.5 4.6 in patients with gaps and 5.8 3.2 in patients without gaps; P < 0.005). The prevalence of atherosclerotic plaques was increased more than twofold among patients with gaps compared with patients without gaps (50% compared with 22%; p < 0.002). Patients with and without auscultatory gaps had similar blood pressures, left ventricular structure and function, serum cholesterol levels, and smoking history. Logistic regression analysis indicated that only female sex (P < 0.02), arterial stiffness (P < 0.002), and atherosclerotic plaque (P < 0.02) were independently associated with the presence of an auscultatory gap. CONCLUSIONS: This study provides strong evidence that auscultatory gaps are related to carotid atherosclerosis and to increased arterial stiffness in hypertensive patients, independent of age. Although these observations need to be confirmed prospectively, they suggest that auscultatory gaps may have prognostic relevance.

Adult↗