Path analysis of familial resemblance in blood pressure in Middle Dalmatia,Croatia

The familial resemblance in blood pressure in Middle Dalmatia, Croatia, has been analyzed using the Path-analytic approach. The sample consisted of 1,126 examinees (526 males and 600 females, aged 17 to 87), inhabitants of the Middle Dalmatia's islands of Brac, Hvar, Korcula and the Peljesac peninsula. The Path analysis was performed with the assumption that each family member (father, mother, offspring 1 and 2) has a latent variable (C) that influences both the blood pressure values (P) and the morphological dimensions significantly correlated with blood pressure (Q). According to the estimates revealed from the most parsimonious models, the diastolic blood pressure has a more pronounced genetic component (h2 = 30-32%) than the systolic blood pressure (h2 = 15%). In contrast to the low intergenerational influences, the members of the same generation showed pronounced effects of shared environment. Common (non-transmitted) offsprings' environment (B) explains 44% of variance of the individual offspring's environment (C) in systolic and 33-35% in diastolic blood pressure. The correlation of father's and mother's environment (u2) was high in the case of diastolic blood pressure (33-44%) but for the systolic blood pressure it was not significantly different from zero. According to the presented results in insular/peninsular population of Middle Dalmatia, family resemblance of systolic and diastolic blood pressure differs. The resemblance is higher in diastolic blood pressure with stronger additive genetic component and stronger environmental and/or genetic component related with morphology. The sources of high heritability of diastolic blood pressure in Middle Dalmatia as well as the sources of high prevalence of hypertension in the same population are the phenomena that might be connected and thus deserve to be further explored in incoming analyses.     

Predicting systolic and diastolic aortic blood pressure and stroke volume in the intact sheep.

We developed a mathematical model describing the interaction between the heart and the arterial system. The model was constructed and tested on basis of invasive hemodynamic data in six sheep. Data from a first group of three animals (49 cardiac cycles) were used to assess a template time-varying elastance curve for the left ventricle, while the baseline steady-state data of a second group of three animals were used to assess reference cardiac and arterial parameters in sheep. The model is fully characterized by nine parameters, which were converted into 6 dimensionless numbers using the Buckingham pi theorem. The model was then used to generate LV pressure and volume and aortic pressure and flow for 86 conditions obtained by varying parameters 50 to 200% of their reference value. Systolic (SBP) and diastolic (DBP) blood pressure and stroke volume (SV) were determined from these model-generated curves and multiple linear regression analysis yielded the following expressions: SBP = Pisovolumic [0.638 - 0.0773 Emax C + 0.0507 RC/T] (r2 = 0.89); DBP = Pisovolumic [0.438-0.0712 Emax C + 0.0655RC/T] (r2 = 0.88) and SV = LVEDV [1.265-1.040 LVEDV/(LVEDV - Vd) + 0.125 Emax C-0.0777RC/T] (r2 = 0.93) with Pisovolumic = Emax (LVEDV - Vd), Emax and Vd being the slope and intercept of the end-systolic pressure-volume relation, R and C the total peripheral resistance and compliance, LVEDV the left ventricular end-diastolic volume, and T the cardiac cycle length. These expressions were validated using data from the second group of three animals obtained during vena cava occlusion at baseline and during administration of dobutamine (61 cycles). The correlation between measured and predicted values was 0.98, 0.97 and 0.92 for SBP, DBP and SV, respectively. Compared to the measured values, SBP and DBP were, on average, underestimated by 5 and 6mmHg, respectively, and SV overestimated by 1.4 ml. We conclude that the derived expressions for blood pressure and stroke volume remain valid in the intact sheep for various hemodynamic conditions, and, taking into account their dimensionless form, may hold in other species and in humans.     

The technique of detecting systolic and diastolic pressure from the transducer output of a PC-based blood pressure monitoring system

A pressure to voltage transducer is used along with a cuff, in a PC-based blood pressure and pulse rate monitoring system for human body. During the blood pressure measurement cycle, the output voltage of the pressure to voltage transducer is recorded digitally using a data acquisition system. The recorded data are then analyzed using software routines to determine the blood pressure and pulse rate of the person under test. However, it is difficult to identify the points of systole and diastole correctly from the recorded data. This paper presents the technique that may be used to determine the systolic and diastolic pressure from the collected data.     

The technique of detecting systolic and diastolic pressure from the transducer output of a PC-based blood pressure monitoring system

A pressure to voltage transducer is used along with a cuff, in a PC-based blood pressure and pulse rate monitoring system for human body. During the blood pressure measurement cycle, the output voltage of the pressure to voltage transducer is recorded digitally using a data acquisition system. The recorded data are then analyzed using software routines to determine the blood pressure and pulse rate of the person under test. However, it is difficult to identify the points of systole and diastole correctly from the recorded data. This paper presents the technique that may be used to determine the systolic and diastolic pressure from the collected data.     

Dicrimination of systolic blood pressure

The ability of humans to discriminate systolic blood pressure (BP) was investigated in two experiments. In Experiment 1, 14 normal subjects were asked to make estimates of their systolic BP while performing both BP-elevating and BP-lowering tasks. They were given intermittent feedback throughout all 10 45-min sessions. Results indicated significant correlations and small absolute differences between estimated and measured BP for all subjects in almost all sessions. Experiment 2, undertaken 6 months after Experiment 1, assessed whether estimation accuracy by subjects who had available both external and interoceptive cues surpassed that of subjects which access to external cues only. Three subjects from the original group who showed consistently high motivation, and who improved in accuracy across the 10 sessions in the previous experiment, made estimates of BP while performing novel tasks with no feedback. Correlations between estimated and measured BP remained high for 2 of the 3. These results were compared with the accuracy of control subjects (3 for each experimental subject) who were asked to estimate experimental subjects' BP using only the cognitive information available to the experimental subjects. Control subjects also had high correlations between their estimates and the experimental subjects' measured BP but at lower levels than two experimental subjects. These findings are discussed in relation to subjects' possible use of interoceptive information.     

Segregation analysis of blood pressure and body mass index in a rural US community

To assess evidence for a gene with large effect on systolic blood pressure (SBP), diastolic blood pressure (DBP), and body mass index (BMI), we conducted segregation analyses on 261 nuclear families collected from a rural Caucasian community in Michigan. The families were ascertained through a hypertensive proband. Each phenotype was adjusted for significant covariate effects (e.g., gender and age). We used class D regressive models to conduct the segregation analyses. Our analysis results support the segregation of a major gene for BMI, but not for SBP or DBP. A recessive locus effect provided the best explanation for BMI where approximately 43% of the variance of BMI was due to this gene.     

Short-term variability of pulse pressure and systolic and diastolic time in heart transplant recipients

In heart transplant recipients (HTR), short-term systolic blood pressure variability is preserved, whereas heart rate variability is almost abolished. Heart period is the sum of left ventricular ejection time (LVET) and diastolic time (DT). In the present time-domain prospective study, we tested the hypothesis that short-term fluctuations in aortic pulse pressure (PP) in HTR were related to fluctuations in LVET. Seventeen male HTR (age 48 +/- 6 yr) were studied 16 +/- 11 mo after transplantation. Aortic root pressure was obtained over a 15-s period using a micromanometer both at rest (n = 17) and following the cold pressor test (CPT, n = 14). There was a strong positive linear relationship between beat-to-beat LVET and beat-to-beat PP in all patients at rest and in 13 of 14 patients following CPT (each P < 0.01). The slope of this relationship showed little scatter both at rest (0.34 +/- 0.07 mmHg/ms) and following CPT (0.35 +/- 0.09 mmHg/ms, P = not significant). Given the essentially fixed heart period, DT varied inversely with LVET. As a result, in 13 of 17 HTR at rest and in 12 of 14 HTR following CPT, there was a negative linear relationship between beat-to-beat PP and DT. In conclusion, our short-term time-domain study demonstrated a strong positive linear relationship between LVET and blood pressure variability in male HTR. We also identified a subgroup of HTR in whom there was a mismatch between PP and DT.     

Oscillometric determination of diastolic, mean and systolic blood pressure--a numerical model

A theoretical model of oscillometric blood pressure measurement is presented. Particular emphasis is paid to the collapse behavior of the artery, and an exponential volume-pressure curve is used. The results of this study suggest that mean blood pressure can be accurately predicted from the peak of the oscillometric curve if corrections related to the cuff pressure waveform are applied. It is also shown, however, that systolic and diastolic pressure may not in general be accurately determined from fixed amplitude ratios based on the oscillometric peak due to the sensitivity of the method to variations in blood pressure waveform, pulse pressure, and arterial compliance. No simple procedures are found to correct for these effects.     

Mean aortic pressure is the geometric mean of systolic and diastolic aortic pressure in resting humans.

The aim of our study was twofold: 1) to establish a mathematical link between mean aortic pressure (MAP) and systolic (SAP) and diastolic aortic pressures (DAP) by testing the hypothesis that either the geometric mean or the harmonic mean of SAP and DAP were reliable MAP estimates; and 2) to critically evaluate three empirical formulas recently proposed to estimate MAP. High-fidelity pressures were recorded at rest at the aortic root level in controls (n = 31) and in subjects with various forms of cardiovascular diseases (n = 108). The time-averaged MAP and the pulse pressure (PP = SAP - DAP) were calculated. The MAP ranged from 66 to 160 mmHg [mean = 107.9 mmHg (SD 18.2)]. The geometric mean, i.e., the square root of the product of SAP and DAP, furnished a reliable estimate of MAP [mean bias = 0.3 mmHg (SD 2.7)]. The harmonic mean was inaccurate. The following MAP formulas were also tested: DAP + 0.412 PP (Meaney E, Alva F, Meaney A, Alva J, and Webel R. Heart 84: 64, 2000), DAP + 0.33 PP + 5 mmHg [Chemla D, Hébert JL, Aptecar E, Mazoit JX, Zamani K, Frank R, Fontaine G, Nitenberg A, and Lecarpentier Y. Clin Sci (Lond) 103: 7-13, 2002], and DAP + [0.33 + (heart rate x 0.0012)] PP (Razminia M, Trivedi A, Molnar J, Elbzour M, Guerrero M, Salem Y, Ahmed A, Khosla S, Lubell DL. Catheter Cardiovasc Interv 63: 419-425, 2004). They all provided accurate and precise estimates of MAP [mean bias = -0.2 (SD 2.9), -0.3 (SD 2.7), and 0.1 mmHg (SD 2.9), respectively]. The implications of the geometric mean pressure strictly pertained to the central (not peripheral) level. It was demonstrated that the fractional systolic (SAP/MAP) and diastolic (DAP/MAP) pressures were reciprocal estimates of aortic pulsatility and that the SAP times DAP product matched the total peripheral resistance times cardiac power product. In conclusion, although the previously described thumb-rules applied, the "geometric MAP" appears more valuable as it established a simple mathematical link between the steady and pulsatile component of aortic pressure.     

Linkage analysis of systolic blood pressure: a score statistic and computer implementation

A genome-wide linkage analysis was conducted on systolic blood pressure using a score statistic. The randomly selected Replicate 34 of the simulated data was used. The score statistic was applied to the sibships derived from the general pedigrees. An add-on R program to GENEHUNTER was developed for this analysis and is freely available.     

Oscillometric measurement of systolic and diastolic blood pressures validated in a physiologic mathematical model

ABSTRACT: BACKGROUND: The oscillometric method of measuring blood pressure with an automated cuff yields valid estimates of mean pressure but questionable estimates of systolic and diastolic pressures. Existing algorithms are sensitive to differences in pulse pressure and artery stiffness. Some are closely guarded trade secrets. Accurate extraction of systolic and diastolic pressures from the envelope of cuff pressure oscillations remains an open problem in biomedical engineering. METHODS: A new analysis of relevant anatomy, physiology and physics reveals the mechanisms underlying the production of cuff pressure oscillations as well as a way to extract systolic and diastolic pressures from the envelope of oscillations in any individual subject. Stiffness characteristics of the compressed artery segment can be extracted from the envelope shape to create an individualized mathematical model. The model is tested with a matrix of possible systolic and diastolic pressure values, and the minimum least squares difference between observed and predicted envelope functions indicates the best fit choices of systolic and diastolic pressure within the test matrix. RESULTS: The model reproduces realistic cuff pressure oscillations. The regression procedure extracts systolic and diastolic pressures accurately in the face of varying pulse pressure and arterial stiffness. The root mean squared error in extracted systolic and diastolic pressures over a range of challenging test scenarios is 0.3 mmHg. CONCLUSIONS: A new algorithm based on physics and physiology allows accurate extraction of systolic and diastolic pressures from cuff pressure oscillations in a way that can be validated, criticized, and updated in the public domain.     

Commingling and segregation analysis of blood pressure in a French-Canadian population.

Using genetic linkage we have localized the gene coding for galactocerebrosidase (GALC) to human chromosome 14. Patients with Krabbe disease and their family members were assayed for GALC activity in leukocytes or fibroblasts and were classified as affected, carrier, noncarrier, or unknown. Polymorphic DNA markers from chromosome 14 demonstrated a multipoint LOD score of 3.40 with GALC located 13 cM centromere distal to CRI-C70 (D14S24). This finding is consistent with the location of the mouse twitcher mutation (a model of human GALC deficiency) on chromosome 12, which has substantial homology to human chromosome 14. Our data do not support a previous report's localization of GALC to chromosome 17.     

The increase in systolic and diastolic blood pressure after exposure to cryogenic temperatures in normotensive men as a contraindication for whole-body cryostimulation

1.

The changes which occur in a human body subjected to cryogenic temperatures are still not completely understood. Thus the aim of this study was to evaluate changes in blood circulation induced by a single exposure to very low temperature during whole-body cryostimulation of young and clinically healthy male subjects. Prior to the study, candidates underwent a medical examination in order to eliminate individuals with contraindications towards cryostimulation.

2.

The study included 40 young men aged 22±0.7 years, average body weight 76.65±7.8 kg and height 175.5±7.2 cm. The participants were exposed to extremely low temperatures in a cryogenic chamber. Each session lasted for 3 min at −130 °C and was preceded by 30 s of adaptation in a vestibule at −60 °C. Blood pressure and heart rate were measured before entering the chamber, immediately after exiting, and 10 and 20 min after exiting.

3.

Our results showed a significant increase in systolic blood pressure after cryostimulation (by an average of 21 mmHg in comparison with the initial level before cryostimulation) and an increase in diastolic blood pressure after the cryostimulation (by 9 mmHg). The increase in systolic blood pressure was accompanied by a significant decrease in heart rate (by about 10 bpm). Cryostimulation of the whole body is a stress factor and a stimulus for the body which significantly increases systolic blood pressure, but the changes are temporary and not harmful for normotensive individuals.