Sudden death due to cardiac arrhythmias

Sudden cardiac death in division I collegiate athletics: analysis of automated external defibrillator utilization in National Collegiate Athletic Association division I athletic programs

OBJECTIVE

To determine current outcomes of automated external defibrillator (AED) interventions in sports medicine programs in National Collegiate Athletic Association (NCAA) division I athletics.

DESIGN

Qualitative scripted telephone interview with all positive responders to prior NCAA division I-wide study on AED utilization and implementation.

SETTING

NCAA division I sports medicine programs. Head athletic trainers were the main data source.

PARTICIPANTS

All positive responders to a previously published study on AED implementation in the NCAA division I sports medicine community. Positive responders were those that indicated that they had used their departmental AEDs in a sudden cardiac death (SCD) scenario.

MAIN OUTCOME MEASUREMENTS

Survival to hospital discharge was the main outcome sought. When available, additional outcomes were time to defibrillation, time to notification of athletic training staff, EMS response time, location of event, and sudden cardiac victim type (i.e., student, coach, fan).

RESULTS

Sixteen departments that previously reported having had an SCD event at their institution responded to this follow-up telephone survey. Twenty percent of AED uses were attributed to student athletes, with 33% of utilizations for athletic department staff and 47% for fans. Defibrillation was actually administered in 53% of AED unit applications. Time to shock was an average of 3.4 minutes, with average EMS response time of 8.2 minutes for those events without EMS on site. Reported survival to hospital discharge in this university athletic department setting for SCD was 0% for students, 75% for staff, 57% for fans, and 61% overall.

CONCLUSIONS

The results of this study demonstrate the need for NCAA division 1 athletic sports medicine programs to examine, and possibly expand, the traditional scope of practice of caring primarily for student athletes to include the larger community of sports participants comprised of athletes, departmental staff, and spectators. Athletic department AED programs were extremely successfully at increasing survival of SCD far above national prehospital standards, mainly in the nonathletic population. Further study is also necessary in the realm of AED placement, maintenance, and training of staff.

Cardiovascular morbidity and mortality in hypertensive patients with a history of atrial fibrillation

OBJECTIVES

We assessed the impact of antihypertensive treatment in hypertensive patients with electrocardiographic (ECG) left ventricular (LV) hypertrophy and a history of atrial fibrillation (AF).

BACKGROUND

Optimal treatment of hypertensive patients with AF to reduce the risk of cardiovascular morbidity and mortality remains unclear.

METHODS

As part of the Losartan Intervention For End point reduction in hypertension (LIFE) study, 342 hypertensive patients with AF and LV hypertrophy were assigned to losartan- or atenolol-based therapy for 1,471 patient-years of follow-up.

RESULTS

The primary composite end point (cardiovascular mortality, stroke, and myocardial infarction) occurred in 36 patients in the losartan group versus 67 in the atenolol group (hazard ratio [HR] = 0.58, 95% confidence interval [CI] 0.39 to 0.88, p = 0.009). Cardiovascular deaths occurred in 20 versus 38 patients in the losartan and atenolol groups, respectively (HR = 0.58, 95% CI 0.33 to 0.99, p = 0.048). Stroke occurred in 18 versus 38 patients (HR = 0.55, 95% CI 0.31 to 0.97, p = 0.039), and myocardial infarction in 11 versus 8 patients (p = NS). Losartan-based treatment led to trends toward lower all-cause mortality (30 vs. 49, HR = 0.67, 95% CI 0.42 to 1.06, p = 0.090) and fewer pacemaker implantations (5 vs. 15, p = 0.065), whereas hospitalization for heart failure took place in 15 versus 26 patients and sudden cardiac death in 9 versus 17, respectively (both p = NS). The benefit of losartan was greater in patients with AF than those with sinus rhythm for the primary composite end point (p = 0.019) and cardiovascular mortality (p = 0.039).

CONCLUSIONS

Losartan is more effective than atenolol-based therapy in reducing the risk of the primary composite end point of cardiovascular morbidity and mortality as well as stroke and cardiovascular death in hypertensive patients with ECG LV hypertrophy and AF.

The sensitivity of the heart to static magnetic fields

Static magnetic fields induce flow potentials in arterial flows in and around the heart, that have been detected as distortions in the ECG. The resultant currents flowing through the myocardium could alter the rate or rhythm of the heart. No such changes have been seen in animal experiments, or with humans, in static fields up to 8 T. The possible effects of such currents induced by fields larger than 8 T on cardiac pacemaker rate, and arrhythmogenesis are reviewed, using virtual cardiac tissues-computational models of cardiac electrophysiology. Arrhythmogenesis can be by the initiation of ectopic beats, or by re-entry, whose probability of occurrence is increased by any increase in the electrical heterogeneity, in particular, the action potential duration heterogeneity of the ventricle. Focal ectopic activity would be readily detectable, but since re-entrant arrhythmias are very rare events, even a large increase in their probability of occurrence still leaves them unlikely to be observed. Both of these two arrhythmogenic mechanisms would show a steep sigmoidal, or threshold dependence on induced current intensity, with the threshold for increasing the vulnerability to re-entry less than the threshold for initiating activity. Failure to observe them at fields less than 8 T provides only a lower bound for any threshold for arrhythmogenesis.

QTc prolongation by grapefruit juice and its potential pharmacological basis: HERG channel blockade by flavonoids

BACKGROUND

A high intake of dietary flavonoids, which are abundant in fruits, vegetables, tea, and wine, is known to reduce cardiovascular mortality. The effects of flavonoids on cardiac electrophysiology, which theoretically may have both antiarrhythmic and proarrhythmic consequences, have not been studied systematically to date.

METHODS AND RESULTS

We screened a broad spectrum of flavonoids for their inhibitory activity on HERG channels by using heterologous expression in Xenopus oocytes. At a concentration of 1 mmol/L, 10 compounds caused a significant inhibition of HERG currents, whereas 11 other flavonoids had no effect. The IC50 value for HERG block by naringenin, the most potent inhibitor, was 102.3 micromol/L in Xenopus oocytes and 36.5 micromol/L in HEK cells. To demonstrate the physiological relevance of these findings, we studied the effects of pink grapefruit juice, which contains large amounts of naringenin glycosides (>1000 micromol/L), in human volunteers. In 10 persons, we observed a peak QTc prolongation of 12.5+/-4.2 ms 5 hours after oral ingestion of 1 L of grapefruit juice. This effect was significant (P=0.02).

CONCLUSIONS

We found a significant QTc prolongation by grapefruit juice in healthy volunteers, probably caused by block of HERG channels by flavonoids. These findings reveal new perspectives on the potential for dietary modification of cardiac electrophysiology.

[Resuscitation after prehospital cardiovascular arrest]

Initiation of effective cardiopulmonary resuscitation (CPR) at the earliest possible moment is the most important determinant of prognosis for prehospital cardiac arrest. The prognosis is essentially defined by two parameters: survival to hospital admission and survival to discharge. In connection with prehospital cardiac arrest, early defibrillation is particularly important, including the widespread availability of (semi)automatic defibrillators. Further aspects of CPR have recently received increased attention: on the one hand, changed study status regarding the use of antiarrhythmic agents (especially amiodarone), on the other hand, administration of vasopressin during resuscitation, and finally, the efficacy of mild hypothermia following prehospital cardiac arrest. These aspects represent the main subject of the present overview, which also addresses the latest revision of the International Liaison Committee on Resuscitation (ILCOR) guidelines on CPR that resulted in corresponding changes in the European Resuscitation Council (ERC) guidelines.

Prognostic value of plasma brain natriuretic peptide combined with left ventricular dimensions in predicting sudden death of patients with chronic heart failure

BACKGROUND

We evaluated a combined assessment of brain natriuretic peptide (BNP) with left ventricular dimensions as a prognostic marker for sudden death in patients with chronic heart failure (CHF). Ventricular dimensions and BNP are separately recognized as prognostic markers for sudden death in patients with CHF.

METHODS AND RESULTS

CHF patients at Stage C and B were registered for a prospective study. From the database, we analyzed 417 patients with coronary arterial disease (CAD) or primary/secondary dilated cardiomyopathy (DCM). Main effects of BNP, left ventricular ejection fraction (EF), LV diastolic dimension (LVDD), and interaction of BNP with the EF and LVDD were tested with Cox's proportional hazard model. BNP in sudden death patients was significantly higher than that in event-free patients. Although multivariate analysis revealed that BNP by itself was not an independent risk factor for sudden death after adjustments, it was revealed that BNP entered the model via interaction with EF as a risk factor associating with sudden death. On the other hand, BNP was an independent risk factor associating with heart failure events (death and hospitalization), and BNP did not enter the model via an interaction with EF.

CONCLUSION

BNP by itself was an independent risk factor for the heart failure events, but not for sudden death in CHF patients of the present study. However, BNP should be important in predicting sudden death when measured with EF.

Magnetocardiograms in clinical medicine: unique information on cardiac ischemia, arrhythmias, and fetal diagnosis

Cardiac diseases are the leading cause of death in population. Diagnostic tests to detect cardiac dysfunction at an early stage of the disease are desirable. The major focus has been centered on tests evaluating the perfusion of the heart with imaging techniques or detecting alterations in electrical or mechanical function of the heart. The heart generates magnetic fields that can be detected by body surface mapping utilizing super conducting quantum interference device sensors giving magnetocardiograms (MCGs). The advantages of MCG over traditional electrocardiograms (ECGs) are increased sensitivity to small signals and lack of conductivity in body tissues, presentation of direct component signals and primary currents. This review will highlight the basic principles and recent advantages of MCGs, and the application of MCG in clinical diagnosis, especially in cases whose ECGs are non-diagnostic or not specific, such as detecting baseline shift in ischemic heart disease, noninvasive His potential recording, detection of arrhythmic mechanism defining reentrant circuits vs non reentrant mechanism, diagnosis of fetal arrhythmias and prolongation of QT interval. Areas of future basic and clinical research are also discussed.

Incidence of Ventricular Fibrillation in Patients With Out-of-Hospital Cardiac Arrest in Japan Survey of Survivors After Out-of-Hospital Cardiac Arrest in Kanto Area (SOS-KANTO)

BACKGROUND

Although there is a close connection between emergency medical services (EMS) system and the outcome of out-of-hospital ventricular fibrillation (VF), few data are available regarding the situation in Japan.

METHODS AND RESULTS

A prospective multicenter study of out-of-hospital cardiac arrest was conducted according to the Utstein guidelines. A total of 4,383 patients who were given cardiopulmonary resuscitation (CPR) by EMS personnel for out-of-hospital cardiac arrest were enrolled. The proportion of VF or pulseless ventricular tachycardia (VT) as the first cardiac rhythm after cardiac arrest was 16.2% with a mean call-to-initial-recorded-electrocardiogram (ECG) interval of 11.1 min. In a subgroup of patients with witnessed collapse, the predicted incidence of VF or pulseless VT was 62.7% at the time of cardiac arrest, and the decline accelerated with every minute that the collapse-to-initial ECG interval was delayed. Multivariate analysis showed that the odds ratio for VF or pulseless VT after collapse-to-initial ECG interval was 0.91 (95% confidence interval (CI), 0.89-0.94, p<0.001), and 1.54 (95%CI, 1.24-1.97, p<0.001) after bystander CPR.

CONCLUSIONS

In Japan, VF occurred in 63% of cases at the time of cardiac arrest and the performance of bystander CPR appeared to prolong VF.

Clinical Assessment and Management of Patients With Implanted Cardioverter-Defibrillators Presenting to Nonelectrophysiologists

All physicians increasingly will encounter patients who have implanted cardioverter-defibrillators (ICDs) for protection from ventricular arrhythmias. This advisory provides a concise summary relevant to the assessment and management of patients with ICDs, including those who present to primary care or emergency department physicians with symptoms suggesting arrhythmia or ICD malfunction and those who require cardiac or surgical procedures.

Coexistence of Two Types of Ventricular Fibrillation During Acute Regional Ischemia in Rabbit Ventricle

INTRODUCTION

We previously reported that a normal ventricle can demonstrate two types of ventricular fibrillation (VF), depending on the underlying electrophysiologic characteristics at the time of VF induction. We hypothesize that the two types of VF can coexist in acutely ischemic ventricles.

METHODS AND RESULTS

Optical mapping studies were performed with di-4ANEPPS in 15 Langendorff-perfused rabbit hearts. Coronary artery branches were ligated to create regional ischemia in 10 hearts. Action potential duration measured to 50% repolarization (APD50) during ischemia showed an area with uniformly shortened APD50 (zone 1), an area with normal or lengthened APD50 (zone 3), and an area in between with an APD50 gradient (zone 2). Ischemia flattened APD restitution (APDR) slope and reduced conduction velocity in zone 1, creating a condition for type II VF. APDR steepened and the conduction velocity changed little in the nonischemic zone (zone 3), creating a condition for type I VF. During induced VF, the dominant frequency in zones 2 and 3 progressively increased after ischemia onset. The dominant frequency in zone 1 (ischemic zone) first decreased and then slightly increased but typically remained less than the dominant frequency in zone 3. The number of wavebreaks increased with time in all three zones (baseline: 4.3 +/- 1.5; 30 min: 11.7 +/- 5.6; 60 min: 15.6 +/- 11 per frame; P < 0.01).

CONCLUSION

Two types of VF can coexist during acute regional ischemia. Both ischemic and nonischemic regions develop proarrhythmic changes during regional ischemia, thus contributing to increased ventricular vulnerability to VF and sudden death during acute coronary occlusion.

Effects of air pollution on blood pressure and heart rate variability: a panel study of vehicular traffic controllers in the city of São Paulo, Brazil

AIMS

Evaluating the effects of air pollution on Sao Paulo city's vehicular traffic controllers by means of risk indicators for cardiovascular diseases.

METHODS AND RESULTS

Twenty-four hour blood pressure recordings and an electrocardiogram were obtained in 48 healthy, non-smoking vehicular traffic controllers, aged 31-55 years, during three periods: winter 2000, summer 2001, and winter 2001. Effects of air pollutants on the outcomes were estimated using linear regression based on generalized estimated equations, controlling for age, body mass index, humidity, and temperature. An interquartile range (IQR) increase in CO (1.1 p.p.m.) was associated with increases of 2.6 mmHg (95% CI 1.0, 4.2), 1.8 mmHg (95% CI 0.8, 2.8), and 2.4 mmHg (95% CI 1.1, 3.6) in systolic, diastolic, and mean 24 h ambulatory blood pressures. SO(2) also had relevant effects on blood pressure. On heart rate variability, an IQR increase of SO2 (9.6 microg/m3) was negatively associated with the standard deviation (SD) of normal RR intervals (SDNN) -7.93 ms (95% CI -15.3, -0.6).

CONCLUSION

This study supplies biological plausibility for observational studies on air pollution-related cardiovascular morbidity and mortality.

Implantable cardioverter defibrillator therapy in postinfarction patients

PURPOSE OF REVIEW

In the past few years, new clinical trials were conducted to determine the effectiveness of implantable cardioverter defibrillators (ICDs) for prevention of mortality in patients with ischemic and nonischemic cardiomyopathies. This paper aims to provide an overview of the current state of knowledge regarding ICD therapy in postinfarction patients.

RECENT FINDINGS

Postinfarction patients with severe left ventricular dysfunction are at high risk of sudden cardiac death. Antiarrhythmic therapy does not improve survival in such patients and, therefore, ICDs emerged as treatment of choice for both primary and secondary prevention of mortality after MI. The MADIT (Multicenter Automatic Defibrillator Implantation Trial) and MUSTT (Multicenter Unsustained Tachycardia Trial) trials were the first primary prevention ICD trials documenting a substantial reduction in mortality with an ICD in postinfarction patients with depressed ejection fraction, nonsustained ventricular tachycardia, and inducible sustained ventricular tachycardia. The recently completed MADIT II trial broadened indications for prophylactic use of ICD in postinfarction patients with ejection fraction of 30% or less without a requirement for additional risk stratifiers. The benefit from ICD therapy in patients with low ejection fraction was recently confirmed by results from the SCD-HeFT (Sudden Cardiac Death in Heart Failure) and COMPANION (Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure) trials.

SUMMARY

Recent clinical trials established ICD as an important therapeutic modality for primary and secondary prevention of mortality in postinfarction patients.

Bedside programmed ventricular stimulation for sudden death risk stratification

BACKGROUND

Patients with myocardial infarction and left ventricular dysfunction are at risk for sudden death. This research was conducted to determine the applicability and safety of a bedside programmed stimulation protocol to determine the risk for sudden death in these patients.

METHODS

Four hundred and twelve patients with acute myocardial infarction were studied. Left ventricular ejection fraction was evaluated by means of an echocardiogram. Ventricular arrhythmia, late potentials and heart rate variability were determined by means of Holter recordings. Fifty patients (60 +/- 14-year-old; 85% male) presented a left ventricular ejection fraction lower than 0.40 (0.36 +/- 0.10) associated with late potentials, low heart rate variability or ventricular arrhythmia greater than Lown I. After a central venous access was placed under fluoroscopy guidance and ECG monitoring, a quadripolar catheter was advanced to the right ventricular apex to perform programmed ventricular stimulation with up to three extrastimuli. The patients were followed-up to determine in-hospital morbidity and/or mortality.

RESULTS

No patient suffered complications. Ventricular tachycardia or ventricular fibrillation was induced in six patients. All of them received amiodarone and in five an automatic cardioverter-defibrillator was implanted. After a 22 +/- 6 month follow-up, five patients had received appropriate discharges from the implanted device and none had suffered from arrhythmic sudden death.

CONCLUSION

Bedside programmed stimulation is a safe and useful means for sudden death risk stratification in post myocardial infarction patients. It moreover presents the advantage of being cheaper than conventionally used procedures.

Protection against ventricular arrhythmias and cardiac death using adenosine and lidocaine during regional ischemia in the in vivo rat

Despite decades of research, there are few effective ways to treat ventricular fibrillation (VF), ventricular tachycardia (VT), or cardiac ischemia that show a significant survival benefit. Our aim was to investigate the combined therapeutic effect of two common antiarrhythmic compounds, adenosine and lidocaine (AL), on mortality, arrhythmia frequency and duration, and infarct size in the rat model of regional ischemia. Sprague-Dawley rats (n = 49) were anesthetized with pentobarbital sodium (60 mg.ml(-1).kg(-1) i.p.) and instrumented for regional coronary occlusion (30 min) and reperfusion (120 min). Heart rate, blood pressure, and a lead II electrocardiogram were recorded. Intravenous pretreatment began 5 min before ischemia and extended throughout ischemia, terminating at the start of reperfusion. After 120 min, hearts were removed for infarct size measurement. Mortality occurred in 58% of saline controls (n = 12), 50% of adenosine only (305 microg.kg(-1).min(-1), n = 8), 0% in lidocaine only (608 microg.kg(-1).min(-1), n = 8), and 0% in AL at any dose (152, 305, or 407 microg.kg(-1).min(-1) adenosine plus 608 microg.kg(-1).min(-1) lidocaine, n = 7, 8, and 6). VT occurred in 100% of saline controls (18 +/- 9 episodes), 50% of adenosine-only (11 +/- 7 episodes), 83% of lidocaine-only (23 +/- 11 episodes), 60% of low-dose AL (2 +/- 1 episodes, P < 0.05), 57% of mid-dose AL (2 +/- 1 episodes, P < 0.05), and 67% of high-dose AL rats (6 +/- 3 episodes). VF occurred in 75% of saline controls (4 +/- 3 episodes), 100% of adenosine-only-treated rats (3 +/- 2 episodes), and 33% lidocaine-only-treated rats (2 +/- 1 episodes) of the rats tested. There was no deaths and no VF in the low- and mid-dose AL-treated rats during ischemia, and only one high-dose AL-treated rat experienced VF (25.5 sec). Infarct size was lower in all AL-treated rats but only reached significance with the mid-dose treatment (saline controls 61 +/- 5% vs. 38 +/- 6%, P < 0.05). We conclude that a constant infusion of a solution containing AL virtually abolished severe arrhythmias and prevented cardiac death in an in vivo rat model of acute myocardial ischemia and reperfusion. AL combinational therapy may provide a primary prevention therapeutic window in ischemic and nonischemic regions of the heart.

Primary prevention of sudden cardiac death

Sudden cardiac death (SCD) is the leading cause of death in the United States. Although SCD occurs most commonly in patients with established heart disease, SCD can also be the initial manifestation of cardiovascular disease. Efforts to reduce the incidence of SCD include aggressive treatment of heart disease and its risk factors with pharmacologic and nonpharmacologic strategies. Public health measures to improve the response to cardiac arrest, including dissemination of automated external defibrillators in the community, are extremely important. Implantation of implantable cardioverter defibrillators (ICDs) in patients at high risk of SCD improves survival in these patients. Clinical trials have identified patients with ischemic and nonischemic cardiomyopathy who may benefit from prophylactic ICD implantation.

Cardiac neurotransmission SPECT imaging

The sympathetic nervous system has great influence on cardiovascular physiology. Cardiac neurotransmission single photon emission computed tomography (SPECT) imaging allows in vivo noninvasive assessment of presynaptic reuptake and storage of neurotransmitters, which offers characterization of the cardiac neuronal function in different diseases of the heart and other altered metabolic or functional conditions. Therefore assessment of the integrity of cardiac sympathetic innervation may help in the diagnosis of these disorders, as well as in prognostication, and will result in better therapy and outcome. At present, the most widely available SPECT tracer by which to assess cardiac neurotransmission is metaiodobenzylguanidine labeled with iodine 123. This article focuses on reviewing the characteristics of cardiac SPECT imaging with I-123 metaiodobenzylguanidine and its role in the assessment of pathophysiologic changes during relevant clinical conditions.

Cardiac Autonomic Derangement and Arrhythmias in Right-Sided Stroke With Insular Involvement

BACKGROUND AND PURPOSE

The insula of the right cerebral hemisphere may have a major role in cardiac autonomic control. This study was aimed at assessing the effects of acute right insular ischemic damage on heart rate variability (HRV) and arrhythmias.

METHODS

Holter monitoring for 24 hours was performed in 103 consecutive patients with first-ever acute ischemic stroke. Time and frequency domain measures of HRV and arrhythmias were considered in all cases.

RESULTS

Forty-nine patients (47.5%) had a right-sided infarction, whereas 54 (52.5%) had a left-sided infarction. Insular involvement was present in 33 patients with right-sided stroke (67.3%) and in 36 patients with left-sided stroke (66.6%). When compared with all other stroke patients, subjects with right-sided insular damage showed significantly lower values of the standard deviation of all normal-to-normal (SDNN) R wave to R wave (RR) intervals and of the root mean square of differences (rMSSD) of adjacent normal-to-normal RR intervals, and higher low-frequency/high-frequency ratio values (P<0.05). Right insular stroke was also associated with more complex arrhythmias than any other localization (P<0.05). Moreover, in the whole population of stroke patients, lower values of SDNN were associated with the presence of more frequent and complex arrhythmias.

CONCLUSIONS

These findings further support the notion that the right insula is implicated in the autonomic control of cardiac activity and that acute right insular damage may lead to a derangement of cardiac function with potential prognostic implications.

Cardiac defibrillation and resynchronization therapies: principles, therapies, and management implications

Patients with heart failure remain at high risk for sudden cardiac death (SCD) and death due to heart failure progression, despite the incorporation of pharmacologic agents into clinical practice that have been shown to decrease mortality in clinical trials. Most patients experience SCD as their first dysrrhythmic event. The implantable cardioverter defibrillator (ICD) effectively terminates ventricular tachycardia/fibrillation (VT/VF) aborting SCD. Cardiac resynchronization therapy (CRT) complements pharmacologic therapy improving cardiac performance, quality of life, functional status, and exercise capacity in patients with systolic dysfunction despite optimal medical therapy who have a prolonged QRS duration; furthermore, it decreases mortality when compared with optimal medical therapy alone. Implantation of a combination CRT and ICD device, a CRT-D, reduces mortality by aborting SCD and providing the functional benefits of CRT. This article discusses the evolution of CRT-D therapy, the mechanism of operation of a CRT-D device, and nursing implications.

The worsening of left ventricular hypertrophy is the strongest predictor of sudden cardiac death in haemodialysis patients: a 10 year survey

BACKGROUND

Although the incidence of sudden cardiac death (SCD) is high among haemodialysis (HD) patients, there are few papers available on this topic. The aim of this study on a single-centre HD population observed over a 10 year period was to identify patient- and HD-related specific factors that might be associated with a higher risk of SCD.

METHODS

The study included 123 patients (76 men; age 29-79 years) undergoing renal replacement therapy at our dialysis unit for at least 6 months. For each patient, routine laboratory tests were performed monthly, blood pressure was measured both at the start and the end of each dialysis session, haemoglobin and pre-dialysis serum K(+) were determined weekly, serum iPTH was assessed thrice yearly, and an echocardiographic study was performed annually to determine the left ventricular mass index (LVMi). The prevalence of cardiovascular (CV) co-morbidities, and the incidence of new events were also recorded.

RESULTS

During the 10 years, 85 patients died-16 from SCD, 30 from cardiac causes (CC) other than SCD, and 39 from other causes (OC); 38 patients were still alive (AL) at the end of the observation period. Comparative analysis of SCD, CC, OC and AL, reveals that the male prevalence (13/3) was higher in SCD than in AL, while AL were younger than the deceased patients regardless of the cause of death (P<0.0001; ANOVA), the duration of arterial hypertension was higher in SCD (129+/-104 months; P = 0.0005; ANOVA), despite similar antihypertensive therapies, and the difference between LVMi at end-point and at inception (deltaLVMi) was significantly higher in SCD [+56+/-38 g/m(2) body surface area] compared with OC (-5+/-35), AL (-17+/-25) and even CC (7+/-30) (P<0.0001; ANOVA); finally, the prevalence of patients with ischaemic heart disease (IHD) was higher in the SCD group (11/5; P<0.0001, chi(2)). Univariate Cox regression analysis demonstrated that the factors increasing the risk of SCD were IHD (P = 0.002), the worsening of left ventricular hypertrophy (LVH) (P<0.0001), and the presence of long-lasting arterial hypertension (P = 0.001). An increase in LVH was the sole risk factor for SCD when comparing SCD with CC patients (P = 0.003). By multivariate Cox regression analysis deltaLVMi was identified as the strongest predictor of SCD (P<0.0001).

CONCLUSION

While confirming the role of common CV risk factors for SCD in dialysis patients such as IHD and arterial hypertension, this study is the first to demonstrate that the worsening of LVH is the strongest predictor of sudden death.

Coronary calcium screening in asymptomatic patients as a guide to risk factor modification and stress myocardial perfusion imaging

BACKGROUND

Previous studies have demonstrated a correlation between the extent of coronary artery calcification (CAC) and atherosclerotic plaque. As a result, CAC screening could be useful in predicting cardiovascular risk in individuals in whom atherosclerosis is developing. One possible method of detecting and quantifying CAC is by x-ray computed tomography, which potentially allows one to stratify patients into groups requiring risk factor modification or follow-up testing such as myocardial perfusion single photon emission computed tomography (SPECT).

METHODS AND RESULTS

This study was designed to evaluate the clinical utility of multidetector computed tomography (MDCT) in a cardiology practice setting. A retrospective analysis was performed on data from 794 asymptomatic patients who underwent CAC screening over an 8-month period. On the basis of the CAC score and physician consultation, 102 patients underwent subsequent myocardial perfusion SPECT imaging. A substudy was also conducted in 306 patients to measure the interscan variability of MDCT across different CAC score ranges. CAC was detected in 422 of 794 patients. Of these, the CAC was moderate (Agatston score = 101-400) in 14% and severe (>400) in 9%. Patients with 3 or more cardiac risk factors were most likely to exhibit moderate to severe CAC. In myocardial perfusion SPECT testing, no patient with an Agatston score lower than 100 had an abnormal study. In contrast, 41% of patients with severe CAC had an abnormal SPECT study. In the reproducibility substudy the minimal CAC group had the largest variability (86.0%) whereas the severe CAC group had the lowest variability (9.5%).

CONCLUSION

CAC screening with MDCT is justified for asymptomatic patients with 3 or more cardiac risk factors. However, risk factor assessment is poor at predicting which individuals will have CAC if fewer risk factors are present. In terms of the interscan variability, MDCT is capable of following changes in CAC for patients with Agatston scores greater than 100. Finally, this study demonstrated that an Agatston score of 400 is a logical threshold to initiate follow-up myocardial perfusion SPECT testing.

Hibernating Myocardium

The inability to reproduce spontaneous ventricular fibrillation in an animal model of chronic coronary artery disease has limited advances in understanding mechanisms of sudden cardiac death (SCD). Swine with hibernating myocardium arising from a chronic left anterior descending coronary artery (LAD) occlusion have a high rate of SCD that parallels the poor clinical survival of medically treated patients with hibernating myocardium. Kaplan-Meier analysis (n=426) demonstrated a cumulative mortality of 49% after 5 months that was almost entirely attributable to spontaneous SCD. Using implantable loop recorders, ventricular fibrillation was documented as the arrhythmic mechanism of death in all animals (n=10) and was usually preceded by ventricular tachycardia (n=8). Physiological studies before SCD (n=7) demonstrated total LAD occlusion and collateral-dependent myocardium (n=5), excluding acute occlusion as a major trigger of arrhythmia. The physiological substrate of hibernating myocardium was present before SCD, with reductions in LAD perfusion (SCD 0.79+/-0.13 versus 0.80+/-0.08 mL/min per g) and wall thickening (SCD 28+/-3% versus 22+/-3%) that were similar to survivors (n=14). Triphenyltetrazolium chloride infarcts among animals with SCD were infrequent (4 of 32) and small, averaging 4.6% of LV mass. Histology (n=4) showed postmortem changes but no acute inflammation nor contraction band necrosis. These data support the notion that hibernating myocardium is a pathophysiological substrate at high risk of SCD. This is independent of changes in functional stenosis severity, acute myocardial necrosis, or fibrotic scar. Thus, regional adaptations that promote myocyte survival in the setting of chronic repetitive ischemia result in a substrate with enhanced vulnerability to lethal arrhythmias and SCD.

Value of programmed ventricular stimulation after tetralogy of fallot repair: a multicenter study

BACKGROUND

Studies have consistently shown that ventricular tachycardia (VT) and sudden cardiac death (SCD) complicate the long-term outcome after tetralogy of Fallot repair, yet the diagnostic and predictive value of electrophysiological testing in this population is uncertain.

METHODS AND RESULTS

A multicenter cohort of 252 patients with repaired tetralogy of Fallot undergoing programmed ventricular stimulation was followed up for 18.5+/-9.6 and 6.5+/-4.5 years after corrective surgery and electrophysiological testing, respectively. Clinical VT and/or SCD occurred in 24.6%. Sustained monomorphic VT and polymorphic VT were induced in 30.2% and 4.4%. Including polymorphic VT in the definition of inducibility improved sensitivity (66.1+/-6.0% versus 77.4+/-5.3%, P=0.0082) with a marginal reduction in specificity (81.6+/-2.8% versus 79.5+/-2.9%, P=0.0455). Positive and negative predictive values were 55.2+/-5.3% and 91.5+/-2.2%. Independent risk factors for inducibility were age at study > or =18 years (OR, 3.3), palpitations (OR, 2.8), prior palliative surgery (OR, 3.1), modified Lown criteria > or =2 (OR, 5.6), and cardiothoracic ratio > or =0.6 (OR, 3.3). Event-free survival rates in noninducible and inducible patients at 1, 5, 10, and 15 years were 97.9%, 92.8%, 89.3%, and 89.3% versus 79.4%, 62.6%, 58.7%, and 50.3%, respectively (P<0.0001). Both inducible monomorphic VT [relative risk (RR), 5.0; P=0.0002] and polymorphic VT (RR, 12.9; P<0.0001) predicted future clinical VT and SCD. In a multivariate analysis, inducible sustained VT was an independent risk factor for subsequent events (RR, 4.7; 95% CI, 1.2 to 18.5; P=0.0268).

CONCLUSIONS

Programmed ventricular stimulation is of diagnostic and prognostic value in risk stratifying patients with repaired tetralogy of Fallot. In this patient population, inducible sustained polymorphic VT should not be disregarded as nonspecific.

Noninvasive risk stratification in postinfarction patients with severe left ventricular dysfunction and methodology of the MADIT II noninvasive electrocardiology substudy

Sudden cardiac death occurs as a result of a complex interplay of changes in myocardial substrate, imbalance of autonomic regulation of the heart, and myocardial vulnerability. Noninvasive electrocardiology serves as a comprehensive tool for investigating factors representing mechanistic pathways leading to cardiac events. Heart rate variability, nonlinear dynamics of heart rate, and heart rate turbulence provide insight into autonomic control of the heart. Prognostic value of these parameters in postinfarction patients is well established for predicting cardiac death, but there is less evidence for their association with sudden death or arrhythmic events. Electrical manifestation of changes in myocardial substrate include QRS and QTc prolongation, presence of conduction disturbances, presence of late potentials, abnormalities of repolarization morphology, and presence of nonsinus rhythm, namely atrial fibrillation. Electrocardiogram (ECG) measures reflecting myocardial vulnerability to arrhythmias include frequent ventricular premature beats, T wave alternans, or QT variability. Prognostic significance of these parameters is documented in studies focused mostly on them as individual markers of risk. The noninvasive electrocardiology substudy of the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) allows for simultaneous analysis of several of the above ECG markers of risk and will provide insight about relative contribution of mechanistic pathways leading to cardiac death in postinfarction patients with severe left ventricular dysfunction. Combination of a standard 12-lead ECG and 10-minute high-resolution Holter recordings serves to evaluate the prognostic significance of noninvasive electrocardiology parameters for mortality in patients randomized to conventional treatment and for arrhythmic events in patients randomized to implantable cardioverter defibrillator therapy.

Sudden cardiac death

Sudden cardiac death (SCD) due to ventricular tachyarrhythmias is a leading cause of death in the United States. This phenomenon is associated with coronary artery disease, valvular heart disease, nonischemic cardiomyopathies, congenital heart disease, primary electrical abnormalities, autonomic nervous system abnormalities, and other less common disorders. Evaluation and management of patients at risk for SCD (primary prevention) and of patients who have survived at least 1 episode of SCD (secondary prevention) have evolved in recent years because clinical trials have shown consistent benefit from implantation of cardioverter-defibrillators in appropriately selected patients. An evidence-based approach to primary and secondary prevention of SCD is presented.

Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis

The objective of this meta-analysis was to estimate quantitatively the associations between intake of alpha-linolenic acid [ALA, the (n-3) fatty acid in vegetable oils], mortality from heart disease, and the occurrence of prostate cancer in observational studies. We identified 5 prospective cohort studies that reported intake of ALA and mortality from heart disease. We also reviewed data from 3 clinical trials on ALA intake and heart disease. In addition, we identified 9 cohort and case-control studies that reported on the association between ALA intake or blood levels and incidence or prevalence of prostate cancer. We combined risk estimates across studies using a random-effects model. High ALA intake was associated with reduced risk of fatal heart disease in prospective cohort studies (combined relative risk 0.79, 95% CI 0.60-1.04). Three open-label trials also indicated that ALA may protect against heart disease. However, epidemiologic studies also showed an increased risk of prostate cancer in men with a high intake or blood level of ALA (combined relative risk 1.70; 95% CI 1.12-2.58). This meta-analysis shows that consumption of ALA might reduce heart disease mortality. However, the association between high intake of ALA and prostate cancer is of concern and warrants further study.

Automated external defibrillators in National Collegiate Athletic Association Division I Athletics

BACKGROUND

Sudden cardiac death is the leading cause of death in athletes. Evidence on current sudden cardiac death prevention through preparticipation history, physicals, and noninvasive cardiovascular diagnostics has demonstrated a low sensitivity for detection of athletes at high risk of sudden cardiac death. Data are lacking on automated external defibrillator programs specifically initiated to respond to rare dysrhythmia in younger, relatively low-risk populations.

METHODS

Surveys were mailed to the head athletic trainers of all National Collegiate Athletic Association Division I athletics programs listed in the National Athletic Trainers' Association directory. In all, 303 surveys were mailed; 186 departments (61%) responded.

RESULTS

Seventy-two percent (133) of responding National Collegiate Athletic Association Division I athletics programs have access to automated external defibrillator units; 54% (101) own their units. Proven medical benefit (55%), concern for liability (51%), and affordability (29%) ranked highest in frequency of reasons for automated external defibrillator purchase. Unit cost (odds ratio = 1.01; 95% confidence interval, 1.01-1.0), donated units (odds ratio = 1.92; confidence interval, 3.66-1.01), institution size (odds ratio =.0001; confidence interval, 1.3 E-4 to 2.2E-05), and proven medical benefit of automated external defibrillators (odds ratio = 24; confidence interval, 72-8.1) were the most significant predictors of departmental defibrillator ownership. Emergency medical service response time and sudden cardiac death event history were not significantly predictive of departmental defibrillator ownership. The majority of automated external defibrillator interventions occurred on nonathletes.

CONCLUSIONS

Many athletics medicine programs are obtaining automated external defibrillators without apparent criteria for determination of need. Usage and maintenance policies vary widely among departments with unit ownership or access. Programs need to approach the issue of unit acquisition and implementation with knowledge of the surrounding emergency medical service system, geography of their individual sports medicine facilities, numbers and relative risk of their athletes, and budgetary constraints.

EEG and ECG in Sudden Unexplained Death in Epilepsy

PURPOSE

Sudden unexpected death in epilepsy (SUDEP) is a major cause of mortality for patients with epilepsy. Cardiac factors may be involved and were evaluated in this study.

METHODS

EEG and ECG data for 21 patients with definite (n = 6) or probable (n = 15) SUDEP were compared with data from a group of 43 patients with refractory partial epilepsy. ECG abnormalities and heart rate (HR) changes were correlated with clinical data.

RESULTS

Fourteen patients died in their sleep; two were awake. Ictal maximal HR (90 seizures from 16 of 21 patients) was significantly higher in SUDEP (mean, 149 beats/min, BPM) than in comparison patients (mean, 126 BPM; p < 0.001). Greater increases in HR were associated with seizures arising from sleep (78 BPM increase) than from wakefulness (47 BPM; p < 0.001) in SUDEP, as compared with the non-SUDEP group (52 BPM in sleep, 43 BPM in wakefulness; p = 0.27). Ictal cardiac repolarization and rhythm abnormalities occurred in 56% of SUDEP (including two atrial fibrillation, two ventricular premature depolarizations, two marked sinus arrhythmia, two atrial premature depolarizations, one junctional escape, one ST-segment elevation), and 39% of comparison patients (p = 0.39). No specific seizure onset (laterality or lobe) was associated with SUDEP.

CONCLUSIONS

This study reveals, for the first time, evidence of increased autonomic stimulation (as measured by HR) associated with seizures, particularly in sleep, in patients with SUDEP, as compared with a clinically similar group of patients with refractory epilepsy.

Increased susceptibility to ventricular arrhythmias in a rodent model of experimental depression

Depression is an important public health problem and is considered to be an independent risk factor for coronary artery disease. The pathophysiological mechanisms that link depression with adverse cardiovascular events (e.g., myocardial ischemia, myocardial infarction, and sudden death) are not well established. It is possible that an increased susceptibility to life-threatening cardiac arrhythmias in depressed patients influences the risk of morbidity and mortality in coronary artery disease. This idea was tested with the use of an experimental model of depression that was developed to induce anhedonia, the reduced responsiveness to pleasurable stimuli observed in human depressed patients. Rats exposed to 4 wk of chronic mild stress (e.g., paired housing, strobe light, and white noise) displayed anhedonia, which was operationally defined by the reduced intake of a palatable sucrose solution relative to an established baseline and to control animals. Furthermore, compared with control rats, the anhedonic rats showed increased basal heart rate and decreased heart rate variability. In response to an intravenously infused chemical challenge, aconitine, anhedonic rats exhibited an increased vulnerability to ventricular arrhythmias, as indicated by a reduced threshold for premature ventricular complexes, salvos, and ventricular tachycardia. These findings suggest that the presence of depressive symptoms is associated with a lower threshold for ventricular arrhythmias, which may contribute to the increased risk for adverse cardiovascular events in patients with depression.

Rationale and design of a randomised controlled clinical trial on supplemental intake of n-3 fatty acids and incidence of cardiac arrhythmia: SOFA

BACKGROUND

Evidence from earlier studies indicates that intake of very long-chain n-3 polyunsaturated fatty acids (n-3 PUFA, also named omega-3 fatty acids) as present in fish oil reduces the risk of sudden death. Sudden death forms a major part of mortality from cardiovascular disease and is in most cases a direct consequence of cardiac arrhythmia. n-3 PUFA may exert their protective effect through reducing the susceptibility for cardiac arrhythmia.

OBJECTIVE

To investigate the effect of n-3 PUFA on the incidence of recurrent ventricular arrhythmia. This paper presents the rationale, design and methods of the Study on Omega-3 Fatty acids and ventricular Arrhythmia (SOFA) and discusses problems encountered in conducting a multicentre clinical trial on food.

DESIGN

A randomised, parallel, placebo-controlled, double blind intervention study, which obeys the guidelines for Good Clinical Practice.

SETTING

Multiple cardiology centres in Europe.

SUBJECTS

A total of 500 patients with an implantable cardioverter defibrillator (ICD). An ICD detects, treats and stores cardiac arrhythmic events in its memory chip.

INTERVENTIONS

Patients receive either 2 g/day of fish oil, containing approximately 450 mg eicosapentaenoic acid and 350 mg docosahexaenoic acid, or placebo for 12 months.

PRIMARY OUTCOME

Spontaneous ventricular tachyarrhythmias as recorded by the ICD or all-cause mortality.

CONCLUSION

SOFA is designed to answer the question whether intake of n-3 PUFA from fish-a regular food ingredient-can reduce the incidence of life-threatening cardiac arrhythmia. If this proves to be true, increasing the intake of n-3 PUFA could be an easy, effective and safe measure to prevent fatal arrhythmia in the general population.

Comparison of calcium scores from thick- and thin image slice-computed tomography scanning in predicting future coronary events

Computed tomographic image slices between 2.5 and 3.0 mm are commonly used for coronary calcium scanning. To evaluate the comparative accuracy of thicker image slices (5 to 6 mm) for predicting coronary events, we acquired both types of scans in 280 research participants and clinically followed them up for 7 years. We found that thick-slice image scanning and image assessment ranked calcium scores similarly and that measurements from both scanning methods predicted coronary heart disease events equally.

Natriuretic peptides as predictors of non-sudden and sudden cardiac death after acute myocardial infarction in the beta-blocking era

OBJECTIVES

This prospective study tested whether the natriuretic peptides predict cardiac death among patients using beta-blocking therapy after an acute myocardial infarction (AMI).

BACKGROUND

Natriuretic peptides have provided prognostic information after AMI, but their predictive value has not been well established in the era of beta-blocker use.

METHODS

A series of 521 patients (mean age 61 +/- 10 years) with AMI was included in the study. The end points were total mortality and non-sudden and sudden cardiac death (SCD). Plasma concentrations of atrial natriuretic peptide (ANP), N-terminal atrial natriuretic propeptide (N-ANP), brain natriuretic peptide (BNP), and ejection fraction (EF) were analyzed before hospital discharge. The cardiac medication was optimized (e.g., adherence to beta-blocking therapy was 97% at discharge and 95% at one year after AMI).

RESULTS

During a mean follow-up of 43 +/- 13 months, total mortality was 11.5% (60/521), cardiac mortality was 6.3% (33/521), and 3.1% (16/521) experienced SCD. On univariate analysis, high levels of all measured peptides and low EF predicted the occurrence of non-SCD (p < 0.001 for all). Peptides and EF also predicted the occurrence of SCD (p < 0.05), with elevated BNP (>23.0 pmol/l) being the most powerful predictor (hazard ratio [HR] 4.4, 95% confidence interval [CI] 1.4 to 13.8; p = 0.01). After adjusting for clinical variables, only elevated BNP (HR 3.9, 95% CI 1.2 to 12.3, p = 0.02) and low EF (<40%) (p = 0.03) remained as significant predictors of SCD.

CONCLUSIONS

Natriuretic peptides retain their prognostic value in the beta-blocking era among survivors of AMI. Elevated BNP provides information on the risk of subsequent SCD, independent of clinical variables and left ventricular EF.

Clinical efficacy of a wearable defibrillator in acutely terminating episodes of ventricular fibrillation using biphasic shocks

The Wearable Cardioverter Defibrillator (WCD) automatically detects and treats ventricular tachyarrhythmias without the need for assistance from a bystander, while at the same time allowing the patient to ambulate freely. It represents an alternative to emergency medical services for outpatient populations with a temporary risk of sudden cardiac death. While the original devices used a monophasic truncated exponential waveform for cardioversion/defibrillation shocks, a new, biphasic shock was developed for the next device generation. In 12 patients undergoing electrophysiological testing for ventricular tachyarrhythmias, termination of electrically induced ventricular fibrillation (VF) was attempted via the WCD. In 22 episodes, induced VF was promptly terminated by the first 70 J (n=12) or 100 J (n=10) biphasic shocks. Time between arrhythmia initiation and shock delivery was 22 +/- 6 seconds (70 J) and 21 +/- 6 seconds (100 J) (P=NS). The measured transthoracic impedance was 71 +/- 5 Ohms (64-79 Ohms) for the 70 J shock and 64 +/- 8 Ohms (47-72 Ohms) for the 100 J shock. The present study demonstrates that a single low energy biphasic shock delivered by the WCD, reliably terminates electrically induced VF (100% of episodes). The results of this study suggest that there is an acceptable safety margin to the maximum output of the device (150 J). Despite our promising data, we recommend that programming all shocks for maximum energy output should be done when using the WCD in ambulatory patients.

Clinical covariates of abnormal heart rate turbulence in coronary patients

BACKGROUND

The aim of this study is to evaluate the association between heart rate turbulence (HRT) parameters and clinical characteristics of coronary artery disease (CAD) patients.

METHODS AND RESULTS

In 122 patients (mean age 62 +/- 9 years) with angiographically documented CAD, 24-hour Holter monitoring with HRT analysis was performed to evaluate turbulence onset (TO) and turbulence slope (TS). There was a significant correlation between TO and TS (P =-0.31; P < 0.001). According to quartile values, TO >or=-0.37% and TS <or= 4.25 ms/RR were considered as abnormal in this patient population. Average values of TO were higher and TS lower in patients over 60 years, in patients with a past history of myocardial infarction and in those with EF < 40%. Considering pharmacotheraphy, higher (better) values of TS were observed in patients on statins, nitrates, and beta-blockers while lower TS values were noted in patients on calcium blockers. Patients with abnormal parameters of HRT compared to group with normal HRT values were characterized by features of more advanced CAD: age over 60 years (75% vs 49%), past history of MI (75% vs 64%), and EF < 40% (25% vs 3%). Multivariate analysis revealed age > 60 years (OR 1.27; P = 0.002) and EF < 40% (OR 1.39; P = 0.001) as independent clinical factors associated with abnormal HRT parameters.

CONCLUSIONS

HRT parameters are influenced by clinical characteristics and pharmacotherapy of studied patients with TS more than abnormal TO depending on clinical characteristics of patients. Advanced age, prior myocardial infarction and left ventricular dysfunction are key factors influencing values of HRT parameters.

The effects of age on quality of life in implantable cardioverter defibrillator recipients

BACKGROUND

The implantable cardioverter defibrillator shows superiority over conventional pharmacological therapy. The implantable cardioverter defibrillator has been implanted with increasing frequency in patients who are either at risk for or have experienced a life-threatening dysrhythmia. Implantable cardioverter defibrillator recipients experience a myriad of physical, emotional and social adjustments, with little being known about the impact of age on trajectory. AIMS, OBJECTIVES AND DESIGN: Therefore the purpose of the study is to examine the effects of age on health status, quality of life, and mood states of implantable cardioverter defibrillator recipients during the first year after implantation using a repeated measures design.

METHODS

A comparison of implantable cardioverter defibrillator patients' scores with other samples, both ill and well, are discussed to see how the two implantable cardioverter defibrillator age groups compare on the various measures. Human subjects approval was obtained from the institutional review board.

RESULTS

Seventy subjects, 51 males and 19 females, were recruited. There were 31 subjects between the ages of 21 and 62 years, mean age of 51 years, that comprised the younger age group, and 39 subjects between the ages of 67 and 84 years, mean age of 74 years, that comprised the older age group. Each subject completed the Medical Outcomes SF-36, the Ferrans and Powers Quality of Life Index, and the Profile of Moods States at time of implantable cardioverter defibrillator implantation, and 6 and 12 months later.

CONCLUSIONS

The older age group was as expected less physically active, less satisfied with their physical functioning, and had slightly more anxiety at 6 and 12 months than the younger counterparts. The younger implantable cardioverter defibrillator recipients demonstrated some improvements over time in the perception of their physical adjustment and anxiety.

RELEVANCE TO CLINICAL PRACTICE

Comparison of the SF-36 with other populations with or without a medical condition revealed scores below norms in physical health for both groups, and only slightly higher than patients with heart failure for the older group.

Anticipating events of in-hospital cardiac arrest

STUDY OBJECTIVES

To determine whether in-hospital cardiac arrests occurring in regular wards are preceded by some event(s), and the diagnostic and therapeutic measures adopted.

METHODS

From 1 May 1999 to 31 December 2001, events occurring in the 6 h preceding cardiac arrest were reviewed by checking the medical and nurse records and interviewing the attending staff. Exclusion criteria were (a) location in the Coronary Care Unit, the Intensive Care Unit, the Emergency Department and the operating rooms; (b) the presence of rapidly fatal disease; (c) the lack of adequate documentation.

RESULTS

Overall, 263 cardiac arrests occurred in the period under consideration. A total of 148 patients (61 women, 87 men, aged 74.3+/-1.2 years) fulfilled the entry criteria. Anticipating events were reported in 128 patients (86.4%). These included alterations in consciousness, cardiac arrhythmias, dyspnoea and chest pain. The restoration of cardiac rhythm was obtained in 23 patients (15.5%). Eight (5.4%) survived without major neurological sequelae. Survivors were significantly younger than non-survivors (survivors 44.3+/-6.8 years; non-survivors 76.7+/-2.1 years; P<0.005). In a substantial number of cases, ranging from 23 to 81%, according to the anticipating event, no diagnostic investigations were performed.

CONCLUSION

Most in-hospital cardiac arrests are preceded by events that often go overlooked and whose correct interpretation could be associated with a reduced mortality rate.

Enhanced Detection of Arrhythmia Vulnerability Using T Wave Alternans, Left Ventricular Ejection Fraction, and Programmed Ventricular Stimulation:. A Prospective Study in Subjects with Chronic Ischemic Heart Disease

INTRODUCTION

In previous studies, the prognostic value of T wave alternans (TWA) was similar to that of programmed ventricular stimulation (PVS). However, presently it is unclear if TWA and PVS identify the same patients or provide complementary risk stratification information. In addition, the effects of left ventricular ejection fraction (LVEF) on the prognostic value of TWA are unknown. The aim of this study was to determine if combined assessment of TWA, LVEF, and PVS improves arrhythmia risk stratification.

METHODS AND RESULTS

This was a prospective study of 144 patients with coronary artery disease and LVEF < or =40% who were referred for PVS for standard clinical indications. The endpoint was the combined incidence of death, sustained ventricular arrhythmias, and appropriate implantable cardioverter defibrillator (ICD) therapy. TWA (hazard ratio 2.2, P = 0.03) and PVS (hazard ratio 1.9, P = 0.05) both were significant predictors of endpoint events, and TWA was the only independent predictor. LVEF markedly influenced the prognostic value of TWA, which was a potent predictor of events in subjects with LVEF between 30% and 40% (event rates: TWA+ 36%, TWA- 0%, P = 0.001) but did not predict events in subjects with LVEF <30% (hazard ratio 1.1, P > 0.5). PVS successfully identified additional low-risk patients within the cohort with negative or indeterminate TWA results (hazard ratio 4.7, P = 0.015) but did not provide incremental prognostic information for TWA+ patients (hazard ratio 0.9, P > 0.5).

CONCLUSION

The combined use of TWA, LVEF, and PVS is a promising new approach to arrhythmia risk stratification that permits identification of high-risk and very-low-risk patients.

Hidden cardiac lesions and psychotropic drugs as a possible cause of sudden death in psychiatric patients: a report of 14 cases and review of the literature

OBJECTIVE

To confirm the hypothesis that psychotropic drugs, especially neuroleptics, lithium, and antidepressants, are implicated as a cause of unexpected sudden death in psychiatric patients because of their cardiotoxicity, especially when hidden cardiac lesions are present.

METHOD

We performed a full pathological examination of 14 psychiatric patients who unexpectedly and suddenly died between 1980 and 1999.

RESULTS

Neuroleptics were involved in 13 instances, antidepressants in 9, and anxiolytics in 5. Psychotropic drugs were combined in all but a single patient. In all 14 patients, toxicological analyses discarded drug overdose as cause of death. At postmortem examination, the brain and abdominal organs were normal. In 13 patients, the following lesions were found in the heart and lungs: dilated cardiomyopathy (6 patients), left ventricular hypertrophy (2 patients, 1 of which was associated with mitral prolapse and anomalies of His bundle), arrhythmogenic cardiopathy of the right ventricle (1 patient), pericarditis (1 patient), mitral prolapse (1 patient), muscular bridge on the anterior interventricular artery (1 patient), and Mendelsons syndrome (1 patient). In 1 case, no changes were seen. Most of the drugs that were taken immediately prior to death can induce arrhythmias either by prolonging the QT interval, potentially resulting in torsades de pointes, or by widening QRS complexes, possibly leading to reentry and ventricular fibrillation.

CONCLUSION

Our findings suggest that the arrhythmogenic effects of psychotropic drugs can be exacer bated when preexisting hidden cardiac lesions are present and can result in sudden death. Patients should be systematically evaluated for cardiac lesions prior to starting any treatment with psychotropic drugs; the minimal effective dosage should be used.

Prolongation of the corrected QT interval in adult patients with anti-Ro/SSA-positive connective tissue diseases

OBJECTIVE

Newborns of mothers positive for anti-Ro/SSA autoantibodies may develop a series of electrocardiographic (EKG) disturbances. Prolongation of the corrected QT (QTc) interval was recently reported in a significant proportion of children with maternally acquired anti-Ro/SSA antibodies, with a concomitant disappearance of EKG abnormalities and acquired maternal autoantibodies during the first year, suggesting a direct, reversible electrophysiologic effect of anti-Ro/SSA antibodies on the ventricular repolarization. On this basis, we investigated whether these antibodies may also affect cardiac repolarization in anti-Ro/SSA-positive adult patients with connective tissue diseases.

METHODS

Fifty-seven patients with connective tissue diseases were selected: 31 had anti-Ro/SSA antibodies and 26 did not (controls). In all subjects, we analyzed the QTc interval, heart rate variability, and signal-averaged high-resolution EKG recording.

RESULTS

Anti-Ro/SSA-positive patients showed a significant prolongation of the mean QTc interval compared with the controls (mean +/- SD 445 +/- 21 versus 419 +/- 17 msec; P = 0.000005). Eighteen of the 31 anti-Ro/SSA-positive patients (58%) and none of the 26 anti-Ro/SSA-negative patients had QTc values above the upper limit of normal (440 msec). Both groups had a reduction in heart rate variability, with a prevalence for the sympathetic nervous system and a high incidence of ventricular late potentials; these values were not significantly different between the 2 groups.

CONCLUSION

Adult patients with anti-Ro/SSA-positive connective tissue diseases showed a high prevalence of QTc interval prolongation. This feature, with the concomitant abnormalities in the autonomic tone and ventricular late excitability observed in all patients studied, suggests that anti-Ro/SSA-positive patients may have a particularly high risk of developing life-threatening arrhythmias.

The incidence of sudden cardiac death in the general population

BACKGROUND AND OBJECTIVES

To determine the incidence of sudden cardiac death in a general (Dutch) population.

METHODS

Cohort study in the Integrated Primary Care Information (IPCI) project, a database with all medical data from 150 general practices in The Netherlands. The study population comprised 249,126 subjects with a mean follow-up of 2.54 years.

RESULTS

In this period 4,892 deaths were identified, 582 of which were classified as (probable) sudden cardiac death. The overall incidence of sudden cardiac death in this population was 0.92 cases per 1,000 person-years (95%CI: 0.85-0.99). The risk was 2.3-fold higher in men than in women, and increased with age. The incidence of sudden cardiac death peaked in October and was lowest in August.

CONCLUSIONS

The incidence of sudden cardiac death in the general Dutch population was almost 1 per 1,000 person-years per year during the period 1 January, 1995 to 1 April, 2001. Most of the cases occurred at home.

Risk Stratification and Primary Prevention of Sudden Cardiac Death

The initial challenge in primary prevention of sudden cardiac death (SCD) lies in identifying those at greatest risk, before the index event. Ventricular fibrillation is the leading cause of SCD; however, many clinical conditions predispose fatal ventricular dysrhythmias. In patients with structural heart disease, left ventricular dysfunction is the strongest predictor of SCD. Noninvasive markers such as nonsustained ventricular tachycardia, delayed potentials, decreased heart rate variability and baroreflex sensitivity, and repolarization alternans are further observed to assess risk in ischemic cardiomyopathy; however, most of these markers have poor positive predictive value and lack specificity. The electrophysiologic study has strong positive predictive value, but remains a costly and invasive method for risk stratification. In patients with normal hearts, genetic predisposition may identify patients at risk but clinical markers are not readily recognized. The implantable loop recorder is a useful tool in detecting dysrhythmic causes of syncope and identifying patients at risk for SCD.

Side of Brain Infarction and Long-Term Risk of Sudden Death in Patients With Symptomatic Carotid Disease

Background and Purpose— Current publications suggest increased risk of sudden death in experimental animals with acute right insular lesions and in patients with recent right-sided brain infarction, particularly if the insula is involved.

Methods— Using 3 different time definitions, we related long-term risk of sudden death to presence and side of brain infarction on the baseline brain scan and handedness in 2885 patients with symptomatic carotid disease.

Results— In 1295 patients without brain infarction, 5-year risk of sudden death was 5.3% (24-hour definition); in those with left-sided infarction (n=471), 8.8%; in those with right-sided infarction (n=477), 6.0%; and in those with bilateral infarction (n=535), 9.7%. After accounting for differences of other risk factors (eg, previous myocardial infarction) in Cox regression, adjusted hazard ratios (HRs) compared with no infarction were as follows: left-sided HR, 1.45 (95% confidence interval [CI], 1.00 to 2.10); right-sided HR, 0.96 (95% CI, 0.62 to 1.47); and bilateral HR, 1.40 (95% CI, 0.98 to 2.00). Insular infarction occurred in 41 patients; none died suddenly. Left-handed or ambidextrous patients (n=183) had a lower risk of sudden death than right-handers; the adjusted HR for left-handed or ambidextrous patients was 0.24 (95% Cl, 0.07 to 0.70). These results were essentially the same for the 10- and 60-minute definitions of sudden death.

Conclusions— In the long-term, left-sided, not right-sided, brain infarction is associated with increased risk of sudden death. Left-handed or ambidextrous patients have a lower risk of sudden death than right-handed patients, suggesting a role for the brain.

Ethnic differences in cardiac potassium channel variants: implications for genetic susceptibility to sudden cardiac death and genetic testing for congenital long QT syndrome

OBJECTIVE

To determine the spectrum, frequency, and ethnic-specificity of channel variants in the potassium channel genes implicated in congenital long QT syndrome (LQTS) among healthy subjects.

SUBJECTS AND METHODS

Genomic DNA from 744 apparently healthy individuals-305 black, 187 white, 134 Asian, and 118 Hispanic--was subject to a comprehensive mutational analysis of the 4 LQTS-causing potassium channel genes: KCNQ1 (LQT1), KCNH2 (LQT2), KCNE1 (LQT5), and KCNE2 (LQT6).

RESULTS

Overall, 49 distinct amino acid-altering variants (36 novel) were identified: KCNQ1 (n = 16), KCNH2 (n = 25),KCNE1 (n = 5), and KCNE2 (n = 3). More than half of these variants (26/49) were found exclusively in black subjects. The known K897T-HERG and the G38S-min K common polymorphisms were identified in all 4 ethnic groups. Excluding these 2 common polymorphisms, 25% of black subjects had at least 1 nonsynonymous potassium channel variant compared with 14% of white subjects (P < .01).

CONCLUSIONS

To our knowledge, this study represents the first comprehensive determination of the frequency and spectrum of cardiac channel variants found among healthy subjects from 4 major ethnic groups. Defining the population burden of genetic variants in these critical cardiac ion channels is crucial for proper interpretation of genetic test results of individuals at risk for LQTS. This compendium provides a resource for epidemiological and functional investigation of variant effects on the repolarization properties of cardiac tissues, including susceptibility to lethal cardiac arrhythmias.

Acute Coronary Syndrome

Acute coronary syndromes encompass a heterogenous group of patients with different clinical presentations, who have differences in both the extent and severity of underlying coronary atherosclerosis and who have different degrees of risk of progression to myocardial infarction. For each patient, the pre-hospital practitioner should make individual treatment decisions based on the history and examination, the ECG findings, the facilities and diagnostic equipment available and the transfer time to the nearest appropriate hospital. Patients with acute ischaemic chest pain should have oxygen, aspirin, nitrates and opioid analgesia. A 12 lead ECG should be performed within 5 minutes of initial assessment. If the ECG reveals ST-segment elevation or presumed new LBBB, this signifies acute myocardial infarction and in most cases immediate reperfusion therapy should be considered. The evidence of benefit in terms of mortality and morbidity following prompt anti-platelet and fibrinolytic therapy in such cases is unequivable. Pre-hospital fibrinolysis is now well established and should be undertaken in patients with acute infarction on clinical and ECG grounds if the transfer to hospital is likely to exceed 30 minutes and it is less than 12 hours since the onset of pain. Patients with no ECG evidence of infarction may still be at considerable risk and should still be conveyed to the nearest appropriate medical facility. Whilst en-route, they should receive aspirin, nitrates, low molecular weight heparin (LMWH) and beta blockers provided there are no contra-indications.

Coronary artery calcium and its relationship to coronary artery disease

Electron-beam computed tomography (EBCT) and the recent generation of multi-slice computed tomography scanners (MSCT) permit high-resolution imaging of the beating heart and the coronary arteries. The visualization of coronary calcium offers the opportunity to non-invasively obtain direct information on coronary anatomy and plaque burden. For clinical purposes, coronary calcium represents the presence of arteriosclerotic plaques. Coronary calcium is deposited in an actively regulated process related to lipid content of and apoptosis within coronary plaques. The amount of coronary calcium is related to the extent of coronary plaque disease, which has substantial diagnostic and prognostic implications. Visualization of coronary calcium by cardiac CT allows to non-invasively detect and localize coronary plaques and describe their distribution in the coronary tree. Approximately 50% to 70% of all plaques are calcified. Calcium cannot be used to reliably identify plaques at risk for developing complications such as rupture or erosion with ensuing thrombus formation. However, data are accumulating that indicate that calcium is an indicator of coronary arteriosclerotic disease activity. A scan negative for coronary calcium has a high negative predictive value indicating absence of stenotic coronary artery disease and an excellent short- to mid-term prognosis. Studies using serial CT scans indicate that the annual progression of coronary calcium varies between 30% to 50% in symptomatic or high-risk individuals and 0% to 20% in patients treated effectively with lipid-lowering medication. An increased rate of progression of coronary calcium seems to indicate a substantially increased risk for adverse cardiac events.

Automatic external defibrillators for prevention of out-of-hospital sudden death: effectiveness of the automatic external defibrillator

Approaches to the prevention of sudden cardiac death (SCD) include strategies designed to attack the problem from the multiple perspectives of primary prevention of the underlying diseases, prophylactic treatment of high-risk individuals with identified diseases, and responses to cardiac arrest victims in the community. The latter strategy began with conventional fire department-based emergency rescue systems (emergency medical services [EMS]) that originated in the early 1970s. Although such systems were innovative and impressive at the time, they are limited by less-than-optimal response times that translate to low survival rates. Newer strategies, designed to respond faster, include a variety of methods, including ambulance- and police-based automatic external defibrillators (AEDs), deployment of AEDs in settings in which crowds accumulate and designated rescuers are available, and more general public access sites. The value of conventional EMS systems remains because of their ability to provide advanced life support as part of a dual-response system. These approaches, in conjunction with better primary and secondary prevention strategies, offer the hope of reducing the SCD burden.

Subdiaphragmatic murine electrophysiological studies: sequential determination of ventricular refractoriness and arrhythmia induction

Programmed electrical stimulation (PES) is a crucial aspect of the evaluation of the risk of arrhythmias in cardiac patients and provides a powerful tool for understanding the mechanisms of arrhythmia in experimental models. Whereas PES in the mouse is well characterized, the procedures allowing for follow-up studies in the same animal have not been developed. In this report, we describe a novel subdiaphragmatic approach that allows for repeat electrophysiological studies in the mouse. Under inhaled anesthesia, PES was performed in 36 wild-type mice via a stimulating electrode introduced through an epigastric incision and placed directly into the diaphragmatic surface of the heart. The procedure was repeated 7 days later. Ventricular effective refractory periods (VERP) did not change significantly between the initial and follow-up trials. Chronic treatment with amiodarone, however, was associated with a 70% prolongation in VERP from initial to follow-up studies (P < or = 0.001). In addition, PES of a genetically modified strain with sudden cardiac death, the connexin43 conditional knockout mouse consistently induced lethal polymorphic ventricular tachycardia. Thus sequential PES in mice is feasible with the use of a subdiaphragmatic approach, yields reproducible VERP values, and can be used to follow pharmacologically induced changes in VERP and identify mice at risk of lethal ventricular arrhythmias.