Usefulness of the hyperventilation test in stable exertional angina pectoris in selecting medical therapy

Cardiovascular effects of carbon monoxide poisoning

Carbon monoxide (CO) poisoning is an important health problem. Cardiac abnormalities may occur in patients with CO poisoning; however, the severity and duration of cardiac abnormalities are not well known. In this study, cardiac structures and function in CO poisoning were evaluated prospectively. Twenty patients were enrolled in the study. Echocardiographic examination was performed in all patients on admission, at 24 hours, and within the first week. B-type natriuretic peptide and carboxyhemoglobin levels were measured. Patients with increased cardiac markers underwent coronary angiography. Cardiac markers were high in 6 patients. Patients with high cardiac markers had significantly higher carboxyhemoglobin levels and longer exposure to CO. Left ventricular ejection fraction (LVEF) was <45% in 8 patients (group I) on admission and >55% in 7 patients in group I 24 hours after echocardiography. A significant negative correlation was found between B-type natriuretic peptide and LVEF on admission (r = -0.586, p <0.01). The decrease in LVEF was also negatively correlated with carboxyhemoglobin level and CO exposure duration. All angiograms showed normal coronary arteries. In conclusion, despite normal coronary arteries, myocardial dysfunction may occur in patients with CO poisoning. LV systolic function might be normal or mildly to severely impaired. However, most of the myocardial dysfunction dissipates at 24 hours in patients with CO poisoning.

Phase changes caused by hyperventilation stress in spastic angina pectoris analyzed by first-pass radionuclide ventriculography

To understand the effect of hyperventilation (HV) stress in patients with spastic angina, left ventricular (LV) contraction was analyzed by quantitative phase analysis. The study was performed on 36 patients with spastic angina pectoris, including vasospastic angina pectoris (VspAP: 16 patients) and variant angina pectoris (VAP: 20 patients). First-pass radionuclide ventriculography (first-pass RNV) was performed at rest and after HV stress, and standard deviation of the LV phase distribution (SD) was analyzed. The SD was lower in patients with VspAP than in VAP (12.8+/-1.4 degrees vs. 14.6+/-2.2 degrees, p < 0.005) at rest. After HV stress, the SD (HVSD) tended to increase in VspAP patients (62.5%), whereas the SD decreased in VAP patients (70%). Due to HV stress, the percentage change in SD (%SD) in VspAP patients was 8.9+/-23.7% whereas that in VAP patients was -9.1+/-17.3% (p < 0.01). Moreover, phase histograms were divided into HVSD increase and HVSD decrease groups. The HVSD increase group had a decrease of HVEF, but the HVSD decrease group tended to have more decreased HVEF than the HVSD increase group. These results indicate that spastic angina pectoris patients show various responses to HV stress. The HVSD increase group might have additional myocardial ischemia due to regional coronary spasm. In contrast, in the HVSD decrease group severe LV dysfunction or diffuse wall motion abnormality might have been generated, and this caused a reduction in the SD value. Phase analysis would therefore add new information regarding electrocardiographically silent myocardial ischemia due to coronary spasm, and HV stress might increase sensitivity for the detection of abnormalities in quantitative phase analysis, especially in VspAP patients.

Selection of medical treatment in stable angina pectoris: results of the International Multicenter Angina Exercise (IMAGE) Study

OBJECTIVES

The present study was designed to investigate which characteristics of anginal symptoms or exercise test results could predict the favorable anti-ischemic effect of the beta-adrenergic blocking agent metoprolol and the calcium antagonist nifedipine in patients with stable angina pectoris.

BACKGROUND

The characteristics of anginal symptoms and the results of exercise testing are considered of great importance for selecting medical treatment in patients with chronic stable angina pectoris. However, little information is available on how this first evaluation may be used to select the best pharmacologic approach in individual patients.

METHODS

In this prospective multicenter study, 280 patients with stable angina pectoris were enrolled in 25 European centers. After baseline evaluation, consisting of an exercise test and a questionnaire investigating patients' anginal symptoms, the patients were randomly allocated to double-blind treatment for 6 weeks with either metoprolol (Controlled Release, 200 mg once daily) or nifedipine (Retard, 20 mg twice daily) according to a parallel group design. At the end of this period, exercise tests were repeated 1 to 4 h after drug intake.

RESULTS

Both metoprolol and nifedipine prolonged exercise tolerance over baseline levels; the improvement was greater in the patients receiving metoprolol (p < 0.05). Multivariate analysis revealed that low exercise tolerance was the only variable associated with a more favorable effect within each treatment group. Metoprolol was more effective than nifedipine in patients with a lower exercise tolerance or with a higher rate-pressure product at rest and at ischemic threshold. None of the characteristics of anginal symptoms or exercise test results predicted a greater efficacy of nifedipine over metoprolol.

CONCLUSIONS

The results of a baseline exercise test, but not the characteristics of anginal symptoms, may offer useful information for selecting medical treatment in stable angina pectoris.

Twenty-four-hour activity of felodipine extended release in chronic stable angina pectoris

To investigate the antiischemic efficacy and duration of action of the dihydropyridine calcium antagonist felodipine, 15 patients with stable exertional angina were enrolled in a double-blind, crossover study comparing 2 doses (5 and 10 mg) of felodipine extended release (ER) and placebo given once daily for 1 week. Bicycle exercise tests were repeated at the end of each treatment period 4 and 24 hours after dosing. Four hours after dosing with both felodipine doses, only 5 patients discontinued the exercise test because of greater than 2 mm of ST-segment depression, whereas 10 continued until exhaustion (p less than 0.01 vs placebo). Compared with placebo, total exercise time was increased by 19% (p less than 0.001), with no difference between doses. After 24 hours, exercise duration was prolonged up to physical exhaustion in 6 patients taking felodipine 10 mg (p less than 0.05 vs both placebo and felodipine 5 mg); moreover, 11 patients taking 10 mg and 5 taking 5 mg increased time to 1 mm of ST depression greater than or equal to 15% compared with exercise time during the placebo test. Mean time to 1 mm of ST depression at 24 hours was increased by 8% with 5 mg and by 18% with 10 mg (p less than 0.001 vs placebo; p less than 0.01 between doses). Total exercise time at 24 hours was increased with both doses (p less than 0.001), with greater efficacy with the 10-mg dose (p less than 0.05 vs 5 mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Ability of calcium-entry blockade by felodipine to disclose different pathogenetic mechanisms behind hyperventilation-induced myocardial ischemia in men

To verify that myocardial ischemia occurring during either the overbreathing or recovery phase of the hyperventilation test is based on different pathogenetic mechanisms, 2 consecutive series of patients, selected on the basis of their response to a run-in hyperventilation test, were studied. Group I comprised 15 patients who developed ST-segment depression early during overbreathing, whereas group II consisted of 12 patients showing ST-segment depression late during the recovery phase. A single oral dose of felodipine 10 mg or of placebo was administered on 2 consecutive days according to a randomized, double-blind, crossover design, and the hyperventilation test was repeated, on both days of the study, 3 to 5 hours after drug intake. In group I, ST-segment depression occurred after placebo in all patients during overbreathing, with an increase in rate pressure product (from 112 +/- 31 at baseline to 168 +/- 55 mm Hg x beats/min/100 at the onset of ST-segment depression; p less than 0.01). After felodipine, 13 patients continued to show ST-segment depression during overbreathing, together with an increase in rate pressure product (from 107 +/- 24 at baseline to 158 +/- 46 mm Hg x beats/min/100 at the onset of electrocardiographic changes; p less than 0.01). In group II, all 12 patients showed ST-segment depression during recovery after placebo, with a rate pressure product comparable to baseline conditions (112 +/- 35 at baseline vs 102 +/- 27 mm Hg x beats/min/100 at the onset of ST-segment depression; difference not significant). After felodipine, no patient developed ST-segment depression or chest pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased coronary tone in exertional angina: the beneficial effects of calcium antagonists

Coronary vasoconstriction may play a relevant role in the pathogenesis of exercise-induced myocardial ischemia, not only in patients with Prinzmetal's angina, but also in patients with chronic stable angina. In these patients the use of calcium antagonists, namely, dihydropyridine derivatives, may be beneficial. Hyperventilation is a simple and sensitive test to discriminate patients with effort angina who will improve their exercise capacity after administration of these drugs.