Increased ventricular end-diastolic pressure (VEDP) is a known risk factor for morbidity and mortality in patients with single-ventricle physiology. Spectral Doppler tissue imaging (DTI) has been shown to modestly correlate with direct measurement of VEDP. Strain rate (SR) values, obtained via myocardial deformation, have not yet been compared with VEDP in this patient population. The goal of this study was to evaluate which of these imaging techniques correlates best with VEDP in patients with single-RV (RV) physiology.
Patients with single-RV physiology who underwent simultaneous echocardiography and catheterization were evaluated. Echocardiographic data included global longitudinal SR early diastolic wave (SRe) and SR late diastolic wave (SRa), DTI early diastolic wave (e′) and DTI late diastolic wave (a′) of the right ventricular free wall, and right atrioventricular valve inflow velocities (E and A waves). E/SRe and E/e′ ratios were calculated. VEDP was obtained from the catheterization report.
Twenty-seven studies were performed on patients with single-RV physiology. The median age at the time of catheterization was 11.4 months (range, 0–132 months). The mean VEDP was 9.9 ± 4.5 mm Hg. VEDP correlated significantly with E/SRe ratio ( r = 0.88), global SRe ( r = −0.52), SRe/SR late diastolic wave ratio ( r = −0.42), and valve A velocity ( r = 0.48). There were no significant correlations between VEDP and DTI measurements. Receiver operating characteristic curve analysis using an E/SRe cutoff of 150 cm showed 87.5% sensitivity and 78.9% specificity for predicting VEDP > 10 mm Hg.
In patients with single-RV physiology, VEDP correlated strongly with SR but not with DTI measurements. SR measurements should be considered as a possible means to estimate VEDP in this complex patient population rather than DTI.
Elevated ventricular end-diastolic pressure (VEDP) is a marker for diastolic dysfunction. Increased VEDP is known to be associated with morbidity and mortality in patients with single-ventricle physiology. Cardiac catheterization is the gold standard used to assess VEDP in patients with single-ventricle physiology. Few studies have assessed methods of noninvasively evaluating VEDP in the single-RV (RV) population. If a noninvasive measurement could accurately estimate VEDP in the single-RV patient population, this would assist in caring for this complex population.
Menon et al. showed modest correlations between Doppler tissue imaging (DTI) variables and pulmonary vein Doppler pattern with VEDP in patients with single-ventricle physiology. Learn et al. also showed significant correlations between DTI values and atrioventricular valve early diastolic wave velocity with invasively measured central venous pressures after cardiac surgery in 20 patients with single-ventricle physiology. However, both these studies did not evaluate deformation values in assessing VEDP in this population.
Strain rate (SR) early diastolic wave (SRe) and SR late diastolic wave (SRa) values obtained via myocardial deformation analysis are emerging as a new technique to assess diastolic myocardial function. Kimura et al. showed that speckle-tracking–derived E/SRe ratios in patients with normal heart anatomy demonstrated better correlations with invasively measured ventricular filling pressures (pulmonary capillary wedge pressures) than tissue Doppler. No studies have evaluated the validity of SR in assessing VEDP in patients with single RVs.
The goal of this study was to determine which noninvasive echocardiographic diastolic parameter had the best correlation with VEDP in patients with single RVs.
The institutional review board approved this prospective study. All consecutive patients with single RVs who underwent cardiac catheterization from 2011 to 2012 were recruited for the study. Informed consent was obtained from parents before cardiac catheterization. Assent was obtained from patients aged > 9 years. All patients with single RVs undergoing catheterization for any indication were included. Exclusion criteria were poor echocardiographic image quality such that SR analysis could not be performed on a six-segment model of the single RV with postprocessing, absent or near absent interventricular septum that did not allow six-segment analysis in patients with the diagnosis of double-outlet RV or unbalanced atrioventricular septal defect, nonatrial rhythm, and failure to obtain consent. Thirteen patients were excluded, five for poor image quality, one for junctional rhythm, one for a missing electrocardiogram, four for absent or near absent interventricular septum, and two for incomplete catheterization data.
All echocardiographic studies were obtained using a Vivid I or Vivid 7 machine (GE Healthcare, Wauwatosa, WI) after the patient was under general anesthesia and just before the start of the cardiac catheterization. Frame rates were maintained at >80 frames/sec in all studies. Views equivalent to a standard apical four-chamber view were obtained ( Figure 1 ). Images were optimized for the visualization of the epicardial and endocardial borders of the single RV. Postprocessing of all images was completed offline using EchoPAC version 10 (GE Healthcare), which obtains SR values via speckle-tracking analysis. All measurements were made in triplicate by a single observer blinded to the results of the cardiac catheterization measurements.
DTI measurements of the right ventricular free wall at the level of the atrioventricular valve annulus were obtained in the apical four-chamber view. DTI early diastolic wave (e′) and DTI late diastolic wave (a′) of the right ventricular free wall were obtained using pulsed spectral Doppler sampling in all patients. Right atrioventricular valve peak inflow velocities, early diastolic wave (E) and late diastolic wave (A), were also obtained from the same view. E/e′, e′/a′, and E/A ratios were derived from these values. Myocardial performance index was also calculated ([isovolumetric contraction time + isovolumetric relaxation time]/ejection time) using corresponding DTI values for the free right ventricular wall.
The endocardial border of the single RV in an apical four-chamber view was traced from the septal-atrioventricular annular hinge point to the apical septum and then to the right ventricular lateral wall at the lateral-atrioventricular annular hinge point. The automated epicardial-to-endocardial computer-generated border, or region of interest, was adjusted to include the epicardium. The single RV was divided automatically into a six-segment model. Borders were accepted if both visual inspection and the software indicated adequate tracking for all segments. Patients whose segments did not track well because of artifacts or inadequate visualization of the lateral borders of the RV were excluded. Longitudinal peak global SRe and global SRa were obtained on postprocessing evaluation of the global SR curve ( Figure 2 ). Global values were obtained by averaging the values of six-segment model in EchoPAC. E/SRe and SRe/SRa ratios were calculated from these variables, similarly to DTI measurements.
All hemodynamic measurements were performed under general anesthesia under the same steady-state conditions as for echocardiography. VEDP of the single RV was measured on the ventricular pressure tracing as the point just before the rapid rise in ventricular pressure corresponding to ventricular systole. VEDP numeric values were obtained from cardiac catheterization reports. All cardiac catheterization data were obtained before any interventional procedure was performed.
Correlations of continuous variables with VEDP were examined using linear regression analysis and Pearson’s r correlation coefficients. Areas under the curve with χ 2 difference tests were used to examine differences in logit models comparing E/SRe ratio ≥ 150 cm and E/SRe ratio ≥ 200 cm. A VEDP of 10 mm Hg was used as a cutoff value on the basis of previous studies and the increased likelihood that VEDP above this value would be suboptimal for single-ventricle palliation. P values ≤ .05 were considered significant.
To examine interobserver and intraobserver variability, three measurements were taken for each parameter on a random sample of 10 subjects and completed by one observer. An additional observer completed a single set of measurements on the same 10 subjects on all the parameters. Intraclass correlation coefficients were used to measure the levels of interobserver and intraobserver variability. Agreement was considered excellent (>0.75), good (0.60–0.74), or poor (<0.40) as defined by the intraclass correlation coefficient.
All analysis was conducted using Stata version 12 SE (StataCorp LP, College Station, TX). Results are presented as means and standard deviations unless otherwise specified.
Forty patients were enrolled, and 13 studies were excluded. There were no significant differences in the excluded patients’ ages (mean, 4.8 ± 4.3 years), gender (seven male, six female), diagnoses (seven with hypoplastic left heart syndrome, five with double-outlet RVs, one with an unbalanced atrioventricular septal defect), stage of palliation (two hybrid, seven comprehensive stage II/bidirectional Glenn, four Fontan), or oxygen saturation (mean, 84 ± 6%) compared with the included patients. A total of 27 studies were thus included in the analysis. Baseline demographics and individual data are presented in Tables 1 and 2 Most patients had the diagnosis of hypoplastic left heart syndrome. The majority of patients were in their early postoperative period from a hybrid stage I procedure (with bilateral pulmonary artery banding and stenting of the ductus arteriosus), with the rest being either postoperative Glenn/comprehensive stage II or Fontan procedure ( Tables 1 and 2 ). The mean systemic arterial oxygen saturation was 78 ± 10%, and VEDP ranged from 5 to 24 mm Hg (median, 9 mm Hg). Eight patients had VEDP > 10 mm Hg. Mean and individual DTI and strain values are given in Tables 3 and 4 .
|Age (mo), median (range)||11.4 (0–132)|
|Hypoplastic left heart syndrome||20|
|Double-outlet right ventricle/tetralogy of Fallot||5|
|Unbalanced atrioventricular septal defect||2|
|Hybrid stage I||12|
|Comprehensive stage II/bidirectional Glenn||7|
|Oxygen saturation at the time of catheterization (mg/L), mean ± SD||78 ± 10|
|Patient||Demographic variables||Clinical variables|
|Age (y)||Sex||Diagnosis||Stage of palliation||VEDP (mm Hg|