Cardiac Electrical Instability Research Articles

Infants with apparent life threatening events. Cardiac rhythm and conduction.

The role of cardiac dysrhythmias in the pathogenesis of Sudden Infant Death Syndrome (SIDS) is uncertain, but there have been several reports of infants with Apparent Life Threatening Events (ALTE) due to significant dysrhythmias. To further characterize the cardiac rhythm and conduction of these "at-risk for SIDS" infants, we performed 24-hour continuous (Holter) electrocardiograms on 100 full term, healthy infants with ALTE. Sixty-two patients (62%) had one or more dysrhythmias on Holter monitor. Twenty-five patients (25%) had premature ventricular depolarizations (PVD), including five with couplets. Thirty (30%) had QTc greater than 2 SD above the mean, and, of these, 40 percent had PVD's. Fifteen (15%) had premature atrial depolarizations and 39 (39%) had evidence of moderate or marked sinus node irregularity. There was no prexcitation, supraventricular tachycardia, ventricular tachycardia, or atrioventricular block. Two patients with marked sinus node dysfunction were treated with propantheline and did well. All patients were monitored at home, with no deaths or clinically significant dysrhythmias on follow-up (1-32 months (mean = 18]. In summary, when Holter monitoring was performed, a high incidence of dysrhythmia was found in infants with ALTE. Most dysrhythmias were clinically insignificant. The incidence of ventricular dysrhythmias and long QTc are consistent with previously advanced theories of cardiac electrical instability in some of these patients, but no patient with ventricular dysrhythmias required therapy. The incidence of sinus node dysfunction requiring therapy was 2 percent. Although Holter monitoring of infants with ALTE only infrequently determines therapy, it may provide data linking theories of cardiac etiology of SIDS with actual clinical events.

Electrical alternans and cardiac electrical instability.

We investigated the relationship between electrical alternans and cardiac electrical stability in a series of 20 dog experiments and in a pilot clinical study. Electrical alternans was detected in both the QRS complex and the ST-T wave by use of a novel multidimensional spectral technique. The magnitude of the alteration was expressed as the alternating electrocardiographic morphology index (AEMI), expressed as parts per million of waveform energy. Electrical stability in the dog preparations was assessed via the ventricular fibrillation threshold measurement, and in the clinical studies via programmed stimulation. In 10 dog experiments, systemic hypothermia resulted in a 60% decrease in ventricular fibrillation threshold (VFT) (p less than .0001) and a significant increase in both AEMI(QRS) form 3.7 +/- 3.0 to 1448 +/- 548 (p less than .0001) and AEMI(ST-T) from 43.9 +/- 18.4 to 19,178 +/- 5579 (p less than .0001). In 10 dog experiments, transient coronary artery ligation also resulted in a 60% decrease in VFT (p less than .0001), an increase from 76.3 +/- 46.5 to 245 +/- 11 in AEMI(QRS) (p less than .05), and an increase from 842 +/- 505 to 1365 +/- 392 in AEMI(ST-T) (p less than .002). In 119 observations in 20 animal experiments, the rank correlation between VFT and AEMI(QRS) was -.30 (p less than .001), with that between VFT and AEMI(ST-T) being -.55 (p less than .0001). In a double-blind pilot clinical trial consisting of 23 studies in 19 patients, the result of electrophysiologic testing was used as an independent measure of cardiac electrical stability. Alternation in waveform morphology identified the inducible patient population with a sensitivity of 92%, a positive predictivity of 70%, and a specificity of 50% (p less than .05). We conclude that analysis of subtle beat-to-beat variability in electrocardiographic morphology may provide a noninvasive measure of cardiac electrical stability.

Increased cardiac electrical instability concomitant with pacing induced repolarisation abnormalities.

The relation between the occurrence of repolarisation abnormalities after right ventricular pacing and spontaneous arrhythmias was investigated in 16 patients in whom the sick sinus syndrome was suspected. All patients had normal QRS complexes and T waves in the electrocardiogram before pacing and required atrial stimulation and His bundle recording for diagnostic purposes. Patients were randomised into a study group or a control group. In the eight patients in the study group right ventricular pacing was performed for 12 hours, and was followed by inversion of the T wave in surface leads II, III, aVF, and V2-V5 and lengthening of the QTc interval. The frequency and complexity of ventricular arrhythmias increased after pacing in six patients who had ventricular extrasystoles in the baseline Holter recording. As the configuration of the T wave became normal the frequency of ventricular extrasystoles returned to baseline values. In the control group of eight patients ventricular pacing was not performed after the electrophysiological study and no changes were seen in T wave configuration and in the frequency of spontaneous arrhythmias. These results suggest that the post-pacing repolarisation abnormalities reflect abnormal electrical properties of the ventricle and that in some cases they lead to increased electrical instability.

Role of the Autonomic Nervous System in the Genesis of Early Ischemic Arrhythmias

The first minutes of myocardial ischemia are accompanied by a transient phase of cardiac electrical instability with special features, known as "phase 1a." The activation of the autonomic nervous system, associated with the onset of ischemia, seems to play a major role in the genesis of phase 1a arrhythmias and is potentially responsible for their unique characteristics. In this article, the relative influence of the sympathetic and parasympathetic components of cardiac neural activity on the ventricular electrical properties during early ischemia will be discussed. To study the influence of neural activity on acutely ischemic myocardium, and to evaluate the efficacy of antiarrhythmic interventions in conditions of sympathetic hyperactivity, we developed two different experimental models.

Postoperative Arrhythmias in Patients with Congenital Heart Disease

Improvement in cardiac surgical techniques has resulted in increased longevity and improvement in the quality of life for most patients with congenital heart disease who underwent open-heart repair. At present, virtually all patients, even patients with the most complex congenital malformations, are subjected to physiologic or anatomic repair. In recent years, much attention has been focused on postoperative arrhythmias evident in this population of patients. Indeed, with increasing years of follow-up, it seems evident that ever-increasing numbers of patients who underwent surgery in infancy or childhood manifest different forms of cardiac electrical instability.

De subitaneis mortibus. XXIII. Rheumatoid arthritis and ankylosing spondylitis.

The conduction system of the heart was carefully examined at necropsy in two cases of rheumatoid arthritis and one of ankylosing spondylitis. All three patients had cardiac electrical instability and two fo the three died suddenly. The electrophysiological abnormalities of the three patients included paroxysmal atrial fibrillation in the first case, sustained atrial fibrillation with complete heart block and escape atrioventricular (A-V) junctional rhythm in the second case, and progressively increasing heart block eventually became complete in the third case. The sinus node exhibited extensive focal degeneration with and without associated inflammation in all three hearts, but the sinus node artery was not remarkably abnormal in any of these. All three hearts had important focal degenerative disease in the A-V node and His bundle, and in each of these there was marked narrowing of the local nutrient arteries, amounting to virtual occlusion in two hearts. The probable relationship of these postmortem histological findings to the electrocardiographic disturbances in each patient is discussed. Abnormalities in the cardiac conduction system of the hearts of these three patients are compared to ones previously reported for disseminated lupus erythematosus, polyarteritis nodosa, and scleroderma heart disease.

De subitaneis mortibus. XX. Cardiac electrical instability in the presence of a left superior vena cava.

Abnormalities of cardiac rhythm have been reported by others in patients with a persistent left superior vena cava. We present the histological findings from postmortem examination of the cardiac conduction system of two such patients. The first patient was a schoolboy who died suddenly and unexpectedly. His sinus node was abnormally small, his A-V node contained numerous venous lacunae and was stretched out beneath the enlarged coronary sinus, both A-V node and His bundle were dispersed in the central fibrous body in a fetal pattern, and isolated fragments of A-V nodal tissue were connected to the myocardium at the crest of the interventricular septum. The second patient complained of palpitations many months prior to surgical correction of an interventricular septal defect; his postoperative course included multiple arrhythmias and he died suddenly on the 16th postoperative day. Although his sinus node was histologically normal, the nutrient artery contained a polypoid fibromuscular mass virtually occluding its lumen; his A-V node and His bundle were also dispersed in the central fibrous body in the fetal pattern, and the A-V node contained numerous venous lacunae as well as being histologically disorganized in its cytological pattern. These anatomical findings may indicate a basis for various forms of cardiac electrical instability, and deserve consideration in the future evaluation of any patient found to have a persistent left superior vene cava, but particularly if there is clinical evidence suggesting an arrhythmia or conduction disturbance.

De subitaneis mortibus. X. Familial congential heart block.

Complete heart block was found shortly after birth in a brother and sister (not twins). Both were treated by electronic pacing because of symptoms attributable to inadequate cardiac output and electrical instability of heart. The boy has done well with his artificial pacemaker and is now six years old. His sister died of complications due in part to the large size of her pacemaker and small size of her body. At necropsy special studies of her heart included the centers for normal impulse formation and concuction. The primary abnormalities were at the junction of atrial septum with atrioventricular (A-V) node, and at the origin of the two bundle branches from the His bundle. The A-V node was isolated by collagen at all its margins except its junction with the His bundle. The proximal His bundle was essentially normal, but from that point on through the initial protions of both the left and right bundle branches there was extensive caseous degeneration which interrupted any possible conduction. These findings are discussed in relation to fetal and postnatal development of the human A-V node, and the His bundle and its branches; and in the context of a recently observed mathematical relationship between sinus rate and two forms of experimentally produced A-V junctional escape rhythms.

Distribution of autonomic nerves to the canine heart.

ARTICLESDistribution of autonomic nerves to the canine heartMP Kaye, JM Geesbreght, and WC RandallMP Kaye, JM Geesbreght, and WC RandallPublished Online:01 Apr 1970https://doi.org/10.1152/ajplegacy.1970.218.4.1025MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByStimulation of Epicardial Sympathetic Nerves at Different Sites Induces Cardiac Electrical Instability to Various Degrees17 January 2018 | Scientific Reports, Vol. 8, No. 1Myths and realities of the cardiac vagus14 August 2013 | The Journal of Physiology, Vol. 591, No. 17Quantitative analysis of parasympathetic innervation of the porcine heartHeart Rhythm, Vol. 7, No. 8Augmentation of Left Ventricular Contractility by Cardiac Sympathetic Neural StimulationCirculation, Vol. 121, No. 11DIFFERENTIAL CONTROL OF CARDIAC FUNCTIONS BY THE BRAINClinical and Experimental Pharmacology and Physiology, Vol. 33, No. 12Radiofrequency Ablation at the Coronary Sinus Ostium Interrupts the Vagal Efferent Input to the Atrioventricular Node in the Canine HeartJapanese Circulation Journal, Vol. 65, No. 7Anatomical study of the neural ganglionated plexus in the canine right atrium: Implications for selective denervation and electrophysiology of the sinoatrial node in dogThe Anatomical Record, Vol. 255, No. 3Chronotropic and dromotropic responses to stimulation of intracardiac sympathetic nerves to sinoatrial or atrioventricular nodal region in anesthetized dogs.Circulation Research, Vol. 66, No. 5Morphological study of the innervation pattern of the rabbit sinoatrial nodeAmerican Journal of Anatomy, Vol. 185, No. 1Local epicardial chemical ablation of vagal input to sino-atrial and atrioventricular regions of the canine heartJournal of the Autonomic Nervous System, Vol. 11, No. 2Hierarchy of supraventricular pacemakersThe Journal of Thoracic and Cardiovascular Surgery, Vol. 80, No. 5Carotid dP/dt as a Psychophysiological Index of Sympathetic Myocardial Effects: Some ConsiderationsPsychophysiology, Vol. 17, No. 5Intrapericardial denervation of the heartJournal of Surgical Research, Vol. 29, No. 2Effect of Adrenergic Activators and Inhibitors on the Electrical Activity of the HeartNeural effects on sinus rate and atrioventricular conduction produced by electrical stimulation from a transvenous electrode catheter in the canine right pulmonary artery.Circulation Research, Vol. 46, No. 1Cardiac dysrhythmias in the conscious dog after surgically induced autonomic imbalanceThe American Journal of Cardiology, Vol. 38, No. 2Stable T wave effects during improvement of heart rate control with biofeedbackPhysiology & Behavior, Vol. 16, No. 1Electrophysiology and pharmacology of cardiac arrhythmias IX. Cardiac electrophysiologic effects of beta adrenergic receptor stimulation and blockade. Part AAmerican Heart Journal, Vol. 90, No. 4Cardiac Innervation and Synaptic Transmission in HeartAutonomic Nervous Control of the Intrinsic Cardiac Pacemaker and Its Electronic Analogue Simulator More from this issue > Volume 218Issue 4April 1970Pages 1025-1029 Copyright & PermissionsCopyright © 1970 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1970.218.4.1025PubMed5435399History Published online 1 April 1970 Published in print 1 April 1970 Metrics