Left Ventricular Outflow Tract Flow Research Articles

4D flow MRI and T1 -Mapping: Assessment of altered cardiac hemodynamics and extracellular volume fraction in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is associated with altered hemodynamics in the left ventricular outflow tract (LVOT) and myocardial tissue abnormalities such as fibrosis. The aim of this study was to quantify changes in LVOT 3D hemodynamics and myocardial extracellular volume fraction (ECV, measure of fibrosis) and to investigate relationships between elevated flow metrics and left ventricular (LV) tissue abnormalities. Cardiac magnetic resonance imaging (MRI) including 4D flow (field strength = 1.5T, resolution = 2.1-4.0 × 2.1-4.0 × 2.5-3.2 mm(3) ; venc = 150-250 cm/s; TE/TR/FA = 2.2-2.5msec/4.6-4.9msec/15°) for the in vivo assessment of 3D blood flow velocities with full coverage of the LVOT was applied in 35 patients with HCM (54 ± 15 years) and 10 age-matched healthy controls (45 ± 14 years). In addition, pre- and postcontrast myocardial T1 -mapping (resolution = 2.3 × 1.8 mm, slice thickness = 8 mm, TE/TR-FA = 1.0-1.1msec/2.0-2.2msec/35°) of the LV (basal, mid-ventricular, apical short axis) was performed in a subgroup of 23 HCM patients. Analysis included the segmentation of the LVOT and quantification of peak systolic LVOT pressure gradients and rate of viscous energy loss EL ' as well as left ventricular ECV. HCM patients demonstrated significantly elevated peak systolic LVOT pressure gradients (21 ± 16 mmHg vs. 9 ± 2 mmHg) and energy loss EL ' (3.8 ± 2.5 mW vs. 1.5 ± 0.7 mW, P < 0.005) compared to controls. There was a significant relationship between increased LV fibrosis (ECV) with both elevated pressure gradients (R(2) = 0.44, P < 0.001) and energy loss EL ' (R(2) = 0.46, P < 0.001). The integration of 4D-flow and T1 -mapping-MRI allowed for the evaluation of tissue and flow abnormalities in HCM patients. Our findings suggest a mechanistic link between abnormal LVOT flow, increased LV loading, and adverse myocardial remodeling in HCM.

The Yasui operation for patients with adequate-sized ventricles and ventricular septal defect associated with obstructions of the aortic arch and left ventricular outflow tract

To review the surgical outcome of the Yasui operation in patients with adequate-sized ventricles and ventricular septal defect (VSD) associated with obstructions of the aortic arch and left ventricular outflow tract (LVOT). Since 1985, 17 patients have undergone the Yasui operation at our institution. Interrupted aortic arch was present in 11 patients and coarctation of the aorta/hypoplastic arch was present in 6. Twelve patients had aortic stenosis, and 5 patients had aortic atresia. The minimum diameter of the LVOT and the z-score in patients with aortic stenosis were 3.7 ± 0.4 mm and -9.2 ± 1.2, respectively. Primary repair was performed in 6 patients, and 11 patients were staged, with bilateral pulmonary artery banding (PAB) in 8, arch repair with PAB in 2 and Norwood operation in 1. The mean age and body weight at the time of the Yasui operation was 4.7 ± 5.3 months and 4.5 ± 1.8 kg, respectively. The ascending aorta and aortic arch were reconstructed by Damus-Kaye-Stansel (DKS) anastomosis with graft interposition in 2, DKS with direct anastomosis in 6 and Norwood-type reconstruction in 9. VSD was enlarged in 6 patients. Right ventricle to pulmonary artery continuity was established with a valved conduit in 14 patients, the Lecompte manoeuvre in 2 patients and another method in 1 patient. The mean duration of the follow-up was 7.6 ± 9.2 years. There was 1 early death due to myocardial infarction and 1 late death due to non-cardiac cause. The actuarial survival at 10 years was 87.8%. Six patients underwent reoperation, including 5 conduit exchanges, 2 LVOT repairs and 2 aortic arch repairs. The freedom from reoperation for all causes at 5 and 10 years were 71.3 and 28.5%, respectively. In the last echo study, LVOT flow velocity was 1.2 ± 0.8 m/s, and neoaortic valve regurgitation was mild in 1 patient and trivial or absent in the remaining patients. The results of the Yasui operation were excellent, showing low mortality and good mid-term left ventricular function without outflow tract stenosis or neoaortic valve insufficiency. Bilateral PAB as initial palliation is a useful option in symptomatic neonates.

Papillary Fibroelastomas in 19 Patients With Hypertrophic Cardiomyopathy Undergoing Septal Myectomy

The aim of this study was to characterize papillary fibroelastomas (PFEs) and their clinical sequelae in patients with hypertrophic cardiomyopathy (HCM). PFE is the third most common primary cardiac tumor and can be associated with neurologic events. Because endocardial trauma has been implicated in its pathogenesis, the occurrence and outcomes of PFEs in patients with HCM were retrospectively analyzed in this study. Echocardiograms and medical records were reviewed for characteristics of PFEs in 19 patients with HCM who underwent septal myectomy. PFEs were detected preoperatively by transthoracic echocardiography in 5 patients, by transesophageal echocardiography in 2 patients, and perioperatively in 12 others. Three patients had previously undergone septal myectomy. Although the majority of patients (n = 11 [58%]) had 1 PFE, the number ranged from 1 to >40 (median, 1.0). PFEs arose on the aortic valve (47%), in the left ventricular outflow tract (42%), and in the right heart (11%). In this study of patients with HCM, 89% of PFEs were located on the aortic valve or in the left ventricular outflow tract compared with about 40% to 50% in prior studies of PFEs in general. This suggests that endocardial trauma due to turbulent left ventricular outflow tract flow may predispose to PFE development. Because of the high incidence of neurologic events among patients with HCM, PFEs may not be innocuous and should be searched for in patients with HCM and unexplained neurologic events.

In vitro hemodynamic investigation of the embryonic aortic arch at late gestation

This study focuses on the dynamic flow through the fetal aortic arch driven by the concurrent action of right and left ventricles. We created a parametric pulsatile computational fluid dynamics (CFD) model of the fetal aortic junction with physiologic vessel geometries. To gain a better biophysical understanding, an in vitro experimental fetal flow loop for flow visualization was constructed for identical CFD conditions. CFD and in vitro experimental results were comparable. Swirling flow during the acceleration phase of the cardiac cycle and unidirectional flow following mid-deceleration phase were observed in pulmonary arteries (PA), head-neck vessels, and descending aorta. Right-to-left (oxygenated) blood flowed through the ductus arteriosus (DA) posterior relative to the antegrade left ventricular outflow tract (LVOT) stream and resembled jet flow. LVOT and right ventricular outflow tract flow mixing had not completed until ∼3.5 descending aorta diameters downstream of the DA insertion into the aortic arch. Normal arch model flow patterns were then compared to flow patterns of four common congenital heart malformations that include aortic arch anomalies. Weak oscillatory reversing flow through the DA junction was observed only for the Tetralogy of Fallot configuration. PA and hypoplastic left heart syndrome configurations demonstrated complex, abnormal flow patterns in the PAs and head-neck vessels. Aortic coarctation resulted in large-scale recirculating flow in the aortic arch proximal to the DA. Intravascular flow patterns spatially correlated with abnormal vascular structures consistent with the paradigm that abnormal intravascular flow patterns associated with congenital heart disease influence vascular growth and function.

Echocardiographic indices in normal German shepherd dogs

Sixty clinically normal German shepherd dogs, 31 males and 29 females, ranging in age from 1 and 5 years and with a body weight ranging from 22 to 37.2 kg, were examined by the two-dimensional mode, M-mode, and Doppler echocardiography. In Doppler mode, the mitral valve flows were obtained, where the aim was to determine the velocity peaks and ratios of the E and A waves and the mitral E wave deceleration time. The velocity peaks were obtained for the tricuspid, pulmonary and aortic valves. On the left ventricular outflow tract flow, the time velocity integral and aortic cross-sectional area was used to calculate the cardiac output. A statistically significant correlation with the body weight was found for the systolic left atrial and diastolic aortic diameter on two-dimensional mode. On M-mode, there was a significant correlation between the body weight and the systolic left atrium and diastolic aortic dimension, systolic and diastolic left ventricular, septal and posterior wall dimensions. Doppler echocardiography showed that there was no significant correlation between the body weight and the mitral, tricuspid, pulmonary and aortic valves flows. These results demonstrate that it is important to know the normal echocardiographic values for German shepherd dogs because there are some characteristics peculiar to this particular breed. The data obtained is expected to be helpful for studies on small animal cardiology.

Normal Mitral and Aortic Valve Areas Assessed by Three- and Two-Dimensional Echocardiography in 168 Children and Young Adults

Our purpose was to investigate the effects of body size on the sizes of mitral (MV) and aortic valve (AV) areas by three-dimensional (3-D) and two-dimensional (2-D) echocardiography and to create the normal values for 3-D echocardiography. A total of 168 healthy subjects aged 2-27 years were studied by digitized 3-DE, 2-DE, and Doppler echocardiography.3-D echocardiography was performed by using rotational acquisition of planes at 18 degrees intervals from a parasternal view with electrocardiogram gating and without respiratory gating. The annular levels of MV and AV were identified from short-axis cut planes and their areas were measured by planimetry. The diameters of mitral annulus, left ventricular outflow tract (LVOT), and aortic annulus were measured by 2-DE from the apical and parasternal long-axis views. Flow indices were measured by Doppler from MV inflow and the flow in LVOT and in the ascending aorta. Both MV and AV annular areas increased linearly in relation to body size. In the total study group the estimated areas for MV were 5.2 +/- 0.9 cm2/m2 by 3-DE, 3.7 +/- 0.5 cm2/m2 by 2-DE, and 2.0 +/- 0.4 cm2/m2 by continuity equation. The respective values for AV were 2.7 +/- 0.5, 2.1 +/- 0.3, and 1.8 +/- 0.4 cm2/m2. MV velocity time integral (VTI)/ascending aorta VTI increased from 0.80 (0.26) to 0.95 (0.23) with increased body surface area (BSA), whereas MV VTI/LVOT VTI was 1.2 (0.2) in all BSA groups. MV and AV annulus areas increase linearly in relation to body size. 3-DE gives greater estimates for the areas than 2-DE and Doppler equation methods. The data obtained from 168 healthy subjects may serve as a reference for clinical use in patients with various cardiac abnormalities.

Prosthetic mitral regurgitation can be mimicked by Doppler color flow mapping: Avoiding misdiagnosis

Objectives We sought to characterize a region of apparent systolic flow resembling mitral regurgitation (MR) in patients with mechanical disk mitral prostheses as artifact. Background Diagnosing MR in the presence of mechanical prostheses is challenging. Occasionally, important MR is suggested by a substantial region of systolic Doppler color flow in an acoustically shadowed region of the left atrium when, in fact, only trace MR exists. We hypothesized this pseudo-MR is caused by acoustic mirroring of the left ventricular outflow tract (LVOT) flow by sound reflected off the prosthesis, projecting flow into the left atrium because of longer transit time. Methods We reviewed 19 patients with mechanical mitral valves and trace MR by transesophageal echocardiography who had transthoracic echocardiography studies within 1 week (group A), and prospectively studied 22 consecutive patients by transthoracic echocardiography with subtle transducer angulation variation to detect pseudo-MR and characterize it by pulsed Doppler (group B). Results In group A, 12 of 19 patients had evidence of pseudo-MR on review of their transthoracic echocardiograms, absent by transesophageal echocardiography. In group B, this pseudo-MR signal was present in 13 of 22 patients, with velocity and timing by pulsed Doppler comparable with LVOT flow (onset at 125 ± 27 milliseconds vs 135 ± 11 milliseconds from QRS, P = not significant). The angle between the mitral plane and the LVOT, which determines whether this mirroring can occur, was smaller for patients with pseudo-MR. Conclusion Artifactual pseudo-MR is often seen with mechanical mitral prostheses. Its behavior and sensitivity to geometric relationships are consistent with mirroring of LVOT flow. Practically, potential misdiagnosis can be readily avoided by pulsed Doppler sampling, sparing the patient further procedures.

Biphasic left ventricular outflow and its mechanism in hypertrophic obstructive cardiomyopathy

Background Biphasic systolic velocity in the left ventricular (LV) outflow tract (LVOT) occurs in hypertrophic obstructive cardiomyopathy (HOCM). The cause and importance of this observation remain poorly understood. Methods A total of 25 patients with HOCM were matched to 30 control subjects. A function derived from the relation of flow in the proximal descending aorta to that in the LVOT was used to estimate the LVOT systolic flow rate in HOCM. Patients with HOCM were grouped by absence (group I) or presence (group II) of biphasic LVOT velocity. Results Biphasic LVOT velocity was associated with biphasic estimated LVOT outflow ( P = .002). The LVOT pressure gradient was inversely related to LV outflow rate at the time of the peak gradient ( r = −.64, P < .001). Dobutamine increased the gradient and reduced LVOT outflow at the time of the peak gradient. In group II, mitral-septal separation occurred despite a LVOT gradient (36 mm Hg). Conclusion Biphasic LVOT flow in HOCM occurs and may be caused by “afterload mismatch.” The late systolic increase in flow is related to mitral-septal separation. Resolution of systolic anterior motion occurs despite a persistent LVOT pressure gradient, implying a role for forces other than pressure differences.

Impact of left ventricular outflow tract area on systolic outflow velocity in hypertrophic cardiomyopathy: A real-time three-dimensional echocardiographic study

ObjectivesThe aim of this study was to use real-time three-dimensional echocardiography (3DE) to investigate the quantitative relation between minimal left ventricular (LV) outflow tract area (ALVOT) and maximal LV outflow tract (LVOT) velocity in patients with hypertrophic obstructive cardiomyopathy (HCM). BackgroundIn patients with HCM, LVOT velocity should change inversely with minimal ALVOTunless LVOT obstruction reduces the pumping capacity of the ventricle. MethodsA total of 25 patients with HCM with systolic anterior motion (SAM) of the mitral valve leaflets underwent real-time 3DE. The smallest ALVOTduring systole was measured using anatomically oriented two-dimensional “C-planes” within the pyramidal 3DE volume. Maximal velocity across LVOT was evaluated by two-dimensional Doppler echocardiography (2DE). For comparison with 3DE ALVOT, the SAM-septal distance was determined by 2DE. ResultsReal-time 3DE provided unique information about the dynamic SAM-septal relation during systole, with ALVOTranging from 0.6 to 5.2 cm2(mean: 2.2 ± 1.4 cm2). Maximal velocity (v) correlated inversely with ALVOT(v = 496 ALVOT−0.80, r = −0.95, p < 0.001), but the exponent (−0.80) was significantly different from −1.0 (95% confidence interval: −0.67 to −0.92), indicating a significant impact of small ALVOTon the peak LVOT flow rate. By comparison, the best correlation between velocity and 2DE SAM-septal distance was significantly (p < 0.01) poorer at −0.83, indicating the superiority of 3DE for assessing ALVOT. ConclusionsThree-dimensional echocardiography-measured ALVOTprovides an assessment of HCM geometry that is superior to 2DE methods. These data indicate that the peak LVOT flow rate appears to be significantly decreased by reduced ALVOT. Real-time 3DE is a potentially valuable clinical tool for assessing patients with HCM.

Doppler mirror image artifacts mimicking mitral regurgitation in patients with mechanical bileaflet mitral valve prostheses.

To characterize the origin and mechanisms of generation of Doppler mirror images in the left atrium observed in patients with mechanical bileaflet mitral valve prosthesis. We hypothesized that these systolic colour Doppler images are artifactual and generated by reflection of the left ventricular outflow tract flow at the leaflet of the mitral valve prosthesis. Fifty patients with mechanical bileaflet mitral valves were prospectively examined by means of transthoracic Doppler-echocardiography. From different apical views, the left atrium was carefully interrogated for systolic colour flow signals, which were further analysed by pulsed wave Doppler. In all patients, a systolic colour Doppler signal was detected in the left atrium. Pulsed wave Doppler analysis revealed a low velocity signal (= mirror image) corresponding to the shape and duration of the left ventricular outflow tract signal. The peak velocities of these mirror images, however, were consistently lower than the velocities obtained from the left ventricular outflow tract. In addition, if paravalvular mitral valve leakage was present, a high velocity signal identical to the duration of mitral regurgitation time was detected outside the ring of the prosthesis. Mirror image artifacts mimicking mitral regurgitation occur in patients with mechanical mitral valves prosthesis. As mirror image artifacts can be specifically identified by analysis of shape. velocity, and duration of pulsed wave Doppler spectra, their identification will help to avoid misinterpretation of both spectral and colour Doppler signals in patients with prosthetic mitral valves.

Correction of anterior mitral prolapse: Results of chordal transposition

From 1986 to 1992 102 mitral valve repairs were done for mitral regurgitation due to a degenerative disease. Forty-eight patients had an anterior prolapse or prolapse of both leaflets at initial presentation and underwent chordal transposition from the mural leaflet to the anterior leaflet. The corrective procedure was completed by polytetrafluoroethylene or pericardial posterior annuloplasty. Operative mortality was 2.9%, and follow-up (average 22 months) was 100% complete. There were three postreconstruction valve replacements (one earlier and two later) for a probability of freedom from reoperation of 91.5% +/- 5.2% at 3 years. Freedom from all morbidity was 85.5% +/- 5.5% at 3 years. Postoperative echocardiographic studies demonstrated a good mitral valve function: (1) Eighty-seven percent of patients presented no or mild residual regurgitation; (2) transmitral flow indexes were within the norm; (3) left ventricular outflow tract flow was normal in all patients. This study shows that chordal transposition is a safe and effective technique for prolapse of anterior or both leaflets and improves the chances of repair in patients with mitral degenerative disease.

Dynamic changes in left ventricular outflow tract flow velocities after amyl nitrite inhalation in hypertrophic cardiomyopathy

Doppler echocardiography was performed in 21 patients with hypertrophic cardiomyopathy (HC), in nine patients with no evidence of left ventricular (LV) hypertrophy by two-dimensional echocardiography, and in five patients with systemic hypertension and concentric LV hypertrophy. The LV outflow tract (LVOT) peak velocity was recorded by continuous wave Doppler technique at rest and after amyl nitrite inhalation. The LVOT pressure gradient was calculated by the modified Bernoulli equation. A significant increase in heart rate and a drop in systolic blood pressure were observed in all patients after amyl nitrite inhalation; no adverse effects were encountered. The peak LVOT velocity and pressure gradient increased significantly after provocation in all patients, but the increase was much more pronounced in patients with HC (peak LVOT velocity increased from 2.2 ± 0.8 to 4.3 ± 1.0 m/sec and peak gradient increased from 22 ± 17 to 78 ± 36 mm Hg). The Doppler spectral signal in patients with HC demonstrated a characteristic contour, with peak velocity occurring in late systole. However, the observed increase in LVOT peak velocity was not statistically different between treated (with β-blockers and calcium blockers) and untreated patients with HC. We conclude that LVOT peak velocity and pressure gradients in patients with HC can be readily assessed by Doppler echocardiography both at rest and after amyl nitrite inhalation. The dynamic changes in LVOT velocity induced by this provocation have certain characteristic features in obstructive HC but appear to be independent of the medical regimen used, at least in the dosages tested in our study.

Doppler color flow mapping studies of jet formation and spatial orientation in obstructive hypertrophic cardiomyopathy

To help clarify the mechanism of outflow tract obstruction and systolic anterior motion of the anterior leaflet of the mitral valve and their relation to the geometry of the left ventricle, we studies left ventricular outflow tract flow in 20 patients with hypertrophic cardiomyopathy (HCM) using two-dimensional Doppler flow mapping. We compared our results with outflow tract flow in 10 patients with isolated valvular aortic stenosis, (AS) and with those in 10 healthy volunteers. In HCM, a 94- to 145-degree angle (mean 111.4 ± 11.9 degrees) developed between the direction of left ventricular outflow tract flow acceleration and aortic valve outflow, resulting in posterolaterally directed left ventricular outflow jets. The angle of the outflow jet and the peak velocity of the jet measured with continuous wave Doppler (as an indicator of the severity of obstruction) correlated well ( r = −0.81, SEE = 7.8 degrees). Jet narrowing during ejection measured just proximal to the point of systolic anterior motion was 42 ± 11% in HCM and was outflow occurred proximal to systolic anterior motion of the mitral valve, and color M-mode demonstrated temporal and spatial flow acceleration proximal to systolic anterior motion, providing evidence for obstruction at that site. In AS, left ventricular outflow tract jets were more parallel to the axis of aortic outflow (129 to 153 degree, 138.4 ± 8.1 degrees). Jet narrowing was only 8 ± 5% compared to HCM (both p < 0.05), and flow acceleration occurred proximal to the stenotic valve. In normal subjects, turbulent jets were not observed and the angle between left ventricular outflow tract flow and aortic flow was 149.6 ± 2.5 degrees. Our results are consistent with a venturi effect proximal to the mitral valve contributing to the development of systolic anterior motion and outflow tract obstruction, and highlight the importance of ventricular geometry as a determinant of obstruction in HCM.

Noninvasive evaluation of aortic stenosis severity utilizing Doppler ultrasound and electrical bioimpedance

Aortic valve area was calculated noninvasively in 30 patients with aortic stenosis undergoing cardiac catheterization. Continuous wave Doppler ultrasound was employed to estimate the mean transvalvular pressure gradient. The mean left ventricular outflow tract flow velocity and cross-sectional area were determined from pulsed Doppler and two-dimensional ultrasound recordings. Electrical Irans-thoracic bioimpedance cardiography performed simultaneously with the ultrasonic study and repeated at the time of catheterization measured heart rate, systolic ejection period and cardiac output. These noninvasive data permitted calculation of aortic valve area using the Gorlin equation (range 0.21 to 1.75 cm2) and the continuity equation (range 0.25 to 1.9 cm2). Subsequent cardiac catheterization showed valve area to range from 0.21 to 1.75 cm2.The mean Doppler pressure gradient estimate was highly predictive of the gradient measured at catheterization (r = +0.92, SEE = 10). Bioimpedance cardiac output measurements agreed with the average of Fick and indicator dye estimates (r = +0.90, SEE = 0.52). Valve area estimates utilizing continuous wave Doppler ultrasound and electrical bioimpedance were superior (r = +0.91, SEE = 0.12) to estimates obtained utilizing the continuity equation (r = +0.76, SEE = 0.29) and were more reliable in the detection of patients with severe aortic stenosis (9 of 11 versus 6 of 11).These data show that 1) electrical bioimpedance methods accurately estimate cardiac output in the presence of aortic stenosis; 2) the hybridized bioimpedance-Doppler ultrasound method yields accurate estimates of aortic stenosis area; and 3) the speed, accuracy and cost-effectiveness of aortic stenosis evaluation may be unproved by this hybridized approach.