Relation of weights of operatively excised stenotic aortic valves to preoperative transvalvular peak systolic pressure gradients and to calculated aortic valve areas

OBJECTIVES: The purpose of this study was to correlate the weights of operatively excised stenotic aortic valves to preoperative transvalvular peak systolic gradients and to calculated aortic valve areas. BACKGROUND: No previous publication has correlated the weights of stenotic aortic valves to the transvalvular gradients or to the calculated aortic valve areas. METHODS: We weighed operatively excised stenotic aortic valves in 324 adults who had undergone preoperative left-sided cardiac catheterization. RESULTS: As the weights of the operatively excised stenotic aortic valves increased (from <1 g to >6 g), the average transvalvular peak systolic pressure gradients progressively increased. For any valve weight, in general, the women had higher average transvalvular gradients (p 相似文献   

Hemodynamic evaluation of stenotic cardiac valves: II. Modification of the simplified valve formula for mitral and aortic valve area calculation

Since the introduction by Gorlin and Gorlin of the hydraulic formulae for calculating valve area, it has become the best parameter for quantitating valve stenosis. Recently Hakki et al proposed a simplified formula for valve area calculation that does not take into account either heart rate (HR) or left ventricular filling or ejection time. The purpose of this study was to analyze the validity of Hakki's formulae under different physiological conditions and to propose an easy correction to improve its accuracy. Our study suggests: (1) that an easy correction for heart rate in certain cases, dividing by 1.35 when HR less than 75 beats per min in mitral stenosis and when HR greater than 90 beats per min in aortic stenosis, significantly improves the accuracy and validity of Hakki's formulae (p less than 0.02 and p less than 0.05); (2) the instantaneous valve gradients (peak gradient for aortic stenosis and average of instantaneous early, middle, and late diastolic gradients for mitral stenosis) are as valid as mean planimetric gradients for valve area calculation. Thus the simplified formulae proposed in this study allow mitral and aortic valve area calculations by means of instantaneous gradients, cardiac output, and heart rate.     

Simplified method for estimating true aortic valve mean gradient from simultaneous left ventricular and peripheral arterial pressure recordings

Estimation of the aortic valve gradient by simultaneous recording of left ventricular and peripheral arterial pressures is subject to error due to delay and modulation of the arterial pressure contour as it propagates from the ascending aorta. This error can be corrected by averaging the mean gradients derived from unaltered and temporally aligned simultaneous left ventricular-peripheral arterial pressure tracings. In 26 patients with aortic stenosis and simultaneous recordings of ascending aortic and femoral arterial pressure we compared this method with a simplified approach in which the peripheral arterial pressure is partially aligned by advancing it against the left ventricular pressure by 50% of the time delay of the simultaneously recorded upstrokes. Gradients measured this way predicted the true aortic valve gradients (left ventricular-ascending aortic) with a mean difference of +1.1 mm Hg (range = +10 to -5 mm Hg). We recommend use of this simplified method of correction because it predicts true aortic valve gradient equally well as the averaging technique (r = 0.977 vs. 0.979) and requires half the time and effort.     

Nomogram for calculation of left ventricular volumes.

A nomogram has been devised for the rapid derivation of left ventricular volumes from single-plane angiograms obtained in the 30 degrees right anterior oblique projection. The left ventricular volumes are derived from the use of the area-length formula of Dodge. The computed left ventricular volumes may then be adjusted to correspond to the actual volumes by an appropriate conversion chart.     

An improved noninvasive method for measurement of cardiac output and evaluation of left-sided cardiac valve incompetence

A time-saving method was developed to label red blood cells in vitro with 99mTc while avoiding centrifugation. After tin incubation, extracellular tin was oxidized by sodium hypochlorite, and EDTA was added for stabilizing the complex prior to 99mTc incubation. Labeling yields were 95%, and in vivo decay showed a high stability with a mean biologic half-life of eleven hours. The first-passage radionuclide technique for determination of cardiac output using the above-mentioned tracer was evaluated by using the left ventricle as area-of-interest with individual background correction after complete mixing of the tracer. This technique showed a high level of agreement with invasive methods. By combining this method for measurement of the forward stroke volume with the multigated equilibrium principle for determination of the total left ventricular stroke volume using similar background corrections, an exact evaluation of regurgitation fractions was obtained. In patients with aortic and mitral valve disease the noninvasive radionuclide technique gave similar but probably more accurate results as compared with contrast aortography and ventriculography. The radionuclide technique may be suitable for monitoring and selecting patients for surgical treatment.     

Heart rate influence on the systolic gradient across the stenotic aortic valve: theoretical evaluation and implications

Peak systolic gradient across the aortic value, measured invasively or noninvasively is used in many laboratories for estimation of the severity of the stenosis (= actual valve area). This study shows that when cardiac output is normal the gradient across the valve is influenced by heart rate (HR) apart from valve area. A rate-corrected peak systolic gradient (PSGc) is defined by the formula (formula; see text) and its importance for clinical decision making is demonstrated. The significance of bradycardia in the pathogenesis of syncope in aortic stenosis is discussed.     

Afterload reduction and cardiac output in patients after mitral valve surgery

Thirteen patients who had mitral valve surgery were studied within 3 hours after operation. The patients were divided into 2 groups: group A with initial low cardiac index (1.70 +/- 0.25), elevated left atrial pressure (16.5 +/- 6.7) and high peripheral vascular resistance (2623 +/- 789); group B with initial normal cardiac index (3.71 +/- 0.54), normal left atrial pressure (13 +/- 3.5) and normal peripheral vascular resistance (1223 +/- 303). In both groups the mean arterial pressure was elevated (98 +/- 8.8, 96 +/0 15.8). An infusion of nitroprusside to reduce the mean arterial pressure to either 80 mmHg or 10% below the initial value had different effects in each group. In group A, cardiac index (CI) increased by 23%, left atrial pressure (LAP) decreased by 20%, pulmonary artery pressure (PAP) by 35%, and peripheral vascular resistance (PRV) by 32%. In group B, CI decreased by 8%, LAP by 32%, PAP by 30% and PVR by 13%. When LAP returned to initial values after an infusion of blood with continued infusion of nitroprusside, CI increased in both groups (27%, 11%) and the PVR remained lower (40%, 29%). The study demonstrates the favorable effect on cardiac output of vasodilator therapy on patients with elevated blood pressure, impaired by left ventricular function and high LAP, after surgery on mitral valve. The optimal effect is achieved by keeping the LAP within normal limits.     

Usefulness of the Doppler mean gradient in evaluation of children with aortic valve stenosis and comparison to gradient at catheterization

To assess the usefulness of the Doppler mean gradient as a noninvasive indicator of the need for intervention, 33 children (ages 3 months to 20 years) with valvular aortic stenosis (AS) underwent a 2-dimensional and Doppler echocardiographic examination a median of 1 day before cardiac catheterization. The clinical decision for intervention was based on finding a catheterization peak-to-peak pressure gradient of greater than 75 mm Hg or from 50 to 75 mm Hg in the presence of symptoms or an abnormal exercise treadmill test result. Of the 33 patients, 23 required intervention. The decision for intervention was compared to the Doppler mean gradient, and the Doppler peak and mean gradients were compared to the catheterization peak-to-peak gradient. All 12 patients with a Doppler mean gradient greater than 27 mm Hg had intervention and had a catheterization peak-to-peak gradient of greater than or equal to 75 mm Hg. All 3 patients with a Doppler mean gradient less than 17 mm Hg had no intervention and had a peak-to-peak gradient less than 50 mm Hg. The remaining 18 patients with Doppler mean gradients between 17 and 27 mm Hg comprised an intermediate group in whom the Doppler mean gradient alone did not predict the need for intervention. From a chi-square table, a Doppler mean gradient greater than 27 mm Hg predicted the need for intervention with 100% specificity (no false positives) and 52% sensitivity (11 false negatives).(ABSTRACT TRUNCATED AT 250 WORDS)     

Assumed oxygen consumption based on calculation from dye dilution cardiac output: an improved formula

This study was performed because of observed differences betweendye dilution cardiac output and the Fick cardiac output, calculatedfrom estimated oxygen consumption according to LaFarge and Miettinen,and to find a better formula for assumed oxygen consumption.In 250 patients who underwent left and right heart catheterization,the oxygen consumption VO₂ (ml. min^–1) was calculatedusing Fick's principle. Either pulmonary or systemic flow, asmeasured by dye dilution, was used in combination with the concordantarteriovenous oxygen concentration difference. In 130 patients,who matched the age of the LaFarge and Miettinen population,the obtained values of oxygen consumption VO₂(dd) were comparedwith the estimated oxygen consumption values VO₂(lfm), foundusing the LaFarge and Miettinen formulae. The VO₂(lfm) was significantlylower than VO₂(dd); – 21.8 ±29.3 ml. min^–1(mean±SD),P<0.001, 95% confidence interval (95% CI) –26.9 to–16.7, limits of agreement (LA) –80.4 to 36.9. Anew regression formula for the assumed oxygen consumption VO₂(ass)was derived in 250 patients by stepwise multiple regressionanalysis. The VO₂(dd) was used as a dependent variable, andbody surface area BSA (m²), Sex (0 for female, 1 for male),Age (years), Heart rate (min^–1) and the presence of aleft to right shunt as independent variables. The best fittingformula is expressed as: VO₂(ass)=(157.3 x BSA+10.0 x Sex –10.5 x In Age+4.8) ml.min^–1, where In Age=the natural logarithm of the age.This formula was validated prospectively in 60 patients. A non-significantdifference between VO₂(ass) and VO₂(dd) was found; mean 20±23.4ml.min^–1,P=0.771, 95% CI= –4.0 to +8.0, LA –44.7 to +48.7.In conclusion, assumed oxygen consumption values, using ournew formula, are in better agreement with the actual valuesthan those found according to LaFarge and Miettinen's formulae.