Acute AT1 receptor blockade does not improve the depressed baroreflex in rats with chronic renal hypertension

To assess the role of angiotensin II in the sensitivity of the baroreflex control of heart rate (HR) in normotensive rats (N = 6) and chronically hypertensive rats (1K1C, 2 months, N = 7), reflex changes of HR were evaluated before and after (15 min) the administration of a selective angiotensin II receptor antagonist (losartan, 10 mg/kg, iv). Baseline values of mean arterial pressure (MAP) were higher in hypertensive rats (195 ± 6 mmHg) than in normotensive rats (110 ± 2 mmHg). Losartan administration promoted a decrease in MAP only in hypertensive rats (16 percent), with no changes in HR. During the control period, the sensitivity of the bradycardic and tachycardic responses to acute MAP changes were depressed in hypertensive rats (~70 percent and ~65 percent, respectively) and remained unchanged after losartan administration. Plasma renin activity was similar in the two groups. The present study demonstrates that acute blockade of AT1 receptors with losartan lowers the MAP in chronic renal hypertensive rats without reversal of baroreflex hyposensitivity, suggesting that the impairment of baroreflex control of HR is not dependent on an increased angiotensin II level

Terapêutica empírica com amiodarona em portadores de miocardiopatia chagásica crônica e taquicardia ventricular sustentada / Long term results of empiric amiodarone therapy in patients with sustained ventricular tachycardia and chronic chagasic myocarditis

Objetivo: Avaliar eficácia e tolerância do uso empírico de amiodarona, a longo prazo, em portadores d e Miocardiopatia Chagásica Crônica (MCC) e Taquicardia Ventricular Sustentada (TVS). Casuística e Métodos: Trinta e cinco portadores de MCC e TVS, 18 (51% ) dos quais, refratários a outras drogas antiarritmicas. A dose de impregnação variou de 600 a 1200 (média de 883 ± 239) mg/dia, por período de uma a quatro semanas. A dose de manutenção foi reduzida progressivamente à média de 356 ± 125 mg/dia ao final de seis a 80 (média de 27 ± 20) meses. Foram construídas curvas de estimativa de recorrência clínica, morte súbida e morte cardíaca, segundo o método de Kaplan e Meier e comparadas variáveis clínicas na avaliação de risco de recorrências e morte súbita, através dos testes do Qui-quadrado de Pearson e t de Student.

Purpose: To evaluate the efficacy and safety of long-term empiric amiodarone therapy in patients with recurrent Sustained Ventricular Tachycardia (SVT) and Chronic Chagasic Myocarditis (CCM). Patiens and Methods: Thirty-five patients with CCM and SVT, eighteen (51%) of them were refratary to other antiarrhythmic drugs. The Amiodarone loading dose was between 600 and 1200 mg/day, mean of 883 ± 239 mg/day, from a period of one to four weeks. The maintenance dose was decreasing in the follow-up period, it fell down to 356 ± 125 mg/day at the end of six to 80 (mean = 27 ± 20) months. Cumulative, event-free interval curves were generated by the Kaplan-Meier method. Clinicals variables were compared with the use of the Student t-test or by means of chi-square tests.