Methods

Thirty-two consecutive patients with cToF undergoing clinical CMR evaluation from July 2008 to July 2009 (age range 8 to 18 years) were prospectively recruited from an ongoing registry (Center for Congenital Heart Disease Amsterdam–Leiden). Exclusion criteria were previous pulmonary valve replacement and any contraindications for CMR, such as claustrophobia, cardiac devices, or arrhythmia. In addition, 19 healthy subjects, matched by age and body surface area, without structural heart disease underwent echocardiography and CMR evaluation within the same time frame. Subjects with history of cardiomyopathy, valvular heart disease, or arrhythmic disorders were excluded. CMR and transthoracic echocardiography were performed to study LV and RV performance and to assess ventricular–ventricular interactions. RVEF, RV end-diastolic and end-systolic volumes, LVEF, and LV end-diastolic and end-systolic volumes were assessed with CMR. RV and LV longitudinal strains and LV twist were evaluated with 2-dimensional speckle tracking. Ventricular–ventricular interaction was studied by assessing the relations between RV and LV strains and LV rotation. The study protocol was approved by the institutional review board of Leiden University Medical Center and all subjects gave written, informed consent.

CMR was performed on a 1.5-T pulsar gradient system (Intera 11; Philips Medical Systems, Best, The Netherlands) with 33-mT/m amplitude, 100-mT/m/ms slew rate, and 0.33-ms increase time. A 5-element cardiac coil was used for signal reception. After acquiring a series of localizing thoracic scout images, multisection transversal cine imaging was performed. A stack of slices was planned in the transversal plane, covering the 2 ventricles throughout the cardiac cycle. Images were acquired with a steady-state free precession sequence during breath-hold at end-expiration with repetition time 3.9 ms, echo time 1.5 ms, flip angle 50°, slice thickness 8 mm, matrix 160 × 256, field of view 350 mm, and temporal resolution 25 ms.

Images were analyzed using MASS (Medis, Leiden, The Netherlands). LV and RV volumes were calculated by manually tracing the endocardial borders at end-systole and end-diastole in all slices and multiplying the area by slice thickness. Subsequently, LVEF and RVEF were automatically calculated by MASS. LV and RV volumes were indexed for body surface area.

All subjects were imaged in the left lateral decubitus position with a commercially available system (Vingmed Vivid 7, General Electric Medical Systems, Milwaukee, Wisconsin) equipped with a 3.5-MHz transducer. Standard 2-dimensional images and Doppler and color Doppler data were acquired from the parasternal and apical views and digitally stored in cine-loop format. Analyses were performed off-line using EchoPac 108.1.5 (General Electric Medical Systems). For speckle tracking analysis, standard 2-dimensional gray-scale images with a frame rate ≥40 frames/s were used. Three cardiac cycles were obtained and stored in cine-loop format for off-line analysis. All echocardiographic measurements were averaged from 3 cardiac cycles. Presence of pulmonary regurgitation was systematically evaluated with continuous-wave Doppler echocardiography, by measuring duration of pulmonary regurgitation, and color Doppler echocardiography, by measuring width of regurgitant jet, as previously described by Li et al.

Global longitudinal RV strain was assessed with 2-dimensional speckle tracking analysis in the apical 4-chamber view, measuring the longitudinal peak systolic strain of the RV free wall, as described previously ( Figure 1 ). The weighted average of the 3 regional values of the RV free wall (basal, mid, and apical segments) provided the value of global longitudinal RV strain. Regional longitudinal peak systolic strain of the right ventricle was assessed at the basal, mid, and apical components of the RV free wall. Intra- and interobserver reproducibilities for RV strain measurement have been previously reported showing small bias and no significant trend (−0.2 ± 3.6% and 0.6 ± 3.8%, respectively).

(A) Two-dimensional speckle tracking echocardiogram of RV longitudinal strain in a patient with cToF. Global and segmental strain curves are automatically calculated, providing global and regional peak systolic longitudinal strains, with global RV (white dotted curve) , apical RV (green curve) , mid RV (blue curve) , and basal RV (yellow curve) strains displayed. (B) Two-dimensional speckle tracking echocardiographic “bull’s eye” plot of LV longitudinal strain in a patient with cToF. Longitudinal strain is most decreased at the apical level. (C) Two-dimensional speckle tracking echocardiographic apical and basal rotations and LV twist in a patient with cToF. LV twist is decreased, mainly due to decreased apical rotation. Displayed are basal rotation (purple curve) , apical rotation (blue curve) , and LV twist (white curve) . A2C = apical 2-chamber view; A4C = apical 4-chamber view; AFI = automated functional imaging; AVC_AUTO = aortic valve closure detected automatically; AVC_MEAS = aortic valve closure detected manually; Avg = average peak strain of the left ventricle; GLPS = global longitudinal peak strain; HR_ApLAX = heart rate during acquisition of apical long-axis view; LAX = apical long-axis view.

Global longitudinal LV strain was measured in apical long-axis and 2- and 4-chamber views using automated function imaging, a novel 2-dimensional speckle tracking algorithm. End-systolic frame is defined in the apical long-axis view. Closure of the aortic valve is marked and the software measures the interval between the R wave and aortic valve closure. This interval is used as a reference for apical 2- and 4-chamber views. After defining the mitral annulus and LV apex with 3 index points at the end-systolic frame in each apical view, the automated algorithm places the region of interest including the entire myocardial wall. The tracking algorithm follows the endocardium from this single frame throughout the cardiac cycle and allows for manual adjustment of the region of interest. The left ventricle is divided into 6 segments in each view and the tracking quality is manually validated for each segment. The algorithm displays regional and global longitudinal LV peak strains in a 17-segment model “bull’s-eye” plot, with average values of peak longitudinal strain for each view and averaged global peak longitudinal strain for the entire left ventricle ( Figure 1 ). Regional longitudinal LV strain was evaluated at basal, mid, and apical levels by calculating average strain values of basal, mid, and apical segments in apical long-axis and 2- and 4-chamber views. Intra- and interobserver reproducibilities for automated function imaging measurements have been previously reported with small bias and no significant trend (−0.3 ± 0.6% and −0.2 ± 2.6%, respectively).

LV rotation was measured at apical and basal levels in the parasternal short-axis view using 2-dimensional speckle tracking. The basal plane was identified by the presence of the mitral valve. The apical plane was defined as the smallest cavity during systole below the papillary muscles. Off-line, the endocardial border was traced at an end-systolic frame and the region of interest was placed to fit the entire myocardium. Subsequently, LV rotation of apical and basal planes was automatically calculated. Counterclockwise rotation provided a positive value, whereas clockwise rotation provided a negative value, as viewed from the apex. LV twist was defined as the maximal net difference in rotation between the LV apex and base at isochronal time points ( Figure 1 ).

Continuous variables are expressed as mean ± SD. Comparisons between patients and controls were analyzed using Mann-Whitney U test. Categorical variables are presented as numbers and percentages and were compared with Fisher’s exact test. Differences in RV apical strain between controls and subgroups of patients with cToF with mild, moderate, and severe pulmonary regurgitation were assessed with Kruskal-Wallis test. Furthermore, linear regression analysis was used to assess the relation between LVEF and RVEF and between global RV strain and global LV strain and LV twist. In addition, regional ventricular–ventricular interaction was studied by evaluating the relation between RV strain and LV strain and rotation at basal and apical levels with linear regression. To analyze whether surgical technique could determine RV and LV strains or LV rotational mechanics, univariate regression analysis was performed. A p value <0.05 was considered statistically significant.

Results

Characteristics of patients with cToF and healthy subjects are listed in Table 1 . All patients were in New York Heart Association functional class I. Baseline characteristics were not significantly different between patients with cToF and healthy controls with the exception of QRS duration (134 ± 19 ms in patients vs 94 ± 8 ms in controls, p <0.001). RV end-diastolic volume and RV end-systolic volume were larger in patients with cToF and RVEF was significantly decreased. LV dimensions and LVEF did not differ in patients with cToF compared to controls.

Assessment of RV function with 2-dimensional speckle tracking demonstrated significantly decreased global longitudinal RV strain in patients with cToF (−20.5 ± 4.2% vs −30.7 ± 3.3%, p <0.001) compared to controls ( Table 2 ). When assessing regional longitudinal RV strain, patients with cToF had significantly decreased strain in all segments of the RV free wall (basal, mid, and apical; Table 2 ). In addition, RV apical longitudinal strain was significantly different in controls and in patients with cToF with mild, moderate, and severe pulmonary regurgitation (−32.6 ± 4.7%, −20.2 ± 9.6%, −23.6 ± 6%, and −18.0 ± 5.3%, respectively; p <0.001).

Table 2

Global and regional right ventricular and left ventricular longitudinal peak systolic strains and left ventricular rotation and twist

2-Dimensional Speckle Tracking Parameters	Patients (n = 32)	Controls (n = 19)	p Value
Global right ventricular longitudinal peak systolic strain (%)	−20.5 ± 4.2	−30.7 ± 3.3	<0.001
Regional right ventricular longitudinal peak systolic strain (%)
Basal	−21.9 ± 6.2	−28.0 ± 5.5	0.001
Mid	−23.8 ± 3.7	−30.4 ± 4.2	<0.001
Apical	−20.7 ± 6.9	−32.6 ± 4.7	<0.001
Global left ventricular longitudinal peak systolic strain (%)	−17.2 ± 1.3	−20.4 ± 1.3	<0.001
Regional left ventricular longitudinal peak systolic strain (%)
Basal	−18.6 ± 2.5	−19.2 ± 2.4	0.519
Mid	−18.1 ± 2.1	−19.7 ± 2.7	0.014
Apical	−15.9 ± 2.8	−22.1 ± 3.4	<0.001
Left ventricular twist (°)	8.8 ± 3.3	14.8 ± 3.2	<0.001
Apical rotation (°)	5.6 ± 2.4	10.0 ± 2.0	<0.001
Basal rotation (°)	−4.1 ± 2.0	−5.3 ± 2.3	0.073

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Comparison of Platelet Reactivity and Periprocedural Outcomes in Patients With Versus Without Diabetes Mellitus and Treated With Clopidogrel and Percutaneous Coronary Intervention
2. Echocardiographic Predictors for Persistent Functional Mitral Regurgitation After Aortic Valve Replacement in Patients With Aortic Valve Stenosis
3. Effect of Candesartan Treatment on Left Ventricular Remodeling After Aortic Valve Replacement for Aortic Stenosis
4. A Meta-Analysis of Association Between Serum Lipoproteins and Abdominal Aortic Aneurysm

Stay updated, free articles. Join our Telegram channel

Join