Comportamento das propriedades elásticas arteriais e do fluxo sanguíneo regional em pacientes cardiopatas frente à variação da frequência cardíaca / Response of arterial elastic properties and regional blood flow of patients with cardiopathy induced by changes in heart rate

Variações da freqüência cardíaca (FC) podem modificar a complacência arterial (C), e assim o equilíbrio entre a interação coração-sistema arterial. Os objetivos deste trabalho foram: analisar os efeitos das alterações agudas da FC sobre as propriedades elásticas arteriais; a influência sobre o desempenho cardíaco; a importância da fração de ejeção (FE) ventricular esquerda e o comportamento do sistema neurohumoral. Portadores de marcapasso cardíaco (MP) foram submetidos a estudo ecocardiográfico e duplex-scan das artérias carótida e braquial. Foram coletadas amostras para a determinação da concentração plasmática de renina e catecolaminas. A variação da FC por meio da reprogramação do MP determinou uma queda significativa do volume sistólico acompanhado de um aumento do débito cardíaco e da C. Não foi demonstrada influência direta da FE. Houve redução significativa da concentração plasmática de renina e de norepinefrina / Changes in heart rate (HR) can result in modification in the arterial compliance (AC), interfering with adequate balance between the heart and the arterial system. The study objectives were: analyze the effects of the changes of HR on arterial elastic properties; its influence on cardiac function; determine the importance of the ejection fraction and the response of the neurohumoral system. Patients with permanent cardiac pacing were evaluated through echocardiographic study and duplex scan of carotid and brachial arteries. Blood samples were drawn to determine the serum concentrations of rennin and catecholamines. Sequential increase on HR through the pacemaker reprogramming was negatively correlated with systolic volume and a positive relationship with cardiac output and AC. There was not associated interference by ejection fraction of left ventricule. There was significant reduction in the serum concentration of rennin and norepinephrine...

Non-invasive assessment of systemic elastic behaviour in hypertensive patients: analysis of possible determinants.

Knowledge about the viscoelastic behaviour of the arterial wall has been proved to have physiological importance and clinical usage. Our purpose was to study the changes of the systemic arterial wall's elastic properties non-invasively, in patients with established essential and with borderline hypertension, and to evaluate its possible determinants. Three groups of normotensive, borderline and established essential hypertensive patients were evaluated. Arterial pulse wave velocity (PWV) was measured and arterial compliance (Cm) was derived in all patients. Pulse wave velocity was obtained from the pressure values of digitized carotid and radial arteries. Arterial compliance (Cm = dD/dP with P pressure and D diameter) was calculated using a formula derived from the Bramwell and Hill equation: Cm = (1,334 x D)/(2 rho x PWV2), where for D humeral diameter was used as measured by high resolution echograph, and rho is the blood density (rho = 1.06). Pulse wave velocity was significantly higher in established essential hypertensive patients with respect to normotensive patients (p < 0.05). Arterial compliance was significantly diminished in established and in borderline hypertensive patients with respect to normotensive patients (p < 0.05), which implies early alterations in hypertensive cardiovascular disease. Multiple regression analysis of the cofactors showed that age and diastolic pressure are independent determinants of Cm. Impairment of the arterial wall's intrinsic elastic properties was demonstrated in established essential hypertension, independent of age and diastolic pressure.