Positive end-expiratory pressure influences echocardiographic measures of diastolic function: a randomized, crossover study in cardiac surgery patients.

BACKGROUND: Ultrasonography of the cardiovascular system is pivotal for hemodynamic assessment. Diastolic function is evaluated with a combination of tissue Doppler (e' and a') and pulsed Doppler (E and A) measures of transmitral- and mitral valve annuli velocities. However, accurate echocardiographic evaluation in the intensive care unit or perioperative setting is contingent on relative resistance to positive pressure ventilation and changes in preload. This study aimed to evaluate the effects of positive end-expiratory pressure (PEEP) and positioning on echocardiographic measures of diastolic function. METHODS: The study was a prospective, randomized, crossover study. Cardiac surgery patients with ejection fraction greater than 45% and averaged e' of 9 or more were included. Postoperatively, anesthetized patients were randomized into six combinations of PEEP (0, 6, 12 cm H2O) and positions (horizontal, Trendelenburg). At each combination, e' (primary endpoint), a', E, and A were obtained with transesophageal echocardiography along with left ventricular area. Image analysis was performed blinded to the protocol. RESULTS: Thirty patients completed the study. PEEP decreased lateral e' from 6.6±3.6 to 5.3±3.0 cm/s (P<0.001) in the horizontal position and from 7.4±4.2 to 6.5±3.3 cm/s (P<0.001) in Trendelenburg. Similar results were found for septal e', a' bilaterally and transmitral pulsed Doppler measures, and PEEP decreased left ventricular area. E/A, E/e', and e'/a' remained unaffected by PEEP and positioning. CONCLUSIONS: When evaluating diastolic function by echocardiography, the levels of PEEP and its effect on ventricular area have to be taken into account. In addition, this study dissuades the use of E/e' for tracking changes in left ventricular filling pressures in cardiac surgery patients.

Clinical utility of semi-automated estimation of ejection fraction at the point-of-care.

INTRODUCTION: To compare estimation of ejection fraction at the bedside by AutoEF compared with conventional methods and to assess feasibility and time consumption. METHODS: A total of 102 relatively hemodynanically stable mixed medical and surgical patients were included. All patients underwent ultrasonography of the heart at the bedside performed by a novice examiner. Three assessments of ejection fraction were made: 1) Expert eyeballing by a single specialist in cardiology and expert in echocardiography; 2) Manual planimetry by an experienced examiner; 3) AutoEF by a novice examiner with limited experience in echocardiography. RESULTS: Expert eyeballing of ejection fraction was performed in 100% of cases. Manual planimetry was possible in 89% of cases and AutoEF was possible in 83% of cases. The correlation between expert eyeballing and AutoEF was r=0.82, p < 0.001, for manual planimetry and for AutoEF it was r=0.82, p < 0.001; for expert eyeballing and manual planimetry it was r=0.80, p < 0.001. The mean time consumption for manual planimetry was 98 ( 90-106 ) seconds; correspondingly the mean time spent for AutoEF was 41 ( 36-46 ) seconds, which was significantly less (p < 0.001). CONCLUSIONS: AutoEF seems to be a valid supplement to the clinical assessment of ejection fraction in the hands of less experienced examiners, yielding result similar to manual planimetry with less time consumption and less intra-observer variability. However, manual editing may be required and training is thus recommended before AutoEF is applicable for use by novices.

Echocardiographic Measures of Diastolic Function Are Preload Dependent during Triggered Positive Pressure Ventilation: A Controlled Crossover Study in Healthy Subjects.

Background. The use of echocardiography in intensive care settings impacts decision making. A prerequisite for the use of echocardiography is relative resistance to changes in volume status and levels of positive pressure ventilation (PPV). Studies on indices of diastolic function report conflicting results with regard to dependence on volume status. Evidence is scarce on PPV. Methods. Ten healthy subjects were exposed to 6 levels of positive end-expiratory pressure (PEEP) and pressure support (PS) following a baseline reading. All ventilator settings were performed at three positions: horizontal, reverse-Trendelenburg, and Trendelenburg. Echocardiography was performed throughout. Results. During spontaneous breathing, early diastolic transmitral velocity (E) changed with positioning (P < 0.001), whereas early diastolic velocity of the mitral annulus (e') was independent (P = 0.263). With PPV, E and e' proved preload dependent (P values < 0.001). Increases in PEEP, PS, or a combination influenced E and e' in reverse-Trendelenburg- and horizontal positions, but not in the Trendelenburg position. Discussion. The change towards preload dependency of e' with PPV suggests that PPV increases myocardial preload sensitivity. The susceptibility of E and e' to preload changes during PPV discourages their use in settings of volume shifts or during changes in ventilator settings. Conclusion. Positioning and PPV affect E and e'.