The relationship between the elastic properties of the aorta and resistant hypertension in hypertensive patients

Introduction and Objective: Resistant hypertension is a situation that its frequency increases with age and it is being tought that, many factors including arterial stiffness take part in its etiology. All factors that may cause resistant hypertension should be defined in order to take effective precautions and prevent possible cardiovascular events that may occur in the future. Arterial stiffness might be a strong and independent predictor of resistant hypertension and it might take a central role in the resistant hypertension pathogenesis. In this trial, our objective is to evaluate the relationship between augmentation index and arterial stiffness parameters which are aortic strain, distancibility, pulse wave velocity.Methodology: Participants of this trial have been selected among patients who applied to Dokuz Eylül University Faculty of Medicine Cardiology Department between May 2010-August 2010. Patients whose blood pressure is above targetted values despite 3 different antihypertensives (ideally one of those antihypertensives should be diuretic and all drugs should be used in optimal dosages) have been assigned to the resistant hypertension group, patients who have regulated hypertension have been assigned to the hypertension group and patients with no hypertension have been assigned to the control group. Demographic and clinical information of all patients were obtained and their BP values were measured. Aortic strain and distensibility from arterial stiffness parameters were calculated by measuring systolic and diastolic diameters of aorta echocardiographically. At the same time, mitral inflow currents in terms of diastolic disfunction were evaluated with doppler, left atrium volume index and left ventricule mass index were calculated. Pulse wave velocity and augmentation index were calculated via Complior device (Createch Industrie, France). Arteria carotis communis and radial arteria pressure wave forms were measured as non-invasively by using SphygmoCor tonometer device (AtCor Medical Instruments)Findings: In the resistant hypertensive patient group, pulse wave velocity (PWV) and augmentation index were determined significantly higher than regulated hypertensives (sequentially p:0.000 and p: 0.05) and the control group (sequentially p:0.000 and p: 0.001). No difference was determined for both parameters between regulated hypertensive group and control group. In the resistant hypertensive group, aortic strain and distensibility were determined significantly low according to the regulated hypertensives (sequentially p:0.001 and p: 0.001) and control group (sequentially p:0.00 and p: 0.021). Similarly, no difference was determined in terms of aortic strain and distensibility, between two groups. Left atrial volume index was determined significantly higher than the control group (p:0.01) in the resistant hypertensive group. Again, in the resistant hypertensive group, left ventricule mass index was determined as higher than the control group (p: 0.023). Significant revers correlation was fixed between body mass index and aortic distensibility ( r:-0.377 p:0.040) and between body mass index and aortic strain (r:-0.499 p:0.01). Congruently, there was significant revers correlation between left ventricule mass index and aortic strain (r:-0.489 ve p:0.007) and between left ventricule mass index and aortic distensibility ( r:- 0.371 ve p:0.04). When parameters used in aortic stiffness measurement were evaluated between themselves, a significant reverse correlation was recorded between pulse wave velocity and aortic strain-distensibility (sequentially r-0.399,p: 0.029 ve r:-0.459 ve p:0.014), similarly, revers correlation was determined between augmentation index and aortic strain-distensibility (sequentially r -0.545, p:0.002 ve r:-0.620, p:0.00).Results: In this research, arterial stiffness which is evaluated with aortic strain, aortic distensibility, pulse wave velocity and augmentation index parameters, was determined significantly high in resistant hypertensive patients according to regulated hypertensives and non-hypertensives. To determine the increase of arterial stiffness in resistant hypertensive patients according to other groups, is an important data in order to indicate that, arterial stiffnes acts an active role in the etiology of resistant hypertension rather than its outcome. In light of consideration of this information, new therapeutic procedures can be developed or, it can be possible to block the resistant hypertension occurence by preventing the elastin fiber degeneration which is formed by hypertension in years, and which cause aortic stiffness in mild hypertensive patients with aortic stiffness at early ages, by initiating the hypertensive treatment earlier.Key words: Resistant hypertension, arterial stiffness, pulse wave velocity, diastolic disfunction.