Electrophysiologic and haemodynamic correlates in supraventricular tachycardia.

In 16 subjects with paroxysmal supraventricular tachycardia (SVT) we sought a relationship between haemodynamic changes associated with artificially induced arrhythmias and the electrophysiological properties of the related atrioventricular (AV) nodal reentry circuit. In 10 patients (group 1) induced SVT was typical (long AH) and caused a significant fall in cardiac output (-1.720 ml min-1) and arterial systolic pressure (-18 mmHg). In six subjects (group 2), induced SVT was atypical (long HA) and did not significantly alter the output of the heart and systolic pressure, despite the elicitation of similar tachycardia. The opposite AV nodal reciprocation pattern which resulted in a substantial increase in AH/HH in group 1 and in a slight rise of the same variable in group 2, may explain these haemodynamic differences. In fact, atrial and ventricular systoles occurred simultaneously and impeded the ventricular filling in the former group, while a regular subsequence of contraction was maintained in the latter group. In group 2, systolic arterial pressure and cardiac output fell to the same level as in group 1 when right atrial pacing, at a similar rate of SVT, determined an increase of AH/HH similar to that observed during typical tachycardia. Thus, the haemodynamic response to SVT differs significantly between the two types of reciprocating tachycardia, particularly as regards cardiac output and blood pressure, and is mainly influenced by the temporal relationship between atrial and ventricular systole, independent of the rate of contraction. The different conduction velocities of the reciprocating circuit limbs and their interrelation seem to be major determinants of the haemodynamic pattern of SVT.