Hemodynamic changes after meals and placebo treatment in chronic congestive heart failure.

To determine whether significant spontaneous hemodynamic changes occur without therapeutic intervention, 15 patients with stable heart failure underwent right-sided cardiac catheterization and were observed without active treatment during an 8-hour period. Significant changes that mimic those seen during treatment with vasodilating medications were found. Increases were seen in heart rate (minimum 82 +/- 19 beats/min, maximum 88 +/- 18 beats/min, p less than 0.05) and cardiac index (minimum 2.14 +/- 0.45 liters/min/m2, maximum 2.42 +/- 0.79 liters/min/m2, p less than 0.05). Decreases were observed in pulmonary artery wedge pressure (maximum 24 +/- 7 mm Hg, minimum 21 +/- 7 mm Hg, p less than 0.05) and systemic vascular resistance (maximum 1,600 +/- 280 dynes-s-cm5, minimum 1,390 +/- 310 dynes-s-cm-5, p less than 0.05). Except for the decrease in pulmonary artery wedge pressure, all hemodynamic changes appeared to be related to eating. In addition, a statistically significant postprandial decrease in mean blood pressure (before meal 85 +/- 12 mm Hg, after meal 78 +/- 11 mm Hg, p less than 0.05) was seen. These data reinforce the need for caution in interpreting small hemodynamic changes, even if statistically significant, and they indicate the desirability of including placebo groups or phases in drug studies and of performing hemodynamic measurements the postabsorptive state.