[The influence of nitroglycerin on sinus node chronotropic response in ischemic heart disease]

Sick sinus syndrome (SSS) is frequently observed in patients with coronary artery disease (CAD). The influence of nitrates administered in CAD on sinus node function has not been established yet. It is not yet clear whether nitrates improve the sinus node blood supply or whether they directly influence the sinus node authomaticity. The second hypothesis is seems to be supported by the results of animal studies.

Evaluation of sinus node chronotropic response to the stimulation by nitric oxide (NO) donors, after pharmacological blockade in patients with different types of SSS with ischemic etiology. We studied 102 patients with suspected sinus node dysfunction and clinically diagnosed ischemic heart disease.

Test of sinus node chronotropic response was performed after pharmacological blockade with atropine and propranolol. A bolus of 100 microg nitroglycerin was administered to all patients. The following parameters were assessed: heart rate before (HR(NTG 0)), and after NTG bolus; maximal (HRNTG max) and mean at 5t second (HR(NTG 5)). Based on results of stimulation patients were divided into two groups: group I--70 patients with electrophysiological signs of SSS and group II--32 patients without the above mentioned signs. One subgroup with decreased IHR alone and three subgroups with different types of SSS were assigned from group I.

Heart rate before (HR0) and after bolus of 100 microg nitroglycerin (HR(NTG max), HR(NTG 5)) were significantly lower in patients with SSS than in subjects with normal sinus node function. There were no significant differences of absolute and relative HR increase after NTG bolus between both groups of patients. The values of HR(NTG max) and HR(NTG 5) did not vary significantly between subgroups of patients with different types of SSS. Patients with intrinsic SSS revealed positive correlation between HR0 and both: HRmax and HR(NTG 5). whereas persons with other types of SSS did not show this relation.

(1) Significant positive chronotropic response of sinus node to the stimulation by NO donor was observed in both patients: with and without electrophysiological signs of SSS. (2) The positive chronotropic response of sinus node to NTG bolus was observed despite of type of SSS.