Prognostic value of strain and strain rate in the prediction of postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting: a systematic literature review

Document Type: Systematic review

Authors

1 Department of Cardiology, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran.

2 Cardiovascular Research Center, Ghaem Hospital, School of Medicine, Mashhad University of Medical Sciences, Iran.

3 Department of Cardiac Surgery, Ghaem Hospital, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

Abstract

Introduction: Atrial fibrillation (AF) is a common dysrhythmia postoperatively after coronary artery bypass grafting (CABG). Myocardial strain and strain-rate imaging is used for the assessment of postoperative atrial fibrillation (POAF) as a new echocardiographic method.
Methods: PubMed and Scopus were searched thoroughly using the following search terms: (strain and strain rate) AND (atrial fibrillation OR AF) on March 2015 to find English articles in which the strain and strain-rate echocardiographic imaging had been used for the evaluation of AF in patients undergone CABG. Full text of the relevant papers was fully reviewed for data extraction.
Result: Of overall 6 articles found in PubMed, 10 records found in Scopus and 4 articles found through reference list search, only 6 papers fully met the inclusion criteria for further assessment and data extraction. The results of strain and strain-rate assessment showed that in total of 542 patients undergoing CABG, POAF occurred in 106 patients. Studies showed that the reduction of left atrial (LA) strain rate is correlated with AF. Consistently, the results of present review showed that LA strain and strain-rate in patients who developed AF postoperatively after CABG are significantly reduced, suggesting that strain and strain-rate could be a predictor of POAF.
Conclusion: Based on the obtained results, strain and strain-rate is a suitable and accurate echocardiographic technique in the assessment of left atrial function , and it might be helpful to detect the patients who are at high risk of POAF.

Keywords


Introduction
 Atrial fibrillation (AF) is a common postoperative arrhythmia, which may occur after cardiac surgery. Although the true incidence of postoperative AF is not clear, the reported cases varied between 10% and 65% among studies (1-3). This arrhythmia may increase postoperative complications, and leads to severe cardiac problems. As well, it may increase the risk of thrombotic events, hospital costs, use of financial resources, and the length of hospital stay (4,5). As the name suggests, AF originates from the atrium. Previously, it was thought that this arrhythmia was benign, but now it is believed that this arrhythmia is not so benign and may increase the rate of morbidity and mortality, especially in the elderly. Moreover, AF may lead to hemodynamic instability, heart attack, stroke, and other thromboembolic events (6,7). Findings show that the incidence of AF after coronary artery bypass grafting (CABG) surgery is a common postoperative cardiac dysrhythmia that might increases the risk of cardiac-related mortality and stroke. Therefore, identifying patients who are at high risk of AF after surgery requires special attention (8,9).
AF is clinically divided into three categories, including paroxysmal, persistent, and permanent. Atrial fibrillation is permanent, when the AF remains in sinus rhythm after electrical cardioversion. While in persistent type, the sinus rhythm lasts for more than a week. In the paroxysmal, the fibrillation rhythm is spontaneously converted to sinus rhythm. It is suggested that all three types of arrhythmias could increase the rate of mortality. Left atrial function (LAF) is usually impaired in patients with coronary artery disease (CAD). As a result, evaluation of atrial function postoperatively might be helpful to prevent future cardiovascular complications.
So far, several predictive factors for cardiovascular disease have been identified in different studies (10,11). Furthermore, it is evident that valuable clinical information about the risk of cardiovascular disease could be obtained through the assessment of these factors. Thus, it is possible to prevent the incidence of arrhythmias and subsequent cardiovascular disease through the identification of at risk individuals by these methods or other preventive measures. One of the important factors of risk assessments is a measurement of specific echocardiographic parameters, especially the size of the left atrium (LA), myocardial tissue velocities, and determination of LA strain-rate. Echocardiographic criteria are of the most important predictors of AF. Left atrial function has a relatively great importance in the prediction of postoperative atrial fibrillation (POAF) after CABG (12,13). Therefore, since there is relationship between the size of LA and POAF, and the reduction of LA strain rate is suggested to be associated with AF, strain and strain-rate as a novel and non-invasive echocardiographic method is used for the assessment of LAF (14-17). Therefore, in the presents study, we aim to systematically review the literatures in which the AF is evaluated by strain and strain rate echocardiographic methods in patients undergoing CABG.

Methods
Literature search strategy
Scopus and PubMed were searched comprehensively for articles in which the strain and strain rate echocardiographic method had been used for the evaluation of AF in patients who had undergone CABG. Literature search was performed by two reviewers independently using the key terms, “strain and strain rate”, “atrial fibrillation” and “coronary artery bypass grafting” in the title, keywords, and abstract. All possible relevant articles with the following search terms (strain and strain rate) AND (atrial fibrillation OR AF) were selected and analyzed for data extraction. The search strategy was customized by limiting the records to those patients who had undergone CABG. The databases were searched with the last update on 1 March 2013. Google Scholar was also searched using the previously described search terms to relevant papers in the early stages of article selecion. Studies conducted on animals were also  miimize the possibility of any missing documents. Additionally, we searched the reference list of included papers to include other potentially related articles. Papers were omitted in different steps of selection process, if they were inappropriate and unrelated to the main purpose of this review.

Study selection and inclusion/exclusion criteria
No time limitation was defined in selection process, and we only included articles in English language to minimize any possible errors during the analysis of extracted data in the subsequent data analyzing processes. We included various types of the articles with different study designs including the clinical trials, case-controls, case reports, cross-sectional, and cohort studies in this literature review. However, review articles and meta-analysis were excluded. Conference papers and letters to the editor were also excluded. Inclusion criteria were all articles in which the AF had been evaluated by strain and strain rate echocardiographic method in patients who had undergone CABG. By reviewing the title, keywords, and abstract of papers, we excluded duplicated and irrelevant papers in the early stages of article selection. Studies conducted on animals were also excluded from further assessment.

Data extraction
General information of the selected articles including the name of first author, publication year, country, type of study design, and critical findings were extracted and sorted based on the purpose of this literature review. Moreover, other available information including the total number of participants enrolled in the selected literatures and also demographic data were collected as possible, regarding to the inclusion and exclusion criteria. Data were sorted on the basis of the reported results in which the predictive value of strain and strain rate imaging method had been described in the prediction of POAF in patients who had undergone CABG. All processes of data extraction and study selection were based on the recommendation of PRISMA 2009 checklist (18).
Results
Study search results
From overall 6 articles found in PubMed, and 10 papers in Scopus, 7 articles were excluded in the first step due to duplication or language irrelevancy, and only 9 unique records seemed to be potentially relevant to the purpose of this study. Four additional papers were also included by manual reference skimming of the previously selected papers. After detailed sympathetically reviewing of the included articles, only 6 papers, which fully met the inclusion criteria were obtained, and the desired data were extracted concerning the main purpose of this study. Figure 1 shows the step by step process of literature search and study selection.

Characteristics of the included literatures
The earliest and the most recent articles included in the selected literatures were published in 2010 and 2014, respectively. The total number of participants enrolled in the selected reviewed literatures in which the AF had been evaluated postoperatively by strain and strain rate imaging method was 542 patients. Although the age of patients enrolled in the selected articles had not been mentioned in some studies, but it varied from 60 to 70 years old in those reported. In addition, minimum number of the patients in the selected articles was 53 in a prospective study, and maximum number was 176 participants in a cross-sectional study. As shown in the Table 1, the study designs of the selected literatures include prospective, respective, and cross-sectional studies.
As presented in Table 1, strain and strain rate had been evaluated by different methods in the selected studies. Because age and sex ratio had not been mentioned in some studies, data could not be categorized and analyzed based on demographic data. It was almost mentioned in all the included studies that more than half of the patients enrolled in the selected literatures were male.

Study results
Articles were selected according to the inclusion/exclusion criteria, and the desired data were extracted based on the main purpose of this survey. According to the obtained results, AF occurred postoperatively in 106 patients undergoing CABG. Comparison of the data among the studied individuals showed that POAF occurred more frequency in older patients. The value for strain and strain rate had not been mentioned in two studies; however, reduction of the values had been noted (Table 2).
The results of the present review also demonstrate that strain and strain rate is relatively low in patients with POAF compared to those with normal sinus rhythm. Table 2 shows the postoperative values of strain and strain rate in patients undergoing CABG.

Discussion
As previously described, AF is a common postoperative dysrhythmia after CABG, and is a leading cause of mortality due to cardiac- related disease (25,26). Due to the potential risks of this type of heart irregularities in the incidence of irreversible heart damage, development of a non-invasive and a more accurate technique seems very important to evaluate the biochemical and physical markers of cardiac disease, especially LAF. Several prognostic methods have been developed to predict upcoming cardiovascular disease by the evaluation of left ventricular dimension, LAF, ventricular mass, and systolic and diastolic blood pressures. Among them, strain and strain rate is thought to be more accurate and suitable for the evaluation of cardiac function. According to reported values, the normal range for strain and strain rate is 15% to 25% and 1.0 S-1 to 1.4 S-1, respectively (27). Comparison of the data among patients with cardiac abnormalities and healthy individuals showed that strain and strain rate deviated from normal range in response to physiological changes in the heart (28). Prognostic value of strain and strain rate imaging, as a noninvasive and quantitative technique in acute myocardial infarction, ischemic mitral regurgitation, amyloidosis and other myocardial functional abnormalities, has been demonstrated in several studies (28-31).
Strain and strain rate imaging technique could facilitate and accelerate comprehensive assessment of LA function, AF, and other cardiovascular functions. As well, LA strain and strain rate is suggested as a powerful predictor of postoperative AF (32). The results of studies on LA strain and strain rate of patients with prior CABG showed that the reduction of LA strain rate was closely associated with paroxysmal AF (16). Moreover, it was shown that strain and strain rate significantly decreased in patients with AF (20). In consistent with the reported findings, the results of all included literatures show that LA strain and strain rate markedly reduced compared to those in patients with normal sinus rhythm in patients who developed AF after CABG, suggesting that strain and strain rate of LA could be considered as an independent predictor of postoperative AF after CABG. Moreover, the results of this study suggest that strain and strain rate could be used to identify the patients with abnormal postoperative cardiac function.
The results of included studies showed that the strain imaging might have a prognostic value in the assessment of potential upcoming cardiovascular risks, cardiac dysrhythmia, and AF. Furthermore, this method might be useful in identifying the patients who are at higher risk of POAF. Therefore, this type of echocardiographic imaging could be used as a valuable diagnostic method for the prediction and evaluation of cardiac function, particularly in older patients.
Limitations of this systematic review include the small number of studies in the related subject. Moreover, demographic data were missed in some studies; therefore, the results could not be sorted and analyzed according to sex and age. Small number of patients in the selected articles was another limitation to the assessment and analysis of the literature that might lead to the insignificant results.

Conclusion
According to the results of the selected literatures, strain and strain rate imaging is a suitable and accurate echocardiographic technique for the assessment of LAF. The findings suggest that strain and strain rate could be considered as an independent predictors of POAF after CABG. Moreover, it is suggested that strain and strain rate imaging might be helpful in clinical practice to detect the patients who are at high risk of POAF.

Acknowledgement
We would like to thank Clinical Research Development Unit of Ghaem Hospital for their assistant in this manuscript.

Conflict of Interest
The authors declare no conflict of interest.

 

  1. Lloyd-Jones DM, Wang TJ, Leip EP, et al. Lifetime risk for development of atrial fibrillation: the Framingham Heart Study. Circulation. 2004;110:1042-1046.
  2. Levy D, Kannel WB. Postoperative atrial fibrillation and mortality: do the risks merit changes in clinical practice? J Am Coll Cardiol. 2004;43:749-751.
  3. Alqahtani AA. Atrial fibrillation post cardiac surgery trends toward management. Heart Views. 2010;11:57-63.
  4. Villareal RP, Hariharan R, Liu BC, et al. Postoperative atrial fibrillation and mortality after coronary artery bypass surgery. J Am Coll Cardiol. 2004;43:742-748.
  5. Mariscalco G, Klersy C, Zanobini M, et al. Atrial fibrillation after isolated coronary surgery affects late survival. Circulation. 2008;118:1612-1618.
  6. Darby AE, Dimarco JP. Management of atrial fibrillation in patients with structural heart disease. Circulation. 2012;125:945-957.
  7. Mann CJ, Kendall S, Lip GY. Acute management of atrial fibrillation with acute haemodynamic instability and in the postoperative setting. Heart. 2007;93:45-47.
  8. Haghjoo M, Basiri H, Salek M, et al. Predictors of postoperative atrial fibrillation after coronary artery bypass graft surgery. Indian Pacing Electrophysiol J. 2008;8:94-101.
  9. Verdejo H, Roldan J, Garcia L, et al. Systemic vascular cell adhesion molecule-1 predicts the occurrence of post-operative atrial fibrillation. Int J Cardiol. 2011;150:270-276.
  10. Danis R, Ozmen S, Akin D, et al. Predictive Factors of Cardiovascular Disease in Patients on Maintenance Hemodialysis. Dial Transplant. 2008;37:58-66.
  11. Van holten TC, Waanders LF, De groot PG, et al. Circulating biomarkers for predicting cardiovascular disease risk; a systematic review and comprehensive overview of meta-analyses. PLoS One. 2013;8:e62080.
  12. Nakai T, Lee RJ, Schiller NB, et al. The relative importance of left atrial function versus dimension in predicting atrial fibrillation after coronary artery bypass graft surgery. Am Heart J. 2002;143:181-186.
  13. Leung JM, Bellows WH, Schiller NB. Impairment of left atrial function predicts post-operative atrial fibrillation after coronary artery bypass graft surgery. Eur Heart J. 2004;25:1836-1844.
  14. Dandel M, Lehmkuhl H, Knosalla C, et al. Strain and strain rate imaging by echocardiography-basic concepts and clinical applicability. Curr Cardiol Rev. 2009;5:133-148.
  15. Sadeghpour A. Myocardial Strain and Strain Rate Imaging: Comparison between Doppler Derived Strain Imaging and Speckle Tracking Echocardiography. Arch Cardiovasc Imaging. 2013;1:19-20.
  16. Tsai WC, Lee CH, Lin CC, et al. Association of left atrial strain and strain rate assessed by speckle tracking echocardiography with paroxysmal atrial fibrillation. Echocardiography. 2009;26:1188-1194.
  17. Pellerin D, Sharma R, Elliott P, et al. Tissue Doppler, strain, and strain rate echocardiography for the assessment of left and right systolic ventricular function. Heart. 2003;89 Suppl 3:iii9-17.
  18. Liberati A, Altman DG, Tetzlaff J, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. Annals Intern Med. 2009;151:W-65-W-94.
  19. Tayyareci Y, Yildirimturk O, Aytekin V, et al. Preoperative left atrial mechanical dysfunction predicts postoperative atrial fibrillation after coronary artery bypass graft operation - a velocity vector imaging-based study. Circ J. 2010;74:2109-2117.
  20. Gabrielli L, Corbalan R, Córdova S, et al. Left Atrial Dysfunction Is a Predictor of Postcoronary Artery Bypass Atrial Fibrillation: Association of Left Atrial Strain and Strain Rate Assessed by Speckle Tracking. Echocardiography. 2011;28:1104-1108.
  21. Albers J, Ister D, Kayhan N, et al. Postoperative non-invasive assessment of pulmonary vascular resistance using Doppler echocardiography. Interact Cardiovasc Thorac Surg. 2011;13:579-584.
  22. Her AY, Kim JY, Kim YH, et al. Left Atrial Strain Assessed by Speckle Tracking Imaging Is Related to New-Onset Atrial Fibrillation After Coronary Artery Bypass Grafting. Can J Cardiol. 2013;29:377-383.
  23. Machino-Ohtsuka T, Seo Y, Ishizu T, et al. Efficacy, safety, and outcomes of catheter ablation of atrial fibrillation in patients with heart failure with preserved ejection fraction. J Am Coll Cardiol. 2013;62:1857-1865.
  24. Parsaee M, Moradi B, Esmaeilzadeh M, et al. New onset atrial fibrillation after coronary artery bypasses grafting; an evaluation of mechanical left atrial function. Arch Iran Med. 2014;17:501-506.
  25. Tulla H, Hippelainen M, Turpeinen A, et al. New-onset atrial fibrillation at discharge in patients after coronary artery bypass surgery: short- and long-term morbidity and mortality. Eur J Cardiothorac Surg. 2015;48:747-752.
  26. Nair SG. Atrial fibrillation after cardiac surgery. Ann Card Anaesth. 2010;13:196-205.
  27. Sun JP, Popovic ZB, Greenberg NL, et al. Noninvasive quantification of regional myocardial function using Doppler-derived velocity, displacement, strain rate, and strain in healthy volunteers: effects of aging. J Am Soc Echocardiogr. 2004;17:132-138.
  28. Moustakidis P, Cupps BP, Pomerantz BJ, et al. Noninvasive, quantitative assessment of left ventricular function in ischemic cardiomyopathy. J Surg Res. 2004;116:187-196.
  29. Van Garsse L, Gelsomino S, Lucà F, et al. Left atrial strain and strain rate before and following restrictive annuloplasty for ischaemic mitral regurgitation evaluated by two-dimensional speckle tracking echocardiography. Eur Heart J Cardiovasc Imaging. 2013;14:534.
  30. Antoni ML, Mollema SA, Delgado V, et al. Prognostic importance of strain and strain rate after acute myocardial infarction. Eur Heart J. 2010;31:1640-1647.
  31. Koyama J, Falk RH. Prognostic significance of strain Doppler imaging in light-chain amyloidosis. JACC Cardiovasc Imaging. 2010;3:333-342.
  32. Yasuda R, Murata M, Roberts R, et al. Left atrial strain is a powerful predictor of atrial fibrillation recurrence after catheter ablation: study of a heterogeneous population with sinus rhythm or atrial fibrillation. Eur Heart J Cardiovasc Imaging. 2015;16:1008-1014.