Analysis of Left and Right Ventricular Doppler Tissue Imaging in Patients undergoing Percutaneous Closure of Patent Foramen Oval
- Volume 19 - Issue 6 - June, 2007
- Posted on: 8/1/08
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Patent foramen ovale (PFO) has been identified as a source of paradoxical embolism and cryptogenic stroke.1 Percutaneous PFO closure seems to be a highly efficient and safe procedure for the prevention of interatrial shunting,2 and is intended to reduce the recurrence of paradoxical emboli and cryptogenic stroke. Implantable PFO occluders of different types are of variably-sized (20–35 mm diameter) metal-containing devices. It is not clear whether implantation of these devices in the interatrial septum affects the motion of the nearby structures and biomechanics of the heart. Doppler tissue imaging (DTI) allows for the quantitative assessment of regional myocardial tissue velocities. We prospectively evaluated DTI parameters before and after percutaneous PFO closure in patients with an otherwise structurally normal heart.
Patients. We prospectively examined 14 consecutive patients who underwent percutaneous transcatheter PFO closure in our department from March 1999 to October 2005.
All patients were in sinus rhythm and had normal-sized heart chambers relative to body surface area, normal biventricular systolic function, normal age-related left ventricular (LV) diastolic filling patterns and no valvular or pericardial disease. PFO occlusion technique. All patients underwent percutaneous PFO closure using either an Amplatzer or a Helex septal occluder. The device type and size were selected by the attending physician according to the size and morphologic characteristics of the defect. All device implantations were conducted under general anesthesia with transesophageal echocardiographic and fluoroscopic guidance.
Echocardiographic evaluation. All patients underwent transthoracic echocardiography in the semilateral supine position using a 4.0 MHz transducer linked to a Phillips 7500 machine (Philips Medical Systems, Best, The Netherlands). Echocardiography was initially performed upon admission, prior to cardiac catheterization and then 24 hours, 10 days and 1 month after PFO occlusion. The study included conventional echocardiographic assessment. Pulse-wave Doppler examination was performed to obtain the indexes of LV diastolic function (peak early diastolic (E) and late diastolic (A) mitral inflow velocities, E/A ratio and E-wave deceleration time). Pulsed DTI was obtained from the apical 4-chamber mitral annular junction, the basal part of the interventricular septum adjacent to the hinge points of the atrioventricular valves and the basal right ventricular (RV) free-wall tricuspid annular junction. The measurements that were performed from the DTI recording in each of the 3 sites included: peak early diastolic myocardial tissue velocity (e), peak late diastolic myocardial tissue velocity (a), e/a ratio, and peak systolic myocardial tissue velocity (s). The ratio of transmitral velocity in early diastole to peak early diastolic mitral annular velocity (E/e) was calculated. The LV Tei index was calculated as (a-b)/b, where a is the time interval from the end of the a-wave to the onset of the e-wave of the next cardiac cycle, and b is the duration of the mitral annular s-wave (ejection time). All measurements were made in 3 consecutive cardiac cycles, and the average was calculated for subsequent analysis.
Statistics. All data were expressed as mean ± standard deviation (SD). The statistical analysis was performed using ANOVA repeated measurements. A p-value < 0.05 was considered statistically significant.
A total of 14 patients were prospectively evaluated; 1 male and 13 females. The mean age of the patients was 51.4 ± 10.1 years. The indications for PFO closure were: central nervous system embolic events in 11 patients, retinal artery emboli in 1 patient, splenic infarction in 1 patient and peripheral emboli (ischemic foot) in 1 patient. An Amplatzer septal occluder (AGA Medical Corp., Golden Value, Minnesota) was used in 9 patients, and a Helex Septal occluder (W.L. Gore & Associates, Inc., Elkton, Maryland) was used in the remaining 5 patients. The mean diameter of the occlusive devices was 25.9 ± 6 mm. There were no significant changes in heart rate or blood pressure values during the study period (Table 1). Consecutive 2-dimensional and Doppler echocardiographic studies did not reveal alterations in global and segmental ventricular function, valvular pathology or pericardial effusion. The mitral inflow E/A ratio did not change significantly, but a slight shortening in the E-wave deceleration time was observed.
The TDI measurements are presented in Table 2. A slight, but statistically significant, reduction in the systolic motion of the basal interventricular septum was observed, without a significant alteration in its diastolic motion. The systolic and diastolic motion of the free-wall mitral annulus junction and the free-wall tricuspid annulus junction remained unchanged, as shown by consecutive measurements. The myocardial performance index (Tei index) also remained unchanged during the study period (Table 2).
Percutaneous transcatheter PFO closure has become a widespread procedure for the prevention of recurrent paradoxical emboli.1 Various types of devices have been used for transcatheter PFO occlusion. All of them are metal-containing foreign bodies which are implanted in the interatrial septum. Postmortem and animal studies have shown good incorporation and complete endothelialization of the devices during the first postprocedural months,3 but it was not clear whether PFO occluders affected the function of structurally normal human hearts. Conventional 2-dimensional and Doppler echocardiography may detect pericardial effusion, valve dysfunction or other obvious mechanical complications of percutaneous PFO closure. In our study group, the analysis of the mitral valve inflow Doppler pattern, which was performed during echocardiographic follow up, revealed a mild, but statistically significant, shortening of the E-wave deceleration time (from 190 ± 29 to 174 ± 16 milliseconds; p = 0.05), reflecting minor changes in diastolic LV function.
The TDI allows for the detection of changes in regional myocardial motion. This method is widely used in the evaluation of diastolic ventricular function.4 We used the TDI for the detection of changes in myocardial motion before and following device implantation. The TDI analysis was performed in regions that are anatomically closed to the implanted device: the basal interventricular septum, mitral annulus-LV free-wall attachment and the tricuspid annulus-RV free-wall attachment. The analysis performed showed a reduction in the systolic motion velocity of the basal interventricular septum from 7.6 ± 1.8 to 6.4 ± 2.0 (p = 0.03), without changes in diastolic velocities. No changes in the systolic and diastolic velocities of the free-wall mitral annulus junction or the free-wall tricuspid annulus junction were observed.
The Tei index, which represents the sum of the isovolumic relaxation time and the isovolumic contraction time, divided by the LV ejection time, has been used as a sensitive measure of LV performance, including systolic and diastolic function.5 In our study group, the Tei index remained unchanged by consecutive measurements, reflecting the lack of influence of PFO occluding device closure on global myocardial performance. The described changes represent minor echocardiographic findings and are without clinical impact in our patients. These minor alterations were observed at the basal interventricular septum, which is the nearest point of investigation to the occlusive device.
In previously published studies, the TDI was used to detect changes in regional ventricular motion after transcatheter and surgical closure of atrial septal defects.6–9 Salaymeh at al showed that the Amplatzer atrial septal occluder may cause atrial septal distortion.10 But to the best of our knowledge, the influence of a PFO septal occluder on a structurally normal heart has not been previously examined. Study limitations. The limitations of this study may be the relatively small number of patients and the short follow-up period. We shall continue to enroll more patients for this prospective study and perform consecutive evaluations at 6 and 12 months following PFO closure to look for late changes in myocardial velocities and cardiac performance. A large, preferably multicenter study with a long follow-up period may provide more conclusive data concerning TDI findings after transcatheter PFO closure and the exclusion of potential clinical implications.