Exercise intensity prescription after myocardial infarction in patients treated with beta-blockers.

PURPOSE: The aim of our study was to answer the following questions: (1) Is it possible to estimate the exercise training intensity according to heart rate in patients treated with beta-blockers after myocardial infarction? and (2) Are there any other appropriate alternate possibilities to estimate the training intensity? METHODS: This study involved 112 men (60.2 +/- 8.6 years) with a previous myocardial infarction treated with beta-blockers. Patients underwent exercise echocardiography and also completed a symptom-limited cardiopulmonary ramp test to determine peak exercise capacity, maximal heart rate, heart rate (HR) at the anaerobic threshold (AT), peak oxygen uptake (VO2peak) VO2 consumption at AT, and exercise capacity at AT. RESULTS: The mean value of HR at AT was 104.7 +/- 13.3 bpm, corresponding to 81.0% +/- 8% of VO2peak and 87.9% +/- 5.6% of HRpeak. The mean HR at 80% HRpeak was 96 +/- 13.7 bpm, at 70% heart rate reserve (HRR) 103.3 +/- 13.1 bpm and at 80% HRR 108 +/- 14.4 bpm. A close correlation was observed between HR at AT and values at 80% HRpeak (r = 0.86, P < .01). A similar correlation was found also for 70% and 80% HRR (r = 0.87 and 0.88, respectively, P < .01). Exercise intensity at AT occurred close to the value of 1 W/kg(bodyweight). CONCLUSIONS: As an upper limit in determining training intensities, the assessment of AT is the gold standard. However, findings suggest that %HRpeak, %HRR, and %VO2peak can be used alternatively. The use of workload expressed as in W/kg also appears useful.

Dynamic stress echocardiography in asymptomatic patients who received chemotherapy in childhood because of a malignant disease.

BACKGROUND: Introducing anthracycline antibiotics into the treatment of children's malignancies contributed enormously to the excellent outcome in children and adolescents. Nevertheless, the cardiotoxicity of such was discovered as early as in the 1970's. Only recently stress tests have been used to detect late cardiotoxic effects of anti-neoplastic drugs. AIM: To determine the function of the left ventricle (LV) in asymptomatic patients who were treated with chemotherapy containing anthracyclines in childhood or adolescence. METHODS: We examined 137 patients (81 men, 56 women), aged 16.6+/-4.8 years, in whom a malignant disease was diagnosed at the age of 9.1+/-4.8 years and who were treated with a cumulative dose of anthracyclines of 242+/-110 mg/m(2). The control group comprised 30 subjects (14 men, 16 women, mean age 19.5+/-5.2 years). The echocardiographic examination was carried out at rest and also immediately after a dynamic stress test. RESULTS: A decrease in the fractional shortening (FS) <30% was found in 11 (8%) patients. The values of ejection fraction (EF), mean velocity circumferential fibre shortening, end-systolic wall stress, excursion and systolic thickening of the LV posterior wall were significantly impaired in comparison with the group who had the FS > or =30% as well as with the control group. The maximal decrease in EF was reduced to 40% and FS - to 20%. The values of the index of the global function of LV were, in comparison with the control group, impaired in both subgroups of the patients. We did not find any differences in the exercise tolerance between the groups. The EF values both at rest and at stress were significantly lower in the group with FS <30% when compared with other groups. The values of percentage EF stress increment were increased in all the groups. A decrease in EF after exercise was not observed. CONCLUSIONS: Anthracycline chemotherapy leads to a late impairment of LV function. Asymptomatic patients with a decrease of EF to 40% or FS to 20% show preserved exercise tolerance as well as contractile reserve of the LV. These findings represent a better prognosis for the patient. Echocardiography at rest should be carried out repeatedly after the termination of the treatment and in the case of a pathological finding it is necessary to perform stress tests to evaluate the contractile reserve.

The late consequences of anthracycline treatment on left ventricular function after treatment for childhood cancer.

UNLABELLED: The purpose of this study was to determine the incidence of changes in left ventricular function in patients in long-term remission after treatment with anthracyclines for a childhood malignancy. The authors examined 155 patients in disease remission who underwent treatment protocols utilising anthracyclines in childhood. The group comprised 90 males and 65 females aged 15+/-4.9 years (range 5-29 years, median 15 years). The age at the time of diagnosis and start of treatment was 8.6+/-4.9 years (range 1-18 years, median 8 years). The time of follow-up was 7.3+/-4 years (range 1-21 years, median 6.3 years). The patients were given a cumulative dose of doxorubicin or daunorubicin of 250+/-131 mg/m2 (range 50-1200 mg/m2, median 240 mg/m2). The values of ejection fraction below 55% and fractional shortening below 30% assessed by means of echocardiography were considered as pathological. The control group consisted of 41 volunteers. Pathological values of fractional shortening were found in 12 patients (8%). Only one patient (0.64%) showed the development of heart failure due to cardiomyopathy. The group of the patients after chemotherapy revealed significantly worse values of left ventricular endsystolic wall stress, mean velocity of circumferential fibre shortening, Tei index, and isovolumic relaxation period in comparison with the control group. We found a correlation between the given cumulative dose of anthracyclines and indicators of systolic function of the left ventricle, but not a relation to the time indicators (age at diagnosis, time of follow-up). CONCLUSION: in the mean period of 6 years after chemotherapy, subclinical cardiotoxicity was found in 11 patients (7%) and cardiomyopathy with heart failure in one patient. Further indicators of subclinical damage are elevation of afterload (end-systolic stress), impaired relaxation and increased value of the Doppler index of global left ventricular function. Further monitoring and evaluation of the relevant subclinical abnormalities over a longer period of time are needed.