β Blockade in congestive heart failure: Persistent adverse haemodynamic effects during chronic treatment with subsequent doses

Objective - To determine whether the acute adverse haemodynamic effects of β blockade in patients with congestive heart failure persist during chronic treatment. Design - Sequential haemodynamic evaluation of heart failure patients at baseline and after three months of continuous treatment with the β₁ selective antagonist metoprolol. Setting - Cardiac care unit in university hospital. Patients - 26 patients with moderate to severe congestive heart failure (New York Heart Association grade II to IV) and background treatment with digoxin, diuretics, and angiotensin converting enzyme inhibitors, and with a left ventricular ejection fraction < 25%. Methods - Baseline variables included a six minute walk, maximum oxygen consumption, and right heart catheterisation. All patients received metoprolol 6.25 mg orally twice daily initially and the dose was gradually increased to a target of 50 mg twice daily. Haemodynamic measurements were repeated after three months of treatment, both before (trough) and after drug readministration. Results - Long term metoprolol had functional, exercise, and haemodynamic benefits. It produced decreases in heart rate, pulmonary capillary wedge pressure, and systemic vascular resistance, and increases in cardiac index, stroke volume index, and stroke work index. However, when full dose metoprolol was readministered during chronic treatment, there was a reduction in cardiac index (from 2.8 (SD 0.46) to 2.3 (0.38) 1/min/m², p << 0.001) and stroke work index (from 31.4 (11.1) to 26.6 (10.0) g.m/m², p < 0.001) and an increase in systemic vascular resistance (from 943 (192) to 1160 (219) dyn.s.cm^-5, p << 0.001). Conclusions - Adverse haemodynamic effects of β blockers in heart failure persist during chronic treatment, as shown by worsening haemodynamic indices with subsequent doses.