Certain clinical states and pathologic changes associated with deeply inverted T waves in the precordial electrocardiogram

A correlation of the clinical and electrocardiographic findings was undertaken in 110 cases which had in common the presence of deeply inverted T waves in central terminal leads centered about position 3 on the precordium. The results of this study are reviewed. A summary is presented of changes encountered at the time of necropsy in nine cases in which electrocardiographic changes of similar type had been recorded. These observations are integrated with concepts derived from the dipole theory. The total evidence is viewed in relation to observations reported by other investigators.

A depressant effect of acetylcholine on the idio-ventricular pacemaker of the isolated perfused rabbit heart

In Langendorff preparations of the isolated rabbit heart, excision of the atria and severance of the atrio-ventricular bundle resulted in the onset of idio-ventricular rhythm at a rate much below the original sino-atrial rate. The mean decrease in rate in twelve experiments was 61%. Acetylcholine perfusion decreased the idio-ventricular rate still further. Physostigmine augmented this effect while atropine prevented or abolished it. Similar results were obtained with a rat heart. The results indicate that a cholinergic receptor mechanism is present at pacemaker sites in mammalian ventricles. However, when rabbit ventricles, beating under atrio-ventricular nodal rhythm or idio-ventricular rhythm, were cooled to the point of cardiac arrest, acetylcholine failed to cause reappearance of the cardiac beat.

Anoxia and ventricular fibrillation; with a summary of evidence on the cause of fibrillation

Experiments are described showing that ventricular fibrillation is more readily produced in isolated rabbit hearts by electrical stimulation when the oxygen supply to the heart is reduced. This evidence completes investigations which have been made into factors affecting the production of fibrillation. These investigations have shown that factors which shorten the duration of the action potential, particularly those which cause the "plateau" to disappear, facilitate fibrillation, and those which lengthen the duration of the action potential prevent fibrillation. The reason for the length of the cardiac action potential may therefore be to prevent fibrillation. When the action potential is of normal length the fact that two adjacent fibres are out of phase does not matter; the one which is first to contract is not re-excited by the one which is second to contract, because at that moment the first is inexcitable. If the action potential is short, then the first may be already repolarized and may be excited by spread of excitation from the second. Factors which inhibit metabolism shorten the action potential.

A comparison of tests for antifibrillatory action

THE OBJECT OF THE EXPERIMENTS WAS TWOFOLD: first, to choose the most satisfactory test for antifibrillatory action; secondly, to place several drugs with reputed antifibrillatory activity in an order of potency as a preliminary to investigating their mode of action. Measurements were made on isolated rabbit atria at 34 degrees C of (1) the maximum driving frequency the atria would follow, (2) conduction velocity, (3) contractions, and of the threshold for the production of (4) extrasystoles, (5) flutter and (6) fibrillation. Log dose-response curves were plotted for quinidine, papaverine, procaine, dibenamine and procaine amide. The maximum frequency test and fibrillation threshold test gave similar results with all the drugs, and the results gave the order quinidine 1.0, procaine 0.53, Dibenamine 0.47, papaverine 0.43 and procainamide 0.26. Thresholds for extrasystoles and flutter were much more variable. The regressions relating changes in conduction velocity and contraction to log dose were different from those for maximum driving frequency and fibrillation threshold for procaine, papaverine and dibenamine, but the regressions for quinidine and procaine amide were nearly parallel in all tests. Serpajmaline contained a substance with antifibrillatory activity as great as that of quinidine and with no greater depressant action on contractions.

Polyuria in paroxysmal tachycardia and paroxysmal atrial flutter and fibrillation

When Paul Wood spoke about this to the British Cardiac Society in 1961, we were impressed by the originality of his work on a subject that so many had noticed but failed to investigate. A few months before his death in July 1962, when I asked him if his paper was ready for the journal, he said that he had not yet been able to get all the evidence he hoped for to establish the full explanation. Unfortunately, he had not the time to complete this. I have, therefore, tried to set out as clearly as possible the stage that he had reached. Maurice Campbell

Pacemaker failure in complete heart block

Atrioventricular conduction blocks were produced in dogs, and ventricular stimulation was accomplished by the use of electrodes implanted either into normal myocardium or scar tissue on the myocardium. Stimulation through scar tissue requires several times the power necessary for stimulation through normal myocardium, but both are well within the limit of standard, commercially available, transistorized pacemakers. Failure of stimulation of the ventricle was not due to excessive scarring. Failure of stimulation was in every instance due to wire breakage or actual loss of contact between the wire and the myocardium.

STUDIES ON STARLING'S LAW OF THE HEART. IX. THE EFFECTS OF IMPEDING VENOUS RETURN ON PERFORMANCE OF THE NORMAL AND FAILING HUMAN LEFT VENTRICLE

The acute circulatory responses to impeding venous return to the heart by the inflation of a balloon in the inferior vena cava were determined in 14 patients undergoing left heart catheterization. In the five patients without clinical or hemodynamic evidence of impaired left ventricular function, left ventricular end-diastolic pressure fell, and the decrease was accompanied by reductions in the cardiac index, left ventricular stroke volume, and left ventricular stroke work. In nine patients with impaired left ventricular function, directionally similar responses were noted, although the left ventricular function curves relating left ventricular end-diastolic pressure to left ventricular stroke work were generally flatter and lower than those in the patients without left ventricular disease. In none of the patients did a significant increase in cardiac index, stroke volume, or left ventricular stroke work occur during inflation of the balloon. It is concluded that the Starling relationship appears to operate in a directionally similar manner both in the normal and the depressed human left ventricle, and that the left ventricles of patients with impaired function are not on a descending limb of the curve. However, a descending limb of the left ventricular Starling curve may become apparent when an additional work load is imposed on the diseased ventricle.

BUNDLE-BRANCH BLOCK: AN EPIDEMIOLOGIC STUDY

As part of an inclusive health examination of the population of Tecumseh, Michigan, electrocardiograms were recorded from 8,641 persons of all ages, 87.9 per cent of those living in the study area. Eighteen persons, twelve men and six women, had complete right bundle-branch block and a like number, composed of six men and 12 women, had left. All affected persons were past 20 years of age and 67 per cent were past 60.

Twenty-five of the 36 persons had no clinical evidence of valvular heart disease, angina pectoris, or myocardial infarction.

Bundle-branch block occurred mostly in the older age groups where there was a high prevalence of hypertension, hypercholesteremia, hyperglycemia, and obesity, although these conditions were no more frequent among the affected persons than among others of the same age and sex.

DEMONSTRATION OF PERIPHERAL CONDUCTION SYSTEM IN HUMAN HEARTS

The peripheral conduction system was demonstrated grossly by iodine staining in a normal newborn heart and in one with a muscular ventricular septal defect. Staining of the conduction system was unsuccessful in a third heart when attempted over 2 hours after death. The left ventricular conduction system was easily visualized; however, the arborizations of conduction tissue over the right ventricular free wall endocardium were demonstrated poorly.

TRANSIENT BUNDLE-BRANCH BLOCK

Fourteen patients with transient bundle-branch block have been personally studied. All but one suffered from ischemic heart disease commonly accompanied by hypertension. The conduction defect was observed to appear during acute infarction, attacks of prolonged chest pain, and episodes of left ventricular failure. Not infrequently, however, the appearance and disappearance of bundle-branch block was unaccompanied by any recognizable change in the patient's physical condition.

Bundle-branch block may revert to normal intraventricular conduction after many years. In one patient bundle-branch block disappeared on three separate occasions after having been present for over 12 months. Another patient is described in whom normal conduction returned after left bundle-branch block had been established for a record duration of 6 years.

The etiology, prognosis, and pathogenesis of transient bundle-branch block have been discussed and the practical importance of this conduction defect in the electrocardiographic diagnosis of myocardial infarction is mentioned.

THE EFFECTS OF PRONETHALOL, DICHLOROISOPRENALINE AND DISOPYRAMIDE ON THE TOXICITY TO THE HEART OF OUABAIN AND ANAESTHETICS

An intermittent infusion of ouabain, 4 mug during 30 sec every 1.5 min, regularly caused ventricular fibrillation in guinea-pigs. The beta-receptor blocking drug, pronethalol (5 mg/kg), increased the dose of ouabain required to produce extrasystoles, completely prevented fibrillation, and significantly raised the lethal dose of ouabain. Dichloroisoprenaline had similar effects, but a dose of 15 mg/kg was required. When fibrillation had already been produced by ouabain, pronethalol (3 to 4 mg) administered slowly restored a regular rhythm, but rapid injection sometimes produced cardiac arrest. As much as 20 to 25 mg/kg of pronethalol could be given to animals deeply anaesthetized with urethane or pentobarbitone, but with light chloroform or ether anaesthesia, 5 mg/kg of pronethalol caused a large fall in blood pressure and complete heart-block.

MECHANISM OF ATRIAL FLUTTER AND FIBRILLATION INDUCED BY ACONITINE IN THE DOG, WITH OBSERVATIONS ON THE ROLE OF CHOLINEGIC FACTORS

The topical application of aconitine nitrate to the right atrial appendage in the "intact" anaesthetized dog produced atrial flutter. Premature systoles with fixed coupling preceded the development of flutter. In early stages of the arrhythmia, atrial rate was irregularly irregular. Also, the form of flutter beats was similar to that of preceding premature systoles. The fibrillatory activity of acetylcholine described by earlier workers has been confirmed. Transient atrial dissociation was seen after intravenous injection or topical application of acetylcholine. The occurrence of fibrillation in the left atrium after focal application of acetylcholine has been demonstrated, while the right atrial appendage containing the ectopic focus induced by aconitine continued to flutter. Aconitine produced slow-rate flutter in dogs treated with atropine or hemicholinium; this flutter was easily distinguishable from the sinus tachycardia produced by these drugs, by recording the electrocardiogram from a direct atrial lead from the area treated with aconitine, but not from limb lead II. The importance of these findings in the interpretation of the mechanism of atrial flutter and fibrillation is discussed.