The effect of digitalis on sinoatrial conduction in man

Q WAVES AND ASYNERGY: PREDICTIVE VALUE AND HEMODYNAMIC SIGNIFICANCE OF ANATOMIC LOCALIZATION Monty Bodenheimer, MD; Vidya S. Banka, MD; Richard H. Helfant, MD, FACC, Presbyterian-University of Pennsylvania Medical Center, Philadelphia, Pennsylvania To better delineate the significance of pathologic Q waves (5.04 set) in predicting location and functional effect of asynergy, 124 consecutive patients with asynergy were reviewed. 105 had coronary artery disease and 19 were classed as cardiomyopathy (CM) (diffuse hypokinesis and normal coronary arteriograms). 57 patients (54%) had pathologic Q waves; 27 anterior, 29 inferior and one both. Anterior Q's denoted asynergy in 27 of 27 (loo%), anterior asynergy in 26 of 27 (96%) and frank aneurysm (akinesis or dyskinesis) in 22 of 27 (78%). Inferior Q's indicated asynergy in 26 of 29 (90%). inferior asynergy in 21 of 29 (78%) and aneurysm in 9 of 21 (31%). Conversely, of 47 frank aneurysms, 83% had Q's. Anterior aneurysms had Q's in 29 of 36 (80%) while inferiors had 13 of 15 (86%). Hemodynamitally, the left ventricular end-diastolic pressure (LVEDP) was elevated in 15 of 27 (56%) with anterior Q's versus only 7 of 22 (31%) with inferior Q's (pc.025). Anterior asynergy alone was associated with an elevated LVEDP in 13 of 28 (46%) contrasted with 6 of 21 (22%) with inferior asynergy. Patients with combined or diffuaa asynergy had elevated LVEDP in 43% and 45% respectively. Of the 19 patients with CM none had Q's. In sunsnary, pathologic Q waves correlated highly with the presence of asynergy, accurately localized the site of the aneurysm and aided in predicting the degree of left ventricular dysfunction. Q's were not seen in cardiomyopathy. THE EFFECT OF DIGITALIS ON SINOATRIAL CONDUCTION IN MAN Roger C. Bond, M.D., Toby R. Engel, M.D., and Stephen F. Schaal, M.D., The Ohio State University College of Medicine, Columbus, Ohio. Digitalis induced abnormalities of sinoatrial (SA) conduction are not recognized unless SA block is observed. The effect of digitalis on SA conduction has not been determined in man. A catheter advanced to the high right atrium was used to apply a premature atria1 impulse after every eighth basic beat. When the premature beat is applied in the midzone of the basic cycle, analysis of the basic cycle interval and the interval from the atria1 premature depolarization (APD) to the recovery beat allows computation of the sinoatrial conduction time (SACT). This interval represents the conduction time required for the impulse to travel to the SA node and return to the atria1 recording catheter. Five normal patients were studied before and after ouabain (0.01 mgfkg). The SACT was prolonged after ouabain in all patients with an average change of 52.8 msec. The increase of the SACT correlated with the prolongation of atrioventricular conduction (r = 0.92). In two patients with sinus rhythym and digitalis induced SA block, application of APD's defined two separate groups of recovery intervals differing by one basic cycle length; this represented second degree SA block. This study defines a means of measuring sinoatrial conduction and demonstrates that digitalis prolongs SA conduction. BENEFICIAL EFFECTS OF LIDOCAINE ON INCIDENCE OF VENTRICULAR FIBRILLATION DURING CORONARY OCCLUSION IN DOGS. Jeffrey S. Borer, MD; Lura Harrison, PhD; Richard Levy, MD; Kenneth M. Kent, MD; Robert E. Goldstein, MD; and Stephen E. Epstein, MD, NHLI, Bethesda, Md. Several studies have questioned the efficacy of lidocaine in reducing the incidence of ventricular fibrillation(VF) shortly after acute myocardial infarction(AMI), when arrhythmogenic mechanisms are believed to be different from those operative several hours later. To determine whether lidocaine inhibits occurrence of early VF, open-chest anesthetized dogs were randomized into 3 groups: a control group (saline infusion); a moderate dose lidocaine-treated group (2 mg/kg bolus and 70 Ug/kg/min infusion); and a high dose lidocaine-treated group (2 mg/kg bolus and 100 bg/kg/min infusion). After 10 min of infusion the left anterior descending and septal coronary arteries were occluded at their origins. Infusions continued until VF occurred or 30 min elapsed. Fourteen of 16 control dogs died in VF. Sixteen dogs received lidocaine. Of the 11 treated dogs maintaining lidocaine blood levels within the accepted therapeutic range (1.2 to 5.5 wg/ml), 6 survived (pc.05). Ten of these 11 received the moderate dose regimen. Five other dogs received the high dose regimen; all died, with blood levels z6.3 kg/ml at the time of death. Since it has been suggested that detrimental effects may result from low blood levels of lidocaine, VF threshold (VFT) was determined in 3 dogs given lidocaine to maintain blood levels 51.2 wg/ml. No reduction in VFT was found. CJe conclude that lidocaine, at blood levels ranging from 1.2 to 5.5 Kg/ml, significantly reduces the incidence of VF occurring early after coronary occlusion and that no decrease in ventricular electrical stability occurs at lower blood levels. Administration of this agent therefore may be of particular value in the early phases of acute myocardial infarction. HEMODYNAMIC EFFECTSOFl-ISOPROPYLAMINO-3-(2-THIAZOLOXY)2-PROPANOL.HCl IN THE EXPERIMENTALLY INFARCTED DOG Howard T. Buckley, MD, Arthur M. Strosberg,PhD, Donald C. Harrison, MD, FACC, Cardiology Division, Stanford University School of Medicine, Stanford, CA and Department of Pharmacology, Syntex Research, Palo Alto, CA ITP (l-isopropylamino-3-(2-thiazoloxy)-2-propanol.HCl) is a selective myocardial B-stimulant with selective myocardial B-blocking activity which has previously been shown to increase (1) myocardial contractility, cardiac output (CO), coronary blood flow, heart rate (HR); moderately decrease (C) total peripheral resistance (TPR) and produce little or no effect on systemic blood pressure. We studied the effects of ITP (0 mg/kg, I.V. bolus), saline (0.1 cc/kg, I.V. bolus) and isoproterenol (0.1 pg/kg, I.V. infusion) administered to three groups of experimentally infarcted dogs. A 40-50% myocardial infarction of the left ventricle (LV) (measured by Evans Blue injection) was produced in each dog. Saline produced no significant hemodynamic effects. ITP produced sii LV dp/dt, 36%; stro!te volume (SV), 21%; but produced no significant changes i? aortic pressure, LV pressure or S-T segment elevation. I'PR decreased. Isoproterenol produced greater increase; in CO, SV, HR and a greater i in TPR. Isoproterenol, !,owever, appeared to 4 S-T segment elevation to a significant degree. We conclude that ITP is effective in the treatment of myocardial failure in the dog and would seem a useful adjunct in the treatment of heart failure. Studies in humans are now underway. 120 January 1974 The American Journal of CARDIOLOGY Volume 33