Dynamic preload assessment tests, especially pulse pressure variation (PPV) and stroke volume variation (SVV), are increasingly acknowledged in mechanically ventilated patients as being predictors of fluid responsiveness. However, the limitations of this method are often neglected or overlooked. One of the prerequisites for PPV and SVV evaluation, in addition to intermittent positive pressure ventilation, is a "regular heart rhythm," which may be an ambiguous term. We present a case where, despite a regular (paced) rhythm, atrioventricular dissociation was present and resulted in marked PPV elevation, which subsequently disappeared once sinus rhythm returned. Our case indicates that PPV and SVV should be interpreted with caution when atrioventricular dissociation is present.