Study Population

We retrospectively screened 195 consecutive patients with CP seen at the Cleveland Clinic Center for the Diagnosis and Treatment of Pericardial Diseases from January 1, 2007, to December 31, 2010. Pericardiectomy was performed in 123 patients from this cohort. Of these, patients with any of absence of presurgical or postsurgical echocardiographic examination ( n = 46); severe valvular heart disease, concomitant valvular surgery at the time of pericardiectomy, or atrial fibrillation ( n = 12); left atrium not decorticated at the pericardiectomy ( n = 4); and uninterpretable echocardiographic images ( n = 9) were excluded from analysis. The final study population of 52 subjects had transthoracic echocardiographic images suitable for speckle-tracking echocardiographic analysis obtained both before and after pericardiectomy. We recruited 19 healthy volunteers (>50 years of age) with normal echocardiographic findings. Subjects were deemed healthy after undergoing thorough medical histories and physical examinations. Clinical data were obtained from medical records. New York Heart Association functional class was evaluated before and approximately 1 month after the procedure at an outpatient clinic. The study was approved by the local institutional review board.

Echocardiographic Protocol

In all patients, conventional transthoracic echocardiography was performed before (median, 12 days; interquartile range, 5–34 days) and after (median, 20 days; interquartile range, 5–64 days) pericardiectomy. Echocardiograms were stored digitally and reviewed using offline software (syngo Dynamics version 9.0; Siemens Medical Solutions, Erlangen, Germany). Apical four-chamber, two-chamber, and long-axis views were recorded at end-expiration. Two-dimensional and M-mode echocardiography from the parasternal short-axis view was used to derive LV end-diastolic and end-systolic dimensions. LV end-diastolic and end-systolic volumes, as well as ejection fraction, were calculated using Simpson’s rule. LA volume was determined using the modified Simpson’s method from apical four-chamber and two-chamber views at end–ventricular systole, just before atrial contraction, and at end–ventricular diastole to determine LA phasic function. To determine LA conduit volume, the following formula was used: LA conduit volume = LV stroke volume − LA stroke volume. The values for two-dimensional echocardiographic parameters were obtained after averaging three consecutive cycles.

Pulsed Doppler echocardiography of transmitral flow and pulmonary venous flow was performed as previously described. From transmitral recordings, the peak early (E) and late (A) diastolic filling velocities, the E/A ratio, E-wave deceleration time, E-wave velocity-time integral (VTI _E ), A-wave VTI (VTI _A ), and LA filling fraction ({VTI _A /[VTI _E + VTI _A ]} × 100) were obtained. The following measurements were taken from pulmonary vein velocities: peak S-wave inflow (S) velocity during ventricular systole, peak D-wave inflow (D) velocity during the early phase of ventricular diastole, and peak reversed atrial wave (Ar) velocity during LA contraction. Peak velocities were measured after the onset of inspiration and expiration, and the average of three to six respiratory cycles was calculated. The percentage change in transmitral flow peak early diastolic velocities from expiration to inspiration was calculated using the formula (expiration − inspiration)/expiration × 100%, according to previous methods used by Appleton et al.

Measurement of LA Longitudinal ϵ with Velocity Vector Imaging (VVI)

Only clips with good-quality images, enough depth to include the whole left atrium, and acquired at high frame rates were used for analysis. The average frame rate of the clips for LA ϵ analysis was 57 ± 14 frames/sec. We used the onset of the P wave as the reference point for the calculation of LA ϵ, as previously proposed. The use of the P wave as the reference point enabled the recognition of peak positive global LA ϵ (ϵ _positive ), which corresponded to LA conduit function; peak negative global LA ϵ (ϵ _negative ), which corresponded to LA contractile function; and the sum of these values, total global LA ϵ (ϵ _total ), which corresponded to LA reservoir function. The measurements were performed offline using dedicated software (VVI; Siemens Medical Solutions USA, Inc., Mountain View, CA). One cardiac cycle was selected for each apical view, and the endocardial border was traced manually. The software subsequently traced the borders in the other frames automatically. The vectors of the velocities of the endocardial points were then displayed and overlaid onto the B-mode images. In segments with poor tracking (assessed subjectively), endocardial borders were readjusted until better tracking was achieved. If this was unattainable, those segments were excluded. Graphical displays of deformation parameters for each segment and averaged ϵ curves were then generated automatically and were used for the measurement of LA ϵ values ( Figure 2 ). Global LA longitudinal ϵ was measured from three standard apical views, as previously described. In the three-chamber view, we included only the inferolateral wall, because the opposing wall includes the ascending aorta. Any view in which two or more segments could not be tracked was not included in the analysis, and the remaining apical views were averaged to calculate global longitudinal LA ϵ. To calculate regional LA ϵ in the septal and lateral walls, we combined basal and mid septal ϵ as septal variables and basal and mid lateral ϵ as lateral variables. We excluded posterior apical segments in this calculation. We then compared LA ϵ between the septal and lateral LA walls to assess the laterality of constrictive tethering and its recovery.

Measurement of LA longitudinal ϵ using speckle-tracking imaging in patients before and after pericardiectomy. Graphical displays of deformation parameters for each segment were generated automatically and were used for the measurement of LA ϵ values. (A) This patient showed depressed LA ϵ variables in the lateral walls ( yellow and sky blue ) and high variables in the septal walls ( red and blue ). (B) Lateral LA ϵ was increased, septal LA ϵ was decreased, and global LA ϵ ( black ) improved after the procedure.

Operative Details

Pericardiectomy was performed through a sternotomy or left thoracotomy incision. The standard pericardial resection at our institution is a comprehensive pericardiectomy, with wide excision of the pericardium anteriorly between the two phrenic nerves and from the great arteries superiorly to the diaphragm inferiorly, posterior to the left phrenic nerve to the left pulmonary veins, and including the pericardium on the diaphragmatic and posterior surfaces of the ventricles. The atria and venae were decorticated if the dissection could be accomplished without risk for hemorrhage.

Reproducibility

Interobserver and intraobserver variability for global LA ϵ (negative, positive, and total) was examined. Measurements were performed in a group of 10 randomly selected subjects by one observer who repeated it twice and by two investigators who were unaware of each other’s measurements and study time points. The bias (mean difference), limits of agreement (1.96 SDs of difference), and coefficient of variation between the first and second measurements were determined.

Statistical Analysis

Continuous variables are expressed as mean ± SD if normally distributed and as medians and interquartile ranges if not normally distributed. Normality was assessed using the Kolmogorov-Smirnov test. Paired t tests were used to compare the clinical and echocardiographic parameters before and after pericardiectomy if normally distributed, and Wilcoxon’s signed-rank test was used if not normally distributed. Student’s t test was used to compare the clinical and echocardiographic data between patients and controls if normally distributed and the Mann-Whitney U test if not normally distributed. To measure the strength of the correlation between LA ϵ variables and conventional parameters of LA function, linear regression analysis with Pearson’s correlation coefficient was performed. Two-way repeated-measures analysis of variance was used for group comparison. Statistical analyses were performed using a commercially available software program (StatView version 5.0; SAS Institute Inc., Cary, NC). P values < .05 were considered statistically significant.

Patient Characteristics

A total of 52 patients who met the inclusion and exclusion criteria and 19 control subjects were included in this study. In most patients, radical pericardiectomy was performed. Concomitant operation with coronary artery bypass grafting was performed in four patients. Population characteristics are summarized in Table 1 . The CP etiology was idiopathic in 35 (67.3%), previous cardiac surgery in 11 (21.1%), previous radiation therapy in three (5.8%), and miscellaneous (postpericarditis) in three (5.8%) patients. B-type natriuretic peptide did not show a significant change, but serum creatinine and total bilirubin improved significantly after the procedure ( Table 1 ). Symptomatic alleviation was observed in 35 patients (67%) at 1 month after the procedure ( Figure 3 ).

Improvement of New York Heart Association (NYHA) functional class after pericardiectomy. Symptomatic alleviation was observed in 35 patients (67%) at 1 month after the procedure.

Standard and Doppler Echocardiographic Parameters

Two-dimensional echocardiographic features are described in Table 2 . LV end-diastolic and end-systolic volumes increased significantly after pericardiectomy, with preserved LV ejection fraction. LA phasic volume indexes did not change significantly after the procedure. Doppler echocardiographic characteristics are summarized in Table 3 . Respiratory variation of the transmitral E wave showed significant decrease after pericardiectomy. In pulmonary vein flow velocities, patients showed significant increases in S and Ar velocities after the procedure. In terms of LA phasic function estimated by two-dimensional LA volume analysis, contractile and reservoir function (active and total LA stroke volume) improved after the surgical procedure, but other variables, including LA emptying fraction, did not show significant changes ( Table 4 ).

Table 3

Doppler echocardiographic characteristics

Variable	Pre ( n = 52)	Post ( n = 52)	Normal ( n = 19)	P value
				Pre vs post	Pre vs normal	Post vs normal
E (cm/sec)	84 ± 29	97 ± 30	72 ± 19	.003	.054	.002
A (cm/sec)	56 ± 20	63 ± 26	67 ± 17	.029	.080	.622
LA filling fraction (%)	33 ± 8	31 ± 11	35 ± 3	.249	.364	.221
E-wave deceleration time (msec)	161 ± 47	183 ± 61	208 ± 36	.067	<.001	.183
%E	20.4 ± 8.1	12.5 ± 6.4		<.0001
S (cm/sec)	49 ± 14	57 ± 14	64 ± 12	.028	<.001	.015
D (cm/sec)	58 ± 16	64 ± 11	48 ± 8	.078	.018	<.001
Ar (cm/sec)	28 ± 5	33 ± 11	32 ± 5	.025	.019	.807

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