Noninvasive measurements of digital arterial pressure and compliance in man

A noninvasive method was developed for measuring the digital arterial pressure and the compliance by using a fingertip pneumoplethysmograph and a pneumatic cuff. The compliance (C) of the digital artery was obtained from the peak amplitude of the volume pulse wave (deltaVp-a) under the effect of the cuff pressure (Po-a) by the equation: C = deltavp-a/(Ps - P-o-a) during the dicrotic phase defined in this study. The normal mean value was 11.37 +/- 0.59 X 10(-5) cm3/mmHg. On lowering of the cuff pressure, the moment when the deltaVp value becomes positive is regarded as the systolic pressure (Ps). At the end of the dicrotic phase, the mean amplitude (deltaVss') of the pulse wave during one pulse cycle (SS') and the ratios (deltaVss'/deltaVsd), where deltaVsd is the mean amplitude of the wave during the systolic period (SD), of successive waves after a particular wave fail to increase at the same rate when the cuff pressure decreased below the diastolic pressure. The cuff pressure corresponding to this particular wave is regarded as the diastolic pressure (Pd). The mean value of the mean digital pressure of normotensive subjects was 80.6 +/- 1.2 mmHg.     

Complex and frequency-dependent compliance of viscoelastic windkessel resolves contradictions in elastic windkessels

Based on simulated data, recent studies by others showed that fitting measured pulse pressure with the pulse pressure predicted by the two-element windkessel (W2-based pulse pressure method, PPM) yielded estimates of total arterial compliance closer to simulated values than other estimation methods that use either the W2 model or the three-element windkessel (W3). A later experimental application of the PPM, made by us, however, yielded relatively non pressure dependent estimates of compliance that were in contradiction with pressure dependent estimates obtained from the W2 model by fitting to the full aortic pressure wave (full pressure method, FPM). To explain these contradictory findings, in the present study we interpreted the aortic input impedance in terms of a viscoelastic windkessel (VW), where total peripheral resistance is connected in parallel to a complex and frequency dependent compliance, Cc(j omega), described by the Voigt cell. Using ascending aortic pressure and flow taken from four dogs, under a variety of haemodynamic states, we compared the estimates of compliance obtained from the W3 and VW models and from different W2-based estimation methods: the FPM (Cw2), the PPM (Cpp), the decay time method, DTM (Cdt), and the area method, AM (C(am)). The VW-based estimates of complex compliance resolved contradictions in the W2-based estimates. Static compliance of VW-model, Cvw = Cc(0), showed a good correlation (p = 0.999) with Cw2. Correlation of static compliance with C(am) and Cdt estimates was affected by distortions in diastolic pressure decay. The modulus of VW model's dynamic compliance, ?Cc(omega(h))?, at the heart pulsation omega(h), was well correlated (p = 0.975) with Cpp. Analysis of data fit and compliance estimates indicated that the VW model yields an improvement over the W3 in the physical interpretation of the overall arterial properties.     

Reduced systemic arterial compliance is associated with left ventricular hypertrophy and diastolic dysfunction in older people

OBJECTIVES: To study the relationship between left ventricular diastolic function and systemic arterial compliance in the older population. DESIGN: Cross-sectional survey. PARTICIPANTS: A total of 67 older volunteer participants (aged 67 +/- 5.4 years). MEASUREMENTS: Systemic arterial compliance (SAC) was measured using applanation tonometry and aortic velocimetry, and diastolic function was assessed using Doppler filling. Left ventricular mass was determined echocardiographically. RESULTS: There were significant univariate correlations between diastolic filling, as measured by E/A ratio, systemic arterial compliance (0.34, P < .01), and left ventricular mass (-0.41, P < .001). In multiple regression analysis, using diastolic filling as the dependent variable and heart rate, age, left ventricular mass corrected for body surface area, systolic and diastolic blood pressures, and arterial compliance as independent variables, the major determinants of diastolic filling were heart rate, left ventricular mass, and diastolic blood pressure. Arterial compliance did not make a significant independent contribution. CONCLUSION: This study demonstrates a positive relationship between diastolic filling and arterial compliance in the older population. However, in multiple regression analysis, heart rate, diastolic blood pressure, and left ventricular mass were the independent predictors of diastolic filling (E/A), whereas arterial compliance was not. These findings imply that therapeutic modulation of aortic stiffness would not, of itself, contribute to improvement in diastolic function.     

Pulse pressure response to the strain of the valsalva maneuver in humans with preserved systolic function

Arterial pulse pressure response during the strain phase of the Valsalva maneuver has been proposed as a clinical tool for the diagnosis of left heart failure, whereas responses of subjects with preserved systolic function have been poorly documented. We studied the relationship between the aortic pulse amplitude ratio (i.e., minimum/maximum pulse pressure) during the strain phase of the Valsalva maneuver and cardiac hemodynamics at baseline in 20 adults (42 +/- 14 yr) undergoing routine right and left heart catheterization. They were normal subjects (n = 5) and patients with various forms of cardiac diseases (n = 15), and all had a left ventricular ejection fraction >/=40%. High-fidelity pressures were recorded in the right atrium and the left ventricle at baseline and at the aortic root throughout the Valsalva maneuver. Aortic pulse amplitude ratio 1) did not correlate with baseline left ventricular end-diastolic pressure, cardiac index (thermodilution), or left ventricular ejection fraction (cineangiography) and 2) was positively related to total arterial compliance (area method) (r = 0.59) and to basal mean right atrial pressure (r = 0.57) (each P < 0.01). Aortic pulse pressure responses to the strain were not related to heart rate responses during the maneuver. In subjects with preserved systolic function, the aortic pulse amplitude ratio during the strain phase of the Valsalva maneuver relates to baseline total arterial compliance and right heart filling pressures but not to left ventricular function.     

Hematopoietic effects and clinical uses of granulocyte-macrophage colony-stimulating factor and PIXY321

We tested the influence of in vivo volume resuscitation on intrinsic contractile properties of left ventricular (LV) preparations of endotoxemic guinea pigs. Escherichia coli endotoxin (LPS)-injected animals were divided into nonresuscitated and resuscitated groups. Volume resuscitation improved cardiac output and stroke volume, increased arterial pH and body temperature, and decreased mortality. In isovolumetric LV preparations isolated 4 h after LPS injection, LV systolic pressures (in mmHg) preparations isolated 4 h after LPS injection, LV systolic pressures (in mmHg) of LPS with (42 +/- 3) and without (42 +/- 2) fluid resuscitation were consistently less than control values (70 +/- 3). LV end-diastolic pressure-volume (compliance) decreased in LPS-nonresuscitated hearts, while LV compliance of LPS-resuscitated hearts was similar to control. Thus, intravascular volume expansion selectively improved LV diastolic compliance of LPS hearts without affecting LV systolic function. These findings suggest that LV systolic and diastolic dysfunctions associated with endotoxemia and Gram-negative sepsis may involve separate pathogenic mechanisms.     

Iatrogenic myocardial edema: increased diastolic compliance and time course of resolution in vivo

BACKGROUND: Perfusion-induced edema reduces diastolic compliance in isolated hearts, but this effect and the time for edema to resolve after blood reperfusion have not been defined in large animals. METHODS: Edema was induced by coronary perfusion with Plegisol (750 mL, 289 mOsm/L) during a 1-minute aortic occlusion in 6 pigs. This was followed by whole blood reperfusion, inotropic support, and circulatory assistance until sinus rhythm and contractile function were restored. A control group (n = 6) was treated similarly, with 1 minute of electrically induced ventricular fibrillation and no coronary perfusion. Recorded data included electrocardiogram, left ventricular pressure and conductance, aortic flow, and two-dimensional echocardiography. Preload reduction by vena caval occlusion was used to define systolic and diastolic properties. Data were recorded at baseline and at 15-minute intervals for 90 minutes after reperfusion. RESULTS: In the edema group, average left ventricular mass (132 +/- 7 [standard error of the mean] versus 106 +/- 4 g) and ventricular stiffness constant (0.15 +/- 0.02 versus 0.05 +/- 0.01) increased after Plegisol versus baseline (p < 0.05), returning to normal after 45 minutes of reperfusion. In controls, mass (118 +/- 6 versus 116 +/- 4 g) and ventricular stiffness (0.06 +/- 0.01 versus 0.05 +/- 0.01) did not change significantly. There was no significant change in systolic function. Myocardial water content at the end of the study was not different for the two groups. CONCLUSIONS: Crystalloid-induced edema and diastolic stiffness resolve after 45 minutes in pigs. This suggests that edema caused solely by cardioplegia during cardiac operations should not cause significant perioperative ventricular dysfunction.     

Microalbuminuria in essential hypertensives in treatment for hypertension

Urinary albumin excretion (UAE) was evaluated in 26 subjects with essential hypertension and no diabetes (5 men, 21 women; 19 whites and 7 blacks), with creatinine clearance (Ccreat) > or = 75 ml/min/1.73 m2, in individualized treatment with various antihypertensive drugs. Clinical and laboratorial data were the following: mean age, 53 +/- 2 years (SEM); duration of hypertension, 14.9 +/- 2.2 years; body mass index (BMI), 26.8 +/- 0.7; arterial blood pressure, 142 +/- 4/89 +/- 3 mmHg; serum creatinine, 0.8 +/- 0.03 mg/dL; Ccreat, 99.3 +/- 3.8 ml/min/1.73 m2 and UAE, 9.3 +/- 1.5 micrograms/min. No significant difference was found when data were evaluated for gender and race. Microalbuminuria, defined as UAE > 13.9 micrograms/min, was found in 19% of the hypertensives (range: 16.3 to 28.1 micrograms/min). UAE correlated positively and significantly with systolic (r = 0.6309; P = 0.0005), diastolic (r = 0.4146; P = 0.0352), and mean blood pressure (r = 0.5000; P = 0.0093). The correlation between UAE and systolic pressure was stronger than with diastolic pressure. There was a positive and significant correlation between BMI and UAE values (r = 0.5623; P = 0.0028), and between BMI values with those of systolic (r = 0.5271; P = 0.0057) and mean blood pressure (r = 0.3930; P = 0.470). No correlation was found between UAE and age, duration of hypertension or Ccreat. Systolic, diastolic and mean blood pressures were significantly higher in microalbuminuric than in non microalbuminuric hypertensives. Obese hypertensives presented higher mean values of UAE, systolic, diastolic and mean pressures than non obese.     

Identification of the three-element windkessel model incorporating a pressure-dependent compliance

A new one-step computational procedure is presented for estimating the parameters of the nonlinear three-element windkessel model of the arterial system incorporating a pressure-dependent compliance. The data required are pulsatile aortic pressure and flow. The basic assumptions are a steady-state periodic regime and a purely elastic compliant element. By stating two conditions, zero mean flow and zero mean power in the compliant element, peripheral and characteristic resistances are determined through simple closed form formulas as functions of mean values of the square of aortic pressure, the square of aortic flow, and the product of aortic pressure with aortic flow. The pressure across as well as the flow through the compliant element can be then obtained so allowing the calculation of volume variation and compliance as functions of pressure. The feasibility of this method is studied by applying it to both simulated and experimental data relative to different circulatory conditions and comparing the results with those obtained by an iterative parameter optimization algorithm and with the actual values when available. The conclusion is that the proposed method appears to be effective in identifying the three-element windkessel even in the case of nonlinear compliance.     

Determinants of echocardiographic aortic root size. The Framingham Heart Study

BACKGROUND: Previous studies that evaluated the determinants of aortic root size have not yielded uniform results. We examined the relations of age, height, weight, body surface area, sex, and blood pressure to echocardiographically determined aortic root size in a population-based cohort. METHODS AND RESULTS: The study sample consisted of 1849 men and 2152 women in the Framingham Heart Study and Framingham Offspring Study who were free of clinically apparent cardiac disease when echocardiography was performed. Aortic root measurements were made by M-mode echocardiography using a leading-edge-to-leading-edge technique. The relations of age, height, weight, body surface area, and blood pressure variables (contemporary and those obtained 8 years before) to aortic root dimension were examined by use of sex-specific correlations and linear regression analyses. Age, height, weight, and sex emerged as the principal determinants of aortic root dimensions in adults (cumulative R2 = .2085 in men and .2327 in women). The additional effect of contemporary or previous blood pressure measures was small and revealed direct associations of aortic root dimension with mean arterial and diastolic blood pressures and inverse associations with pulse and systolic blood pressures. Previous blood pressure measurements did not contribute significantly to prediction of aortic root size once contemporary blood pressure variable entered the models. Results of regression analyses using a sex-pooled data set showed that on average, the aortic root measurement in women was 2.4 mm smaller than that of men of comparable age, height, and weight. Logistic regression was used to assess the likelihood of aortic root enlargement according to blood pressure levels. After adjustment for age, height, and weight, the odds ratio of aortic dilation for a 1-SD increment in systolic pressure was 0.70 (95% CI, 0.52 to 0.95) in men and 0.79 (95% CI, 0.60 to 1.04) in women; the odds ratio for a 1-SD increment in diastolic pressure was 1.22 (95% CI, 0.91 to 1.63) in men and 1.33 (95% CI, 1.01 to 1.73) in women. CONCLUSIONS: Age, height, weight, and sex emerged as the principal determinants of aortic root dimensions. The additional influences of blood pressure measurements were small; direct associations of aortic root dimensions with mean arterial and diastolic blood pressures and inverse associations with pulse and systolic blood pressures were observed. Additional prospective studies are needed to confirm these observations and to assess the impact of aortic root dimensions on the incidence of hypertension.     

Phasic changes in human right coronary blood flow before and after repair of aortic insufficiency

We have shown previously that acute aortic insufficiency in chronically instrumented dogs reverses the normally high ratio of diastolic to systolic coronary blood flow. Phasic blood flow in the dominant right coronary artery was measured directly with an electromagnetic flow meter during surgery in eight patients with severe aortic insufficiency before and after relacement of the aortic valve. Before the insufficiency was eliminated, right coronary flow average 116 +/- 37 ml./minute and the diastolic to systolic flow ratio was 0.88 +/- 17. Mean arterial blood pressure averaged 106 +/- 17 mm. Hg, heart rate 84 +/- 19 beats/minute, and mean diastolic pressure averaged 67 +/- 10 mm. Hg. After the aortic valve was replaced with an average heart rate of 90 +/- 15 and mean blood pressure of 103 +/- 13 mm. Hg, the average right coronary blood flow increased to 180 +/- 40 ml./minute with a D/S ratio of 2.18 +/- 0.8. In all cases the right coronary blood flow increased after the aortic insufficiency was eliminated surgically. Right coronary flow probably increased because of the improved diastolic perfusion pressure and the change from predominantly systolic to diastolic coronary flow.     

Relationship between end-systolic aortic pressure and mean aortic pressure in adults

The mean blood pressure is an accurate estimate of the end-systolic aortic pressure in children. The aim of this study was: 1) to assess the relationship between the pressure at the incisura (PIAo) and the mean (MAoP) and pulse (PAoP) pressures of the supravalvular aorta in adults: and 2) to evaluate MAoP as an estimate of PIAo in adults. High fidelity pressure recordings were carried out in the supravalvular aorta in 17 men. The pressures were measured at rest in 10 consecutive beats and. In 6 subjects, during a Valsalva manoeuvre. At rest, PIAo was greater than the MAoP (109 +/- 17.9 versus 99.6 +/- 12.5 mmHg, p = 0.0001). There was a positive linear correlation between PIAo and MAoP (r = 0.93) and between PIAo and PAoP (r' = 0.77) whereas no correlation was observed between PIAo and heart rate, cardiac output or estimated total systemic arterial compliance. A beat-to-beat relationship was observed between PIAo and MAOP: 1) at rest in 16 of the 17 subjects and 2) in each subject who performed a Valsalva manoeuvre. Both at rest and during Valsalva, MAOP underestimated PIAo significantly, especially when PIAo was increased (p = 0.0001). The authors conclude that end-systolic supraaortic pressure is mainly related to the mean component of aortic pressure. MAOP slightly but constantly underestimated PIAo and this should lead to caution in assimilating MAOP to end-systolic aortic pressure in adults, especially in subjects with very high aortic pressures.     

Ambulatory 24-h blood pressure monitoring in healthy, middle-aged smokeless tobacco users, smokers, and nontobacco users

Ambulatory 24-h blood pressure monitoring was conducted in 135 healthy, normotensive, middle-aged (35 to 60 years) men, with no antihypertensive medication, to study the influence of habitual smokeless tobacco use (n = 47) and smoking (n = 29) on diurnal blood pressure and heart rate. Comparisons were made with nonusers of tobacco (n = 59). Adjustments were made for differences in age, body mass index, waist-hip ratio, physical fitness, and alcohol intake. Daytime ambulatory heart rates were significantly (P < .05) elevated in both smokeless tobacco users and smokers compared with nonusers (69 +/- 14 and 74 +/- 13 beats/min, respectively, versus 63 +/- 12 beats/min). In subjects > or = 45 years old, ambulatory daytime diastolic blood pressures were significantly elevated, on average by 5 mm Hg, in both smokeless tobacco users and smokers (P < .001) compared with nonusers. Clinical measurements of heart rate and systolic blood pressure in smokers were significantly lower compared with the ambulatory mean values. Nighttime measurements showed only minor differences between the tobacco habit groups. The higher heart rates and blood pressures noted during the daytime in smokers and smokeless tobacco users were most likely due to the effects of nicotine. A strong positive relationship was found between cotinine (major nicotine metabolite) and blood pressure in smokeless tobacco users (systolic blood pressure, r = 0.48, P < .001; diastolic blood pressure, r = 0.41, P = .005), whereas an inverse relationship was found in smokers (systolic blood pressure, r = -0.12, P = .47; diastolic blood pressure, r = -0.03, P = .84), indicating additional and more complex influences on vascular tone in smokers than the influence of nicotine in smokeless tobacco users.     

Influence of one bout of intensive running on lymphocyte micronucleus frequencies in endurance-trained and untrained men

This clinical investigation was designed to determine the effect of changes in loading patterns on left ventricular (LV) relaxation when heart rate was maintained constant. Not only were changes noted in total load or time in which load is changed, but also the contour of the ascending aortic systolic pressure wave. Twenty patients were studied. LV and ascending aortic pressure were measured by a multisensor catheter under baseline conditions (C) and after an intravenous injection of 2.5 microg angiotensin (A) and sublingual administration of 0.3 mg nitroglycerin (N). A bipolar pacing catheter was placed in the right atrium to maintain a constant heart rate throughout the protocol. The augmentation index (AI), which characterizes the contour of the ascending aortic systolic pressure wave, was defined as the ratio of the height of the late systolic shoulder/peak to that of the early systolic shoulder/peak in the pulse. The rate of isovolumic LV pressure decline was calculated as a time constant (Tau). Ascending aortic systolic pressures (mmHg) were 127+/-29 (C), 158+/-20 (A) and 109+/-15 (N). AI were 1.61+/-1.14 (C), 2.08+/-1.11 (A) and 1.27+/-1.14 (N). Tau values (msec) were 49+/-4 (C), 54+/-4 (A) and 45+/-5 (N). Tau was prolonged proportionally with increasing AI (p<0.001, r=0.64). It was concluded that late systolic pressure augmentation in the ascending aorta is one important factor that influences the rate of isovolumic left ventricular pressure decline in humans.     

The importance of cardioplegic infusion pressure in neonatal myocardial protection

BACKGROUND: Cardioplegia infusion pressure is usually not directly monitored during neonatal heart operations. We hypothesize that the immature newborn heart may be damaged by even moderate elevation of cardioplegic infusion pressure, which in the absence of direct aortic monitoring may occur without the surgeon's knowledge. METHODS: Twenty neonatal piglets received cardiopulmonary bypass and the heart was protected for 70 minutes with multidose blood cardioplegia infused at an aortic root pressure of 30 to 50 mm Hg (low pressure) or 80 to 100 mm Hg (high pressure). Group 1 (n = 5, low pressure), and group 2 (n = 5, high pressure) were uninjured (nonhypoxic) hearts. Group 3 (n = 5, low pressure) and group 4 (n = 5, high pressure) first underwent 60 minutes of ventilator hypoxia (FiO2 8% to 10%) before initiating cardiopulmonary bypass to produce a clinically relevant hypoxic stress before cardiac arrest. Function was assessed using pressure volume loops (expressed as a percentage of control), and coronary vascular resistance was measured with each cardioplegic infusion. RESULTS: In nonhypoxic (uninjured) hearts (groups 1 and 2) cardioplegic infusion pressure did not significantly affect systolic function (end systolic elastance, 104% versus 96%), preload recruitable stroke work (102% versus 96%) diastolic compliance (152% versus 156%), or coronary vascular resistance but did raise myocardial water (78.9% versus 80.1%; p < 0.01). Conversely, if the cardioplegic solution was infused at even a slightly higher pressure in hypoxic hearts (group 4), there was deterioration of systolic function (end systolic elastance, 28% versus 106%) (p < 0.001) and preload recruitable stroke work (31% versus 103%; p < 0.001), rise in diastolic stiffness (274% versus 153%; p < 0.001), greater myocardial edema (80.5% versus 79.6%), and marked increase in coronary vascular resistance (p < 0.001) compared to hypoxic hearts given cardioplegia at low infusion pressures (group 3), which preserved function. CONCLUSIONS: Hypoxic neonatal hearts are very sensitive to cardioplegic infusion pressures, such that even moderate elevations cause significant damage resulting in myocardial depression and vascular dysfunction. This damage is avoided by using low infusion pressures. Because small differences in infusion pressure may be difficult to determine without a direct aortic measurement, we believe it is imperative that surgeons directly monitor cardioplegia infusion pressure, especially in cyanotic patients.     

Comparative accuracy of three automated techniques in the noninvasive estimation of central blood pressure in men

Automated devices have regularly replaced manual sphygmomanometry for the determination of blood pressure not only in homes and clinics, but also in emergency and critical care settings. Few studies exist that correctly assess the accuracy of these devices, and even fewer that specifically compare commercially available units that rely on different physiologic events for measurement. Six hundred pressure measurements were obtained from 120 subjects using 1 of 3 randomly selected blood pressure monitors. In addition, central arterial pressure measurements were obtained simultaneously and directly from the ascending aorta of each subject. Overall, these devices tended to overestimate diastolic (+2.5 mm Hg, p < 0.0001) and mean (+3.8 mm Hg, p < 0.0001) pressures, but not systolic (+0.7 mm Hg, p = NS) pressure. Compared with the other 2 devices, device I, relying on oscillometric detection, demonstrated a significantly smaller mean absolute error for diastolic pressure (4.9 +/- 3.0 vs 7.0 +/- 4.8 and 6.2 +/- 5.3 mm Hg, p < 0.0001) and mean pressure (4.0 +/- 3.2 vs 7.8 +/- 5.9 and 8.6 +/- 7.5 mm Hg, p < 0.0001), and a trend toward smaller error with systolic pressure (6.8 +/- 6.5 vs 7.3 +/- 6.8 and 8.0 +/-5.6 mm Hg, p = 0.19). Clinically significant (+/-10 mm Hg) errors were common with each device (24.8% overall), but serious (+/-20 mm Hg) errors were unusual (3.2%) and did not occur at all with device I during diastolic and mean pressure measurement. All of the devices tested could be expected to perform satisfactorily in most clinical settings provided that an average error of 4.0 to 8.6 mm Hg is tolerable. This level of accuracy typically extended throughout the range of pressures anticipated in most noncritical clinical situations. As implemented in the devices tested, noninvasive measurement by oscillometry with stepped deflation is more accurate than automated auscultation.     

Nonconservative amino acid substitution variants exist at polymorphic frequency in DNA repair genes in healthy humans

BACKGROUND: Dyslipidemia is a primary risk factor for the development of atherosclerosis. Aortic distensibility is an important determinant of left ventricular function and coronary blood flow whose possible alterations in patients with dyslipidemia have not been fully investigated. METHODS: To assess the effect of dyslipidemia on the elastic properties of the aorta, we studied 60 patients (mean age 37+/-11 years) with heterozygous familial hypercholesterolemia and no manifest arterial disease and compared them with 20 of their normolipidemic siblings (mean age 34+/-10 years). Two indexes of the aortic elastic properties were measured: aortic distensibility was calculated by use of the formula: 2 x (AoS-AoD)/PP x AoD, and aortic stiffness index was calculated by use of the formula: In (SBP/DBP)/(AoS-AoD)/AoD, where AoS and AoD are aortic root end-systolic and end-diastolic diameters, respectively, SBP and DBP are systolic and diastolic arterial pressure, respectively, and PP is pulse pressure. Internal aortic root diameters were measured at 3 cm above the aortic valve by use of two-dimensional guided M-mode transthoracic echocardiography, and arterial pressure was measured simultaneously at the brachial artery by sphygmomanometry. RESULTS: The mean aortic systolic and diastolic diameter index did not differ significantly between the two groups. In contrast, aortic distensibility was found to be significantly reduced in subjects with isolated familial hypercholesterolemia compared with that in the control group (2.15+/-1.72 cm2.dynes(-1).10(-6) vs 3.18+/-1.58 cm2.dynes(-1).10(-6), p < 0.02). In addition, the mean aortic stiffness index was double in patients with familial hypercholesterolemia compared with that in normolipidemic subjects. CONCLUSIONS: Severe dyslipidemia does not overtly influence aortic dimensions but leads to impairment of aortic elastic properties before the occurrence of clinical manifestations of atherosclerotic disease.     

Laparoscopically assisted abdominal aortic aneurysm repair: first 20 cases

PURPOSE: Laparoscopic surgery decreases postoperative pain, shortens hospital stay, and returns patients to full functional status more quickly than open surgery for a variety of surgical procedures. This study was undertaken to evaluate laparoscopic techniques for application to abdominal aortic aneurysm (AAA) repair. METHODS: Twenty patients who had AAAs that required a tube graft underwent laparoscopically assisted AAA repair. The procedure consisted of transperitoneal laparoscopic dissection of the aneurysm neck and iliac vessels. A standard endoaneurysmorrhaphy was then performed through a minilaparotomy using the port sites for the aortic and iliac clamps. Data included operative times, duration of nasogastric suction, intensive care unit days, and postoperative hospital days. Pulmonary artery catheters and transesophageal echocardiography were used in seven patients. For these patients data included heart rate, pulmonary artery systolic and diastolic pressures, mean arterial pressure, central venous pressure, pulmonary capillary wedge pressure, cardiac index, and end diastolic area. Data were obtained before induction, during and after insufflation, during aortic cross-clamp, and at the end of the procedure. RESULTS: Laparoscopically assisted AAA repair was completed in 18 of 20 patients. Laparoscopic and total operative times were 1.44 +/- 0.44 and 4.1 +/- 0.92 hours, respectively. Duration of nasogastric suction was 1.3 +/- 0.7 days. Intensive care unit stay was 2.2 +/- 0.9 days. The mean length of hospital stay was 5.8 days excluding three patients who underwent other procedures. There were two minor complications, one major complication (colectomy after colon ischemia), and no deaths. For the eight patients who had intraoperative transesophageal echocardiographic monitoring, no changes were noted in heart rate, pulmonary artery systolic pressure, pulmonary capillary wedge pressure, and cardiac index. Pulmonary artery diastolic pressure and central venous pressure were greatest during insufflation without changes in end-diastolic area. Volume status, as reflected by end-diastolic area and pulmonary capillary wedge pressure, did not change. CONCLUSIONS: Laparoscopically assisted AAA repair is technically challenging but feasible. Potential advantages may be early removal of nasogastric suction, shorter intensive care unit and hospital stays, and prompt return to full functional status. The hemodynamic data obtained from the pulmonary artery catheter and transesophageal echocardiogram during pneumoperitoneum suggest that transesophageal echocardiography may be sufficient for evaluation of volume status along with the added benefit of detection of regional wall motion abnormalities and aortic insufficiency. Further refinement in technique and instrumentation will make total laparoscopic AAA repair a reality.     

Evaluation of segmental elastic properties of the aorta in normotensive and medically treated hypertensive patients by intravascular ultrasound

DESIGN AND METHODS: Local elastic properties of the descending aorta at different levels were evaluated by means of intravascular ultrasound images and pressure measurements. For this purpose, 30 normotensive patients and 30 age-matched medically treated patients with essential hypertension, all undergoing diagnostic cardiac catheterization, were studied. RESULTS: Hypertension was well controlled in the essential hypertensives (137.1 +/- 6.79/74.5 +/- 2.65 mmHg). Systolic but not diastolic blood pressure in the hypertensive patients was significantly different from that of the normotensives (118.8 +/- 4.38/69.7 +/- 1.65 mmHg). The continuous loss of volume compliance with increasing distance from the heart was significantly higher in the hypertensives than in the normotensive patients [normotensives (1.45 +/- 0.19) x 10(-10) m5/N at the thoracic aorta, (0.08 +/- 0.05) x 10(-10) m5/N at the external iliac artery; hypertensives (0.81 +/- 0.09) x 10(-10) and (0.05 +/- 0.01) x 10(-10) m5/N at the corresponding sites]. Similarly, the hypertensives had an elevated elastic modulus proximal to the aortic bifurcation compared with the normotensives (244.47 +/- 44.06 versus 108.10 +/- 17.76 m/s, respectively). The decrease in buffering function of the vessel at this site is presumably caused by a turbulent flow pattern. Compared with the normotensives, the treated hypertensives had a significantly higher elastic modulus at each site where this was measured, whereas volume compliance and sectional compliance were lower. CONCLUSION: The differences in elastic modulus and compliance between hypertensive and normotensive patients seem disproportionate to the difference in systolic blood pressure (within the normal range in both the treated hypertensives and the normotensives). Therefore, normalization of high blood pressure by long-term antihypertensive treatment may not fully reverse changes, caused by arterial hypertension, in the viscoelastic properties of the arterial wall.     

Sodium sensitivity in young adults with high resting end-tidal CO2

BACKGROUND: Previous research with normotensive adults aged over 40 years ('older') found that sensitivity of blood pressure of subjects with high resting end-tidal partial pressures of CO2 to high sodium intake was greater than normal. OBJECTIVE: To test the hypothesis that the lesser sensitivity of blood pressure of young normotensive adults to high sodium intake is also a function of resting end-tidal partial pressure of CO2. DESIGN: Forty-eight Caucasian men and women (age 28.5 +/- 1.4 years) had a lower than normal dietary intake of sodium chloride for 4 days, and then ingested sodium chloride capsules for 7 days (an additional 190 mmol/day sodium chloride). Resting end-tidal partial pressure of CO2 and blood pressure, and 24 h ambulatory blood pressure, were measured before and after the high-sodium diet. Overnight urine samples were collected before and after the high-sodium diet to determine dietary compliance, and to assess changes in urinary excretion of endogenous digitalis-like factors (a ouabain-like factor, and a marinobufagenin-like factor) that covary with plasma volume. RESULTS: Subjects with high end-tidal partial pressures of CO2 had lower resting heart rates and lower urinary excretion of ouabain-like factor before sodium loading. Sodium loading decreased mean partial pressure of CO2 (by 0.8 +/- 0.2 mmHg) and increased only ambulatory systolic blood pressure (by 2.1 +/- 0.8 mmHg) for the whole group. However, the changes in resting systolic (r = 0.32, P < 0.025) and diastolic (r = 0.36, P < 0.01) blood pressures and in 24 h systolic (r = 0.28, P < 0.05) blood pressure after sodium loading were all positive functions of individual resting end-tidal partial pressures of CO2. Sodium loading increased urinary excretion of marinobufagenin-like factor (by 1.78 +/- 0.88 nmol) and the magnitude of the individual increase was a function of end-tidal partial pressure of CO2. CONCLUSIONS: The results indicate that a high resting partial pressure of CO2 augments the effects of high sodium intake on plasma volume, levels of endogenous digitalis-like factors, and blood pressure in young normotensive humans.     

The impact of ibuprofen on the efficacy of antihypertensive treatment with hydrochlorothiazide in elderly persons

BACKGROUND: Nonsteroidal antiinflammatory drugs (NSAIDs) may alter blood pressure through their inhibitory effects on prostaglandin biosynthesis. Such potential hypertensive effects of NSAIDs have not been adequately examined in the elderly, who are the largest group of NSAID users. METHODS: We performed a randomized, double-blind, two-period crossover trial of ibuprofen (1800 mg per day) vs placebo treatment in patients older than 60 years of age with hypertension controlled with hydrochlorothiazide. While continuing their usual thiazide dosage, subjects were randomized to a 4-week treatment period (ibuprofen or placebo) followed by a 2-week placebo wash-out period and a second 4-week treatment period with the alternative therapy. Supine and standing systolic and diastolic blood pressures were measured weekly. RESULTS: Of 25 randomized subjects, 22 completed the study protocol (mean age = 73 +/- 6.7 years). Supine systolic blood pressure and standing systolic blood pressure were increased significantly with ibuprofen treatment, compared with placebo. Mean supine systolic blood pressures were 143.8 +/- 21.0 and 139.6 +/- 15.9 mmHg on ibuprofen and placebo, respectively (p = .004). Mean standing systolic blood pressures were 148.1 +/- 19.9 and 143.4 +/- 17.9 mmHg on ibuprofen and placebo, respectively (p = .002). CONCLUSION: We conclude that 1800 mg per day of ibuprofen does induce a significant increase in systolic blood pressure in older hypertensive patients treated with hydrochlorothiazide. NSAID therapy may negatively impact the control of hypertension in elderly patients.