A Review of Why and How We May Use β-Blockers in Congestive Heart Failure: Histologic vs Hemodynamic Criteria for Prognosis With β-Blockers
Conventional hemodynamic criteria cannot predict who will respond to β-blockers. Histologic criteria are more predictive. In 1993, Yamada et al reported that almost all patients with interfascicular fibrosis responded well, while only one third with intercellular fibrosis responded.
In 1995, Yamada et al53 reported that the extent of myocardial fibrosis could be estimated by means of their signal averaging criteria which, in turn, could predict the effectiveness of long-term metoprolol therapy with a sensitivity of 85% and specificity of 91%.
Heart Rate and Prognosis with β-Blockers
Although Schwartz et al claimed that a basic rapid heart rate was the best predictor of success with β-blockers, Swedberg et a found that rapid heart rates gave no better prediction of success than those with average heart rates.
How To Use β-Blockers β1-Blockers and Acute CHF
Increased norepinephrine and sympathetic drive are essential to maintain cardiac output and tissue perfusion during the acute stages. These compensatory mechanisms however, can become detrimental when continued long term. The patient should ideally be in a state of chronic stable CHF before a trial of β-blocker therapy is attempted. canadian family pharmacy online
β-Blockers and Hydralazine
Hydralazine and nitrates are also useful in the treatment of DCM in failure because of the improvement in function and survival seen in the vasodilator-heart failure trial study. They are usually employed if the patient does not tolerate ACE inhibitors. It is unknown whether this combination should be used with β-blockers because hydralazine tends to stimulate the sympathetic nervous outflow and may counteract the β-blocker effect.
β-Blockers and Digitalis
Digitalis should be additive because the inotropic response to calcium is unchanged by CHF. Also, digitalis may have direct neurohormonal effects that decrease sympathetic stimulation. However, the above beneficial effects may be counterbalanced to various degrees by its tendency to downregulate β-receptors due to the ability of digitalis to inhibit norepinephrine active transport that involves a process involving sodium and potassium adenosine triphosphatase.