In patients with varying degrees of chronic obstructive pulmonary disease (COPD), simultaneous measurements of central hemodynamics and left ventricular radionuclide ventriculograms at rest and during exercise were made. In 21 of these patients, satisfactory echocardiograms could be performed. In seven of the patients, arterial blood pressure at rest was increased. Decreased compliance of the left ventricle was thought to be present in patients with COPD and additional arterial hypertension. The left ventricular ejection fraction (LVEF) at rest was in the high normal range in all patients. During exercise, no further increase was observed. This pattern of LVEF response seems to be typical in patients with COPD. Because the highest values were observed in the more severe COPD and right ventricular hypertrophy, it is unlikely that an impairment of left ventricular function is caused by COPD. In five of 27 patients, an abnormal decrease of LVEF and regional hypokinesis occurred during exercise, thus suggesting additional coronary heart disease. The fact that at least 30% of the patients with COPD suffered from arterial hypertension and 20% of the patients exhibited unexpected ischemia detected by regional hypokinesis in RNV during exercise, but not in the ECG, may be of practical relevance. Coronary angiography was not indicated because most of these patients were over 65 and the factor limiting the working capacity was ventilatory impairment and not angina pectoris, in all patients. For this reason, a diagnostic uncertainty remains with regard to additional coronary heart disease in the older patients with advanced chronic obstructive pulmonary disease.

SUMMARY A consecutive series of 56 patients with chest pain but no evidence of previous myocardial infarction was prospectively studied by radionuclide ventriculography to determine the value of global and regional radionucide indices in detecting coronary artery disease. The results were correlated with the clinical judgment of chest pain, the results of the exercise electrocardiogram, and the right heart haemodynamic measurements during exercise. As a result of the criteria for entry, the study group was representative of the population seen in such a clinical setting. Only 25% of patients had coronary artery disease. The predictive power of radionuclide ventriculography was limited. The conventionally used criterion that normal subjects have an increase in left ventricular ejection fraction of at least 5% with exercise provided only 78% sensitivity and 57% specificity. Fourier analysis and visual interpretation of radionuclide studies wrongly diagnosed three out of 10 patients with extensive disease requiring surgery.These results suggest that radionuclide ventriculography is of limited value in the non-invasive diagnosis of coronary artery disease.

Right-heart catheterization and ergometry with arterial and mixed venous blood gas analysis were performed in 27 patients with a wide range of chronic obstructive pulmonary diseases. The purpose of the examination was to evaluate the risk in patients for lung surgery or to detect additional heart diseases. Patients who developed ex-ertional hypoxia (group 1) were compared with others who did not (group 2). In all patients the steady-state maximal workload was determined by ventilatory dysfunction. Both groups had normal values for mixed venous pO₂ and normal increase of the circulatory parameters during exercise. The patients with exertional hypoxia differed from the others in that they showed no decrease of venous admixture and alveolar-arterial oxygen gradient. In addition, these patients had increasing pCO₂ values at rest compared with exercise, indicating alveolar hypoventilation and ventilation-perfusion mismatching. Because of the good correlation of the absolute values of FEV₁ (forced expiratory volume in 1 s) with pulmonary artery pressures, parameters of gas exchange and working capacity, this lung function parameter seems to have a central role in predicting the functional state of patients with chronic obstructive disease. Ergometry and blood gas analysis should be performed in addition because these values cannot be predicted with the calculated postoperative FEV₁

WEISMULLER, P., ET AL.: Rate Reduction by Overdrive Stimulation at the Origin of an Ectopic Ventricular Tachycardia in the Intact Pig Heart-Evidence of Vagal Activation. Overdrive stimulation is used in the treatment of tachycardias. In this study, the effect of overdrive stimulation on a focal ventricular tachycardia was investigated. In 12 landrace pigs thoracotomy was performed. Stable ectopic ventricular tachycardias with a rate of 120-170/min were induced by subepicardial infusion of a solution of norepinephrine (10'^ M). Unipolar cathodal stimulation was carried out by an epicardial screw-in electrode. During tachycardia, overdrive stimulation was undertaken in different distances to the ectopic focus, with different stimulus amplitude and duration. A significant rate reduction of the ventricular tachycardia was observed after stimulation. When stimulated directly at the focus the extent of rate reduction was larger than after stimulation in a distance of 10-40 mm. At the infusion site the rate of the tachycardia was lowered in direct relation to the stimulation amplitude and stimulus width. The marked reduction in rate after overdrive stimulation (18%) was nearly completely antagonized by atropine. This indicates that rate reduction caused by local overdrive stimulation is due to local acetylcholine liberation caused by vagal stimulation in the ventricular working myocardium in this experimental model. (J Electrophysiol, 3:417-425, 1989) ventricular tachycardia, norepinephrine, vagal stimulation, acetylcholine, overdrive suppression

WEISMULLER, P., ET AL.: Rate Reduction by Overdrive Stimulation at the Origin of an Ectopic Ventricular Tachycardia in the Intact Pig Heart-Evidence of Vagal Activation. Overdrive stimulation is used in the treatment of tachycardias. In this study, the effect of overdrive stimulation on a focal ventricular tachycardia was investigated. In 12 landrace pigs thoracotomy was performed. Stable ectopic ventricular tachycardias with a rate of 120-170/min were induced by subepicardial infusion of a solution of norepinephrine (10'^ M). Unipolar cathodal stimulation was carried out by an epicardial screw-in electrode. During tachycardia, overdrive stimulation was undertaken in different distances to the ectopic focus, with different stimulus amplitude and duration. A significant rate reduction of the ventricular tachycardia was observed after stimulation. When stimulated directly at the focus the extent of rate reduction was larger than after stimulation in a distance of 10-40 mm. At the infusion site the rate of the tachycardia was lowered in direct relation to the stimulation amplitude and stimulus width. The marked reduction in rate after overdrive stimulation (18%) was nearly completely antagonized by atropine. This indicates that rate reduction caused by local overdrive stimulation is due to local acetylcholine liberation caused by vagal stimulation in the ventricular working myocardium in this experimental model. (J Electrophysiol, 3:417-425, 1989) ventricular tachycardia, norepinephrine, vagal stimulation, acetylcholine, overdrive suppression