Using pulse pressure variation or stroke volume variation to diagnose right ventricular failure?

We read with interest two recent studies suggesting that pulse pressure variation (PPV) is not an accurate predictor of fluid responsiveness in subjects with pulmonary hypertension [1,2]. 
 
We agree that PPV and stroke volume variation (SVV) may not work in patients with right ventricular (RV) failure. Indeed, when PPV and SVV are related to an inspiratory increase in RV afterload (and not to a decrease in RV preload), they cannot serve as indicators of fluid responsiveness [3]. 
 
This is indeed a limitation but can also be seen as useful information for clinicians who do not have an echo probe on the ends of their fingers. PPV and SVV are now available on virtually all bedside and hemodynamic monitors. These parameters have been shown to be very useful for predicting fluid responsiveness in many patients with an arterial line who are mechanically ventilated [3]. When part of goal-directed strategies, these parameters have also been shown able to improve patient outcome [4,5]. As a result, PPV and SVV are now widely used by clinicians in the decision-making process regarding fluid therapy. In this context, the lack of response to a volume load while PPV or SVV is high should be seen as an indicator of RV dysfunction, and should trigger an echocardiographic evaluation to confirm the diagnosis and to understand the underlying mechanisms. 
 
In other words, we believe PPV and SVV may actually help clinicians to diagnose quickly and treat properly shock states related to RV failure!

We read with interest two recent studies suggesting that pulse pressure variation (PPV) is not an accurate predictor of fl uid responsiveness in subjects with pulmonary hypertension [1,2].
We agree that PPV and stroke volume variation (SVV) may not work in patients with right ventricular (RV) failure. Indeed, when PPV and SVV are related to an inspiratory increase in RV afterload (and not to a decrease in RV preload), they cannot serve as indicators of fl uid responsiveness [3].
Th is is indeed a limitation but can also be seen as useful information for clinicians who do not have an echo probe on the ends of their fi ngers. PPV and SVV are now available on virtually all bedside and hemodynamic moni tors. Th ese parameters have been shown to be very useful for predicting fl uid responsiveness in many patients with an arterial line who are mechanically ventilated [3]. When part of goal-directed strategies, these parameters have also been shown able to improve patient outcome [4,5]. As a result, PPV and SVV are now widely used by clinicians in the decision-making process regarding fl uid therapy. In this context, the lack of response to a volume load while PPV or SVV is high should be seen as an indicator of RV dysfunction, and should trigger an echocardiographic evaluation to confi rm the diagnosis and to understand the underlying mechanisms.
In other words, we believe PPV and SVV may actually help clinicians to diagnose quickly and treat properly shock states related to RV failure!

Authors' response
Stephan M Jakob and Jukka Takala We agree with Michard and colleagues that failure to respond to fl uid loading despite PPV may indicate RV failure. We refer to the commentary of Sheldon Magder where he discusses the various factors that can infl uence PPV [6]. We also agree with Michard and colleagues that PPV and SVV may be reasonable to guide volume therapy in such conditions where simple hypo volemia in patients undergoing controlled mechanical ventilation is the main factor infl uencing PPV -typically perioperatively in patients without con founding cardio pulmonary abnormalities. In contrast, the usefulness of PPV and SVV in the intensive care unit is at best limited due to the many factors that infl uence heart-lung inter actions [6]. Th ese factors include the presence of spontaneous ventilatory eff orts, irregular heart rhythm, ventilator settings diff erent from those in the original studies [7,8], cardiovascular drugs [8], pulmonary artery hypertension and impeding or manifest right heart failure [1,2] -one or several of these factors may be present even in the majority of intensive care unit patients.
PPV has been advocated to indicate volume responsiveness -in part in order to avoid unnecessary fl uid loading. In the particular case of RV failure, PPV may induce the clinicians to do exactly what should be avoided -to load the already overloaded right ventricle. On top of this, we fully endorse Magder's opinion that even if PPV does predict volume responsiveness, it does not mean that the patient actually needs volume or that volume is the best management choice [6].