Hospital Ventricular Fibrillation Research Articles

Abstract 19084: The Deadly Squeeze - Coronary Vasospasm Complicated by Myocardial Infarction and Cardiac Arrest

Introduction: Acute coronary syndrome (ACS) typically results from atherosclerotic plaque rupture. However, about 6% of ST elevation Myocardial Infarction (STEMI) patients have no obstructive disease. We present a case of STEMI, diagnosed with coronary vasospasm. Hypothesis: Methods: A 54-year-old female with alcohol abuse, smoking and uncontrolled hypertension presented after an out of hospital ventricular fibrillation cardiac arrest. EKG showed anterolateral ST elevation (STE). Left heart catheterization (LHC) showed moderate to severe multi-vessel disease without a definitive culprit lesion. STE resolved. Heart team approach for revascularization was contemplated. Echocardiogram showed systolic dysfunction with ejection fraction (EF) of 25%. Patient had another cardiac arrest and EKG showed recurrent anterolateral STE. Repeat LHC showed severe vasospasm of Left anterior descending (LAD) artery and diagonal branch, which improved with intracoronary (IC) nitroglycerin. Vasospasm was attributed to smoking and catecholamine excess from alcohol withdrawal. She was started on intravenous nitroglycerin and amlodipine. Her hospital course was complicated by high degree AV block requiring temporary pacer. She was eventually extubated with good neurological recovery and recovered systolic function (EF 60%). She was counselled on smoking and alcohol cessation and discharged home on isosorbide dinitrate and Amlodipine with planned surgical revascularization. Results: Coronary vasospasm (CVS) can occur both in normal and diseased coronaries. Risk factors include smoking, alcohol use and withdrawal, cocaine, mental stress, etc. Vasospasm may present as Prinzmetal’s angina, myocardial infarction, AV block, or fatal arrhythmias. IC nitroglycerine during LHC aids in diagnosis of CVS in setting of ACS. IVUS (Intravascular ultrasound) may help diagnose presence or absence of concomitant atherosclerotic disease. Provocative testing with IC ergonovine and acetylcholine may be considered in non-ACS setting. Conclusions: This case emphasizes the need to have a high index of suspicion for vasospasm to prevent associated complications and establish an accurate diagnosis and guide proper management of this potentially fatal disease.

Rapidly Worsening Left Ventricular Systolic Function and in Hospital Ventricular Fibrillation After Permanent Pacemaker Implantation - Is There a Missing Link?

Rapidly Worsening Left Ventricular Systolic Function and in Hospital Ventricular Fibrillation After Permanent Pacemaker Implantation - Is There a Missing Link?

Acute ST Elevation Myocardial Infarction Complicated by Out of Hospital Ventricular Fibrillation Cardiac Arrest as the First Clinical Presentation of COVID-19

Acute ST Elevation Myocardial Infarction Complicated by Out of Hospital Ventricular Fibrillation Cardiac Arrest as the First Clinical Presentation of COVID-19

Coronary artery ectasia presenting with ST-elevation myocardial infarction in a young indigenous man: a case report

BackgroundCoronary artery ectasia (CAE) is often an incidental finding on angiography, however, patients can present with acute coronary syndrome due to a large thrombus burden requiring treatment with percutaneous coronary intervention or with emergency surgery.Case summaryA 26-year-old Indigenous Australian male was admitted with anterior ST-elevation myocardial infarction associated with an out of hospital ventricular fibrillation arrest. Coronary angiography demonstrated thrombotic occlusion of the proximal left anterior descending (LAD) artery with heavy thrombus burden and prominent vascular ectasia of all three coronary arteries. He was managed with surgical thrombectomy and coronary artery bypass graft of his LAD.DiscussionThis is the first case of triple CAE in an Indigenous Australian. The case highlights the lack of consensus approach in the management of CAE due to paucity of prospective studies.

711 Triple Vessel Coronary Artery Ectasia Presenting With ST Elevation Myocardial Infarction in a Young Indigenous Man

We present the first case of triple coronary artery ectasia in a previously well Indigenous Australian presenting with ST-elevation myocardial infarction. A 26 year old previously well Indigenous Australian male was admitted with anterior ST elevation myocardial infarction associated with an out of hospital ventricular fibrillation arrest. The patient was loaded with dual antiplatelet therapy and thrombolysed with 50mg tenecteplase prior transfer to our tertiary centre for rescue percutaneous coronary intervention due to <50% ST segment resolution and ongoing chest pain. Coronary angiography demonstrated thrombotic occlusion of the proximal left anterior descending artery with prominent vascular ectasia of all three arteries. Thrombus aspiration was not performed due to perceived high risk of systemic cardioembolic events. PCI was not attempted due to significant vascular ectasia preventing stent apposition within the grossly dilated vessel wall. He was managed with surgical thrombectomy and coronary artery bypass graft of the left anterior descending artery. There is no consensus approach in the management of isolated coronary artery ectasia presenting with acute coronary syndrome due to the paucity of prospective trials in its management. The management principles currently are to administer aspirin and to relieve the underlying obstructive lesion by percutaneous coronary intervention and failing that, cardiac surgery.

Extracorporeal life support for refractory ventricular tachycardia.

Extracorporeal life support (ECLS) is a very effective bridging therapy in patients with refractory ventricular tachycardia (VT) associated with cardiogenic shock. A moribund patient in extremis, is not amenable to optimization by standard ACC/AHA guidelines. New approaches and novel salvage techniques are necessary to improve outcomes in patients with refractory clinical settings such as malignant ventricular arrhythmias, cardiac arrest, cardiogenic shock and/or pulmonary failure until further management options are explored. Data base searches were done using key words such as ECLS, VT, cardiac arrest, VT ablation, venoarterial extra-corporeal membrane oxygenation (VA-ECMO). The use of ECLS has been described in a few case reports to facilitate VT ablation for incessant VT refractory to medical therapy. For patients with, out-of- hospital ventricular fibrillation (VF) and VT, Minnesota Resuscitation Consortium has implemented emergent advanced perfusion and reperfusion strategy, followed by coronary angiography and primary coronary intervention to improve outcome. The major indications for ECLS are cardiogenic shock related to acute myocardial infarction, myocarditis, post embolic acute cor pulmonale, drug intoxication and post cardiac arrest syndrome with the threat of multi-organ failure. ECLS permits the use of negative inotropic antiarrhythmic drug therapy, facilitates the weaning of catecholamine administration, thereby ending the vicious cycle of catecholamine driven electric storm. ECLS provides hemodynamic support during ablation procedure, while mapping and induction of VT is undertaken. ECLS provides early access to cardiac catheterization laboratory in patients with cardiac arrest due to shockable rhythm. The current evidence from literature, supports the use of ECLS to ensure adequate vital organ perfusion in patients with refractory VT. ECLS is a safe, feasible and effective therapeutic option when conventional therapies are insufficient to support cardiopulmonary function. A highly driven multidisciplinary team approach is essential to accomplish this task.

Correlation of the predictive ability of early warning metrics and mortality for cardiac arrest patients receiving in-hospital Advanced Cardiovascular Life Support

BackgroundThe Modified Early Warning Score (MEWS) helps identify patients experiencing a decline in physiological parameters that indicate risk for cardiac arrest (CA). ObjectivesTo assess the association between MEWS values and patient survival following in-hospital CA. MethodsRetrospective cohort study of patients who experienced in-hospital CA. The relationship between CA survival and MEWS values as well as other risk factors such as age, gender and type of electrographic cardiac rhythms was analyzed using logistic regression. ResultsSurvival rate to hospital discharge was 21%. Strong predictors for survival were MEWS values at hospital admission (p < .002), younger age (p < .005), ventricular fibrillation (p < .0001), and ventricular tachycardia (p < .0001). Gender and MEWS 4 hours prior to CA were not significantly associated with survival. ConclusionsSurvival following CA was significantly associated with MEWS at hospital admission but not 4 hours prior to CA. The type of cardiac rhythm and age were also predictive of survival.

Hypokalaemia, Drugs and the QT interval – A Recipe for Disaster

We enjoyed the recent article by Heaps and Gormley.1 It highlights both the importance of electrolyte disturbance and the QT interval, in the context of acute drug overdose or substance misuse. We recently managed a 40 year old gentleman who was admitted to our intensive care unit after resuscitation from an outof- hospital ventricular fibrillation (VF) cardiac arrest. He had a long history of smoking heroin, and occasional cannabis use. There was no other relevant past medical history and he had not reported any preceding illness. He was on an established methadone drug rehabilitation programme, taking 120mls/day, but took no other regular medications. There was no known family history of sudden cardiac death.

CT scan findings in oesophagogastric perforation after out of hospital cardiopulmonary resuscitation

Rupture of the oesophagus or stomach at the time of cardiopulmonary resuscitation can occur with accidental oesophageal intubation. The common site of rupture is the lesser curvature of the stomach,...

Abstract 5: CPR Fraction Prior to Defibrillation Determines Survival in Prehospital Cardiac Arrest in the Resuscitation Outcomes Consortium (ROC) Epistry

Introduction : In 2005, the American Heart Association recommended increased “hands-on time” during cardiopulmonary resuscitation (CPR) based on animal research and small case series. This study estimated the effect of increasing CPR fraction (proportion of resuscitation time with active CPR) on survival in a cohort of patients with out-of hospital ventricular fibrillation or ventricular tachycardia (VF/VT). Methods: Patients were selected from the ROC Epistry who had a confirmed VF/VT cardiac arrest that was not witnessed by Emergency Medical Services (EMS), received no public access defibrillation shock prior to EMS arrival, and had impedance recordings of CPR before the first shock. The proportion of each minute with active CPR, from defibrillator pad application until the first shock, was measured from the electronic resuscitation record by skilled readers who were blinded to hospital discharge outcome. The effect of increasing CPR fraction on survival to hospital discharge was adjusted for age, sex, bystander CPR, public location, interval from 911 call to defibrillator activation, chest compression rate, and ROC community. Results: Of 7963 EMS-treated cases of cardiac arrest without public access defibrillation, 1893 had an initial rhythm of VF/VT and 283 of those had electronic tracings and confirmed outcome. Mean age was 63 years and 81% were male. Bystanders performed CPR on 51% and 41% arrested in a public location. Outcomes and odds ratios (OR) with 95% confidence intervals (CI) of survival are shown from lowest to highest category of CPR fraction. Conclusions: This study provides preliminary evidence that increasing CPR fraction is associated with increased survival from VF/VT cardiac arrest. Though the study was observational, relatively small, and able only to measure CPR fraction after pad application, these findings suggest that provision of minimally interrupted CPR has direct clinical impact on survival after VF cardiac arrest.

The role of vasopressin in cardiorespiratory arrest and pulmonary hypertension

Vasopressin is a peptide synthesized in the hypothalamus whose primary role is in fluid homeostasis. It has recently gained interest as a potential agent in the treatment of cardiorespiratory arrest. Initial human studies have shown benefits with vasopressin in patients with out of hospital ventricular fibrillation and asystolic cardiac arrest. One subgroup of patients not included in these trials is patients with pulmonary hypertension, who have a five-year mortality rate of 50%. Animal studies have shown vasopressin to be a vasodilator in the pulmonary vascular system of rats, under normoxic and hypoxic conditions, with conflicting results in canines. Human studies have shown conflicting results with increases, decreases and no changes seen in pulmonary artery pressures of patients with a variety of clinical conditions. Research needs to be done in patients with pulmonary hypertension regarding the potential role of vasopressin during cardiac arrest in this subgroup.

Fatores prognósticos da revascularização na fase aguda do infarto agudo do miocárdio

OBJETIVO: Determinar os fatores preditores de má evolução nos pacientes submetidos a revascularização do miocárdio (RM) na fase aguda do infarto do miocárdio (IAM). CASUÍSTICA E MÉTODOS: No período de março de 1998 a novembro de 1999, 49 pacientes foram submetidos a RM na fase aguda do IAM. Foram excluídos pacientes portadores de complicações mecânicas do IAM e submetidos a procedimentos associados a RM. Os pacientes foram divididos em: Grupo I - 29 casos que não apresentaram complicações decorrentes do IAM e Grupo II - 20 casos com uma ou mais complicações. As complicações consideradas foram: isquemia recorrente (18 pacientes), insuficiência cardíaca congestiva (11), choque cardiogênico (9), hipotensão (7), reinfarto (4), taquicardia ventricular sustentada (4) e fibrilação ventricular (3). Os grupos foram considerados comparáveis em relação às características pré-operatórias, exceto pela idade mais avançada no grupo II. No intuito de identificar os fatores determinantes de pior prognóstico pós-operatório, foram correlacionadas e analisadas as características dos pacientes e as complicações do IAM, estudados pelo teste de variância e análise multivariada. RESULTADOS: A mortalidade global foi de 6,12% (3 pacientes), sendo somente no grupo II. A análise multivariada identificou como fatores preditores de mortalidade hospitalar a hipotensão arterial (p=0,045), o choque cardiogênico (p=0,001) e a fibrilação ventricular (p=0,012). CONCLUSÕES: A RM na fase aguda do IAM é um procedimento seguro em pacientes sem complicações, sem mortalidade operatória. A presença de complicações pré-operatórias como choque cardiogênico, fibrilação ventricular e hipotensão são considerados fatores de mau prognóstico nesta condição.

The challenge of acute coronary syndromes

I n t roduc t ion Acute coronary syndromes (ACS) pose multiple challenges to physicians, cardiologists, internists, and emergency department physicians, as well as to general practitioners. General practitioners are responsible for early recognition of ACS among patients with chest discomfort and identification of patients who require hospital admission; cardiologists and other specialists prescribe initial and subsequent medical therapy and select patients for immediate, early, or elective revascularisation by percutaneous techniques (balloon angioplasty, stent) or bypass surgery. A systematic approach may guide the physicians to meet these challenges (table). The term ACS encompasses a spectrum of patients who present with chest discomfort or other symptoms caused by myocardial ischaemia. The unification of these manifestations of coronary artery disease under a single term reflects the understanding that these are caused by a similar pathophysiology, characterised by erosion, fissuring, or rupture of a pre-existing plaque, leading to intravascular thrombosis and impaired myocardial blood supply? The presence or absence of mechanical obstruction by the plaque and its contents, the amount and extent of associated thrombus formation, and the degree of collateral circulation determine the outcome of patients, particularly whether myocardial ischaemia recovers fully or results in minor or major myocardial necrosis. The common pathophysiology of different clinical presentations of ACS logically requires a similar therapeutic approach. In the 1970s, attention focused on management of lifethreatening arrhythmias. Coronary care units were introduced to detect and treat such arrhythmias by pacemakers (A-V block) or defibrillation (ventricular fibrillation). 2-~ Defibrillators were also introduced in ambulances. Antiarrhythmic drugs were also introduced to prevent ventricular fibrillation. Subsequently, attention shifted to measures to reduce myocardial oxygen consumption with [3-blockers, nitrates, and calcium antagonists. ' These agents prevented progression to myocardial infarction in patients with unstable angina, and improved outcome in selected patients with evolving infarction." In the past 10 years, reperfusion therapy has been introduced, supported by intensive antithrombotic and anticoagulant therapy. The value of reperfusion therapy with coronary occlusion (evolving infarction) by thrombolytic therapy or direct angioplasty has been well established. 9-n However, the indications for, and opt imum timing of, percutaneous or surgical coronary intervention in the spectrum of patients with unstable angina are still debated. H

Two cases of torsades de pointes caused by sotalol therapy

An 84 year old woman developed complete atrioventricular block with a ventricular escape rhythm of 34 beats per minute after taking two tablets of sotalol (=320 mg) for sudden atrial fibrillation with fast ventricular response. During emergency transport to hospital ventricular fibrillation occurred which was successfully treated by electrical defibrillation. On admission neither her medical history nor ECG could reveal evidence of ischaemic heart disease or heart failure. Concomitant medication consisted of amlodipine 5mg once a day and dimetindene for itching. During her stay in the emergency department and hospitalisation, a total atrioventricular block with slow ventricular escape rhythm was noted associated with pause-dependent torsades de pointes (QT=490 ms) (Fig. 1). Sotalol therapy was discontinued and an idiopathic hypokalemia of 2.4 meq l was corrected. No valid explanation for this hypokalemia could be found. Except for the potassium disorder, haematology and biochemistry blood values were normal. Creatinine and urea levels were 1.3 and 61 mg dl, respectively. There was a euthyroid status. After therapy with intravenous isoproterenol and magnesium sulphate failed, temporary pacing at 70 beats per minute was initiated. After 12 days the patient was discharged from hospital uneventfully and the atrial fibrillation was managed conservatively with digitalis and aspirin. A 73 year old lady on chronic haemodialysis for terminal nephropathy was admitted to the emergency department in March, 1996 because of sudden atrial tachycardia with a fast ventricular rate. Her medical history revealed a cerebrovascular accident in 1985, with arterial hypertension. In 1986 she developed analgesic nephropathy. After 5 years, she had a temporary nephrostomy after renal papillary necrosis and right ureteral obstruction. In 1995 she was haemodialysed for the first time: urea and creatinine levels then were 99 and 7.1 mg dl, respectively. Potassium level reached 4.6 meq l. During her stay in the emergency room, she was given 160 mg of sotalol orally. An echocardiographic examination showed right atrial and ventricular enlargement, further with left atrial enlargement. The left ventricle had normal dimensions with global and regional contractility preserved. There was no left ventricular hypertrophy nor pericardial effusion. Discrete mitral, aortic, tricuspidal and pulmonary valve insufficiency were observed. Eventually, examination revealed pulmonary hypertension. On admission, blood biochemistry showed a urea level of 35 mg dl, a creatinine level of 3.2 mg dl with a potassium of 4.7 meq l and * Corresponding author. Tel.: +32-53-724461; fax: +32-53724505; e-mail: Ignace.Demeyer@olvz-aalst.be.

Clinical impact of introducing thrombolytic and aspirin therapy into the management policy of a coronary care unit

purpose: To evaluate the impact of introducing thrombolytic and aspirin therapy into the management policy of a coronary care unit, with particular reference to its effects on the hospital course of nonselected patients with acute myocardial infarction. End points chosen were the utilization of thrombolytic and aspirin therapy, hospital mortality, discharge diuretic requirements, and the incidence of ventricular fibrillation and cardiogenic shock. patients and methods: A total of 336 patients with acute myocardial infarction were studied, comprising consecutive admissions to the coronary care unit over two separate 12-month periods: January to December 1986 (n = 158) and September 1989 to August 1990 (n = 178), before and after thrombolytic and aspirin therapy had been introduced into the management policy of the unit. results: Thrombolytic and aspirin therapy was given to 87% and 93%, respectively, of all patients in the 1989/1990 cohort. This high treatment rate led to substantial improvements in morbidity and mortality. Thus, comparison of the 1986 and 1989/1990 cohorts showed reductions in hospital mortality (24 % to 11%, p <0.005), ventricular fibrillation (22% to 13%, p = 0.05), and cardiogenic shock (20% to 6%, p <0.001), particularly in patients aged over 60. Reductions in the incidence of lesser degrees of heart failure are reflected in the proportions of patients discharged with diuretic requirements, which declined from 43% in 1986 to 22% in 1989/1990 (p <0.001). The duration of hospital stay for patients who survived showed no change between 1986 and 1989/1990, but time spent in the coronary care unit decreased from 3.1 ± 1.8 to 2.1 ± 1.4 days ( p <0.001). conclusion: The great majority of nonselected patients with acute myocardial infarction are candidates for thrombolytic and aspirin therapy, which can be given safely, leading to profound reductions in mortality and the incidence of major complications, particularly in the older age group.

Nimodipine after resuscitation from out- of hospital ventricular fibrillation: A placebo-controlled, double-blind, randomized trial : Roine RO, Kaste M, Kinnunen A, Nikki P, Sarna S, Kajaste S. JAMA. 1990;264:3171–3177

Nimodipine after resuscitation from out- of hospital ventricular fibrillation: A placebo-controlled, double-blind, randomized trial : Roine RO, Kaste M, Kinnunen A, Nikki P, Sarna S, Kajaste S. JAMA. 1990;264:3171–3177

Long-term outcome in patients who survive out of hospital ventricular fibrillation and undergo electrophysiologic studies: Evaluation by electrophysiologic subgroups

The long-term outcome of 241 survivors of out of hospital ventricular fibrillation who underwent programmed electrical stimulation was evaluated. Patients were categorized according to the rhythm induced at baseline drug-free electrophysiologic testing. Ventricular fibrillation was induced in 39 (16%) (Group 1), sustained ventricular tachycardia in 66 patients(27%) (Group 2) and nonsustained ventricular tachycardia in 34patients (14%) (Group 3); 102 patients (42%) (Group 4) did not have an arrhythmia inducible at baseline electrophysiologic testing. Antiarrhythimic drugs were administered over the long term to 92% of patients in Group 2, 91% of patients in Group 1 and 47% of patients in Group 4. At a mean follow-uptime of 30 ± 15 months, recurrent sudden cardiac death or nonfatal ventricular fibrillation occurred in 11 (28%) of 39 patients with inducible ventricular fibrillation (Group 1), 14 (21%) of 66 patients with inducible sustained ventricular tachycardia (Group 2), 4 (12%) of 34 patients with inducible nonsustained ventricular tachycardia (Group 3) and 16 (16 %) of 102 patients without inducible arrhythmias (Group 4). Actuarial analysis revealed a 2 year cumulative arrhythmia-free survival rate of 65% for patients in Group 2, 71% for patients in Group 1, 79% for patients in Group 3 and 81% for patients in Group 4 (p = 0.02).Actuarial survival of patients with inducible sustained ventricular tachycardia or ventricular fibrillation suppressed by electrophysiologically guided drug therapy was not significantly different from that in patients whose arrhythmia was not suppressed. Multivariate regression analysis revealed that only the presence of congestive heart failure was an indepeedent predictor of outcome in these patients. The prognostic significance of inducibility at baseline electrophysiologic testing in survivors of ventricular fibrillation is dependent on the status of their left ventricular function and does lot independently predict poor outcome. Patients with inducible sustained ventricular tachycardia or ventricular fibrillation that was subsequently randered noninducible by electrophysiologically guided drug therapy with class I antiarrhythmic drugs did not have an improved survival rate compared with that of patients whose tachyarrhythmia could not be suppressed.

Integration of ambulance staff trained in cardiopulmonary resuscitation with a medical team providing prehospital coronary care.

Ambulance staff with advanced training in cardiopulmonary resuscitation and equipped with monitor/defibrillators were used as the initial responders to collapse calls within a medically based prehospital coronary care system. During 21 months, in a population of approximately 120,000, ambulance staff successfully resuscitated six patients from ventricular fibrillation; there were four long term survivors. The median response time of emergency ambulances to collapse calls was eight minutes compared with 20 minutes for the medically manned mobile coronary care unit. None of the patients resuscitated by ambulance staff would have survived if they had been dependent on the mobile coronary care unit acting alone. Nineteen other patients with important arrhythmias were referred for earlier medical management which in some cases may have saved lives. An additional eight long term survivors of out of hospital ventricular fibrillation were resuscitated by medical staff. The integration of paramedical with medical prehospital coronary care improved survival after out of hospital cardiac arrest.

A prospective randomized evaluation of biphasic versus monophasic waveform pulses on defibrillation efficacy in humans

Biphasic waveforms have been suggested as a superior waveform for ventricular defibrillation. To test this premise, a prospective randomized intraoperative evaluation of defibrillation efficacy of monophasic and biphasic waveform pulses was performed in 22 survivors of out of hospital ventricular fibrillation who were undergoing cardiac surgery for implantation of an automatic defibrillator.The initial waveform used in a patient for defibrillation testing, either monophasic or biphasic, was randomly selected. Subsequently, each patient served as his or her own control for defibrillation testing of the other waveform. The defibrillation threshold was defined as the lowest pulse amplitude that would effectively terminate ventricular fibrillation with a single discharge delivered 10 s after initiation of an episode of ventricular fibrillation induced with alternating current. Each defibrillation pulse was recorded oscilloscopically, and defibrillation pulse voltage, current, resistance and stored energy were measured.Fifteen (68%) of the 22 patients had a lower defibrillation threshold with the biphasic pulse, 3 (14%) had a lower threshold with the monophasic pulse and 4 (18%) had equal defibrillation thresholds (within 1.0 J) regardless of waveform. The mean leading edge defibrillation threshold voltage was 317 ± 105 V when the monophasic pulse was used and 267 ± 102 V (16% less) when the biphasic pulse was used (p = 0.008). Mean leading edge defibrillation threshold current was 7.9 ± 3.7 A when the monophasic pulse was used and 6.8 ± 3.8 A (14% less) when the biphasic pulse was used (p = 0.051). There were no differences in system resistance with the two waveforms: the leading edge resistance for the monophasic pulse was 45.3 ± 17.5 and 44.1 ± 14.4 ω for the biphasic pulse (p = 0.183). The stored energy defibrillation threshold was 8.5 ± 6.1 J when the monophasic pulse was used and 6.3 ± 5.2 J (26% less) when the biphasic pulse was used (p = 0.028). These findings show that in the majority of patients, biphasic pulse defibrillation is more efficient than monophasic pulse defibrillation.

Energy requirement for early defibrillation.

The appropriate energy requirement for defibrillation of out-of-hospital ventricular fibrillation has been a matter of discussion. We analysed the effects of 360 J, 200 J or a combination of 200 and 360 J DC shocks given by ordinary manual defibrillators or semiautomatic defibrillators. 120 of 127 ventricular fibrillation episodes were converted by three or less 360 J DC shocks delivered by a manual defibrillator. All 28 ventricular fibrillation episodes were converted by an average of 1.9 DC shocks when 360 J were delivered by a semiautomatic defibrillator. 139 of 152 ventricular fibrillation episodes were converted by three or fewer 200 J DC shocks and 52 of 53 by 2 x 200 J followed, if needed, by 1 x 360 J DC shock delivered by the same semiautomatic defibrillator. Three or fewer 360 J DC shocks seems completely adequate for conversion of most episodes of out-of-hospital ventricular fibrillation. There is no difference in the result of defibrillation by manual and semiautomatic defibrillators.