Circulation, Vol 90, 2695-2700, Copyright © 1994 by American Heart Association
GA Lanza, A Manzoli, E Bia, F Crea and A Maseri
BACKGROUND: Sublingual nitrates are much more effective in relieving angina
pectoris in patients with coronary artery disease than in patients with
syndrome X, but it is not known whether their effect on exercise tolerance
is also different in these two groups of patients. METHODS AND RESULTS:
Treadmill exercise testing was performed before and after administration of
sublingual isosorbide dinitrate (ISDN, 5 mg) in 18 patients with syndrome X
(effort angina and normal coronaries, group X) and in 33 patients with
documented coronary artery disease (group C). As a selection criterion, all
patients had ST- segment depression > or = 1 mm on the control exercise
test. Compared with the control test, the main differences in the two
groups observed during the exercise test after administration of ISDN were
(1) heart rate at 1-mm ST-segment depression was higher (126 +/- 25 versus
104 +/- 15 beats per minute [bpm], P < .01) in group C, whereas it was
not different (125 +/- 15 versus 126 +/- 16 beats per minute) in group X;
(2) the rate-pressure product at 1-mm ST-segment depression, the time to
1-mm ST-segment depression, and the exercise duration were significantly
improved in group C (P < .01 for all) but were worsened in group X
(18,047 +/- 4159 versus 20,535 +/- 4507 bpm . mm Hg, P = .014; 268 +/- 312
versus 429 +/- 214 seconds, P < .01; 494 +/- 279 versus 622 +/- 194
seconds, P = .013, respectively); (3) a normalization of the ECG (no
ST-segment depression) was obtained in 10 patients (30%) of group C but in
only 1 (5%) of group X (P < .01); (4) angina was prevented in 10 of 19
patients of group C but in no patient of group X (P < .01). CONCLUSIONS:
In patients presenting with anginal chest pain, the effects of sublingual
nitrates on exercise testing appear to be clinically useful to distinguish
patients with coronary artery stenoses from patients with syndrome X.
Indeed, worsening of exercise tolerance is highly predictive of normal
coronary arteries. Furthermore, the failure of nitrates to improve exercise
tolerance in patients with syndrome X suggests that a deficiency in
coronary prearteriolar nitric oxide production is unlikely to play a key
role in the pathophysiology of the syndrome.
ARTICLES
Acute effects of nitrates on exercise testing in patients with syndrome X. Clinical and pathophysiological implications
Istituto di Cardiologia, Universita Cattolica del Sacro Cuore, Rome.
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