1,720,997 research outputs found
Sensibilità cardiopolmonare e chemosensibilità
No full textThe autonomic control of the cardiovascular system plays an important role in maintaining the arterial pressure at the levels necessary for adequate tissue perfusion. In cardiovascular diseases, the impairment of the basic reflex mechanisms that are responsible for the moment-to-moment regulation could increase sympathetic activity and is correlated with an adverse outcome. The objective of the present review was to provide information about the methodological aspects exploring cardiopulmonary and chemoreceptor reflexes. Different techniques are available and all of them include assessment of reflexes through the activation or deactivation of either the cardiopulmonary baroreceptors or chemoreceptors. Intravenous saline load, head-down tilt, passive legs raising, head-out water immersion and the application of a lower body positive pressure are the principal methods utilized for activating cardiopulmonary baroreceptors; on the contrary deactivation could be achieved by acutely induced hypovolemia by furosemide or blood donation, inflation of a congestion cuff on the thighs or application of a negative pressure on the lower body. The transient exposure to a hypoxic or a hypercapnic gas mixture is frequently used to determine the peripheral and central chemoreflexes, respectively. The reflexes are quantified by the gain between output (i.e. heart rate, sympathetic activity, vascular resistance, ventilation) and input (oxygen saturation, end-tidal CO2 or changes in central venous pressure). One important limitation in assessing the cardiopulmonary baroreflex by using currently available techniques is that the involvement of the arterial baroreflex cannot be avoided. In addition, chemoreflexes cannot be interpreted unless the breathing rate is controlled. To date, several techniques are available for the quantification of cardiopulmonary baroreceptor and chemoreceptor reflexes and could provide new information on the abnormal autonomic mechanisms contributing to the pathophysiology of several cardiovascular diseases
Alpha- and beta-adrenergic receptor polymorphisms in hypertensive and normotensive offspring
No full textBACKGROUND: The offspring of hypertensive families are characterized by higher arterial blood pressure values and a depressed autonomic control of heart rate. The present study aimed to verify whether these differences are associated with a different genotype distribution of functionally relevant polymorphisms of the alpha- and beta-adrenergic receptor (AR) genes. METHODS: We selected 109 age- and sex-matched young normotensive subjects with (FH+, n = 56) and without (FH-, n = 53) a family history of hypertension who underwent evaluation of arterial pressure; 24-h electrocardiogram monitoring to assess time-domain parameters of autonomic heart rate control [i.e. mean RR interval (NN), SD of RR intervals (SDNN) and mean square root of the differences of consecutive RR intervals (rMSSD)]; spectral baroreflex sensitivity measurement; and echo-Doppler to assess diastolic function and left ventricular mass. They were also characterized for the following polymorphisms by means of polymerase chain reaction-restriction fragment polymorphism analysis: Arg492Cys in the α1a-AR; Del301-303 in the α2b-AR; Ser49Gly and Arg389Gly in the β1-AR; and the 5′ leader cistron Arg19Cys, Arg16Gly and Gln27Glu in the β2-AR. RESULTS: FH+ individuals showed a higher systolic pressure, a lower SDNN and a greater isovolumic relaxation time compared to normotensive offspring. No differences were found between the two groups when genotype distribution of the studied polymorphisms was considered. Subjects carrying α1a-AR Cys492 allelic variant showed lower values of NN, SDNN and rMSSD, independent of age, gender and body mass index. CONCLUSIONS: The functionally relevant polymorphisms of α2b-, β1- and β2-AR genes are not associated with a family history of essential hypertension. The Arg492Cys polymorphism of the α1a-AR gene, although not associated with a family history of hypertension, was strongly related to autonomic control of heart rat
Electrocardiographic patterns during Holter monitoring in patients with first and second degree A-V block due to 'dual A-V nodal pathways'.
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Successful ablation of atrioventricular nodal reentry tachycardia in a patient with persistent left superior vena cava.
No full textInfluence of gender and family history of hypertension on autonomic control of heart rate, diastolic function and brain natriuretic peptide
No full textOBJECTIVE: To verify in a unitary view whether autonomic control of heart rate and cardiac structure and function are modified early in offspring of hypertensive families.
METHODS AND RESULTS: We selected 87 age- and sex-matched young normotensive subjects with (n = 45) and without (n = 42) a family history of hypertension who underwent evaluations of arterial pressure, time-domain parameters of autonomic heart rate control (24-h ECG monitoring), spectral baroreflex sensitivity, left ventricular geometry and function (echo-Doppler) and plasma brain natriuretic peptide levels (BNP). The group with a family history of hypertension significantly differed from their counterparts for systolic pressure (119 +/- 11 versus 114 +/- 9 mmHg, P< 0.05), heart rate (RR interval, 766 +/- 64 versus 810 +/- 93 ms, P< 0.05), heart rate variability [the standard deviation of normal RR intervals (SDNN), 147 +/- 29 versus 171 +/- 33 ms, P < 0.051, diastolic function (isovolumetric relaxation time, 65 +/- 9 versus 60 +/- 8 ms, P< 0.05) and BNP (23 +/- 13 versus 37 +/- 10 pg/ml, P< 0.05). Baroreflex sensitivity values did not differ between the two groups. When gender was considered, all the above-mentioned measures, as well as baroreflex sensitivity, were significantly different between males with and without a family history of hypertension but not between females, except for BNP, which was lower in males and females with a history of hypertension (males, 24 +/- 11 versus 38 +/- 8 pg/ml, P< 0.01; females 21 +/- 14 versus 36 +/- 13 pg/ml, P < 0.05).
CONCLUSIONS: Male, but not female, hypertensive offspring have modified diastolic function and autonomic control of heart rate; BNP is the only parameter able to characterize hypertensive offspring independently from the influence of gender. This provides the hypothesis that the impaired production of this hormone could play a primary role in the pre-hypertensive state
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