Early myocardial abnormalities in asymptomatic patients with severe isolated congenital aortic regurgitation: An ultrasound tissue characterization and strain rate study

Aortic Regurgitation and Heart Failure: Advances in Diagnosis, Management, and Interventions

This review discusses the contemporary clinical evaluation and management of patients with comorbid aortic regurgitation (AR) and heart failure (HF) (AR-HF). Importantly, as clinical HF exists along the spectrum of AR severity, the present review also details novel strategies to detect early signs of HF before the clinical syndrome ensues. Indeed, there may be a vulnerable cohort of AR patients who benefit from early detection and management of HF. Additionally, while the mainstay of operative management for AR has historically been surgical aortic valve replacement, this review discusses alternate procedures that may be beneficial in high-risk cohorts.

Ventricular mechanics in patients with aortic valve disease: longitudinal, radial, and circumferential components

BACKGROUND

Reduced long-axis shortening despite enhanced global function has been reported in aortic stenosis. We sought to improve the understanding of this phenomenon using multi-dimensional strain analysis in conjunction with the evaluation of left ventricular rotation and twist - ventricular torsion - using tissue Doppler techniques.

METHODS

A total of 57 patients with variable severity of aortic stenosis, aortic regurgitation, or mixed aortic valve disease, subdivided into six groups, were studied. Ventricular morphology was assessed using long-axis/short-axis and mass/volume ratios, afterload using end-systolic meridional wall stress, and global performance using ejection fraction. The circumferential and longitudinal strain was measured from two-dimensional images, and left ventricular rotation and twist were estimated as the difference in rotation between the base and apex of the ventricle.

RESULTS

Aortic stenosis was associated with higher mass/volume, ejection fraction, circumferential strain and left ventricular rotation and twist, significantly lower end-systolic wall stress, and a trend towards lower longitudinal strain compared with normal. Myocardial mechanics in aortic regurgitation were normal despite ventricular dilation. Mixed aortic valve disease showed findings similar to aortic stenosis. Left ventricular rotation and twist correlated with midwall circumferential strain (r = 0.62 and p < 0.0001), endocardial circumferential strain (r = 0.61 and p < 0.0001), and end-systolic wall stress (r = 0.48 and p < 0.0001), but not with longitudinal strain (r = 0.18 and p > 0.05).

CONCLUSIONS

Myocardial mechanics are normal in patients with aortic regurgitation, independent of abnormalities in cardiac geometry. Conversely, in aortic stenosis and mixed aortic valve disease, significant alterations in the patterns of fibre shortening are found. The effects of stenosis on cardiac function seem to dominate the effect of ventricular remodelling.

Echocardiographic predictors of early postsurgical myocardial dysfunction in pediatric patients with aortic valve insufficiency

In chronic aortic insufficiency (AI), left-ventricular (LV) dysfunction must be detected early to allow timely surgery. Strain and strain rate have been used for this purpose in adults, but the value of this method in pediatric AI has not been established. Forty patients with moderate to severe AI were included in this retrospective study. LV function was assessed by strain analysis and conventional echocardiography both before and after surgery. Of the 32 patients with preserved preoperative ejection fraction (EF; >50 %), 8 had postoperative dysfunction (<50 %). Mean conventional indices of global LV systolic performance for the entire cohort of patients with AI were predominantly in the normal range before surgery. Preoperative values for LV global longitudinal strain (GLS) and strain rate (GLSr) were normal. After surgery, there was a significant decrease in shortening and EF. There was a significant decrease from preoperative to postoperative values for both GLS (-16.07 ± 3.82 vs. -11.06 ± 3.88; p < 0.0001) and GLSr (-0.89 ± 0.24 vs. -0.72 ± 0.27; p = 0.0021). A preoperative GLS of -15.3 (AUC = 0.83, CI = 0.69-0.98, p < 0.0001) and a GLSr of -0.79/s (AUC = 0.86, CI = 0.73-0.98, p < 0.0001) were determined to be predictors of early postoperative dysfunction after surgical repair of moderate to severe AI. A preoperative GLS value of ≤-15.3 and GLSr value of -0.79/s or less are predictors of postoperative ventricular dysfunction, which is defined by EF <50 %. GLS and GLSr value determination may be useful as part of the echocardiographic assessment AI and may help determine the optimal timing of surgery in pediatric patient with at least moderate AI.

Usefulness of bidimensional strain imaging for predicting outcome in asymptomatic patients aged ≤ 16 years with isolated moderate to severe aortic regurgitation

Aortic regurgitation (AR) has increased in the pediatric population because of the expanded use of new surgical and hemodynamic procedures. Unfortunately, the exact timing for operation in patients with AR is still debated. Conventional echocardiographic parameters, left ventricular (LV) dimensions and the LV ejection fraction, have limitations in predicting early LV dysfunction. Two-dimensional strain imaging, an emerging ultrasound technology, has the potential to better study those patients. The aim of this study was to assess the prognostic value of 2-dimensional longitudinal strain in young patients with congenital isolated moderate to severe AR. Twenty-six young patients with asymptomatic AR (aged 3 to 16 years) were studied. The mean follow-up duration was 2.9 ± 1.2 years (range 0.5 to 6). Baseline LV function by speckle-tracking and conventional echocardiography in patients with stable disease was compared with that in patients with progressive AR (defined as development of symptoms, increase in LV volume ≥15%, or decrease in the LV ejection fraction ≤10% during follow-up). LV ejection fractions were similar between groups. The jet area/LV outflow tract area ratio was significantly increased in patients with AR with progressive disease (31.2 ± 5.6% vs 39.2 ± 3.8%, p <0.001). The peak transmitral early velocity/early diastolic mitral annular velocity ratio was significantly increased in patients with progressive AR (p = 0.001). LV average longitudinal strain was significantly reduced in patients with progressive AR compared to those with stable AR (-17.8 ± 3.9% vs -22.7 ± 2.7%, p = 0.001). On multivariate analysis, the only significant risk factor for progressive AR was average LV longitudinal strain (p = 0.04, cut-off value >-19.5%, sensitivity 77.8%, specificity 94.1%, area under the curve 0.889). In conclusion, 2-dimensional strain imaging can discriminate young asymptomatic patients with progressive AR. This could allow young patients with AR to have a better definition of surgical timing before the occurrence of irreversible myocardial damage.

High-frequency high-resolution echocardiography: first evidence on non-invasive repeated measure of myocardial strain, contractility, and mitral regurgitation in the ischemia-reperfused murine heart

Ischemia-reperfusion (IR) was surgically performed in murine hearts which were then subjected to repeated imaging to monitor temporal changes in functional parameters of key clinical significance. Two-dimensional movies were acquired at high frame rate (8 kHz) and were utilized to estimate high-quality myocardial strain. Two-dimensional elastograms (strain images), as well as strain profiles, were visualized. Results were powerful in quantitatively assessing IR-induced changes in cardiac events including left-ventricular (LV) contraction, LV relaxation and isovolumetric phases of both pre-IR and post-IR beating hearts in intact mice. In addition, compromised sector-wise wall motion and anatomical deformation in the infarcted myocardium were visualized. The elastograms were uniquely able to provide information on the following parameters in addition to standard physiological indices that are known to be affected by myocardial infarction in the mouse: internal diameters of mitral valve orifice and aorta, effective regurgitant orifice, myocardial strain (circumferential as well as radial), turbulence in blood flow pattern as revealed by the color Doppler movies and velocity profiles, asynchrony in LV sector, and changes in the length and direction of vectors demonstrating slower and asymmetrical wall movement. This work emphasizes on the visual demonstration of how such analyses are performed.

Preoperative systolic strain rate predicts postoperative left ventricular dysfunction in patients with chronic aortic regurgitation

BACKGROUND

The best predictor for postoperative left ventricular (LV) systolic dysfunction in patients with chronic aortic regurgitation is still a matter of debate. The aim of this study was to assess the clinical significance of preoperative systolic radial strain rate (Ssr) derived from tissue Doppler echocardiography as a predictor of postoperative LV systolic dysfunction in patients with chronic aortic regurgitation.

METHODS AND RESULTS

In 52 patients (mean age, 58 years; 13 women) with isolated chronic aortic regurgitation, we performed standard and tissue Doppler echocardiography before and after operation, obtained echocardiographic parameters such as LV dimensions and LV ejection fraction, and measured Ssr in 4 walls of the LV. Linear regression analysis determined correlations between preoperative parameters and postoperative LV ejection fraction. Receiver-operating characteristic curve analysis assessed the optimal cutoff values of parameters that predicted postoperative LV systolic dysfunction (ejection fraction <50%). The operation caused significant decreases in LV dimensions and volumes and significant increases in Ssr (1.94+/-0.64 to 2.39+/-0.83 per second; P<0.001) and ejection fraction (53.0+/-8.7 to 59.0+/-8.8%; P<0.001). Multiple regression analysis demonstrated that averaged Ssr was the only independent predictor of postoperative LV systolic dysfunction among the covariates examined (P<0.001). Using receiver-operating characteristic curve analysis, averaged Ssr yielded the greatest area under the curve among preoperative parameters (0.80) and was indicated to be a good predictor of postoperative LV dysfunction, with 90.9% sensitivity and 73.2% specificity (cutoff value, 1.82 per second).

CONCLUSIONS

Measurement of preoperative averaged Ssr is useful in predicting postoperative LV systolic dysfunction and optimizing surgical timing in patients with isolated chronic aortic regurgitation.

Two-dimensional strain imaging: a new echocardiographic advance with research and clinical applications

Over the past two decades the quest for quantitative evaluation of left ventricular function and regional wall motion has escalated, allowing several aspects of myocardial contractile patterns to be quantified, both during stress echocardiography and in the assessment of dyssynchrony. Most of the literature to date has used Tissue Doppler Imaging (TDI) techniques to assess essentially long-axis function due to the angle dependency of Doppler based techniques. This brief review introduces the early development, validation and potential clinical applications of a new technique of quantifying two-dimensional (radial and circumferential) strains and strain rates through tracking myocardial "speckles". In-vivo and in-vitro validation of this 2D-strain imaging technique has been undertaken and reached a point where it is considered ready for more widespread investigations into clinical utility. One important advantage over TDI techniques is that it is not limited by dependency on the angle of insonation. Several recent studies looking at ventricular function in specific groups of patients have reported practical ability to distinguish the abnormally from the normally contracting regions of ventricular walls. It provides new and complementary quantitative information about ventricular dyssynchrony and regional wall motion abnormalities. More research studies are needed to determine the sensitivity and specificity of the measurements obtained using this technique and define its strengths and limitations. In particular, whether the measured values correlate well with clinical outcomes will need to be established in longitudinal interventional studies. The clinical utilities of this technique over the coming years are likely to expand rapidly.

Actualización en técnicas de imagen cardiaca. Ecocardiografía, resonancia magnética en cardiología y tomografía computarizada con multidetectores

This article contains a review of the most significant publications on non-invasive recent cardiac imaging techniques in 2005. The increasing importance of technological innovation in echocardiography is reflected in the sections on three dimensional echocardiography, contrast echocardiography, and myocardial deformation measurement techniques (i.e., strain echocardiography). The most important developments affecting cardiology in the techniques of magnetic resonance imaging and multidetector computed tomography are also summarized. This review ends with a detailed description of the contributions made by imaging techniques to the diagnosis of aortic disease.

Echocardiography in congenital heart disease: usefulness, limits and new techniques

Echocardiography represents the non-invasive tool most commonly used in pediatric cardiology. Indeed, it enables the definition of both the morphological and functional findings in congenital heart disease (CHD), as completely as possible in almost all the cases. In comparison with adult subjects, the echocardiographic evaluation in pediatric patients requires a different approach, providing information on the heart position in the thorax, the atrial situs viscerum, the vein-atrial and the atrio-ventricular connections, the relationship between the ventricles, the ventriculo-arterial connection and the relationship of the great arteries (segmental analysis). In addition, the echocardiographic study should include a non-invasive study of ventricular function, as mandatory to warrant an optimal pre- and postoperative management in patients with CHD. The indices most commonly utilized to assess ventricular mechanics are the 'pump indices' (i.e. ejection fraction or fractional shortening). Unfortunately, they may lead to invalid data, because of their dependence on loading conditions and heart rate. As a consequence, echocardiographic indices should be used (i.e. fiber shortening or rate-corrected velocity of circumferential fiber shortening-end systolic stress relationship), which better reflect the intrinsic myocardial contractility. More recently, evidence is mounting that new echocardiographic techniques (i.e. Doppler myocardial imaging, strain/strain rate and backscatter) may offer new insights in terms of regional functional and textural findings of the myocardium. However, long-term follow-up studies will be necessary to better define their real impact in the clinical setting.