[Effects of nifedipine and acebutolol alone and combined on work capacity in patients with exertional angina].
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Biomedical subjects
Publications and source records attributed to B Carù.
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The action of nifedipine (N), acebutolol (A), and their association (A+N) was studied in 16 patients suffering from effort angina with documented coronary artery disease. The therapeutic action was valued by bicycle effort stress test after oral administration of medications in comparison with placebo (P), following a double-blind random sequence of treatments. Working capacity significantly increased after A (507 +/- 450 mkp, p less than 0.05), after N (1,140 +/- 767 mkp, p less than 0.001), and after A+N (1,198 +/- 644 mkp, p less than 0.01). The increments of work after P administration were not significant. Moreover, fatigue instead of angina appeared as a stopping criterion in 8 patients after A+N, and in only 1 patient after P, A, and N.
100 healthy children, between 5 and 12 years of age underwent maximal exercise test on a bicycle ergometer in sitting position. Particularly interesting seem to be the observations on maximal heart rate during exercise, maximum work load, energy cost in terms of heart rate, EGG during exercise. As concerning the maximal heart rate, it was observed a levelling of around 195 beats min. for all the subjects. A low increase of systolic blood pressure was observed during strenuous exercise. The maximum tolerated work load increases accordingly with the increase of body surface area and age; taking into account the maximum value of heart rate during exercise (195 for all subjects), it arises a different energetic cost in terms of beats per min. in favour of 12 years subjects compared to youngers. None rhythm or conduction disturbances was observed during exercise, neither variations of the ventricular repolarization appeared during exercise.
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According to the experimental model of a 5 X 5 Latin square, 5 treatments were studied single blind in 5 patients, affected by stable-effort angina, by means of exercise tests. In the period of maximal supposed effect the following treatments were investigated: placebo (P), 1 tablet, orally; isosorbide dinitrate (ISDN), 5 mg, sublingually; propranolol (Pr), 40 mg, orally; nifedipine (N), 10 mg, orally; verapamil (V), 160 mg, orally. Placebo, compared with its own control tests, did not change any of the examined parameters. Comparison of the 'active' treatments with P showed the following results. All the treatments increased the duration of work before ECG positivity appearances. An increase in duration of work and total work performed before angina was seen after administration of ISIDN, N and V; the improvement observed after treatment with Pr was not significant. Comparison of treatments showed that work performance before angina was the same after administration of ISDN, N and V; these treatments were more effective than that with 40 mg Pr. Duration of work before ECG positivity was significantly longer after ISDN and N than after Pr. The changes in heart rate, maximal arterial pressure, ejection time index and triple product confirmed the activity of the administered doses. According to the observed effects on exercise tolerance, in comparison with P the same level of work was performed with the same triple product after Pr, and with lower triple products after ISDN, N and V.
20 subjects affected by ventricular pre-excitation, without any other associated cardiac disorder, underwent to maximal exercise test on bicycle ergometer; the aim of the research is to analyse their maximum levels of aerobic power, to study their electrocardiographic behaviour during exercise, with a particular reference to the ventricular repolarization, and finally to evaluate the incidence of arrhythmias during exercise. The maximum aerobic power was slightly lower than the reference standards (on average 78.32%); the muscular work, in 1 patient only, gave rise to cardiac arrhythmias during exercise. In these patients we assume as non specific, the "like ischemic" variations of the ventricular repolarisation during exercise.
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The effect of nifedipine on effort angina was investigated by means of exercise tests with bycicle ergometer and compared, in the same patients, with the effects of a nitroderivative and a betablocking agent. Five patients with stable effort angina entered the study, after an hemodynamic and contrasto-graphic control. According to the protocol of a latin square 5 X 5, all the patients received in a random sequence the following treatments: placebo, 1 c. orally; isosorbide dinitrate, 5 mg sublingually; propranolol, 40 mg orally; nifedipine, 10 mg sublingually; nifedipine, 10 mg orally. No significant change of any of the considered parameters was observed after the placebo. Isosorbide dinitrate and nifedipine produced significant increases of the duration of work before appearance of pain and EKG positivity, and of total work performed before anginal pain. Only the duration of work before EKG positivity was improved by propranolol. The comparisons between treatments showed no significant difference of the effects of the administered doses of isosorbide dinitrate and nifedipine. The improvements observed after propranolol were significantly lower than that observed after isosorbide dinitrate and oral nifedipine. On the basis of the observed changes of cardiac rate, maximal arterial pressure, ejection time index and triple product, the authors evaluate the possible mechanism of action of nifedipine.
The incidence of ventricular arrhythmias during muscular work in 400 patients hospitalized for clear or suspected coronary artery disease who underwent coronaroangiography and exercise test was studied. The correlations between the arrhythmias and some hemodynamic parameters and the coronaroangiogrphy patterns and left ventricle cineangiography were investigated. None of the factors that were supposed to be significant in the mechanism of the ventricular arrhythmias, such as high left ventricular end dyastolic pressure, modified myocardial contractility, previous myocardial infarct, or higher lesions of coronary arteries, gave significant correlations. In the present study, the ventricular arrhythmias during muscular work do not seem to be of diagnostic significance.
Among 173 patients with typical effort angina (159 men and 14 women) which underwent exercise test and coronary angiography, significant stenosis (greater than or equal to 70%) of one or more of important coronary branches were present in 93,1% of the cases (96,3% among the males and 57% among the females). In the same group the exercise test sensitivity was 88,8%; when 3 coronary branches were involved the sensitivity rises to 94,3%. The 96,6% of patients with positive exercise test had coronary lesions too (true positives). We did not find any correspondence between the site of transient subendocardial ischemia occurred during the exercise test and coronary branch involved, when the stenosis was limited only one important coronary branch. Finally the researche of correlation between the entity of coronary disease (number of coronary vessels involved, entity of left ventricular contractility impairment) and behavior of patient during exercise test, evaluated with different parameters measured at the moment of stopping of exercise (heart rate and threshold work load, rate-pressure product, maximal downsloping of ST segment, different positivity criteria for exercise test) allowed us to show a good correlation only between the extent of coronary involvement and rate-pressure product or maximal downsloping of ST segment.
Fifty patients with exertional coronary insufficiency performed an exercise test on a bicycle-ergometer and an isometric exercise with an instrument set up by the authors with the collaboration of the technical laboratory of the hospital. All cases had EKG positivity during dynamic exercise and only 2 patients had a positive EKG answer during isometric exercise. Angina occured in 70% of cases during dynamic exercise and in 12% of cases during isometric exercise. The difference in the increasing heart rate of the two types of exercise was statistically significant, as was the difference between absolute values of heart rate reached at the end of the exercise. The difference in the values of arterial pressure reached in the two types of exercise was also statistically significant. Moreover the comparison of product heart rate, time arterial pressure, time 10(-2) bordered on statistical significance. 31 of the 50 patients who underwent coronary angiography, demonstrated severe impairment. During isometric exercise a higher percentage of disturbances was observed. The authors came to the conclusion that isometric exercise is not advisable for the diagnosis of coronary insufficiency, either for the low specificity or the potential risk.
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