Five hundred patients with myocardial infarction monitored within one hour of symptoms.

Of 2886 patients monitored during acute myocardial infarction, 500 were observed within one hour of the onset of symptoms. Half of the early admission group were admitted in response to emergency 999 calls and 435 of them travelled in resuscitation ambulances, where surveillance for arrhythmias was instituted. Pulmonary oedema occurred in 130 patients (26%), cardiogenic shock supervened in 60 (12%), and 115 (23%) died in hospital. Ventricular fibrillation was observed in 98 patients (20%). Forty two of them survived to be discharged, including 20 of the 24 with primary fibrillation which had occurred first in hospital. In only one case did primary ventricular fibrillation occur after the first 10 hours of onset of illness. Sinus bradycardia, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation were all observed more frequently in patients admitted within one hour after the onset of symptoms than in those admitted later. An element of selection is inevitable when early admission is encouraged by the existence of a resuscitation ambulance system; this will depend in part on the early recognition of risk and the geographical location of the attack. These factors may bias the group towards relatively high risk. Nevertheless, prompt admission after myocardial infarction should improve survival by permitting successful management both of ventricular fibrillation and of other arrhythmias which may influence short term and long term prognosis.     

Premature Ventricular Contractions and Non-sustained Ventricular Tachycardia: Association with Sudden Cardiac Death,Risk Stratification,and Management Strategies

Premature ventricular contractions (PVCs) and non-sustained ventricular tachycardia (NSVT) are frequently encountered and a marker of electrocardiomyopathy. In some instances, they increase the risk for sustained ventricular tachycardia, ventricular fibrillation, and sudden cardiac death. While often associated with a primary cardiomyopathy, they have also been known to cause tachycardia-induced cardiomyopathy in patients without preceding structural heart disease. Medical therapy including beta-blockers and class III anti-arrhythmic agents can be effective while implantable cardiac defibrillators (ICD) are indicated in certain patients. Radiofrequency ablation (RFA) is the preferred, definitive treatment in those patients that improve with anti-arrhythmic therapy, have tachycardia-induced cardiomyopathy, or have certain subtypes of PVCs/NSVT. We present a review of PVCs and NSVT coupled with case presentations on RFA of fascicular ventricular tachycardia, left-ventricular outflow tract ventricular tachycardia, and Purkinje arrhythmia leading to polymorphic ventricular tachycardia.     

Ventricular arrhythmias.

Sudden cardiac death claims thousands of Canadians annually. Ventricular tachycardia and fibrillation account for up to 85% of these deaths. Identifying the patients at risk remains a major challenge. Those who have recurrent ventricular tachycardia or have been resuscitated from ventricular fibrillation are generally considered to be at highest risk. Although ventricular premature beats in the absence of previous ventricular tachycardia or fibrillation are not helpful in identifying such patients in most cases, they can indicate increased risk for sudden cardiac death in the presence of a structural cardiac abnormality, particularly recent myocardial infarction; however, the need for treatment in such cases is speculative and is being investigated. Treatment is mandatory for survivors of an episode of ventricular fibrillation and those with recurrent sustained ventricular tachycardia or torsade de pointes ventricular tachycardia. The approach to management is either invasive or noninvasive. Selection of an antiarrhythmic agent is facilitated by knowledge of some basic electrophysiologic features of the heart and of the classification of antiarrhythmic drugs. However, drug therapy has to be individualized on the basis of efficacy, left ventricular function and adverse effects or potential adverse effects of the drug. Amiodarone therapy or nonpharmacologic therapy should be considered if a suitable antiarrhythmic agent cannot be found.     

Non-Synchronized Direct-Current Countershock in Cardiac Arrhythmias

One hundred and thirty-two direct-current shocks were administered to 82 patients in an attempt to convert supraventricular tachyarrhythmias. Sinus rhythm was restored in 74 patients. In at least seven instances the shock was delivered during the T wave. Ventricular fibrillation did not occur. One episode of ventricular tachycardia and one of third-degree heart block followed countershock and terminated spontaneously. Excessive digitalis was considered to be a contributing factor in these two arrhythmias. Non-synchronized countershock is considered a safe and effective method of converting atrial fibrillation and flutter.     

Resuscitation from cardiac arrest: assessment of a system providing only basic life support outside of hospital

Resuscitation outside of hospital of victims of cardiac arrest is a major challenge to our emergency care system. Most cities in Canada do not have a mobile advanced life support service; instead they rely on basic life support outside of hospital. The outcome in such cases and the factors affecting the outcome are largely unknown. Thus, it is difficult to estimate the lifesaving potential of adding advanced life support to the existing measures available for care outside of hospital.A prospective study of all resuscitation attempts begun outside of hospital was conducted during 18 consecutive months in 1977-78 in Winnipeg; at that time only basic life support was available outside of hospital. Resuscitation was attempted 849 times, and 33 patients (4%) survived to be discharged from hospital. Data analysis revealed that: (a) none of the 58% of patients in asystole at the time of arrival at a hospital survived to be discharged, but 11% of the patients with ventricular fibrillation or tachycardia (27% of the entire group) survived; (b) the survival rate was lower when the interval from the emergency telephone call to the patient''s arrival at the hospital exceeded 10 minutes; and (c) basic life support was begun immediately in 29% of the patients with ventricular fibrillation or tachycardia, and increased the survival rate fivefold.The training of private citizens in basic life support is a vital component of total emergency cardiac care. A mobile advanced life support service will be effective in saving lives if it reduces the delay before definitive care is instituted, preferably to less than 10 minutes.     

Sudden Death in Hospital after Discharge from Coronary Care Unit

In a group of 339 patients with acute myocardial infarction treated in a coronary care unit, 273 left the unit while improving and were expected to leave hospital alive; 23 had a cardiac arrest or died suddenly while still in hospital—17 died immediately or after temporary resuscitation and six were resuscitated to leave hospital alive. Ventricular fibrillation was found in 13 of the 20 patients attended by the cardiac arrest team. The incidents were scattered from the 4th to the 24th day after the onset of infarction. Risk factors in these “late sudden death” patients were compared with the 250 patients who left the unit while improving and did not die or suffer cardiac arrest. The patients susceptible to late sudden death were characterized early in their hospital course by the findings of severe, predominantly anterior infarction, left ventricular failure, persistent sinus tachycardia, and frequent ventricular arrhythmias. It is suggested that such patients be chosen for prolonged observation in a second-stage coronary care unit.     

经食道心房调搏术及食道心电图在心律失常中的应用

目的:分析经食道心房调搏术(TEAP)及食道内心电图(EECG)在心律失常中的应用价值。方法:选取2018年6月至2019年12月于我院行食道心电图及经食道调搏的患者189例,其中男80例,女109例,年龄11~83岁。结果:54例为房室结折返性心动过速(AVNRT),34例为房室折返性心动过速(AVRT),8例为房性心动过速(AT),4例为心房扑动(AF),6例为心房颤动(Af),5例为室性心过速,78例为室早或其他。共105例心律失常患者拟行食道心房调搏终止心动过速,所有AVNRT和AVRT患者及17例AT患者经食道心房调搏S1S1成功转为窦律,50例AVNRT、32例AVRT、6例AT、3例AF及2例VT患者通过射频消融术成功根治。其中1例11岁AT患者因无法耐受食道调搏,未能转为窦律,患者经静推普罗帕酮后次日转为窦律。共97例患者拟行食道心房调搏诱发,共49例诱发出心动过速,1例左后分支型室速经静滴异丙肾上腺素后诱发心动过速,且仍需静滴异丙肾上腺素后经心房食道调博终止心动过速,后经射频消融术成功根治。结论:TEAP及EECG可用于复杂心律失常的诊断及治疗,是一种相对安全、临床容易掌握的技术,值得推广。     

The effects of sympathetic denervation on spontaneous ventricular defibrillation in the rat.

Ventricular tachycardia or ventricular fibrillation was electrically induced in 38 normal rats (group 1) and 24 sympathetically denervated rats (6-hydroxydopamine) (group 2). The time for spontaneous reversion to sinus rhythm was measured during (1) control, (2) isoproterenol, and (3) the combination of isoproterenol and phenylephrine. The time for spontaneous reversion was the same in both groups in the three states. The reversion time was prolonged threefold by isoproterenol, and restored to control values when phenylephrine was added to the infusion of isoproterenol. The tachycardia duration and the refractory period were inversely related: log10 (tachycardia duration) = 3.466-0.091 (refractory period). Ventricular tachycardia/fibrillation induction was examined as follows: (i) Ventricular tachycardia/fibrillation was induced in 100% of normal rats (group 1), but only 42% of the denervated rats (group 2, p less than 0.001); (ii) during isoproterenol, ventricular tachycardia/fibrillation was induced in 100% of rats of both groups; and (iii) when phenylephrine was added to isoproterenol, ventricular tachycardia/fibrillation was induced in 100% of group 1 rats versus 82% of group 2 rats, (p = NS). These observations suggest (1) the induction of ventricular tachycardia/fibrillation is highly dependent on intact sympathetic innervation, and (2) exogenous adrenergic agonists modulate the duration of ventricular fibrillation through their effects on ventricular refractory period, independent of sympathetic innervation.     

A Canadian hospital's experience with the automatic implantable cardioverter/defibrillator.

The automatic implantable cardioverter/defibrillator is a device that can be implanted in patients for treatment of recurrent ventricular tachycardia and ventricular fibrillation. It was recently approved for clinical use in Canada. The authors describe their experience with 12 patients (mean age 51.3 years) who underwent implantation of a defibrillator. All 12 patients had a history of documented ventricular fibrillation, which was idiopathic in 3 and due to ischemic heart disease in 9. Electrophysiologic testing revealed inducible ventricular tachycardia or ventricular fibrillation in 8 of the 10 patients tested. An important criterion for selection for implantation was failure of pharmacologic therapy to suppress ventricular arrhythmias induced during electrophysiologic testing. Of the 12 patients, 1 died within 24 hours after implantation. During a mean follow-up period of 15.5 months there were no further deaths. All the surviving patients expressed satisfaction with the device; five of the seven under the age of 60 years have returned to work, and one has returned to school. This initial favourable experience with the automatic implantable cardioverter/defibrillator suggests that future increases in the availability of the device and improvements in its function will lead to much more widespread use, as the population of patients at risk of sudden cardiac death is large.     

Patient-initiated transtelephone transmission of electrocardiographic signals in the diagnosis of arrhythmias.

Thirty-one patients who had complained of recurrent palpitations were given transtelephone transmitters of electrocardiographic signals and instructed to use the transmitters while they were having symptoms. From the transcribed electrocardiograms sinus tachycardia was documented in 12 patients, paroxysmal atrial tachycardia in 7, atrial fibrillation in 4, atrial flutter in 3, frequent ventricular premature beats in 4 and ventricular tachycardia in 1. Patient-initiated transtelephone transmission of electrocardiographic signals was found to be an effective means of documenting the nature of symptomatic paroxysmal tachycardia.     

Sudden death during ambulatory monitoring.

Three patients with ischaemic heart disease died suddenly while being monitored with an ambulatory tape recorder. Two had terminal ventricular fibrillation initiated by paired bidirectional ventricular ectopic beats against a background of scattered ectopic activity; both had had ventricular tachycardia during routine treadmill exercise testing in the week before death. The third patient developed bizarre ventricular complexes followed by asystole. Sudden death may be due to ventricular fibrillation initiated by paired ventricular ectopic beats with changing morphology, or asystole following bizarre ventricular complexes. Exercise testing may have an important predictive value.     

Magnesium Therapy for Intractable Ventricular Tachyarrhythmias in Normomagnesemic Patients

Intractable ventricular tachyarrhythmia associated with hypomagnesemia responds well to magnesium given intravenously. Two patients with recurrent ventricular tachycardia and ventricular fibrillation associated with normal serum magnesium levels and resistant to treatment with potassium chloride, lidocaine and bretylium tosylate responded dramatically to the administration of magnesium sulfate. A third patient in whom the serum magnesium level was unknown also showed dramatic response to magnesium therapy.Magnesium depletion probably interferes with sodium-potassium adenosine triphosphatase enzyme activity and causes ionic imbalance and electrical instability of purkinje''s fibers. Without obvious magnesium depletion this element in high concentration may still prolong transient inward current, prolong the effective refractory period, increase the membrane potential and control ventricular tachyarrhythmia.When ventricular fibrillation or malignant ventricular tachycardia cannot be controlled with lidocaine and other conventional drugs, we recommend infusing magnesium sulfate, 2 to 3 grams in one minute, followed by 10 grams over five hours.     

CARDIAC RESUSCITATION THROUGH THE INTACT CHEST

External cardiac compression and external defibrillation were successful in resuscitating 27 consecutive dogs after the production of ventricular fibrillation. Twelve patients survived following circulatory arrest treated with closed chest cardiac compression and, when indicated, defibrillation. Five additional patients were successfully resuscitated but died in the hospital. In fifteen cases, resuscitation was not successful.     

Resuscitation of patients with cardiac arrest by ambulance staff with extended training in West Yorkshire.

OBJECTIVE--To investigate the results of resuscitation of patients with cardiac arrest by ambulance staff with extended training in West Yorkshire. DESIGN--Study of all such attempts at resuscitation over 32 months, based on the standard report form for each call made by the ambulance staff and the electrocardiogram that showed the initial rhythm in each patient. SETTING--Area covered by West Yorkshire ambulance service. SUBJECTS--1196 Patients with cardiac arrests attended by 29 ambulance staff with extended training. MAIN OUTCOME MEASURE--Result of resuscitation. RESULTS--The initial rhythm was asystole or electromechanical dissociation in 740 patients and ventricular fibrillation in 456 patients; overall 65 patients survived to be discharged from hospital. Sixty four of the 456 patients in whom ventricular fibrillation was the initial rhythm recorded, and 46 in whom ventricular fibrillation persisted after the ambulance staff arrived, survived. Only one of the 740 patients who initially had asystole or electromechanical dissociation survived. Factors associated with a greater chance of ventricular fibrillation occurring were: age less than 71, the arrest being witnessed by a bystander, resuscitation by a bystander, the arrest occurring in a public place, and a response time by the ambulance staff of less than six minutes. For patients found in ventricular fibrillation a shorter response time was associated with improved survival but resuscitation by a bystander was not. Additional skills learnt during extended training were used for 51 of the 65 patients who survived. CONCLUSIONS--Ambulance staff with extended training can save the lives of patients with cardiac arrest due to fibrillation, though asystole and electromechanical dissociation have a poor prognosis and should perhaps receive little attention during extended training.     

Ventricular Tachycardia Precipitated by Short-long-short Sequence in a Patient with Implantable-cardioverter Defibrillator

Abrupt changes in heart rate, particularly short-long-short sequences in the ventricular cycle length (CL), might precede initiation of ventricular tachycardia/fibrillation (VT/VF). These changes may be facilitated or caused by pacing activity in patients with pacemakers or implantable-cardioverter defibrillators (ICDs). We describe a patient with two episodes of acquired VT precipitated by short-long-short sequences and diagnosed from the ICD recordings. In such cases, the knowledge of the device parameters is extremely important for a correct diagnosis and management.     

Hospital resuscitation from ventricular fibrillation in Brighton.

The overall results over three and a half years of the treatment of ventricular fibrillation secondary to ischaemic heart disease in the Royal Sussex County Hospital were reviewed. Records of all patients who were brought to hospital by resuscitation ambulances or who were admitted to the coronary care unit from any source were analysed. Eighty-seven of the 174 patients (50%) who developed ventricular fibrillation were discharged. The survivors included 13 out of 61 patients (21%) in whom fibrillation was secondary to cardiogenic shock or severe left ventricular failure. The presence of resuscitation equipment and nursing staff trained to use it in the general wards and emergency areas ensured a uniformly high success rate throughout the hospital, similar to that achieved in the coronary care unit. Prompt defibrillation in the general wards and the accident and emergency department may improve overall survival.     

Electrical requirements for ventricular defibrillation.

Most deaths from ischaemic heart disease are sudden, occur outside hospital, and result from ventricular fibrillation. But defibrillators have only limited availability because of their size and weight. A miniature defibrillator has been developed. A singe low-energy shock succeeded in removing ventricular fibrillation in 73 out of 82 episodes, and a further shock was successful in seven more episodes. Primary ventricular fibrillation probably always responds to low-energy electrical shocks, which challenges the conventional view that correction of ventricular fibrillation requires high-energy direct-current shock. Thus even smaller and lighter defibrillators are possible. Furthermore low-energy shocks cause less myocardial damage.     

Electrical storm: Incidence, Prognosis and Therapy

Implantable defibrillators are lifesavers and have improved mortality rates in patients at risk of sudden death, both in primary and secondary prevention. However, they are unable to modify the myocardial substrate, which remains susceptible to life-threatening ventricular arrhythmias. Electrical storm is a clinical entity characterized the recurrence of hemodynamically unstable ventricular tachycardia and/or ventricular fibrillation, twice or more in 24 hours, requiring electrical cardioversion or defibrillation. With the arrival of the implantable cardioverter-defibrillator, this definition was broadened, and electrical storm is now defined as the occurrence of three or more distinct episodes of ventricular tachycardia or ventricular fibrillation in 24 hours, requiring the intervention of the defibrillator (anti-tachycardia pacing or shock). Clinical presentation can be very dramatic, with multiple defibrillator shocks and hemodynamic instability. Managing its acute presentation is a challenge, and mortality is high both in the acute phase and in the long term. In large clinical trials involving patients implanted with a defibrillator both for primary and secondary prevention, electrical storm appears to be a harbinger of cardiac death, with notably high mortality soon after the event. In most cases, the storm can be interrupted by medical therapy, though transcatheter radiofrequency ablation of ventricular arrhythmias may be an effective treatment for refractory cases.This narrative literature review outlines the main clinical characteristics of electrical storm and emphasises critical points in approaching and managing this peculiar clinical entity. Finally focus is given to studies that consider transcatheter ablation therapy in cases refractory to medical treatment.     

Pharmacological treatment of short-coupled idiopathic ventricular fibrillation: A review

Short-coupled idiopathic ventricular fibrillation (IVF) is a subtype of IVF in which episodes of polymorphic ventricular tachycardia or ventricular fibrillation are initiated by short-coupled premature ventricular contractions (PVCs). Our understanding of the pathophysiology is evolving, with evidence suggesting that these malignant PVCs originate from the Purkinje system. In most cases, the genetic underpinning has not been identified. Whereas the implantation of an implantable cardioverter-defibrillator is uncontroversial, the choice of pharmacological treatment is the subject of discussion. In this review, we summarize the available knowledge on pharmacological therapy in short-coupled IVF and provide our recommendations for management of patients with this syndrome.