Respiratory Variations of R-Wave Amplitude in Lead II Are Correlated With Stroke Volume Variations Evaluated by Transesophageal Doppler Echocardiography

ObjectiveThe authors hypothesized that variations in electrocardiographically derived R-wave amplitude might be correlated with mechanical ventilation-induced variations in stroke volume as determined by transesophageal echocardiography.DesignObservational prospective study.SettingSingle university hospital.ParticipantsThirty-four patients undergoing coronary artery bypass surgery.InterventionsNone.Measurements and Main ResultsRespiratory R-wave variations in lead II (ΔRII) were correlated with aortic velocity time integral variations (r = 0.82, p < 0.0001). Respiratory R-wave variations in leads III and aVF and pulse pressure variation also were correlated with aortic velocity time integral variations (r = 0.49, p = 0.015; r = 0.61, p = 0.0016; and r = 0.72, p < 0.0001, respectively). R-wave respiratory variations in lead V5 were not correlated with aortic velocity time integral variations. ΔRII was correlated with pulse pressure variation (r = 0.71, p < 0.0001). A ΔRII cutoff value of 15% accurately predicted stroke volume variations >15%, with a specificity of 92%, a sensitivity of 86%, a positive likelihood ratio of 11.1, a negative likelihood ratio of 0.15, a positive predictive value of 95%, and a negative predictive value of 80%.ConclusionsΔRII is correlated with stroke volume variations as determined by transesophageal echocardiography in mechanically ventilated patients and can identify the stroke volume variation cutoff of 15%, previously determined to be the cutoff for volume responsiveness.