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Biomedical subjects

G A Harshfield

Publications and source records attributed to G A Harshfield.

At least 37 records · Page 2Linked to original sources
PubMed1991

Ambulatory blood pressure patterns in children and adolescents: influence of renin-sodium profiles.

A renin-sodium nomogram for normotensive children and adolescents was developed at our institution. The ambulatory blood pressure patterns of subjects classified by the nomogram were then compared. A biracial sample of 159 children and adolescents were classified as having a low, intermediate, or high renin-sodium profile based on the relationship between their plasma renin activity and 24-hour urinary sodium excretion. Casual (106/58 vs 107/61 vs 106/62 mm Hg) and awake (116/69 vs 117/69 vs 116/70 mm Hg) blood pressure values were comparable among subjects with low, intermediate, and high renin-sodium profiles. Subjects with high renin-sodium profiles, however, had a smaller decline in systolic blood pressure with sleep than did subjects with low renin-sodium profiles (7 vs 11 mm Hg; P less than .04), and higher diastolic blood pressure readings during sleep than subjects with intermediate renin-sodium profiles (65 vs 62 mm Hg; P less than .05). Subjects with high renin-sodium profiles also had greater variance of diastolic blood pressure readings during sleep than either subjects with low renin-sodium profiles (P less than .01) or those with intermediate renin-sodium profiles (P less than .02). The blunted nocturnal decline and increased nocturnal variance of blood pressure among subjects with high renin-sodium profiles may be a marker or mechanism for the future development of essential hypertension.

Adolescent↗
PubMed1990

Heritability of cognitive performance in aging twins. The National Heart, Lung, and Blood Institute Twin Study.

The genetic contribution to performance on scales designed to measure mild to moderate decrements in cognitive functioning in a population at risk is unknown. In the present analysis, 134 monozygotic and 133 dizygotic male twin pairs (mean age, 63 years) were given three cognitive tests: the Mini-Mental State examination, the Iowa Screening Battery for Mental Decline, and, for comparison, the Digit Symbol Substitution Test from the Wechsler Adult Intelligence Scale. The primary objective of the analysis was to test for a significant heritable component to performance on these measures. A secondary objective was to determine the extent to which shared variance with significant confounders such as education, age, and depression affects the outcome of the heritability analysis. Results indicate that performance on tests intended to measure cognitive decline in the elderly does have a significant genetic component and that these estimates tend to increase after adjustment for covariates. Heritability estimates adjusted for covariates were 30% for the Iowa Screening score, 60% for the Mini-Mental State score, and 67% for the Digit Symbol Substitution score.

Age Factors↗
PubMed1990

Genetic and environmental influences on echocardiographically determined left ventricular mass in black twins.

Genetic and environmental influences on left ventricular mass were examined in normotensive black twins. Left ventricular mass was measured echocardiographically in 7 sets of monozygotic (MZ) and 15 sets of dizygotic (DZ) twins and adjusted for body surface area (LVMI). Regression analyses showed significant effects of gender (R2 = 0.48; P less than .01), systolic blood pressure (R2 = 0.21; P less than .01) and age (R2 = 0.10; P less than .05) on LVMI but did not show an effect for either diastolic blood pressure or caloric expenditure. Monozygotic twins showed smaller within-pair differences (7 +/- 5) than DZ twins (17 +/- 11) for LVMI following adjustment for gender, systolic blood pressure and age (P less than .03). The intraclass correlation for MZ twins was 0.90 (P less than .01) and 0.33 (P = NS) for DZ twins. These results indicate that both genetic and environmental factors are important determinants of left ventricular mass in blacks, independent of gender, blood pressure and age.

Adult↗
PubMed1990

Aerobic fitness and the diurnal rhythm of blood pressure in adolescents.

We examined the effects of aerobic fitness and race on the diurnal rhythm of blood pressure of 175 healthy adolescents who performed a cycle ergometer maximal exercise test while oxygen consumption was measured. A median split of maximum oxygen consumption for boys and girls separately classified them as either "more-fit" or "less-fit" subjects. Ambulatory blood pressure recordings were also performed, and the data were analyzed for means while subjects were awake and asleep. Less-fit black boys had higher systolic pressures than more-fit black boys while awake (124 vs. 115 mm Hg; p less than 0.009) and asleep (117 vs. 108; p less than 0.001). Less-fit black boys also had higher systolic pressures than less-fit white boys while awake (114; p less than 0.002) and asleep (105; p less than 0.001), and they had higher systolic pressures than more-fit white boys while asleep (105; p less than 0.01). Less-fit black girls had higher systolic pressures than more-fit black girls while awake (116 vs. 109; p less than 0.004) and asleep (109 vs. 100; p less than 0.001). Less-fit black girls also had higher diastolic pressures than more-fit black girls while awake (71 vs. 66; p less than 0.002) and asleep (66 vs. 61; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Circadian variation of blood pressure in blacks: influence of age, gender and activity.

The purpose of the present study was to examine the circadian variation of blood pressure in black adults and determine the factors associated with this variation. Ambulatory blood pressure recordings were performed with a non-invasive recorder on 60 black subjects, 22 males and 38 females, with a mean age of 31 +/- 11 years and a mean causal blood pressure of 121/93 mm Hg. Only diastolic blood pressure exhibited a significant time of day effect (P less than 0.05). Age and gender were found to have both independent (r2 = 0.10 for each) and interactive effects (r2 = 0.26) on the level of systolic blood pressure during the day, but did not affect the diurnal pattern per se. Blood pressure at work (128/81 mm Hg) was higher (P less than 0.05) than blood pressure during miscellaneous activities (119/75 mm Hg) or sleep (119/73 mm Hg) but did not differ from blood pressure at home (123/77 mm Hg). Blood pressures at home while awake and during sleep were not different. These data show that blacks have a circadian rhythm of blood pressure which is characterized by a blunted nocturnal decline. In addition age, gender and activity are important determinants of the circadian variation. These results may help to explain racial differences in the prevalence of hypertension.

Activities of Daily Living↗
PubMed1989

Race and gender influence ambulatory blood pressure patterns of adolescents.

The purpose of this study was to examine ambulatory blood pressure and heart rate patterns in healthy, normotensive adolescents and to determine the influence of race and gender on these patterns. Ambulatory blood pressure recordings were performed on 199 adolescents; 42 were black males, 55 were white males, 65 were black females, and 37 were white females. The mean age (+/- SD) was 13 +/- 2 years. Blood pressure readings were obtained with an automatic, noninvasive recorder. Black adolescents and white adolescents had similar blood pressures while awake (116/69 vs. 116/69 mm Hg), with boys having higher levels of systolic blood pressure (118 vs. 114 mm Hg) and comparable levels of diastolic blood pressure (69 vs. 69 mm Hg) relative to girls. The patterns while the adolescents were asleep, however, were different. White boys (106 mm Hg), white girls (105 mm Hg), and black girls (105 mm Hg) had similar systolic blood pressures during sleep. Black boys (112 mm Hg), however, had significantly higher systolic blood pressures while asleep. Black adolescents, as a group, had significantly higher diastolic blood pressures than white adolescents while asleep (64 vs. 61 mm Hg). Changes in blood pressure from awake to asleep were not related to changes in heart rate. Results of this study indicate that both race and gender are important determinants of the diurnal pattern of blood pressure and heart rate in adolescents.

Adolescent↗
PubMed1988

How common is white coat hypertension?

Twenty-one percent of 292 patients with untreated borderline hypertension (clinic diastolic blood pressures persistently between 90 and 104 mm Hg) were found to have normal daytime ambulatory pressures (defined from a population of normotensive subjects). These patients were defined as having "white coat" hypertension, and they were more likely to be female and younger, to weigh less, and to be more recently diagnosed than patients whose pressure was elevated both in the clinic and during ambulatory monitoring. Patients with white coat hypertension did not show a generalized increase of blood pressure lability, nor an exaggerated pressor response while at work. The phenomenon is more pronounced when blood pressure is measured by a physician than by a technician. In such patients, the pressor response may be relatively specific to the physician's office and lead to significant misclassification of hypertension.

Adult↗
PubMed1988

Sex differences in factors affecting the daily variation of blood pressure.

The purpose of this study was to examine whether the life experiences described by postural, situational, and emotional changes during the day have similar effects on the blood pressure of men and women. The subjects of the study were 137 men and 67 women from the clinical population of the Hypertension Center at The New York Hospital-Cornell Medical Center. There were 3023 individual pressure measurements available for study, 2072 from the men, and 951 from the women, which were taken using noninvasive ambulatory blood pressure monitoring techniques. Pressures were transformed to z-scores using the subject's daily mean pressure and standard deviation to assess the relative elevation during the various effects. Separate but identical ANOVA models were run for each sex. The results show that there were differences between men and women in the parameters associated with the level of systolic and diastolic pressure. Men's systolic pressure varied by situation of measurement (P less than 0.0001) and emotional state (P less than 0.0001), while that of women varied by posture (P less than 0.0005) and situation of measurement (P less than 0.0001). The diastolic pressure of men varied by emotional state as did that of women, except that men's diastolic pressure tended to be highest during reported anger while that of women tended to be highest during reported anxiety. Differences in occupation or environment, hormones, or in behavioral patterns related to the socialization process may all contribute to the differences between the sexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1988

Do laboratory tests of blood pressure reactivity predict blood pressure changes during everyday life?

This study was undertaken to examine whether blood pressure reactivity measured in the controlled setting of a laboratory could be correlated with blood pressure changes occurring during daily life. The subjects were 164 untreated hypertensives with mild hypertension, all of whom had a 24-hour ambulatory blood pressure recording, during which their activities were unrestricted. One hundred thirteen performed a treadmill exercise test, and 51 performed two active coping tasks (playing a video game or mental arithmetic). Blood pressure was monitored at baseline and during the tasks. Significant correlations were observed between the absolute levels of pressure measured during the laboratory tests and ambulatory monitoring, but these were higher for the active coping tasks (r = 0.53 to 0.75) than the exercise testing (r = 0.26 to 0.46) and were no higher for pressures measured during the tasks than at baseline. Correlations between the changes of blood pressure during the laboratory tasks and the changes occurring during ambulatory monitoring were analyzed in three ways, using simple, multiple, and canonical correlations. In no case were these correlations substantively significant. We conclude that blood pressure reactivity measured in the laboratory may not be readily generalized to changes of pressure in everyday life, as measured by noninvasive ambulatory recorders.

Adult↗
PubMed1988

A validation study of the Del Mar Avionics Pressurometer IV according to AAMI guidelines.

Guidelines for the evaluation of automatic non-invasive blood pressure (BP) measurement devices have recently been established by the Association for the Advancement of Medical Instrumentation (AAMI). We evaluated the Del Mar Avionics Pressurometer IV (P4) in tests on 109 subjects, according to these guidelines. Three readings by two observers using a double stethoscope were first compared to each other to determine a standard and then averaged and compared to readings obtained using the P4. The two observers agreed within +/- 6 mmHg or 90% of the readings for both systolic and diastolic BP, with correlations of 0.99 and 0.98 for systolic and diastolic BP, respectively. The observers and the P4 in turn agreed to within +/- 6 mmHg for 85% of the readings for systolic BP, with a correlation of 0.98, and 65% of the readings for diastolic BP, with a correlation of 0.69. The correlations for both systolic and diastolic BP increased to 0.99 when readings were restricted to those obtained in individuals who fulfilled our previously defined calibration criterion of +/- 5 mmHg. In addition, we evaluated nine measurements of performance over 60 ambulatory recordings. The most serious problem was that of missing data which occurred in 85% of the recordings, primarily during sleep hours, and was generally attributed to either detection of Korotkoff sounds below 40 mmHg or a failure to detect Korotkoff sounds.

Adult↗
PubMed1988

Wideband external pulse recording during cuff deflation: a new technique for evaluation of the arterial pressure pulse and measurement of blood pressure.

Analysis of the external brachial pulse recorded during standard blood pressure cuff deflation with use of a transducer with a wide frequency response has revealed a reproducible pattern with three distinct components that we have labeled K1, K2, and K3. K1 is a low-amplitude, low-frequency signal that is present with cuff pressures above systolic pressure. K2 is a triphasic signal appearing at systolic pressure and disappearing at diastolic pressure, which approximately corresponds to the audible Korotkoff sound. K3 appears with cuff pressure between systolic and diastolic pressure and continues to be present below diastolic pressure. Intra-arterial pressure recordings made with a high-fidelity Millar catheter-tip manometer revealed K2 and K3 analogs. K3 resembles the intra-arterial pressure waveform and when calibrated according to the pulse pressure, noninvasive dK3/dt determinations correlated well with intra-arterial dP/dt measurements. The appearance/disappearance property of K2 was designated as the "K2 algorithm" and represents a new, objective noninvasive method for measurement of blood pressure. The K2 algorithm compares favorably with intra-arterial measurements, is more accurate than the auscultatory technique, and may be especially useful in clinical situations in which the auscultatory technique does not work well.

Adolescent↗
PubMed1988

The reproducibility of average ambulatory, home, and clinic pressures.

The reproducibility of ambulatory, home, and clinic blood pressures was compared in 13 untreated mildly hypertensive and 14 normotensive subjects. Each subject had two sets of daily ambulatory recordings, home self-measured readings (over 6 days), and clinic measurements taken 2 weeks apart. Comparisons over the 2 weeks within and among the methods of measurements were made using a repeated-measures analysis of variance. The results showed that there was no consistent average change in the ambulatory or home pressures and no change in clinic diastolic pressures, but the clinic systolic pressure of the hypertensive subjects dropped 6 mm Hg (p less than 0.05), while that of the normotensive subjects showed no significant change. Test-retest correlations of each of the three methods were similar in magnitude, indicating a similar level of reliability. Test-retest correlations of the ambulatory standard deviations, however, were low, indicating a low reliability of this measure of daily pressure variability. These results suggest that the reproducibility of ambulatory pressures may be as good or better than that of home or clinic measurements. They also suggest that the average ambulatory pressure may be preferable as the measurement in clinical trials, since it may be less influenced by measurement anxiety, particularly in hypertensive subjects.

Activities of Daily Living↗
PubMed1987

A quantitative analysis of the effects of activity and time of day on the diurnal variations of blood pressure.

The effects of activity and time of day on blood pressure (BP) were analyzed in 461 patients with untreated hypertension who wore a noninvasive portable BP recorder which took readings every 15 minutes for 24 hours. Patients recorded activity and location in a diary. The data were analyzed separately for two groups of patients: the 190 who stayed at home and the 271 who went to work. The effects of 16 different activities on BP were estimated by relating the BP to the associated activity and to the individual's clinic BP. Blood pressure was higher at work than at home, but the increment of BP for individual activities was similar in the two locations. The overall effect of activities on BP variability was computed using a one-way analysis of covariance model. For the patients who went to work this model accounted for 40% of the observed variation (R2) for systolic and 39% for diastolic BP. A similar model using time of day instead of activity accounted for 33% of variability in both systolic and diastolic BP. Combining activity and time of day was little better than activity alone (41% for both). After allowing for the effects of activity on BP, where sleep is one of the activities, there was no significant diurnal variation of BP. We conclude that there is no important circadian rhythm of BP which is independent of activity.

Adolescent↗
PubMed1986

Behavioral determinants of 24-hour blood pressure patterns in borderline hypertension.

Borderline hypertension is a heterogeneous condition; only a minority of patients will progress to fixed essential hypertension or suffer cardiovascular damage. Ambulatory blood pressure monitoring can detect the subgroup of borderlines with sustained blood pressure elevation outside the office setting and can also provide a measure of blood pressure variability. Patients in the former group may be at greatest risk for cardiovascular complications while the latter have been theorized to be at risk for progression to fixed hypertension. Evidence we have gathered utilizing ambulatory monitoring does not support the contention that there is a subgroup of borderline hypertensives with excessive blood pressure variability in natural settings. Such recordings have been of benefit in identifying patients with excessive pressor responses to office visits. Future studies employing ambulatory monitoring may be useful in the detection of clinically important subgroups of borderline hypertension.

Behavior↗
PubMed1986

Value of echocardiographic measurement of left ventricular mass in predicting cardiovascular morbid events in hypertensive men.

To assess whether echocardiographic and electrocardiographic detection of left ventricular hypertrophy could predict cardiovascular morbid events in patients with uncomplicated essential hypertension, we followed 140 men for a mean of 4.8 years. Initial echocardiographic measurements of left ventricular mass were normal (less than 125 g/m2 body surface area) in 111 patients and revealed hypertrophy in 29 patients. Morbid events occurred in more patients with hypertrophy on echocardiography (7 of 29, 4.6/100 patient-years) than with normal ventricular mass (7 of 111, 1.4/100 patient-years; p less than 0.01). Electrocardiography showed hypertrophy in too few patients to be of predictive value. Multiple logistic regression analysis showed that left ventricular mass index had the highest independent relative risk for future events and that systolic and diastolic pressures and age had slightly lower relative risks. In men with mild uncomplicated hypertension, left ventricular hypertrophy detected by echocardiography identifies patients at high risk for cardiovascular morbid events and is a significant risk factor for future morbid events independent of age, blood pressure, or resting ventricular function.

Adolescent↗
PubMed1984

Predictive value and changes of renin secretion in hypertensive patients with unilateral renovascular disease undergoing successful renal angioplasty.

Peripheral and renal vein renin activity was measured in 46 hypertensive patients with arteriographically diagnosed unilateral renal artery stenosis before and six months after technically successful renal angioplasty. The renin-sodium profile was high in 80 percent before angioplasty, fell in all patients, and became normal or low in 85 percent after angioplasty. Renal vein renin activity, which initially showed lateralization of renin secretion to the ischemic kidney with contralateral suppression, became normal. Renal vein renin activity was more reliable for predicting the therapeutic response when expressed as the increment of renin for each renal vein over the infrarenal vena caval value (sensitivity 74 percent, specificity 100 percent) than as the ratio between the two renal veins (sensitivity 62 percent, specificity 60 percent). The predictive value of renal vein renin activity is poor when plasma renin activity is stimulated by long-term administration of captopril. These data support the usefulness and define the limitations of peripheral and renal vein renin measurements in selecting patients for treatment by renal angioplasty.

Adult↗