Catheter-tip Manometer Research Articles

High-frequency oscillatory ventilation versus conventional ventilation: hemodynamic effects on lung and heart.

High‐frequency oscillatory ventilation (HFOV) may improve gas exchange in patients who are inadequately ventilated by conventional mechanical ventilation (CV); however, the hemodynamic consequences of switching to HFOV remain unclear. We compared the effects of CV and HFOV on pulmonary vascular conductance and left ventricular (LV) preload and performance at different airway and filling pressures. In anesthetized dogs, we measured LV dimensions, aortic and pulmonary artery (PA) flow, and mean airway (AW) and pericardial pressures. Catheter‐tip pressure manometers measured aortic, LV, left atrial, and PA pressures. The pericardium and chest were closed. At LV end‐diastolic pressure (PLVED) = 5 mmHg and 12 mmHg, PEEP was varied (6 cm H2O, 12 cm H2O, and 18 cm H2O) during CV. Then, at airway pressures equal to those during CV, HFOV was applied at 4 Hz, 10 Hz, and 15 Hz. Increased AW decreased pulmonary vascular conductance. As cardiac output increased, conductance increased. At PLVED = 12 mmHg, conductance was greatest during HFOV at 4 Hz. LV preload (i.e., ALV, our index of end‐diastolic volume) was similar during HFOV and CV for all conditions. At PLVED = 12 mmHg, SWLV was similar during CV and HFOV, but, at PLVED = 5 mmHg and AW 10 cm H2O, SWLV was lower during HFOV than CV. Compared to pulmonary vascular conductance at higher frequencies, at PLVED = 12 mmHg, conductance was greater at HFOV of 4 Hz. Effects of CV and HFOV on LV preload and performance were similar except for decreased SWLV at PLVED = 5 mmHg. These observations suggest the need for further studies to assess their potential clinical relevance.

Biventricular Pacing Improves Left Ventricular Isovolumetric Relaxation and Compliance More Excellently Than LV Pacing Alone

Introduction: There are few reports that evaluated the effectiveness of cardiac resynchronization therapy (CRT) for left ventricular (LV) diastolic function by an invasive method. We aimed to clarify the hemodynamic improvement brought by CRT, especially throughout diastole. Methods: Twenty-seven patients who underwent CRT were enrolled. We measured 4 LV hemodynamic parameters; +dP/dtmax, −dP/dtmax, tau and LV end-diastolic pressure (LVEDP), using a manometer-tipped catheter. During the measurements, each patient was paced at the same heart rate in 4 different pacing modes; AAI (atrial pacing), DDDRV (right ventricular pacing), DDDLV (LV pacing), DDDBV (biventricular pacing). We compared the parameters in DDDBV with those in the other pacing modes, using repeated measures ANOVA. Results: In DDDBV, both +dP/dtmax and −dP/dtmax were significantly higher, and both tau and LVEDP were prominently lower than those in AAI. The systolic improvement (+dP/dtmax) in DDDLV (1132±275 mmHg/s) was similar to that in DDDBV (1142±270 mmHg/s). Surprisingly, the improvement of LV relaxation (−dP/dtmax, tau) and LV compliance (LVEDP) in DDDBV was superior to those in DDDLV (1117±290 mmHg/s vs 1036±282 mmHg/s; p=0.0189, 51.4±12.8 ms vs 57.0±16.3 ms; p=0.0014, 11.5±8.4 mmHg vs 13.7±8.9 mmHg; p=0.0027, respectively). Conclusions: Biventricular pacing improved both LV relaxation and compliance better than single-LV pacing, probably due to favorable interaction of biventricular contraction and LV elastic recoil.

Force-frequency relationship as a predictor of long-term prognosis in patients with heart diseases

Adequate evaluation of the nature of the residual failing myocardium, as well as the severity of myocardial injury, is important for managing patients with heart failure. The aim of this study was to investigate the myocardial function and the prognosis of patients with heart diseases using the force-frequency relationship (FFR). We enrolled 76 patients with sinus rhythm who had miscellaneous heart diseases and performed incremental right atrial pacing at the time of diagnostic cardiac catheterization. The first derivatives of left ventricular pressure (dP/dt) were recorded using a micro manometer-tipped catheter during the study. To represent properties of FFR, two parameters-the peak force rate (PFR) and force gain (FG)-were estimated. PFR was defined as the heart rate at which dP/dt became maximum. FG was defined as the difference between dP/dt at PFR and dP/dt at the basal heart rate. FG decreased as the severity of left ventricular (LV) dysfunction increased (372.0 ± 110.7, 209.5 ± 29.1 and 116.3 ± 13.1 mmHg/s for normal LV function, mild LV dysfunction and severe LV dysfunction groups, P < 0.05, respectively). PFR correlated with cardiac index (r = 0.375, P = 0.001). FG correlated with LV end systolic volume index (r = -0.297, P = 0.010) and LV ejection fraction (r = 0.539, P < 0.001). Furthermore, pulmonary arterial wedge pressure [hazard ratio (HR) 1.126, P < 0.01] and FG (HR 0.992, P = 0.061) tended to be independent predictors for cardiovascular death. Analysis of FFR, especially FG, seems to be useful to evaluate the nature of the failing myocardium and the prognosis of patients with heart diseases.

Impact of a Single Intracoronary Administration of Adiponectin on Myocardial Ischemia/Reperfusion Injury in a Pig Model

Adiponectin plays a protective role in the development of obesity-linked disorders. We demonstrated that adiponectin exerts beneficial actions on acute ischemic injury in mice hearts. However, the effects of adiponectin treatment in large animals and its feasibility in clinical practice have not been investigated. This study investigated the effects of intracoronary administration of adiponectin on myocardial ischemia-reperfusion (I/R) injury in pigs. The left anterior descending coronary artery was occluded in pigs for 45 minutes and then reperfused for 24 hours. Recombinant adiponectin protein was given as a bolus intracoronary injection during ischemia. Cardiac functional parameters were measured by a manometer-tipped catheter. Apoptosis was evaluated by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling staining. Tumor necrosis factor-alpha and interleukin-10 transcripts were analyzed by real-time polymerase chain reaction. Serum levels of derivatives of reactive oxygen metabolites and biological antioxidant potential were measured. Adiponectin protein was determined by immunohistochemical and Western blot analyses. Intracoronary administration of adiponectin protein led to a reduction in myocardial infarct size and improvement of left ventricular function in pigs after I/R. Injected adiponectin protein accumulated in the I/R-injured heart. Adiponectin treatment resulted in decreased tumor necrosis factor-alpha and increased interleukin-10 mRNA levels in the myocardium after I/R. Adiponectin-treated pigs had reduced apoptotic activity in the I/R-injured heart and showed increased biological antioxidant potential levels and decreased derivatives of reactive oxygen metabolite levels in the blood stream after I/R. These data suggest that adiponectin protects against I/R injury in a preclinical pig model through its ability to suppress inflammation, apoptosis, and oxidative stress. Administration of intracoronary adiponectin could be a useful adjunctive therapy for acute myocardial infarction.

Superoxide-Dependent Cathepsin Activation Is Associated with Hypertensive Myocardial Remodeling and Represents a Target for Angiotensin II Type 1 Receptor Blocker Treatment

The elastolytic activity of cathepsins in the myocardium is implicated in hypertensive heart failure (HF). Given that reactive oxygen species are also implicated in protease activation associated with cardiac remodeling, we examined the role of the reactive oxygen species-induced cathepsin activation system in cardiac remodeling during the development of hypertensive HF. Dahl salt-sensitive hypertensive rats maintained on a high-salt diet were treated with vehicle, the cathepsin inhibitor E64d, or the angiotensin receptor blocker olmesartan from 12 to 19 weeks of age. Cathepsin expression and activity were increased in the left ventricle of HF rats; olmesartan inhibited these effects, restored the balance between elastin and collagen in the left ventricle, and suppressed degradation of the elastic lamina of coronary arteries of HF rats. Furthermore, olmesartan inhibited up-regulation of NADPH oxidase subunits and activity as well as superoxide generation. These effects of olmesartan were mimicked by E64d and were accompanied by amelioration of cardiac fibrosis. Finally, olmesartan and apocynin reduced angiotensin II-induced increases in cathepsin mRNA and protein levels in cultured rat neonatal cardiac myocytes. These data suggest that cathepsins likely trigger and promote cardiac remodeling and that blocking the angiotensin II type 1 receptor attenuates cathepsin expression and activity by inhibiting the production of superoxide by NADPH oxidase, thereby attenuating cardiac remodeling and dysfunction.

Evaluation of Cardiac Function in the Clinical Scene

Pulmonary arterial catheterization (PAC) has been quite often used for bedside evaluation of hemodynamics and cardiac function in Japan. Forrester's subsets based on hemodynamic data obtained by PAC are widely used to predict patients prognosis and to determine the choice of treatment. However, since PAC is an invasive procedure, new classification by Nohria et al. derived from non-invasive physical examination is rather recommended in recently published guidelines. In routine diagnostic cardiac catheterization, most useful index of systolic function is left ventricular ejection fraction. This index is however, dependent on loading conditions and is not a pure index of contractility. As for the index of LV contractility, peak positive dP/dt and its derivatives are used. High fidelity pressure data obtained by catheter-tip manometer is necessary to calculate these indexes. Emax is the most reliable index of contractility although this is not practical for routine evaluation. As for the indexes of relaxation, peak negative dP/dt and tau are calculated from high fidelity pressure data. The ratio of LVEDP to LVEDV is a simple index for diastolic distensibility. For further evaluation of diastolic function, cubersome plotting of left ventricular pressure and volume data is required.

The relationship between aortic augmentation index and pulse wave velocity: an invasive study

The aortic augmentation index (AI) and aortic pulse wave velocity (PWV) are known to be indicators of arterial stiffness. However, it is not clear whether aortic AI and PWV reflect aortic stiffness in similar ways. We investigated the relationship between aortic AI and PWV by measuring them directly using a catheter technique. Forty-one patients, aged 34-79 years, were studied during diagnostic cardiac catheterization. Aortic pressures were measured using a catheter-tip manometer at two points, one in the ascending aorta and one 40 cm distally in the descending aorta. Aortic AI was defined as the difference between early and late pressure peaks divided by the pulse pressure of the ascending aorta. Aortic PWV was calculated as the distance between the two measuring sites divided by the transit time. We also examined the effects of vasodilatation on AI and PWV by the intra-aortic administration of nitroglycerin in 15 patients. AI was significantly related to age, systolic aortic pressure, heart rate, left ventricular ejection time, and height. Aortic PWV showed an association only with age and systolic aortic pressure. There was no significant relationship between aortic AI and PWV (r = 0.28, NS). Nitroglycerin also produced different effects on aortic AI and PWV: aortic AI was significantly decreased (-0.17, P < 0.01) after nitroglycerin, but PWV remained unchanged (+0.4 m/s, NS). Aortic AI and PWV cannot be used interchangeably as an index of arterial stiffness. AI may not be a true indicator of arterial stiffness, but an index of wave reflection including PWV.

Changes in finger-aorta pressure transfer function during and after exercise

Noninvasive finger blood pressure has become a surrogate for central blood pressure under widely varying circumstances. We tested the validity of finger-aorta transfer functions (TF) to reconstruct aortic pressure in seven cardiac patients before, during, and after incremental bicycle exercise. The autoregressive exogenous model method was used for calculating finger-aorta TFs. Finger pressure was measured noninvasively using Finapres and aortic pressure using a catheter-tip manometer. When applying the individual TFs found during rest for reconstruction of aortic pressure during all workloads, systolic pressure was increasingly underestimated, with large variation between subjects: +4.0 to -18.1 mmHg. In most subjects, diastolic pressure was overestimated: -3.9 to +5.5 mmHg. Pulse pressure estimation varied between +4.5 and -21.9 mmHg. In all cases, wave distortion was present. Postexercise, error in reconstructed aortic systolic pressure slowly declined, and diastolic pressure was overestimated. During rest, the TF gain had a minimum between 3.65 and 4.85 Hz (Fmin). During exercise, Fmin shifted to frequencies between 4.95 and 7.15 Hz at the maximum workload, with no change in gain. Postexercise, gain in most subjects shifted to values closer to unity, whereas Fmin did not return to resting values. Within each subject, aorta-Finapres travel time was linearly related to mean pressure. During exercise, Fmin was linearly related to both delay and heart rate. We conclude that, during increasing exercise, rest TFs give an increasingly unreliable reconstruction of aortic pressure, especially at higher heart rates.

Diastolic left ventricular function Experimental study of the early filling period using the Voigt model

The left ventricular (LV) diastolic function is usually described by the diastolic part of the LV pressure-volume relationship (PVR). The mathematical analysis of the PVR provides parameters of diastolic LV as well as myocardial function. Up to now, all approaches assume the myocardium as a passive elastic medium. This implies that each increase in LV volume is associated with a corresponding increase in LV pressure. Obviously this does not agree with actual PVR's during the LV early filling phase, where a decrease of pressure (due to relaxation) can be observed. Therefore, we analysed the LV diastolic PVR using the Voigt model to provide a better understanding of the concomitant processes of relaxation and filling especially during the early diastole. LV volumes and pressures were measured in an experimental study (6 pigs) using biplane cineangiography (100 frames/s) and simultaneous pressure measurements (catheter tip manometer). LV volumes were determined from all cine frames of total cardiac cycles. Instantaneous (beat to beat) changes in duration (Deltat(f)) of the LV filling period were achieved by atrial stimulation and by releasing post-extrasystolic beats. A total of 26 PVR's with different Deltat(f) were evaluated. According to the Voigt model the compliance (product of the resting volume V(0) and the elastic coefficients) of the total muscle fibre (V(0).K(tot)) and of the serial elastic element (V(0).K(se)) were calculated (average: V(0).K(tot) = 3.43 ml/ mmHg; V(0).K(se) = 5.07 ml/mmHg; n = 26). The interindividual differences between the compliances were in some individuals significant (V(0).K(tot): p < 5% in 6 of 15 Wilcoxon tests ; V(0).K(se): p < 5% in 3 of 15 Wilcoxon tests) but the intraindividual range of these parameters (due to different Deltat(f)) were in some cases as pronounced as the interindividual differences. As in 22 of 26 measurements V(0).K(tot) is less than V(0).K(se) it must be concluded that the early diastolic PVR cannot be described by passive elasticity and the laws of elastomechanics only. These inconsistencies can be explained by the early diastolic LV suction (untwisting) as well as by recent findings regarding the titin filament. Both mechanisms augment LV diastolic filling even in unfavourable working conditions (shortened filling) such as exercise.

Tissue Doppler-derived myocardial acceleration for evaluation of left ventricular diastolic function

Our purpose was to evaluate a tissue Doppler-based index-peak myocardial acceleration (pACC)-during isovolumic relaxation and in evaluating left ventricular (LV) diastolic function. Simple, practical indexes for diastolic function evaluation are lacking, but are much desired for clinical evaluation. We examined eight sheep by using tissue Doppler ultrasound images obtained in the apical four-chamber views to evaluate mitral valve annular velocity at the septum and LV wall. The pACC thus derived was analyzed during isovolumic relaxation (IVRT) and during the LV filling period (LVFP). We then changed the hemodynamic status of each animal by blood administration, dobutamine, and metoprolol infusion. We compared the pACC values during IVRT and LVFP over the four different hemodynamic conditions with a peak rate of drop in LV pressure (-dP/dt(min)) and the time constant of LV isovolumic pressure decay (tau), as measured with a high-frequency manometer-tipped catheter. The pACC of the septal side of the mitral valve annulus during IVRT showed a good correlation with -dP/dt(min) (r = -0.80, p < 0.0001) and tau (r = -0.87, p < 0.0001). The mean left atrial pressure (LAP) correlated well with the septal side pACC during LVFP (r = 0.81, p < 0.0001). There was a weak correlation between the mitral valve annulus pACC at the LV lateral wall and mean LAP. The pACC during IVRT is a sensitive, preload-independent marker for evaluation of LV diastolic function. In addition, pACC during LVFP correlated well with mean LAP.

Wavelet and Fourier analysis of ventricular and main arteries pulsations in anesthetized dogs

The purpose of this study was to characterize time-frequency behavior using the Continuous Wavelet Transform (CWT) and Fast Fourier Transform (FFT) to analyze ventricular and arterial pressure signals from anesthetized mongrel dogs. Both ventricular and arterial pressure pulsations were recorded using catheter-tip manometers and the CWT was applied to these signals to obtain module coefficients, associated contours, and the 3-D representation of these modules. FFT was applied to obtain the Fourier spectrum. The mathematical analysis of the cardiovascular pressure pulsations permitted the identification of the evolution of the frequency components for the aortic and pulmonary valve functions as well as the intra-ventricular and respiratory influences on the cardiovascular dynamics. The CWT is a very sensitive and reliable procedure for determining the three-dimensional (time-frequency-amplitude) of the oscillatory phenomena during each cardiac cycle, providing more, although complementary, information than the spectral analysis obtained with the FFT. Thanks to the FFT, exact values in Hz could be found for the different events produced in each cycle, and thus the information provided by CWT could be related to the information provided by FFT. The combination of both mathematical methodologies permitted identification of each component of the analyzed signals. The 3D representation allowed an easy comparison of the relative importance of the complex magnitudes in frequency for the different components of the pulsatile waves.

Acute volume reduction with aortic valve replacement immediately improves ventricular mechanics in patients with aortic regurgitation

Objectives: Few data have been available regarding the immediate response in ventricular mechanics to acute volume reduction caused by aortic valve replacement for aortic regurgitation. Methods: We studied 9 patients in the operating room immediately before and after the institution of cardiopulmonary bypass. Left ventricular pressure and cross-sectional area (a surrogate of left ventricular volume) were measured with a catheter-tip manometer and a transesophageal echocardiographic system equipped with automated border-detection technology. Left ventricular pressure-area loops were constructed, and the caval occlusion method was used to obtain the slope of the end-systolic pressure-area relationship and the end-systolic area associated with 100 mm Hg. From the steady-state beats, stroke area was obtained by subtracting the minimum area from the maximum area. Effective arterial elastance, a measure of ventricular afterload, was calculated from end-systolic pressure, and stroke area as follows: effective arterial elastance equals end-systolic pressure divided by stroke area. Results: Reductions in maximum area (21.0 ± 8.5 to 16.0 ± 6.8 cm2 [SD])and minimum area (15.3 ± 8.4 to 12.0 ± 6.1 m2) shifted the baseline pressure-area loops to the left. The slope of the end-systolic pressure-area relationship (11.6 ± 4.8 to 16.0 ± 7.5 mm Hg/cm2) and afterload (effective arterial elastance, 17.9 ± 11.6 to 26.3 ± 16.4 mm Hg/cm2) were increased, and the end-systolic area associated with 100 mm Hg was reduced (18.3 ± 10.0 to 13.7 ± 5.8 cm2). Conclusion: Correction of volume overload reduced preload (minimum area), shifted the end-systolic pressure-area relationship to the left (decreased end-systolic area), and improved ventricular contractility (increased slope of the end-systolic pressure-area relationship). The result indicated that acute volume reduction favorably influenced ventricular mechanical parameters immediately after the operation.J Thorac Cardiovasc Surg 2003;125:283-9

Can a clinically useful aortic pressure wave be derived from a radial pressure wave?

The information contained in arterial pressure waveforms is probably underused by most clinicians who manage critically ill patients. It is not generally known that an aortic pressure wave can be synthesized by applying a generalized transfer function to the radial arterial pressure wave. We validated a commercially available system, SphygmoCo (PWV Medical, Sydney). Ascending aortic pressure waves were synthesized and comparisons were made between the synthesized aortic waveforms, the measured aortic and radial arterial waveforms. Ascending aortic pressure waves (catheter-tip manometer) and radial artery pressure waves (short fluid-filled catheter) were recorded simultaneously in 12 patients with angina pectoris (age 62-76 years) undergoing cardiac catheterization. Patients were studied at rest, following midazolam, sublingual nitroglycerin and during Valsalva manoeuvres. Both midazolam and nitroglycerin lowered mean arterial pressure but nitroglycerin caused a more selective decrease in the measured and synthesized aortic systolic pressures than in the radial artery pressure. The synthesized aortic systolic pressure was less, by 6-8 mm Hg (SD 2-3) and the synthesized aortic diastolic pressure greater, by 4 mm Hg (SD 2). Despite these differences in pulse pressure, the synthesized waveform tracked the measured waveform before and during interventions. By deriving an aortic waveform from the radial pulse, monitoring of left ventricular afterload can improve without more invasive means.

Hemodynamic changes with right lateral decubitus body positioning in the tilted porcine heart

Background. In beating-heart coronary surgical procedures, exposure of posterior vessels through sternotomy causes cardiac function to deteriorate. We hypothesized that turning the subject to the right lateral decubitus position before cardiac retraction improves exposure of posterior vessels and preserves cardiac pump function on displacement. Methods. Eight 80-kg open-chest pigs were instrumented with catheter-tip manometers. After a stepwise 60-degree turn to the right lateral decubitus position of the body, the heart was retracted anteriorly to 90 degrees with a suction stabilizer. Results. Right lateral body positioning caused an approximately 45-degree right deviation of the apex, thereby exposing the left atrial groove. Stroke volume, mean arterial pressure, right atrial pressure, and right ventricular end-diastolic pressure increased to 106% ± 5% (mean ± standard error of the mean, p = 0.31), 106% ± 3% ( p = 0.01), 129% ± 8% ( p = 0.001), and 171% ± 14% ( p = 0.002), respectively, compared with control values. In contrast, left atrial pressure decreased to 73% ± 6% ( p = 0.007), whereas left ventricular preload remained unchanged (110% ± 8%, p = 0.26). Additional anterior displacement to 90 degrees fully exposed the posterior vessels, and stroke volume decreased to 90% ± 3% ( p = 0.01) and mean arterial pressure to 93% ± 5% ( p = 0.07) at the expense of further increased right ventricular preload (256% ± 28%, p < 0.001). Conclusions. By placing the subject in the right lateral decubitus position, exposure through sternotomy of posterior vessels in the beating porcine heart was facilitated while mean arterial pressure was maintained.

Arterial waves in humans during peripheral vascular surgery

The purpose of this study was to investigate the effect of aortic clamping on arterial waves during peripheral vascular surgery. We measured pressure and velocity simultaneously in the ascending aorta, in ten patients (70+/-5 years) with aortic-iliac disease intra-operatively. Pressure was measured using a catheter tip manometer, and velocity was measured using Doppler ultrasound. Data were collected before aortic clamping, during aortic clamping and after unclamping. Hydraulic work in the aortic root was calculated from the measured data, the reflected waves were determined by wave-intensity analysis and wave speed was determined by the PU-loop (pressure-velocity-loop) method; a new technique based on the 'water-hammer' equation. The wave speed is approx. 32% (P<0.05) higher during clamping than before clamping. Although the peak intensity of the reflected wave does not alter with clamping, it arrives 30 ms (P<0.05) earlier and its duration is 25% (P<0.05) longer than before clamping. During clamping, left ventricule (LV) hydraulic systolic work and the energy carried by the reflected wave increased by 27% (P<0.05) and 20% (P<0.05) respectively, compared with before clamping. The higher wave speed during clamping explains the earlier arrival of the reflected waves suggesting an increase in the afterload, since the LV has to overcome earlier reflected compression waves. The longer duration of the reflected wave during clamping is associated with an increase in the total energy carried by the wave, which causes an increase in hydraulic work. Increased hydraulic work during clamping may increase LV oxygen consumption, provoke myocardial ischaemia and hence contribute to the intra-operative impairment of LV function known in patients with peripheral vascular disease.

Therapeutic Arteriogenesis Has Arrived

The report by Seiler et al1 on a clinical trial using granulocyte-macrophage colony-stimulating factor (GM-CSF) to stimulate the growth of coronary collateral vessels is the temporary culminating point of a long history of research that started in the early 1940s with the observation that the pressure measured in the distal stump of an occluded canine coronary (or femoral or carotid) artery rose as a function of time and was caused by the development of a collateral circulation.2,3 Strandness4 and Schoop and Jahn5 were probably the first to measure the pressure in the distal stump of a peripheral artery in the leg of patients for an estimation of residual perfusion. See p 2012 Almost 30 years after Gregg, my group presented the first systematic analysis of peripheral coronary pressure (PCP), provided a theoretical framework, and described the influence of coronary collateral growth and of collateral blood flow on PCP.6 This led to the formulation of an electrical analog of the coronary arterial system that was later refined by Scheel et al7 and Harrison et al.8 The electrical analog could be displayed on an Apple Macintosh computer and served as a great educational aid for training young cardiologists and physiologists. This was necessary because the complex network of coronary resistances sometimes behaved counterintuitively, but the program helped solve problems of interpretation. A classic case of confusion to the uninitiated is the fall in PCP with increasing collateral blood flow and vice …

Subvalvular gradients in patients with valvular aortic stenosis: prevalence, magnitude, and physiological importance.

Although subvalvular gradients in patients with aortic stenosis have been described, their behavior and response to exercise have not been well characterized. Left ventricular and aortic pressures and linear flow velocity were measured with a catheter-tip manometer at rest and during supine exercise in 27 patients with valvular aortic stenosis. A subvalvular gradient was measured in each patient that represented, on average, 48% of the total resting transvalvular gradient. With exercise, both total (rest: 80+/-26 mm Hg; exercise: 90+/-25 mm Hg) and subvalvular gradients (rest: 37+/-13 mm Hg; exercise: 60+/-22 mm Hg) increased significantly. There was a significant inverse relationship between change in exercise cardiac output and total and subvalvular gradients. However, only the exercise subvalvular gradient predicted cardiac output response. Subvalvular pressure gradients are universally present in patients with severe aortic stenosis and comprise approximately half of the total transvalvular gradient. The extent of exercise cardiac output increase is inversely related to the subvalvular gradient magnitude.

Pulmonary arterial compliance in children with atrial and ventricular septal defect

Previous studies have documented the normal values of pulmonary arterial compliance (Cp) in animals and adult humans. In the past, variations in Cp and its measurement in children with septal defects has been unknown. In the present study, we found the Windkessel model, which uses compliance and resistance as parameters, to be a useful tool in understanding Cp in pediatric patients. Calculations of Cp were based on the pulmonary arterial diastolic pressure waveform as an exponential function of time. First, Cp was estimated by studying pressure tracings of the main pulmonary artery (MPA) obtained from both routine cardiac catheterization and pressure measured by a catheter-tip manometer, which was performed during a catheterization study of seven children with various congenital heart diseases. Second, 124 children with atrial and ventricular septal defects aged between 45 days and 12 years were studied using the data obtained from routine catheterization. Hemodynamic data were used to calculate pulmonary vascular resistance (Rp), pulmonary arterial time constant (Tp) and Cp. A strong correlation (r = 0.954) was found in the Cp value estimated by data obtained from routine catheterization and from the catheter-tip manometer study. The present study shows an estimated mean (SEM) Cp in normal children of 1.53 (0.17) ml/mmHg per m2. The estimated mean (SEM) Cp was 1.91 (0.10) and 1.70 (0.11) ml/mmHg per m2 in children with atrial septal defect (ASD) and ventricular septal defect (VSD), respectively. It was found that Cp was significantly (P = 0.04) higher in female patients with a VSD. Also, a significantly low Cp (0.95 +/- 0.06 ml/mmHg per m2) was observed in patients with a VSD and pulmonary hypertension (VSDPH). In conclusion, Cp was calculated by the exponential decay portion of the MPA diastolic pressure waveform. A normal Cp value was observed in ASD and VSD patients and a significantly low Cp was observed in children with a VSDPH. Cp was higher in female VSD patients than in male VSD patients.

Druckentlastung im Aneurysmasack nach endovaskulärer Therapie von Aortenaneurysmen*

Stent grafting of aortic aneurysms should result in relief of pressure within the excluded aneurysmal sac, however confirming data are not available. This study evaluates the intra-extraluminal pressure translation and translation of maximum pressure increase (dp/dtmax) into the excluded aneurysmal sac after endovascular treatment of experimental aortic aneurysms. Experimental autologous aneurysms were created surgically using a patch from the sheath of the rectus abdominis muscle in 12 mongrel dogs. After 12 weeks reconvalescence, endovascular treatment was performed viafemoral access using dacron-covered nitinol stents. Spiral CT and angiography were performed at one week and six weeks follow-up and 6 animals each. Laparotomy was performed for hemodynamic measurements. A manometer-tipped catheter was introduced into the excluded aneurysmal sac. A second manometer-tipped catheter was placed intraluminally within the stent graft. Pressure curves and their first derivative dp/dt were simultaneously recorded to calculate the intra-extraluminal transmembraneous pressure transmission. At one week follow-up systolic blood pressure and mean blood pressure were significantly reduced by factors of 0.60 +/- 0.17 (p < 0.01) and 0.78 +/- 0.3 (p < 0.05), respectively in the excluded aneurysm sac. The maximal pressure increase, dp/dt max, was considerably reduced by a factor of 0.06 +/- 0.05 (p < 0.01). However, the diastolic blood pressure was not significantly changed. There were no hemodynamic differences between one and six weeks follow-up. In experimental aortic aneurysms, endovascular treatment with stent grafts significantly reduces the systolic peak pressure and dp/dt max in the excluded aneurysmal sac, and thereby significantly reduces the wall stress in the diseased aneurysm wall. Despite complete exclusion of the aneurysm, a considerable pressure load remains in the excluded aneurysmal sac.

Right ventricular diastolic function in patients with hypertrophic cardiomyopathy--an invasive study.

To assess diastolic function of the right ventricle (RV) in patients with hypertrophic cardiomyopathy (HCM), biplane RV angiograms and RV pressures were analyzed in 19 HCM patients and in 13 normal subjects. RV and left ventricle (LV) pressures were measured using catheter-tip manometers. RV volumes were obtained from frame-by-frame tracings of angiograms. Ventricular relaxation was assessed by the time constant of isovolumic pressure decay (T). The peak filling rate (PFR) and the time to PFR (TPFR) were used as parameters of early diastolic filling, and the right atrial contribution to RV filling (%AF) was used as a parameter of late diastolic filling. The T for the RV was significantly prolonged in HCM patients. However, there was no significant correlation between the T for the RV and LV, nor did the T for the RV correlate with the RV ejection fraction or interventricular septal wall thickness. The TPFR, but not PFR, was significantly greater in HCM patients, and the %AF tended to be increased in HCM, but not significantly. The RV diastolic pressure-volume relations in the HCM patients shifted upward. In conclusion, impaired isovolumic relaxation and delayed diastolic filling and decreased diastolic distensibility are present in the RV of HCM patients.