PAROXYSMAL VENTRICULAR FIBRILLATION WITH SPONTANEOUS REVERSION TO SINUS RHYTHM

Short-Coupled Idiopathic Ventricular Fibrillation: A Literature Review With Extended Follow-Up

Idiopathic ventricular fibrillation is responsible for approximately 10% of cases of aborted cardiac arrest. Recent studies have shown that short-coupled ventricular premature complexes are present at the onset of idiopathic ventricular fibrillation in 6.6%-17% of patients. The present review provided information on 86 patients with short-coupled malignant ventricular arrhythmias that were reported as case reports or small patient series during the last 70 years. In 75% of the 81 cases published during the last 40 years, extended information and follow-up (from 2.63 ± 4.5 to 10.67 ± 7.8 years; P < 0.001, between the original publication to the latest update) could be obtained from the authors. The review shows that short-coupled malignant ventricular arrhythmias occurred almost equally in males and females, at the mean age of 40 years. A tendency for later occurrence of the arrhythmia by 4 years was observed in females. A prior history of syncope was noted in 45.3% of the patients, whereas arrhythmic storm occurred in 42% at presentation. The most common mode of revelation of short-coupled malignant ventricular arrhythmias was syncope (53.5%), followed by aborted cardiac arrest (26.7%) and recurrent arrhythmic event after prior implantable-cardioverter defibrillator implantation for idiopathic ventricular fibrillation (17.4%). For the first time, short-coupled malignant arrhythmias exhibiting "not-so-short" coupling intervals (≥350 ms) were found in a significant proportion of patients (17.4%). During long-term follow-up, quinidine yielded a slightly higher success rate in arrhythmia control than ablation. Larger studies are necessary to assess the best strategy for the management of this potentially lethal arrhythmia.

Autoresuscitation (Lazarus phenomenon) after termination of cardiopulmonary resuscitation - a scoping review

BACKGROUND

Autoresuscitation describes the return of spontaneous circulation after termination of resuscitation (TOR) following cardiac arrest (CA). We aimed to identify phenomena that may lead to autoresuscitation and to provide guidance to reduce the likelihood of it occurring.

MATERIALS AND METHODS

We conducted a literature search (Google Scholar, MEDLINE, PubMed) and a scoping review according to PRISMA-ScR guidelines of autoresuscitation cases where patients undergoing CPR recovered circulation spontaneously after TOR with the following criteria: 1) CA from any cause; 2) CPR for any length of time; 3) A point was reached when it was felt that the patient had died; 4) Staff declared the patient dead and stood back. No further interventions took place; 5) Later, vital signs were observed. 6) Vital signs were sustained for more than a few seconds, such that staff had to resume active care.

RESULTS

Sixty-five patients with ROSC after TOR were identified in 53 articles (1982-2018), 18 (28%) made a full recovery.

CONCLUSIONS

Almost a third made a full recovery after autoresuscitation. The following reasons for and recommendations to avoid autoresuscitation can be proposed: 1) In asystole with no reversible causes, resuscitation efforts should be continued for at least 20 min; 2) CPR should not be abandoned immediately after unsuccessful defibrillation, as transient asystole can occur after defibrillation; 3) Excessive ventilation during CPR may cause hyperinflation and should be avoided; 4) In refractory CA, resuscitation should not be terminated in the presence of any potentially-treatable cardiac rhythm; 5) After TOR, the casualty should be observed continuously and ECG monitored for at least 10 min.

Self-termination of ventricular fibrillation during transport by emergency medical service

Ventricular fibrillation (VF) is usually sustained, and it typically results in death unless electrical defibrillation is successfully performed within minutes. Although VF has been reported to spontaneously occur in vivo in some animal models and a few cases of self-terminating VF have been documented in clinical practice, no such case has been previously reported involving out-of-hospital emergency medical service(EMS) personnel. We report a case of self-terminating VF due to ST segment elevation myocardial infarction that was documented by continuous electrocardiogram (ECG) strip monitoring. A 70-year-old woman was transported to the emergency department by EMS due to chest discomfort. The EMS personnel monitored her by ECG using an automated external defibrillator with a 3-limb lead. During transport, she developed VF, which persisted for 43 seconds. Chest compression and defibrillation were not applied. The VF self-terminated, after which the patient promptly awoke. Emergency coronary angiography was performed,and a total occlusion of the middle left circumflex coronary artery was treated by percutaneous coronary intervention. Since then, no symptomatic arrhythmia or ST-segment change was detected by continuous ECG monitoring. The patient was discharged home without any sequelae on the fourth hospital day.

Transient ventricular fibrillation. A clinical case report

Self-terminating ventricular fibrillation (VF) was recorded in a 42-year-old woman without coronary artery or structural heart disease. Reviewing the scientific literature, we found that this type of VF had appeared in vivo in some animal models but was sparsely described in clinical practice. This most unusual case shows that potentially lethal arrhythmias may be self-terminating.

Factors determining spontaneous ventricular defibrillation

Ventricular fibrillation (VF) is defined as a sustained, fatal reentrant arrhythmia that never terminates spontaneously and requires artificial electrical defibrillation. For many years it was believed that spontaneous ventricular defibrillation (SVD) appears only in hearts with small muscle mass that cannot continue fibrillating. SVD appears even in humans, and some drugs transform sustained VF into a transient VF, reverting spontaneously into sinus rhythm. The present criteria for VF were based on the wavelength theory. Accordingly, the persistence of fibrillation depends on the wavelength of the reentrant impulse. Fibrillation can be sustained only if the reentrant circuit is smaller than the length of the refractory tissue. Following this assumption, lengthening of action potential duration (APD) and effective refractory period (ERP) were accepted as factors that determine antiarrhythmic defibrillating ability. The results of recent studies questioned this postulation and clearly showed that prolongation of APD is proarrhythmic. In examining the differences between transient and sustained VF in various mammals, it was hypothesized that SVD requires a high degree of myocardial gap junctional coupling and synchronization. Thus, any compound or condition that enhances intercellular coupling and synchronization or attenuates the dispersion of refractoriness can facilitate SVD. Because one of the main factors involved in intercellular uncoupling is an excess concentration of cytoplasmic free Ca(2+), it seems plausible that a compound that protects against Ca(2+) overload and has a positive inotropic effect can serve as a potent defibrillating agent. Evaluation of the anti-arrhythmic properties of various defibrillating compounds showed that a defibrillating drug has the ability to prevent or to attenuate Ca(2+) overload. By decreasing increased diastolic Ca(2+) concentration, they enhance intercellular coupling and synchronization, and consequently facilitate SVD, while prolongation of APD or ERP facilitates the appearance of arrhythmias and VF. The novel approach based on upregulation of intercellular coupling to enhance synchronization and on decreased dispersion of refractoriness without prolongation of APD should be taken into consideration in future development of new potent cardioprotective-defibrillating drugs.

Improved nonthoracotomy defibrillation based on ventricular fibrillation waveform characteristics

The heart has been shown to be more susceptible to defibrillation at a higher absolute ventricular fibrillation voltage (AVFV) measured on the surface ECG. This study evaluated in a closed-chest canine model (n = 7) the clinical applicability of using a real-time VF waveform analysis system using an electrogram defined between the generator can and an RV endocardial electrode. Under fluoroscopic guidance, superior vena cava and RV spring coil catheter electrodes were inserted through the external jugular vein. A subcutaneous patch was placed on the left chest. A two-parameter tracking algorithm was used to dynamically identify the high AVFV area, and a biphasic shock was triggered synchronously at the next peak. The performance of this new peak shock method (PSM) was compared to the conventional method of shocking at a fixed time in 175 paired trials. Five shocks per voltage and five voltages per animal were randomized between the two methods to permit the generation of sigmoidal dose response curves for the estimation of 50% (E50), 75% (E75), and 100% (E100) success energies. Induction of VF and discharge voltage were kept constant while energy delivered, impedance (R), and AVFV at the point of shock were measured. Energy (8.63 +/- 0.40 vs 8.64 +/- 0.40 J), R (48.60 +/- 0.30 vs 48.59 +/- 0.30 omega), and current (7.50 +/- 0.18 vs 7.51 +/- 0.16 A) were not significantly different between trials for either the conventional or the PSM. The time from the onset of VF until the defibrillation shock was 7.98 +/- 1.44 seconds. Higher overall successes (46.3% vs 33.1%; P < 0.01) and lower E50, E75, and E100 were observed for the PSM. Finally, the significantly higher AVFV (9.12 +/- 0.32 vs 4.73 +/- 0.34 mV; P < 0.0001) with the peak method suggests that the high VF voltage could be detected as it occurred in real-time. The improved defibrillation success supports the use of this method for nonthoracotomy defibrillation.

Defibrillation success is associated with myocardial organization. Spatial coherence as a new method of quantifying the electrical organization of the heart

The relationship between the degree of electrical organization of ventricular fibrillation (VF) and defibrillation success was investigated in this study using a new technique to quantify organization--spatial coherence. This technique employs the use of the magnitude-squared coherence spectrum to analyze multichannel electrograms obtained during a cardiac mapping study. Magnitude-squared coherence values for all possible pairs of electrograms recorded from an epicardial plaque consisting of 112 electrodes were computed. Average coherence was plotted versus electrode separation distance, and the data were fit with an exponentially decaying curve. Two parameters indicative of myocardial organization were extracted from the curve. The coherence length (d) was defined as the distance (mm) at which the average coherence dropped to a given level, and the coherence strength was defined as the average coherence value at a given distance. Higher values for these parameters were hypothesized to indicate higher levels of organization. The spatial coherence technique was tested previously in a canine study of ventricular fibrillation (VF) and normal sinus rhythm, and the results suggested that spatial coherence parameters may be used to compare cardiac rhythms in terms of their organization. To test the hypothesis that organization is related to defibrillation success, 164 mapping sessions recorded during repeated VF induction and defibrillation trials using a monophasic waveform were performed in a close-chested canine study (n = 9) using a fixed energy and VF duration (10 seconds). Three coherence lengths and five coherence strengths were calculated for each VF episode. Results using a two-way analysis of variance with blocking between dogs showed that all of the coherence length and three of the coherence strength parameters were higher for those VF episodes that were successfully defibrillated than for those that were not (P < .05). Energy delivered and transmyocardial impedance were not significantly different between the groups. The authors conclude (1) the organization of a VF episode, as reflected in the spatial coherence parameters, is related to defibrillation success and may be partially responsible for the probabilistic nature of defibrillation and (2) the spatial coherence technique provides a means of quantifying myocardial electrical organization and is an important experimental tool that may be used to obtain a better understanding of VF and its termination.

How can we facilitate spontaneous termination of ventricular fibrillation and prevent sudden cardiac death? A working hypothesis

Ventricular fibrillation (VF) is one of the most life-threatening arrhythmias encountered in daily clinical practice. Its occurrence cannot be completely prevented by currently used antiarrhythmic drugs, and, in most instances, VF is sustained and leads to the patient's death unless a successful DC defibrillation is applied. However, spontaneous reversion of VF to sinus rhythm has been observed in various animals and occasionally even in man. Hence, facilitation of self-ventricular defibrillation must be explored as an alternative therapeutic approach. In experimental studies using several mammalian species, we have found that self ventricular defibrillation requires a good intercellular coupling and well synchronized electrical activity in the ventricles, which, in untreated animals, depend on their myocardial catecholamine content. It can then be hypothesized that any agent that elevates the catecholamine level during VF would facilitate spontaneous ventricular defibrillation, and drugs inhibiting extraneuronal catecholamine reuptake have indeed been shown to possess this ability. It is suggested that their effects are mediated by an increase in the intracellular cAMP level, and any compounds sharing this property could well prove efficacious in making VF transient and in reducing sudden cardiac death.

The role of catecholamines on intercellular coupling, myocardial cell synchronization and self ventricular defibrillation

Ventricular fibrillation (VF) is one of the most life threatening events. Although in humans VF is generally sustained (SVF) requiring artificial defibrillation, in various mammals and in some cases in humans VF terminates by itself, reverting spontaneously into sinus rhythm. Since VF is one of the main causes of sudden death, one of the important clinical problems today is if and how we can transform the fatal SVF into a self limited transient one (TVF). From electrophysiological studies carried out on anaesthetized open chest animals, we have found that TVF requires a high degree of intercellular coupling and synchronization. Cardiac myocytes are electrically coupled with adjacent cells. The intercellular coupling is a focus of low electrical resistance which allows rapid transmission of electrical impulses between cells. Any decrease in intercellular coupling decreases the ability of the heart for self defibrillation. The cell-to-cell coupling decreases with age, ischemia, VF and variations in physiological conditions probably due to an increase in intercellular resistance (Ri), widening in the internexal gaps, decrease in electrotonic space constant (lambda) etc. All of these factors are known to be affected by intracellular concentration of free Ca++ ([Ca++]). On the basis of studies carried out on various mammals at different ages, we hypothesized that the ability of the heart to defibrillate depends on the cardiac catecholamine level [CA], during VF. This hypothesis is supported by the facts, known from the literature, that increase in [CA] decreases intracellular free Ca++ concentration, decreases Ri and increases lambda.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural-functional basis for spontaneous termination of ventricular fibrillation in mammals

Ventricular fibrillation in humans is generally sustained (SVF), but it can be also transient (TVF), reverting spontaneously to sinus rhythm. In previous studies we have shown that: a) TVF appears in all young mammals and varies according to age and species; b) it requires synchronization of myocardial cell activity; c) infusion of certain drugs may change the type of ventricular fibrillation from sustained into transient. We hypothesize that the synchronization required for TVF depends on the electrical conductivity of intercellular structures. These intercellular couplings differ among species and decrease with age. Comparison between the inter- and intra-specific variations of intercellular connective structure described in the literature with the type of ventricular fibrillation found in our previous studies on various animals of different ages showed a clear relationship between these histological variations and the changes in the type of ventricular fibrillation. In this study we examined intercellular connective structures ultrastructurally in 3 groups of cats: a. control, untreated cats exhibiting sustained ventricular fibrillation; b. untreated cats exhibiting transient ventricular fibrillation; c. treated cats exhibiting sustained ventricular fibrillation before infusion of a defibrillating drug and transient ventricular fibrillation thereafter. It was found that the intercellular connective structure in cats exhibiting sustained ventricular fibrillation differs significantly from that in cats exhibiting transient fibrillation. In hearts exhibiting sustained ventricular fibrillation, many intercellular connective structures are widened and the degree of widening is pronounced, forming a continuous line, while in hearts exhibiting transient ventricular fibrillation the widened junctions are rare and isolated and the widening is relatively small. These preliminary results strongly support our above-mentioned hypothesis, providing an explanation for the origin of transient ventricular fibrillation and a tool for the development of new defibrillating drugs.

Ethmozine and ethacizine--new antiarrhythmic drugs with defibrillating properties

Ventricular fibrillation (VF) is a life-threatening arrhythmia that leads to death unless electrical defibrillation is applied in time. Recent publications indicate that VF can be either sustained (SVF), requiring electrical defibrillation, or transient (TVF), reverting spontaneously into sinus rhythm. Since VF cannot be totally prevented by drugs, a new antiarrhythmic therapeutic approach has been proposed: drug-induced enhancement of the ability of the heart to defibrillate by itself. In this study we examined the defibrillating potency of two antiarrhythmic phenothiazines, ethmozine (ETM) and ethacizine (ETA), as well as their effects on catecholamine uptake and on the electrophysiological properties of the myocardial cell membrane. The antiarrhythmic-defibrillatory activity was examined in cats; the inhibitory effect on [3H]-norepinephrine (NE) uptake was examined in rat brain synaptosomes, and the electrophysiological membrane effects were examined by microelectrode recordings in perfused strips of heart ventricle from guinea-pigs. The results indicate that: 1. ETA exhibits similar but stronger antiarrhythmic-defibrillating and NE reuptake inhibitory effects than ETM; 2. ETA at 10-6 M decreases ventricular conduction time and increases Vmax while ETM at this concentration does not change them; 3. The defibrillating ability of the drugs can be related to their inhibitory potency on NE reuptake. We suggest that the risk of sympathomimetic arrhythmogenicity is prevented by the previously described, membrane stabilizing Class 1 antiarrhythmic properties of these drugs.

Ventricular defibrillating properties of catecholamine uptake inhibitors

Ventricular fibrillation (VF) is a fatal event in humans unless electrical defibrillation is applied within minutes. Recent publications describe spontaneous termination of VF in various animals and even in humans. Certain drugs can transfer a fatal, sustained VF (SVF) into a self-terminating, transient VF (TVF). Based on results obtained in animals of various species and ages, we have suggested that the occurrence of TVF requires a high cardiac catecholamine level at the time of VF. According to our hypothesis, drugs which decrease catecholamine reuptake by the sympathetic nerve terminals will increase the ability of the heart ventricles to defibrillate spontaneously. In the present study, we examined the effects of desipramine, maprotiline, mianserin, iprindole, cocaine and amphetamine on the type of VF in cats exhibiting SVF prior to the treatment. The results show that the ability of these compounds to transfer SVF to TVF is closely related to their potency to inhibit catecholamine reuptake. The establishment of the catecholamine related mechanisms of TVF may lead to the development of a new class of antiarrhythmic-defibrillatory drugs.

The transition to ventricular fibrillation induced by reperfusion after acute ischemia in the dog: a period of organized epicardial activation

Ventricular fibrillation was induced in eight of 10 open-chest dogs by reperfusion after a 15-minute occlusion of the proximal circumflex coronary artery. Simultaneous recordings were made from 27 epicardial electrodes spaced over both ventricles. Analysis of the initial 1.5--2.5 seconds of the transition from sinus rhythm or ventricular tachycardia to fibrillation revealed that ventricular activation occurred in an orderly, rapidly repeating sequence in all hearts. Each activation from arose near the border of the ischemic-reperfused region and passed across the nonischemic portion of the ventricles to the opposite side of the heart as a single, organized wavefront. As the arrhythmia progressed, the time between the appearance of successive activation fronts on the epicardium decreased. Concurrently, the time for each activation front to traverse the ventricles increased. The stimulation increase in rate of appearance and decrease in conduction velocity for each successive cycle resulted in overlapping cycles in which a new activation front arose from the ischemic-reperfused region before the previous front terminated over the right ventricle. The overlap between successive activation fronts increased as the arrhythmia continued. Thus, ventricular activation during the transition to ventricular fibrillation arose near the border of the ischemic-reperfused region and was organized as it passed across the nonischemic tissue, but the body surface ECG appeared disorganized because of variable spacing between successive, coexistent activation fronts.

Resuscitation of patients with ischaemic heart disease before admission to hospital

This paper provides data about the efficacy of resuscitation before hospital admission of 139 patients with myocardial infarction. Successful resuscitation was effected in 43 (30.9 percent) patients, of whom 29 (20.9 percent) survived and were discharged from hospital. An organizational scheme is given for resuscitation measures before admission, in which the following teams participate: premedical, general first-aid ambulance team and specialized first-aid cardiological team (Mobile Coronary Care Unit, MCCU - definition of World Health Organization). The effectiveness of resuscitation depends upon the patient's age, and the presence and degree of circulatory insufficiency before clinical death. It proved possible to revive successfully patients of advanced age and with proceding mild or moderate acute circulatory insufficiency. Resuscitation was not successful in patients with preceding severe circulatory insufficiency. Blood electrolytes were studied in the post-resuscitation period. There was a statistically significant decline in plasma potassium ion concentration. Potassium salts should be introduced in the form of a polarizing mixture, especially to patients with an irregular cardiac rhythm in the post-resuscitation period. Problems of intracardiac injections of drugs, intubation, and pervenous electric pacing in patients with myocardial infarction during resuscitation are discussed. It has been concluded that the optimum form of resuscitation before admission of patients with myocardial infarction involves rendering maximal aid at the place of occurrence of the infarction.