Quantitative assessment of systolic and diastolic ventricular function with tissue Doppler imaging after Fontan type of operation

International Journal of Cardiology 102 (2005) 61 – 69 www.elsevier.com/locate/ijcard

Quantitative assessment of systolic and diastolic ventricular function with tissue Doppler imaging after Fontan type of operationB Antonio Vitarelli*, Ysabel Conde, Ester Cimino, Ilaria D’Angeli, Simona D’Orazio, Franca Ventriglia, Giovanna Bosco, Vincenzo Colloridi Adult and Pediatric Cardiology, bLa SapienzaQ University, Rome, Italy Received 29 July 2003; received in revised form 30 March 2004; accepted 2 April 2004 Available online 23 November 2004

Abstract Background: There is evidence that binappropriate hypertrophyQ of the single left ventricle, which occurs as a result of acute preload reduction, leads to adverse consequences on ventricular function. However, a systematic study of the capability of tissue Doppler imaging (TDI) to assess systolic and diastolic ventricular functions after the Fontan procedure is still missing. Methods: Twenty-four postoperative patients aged 12–33 years were prospectively evaluated with two-dimensional echocardiography equipped with TDI capabilities. Nineteen age-matched normal subjects were selected as controls. Good-quality echoes for the measurement of ejection fractions were available in 21 patients. Ten patients (group 1) had systolic dysfunction (ejection fraction b50%), and 11 patients (group 2) had normal systolic function. Peak systolic and diastolic wall velocities were acquired from the two-chamber view in the myocardia and mitral annulus. Results: Compared with controls, the Fontan patients had a significantly reduced peak systolic velocity at wall and annulus sites. A linear correlation existed between ejection fraction and systolic myocardial velocity from the annular sites. Group 1 patients had lower wall velocities and lower annulus velocities both in systole and diastole. Group 2 patients had preserved systolic velocities but decreased regional and annular early diastolic velocities, suggesting impaired filling. Multiple correlation analysis showed a relation between peak early diastolic mitral velocity and ventricular ejection fraction, mean mitral annular motion at systole, mass/volume ratio, and the number of years post Fontan revision. Conclusions: Myocardial velocities recorded after the Fontan operation give insight into systolic and diastolic ventricular functions. The peak systolic mitral annular velocity correlated well with the ventricular ejection fraction. The peak early diastolic velocity and the ratio between the early and late diastolic mitral annular velocity are reduced and reflect diastolic dysfunction even in the presence of normal systolic ejection fraction. D 2004 Published by Elsevier Ireland Ltd. Keywords: Tissue Doppler echocardiography; Ventricular function; Single ventricle; Tricuspid atresia; Fontan operation

1. Introduction Fontan and Baudet [1] first reported a successful total right-sided cardiac bypass in patients with a single funcB Presented in part at the Fifth EuroEcho meeting, Nice, France, December 5–8, 2001. * Corresponding author. Via Lima 35, Rome 00198, Italy. Tel.: +39 6 85301427; fax: +39 6 8841926. E-mail address: [email protected] (A. Vitarelli).

0167-5273/$ - see front matter D 2004 Published by Elsevier Ireland Ltd. doi:10.1016/j.ijcard.2004.04.008

tional ventricle in 1971. Since then, advances in operative technique and postoperative management have been accompanied by an improvement in early survival [2–4]. As more patients survive the operation and as the duration of followup increases, physicians are becoming increasingly aware of a continued risk of late failure of the Fontan circulation. A progressive deterioration in functional status may occur and the absence of other predicting risk factors suggests that the Fontan state itself or the transition to it is the risk factor for such decline. There is evidence that the binappropriate

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hypertrophyQ of the left ventricle, which occurs as a result of acute preload reduction, leads to adverse consequences manifested by prolonged isovolumic relaxation time, reduction in early rapid filling, abnormal wall motion, and intracavitary flow during isovolumic relaxation [5–11]. Tissue Doppler imaging (TDI) is a new echocardiographic technique that records myocardial velocities during the cardiac cycle [12–14]. Both the systolic and diastolic velocities can be recorded quantitatively by TDI and thereby provide a new way of assessing ventricular function. The conventional echocardiographic methods for assessing cardiac function are based on endocardial movement and/or wall thickening and have several limitations, especially in cases of unsatisfactory echo quality. Assessment of cardiac function by TDI may be more sensitive than traditional methods. Previous studies from our laboratory and others have described this technique as a feasible method of assessing systolic and diastolic left ventricular function [15–19]. However, a systematic study on the capability of TDI to assess systolic and diastolic ventricular function after the Fontan operation is still missing. The aim of the present study is to evaluate the effects of the Fontan procedure on the TDI velocity profile of the left ventricle during systole and diastole and to compare them with standard echocardiographic indexes.

2. Materials and methods 2.1. Population Twenty-four patients (15 males and 9 females) who underwent the Fontan procedure at mean (S.D.) 7.3 (4.1) (range 1.8–13.7) years old were studied at 7.4 [2,8] years after the operation. Ten of these had double inlet ventricle, 13 had tricuspid atresia (with concordant ventriculo-arterial connection in 11 and discordant connection in 2), and 1 had a more complex lesion (including atresia of an atrioventricular valve other than typical tricuspid atresia). Total cavopulmonary anastomosis was performed in five patients, and atriopulmonary anastomosis in nineteen. None of the Fontan patients had baffle leaks or a shunt through a surgically created fenestration. Patients with a single ventricle other than the left ventricular type were excluded from study. In addition, patients were excluded if they were receiving antiarrhythmic medication other than digoxin at the time of the study, were not in sinus rhythm, had insufficiency of atrioventricular or arterial valves that was greater than that of a mild degree as assessed by color Doppler echocardiography, or had a permanent pacemaker. Nineteen age-matched healthy subjects without a history of cardiac disease and who had normal findings on resting electrocardiogram (ECG) and echocardiography served as controls.

2.2. Echocardiography The patients were examined in the left lateral decubitus position with a Toshiba 390A (Tokyo, Japan) phased array system equipped with TDI technology. Measurements of different cardiac chambers were made according to established criteria [20]. Fractional shortening was taken as the percentage of reduction in ventricular cavity dimension at end systole with respect to that at end diastole. The ejection fraction was calculated as the percentage of change in ventricular chamber volumes between diastole and systole from apical four- and two-chamber views with a modified Simpson method. Left ventricular mass index was calculated and the mass/volume ratio was determined. Endsystolic left ventricular meridional wall stress (ESSm) and circumferential wall stress (ESSc) were obtained [21–23]. Trans A–V valve Doppler flow velocities were recorded at a speed of 100 mm/s from the apical four-chamber view with use of the same machine and transducer in the pulsed wave Doppler mode, with the sample volume positioned at the tips of the A–V valve leaflets. Peak early and late diastolic velocities were measured. Deceleration time was calculated [24] as the time interval from peak E to the extrapolation of the early deceleration phase to the zero line. Left ventricular isovolumic relaxation time was recorded from the apical four-chamber view [25] by simultaneous recording of the mitral and aortic flows at a speed of 100 mm/s and defined as the time interval between the aortic valve closure and the onset of the A–V valve opening. From the pulmonary venous Doppler recordings, peak velocity during ventricular systole and diastole, their ratio, and peak reverse flow velocity during atrial contraction were obtained. Echocardiographic estimates of the ejection fraction were compared in 13 patients with measurements obtained by radionuclide imaging. A semiautomatic commercially available program (GE protocol) was used for nuclear analysis. Maximum and minimum values of the background corrected time–activity curves were used for calculations of the ejection fraction. The evaluation was performed by an experienced nuclear cardiologist blinded to the echocardiographic results. 2.3. Tissue Doppler echocardiography The general principles that underlie the TDI modalities have been described previously [17]. Briefly, by excluding the low-intensity flow signals, the strong tissue signals derived from myocardial motion are sent directly into the autocorrelator without high-pass filtering. Recordings were stored digitally as 2D cineloops and transferred to an optical disk medium for offline analysis with the use of commercially available postprocessing software. With this software, the images showing the velocity of tissue motion are superimposed on the 2D echocardiographic image for realtime display in color. By using the apical two-chamber plane, the myocardial longitudinal wall motion velocities

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are assessed during the cardiac cycle. Velocities toward the transducer are color-coded red, and velocities away from the transducer are coded blue. These color-coded velocities are automatically decoded into numeric values for analysis. By marking a region of interest on the 2D image, a velocity trace throughout the cardiac cycle for this area can be generated. This trace represents the mean of the instantaneous velocity spectrum. 2D tissue velocity images of the left ventricle were obtained at 69F15 frames/s, which implies a temporal resolution of approximately 15 ms. Measurements were obtained from three regions along the anterior wall (apical, mid, and basal) and from the corresponding regions on the inferior wall (Fig. 1). Apical velocities were assessed from the most proximal part of the apical segment because of potential problems with interpretation of apical velocities. Technically adequate recordings were present when smooth velocity traces throughout systole and diastole could be obtained by repeated measurements in the different segments of the left ventricle. The TDI velocity traces were examined for numeric values, distinctive features, and velocity direction of myocardial move-

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ments. Velocities were determined during the different phases of the cardiac cycle. Systolic acceleration was measured from the end of isovolumic contraction to the first peak systolic velocity. The isovolumic relaxation was defined from the 2D loop as the period after systole and before mitral valve opening. The distinct signal from mitral valve movements could be assessed from the same 2D loop as velocity measurements from the myocardium. Two different sites at the mitral annulus were also selected. In the apical two-chamber view, peak systolic and diastolic velocities were recorded at the anterior and inferior sides in such a way that the mitral annulus moved along the sample volume line (Fig. 1). A mean value from the above two sites was used to assess global systolic and diastolic function. 2.4. Statistics Data are presented as meanFS.D. Linear correlations and multiple correlation analyses were used for comparisons. Comparisons between different regions were analysed with

Fig. 1. Two-dimensional tissue Doppler image from apical two-chamber view. (A) Two-dimensional image with sample sites in the inferior wall and mitral annulus. (B) Simultaneous velocity profiles from wall and mitral annular sites. (C) The systolic (S), early diastolic (E), and atrial-induced (A) velocities are shown. LA=left atrium; LV=left ventricle.

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an unpaired Student’s t test. Differences were considered statistically significant when the p value was b0.05. To test intraobserver variability, measurements of systolic and diastolic TDI were made at 50 sites on two different occasions. For interobserver variability, a second investigator randomly made measurements at 30 of the above different ventricle sites without knowledge of other echocardiographic parameters. The intraobserver and interobserver variabilities were determined (as the difference between the two sets of observations divided by the mean of the observations and expressed as a percentage).

3. Results The results are summarized in Tables 1–5. The intraobserver error was low for wall velocities (4.3F3.9%, 5.7F4.6%, and 6.4F4.9% for peak systolic, peak early diastolic, and peak late diastolic velocities, respectively) and annular velocities (4.2F3.6%, 5.9F4.3%, and 6.2F5.1% for peak systolic, peak early diastolic, and peak late diastolic velocities, respectively). The interobserver error was also low for wall velocities (4.9F4.1%, 6.1F5.6%, and 6.7F6.1%, respectively) and annular velocities (4.7F 3.7%, 6.2F5.4%, and 6.4F6.3%, respectively). The clinical and echocardiographic parameters for the patients and the healthy subjects are given in Tables 1 and 2. Left ventricular ejection fraction, mass index, and wall stress were increased ( pb0.01) compared to normals. Early diastolic mitral inflow velocity was slightly diminished and isovolumic relaxation time was slightly increased compared to controls ( pb0.05). 3.1. Systolic myocardial velocity Compared with healthy subjects, the Fontan patients had a significantly reduced peak systolic velocity at wall and Table 1 Basic clinical and echocardiographic parameters Age (years) HR (beats/min) SBP (mm Hg) DBP (mm Hg) LVED (mm) FS (%) EF (%) Mass index (g/ m2) ESSc (g/cm2) ESSm (g/cm2)

Table 2 Conventional Doppler parameters Normal subjects

Fontan patients

Transmitral flow E (m/s) A (m/s) E/A ratio E-wave deceleration (ms) IVRT (ms)

0.69F0.1 0.61F0.1 1.12F0.2 197F27 87F12

0.64F0.2* 0.65F0.4 0.95F0.3* 205F48 97F16*

Pulmonary venous waves Systolic (m/s) Diastolic (m/s) Systolic/diastolic Atrial systole (m/s)

0.61F0.1 0.45F0.1 1.4F0.2 0.27F0.1

0.56F0.2 0.50F0.2 1.12F0.3 0.33F0.1

Results are expressed as the mean and S.D. A=atrial-induced velocity; E=early diastolic velocity; IVRT=isovolumic relaxation time. * pb0.05 compared with normals.

annulus sites (Tables 3 and 4). Recordings of mitral annular velocities by TDI were possible in all the patients. Good-quality echoes for the measurement of ejection fractions were available in 21 patients (87%) with a mean (S.D.) value of 43% (11%). A good linear correlation (Fig. 2A) existed between ejection fraction and the systolic myocardial velocity from the annular site (r=0.78, pb0.001). In the 13 patients who underwent radionuclide imaging, a significant correlation was found between radionuclide and echo-determined ejection fraction (r=0.71, pb0.001). When the patients were divided into two different groups with respect to left ventricular ejection fraction, 10 patients had left ventricular systolic dysfunction (EFb50%) and 11 patients had normal left ventricular

Table 3 Mitral annular peak systolic and diastolic velocity assessed by TDI at different sites Location Anterior

Normal subjects

Fontan patients

24F5 61F7 120F6 75F8 53F4 33F4 63F6 74F14 49F5 43F6

22F8 60F9 117F7 70F6 59F8* 23F8* 43F11* 97F46* 89F8* 77F5*

MeanFS.D. DBP=diastolic blood pressure; FS=left ventricular fractional shortening; HR=heart rate; EF=left ventricular ejection fraction; ESSc=circumferential end-systolic wall stress; ESSm=meridional end-systolic wall stress; LVED=left ventricular end diastolic dimension; SBP=systolic blood pressure. * pb0.01 compared with normals.

Inferior

Mean

Normal subjects Fontan patients Normal subjects Fontan patients Normal subjects Fontan patients

S a (cm/s)

E a (cm/s)

A a (cm/s)

E a/A a

9.3F1.5

12.2F3.1

11.2F1.8

1.3F0.3

10.9F1.4z

0.7F0.1y

10.1F2.9

1.4F0.2

9.6F2.4

0.9F0.1z

11.4F1.7

1.3F0.2

10.6F1.3

0.8F0.1y

6.1F1.3* 9.6F1.4 8.1F1.1 9.4F1.1 7.5F1.4

6.6F1.9y 11.7F2.6 8.9F2.1§ 12.6F2.3 8.1F2.2§

Results are presented as the mean and S.D. A a=mitral annular late diastolic (atrial) velocity; E a=mitral annular early diastolic velocity; S a=mitral annular systolic velocity. * pb0.001 compared with normals. y pb0.0001 compared with normals. z pb0.01 compared with normals. § pb0.005 compared with normals.

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Table 4 Myocardial velocities in anterior and inferior walls assessed by TDI during the cardiac cycle Location

Sw (cm/s)

Ew (cm/s)

Aw (cm/s)

IVRw (cm/s)

Anterior wall Basal Normal Fontan Mid Normal Fontan Apical Normal Fontan

5.9F1.7 4.6F1.8* 4.7F1.6 3.9F1.7y 2.9F1.3 2.1F1.1

6.8F1.8 5.1F1.3* 6.5F1.7 5.8F1.6y 4.5F1.9 3.3F1.5§

5.9F1.6 5.6F1.7 5.1F1.8 4.5F1.8z 3.8F1.6 3.3F1.9

1.9F0.6 1.2F0.5 1.8F0.4 1.6F0.3* 1.3F0.3 1.1F0.2*

Inferior wall Basal Normal Fontan Mid Normal Fontan Apical Normal Fontan

6.2F1.8 4.1F1.3* 4.9F1.7 3.2F1.4z 3.3F1.9 2.1F1.3

6.3F1.7 4.2F1.4y 5.8F1.9 4.7F1.4z 3.6F1.5 2.8F1.6

5.5F1.5 4.9F1.7 4.9F1.6 4.2F1.5 3.6F1.8 3.1F1.2

1.7F0.4 1.5F0.2 1.6F0.4 1.1F0.3 1.2F0.1 0.6F0.2

Results are presented as the mean and S.D. Aw=myocardial wall atrial-induced velocity; E w=myocardial wall early diastolic velocity; IVRw=myocardial wall isovolumic relaxation velocity; S w=myocardial wall systolic velocity. * pb0.001 compared with normals. y p b 0.0005 compared with normals. z p b 0.05 compared with normals. § p b 0.01 compared with normals.

systolic function (EFz50%). A cutoff point of mean systolic mitral annular velocity of z7 cm/s had a sensitivity of 80% and a specificity of 89% in predicting preserved global ventricular systolic function (20 true-positive, 2 false-positive, 19 true-negative, and 4 false-negative results). Table 5 Results of linear regression analysis of the relation between early diastolic mitral annular velocity and other echocardiographic and clinical parameters in patients with single left ventricle after Fontan procedure Independent variable

Dependent variable

R

p

Intercept

Ea Ea Ea Ea Ea Ea Ea Ea Ea Ea Ea Ea Ea Ea Ea Ea

ESV EDV H/R ratio M/V ratio Mass index Annulus motion ESSc EF FS IVRT DT E vel E/A PVF S/D Age at operation Years post Fontan

0.25 0.55 0.61 0.75 0.59 0.65 0.36 0.77 0.79 0.26 0.39 0.29 0.19 0.21 0.28 0.71

NS b0.05 b0.05 b0.005 b0.05 b0.05 NS b0.005 b0.005 NS NS NS NS NS NS b0.05

1.89 1.57 0.18 1.12 0.26 2.95 21.9 31.7 29.2 8.7 9.27 3.11 4.48 6.35 7.19 1.03

vel vel vel vel vel vel vel vel vel vel vel vel vel vel vel vel

vs. vs. vs. vs. vs. vs. vs. vs. vs. vs. vs. vs. vs. vs. vs. vs.

FS=fractional shortening; DT=deceleration time; E vel=early diastolic mitral inflow velocity; E a vel=early diastolic mitral annular velocity; EF=ejection fraction; ESSc=end-systolic circumferential wall stress; H/R=ventricular wall thickness/radius; IVRT=isovolumic relaxation time; M/V=mass/ volume; PVF=pulmonary venous flow.

Fig. 2. (A) Correlation between left ventricular ejection fraction and the systolic mitral annular velocity in patients with Fontan operation. (B) Correlation between mass/volume ratio and the early diastolic mitral annular velocity in the same patients. E a=early diastolic mitral annular velocity; S a=systolic mitral annular velocity.

3.2. Diastolic myocardial velocity In Fontan patients, the early diastolic mitral annular velocity was significantly diminished compared with that in healthy subjects at all sites (Tables 3 and 4). The late diastolic mitral annular velocity was similar to that in healthy subjects at almost all sites. However, compared with that in healthy subjects, the ratio between the early and late diastolic mitral annular velocity was reduced, suggesting impaired filling (E a/A a 0.84F0.13 vs. 1.33F0.23, pb0.0001). A relatively good linear correlation (Fig. 2B) existed between mass/ volume ratio and the early diastolic myocardial velocity from annular site (r=0.75, pb0.005). Group 1 patients (EFb50%) had lower systolic and diastolic velocities compared to normal controls ( pb0.001). Group 2 patients (EFN50%) had preserved systolic velocities but decreased ( pb0.005) regional and annular early diastolic velocities (Fig. 3). E a/A a was 0.81F0.31 in Group 1 patients and 0.85F0.11 in Group 2 patients ( p=NS). Isovolumic velocities became dominantly positive in 17/ 24 patients at mid and apical anterior wall levels (Table 4) with a mean value of 1.6F0.3 and 1.1F0.2 cm/sec, respectively ( pb0.001 vs. controls), indicating postsystolic shortening (PSS).

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Fig. 3. Peak early diastolic mitral annular velocity in Fontan patients with EFb50% and Fontan patients with EFN50%. E a=early diastolic mitral annular velocity. *pb0.001 compared to normals; ypb0.005 compared to normals.

The results of the multiple correlation analysis are given in Table 5. The peak mitral annular early diastolic velocity correlated well with the ventricular ejection fraction (r=0.77, pb0.005), mean mitral annular motion at systole (r=0.65, pb0.05), mass index (r=0.59, pb0.05), mass/ volume ratio (r=0.75, pb0.005), and the number of years post Fontan revision (r=0.71, pb0.05). There was poor correlation between the early diastolic velocity and transmitral E-wave, transmitral A-wave, E/A ratio, transmitral Ewave deceleration time, IVRT, different pulmonary venous waves, or age at operation. The ratio between mitral annular early and late velocity showed no correlation with any of the transmitral flow velocities or IVRT.

4. Discussion This study shows changes in systolic tissue Doppler indexes late after the Fontan procedure correlating with reduction in left ventricular ejection fraction and changes in diastolic tissue Doppler indexes, consistent with persisting abnormalities of ventricular filling in the presence of normal systolic ejection fraction. 4.1. Systolic left ventricular function by TDI in Fontan surgery Previous studies have shown the presence of systolic dysfunction as well as delayed onset of ventricular contraction and areas of regional hypokinesis in patients with a univentricular atrioventricular connection [6,8,26]. The aetiology of this systolic incoordination may be related to an alteration in the arrangement of muscle fibres and ventricular geometry resulting from an underlying congenital heart lesion or chronic volume overload, or it may be secondary to myocardial necrosis or fibrosis manifested in the myocardium of some patients with congenital heart disease from an early age. Fundamental differences in ventricular geometry account for the spherical shape of the left ventricle when function-

ally single when compared to the bbullet shapeQ of the normal left ventricle. Several findings suggest [4] that partial or complete volume offloading after Fontan operation offers protection to the single ventricle but does not prevent late deterioration. Although the myocardial velocity and ejection fraction are two different measurements, our study shows a relatively significant correlation between the peak systolic velocity of the mitral annulus and the left ventricular ejection fraction. This indicates that systolic velocity plays an important role in the pumping function of the ventricle. In addition, a peak systolic velocity of z7 cm/s predicts a preserved ejection fraction (z0.50) with relatively high sensitivity and specificity, corroborating previous results in patients with different pathologies [27,28]. The correlation between EF and S a is not unexpected, although the use of a threshold for S a (7 cm/s) with adequate sensitivity and specificity can be helpful, especially in patients with no good-quality 2D echo recordings. We used left ventricular ejection fraction determined by echocardiography as the reference method. Two-dimensional echocardiographic determination of ventricular volumes in patients with single left ventricle after Fontan operation has been reported [26]. On comparing the peak systolic mitral annular velocity with left ventricular ejection fraction, only the high-quality recordings were accepted since the major problem using two-dimensional echocardiography is that the correct outlining of endocardial borders is sometimes impossible. Additional isotope studies were performed to assess left ventricular function and to corroborate echocardiographic data. Our results are in agreement with previous studies that have shown a good correlation between the left ventricular ejection fraction determined by radionuclide angiography and the mean mitral annular motion assessed by M-mode echocardiography [29]. 4.2. Diastolic left ventricular function by TDI in Fontan surgery By separating the pulmonary and systemic circulations, the Fontan operation imposes an acute preload reduction on a previously volume-loaded ventricle. Early after the Fontan procedure [6,7], an impaired systemic ventricular relaxation has been shown, coincident with the increase in mass/volume ratio and acquired bhypertrophyQ of the ventricle. A persistent late impairment of left ventricular isovolumic relaxation time and shortening of E-wave deceleration time have also been reported [9], suggesting a trend towards reduced ventricular compliance—an additional mechanism that has been invoked to explain the longitudinal changes. Reduction of volume load in response to surgical palliation results in moving operant chamber volume lower on the diastolic stress–strain curve and in reduced filling of the systemic ventricle. This may modify ventricular

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compliance as it has been shown invasively in patients with mitral stenosis [30] and single ventricle [31]. In addition, hemodynamic responses to h-adrenergic stimulation in patients with Fontan circulation [32] are consistent with a limited h-adrenergic reserve that was attributable to a limited preload reserve rather than a decreased inotropic response. Furthermore, increased systemic vascular resistance is characteristic in patients after the Fontan procedure [10,32], and abnormalities of ventriculo-arterial coupling may have an adverse effect with slowing of the ventricular relaxation velocity. Several studies examined short-term hemodynamic effects of afterload-reducing therapy on Fontan hemodynamics and demonstrated a significant increase in cardiac output associated with a decrease in systemic vascular resistance [33,34]. In contrast, there have been only a few studies of the long-term effects of vasodilator therapies in patients after Fontan surgery [35,36], and results of these studies are not consistent. Further evaluation of this question is warranted in a larger population with and without evidence of ventricular dysfunction. In our study, the peak early diastolic velocity of the left ventricle along its long axis was significantly decreased compared with that in healthy subjects (Tables 3 and 4). The ratio of early-to-late diastolic mitral annular velocity was also significantly lower as the result of a significant decrease in the early diastolic velocities in the patient population. The small decrease in A annular velocity supports the possibility of decreased left ventricular compliance. These findings agree with previous data obtained by cardiac catheterization, showing an increased contribution of atrial contraction to ventricular filling in patients with the Fontan circulation [32]. The presence of diastolic filling abnormalities may lead to inadequate cardiac output even though the ejection fraction is normal or near-normal and may induce neurohumoral upregulation that eventually results in late systolic dysfunction [4]. We also found increased (dominantly positive) isovolumic velocities in 17 of 24 patients at mid-apical anterior wall level (Table 4), indicating PSS. PSS (i.e., contraction after aortic closure) has been described in ischemia and myocardial infarction [37] as well as in cardiomyopathies [38], and its presence may affect diastolic filling. The mechanism could be inhomogeneity of contraction, with prolonged contraction in one area, resulting in a second shortening when adjoining segments relax. This may be due to ischemia, either because of hypertrophy or true ischemia, or simply from muscular disarrangement. Multiple correlation analysis indicated that early diastolic mitral annular velocity was related to mass index as well to end-diastolic volume index, suggesting that diminished early diastolic velocity was attributable to limited preload reserve: One would expect the greatest increase in compliance in patients with less capacity for remodeling because of the largest decrease in volume overload—and hence the largest mass/volume ratio after

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surgery; the positive correlation between the E a velocity and time since Fontan suggests that remodeling may be occurring in some patients. Patients may develop different degrees of diastolic dysfunction. With conventional Doppler parameters, these changes may be detected by the development of abnormal ventricular relaxation, pseudonormalization, or a restrictive pattern. The early diastolic mitral annular velocity measured by TDI has been postulated to be independent of the filling pressure [39]. This may be the reason for the poor correlation between the early diastolic velocity determined by TDI and the conventional Doppler parameters. The higher discriminating power of E a velocity compared to controls (Table 3) and the presence of changes in diastolic function related to years following Fontan operation (Table 5) suggest that TDI is more sensitive compared to conventional Doppler velocity imaging variables in evaluating diastolic impairment as well as following the progression of diastolic dysfunction. 4.3. Limitations This study analyzes the possibilities of assessing ventricular function by using the myocardial velocity along the long axis. No consideration was taken of the contraction of the left ventricle along its short axis caused by circumferential fiber. However, the amplitude of the left ventricular shortening along its long axis has been used previously [15] to assess both regional and global left ventricular function. Another limitation is that EF is not a load-independent index for systolic function [23], and preload and afterload may also have an effect on S a values as well as on standard mitral inflow parameters. However, since E a may be preload-independent [39], the most valuable information in the paper rests on the finding that E a and E a/A a ratio are diminished in Fontan patients when compared to normal subjects, and our data contribute to the understanding of both the technique itself and the functional status in the patient population being studied.

5. Conclusions Myocardial velocities recorded after the Fontan operation give insight into systolic and diastolic ventricular function. The peak systolic mitral annular velocity correlated well with the ventricular ejection fraction. The peak early diastolic velocity and the ratio between the early and late diastolic mitral annular velocity are reduced and reflect diastolic dysfunction even in the presence of normal systolic ejection fraction. Thus, quantification of the myocardial velocity by TDI opens up a new possibility of assessing ventricular performance (even after medical interventions) in patients with Fontan-type circulation.

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