A combination of electrocardiographic methods represents a further step toward the noninvasive identification of patients with syndrome X

Differentiating syndrome X from coronary artery disease by treadmill exercise test in patients with chest pain and exercise-induced myocardial ischemia

Even though the underlying mechanisms of myocardial ischemia may be different, it is difficult to differentiate syndrome X from coronary artery disease (CAD) by means of the treadmill exercise test in elderly patients with chest pain and exercise-induced myocardial ischemia. One hundred sex- and age-matched patients-42 with syndrome X and 58 with CAD-were studied. Another 10 subjects with atypical chest pain, negative treadmill exercise test, and normal-appearing coronary angiograms served as controls. We evaluated the difference in exercise performance between patients with syndrome X and CAD, and the treadmill exercise test was undertaken with modified Bruce protocol within 2 weeks before coronary angiography. Parameters including time to 1 mm ST segment depression (STD), exercise duration (ED), heart rate (HR), systolic blood pressure, rate-pressure product (RPP), and percentage of age-predicted maximum HR (% HR) at different stages of the test were measured and then compared among the three groups of patients. Compared with CAD patients, syndrome X patients had significantly higher HR, % HR, and RPP at the time of 1 mm STD and at peak exercise. The time to 1 mm STD and ED were longer in syndrome X than in CAD patients. However, ED was shorter and HR, % HR, and RPP at peak exercise were similar in syndrome X patients as compared with control subjects. The new criterion of combined ED (> or =315 seconds) and RPP at peak exercise (> or =24,000 beats x mmHg/min) was found to be highly specific (86%) and moderately sensitive (64%) in differentiating syndrome X from CAD patients. The positive likelihood ratio for this criterion was 4.57 and negative likelihood ratio was 0.42. In conclusion, syndrome X patients had better exercise performance than CAD patients, but less ED and similar workload when compared with control subjects. The new criterion proposed in this study may provide a quick and simple way to differentiate syndrome X from CAD in a group of aged and predominantly male patients with chest pain and positive treadmill exercise test.

Usefulness of a quantitative analysis of the recovery phase patterns of the ST-segment depression in the diagnosis of coronary artery disease

PURPOSE

To assess the diagnostic value of the recovery phase patterns of the ST-segment depression in patients referred for chest pain.

PATIENTS AND METHODS

Continuous plots of ST-segment depression against heart rate during exercise and recovery were constructed within a population of 160 consecutive symptomatic patients who all had undergone catheterization (80 with > or = 1 stenosis > or = 50%). We used a new quantitative method of measurement allowing all kinds of rate recovery loops (even the so-called "intermediate" loops) to be considered for analysis. The measurements of the heart rate (HR)-adjusted ST-segment depression were performed at 20 and 60 ms from the J point, providing two different values of a quantified recovery loop index (RLI): RLI 20 and RLI 60.

RESULTS

Both RLI showed a higher specificity (0.81 +/- 0.04 and 0.74 +/- 0.05, respectively) than did the standard criterion (0.65 +/- 0.10), but the difference was significant regarding RLI 20 only (P = 0.011). As to the sensitivity, no significant differences were found among all of the criteria (0.74 +/- 0.05, 0.80 +/- 0.04, 0.76 +/- 0.05, respectively). The timing of measurements of the RLI within the repolarization phase did not affect their overall accuracy (0.77 +/- 0.03 for both RLI). The values of the receiver-operating characteristic (ROC) curve areas were significantly greater for both RLI (0.83 +/- 0.06 and 0.84 +/- 0.06 respectively) than for the standard criterion (0.75 +/- 0.07; P < 0.02). Finally, both RLI allowed to differentiate accurately the study subjects according to the number of diseased vessels, whereas the standard criterion could only distinguish between CAD patients and subjects with normal angiograms.

CONCLUSION

The quantitative analysis of the rate recovery phase patterns appears to be useful for the diagnosis of coronary heart disease and the assessment of its severity in symptomatic patients.

Acute effects of nitrates on exercise testing in patients with syndrome X. Clinical and pathophysiological implications

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.