|Year : 2018 | Volume
| Issue : 1 | Page : 30-33
Mean platelet volume as a new biomarker for left atrial thrombus or thromboembolic events in nonvalvular atrial fibrillation: Weighing the evidence
Bayushi Eka Putra1, Achmad Yusri2, Eka Dharma Sastra3
1 Department of Cardiology and Vascular Medicine, Faculty of Medicine Universitas Indonesia, National Cardiovascular Center Harapan Kita, Jakarta, Indonesia
2 Interventional Cardiologist, Department of Cardiology, Kanujoso Djatiwibowo Hospital, Balikpapan, Indonesia
3 Internist, Department of Internal Medicine, Berkah Pandeglang Hospital, Banten, Indonesia
|Date of Web Publication||23-Jul-2018|
Dr. Bayushi Eka Putra
Department of Cardiology and Vascular Medicine, Faculty of Medicine Universitas Indonesia, National Cardiovascular Center Harapan Kita, Jakarta
Source of Support: None, Conflict of Interest: None
Background: Mean platelet volume (MPV) is a new biomarker for left atrial appendage (LAA) thrombus or thromboembolic event with great potential. Considering its applicability and cost, it can be the chosen examination for the detection of LAA thrombus in patients with nonvalvular atrial fibrillation. This study aimed to evaluate MPV as a new biomarker for left atrial thrombus or thromboembolic events in comparison with transesophageal echocardiography. Methods: We did electronic searches on PubMed, ScienceDirect, and SpringerLink databases. Appraisal of studies was performed using critical appraisal sheets provided by the Centre for Evidence-Based Medicine. Test characteristic was extracted from the literature. Meanwhile, sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were calculated based on the test characteristic. Results: Two studies met the selection criteria. Different cutoff was used in the studies (>10.5 fL and >9.4 fL) which showed significant differences in sensitivity, specificity, and positive predictive value. However, both the studies have fairly high NPV (78.95% and 72.65%, respectively). Conclusion: Currently, the best MPV cutoff value in determining the absence of thrombus in the left atrium is 10.5 fL. Although the clinical application of MPV remains limited, it can be further improved by more studies to obtain the optimal cutoff value and to increase the value of MPV by combining with other biomarkers and clinical prediction tools.
Keywords: Biomarker, left atrial appendage thrombus, mean platelet volume, nonvalvular atrial fibrillation, thromboembolic
|How to cite this article:|
Putra BE, Yusri A, Sastra ED. Mean platelet volume as a new biomarker for left atrial thrombus or thromboembolic events in nonvalvular atrial fibrillation: Weighing the evidence. Int J Heart Rhythm 2018;3:30-3
|How to cite this URL:|
Putra BE, Yusri A, Sastra ED. Mean platelet volume as a new biomarker for left atrial thrombus or thromboembolic events in nonvalvular atrial fibrillation: Weighing the evidence. Int J Heart Rhythm [serial online] 2018 [cited 2018 Dec 12];3:30-3. Available from: http://www.ijhronline.org/text.asp?2018/3/1/30/237368
| Case Illustration|| |
We were handling a 57-year-old Indonesian woman who came to the emergency room with palpitation. The patient had no history of heart disease, diabetes mellitus, pulmonary, or hypertension. On examination, she was conscious with blood pressure of 120/80 mmHg, radial artery pulse of 102 bpm (irregular), heart rate of 135 beats/min (irregular), and temperature of 36.8°C.
The electrocardiogram showed atrial fibrillation (AF) with QRS rate of 160 bpm, normal axis, with multiple P wavelets, QRS duration of 0.08 s, ST-segment deviation (−), T-inverted (−), Left ventricular hypertrophy (LVH) (−), Right ventricular hypertrophy (RVH) (−), and Bundle branch block (BBB) (−).
The patient was diagnosed as unstable rapid ventricular response AF. The patient was under consideration to be converted from AF to sinus rhythm using electrical cardioversion. We are wondering if there is a thrombus in left atrial appendage (LAA) or risk of thromboembolic events. Transesophageal echocardiography (TEE) and magnetic resonance imaging (MRI) are not available because of the work in remote area.
| Background|| |
Complications of AF in the form of death, stroke, and long hospitalization increased based on the thromboembolic complications. Impaired blood flow in patients with AF is based on the discovery of conditions that tend to slow blood flow (sluggish) or stasis-based inspection using TEE. Impaired blood flow will result in thrombus formation; this may lead to thromboembolic potential for the occurrence of stroke or even death. About 90% of the total emboli in the left atrium are originating from the LAA, the structure of empty space which is shaped like a pocket in the left atrium.,,
TEE is the modality of choice for the evaluation of LAA because of its capability of showing complete delineation of LAA. However, TEE is only available in very limited hospitals in Indonesia, and the availability of the operators trained to do the examination is very limited. Therefore, the need for readily available and cost-effective marker is needed to substitute TEE modality.
Mean platelet volume (MPV) is one of the newly investigated biomarkers which are associated with thrombosis and inflammation; the larger the volume, the higher the risk of thrombosis. The nature of the biomarker was also found to have an effect on identifying the risk of thrombus formation and thromboembolic event originating from the left atrium, especially in mitral regurgitation, mitral stenosis, and AF.,,, This study aimed to evaluate MPV as a novel biomarker for identifying the risk of thrombosis compared to TEE as the gold standard examination.
Can MPV perform well as a new biomarker in the presence of thrombus in nonvalvular AF compared to TEE?
| Methods|| |
Literature search was performed in the databases of PubMed, ScienceDirect, and SpringerLink [Table 1]. Inclusion and exclusion criteria were used to screen the literature.
Literature appraisal was conducted using critical appraisal sheets provided by the Centre for Evidence-Based Medicine.
Test characteristic was extracted from the literature. Meanwhile, sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were calculated based on the test characteristic.
| Results|| |
Characteristic of selected studies
Through search and elimination process, two studies were selected to be appraised in this study. One study was conducted in China, while the other was conducted in Portugal. Both the studies have significant different characteristics in terms of subject's race and sample size. Study design, study population, proposed diagnostic test, comparator, and outcomes are summarized in [Table 2]. Considering the result of appraisal study, both of the studies were considered as passable to be used in this study [Table 3].
Proposed diagnostic test and comparator
Both studies used the same proposed diagnostic test with different cutoff [Table 2]. The study by Providência et al. used MPV >9.4 fL as the cutoff, while the study by Xu et al. used MPV >10.5 fL as the cutoff value. As for the standard reference, Providência et al. used TEE as the only standard reference to determine the outcome, and in contrast, Xu et al. used the combination of brain computed tomography (CT), TEE, ultrasonic cardiogram, diffusion-weighted MRI (DW-MRI), and pulmonary vein imaging as the reference standard.
The reason that Xu et al. used brain CT, DW-MRI, and even pulmonary vein imaging was to determine the thromboembolic event in addition to determine whether or not thrombus was present in the left atrium. Meanwhile, Providência et al., using the TEE, tried to determine the left atrial (LA) abnormality which comprised at least one of the following: LAA thrombus, dense spontaneous echo contrast, and low flow velocity (≤20 cm/s).
Characteristics of the included studies are presented in [Table 2]; the validity of the proposed diagnostic tool is measured by sensitivity, specificity, positive predictive value, and NPV [Table 4]. The study conducted by Providência et al. with MPV cutoff value of >9.4 fL showed a rather poor sensitivity (54.1%) and positive predictive value (43.41%); furthermore, the specificity (63.35%) and NPV (72.65%) were considered fair. Contrary to the results gained from Providência et al., Xu et al. showed more stable results in sensitivity (78.5%), specificity (77.59%), positive predictive value (77.19%), and NPV (78.95%). In addition, based on the multivariate logistic regression of the predictors, the odds ratio (OR) represented in the study of Xu et al. (OR = 3.1, 95% confidence interval [CI]: 1.6–5.1, P = 0.000) was higher than that in the study of Providência et al. (OR = 2.656; 95% CI: 1.063–6.633, P = 0.036).
|Table 4: Performance indicator of mean platelet volume for left atrial abnormality/thromboembolic event in atrial fibrillation patients|
Click here to view
| Discussion|| |
There are several biomarkers which were studied to determine the presence of thrombus in the left atrium, such as uric acid, brain natriuretic peptide, and C-reactive protein.,,, MPV is relatively a new biomarker compared to others. Besides in AF, MPV was also studied as the biomarker for thrombus or thromboembolic risk in sinus rhythm with mitral stenosis; however, the number of studies was less than in AF.
The main goal of this study was to find a replacement of TEE or MRI to predict the presence of thrombus in the LA or LA abnormality, which are usually not readily available in remote hospital. Therefore, the most useful indicator mentioned in [Table 4] for this purpose is the NPV. NPV showed how many of the negative tests are “truly negatives.” Therefore, the higher the percentage of NPV, the better it represents the gold standard. Looking at this case, if the patients have MPV ≤9.4 fL, the possibilities of there is no abnormality in the left atrium is 72.65% based on the study by Providência et al.; meanwhile, Xu et al. showed that if the MPV was less than or the same with 10.5 fL, the possibilities of there is no risk of thrombus or thromboembolic event was 78.95%. Relating to the illustrated case, there is still a risk of “false negative” about 10%–20% of the cases which can lead to the occurrence of thromboembolic event if electrical cardioversion was considered to be done only using MPV as the newly proposed biomarker. From the current standpoint, using MPV as a single biomarker to determine the presence of thrombus in LAA or the risk of thromboembolic event is still precarious; therefore, it still cannot replace TEE as the gold standard to determine the presence of LA thrombus.
In the bright side, the NPVs of MPV were fairly high based on the appraised studies. The value of NPV might possibly be improved by more studies to determine the better cutoff point for MPV and also by combining with another biomarkers or with clinical prediction rules such as congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, stroke/transient ischemic attack (CHADS2) score; congestive heart failure, hypertension, age ≥75 (doubled), diabetes mellitus, prior stroke or transient ischemic attack (doubled), vascular disease, age 65–74, female (CHA2 DS2- VASc) score; and renal dysfunction, congestive heart failure, hypertension, age, diabetes, stroke/transient ischemic attack (R2 CHADS2) score.
MPV is a new biomarker for LAA thrombus or thromboembolic event with great potential. Currently, the optimal MPV cutoff value for determining the absence of thrombus in the left atrium is 10.5 fL. Although currently it is not clinically ready, it can further be improved by more studies to determine the optimal cutoff value and to increase the value of MPV by combining with other biomarkers and clinical prediction rules.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]