|Year : 2016 | Volume
| Issue : 2 | Page : 418-422
Assessment of right ventricular function in patients with first inferior myocardial infarction: strain imaging study
Ahmed A Reda, Mohamed F El-Noamany, Naglaa F Ahmed, Hesham M Saad Tayel
Department of Cardiology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
|Date of Submission||03-Nov-2014|
|Date of Acceptance||16-Dec-2014|
|Date of Web Publication||18-Oct-2016|
Hesham M Saad Tayel
Shanwan, Shbeen Elkoom, Menoufia, 32511
Source of Support: None, Conflict of Interest: None
The aim of the study was to assess strain and strain rate (SR) properties of the right ventricle (RV) in patients with RV myocardial infarction (MI).
Quantitative assessment of RV function is still challenging due to its complex anatomy and thin wall structure, and therefore is not incorporated into daily clinical practice. Two-dimensional strain and SR analyses are novel Doppler-independent techniques to obtain these measurements of myocardial movement and deformation. These methods have been frequently used to assess left ventricular function; however, they have yet rarely been used to examine RV function, despite RV function is an important prognostic factor in patients with acute first inferior MI.
Patients and methods:
A total of 40 patients with acute inferior MI were included in this study; 20 patients had ECG signs of inferior MI without RV infarction (group II) and 20 patients had ECG signs of inferior MI with RV infarction (group III). In all, 20 age-matched and sex-matched healthy volunteers were included as a control group (group I), using two-dimensional speckle tracking measurements of RV free wall longitudinal strain and SR in the apical four-chamber.
A statistically highly significant difference was found among the three groups regarding the peak systolic longitudinal strain at apical, mid, and basal segments of RV free wall (P < 0.0001), and significant difference was found among the three groups regarding The peak systolic SR at basal and mid segments of RV free wall (P < 0.05).
This study demonstrates that RV strain and SR were lower in patients with left ventricular inferior wall MI with RV infarction compared with those without RV infarction.
Keywords: acute myocardial infarction, right ventricular function, strain rate imaging
|How to cite this article:|
Reda AA, El-Noamany MF, Ahmed NF, Saad Tayel HM. Assessment of right ventricular function in patients with first inferior myocardial infarction: strain imaging study. Menoufia Med J 2016;29:418-22
|How to cite this URL:|
Reda AA, El-Noamany MF, Ahmed NF, Saad Tayel HM. Assessment of right ventricular function in patients with first inferior myocardial infarction: strain imaging study. Menoufia Med J [serial online] 2016 [cited 2019 Dec 15];29:418-22. Available from: http://www.mmj.eg.net/text.asp?2016/29/2/418/192438
| Introduction|| |
Myocardial infarction (MI) is a major cause of death and disability worldwide. Coronary atherosclerosis is a chronic disease with stable and unstable periods. During unstable periods with activated inflammation in the vascular wall, patients may develop a MI. MI may be a minor event in a lifelong chronic disease; it may even go undetected, but it may also be a major catastrophic event leading to sudden death or severe hemodynamic deterioration. A MI may be the first manifestation of coronary artery disease, or it may occur repeatedly in patients with established disease .
Right ventricular (RV) infarction may occur alone or in association with left ventricular (LV) inferior wall infarction.
ST-segment elevation in the right precordial lead, V4 R, is one of the most reliable ECG signs of acute RV infarction .
It is well understood that ECG evidence of RV infarction is associated with a poor prognosis .
A hypokinetic or akinetic segment of the RV observed by echocardiography also could be used to detect RV dysfunction after RV infarction .
However, quantitative assessment of RV function is still challenging due to its complex anatomy and thin wall structure, and therefore is not incorporated into daily clinical practice .
Myocardial function is traditionally assessed by visual estimation of wall motion, ventricular volumes, and calculation of ejection fraction (EF). Echocardiographic assessment of RV-EF is difficult and underlies several limitations .
Strain rate (SR) imaging allows the determination of velocity gradients between two points in space. The resulting contraction variable is independent of passive tethering effects from other regions, and therefore appears promising for quantification of regional myocardial function .
Strain is a measure of tissue deformation. As the ventricle contracts, muscle shortens in the longitudinal and circumferential dimensions (a negative strain) and thickens or lengthens in the radial direction (a positive strain) .
Two-dimensional strain and SR analyses are novel Doppler-independent techniques to obtain these measurements of myocardial movement and deformation. These methods have been frequently used to assess LV function; however, they have yet rarely been used to examine RV function , despite RV function is an important prognostic factor in patients with acute first inferior MI .
| Patients and Methods|| |
The study excluded patients with inferior and anterior MI, previous STEMI, previous coronary artery bypass graft surgery, The presence of a pacemaker or defibrillator lead in the RV, atrial fibrillation or complete heart block, complete right or left bundle branch block, chronic obstructive pulmonary disease, pulmonary hypertension, pulmonary thromboembolic disease, signs of valvular heart disease, organic tricuspid or pulmonary valve disease, dilated cardiomyopathy, myocardial disease, and RV involving, for example, HOCM, amyloidosis, renal dysfunction, pregnancy, severe hypotension (systolic blood pressure <80 mmHg), pericardial disease, poor image quality, and inability to give consent. A total of 40 patients with first inferior MI with and without RV MI were included, in addition to 20 age-matched and sex-matched healthy volunteers as a control group. A standard 12-lead ECG and a right precordial ECG (lead V4 R) were recorded immediately after arrival to the coronary care unit. The diagnosis of MI was based on characteristic chest pain, ECG changes, and diagnostic serial changes in cardiac enzymes. Inferior MI was defined as ST-segment elevation at least 1 mm in inferior leads (leads II, III, and aVF) . The presence of RV infarction in association with an inferior MI was defined by an ST-segment elevation 0.1 mV in lead V4 R . According to this definition, 20 patients had ECG signs of inferior MI without RV infarction (group II), and 20 patients had ECG signs of inferior MI with RV infarction (group III). In all, 20 age-matched and sex-matched healthy volunteers were included as a control group (group I). Blood pressure was measured with a mercury sphygmomanometer at the brachial artery. Hypotension was defined as a systolic blood pressure less than 100 mmHg.
The ethics committee of our institute approved the study protocol and all patients gave written informed consent for the study.
An echocardiographic study was performed with the patients in the left lateral decubitus position within the first 6 h of MI. Echocardiography was performed using a Vivid 9 (GE Vingmed, Horten, Norway) equipped with a harmonic M5S variable-frequency (1.7–4 MHz) phased-array transducer. All echocardiographic recordings were performed by another physician blinded to the ECG findings. The conventional echocardiographic measurements were performed according to the recommendations of the American Society of Echocardiography . Right atrial dimension was determined through the four-chamber view from the maximal medial to lateral dimension at end-ventricular systole (which corresponds to maximal atrial volume). RV dimension was determined in the four-chamber view from the maximal medial to lateral dimension at midcavity but end-diastole. LV end-systolic and end-diastolic dimensions were measured in the parasternal long-axis view. LV EF was assessed by apical two-chamber and four-chamber views with the modified Simpson rule .
Assessment of Doppler tissue velocity, strain rate, and strain
Two-dimensional color Doppler myocardial imaging data for longitudinal function were recorded from the RV free wall using standard apical four-chamber view. Free wall of the RV was divided into three regions: basal, mid, and apical. All data were acquired at a frame rate ranging 59–82 frame/s; mean 72 + 6 frame/s. An appropriate velocity scale was chosen to avoid color Doppler myocardial imaging data aliasing. At least three consecutive cardiac cycles were recorded. All recordings of the patients were performed on a magneto-optical disk for subsequent analysis. Measurements recorded on the magneto-optical disk, however, were analyzed by another physician who was unaware of the patients with RV infarction. Offline analysis of the myocardial color Doppler data for regional systolic tissue velocity, SR, and strain curves was performed using a special software program (Echopac PC, version1.8.1.X; GE Healthcare, United Kingdom). Systolic tissue velocity was obtained by placing a sample volume (3×3 pixel) at the basal, middle, and apical portion of RV free wall. As calculable parameters of the tissue Doppler data, strain and SR could be measured using the same software. They were assessed for the basal, middle, and apical segments of the RV. In short, peak systolic SRs were estimated by measuring the spatial velocity gradient over a computation area of 10 mm longitudinally. To derive systolic tissue velocity and SR profiles from a segment, the region of interest was maintained in a constant position within the segment being interrogated using a semiautomatic tracking algorithm. The timing of end-systole (pulmonary valve closure) and end-diastole (onset of isovolumic contraction) of the RV was derived using a myocardial tissue velocity profile. Natural strain profiles were obtained by integrating the SR values over time using end-diastole as the reference point ([Figure 1]). Strain and SR were analyzed by another physician blinded to the ECG findings.
|Figure 1: Two-dimensional measurements of longitudinal strain (Ss-1) in the apical four-chamber view in a control individual (normal values) of basal, mid, and apical segments of septal and lateral free wall (right wall). Peak S (Ss-1) (peak longitudinal systolic strain).|
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The data collected were tabulated and statistically analyzed by SPSS statistical package (SPSS, v17) on IBM personal computer and the statistical package SPSS (version 17; SPSS Inc., Chicago, Illinois, USA). . Statistical presentation and analysis of the present study was conducted, using two types of statistics: Descriptive statistics, for example, mean (x−) and SD, and analytic statistics, for example, F-test (analysis of variance). A value of P less than 0.05 was considered statistically significant.
| Results|| |
There were no differences between groups for LV EF, LV end-diastolic, and systolic diameter. Comparison between the study groups (control, inferior MI without RV MI, and inferior MI with RV MI) regarding RV free wall strain and SR strain at basal (−22.5 ± 7 vs. −12 ± 5%, −1.4 ± 0.4 vs. −1.1 ± 0.4/s; P<0.01, < 0.01) and mid segment (−26 ± 4 vs. −14 ± 3%, −1.6 ± 0.4 vs. −1.3 ± 0.3/s; P<0.001, < 0.001, < 0.001, respectively) is shown in [Table 1] and [Table 2].
|Table 1: Comparison between the study groups regarding RV free wall peak systolic longitudinal strain (Esys %)|
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|Table 2: Comparison between the study groups regarding RV free wall strain rate at peak systole (SRs s-1)|
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A statistically significant difference was found among the three groups regarding The peak systolic SR at basal and mid segment (P<0.05) ([Table 2] and [Figure 2]). When matching group II (inferior MI without RT MI) with group I (control) and group III (inferior MI with RT MI) with group I (control), there was significant difference at basal and mid segment (P1 and P2<0.05) ([Table 2]).
|Figure 2: Comparison between the study groups regarding right ventricular free wall strain rate at peak systole (SRs s-1).|
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| Discussion|| |
RV involvement as assessed by various diagnostic criteria has been shown to occur in 30–50% of patients suffering from inferior MI. In these patients, a significantly increased risk for major complications and in-hospital death has been reported. RV infarction is usually associated with depressed RV function, although it does not always lead to hemodynamic impairment ,,. Tissue Doppler echocardiography (TDE) has the potential to assess ventricular contractile function independent of the shape of the ventricle.
TDE has been considered to be a technique that leads to the assessment of RV function .
However, the magnitude of ejection phase myocardial velocities has been shown to be preload and afterload dependent. Experimental data suggest that Doppler-derived myocardial tissue acceleration during the isovolumic contraction phase may be a load-independent predictor of RV systolic function . In addition, TDE has obvious advantages and has been accurate in investigation of single-dimension motion. The heart, however, has a very complex motion pattern, rotation, contraction, and shortening, and it is affected by adjacent structures and tethering of neighboring segments . Strain and SR analyses are new techniques for the assessment of regional myocardial function . Strain represents relative amount of deformation and SR represents the local rate of myocardial deformation . In principle, myocardial strains are independent of translational motion and other through-plane motion effects and should be relatively uniform throughout the normal LV myocardium. In contrast, myocardial velocities show marked nonuniformity in the normal ventricle, and this complicates data interpretation. The assessment of myocardial strain by TDE could simplify the analysis of regional contractile function by providing a more objective and uniform parameter of myocardial function . Therefore, myocardial strain should be preferred to velocity information because it is less influenced by tethering effects and over all cardiac function . Nevertheless, Doppler-derived tissue velocity imaging, the most commonly used method for the assessment of LV strain, is angle dependent . LV regional myocardial function can be quantified using segmental strain and SR in various pathophysiological situations, including ischemia, stunning, myocardial hypertrophy, and pump failure. A few studies showed that longitudinal strain and SR imaging appears well suited for functional assessment of the heterogeneous and complex anatomy of the RV [4, 6, 24–26]. Yet, the accuracy of SR imaging to quantify RV deformation in patients with RV MI remains to be evaluated. Our study showed that the highest strain and SR values of groups 1 and 2 were mid segments. These heterogeneous values are in agreement with the results of the study by Dambrauskaite et al. . They found that the RV segmental strain/SR values were inhomogeneous (higher in the mid segments) in healthy individuals; however, Kowalski et al.  demonstrated that the higher strain and SR values were in apical part of the RV free wall. In our study, tissue velocity values were progressively decreased from the base toward the apex, mainly attributable to the through-plane motion of the heart. In a study by Weideman et al. , in which they evaluated the effects of changing inotropic state on normal myocardial function in pigs using strain and SR imaging, it was demonstrated that β-blockers decreased strain values by 50%. β-Blocker might have led to lower strain values than normal in patients without RV infarction by influencing RV contractile function. In the study by Urheim et al. , they compared RV stroke volume index with the mean of strain values obtained from the apical and basal segments of the RV for the assessment of RV systolic function. A cutoff value of 20% with 91% sensitivity and 63% specificity was obtained for RV systolic strain values to demonstrate RV dysfunction; RV stroke volume index of at least 30 ml/m 2 was considered an indicator of normal RV systolic function. These results were consistent with the cutoff values obtained in our study from basal and middle segments of the patients with inferior MI with RV involvement.
The data presented here were obtained from a small group of patients, and the receiver operator curves had some limitations. This study measured strain and SR in the RV in patients with inferior wall MI but did not directly compare the diagnostic accuracy of these measures with other echocardiographic indices of RV infarction. In our study, there were hemodynamic differences between the groups. The ideal study would compare isolated inferior MI versus inferior MI with RV involvement with similar hemodynamics. Strain and SR were measured only in longitudinal direction. Radial strain and SR may provide further interesting evidence of abnormal strain and SR values. Strain and SR imaging analysis in patients with RV infarction clearly demands extensive validation studies. In addition, the negative effect of angle on peak systolic velocity increases at the apex as a result of the curvature of the LV wall with possible velocity underestimation. This can potentially affect SR measurement.
| Conclusion|| |
This study demonstrates that RV strain and SR were lower in patients with LV inferior wall MI with RV infarction compared with those without RV infarction.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]