Correlation between Aortic Stiffness and Left Ventricular Diastolic Dysfunction

Abstract

SUMMARY T he normal human aorta is not a stiff tube, but is characterized by elastic properties. During systole, the left ventricle ejects a stroke volume into the arterial system. A half of this stroke volume is directly forwarded to the peripheral circulation, but because of peripheral resistance and elastic extension of the aortic wall, the other half of the stroke volume is stored in the aorta (Bader, 1983). Normally, LV ejection causes a pressure pulse with a relatively slow pulse wave velocity (PWV). When this wave is reflected by the peripheral circulation, it returns to the ascending aorta during early diastole inducing the dicrotic wave. This second increase in pressure is normally dampened by the Windkessel function (O’Rourke et al., 1990). Many studies have examined the effect of cardiovascular risk factors on the vessels. It is also recognised that these factors cause structural alteration, which leads to stiffness in large arteries (Arnett et al., ). The aim of this study is to assess the relation between Aortic stiffness and left ventricular Diastolic dysfunction as compared to traditional Doppler and tissue Doppler measurements of diastolic function. Furthermore, the relationship between aortic stiffness and LV end diastolic pressure were studied. This study included 300 patients presented to Ain Shams university echocardiography unit and Specialized Ain Shams hospital and all have LV diastolic dysfunction with normal systolic function. The patients were all above 40 years old with range (40-85) years old, they were divided into 4 groups according to grade of diastolic dysfunction. Patients with Atrial fibrillation, prothetic valves, Rheumatic valvular affection, LVEF<50% and coronary artery disease were excluded. Transthoracic Echocardiography was performed to every patient and the following echocardiographic variables were measured or derived: 1. Left ventricular ejection fraction, dimensions and wall thickness 2. LA diameter, Aortic root diameter ,Aortic systolic and diastolic diameters 3. Mitral inflow velocities (A and E waves) 4. Deceleration time and IVRT 5. Septal mitral E’ velocity by tissue Doppler imaging 6. E/E’ and estimated LVEDP.

AS, AD and ASI were calculated from above measured data and correlated to grade of Diastolic dysdfunction. Most importantly it was found that Aortic Strain (AS) was significantly decresed by increasing of grades being (17.8±3.1%) in grade I and falls to reach (5.81±0.34%) in grade III with a p value 0.000.Similarly, Aortic distensibility (AD) was highest in grade I (0.84±0.18 cm2/dyn/103) and then significantly falls by increasing grades to reach (0.17±0.01 cm2/dyn/103) in grade III with (p=0.000).On the other hand Aortic stiffness index (ASI) was significantly increased by increasing grades as it was (2.99± 1.81) and rises to reach (9.15± 0.49) in grade III with a p value=0.000. Regarding demographic data affecting Aortic stiffness parameters it was found that Age, BMI both significantly affected Aortic stiffness parameters as they increased with increasing ASI and the reverse was with AS. (p>0.05). Regarding Echocardiographic data affecting Aortic Stiffness it was fond that LVEDD, LVESD, EF, FS and PWT found not to be affected by Aortic stiffness parameters(AS and ASI). LA and SWT affect AS and ASI as both increased with decreasing of AS with the opposite affection by ASI (p=0.000). E and A waves also was affected as E wave was found to be increasing with the increasing of ASI and the opposite was with AS, but A wave decreased with increasing ASI and increased with increasing AS (p=0.000).E/A ratio also was the similar to E wave as increasing with increased ASI and decreased with increased AS. (p=0.000). DT and IVRT increased with decreasing ASI and the reverse was with AS. (p=0.000). When we reclassified study population according to presence of hypertension and diabetes into 4 groups as: group 1 (not HTN not DM), group 2 (HTN patients), group 3 (DM patients) and group 4 (both HTN and DM patients). We found that there was significance in AS between groups that decreased from group I (17.47±3.69%) to reach (6.30±1.25%) in group IV with (p=0.000). On the other hand ASI increased significantly from group I (2.99± 1.81) to reach (9.15± 0.49) in group IV with (p=0.000). We recommended that AS, AD and ASI should be calculated in routine echocardiography and considered in the grading of LV Diastolic dysfunction. Grades I and Ia of Diastolic dysfunction should be clearly discriminated and described as two separate groups owing to the major differences in E/E’ ratio, and LVEDP between th