Secondary Ventricular Fibrillation Research Articles

Association between new-onset right bundle branch block and primary or secondary ventricular fibrillation in ST-segment elevation myocardial infarction

Abstract Funding Acknowledgements Type of funding sources: None. Background New-onset right bundle branch block (RBBB) in myocardial infarction (MI) is often associated with ventricular fibrillation (VF) but the nature of this relationship has not been determined. Aims To investigate the association between new-onset RBBB and VF in ST-segment elevation MI (STEMI) as well as its peculiarities attending to the permanent or transient character of RBBB and the distinction of VF as primary or secondary. Methods and results Between 1998 and 2014, among other data, incidence and duration of RBBB and VF occurrence were prospectively collected in 5301 patients with ST-segment elevation MI (STEMI) admitted to two Coronary Care Units. Multinomial adjusted logistic regression analyses were used to examine the association between RBBB, attending to its duration, and VF according to its primary VF (PVF) (<24h from symptom-onset and Killip I) or secondary VF (SVF) (>24h from symptom-onset and/or Killip>I) character. Among 284 (5.4%) patients with new-onset RBBB, 158 were transient and 126 permanent. VF occurred in 339 (6.4%) patients, 201 PVF and 138 SVF, documented within the first 2 h of symptoms-onset in 78% and 60%, respectively. Newonset RBBB was more frequent in PVF (11.4%) and SVF (20.3%), than in non-VF (4.7%). Transient RBBB incidence was higher in PVF (9.0%) and SVF (9.4) than in non-VF (2.6%), whereas permanent RBBB was higher in SVF (10.9%) than PVF (2.5%) and non-VF (2.1%). New-onset RBBB 1.83 [95% confidence interval (CI): 1.07–3.11] and new-onset transient RBBB 2.39 (95% CI: 1.32–4.32) were independently associated with PVF. New-onset 3.03 (95% CI: 1.83–5.02), transient 2.40 (95% CI: 1.27–4.55), and permanent 2.99 (95% CI: 1.52–5.86) RBBB were independently associated with SVF. Conclusion New-onset RBBB and VF in STEMI are independently associated and show particularities based on the duration of the conduction disturbance and/or the primary or secondary character of the arrhythmia.

Sex differences among patients with tachyarrhythmias and bradyarrhythmias following acute myocardial infarction

Abstract Background Acute myocardial infarction (AMI) is commonly complicated by ventricular, supraventricular tachycardias and high-grade atrioventricular block (HAVB) which may result in increased morbidity and mortality. Purpose To evaluate the sex differences in tachyarrhythmias and HAVB, and their associated outcomes following AMI. Methods Using the Acute Coronary Syndrome Israeli Survey (ACSIS) survey database from 2000–2018, we analyzed the specific incidence rates for arrhythmias including: sustained ventricular tachycardia (VT), ventricular fibrillation (VF), new-onset atrial fibrillation (AF) and HAVB in men and women after AMI. Unadjusted and multivariable-adjusted logistic regression analyses were performed to assess the sex differences of in-hospital arrhythmias after AMI. Multivariate cox proportional hazard models were performed to assess the impact of arrhythmias on 1-year mortality. Results In this cohort study of 14280 patients with 3159 (22.1%) women and 11121 (77.9%) men, 316 (2.2%) experienced ventricular arrhythmias (VAs) (sustained VT or secondary VF) with similar rates among men and women (2.3% and 2.2%, respectively, p=0.62). Compared to men, women were less likely to experience primary VF (1.6% vs 2.3%, p=0.034), but more likely to experience AF (8.6% and 5.0%, p<0.001). 372 (2.6%) patients experienced HAVB with higher rates of HAVB in women than men (3.7% and 2.3%, respectively, p<0.001). After multivariate analyses, the association with primary VF was attenuated (adjusted Odds Ratio (OR) = 0.80, p=0.15) but women remained more likely to experience AF (adjusted OR =1.24, p=0.01) and HAVB (adjusted OR =1.28, p=0.04). The occurrence of VAs was found to be associated with increased mortality in both men (adjusted Hazard Ratio (HR) =3.68, p<0.01) and women (adjusted HR=3.87, p<0.01) without a significant difference between the groups (p for interaction=0.203). The occurrence of AF was found to be associated with increased mortality in both men (adjusted HR=1.64, p<0.001) and women (adjusted HR=1.34, p<0.001) with a significant difference between the groups (p for interaction<0.001). HAVB was found to be associated with increased mortality in both men (adjusted HR=2.31, p<0.001) and women (adjusted HR=2.26, p<0.001) without a significant difference between the groups (p of interaction=0.21). Conclusions The incidence rates of VAs after AMI were similar in men and women, except for primary VF, which was more common among men. Women experienced more AF and HAVB than men. VAs, AF and HAVB were found to be associated with increased mortality. Funding Acknowledgement Type of funding sources: None.

Association between new-onset right bundle branch block and primary or secondary ventricular fibrillation in ST-segment elevation myocardial infarction.

New-onset right bundle branch block (RBBB) in myocardial infarction (MI) is often associated with ventricular fibrillation (VF) but the nature of this relationship has not been determined. Between 1998 and 2014, among other data, incidence and duration of RBBB and VF occurrence were prospectively collected in 5301 patients with ST-segment elevation MI (STEMI) admitted to two University Hospitals in Murcia (Spain). Multinomial adjusted logistic regression analyses were used to examine the association between RBBB, attending to its duration, and VF according to its primary VF (PVF) or secondary VF (SVF) character. Among 284 (5.4%) patients with new-onset RBBB, 158 were transient and 126 permanent. VF occurred in 339 (6.4%) patients, 201 PVF and 138 SVF, documented within the first 2 h of symptoms-onset in 78% and 60%, respectively. New-onset RBBB was more frequent in PVF (11.4%) and SVF (20.3%), than in non-VF (4.7%). Transient RBBB incidence was higher in PVF (9.0%) and SVF (9.4) than in non-VF (2.6%), whereas permanent RBBB was higher in SVF (10.9%) than PVF (2.5%) and non-VF (2.1%). New-onset RBBB 1.83 [95% confidence interval (CI): 1.07-3.11] and new-onset transient RBBB 2.39 (95% CI: 1.32-4.32) were independently associated with PVF. New-onset 3.03 (95% CI: 1.83-5.02), transient 2.40 (95% CI: 1.27-4.55), and permanent 2.99 (95% CI: 1.52-5.86) RBBB were independently associated with SVF. New-onset RBBB and VF in STEMI are independently associated and show particularities based on the duration of the conduction disturbance and/or the primary or secondary character of the arrhythmia.

Secondary Ventricular Fibrillation or Pulseless Ventricular Tachycardia During Cardiac Arrest and Epinephrine Dosing

Development of ventricular fibrillation or pulseless ventricular tachycardia after an initial rhythm of pulseless electrical activity or asystole is associated with significantly increased cardiac arrest mortality. To examine differences in epinephrine administration during cardiac arrest between patients who had a secondary ventricular fibrillation or ventricular tachycardia develop and patients who did not. Data were collected for 2 groups of patients with in-hospital cardiac arrest and an initial rhythm of pulseless electrical activity or asystole: those who had a secondary ventricular fibrillation or ventricular tachycardia develop (cases) and those who did not (controls). Dosing of epinephrine during cardiac arrest and other variables were compared between cases and controls. Of the 215 patients identified with an initial rhythm of pulseless electrical activity or asystole, 51 (23.7%) had a secondary ventricular fibrillation or ventricular tachycardia develop. Throughout the total duration of arrest, including periods of return of spontaneous circulation, the dosing interval for epinephrine in patients who had a secondary ventricular fibrillation or ventricular tachycardia develop was 1 mg every 3.4 minutes compared with 1 mg every 5 minutes in controls (P= .001). For the total duration of pulselessness, excluding periods of return of spontaneous circulation during the arrest, the dosing interval for epinephrine in patients who had a secondary ventricular fibrillation or ventricular tachycardia develop was 1 mg every 3.1 minutes versus 1 mg every 4.3 minutes in controls (P= .001). More frequent administration of epinephrine during cardiac arrest is associated with development of secondary ventricular fibrillation or ventricular tachycardia.

Myocardial Substrate in Secondary Ventricular Fibrillation: Insights from Quantitative Waveform Measures

Background. Some patients presenting with nonshockable cardiac arrest rhythms will subsequently manifest ventricular fibrillation. Their prognosis remains poor despite transition to a shockable rhythm. Quantitative waveform measures assess the electrophysiologic status of the fibrillating heart and predict outcome. Objective. To use waveform measures to compare those who presented initially with ventricular fibrillation (primary group) with those who manifested ventricular fibrillation after initially presenting with a nonshockable arrest rhythm (secondary group). Methods. We conducted an observational study using a convenience sample to compare waveform measures of amplitude spectrum area (AMSA), cardioversion output predictor (COP), and detrended fluctuation analysis (DFA) prior to initial shock between the primary (n = 178) and secondary (n = 28) groups. We produced a primary group matched to the secondary group based on the average waveform values to evaluate the observed versus expected outcomes in the secondary group. Results. Survival was 42% in the primary group and 0% in the secondary group. There was a trend toward more favorable waveform values in the primary compared with the secondary group (9.48 versus 9.29, p = 0.10 for AMSA; 13.75 versus 14.12, p = 0.003 for COP; and 0.36 versus 0.44, p = 0.09 for DFA). The restricted, matched primary group experienced a survival of 37%, compared with 0% for the secondary group. Conclusions. Taken together, the findings suggest that the electrophysiologic status of the heart may be suitable for resuscitation in at least some secondary ventricular fibrillation cases and that other pathophysiology may contribute substantially to the poor prognosis. Alternately, waveform measures may not predict clinical outcomes in secondary ventricular fibrillation.

A prospective study of outcome of in-patient paediatric cardiopulmonary arrest

Few prospective studies of the incidence and outcome of paediatric in-hospital cardiopulmonary arrest have been reported to enable quality assurance comparisons within and between institutions. All cardiac and respiratory arrests and their management over a 41-month period in children not subject to palliative treatment or to a 'do not resuscitate' order were recorded and analysed using the Utstein template. Cardiac arrest occurred in a total of 111 of 104,780 admissions (1.06/1000) while respiratory arrest alone occurred in 36 (0.34/1000). Return of spontaneous circulation (ROSC) was achieved in 81 patients (73%) in cardiac arrest but only 40 (36%) were discharged from hospital and 38 (34%) survived for 1 year. The 1-year survival from respiratory arrest alone was 97%. Cardiac arrest was four times more common (89 versus 22) and approximately 90 times the incidence in the intensive care unit compared with wards but 1-year survival was similar (34% versus 36%). The initial heart rhythms were hypotensive-bradycardia in 73 (66%) with 38% survival; asystole in 17 (15%) with 12% survival; ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) in 10 (9%) with 40% survival; pulseless electrical activity (PEA) in 10 (9%) with 30% survival and SVT in 1 with survival. Secondary ventricular fibrillation occurred in 15 children given adrenaline (epinephrine) for treatment of asystole, hypotensive-bradycardia or PEA of whom 11 had received adrenaline in an initial dose of > 15 mcg/kg and 4 had < 15 mcg/kg (P = 0.0013). Eleven of 15 patients (73%) in secondary VF never achieved ROSC. In-patient paediatric cardiac arrest has a mediocre outcome with a better outlook if the initial rhythm is hypotensive-bradycardia, VF or pulsatile VT. Doses of adrenaline greater than 15 mcg/kg given for non-shockable rhythms may cause secondary VF which has a worse outcome than primary VF.

Ventricular fibrillation in acute myocardial infarction in Spanish patients: Results of the ARIAM database.

The aim of this study has been to investigate the factors predisposing to primary or secondary ventricular fibrillation (VF) and the prognosis in Spanish patients with acute myocardial infarction (AMI) during their admission to the intensive care unit or the coronary care unit. A retrospective, observational study. The intensive care units and coronary care units of 119 Spanish hospitals. A retrospective cohort study including all the AMI patients listed in the ARIAM registry (Analysis of Delay in Acute Myocardial Infarction), a Spanish multicenter study. The study period was January 1995 to January 2001. Factors associated with the onset of VF were studied by univariate analysis. Multivariate analysis was used to evaluate the independent factors for the onset of VF and for mortality. A total of 17,761 patients with AMI were included in the study; 964 (5.4%) developed VF (primary in 735 patients, secondary in 229). In multivariate analysis, the variables that continued to show an association with the development of VF were the Killip and Kimball class, peak creatine kinase, APACHE II score, age, and time from the onset of symptoms to the initiation of thrombolysis. The mortality in the patients with any VF was 31.8% (27.8% in patients with primary VF and 49.1% in patients with secondary VF). The development of VF is an independent predictive factor for mortality in patients with AMI, with a crude odds ratio of 5.12 (95% confidence interval, 4.41-5.95) and an adjusted odds ratio of 2.73 (95% confidence interval, 2.12-3.51). Despite the considerable improvement in the treatment of AMI in recent years, the onset of either primary or secondary VF is associated with a poor prognosis. It is usually accompanied by extensive necrosis.

Ventricular fibrillatory frequency and its correlation with transthoracic defibrillation current requirement

Correlation between ventricular fibrillatory frequency (VFF) in patients with ventricular fibrillation (VF) and transthoracic defibrillation current was studied. Strong positive correlation between VFF and optimal defibrillation current was revealed in patients with primary VF. There was a significant negative correlation between TTI and defibrillation current, that ceased secondary VF, and there was no significant correlation between TTI and current in patients with primary VF.

Early discharge after acute myocardial infarction: risks and benefits.

Thrombolytic treatment reduces mortality in patients with acute myocardial infarction but is associated with recurrent thrombotic events after admission, and it is unclear whether current practices of early hospital discharge are safe. Timing of first major adverse events (death, reinfarction, unstable angina, secondary ventricular fibrillation) in the early post-infarction period was studied to determine the risks. Follow up study. 608 consecutive patients (447 men and 161 women) with confirmed myocardial infarction who were admitted to the coronary care unit of a district general hospital between January 1989 and December 1991. Clinical details, including the development of left ventricular failure and in hospital adverse events, were recorded prospectively. Follow up for out of hospital adverse events was carried out by review of the case notes, postal questionnaire, and where necessary, by telephone contact with the patient and his general practitioner. The risk (95% confidence interval) of major adverse events in the first 10 days was 32.3% (26.3 to 39.4%) in patients with heart failure and 7.3% (5.1 to 9.2%) in those without. Smoothed estimates of the event rate in patients without heart failure decreased from 5.9 events/1000 persons/day on day 6 to 3.4 events/1000 persons/day on day 10 and 0.9 events/1000 persons/day on day 21. The corresponding cumulative risk estimates suggest that about 11 in every 1000 patients suffer a major, but often unpreventable, adverse event on day 6 or 7 after admission, and 23 in every 1000 do so between days 6 and 10. The point at which the risk to the individual becomes acceptably low is a matter of judgement, but the risk of a major adverse event declines rapidly after a heart attack, and particularly for patients without heart failure discharge within a few days may be appropriate. Prolonging stay unnecessarily may use resources which could be more effectively used to treat cardiac disease in other ways.

Frequency and prognostic significance of secondary ventricular fibrillation complicating acute myocardial infarction

The incidence of secondary ventricular fibrillation (VF) complicating acute myocardial infarction (AMI) was 2.4% in a large cohort of unselected patients with AMI (142 of 5,839). Secondary VF was more frequent in patients with recurrent AMI (4%) than in those with a first AMI (1.9%) (p < 0.01). The hospital course was more complicated and in-hospital mortality was significantly higher in patients with secondary VF than in those with the same clinical hemodynamic condition but without VF (56 vs 16%; p < 0.0001). Multivariate analyses confirmed secondary VF complicating AMI as an independent predictor of high in-hospital mortality, with an odds ratio of 7 (95% confidence interval 4.6–10.6). However, long-term mortality after discharge (mean follow-up 5.5 years) was not increased in patients with as compared with those without secondary VF (39 vs 42%). These findings were also true when patients receiving β blockers and antiarrhythmic therapy were excluded from analysis. Thus, this life-threatening arrhythmia occurring during hospitalization is not a marker of recurrent susceptibility to VF or an indicator of increased mortality after discharge from the hospital.

Ventricular fibrillation markers on admission to the hospital for acute mcardial infarction

Primary ventricular fibrillation (VF) is an early complication of acute myocardial infarction (AMI), which was recently associated with high in-hospital mortality. 1 The usefulness of preventive antiarrhythmic drugs in patients with symptoms of acute coronary ischemia has been addressed in different studies, 2,3 but less attention has been given to the identification of AMI patients with a high risk for VF. Admission data for predicting VF in AMI have been assessed by Flugelman et al 4–5 and Molstad 6 using multiple logistic regression formulas. In the first study, however, ventricular tachycardia was included as the end point for analysis, and no distinction was made between primary and secondary VF, whereas in the second study, only variables of doubtful value in clinical practice were considered. We investigated the usefulness of routine clinical, electrocardiographic and laboratory parameters for predicting the development of VF in patients with AMI in Killip's functional class I and II.

Frequency Analysis of Ventricular Fibrillation and Resuscitation Success

In 56 patients, frequency analysis of the electrocardiogram of ventricular fibrillation exhibited power spectra with a distinct dominant frequency. The greatest success for resuscitation from ventricular fibrillation is recorded when ventricular fibrillation develops after the patient comes under coronary care. Of the 41 patients in whom the onset and first 8 s of ventricular fibrillation were artefact-free the mean dominant frequency of primary ventricular fibrillation (no cardiogenic shock or cardiac failure) in 21 patients was 6.2 +/- 0.2 Hz, significantly higher than the mean dominant frequency of the first 8 s of secondary ventricular fibrillation (cardiogenic shock or heart failure) (4.0 +/- 0.2 Hz, 20 patients, p = 0.0001). In these patients the peak-to-trough amplitude (ECG) of the first 8 s of ventricular fibrillation was similar in both primary and secondary ventricular fibrillation as was the mean duration of ventricular fibrillation prior to the first DC shock. There was a significantly lower success rate for resuscitation from secondary ventricular fibrillation (6 of 20 patients) compared with resuscitation from primary ventricular fibrillation (18 of 21 patients, chi 2 17.8, p = 0.001). Of the remaining 15 patients who were collapsed between 3 and 20 min before the arrival of the mobile coronary care unit, the dominant frequency of the first 8 s of ventricular fibrillation fell with increased duration of collapse (from 5.5 Hz at 3 min to a mean of 2.1 Hz at 20 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Time course of creatine kinase release after termination of sustained ventricular dysrhythmias

Differentiation between primary and secondary (caused by acute myocardial infarction) ventricular fibrillation has important therapeutic and prognostic implications. The diagnosis of myocardial infarction is based on clinical, ECG, and creatine kinase MB isoenzyme (MBCK) activity. Enzymatic criteria might not be able to confirm the diagnosis of myocardial infarction after recent cardioversion. The routine use of electrophysiologic studies involving the induction and termination of ventricular dysrhythmias provides a setting in which enzyme release as a result of cardioversion alone can be examined. Therefore a systematic investigation of the magnitude and time course of creatine kinase (CK) and MBCK release was performed after termination of ventricular dysrhythmias in 57 patlents undergoing electrophysiologic studies. Of patients requiring external cardioversion, only 50% had an elevation in CK and MBCK activity. Elevation when present correlated with the number of shocks and cumulative energy delivered. The magnitude of MBCK release exceeded 10% of the total CK activity in 9% of observations. Pace-termination of ventricular tachycardia did not result in enzyme release. Arrhythmia characteriatics, coronary artery disease, and left ventricular function did not affect the magnitude of the time course of enzyme release. These data suggest that cardioversion with multipile shocks may result in a component of MBCK release, and thus a false positive diagnosis of primary acute myocardial infarction may be made by relying exclusively on the enzyme release pattern.

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.

Early streptokinase reduces the risk of late secondary ventricular fibrillation

Early streptokinase reduces the risk of late secondary ventricular fibrillation

Incidence and prognosis of secondary ventricular fibrillation in acute myocardial infarction. Evidence for a protective effect of thrombolytic therapy. GISSI Investigators.

The multicenter randomized study of the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico has provided the opportunity to analyze the impact of thrombolytic treatment on secondary ventricular fibrillation incidence in a large population of patients (11,712) with acute myocardial infarction. A reduction of about 20% in the frequency of secondary ventricular fibrillation was observed among patients allocated to thrombolytic treatment (streptokinase, 2.4% versus control, 2.9%; relative risk, 0.80; 95% confidence interval, 0.64-1.00). Streptokinase appeared to exert its protective effect specifically in patients treated within 3 hours of onset of symptoms (streptokinase, 2.6% versus control, 3.7%; relative risk, 0.71; 95% confidence interval, 0.53-0.95). This protection was essentially due to a reduced incidence of late ventricular fibrillation occurring after the first day of hospitalization. The 311 patients with secondary ventricular fibrillation represented an overall incidence of 2.7%. Such incidence was not related to infarct location or sex but was significantly more common in patients older than 65 years (3.3% versus 2.3% in younger patients). A significant excess of in-hospital deaths was found in patients with secondary ventricular fibrillation compared with those in the reference group (38% versus 24%; relative risk, 1.98; 95% confidence interval, 1.56-2.52). Conversely, secondary ventricular fibrillation was not a predictor of 1-year mortality for hospital survivors. Thrombolytic treatment with intravenous streptokinase affords protection against secondary ventricular fibrillation most probably by a limitation of infarct size. When the arrhythmia complicates the course of infarction, it is associated with an adverse short-term outcome, whereas the long-term prognosis is not influenced.

Prognosis of late versus early ventricular fibrillation in acute myocardial infarction

To determine the prognosis of late ventricular fibrillation (VF) after acute myocardial infarction (AMI), the length of the monitoring period after AMI was extended. All patients in this series were continuously monitored in a coronary care unit to ensure observation of all VF within 18 days of AMI. From 1977 to 1985, 4,269 patients were admitted with AMI and 413 (9.6%) had in-hospital VF. Of these 281 (6.8%) had early VF (<48 hours after AMI) and 132 (3.2%) had late VF (≥48 hours after AMI). In-hospital mortality was 50 and 54% for early and late VF, respectively (p = 0.31). Kaplan-Meier survival analysis showed better survival after discharge for patients with early versus late VF (p = 0.009) but this difference was fully explained by the presence of heart failure. Survival analysis showed the same prognosis after 1, 3 and 5 years for early and late VF, when VF was not associated with heart failure. When VF was associated with heart failure (secondary VF) early VF had a greater mortality than late VF after 2 and 5 years. Logistic regression analysis showed that heart failure (relative risk 1.9 [1.1 to 3.1]) and cardiogenic shock (relative risk 3.9 [1.8 to 8.5]) were significant risk factors for in-hospital death. Late VF compared to early VF had no prognostic implication (relative risk 1.0 [0.6 to 1.6]). For patients discharged from the hospital, risk factors were heart failure (1.8 [1.1 to 2.8]) and previous AMI (1.6 [1.3 to 2.1]). Late VF showed a trend (1.2 [0.8 to 1.8]) toward poorer long-term prognosis than early VF. There is no special risk for patients with late VF compared to patients with early VF after AMI when they are monitored as described.

The size of infarction as judged enzymatically in 1974 patients with acute myocardial infarction. Relation with symptomatology, infarct localization and type of infarction

A common data base of six coronary care units containing personal and clinical data of 17462 patients was used to investigate the relation between clinical symptoms of patients with acute myocardial infarction and size of infarction. In 1974 of the 5110 patients, in whom a final diagnosis of infarction was made, size of infarction was determined according to serially measured levels of serum α-hydroxybutyrate dehydrogenase. The episode of infarction was the first in 1396 patients, was recurrent in 497, and undetermined in 81 patients. We calculated the size factor (defined as the mean size of infarction of patients with a particular symptom divided by the mean size of infarction of patients without that symptom) to evaluate the role of the size of infarction to manifestation of certain clinical symptoms. Bradycardia, shock and right-sided failure when noted on admission to the coronary care unit, had factors for size of infarction significantly greater than 1.0 (1.15, 1.79 and 1.30, respectively) in patients suffering an initial infarction, but not significantly different from 1.0 in patients with recurrent infarction. The occurrence of primary and secondary ventricular tachycardia and/or fibrillation, left heart failure (Killip class II–IV), symptomatic supraventricular tachycardia, high-degree atrioventricular blocks, ruptures and death in the coronary care unit was associated with factors significantly greater than 1.0 in those patients having both initial and recurrent infarctions. The size of infarction as judged enzymatically was significantly larger in patients with anterior than inferior and lateral infarction. The size of infarctions without Q waves was judged to be generally 35% smaller than infarctions producing Q waves.It is concluded that the size of infarction determines the occurrence of several symptoms and complications diagnosed at admission or during stay in the coronary care unit.

Relationship between infarct size and incidence of severe ventricular arrhythmias in a double-blind trial with metoprolol in acute myocardial infarction

In 585 patients having an acute myocardial infarction for the first time the relationship was investigated between estimated infarct size and the incidence of ventricular fibrillation and treated ventricular tachycardia during hospitalization. The size of the infarct was estimated from analyses of heat stable lactate dehydrogenase (LD) (EC 1.1.1.27.) in serum collected every 12 hr for 48–108 hr. All patients participated in a double-blind comparison of the β 1-selective blocker metoprolol with placebo in suspected acute myocardial infarction. A correlation was observed between the enzymatically estimated infarct size and the incidence of ventricular fibrillation and treated ventricular tachycardia in patients on placebo ( P < 0.001), while this could not be demonstrated in patients on the beta-blocker ( P > 0.2). In placebo treated patients there was a correlation between the maximum heat stable LD activity and early ventricular fibrillation ( P = 0.034), late ventricular fibrillation ( P < 0.001), primary ventricular fibrillation ( P = 0.002) as well as secondary ventricular fibrillation ( P = 0.034). It is concluded that there seems to be a relatively strong correlation between the final size of the infarction and the occurrence of severe ventricular arrhythmias. Treatment with beta-blockade appeared to disturb this correlation.

Determinants of defibrillation: Prospective analysis of 183 patients

Previous studies have suggested that a number of factors may influence the ability to defibrillate: the transthoracic resistance and resultant current flow, the paddle electrode size, the duration of preshock ventricular fibrillation (VF) and cardiopulmonary resuscitation, metabolic abnormalities, body weight, the shock energy selected, and whether the patient is receiving lidocaine. To examine the effect of these variables, a prospective study was conducted of 183 patients who received direct-current shocks for VF. Overall defibrillation rates approached 90%, even in patients with secondary VF, but rates of successful resuscitation and survival were much lower. Patients who never defibrillated despite multiple shocks had a prolonged duration of cardiopulmonary resuscitation preceding the first shock (21 ± 14 minutes) and systemic hypoxia and acidosis. These conditions tended to occur in patients who initially had cardiac arrest from causes other than VF: asystole, severe bradycardia and electromechanical dissociation. In such patients, VF developed only as a late event, which was then often unresponsive to attempted defibrillation. The other factors examined were not major determinants of defibrillation.