Hemodynamic Findings During Sinus Rhythm, Atrial and AV Sequential Pacing Compared to Ventricular Pacing In a Dog Model

The hemodynamic responses of atrial lAF], atrioventricu-lar sequential (AVP) and ventricuJar pacing (VP) were compared to sinus rhythm (SfiJ in seventeen anesthetized dogs with intact AV conduction. The atrium and/or ventricle were paced at fixed rates above the control sinus rate. An AV interval shorter than normal conduction was selected to capture the ventricle. The changes of pulmonary capillary wedge pressure (PCWP, mmHg). mean aortic pressure (MAP, mmHg), cardiac output (CO, L/min), systemic vascular resistance (SVR, dynes/s/cm⁻⁵), left ventricular stroke work index (SWI) and mean systolic ejection rate (MSER, ml/s) during sinus rhythm, atrial pacing and atrio-ventricular sequential pacing (expressed in percentages of the individual values during ventricular pacing) were:
The importance of atrial systole for cardiac performance was clearly demonstrated in dogs with normally compliant hearts. In both atrial and atrioventricular sequential pacing compared to ventricular pacing there was a reduction of pulmonary capillary wedge pressure (PCWP) (p < 0.01) and systemic vascular resistance (SVR) (p < 0.01) despite an increase in cardiac output (CO). The lesser mean systolic ejection rate (MSER) found during atrioventricular sequential pacing compared to sinus rhythm and atrial pacing may be explained by the abnormal ventricular depolarization in this pacing mode; nevertheless, the mean systolic ejection rate was still greater than that found during ventricular pacing (p < 0.05).