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P Vandervoort

Publications and source records attributed to P Vandervoort.

13 recordsLinked to original sources
PubMed2004

Assesment of LV diastolic filling using color M-mode Doppler echocardiography: validation in new hydoraulic model.

The effect of LV properties on v(p) and the E/v(p) ratio remains a matter of debate. Therefore,the objective of this study is to explore - in a new hydraulic model - the individual contributions of LV relaxation, filling pressure and compliance in changes of E, v(p) and E/v(p) for different stages of diastolic function. A new hydraulic model, consisting of an open cylindrical LA connected to an ellipsoidal LV, is designed. E and v(p) are measured for varying values of tau (45-60-90 ms), LV compliance (0.45-1.35 ml/mmHg) and filling pressure (3-10-30 mmHg). The results are used for predicting the evolution of E, v(p) and E/v(p) during different stages of diastolic function. An increase in compliance decreases E, whereas it augments v(p). v(p) is less load-dependent than E. E decreases with delayed relaxation, increases for the case of pseudonormalisation, and becomes higher than the reference values during restrictive filling. The v(p) value is lower for the case of delayed relaxation than for the reference situation. During pseudonormalisation, the value of v(p) remains lower than the reference value but higher than the value for delayed relaxation. v(p) further decreases during restrictive filling. In conclusion, the effect of simultaneous changes in compliance and loading counterbalance changes in v(p). Therefore, under normal physiologic conditions where load and compliance are coupled, v(p) is apparently load-intensive and E/v(p) increases as filling pressure increases. Moreover, in the different stages of diastolic dysfunction, due to the interference of the co-varying relaxation, the increase in E/v(p) is more pronounced.

Biomechanical Phenomena↗
PubMed2001

A semiautomated objective technique for applying the proximal isovelocity surface area method to quantitate mitral regurgitation: Clinical studies with the digital flow map.

BACKGROUND: Clinical application of the color Doppler proximal isovelocity surface area (PISA) method to quantify mitral regurgitation (MR) has been limited by the often inaccurate assumption that isovelocity surfaces are hemispheric. This study applied an objective method for selecting the region where the hemispheric geometry holds best on the basis of mathematic analysis of results at different distances from the orifice. We aimed to demonstrate this approach can be applied accurately in the clinical setting and can be semiautomated to promote routine use by extracting velocities from the digital Doppler output and then performing all the calculations automatically. METHODS: In 75 patients with isolated MR, centerline velocities (V(r)) at each distance (r) from the orifice in the proximal flow field were extracted digitally. The automated analysis calculated peak MR flow rates as 2pir(2)V(r) and plotted these against their respective velocities. The optimal value for peak flow rate was obtained mathematically at the site where the slope of this curve was minimal (least inaccuracy). This value was combined with continuous wave Doppler data to provide regurgitant stroke volume (RSV) and orifice area (ROA), which were compared with quantitative Doppler in 75 patients and angiography in 42. RESULTS: RSV and ROA by this optimized, semiautomated PISA method correlated and agreed well with values from quantitative Doppler (y = 0.9x + 1.9, r = 0.90, standard error of the estimate [SEE] = 8.1 mL, mean difference = -0.7 +/- 8.5 mL for RSV; y = 0.9x + 0.02, r = 0.90, SEE = 0.048 cm(2), mean difference = -0.005 +/- 0.1 cm(2) for ROA) and correlated well with angiography (rho = 0.90 for both RSV and ROA). CONCLUSIONS: This objective PISA method for quantifying MR is accurate in the clinical setting and has been semiautomated by use of analysis of digital velocity data to provide a rapid and practical technique suitable to facilitate more extensive application in routine practice.

Algorithms↗
PubMed1998

Age independence of the difference in duration of pulmonary venous atrial reversal flow and transmitral A-wave flow in normal subjects.

Aging influences pulmonary venous flow and mitral inflow velocities. The duration of pulmonary venous atrial reversal flow exceeds that of the mitral inflow A wave in patients with left ventricular end-diastolic pressures greater than 15 mm Hg. The objective of this study was to investigate the effect of age on the difference between the duration of pulmonary venous atrial reversal flow and that of the mitral inflow A wave in a large number of normal individuals. Pulsed wave Doppler transthoracic echocardiograms of the pulmonary venous flow and the transmitral inflow with respiratory monitoring were made of 72 normal volunteers (40 women) ranging in age between 23 and 84 years. The differences in the durations of pulmonary venous atrial reversal flow and mitral inflow A wave were measured and their correlation with age assessed. Age was not highly correlated with the duration of pulmonary venous atrial reversal flow (r = 0.25) nor the duration of the mitral inflow A wave (r = 0.33). The duration of pulmonary venous atrial reversal flow exceeded the duration of the mitral inflow A-wave flow only in three (4%) of 72 subjects, and age was not related to the index in this group (r = -0.16; p = 0.19). The difference in durations was not significantly affected by the phase of respiration. Men had higher values on all measurements than women. The difference between the pulmonary venous atrial reversal duration and the mitral inflow A-wave duration is independent of age and thus may be used as a reliable index of left ventricular end-diastolic pressure, even in elderly patients.

Adult↗
PubMed1997

An index of early left ventricular filling that combined with pulsed Doppler peak E velocity may estimate capillary wedge pressure.

OBJECTIVES: This study sought to determine the applicability of the combined information obtained from transmitral Doppler flow and color M-mode Doppler flow propagation velocities for estimating pulmonary capillary wedge pressure. BACKGROUND: Although Doppler-derived measurements of left ventricular (LV) filling have been applied to determine left atrial pressure, their accuracy has been limited by the variable effect of ventricular relaxation in these indexes. Recently, flow propagation velocity measured by color M-mode Doppler echocardiography has been suggested as an index of ventricular relaxation. METHODS: We studied 45 patients admitted to the intensive care unit who underwent invasive hemodynamic monitoring. We measured peak early (E) and late (A) transmitral Doppler velocities, E/A ratio and flow propagation velocity (vp) and compared them by linear regression with pulmonary capillary wedge pressure (pw). RESULTS: We found a modest positive correlation between pw and E (r = 0.62, p < 0.001) and the E/A ratio (r = 0.52, p < 0.001) and a negative correlation between pw and vp (r = -0.34, p = 0.02). By stepwise linear regression, only E and vp were statistically significant predictors of pw. However, the E/vp ratio provided the best estimate of pw (r = 0.80, p < 0.001; pw = 5.27 x [E/vp] + 4.6, SEE 3.1 mm Hg). CONCLUSIONS: The ratio of component velocity (E) over the color M-mode propagation velocity during early LV filling, by correcting for the effect of LV relaxation, provides a better estimate of pw than standard measurements of transmitral Doppler flow.

Aged↗
PubMed1997

Ondansetron, a 5-HT3 antagonist, improves cerebellar tremor.

It has been previously shown that ondansetron, a 5-HT3 antagonist, can ameliorate vertigo in patients with acute brainstem disorders. A coincidental benefit was the improvement of cerebellar tremor in some patients with both vertigo and tremor. To further evaluate this effect, a placebo controlled, double blind, crossover study was conducted of a single dose of intravenous ondansetron in 20 patients with cerebellar tremor caused by multiple sclerosis, cerebellar degeneration, or drug toxicity. The principal outcome measures were the change in blind assessment of a writing task (spiral copying) and the timed completion of a nine hole peg test. Thirteen of 19 patients were deemed to have improved spiral copying after treatment with ondansetron when compared with baseline performance. One patient had a better response to the placebo compared with baseline performance (P = 0.00024). Patients completed the nine hole peg test in less time after ondansetron than after placebo (P = 0.08). Twelve patients thought that their tremor was functionally improved with the ondansetron treatment. None thought that the placebo gave improvement (P = 0.00098). The efficacy of orally administered ondansetron in tremor control is currently under study.

Cerebellar Diseases↗
PubMed1996

Bench repair of donor mitral valve before heart transplantation.

Bench repair of the donor mitral valve was performed before orthotopic heart transplantation in a 57-year-old status I recepient. Mitral regurgitation in the structurally normal mitral valve was due to annular dilatation at the attachment of the posterior leaflet and was corrected with posterior annuloplasty. The patient is clinically well 18 months after transplantation.

Heart Transplantation↗
PubMed1996

Mechanisms of hemolysis with mitral prosthetic regurgitation. Study using transesophageal echocardiography and fluid dynamic simulation.

OBJECTIVES: The aims of this study were to define the hydrodynamic mechanisms involved in the occurrence of hemolysis in prosthetic mitral valve regurgitation and to reproduce them in a numeric simulation model in order to estimate peak shear stress. BACKGROUND: Although in vitro studies have demonstrated that shear stresses > 3,000 dynes/cm2 are associated with significant erythrocyte destruction, it is not known whether these values can occur in vivo in conditions of abnormal prosthetic regurgitant flow. METHODS: We studied 27 patients undergoing reoperation for significant mitral prosthetic regurgitation, 16 with and 11 without hemolysis. We classified the origin and geometry of the regurgitant jets by using transesophageal echocardiography. By using the physical and morphologic characteristics defined, several hydrodynamic patterns were simulated numerically to determine shear rates. RESULTS: Eight (50%) of the 16 patients with hemolysis had paravalvular leaks and the other 8 had a jet with central origin, in contrast to 2 (18%) and 9 (82%), respectively, of the 11 patients without hemolysis (p = 0.12, power 0.38). Patients with hemolysis had patterns of flow fragmentation (n = 2), collision (n = 11) or rapid acceleration (n = 3), whereas those without hemolysis had either free jets (n = 7) or slow deceleration (n = 4) (p < 0.001, power 0.99). Numeric simulation demonstrated peak shear rates of 6,000, 4,500, 4,500, 925 and 950 dynes/cm2 in these five models, respectively. CONCLUSIONS: The distinct patterns of regurgitant flow seen in these patients with mitral prosthetic hemolysis were associated with rapid acceleration and deceleration or high peak shear rates, or both. The nature of the flow disturbance produced by the prosthetic regurgitant lesion and the resultant increase in shear stress are more important than the site of origin of the flow disturbance in producing clinical hemolysis.

Aged↗
PubMed1996

Value of proximal regurgitant jet size in tricuspid regurgitation.

Recent studies have shown good agreement between proximal regurgitant jet size obtained with transthoracic color flow mapping and regurgitant fraction in patients with mitral regurgitation. To evaluate this in patients with tricuspid regurgitation, we analyzed 40 patients in sinus rhythm, 16 with free jets and 24 with impinging jets, comparing proximal jet size (millimeters) with parameters derived from the Doppler two-dimensional echocardiographic method (regurgitant fraction) and the flow-convergence method (peak flow rate, effective regurgitant orifice area, and momentum). Good agreement was noted between peak flow rate (r = 0.80, p < 0.001), momentum (r = 0.80, p < 0.001), and effective regurgitant orifice area (r = 0.78, p < 0.001), with proximal jet size measured in the apical four-chamber view in patients with free jets. The average of jet proximal size in three planes also had good correlation with peak flow rate (r = 0.75, p < 0.001), regurgitant fraction, momentum, and effective regurgitant orifice area (r = 0.74, p < 0.001). In patients with impinging jets, agreement was fair between effective regurgitant orifice (r = 0.65, p < 0.001), peak flow rate (0.65, p < 0.001), and momentum (r = 0.62, p < 0.001) with mean jet proximal size. Jet proximal size obtained with transthoracic color flow mapping is a good semiquantitative tool for measuring tricuspid regurgitation in free jets that correlates well with established measures of the severity and with new parameters available from analysis of the proximal acceleration field. In patients with eccentrically directed wall jets, the correlation weakens but still appears clinically significant.

Adult↗
PubMed1996

Pulmonary vein thrombosis and peripheral embolization.

A 78-year-old-woman was admitted to the hospital with bilateral femoral arterial occlusion. Her medical history disclosed atrial fibrillation and a left thoracoplasty performed 50 years earlier for treatment of tuberculosis. A transesophageal echocardiogram demonstrated intraluminal thrombus in a left pulmonary vein. The patient recovered after thromboembolectomy. This case documents another uncommon cause of cardiac thromboembolism in which a transesophageal echocardiogram was essential to make the diagnosis.

Aged↗
PubMed1995

Proximal jet size by Doppler color flow mapping predicts severity of mitral regurgitation. Clinical studies.

BACKGROUND: Recent studies have shown that many instrument and physiological factors limit the ability of color Doppler total jet area within the receiving chamber to predict the severity of valvular regurgitation. In contrast, the proximal or initial dimensions of the jet as it emerges from the orifice have been shown to increase directly with orifice size and to correlate well with the severity of aortic insufficiency. Only limited data, however, are available regarding the value of proximal jet size in mitral regurgitation, and it has not been examined in short-axis or transthoracic views. The purpose of the present study, therefore, was to evaluate the relation between proximal jet size and other measures of the severity of mitral regurgitation. METHODS AND RESULTS: In 49 patients, the anteroposterior height of the proximal jet as it emerges from the mitral valve was measured in the parasternal long-axis view; proximal jet width and area were measured in the short-axis view at the same level. Results were compared with regurgitant volume and fraction by pulsed Doppler subtraction of aortic and mitral flows in 47 patients without more than trace aortic insufficiency; with angiographic grade determined within 24 hours in 33 catheterized patients; and with angiographic regurgitant fraction in 13 patients who were in normal sinus rhythm and had no significant aortic and tricuspid insufficiency. Proximal jet height, width, and area correlated well with Doppler regurgitant volume and fraction (r = .86 to .95; SEE = 7.7 to 9.0 mL; 5.9% to 7.3%). Proximal jet size could also be used to distinguish angiographic grades of mitral regurgitation with minimal overlap (P < .0001) and correlated well with angiographic regurgitant fraction (r = .85 to .91; SEE = 4.1% to 5.1%). CONCLUSIONS: Proximal jet size correlates well with established measures of the severity of mitral regurgitation. It is conveniently available with transthoracic clinical scanning and should be useful in the routine evaluation of patients with mitral regurgitation.

Adult↗
PubMed1987

Bilateral occlusion of the internal carotid arteries. Presenting symptoms in 74 patients and a prospective study of 34 medically treated patients.

The presenting characteristics of 74 patients with atherosclerotic occlusion of both internal carotid arteries are described. All had suffered either ischaemic hemisphere infarcts (80%) and/or transient ischaemic attacks (80%) involving one (78%) or both (22%) carotid territories. In addition, 10 subjects (14%) incurred recurrent vertebrobasilar or presyncopal episodes, many of which appeared secondary to haemodynamic insufficiency. The incidence of risk factors and concomitant vascular disease was high; 93% gave a history of heavy smoking. Thirty-four subjects were treated conservatively and followed prospectively for a mean of 42 months. Eighteen patients (53%) suffered further cerebrovascular events, an ischaemic event rate of 15% per patient per year. These were isolated transient ischaemic attacks (TIAs) in 7 and stroke in 11 patients. The latter suffered a total of 15 strokes during the follow-up period of 42 months; the annual stroke rate was 13% per patient year. Patients who had presented with ischaemic events involving more than one carotid territory were significantly more prone to subsequent cerebral infarction than those in whom symptoms had been confined to one territory (P less than 0.05). None of the 5 patients with haemodynamic TIAs who were managed conservatively developed a stroke during the follow-up period and their symptoms remitted spontaneously. Deaths per year amounted to 8%. Twenty-four patients (71%) survived, of whom half were either symptom-free or minimally disabled. In this group of preselected patients, which excludes those with severe deficits at presentation, bilateral occlusion of the carotid arteries may be a condition compatible with useful existence.

Adult↗