Influence of atenolol on the relationship between heart rate and QT interval in patients with exercise-induced myocardial ischemia.

The aim of this study was to analyze the relationship between heart rate and QT interval (HR-QT) during exercise in control subjects (Group A) and in patients with coronary artery disease (CAD) with effort angina and without previous myocardial infarction (MI) (Group B). The diagnosis of CAD was confirmed by coronarographic examination. The correlation HR-QT was significant (p < 0.001) in both groups on effort and at recovery. The analysis of the regression HR-QT was carried out separately, both on effort in upright position and at rest in supine position, to avoid the influence of posture on QT length. During effort, the regression line showed lower slope and intercept values in Group B (p < 0.001) than those for Group A. A similar behavior was also observed at rest. Thus, at the highest heart rate, where ECG signs of ischemia (ST depression > 1 mm) frequently occurred, a longer QT interval was present in Group B. Moreover, in Group B, the QT interval in the presence of ECG signs of ischemia was significantly longer (p < 0.01) than in Group A at comparable heart rates both on effort and at rest, thereby confirming the result obtained by comparing both regression lines. The same effort protocol was repeated in Group B patients after acute administration of atenolol 100 mg per os. After atenolol administration, the analysis of the regression HR-QT in Group B clearly showed a shorter QT interval than that obtained in washout period during the baseline test at the highest heart rates where the ECG frequently showed signs of ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

[HR/QT ratio during ergometric test: influence of ischemia and beta blocking therapy]. / Relazione FC/QT durante test ergometrico: influenza dell'ischemia e della terapia betabloccante.

The aim of this study was to analyze the HR/QT relation during exercise in a group of patients with effort angina (Group B) in comparison with the same relation obtained in a group of normal subjects (Group A) comparable for age and sex. The regression analysis was carried out separately during effort in upright position and during rest in clinostatic position to avoid influences on QT by the patient's posture. During effort in patients of the Group B the regression shows a lower value of the slope and of the intercept (p less than 0.001) than those obtained in the subjects of the Group A. A similar behaviour is shown also from the regressions obtained during rest in the same groups. Thus at the highest HRs we observed a longer QT in the Group B. Moreover QT of ischemic patients in the presence of ECG signs of ischemia (ST less than or equal to 1 mm) resulted significantly longer (p less than 0.01) either during effort and at rest, respect to that obtained in Group A at comparable HRs. The analysis of the regression HR/QT after administration of atenolol 100 mg per os in a subgroup of patients of Group B clearly shows a less prolonged QT at the highest HRs where ECG ischemia frequently appears. This fact is demonstrated by the presence of a higher slope (p less than 0.05) respect to that obtained in the same group without therapy. In conclusion, myocardial transient ischemia provokes a longer QT in patients with ischemic heart disease in comparison with normal subjects. Acute therapy with atenolol per os is able to condition the regression HR/QT showing a relative shortening of QT at the highest HRs respect to that carried out in the same patients in absence of therapy.

[Cardioscintigraphic evaluation of obese subjects with or without arterial hypertension]. / Valutazione cardioscintigrafica dell'obeso con o senza ipertensione arteriosa.

A group of normotensive obese subjects (group A), a group of hypertensive obese subjects (group B) and a group of control subjects (group C) were submitted to radionuclide ventriculography using 99mTc to investigate cardiac function and haemodynamic situation in the presence of an increased preload (group A), preload and afterload (group B). Results show a significant reduction in ejection fraction and systolic blood pressure/end systolic volume in group A. Group B shows better cardiac function probably for the presence of cardiac concentric hypertrophy. Left ventricle work either in a minute and for each beat is greatest in patients of group B. Thus the simultaneous presence of obesity and hypertension can cause a worse prognosis in such patients for cardiac ischaemia and/or sudden death.