Journal of The Egyptian Society of Nephrology and Transplantation

ORIGINAL ARTICLE
Year
: 2017  |  Volume : 17  |  Issue : 1  |  Page : 30--37

Role of cardiac magnetic resonance imaging and echocardiography in assessing the left ventricle in hemodialysis patients


Amr M Ebeid1, Eman M Elsharkawy2, Sara K El Fawal3, Yasmine S Naga1, Marwa F Oraby1,  
1 Department of Internal Medicine, Faculty of Medicine, Alexandria University, Alexandria, Egypt
2 Department of Cardiology and Angiology, Faculty of Medicine, Alexandria University, Alexandria, Egypt
3 Department of Diagnostic Radiology, Faculty of Medicine, Alexandria University, Alexandria, Egypt

Correspondence Address:
Marwa F Oraby
Department of Internal Medicine, Faculty of Medicine, Alexandria University, Alexandria, 21111
Egypt

Abstract

Background End-stage renal disease (ESRD) patients on hemodialysis (HD) are at increased risk for developing left ventricular hypertrophy (LVH), which is a predisposing factor for premature cardiovascular mortality. Although echocardiography (ECHO) has been the most commonly used technique for assessing LVH, cardiac magnetic resonance imaging (CMR) is now considered the gold standard and the most accurate tool for volume-independent determination of left ventricular mass (LVM). Objectives This study aimed to evaluate the agreement in LVM measurement and LVH detection between CMR and ECHO. Patients and methods A single-center, cross-sectional study including 30 ESRD patients on HD (group I) and 15, matched, healthy controls (group II) was performed to compare LVM measurement and LVH detection by ECHO and CMR. Result In both groups, ECHO overestimated LVM and left ventricular mass index (LVMI) in comparison with CMR. The Bland–Altman analysis demonstrated wider agreement limits (38.6 to −275.9 g) in LVM measurements by ECHO and CMR in group I (mean difference, 118.63 g, P≤0.001) than in group II (mean difference, 79.29 g; limits, −23.7 to −134.8 g, P≤0.001). Agreement was poor and not statistically significant in group I. Regarding LVMI measurement, there were wider agreement limits (145.5 to −18.8 g/m2) by ECHO and CMR in group I (mean difference, 63.33 g/m2, P≤0.001) than in group II (mean difference, 44 g/m2; limits, 71.3–16.7 g/m2, P≤0.001). Agreement was fair and statistically significant in group I. LVH prevalence by ECHO and CMR was 66.6 and 36.7%, respectively, in group I and 26.6 and 0%, respectively, in group II, with moderate agreement between both techniques (P=0.004) in group I. Conclusion ECHO overestimates LVM and LVMI as well as LVH detection in comparison with CMR in ESRD patients on HD. Therefore, for accurate assessment of LVM, CMR may be a better option to detect LVH in this high cardiovascular risk group.



How to cite this article:
Ebeid AM, Elsharkawy EM, El Fawal SK, Naga YS, Oraby MF. Role of cardiac magnetic resonance imaging and echocardiography in assessing the left ventricle in hemodialysis patients.J Egypt Soc Nephrol Transplant 2017;17:30-37


How to cite this URL:
Ebeid AM, Elsharkawy EM, El Fawal SK, Naga YS, Oraby MF. Role of cardiac magnetic resonance imaging and echocardiography in assessing the left ventricle in hemodialysis patients. J Egypt Soc Nephrol Transplant [serial online] 2017 [cited 2017 Aug 17 ];17:30-37
Available from: http://www.jesnt.eg.net/text.asp?2017/17/1/30/207905


Full Text

 Introduction



Left ventricular hypertrophy (LVH) is a common finding in end-stage renal disease (ESRD) patients. It is a component of uremic cardiomyopathy and an independent risk factor for sudden cardiac death, heart failure, and cardiac arrhythmias in the general population and in hemodialysis (HD) patients [1],[2],[3]. It becomes manifest before overt cardiovascular events and predicts increased mortality [4],[5].

Cardiovascular mortality is 3.5 times higher in renal patients than in the general population [6]. Heart failure represents 15%, myocardial infarction 10%, and uremic pericarditis 3% of dialysis-associated mortality [7]. Sudden cardiac death accounts for 60% of cardiovascular mortality, and the cause of death in 25% of them is due to arrhythmogenic sudden cardiac death [8],[9],[10].

An increase in left ventricular mass (LVM) and cardiac fibrosis has profound consequences in patients with chronic kidney disease and ESRD. These include sudden cardiac death due to abnormal electrical conduction in the distorted and fibrotic ventricle and ischemic cardiac disease, such as coronary artery atherosclerosis. The late stage of LVH and cardiac fibrosis lead to both diastolic and systolic dysfunction and ultimately to clinically recognizable CHF, which has an adverse effect on long-term survival in chronic kidney disease and ESRD patients [11].

LVH, left ventricular (LV) systolic dysfunction, and also significant diastolic dysfunction all are independent predictors of cardiovascular outcome and adverse cardiovascular events in dialysis patients [7],[12],[13]. Moreover, regression of LVH with a reduction of LVM has been associated with favorable outcomes such as lowered likelihood of developing heart failure [14], improvement in systolic function, reduction in the risk forventricular arrhythmias and atrial fibrillation [15],[16],[17], and lower all-cause mortality [18].

Echocardiography (ECHO) shows abnormalities in more than 75% of ESRD patients in the form of thickened LV wall and increased LVM [4],[5].

Doppler ECHO is a useful noninvasive tool for the diagnosis of LV abnormalities − an important step for the characterization of individuals with higher cardiovascular risk [19]. Traditionally, the M-mode and the two-dimensional Doppler ECHO allow assessment of ventricular mass and volumes, with excellent accuracy for the diagnosis of hypertrophy, definition of its geometric pattern (concentric or eccentric), and systolic function estimate (qualitative or quantitatively) [20]. For each parameter, superior techniques exist, but are not routinely used because of expense, unavailability, or invasiveness. Cardiac magnetic resonance imaging (CMR) is superior to others in assessing LVM and cavity volume in patients with ESRD, whereas cardiac function is measured better with invasive techniques. In practice, ECHO is a reasonable, widely available tool and highly suitable for research purposes [21].

Although CMR is not widely available and of higher cost in comparison with ECHO, it is safe, has high accuracy, and is more reproducible with superior interobserver and intraobserver reliability [22],[23].

The objective of the present study was to compare LVM measurement and LVH detection by ECHO and CMR in ESRD patients on maintenance hemodialysis (MHD).

 Patients and methods



A total of 45 (30 ESRD on MHD and 15 matched, healthy controls) participants were recruited. Approval of the Ethics Committee of the Faculty of Medicine at Alexandria University was obtained, and all patients gave their written informed consents. Patients were studied on the morning following HD, and they underwent both ECHO and CMR measurements of LV dimensions and function, which were performed by two independent observers on the same day.

ECHO was performed with a Philips Envisor CHD ultrasound system equipped with a 2.5-MHz broadband transducer. Comprehensive examination was performed with the patient in the left lateral decubitus position for the parasternal and apical views. All ECHO measurements were made in accordance with the recommendations of the American Society of Echocardiography guidelines [24]. Measurements of LV size and function with assessment of LVM and left ventricular mass index (LVMI) were performed.

All patients underwent CMR with a 1.5 T MRI scanner (Achieva; Philips Medical Systems, Philips Achieva, release 3.2.3.3, 2014, Netherlands) equipped with a standard, five-element synergy cardiac coil. Patients were examined in the supine position. ECG leads were placed on the chest for gating purposes. Non-ECG-gated localizers scans in three orthogonal planes − axial, coronal, and sagittal − were obtained, followed by the reference scan for coil sensitivity. ECG-gated, breath-hold, bright-blood (steady state free precession) sequences were acquired in two-chamber, four-chamber, and short-axis planes for the assessment of LV volume, systolic function, and myocardial mass. A dedicated cardiac software package (Viewforum, Release 9; Philips Medical Systems) was used for measurement of LV end-systolic and end-diastolic volumes and myocardial mass, with calculation of global systolic function.

Definition of left ventricular hypertrophy

Patients were categorized as having LVH or not on the basis of accepted cutoff values for LVMI for ECHO (men >115 g/m2, women >95 g/m2) [24] and CMR (men >91 g/m2, women >77 g/m2) [25]. The measured relative wall thickness (RWT) allowed for further classification of LVH as either concentric hypertrophy (RWT >0.42) or eccentric hypertrophy (RWT ≤0.42).

Statistical analysis [26]

SPSS, version 20.0 (IBM Corp., Armonk, New York, USA) [27] was used for all statistical analyses. Data are expressed as mean±SD. Proportions were compared using χ2 analysis. Student’s t-test, analysis of variance, and Mann–Whitney tests were used for group comparison. A correlation analysis was performed using Spearman’s correlation coefficient. The measurements of LVM obtained in the study were compared by the Bland and Altman method [28].

 Result



The present study included 30 ESRD patients on MHD from the dialysis unit of Alexandria Main University Hospital (15 males, 15 females) and 15, matched, healthy patients (nine females, six males). The studied variables are summarized in [Table 1]. The etiology of ESRD in the HD cohort was hypertension in 11 patients, DM, chronic GN, drug-induced, pyelonephritis, ADPKD, and SLE in two patients each, and seven patients had an unknown etiology.{Table 1}

LA diameter, left ventricular end-diastolic diameter, left ventricular end systolic diameter, LVM, and LVMI by ECHO were all significantly higher in group I than in group II (P≤0.001, P≤0.001, P=0.002, P≤0.001, P≤0.001, respectively).

LV dilatation by ECHO was found in 11 (36.7%) cases in group I and in none (0%) of them in group II. Mild mitral regurgitation was found in 6 cases (20%) cases in group I and in none (0%) of them in group II.

Left ventricular geometry by ECHO was normal in seven (23.3%) cases in group I and in six (40%) cases in group II. Concentric remodeling was present in three (10%) cases in group I and in five (33.3) cases in group II. In group I, 66.6% of patients met ECHO criteria for LVH (23.3% eccentric LVH, 43.3% concentric LVH), whereas in group II LVH was designated by ECHO in 26.6% of patients (13.3% eccentric LVH, 13.3% concentric LVH).

LVH was mild in eight (26.7%) cases in group I and in four (26.7%) cases in group II, was moderate in one (3.3%) case in group I and in none (0%) in group II, and was severe in 11 (36.7%) cases in group I and in none (0%) in group II.

LVM and LVMI by CMR were significantly higher in group I in comparison with group II (P≤0.001 and 0.001, respectively).

Mass-to-cavity ratio (mass/LV end-diastolic volume) was significantly higher in group I (0.77±0.19) in comparison with group II (0.62±0.12), with a P value of 0.007.

LVH criteria by CMR were met by 11 cases (36.7%) in group I (6.7% concentric LVH, 30% eccentric LVH) and by none (0%) of them in group II. Cohen’s κ for LVH detection was 0.449 (P=0.004) in group I and 0.441 (P≤0.001) in the total sample, reflecting moderate agreement, whereas Cohen’s κ for LVH geometry classification as concentric and eccentric was 0.372 (P≤0.001) in group I and 0.363 (P≤0.001) in the total sample, reflecting fair agreement.

There was a statistically significant, positive correlation between ECHO and MRI regarding LVM with a P value of less than 0.001.

The Bland–Altman analysis ([Figure 1] and [Figure 2], [Table 2] and [Table 3]) demonstrated wider agreement limits in LVM measurement by ECHO and CMR in group I (mean difference, 118.63 g; limits, 38.6 to −275.9 g, P≤0.001) than in group II (mean difference, 79.29 g; limits, −23.7 g to −134.8 g, P≤0.001) and the limits in the total sample (mean difference, 105.52 g; limits, 242 g to −31.0 g, P≤0.001). Cohen’s κ ([Table 4]) for group I was 0.194 (P=0.0.073), reflecting poor agreement, and in the total sample it was 0.219 (P=0.019), reflecting fair agreement.{Figure 1}{Figure 2}{Table 2}{Table 3}{Table 4}

There was a statistically significant, positive correlation between ECHO and MRI regarding LVMI with a P value of less than 0.001.

The Bland–Altman analysis ([Figure 3] and [Figure 4], [Table 5] and [Table 6]) demonstrated wider agreement limits in LVMI measurement by ECHO and CMR. There were wider agreement limits in LVMI measurements by ECHO and CMR in group I (mean difference, 63.33 g/m2; limits, 145.5 to −18.8 g/m2, P≤0.001) than in group II (mean difference, 44 g/m2; limits, 71.3–16.7 g/m2, P≤0.001) and in the total sample (mean difference, 56.89 g/m2; limits, 127.7 to −13.9 g/m2, P≤0.001). Cohen’s κ ([Table 7]) was 0.353 (P=0.0029) for group I and was 0.353 (P=0.001) for the total sample, reflecting fair agreement.{Figure 3}{Figure 4}{Table 5}{Table 6}{Table 7}

 Discussion



ECHO LVH represents an adverse prognostic factor independent of age, diabetes, hyperlipidemia, smoking status, and hypertension even in nonrenal populations [3],[29],[30].

In this study, LVM and LVMI by ECHO and CMR were significantly greater in group I in comparison with group II. LVH criteria were met by 66.6% of patients in group I (23.3% eccentric LVH, 43.3% concentric LVH), whereas in group II LVH was designated by ECHO in 26.6% of patients (13.3% eccentric LVH, 13.3% concentric LVH). CMR criteria of LVH were met by 11 (36.7%) cases in group I (6.7% concentric LVH, 30% eccentric LVH) and by none (0%) in group II. Cohen’s κ for LVH detection was 0.449 in group I and was 0.441 for the total sample, reflecting moderate agreement, whereas Cohen’s κ for LVH geometry classification as concentric and eccentric was 0.372 in group I and 0.363 for the total sample, reflecting fair agreement.

A study by Zoccali et al. [31] reported a prevalence of LVH in 77% of the ESRD population on HD. A recent study conducted by Laddha et al. [32] in 2014 reported that the authors detected LVH in 74% of ESRD patients on HD. In another study by Tian et al. [33] in Chinese HD and peritoneal dialysis patients, the prevalence of LVH according to the Framingham criteria was 68.8% in HD patients and 45.2% in peritoneal dialysis patients. However, in a study by Singh et al. [34], LVH was present only in 48% of cases.

In a study by Arnold et al. [35] in a paediatric cohort, ECHO findings showed that the prevalence of LVH was 32%, and by CMR the prevalence was only 24% in the same cohort. They also compared the classification of LVH using accepted standards (95th percentile cutoffs of LVMI for echo and LVM for CMR), which still resulted in only poor agreement between the two methods with Cohen’s κ. The agreement for detecting LVH showed that the number of children with Echo-LVMI above the 95th percentile was much higher than those with CMR LVM above the 95th percentile. Thus, the agreement between the two methods was only poor with a Cohen’s κ of 0.08, presuming CMR to be the gold standard [35].

LVM assessed by MRI versus ECHO in the present study was lower. This has been shown in head-to-head comparisons of CMR versus ECHO by Stewart et al. [21], where CMR detected lower LVM. This has also been detected by Jakubovic et al. [36].

Analysis of LVM measurements by ECHO and CMR in a study by Supe-Markovina et al. [37] in hypertensive children also demonstrated that ECHO overestimates LVM.

The discrepancy between ECHO and CMR can be explained by the way each modality assesses LVM. ECHO depends on geometric assumptions derived from normal hearts to calculate LVM and cavity size. It has many confounders that affect its results, such as volume status of the patient and body habitus, and it is operator dependent [38]. In contrast, CMR measures LVM through direct mathematical calculation using three-dimensional data [39],[40]. Therefore, CMR is less sensitive to volume status changes [41], as it directly measures cardiac mass, overcoming the problem of geometric assumptions and calculations used in ECHO [41],[42].

ECHO overestimated LVM particularly at higher values, in comparison with CMR, which is not affected by volume status; therefore, CMR seems to be a more accurate and precise modality for the assessment of LVM in patients on MHD as has been shown in a study that was performed on the same patients before and after dialysis [21],[40],[43],[44]. The ellipsoid shape of the heart is the major contributor to inaccurate measurement of LVM by ECHO in HD patients [45],[46], as it omits the effect of pressure and volume overload that lead to morphological changes of the heart, resulting in various types and combination of hypertrophy. The endocardial border is not well defined on ECHO, and LV wall thickness is not uniform across all myocardial segments. In addition, ECHO calculation of LVM is based on a formula that is dependent primarily on the internal dimensions of the LV [47], and thus ECHO estimation of LVM varies greatly between the predialytic and the postdialytic period solely because of fluctuation in intravascular volume, and consequently the variation in the intracardiac volume [47],[48].

 Conclusion



ECHO overestimates LVM and LVMI as well as LVH detection in comparison with CMR in ESRD patients on HD. Therefore, when accurate assessment of LVM is needed, CMR may be a better option to detect LVH in this high cardiovascular risk group.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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