Doppler Pressure Research Articles

Accuracy of Two-Dimensional Echocardiographic Planimetry of the Mitral Valve Area before and after Balloon Valvuloplasty

The purpose of this study was to assess the accuracy of planimetry after percutaneous balloon mitral valvuloplasty (PBMV). The mitral valve area (MVA) was estimated in 34 patients before and after PBMV, using two-dimensional echocardiographic planimetry, Doppler pressure half-time (PHT), and the Gorlin formula. There was no significant difference in the correlation of planimetry and PHT before (r = 0.53, p = 0.001) and after PBMV (r = 0.56, p < 0.001). A similar correlation was found between planimetry and the Gorlin formula (r = 0.44, p = 0.01 before PBMV, r = 0.37, p = 0.03 after PBMV). The concordance between planimetry, PHT, and the Gorlin formula in classifying patients into mild, moderate, or severe mitral stenosis was not worse after PBMV. Planimetry-derived MVA was not less accurate after PBMV than before PBMV. However, the correlation between the two echocardiographic measurements and the Gorlin formula was only moderate.

Doppler pressure half-time method of assessing mitral valve area: Aortic insufficiency does not adversely affect validity

Objectives This study evaluated the effect of aortic insufficiency on the correlation of pressure half-time–derived mitral valve area with each of 2 standards for mitral valve area (planimetry and cardiac catheterization) in a prospectively assembled cohort of patients scheduled for percutaneous balloon mitral commissurotomy. Background Although Doppler pressure half-time has been validated as a method for assessing mitral valve area, most previous studies have suggested that this noninvasive technique overestimates mitral valve area in the setting of coexistent aortic insufficiency. Methods and Results Echocardiography and cardiac catheterization were performed on 212 consecutive patients scheduled for percutaneous balloon mitral commissurotomy. After excluding 35 patients who did not have aortography, the rest were divided into a “no aortic insufficiency [AI] group” ( n = 146) including those with trivial or no aortic insufficiency at catheterization and an “AI group” ( n = 31) including those with mild or moderate aortic insufficiency. The pressure half-time mitral valve area tended to slightly underestimate invasive valve area by 0.04 cm 2 in the AI group and to slightly overestimate invasive valve area by 0.06 cm 2 in the no AI group. This difference between the groups was not statistically significant ( P = .13). The pressure half-time mitral valve area tended to underestimate planimetered valve area by 0.11 cm 2 in the AI group and by 0.10 cm 2 in the no AI group. There was no difference between the 2 groups ( P = .94). Potential confounders that could theoretically mask the effect of aortic insufficiency on the pressure half-time (including age, heart rate, blood pressure, left ventricular diastolic pressure, ejection fraction, mitral regurgitation, and atrial fibrillation) were excluded by multivariable analyses. Conclusions The pressure half-time method of determining mitral valve area is not adversely affected by mild to moderate aortic insufficiency. This finding has implications for the utility of this technique in the rheumatic valvular disease population, in which mitral and aortic valve disease frequently coexist. (Am Heart J 1998;136:718-23.)

Flowfield Investigation of the Effect of Rib Open Area Ratio in a Rectangular Duct

The spatially periodic turbulent fluid flows and friction in a rectangular passage of width-to-height ratio of 4:1 with perforated rectangular ribs mounted on one wall have been studied using laser Doppler velocimetry and pressure probing. The parameters fixed were rib height to duct hydraulic diameter ratio of 0.106, rib width-to-height ratio of 0.76, rib pitch-to-height ratio of 10, and Reynolds number of 2 × 104, while the main parameter investigated was the rib open-area ratio (β) with values of 0%, 10%, 22%, 38%, and 44%. Two critical ranges of β and three characteristic flow regimes were identified, which provides useful references of practical tests of computational models. The results also showed that the dominant fluid dynamic factors responsible for the reported peak values of local Nusselt number distribution could be recognized. Moreover, the secondary-flow mean velocity components were found to be one to two orders of magnitude smaller than the bulk mean velocity.

Management of iliac occlusions with a new self-expanding endovascular stent

To determine the patency and acceptability of the Memotherm endovascular stent in the treatment of iliac arterial occlusions. Twenty-two patients (12 males and 10 females) underwent stenting of iliac occlusions of the aortoiliac bifurcation, the common iliac artery and the external iliac artery. All patients were reassessed at 3, 6 and 12 month intervals and then yearly to evaluate their symptoms and Doppler pressure measurements. Comparison was made with results from other studies treating iliac occlusions by angioplasty alone or combined with stenting. Out of 22 patients, 21 had an immediate and sustained improvement over the whole of the follow-up period. The Ankle-brachial Index (ABI) increased from a mean value of 0.49 to 0.81 3-months postprocedure and improved to 0.85 at 12 months (paired t-test p < 0.001). At 6 and 12 months the stent patency remained at 95.5%, which compares favourably with other studies. There were four minor and one major complication associated with the stenting procedure. The Memothern self-expanding stent is a useful, safe and effective device suitable for the majority of iliac occlusions. Further long-term evaluation is warranted to confirm its advantages over open surgery.

What Is the Validity of Continuous Wave Doppler Grading of Aortic Regurgitation Severity? A Chronic Animal Model Study

Continuous wave Doppler methods have been widely used clinically for evaluating the severity of aortic regurgitation; however, there have been no studies comparing these continuous wave Doppler methods with a strictly quantifiable reference for regurgitant severity. The purpose of this study was to test the applicability of continuous wave Doppler methods (deceleration slope and pressure half-time) for evaluation of chronic aortic regurgitation in an animal model. Eight sheep were studied 8 to 20 weeks after surgery to create chronic aortic regurgitation. Twenty-nine hemodynamically different states were obtained pharmacologically. A Vingmed 775 system was used for recording continuous wave Doppler traces with a 5 MHz annular array transducer directly placed on the heart near the apex. The aortic regurgitation was quantified as peak and mean regurgitant flow rates, regurgitant stroke volumes and regurgitant fractions determined with pulmonary and aortic electromagnetic flow probes and meters balanced against each other. Peak regurgitant flow rates varied from 1.8 to 13.6 L/min (6.3 ± 3.2 L/min) (mean ± SD), mean regurgitant flow rates varied from 0.7 to 4.9 L/min (2.7 ± 1.3 L/min), regurgitant stroke volume varied from 7.0 to 48.0 ml/beat (26.9 ± 12.2 ml/beat), and regurgitant fraction varied from 23% to 78% (53% ± 16%). Only marginal correlations were obtained between reference indexes and continuous wave Doppler deceleration slope and pressure half-time ( r = 0.55 to 0.74). A deceleration slope greater than 3 m/sec 2 and pressure half-time less than 400 msec did, however, provide 100% specificity for detecting severe AR (regurgitant fraction >50%). Our study shows that the continuous wave Doppler deceleration slope and pressure half-time methods have limited use for quantifying aortic regurgitation. (J Am Soc Echocardiogr 1998;11:332-7.)

A strategy for increasing use of autogenous hemodialysis access procedures: Impact of preoperative noninvasive evaluation

Purpose: We studied the efficacy of preoperative noninvasive assessment of the upper extremity to identify arteries and veins suitable for hemodialysis access to increase our use of autogenous fistulas (AF). Methods: From Sep. 1, 1994, to Apr. 1, 1997, 172 patients who required chronic hemodialysis underwent segmental upper extremity Doppler pressures and duplex ultrasound with mapping of arteries and veins. The following criteria were necessary for satisfactory arterial inflow: absence of a pressure gradient between arms, patent palmar arch, and arterial lumen diameter 2.0 mm or more. The criteria necessary for satisfactory venous outflow were venous luminal diameter greater than or equal to 2.5 mm for AF and greater than or equal to 4.0 mm for synthetic bridging grafts (BG) and continuity with distal superficial veins in the arm. Intraoperative and duplex ultrasound measurements were compared. Contemporary experience was compared with the 2-year period (1992 to 1994) before implementation of the protocol. Results: During the period from Sep. 1, 1994, to Apr. 1, 1997, 108 patients (63%) had AF, 52 (30%) had prosthetic BG, and 12 (7%) had permanent catheters (PC) placed. Early failure was seen in 8.3% of AFs. Primary cumulative patency rates were 83% for AF and 74% for BG at 1 year ( p < 0.05), with a mean clinical follow-up of 15.2 months. No postoperative infections were observed with AF, whereas six infections (12%) were observed with BG and two (17%) with PC insertion. During the period from June 1, 1992, to Aug. 31, 1994, 183 procedures were performed with a distribution of 14% AF, 62% BG, and 24% PC. In this earlier period the AF early failure rate was 36%, and the patency rates were 48%, 63%, and 48% for AF, BG, and PC, respectively (mean follow-up, 13.8 months). Conclusions: A protocol of noninvasive assessment increased use of AFs. The cumulative patency rate of AFs was improved, and early failure rates were reduced when compared with the preceding institutional experience. Routine noninvasive assessment is recommended to document adequacy of arterial inflow and delineate venous outflow to maximize opportunities for AF. (J Vasc Surg 1998;27:302-8.)

Accuracy of mitral valve area in patients with mitral stenosis measured by echocardiography : Compared with operative mitral valve area

Background:Measurement of echocardiographic mitral valve area(MVA) is a useful non-invasive method of estimating the stenotic mitral valve area. This study was undertaken to evaluate the accuracy of echocardiographic MVA measurements by comparing MVAs measured by the planimetric and the pressure half-time method versus direct MVA measurement by using a cone shaped device specifically made for direct measurement of MVA. Methods and Results:The study population consisted of 22 consecutive patients from August 1993 to February 1996. All the patients underwent 2D planimetry and Doppler echocardiographic MVA measurements before and after valve replacement surgery;direct measurement also was performed after surgery. Five patients(22.7%) had normal sinus rhythm, and the rest of the patients had atrial fibrillation. Two-dimensional echocardiographic examinations were attempted in 22 patients, and adequate measurements were obtained in 21 of the patients studied. Mean mitral valve area were 0.99±0.32cm ranged from 0.42 to 1.68cm on 2D planimetry method, 0.93±0.32cm ranged from 0.42 to 1.68cm on Doppler pressure half-time method, 1.17±0.20cm ranged from 0.93 to 1.68cm on direct measurement of mitral valve area after surgery. 2D planimetry method(r=0.621, p=0.003, SE=0.165), pressure half-time method(r=0.454, p=0.003 SE=0.187), and transmitral peak velocity (r=-0.480, p=0.026, SE=0.189) was relatively well correlate with operative mitral valve area. There was relatively good agreement between direct and 2D planimetric measurements and between

Role of transcranial Doppler and stump pressure during carotid endarterectomy.

The aim of our study was to clarify the pathophysiology of perioperative cerebral complications during carotid endarterectomy in our series. By means of transcranial Doppler ultrasonography and stump pressure measurement, we monitored 112 patients who underwent carotid endarterectomy under general anesthesia for symptomatic or asymptomatic severe carotid stenosis. Of 18 patients who underwent carotid endarterectomy with intra-arterial shunt, 2 (11.1%) developed an ischemic stroke. Of the other 94 patients, one suffered a nucleocapsular hemorrhage and 5 had cerebral ischemic complications. In these 5 patients, the duration of clamping was significantly longer (mean +/- SD, 16.4 +/- 1.1 versus 12.7 +/- 2.6 minutes; P = .0019), and the decrease of middle cerebral artery mean velocity on clamping was significantly greater (mean +/- SD, 56.4 +/- 4.9% versus 28.8 +/- 20.2%; P = .0031), while stump pressure was not significantly different. Microembolic signals were recorded in 70 patients (62.5%) and were not associated with cerebral ischemic complications. The 7 patients who developed cerebral ischemic complications had a significantly higher percentage of stenosis in the contralateral internal carotid artery (mean +/- SD, 82.0 +/- 17.8% versus 29.3 +/- 36.4%; P = .0018). The results of our study suggest that the major complications of carotid endarterectomy may be due to hemodynamic factors. Stump pressure alone is not a reliable indicator of hemodynamic changes that predict cerebral ischemia. Particulate microembolism may cause more subtle changes in cerebral parenchyma, but further studies are needed to clarify this point.

Failed Vascular Reconstructive Procedures with Profoundly Ischemic Limbs—Treated by Lumbar Sympathectomy

The purpose of this study was to assess the impact of lumbar sympathectomy on limb loss in patients with prior reconstructive vascular surgery. One hundred and one patients underwent 118 lumbar sympathectomies. The 118 limbs were grouped presympathectomy into: rest pain (41), tissue breakdown (55), and gangrene (22). All vascular procedures were femoral-popliteal or femoral-distal bypass. No change in segmental Doppler pressures occurred after lumbar sympathectomy. Sixty-nine of 118 (58%) limbs underwent amputation following sympathectomy, a mean of two (range: one to twenty-two) months following the procedure. Of those limbs with an amputation (69/118), 14/69 (20%) had one reconstructive procedure, 41/69 (60%) had two reconstructive procedures, and 14/69 (20%) had three reconstructive procedures. Of those without an amputation (49/118 limbs), 27 had one vascular recon structive procedure, 9 had two reconstructive procedures, and 3 had three reconstructive procedures before sympathectomy. (continued on next page) Of the patients with diabetes (47), 44/47 (94%) underwent amputation, 35/44 (80%) with below-the-knee and 9/44 (20%) with above-the-knee amputation. Limb loss (69 limbs) by category was: rest pain, 21/41 (51%); nonhealing ulcers, 38/55 (69%); and gangrene, 10/12 (83%). Lumbar sympathectomy may be a useful procedure in very selected patients; diabetic patients who undergo reconstructive vascular surgery are not good candidates. Segmental Doppler pressures do not help predict successful or improved outcome following lumbar sympathectomy.

Echocardiography in Percutaneous Balloon Mitral Valvuloplasty

Percutaneous balloon valvuloplasty (BV) has been used successfully in recent years for the relief of mitral stenosis, and in many instances, as an alternative to cardiac surgery. This procedure requires precise evaluation of both valve morphology and function for preprocedure decision making and follow-up of patients. Two-dimensional (2-D) echocardiography is a unique, noninvasive tool for evaluating morphologic characteristics of valve, subvalvular apparatus, and valve annular size. Doppler echocardiography provides functional information on transvalvular flow velocity, which can be used to derive pressure gradient across valve and regurgitant flow. Mitral valve area can be either obtained from 2-D echocardiography or derived from Doppler pressure half time. Echocardiography is currently the most widely used technique for assessing results of percutaneous BV. More recently, transesophageal echocardiography (TEE) has been used for the evaluation of patients undergoing percutaneous mitral BV in whom left atrial thrombus is suspected and for the intraoperative monitoring of the valvuloplasty procedure. In this article we discuss the advantages and limitations of both transthoracic echocardiography and TEE, its recent developments in monitoring the procedure, evaluation of immediate results and long term follow-up after the valvuloplasty procedure, and its clinical utility in the selection of patients for percutaneous BV.

Comparison of the Usefulness of Doppler Pressure Half-Time in Mitral Stenosis in Patients &lt;65 and &gt;65 Years of Age

Comparison of the Usefulness of Doppler Pressure Half-Time in Mitral Stenosis in Patients &lt;65 and &gt;65 Years of Age

Accurate assessment of mitral valve area in patients with mitral stenosis by three-dimensional echocardiography

The accuracy of measurements of mitral valve orifice area (MVA) from three-dimensional echocardiographic (3DE) image data sets obtained by a transthoracic or transesophageal rotational imaging probe was studied in 15 patients with native mitral stenosis. The smallest MVA was identified from a set of eight parallel short-axis cut planes of the mitral valve between the anulus and the tips of leaflets (paraplane echocardiography) and measured by planimetry. In addition, MVA was measured from the two-dimensional short-axis view (2DE). Values of MVA measured by 3DE and 2DE were compared with those calculated from Doppler pressure half-time (PHT) as a gold standard. Observer variabilities were studied for 3DE. MVA measured from PHT ranged between 0.55 and 3.19 cm 2 (mean ± SD 1.57 ± 0.73 cm 2), from 3DE between 0.83 and 3.23 cm 2 (mean ± SD 1.55 ± 0.67 cm 2), and from 2DE between 1.27 and 4.08 cm 2 (mean ± SD 1.9 ± 0.7 cm 2). The variability of intraobserver and interobserver measurements for 3DE measurements was not significantly different ( p = 0.79 and p = 0.68, respectively); for interobserver variability, standard error of the estimate = 0.25. There was excellent correlation, close limits of agreement (mean difference ± 2 SD), and nonsignificant differences between 3DE and PHT for MVA measurements ( r = 0.98 [0.02 ± 0.3] and p = 0.6), respectively. There was moderate correlation, wider limits of agreement, and significant difference between 2DE and PHT for MVA measurements ( r = 0.89 [0.32 ± 0.66] and p = 0.002), respectively. This may be related to the difficulties in visualization of the smallest orifice in precordial short-axis views. This study suggests that three-dimensional image data sets, by providing the possibility of “computer slicing” to generate equidistant parallel cross sections of the mitral valve independently from physically dictated ultrasonic windows, allow accurate and reproducible measurement of the MVA. (J Am Soc Echocardiogr 1997;10:133-40.)

The ankle-brachial index in normal neonates and infants is significantly lower than in older children and adults

Vascular trauma from accidental or iatrogenic causes is becoming more common in children. In early infancy, the most common arterial injuries are caused by diagnostic or interventional cardiac catheterizations. Doppler arterial pressure measurements and the computed ankle-brachial pressure index (ABI) are the most helpful diagnostic modalities in the assessment and follow-up of the ischemic extremity. Because normative ABI data in small children are not available, an ABI of 0.9 or less (based on data obtained from an adult population), is used to indicate limb ischemia in young infants. The purpose of this study was to define the normal values of ABI in newborns and infants. Materials and Methods: Three hundred and fifty patients were divided into two groups: group 1 (n = 200; male-to-female ratio, 1:1) were full-term (gestational age 40 ± 1.3 weeks, surface area 0.22 ± 0.02 m 2) healthy newborns following uneventful pregnancy and delivery. Group 2 (n = 150) were healthy patients aged 2 weeks to 2.5 years admitted for elective hernia repair. All the patients underwent a complete physical examination, which excluded any cardiovascular pathology. The systolic blood pressure (BP) was measured bilaterally over the brachial, tibialis posterior, and dorsalis pedis arteries. All BP data were obtained in the supine position, using an ultrasonic Doppler flow detector, an appropriately-sized pneumatic cuff and a sphygmomanometer. The chosen cuff size was long enough to completely encircle the circumference and wide enough to cover 75% of the length of the upper arm. The same cuff was applied around the ankle above the malleoli. BP values were expressed as mean ± SD in mm Hg. If there was a difference between the BP in the two arms, the higher pressure was used for calculation of the ABI. Results: The BP measurements in newborns (group 1) were left brachial, 98 ± 11; right brachial, 90 ± 10 ( P < .001), left and right tibialis posterior and left and right dorsalis pedis were 83, 81, 84, and 82 mm Hg, respectively. The mean computed ABI was 0.88 ± 0.11. Fifty eight percent of the newborns had an ABI less than 0.9 (lower limit of normal in adults). The ABI values in patients belonging to group 2 increased with age and surface area. The mean ABI was 1.0, 1.1, and more than 1.1 in patients aged 1, 1.5, and 2 years with surface areas of 0.4, 0.5 and 0.6 m 2, respectively ( P < .001 compared with group 1). Conclusion: The normative ABI in newborns and infants is significantly lower than in older children and reaches normal (adult) values during the second year of life. These data may be used as a reference when assessing lower extremity ischemia caused by trauma in young patients.

Calculation of mitral valve area in mitral stenosis using the proximal isovelocity surface area method. Comparison with two-dimensional planimetry and Doppler pressure half time method.

Two-dimensional echocardiographic (2-D) planimetry and the Doppler pressure half-time (PHT) method have been used to estimate mitral valve area (MVA) in patients with mitral stenosis (MS). Recently, the proximal isovelocity surface area (PISA) method has been shown to be accurate for calculating MVA. The purpose of this study was to compare the PISA method with previous methods. Thirty patients with MS were studied; 17 had pure MS, 4 combined mild MR, 6 combined mild AR, and 3 combined MR and AR. Color Doppler flow mapping was performed at an aliasing (blue-red interface) velocity of 14 cm/sec using the zero-baseline shift. MVA was calculated as 2 x 3.14 x R2 x 14 x (theta/180) / PFV, where R is the distance from aliasing to orifice, 14 is the aliasing velocity, theta is the internal angle of the mitral valve, and PFV is the peak flow velocity at the mitral orifice. MVA was also calculated using the 2-D and PHT methods, and compared with the PISA method. MVA calculated using the PISA method correlated well with the 2-D (r=0.90, p < 0.01, SEE = 0.18 cm2) and PHT methods (r=0.82, p < 0.01, SEE = 0.24 cm2). Compared with the 2-D method, the standard error of the estimate of the PISA method was - 0.14+/-0.18 cm2 and the percent error was -10.4+/-18.9%. Compared with the PHT method, the standard error of the estimate of the PISA method was + 0.01+/-0.24 cm2 and the percent error was +3.4+/-34.6%. MVA calculated using the PISA method correlated well with the 2-D and PHT methods in patients with pure MS or with MS combined mild regurgitation. The PISA method may be useful for calculating MVA as an alternative method.

Phase shift of the hepatic vein flow velocity waveform in chronic liver disease: Experimental and clinical studies

We examined animal models and studied patients with chronic liver disease to evaluate phase shift of the flow-velocity waveform of the hepatic vein (HV). We decided the Doppler-Pressure (DP) ratio using electrocardiography, the HV Doppler waveform and HV pressure curves, and we calculated the DP ratios. In animal models, the mean DP ratio was 1.04 in controls, 0.68 in cirrhosis, and 1.22 in fatty liver. There were significant differences among these groups ( p < 0.005). In the clinical study, the mean DP ratio was 1.03 in controls, 0.95 in chronic hepatitis and 0.79 in cirrhosis. The DP ratio in the Cirrhosis Group was significantly different from that in the Control Group ( p < 0.001) and that in the Chronic Hepatitis Group ( p < 0.05). We conclude that the DP ratio is decreased in certain hepatic disease states.

Microcirculatory Compensation to Progressive Atherosclerotic Disease

The precapillary resistance in the skin of the foot increases with standing. This mechanism, termed the venoarterial reflex (VAR) restricts arterial inflow, and avoids an excessive rise in capillary pressure. This study tests the hypothesis that there is microcirculatory compensation to atherosclerotic disease of increasing severity. Foot skin perfusion (FSP) was measured in 100 limbs with a laser Doppler placed on the plantar aspect of the great toe. Limbs were categorized as normal (n = 31) with an ankle brackial index (ABI) > or = 0.96, claudicants (n = 42) ABI 0.5-0.86, and critical ischemia (n = 27) with an ABI < or = 0.49 or a pulse volume recording consistent with severe peripheral vascular disease and symptoms of rest pain or tissue loss. Segmental Doppler pressures and pulse volume recordings were performed prior to laser Doppler measurements. Subjects with clinical signs or symptoms of chronic venous insufficiency were excluded. The resting foot skin perfusion was measured in the horizontal and dependent position, with the patient supine and sitting. Comparisons within categories were done using Wilcoxon matched pairs signed rank test and between groups with Mann-Whitney U test for unpaired data. Differences were considered significant if they exceeded the 95% confidence level (p value < or = 0.05). Resting supine skin perfusion was similar between nondiabetic normals and claudicants and diabetic normals and claudicants. There was a significant decrease in the foot skin perfusion (mean FSP +/- SEM) in the normal limb with a change from the supine (7.8 +/- 2.2 ml/min/100 g) to the dependent (2.8 +/- 0.6 ml/min/100 g) position indicating an intact VAR. This was absent in 33% of the limbs with claudication. Limbs with critical ischemia demonstrated an increase in FSP with dependency (supine 4.0 +/- 1.0 ml/min/100 g) versus dependent (8.4 +/- 1.8 ml/min/100 g) and was present in both diabetic and nondiabetic limbs. Microcirculatory compensation occurs early in atherosclerotic limbs. Although supine FSP is similar in normals and claudicants, a greater percentage of claudicants demonstrate a loss of the VAR. Critically ischemic limbs have increased FSP in the dependent position. These observations indicate that there are microcirculatory alterations in limbs with claudication and assist in explaining why patients with ischemic rest pain obtain relief and develop edema with dependency.

Comparison of the Usefulness of Doppler Pressure Half-Time in Mitral Stenosis in Patients &lt;65 and ≥65 Years of Age

Comparison of the Usefulness of Doppler Pressure Half-Time in Mitral Stenosis in Patients &lt;65 and ≥65 Years of Age

Turbulent/viscous interactions control Doppler/catheter pressure discrepancies in aortic stenosis. The role of the Reynolds number.

Despite good correlation between Doppler and catheter pressure drops in numerous reports, it is well known that Doppler tends to apparently overestimate pressure drops obtained by cardiac catheterization. Neither (1) simplification of the Bernoulli equation nor (2) pressure recovery effects can explain this dilemma when taken alone. This study addressed the hypothesis that a Reynolds number-based approach, which characterizes (1) and (2), provides a first step toward better agreement of catheter and Doppler assessments of pressure drops. Doppler and catheter pressure drops were studied in an in vitro model designed to isolate the proposed Reynolds number effect and in a sheep model with varying degrees of stenosis. Doppler pressure drops in vitro correlated with the directly measured pressure drop for individual valves (r = .935, .960, .985, .984, .989, and .975) but with markedly different slopes and intercepts. A Bland-Altman type plot showed no useful pattern of discrepancy. The Reynolds number was successful in collapsing the data into the profile proposed in the hypothesis. Parallel results were found in the animal model. Apparent overestimation of net pressure drop by Doppler is due to pressure recovery effects, and these effects are countered by both viscous effects and inertial/turbulent effects. Only by reconciliation of discrepancies by use of a quantity such as Reynolds number that embodies the relative importance of competing factors can the noninvasive and invasive methods be connected. This study shows that a Reynolds number-based approach accomplishes this goal both in the idealized in vitro setting and in a biological system.

Evaluation of contractile reserve by dobutamine echocardiography: Noninvasive estimation of the severity of heart failure

Functional status in chronic heart failure is evaluated in general by subjective means, such as the New York Heart Association class, or by invasive techniques difficult to use routinely. The aim of this study was to evaluate noninvasively the contractile reserve in cases of heart failure as a means to define the functional status of the patients. Cardiac peak power, a new noninvasively obtained afterload-independent index of contractility, was calculated from online Doppler and central arterial blood pressure estimated non-invasively in 35 patients with heart failure and 10 healthy subjects during dobutamine infusion. Cardiac output increased in all patients to the same extent, without differentiation among the functional classes. Contractile reserve, as assessed by peak power, was found to be a good marker of functional class: it was significantly higher in functional class 1 than in functional classes 2 through 4. A correlation of r = 0.99 and probability of p < 0.001 was found with the functional status. This new, noninvasive contractility index, peak power, allows an objective evaluation of the severity of heart failure.

Comparison of the usefulness of doppler pressure half-time in mitral stenosis in patients

Doppler pressure half-time is a reliable method for estimating mitral valve area when net left atrial and ventricular compliance remain stable. The accuracy of Doppler pressure half-time in estimating mitral valve area in older patients is unknown. We studied 80 patients (65 women and 15 men, aged 56 ± 14 years) with cardiac catheterization and echocardiography. Mitral valve area was calculated using the Gorlin formula and by the Doppler pressure half-time method. Patients were stratified into those aged < 65 years (n = 57), and those aged ≥65 years (n = 23). The discordance between pressure half-time and Gorlin-derived mitral valve area was assessed and related to multiple clinical, echocardiographic, and hemodynamic variables. The difference between pressure half-time and Gorlin-derived mitral valve area was greater in the older than in the younger patient (0.34 ± 0.30 vs 0.15 ± 0.27 cm 2, p = 0.009) but the older group had smaller mitral valve areas by the Gorlin method (0.72 ± 0.18 vs 0.89 ± 0.32 cm 2, p = 0.02) and lower cardiac output. The difference between pressure half-time and Gorlin remained greater in the group of older patients (0.32 ± 0.30 vs 0.19 ± 0.22 cm 2, p = 0.04), even when the analysis was restricted to patients with similar mitral valve area (< 1 cm 2 by the Gorlin method). Using multivariate analysis, age ≥65 years remained the only significant predictor of the discrepancy between pressure half-time and Gorlin mitral valve area. Thus, when compared with Gorlin-derived mitral valve area, pressure half-time overestimated valve area in older patients, and this technique for estimating mitral valve area should be used with caution in patients ≥65 years of age.