Fine Ventricular Fibrillation Research Articles

In-hospital cardiac arrest rhythm analysis by anesthesiologists: a diagnostic performance study.

In-hospital cardiac arrest is associated with high morbidity and mortality, with an overall survival rate at one year of approximately 13%. The first cardiac rhythm is often analyzed by anesthesiologist-intensivists. We aimed to determine the diagnostic performance of anesthesiologist-intensivists when distinguishing between shockable and nonshockable rhythms. We conducted a simulation-based, multicentre, prospective, observational study between May 2019 and March 2020. The responses of the participants were used to calculate individual sensitivity (defined as the proportion of decisions to shock for shockable rhythms) and individual specificity (defined as the proportion of decisions not to shock for nonshockable rhythms). The main outcome measure was the overall diagnostic performance, defined as the overall sensitivity and specificity. Secondary outcome measures were the sensitivity and specificity of participants' decisions for each type of cardiac arrest rhythm and their decision-making times. Among the 267 physicians contacted, 179 (67%) completed the test. The median [interquartile range (IQR)] overall sensitivity was 88 [79-95]% and the median overall specificity was 86 [77-92]%. Among shockable rhythms, the median [IQR] sensitivity was 100 [100-100]% for ventricular tachycardia (VT), 100 [100-100]% for coarse ventricular fibrillation (VF), and 60 [20-100]% for fine VF. The median [IQR] specificities for nonshockable rhythms were 93 [86-100]% for asystole and 83 [72-86]% for pulseless electrical activity. The median decision times ranged from 2.0 to 3.5 sec. Anesthesiologist-intensivists were quickly and effectively able to analyze rhythms in this simulation-based study. Participants' sensitivity in deciding to deliver shocks for VT and coarse VF was excellent, while specificity of their decisions for pulseless electrical activity was insufficient.

Assessment of emergency physicians’ performance in identifying shockable rhythm in out-of-hospital cardiac arrest: an observational simulation study

BackgroundEmergency physicians can use a manual or an automated defibrillator to provide defibrillation of patients who had out-of-hospital cardiac arrest (OHCA). Performance of emergency physicians in identifying shockable rhythm with...

B-PO03-207 THE SHOCKING SECRET BEHIND LEAD NOISE

We present a case of fine ventricular fibrillation (VF) misdiagnosed as right ventricular (RV) lead noise in a patient with left ventricular assist device (LVAD). To demonstrate that fine VF may be misdiagnosed as lead noise. N/A A 66 year old man with non-ischemic cardiomyopathy with Heartmate II LVAD and an Abbott/St Jude biventricular implantable cardioverter-defibrillator (ICD), permanent atrial fibrillation and prior ventricular tachycardia (VT) storm presented with complaints of multiple shocks and was found to be in fine VF. LVAD flow was at 3.2 L/min and pulsatility index (PI) was low at 1.4 indicating lack of myocardial contractility. Amiodarone was initiated and he was transferred to our center. Upon arrival, he remained in VF (Figure 1). Device interrogation revealed VT with appropriate shocks initiating the VF, and that fine VF was labelled as RV lead noise (Figure 1) and therapy withheld. He previously had Secure Sense turned off because of under sensing of VT; due to low amplitude of near field electrogram (EGM), (0.1mV), the device sensed it as RV lead noise. With LVAD support, he remained awake for 7 hours. Due to intolerance of amiodarone or sotalol therapy in the past, lidocaine was added without effect; he was then switched to procainamide drip and was externally cardioverted successfully with 300J. Instantaneously, his mean arterial pressures improved and his LVAD monitor showed a flow of 4.4 L/min and a PI of 2.4. The patient’s device appropriately recognized and shocked his initial VT. However, it has failed to recognize fine VF regardless of appropriate lead function due to low amplitude EGM. LVAD kept him alive for 7 hours.

Evaluation of out-of-hospital cardiac arrest using transesophageal echocardiography in the emergency department

BackgroundTransesophageal echocardiography (TEE) has been proposed as a modality to assess patients in the setting of cardiac arrest, both during resuscitation care and following return of spontaneous circulation (ROSC). In this study we aimed to assess the feasibility and clinical impact of TEE during the emergency department (ED) evaluation during out-of-hospital cardiac arrest (OHCA). Materials and methodsWe conducted a prospective observational study consisting of a convenience sample of adult patients presenting to the ED of an urban university medical center with non-traumatic OHCA. TEE was performed by emergency physicians following intubation. Images and clinical data were analyzed. TEE was used intra-arrest in order to assist in diagnosis, assess cardiac activity and determine CPR quality by assessing area of maximal compression (AMC), using a 4 view protocol. ResultsA total of 33 OHCA patients were enrolled over a one-year period, 21 patients (64%) presented with ongoing CPR and 12 (36%) presented with ROSC. The 4-view protocol was completed in 100% of the cases, with an average time from ED arrival to TEE of 12 min (min 3 max 30 SD 8.16). Fine ventricular fibrillation (VF) was recognized in 4 (12%) cases thought to be in asystole, leading to defibrillation, and 2 cases of pseudo-PEA were identified. Right ventricular (RV) dilation, was seen in 12 (57%) intraarrest cases. Intra-cardiac thrombus was found in one case, leading to thrombolysis. The AMC was identified over the aortic root or LVOT in 53% of cases. TEE was found to have diagnostic, therapeutic or prognostic clinical impact in 32 of the 33 cases (97%). ConclusionsTEE is feasible and clinically impactful during OHCA management. Resuscitative TEE may allow for characterization of cardiac activity, including identification of pseudo-PEA and fine VF, determination of reversible pathology, and optimization of CPR quality.

T-wave oversensing is more dependent on ICD sensitivity algorithm than lead sensing configuration

Modern implantable cardioverter defibrillators (ICD) employ dynamic sensing algorithms in order to protect against fine ventricular fibrillation without oversensing intrinsic activity. We present a patient with a Medtronic ICD who had inhibition of pacing and not inappropriate shocks due to T wave oversensing (TWOS) in both true bipolar (TB) and integrated bipolar (IB) sensing configurations. Rather than alternatives such as lead revision or programming to an unacceptably insensitive value, this was solved by exchanging for a Boston Scientific ICD. Although the literature suggests lead sensing configuration impacts TWOS, this case demonstrates ICD sensitivity algorithm may be a key determinant.

Deciphering the electrogram in ventricular fibrillation to extract physiological information

d w m e a u T m The term ventricular fibrillation (VF) is a challenging one: defining it and describing it, let alone understanding it, has been a daunting task for physiologists and clinicians. In its most basic conceptualization, VF is purely a pattern in the electrogram, rather than a pathophysiological event. Definitions in nursing, physiology, and medicine textbooks are vague and purely descriptive: “. . .grossly irregular undulations of varying amplitudes, contours, and rates. . . .” Such definitions contain little insight, but have been clinically useful because they are effective in communications and interactions among clinicians, similar to the idea that “you will know it when you see it.” Although most health professionals at all levels would have little problem recognizing VF based on these vague but intuitive definitions, few could actually give a cogent description or meaningful account of the mechanisms of the underlying physiological phenomenon. To health professionals involved in sudden death resuscitation, it is obvious that not all VFs are the same, and that during the course of resuscitation efforts in individual patients, there are changes in the electrocardiographic waveform that roughly correlate with the progress of such efforts. For example, most clinicians would understand terms such as agonal fibrillation when referring to the slow fibrillatory undulations that precede asystole in failing resuscitations, particularly in comparison with the fine fibrillation patterns present at VF initiation. The terms agonal and fine are vague and gross, but effective when used in individual examples (Figure 1). Most readers will agree that VF changes during the example shown, and would correctly identify fine VF as the initial VF, and agonal VF as the final VF. Again, the pervasive paradigm of “you’ll know it when you see it,” effective in communicating but deceptive in understanding. Physiologists have attempted to correlate electrocardiographic patterns in VF with specific activation patterns and thereby mechanisms of VF, but such correlations require

Identifying fine ventricular fibrillation during cardiac arrest is difficult: Should we be just recommending defibrillation?

Identifying fine ventricular fibrillation during cardiac arrest is difficult: Should we be just recommending defibrillation?

Favourable outcome after 26 minutes of "Compression only" resuscitation: a case report

Case presentationA 49 year old man had ventricular fibrillation in his home, at room temperature, due to an ST-elevation myocardial infarction. He received Cardiac compression only resuscitation (CC-only) for 26 minutes by his wife, followed by four minutes of standard CPR by other lay persons until EMS-arrival. Gasping and moaning were observed during most of the CC-only period. The ambulance arrived at 30 minutes. The first ECG showed a fine ventricular fibrillation. Restoration of spontaneous circulation (ROSC) was achieved at 49 minutes after a total of four defibrillatory shocks. The patient recovered without any cerebral damage, and was discharged to his home after eight days hospitalization.ConclusionsThis case demonstrates that early and powerful cardiac compressions alone without rescue breaths may maintain sufficient circulation and gas exchange to prevent neurological damage for more than 25 minutes. This should be kept in mind for Emergency Medical Dispatch Centrals giving Pre-arrival instructions to bystanders.

The prohibition on shocking apparent asystole: a history and critique of the argument

A recommendation against shocking asystole has been part of the American Heart Association's Emergency Cardiovascular Care (ECC) Guidelines since 1992. The principal rationale offered then for the prohibition on shocking apparent asystole (PSAA) has since been refuted and has gradually been dropped, but the recommendation itself remains in the 2005 Guidelines. The PSAA now rests mainly on the lack of solid evidence of a survival benefit—a curious criterion given the lack of such evidence for most ECC treatment recommendations. “Occult” ventricular fibrillation and problems with distinguishing between fine ventricular fibrillation and asystole may lead to delays and omissions of potentially lifesaving shocks. No studies on the subject have been conducted since the PSAA first appeared. Removal of the PSAA from the ECC Guidelines is warranted to reopen research on this topic and support the goal of early defibrillation.

Inappropriate Analyses of Automated External Defibrillators Used During In-Hospital Ventricular Fibrillation

The use of automated external defibrillators (AEDs) has increased the number of survivors of out-of-hospital cardiac arrest. The AED has a high specificity and moderately high sensitivity in detecting rhythms appropriately treated by defibrillation. However, a few shockable rhythms are misdiagnosed by the AED. Two cases of inappropriate analyses by AEDs in patients with in-hospital ventricular fibrillation are presented. In the first case, the AED failed to recognize ventricular fibrillation because of the presence of pacemaker spikes. In the second case, the fine ventricular fibrillation and the presence of artifacts were suspected as the causes of inappropriate analysis by the AED. Both patients were resuscitated by advanced cardiovascular life support with a manual defibrillator. Trained healthcare providers should be aware of the limitations of AED in specific situations.

Waveform analysis of ventricular fibrillation to predict defibrillation

Ventricular fibrillation occurs during many cases of cardiac arrest and is treated with rescue shocks. Coarse ventricular fibrillation occurs earlier after the onset of cardiac arrest and is more likely to be converted to an organized rhythm with pulses by rescue shocks. Less organized or fine ventricular fibrillation occurs later, has less power concentrated within narrow frequency bands and lower amplitude, and is less likely to be converted to an organized rhythm by rescue shocks. Quantitative analysis of the ventricular fibrillation waveform may distinguish coarse ventricular fibrillation from fine ventricular fibrillation, allowing more appropriate delivery of rescue shocks. A variety of studies in animals and humans indicate that there is underlying structure within the ventricular fibrillation waveform. Highly organized or coarse ventricular fibrillation is characterized by large power contributions from a few component frequencies and higher amplitude. Amplitude, decomposition into power spectra, or probability-based, nonlinear measures all can quantify the organization of human ventricular fibrillation waveforms. Clinical data have accumulated that these quantitative measures, or combinations of these measures, can predict the likelihood of rescue shock success, restoration of circulation, and survival to hospital discharge. Many quantitative ventricular fibrillation measures could be implemented in current generations of monitors/defibrillators to assist the timing of rescue shocks during clinical care. Emerging data suggest that a period of chest compressions or reperfusion can increase the likelihood of successful defibrillation. Therefore, waveform-based prediction of defibrillation success could reduce the delivery of failed rescue shocks.

P HYSICIAN I NTERPRETATION AND Q UANTITATIVE M EASURES OF E LECTROCARDIOGRAPHIC V ENTRICULAR F IBRILLATION W AVEFORM

Objectives. The characteristics of the ventricular fibrillation (VF) waveform may influence treatment decisions and the likelihood of therapeutic success. However, assessment of VF as being fine or coarse and the distinction between fine VF and asystole are largely subjective. The authors sought to determine the level of agreement among physicians for interpretation of varying VF waveforms, and to compare these subjective interpretations with quantitative measures. Methods. Six-second segments of waveform from LIFEPAK 300 units were collected. Fifty segments, including 45 VF and five ventricular tachycardia (VT) distracters, were graphed to simulate rhythm strips. These waveforms were quantitatively described using scaling exponent, root-mean-squared amplitude, and centroid frequency. Thirty-two emergency medicine residents were asked to interpret the arrhythmias as VT, “coarse” VF, “fine” VF, or asystole. Their responses were compared with the qantitative measures. Interphysician agreement was assessed with the kappa statistic. Results. One thousand four hundred forty interpretations were analyzed. There was fair agreement between physicians about the classification of arrhythmias (κ = 0.39). Mean values associated with coarse VF, fine VF, and asystole differed in all three quantitative measure categories. The decision whether to defibrillate was highly correlated with the distinction between VF and asystole (Pearson chi-square = 1,170.40, df = 1, p[two-sided] < 0.001). Conclusions. With only fair agreement on the threshold of fine VF and asystole, defibrillation decisions are largely subjective and caregiver-specific. These data suggest that quantitative measures of the VF waveform could augment the current standard of subjective classification of VF by emergency care providers.

Determinants of successful transthoracic defibrillation and outcome in ventricular fibrillation.

To examine factors determining defibrillation success and outcome in patients with ventricular fibrillation. Observational prospective study of age, sex, transthoracic impedance, site of cardiac arrest, ventricular fibrillation duration and amplitude, primary or secondary ventricular fibrillation, aetiology, number of shocks to correct ventricular fibrillation, and drug treatment. A teaching hospital and a mobile coronary care unit with a physician. 70 consecutive patients (50 male, 20 female) mean age 66.5 years. Before the first countershock was administered transthoracic impedance using a 30 kHz low amplitude AC current passed through 8 cm/12 cm self-adhesive defibrillator electrode pads applied in the anteroapical position was measured. The first two shocks were 200 J delivered energy (low energy) and further shocks of 360 J (high energy) were given if required. Countershock success and outcome from ventricular fibrillation. First shock success was significantly greater in inhospital arrests (37/53) than in out-of-hospital arrests (5/17) and in those receiving antiarrhythmic treatment (13/15, 86.7%) v (27/51, 52.9%). Transthoracic impedance was similar in those who were successfully defibrillated with one or two 200 J shocks (98.7 (26) omega) and those who required one or more 360 J shocks (91.4 (23) omega). Success rates with two 200 J shocks were similar in those patients with "high" transthoracic impedance (that is, greater than 115 omega) and those with transthoracic impedance (less than or equal to 115 omega) (8/12 (67%) v 44/58 (76%]. Fine ventricular fibrillation was significantly more common in the patients with a transthoracic impedance of greater than 95 omega (41% (13/32] than in those with a transthoracic impedance less than or equal to 95 omega (13% (5/38]. Death during arrest was significantly more common in patients who needed high energy shocks (14/18 (78%] than in those who needed low energy shocks (16/52 (31%]. Multiple regression analysis identified ventricular fibrillation with an amplitude of greater than or equal to 0.5 mV, age less than or equal to 70 years, and arrests that needed less than or equal to two shocks for defibrillation, in rank order as independent predictors of survival to discharge.

Ventricular Fibrillation Complicating Acute Myocardial Infarction: Two Distinct Clinical and Electrocardiographic Features

Two distinct electrocardiographic patterns of ventricular fibrillation (VF) complicating acute myocardial infarction (AMI) were observed in 34 patients during the first 24 hours from initial symptoms. Type 1 (seven patients) was characterized by fast disorganized ventricular activity, small voltage, and no clear identifiable QRS complexes (fine VF). Type 2 (27 patients) was defined as multiform QRS configuration (greater than 300/min) with marked changes in the amplitude (polymorphous VF). Type 1 rhythm was seen mostly during the hyperacute ischemic phase, probably associated with total coronary vessel occlusion; type 2 was observed when Q waves were already present in the electrocardiogram.

Ventricular fibrillation: The importance of being coarse?

Ventricular fibrillation (VF) has been classified electrocardiographically as "fine amplitude" or "coarse amplitude" VF. It has been suggested that coarse VF represents increased "synchronization" of myocardial activation which could result in lower thresholds for defibrillation. To test the "synchronization" differences between coarse VF and fine VF, we induced VF in ten normal anaesthetized dogs. Standard limb lead and His bundle electrograms were recorded simultaneously with 12 bipolar epicardial electrograms (eight dogs) and six lead ECG (two dogs). Activation "synchronization" was assessed by calculating the standard deviations (SD) of electrogram activation times during one coarse VF and one fine VF cycle. Less synchronization during VF was indicated by a 50% larger SD (CVF: 29.3 +/- 1.1 msec, FVF: 32.6 +/- 1.6 msec) compared to ventricular pacing (21.2 +/- 1.6 msec) and 500% larger than sinus rhythm (6.5 +/- 0.5 msec). Coarse VF and fine VF did not differ. In addition, the 6-lead ECG recorded during early VF had episodes of coarse VF and fine VF occurring simultaneously. The amplitude of all electrograms diminished over 15 minutes until only fine VF could be recorded. We conclude that coarse VF does not reflect greater synchronization of activity than fine VF early in fibrillation (five minutes). Rather, differences are due to lead orientation. Later in the fibrillation bout, fine VF probably reflects metabolically induced degeneration of cellular excitability.

Safety and effectiveness of a portable external automatic defibrillator-pacemaker.

Sudden cardiac death in the community can be reduced by early resuscitation. The commonest arrhythmia encountered in this setting is ventricular fibrillation. A portable external automatic defibrillator-pacing machine for use by emergency services and laymen after basic training, has recently been introduced. This device has a tongue-abdominal pathway for sensing the electrocardiogram and respiration, as well as delivery of current. In its automatic mode, the machine cannot defibrillate unless the patient's breathing and gag reflex are virtually absent. The decision-making characteristics of the machine were defined in isolation from the patient using simulated ECG signals and recordings of arrhythmias obtained during cardiac surgery and during electrophysiological studies. The pathway was evaluated separately by attaching it to a conventional defibrillator and using it in the elective cardioversion of 15 patients. Electrode sites were examined and creatine phosphokinase (CPK) and creatinine phosphokinase isoenzyme (CPKMB) release determined following conversion. Repeated playback of the same 34 minutes of selected recordings showed that decisions were consistent 95% of the time. Automatic pacing always occurred with asystole. ECG signals less than 0.35 mV in amplitude were not recognized, but a manual override switch could be operated in those circumstances where there was failure to act upon fine ventricular fibrillation. Defibrillation of 50% of the recordings of supraventricular and ventricular tachycardia did occur, but this could not have happened in practice unless the patient was unconscious, and in addition, the operator failed to countermand this decision. The tongue-abdominal pathway yielded good recordings of the ECG.(ABSTRACT TRUNCATED AT 250 WORDS)