Summary:A dynamic electrocardiographic Holter monitoring study was performed in 32 healthy children (20 males and 12 females, age range 6-1 1 years old), without heart disease, according to clinical and noninvasive instrumental examination. We evaluated atrioventricular conduction time (PR), heart rate (HR). and QT interval patterns defining the range of normality of these electrocardiographic parameters. The PR interval ranged from 154f10 ms (meanfSD) for H R s 6 0 to 102f12 ms for HR L 120 (range 85-180). The absolute mean HR was 87 f 10 beatshin (range 72-104), the minimum observed HR being 61 f 10 (range 51-79), the maximum 160k20 beats/min (range 129-186). Daytime mean HR gave a mean value of 93 k 10 (range 71-148), while during night hours it was 74f 1 1 (range 54-98). The minimum QT interval averaged 261 f 10 ms for HR > 120 and the maximum 389 k 9 ms for HR 5 60; the corresponding mean value of QTc (i.e., QT corrected for HR) ranged from 388 f 8 for HR 5 60 beats/min to 403 f 14 ms for HR > 120 beatdmin. The results of the present study provide data of normal children which can be readily compared against those of subjects in whom cardiac abnormalities are suspect or patent. Some of the data reported here differ from those currently available, as for PR and HR, obtained from standard resting electrocardiogram, and cast doubt on the usefulness of correcting for HR in the QT interval in these subjects.
inimary:The assessment of chronic phannacological atnient of stable angina requires serial exercise stress ;rings. It is well known that exercise tolerance can be ,proved by the training effect of performing repeated ;tings. Our study investigated the values of heart rate, stolic blood pressure, rate-pressure product, and duratn of exercise at 0.1 mV ST depression during exercise d the same parameters plus the maximal ST-segment pression at peak exercise, collected from three differt tests. The first and second werc performed at one-week ervals before, and the third (75 days after the first), was rformed after a double-blind study with a drug versus tcebo. We found a significant increase of exercise duion at 0.1 mV ST depression and at peak exercise, while if 12 patients increased exercise duration from the send to the third test. Individual variability of exercise ration showed increasing values, ranging from 0 to 7 1 % rst vs. third test). In contrast, the ratio of heart rate and rtolic blood pressure did not differ between the tests. ir data criticized the use of mean values of exercise time -phamiacological studies; moreover, individual variaity could affect results independently of drug or placebo ministration. These findings should be taken into acunt in order to exclude misleading results. . dc Arcangelis is presently a medical student.
We used an upright bicycle exercise to study recovery systolic blood pressure (SBP) response in 183 subjects (166 males and 17 females, ranging in age from 17 to 73 years). We calculated the recovery SBP ratio (recovery ratio - RR) (recovery 1 and 3 min SBP divided by the peak exercise SBP, measured immediately before end point and evaluated their data according to clinical presentation, atypical chest pain, typical angina), hypertension (n = 49), presence of previous myocardial infarction (n = 34), and coronary artery disease (n = 93). A control group was formed of 26 normal young volunteers and 25 subjects with a normal coronary tree or trivial lesions (O-V group). In the former group, RR were 0.85 ± (SD) 0.09 and 0.73 ± 0.08 respectively, while in the latter group were 0.85 ± 0.08 and 0.71 ± 0.08, respectively. Both ratios were significantly higher than in the O-V group only in patients with multivessel disease (with or without myocardial infarction) both in normotensive and hypertensive groups. To assess the role of an abnormal recovery SBP response for detecting presence of coronary stenoses or residual stenoses after myocardial infarction, we calculated upper limits of normal response (2 SD above the mean values of both ratios in controls; 1.01 and 0.88 respectively in first and third minute of recovery). An abnormal RR response was found in 28% of patients with coronary stenoses or residual stenoses, while we found an abnormal ratio in 2 subjects without coronary stenoses (n = 51) or residual stenoses after infarction (n = 5). Hypertension increased the incidence of abnormal ratios, thereby affecting the use of this criterion. In conclusion, an abnormal recovery SBP ratio, not related to exercise blood pressure value or heart rate, was rarely observed in patients with coronary artery disease, but, when noted during stress testing procedures in normotensive patients, should be considered a highly specific indicator and therefore potentially useful clinical tool.
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