Clinical applications and prognostic implications of strain and strain rate imaging

Abstract

Strain and strain rate imaging (also known as deformation imaging) are techniques used to measure myocardial deformation. These newer echocardiographic modalities overcome the limitations of conventional echocardiography and provide a sensitive means of objectively quantifying regional and global myocardial function. It has enabled us to better understand regional myocardial function and risk stratify patients with coronary artery disease, cardiomyopathies and valvular heart disease. Also, they have been used to assess left ventricular dyssynchrony, predict responders and optimize cardiac resynchronization therapy. However, the lack of standardization and inter-vendor variability in measurements are major roadblocks to using deformation imaging in routine clinical practice. This article discusses the fundamental concept of deformation, in particular relating to strain and strain rate imaging using speckle tracking imaging and tissue Doppler imaging, the clinical applications and its prognostic implications.

Keywords:

• amyloidosis
• cardiac strain
• cardiac strain rate
• cardiomyopathy
• deformation imaging
• hypertrophic cardiomyopathy
• ischemia
• onco-cardiotoxicity
• valvular heart disease

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Key issues

• Myocardial deformation imaging, strain (S) and strain rate (SR), provides sensitive objective measure of myocardial function and is independent of translational and tethering motion from surrounding myocardium.

• Semiautomated offline speckle tracking imaging (STI) software allows for faster quantification of myocardial deformation as compared to time-consuming and technically demanding tissue Doppler imaging (TDI) making STI a preferable option for SR and S imaging. Yet, proprietary nature of the software and resulting intervendor variability and lack of reproducibility is a major roadblock for routine clinical use of STI.

• Global longitudinal strain (GLS) is impaired in coronary artery disease (CAD). It identifies ischemic myocardium with similar accuracy as wall motion score index (WMSI). Lower GLS and SR have been associated with worse mortality in patients with CAD.

• GLS, pre-systolic myocardial lengthening, peak radial strain rate and improvement in SR with low-dose dobutamine have been reported to predict myocardial viability and hence improvement in myocardial function after revascularization.

• Myocardial deformation imaging detects the subclinical myocardial dysfunction and predicts the development of cardiotoxicity amongst the patients receiving chemotherapy.

• Impaired GLS in hypertrophic cardiomyopathy (HCM) has been reported to be a surrogate marker of myocardial fibrosis and predict non-sustained ventricular tachycardia (NSVT) and mortality.

• SR and S are altered earlier than traditional echocardiographic parameters in CA. A typical apical sparing pattern has been noted in CA patients.

• GLS is a much robust predictor of mortality than left ventricular ejection fraction (LVEF). In patients with HFrEF, each standard deviation change in GLS predicts major adverse cardiovascular events (MACE) more strongly than change in LVEF.

• Numerous dyssynchrony parameters have been proposed that utilizes deformation imaging to predict and assess the response to cardiac resynchronization therapy (CRT).

• GLS worsens with increasing severity of aortic stenosis (AS) and strongly predicts morality in this population.

• GLS and peak longitudinal stain and strain rate with dobutamine stress predicts mortality in LFLG AS.

• GLS and GLS normalized to end-diastolic volume are impaired in patients with AI, and these parameters return to normal after aortic valve replacement.

• Lower S and SR in mitral regurgitation (MR) is associated with lower decrease in LVEF in the post operative period after mitral valve replacement.

Notes