© 2014, Wiley Periodicals, Inc. DOI: 10.1111/echo.12523
Echocardiography
Which Technique Is Better for Detection of Right-toLeft Shunt in Patients with Patent Foramen Ovale: Comparing Contrast Transthoracic Echocardiography with Contrast Transesophageal Echocardiography Yue Li, M.D., Zhai Ya-nan, M.D. and Wei Li-qun, M.D. Ultrasound Department of Chinese, PLA General Hospital, Beijing, China
Background: At present there is no consensus on which technique is more suitable for the detection of right-to-left shunt (RLS) in patients with patent foramen ovale (PFO). The aim of study was to compare the efficacy of contrast transthoracic echocardiography (cTTE) and contrast transesophageal echocardiography (cTEE) in the detection of RLS. Methods: A prospective study was undertaken in 29 patients with PFO. Both cTTE with harmonic imaging modality and cTEE with fundamental imaging modality were performed for all the patients. The severity of RLS were semiquantitatively assessed with a fourlevel grade system by scaling the numbers of microbubbles (MBs) in the left atrium after complete opacification of the right atrium within the first 3 cardiac cycles. Level 1 represents no MBs, indicating no RLS. Level 2, ≤10 MBs, indicating mild RLS. Level 3, 11–30 MBs, indicating moderate RLS and Level 4, >30 MBs, indicating severe RLS. Results: Contrast TTE demonstrated significantly higher sensitivity for detection of RLS than cTEE (86% vs. 56%, P < 0.05). For cTTE, there were 4, 1, 5, and 19 cases determined at levels 1, 2, 3, and 4, respectively, whereas for the same group of patients 13, 2, 6, and 7 cases were identified by cTEE at levels 1, 2, 3, and 4, respectively. The severity of RLS detected by cTTE was significantly greater than that by cTEE (P < 0.01). Conclusions: Contrast TTE is more efficacious in the detection of RLS than cTEE. The former can be used as an alternative to the latter in clinical practice. (Echocardiography 2014;31:1050–1055) Key words: patent foramen ovale, right-to-left shunt, contrast echocardiography, transthoracic echocardiography, transesophageal echocardiography Patent foramen ovale (PFO) is a remnant of the fetal circulation, which exists in about 25% of population. Some diseases, such as cryptogenic stroke,1 migraine headache,2 arterial gas embolism due to decompression,3 and platypneaorthodeoxia syndrome,4 may be associated with the transient shunting of blood from the right atrium to left atrium across PFO (RLS-PFO). Thus, the diagnosis and quantification of the RLS-PFO is important in clinical practice. Contrast echocardiography with agitated saline is commonly used for the detection of RLS-PFO. There are 2 techniques; contrast transthoracic echocardiography (cTTE) and contrast transesophageal echocardiography (cTEE). Both are used by clinicians in this case. However, there is no consensus on which technique is more suitable in routine diagnosis and evaluation of such patients. The aim of this Address for correspondence and reprint requests: Yue Li, M.D., Ultrasound Department of Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853, China. E-mail: [email protected]
1050
study was to compare the efficacy of the 2 techniques in the detection of RLS-PFO. Methods: Patients: A prospective study was undertaken in 29 consecutive patients with PFO who were referred to our department as outpatients for diagnosis and treatment of migraine or cryptogenic stroke (13 male; 16 female; 15–54 years of age; mean age: 39 16.6 years). The diagnosis of PFO was based on transesophageal echocardiography (TEE) or transthoracic echocardiography (TTE) observations of the anatomic feature of interatrial septum. The diagnoses of migraine and cryptogenic stroke were made by neurologists of our hospital using the criteria of the International Headache Society and American Stroke Association. Exclusion criteria included other cardiovascular defects: atrial septal defect, mitral stenosis, enlarged left atrium, heart failure, and any cases with increase in left atrial pressure which may affect the results of contrast echocardiography in the detection of RLS-PFO.
Technique for Detection of RLS in PFO
Contrast Echocardiography: The cTTE examinations were performed using the Vivid 7 system (General Electric, Vingmed Ultrasound AS, Horten, Norway) fitted with a multifrequency probe with a harmonic imaging modality (transmitting frequency 1.7–2.0 MHz, receiving frequency 3.4–4.0 MHz). The cTEE examinations were performed using the same system with a fundamental imaging modality (transmitting frequency 3.5–7 MHz). Agitated saline was used as the contrast agent. Gain settings were adjusted individually to optimize the visualization of the microbubbles (MBs) and the interatrial septum. The cTTE was performed first and cTEE was performed approximately 30 minutes later in every patient. Each technique was repeated for at least 3 times and the interval between examinations was kept over 5 minutes. The contrast agent was prepared by agitating 1 mL of air with 9 mL of sterile saline solution using two 10 mL syringes and a 3-way stopcock. Agitated saline was rapidly administrated from an antecubital vein at rest and during the maintenance stage or release phase of Valsalva maneuver. The presence of RLS-PFO was confirmed when mircobubbles (MBs) were seen in the left atrium within the first 3 cardiac cycles after contrast appearance in the right atrium at rest or during the maintenance stage or release phase of Valsalva maneuver. Image acquisition involved the capture of 10 consecutive beats on digital storage media before and after the release phase of Valsalva maneuver. The severity of RLS-PFO was semiquantified into a four-level scale, level 1 indicating no MBs appeared in the left atrium in every single frame image, namely no RLS-PFO, level 2 indicating ≤10 MBs, namely mild RLS-PFO, level 3 indicating 11–30 MBs, namely moderate RLSPFO, and level 4 indicating >30 MBs, namely severe RLS-PFO. Statistical Analysis: The sensitivity for detection of RLS-PFO was determined by dividing the number of positive contrast echocardiography with each modality by 29, the total numbers of patients. Specificity was not calculated because all 29 patients had been diagnosed as PFO and no false positive was expected. For the comparison of sensitivity between the 2 techniques the Fisher’s exact test (2-sided) was used. The Wilcoxon signed rank-sum test was used to assess the severity of RLS-PFO based on the semiquantified scales derived from the 2 techniques. The SPSS 13.0 software package (SPSS Inc, Chicago, IL, USA) was used for statistical analysis. A P value of 30 MBs appearance in the left atrium after complete opacification of the right atrium within first 3 cardiac cycles in every single frame image.
fundamental imaging modality could lead to an increase in sensitivity for detecting of RLS-PFO from 22–62% to 63–100%.9,16,20 Second, the left atrial pressure is normally greater than the right atrial pressure throughout most of a cardiac cycle. In patients with PFO, the directions of the shunts between left and right atrium are dynamic and closely linked to right and left atrial pressures. In early ventricular systole, a temporary pressure reversal occurs with the Valsalva maneuver, that is, the right atrial pressure exceeds that of the left atrial pressure. It has been generally accepted that Valsalva maneuver can improve the sensitivity of RLS-PFO detected by contrast echocardiography. Valsalva maneuver has become an integral part of saline contrast studies for detecting of RLS-PFO.21–25 It is difficult for a patient to perform a strenuous Valsalva maneuver during cTEE because esophageal intubation could prevent effective glottic closure. The mean gradient between right atrial pressure and left atrial pressured during the Valsalva maneuver with or without TEE was significantly different: 12.1 3.1 mmHg (without TEE) versus 7.8 5.8 mmHg (with TEE).21 The pressure reversal between right and left atrium during Valsalva maneuver often coincided with the bulging of the septum with convexity toward the left atrium. In our study, the rate of right-to-left septal shifting detected with TEE modality was 48% (14/29), whereas with TTE modality, 72% (21/29). Thus, cTEE has a higher false negative rate in the detection of RLS-PFO due to ineffective or inadequate Valsalva maneuver. Third, as mentioned above the gradients of the reversal pressure between the left and right atrium is low
and brief during a cardiac circle. Some other factors associated with the TEE examination, such as fasting state, sedation, and pharyngeal reflex caused by intubation before and during the examination, may induce hypotention and thus decrease the right atrial pressure. This further lowers or even eliminates the reversal pressure gradients between 2 atria during Valsava maneuver. These factors all limit the efficacy of TEE in the detection of RLS-PFO. Although the efficacy in the detection of RLSPFO with cTTE is higher than that with cTEE, TEE permits detailed study of the interatrial septum as it better visualizes the septum primum coaptation over the fossa ovale. The TTE definition in detailed studies of interatrial septal anatomy is inferior to that of TEE and the latter is currently still considered the golden standard in terms of establishing the presence of PFO anatomically. However, with the help of a contrast agent cTTE can be used as the first imaging modality to effectively detect RLS-PFO. There are several advantages when using cTTE as an alternative to cTEE. It can increase the relevance ratio and the semiquantitative accuracy as verified by our study and some previous reports. If a patient has a good acoustic window and the PFO can be diagnosed by TTE. When using cTTE the discomfort and complications that could occur during TEE are avoided. cTTE can also be used in some patients with swallowing dysfunction, a contraindication or poor cooperation for cTEE. Most importantly, a negative cTTE study may obviate the need to perform a TEE. In theory, the existence of the right-to-left shunt or its severity is the most critical problem in patients with PFO. If 1053
Li, Ya-nan and Li-qun
a patient with cryptogenic stroke or migraine shows no evidence of RLS-PFO, we should suspect other cardiac sources of embolism or pathomechanism for the diseases. As we know, 25% of the population has PFO but only a portion of them develop a neurological condition. Our study has some limitations. The first one would be the small sample size. In consideration of this our research employed a paired study design. We performed cTTE and cTEE in the same day and controlled the examination conditions as much as possible. Therefore, the results of our study still have certain reference value. They are in agreement with the findings from a previous report derived from a large sample study.18 The second limitation would be that only a single contrast agent, that is, agitated saline, was used. Some research showed that the second harmonic imaging modality seemed to have variant effects on different contrast agents.26 However, agitated saline is the most widely used contrast agent for detection of RLS worldwide.27 It has obvious advantages of being easy to prepare and economic. There are no generally accepted quantitative grading systems for assessing the severity of RLS-PFO up to now.9,28,29 Our scales were based on the numbers of MBs appeared in left atrium. Although a severe RLS may sound misleading as the RLS volumes in most patients with PFO are small, these scales are still useful to evaluate the efficacy of 2 techniques in the detection of RLSPFO. Patients with severe RLS-PFO may be more likely to suffer from the diseases associated with PFO, but that is another question and requires further study. Conclusions: Contrast TEE with a harmonic imaging modality was shown to be more effective than cTEE in the detection of RLS-PRO. cTEE with a fundamental imaging modality underestimated the severity of RLS-PFO. cTTE could be used as an alternative to cTEE in screening RLS-PFO in clinical practice. References 1. Schuchlenz HW, Weihs W, Horner S, et al: The association between the diameter of a patent foramen ovale and the risk of embolic cerebrovascular events. Am J Med 2000;109:456–462. 2. Sharma A, Gheewala N, Silver P: Role of patent foramen ovale in migraine etiology and treatment: A review. Echocardiography 2011;28:913–917. 3. Knauth M, Ries S, Pohimann S, et al: Cohort study of multiple brain lesions in sport divers: Role of a patent foramen ovale. BMJ 1997;314:701–705. 4. Godart F, Rey C, Prat A, et al: Atrial right-toleft shunting causing severe hipoxaemia despite normal right-sided pressures: Report of 11 consecutive cases corrected by percutaneous closure. Eur Heart J 2000;21:483–489. 5. Sevgi EB, Erdener SE, Demirci M, et al: Paradoxical air microembolism induces cerebral bioelectrical abnormalities and occasionally headache in patent foramen ovale
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7. 8. 9. 10. 11.
12.
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19. 20.
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22. 23.
patients with migraine. J Am Heart Assoc 2012;1: e001735. Mojadidi MK, Khessali H, Gevorgyan R, et al: Visual migraine aura with or without headache: Association with right to left shunt and assessment following transcutaneous closure. Clin Ophthalmol 2012;6:1099–1105. Guchlerner M, Kardos P, Liss-Koch E, et al: PFO and right-to-left shunting in patients with obstructive sleep apnea. J Clin Sleep Med 2012;8:375–380. Rajani R, Lee L, Sohal M, et al: Redo patent foramen ovale closure for persistent residual right-to-left shunting. EuroIntervention 2011;6:735–739. Soliman OI, Geleijnse ML, Meijboom FJ, et al: The use of contrast echocardiography for the detection of cardiac shunts. Eur J Echocardiogr 2007;8:S2–S12. Matsuoka H: Paradoxical brain embolism. Brain Nerve 2008;60:1134–1143. Caputi L, Carriero MR, Falcone C, et al: Transcranial Doppler and TEE: Comparison of both techniques and prospective clinical relevance of transcranial Doppler in patent foramen ovale detection. J Stroke Cerebrovasc Dis 2009;18:343–348. Li Y, Wen CY, Li YM, et al: Echocardiographic value in transcatheter closure and discussion of shunt derection of patert foramen ovale. Chin J Med Imaging Technol 2004;20:1570–1573. Fenster BE, Curran-Everett D, Freeman AM, et al: Saline contrast echocardiography for the detection of patent foramen ovale in hypoxia: A validation study using intracardiac echocardiography. Echocardiography 2014; 31:420–427. Jesurum JT, Fuller CJ, Renz J, et al: Diagnosis of secondary source of right-to-left shunt with balloon occlusion of patent foramen ovale and power M-mode transcranial Doppler. JACC Cardiovasc Interv 2009;2:561–567. Pepi M, Evangelista A, Nihoyannopoulos P, et al: European Association of Echocardiography. Recommendations for echocardiography use in the diagnosis and management of cardiac sources of embolism: European Association of Echocardiography (EAE). Eur J Echocardiogr 2010;11:461–476. Dani€els C, Weytjens C, Cosyns B, et al: Second harmonic TTE: The new reference screening method for the detection of patent foramen ovale. Eur J Echocardiogr 2004;5:449–452. Madala D, Zaroff JG, Hourigan L, et al: Harmonic imaging improves sensitivity at the expense of specificity in the detection of patent foramen ovale. Echocardiography 2004;21:33–36. Thanigaraj S, Valika A, Zajarias A, et al: Comparison of transthoracic versus TEE for detection of right-to-left atrial shunting using agitated saline contrast. Am J Cardiol 2005;96:1007–1010. Paelinck BP, Kasprzak JD: Contrast-enhanced echocardiography: Review and current role. Acta Cardiol 1999;54:195–201. Van Camp G, Franken P, Melis P, et al: Comparison of TTE with second harmonic imaging with TEE in the detection of right to left shunts. Am J Cardiol 2000;86:1284e7. Pfleger S, Konstantin Hasase K, Stark S, et al: Haemodynamic quantification of different provocation manoeuvres by simultaneous measurement of right and left atrial pressure: Implications for the echocardiographic detection of persistent foramen ovale. Eur J Echocardiogr 2001;2:88–93. Gorgulu S, Eksik A, Eren M, et al: Assessment of the effects of various maneuvers on both atrial pressure changes. Int J Cardiol 2003;92:241–245. Marriott K, Manins V, Forshaw A, et al: Detection of right-to-left atrial communication using agitated saline contrast imaging: Experience with 1162 patients and
Technique for Detection of RLS in PFO
recommendations for echocardiography. J Am Soc Echocardiogr 2013;26:96–102. 24. Lam YY, Yu CM, Zhang Q, et al: Enhanced detection of patent foramen ovale by systematic transthoracic saline contrast echocardiography. Int J Cardiol 2011;152: 24–27. 25. Woods TD, Patel A: A critical review of patent foramen ovale detection using saline contrast echocardiography: When bubbles lie. J Am Soc Echocardiogr 2006;19: 215–222. 26. Lef evre J, Lafitte S, Reant P, et al: Optimization of patent foramen ovale detection by contrast TTE using second
harmonic imaging. Arch Cardiovasc Dis 2008;101: 213–219. 27. Cruz-Gonzalez I, Solis J, Inglessis-Azuaje I, et al: Patent foramen ovale: Current state of the art. Rev Esp Cardiol 2008;61:738–751. 28. Homma S, Sacco RL, Di Tullio MR, et al: Effect of medical treatment in stroke patients with patent foramen ovale: Patent foramen ovale in Cryptogenic Stroke Study. Circulation 2002;105:2625–2631. 29. Kobayashi K, Iguchi Y, Kimura K, et al: Contrast transcranial Doppler can diagnose large patent foramen ovale. Cerebrovasc Dis 2009;27:230–234.
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Echocardiography
Which Technique Is Better for Detection of Right-toLeft Shunt in Patients with Patent Foramen Ovale: Comparing Contrast Transthoracic Echocardiography with Contrast Transesophageal Echocardiography Yue Li, M.D., Zhai Ya-nan, M.D. and Wei Li-qun, M.D. Ultrasound Department of Chinese, PLA General Hospital, Beijing, China
Background: At present there is no consensus on which technique is more suitable for the detection of right-to-left shunt (RLS) in patients with patent foramen ovale (PFO). The aim of study was to compare the efficacy of contrast transthoracic echocardiography (cTTE) and contrast transesophageal echocardiography (cTEE) in the detection of RLS. Methods: A prospective study was undertaken in 29 patients with PFO. Both cTTE with harmonic imaging modality and cTEE with fundamental imaging modality were performed for all the patients. The severity of RLS were semiquantitatively assessed with a fourlevel grade system by scaling the numbers of microbubbles (MBs) in the left atrium after complete opacification of the right atrium within the first 3 cardiac cycles. Level 1 represents no MBs, indicating no RLS. Level 2, ≤10 MBs, indicating mild RLS. Level 3, 11–30 MBs, indicating moderate RLS and Level 4, >30 MBs, indicating severe RLS. Results: Contrast TTE demonstrated significantly higher sensitivity for detection of RLS than cTEE (86% vs. 56%, P < 0.05). For cTTE, there were 4, 1, 5, and 19 cases determined at levels 1, 2, 3, and 4, respectively, whereas for the same group of patients 13, 2, 6, and 7 cases were identified by cTEE at levels 1, 2, 3, and 4, respectively. The severity of RLS detected by cTTE was significantly greater than that by cTEE (P < 0.01). Conclusions: Contrast TTE is more efficacious in the detection of RLS than cTEE. The former can be used as an alternative to the latter in clinical practice. (Echocardiography 2014;31:1050–1055) Key words: patent foramen ovale, right-to-left shunt, contrast echocardiography, transthoracic echocardiography, transesophageal echocardiography Patent foramen ovale (PFO) is a remnant of the fetal circulation, which exists in about 25% of population. Some diseases, such as cryptogenic stroke,1 migraine headache,2 arterial gas embolism due to decompression,3 and platypneaorthodeoxia syndrome,4 may be associated with the transient shunting of blood from the right atrium to left atrium across PFO (RLS-PFO). Thus, the diagnosis and quantification of the RLS-PFO is important in clinical practice. Contrast echocardiography with agitated saline is commonly used for the detection of RLS-PFO. There are 2 techniques; contrast transthoracic echocardiography (cTTE) and contrast transesophageal echocardiography (cTEE). Both are used by clinicians in this case. However, there is no consensus on which technique is more suitable in routine diagnosis and evaluation of such patients. The aim of this Address for correspondence and reprint requests: Yue Li, M.D., Ultrasound Department of Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853, China. E-mail: [email protected]
1050
study was to compare the efficacy of the 2 techniques in the detection of RLS-PFO. Methods: Patients: A prospective study was undertaken in 29 consecutive patients with PFO who were referred to our department as outpatients for diagnosis and treatment of migraine or cryptogenic stroke (13 male; 16 female; 15–54 years of age; mean age: 39 16.6 years). The diagnosis of PFO was based on transesophageal echocardiography (TEE) or transthoracic echocardiography (TTE) observations of the anatomic feature of interatrial septum. The diagnoses of migraine and cryptogenic stroke were made by neurologists of our hospital using the criteria of the International Headache Society and American Stroke Association. Exclusion criteria included other cardiovascular defects: atrial septal defect, mitral stenosis, enlarged left atrium, heart failure, and any cases with increase in left atrial pressure which may affect the results of contrast echocardiography in the detection of RLS-PFO.
Technique for Detection of RLS in PFO
Contrast Echocardiography: The cTTE examinations were performed using the Vivid 7 system (General Electric, Vingmed Ultrasound AS, Horten, Norway) fitted with a multifrequency probe with a harmonic imaging modality (transmitting frequency 1.7–2.0 MHz, receiving frequency 3.4–4.0 MHz). The cTEE examinations were performed using the same system with a fundamental imaging modality (transmitting frequency 3.5–7 MHz). Agitated saline was used as the contrast agent. Gain settings were adjusted individually to optimize the visualization of the microbubbles (MBs) and the interatrial septum. The cTTE was performed first and cTEE was performed approximately 30 minutes later in every patient. Each technique was repeated for at least 3 times and the interval between examinations was kept over 5 minutes. The contrast agent was prepared by agitating 1 mL of air with 9 mL of sterile saline solution using two 10 mL syringes and a 3-way stopcock. Agitated saline was rapidly administrated from an antecubital vein at rest and during the maintenance stage or release phase of Valsalva maneuver. The presence of RLS-PFO was confirmed when mircobubbles (MBs) were seen in the left atrium within the first 3 cardiac cycles after contrast appearance in the right atrium at rest or during the maintenance stage or release phase of Valsalva maneuver. Image acquisition involved the capture of 10 consecutive beats on digital storage media before and after the release phase of Valsalva maneuver. The severity of RLS-PFO was semiquantified into a four-level scale, level 1 indicating no MBs appeared in the left atrium in every single frame image, namely no RLS-PFO, level 2 indicating ≤10 MBs, namely mild RLS-PFO, level 3 indicating 11–30 MBs, namely moderate RLSPFO, and level 4 indicating >30 MBs, namely severe RLS-PFO. Statistical Analysis: The sensitivity for detection of RLS-PFO was determined by dividing the number of positive contrast echocardiography with each modality by 29, the total numbers of patients. Specificity was not calculated because all 29 patients had been diagnosed as PFO and no false positive was expected. For the comparison of sensitivity between the 2 techniques the Fisher’s exact test (2-sided) was used. The Wilcoxon signed rank-sum test was used to assess the severity of RLS-PFO based on the semiquantified scales derived from the 2 techniques. The SPSS 13.0 software package (SPSS Inc, Chicago, IL, USA) was used for statistical analysis. A P value of 30 MBs appearance in the left atrium after complete opacification of the right atrium within first 3 cardiac cycles in every single frame image.
fundamental imaging modality could lead to an increase in sensitivity for detecting of RLS-PFO from 22–62% to 63–100%.9,16,20 Second, the left atrial pressure is normally greater than the right atrial pressure throughout most of a cardiac cycle. In patients with PFO, the directions of the shunts between left and right atrium are dynamic and closely linked to right and left atrial pressures. In early ventricular systole, a temporary pressure reversal occurs with the Valsalva maneuver, that is, the right atrial pressure exceeds that of the left atrial pressure. It has been generally accepted that Valsalva maneuver can improve the sensitivity of RLS-PFO detected by contrast echocardiography. Valsalva maneuver has become an integral part of saline contrast studies for detecting of RLS-PFO.21–25 It is difficult for a patient to perform a strenuous Valsalva maneuver during cTEE because esophageal intubation could prevent effective glottic closure. The mean gradient between right atrial pressure and left atrial pressured during the Valsalva maneuver with or without TEE was significantly different: 12.1 3.1 mmHg (without TEE) versus 7.8 5.8 mmHg (with TEE).21 The pressure reversal between right and left atrium during Valsalva maneuver often coincided with the bulging of the septum with convexity toward the left atrium. In our study, the rate of right-to-left septal shifting detected with TEE modality was 48% (14/29), whereas with TTE modality, 72% (21/29). Thus, cTEE has a higher false negative rate in the detection of RLS-PFO due to ineffective or inadequate Valsalva maneuver. Third, as mentioned above the gradients of the reversal pressure between the left and right atrium is low
and brief during a cardiac circle. Some other factors associated with the TEE examination, such as fasting state, sedation, and pharyngeal reflex caused by intubation before and during the examination, may induce hypotention and thus decrease the right atrial pressure. This further lowers or even eliminates the reversal pressure gradients between 2 atria during Valsava maneuver. These factors all limit the efficacy of TEE in the detection of RLS-PFO. Although the efficacy in the detection of RLSPFO with cTTE is higher than that with cTEE, TEE permits detailed study of the interatrial septum as it better visualizes the septum primum coaptation over the fossa ovale. The TTE definition in detailed studies of interatrial septal anatomy is inferior to that of TEE and the latter is currently still considered the golden standard in terms of establishing the presence of PFO anatomically. However, with the help of a contrast agent cTTE can be used as the first imaging modality to effectively detect RLS-PFO. There are several advantages when using cTTE as an alternative to cTEE. It can increase the relevance ratio and the semiquantitative accuracy as verified by our study and some previous reports. If a patient has a good acoustic window and the PFO can be diagnosed by TTE. When using cTTE the discomfort and complications that could occur during TEE are avoided. cTTE can also be used in some patients with swallowing dysfunction, a contraindication or poor cooperation for cTEE. Most importantly, a negative cTTE study may obviate the need to perform a TEE. In theory, the existence of the right-to-left shunt or its severity is the most critical problem in patients with PFO. If 1053
Li, Ya-nan and Li-qun
a patient with cryptogenic stroke or migraine shows no evidence of RLS-PFO, we should suspect other cardiac sources of embolism or pathomechanism for the diseases. As we know, 25% of the population has PFO but only a portion of them develop a neurological condition. Our study has some limitations. The first one would be the small sample size. In consideration of this our research employed a paired study design. We performed cTTE and cTEE in the same day and controlled the examination conditions as much as possible. Therefore, the results of our study still have certain reference value. They are in agreement with the findings from a previous report derived from a large sample study.18 The second limitation would be that only a single contrast agent, that is, agitated saline, was used. Some research showed that the second harmonic imaging modality seemed to have variant effects on different contrast agents.26 However, agitated saline is the most widely used contrast agent for detection of RLS worldwide.27 It has obvious advantages of being easy to prepare and economic. There are no generally accepted quantitative grading systems for assessing the severity of RLS-PFO up to now.9,28,29 Our scales were based on the numbers of MBs appeared in left atrium. Although a severe RLS may sound misleading as the RLS volumes in most patients with PFO are small, these scales are still useful to evaluate the efficacy of 2 techniques in the detection of RLSPFO. Patients with severe RLS-PFO may be more likely to suffer from the diseases associated with PFO, but that is another question and requires further study. Conclusions: Contrast TEE with a harmonic imaging modality was shown to be more effective than cTEE in the detection of RLS-PRO. cTEE with a fundamental imaging modality underestimated the severity of RLS-PFO. cTTE could be used as an alternative to cTEE in screening RLS-PFO in clinical practice. References 1. Schuchlenz HW, Weihs W, Horner S, et al: The association between the diameter of a patent foramen ovale and the risk of embolic cerebrovascular events. Am J Med 2000;109:456–462. 2. Sharma A, Gheewala N, Silver P: Role of patent foramen ovale in migraine etiology and treatment: A review. Echocardiography 2011;28:913–917. 3. Knauth M, Ries S, Pohimann S, et al: Cohort study of multiple brain lesions in sport divers: Role of a patent foramen ovale. BMJ 1997;314:701–705. 4. Godart F, Rey C, Prat A, et al: Atrial right-toleft shunting causing severe hipoxaemia despite normal right-sided pressures: Report of 11 consecutive cases corrected by percutaneous closure. Eur Heart J 2000;21:483–489. 5. Sevgi EB, Erdener SE, Demirci M, et al: Paradoxical air microembolism induces cerebral bioelectrical abnormalities and occasionally headache in patent foramen ovale
1054
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7. 8. 9. 10. 11.
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19. 20.
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