Use of exercise test parameters to predict presence and duration of ambulatory ischemia in patients with coronary artery disease

Randomized comparison of T-type versus L-type calcium-channel blockade on exercise duration in stable angina: results of the Posicor Reduction of Ischemia During Exercise (PRIDE) trial

BACKGROUND

Mibefradil is a T-type calcium-channel antagonist and arterial vasodilator with negative chronotropic effects. It is not known if T-type calcium-channel blockade is superior to L-type calcium-channel blockade in patients with stable angina pectoris.

METHODS

A multicenter, randomized, double-blind trial was conducted in patients with documented coronary disease and stable angina to compare a 360 mg dose of diltiazem CD with 100 mg dose of mibefradil. The primary end point was change in time to symptom-limited exercise termination from baseline to 8 weeks. Secondary efficacy parameters included time to onset of persistent ST-segment depression, time to awareness of angina, and change in exercise duration from baseline to 2 and 4 weeks of treatment.

RESULTS

A total of 121 patients were randomized to mibefradil and 113 to diltiazem CD. At 8 weeks, the increase in exercise duration was 24.5 seconds greater in the mibefradil group (P =.017; 95% CI 4.4-44.7 seconds). At 8 weeks, time to development of > or =1 mm ST-segment depression was greater by 45.3 seconds (P =.0025; 95% CI 16.2-74.5) with mibefradil, but time to development of angina was not significantly different.

CONCLUSION

T-type calcium-channel antagonism with mibefradil improved treadmill exercise parameters compared with diltiazem in patients with chronic stable angina. Further investigation and development of antagonists of T-type calcium channels with fewer adverse drug interactions is warranted and may be promising in the management of ischemic heart disease.

Efficacy of mibefradil compared with amlodipine in suppressing exercise-induced and daily silent ischemia: results of a multicenter, placebo-controlled trial

BACKGROUND

Mibefradil is a new benzimidazolyl-substituted tetraline-derivative calcium antagonist. Its vasodilatory activity combined with an ability to lower heart rate without negative inotropic effects as well as its long duration of action make it a promising anti-ischemic agent.

METHODS AND RESULTS

Three hundred nine patients with coronary artery disease, stable angina pectoris, and positive exercise tests were randomized to receive mibefradil (50, 100, or 150 mg), amlodipine (10 mg), or placebo. The anti-ischemic effects of mibefradil on exercise test and silent ischemia parameters were assessed. At doses of 100 and 150 mg, mibefradil increased exercise duration (by 55.5 and 51.0 seconds, respectively; P<.001 for both), increased time to onset of angina (by 98.3 and 82.7 seconds, respectively; P<.001), and increased time to 1-mm ST depression (by 81.7 and 94.3 seconds, respectively; P<.001). By comparison, a 10 mg/d dose of amlodipine significantly improved only time to onset of angina (treatment effect: 38.5 seconds, P=.036). Mibefradil 100 mg and 150 mg decreased the number of episodes of silent ischemia (treatment effects: -3.1 and -3.6, respectively; P<.001) and the duration of silent ischemia (treatment effects: -9.2 minutes, P=.048, and -14.6 minutes, P=.002, respectively). The decrease in the number of episodes of silent ischemia was also statistically significant in the group receiving 10 mg of amlodipine (-1.5; P=.036).

CONCLUSIONS

Once-daily doses of 100 and 150 mg mibefradil were effective in improving exercise tolerance and reducing ischemic episodes during ambulatory monitoring in patients with coronary artery disease.

Asymptomatic Cardiac Ischemia Pilot (ACIP) Study. Relationship between exercise-induced and ambulatory ischemia in patients with stable coronary disease

BACKGROUND

We investigated whether the presence and frequency of asymptomatic ischemic episodes recorded during ambulatory ECG (AECG) monitoring could be predicted on the basis of clinical characteristics or exercise treadmill test (ETT) performance in patients with stable coronary disease and whether the estimate of ischemia severity was similar between the AECG and ETT.

METHODS AND RESULTS

Patients screened for the Asymptomatic Cardiac Ischemia Pilot (ACIP) study were selected for the current analysis if data were available from 48-hour AECG monitoring as well as from an ETT during which the patient developed > or = 1-mm ST-segment depression. Exercise ECG data were available for 143 of the 910 patients without ischemic episodes and for 659 of the 910 patients with ischemic episodes during AECG monitoring. Angina was more frequent among patients with ambulatory ischemic episodes than among patients without such ischemia (P < .001). Patients with AECG ischemia had a consistently more marked ischemic response on the ETT than patients without AECG ischemia; patients likely to have AECG ischemia could be predicted on the basis of ETT performance characteristics. However, the correlation coefficients between the severity of ischemia estimated by ETT and by AECG were small.

CONCLUSIONS

There are significant relations between ischemia detected by AECG monitoring and by ETT, but the relations are limited, indicating that the two tests are not redundant to characterize coronary patients. A larger study investigating the prognostic significance of the ischemia identified by each modality, with follow-up for clinical events, will be necessary to determine the most appropriate methods to evaluate patients with stable coronary disease.