Pressure Casting

Validation of Peripheral Pulse Wave Analysis Technique to Detect Aortic Valve State in Continuous-Flow LVADs1

The nicotinamide adenine dinucleotide phosphate (NADPH) oxidase produces superoxide, thus regulating redox state in the vessel wall. Three single-nucleotide polymorphisms (SNPs; -930A/G, A640G and C242T) of the p22(phox) subunit have been associated with hypertension; however, their role in peripheral and central pressures in normotensive individuals has not been addressed. A total of 210 healthy, normotensive individuals were studied. Genotypes for the -930A/G, A640G and C242T polymorphisms were determined by polymerase chain reaction. Peripheral pressures were measured by mercury sphygmomanometer and aortic pressures by a validated device using applanation tonometry. Both peripheral and central pressures differed across -930A/G genotypes. G allele carriers showed higher levels of peripheral systolic blood pressure (PSBP; AA: 113+/-12, GG/AG: 119+/-12 mm Hg; P<0.01) and peripheral diastolic blood pressure (AA: 70+/-9, GG/AG: 73+/-10 mm Hg; P<0.05). Regarding central pressures, AA homozygotes had lower central systolic blood pressure (CSBP; AA: 103+/-12, GG/AG: 108+/-12 mm Hg; P<0.01) and central diastolic blood pressure (AA: 71+/-9, GG/AG: 74+/-10 mm Hg; P<0.05). In multiple linear regression analysis, presence of the G allele (AG or GG) independently predicted CSBP. Blood pressure levels did not differ across A640G and C242T genotypes. The -930A/G polymorphism of p22(phox) is a determinant of peripheral and central pressures in normotensive individuals. The G allele is associated with higher blood pressure in the brachial artery, as well as in the aorta. These findings further elucidate the role of this polymorphism in the regulation of blood pressure. In contrast, the A640G and C242T SNPs do not influence peripheral and central pressures in normotensives.

Greater maternal adiposity is a potentially modifiable risk factor for elevated blood pressure during pregnancy; however, the association has been little studied in Asian populations, and no study has evaluated potential differences in the adiposity-blood pressure relation between ethnic groups or interaction with gestational diabetes. We performed a cross-sectional evaluation of a Singapore mother-offspring cohort comprising 799 pregnant Chinese, Malay and Indian women. Data on body weight, height, skinfold thickness and glycaemia (oral glucose tolerance test) were collected during the 2nd trimester; peripheral SBP and DBP were measured using an oscillometric device and central pressures by noninvasive radial applanation tonometry. The associations between adiposity measures BMI and sum of skinfold thickness and blood pressure outcomes were examined by linear regression with adjustment for potential confounders. Higher maternal BMI was associated with elevated peripheral and central pressures: the increases in pressure (mmHg) for each kg/m(2) increase in BMI were 1.19 (95% confidence interval, 1.03-1.36) for peripheral SBP, 0.76 (0.63-0.89) for peripheral DBP, 1.02 (0.87-1.17) for central systolic pressure and 0.26 (0.16-0.37) for central pulse pressure. The associations were generally stronger in Chinese women (P-interaction = 0.03 for central pulse pressure) and individuals with gestational diabetes (P-interaction = 0.03 for DBP and P-interaction = 0.046 for central systolic pressure). Similar patterns of results were found when using skinfold thickness as the measure of adiposity. Maternal adiposity is associated with higher peripheral and central blood pressures during pregnancy. Stronger associations in Chinese women and individuals with gestational diabetes warrant further investigation.

Pulse pressure varies throughout the arterial tree, resulting in a gradient between central and peripheral pressure. Factors such as age, heart rate, and height influence this gradient. However, the relative impact of cardiovascular risk factors and atheromatous disease on central pressure and the normal variation in central pressure in healthy individuals are unclear. Seated peripheral (brachial) and central (aortic) blood pressures were assessed, and the ratio between aortic and brachial pulse pressure (pulse pressure ratio, ie, 1/amplification) was calculated in healthy individuals, diabetic subjects, patients with cardiovascular disease, and in individuals with only 1 of the following: hypertension, hypercholesterolemia, or smoking. The age range was 18 to 101 years, and data from 10 613 individuals were analyzed. Compared with healthy individuals, pulse pressure ratio was significantly increased (ie, central systolic pressure was relatively higher) in individuals with risk factors or disease (P<0.01 for all of the comparisons). Although aging was associated with an increased pulse pressure ratio, there was still an average+/-SD difference between brachial and aortic systolic pressure of 11+/-4 and 8+/-3 mm Hg for men and women aged >80 years, respectively. Finally, stratifying individuals by brachial pressure revealed considerable overlap in aortic pressure, such that >70% of individuals with high-normal brachial pressure had similar aortic pressures as those with stage 1 hypertension. These data demonstrate that cardiovascular risk factors affect the pulse pressure ratio, and that central pressure cannot be reliably inferred from peripheral pressure. However, assessment of central pressure may improve the identification and management of patients with elevated cardiovascular risk.

To the Editor: We read with great interest the meta-analysis by Chida and Steptoe1 linking poor responses to mental stress with future cardiovascular (CV) risk. The authors eloquently present the pros and cons of laboratory tests that are used to provoke stress, highlight the importance of immediate response to stimuli, as well as of subsequent poststress recovery, and focus on published studies that present longitudinal data regarding CV risk of the subjects that were exposed to the stressor test. In longitudinal studies, the choice of end points and surrogate markers for assessing the effect of interventions is …

Objective: The importance of central blood pressure evaluation for cardiovascular risk stratification has been emphasized. The aim of this study is to evaluate whether brachial blood pressure obtained by the oscillometric method accurately reflects central blood pressure. Methods: The subjects consisted of 84 consecutive patients with suspected coronary artery disease who underwent cardiac catheterization. Central blood pressure was invasively measured in the origin of the left subclavian artery by using the fluid-filled system, and at the same time, brachial blood pressure in the left upper arm was measured by the oscillometric method. Results: No significant difference was found between central systolic pressure and brachial systolic pressure (144.49±18.84 mmHg vs. 142.44±14.96 mmHg, P=0.063). Bland-Altman analysis accounted for only a small bias of +2.25 mmHg, and the limits of agreement were 24.15 mmHg and -19.65 mmHg. Central diastolic pressure was significantly lower than brachial diastolic pressure (75.80± 8.74 mmHg vs. 86.70±10.48 mmHg, P<0.001). Bland-Altman analysis showed a significant bias of -5.45 mmHg, and the limits of agreement were 2.83 mmHg and -13.73 mmHg. Conclusion: These results indicate that central systolic pressure can be directly estimated from brachial systolic pressure using the noninvasive oscillometric method and observed biases seem to remain within the practical range. However, use of the brachial diastolic pressure and pulse pressure measured by the noninvasive oscillometric method is doubtful in clinical practice because of their large biases.

Investigating the effects of time pressure on new product development teams

The functional plasminogen activator inhibitor-1 (PAI-1) 4G/5G polymorphism has previously been associated with hypertension. In recent years, central blood pressure, rather than brachial has been argued a better measure of cardiovascular damage and clinical outcome. The aim of this study was to investigate the possible influence of the 4G/5G polymorphism on central arterial blood pressure in a cohort of elderly individuals. We studied 410 individuals, 216 men and 194 women, aged 70-88. Central pressures and pulse waveforms were calculated from the radial artery pressure waveform by the use of the SphygmoCor system and a generalized transfer function. Brachial pressure was recorded using oscillometric technique (Dinamap, Critikon, Tampa, FL). PAI-1 antigen was determined in plasma. The results showed that central pressures were higher in women carrying the PAI-1 4G/4G genotype compared to female carriers of the 5G/5G genotype, (P = 0.025, P = 0.002, and P = 0.002 for central systolic-, diastolic-, and mean arterial pressure, respectively). The association remained after adjustment for potentially confounding factors related to hypertension. No association of the PAI-1 genotype with blood pressure was found in men. Multiple regression analysis revealed an association between PAI-1 genotype and plasma PAI-1 levels (P = 0.048). Our findings show a gender-specific association of the PAI-1 4G/5G polymorphism with central arterial blood pressure. The genotype effect was independent of other risk factors related to hypertension, suggesting that impaired fibrinolytic potential may play an important role in the development of central hypertension in women.

Fecal incontinence (FI) is frequently associated with low sphincter pressures, sensory abnormalities, and advanced age. Twenty-three percent of patients with FI and 22% of healthy patients demonstrate dyssynergic defecation (DD) on high-resolution anorectal manometry. Overflow incontinence occurs in some DD patients with normal resting and squeeze anal sphincter pressures. Our aim was to identify factors associated with normal sphincter pressures in women with FI. We reviewed medical records of 134 women with FI. Patients with normal resting and squeeze anal pressures were compared with those with abnormal pressures using Wilcoxon rank sum test and Fisher exact. Multivariable logistic regression was performed to identify factors associated with normal resting and squeeze anal pressures. Among 134 women, abnormal resting and/or squeeze pressures were identified in 113 and normal pressures were identified in 21. Women with normal sphincter pressures were younger (mean age 52.7 ± 10.8 years vs 59.0 ± 14.0 years, P = 0.036), more often had abnormal defecation indices (100% vs 83.2%, P = 0.043) and higher rectal defecation pressures (30.8 ± 18.8 mm Hg vs 50.8 ± 22.6 mm Hg, P < 0.001). There was an overall association between DD subtype and normal and abnormal sphincter pressure groups (P = 0.021). Dyssynergia subtypes I or III (odds ratio, 7.2; 95% confidence interval, 1.8-28.8) and age younger than 67 years (odds ratio, 8.5; 95% confidence interval, 1.5-48.6) were associated with greater odds of having normal sphincter pressures. Female FI patients with normal anal sphincter pressures are younger, have higher rectal defecation pressures, and more often have type I or type III DD.

Hemodynamic and central blood pressure differences between carvedilol and valsartan added to lisinopril at rest and during exercise stress

Peripheral systolic blood pressure is amplified above central aortic systolic pressure, but the late systolic shoulder of the peripheral pulse may approximate central systolic pressure. Because late systolic pressure also determines the peripheral augmentation index, a measure of pressure wave reflection within the systemic circulation, this implies a direct relationship between amplification and augmentation. We compared the late systolic shoulder of the peripheral pressure waveform with estimates of central systolic pressure obtained using a transfer function in 391 subjects undergoing diagnostic coronary angiography and/or elective angioplasty (30% with insignificant coronary artery disease). In a subset (n=12) we compared the late systolic shoulder of the peripheral pulse with central pressure obtained with a catheter placed in the aortic root. Measurements were made at baseline, during atrial pacing, and during administration of nitroglycerin. Late systolic shoulder pressure closely approximated transfer function estimates of central pressure (R=0.96; P<0.0001; mean difference+/-SD: 0.5+/-5.2 mm Hg). Despite changes in waveform morphology induced by pacing and nitroglycerin (reducing mean values+/-SE of the augmentation index from 76+/-3.8% to 66+/-4.6% and 60+/-3.3%, respectively), there was close agreement between the late systolic shoulder of the peripheral pulse and measured values of central pressure (R=0.96; P<0.001; mean difference: 1.7+/-4.8 mm Hg). In conclusion, the late systolic shoulder of the peripheral pulse closely approximates central systolic pressure and peripheral augmentation index, the ratio of central:peripheral pulse pressure. Interventions to lower augmentation index and peripheral vascular resistance will have multiplicative effects in lowering central blood pressure.

Background: Blood pressure (BP) monitoring is the basic hemodynamic parameter necessary to monitor the hemodynamic changes occurring under general anesthesia (GA) to maintain adequate perfusion to major organs such as the heart, brain, and kidneys. Physicians heavily rely upon peripheral hemodynamic measurements despite availability of devices suitable for measurement of central blood pressure through non-invasive manner paving a gap in the literature concerning the effects of GA on central pressure. Aims and Objective: In this comparative cross-over study, authors have aimed to find out the degree of changes in central and peripheral BP after the introduction of GA among adult patients of different age groups scheduled for routine surgical procedures with an objective to maintain vital functions more precisely – considering the fact that vital organ perfusions (heart, brain etc.,) depend more on the required values of CBP than that of PBP. Material &amp; Methods: Following approval from IEC, sixty adult patients with ASA physical status 1 or 2 undergoing routine surgical procedures under general anesthesia were enrolled in this prospective cross-over study where each patient was case as well control for measurement and comparison of his/her central and peripheral blood pressure. Patients, being divided into three groups as per age range - 20-40 years (Group A), 40-60 years (Group B), and 60-80 years (Group C) had their normal Riva Rocci BP cuff (Space Lab Inc. USA) placed in one arm for peripheral BP measurement and special Riva Rocci (Uscom Ltd., Australia).) BP cuff for on another arm for Central BP measurement. After patient’s arrival into operation theatre, baseline hemodynamic parameters were taken followed by sequential measurements of CBP and PBP with an interval of 2 minutes till 30-40 mins of operation. There were alternative measurements of these pressures with recording of data from either of the devices as mentioned for further comparison and analysis. Results: From baseline values, it was found that all the three groups were comparable in respect of age, height, weight, PBP and CBP. When measured pressure of all groups combined, that there was a fall in both Central and Peripheral SBP as well as DBP after giving intravenous induction agent (propofol) and rise in both central and peripheral SBP and DBP after laryngoscopy and intubation. Degree of systolic blood pressure change in both peripheral &amp; central that is fall of BP in 3rd reading &amp; rise of BP in 5th reading was greatest in group C, followed by group B, then group A [p - 0.005]. While comparing three subgroups, the baseline Augmentation Index (AI) was highest in group C and lowest in group A. Following the administration of general anesthesia (GA), the change in Augmentation Index (ΔAI), was most pronounced in the third reading corresponding to the time after the administration of the induction agent. Conclusion: Measurement of CBP through peripheral placement of cuff is a unique feasible method to detect real changes of circulation with actual pressure in vital organs. Thus, the study suggests that central blood pressure measurements can provide a more accurate reflection of hemodynamic changes during general anesthesia, especially in older individuals or those with different cardiovascular conditions allowing better vital management of body circulation.

Impact of Heart Rate on Central Aortic Pressures and Hemodynamics: Analysis From the CAFE (Conduit Artery Function Evaluation) Study: CAFE-Heart Rate

At a site where compressed air was being used in the construction of a tunnel, 34 men sorted cards twice, once at normal atmospheric pressure and once at 3½, 2½, or 2 atmospheres absolute pressure. An additional six men sorted cards twice at normal atmospheric pressure. When the task was carried out for the first time, all the groups of men performing at raised pressure were found to yield a reliably greater proportion of very slow responses than the group of men performing at normal pressure. There was reliably more variability in timing at 3½ and 2½ atmospheres absolute than at normal pressure. At 3½ atmospheres absolute the average performance was also reliably slower. When the task was carried out for the second time, exposure to 3½ atmospheres absolute pressure had no reliable effect. Thus compressed air affected performance only while the task was being learnt; it had little effect after practice. No reliable differences were found related to age, to length of experience in compressed air, or to the duration of the exposure to compressed air, which was never less than 10 minutes at 3½ atmospheres absolute pressure.

We previously demonstrated stronger relations of central vs. brachial blood pressure, particularly pulse pressure, to carotid artery hypertrophy and extent of atherosclerosis. Data regarding the relative impacts of central and brachial pressures on left ventricular hypertrophy and geometry are limited. Echocardiography and radial applanation tonometry were performed in American Indian participants in the 4th Strong Heart Study examination. Left ventricular mass was calculated using an anatomically validated formula and adjusted for height. Brachial blood pressure was measured according to a standardized protocol. Central pressures were derived using a generalized transfer function. Of 2585 participants in the analysis, 60% were women, 21% had diabetes and 33% were hypertensive; the mean age was 40 +/- 17 years. All blood pressure variables were significantly related to left ventricular absolute and relative wall thicknesses and left ventricular mass index (all P < 0.001), with considerable variation in correlation coefficients (r = 0.135-0.432). Central and brachial systolic pressures were uniformly more strongly related to left ventricular wall thicknesses, diastolic diameter and mass index than their respective pulse pressures (all P < 0.005 by z statistics). Left ventricular relative wall thickness and mass index were more strongly related to central than brachial pressures. Left ventricular hypertrophy is more strongly related to systolic pressure than to pulse pressure. Furthermore central pressures are more strongly related than brachial pressures to concentric left ventricular geometry. These data suggest that absolute (systolic) pressure is more important in stimulating left ventricular hypertrophy and remodeling, whereas pulsatile stress (pulse pressure) is more important in causing vascular hypertrophy and atherosclerosis.