CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Wilfried Mullens, MD,
Gary S. Francis, MD, FACC and
W.H. Wilson Tang, MD, FACC*
* Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue, Desk J3-4, Cleveland, Ohio 44195 (Email: tangw{at}ccf.org).
We thank Drs. O'Rourke and Nichols for their enthusiastic interest and insightful comments regarding our report on the potential benefits of sodium nitroprusside (SNP) in the setting of advanced decompensated heart failure (ADHF) (1). We are in complete agreement regarding the many factors that influence left ventricular (LV) afterload, including the concept that aortic impedance can be a more integrated measure of LV afterload. We would like to emphasize that throughout the article there had not been any assertion or assumptions that measuring systemic vascular resistance in ADHF better reflects LV afterload compared with aortic input impedance. It is also not the intention of our retrospective case series to compare the effectiveness or safety of administration of SNP guided by a reduction in vascular resistance or aortic input impedance. In fact, titration of SNP doses was based on achieving a measured target mean arterial blood pressure of 65 to 70 mm Hg and not on achieving a normal derived systemic vascular resistance. Nevertheless, even with this relatively crude method in the absence of specialized equipment, the substantial improvement in cardiac output secondary to sodium nitroprusside therapy was associated with more favorable (rather than adverse) long-term outcomes. Although invasive measurements were used in our protocol, it is not the intention of these data to always imply the need for invasive monitoring, but solely to understand the hemodynamic contributors and subsequent changes induced by sodium nitroprusside during the treatment of ADHF. As with interpreting the clinical utility of any biomarker, there is an important distinction between identifying individual patients who may have the appropriate hemodynamic profiles to benefit from a specific intervention versus using specific indexes of LV afterload as targets of therapeutic interventions. We agree that much promise exists regarding the use of noninvasive hemodynamic monitoring. Nevertheless, in much the same way that pharmacotherapeutics require rigorous placebo-controlled testing in the specific population with the specific treatment goals to be certain of benefit, diagnostic tools intended to guide therapy may require the same validation, especially regarding use in the acutely ill heart failure population.
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References
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1. Mullens W, Abrahams Z, Skouri H, et al. Sodium nitroprusside for advanced low-output heart J Am Coll Cardiol 2008;52:200-207.[Abstract/Free Full Text]
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