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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 6  |  Issue : 3  |  Page : 81-89

The prediction of left main and/or triple-vessel coronary artery disease by tissue doppler-based longitudinal strain and strain-rate imaging


1 Department of Cardiology, King George Medical University, Lucknow, Uttar Pradesh, India
2 Department of Cardiology, Sardar Patel Hospital and Heart Institute, Ankleshwar, Gujrat, India

Date of Web Publication12-Sep-2018

Correspondence Address:
Dr. Gaurav Kumar Chaudhary
Department of Cardiology, King George Medical University, Lucknow, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/heartindia.heartindia_30_18

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  Abstract 


Background: In the absence of evident regional wall motion abnormality (RWMA) at rest, detection of severe coronary artery disease (CAD) usually requires a stress test. Ventricular strain is a more sensitive parameter of myocardial systolic function and may be abnormal in patients with severe CAD. Thus, this study aimed to evaluate the longitudinal strain and strain-rate imaging for prediction of left main (LM) and triple-vessel disease CAD with normal left ventricular ejection fraction (LVEF) and no RMWA.
Materials and Methods: Patients included were of stable CAD, unstable angina, or non-ST segment elevation myocardial infarction with LVEF >50% and without RWMA. A thorough echocardiographic evaluation to assess peak systolic longitudinal strain (PSLS) and PSLS rate (PSLSR) in 16 segments of the left ventricle was done. The visual evaluation of percent diameter stenosis of the angiographic lesions was done according to the American Heart Association classification. Patients were grouped into high-risk group (LM or triple-vessel CAD), low-risk group (CAD other than high risk), and normal group (absence of CAD).
Results: A total of 86 patients were studied. Of which, 60 were male and 26 were female. The global PSLS and PSLSR were lower in the high-risk group as compared to the other two groups (P < 0.001). The combined basal plus mid-PSLS and PSLSR were lower in the high-risk group (P < 0.001). Receiver operating characteristic curve analysis showed an optimal cutoff value of −17.3% (sensitivity 82% and specificity 80%) for global PSLS and −15.0% (sensitivity 75% and specificity 73%) for basal plus mid-PSLS for detection of high-risk CAD. Similarly, a cutoff value of −0.74 s−1 (sensitivity 82% and specificity 73.6%) for global PSLSR and −0.66 s−1 (sensitivity 85.7% and specificity 86.7%) for basal plus mid-PSLSR were calculated for the prediction of high-risk CAD.
Conclusion: The PSLS and PSLSR were lower in patients having high-risk CAD that included LM and triple-vessel disease, even when resting wall motion and LVEF were normal. The study concluded that PSLS and PSLSR are sensitive and specific noninvasive modalities for predicting the possibility of high-risk CAD in the presence of normal LV systolic function and absence of resting RWMA.

Keywords: Coronary artery disease, strain-rate imaging, tissue doppler echocardiography


How to cite this article:
Sharma AK, Chaudhary GK, Kharwar RB, Saran M, Chandra S, Dwivedi SK, Narain VS. The prediction of left main and/or triple-vessel coronary artery disease by tissue doppler-based longitudinal strain and strain-rate imaging. Heart India 2018;6:81-9

How to cite this URL:
Sharma AK, Chaudhary GK, Kharwar RB, Saran M, Chandra S, Dwivedi SK, Narain VS. The prediction of left main and/or triple-vessel coronary artery disease by tissue doppler-based longitudinal strain and strain-rate imaging. Heart India [serial online] 2018 [cited 2018 Sep 23];6:81-9. Available from: http://www.heartindia.net/text.asp?2018/6/3/81/241070




  Introduction Top


Although Doppler myocardial velocities can detect abnormal regional function, due to tethering to adjacent myocardial segments, the exact position of the ischemic segment within a cardiac wall cannot be determined. Thus, myocardial velocity is more of a global rather than regional estimate of ventricular function. Strain and strain rate imaging (SRI) (deformation analysis) are more useful than wall motion analysis (velocity and displacement) for detection of regional myocardial dysfunction.[1],[2]

Strain is a measure of myocardial deformation and can be measured using either tissue Doppler imaging (TDI) or two-dimensional (2D) speckle-tracking echocardiography. Although speckle-tracking-derived 2D strain and TDI-derived strain calculations do not give the same values (2D strain imaging gives lower SR values), strain and SR measurements obtained by these two different imaging techniques correlate well.[3] Each of these methods has their own advantages and disadvantages.

Non-Doppler 2D strain imaging derived from speckle motion tracking has the advantage of being 2D and angle independent.[3] However, the necessity of high image quality is a major limitation for routine clinical applicability in all patients. TDI, is currently accepted as a sensitive and sufficiently accurate echocardiographic tool for quantitative assessment of cardiac function.[1],[2],[4],[5],[6],[7],[8],[9] In the hands of very experienced and highly trained operators, this method can be a valuable noninvasive tool for routine clinical use to evaluate the myocardial contractile function.

A regional measurement of deformation, Doppler strain imaging (DSI), was developed to overcome the limitations of velocities by Heimdal et al.[10] DSI is obtained by the use of velocities and includes the modalities of strain and strain rate. As the ventricle contracts, its muscle shortens in the longitudinal and circumferential dimensions (a negative strain) and thickens in the radial direction (a positive strain). Strain rate measures the time course of deformation and is the primary parameter of deformation derived from tissue Doppler. DSI is not affected by tethering or aliasing. SRI has been shown to quantify regional myocardial function in experimental studies with sonomicrometry,[1] magnetic resonance imaging,[5] and ultrasonography.[2],[6],[7] It has also been established that DSI can be used to diagnose viability[8],[9] and some cardiomyopathies.[11],[12],[13] The use of SRI during dobutamine stress echocardiography was found to be not just feasible but more sensitive than wall motion score in two small studies.[14],[15],[16]

Although patients with left main (LM) coronary artery disease (CAD) or triple-vessel CAD present to be a high-risk subset,[17],[18],[19] in the absence of previous myocardial infarction or stunning, the resting left ventricular (LV) wall motions are essentially normal in these patients.

It has been previously reported that tissue Doppler longitudinal velocity is reduced in patients with three-vessel CAD, but the number of study patients was small and results were inconsistent.[20],[21],[22],[23]

Based on the above literature, we hypothesized that repetitive ischemia of LV myocardium in significant CAD would reduce systolic longitudinal function, although resting regional wall motion remains normal. Based on this hypothesis, we designed our study to evaluate the usefulness of global and segmental peak systolic longitudinal strain (PSLS) and PSLS rate (PSLSR) measured by the TDI in identifying severe CAD.

Owing to the huge costs and lack of easy accessibility of 2D strain imaging in our country, we used DSI and offline analysis to calculate global and segmental PSLS and PSLSR.


  Materials and Methods Top


This was a prospective, cross-sectional, observational, single-center study. All patients who underwent coronary angiography for suspected stable or unstable CAD with LV ejection fraction >50% and no resting regional wall motion abnormality (RWMA) were included in the study. Patients with heart rhythm other than normal sinus rhythm, valvular lesions of more than mild-grade severity, poor transthoracic window, or poor signal on TDI were excluded. Informed consent was obtained from all the patients. The patients underwent echocardiographic examination using Vivid 7 dimension imaging system (GE Vingmed; Horten, Norway). Narrow sector imaging with high frame rates (>100 FPS) keeping the area under investigation as much parallel to the transducer imaging line was done using a 3.5 MHz transducer in the apical long axis, four chamber and two chamber views for the segmental and global analysis of PSLS and PSLSR. Segmental analysis of PSLS and PSLSR [Figure 1] and [Figure 2] was done in 16 segments of the left ventricle (septal and lateral wall – base, mid, and apex in apical four-chamber view; anterior and inferior wall – base, mid, and apex in apical-two chamber view; and posterior and anteroseptal wall – base and mid in the apical long-axis view). Global PSLS and global PSLSR were calculated by average of the 16 segmental PSLS and PSLSR of a left ventricle. Three consecutive cardiac cycles were saved in digital format. Strain and strain rate analysis was done offline by one investigator before angiogram.
Figure 1: The offline analysis of tissue Doppler-based peak longitudinal segmental strain analysis in septal (a), lateral (b), inferior (c), anterior (d), posterolateral (e), and anteroseptal (f) walls of the left ventricle in one of the patient enrolled in the study

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Figure 2: The offline analysis of tissue Doppler-based peak longitudinal segmental strain rate analysis in septal (a), lateral (b), inferior (c), anterior (d), posterolateral (e), and anteroseptal (f) walls of the left ventricle in one of the patients enrolled in the study

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The visual assessment of percent diameter stenosis of the angiographic lesion was done according to the American Heart Association Classification. The number of affected vessels was assessed, using a cutoff of percent diameter stenosis ≥70% for three epicardial vessels and ≥50% for LM coronary artery. Patients were grouped into high-risk group (LM or triple-vessel CAD), low-risk group (CAD other than high risk), and normal group (absence of CAD).

Statistical analysis

Continuous variables are presented as mean ± standard deviation, whereas categorical variables are expressed as percentages. Data were analyzed using SPSS (IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. IBM Corp, Armonk, NY) Chi-square test and analysis of variance were used to compare the data. Receiver-operator curve analysis was performed to find out discriminant values of different parameters being studied. P < 0.05 was considered as indicator of a significant association.


  Results Top


Demographic and angiographic details

A total of 100 patients were enrolled in the study, but due to poor transthoracic echo window and poor signals on TDI, 14 patients were excluded. Hence, 86 patients were evaluated by both echocardiography and coronary angiography. Sixty patients were male and 26 were female. The demographic and angiographic characteristics of different groups are outlined in [Table 1].
Table 1: The demographic and angiographic characteristics of different groups

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Global and segmental strains and strain rates

The mean global and segmental PSLS and PSLSR in all the three groups are shown in [Table 2]. Global PSLS and PSLSR were significantly lower in the high-risk group as compared to the low risk and the normal group (P < 0.001). The difference was also significant between the low-risk and normal group.
Table 2: The strain and strain rate analysis in different groups

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Segmental PSLS was also significantly lower in the high-risk group in all segments except the apical segment. With the exception of apical and basal segments, PSLSR for the remaining segments were also significantly lower in the high-risk group (P < 0.001). The combined basal plus mid-PSLS and PSLSR were lower in the high-risk group as compared to the other two groups (P < 0.001) [Table 2] and [Figure 3], [Figure 4].
Figure 3: Comparison of global and segmental peak systolic longitudinal strain by study group using one-way analysis of variance with post hoc analysis and Bonferroni's correction

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Figure 4: Comparison of global and segmental peak systolic longitudinal strain rate by study group using one-way analysis of variance with post hoc analysis and Bonferroni's correction

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According to receiver operating characteristic curve analysis, the optimal cutoff value for global PSLS for detection of high-risk CAD was −17.3% (sensitivity 82% and specificity 80%) and for basal plus mid-PSLS was −15.0% (sensitivity 75% and specificity 73%) [Table 3] and [Figure 5]. The cutoff value of −0.74 s−1 for global PSLSR detected severe CAD with sensitivity of 82% and specificity of 73%. The cutoff value of –0.66 s−1 for basal plus mid-PSLSR detected severe CAD with sensitivity of 85% and specificity of 86% [Table 4].
Table 3: The predictive characteristics of strain for detection of high-risk coronary artery disease

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Figure 5: Receiver operating characteristic curve analysis for prediction of high-risk coronary artery disease as defined by left main or triple-vessel disease. B: Basal, M: Mid, A: Apical, G: Global, BM: Basal plus mid, PSLS: Peak systolic longitudinal strain, PSLSR: Peak systolic longitudinal strain

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Table 4: The predictive characteristics of strain rate for detection of high-risk coronary artery disease

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  Discussion Top


Unprotected LM CAD and triple-vessel disease carry a poorer prognosis probably because of a large jeopardized myocardium. Although stress testing is generally performed to diagnose significant CAD in the absence of LV dysfunction and RWMA, it comes with a greater risk of MI and death.[24] Stress perfusion and dobutamine stress echo have been shown to be fairly sensitive and specific test for the diagnosis of CAD,[25],[26] however, the results may not be reliable in LM disease owing to the phenomenon of balanced ischemia.[27] Hence, detection of significant CAD without the need for provocation is much desirable.

TDI has been shown to be fairly sensitive and specific tool for evaluation of cardiac function. Stress and strain parameters have been used to prognosticate patients with major cardiac illnesses. In our study, various strain parameters showed similar sensitivity and specificity to standard tests. Global strain parameters have been shown to be better than segmental analysis. Global PSLS showed a sensitivity of 82% and specificity of 80% which is comparable to stress echo sensitivity and specificity of 84% and 82%, respectively. The standard positron emission tomography-computed tomography and stress echo require subjective and visual evaluation of results; however, on the other hand, strain parameters are more objective and reproducible. Although strain parameters are difficult to compute, constant practice can make it a useful tool.

Some previous investigations have also tried to predict CAD using strain analysis at rest. Tsai et al.[20] examined the diagnostic value of segmental longitudinal strain by automated function imaging in CAD patients with and without RWMA. Nucifora et al.[21] reported different results from ours in a similar study population and advocated the use of global PSLS for the prediction of CAD by computed tomography. In a study by Choi et al.[22] on 108 patients, having similar patient profile to the present study, using automated functional imaging (AFI) software with 2D strain method, mid plus basal PSLS value of −17.9% predicted the presence of LM or triple-vessel disease with a sensitivity and specificity of 79% and 79%, respectively, similar to our cutoff value of −17.3% (sensitivity-82% and specificity-80%). The latter study did not derive the PSLSR cutoff value as PSLSR cannot be directly derived from AFI software. The present study used TDI-based strain and strain rate for prediction of severe CAD. Although speckle-tracking-derived 2D strain and TDI-derived strain calculations do not give the same values, strain and strain rate measurements obtained by these two different imaging techniques correlate well. The tracking was done manually in the present study, yet it provided results as good as the AFI software, albeit at a greater consumption of time at offline analysis with the TDI method.

In the present study, PSLSs and PSLSRs of mid- and basal-LV segments were significantly lower than those of the apical segment. Apex of LV has prominent rotational movement in addition to longitudinal and short-axis motion, and this might result in the incorrect estimation of longitudinal function in this segment. Moreover, inner myocardium, which is known to be most susceptible to myocardial ischemia, and which is the major component responsible for long-axis function, has a helical fiber orientation.[23] This helical structure might result in parallel alignment of longitudinal axis and inner myocardium only in the LV mid or base. Apical myocardium is rather aligned in a circular direction, which might be associated with short-axis function or rotational movement.

The present study showed that the PSLS and PSLSR, considered as measures of LV function, are reduced in patients with LM or triple-vessel disease as compared to those with less severe form of disease or in whom CAD was absent. However, the study was limited the facts that the sample size was relatively small and the study being carried out in a tertiary care hospital was prone to selection bias. Furthermore, the values of PSLS and PSLSR are load dependent. Demographic comorbidities such as diabetes mellitus, dyslipidemia, hypertension, and smoking were higher in high and lower risk groups in comparison to normal. A large number of high- and low-risk group patients were taking medications such as angiotensin-converting enzyme inhibitors/angiotensin receptor blocker, beta-blockers, nitrates, and calcium-channel blockers which affect the loading conditions for the heart. This might have affected the values of PSLS and PSLSR. The angiographic evaluation of coronary stenosis was visual and was not determined by quantitative methods such as intravascular ultrasound and fractional flow reserve. The reduction in PSLS and PSLSR may not be specific to CAD and may be present in other myopathies too requiring further evaluation. The angle dependency, one-dimensional strain measurements, need for imaging at high temporal resolution, necessity of expert readers, high sensitivity to signal noise, high interobserver variability, more time requirement for acquisition, and offline analysis are some of the inherent limitations of TDI which was used in the present study for calculation of PSLS and PSLSR. Only those patients who did not have RWMA were included in the study. Hence, our study results cannot be generalized, especially for patient with RWMAs.


  Conclusion Top


PSLS and PSLSR is a sensitive and specific noninvasive modality for predicting the possibility of high-risk CAD in the presence of normal LV systolic function and absence of resting RWMA. This study was performed as a hypothesis-generating study and larger prospective studies are required for validating our findings.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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