Cardiac arrhythmias in acute myocardial infarction. II. Incidence of the common arrhythmias with special reference to ventricular tachycardia

Continuous electrocardiographic monitoring in patients with sickle-cell anemia during pain crisis

Electrocardiographic studies in patients with sickle-cell anemia have been performed during the normal resting state with routine twelve-lead ECGs. We studied 30 patients with sickle-cell disease in acute crisis with 24-hour continuous electrocardiographic monitoring. The standard ECG demonstrated a high incidence of abnormalities, but only three patients had arrhythmias. These findings contrasted sharply with the results of continuous monitoring, during which arrhythmias were detected in 24 of 30 patients. They were fairly evenly split between atrial (60%) and ventricular (67%). Nine of the patients had "complex arrhythmias" including two with episodes of ventricular tachycardia. Seventeen patients subsequently underwent equilibrium gated-blood pool scans. Eight patients had abnormal contractility and tended to have more arrhythmias on monitoring than those with normal contractility. Thus, continuous electrocardiographic monitoring of sickle-cell patients during crisis revealed a higher incidence of arrhythmias than previously thought.

Superiority of 24-hour outpatient monitoring over multi-stage exercise testing for the evaluation of syncope

Twenty-four hour outpatient monitoring was compared with maximum multi-stage Treadmill exercise testing for the detection of dysrhythmias producing syncope or near syncope in 119 patients. All patients had cardiovascular disorders; only 21% had coronary artery disease. Patients with obvious cause of syncope and/or significant dysrhythmias by resting electrocardiograms (ECGs) were excluded. A significant dysrhythmia was found which was considered the probable cause of syncope or pre-syncope in 76 patients (64%). A non-cardiac cause was found in tachycardia, exercise testing identified only patients with complex ventricular dysrhythmias and missed 64% of these. Overall, dysrhythmias were found by ambulatory monitoring alone in 63 patients, by exercise testing alone in only three, and by both in 10. It is concluded that: 1) in the majority of patients with syncope or pre-syncope suspected to be of a cardiac origin, a dysrhythmia can be found; 2) ambulatory monitoring is far superior to exercise testing for detection of dysrhythmias; 3) exercise testing increases the yield for complex ventricular dysrhythmias.

Exercise testing and portable ECG recording in arrhythmia-prone patients

To detect transient arrhythmias or conduction disturbances, 200 patients with the symptoms of palpitations, syncope or dizziness, and patients with coronary heart disease, angina pectoris, arrhythmias or conduction disturbances on resting 12-lead electrocardiogram, were studied by submaximal treadmill exercise and portable Holter recording. Thirty-nine patients (19.5%) had arrhythmias on the resting 12-lead ECG, 136 patients (68%) showed arrhythmias either on treadmill or Holter recording or both. Eighty-nine patients (44.5%) showed arrhythmias on exercise, while 123 patients (61.5%) had rhythm or conduction disturbances on Holter recording. Twenty-two patients (11%) had arrhythmias only on treadmill walking, while 68 (34%) had arrhythmias only with the Holter. In six patients different arrhythmias was noted by each method. Although the Holter recording technique affords a higher yield of recording transient arrhythmias than did exercise testing, both methods are useful and complementary in evaluating the ambulatory patients suspected of having rhythm or conduction disturbances.

Subendocardial origin of ventricular arrhythmias in 24-hour-old experimental myocardial infarction

In 12 anesthetized open-chest dogs, ventricular epicardial activation maps were constructed and electrograms were recorded from the bundle of His, left bundle branch, and subendocardial Purkinje fibers 24 hours following Harris 2-stage ligation of the left anterior descending coronary artery. All animals developed ectopic ventricular depolarizations and/or ventricular tachycardia. The earliest area of epicardial activation was located along the border of the infarct in the left ventricle in all animals. Bipolar recording from various levels of the conduction system and ventricular myocardium revealed that the earliest recorded electrical activity originated in subendocardial Purkinje fibers which had survived the acute myocardial infarction. The origin of these arrhythmias was further studied by pacing through the electrode which had recorded the early Purkinje activity and comparing the surface ECG and activation sequence with that of the spontaneous rhythm. These data tend to support the hypothesis that ventricular arrhythmias occurring 24-72 hours following acute myocardial infarction have their origin in the subendocardial Purkinje network which has survived the infarction.

Incidence and description of accelerated ventricular rhythm complicating acute myocardial infarction

One hundred and nineteen episodes of accelerated ventricular rhythm (less than 125/min) were noted in 37 patinets with acute myocardial infarction during a 1 year period. The incidence was 12.7 per cent. Twenty-seven episodes of fast ventricular tachycardia (less than 125/min) were noted in 16 of these patients. Eighteen patients had anterior myocardial infarction and 19 inferior myocardial infarction. The mechanism of onset of accelerated ventricular rhythm was classified as escape in 65 episodes. Ventricular premature beats were noted close to episodes of accelerated ventricular rhythm in 31 patients and fast ventricular tachycardia in 14 patients. The morphology of accelerated ventricular rhythm was similar to the ventricular premature beats in 27 patients and similar to the fast ventricular tachycardia in 12. In 11 patinets the morphology of ventricular premature beats, accelerated ventricular rhythm and fast ventricular tachycardia were all the same. In six patients the coupling time of the ventricular premature beats and the onset of the accelerated ventricular rhythm were the same. In seven patients the morphology of the accelerated ventricular rhythm and fast ventricular tachycardia were the same, and the rate of the accelerated ventricular rhythm was exactly half that of the fast ventricular tachycardia. There were three deaths due to shock and heart failure. Three episodes of fast ventricular tachycardia progressed to ventricular fibrillation and were successfully cardioverted. It is concluded that accelerated ventricular rhythm and fast ventricular tachycardia were all the same. In six patients the coupling time of the ventricular premature beats and the onset of the accelerated ventricular rhythm were the same. In seven patients the morphology of the accelerated ventricular rhythm and fast ventricular tachycardia were the same, and the rate of the accelerated ventricular rhythm was exactly half that of the fast ventricular tachycardia. There were three deaths due to shock and heart failure. Three episodes of fast ventricular tachycardia progressed to ventricular fibrillation and were successfully cardioverted. It is concluded that accelerated ventricular rhythm is a relatively common complication of both anterior and inferior myocardial infarction. The high incidence of concomitant fast ventricular tachycardia, the frequency of ventricular premature beats with similar morphology and coupling time, and the instances of two arrhythmias having common rate multiples, suggest that at least in some instances accelerated ventricular rhythm may represent an ectopic focus with exit block.

Spontaneous and induced cardiac arrhythmias in subendocardial Purkinje fibers surviving extensive myocardial infarction in dogs

The cellular electrophysiological mechanisms underlying the ventricular arrhythmias that accompany myocardial infarction were studied in isolated, superfused infarcted myocardium excised from dogs previously subjected to a two-stage ligation of the anterior descending coronary artery. Ventricular arrhythmias frequently occurred in the intact heart 24 hours after coronary occlusion. Surviving subendocardial Purkinje fibers in infarcts excised at this time were highly arrhythmic when they were studied with intracellular microelectrodes in vitro. These arrhythmias consisted of rapid, repetitive depolarizations and occurred spontaneously or could be induced by premature electrical stimulation. Premature stimulation also resulted in single unstimulated responses. In such instances, premature impulses conducted extremely slowly through the infarcted region where surviving Purkinje fiber action potential durations were extraordinarily prolonged. Conduction block at some sites in the infarct caused phenomena which were interpreted as reentrant beats. Some surviving subendocardial Purkinje fibers in the infarct demonstrated spontaneous diastolic depolarization and appeared to function as pacemakers in the absence of electrical stimulation. In some instances, these fibers constituted typical parasystolic foci, demonstrating both entrance and exit block. These results suggest that subendocardial Purkinje fibers which survive in an infarct may be the site of origin of some of the ventricular arrhythmias that accompany myocardial infarction.

Electrophysiologic studies during accelerated idioventricular rhythms

Accelerated idioventricular rhythms (AIVR) are ectopic ventricular rhythms with rates intermediate between idioventricular escape rhythms (30 to 40/min) and ventricular tachycardia (120 to 180/min). Differentiation of AIVR from supraventricular arrhythmias rests primarily on demonstration of their ventricular origin. His bundle electrograms (HBE) were recorded in four patients during AIVR. HBE verified the idioventricular nature of the ectopic rhythm and excluded supraventricular rhythm with aberration as a cause. In addition, they permitted the recognition of normally conducted sinus beats, fusion beats, and idioventricular beats. The pacemaker site for the AIVR was below the bundle of His. AIVR became manifest when the heart rate was slowed by increasing vagal tone, premature atrial stimulation, and high degree atrioventricular (A-V) block. AIVR could be suppressed and 1:1 A-V conduction established by increasing the atrial rate with atropine or by atrial pacing.

Catheterization of left ventricle in acutely ill patients

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Idioventricular rhythm complicating acute myocardial infarction

The incidence, natural history, prognosis, and electrocardiographic characteristics of idioventricular rhythm complicating acute myocardial infarction are described. It occurred as a transient arrhythmia nearly always within 24 hours of infarction in 61 (8%) of 737 patients, and was characterized by paroxysms of between 6 and 20 beats with widened bizarre QRS complexes at a rate of between 60 and 90 a minute. Most cases showed fusion beats and P waves dissociated from the QRS complexes, and in many cases idioventricular rhythm started during the slow phase of sinus arrhythmia. Though it usually occurred in patients with moderately severe transmural infarcts, the incidence of ventricular fibrillation and subsequent mortality was no greater than in patients with infarcts of equivalent severity who did not have idioventricular rhythm. It is concluded that this rhythm is a common and relatively benign arrhythmia complicating myocardial infarction, and that it should be distinguished from ventricular tachycardia.

Day-to-day changes in coronary hemodynamics secondary to constriction of circumflex branch of left coronary artery in conscious dogs

The studies were carried out in four dogs. The effects of applying ameroid constrictors to the circumflex branch were observed on the circumflex blood flow, circumflex and peripheral circumflex pressures, circumflex reactive hyperemia and aortic-circumflex pressure difference. Recordings were successfully made for periods of 16 to 64 days. During this time the circumflex branch became completely occluded in three of the dogs. The circumflex blood flow remained in the normal range until reactive hyperemia (following a 10- to 12-second occlusion of the circumflex branch) almost disappeared; the flow then decreased to zero in 5 to 10 days. Although there was some rise in mean peripheral circumflex pressure and aortic-circumflex pressure difference before circumflex blood flow decreased, the major rise in these variables occurred only when flow and reactive hyperemia became markedly decreased. The maximum rate of rise of mean peripheral circumflex pressure varied from 6 to 15 mm Hg/24 hours. The experiments indicate that a severe degree of coronary insufficiency precedes a rise in mean peripheral circumflex pressure to 60 to 70 mm Hg. We interpret such increments in mean peripheral circumflex pressure to mean that large collaterals must be open; the studies with injection of Schlesinger mass confirmed this interpretation.