[Hemodynamic guidelines in the treatment of acute myocardial infarction by means of vasodilators].

Two types of vasodilators are used for treatment of acute myocardial infarction: Nitrates on the one hand with predominant venodilation and agents like Phentolamie and Nitroprusside on the other hand with venodilation as well as arteriolar vasodilation. Different opinions exist with respect to indication of these vasodilators. They are used for reduction of arterial blood pressure, for reduction of left ventricular filling pressure and for increase of cardiac output. A marked decrease in ejection fraction is the hemodynamic basis of application of vasodilators in the latter indication. By reduction of peripheral vascular resistance emptying of the left ventricle in these patients is enhanced.) As a working hypothesis in clinical situation elevated filling pressure indicates a decreased ejection fraction. The first part of this investigation deals with relation of left ventricular and diastolic pressure to ejection fraction. A good correlation between these two parameters was found in 717 patients with coronary artery disease. However variability was so wide that regression from enddiastolic pressure to ejection fraction in the individual seemed impossible. In 26.6% of patients with ejection fraction over 0.6%, filling pressure was 20 mm Hg or more. On the other hand, in 34.7% of patients with ejection fraction below 0.3% filling pressure was 20 mm Hg or less. As a consequence of practical value, reduced ejection fraction has to be assumed, if a patient presents elevated filling pressure and reduced cardiac output. In the second part, the hemodynamic effects of Phentolamine in 12 patients with acute myocardial infarction and elevated filling pressure (PCV resp. PADP greater than 18 mm Hg) are described. Maximal effects on hemodynamic variables were: reduction of peripheral vascular resistance by 31.4%, of left ventricular filling pressure by 16.2%, and of mean arterial pressure by 17.0%. Cardiac output increased by 25.8% and heart rate rose by 14.8%. At optimal efficacy, stroke volume increased by 23.7%. Further increase of infusion rate with concomitant fall of peripheral vascular resistance resulted in decrease of stroke volume and tachycardia. Most serious side effects consisted in sudden fall of blood pressure. Therefore intraarterial monitoring of blood pressure is demanded. The third part deals with hemodynamic effects of nitrates (Isosorbiddinitrate 10 mg p.o.) in patients with acute myocardial infarction and elevated filling pressure. One hour after application peripheral vascular resistance decrease by 16.5%, filling pressure by 20.8%, and mean arterial pressure by 9.0%. Cardiac output stroke volume and heart rate did not change significantly. No side effects were observed with Isosorbiddinitrate although two cases of nitrate syncope occurred with Nitroglycerin, resulting in bradycardia and hypotension. Indications for vasodilator therapy therefore has to be handled as follows: Nitrates should be given to patients with elevated filling pressure and normal cardiac output...