The pulmonary venous flow (PVQ) pattern usually has two antegrade flow waves, corresponding to ventricular systole and diastole, respectively, and is used to assess left atrial pressure. To study the effects of atrioventricular conduction (AVD) and heart rate (HR) on the PVQ pattern, transthoracic pulsed Doppler recordings of pulmonary venous, transmitral, and aortic flow were made in five healthy subjects with dual-chamber pacemakers. Recordings were made at HRs of 80, 100, and 120 beats/min, with AVDs of 75, 150, and 220 msec at each HR. When the AVD was increased, the biphasic PVQ changed to a monophasic pattern in which a single flow wave covered the transition between ventricular diastole and systole. There was a shift of flow from ventricular systole to diastole. When HR was increased, the systolic fraction of the PVQ increased as a result of an increase in the relative duration of systole. In conclusion, AVD and HR influenced the PVQ pattern in subjects without signs of ventricular dysfunction. This may be a limitation to the use of the flow pattern to assess left atrial pressure.