Relation of Biventricular Function Quantified by Stress to Cardiopulmonary Exercise Capacity in Adults With Mustard (Atrial Switch) Procedure for Transposition of the Great Arteries Wei Li, Tim S. Hornung, Darrel P. Francis, Christine O’Sullivan, Alison Duncan, Michael Gatzoulis and Michael Henein Circulation 2004;110;1380-1386; originally published online Aug 23, 2004; DOI: 10.1161/01.CIR.0000141370.18560.D1 Circulation is published by the American Association. 7272 Greenville Avenue, Dallas, TX 72514 Copyright © 2005 American Heart Association. All rights reserved. Print ISSN: 0009-7322. Online ISSN: 1524-4539

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Downloaded from circ.ahajournals.org at NHLI - Royal Brompton on January 29, 2006 Relation of Biventricular Function Quantified by Stress Echocardiography to Cardiopulmonary Exercise Capacity in Adults With Mustard (Atrial Switch) Procedure for Transposition of the Great Arteries

Wei Li, MD, PhD; Tim S. Hornung, MD; Darrel P. Francis, MRCP; Christine O’Sullivan, BSc; Alison Duncan, MRCP; Michael Gatzoulis, MD, PhD; Michael Henein, MD, PhD

Background—Mustard repair for transposition of the great arteries (TGA) is frequently associated with impaired systemic (right) ventricular function and sometimes exercise intolerance. We hypothesized that a simple quantitative measure- ment of ventricular function, during rest and pharmacological stress, could identify abnormalities and predict objective exercise capacity. Methods and Results—We quantified the performance of systemic and pulmonary (left) ventricles by using echocardi- ography, at rest and during dobutamine stress, in 27 adults who had undergone Mustard repair for TGA. Systolic and diastolic function of the systemic were markedly disturbed with respect to pulmonary ventricular function. We also measured exercise capacity by cardiopulmonary exercise testing for peak oxygen uptake. Exercise capacity was significantly predicted by systemic ventricular long-axis excursion both at rest (rϭ0.66, PϽ0.001) and at peak dobutamine stress (rϭ0.53, Pϭ0.006) but not by pulmonary ventricular long-axis excursion at rest (rϭ0.04) or on stress (rϭ0.11). Exercise capacity was also predicted by the septal long-axis excursion at rest (rϭ0.61, Pϭ0.001) but not pulmonary ventricular free wall excursion (PϾ0.05) or fractional shortening (PϾ0.05). Peak aortic velocity at maximum dobutamine stress correlated with exercise capacity (rϭ0.46, Pϭ0.029) but not at rest (rϭ0.36). Multivariate analysis revealed systemic ventricular long-axis excursion to be the sole significant independent predictor of exercise capacity. Conclusions—Systemic ventricular function is depressed in most patients with Mustard repair. Quantitative echocardio- graphic evaluation shows systemic ventricular function to be a key determinant of exercise capacity. (Circulation. 2004; 110:1380-1386.) Key Words: transposition of great vessels Ⅲ echocardiography Ⅲ exercise

fter Mustard repair for transposition of the great arteries, necessitates the use of an external reference to validate Asystemic (right) ventricular function may be impaired. proposed measurements. Cardiopulmonary exercise testing However, assessing function of this ventricle has proved can provide a widely accepted, valid, reproducible, and difficult. Echocardiographic assessment of systemic ventric- objective measure of exercise capacity, which is a good ular function “by eye” is subjective, and formulaic calculation candidate for such an external reference point.4 of ejection fraction can be time-consuming and unreliable The aim of this study was to describe the physiology of the because of its complex geometry. Other techniques such as systemic and pulmonary ventricles at rest and during dobu- MRI have been applied, but they are not widely available. tamine stress in patients who had undergone Mustard repair. Since the relation between ejection fraction and exercise We sought to quantify not only the conventional ventricular capacity is controversial,1–3 it might be argued that systemic short axis but also the long axis. Our second aim was to ventricular function is not an important determinant of validate these echocardiographic measurements by quantify- exercise capacity in these patients. In the case of the systemic ing their relation to objective measurements of exercise capacity by using cardiopulmonary exercise testing. ventricle of a patient with Mustard repair, its unique shape and physiology further adds to the need to broaden our Methods horizon of quantitative measures of ventricular function. From March 2000 to January 2002, 27 patients (29Ϯ7 years of age, The lack of a gold standard test for the assessment of 12 men) with transposition of the great arteries who had undergone ventricular function, especially in this group of patients, the Mustard procedure were studied. The age at the time of Mustard

Received February 27, 2003; de novo received September 26, 2003; revision received April 22, 2004; accepted April 26, 2004. From Royal Brompton Hospital and Imperial College School of Medicine, London, United Kingdom. Correspondence to Dr Michael Henein, Department of Echocardiography, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK. E-mail [email protected] © 2004 American Heart Association, Inc. Circulation is available at http://www.circulationaha.org DOI: 10.1161/01.CIR.0000141370.18560.D1 1380 Li et al Stress Echo/Exercise After Mustard Repair 1381

4-chamber view with the sample volume at the tips of the corre- sponding valve leaflets, using the pulsed wave Doppler technique. Pulmonary flow velocities were recorded from the apical 5-chamber view, and aortic flow velocities were acquired with further anterior angulation of the transducer and images from the same apical 4-chamber view. All M-mode and Doppler flow velocities were recorded photographically with the use of a strip-chart printer (HP 77510A) at a paper speed of 100 mm/s, with an ECG (lead II) and a superimposed on each. Myocardial tissue Doppler velocities were similarly recorded but at a 50 mm/s paper speed. Dobutamine Stress Protocol Dobutamine was administered through an infusion pump (IVAC 770 syringe driver, Alaris Medical System), starting at a rate of 5 ␮g/kg per minute, increased every 3 minutes by a similar increment to a maximum dose of 40 ␮g/kg per minute. Stress end points were taken either with the onset of symptoms, arrhythmia (including frequent ventricular extrasystoles), or if the heart rate had reached 85% the predicted target rate for age (220 minus age in years). Blood pressure was recorded at each stage with the use of a Critikon Dinamap monitor (Critikon Inc). All echocardiographic and Doppler parame- ters were repeated at peak stress, with the use of the same resting setup. Cardiopulmonary Exercise Testing Exercise testing was conducted on a treadmill in an air-conditioned room. A was used, with the addition of a “stage 0,” consisting of 3 minutes at a speed of 1 mile per hour with a 5% gradient. Gas exchange was measured breath-by-breath with a heated calibrated pneumotachograph and respiratory mass spectrometer (Amis 2000). Blood pressure was measured from the right arm, while the patient was standing, before, during, and immediately after the exercise test, with the use of a mercury sphygmomanometer. Heart rate and ECG morphology were continuously monitored and recorded. The exercise test was performed to the limit of the patient’s physical endurance, with particular exhortation to continue exercise Figure 1. Apical 4-chamber view, showing M-mode cursor until there was evidence of anaerobic metabolism on gas exchange placed at left, septal, and right AV ring. measurements. Chest pain, sustained arrhythmia, or a fall in systolic blood pressure by Ͼ20 mm Hg were also criteria for cessation, but repair was 4.1Ϯ4.4 years. The time interval between the repair and these end points did not occur in any of the studied patients. the study was 25Ϯ6 years. No patient had a history of or electro- cardiographic evidence for or systemic Measurements hypertension. All patients gave prior written informed consent for Doppler Echocardiographic Measurements this study, which was approved by the local ethics committee. Ϯ Pulmonary ventricular minor axis dimensions were taken at end-di- As a healthy control group, we used data from 22 subjects (38 8 astole (at the onset of q wave of the ECG) and at end-systole (at the years of age) who had been referred for stress echocardiography and onset of the second heart sound on the phonocardiogram), using angiography because of atypical symptoms and in whom both tests leading edge methodology. Fractional shortening was calculated as proved to be normal. All had structurally normal . None had a the difference between the two dimensions with respect to the history of hypertension, diabetes, or typical angina. end-diastolic dimension. Systemic ventricular end-diastolic dimen- sion was measured from a frozen 2D image acquired from the same Resting view at the time of the onset of the q wave. Total ventricular Transthoracic echocardiography was performed with the use of a long-axis excursion was measured as the excursion of left and right Phillips Sonos 5500 echocardiograph interfaced with a multifre- atrioventricular ring motion occurring between the onset of the QRS quency transducer. With the subject in the left semilateral position, and the peak innermost point (toward the ventricular cavity) at or cross-sectional, 2-dimensionally guided, M-mode recordings of the after the second heart sound. Post–ejection shortening was measured pulmonary (left) ventricular minor axis were made from the standard as the extent of inward movement that occurred after the second left parasternal long-axis view with the cursor positioned at the tips heart sound.9 of left atrioventricular (AV) valve leaflets. Systemic ventricular We measured the delay between the onset of electrical activity minor axis dimension was also recorded from the same view in both (QRS) and the onset of shortening in the pulmonary and systemic groups by the standard method used for healthy subjects.5 Pulmonary ventricular free walls (Figure 2). This “q-OS” was previously found and systemic ventricular long-axis recordings were obtained from the to be a sensitive marker of ischemia in patients with coronary artery apical 4-chamber view with the M-mode cursor positioned at the left disease.9,10 We also measured the time interval between the second and septal angles of the left AV ring and right angle of the right AV heart sound and the onset of long-axis lengthening (S2-OL, Figure ring6 (Figure 1). The probe and cursor were positioned to make the 2), a measurement similar to isovolumic relaxation time in value beam direction as parallel as possible to the direction of ring motion. despite the difference in their definitions.10 Basal ventricular myocardial tissue Doppler velocities were ac- We assessed the reproducibility of the timing measurements of the quired at the AV ring level, with the sample volume positioned at the onset of shortening with respect to the onset of the QRS and the onset same angles, respectively.7,8 Trans left and right AV valve (mitral of lengthening with respect to S2. Reproducibility expressed as and tricuspid) flow velocities were obtained from the apical root-mean-square for the intraobserver variability was 11 ms and 14 1382 Circulation September 14, 2004

Systemic Ventricular Function During systole, the patients with Mustard repair had a longer delay in the onset of shortening of the ventricular free wall, a smaller long-axis excursion, and lower systolic velocity and ventricular outflow velocity. Moreover, their stress-induced increment in long-axis excursion, systolic velocity, and ven- tricular outflow velocity was significantly smaller than in the control subjects (Table 1, interaction column). Diastole also was disordered in patients, with delayed onset of long-axis lengthening, reduced myocardial velocities, and higher early trans–AV valve flow velocity. The effect of stress in diastole was not significantly different between patients and control subjects. At rest, 7 patients had no detectable “A” filling Figure 2. M-mode recording of long-axis motion. q-OS, Time wave. During stress, this number rose to 15. from q to onset of shortening; S2-OL, time from second heard sound to onset of lengthening. Pulmonary Ventricular Function Pulmonary ventricular function in patients with Mustard ms, respectively, and the interobserver variability was 15 ms and 19 repair was also abnormal (Table 1). The time from q wave to ms, respectively.9 Peak systolic, early, and late diastolic velocities were measured the onset of ventricular shortening failed to shorten on stress. from tissue Doppler recordings of the pulmonary and systemic Long-axis excursion was lower, with higher peak outflow ventricular free wall longitudinal motion taken at the level of the tract velocity, reflecting an element of outflow tract obstruc- atrioventricular ring. Pulmonary and systemic ventricular filling tion. Outflow tract obstruction, defined as systolic anterior times were also measured as the time interval from the onset of movement of the mitral valve causing outflow tract velocities forward flow to its end. Pulmonary and systemic ventricular ejection times were measured between the onset of forward flow pulse to the to exceed 3.5 m/s, occurred in 10 of 27 patients (1 at rest and onset of the valve closure artifact, respectively. 9 at peak stress). During diastole, lengthening began prematurely, tissue Cardiopulmonary Exercise Testing Doppler early diastolic velocity and early diastolic filling Minute ventilation, oxygen consumption, and carbon dioxide pro- velocity were significantly elevated, and tissue Doppler late duction were calculated online every 10 seconds with the use of a diastolic velocity was abnormally low. The patients showed a standard inert gas dilution technique (Amis 2000). smaller stress-induced increment in late diastolic velocity Statistical Analysis than did the control subjects. For all measured variables, values are expressed as meanϮ SD. Rest and stress values in patients were compared with those in control Incoordination (Post-Ejection Shortening) subjects through the use of 1-way ANOVA. The systemic and At Rest pulmonary ventricles were compared between patients and control Seven of 24 patients presented with incoordination (post-ejection subjects by using the same method. A probability value of Ͻ0.05 shortening) of the long axis (4 had it at the septum at the same was considered significant. The Pearson product-moment method was used for calculating correlation coefficients, and multivariate time) in the absence of left bundle-branch block. regression was performed by the stepwise method with F-to-enter of 4. During Stress Incoordination worsened in 5 of the 7 patients and newly Results developed in 12 other patients (3 septal site, 5 systemic Six patients had undergone redo Mustard operation 8 to 24 ventricle, 4 at both septal and systemic ventricular free wall) years (mean, 15) after their original repair, and 3 had balloon (Figure 3). Thirteen of the total 19 patients who had incoor- dilation for the venous pathway obstruction during recent dination with stress showed abnormal ST-segment shift on follow-up time. Three had a pacemaker at the time of study. the 12-lead ECG. None of the control subjects had incoordi- Sixteen were in Ability Index I, 8 in II, and 3 in III.11 Sixteen nation at rest, nor did any have it during stress. were in New York Heart Association class I, 10 in II, and 1 in III. Twenty-four patients had a trace or mild degree of Exercise Capacity in Patients With Mustard Repair tricuspid regurgitation, and the remaining 3 had moderate Exercise capacity was significantly depressed in many pa- tricuspid regurgitation. tients compared with normal reference values, but the range At peak dobutamine stress, no patient had chest pain, 1 had was wide (Figure 4). Exercise data are shown in Table 2. shortness of breath, and another had lightheadedness. The remaining 25 completed the protocol without any significant Predictors of Exercise Capacity in Patients With limiting symptoms. Twenty-five patients performed cardio- Mustard Repair pulmonary exercise testing; 1 could not tolerate the mouth- Long-Axis Excursion piece, and 1 declined to attempt the test. Exercise capacity correlated significantly with systemic ven- Three patients had pacemakers: 1 AAIR and 2 DDDR. tricular free wall excursion, both at rest (rϭ0.66, PϽ0.001, Only one was receiving ventricular pacing stimuli during the Figure 5) and during dobutamine stress (rϭ0.53, Pϭ0.006). study; timing measurements were not made in him. It also correlated with septal long-axis excursion at rest Li et al Stress Echo/Exercise After Mustard Repair 1383

TABLE 1. Comparison of Ventricular Function Between Patients and Controls

Interaction Between Patient Versus Stress Versus Patient/Control Controls Patients Control Rest and Stress/Rest

Rest Stress Rest Stress MeanϮSD MeanϮSD MeanϮSD MeanϮSD FP F PFP Systemic ventricle Systolic physiology Q to onset of shortening, ms 89.1Ϯ17.2 55Ϯ12.2 119.6Ϯ27.1 95.6Ϯ45.4 29.4 Ͻ0.001 29.0 Ͻ0.0001 0.9 ns Long-axis excursion, cm 1.55Ϯ0.22 1.85Ϯ0.2 1.03Ϯ0.33 1.01Ϯ0.3 92.2 Ͻ0.0001 12.5 Ͻ0.001 16.1 Ͻ0.001 Ventricular systolic velocity, cm/s 8.5Ϯ1.8 14.6Ϯ3.9 8.4Ϯ3.1 10.4Ϯ3.7 7.2 0.01 54.7 Ͻ0.0001 14.3 Ͻ0.001 Peak ventricular outflow velocity, m/s 1.1Ϯ0.13 2.1Ϯ0.21 0.99Ϯ0.15 1.49Ϯ0.32 47.2 Ͻ0.0001 358.5 Ͻ0.0001 46.0 Ͻ0.0001 Diastolic physiology Time from S2 to onset of lengthening, ms 65.5Ϯ13.7 40.9Ϯ10.2 90.4Ϯ39.7 71.9Ϯ45.8 13.3 Ͻ0.001 15.2 Ͻ0.001 0.3 ns Tissue Doppler early diastolic velocity, cm/s 13.4Ϯ3.6 15.1Ϯ2.9 10.8Ϯ3.5 12.8Ϯ3.5 7.0 Ͻ0.05 9.3 Ͻ0.01 0.1 ns Tissue Doppler late diastolic velocity, cm/s 10.9Ϯ2.6 14Ϯ3.3 7.4Ϯ2.8 10.1Ϯ4 19.5 0.0001 13.5 Ͻ0.001 0.1 ns Doppler E wave velocity, cm/s 62.7Ϯ15.5 82.3Ϯ17.2 79.6Ϯ29.6 95.4Ϯ28.7 6.5 Ͻ0.05 21.7 Ͻ0.0001 0.2 ns Pulmonary ventricle Systolic physiology Q to onset of shortening, ms 82.3Ϯ21.9 48.6Ϯ11.7 68.1Ϯ24 61.9Ϯ14.4 0.2 ns 42.0 Ͻ0.0001 20.2 Ͻ0.0001 Long-axis excursion, cm 2.37Ϯ0.16 2.8Ϯ0.3 1.73Ϯ0.44 2.1Ϯ0.47 57.7 Ͻ0.0001 37.9 Ͻ0.0001 0.1 ns Ventricular systolic velocity, cm/s 11.2Ϯ1.8 20.1Ϯ2.6 12.5Ϯ5.2 21.6Ϯ4.8 2.0 ns 176.3 Ͻ0.0001 0.0 ns Peak ventricular outflow velocity, m/s 0.76Ϯ0.11 1.6Ϯ0.47 1.46Ϯ0.92 2.72Ϯ1.29 13.3 Ͻ0.001 80.0 Ͻ0.0001 2.9 ns Diastolic physiology Time from S2 to onset of lengthening, ms 28.6Ϯ22.7 20Ϯ18.5 10Ϯ34.6 3Ϯ17.5 10.3 Ͻ0.01 3.2 ns 0.0 ns Tissue Doppler early diastolic velocity, cm/s 11.6Ϯ2.7 14.1Ϯ3.5 17Ϯ6.4 19.4Ϯ3.3 22.9 Ͻ0.0001 9.6 Ͻ0.01 0.0 ns Tissue Doppler late diastolic velocity, cm/s 11.5Ϯ2.5 19.9Ϯ4.9 10Ϯ4.4 13.4Ϯ3.3 15.0 Ͻ0.001 36.5 Ͻ0.0001 6.9 Ͻ0.05 Doppler E wave velocity, cm/s 43.8Ϯ12 60Ϯ14.1 81.9Ϯ23.8 97.7Ϯ26.3 59.9 Ͻ0.0001 20.1 Ͻ0.0001 0.0 ns

(rϭ0.61, Pϭ0.001) but not with pulmonary ventricular ex- systemic ventricular function, as quantified by echocardio- cursion (rϭ0.042) or with fractional shortening (rϭ0.13). graphic long-axis measurement, is the key correlate of objec- tive exercise capacity. Doppler Flow Velocity Peak aortic velocity on stress correlated with exercise capac- Ventricular Function ity (rϭ0.46, Pϭ0.03) although resting values did not In patients with structurally normal hearts, the conventional (rϭ0.36). approach to assessment of systemic ventricular function is to Multivariate Analysis measure ejection fraction. However, attempting to extend this A stepwise multivariate regression analysis was performed to to the Mustard scenario has proved problematic. The geom- identify which echocardiographic measurements showed in- etry of the right ventricle makes it difficult to measure dependent association with exercise capacity. Systemic ven- ejection fraction by echocardiography, which has prompted tricular free wall long-axis excursion was the strongest simple visual estimation or more complex and expensive correlate of exercise capacity and therefore entered the model techniques such as radionuclide or magnetic resonance first. In its presence, no other variable added significant ventriculography.12,13 predictive value; therefore it alone remained in the multivar- In contrast, simple measurement of long-axis excursion iate analysis (PϽ0.005). gives a rapid and unambiguous measurement,14–16 which has proven utility as a measure of left ventricular function in Discussion patients with coronary artery disease, valve disease, and heart In this quantitative study of ventricular function during failure.17,18 The technique is equally straightforward for the dobutamine stress echocardiography applied to the long axis right ventricle and is especially valid because the main bulk of the heart, we have found that systemic ventricular function of right ventricular myocardial fibers are arranged is substantially impaired in patients with the Mustard proce- longitudinally. dure. Second, objective exercise capacity was impaired in Tissue Doppler also identified depressed early and late many of such patients, even though they considered them- diastolic myocardial velocities in patients with Mustard selves asymptomatic or only minimally symptomatic. Third, repair. Despite this, early diastolic filling velocities were 1384 Circulation September 14, 2004

TABLE 2. Exercise Data

Mean SD Exercise duration, minutes 10.9 3.4 Peak oxygen uptake, mL/kh/min 27.8 7.6 Peak oxygen uptake as percentage of predicted, % 80 17

VE/VCO2 slope 30.2 8.4 Anaerobic threshold, mL ⅐ kgϪ1 ⅐ min 17.0 4.3 Respiratory exchange ratio 1.07 0.11 Rest Heart rate, bpm 87 19 Systolic blood pressure, mm Hg 112 26 Diastolic blood pressure, mm Hg 72 11 Peak exercise Heart rate, bpm 161 31 Systolic blood pressure, mm Hg 147 22 Diastolic blood pressure, mm Hg 76 12 Forced expiratory volume in 1 second, L 2.7 0.8 Forced vital capacity, L 2.9 0.9 Peak expiratory flow rate, L/min 375 118 Height, cm 170 10 Figure 3. At rest (upper panel), shortening of long axis ends at Weight, kg 63.3 13.9 second heart sound (S2). On stress (lower panel), shortening continues beyond second heart sound. This behavior is charac- VE/VCO2 indicates minute ventilation/carbon dioxide production. teristic of subendocardial ischemia. “normal” activity. Moreover, normal everyday activity (other abnormally high. Although there was an age difference than sports) rarely approaches peak exercise levels, and thus between groups, age alone could not explain this combination depressed peak exercise capacity may not encroach much on of findings; rather, there may be diastolic restriction.19 daily life. Nevertheless, in patients (without congenital heart Using this quantitative approach, we found that 80% of disease) with the potentially analogous condition of systemic patients had significantly depressed systemic ventricular left ventricular dysfunction, peak exercise capacity is an long-axis function with stress. This broadly agrees with important predictor of survival.1 findings from radionuclide and MRI studies.12,20 However, since there is no gold standard among imaging techniques for Ventricular Function and Exercise Capacity assessing the abstract concept of “function,” validity of the Previous data on the relation of ventricular function and measurements must be established by reference to an exter- exercise capacity in patients with Mustard repair have been nal, nonimaging, modality. conflicting.3,23,24 Several measures of the systemic ventricular physiology Exercise Capacity were linked to exercise capacity. Multivariate analysis dem- Cardiopulmonary exercise testing with measurement of peak onstrated that the key information that they provided— oxygen uptake is an objective, valid, and reproducible reduced systemic ventricular long-axis function—was com- method of grading exercise capacity.21,22 Even though the majority of patients in the group were asymptomatic or almost so, many had marked exercise impairment. This paradox may result from the lifelong nature of the condition, which allows the patient to downgrade their expectations of

Figure 4. Distribution of exercise capacity (percentage of pre- Figure 5. Relation between right ventricular free wall long-axis dicted oxygen uptake) in patients with Mustard repair. excursion at rest with exercise peak oxygen uptake. Li et al Stress Echo/Exercise After Mustard Repair 1385 mon between them, so that when one variable was in the abnormally high pulmonary ventricular velocities, it does not model, the others did not contribute significantly. prevent exercise capacity being impaired. This suggests that central hemodynamics play a powerful role in limiting exercise capacity in patients who have had the Study Limitations Mustard operation. This relation may be stronger than the We set out to address systemic right ventricular function by corresponding relation1 in patients with chronic heart failure using easily measurable quantitative parameters requiring caused by left ventricular disease because of more frequent widely available equipment. We are therefore unable to coexisting extracardiac pathologies in the latter, who are compare the relative merits of different imaging modalities typically much older. (such as radionuclide or magnetic resonance) against those of Measurement of systemic ventricular free wall motion is echocardiography. However, we found that in every patient, simple and unambiguous and is found to be the measurement we were able to measure the echocardiographic parameters most closely related to exercise capacity in these patients, without ambiguity or contraindication and that systemic whether it is measured at rest or on stress. This supports the ventricular long-axis physiology related usefully to exercise concept that the overwhelmingly important limiting factor to capacity. The healthy subjects were older than the patients. exercise capacity in these patients is disruption of purposeful However, the age difference was not extreme and should not systolic function of the ventricle supporting the systemic cause lower values for cardiac function. Thus, these abnor- circulation. malities found in patients with Mustard repair are likely to represent a significant difference from normal. Evidence of Ischemic Pattern of Ventricular Function Shortening of the long axis normally ends before the end of Conclusions ejection. When there is myocardial ischemia, shortening may Systemic right ventricular function in patients with Mustard continue after ejection (incoordination or “post–ejection repair is impaired at rest and during pharmacological stress shortening”). This phenomenon is sufficiently predictive of (even among asymptomatic ones) and appears to limit exer- coronary artery disease (in patients without congenital heart cise capacity. Pulmonary ventricular function is also impaired disease) in that it can be used as an objective end point but to a lesser degree. Excursion of the systemic ventricular suggesting inducible ischemic dysfunction during diagnostic free wall is the dominant predictor of exercise capacity and stress echocardiography.8,9,25–27 should be considered for the routine periodic assessment of Thirteen of our patients showed post–ejection shortening these patients. of the long axis, in association with abnormal ST-T segments changes on the ECG at peak stress. Although ECG abnor- References malities may be difficult to interpret, the post–ejection 1. Cohn JN, Johnson GR, Shabetai R, et al. Ejection fraction, peak exercise oxygen consumption, cardiothoracic ratio, ventricular arrhythmias, and 9 shortening is characteristic of ischemic dysfunction. 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