Biomedical subjects

F C Yin

Publications and source records attributed to F C Yin.

At least 37 records · Page 2Linked to original sources

PubMed1996

Validation of carotid artery tonometry as a means of estimating augmentation index of ascending aortic pressure.

Our objective was to validate a carotid artery tonometry-derived augmentation index as a means to estimate augmentation index (AI) of ascending aortic pressure under various physiological conditions. A total of 66 patients (50 men, 16 women; mean age, 55 years; range, 21 to 78 years; 44 in Taiwan and 22 in the United States) undergoing diagnostic catheterization were studied. Arterial pressure contours were obtained simultaneously from the right common carotid artery by applanation tonometry with an external micromanometer-tipped probe and from the ascending aorta by a micromanometer-tipped catheter at baseline (n = 62), after handgrip (n = 36), or after sublingual nitroglycerin administration (n = 17). The AI (expressed as percentage values) was calculated as the ratio of amplitude of the pressure wave above its systolic shoulder to the total pulse pressure. The carotid AI was consistently lower than the aortic AI, but the two were highly correlated at baseline and after both handgrip and nitroglycerin. Mean +/- SD and correlation coefficients were baseline (14 +/- 16, 28(+) +/- 17, .77), handgrip (18 +/- 19, 32(+) +/- 15, .86), and nitroglycerin (7 +/- 12, 18(+) +/- 13, .52). In addition, after adjusting for age, sex, height, blood pressure, heart rate, and study site, the changes of both AIs from baseline values with handgrip or nitroglycerin were highly associated such that the aortic AI could be approximated from the carotid AI with appropriate regression equations. The high correlations and predictable changes after interventions between the central AI and those estimated from noninvasive carotid tonometry suggest that this technique may have wide applicability for many cardiovascular studies.

Adolescent↗

PubMed1995

Relation between diurnal variation of blood pressure and left ventricular mass in a Chinese population.

In western populations, patients with hypertension who have a nocturnal decrease in blood pressure (BP) may have less left ventricular (LV) hypertrophy and cardiovascular morbidity than those without a diurnal variation in BP. To further examine this association between nocturnal BP reduction and LV mass index, we studied 720 normotensives (< 140/90 mm Hg), 380 borderline hypertensives (140 to 159/90 to 94 mm Hg), and 582 hypertensives (> or = 160/95 mm Hg) from Taiwan and Quemoy island by using 24-hour ambulatory BP monitoring and 2-dimensional echocardiography to obtain LV mass index during a community-based cardiovascular survey. After controlling for age, sex, height, weight, daytime BP, and daytime heart rate, the nocturnal reduction of systolic BP was found to associate weakly with LV mass index, for the whole population (partial correlation coefficient = -0.06, p < 0.05), as well as for the patients with hypertension (partial correlation coefficient = -0.09, p < 0.05), but these associations were eliminated when 24-hour BP and heart rate were accounted for. The average and percent nocturnal decrease of systolic BP (mean +/- SD; mm Hg, [%]) of 3.2 +/- 5.9 (2.7 +/- 4.8%); 3.3 +/- 7.3 (2.4 +/- 5.4%); and 4.6 +/- 9.0 (3.0 +/- 6.1%) in normotensives, borderline hypertensives, and hypertensives, respectively, was smaller than that found in previous studies. Hence, in this large Chinese population, a small nocturnal BP drop was found and it was only weakly associated with LV mass index. These results emphasize the general need for ambulatory BP reference values based on internal controls.

Adult↗

PubMed1995

Validation of 19F-magnetic resonance determination of myocardial blood volume.

The use of perfluorochemical (PFC) emulsions to study the myocardial circulation by means of 19F NMR requires that the biodistribution of the PFC be known. The authors tested the hypothesis that PFC particles remain within the myocardial vascular space by infusing rats with both a PFC emulsion and 125I-albumin. Measurement of myocardial vascular volume by 19F NMR and by standard radiotracer analysis of the same tissue yielded concordant values by the two methods, establishing the PFC emulsion as an intravascular agent in this tissue. Perfluorochemical emulsions should be useful for the noninvasive study of myocardial vascular physiology by magnetic resonance.

Animals↗

PubMed1995

Biaxial mechanical behavior of excised porcine mitral valve leaflets.

Anterior and posterior leaflets from excised porcine mitral valves were mechanically tested under cyclic equibiaxial and strip biaxial stretch protocols at a strain rate of 4-12%/s after preconditioning. Cauchy stress and Lagrangian strain were calculated for both membrane and three-dimensional cases. The leaflets exhibited nonlinearly elastic, anisotropic behavior. Both anterior and posterior leaflets were less extensible in the circumferential than in the radial direction under equibiaxial stretch, with stress ratios of 5.7 and 4.3, respectively. The posterior leaflets exhibited greater extensibility in both directions and lower circumferential posttransitional moduli (ranges 690-820 vs. 2,500-3,200 N/m for anterior). This larger posterior extensibility may be due to the greater number of chordal attachments, which provide additional mechanical stability to this structure. Coupling of radial and circumferential mechanical behavior was evidenced by the response to different stretch protocols, indicating a complex microstructural coupling between individual collagen fibers or bundles. These are the first biaxial data for mitral valves and are a foundation for the development of a more detailed quantitative material description.

Animals↗

PubMed1995

Different effects of fosinopril and atenolol on wave reflections in hypertensive patients.

We conducted this study to compare the effects of fosinopril versus atenolol on peripheral blood pressure, central arterial wave reflection, and left ventricular mass in a group of patients with essential hypertension. We conducted a double-blind, randomized trial of fosinopril and atenolol in 79 hypertensive patients (52 men, 27 women; mean age, 45.8 +/- 8.5 years; range, 30 to 68 years). Carotid pressure waveforms were recorded noninvasively by applanation tonometry with a Millar micromanometer-tipped probe. The extent of wave reflection was estimated by the augmentation index defined as the ratio of the amplitude of pressure wave above its systolic shoulder to the pulse pressure. The augmentation index, left ventricular mass index by two-dimensional echocardiography, and 24-hour ambulatory blood pressures were determined before and after 8 weeks of daily treatment with fosinopril (10 to 20 mg) or atenolol (50 to 100 mg) with or without diuretics and compared with those values in 79 normotensive control subjects. After 8 weeks of treatment, both drugs lowered 24-hour ambulatory peripheral systolic and diastolic pressures into the normal range to a similar extent (fosinopril, -18/-13 mm Hg; atenolol, -23/-17 mm Hg, both P = NS). On the other hand, whereas the elevated augmentation index in hypertensive patients compared with normotensive subjects (16 +/- 11% versus 10 +/- 8%) was completely normalized by fosinopril (-9.3 +/- 9.8%, P < or = .002), it was lowered by atenolol (-4.8 +/- 8.9%, P < .002) but to a significantly smaller extent (fosinopril versus atenolol effect, P = .04).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Arterial hemodynamics in human hypertension. Effects of the calcium channel antagonist nifedipine.

Previous studies have shown some distinct hemodynamic alterations in essential hypertension, including increased resistance, wave reflections, and pulse wave velocity and decreased arterial compliance. These abnormalities are completely normalized by nonspecific smooth muscle dilation with nitroprusside but not by combined alpha- and beta-adrenergic blockade or angiotensin-converting enzyme inhibition, suggesting an enhanced smooth muscle tone that cannot be attributed solely to the sympathetic nervous or renin-angiotensin systems. Since hypertensive patients have an enhanced calcium influx-dependent vasoconstriction, we performed the present study to examine the extent to which the dihydropyridine calcium channel antagonist nifedipine could normalize the hemodynamic abnormalities in essential hypertension. An essential hypertensive patient group was compared with a normotensive group similar in age, body size, and proportion of men and women. During diagnostic cardiac catheterization, ascending aortic micromanometer pressures and electromagnetic flows were measured at baseline and after sufficient sublingual nifedipine (mean, 24 mg) to normalize blood pressure. From the pressures and flows, aortic input impedance, wave reflection magnitude, and compliance were computed. In the hypertensive group, the hemodynamic alterations were indistinguishable from those summarized above. Nifedipine produced sufficient vasodilation to completely normalize all of these hemodynamic alterations, including wave reflections. From these results, together with those reported in our previous studies, it is clear that the various classes of antihypertensive agents affect hemodynamics differently. All are capable of decreasing blood pressure to normotensive levels, but only nitroprusside and nifedipine can also completely normalize all the other pulsatile hemodynamic alterations. Thus, these hemodynamic effects of the different classes of antihypertensive agents should be considered in choosing a therapeutic modality.

Adult↗

PubMed1995

Short- and long-term effects of antihypertensive drugs on arterial reflections, compliance, and impedance.

This article reviews our work on the effects of different classes of antihypertensive agents on the hemodynamic alterations in essential human hypertension. Short-term studies were done during cardiac catheterization in young normotensive subjects (mean age, 33 years; range, 19 to 40) and several different age-matched (range, 25 to 53 years) groups of patients with essential hypertension. Aortic impedance, resistance, wave reflections, and compliance were calculated from high-fidelity recordings of ascending aortic pressure and flow signals during baseline and after nitroprusside, propranolol followed by phentolamine, phentolamine, captopril, and nifedipine, respectively, at doses sufficient to normalize blood pressure in each hypertensive group. Propranolol exacerbated all the hemodynamic parameters; these effects were only partially overcome by phentolamine. Among the other agents only phentolamine did not completely normalize compliance, and only captopril did not completely normalize wave reflections. The long-term study was a randomized, double-blind comparison of fosinopril and atenolol in 79 normotensive subjects and 79 essential hypertensive patients. Baseline 24-hour ambulatory blood pressures and carotid artery tonometry to index wave reflections were performed in all subjects and in hypertensive patients after 8 weeks of therapy. Both fosinopril and atenolol normalized blood pressure and lowered the elevated augmentation index, but fosinopril had a significantly larger effect than atenolol. Both short- and long-term beta-blockade did not have as beneficial an effect as the other agents. Thus, the differing hemodynamic effects of the various classes of antihypertensive agents might be a consideration in the choice of therapy.

Adult↗

PubMed1995

Short-term and long-term effects of benazepril in mild to moderate hypertensives.

BACKGROUND: Benazepril hydrochloride is a non-sulfhydryl-containing, angiotensin-converting enzyme (ACE) inhibitor. The short-term and long-term antihypertensive effects of benazepril remain to be established in Chinese. METHODS: Hypertensive subjects with diastolic blood pressure 95-110 mmHg, after two week placebo run-in first, entered a four-week double-blind phase with treatment of benazepril 10 mg once daily or captopril 25 mg three times daily, then received one-year open treatment of benazepril 10 mg daily with or without diuretics. Ambulatory blood pressure monitoring was performed at the end of placebo run-in, after four-week double-blind phase, and after one-year open treatment. RESULTS: Of the 75 subjects (41 male, 34 female, mean age 57 +/- 12 years, range 34-88 years) who completed the double-blind phase, 42 subjects finished the one-year extension phase. Reasons for withdrawal from the study included irritable cough (16, 21%), hypotension (1, 1%), and poor compliance (16, 21%). During the short-term double-blind phase, benazepril reduced clinic and mean 24-h ambulatory blood pressure by -21/-10 mmHg and by -17/-10 mmHg respectively, and captopril by -21/-13 mmHg and by -17/-10 mmHg respectively. After one-year open treatment by benazepril for the 42 subjects, the one-year average clinic blood pressure was 134/88 mmHg (155/104 mmHg at entry and 135/93 mmHg at the end of the double-blind phase), and the mean 24-h ambulatory blood pressure was 137/87 mmHg (149/95 mmHg at entry and 132/84 mmHg at the end of the double-blind phase). CONCLUSIONS: The antihypertensive effect of benazepril 10 mg daily with or without diuretics is not significantly different from that of captopril 75 mg daily in the short-term and can reasonably be maintained for one year.

Adult↗

PubMed1994

Regional mechanical properties of passive myocardium.

There is considerable interest in calculating regional stresses in the heart. This, in turn, requires complete information on regional material properties which, surprisingly, is not available. The specific aim of this work, therefore, was to determine if transmural differences exist in the mechanical behavior of passive myocardium in the equatorial region of the heart. Thus, we performed in vitro biaxial experiments on 28 thin, rectangular slabs of noncontracting myocardium excised from four regions within canine hearts: the middle portion of the interventricular septum (n = 8), and the inner (n = 5), middle (n = 9) and outer (n = 6) layers of the lateral left ventricular (LV) free wall. There were three major findings. First, an existing three-dimensional constitutive relation described the nonlinear and anisotropic behavior exhibited in the four regions equally well. Second, the anisotropy was similar in each region. Third, there were, however, regional differences in the strain-energy stored by specimens during identical finite deformations. In particular, specimens from inner and outer portions of the LV free wall tended to be stiffer than those from the middle of the LV free wall and septum. These findings, together with previous results on excised epicardium, suggest that the mechanical properties of the heart are qualitatively similar from region to region, but quantitatively different.

Animals↗

PubMed1994

Accounting for the Gregg effect in tetanised coronary arterial pressure-flow relationships.

OBJECTIVE: Myocardial contraction shifts the diastolic coronary pressure-flow relationship to lower flows at any given pressure, the amount of shift being determined primarily by the contractile level. A portion of this shift may be attributable to the Gregg effect. The purpose of this study was to quantify the influence of the Gregg effect and thereby demonstrate the pure effect of activation at a constant contractile level on the pressure-flow relationships. METHODS: It was first shown in beating canine interventricular septa that transverse stiffness induced by small high frequency indentations transverse to the plane of the tissue was an index of contractility. At constant perfusion pressure and preload, there was an inverse relationship between peak transverse stiffness and contractile level (induced by graded doses of 2,3-butanedione monoxime) for both isotonic and auxotonic contractions. A Gregg effect was next verified by showing a linear dependence between transverse stiffness and perfusion pressure during ryanodine induced tetanizations. Finally, the relationship between changes in flow and transverse stiffness was determined from diastole to tetany at two contractile levels. These relationships suffice to quantify the Gregg effect. RESULTS: Correcting for the Gregg effect from the transverse stiffness measurements obtained concomitantly with previously reported pressure-flow data in six specimens showed the following: using a linear fit to the pressure-flow data, the mean slope of the diastolic pressure-flow relationships decreased from 0.88 to 0.81 and 0.74 ml.min-1 x mmHg-1 during tetanisation at normal and reduced contractile levels, respectively. Correcting for the Gregg effect decreased the tetanised slopes to intermediate values of 0.85 and 0.79 ml.min-1 x mmHg-1, respectively. CONCLUSIONS: A small but clearly discernible portion of the shift in tetanised pressure-flow relationships is attributable to the Gregg effect. Similar conclusions pertained when quadratic regressions were fitted to the pressure-flow data.

Animals↗

PubMed1993

Estimation of myocardial mechanical properties with dynamic transverse stiffness.

There are currently no validated methods for accurately estimating regional ventricular mechanical properties. We recently developed a dynamic indentation system that can determine dynamic transverse stiffness (the slope of the relation between the indentation stress and indentation strain during high frequency indentations) in as little as 10 msec. The apparatus consists of an indentation probe coupled to a linear-motor and a computerized control system. This indentation system was tested on beating, canine ventricular septa that were mounted in a biaxial system that could apply strains in the plane of the septum and measure the resulting in-plane stresses. The probe indented the septa with peak displacements of 0.1-0.5 mm at frequencies of 20 and 50 Hz. The transverse stiffness was shown to be related to the in-plane stress and stiffness in the isolated septa. Dynamic transverse stiffness was then used to study the effects of myocardial perfusion on passive tissue stiffness and on contractility. In addition, the transverse stiffness was studied in intact canine hearts during diastole, where it was related to the chamber stiffness. Thus, dynamic transverse stiffness appears to allow estimation of myocardial mechanical properties.

Animals↗

PubMed1993

Direct evidence that coronary perfusion affects diastolic myocardial mechanical properties in canine heart.

OBJECTIVE: The effect of coronary perfusion on left ventricular chamber distensibility is only indirect evidence that perfusion alters the mechanical properties of the myocardium. The aim of this study was to demonstrate explicitly the effects of coronary perfusion on these mechanical properties. METHODS: The effects of different levels of coronary perfusion were studied both on in-plane stress-strain relations and on transverse stiffness in an isolated, perfused canine interventricular septal preparation. Additionally, to determine the vascular compartment responsible for the mechanical effects of perfusion on tissue properties, we examined the in-plane stress-strain responses and transverse stiffness after embolisation of the vasculature with 15 microns microspheres. RESULTS: The data show a clear dependence of tissue stress-strain properties on perfusion. The in-plane stress-strain relations were shifted to the left and transverse stiffness increased linearly as septal artery perfusion pressure increased. The dependence of both the in-plane stress-strain relations and transverse stiffness on perfusion was significantly decreased following embolisation. CONCLUSIONS: Myocardial tissue stiffness is directly related to perfusion. The linear relationship between transverse stiffness and perfusion makes it easier to assess the effects of perfusion on tissue stiffness than with in-plane stress-strain relations. Perfusion of capillaries and/or venules is largely responsible for these alterations in myocardial stiffness.

Animals↗

PubMed1993

Regional finite deformations of in situ canine pericardium.

The purpose of this study was to determine in situ regional pericardial strains over a wide range of conditions. In five open-chest, anesthetized dogs we examined deformations from biplane cineradiographs of three sets of four 1-mm diameter steel beads glued to basal, midanterior, and apical regions of the pericardium during extremes of pericardial sac sizes (inferior vena caval occlusion, baseline, and tamponade). Finite deformation theory was used to determine the planar components of the Green's strains referenced to the completely unloaded, excised pericardium at the end of each experiment. From the Green's strains the principal components, EI and EII, and the principal direction of strain were determined. The first strain invariant, I1 = EI + EII, in the basal, anterior, and apical regions during caval occlusion (1.27, 0.73, and 0.67) did not differ significantly from those in the baseline state (1.43, 0.86, and 0.76) but increased significantly (P < 0.01) during tamponade to 1.54, 1.30, and 1.08, respectively. Using end systole during inferior vena cava occlusion as a reference, the directions of principal strain in each region during each condition were aligned parallel to the spine pointing toward the tail except at the base during tamponade when there was a 70 degree rotation toward the left limb. The in situ dog pericardium is considerably strained by the underlying heart even during inferior vena cava occlusion, suggesting that a completely unloaded state cannot be achieved in situ. The regional differences in the direction but not the value of principal strain suggest that there are either regional variations in loading or material properties.

Animals↗

PubMed1993

Biaxial mechanical properties of passive and tetanized canine diaphragm.

The architecture, vascular supply, and ease of tetanization make the diaphragm an ideal structure in which to assess multidimensional mechanical properties of active and passive striated muscle. We developed an isolated, perfused canine diaphragm preparation suitable for the assessment of biaxial stress-strain relations in both the resting state and during tetanization. Each of 33 specimens had a wide, flat region (approximately 3 x 3 cm) wherein there was a single predominant fiber direction. Simultaneous, equal stretchings were imposed in the fiber and perpendicular cross-fiber directions over the same strain ranges in both the passive state and during tetanic contraction. Highly nonlinear behavior was seen in the passive state with a limit of extensibility in both directions. The specimens were also markedly anisotropic, with the cross-fiber direction being stiffer than the fiber direction (slopes of the regression line for the stresses in each direction averaged 3.97). Moreover, 31 of the 33 specimens were stiffer in the cross-fiber direction, one was isotropic, and one was stiffer in the fiber direction. During tetanization, the extent and distribution of anisotropy were significantly altered (regression slope averaged 1.08, and 18 specimens were now either isotropic or stiffer in the fiber direction). Disrupting the membranes covering each surface increased extensibility and decreased the anisotropy, thereby suggesting that these membranes bear most of the passive load and contribute greatly to the cross-fiber stiffness and anisotropy of the intact diaphragm. Both before and after disruption of the surface membranes, there was still a consistent increase in cross-fiber stress during tetanization, implying active force generation perpendicular to the fiber direction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Rapid measurements of diastolic intramyocardial vascular volume.

Rapid measurements of coronary vascular volume are necessary for a complete understanding of phasic coronary flow. Because no standard method is capable of making these measurements, we developed a method that uses digital subtraction angiography to image an intravascular contrast agent. The method is capable of measuring vascular volume in 33 ms and can be repeated three times per second. The method was first validated in phantoms. We then used this method to measure coronary vascular volume in the isolated, perfluorochemical-perfused, interventricular canine septum. The speed of the measurements allowed us, for the first time, to directly measure transients in vascular volume following sudden changes in perfusion pressure. At the steady-state and maximal vasodilation, coronary vascular volume varied from 7.5 +/- 1.2 (SE) ml/100 g at a perfusion pressure of 20 mmHg to 12.1 +/- 1.9 ml/100 g at 90 mmHg, which is similar to other reports. After a sudden change of 40 mmHg in perfusion pressure, vascular volume changed with a time constant of 3.2 +/- 0.3 (SE) s. Increasing ventricular wall stretch had no effect on either the steady-state volumes (P = 0.25) or the time constant for volume changes (P = 0.17). The fact that the time constant is longer than the cardiac cycle, yet much shorter than the time necessary to measure vascular volume using other methods, highlights the need for rapid measurements of vascular volume.

Absorptiometry, Photon↗

PubMed1993

Effect of tetanic myocardial contraction on coronary pressure-flow relationships.

Cardiac contraction causes a decrease in coronary flow. Despite many studies, it is still not clear what mechanism or mechanisms are responsible for this flow decrease. The phasic nature of myocardial contraction and the complexities intrinsic to intact heart preparations make it difficult to elucidate the mechanisms. We therefore studied coronary pressure-flow relationships during steady-state (tetanic) contractions in the maximally vasodilated isolated canine interventricular septum to see whether waterfall-type behavior is present. Using ryanodine and electrical stimulation allowed the production of reproducible and reversible tetani. This preparation minimizes the difficulties associated with transmural variations and also the effects of intramyocardial capacitance. Two separate protocols were performed to delineate the pressure-flow relationships in the passive and tetanized states. The first compared diastolic and tetanized pressure-flow relationships. In the second protocol, 2,3-butanedione monoxime was added to obtain an intermediate contractile level, thus allowing the comparison of two contractile states. Both the diastolic and tetanized pressure-flow relationships were curvilinear in the low-pressure range. Linear and nonlinear fits to the data showed that the primary effect of contraction was a shift of the pressure-flow relationships to higher pressures at a given flow. This effect was graded by the level of contractility and was independent of developed stress. Although other mechanisms may also be operative, these results support the presence of waterfall behavior in the coronary vascular bed.

Animals↗

PubMed1993

Effects of age and aerobic capacity on arterial stiffness in healthy adults.

BACKGROUND: It has been well established that arterial stiffness, manifest as an increase in arterial pulse wave velocity or late systolic amplification of the carotid artery pressure pulse, increases with age. However, the populations studied in prior investigations were not rigorously screened to exclude clinical hypertension, occult coronary disease, or diabetes. Furthermore, it is unknown whether exercise capacity or chronic physical endurance training affects the age-associated increase in arterial stiffness. METHODS AND RESULTS: Carotid arterial pressure pulse augmentation index (AGI), using applanation tonometry, and aortic pulse wave velocity (APWV) were measured in 146 male and female volunteers 21 to 96 years old from the Baltimore Longitudinal Study of Aging, who were rigorously screened to exclude clinical and occult cardiovascular disease. Aerobic capacity was determined in all individuals by measurement of maximal oxygen consumption (VO2max) during treadmill exercise. In this healthy, largely sedentary cohort, the arterial stiffness indexes AGI and APWV increased approximately fivefold and twofold, respectively, across the age span in both men and women, despite only a 14% increase in systolic blood pressure (SBP). These age-associated increases in AGI and APWV were of a similar magnitude to those in prior studies of less rigorously screened populations. Both AGI and APWV varied inversely with VO2max, and this relationship, at least for AGI, was independent of age. In endurance trained male athletes, 54 to 75 years old (VO2max = 44 +/- 3 mL.kg-1.min-1), the arterial stiffness indexes were significantly reduced relative to their sedentary age peers (AGI, 36% lower; APWV, 26% lower) despite similar blood pressures. CONCLUSIONS: Even in normotensive, rigorously screened volunteers in whom SBP increased an average of only 14% between ages 20 and 90 years, major age-associated increases of arterial stiffness occur. Higher physical conditioning status, indexed by VO2max, was associated with reduced arterial stiffness, both within this predominantly sedentary population and in endurance trained older men relative to their less active age peers. These findings suggest that interventions to improve aerobic capacity may mitigate the stiffening of the arterial tree that accompanies normative aging.

Aging↗

PubMed1993

Validation of a method for noninvasive measurement of central arterial pressure.

The goal of this study was to validate a newly improved noninvasive method for calibrated measurement of the ascending portion of the central arterial pressure wave in humans. Noninvasive pressure waveforms were generated by measuring the time delay between the R wave of the electrocardiogram and onset of brachial artery flow (by Doppler) during computer-controlled upper arm cuff deflation. This delay shortens with falling cuff pressure (becoming near constant at and below diastolic pressure), so that a plot of pressure versus time delay yields the ascending portion of the arterial waveform. These waveforms were compared with simultaneous invasive ascending aortic pressures in 57 adult patients (31 by fluid manometer [group A] and 26 by catheter-tipped micromanometer [group B]) during routine cardiac catheterization. Patient age ranged from 26 to 77 years. Eighty percent of group A patients and 40% of group B had coronary artery disease. Noninvasive systolic and diastolic pressures were very similar to invasive values in both groups (Pni = 0.98 x Pi, r = 0.99, p < 0.0001). Instantaneous pressure differences between waveforms were also similar in both groups, averaging between 4.5 and 5.5 mm Hg. Micromanometer and noninvasive pressure data were also obtained before and after intravenous nitroglycerin (n = 5) and isometric handgrip (n = 8) and demonstrated good agreement. A potential application of these pressures is for estimating maximal ventricular power to assess systolic function. This was tested using invasive pressure-volume data from four patients under a variety of conditions (exercise, pacing, etc.).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗