Haemodynamic effects of supraventricular tachycardias and their alterations by electrically and verapamil induced termination

The haemodynamic effects of electrically initiated supraventricular tachycardias were studied in 10 otherwise healthy patients. With the beginning of the dysrhythmia there was a sharp decrease of systemic arterial and left ventricular systolic pressure, dP/dtmax, cardiac index, and stroke volume. Then, these parameters except stroke volume exhibited an increase, but were statistically different from control until the tachycardia was electrically stopped at the tenth minute. Mean pulmonary artery pressure rose steadily and remained on an elevated level which was reached between the third and fifth minute. After cessation there was a short augmentation of systemic arterial and left ventricular systolic pressure as well as of dP/dtmax and cardiac index. Mean pulmonary artery pressure steadily decreased and for all parameters control values were reached at about the third minute. When the tachycardia was terminated at about the same time by an i.v. injection of 10 mg of verapamil the 'post-tachycardial potentiation' was less marked or even absent. Mean arterial and left ventricular pressure was lower and mean pulmonary artery pressure remained elevated as compared with the values observed after electrical termination. Cardiac index and dP/dtmax showed no significant differences. It can be concluded that verapamil in a dosage sufficient to terminate the arrhythmia did not exhibit additional negative inotropic effects.