Usefulness of Parameters of Left Ventricular Wall Stress and Systolic Function in the Evaluation of Patients with Aortic Stenosis

A new non-invasive index for prognosis evaluation in patients with aortic stenosis

The global left ventricular (LV) contractility index, dσ*/dt_max measures the maximal rate of change in pressure-normalized LV wall stress. We aim to describe the trend of dσ*/dt_max in differing severity of aortic stenosis (AS) with preserved left ventricular ejection fraction (LVEF) and the association of dσ*/dt_max with clinical outcomes in moderate AS and severe AS. We retrospectively studied a total of 1738 patients with AS (550 mild AS, 738 moderate AS, 450 severe AS) and preserved LVEF ≥ 50% diagnosed from 1^st January 2001 to 31^st December 2015. dσ*/dt_max worsened with increasing severity of AS despite preserved LVEF (mild AS: 3.69 ± 1.28 s^-1, moderate AS: 3.17 ± 1.09 s^-1, severe AS: 2.58 ± 0.83 s^-1, p < 0.001). Low dσ*/dt_max < 2.8 s^-1 was independently associated with a higher composite outcome of aortic valve replacement, congestive cardiac failure admissions and all-cause mortality (adjusted hazard ratio 1.48, 95% CI: 1.25-1.77, p < 0.001). In conclusion, dσ*/dt_max declined with worsening AS despite preserved LVEF. Low dσ*/dt_max < 2.8 s^-1 was independently associated with adverse clinical outcomes in moderate AS and severe AS with preserved LVEF.

Evaluation of left anterior descending coronary artery stenosis severity from myocardial end-diastolic wall stress estimated by tissue-Doppler imaging

PURPOSE

To identify patients with significant coronary artery disease by the noninvasive quantification of myocardial wall stress in diastole.

METHODS

We studied 60 male subjects in sinus rhythm with significant (n = 30) or moderate (n = 30) proximal left anterior descending coronary artery stenosis, and 30 healthy subjects (control group). The average end-diastolic wall stress was estimated at left ventricle anterior and interventricular septum wall segments from regional wall thickness, meridional and circumferential regional radii of curvature, and noninvasively estimated left ventricular end-diastolic pressure.

RESULTS

There were significant differences in left ventricular end-diastolic pressure between patients and controls (p < 0.05). End-diastolic myocardial wall stress was significantly different between patients with significant and moderate coronary stenosis and healthy subjects in all anterior and septal wall segments (p < 0.05) except for the anterior wall at mid level. The receiver-operating characteristic curves showed that septum apex wall stress has the highest discriminatory power for predicting significant stenosis versus healthy coronary artery with 83% area under the curve.

CONCLUSIONS

Estimated end-diastolic myocardial wall stress may help in evaluating regional myocardial dysfunction due to coronary artery disease.

Valvular Aortic Stenosis

Standard echocardiographic evaluation of aortic stenosis (AS) severity includes measurement of aortic velocity, mean transaortic pressure gradient, and continuity equation valve area. Although these measures are adequate for decision making in most patients, there is no single value that defines severe stenosis. Aortic stenosis affects not just the valve, but the entire vascular system, including the left ventricle (LV) and systemic vasculature. More sophisticated measures of disease severity might explain the apparent overlap in hemodynamic severity between symptomatic and asymptomatic patients and might better predict the optimal timing of valve replacement. There have been several approaches to evaluation of stenosis severity based on valve hemodynamics, the ventricular response to increased afterload, ventricular-vascular coupling, or the systemic functional consequences of valve obstruction, such as exercise testing and serum brain natriuretic peptide levels. Aortic valve replacement is indicated when symptoms due to severe AS are present. In most asymptomatic patients, the risk of surgery is greater than the risk of watchful waiting so that management includes patient education, periodic echocardiography, and cardiac risk factor modification. Many adults with AS have comorbid conditions that affect both the diagnosis and management of the valve disease, including aortic regurgitation, aortic root dilation, hypertension, coronary artery disease, LV dysfunction, and atrial fibrillation. Comorbid conditions should be evaluated and treated based on established guidelines, although awareness of the potential effects of therapy in the presence of valve obstruction is needed.

Evolution of regional performance after an acute anterior myocardial infarction in humans using magnetic resonance tagging

Regional remodelling after a left ventricular myocardial infarction is the first step in a cascade that may lead to heart failure and death. To understand better the mechanisms underlying this process, it is important to study not only the evolution in local deformation parameters but also the corresponding loading conditions. Using magnetic resonance (MR) myocardial tagging, we measured the regional contribution to ejection (regional ejection fraction) and loading (systolic blood pressure x radius of curvature (mean of short and long axes)/wall thickness) in 32 regions throughout the left ventricle (LV) in patients 1 week (1W) and 3 months (3M) after a first anterior infarction. Using positron emission tomography (PET), the LV was divided into infarct, adjacent and remote regions. In the remote regions the average deformation decreased between 1W and 3M (from 59.3 +/- 5.6 to 57.9 +/- 6.7 %, P < 0.05) due to an increase in loading conditions only (from 730 +/- 290 to 837 +/- 299 mmHg, P < 0.05). In the adjacent myocardium, no change in function was observed (49.0 +/- 10.8 to 49.0 +/- 6.5 %, P = n.s.), although loading increased (806 +/- 297 to 978 +/- 287 mmHg, P < 0.05). In the infarct region only, an increase in deformation was seen (30.7 +/- 14.2 to 37 +/- 6.9 %, P < 0.05), together with a higher loading level (1229 +/- 422 to 1466 +/- 284 mmHg, P < 0.05), which indicates a true improvement in function. The fact that MR tagging can identify both regional deformation and loading permits us to differentiate between changes due to alterations in regional loading conditions and true changes in function. After an acute myocardial infarction (MI), an improvement can be observed in the deformation-loading relation in the adjacent and infarct regions, but the improvement is mainly in the infarct region. Using this technique, types of intervention leading to even more functional gain could be evaluated.