Survival After A First Episode of Ventricular Tachycardia or Fibrillation

Recent outcome analyses in ventricular tachycardia (VT) and ventricular fibrillation (VF) have included patients undergoing electrophysiological study (EPS) at tertiary care centers. The selection process involved could introduce bias in the reported populations. We analyzed the outcome of 42 consecutive patients (aged 63 ± 11 years) admitted to a coronary care unit within 48 hours of a first episode of VT/VF not associated with reversible causes. All patients recovered neurologically and were candidates for EPS. Nine patients (21%) died during the initial hospitalization (none had EPS), and another nine died during a follow-up of 17 ± 12 months. Actuarial survival at 1 and 2 years was 64% and 62%, respectively. By Cox's model, congestive heart failure functional Class III-IV (P = 0.008; hazard ratio = 3.7) was the only independent prognostic factor. Among patients discharged, subsequent survival did not depend on the performance of EPS or on the antiarrhythmic therapeutic modalities used. Mortality after a first episode of VT/VF is high. Severe congestive heart failure is the most powerful prognostic factor. Studies including successfully referred patients undergoing EPS may not reflect the true natural history of patients with VT/VF.     

Frequency Analysis of Ventricular Fibrillation and Resuscitation Success

SUMMARY In 56 patients, frequency analysis of the electrocardiogramof ventricular fibrillation exhibited power spectra with a distinctdominant frequency. The greatest success for resuscitation fromventricular fibrillation is recorded when ventricular fibrillationdevelops after the patient comes under coronary care. Of the41 patients in whom the onset and first 8 s of ventricular fibrillationwere artefact-free the mean dominant frequency of primary ventricularfibrillation (no cardiogenic shock or cardiac failure) in 21patients was 6.2±0.2 Hz, significantly higher than themean dominant frequency of the first 8 s of secondary ventricularfibrillation (cardiogenic shock or heart failure) (4.0±0.2Hz, 20 patients, p =0.0001). In these patients the peak-to-troughamplitude (ECG) of the first 8 s of ventricular fibrillationwas similar in both primary and secondary ventricular fibrillationas was the mean duration of ventricular fibrillation prior tothe first DC shock. There was a significantly lower successrate for resuscitation from secondary ventricular fibrillation(6 of 20 patients) compared with resuscitation from primaryventricular fibrillation (18 of 21 patients, x² 17.8, p=0.001).Of the remaining 15 patients who were collapsed between 3 and20 min before the arrival of the mobile coronary care unit,the dominant frequency of the first 8 s of ventricular fibrillationfell with increased duration of collapse (from 5.5 Hz at 3 minto a mean of 2.1 Hz at 20 min). Four of these 15 patients whosurvived the initial arrest had a mean dominant frequency of5.2±0.3 Hz, which was significantly higher than the meandominant frequency (3.1±0.3 Hz, p<0.01) of the 11patients who were not resuscitated. This study shows that low frequency ventricular fibrillationis indicative of a poor chance of successful resuscitation.Alteration of the frequency may increase resuscitation success.     

Bench to Bedside Resuscitation from Prolonged Ventricular Fibrillation

Ventricular fibrillation (VF) remains the most common cardiac arrest heart rhythm. Defibrillation is the primary treatment and is very effective if delivered early within a few minutes of onset of VF. However, successful treatment of VF becomes increasingly more difficult when the duration of VF exceeds 4 minutes. Classically, successful cardiac arrest resuscitation has been thought of as simply achieving restoration of spontaneous circulation (ROSC). However, this traditional approach fails to consider the high early post-cardiac arrest mortality and morbidity and ignores the reperfusion injuries, which are manifest in the heart and brain. More recently, resuscitation from cardiac arrest has been divided into two phases; phase I, achieving ROSC, and phase II, treatment of reperfusion injury. The focus in both phases of resuscitation remains the heart and brain, as prolonged VF remains primarily a two-organ disease. These two organs are most sensitive to oxygen and substrate deprivation and account for the vast majority of early post-resuscitation mortality and morbidity. This review focuses first on the initial resuscitation (achieving ROSC) and then on the reperfusion issues affecting the heart and brain.     

Serum Electrolytes and Catecholamines After Cardioversion From Ventricular Tachycardia and Atrial Fibrillation

We have observed hypokalemia after cardioversion from spontaneous out-of-hospital ventricular fibrillation and induced ventricular tachycardia. To test the hypothesis that the hormone response to the hemodynamic stress of the arrhythmia initiated the change in potassium, we compared the electrolytes and hormones in three groups of patients. We observed a decrease in serum potassium and magnesium after cardioversion from ventricular tachycardia induced by programmed Stimulation but not after normal programmed stimulation of the ventricle or after cardioversion from stable atrial fibrillation. These changes were preceded first by a rise in norepinephrine and epinephrine then a rise in glucose, followed by a rise in insulin. The stimulus for these changes was probably the hypotension associated with ventricular tachycardia. The sequence of changes suggests that the decrease of potassium and magnesium after ventricular tachycardia was due to a shift of the electrolytes into cells related to the insulin-mediated movement of glucose from the blood into cells.     

Hospital Readmission From Home Health Care Before and After Prospective Payment

PURPOSE: To describe and compare clients who were readmitted to the hospital during an episode of home health care, before and after the inception of the prospective payment system (PPS). DESIGN: A longitudinal mixed design was used to replicate a study conducted 9 years previously (pre-PPS) in the same home care agency in the central part of the United States. METHODS: Seventy-six closed-case medical records from a not-for-profit hospital-affiliated home care agency were retrospectively reviewed and compared to pre-PPS data. The same data collection tool, the Hospital Readmission Inventory, was used for both pre- and post-PPS studies. Nurse administrators at the data collection agency were interviewed concerning comparative results. FINDINGS: Currently readmitted clients were sicker than were those in the previous research report, they were readmitted sooner for a different diagnosis, and they had less continuity of services. CONCLUSIONS: The home health care industry has undergone a dramatic change in payment for services, from fee-for-service to PPS. Of particular concern is the adverse patient outcome of an unplanned hospital readmission. Prior studies have characterized such patients in home health care, but no comparative reports were found in a literature search since the inception of PPS. Findings from this study indicated that an increased emphasis on cost containment and higher-risk clients appear to have changed patterns of care delivery.     

Prompt Advanced Life Support Improves Survival from Ventricular Fibrillation

Objective. To determine whether the interval between the arrival of basic life support (BLS) providers and the arrival of advanced life support (ALS) providers is associated with patient outcome after cardiac arrest. Methods. We conducted a retrospective cohort study of all witnessed, out-of-hospital ventricular fibrillation (VF) cardiac arrests between January 1, 1991, and December 31, 2007. Eligible patients (n = 1,781) received full resuscitation efforts from both BLS and ALS providers. Results. The BLS-to-ALS arrival interval was a significant predictor of survival to hospital discharge (odds ratio [OR] 0.96, 95% confidence interval [CI] 0.93–0.99); the likelihood of survival decreased by 4% for every minute that ALS arrival was delayed following BLS arrival. Other significant predictors of survival were whether the arrest occurred in public (OR 1.48, 95% CI 1.19–1.85), whether a bystander administered cardiopulmonary resuscitation (CPR) (OR 1.34, 95% CI 1.07–1.68), and the interval between the 9-1-1 call and BLS arrival (OR 0.78, 95% CI 0.73–0.83). Conclusions. We found that a shorter BLS-to-ALS arrival interval increased the likelihood of survival to hospital discharge after a witnessed, out-of-hospital VF cardiac arrest. We conclude that ALS interventions may provide additional benefits over BLS interventions alone when utilized in a well-established, two-tiered emergency medical services (EMS) system already optimized for rapid defibrillation. The highest priorities in any EMS system should still be early CPR and early defibrillation, but timely ALS services can supplement these crucial interventions.     

Age and Other Determinants of Survival After In-hospital Cardiopulmonary Resuscitation

A retrospective review of 274 patients who received in-hospitalcardiopulmonary resuscitation was performed to determine whetherage is independently associated with survival to discharge.Eighty-two (29.9 per cent) of the 274 patients were resuscitatedinitially, but only 25 (9.1 per cent) were discharged alive.Survival to discharge was significantly poorer in patients aged70 years (6/175; 3.4 per cent) than in patients <70 yearsold (19/99; 19.2 per cent) (p<0.001). Severity of illness,assessed by the number of diagnoses and a multifactorial morbidityindex, did not differ between the two age groups. The best resultswere obtained with witnessed arrests, ventricular arrythmiasand resuscitation lasting less than 5 minutes; however, elderlypatients were less likely to be resuscitated in all circumstances.Age (r=–0.31, p<0.001) and the morbidity index r=–0.18,p<0.05) were independently associated with survival by multivariateanalysis. These results indicate that advanced age is an important independentdeterminant of survival after resuscitation. This should betaken into consideration when making in-hospital resuscitationdecisions.     

心肺复苏对室颤频率的影响

目的:观察除颤前心肺复苏(CPR)对室颤频率的影响.方法:将32只健康家猪分为4组,每组动物8只,分别制作闭胸电诱发室颤模型:A组室颤3 min后给予直接除颤:B组室颤3 min后予CPR 2 min后再进行除颤;C组室颤7 min后进行直接除颤;D组室颤7 minn后予CPR 2 min后再进行除颤.结果:室颤发生后频率随时间延长逐渐下降,1 min时室颤频率为12.3±1.8 Hz,3 min时为8.1±1.4 Hz,7 min时为6.8±1.2 Hz(P＜0.05),B组和D组CPR后室颤频率显著增加(B组:13.1±2.1 Hz,D组:10.4±1.5,P＜0.05).A组和B组各8例均经除颤后立即恢复自主循环.除颤后立即恢复自主循环者C组有2例、D组5例:除颤后出现无脉性心电活动,经CPR后恢复自主循环者C组有6例、D组3例(P＞0.05).结论:除颤前CPR可增加室颤的频率,可改善长时间室颤的自主循环恢复率.     

Regular Ventricular Rhythms Before Conversion of Recent Onset Atrial Fibrillation to Sinus Rhythm

The incidence of fast atrial tachycardias with regular ventricular rhythm was assessed in a population of 243 patients with recent onset (< 72 hours) atrial fibrillation (AF), without heart failure, randomly treated with single loading oral dose of propafenone (600 mg), flecainide (300 mg), digoxin (1 mg), or placebo for acute conversion to sinus rhythm (SR). Fast atrial arrhythmias developed in 14 (6%) patients: 6/92 treated with propafenone, 3/34 treated with flecainide, 1/25 treated with digoxin, and 4/ 92 who received placebo (P = NS). Heart rate > 175 beats/min with 1:1 AV conduction ensued in 4 cases: 2 treated with flecainide and 2 treated with placebo; in the other cases 2:1 AV conduction was observed. Widening of QRS during regular tachycardia was observed in 4 patients; 3 who received propafenone and 1 who received flecainide. Conversion to SR within 4 hours was achieved in 55/92 (60%) patients treated with propafenone, 20/34 (59%) patients treated with flecainide, 7/25 (28%) patients treated with digoxin, and 19/92 (20%) treated with placebo (P < 0.001 propafenone vs placebo and flecainide vs placebo; P < 0.05 propafenone vs digoxin and flecainide vs digoxin). Periods of regular tachycardia are expected in recent onset AF and may not necessarily represent a proarrhythmic effect of Class 1C drugs, rather than mark the transition from AF to SR. Class 1C agents are probably responsible for widening of the QRS complex seen during these tachycardias. Propafenone and flecainide appear equally effective in converting recent onset AF.     

Ventricular Fibrillation After Intravenous Atropine in a Patient with Atrioventricular Block

A 69-year-old black woman with complete AV block developed ventricular fibrillation following an IV injection of 1 mg of atropine sulphate. After a successful DC countershock, the ECG showed a polymorphous ventricular tachycardia which subsided spontaneously. Cardiac catheterization revealed a small left ventricular diverticulum and normal coronary arteries. This seems to be the first reported case of atropine-induced ventricular fibrillation in a patient with complete AV block. The fact that this occurred without previous change of the ventricular rate suggests that the adverse action of atropine was mediated through a mere vagolytic effect at the ventricular level.     

Systolic Arterial Pressure Recovery After Ventricular Fibrillation/Flutter in Humans

Although the elective induction of cardiac arrest for implantable defibrillator insertion under general anesthesia is widely used, the hemodynamics of recovery of arterial blood pressure after cardiac arrest is not well-defined. Accordingly, the time course of recovery of systolic arterial pressure was studied in seven patients during the repetitive induction of ventricular fibrillation (n = 6) or ventricular flutter (n = 1). The mean number of episodes of cardiac arrest was 7 ± 2, and the mean drop in systolic pressure was 84 ± 16mmHg. The mean recovery time for systolic pressure was 10 ± 6 seconds, the average systolic pressure recovery rate was 13 ± 14 mmHg/sec, and the mean percent systolic pressure recovery was 94%± 9%. A negative logarithmic relation was found to exist between the rate of systolic arterial pressure recovery and the duration of ventricular fibrillation or flutter with a correlation coefficient of 0.68 to 0.97 (P < 0.05) in five of the seven patients. A linear relation between the time for systolic pressure recovery and duration of asystole was also defined. These results are consistent with the view that prolongation of ventricular fibrillation or flutter increases the duration of arterial pressure recovery through a negative effect on left ventricular contractility. Increased understanding of these relations may lead to increased safety of implantable defibrillator insertion.     

大鼠电刺激诱发心室颤动和机械性心肺复苏模型的建立

目的:建立大鼠交流电电激诱发心室颤动和机械性心肺复苏模型,并探讨其有效性和安全性。方法:选用Sprague-Dawley雄性大鼠20只,应用自主开发研究的心跳骤停和复苏机械装置,持续交流电经右心室内膜致颤。在8min心室颤动后,开始给予6min的心肺复苏,包括200次/min的机械胸外按压和100次/min的同步机械通气。随后双向波经胸体外除颤。结果:14只大鼠复苏成功,自主循环恢复率为70%。电刺激后所有大鼠立刻出现心室颤动,3min的电刺激停止后动物持续表现为室颤而没有自发转复心律现象。心肺复苏期间恢复自主循环组其冠状动脉灌注压恒定在24mmHg左右,显著高于未能恢复自主循环组。大部分大鼠在6min复苏后电击除颤有效恢复自主循环。实验结束后常规解剖未发现器官机械性创伤。结论:本大鼠交流电诱发心室颤动和心肺复苏模型,有效性和安全性高,可最大限度减少实验的误差,具有一定的推广应用前景。     

Catheter Ablation of Ventricular Tachycardia Occurring Late After Myocardial Infarction: A Point-of-View

A Point-of-View. Venfricular tachycardia can be cuntwUed by radiofrequency or chemical ablation of the site of origin of the arrhythmia. However, these techniques are far from being accepted as routine treatment for this problem. This article describes the theoretical and practical background of catheter ablation of ventricuiar tachycardia occurring late after myocardial infarction.     

QT Dispersion Does Not Predict Early Ventricular Fibrillation After Acute Myocardial Infarction

Ventricular arrhythmias may be associated with increased QT dispersion (difference between maximum and minimum QT on standard 12-lead ECG). We performed a case control study to determine if QT dispersion on the admission ECG could predict early VF after acute myocardial infarction. The cases were 24 patients with acute myocardial infarction (14 inferior, 8 anterior, and 2 lateral) with VF within 12 hours of admission. There were 24 control patients without VF matched for site of infarction and ST segment score (sum of ST segment elevation). VF occurred a median of 153 minutes (interquartile range 93–245) after onset of chest pain and 33 minutes (range 7–104) after initial ECG. QT (399 ± 37 and 394 ± 37), QT corrected (440 ± 38 and 429 ± 29), and QT dispersion (68± 20 and 66 ± 27) were similar in patients and controls. By design, ST score was similar (11 ± 9 vs 9 ± 5 mV), although a good match could not be obtained for three patients with extreme ST elevation. Patients with VF presented to the hospital earlier after the onset of chest pain (median 95 min [range 65–188] compared to 150 min [range 80–270], P= 0.05) and had a lower serum sodium (138 ± 2.4 vs 140 ± 2.5, P = 0.05) than controls. Thus, QT interval and QT dispersion, measured on the presenting ECG, did not predict early VF after myocardial infarction.     

Promotion of Ventricular Tachycardia Induction by Procainamide in Dogs with Inducible Ventricular Fibrillation Late After Myocardial Infarction

The influence of procainamide on inducible ventricular tachyarrhythmias was evaluated in 35 dogs with experimental myocardial infarction, and 9 normal dogs. Programmed stimulation was performed from the right ventricular apex via a percutaneously positioned electrode catheter, using up to five extrastimuli before and after intravenous administration of procainamide (15 mg/kg). Procainamide levels in postinfarct dogs were 8.5 +/- 0.7 micrograms/mL (range 5.3-13.6 micrograms/mL). Procainamide exerted its greatest effect in postinfarct dogs with reproducible baseline ventricular fibrillation. Six of nine dogs (P less than 0.05) with ventricular fibrillation had sustained monomorphic ventricular tachycardia (cycle length: 147 +/- 4 msec) induced after procainamide administration. This ventricular tachycardia required significantly more extrastimuli than baseline ventricular fibrillation (3 +/- 0.3 extrastimuli before vs 4 +/- 0.3 extrastimuli after procainamide). Procainamide never converted ventricular fibrillation to ventricular tachycardia in normal dogs. Procainamide had minimal effect on inducible ventricular tachycardia after myocardial infarction. Ventricular tachycardia induction was abolished in only 2 of 17 dogs despite significant prolongation of electrophysiological parameters. Ventricular tachycardia cycle length, and the number of extrastimuli required were unchanged by procainamide in this subgroup. Conclusion: Ventricular tachycardia is insensitive to the antiarrhythmic properties of procainamide in this model. In contrast, procainamide is able to convert postinfarction ventricular fibrillation to ventricular tachycardia, presumably by promoting sustained, organized reentry. This previously undescribed action is an unusual form of proarrhythmic effect, and suggests that this drug should be used cautiously in patients after myocardial infarction.     

Safety of a Single Successful Conversion of Ventricular Fibrillation Before the Implantation of Cardioverter Defibrillators

GOLD, M.R., et al .: Safety of a Single Successful Conversion of Ventricular Fibrillation Before the Implantation of Cardioverter Defibrillators. Multiple successful conversions of ventricular fibrillation (VF) at 10 J below the maximum output of implantable cardioverter defibrillator (ICD) have been recommended as a minimum device implantation criterion. This recommendation is based on the probabilistic properties of defibrillation that necessitates multiple shocks to establish an adequate safety margin for the conversion of subsequent spontaneous arrhythmias. We hypothesized that a single successful shock at a 14 J may suffice. Methods and Results: The Low Energy Safety Study (LESS) enrolled 720 patients undergoing initial ICD implantation with a dual-coil transvenous lead and active pulse generator. At implant, an enhanced defibrillation threshold (DFT++) was determined by a rigorous protocol beginning at 14 J, and requiring at least 4 shocks. Fifty percent of all patients were then randomized to full output shock energy and the conversion rates for spontaneous ventricular tachyarrhythmias at rates >200 beats/min were measured. There were 318 patients randomized to 31 J, of whom 254 were successfully defibrillated by an initial 14 J shock. During a mean follow-up of   24 ± 12   months, 112 spontaneous VF episodes occurred in 31 patients. The combined conversion success of the first and second shock (when needed) did not differ between the subgroup of patients who were successfully defibrillated by an initial 14 J shock, regardless of the results of additional testing, and the whole cohort who underwent more systematic testing (97% vs 97%). All spontaneous episodes of VF were successfully treated during long-term follow-up. Conclusions: A first successful shock of 14 J may be a sufficient endpoint to allow the implantation of ICDs with the Triad lead configuration, when programming all shocks to 31 J. (PACE 2003; 26[Pt. II]:483–486)