Asymptomatic aortic stenosis: management revisited

Aortic stenosis (AS) is common and is the commonest reason for valve surgery in the Western hemisphere. Calcific or a degenerative process is the most common cause of this pathological process and increases with aging population. The current guidelines recommend aortic valve replacement (AVR) only for symptoms or LV dysfunction unless a concomitant cardiac surgery is planned There are no randomized studies to guide therapy. AVR is forbidden by guidelines in severe AS patients with no symptoms. The guidelines are based on an analysis of natural history studies of AS and risk and durability of AVR. We will analyze the basis of current recommendations, unreliability of symptoms for such an important decision and more contemporary data on the natural and unnatural history of asymptomatic aortic stenosis. Based on these data, we recommend that asymptomatic AS should not be a class III recommendation for AVR and surgical options should be considered in most of severe AS patients with high risk profiles.

Effect of respiration on the QT interval

This clinical study was undertaken to investigate the effect of respiration on the QT interval. The QT interval is affected by a variety of factors, including steady changes in heart rate, instantaneous changes in heart rate as in atrial fibrillation, and changes in autonomic tone. Respiration gives rise to cyclical changes in the instantaneous heart rate and autonomic tone. The effect of respiration on the QT interval was analyzed in 25 subjects in sinus rhythm. Cosinor analysis was used to estimate the amplitude of its change from the mean value, its statistical significance, and the timing of the maximum change. Thirteen (52%) subjects revealed significant respiratory change in the QT interval, being the shortest during inspiration in 10 of them. Its amplitude correlated positively with respiratory cycle length (r = .58, P < .01), but not with age, mean heart rate, or the amplitude of change in the RR interval. The mean amplitude of change in the QT interval was 0.8% compared to a change of 2.6% in the RR interval. There is a respiratory variation in the QT interval in subjects in sinus rhythm that is more prominent during slower respirations. However, the amplitude of change in the QT interval is small compared to the change in the RR interval.

Volume-rendered three-dimensional dynamic anatomy of the mitral annulus using a transesophageal echocardiographic technique

Mitral annulus anatomy and dynamics were evaluated in 12 subjects using a three-dimensional transesophageal echocardiographic technique. The mitral annular area, diameters and distance from the left ventricular apex were measured in end-diastole, mid-systole, end-systole and mid-diastole. The mitral annulus had its largest area in end-systole and the smallest area in end-diastole. The shape of the annulus changed during the cardiac cycle with the maximal change occurring in the diameters passing close to the middle of the mitral leaflets. In the vertical plane, the annulus had a shallow ski-slope shape, with the attachment of the anterior leaflet being farthest from the apex. In other words, the highest point of the annulus was situated anteromedially and was visualized in the long axis imaging plane.

Mitral E wave propagation as an index of left ventricular diastolic function. I: Its hydrodynamic basis

BACKGROUND AND AIMS OF THE STUDY

Left ventricular (LV) diastolic dysfunction is an early sign of myocardial disease and an important determinant of symptoms and prognosis in patients with various cardiovascular disorders. Evidence suggests the presence and clinical importance of abnormal LV diastolic function in patients with valvular heart diseases, but it is difficult to measure non-invasively. Mitral E wave propagation inside the left ventricle studied by analysis of digitized color M-mode and pulsed wave Doppler technique is a promising technique for the evaluation of LV relaxation. However, the precise mechanism of its transmission is not clearly defined. Understanding the precise hydrodynamic basis of E wave propagation would be helpful for its meaningful application to the evaluation of LV diastolic performance. This study investigates the hydrodynamic determinants of mitral E wave propagation in an in vitro setting.

METHODS AND RESULTS

Thirty-one sets of experiments were conducted in a linear, pulsatile left ventricle model with varying operative diastolic characteristics. The rate of transmission of the onset of the E wave was strongly related to operative LV diastolic stiffness (r = 0.93, p < 0.0001), and weakly to mean left atrial (LA) pressure (r = 0.46, p < 0.01), heart rate (r = 0.57, p < 0.01) and stroke volume (r = -0.58, p < 0.01) through an effect on operative LV diastolic stiffness. The peak of the E wave transmission was influenced not only by operative LV diastolic stiffness (r = 0.87, p < 0.0001), but also by the mean LA pressure, heart rate and stroke volume, in an independent fashion.

CONCLUSIONS

The rate of transmission of the onset of the mitral E wave is determined solely by operative LV diastolic stiffness, whereas that of the peak is also affected by the mean LA pressure, heart rate and stroke volume. Analysis of mitral E wave propagation in patients with valvular heart disease may give clinically useful insights into LV diastolic function.

Severe bioprosthetic tricuspid valve stenosis with systolic antegrade flow across the tricuspid valve

We report the anatomic and hemodynamic details of severe stenosis of a bioprosthetic tricuspid valve studied by transthoracic and transesophageal echocardiography. This patient also had antegrade systolic flow across the tricuspid valve due to a combination of severe tricuspid valve stenosis and poor right ventricular systolic function.

Mitral E wave propagation to the left ventricular outflow tract. II: Evaluation of left ventricular filling pressures and diastolic stiffness from an analysis of their amplitude and duration in a modeled human left ventricle

BACKGROUND AND AIMS OF THE STUDY

The rate of mitral E wave propagation inside the left ventricle is related to the rate of left ventricular (LV) relaxation. However, the relationship of the amplitude and duration of the transmitted E wave (EOT wave) to the LV diastolic properties is not known. The hypothesis that the amplitude and duration of the EOT wave is related to the LV filling pressures and its diastolic properties was tested in an in vitro setting of modeled left ventricle.

METHODS AND RESULTS

Thirty-one sets of experiments were conducted in a pulsatile left ventricle model with varying LV filling pressures and operative diastolic characteristics. The EOT wave amplitude correlated with the mean left atrial pressure (r = 0.86, p < 0.0001), LV end-diastolic pressure (r = 0.89, p < 0.0001) and average LV diastolic stiffness (r = 0.38, p = 0.05). The EOT wave duration was not related to any of these measures of LV diastolic function, but E wave duration and EOT/E wave duration ratio were significantly related to LV diastolic stiffness (r = -0.88 and 0.71 respectively, both p < 0.0001). Multivariate equations were developed from the amplitudes and durations of E and EOT waves to predict left atrial and LV end-diastolic pressures and LV diastolic stiffness with a high degree of confidence (cumulative R values 0.92, 0.97 and 0.92 respectively).

CONCLUSIONS

These in vitro findings indicate that LV filling pressures and operative diastolic stiffness may potentially be derived from the amplitudes and durations of diastolic flow waves at the mitral inflow and LV outflow. However, these findings need to be confirmed in in vivo settings.

Determinants of the rate of right ventricular pressure rise by Doppler echocardiography: potential value in the assessment of right ventricular function

Tricuspid regurgitation (TR) is common and the rate of right ventricular (RV) pressure rise in early systole can be obtained from the TR velocity profile. Right ventricular function has important implications in patients with valvular heart disease. Fifty five patients with mild or moderate TR and a wide range of pulmonary artery (PA) pressures were studied. The RV dP/dt was obtained as the ratio of the calculated rise in RV pressure from 0.5 m/s to 1.5 m/s of the TR velocity signal (8 mmHg based on simplified Bernoulli equation) to the time taken for this change. The RV dP/dt correlated positively with PA systolic pressure (r = 0.73, p < 0.001), tricuspid anular plane systolic excursion which is an echocardiographic index of RV ejection systolic function (r = 0.45, p < 0.001) and left ventricular (LV) fractional shortening (r = 0.40, p < 0.01). Multivariate analysis showed that all these three parameters independently influenced RV dP/dt (multivariate R = 0.83) accounting for 69% of its variability. In conclusion, it is suggested that right ventricular dP/dt is easily obtainable from Doppler TR velocity signal. It is influenced independently in a positive manner by PA systolic pressure and RV and LV systolic function. Despite its predominant dependence on PA systolic pressure, it may give useful insight into RV systolic function for a given level of PA pressure. It may also be useful for longitudinal follow up of the RV function in patients with heart disease.

A new Doppler method for assessing left ventricular diastolic stiffness based on principles of flow wave propagation: mathematical basis and review of the method

Color flow imaging shows that the transmitral flow is initially directed to the left ventricular (LV) apex and then turns around facing the aortic valve. A pulsed wave Doppler sample placed in the LV outflow tract (LVOT) records two peaks of diastolic flow waves, Er and Ar waves, which follow E and A waves of the transmitral flow respectively. The Er and Ar waves represent transmitted E and A flow waves to the LVOT. Our preliminary clinical and hemodynamic data in human subjects have shown that the A-Ar interval, which is the time taken for the A velocity wave to propagate from the mitral valve to the LVOT, is shorter in those with LV hypertrophy (LVH), the aged and those with elevated LV late diastolic stiffness, suggesting faster A wave transmission in those with stiffer ventricles. We also have shown that velocity and pressure waves propagate similarly in the arterial system. This led to the hypothesis that the A wave transmission inside the LV may follow the principles described in the Moens-Korteweg equation, or a modification of it, and the velocity of A wave transmission inside the LV may reflect its late diastolic stiffness. Studies designed to test this hypothesis in a pulsatile LV model showed a linear relationship between the rate of diastolic flow wave propagation inside the LV and its stiffness. These preliminary data suggest that the velocity of A wave transmission inside the LV reflects LV late diastolic stiffness non-invasively. It is expected to be independent of a direct effect of heart rate and of preload.