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ORIGINAL ARTICLE
Year : 2021  |  Volume : 9  |  Issue : 2  |  Page : 124-129

Evaluation of left ventricular function using speckle tracking echocardiography in patients with severe aortic stenosis with or without symptoms


Department of Cardiology, Dr. RMLIMS, Lucknow, Uttar Pradesh, India

Date of Submission18-Jan-2021
Date of Decision17-Apr-2021
Date of Acceptance19-Apr-2021
Date of Web Publication25-Aug-2021

Correspondence Address:
Dr. Ashish Jha
Department of Cardiology, Dr. RMLIMS, Vibhuti Khand, Gomti Nagar, Lucknow - 226 010, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/heartindia.heartindia_63_21

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  Abstract 


Background: Speckle tracking echocardiography (STE) may be useful in early detection of contractile dysfunction in severe aortic stenosis (AS) patients.
Aims and Objectives: The present study aims to evaluate the global longitudinal strain (GLS), global circumferential strain (GCS), and strain rates in patients with severe AS and the role of STE in predicting the development of symptoms or left ventricular (LV) dysfunction in them.
Methods and Results: This was a single-centered, prospective, observational study, done at a tertiary care hospital in north India. The study recruited 30 patients with severe AS and 10 healthy controls. Patients underwent two-dimensional echocardiography and STE at baseline and 6 months. Baseline characteristics were similar between the cases and controls. Majority of severe AS patients were symptomatic (n = 24; 80%). LV ejection fraction (LVEF) was similar between cases and controls at baseline and 6 months. Cases had a significantly worse GLS (−-19.3 ± 5.66 vs. -30.4 ± 3.63), GCS (−-29.6 ± 8.48 vs. −-33.6 ± 2.55), and strain rate parameters than the controls at baseline and had a significant decline in these parameters at 6 months. Among 6 asymptomatic patients, 3 developed symptoms and these patients had a significantly greater decline in GLS at 6 months as compared to asymptomatic patients.
Conclusions: The present study revealed that patients with severe AS had an abnormal GLS and GCS to begin with, which was not picked by LVEF. Further, there was a significant worsening of these STE parameters at 6 months and those who had a greater decline were more likely to develop new symptoms.

Keywords: Aortic stenosis, global circumferential strain, global longitudinal strain, left ventricular ejection fraction, speckle tracking echocardiography


How to cite this article:
Yadav R, Tiwari BC, Jamwal N, Jha A. Evaluation of left ventricular function using speckle tracking echocardiography in patients with severe aortic stenosis with or without symptoms. Heart India 2021;9:124-9

How to cite this URL:
Yadav R, Tiwari BC, Jamwal N, Jha A. Evaluation of left ventricular function using speckle tracking echocardiography in patients with severe aortic stenosis with or without symptoms. Heart India [serial online] 2021 [cited 2021 Dec 4];9:124-9. Available from: https://www.heartindia.net/text.asp?2021/9/2/124/324608




  Introduction Top


Aortic stenosis (AS) is a common valvular heart disease in the elderly population and is associated with significant morbidity and mortality. Patients with severe AS may remain asymptomatic for a long period of time.[1] The risk of sudden cardiac death is <1% per year in asymptomatic severe AS patients. However, 30% of asymptomatic patients develop symptoms within 2 years,[2] and the outcomes of symptomatic severe AS are uniformly poor without intervention.[3]

Symptomatic severe AS and asymptomatic severe AS with reduced left ventricular ejection fraction (LVEF) are Class I indications for the aortic valve replacement.[3] However, reduction in LVEF is often a late phenomenon in severe AS and carries risk of irreversible myocardial damage. The more sensitive methods are thus needed to assess LV systolic function in these patients.

In patients with severe AS with preserved LV systolic function, the outcome after AVR is excellent, but with reduced LV systolic function, the outcome is worse.[4] These findings suggest that in patients with severe AS, it is as important to follow the progression of LV myocardial dysfunction as it is to follow the severity of obstruction by echocardiography.

Quantitative speckle tracking echocardiography (STE) parameters such as global longitudinal strain (GLS) have been used to accurately characterize global myocardial systolic function and to detect subtle changes in LV performance much before the decrease in LVEF.[5] GLS and strain rate have been shown to correlate strongly with invasively assessed myocardial contractility parameters such as dP/dT and end-systolic pressure–volume relations.[6] STE allows the angle-independent measurement of myocardial strain and is able to provide a better characterization of subtle changes in LV contractile function than LVEF.[7]

There is a subendocardial ischemia in AS patients, which is known to affect longitudinal myocardial fibers first. The use of longitudinal strain (LS) analysis may thus be useful in AS to identify patients with reduced contractility despite normal EF.[8] Previous studies have demonstrated that severe AS patients with preserved LVEF had impaired GLS, and there was an improvement of strain after AVR.[9] However, there is little information about the relation between the progression to symptoms in severe AS and changes in GLS in them.

The aim of this study is to assess LV strain as evaluated by STE in patients with severe AS and to assess whether the patients with severe AS having STE abnormality tend to develop symptoms earlier.


  Subjects and Methods Top


This was a prospective, observational study, conducted at a tertiary care, teaching hospital in north India. This study was carried out on 30 severe AS patients and 10 healthy volunteers of the same age group as controls. Control participants had no detectable cardiovascular risk factors and not receiving any medications, who were volunteers recruited from among the hospital staff and members of the local community. Written informed consent was obtained from all patients, and the study protocol was approved by the institutional ethics committee. All procedures followed were in accordance with the ethical standards of institutional ethics committee and with the Helsinki Declaration of 1964 and later versions. Written informed consent was obtained from all patients participating in the study.

Patients were included in the study if their age was ≥18 years, provided, they had severe AS and consented to participate in the study. Patients were excluded if they had coexistent coronary artery disease or prior myocardial infarction or any established valvular heart disease other than severe AS. Patients with diabetes mellitus, chronic obstructive pulmonary disease, pregnancy, malignancy, CKD, and hypertrophic cardiomyopathy were also excluded. Patients with poor echocardiographic image quality were also excluded.

The history taken from the study patients included symptomatic status according to NYHA class for dyspnea and angina and presence or absence of syncope. Detailed echocardiography and STE were done in all the participants at baseline and after 6 months.

Conventional two-dimensional (2D) echocardiography and 2D speckle tracking imaging were performed by a single operator (first author) using Philips IE 33. Images were obtained with patients in the left lateral decubitus position at end-expiration according to the recommendations of the American Society of Echocardiography. All standard measurements were obtained in the parasternal long and short-axis views and apical four-chamber view. The LV dimensions were quantified using M-mode echocardiography.

STE and 2D strain imaging were done using Philips QLAB 10, cardiac and vascular ultrasound quantification software. After manual tracing of the endocardial border of 2D tomographic images of LV in longitudinal and short-axis plane at the mid cavity level at the end-systolic frame and selecting the appropriate region of interest, including the entire transmural wall, the software automatically determined six segments in each view. Each segmental strain curve was obtained by frame-by-frame tracking of the acoustic markers in the myocardial tissue. The tracking quality was scored as valid or poor. Segments with poor tracking despite manual readjustments of the region of interest were excluded from the analysis. Peak-systolic LS was measured in seven segments (the apex, apical septum, mid inferior septum, basal inferior septum, basal anterolateral wall, mid anterolateral [MAL] wall, and apicolateral walls). Three cardiac cycles were analyzed, and average value was taken as mean of regional and GLS. Peak circumferential strain (CS) was measured in six segments (mid anterior, mid anterior septum, mid inferior septum, mid inferior, mid inferior lateral wall, and MAL wall) from a mid-LV short-axis view. Three cardiac cycles were analyzed, and the values were averaged and taken as the mean CS. The image acquisition was done using the standard protocol.

Statistical analysis

The results were presented in frequencies, mean ± standard deviation, and percentages. Chi-square test was used to compare categorical variables between the groups. The student t-test was used to compare continuous variables at the baseline between the groups. Paired t-test was used to compare the mean change in continuous variables from baseline to 6 months. McNemar's test was used to compare the change in dichotomous variables from baseline to 6 months. The two-sided P < 0.05 was considered as statistically significant. All the analysis was carried out by IBM SPSS 21.0 version (Chicago, IL, Inc., USA).


  Results Top


A total of 30 cases and 10 controls were included in the study. The mean age of cases and controls was 63.40 ± 6.20 and 63.56 ± 7.35 years, respectively [Table 1]. Majority of patients in both cases (76.7%) and controls (70%) were males. There was no significant difference in age or gender distribution between the groups [Table 1].
Table 1: Baseline characteristics and clinical presentation

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Among the case group (n = 30), 6 (20%) patients were asymptomatic. Symptom of angina was present in 24 patients, which was NYHA Class III in 12 (40%), Class II in 6 (20%), and Class IV in 6 (20%) [Table 1]. Symptom of dyspnea was present in 24 patients, of which 12 (40%) were in NYHA Class II, 11 (33%) were in Class III (33%), and 1 (7%) was in Class IV [Table 1].

LVEF of cases at baseline was 63.86 ± 7.55% and of controls was 65.0 ± 2.3% (P = 0.496) [Table 2]. Among the case arm, mean of peak gradient at baseline was 92.41 ± 30.15 mmHg, mean of mean gradient was 50.8 ± 19.55 mm Hg, and mean aortic valve area by continuity equation was 0.87 ± 0.13 cm2. The LV chamber dimensions of the 2 groups were similar [Table 2].
Table 2: Echocardiographic parameters at baseline

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STE revealed that the case group had a significantly worse GLS (−19.3±5.66 vs. −30.4±3.63), global CS (GCS) (−29.6±8.48 vs. −33.6±2.55), and strain rate parameters as compared to control group at baseline [Table 2]. There was a significant decline in GLS, GCS, and segmental strain rates at 6 months as compared to baseline values in case group, whereas no significant difference was seen in control group [Table 2].

The comparison between symptomatic and asymptomatic participants among the case group (n = 30) revealed that symptomatic patients (n = 24) had a significantly lower GLS and GCS at baseline as compared to asymptomatic patients (n = 6) [Table 3]. These symptomatic patients also had a significantly greater percentage reduction in GLS and GCS at 6 months from the baseline values than the asymptomatic patients [Table 3].
Table 3: Speckle tracking echocardiography parameters in asymptomatic versus symptomatic patients in case arm

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Among 6 patients who were initially asymptomatic, 3 developed symptoms during 6-month follow-up. There was a significant greater percentage change in GLS parameter over baseline value in these patients as compared to those who remained asymptomatic at follow-up (23.30 ± 17.23 vs. 2.60 ± 2.33). No significant difference was seen in percentage change in GCS [Table 4].
Table 4: Speckle tracking echocardiography parameter of asymptomatic patients at baseline who developed symptoms during follow-up

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  Discussion Top


Decision-making in the management of severe AS patients, whether conservative or interventional, is a big issue, especially in the asymptomatic patients. Conventional echocardiography allows for the estimation of LV systolic function by measuring LV fractional shortening, LVEF, tissue Doppler velocities, and myocardial performance index.[10] Both LV fractional shortening and LVEF are derived by measuring endocardial displacement and tend to overestimate systolic function in the presence of concentric LVH (which is frequent in severe AS). LVEF represents change in LV volume between end-diastole and end-systole but does not evaluate the intrinsic contractile function of the myocardium.

There is near consensus that specific LVEF cut-off and LV end-systolic dimensions are useful indicators of prognosis and need for intervention, and LVEF is the most routinely used parameter when assessing LV systolic function.[11] However, in AS, it is well known that LVEF may remain normal during the initial phase of chronic pressure overload despite reduced myocardial contractility (by utilizing preload reserve or changes in LV geometry).[12]

In severe AS, initially, there is subendocardial ischemia which can only be detected by GLS. Subsequently, when this ischemia worsens to become transmural, then only does the changes in LVEF appear. The use of GLS analysis may thus be useful in AS to identify patients with reduced contractility despite normal EF.

We studied 30 patients with severe AS of which 24 were symptomatic and 6 asymptomatic and ten healthy, age, and gender-matched controls. The relatively smaller number of asymptomatic patients in the present study may be because symptomatic patients are more likely to report to the hospital for evaluation than asymptomatic ones. Majority of symptomatic patients were having NYHA Class II or III symptoms of dyspnea and angina.

The LVEF and chamber dimensions were similar between the case and control subgroups. Whereas parameters of GLS, GCS, and strain rates were significantly reduced in AS patients at baseline compared to controls. These findings were suggestive of the fact that in patients with severe AS, there was an ongoing diminution of cardiac contractile function which was not detectable by LVEF measurement.

The significant difference in 2D STE parameters found between cases and controls in our study is consistent with several other previous studies. Cengiz et al. studied 45 asymptomatic patients with severe AS and 25 age-and sex-matched controls without any cardiac disease and with preserved LVEF.[13] In their study, LV longitudinal peak systolic strain (10.66% ±1.15% vs. 19.66% ±2.62%; P = 0.0001) and strain rate (0.32 ± 0.07 vs. 1.85 ± 0.32; P = 0.0001) were significantly impaired in the patients compared to the controls, demonstrating subclinical ventricular systolic dysfunction. Study done by Younan in 50 patients with severe AS and 30 age-matched healthy individuals also showed significantly reduced peak longitudinal systolic strain in patients with severe AS compared to the control group (LV-GLS, −12.7 ± 3.6 vs. −19.3 ± 2.7, P < 0.001).[14]

In the present study, a significant reduction of GLS, GCS, and regional strain rates at 6 months as compared to the baseline values was seen in case group, whereas no significant changes were observed in control group. Similar finding was seen in the study done by E. Vollema et al., where in patients of asymptomatic severe AS, after a median follow-up of 12 months, mean LV GLS deteriorated significantly (−18.0 ± 2.6% to −16.3 ± 2.8%; P < 0.001).[15]

Impairment in the global longitudinal systolic strain observed in our study may have resulted from the increased LV subendocardial wall stress, ischemia, and fibrosis in severe AS patients.

Mean GLS, as well as mean GCS was significantly lower in symptomatic patients as compared to that of asymptomatic patients, in our study. Among 6 asymptomatic patients at baseline, 3 became symptomatic during 6-month follow-up. Baseline GLS of patients who became symptomatic was-10.33 ± 4.50 as compared to −28.66 ± 5.13 of patients who remained asymptomatic (P = 0.990). Similar trend was also noted in baseline GCS, which was −22.00 ± 3.46 in patients who became symptomatic as compared to −29.33 ± 4.16 of patients who remained asymptomatic (P = 0.293). Difference, though numerically higher, was not statistically significant due to small number of asymptomatic patients in our study. However, mean percentage reduction of GLS in patients who remained asymptomatic throughout follow-up was −2.60 ± 2.33, as compared to reduction of −23.30 ± 17.23 in patients who became symptomatic, which was statistically significant (P = 0.042).

In the study done by Vollema et al., patients with impaired LV GLS at baseline (<−18.2%) showed a higher risk for developing symptoms (P = 0.02) and requiring aortic valve intervention (P = 0.03) at follow-up compared with patients with more preserved LV GLS (>−18.2%).[15]

During study period, there was no significant reduction in LV ejection fraction (63.86 ± 7.55% at baseline and 63.5 ± 7.9% at 6 months, P = 0.53), while there was significant reduction in all STE parameters, once again signifying role of STE in detecting subclinical LV systolic dysfunction before decrease in LV ejection fraction. This finding is similar to that in study by Vollema et al., where there was a significant reduction in GLS during follow-up of 12 months despite preserved ejection fraction.[15]

The results of our study are comparable to previous studies in terms of various STE parameters in patients with severe AS. Our results also support the role of STE in detecting subclinical LV dysfunction in patients of severe AS, both symptomatic as well as asymptomatic. This advantage of STE parameters over LVEF may be helpful in deciding for early operative intervention for asymptomatic severe AS patients.

Previous studies largely concentrated on GLS and its relation with AS, however in our study we found similar relation with GCS and segmental strain rates also. Our study can form a base for future studies involving a larger number of patients and a longer follow-up.

There are some limitations of the present study. Main limitation is small sample size, which is mainly due to problems regarding adequate follow-up of patients in a limited study period. The sample size calculation and study participant enrolment were mainly based on convenient sampling and the feasibility of the setup.

Another limitation is that we have used 2-dimensional STE in the present study which may be a little less informative than the 3-D STE that has become available recently.

Furthermore, it is not clear whether early identification of subclinical LV systolic dysfunction using 2D-STE will translate into long-term cardiovascular and survival benefits and it warrants further investigation.


  Conclusions Top


This observational, longitudinal study, in patients with severe AS, showed that these patients have abnormal global longitudinal and CS to begin with, which was not picked by the simple parameters like LVEF. There was a progressive worsening in these strain parameters within a short follow-up of 6 months which was again not picked up by LVEF measurement. Moreover, it was observed that those patients who were initially asymptomatic but developed symptoms on follow-up had a numerically higher decline in GLS than those who remained asymptomatic at follow-up.

The use of STE may be helpful in severe AS to identify patients with reduced contractility despite normal EF. Early identification of this subset of severe AS patients is important, as it may help in timely surgical management of them.



Authors' contributions

All the authors have contributed significantly in preparation of the manuscript.

Ethical approval

Ethical clearance was obtained from the Institutional Ethics Committee.



Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Mihaljevic T, Nowicki ER, Rajeswaran J, Blackstone EH, Lagazzi L, Thomas J, et al. Survival after valve replacement for aortic stenosis: Implications for decision making. J Thorac Cardiovasc Surg 2008;135:1270-8.  Back to cited text no. 4
    
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Bhattacharyya S, Hayward C, Pepper J, Senior R. Risk stratification in asymptomatic severe aortic stenosis: A critical appraisal. Eur Heart J 2012;33:2377-87.  Back to cited text no. 5
    
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Cengiz B, Şahin ŞT, Yurdakul S, Kahraman S, Bozkurt A, Aytekin S. Subclinical left ventricular systolic dysfunction in patients with severe aortic stenosis: A speckle-tracking echocardiography study. Turk Kardiyol Dern Ars 2018;46:18-24.  Back to cited text no. 13
    
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    Tables

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



 

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