Kelley C. Stewart

Loss of Adrenergic Augmentation of Diastolic Intra-LV Pressure Difference in Patients With Diastolic Dysfunction : Evaluation by Color M-Mode Echocardiography

OBJECTIVES The aim of this study was to evaluate the hypothesis that the adrenergic response of the intraventricular pressure difference (IVPD) is reduced in patients with preserved ejection fraction (EF) and diastolic dysfunction (DD). BACKGROUND In early diastole, there is a progressive IVPD extending from the left atrium (LA) to the left ventricular (LV) apex. In response to adrenergic stimulation, as occurs during exercise, the IVPD increases allowing rapid filling without an abnormal increase in LA pressure. Patients with heart failure with a reduced EF have impaired adrenergic augmentation of the IVPD. METHODS We studied 166 consecutive patients undergoing dobutamine stress echocardiography who had no inducible ischemia and an EF ≥50%, of which 21 had normal diastolic function, 14 had impaired relaxation (grade 1), 80 had pseudonormal filling (grade 2), and 51 had restrictive filling (grade 3). Color M-mode Doppler (CMMD) images of mitral inflow were obtained at rest and during low (10 μg/kg/min) and peak (20 to 40 μg/kg/min) doses of dobutamine. The total IVPD from the LA to LV apex, LA to mid-LV, and mid-LV to the LV apex were calculated using the CMMD data to integrate the Euler equation. RESULTS Total IVPD was not different between groups at rest. With dobutamine, the total IVPD increased by 2.20 ± 1.95 mm Hg in normal subjects and by only 0.73 ± 1.33 mm Hg, 1.84 ± 1.63 mm Hg, and 1.08 ± 1.57 mm Hg in patients with grades 1, 2, and 3 DD, respectively. This difference was due to a failure in augmentation of IVPD from the mid-LV to the LV apex, indicating reduced apical ventricular suction with DD, whereas the IVPD from the LA to the mid-LV responded similarly to dobutamine in normal subjects and those with DD. CONCLUSIONS In patients with preserved EF, DD is associated with a reduced adrenergic augmentation of the IVPD from the mid-LV to the LV apex, reflecting less apical suction.

Evaluation of LV Diastolic Function From Color M-Mode Echocardiography

OBJECTIVES this study evaluated early diastolic filling dynamics using a semiautomated objective analysis of filling velocities obtained from color M-mode echocardiography. BACKGROUND diastolic function can be evaluated from color M-mode echocardiography by measuring the early diastolic flow propagation velocity (Vp) from the slope of a single linear approximation of an isovelocity contour. However, this method has limitations and may not accurately represent diastolic filling. METHODS we used a semiautomated objective analysis of color M-mode echocardiograms from a development cohort of 125 patients with varying diastolic function to quantify left ventricular filling velocities. Early diastolic filling was not accurately described with a single propagation velocity; instead, the rapid initial filling velocity abruptly decelerated to a slower terminal velocity. Then, we evaluated a new measure of diastolic function in a separate group of 160 patients. RESULTS compared with normal filling, diastolic dysfunction with restricted filling had a lower initial velocity (53 ± 21 cm/s vs. 87 ± 29 cm/s, p < 0.001), and the deceleration point occurred closer to the mitral annulus (2.4 ± 0.6 cm vs. 3.1 ± 0.7 cm, p < 0.05). The product of the initial velocity and the distance to the deceleration point from the mitral annulus, indicating the strength of the early filling (Vs), was progressively reduced with diastolic dysfunction. In a separate validation cohort of 160 patients, Vs better recognized diastolic dysfunction (classified by reduced diastolic intraventricular pressure gradient, elevated pulmonary capillary wedge pressure, or elevated B-type natriuretic peptide) than Vp did. CONCLUSIONS early diastolic flow propagation occurs with an initial rapid velocity that abruptly decelerates to a terminal velocity. With diastolic dysfunction, the initial velocity is slower and the deceleration point occurs closer to the mitral annulus than with normal filling. A new parameter that combines these 2 effects (Vs) provides a more accurate assessment of diastolic function than the conventional propagation velocity.

Left ventricular vortex formation is unaffected by diastolic impairment

Normal left ventricular (LV) filling occurs rapidly early in diastole caused by a progressive pressure gradient within the ventricle and with a low left atrial pressure. This normal diastolic function is altered in patients with heart failure. Such impairment of diastolic filling is manifested as an abrupt deceleration of the early filling wave velocity. Although variations within the early filling wave have been observed previously, the underlying hydrodynamic mechanisms are not well understood. Previously, it was proposed that the mitral annulus vortex ring formation time was the total duration of early diastolic filling and provided a measure of the efficiency of diastolic filling. However, we found that the favorable LV pressure difference driving early diastolic filling becomes zero simultaneously with the deceleration of the early filling wave propagation velocity and pinch-off of the LV vortex ring. Thus we calculated the vortex ring formation time using the duration of the early diastolic filling wave from its initiation to the time of the early filling wave propagation velocity deceleration when pinch-off occurs. This formation time does not vary with decreasing intraventricular pressure difference or with degree of diastolic dysfunction. Thus we conclude the vortex ring pinch-off occurs before the completion of early diastole, and its formation time remains invariant to changes of diastolic function.

Estimation of Left Ventricular Wall Stiffness by Analysis of Late Diastolic Pressure Components

Left ventricular diastolic dysfunction (LVDD) is any abnormality in the filling of the left ventricle and is conventionally evaluated by analysis of the relaxation driven phase, or early diastole. LVDD has been shown to be a precursor to heart failure and the diagnosis and treatment for diastolic failure is less understood than for systolic failure. Diastole consists of two filling waves, early and late and is primarily dependent on ventricular relaxation and wall stiffness.Copyright

Left Ventricular Vortex Ring Dynamics and Their Association to Early Diastolic Filling

Diastolic dysfunction is the impairment of the filling in the left ventricle. Patients with left ventricular diastolic dysfunction (LVDD) lose the ability to adjust left ventricular filling properties without increasing left atrial pressure [1]. Although LVDD is very prevalent, it currently remains difficult to diagnose due to inherent atrioventricular compensatory mechanisms including increased heart rate, increased left ventricular (LV) contractility, and increased left atrial (LA) pressure. Although variations within the early diastolic filling velocity have been previously observed [2], the physical mechanism for the deceleration of the early filling wave is not understood.Copyright

Investigation of the Relationship Between Color M-Mode Early Diastolic Propagation Velocity and Left Ventricular Adverse Pressure Gradients

Left ventricular diastolic dysfunction (LVDD) and diastolic heart failure are conditions that affect the filling dynamics of the heart and affect 36% of patients diagnosed with congestive heart failure [1]. Although this condition is very prevalent, it currently remains difficult to diagnose due to inherent atrio-ventricular compensatory mechanisms including increased heart rate, increased left ventricular (LV) contractility, and increased left atrial pressure (LA). A greater comprehension of the governing flow physics in the left ventricle throughout the introduction of the heart’s compensatory mechanisms has great potential to substantially increase the understanding of the progression of diastolic dysfunction and in turn advance the diagnostic techniques.Copyright

A Relationship Between Pressure Fields and Flow Patterns During Left Ventricular Diastolic Dysfunction Using 2D Phase Contrast MRI

Left Ventricular Diastolic Dysfunction (LVDD) is a disease in which the heart is unable to properly fill the left ventricle before the systolic contraction pushes the blood out of the chamber into the rest of the body [1]. It is frequently characterized by elevated filling pressures within the heart. Over 70 million people in the United States with high blood pressure are at risk for LVDD [2], and numerous studies have shown a link between LVDD and heart failure. However, due to compensatory mechanisms early stage dysfunction can be difficult to diagnose.Copyright

Vortex Ring Formation in Wall-Bounded Domains

Vortex ring formation and propagation have been studied extensively in quiescent semi-infinite volumes. However, very little is known about the dynamics of vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the effect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube parallel to the piston cylinder arrangement which defined the confined downstream domain. Two different domains were studied with diameters twice and four times the size of the piston cylinder. A semi-infinite unbounded volume with no downstream cylinder was also investigated for comparison. The piston stroke-to-diameter ratio (L/D0 ) for the studied vortex rings was varied between 0.75 and 3 with corresponding Reynolds numbers, based on circulation, of approximately 500 to 8,000. Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV). The TRDPIV data were processed using an in-house developed cross-correlation PIV algorithm and post processed using Proper Orthogonal Decomposition to remove high frequency noise. The propagation velocity and vorticity were investigated and vortex identification was used to track the changing size, location, and circulation of the vortices. The combination of these parameters was used to investigate the effects of wall interaction on vortex ring formation and propagation.Copyright

A Hydrodynamic Efficiency Parameter as a Novel Left Ventricular Diastolic Dysfunction Diagnostic Metric

Numerous studies have shown that cardiac diastolic dysfunction and diastolic filling play a critical role in dictating overall cardiac health and demonstrated that the filling wave propagation speed is a significant index of the severity of diastolic dysfunction [1, 2]. However, the governing flow physics underlying the relationship between propagation speed and diastolic dysfunction are poorly understood. More importantly, currently there is no reliable metric to allow clinicians the ability to diagnose cardiac dysfunction on the basis of the wave filling speed.Copyright

A Novel Break Point Parameter as a Diagnostic Tool for Left Ventricular Diastolic Dysfunction

Cardiovascular disease is one of the leading causes of death worldwide and claims one out of every three deaths in the United States [1]. There is a greater need than ever for more accurate and robust diagnostic tools with the increasing number of deaths caused by this disease. Color M-mode echocardiography is a technique that is commonly used in the diagnosis of Left Ventricular Diastolic Dysfunction (LVDD).Copyright