For patients with low gradient (LG) severe aortic stenosis (AS) with preserved ejection fraction (EF), treatment of hypertension with vasodilators, such as sodium nitroprusside, could help lower left ventricular (LV) afterload, leading to decreased LV filling pressures and pulmonary artery pressures.
“Although treatment is controversial, it is generally recommended that such patients undergo aortic valve replacement when symptomatic and no other etiology is found for symptoms,” wrote the authors, led by Mackram F. Eleid, MD, of the Mayo Clinic in Rochester, Minn. Their study was published online Aug. 16 in Circulation. “However, systemic hypertension frequently co-exists in this patient population and the increased arterial afterload may itself cause elevated left ventricular filling pressures which could play a major role in producing symptoms of dyspnea.”
In their study, the researchers compared a group of 18 symptomatic Mayo Clinic patients who presented with LG severe AS with preserved EF to a group of six symptomatic patients with low gradient severe AS and reduced EF. Their research took place between 2006 and 2013.
All patients underwent invasive hemodynamic left and heart catheterization. Patients had severe hypertension, pulmonary hypertension, elevated LV end diastolic pressure and diminished stroke volume at baseline.
They then administered sodium nitroprusside (Nitropress, Abbott) to determine how the reduction in afterload affected the severity of AS. The starting dose was 0.25 mcg/kg/min and increased 0.5 to 1 mcg/kg/min every five minutes.
Nitroprusside reduced afterload as well as average pulmonary artery pressure with a 40 percent decrease in LV end diastolic pressure compared to baseline. Stroke volume and cardiac index increased about 10 percent. Additionally, aortic valve area and average gradient increased on nitroprusside.
“The heterogeneous responses to nitroprusside in this population of patients with LG severe AS and preserved EF underscores the importance of integrating all of the available hemodynamic information into the assessment,” they wrote. This assessment, they explained, should include cardiac output, characteristics of the peripheral circulation and the morphology of the aortic pressure tracing in addition to the mean gradient and valve area information.
While the study yielded important clues about how nitroprusside can be used to determine AS severity, it is still unclear whether this use can be clinically beneficial to patients. Research using a much larger population is warranted.
Despite the small study size, the authors argued that their findings have implications for managing elderly patients with hypertension and LG severe AS with preserved EF as well as managing paradoxical low-flow, LG severe AS.
Brian R. Lindman, MD, MSCI, of Washington University School of Medicine in St. Louis, and Catherine M. Otto, MD, of the University of Washington School of Medicine in Seattle, wrote in an editorial that the study data could have clinical significance.
Hypertension can influence the determination of the severity of AS, which can impact decisions about valve replacements, they explained. With valve replacements, systemic hypertension may develop due to increased flow resulting from diminished valvular afterload, which could minimize the benefits of LV unloading with valve replacement.
“For all these reasons, both before and after valve replacement, treatment of systemic hypertension should be an important objective of medical therapy.”