Value of purinic compounds in assessing sinus node dysfunction in man: a new diagnostic method.

The purpose of this paper is to investigate whether the inhibitory action of purinic compounds (striadyne: STR) on the sinus node is quantitatively different on a pathological sinus node in comparison to a normal one and thus whether it is possible, as suggested by other authors, to use STR as a pharmacological test in the diagnosis of sick sinus syndrome (SSS). With this aim we investigated 55 patients, divided into 3 groups according to ECG and sinus function evaluation tests: 1--normal; 2--SSS (2a: flagrant SSS; 2b: latent SSS); 3--excess vagotonia and/or abnormal response to vagal stimulation. In all patients after a prophylactic insertion of a temporary pacemaker, 30 mg of STR were rapidly injected i.v. and the surface and intracavitary ECG continuously recorded until the basal state was regained; the following parameters were evaluated: average baseline sinus cycle (SC), minimum and maximum SC after the drug. In all patients STR caused first a slowing, then an acceleration of the sinus rate. SC lengthening was moderate in groups 1 and 3 [max SC was respectively 740-1820 ms (1198 +/- 290.9 ms) and 720-1440 ms (1157.5 +/- 223.3 ms)], but it was severe in patients with SSS [max SC in group 2a 2500-11880 ms (5398.3 +/- 2687.4 ms) in group 2b 1620-11140 ms. (4470.7 +/- 3660.6 ms)]. The difference between the max post STR SC of SSS patients, and the control group was highly significant P less than 0.001). Assuming as upper limit of the normal a value of 2071 ms. (corresponding to the mean + 3 standard deviations of the response of the control group) we recorded abnormal responses in 100% in group 2a and in 85.7% in group 2b, whereas there were no abnormal responses in group 3. In addition, nodal atrioventricular block occurred frequently. The authors believe this test could be useful in the diagnosis of SSS, but it is essential to insert a ventricular pacing catheter prophylactically if this test is used.