David H. Silber

Hemodynamic effects of supplemental oxygen administration in congestive heart failure

OBJECTIVES This study sought to determine the hemodynamic effects of oxygen therapy in heart failure. BACKGROUND High dose oxygen has detrimental hemodynamic effects in normal subjects, yet oxygen is a common therapy for heart failure. Whether oxygen alters hemodynamic variables in heart failure is unknown. METHODS We studied 10 patients with New York Heart Association functional class III and IV congestive heart failure who inhaled room air and 100% oxygen for 20 min. Variables measured included cardiac output, stroke volume, pulmonary capillary wedge pressure, systemic and pulmonary vascular resistance, mean arterial pressure and heart rate. Graded oxygen concentrations were also studied (room air, 24%, 40% and 100% oxygen, respectively; n = 7). In five separate patients, muscle sympathetic nerve activity and ventilation were measured during 100% oxygen. RESULTS The 100% oxygen reduced cardiac output (from 3.7 +/- 0.3 to 3.1 +/- 0.4 liters/min [mean +/- SE], p < 0.01) and stroke volume (from 46 +/- 4 to 38 +/- 5 ml/beat per min, p < 0.01) and increased pulmonary capillary wedge pressure (from 25 +/- 2 to 29 +/- 3 mm Hg, p < 0.05) and systemic vascular resistance (from 1,628 +/- 154 to 2,203 +/- 199 dynes.s/cm5, p < 0.01). Graded oxygen led to a progressive decline in cardiac output (one-way analysis of variance, p < 0.0001) and stroke volume (p < 0.017) and an increase in systemic vascular resistance (p < 0.005). The 100% oxygen did not alter sympathetic activity or ventilation. CONCLUSIONS In heart failure, oxygen has a detrimental effect on cardiac output, stroke volume, pulmonary capillary wedge pressure and systemic vascular resistance. These changes are independent of sympathetic activity and ventilation.

Biventricular pacing in congestive heart failure: a boost toward finer living.

With 550,000 new cases each year, congestive heart failure is a major medical problem. Several medical therapies, including digoxin, angiotensin-converting enzyme inhibitors, and beta-blockers, have reduced the number of re-hospitalizations and slowed the progression of congestive heart failure. Angiotensin-converting enzyme inhibitors, some beta-blockers, and the combination of hydralazine with nitrates have improved survival. Despite these benefits, medical therapy frequently fails to improve quality of life. Biventricular pacing has been introduced to resynchronize mechanical and electrical asynchrony frequently observed in patients with heart failure. The most recent pacing trials show an improvement in quality of life and functional class. Long-term data are needed to determine the effect of biventricular pacing on survival. The acute hemodynamic studies suggest that resynchronization pacing therapy may predict a positive long-term benefit for many patients with congestive heart failure.