EFFECTS OF LONG-TERM VASODILATOR THERAPY IN PATIENTS WITH CAROTID-SINUS HYPERSENSITIVITY

Background In patients affected by carotid sinus hypersensitivity, lon g-term vasodilator therapy might increase the risk of syncopal episode s by reducing systolic blood pressure and venous return to the heart. Methods and Results Thirty-two patients (mean age 73 +/- 9 years; 20 m en) who met all the following criteria were included: (1) one or more episodes of syncope occurring during long-term (>6 months) treatment w ith angiotensin-converting enzyme inhibitors, long-acting nitrates, ca lcium antagonists, or a combination of these; (2) a positive response to carotid sinus massage, defined as the reproduction of spontaneous s yncope in the presence of ventricular asystole greater than or equal t o 3 seconds or a fall in systolic blood pressure greater than or equal to 50 mm Hg; (3) negative workup for other causes of syncope. The pat ients were randomly assigned to continue or to discontinue use of vaso dilators; carotid sinus massage was repeated 2 weeks after randomizati on. By the end of the study period, the baseline values of systolic bl ood pressure were significantly different between the 2 groups of pati ents both in supine (P=.01) and upright(P=.03) positions. Syncope had been induced by carotid sinus massage in 81% of patients in the ''on-v asodilator'' group and in 62% of patients in the ''off-vasodilator'' g roup (P=.21). The cardioinhibitory reflex was of similar magnitude in the 2 groups, being found in 50% of the patients in each group, with a maximum ventricular pause of 7.1 +/- 2.7 and 6.7 +/- 1.8 seconds, res pectively. The percentage decrease of blood pressure did not differ be tween the 2 groups, even if, in absolute valves, the baseline differen ce of blood pressure roughly persisted for the duration of the test. I n consequence of that, the rise of blood pressure to similar values wa s delayed approximately 30 seconds in the ''on-vasodilator'' group and rook more than 2 minutes to return to baseline valves. Conclusions In patients affected by carotid sinus hypersensitivity, chronic vasodila tor therapy does not have a direct effect on carotid sinus reflexivity , although the delayed recovery of pretest blood pressure valves could indirectly potentiate the severity of the clinical manifestations of the syndrome. The persistence of hypotension for a longer time after t he end of the massage suggests that vasodilators cause an impairment o f compensatory mechanisms.