Atrioventricular nodal versus atrioventricular supraventricular reentrant tachycardias: characterization by an integrated Doppler electrophysiological hemodynamic study

During reentrant supraventricular tachycardias involving the atrioventricular node (AVN-SVT) or an AV bypass tract (AV-SVT), atrial pressure increases. While in AVN-SVT this increase relates to atrial contraction during ventricular systole, the mechanism remains unclear in AV-SVT. This study sought to clarify this mechanism. During 11 AVN-SVTs and 9 AV-SVTs, anterograde flow through the AV valves and retrograde flow in the pulmonary and hepatic veins were studied by pulsed-wave (PW) Doppler measuring the time interval between the ECG-R wave and (1) the end of venous retrograde flows, and (2) the beginning of valvular anterograde flows. The positive or negative difference between these two time intervals guided recognizing the atrial contraction against open or closed AV valves. Intracavitary pressures and cardiac index were also measured. During AVN-SVTs, venous retrograde flows always ended before the anterograde valvular flows, indicating atrial contraction against closed AV valves. During AV-SVTs, pulmonary retrograde flow ended before the beginning of mitral anterograde flow in five cases, began before but ended during the anterograde flow in three cases, and overlapped to the anterograde flow in one case. A corresponding behavior was observed at the right side of the heart. In both SVTs, atrial pressures increased and end-diastolic ventricular pressure and cardiac index decreased similarly. During AVN-SVT, the atrial contraction always occurs against closed AV valves, and during AV-SVT it generally occurs against totally or partially closed AV valves, explaining similar atrial pressure and cardiac index changes in both SVTs.