[Preoperative digitalization].

OBJECTIVE: To investigate whether the impaired reflex response to cardiopulmonary baroreceptor unloading in hypertensive patients with left ventricular hypertrophy can be promptly improved by a pharmacological challenge. For this purpose we studied the effects of acute digitalis administration on cardiopulmonary baroreflex, evaluated by forearm noradrenaline spillover. METHODS: Eleven hypertensives with left ventricular hypertrophy and 10 age- and sex-matched normotensives underwent the application of -5 and -10 mmHg lower-body negative pressure (LBNP) before and after the administration of digitalis. Forearm noradrenaline spillover, measured using a tracer technique, was used to estimate the reflex sympathetic response. RESULTS: Under control conditions LBNP evoked a similar fall in right atrial pressure in the two study groups. In the normotensives there was a significant increase in forearm noradrenaline spillover. In the hypertensives no significant changes in forearm noradrenaline spillover were found. Intravenous administration of 0.02 mg/kg lanatoside C was associated with an increase in systolic blood pressure and a reduction in forearm noradrenaline spillover in both groups. In the normotensives the percentage change in forearm noradrenaline spillover induced by LBNP increased significantly in response to digitalis administration. However, digitalis restored the response of forearm noradrenaline spillover to LBNP in the hypertensives, so that no significant difference in this response was detected between the two study groups. Digitalis did not modify the effects of LBNP on cardiac pressures in either group. CONCLUSIONS: The present results demonstrate that administration of lanatoside C restores the response of forearm noradrenaline spillover to cardiopulmonary baroreceptor unloading in hypertensive patients with left ventricular hypertrophy. This indicates that the impairment of cardiopulmonary baroreflexes in these patients can be reversed by acute pharmacological treatment. Therefore, impairment of this reflex response seems to be related to functional rather than to structural abnormalities of the hypertrophied ventricle.

Digitalis Glycosides↗

PubMed1992

Digitalis and neurohormonal abnormalities in heart failure and implications for therapy.

A pathophysiologic hallmark of heart failure is neurohormonal excitation, a prominent feature of which is activation of the sympathetic nervous system. Studies from our laboratories demonstrate that clinical heart failure is characterized by marked increases in efferent sympathetic neural outflow to muscle; the magnitude of this sympatho-excitation parallels the degree of cardiac dysfunction. Impairments of cardiopulmonary and arterial baroreflex sensory mechanisms appear to be responsible to a significant degree for this sympatho-excitation, consistent with findings in animal models of heart failure. Digitalis glycosides exert modest inotropic actions when administered to patients with heart failure. Digitalis also has potent autonomic effects that can potentiate impaired arterial and cardiopulmonary baroreflex mechanisms in experimental models of cardiac dysfunction. Acute digitalis administration to patients with moderate-to-severe heart failure produces profound and sustained sympatho-inhibition, which precedes any observed hemodynamic action of the agent. Further, acute digitalization of such patients rapidly normalizes impaired baroreflex-mediated mechanisms. Data now suggest that the mechanism of action of digitalis in humans is an acute potentiation of baroreceptor-mediated afferent regulation of sympathetic neural mechanisms. Prospective, randomized and controlled studies now are required to test the hypothesis that the acute effects of digitalis on autonomic mechanisms also are observed during chronic administration. In theory, the chronic sympatho-inhibitory action of digitalis, combined with its chronic potentiation of impaired baroreflex mechanisms, may offer beneficial effects independent of its inotropic actions in patients with heart failure.

Digitalis Glycosides↗