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Table of Contents
ORIGINAL ARTICLE
Year : 2022  |  Volume : 12  |  Issue : 2  |  Page : 43-48

Left ventricular global longitudinal strain by speckle tracking echocardiography as a noninvasive predictor in evaluation of myocardial infarction


1 Department of Cardiology, Yenepoya Medical College, Mangalore, Karnataka, India
2 Department of Cardiology, Goa Medical College, Bambolim, Goa, India
3 Department of Cardiology, St. John's Medical College and Hospital, Bengaluru, Karnataka, India
4 Department of Cardiology, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Mysore, Karnataka, India

Date of Submission10-Mar-2021
Date of Decision19-Apr-2021
Date of Acceptance14-May-2021
Date of Web Publication21-May-2022

Correspondence Address:
Dr. K P Kumar
Department of Cardiology, Yenepoya Medical College, Mangalore, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jicc.jicc_12_21

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  Abstract 


Background: Coronary artery disease (CAD) has assumed epidemic proportions in the world. Accurate risk stratification and early invasive management when indicated can reduce morbidity and mortality substantially. The study aims to correlate left ventricular (LV) function assessed by global longitudinal strain (GLS) with the extent of CAD in patients with myocardial infarction (MI). Methods: The study was conducted in a tertiary care hospital in Southern India. A total of 105 patients admitted with a diagnosis of non ST-elevation MI were included. All patients had a detailed echocardiogram with the evaluation of LV GLS by two-dimensional speckle tracking echocardiography and ejection fraction by Simpson's method. Coronary angiogram was also done in all patients to study the coronary anatomy and the relation between CAD and LV GLS. Results: The mean age of study population was 53.9 years. Echocardiographic study revealed mean LV ejection fraction (LVEF) was 48.16 + 12.27. The mean LVEF in patients with single-vessel disease was 50.11 + 11.62; with two-vessel disease, it was 51.81 + 10.34, and in patients with triple-vessel disease, it was 41.5 + 11.8. The mean GLS in the abovementioned groups was − 15.6 + 3.33, −13.5 + 3.2, and − 11.02 + 4.14, respectively. The follow-up of patients also showed a considerably lower GLS in patients who suffered higher morbidity and mortality. Conclusion: LV GLS is a good noninvasive predictor of the burden of CAD on the angiogram and also a predictor of future cardiovascular events and mortality.

Keywords: Echocardiography, global longitudinal strain, left ventricular ejection fraction, left ventricular function, myocardial infarction


How to cite this article:
Kumar K P, Piedade JQ, Malali V, Hegde S. Left ventricular global longitudinal strain by speckle tracking echocardiography as a noninvasive predictor in evaluation of myocardial infarction. J Indian coll cardiol 2022;12:43-8

How to cite this URL:
Kumar K P, Piedade JQ, Malali V, Hegde S. Left ventricular global longitudinal strain by speckle tracking echocardiography as a noninvasive predictor in evaluation of myocardial infarction. J Indian coll cardiol [serial online] 2022 [cited 2022 Aug 14];12:43-8. Available from: https://www.joicc.org/text.asp?2022/12/2/43/345621




  Introduction Top


Coronary artery disease (CAD) is the leading cause of death globally, 7.4 million people died from CAD in 2015.[1] With rapid urbanization, India is witnessing a surge in cardiovascular diseases. In 2016, 62.5 million years of life lost prematurely due to CAD in India accounting for around 15%–20% of all deaths in India.[2] Besides mortality, CAD is also responsible for morbidity and loss of quality of life (QOL), also the treatment of CAD is expensive.[3] In view of high mortality and the economic burden, it poses accurate risk stratification and early invasive management when indicated is the need of the hour. CAD is a multifactorial disease with varying clinical phenotypes. A number of different imaging and provocative tests have been developed for the assessment and risk stratification. However, noninvasive evaluation of CAD remains a challenge; more than 50% of the patients had normal or nonobstructive CAD on coronary angiography.[4]

Evaluation of patients with CAD is one of the most important indications of echocardiography. Echocardiography has come a long way from basic two-dimensional (2D) imaging to the present speckle tracking echocardiography (STE) and three-dimensional echocardiography. Although 2D echocardiography does provide a lot of information, it has been noted that left ventricular (LV) strain by speckle tracking echocardiography provides a far more accurate and a better analysis of regional LV systolic function. STE is a simple, rapid, and accurate method for assessing regional contractile function by measuring peak systolic strain rate (SR) or rate of increase of SR.[5] A good correlation has been shown between longitudinal strain and the LV ejection fraction (LVEF); also longitudinal strain assessment of each LV segment allows early detection of systolic dysfunction in patients with preserved LVEF.[5],[6]

Early and more efficient revascularization has drastically improved the QOL of patients after a myocardial infarction (MI).[7] Despite successful early reperfusion therapy and secondary prevention therapy, patients still face a high risk of LV remodeling after MI.[8] LV remodelling after MI is a complex process, is a precursor for the development of heart failure (HF), and an important prognostic indicator of mortality.[9] Studies have shown that cardiac rehabilitation and pharmacological treatment could attenuate the LV remodeling after acute MI (AMI).[10],[11] Global longitudinal strain (GLS) measured by 2D speckle tracking echocardiography predicts LV remodeling and hence also helps in assessing the prognosis after AMI.[12],[13],[14],[15],[16],[17],[18],[19] Recent studies have also shown that LV longitudinal function deteriorates early in any cardiac pathology before the onset of clinical symptoms and reduction in global LV function.[20] Hence, this study intends to correlate LV function by GLS with the extent of CAD in patients with MI and evaluation of strain echocardiography as a predictor of morbidity and mortality after MI.


  Methods Top


Study design and setting

A prospective cross-sectional study was conducted at a tertiary care hospital including 105 patients suffering from CAD and seeking treatment at the hospital over a study period of 18 months from July 2017 to December 2018.

Eligibility criteria

All patients with a diagnosis of non-ST elevation MI (NSTEMI) who underwent a coronary angiogram were included in the study. However, patients with preexisting CAD, bundle branch block, and valvular heart disease were not included as their LV function and GLS could be affected by the above conditions. Furthermore, patients with inadequate ultrasonic images were not included in the study.

Data collection

A preformed case record form was used which collected information on the following aspects:

  • Detailed history from the patient and/or relatives
  • Laboratory parameters such as troponin, lipid profile, and blood sugar levels
  • Electrocardiogram
  • Echocardiography.
  • Echocardiographic examination was done on all patients using Vivid E9 (GE) machine. It included the assessment of LVEF by Simpson's method and LV GLS by 2D speckle tracking echocardiography. It is based on the principle that each piece of the myocardium has a unique speckle pattern that can be traced and distinguished from the neighboring myocardium. A postprocessing computer algorithm (in our case, Automated Functional Imaging) identifies location shift of acoustic markers within a region of interest in the myocardium.[21] For strain assessment, the endocardial margins are carefully demarcated in the apical 4-chamber view, apical 2-chamber view, and the apical 3-chamber view to define the base and apex. Care should be taken not to place the points on the atrial side of mitral annulus or into the LV outflow tract both of which can result in the underestimation of strain values. Once the points are taken, minor manual adjustment of segmental contours is needed for most patients to get an accurate analysis.
  • Coronary angiogram


  • º Normal coronaries or nonobstructive CAD if diameter stenosis is <50%

    º CAD was considered a significant when the diameter stenosis is >50%. Such patients were then further subdivided into single-vessel disease, two-vessel disease, or multivessel CAD based on the number of vessels involved.


After discharge, patients were followed up after discharge in outpatient department visits or through telephone at 1st month, 3 months, 6 months, and every 6 months until completion of study and events were recorded.

Ethics approval and informed consent

The study was approved by our institutional ethics committee and each patient was included in the study after obtaining an informed written consent.

Statistical analysis

Descriptive statistical methods such as frequency, percentage, mean, and standard deviation were used to describe the study variables. A P < 0.05 was considered statistically significant. Correlation technique was used to assess the strength of LV GLS as a noninvasive predictor of severity of CAD. The analyses were done using SPSS software for windows, version 18 (SPSS Inc., Chicago, Illinois, USA).


  Results Top


Patient characteristics

One hundred and five patients admitted with a diagnosis of NSTEMI and who underwent coronary angiogram were enrolled in the study. The mean age of the patients was 53.9 years, majority of them were males (64.5%). Prevalence of Type 2 diabetes mellitus and hypertension among the patients was 54.28% and 64.76%, respectively, and 37.14% were smokers. The most common presentation was chest pain followed by back ache. The mean LDL was 120 mg/dL with a maximum of 234 mg/dL. Most of the patients were hemodynamically stable with a mean systolic blood pressure of 129 mg/dL and diastolic blood pressure of 80 mg/dL [Table 1].
Table 1: Patient characteristics and baseline echocardiographic parameters

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Coronary angiogram and echocardiographic features

Patients with single vessel disease were 36%, with two-vessel disease 24% and 34% had three-vessel CAD. As the number of vessels involved increased, a linear fall in GLS was observed while LVEF did not show such trend [Table 2]. On comparing LVEF and GLS between patients with triple-vessel disease and patients with the involvement of two or lesser vessels, a statistically significant difference in both was observed [Figure 1]. Left anterior descending (LAD) was the most commonly involved coronary artery involved in 74.29% of patients. A lower LVEF when a particular vessel was involved except for left main coronary artery (LMCA) and a statistically significant lower GLS with the involvement of LMCA, LAD, left circumflex artery, and ramus intermedius was noted [Table 3]. The area under the receiver operating characteristic curve of LVEF versus GLS shows slight superiority of GLS to LVEF in assessing the severity of CAD although not statistically significant [Figure 2].
Table 2: Left ventricle function according to extent of coronary artery disease in study population

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Table 3: Variation in left ventricular function according to vascular territory involved/not involved

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Figure 1: Left ventricular function according to the number of vessels involved. TVD: Triple-vessel disease

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Figure 2: Area under the receiver operating characteristic curve of left ventricular ejection fraction versus global longitudinal strain

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Predictor of morbidity and mortality after myocardial infarction

After the first acute coronary syndrome event, 2.85% of patients had persistence or recurrence of angina at 12 months. Among the three patients, one of them had undergone revascularization, while the other two had not undergone any revascularization. The average GLS in patients with the recurrence of angina was much lower than the patients who did not report anginal attack. The mean GLS and LVEF in this group of patients with the recurrence of angina was − 6.4% and 36%, respectively, as against − 13.85% and 48.5% in those without the recurrence of angina. Five patients (4.76%) reported dyspnea at 12 months of follow-up. The mean GLS and LVEF in patients with dyspnea was − 6.46% and 32.4%, respectively, as against − 14% and 48.95% in those without dyspnea. Three patients (2.85%) had been rehospitalized by 12 months and the mean GLS and LVEF in this group of patients was − 6.7% and 30.6%, respectively, as against − 13.84% and 48.67% in those who did not require repeat hospitalization. Two patients (1.9%) had recurrent MI on follow-up. The mean GLS and LVEF in this group was − 7.05% and 28.5%, respectively, as against −13.77% and 48.54% in patients without repeat MI. Three patients (2.85%) died within 12 months of MI. The mean GLS in patients who succumbed was − 7.3% versus −13.83% in survivors. The mean LVEF was 33% in patients who died as against 48.6% in patients who survived at 1-year follow-up.


  Discussion Top


LV function assessed by various modalities has proven to be a good indicator of morbidity and mortality after an event of MI. The study was conducted with an objective to correlate LV function assessed by GLS and the extent of CAD and to evaluate LV strain as a predictor of morbidity and mortality after MI. The major findings of this study can be summarized as follows: the mean age of presentation with CAD was much younger and a higher number of female patients as compared to other studies.[22],[23],[24] A higher prevalence of diabetes mellitus was observed, while the family history of premature CAD, history of smoking, and hypertension was comparable to the other studies.[22],[23],[24] The baseline echo parameters and coronary angiographic findings with respect to the number of vessels involved were similar to previous studies [Table 4].[23],[24],[25] Similar to other studies, the most commonly involved coronary artery was LAD, and the involvement of LMCA was slightly lower than other studies. The average GLS in patients with significant CAD was slightly lower probably because of acute NSTEMI patients in our study.[23],[24]
Table 4: Comparison of different findings of similar studies

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Identification of three-vessel CAD in any patient with MI is very important in determining the prognosis and planning optimal treatment strategy for that particular patient. The average GLS in patients with three-vessel CAD was lower compared to patients with the involvement of up to two vessels on coronary angiogram which corroborates with other studies. Similar finding was noted in the study done by Hoshi et al., the area under curve for GLS to predict three-vessel CAD in their study was 0.745 compared to 0.77 in our study [Figure 2].[26]

The assessment of long-term prognosis after AMI is very important and several conventional echocardiographic parameters such as LV volumes, ejections fraction, wall motion score index, mitral regurgitation, and LA volume have been used to serve this purpose. However, the prognostic value of LVEF after AMI has been questioned, in a study LV end systolic volume was demonstrated as the primary predictor of survival after AMI, and that it was superior to LVEF in patients with depressed ejection fraction (<50%).[27]

Park et al. studied the prognostic importance of strain and SR in fifty patients with acute anterior wall MI and demonstrated an association between strain and LV remodeling and adverse cardiovascular outcomes. In their follow-up of 18 months, ten patients had developed congestive HF and seven patients required hospital admission. A lower baseline LV strain (−6.3% vs. −11.6%) was reported in patients who showed significant LV remodeling or developed congestive HF at follow-up.[12] The patients with clinical events at follow-up had significantly low LV strain (−4.3 vs. −10.6) compared to the group of patients without clinical events at follow-up as seen in our study. Furthermore, strain was a strong independent predictor of LV remodeling (odds ratio [OR] 1.31, 95% confidence interval [CI]: 1.08–1.58) and adverse cardiovascular events (OR: 1.46, 95% CI: 1.14–1.85). Similar finding was noted in a large study, in which 8% of patients succumbed during follow-up and a lower baseline LVEF and GLS was observed in these patients. The study also concluded that a GLS >−15.1 had a 3-year mortality risk of 15%, while a GLS of <−15.1 at baseline had a 3-year mortality risk of 6%; moreover, GLS was an independent predictor of re-infarction, revascularization, and HF hospitalization on follow-up.[28]

Some limitations in our study must be considered. First of all, this study is limited to patients after MI who underwent coronary angiography and included a relatively small sample from a single medical center. Consequently, our results may not be well extrapolated to the general patients after AMI. Second, because the follow-up period was only 12 months, further study with longer follow-up is required to detect the long-term predictive value of strain. Nevertheless, the collection of clinical variables and the follow-up of patients was prospectively planned, and our result is reliable. We believe that our findings add important information about strain parameters in assessing severity and prediction of mortality and morbidity after AMI.

Quantification of LV systolic function is a crucial component of the follow-up of patients after AMI. In the present study, the novel parameter of strain was related with outcome after AMI. Moreover, the present findings suggest that GLS provides stronger prognostic information for risk stratification after AMI than the LVEF measurements of LV systolic function. The semi-automated assessment increases the ease of clinical application of GLS in daily practice. Although these results are promising, more studies are needed to confirm these findings before GLS can be applied in the routine clinical setting after AMI. In addition, the measurements of strain are time consuming, but novel automated techniques have been developed which may overcome this limitation.[29]


  Conclusion Top


LV strain as assessed by 2D speckle tracking echocardiography was a promising, feasible, and noninvasive modality to analyze regional and global LV systolic function in the evaluation of MI in this study. It is a good noninvasive predictor of the burden of CAD on the angiogram. It was also seen that patients with lower strain values had more morbidity with HF and recurrent hospitalizations compared to patients with higher strain values. Mortality during follow-up was also associated with lower strain values in this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



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



 

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