Reduced stimulatory guanine nucleotide binding regulatory protein in idiopathic dilated cardiomyopathy

Lymphocyte G proteins reflect response to treatment in congestive heart failure

Congestive heart failure is associated with chronotropic and inotropic hyporesponsiveness to adrenergic stimulation. A decrease in Gs alpha or an increase in Gi alpha is associated with a decrease in adenylyl cyclase activity. The current study assessed G proteins in response to treatment with direct-acting vasodilators and correlated changes in lymphocyte beta-adrenergic receptor components with changes in hemodynamic variables. Twenty-three patients with severe chronic congestive heart failure (New York Heart Association functional classes III and IV) were studied. Patients were grouped as responders (n = 10) or nonresponders (n = 13) on the basis of clinical assessment of functional status from questionnaires. Therapy was associated with an increase in cardiac index, a decrease in mean arterial pressure, and a decrease in systemic vascular resistance in all patients. Left ventricular filling pressure significantly decreased in responders (26 +/- 2 mm to 13 +/- 3 mm, p < 0.05) but did not change significantly in nonresponders. Similarly, mean right atrial pressure significantly decreased in responders (11 +/- 2 mm Hg to 4 +/- 1 mm Hg, p < 0.05) but did not change in nonresponders. Plasma norepinephrine increased significantly only in nonresponders (679 +/- 100 pg/ml to 1233 +/- 201 pg/ml, p < 0.05). Whereas lymphocyte beta-adrenergic receptor density and Gs did not significantly change, Gi increased after treatment only in the nonresponder group (23 +/- 5 to 51 +/- 11 fmol/mg, p < 0.05). A poor response to direct-acting vasodilators can be distinguished by reactive increases in plasma norepinephrine and lymphocyte Gi in the absence of a decrease in either left- or right-sided filling pressures.

Beta-blockers in heart failure: promising or proved?

Despite recent improvements in the management of congestive heart failure, the prognosis of many patients with this condition remains poor. The level of neurohormonal activation appears to be predictive of survival, and clinical studies indicate that inhibition of overactivated neurohormonal systems may be beneficial. Activation of the renin-angiotensin-aldosterone system is well documented in heart failure, and angiotensin-converting enzyme inhibition now has an established role in treatment based on evidence of hemodynamic, symptomatic and mortality benefit. Sympathetic nervous system activation also occurs as a compensatory mechanism in heart failure but with long-term deleterious effects. Increasing evidence suggests that beta-adrenergic blockade can produce hemodynamic and symptomatic improvement in heart failure of idiopathic or ischemic etiology. Trials of beta-adrenergic blocking agents in patients after myocardial infarction suggest a beneficial effect on mortality, even among those with heart failure. However, there remains uncertainty as to how generalizable are the results from the postinfarction trials, particularly in the current therapeutic environment with routine angiotensin-converting enzyme inhibitor therapy. Appropriately powered randomized, controlled trials are required to determine precisely the balance of benefit and risk resulting from long-term beta-blocker therapy in patients with heart failure of ischemic and other etiology.