Assessment and follow-up of pediatric survivors of sudden cardiac death

Clinical and electrophysiological evaluation of pediatric Wolff-Parkinson-White patients

Objective:

Wolff-Parkinson-White (WPW) syndrome presents with paroxysmal supraventricular tachycardia and is characterized by electrocardiographic (ECG) findings of a short PR interval and a delta wave. The objective of this study was to evaluate the electrophysiological properties of children with WPW syndrome and to develop an algorithm for the management of these patients with limited access to electrophysiological study.

Methods:

A retrospective review of all pediatric patients who underwent electrophysiological evaluation for WPW syndrome was performed.

Results:

One hundred nine patients underwent electrophysiological evaluation at a single tertiary center between 1997 and 2011. The median age of the patients was 11 years (0.1-18). Of the 109 patients, 82 presented with tachycardia (median age 11 (0.1-18) years), and 14 presented with syncope (median age 12 (6-16) years); 13 were asymptomatic (median age 10 (2-13) years). Induced AF degenerated to ventricular fibrillation (VF) in 2 patients. Of the 2 patients with VF, 1 was asymptomatic and the other had syncope; the accessory pathway effective refractory period was ≤180 ms in both. An intracardiac electrophysiological study was performed in 92 patients, and ablation was not attempted for risk of atrioventricular block in 8 (8.6%). The success and recurrence rate of ablation were 90.5% and 23.8% respectively.

Conclusion:

The induction of VF in 2 of 109 patients in our study suggests that the prognosis of WPW in children is not as benign as once thought. All patients with a WPW pattern on the ECG should be assessed electrophysiologically and risk-stratified. Ablation of patients with risk factors can prevent sudden death in this population.

Demographics, bystander CPR, and AED use in out-of-hospital pediatric arrests

BACKGROUND

In 2005 the American Heart Association released guidelines calling for routine use of automated external defibrillators during pediatric out-of-hospital arrest. The goal of this study was to determine if these guidelines are used during resuscitations.

METHODS

We conducted a secondary analysis of prospectively collected data from 29 U.S. cities that participate in the Cardiac Arrest Registry to Enhance Survival (CARES). Patients were included if they were older than 1 year of age and had a documented resuscitation attempt from October 1, 2005 through December 31, 2009 from an arrest presumed to be cardiac in nature. Hierarchical multivariable logistic regression analysis was used to estimate the associations between age, demographic factors, and AED use.

RESULTS

129 patients were 1-8 years of age (younger children), 88 patients were 9-17 years of age (older children), and 19,338 patients were ≥18 years of age (adults). When compared to adults, younger children were less likely to be found in a shockable rhythm (young children 11.6%, adults 23.7%) and were less likely to have an AED used (young children 16.3%, adults 28.3%). Older children had a similar prevalence of shockable rhythms as adults (31.8%) and AED use (20.5%). A multivariable analysis demonstrated that, when compared to adults, younger children had decreased odds of having an AED used (OR 0.42, 95% CI 0.26-0.69), but there was no difference in AED use among older children and adults.

CONCLUSIONS

Young children suffering from presumed out-of-hospital cardiac arrests are less likely to have a shockable rhythm when compared to adults, and are less likely to have an AED used during resuscitation.

Cardiac syncope in pediatric patients

OBJECTIVE

To assess the epidemiology of cardiac syncope in children and evaluate the guidelines on its management.

MATERIAL AND METHODS

We analyzed the etiology to syncope and diagnostic workup in consecutive pediatric patients presenting with syncope in our emergency departments or cardiac outpatient clinics between 1997 and 2005, and who were subsequently diagnosed as having cardiac syncope.

RESULTS

A primary cardiac cause was identified in 11 syncopal patients presenting to the emergency room and 14 patients to the cardiac clinic: supraventricular tachyarrhythmia in 9, ventricular tachyarrhythmia in 10, pacemaker dysfunction in 2, and isolated cases of sick sinus syndrome, hypoxic spell, hypertrophic cardiomyopathy, and primary pulmonary hypertension. Some elements suggested potential cardiac disease as a cause of syncope in all cases. The resting electrocardiogram and the echocardiogram were interpreted as positive and relevant to the diagnosis in 17 and 3 patients, respectively. Exercise electrocardiogram and Holter recording provided diagnostic information previously not seen on the resting electrocardiogram in six and three patients, respectively. Three children have died and one child has neurological sequelae following resuscitation.

CONCLUSION

Our data support the premise that careful history taking with special focus on the events leading up to syncope, as well as a complete physical examination, can guide practitioners in discerning which syncopal children need further cardiac investigations.

Cardioprotective effects of novel tetrahydroisoquinoline analogs of nitrobenzylmercaptopurine riboside in an isolated perfused rat heart model of acute myocardial infarction

We have investigated the cardioprotective effects of novel tetrahydroisoquinoline nitrobenzylmercaptopurine riboside (NBMPR) analog nucleoside transport (NT) inhibitors, compounds 2 and 4, in isolated perfused rat hearts. Langendorff-perfused heart preparations were subjected to 10 min of treatment with compound 2, compound 4, or vehicle (control) followed by 30 min of global ischemia and 120 min of reperfusion. For determination of infarct size, reperfusion time was 180 min. At 1 microM, compounds 2 and 4 provided excellent cardioprotection, with left ventricular developed pressure (LVDP) recovery and end-diastolic pressure (EDP) increase of 82.9 +/- 4.0% (P<0.001) and 14.1 +/- 2.0 mmHg (P<0.03) for compound 2-treated hearts and 79.2 +/- 5.9% (P<0.002) and 7.5 +/- 2.7 mmHg (P<0.01) for compound 4-treated hearts compared with 41.6 +/- 5.2% and 42.5 +/- 6.5 mmHg for control hearts. LVDP recovery and EDP increase were 64.1 +/- 4.2% and 29.1 +/- 2.5 mmHg for hearts treated with 1 microM NBMPR. Compound 4 was the best cardioprotective agent, affording significant cardioprotection, even at 0.1 microM, with LVDP recovery and EDP increase of 76.0 +/- 4.9% (P<0.003) and 14.1 +/- 1.0 mmHg (P<0.03). At 1 microM, compound 4 and NBMPR reduced infarct size, with infarct area-to-total risk area ratios of 29.13 +/- 3.17 (P<0.001) for compound 4 and 37.5 +/- 3.42 (P<0.01) for NBMPR vs. 51.08 +/- 5.06% for control hearts. Infarct size was more effectively reduced by compound 4 than by NBMPR (P<0.02). These new tetrahydroisoquinoline NBMPR analogs are not only potent cardioprotective agents but are, also, more effective than NBMPR in this model.

Comparing pre-hospital clinical diagnosis of pediatric out-of-hospital cardiac arrest with etiology by coroner's diagnosis

OBJECTIVES

Making an accurate clinical diagnosis in the field can be a great challenge with pediatric out-of-hospital cardiac arrest (OHCA). We aimed to compare the etiology of pediatric OHCA by pre-hospital clinical diagnosis with etiology by coroner's diagnosis and autopsy.

DESIGN

As part of the Ontario Pre-hospital Advanced Life Support (OPALS) study, we conducted a prospective cohort study including children below age 19 with OHCA during an 11-year period. Prehospital clinical diagnosis was determined by blinded review and deaths were then matched with provincial coroner's office records. The agreement between prehospital clinical diagnosis and autopsy diagnosis was derived by consensus review. Inter-observer agreement was evaluated using kappa values.

RESULTS

For the period 1992-2002, there were 414 cardiac arrests in children <19 years of age that matched coroner's records. Mean age was 5.9 years (S.D. 6.4 years) with 39.4% of cases under 1 year of age. Etiology by clinical diagnosis was medical 49.5%, trauma 36.0% and undetermined 14.5%. The overall kappa for clinical diagnosis compared to coroner's diagnosis was 0.62. The kappa for medical cases was 0.53, trauma was 0.93 and 'undetermined' was -0.01. Medical clinical diagnosis had a lower agreement with the coroner's diagnosis (62.4%) compared with trauma (96.0%), RR 0.65, 95% CI [0.58, 0.73]. The poorest kappas by diagnosis were for neurological (0.39), respiratory (0.42), 'other' medical (0.56), SIDS (0.58) and cardiac (0.63). The commonest coroner's diagnoses in the 'undetermined' clinical diagnosis category were: pneumonia (17.6%), seizure or post-seizure (11.8%), arrhythmia (9.8%) and aspiration (5.9%).

CONCLUSION

Even in an ideal situation, a clinician in the field might be unable to determine the etiology of pediatric cardiac arrest in 14.5% of cases. There is poorer agreement for 'medical' compared to 'trauma' cases. This is the largest study to date comparing clinical diagnosis of the causes of OHCA in children to the 'gold-standard' of coroner's diagnosis.

Risk stratification in the asymptomatic child with Wolff–Parkinson–White syndrome

PURPOSE OF REVIEW

As the safety and efficacy of invasive electrophysiologic studies and ablation therapy in pediatrics improves, there has been a greater interest in developing adequate risk stratification criteria for the asymptomatic pediatric patient with Wolff-Parkinson-White syndrome. This review will discuss the recent literature regarding this debate.

RECENT FINDINGS

Recent retrospective and prospective studies of Wolff-Parkinson-White syndrome in asymptomatic pediatric patients have shown that the well established adult criteria for risk stratification may not be applicable in children. Both symptomatic and asymptomatic children had similar accessory pathway effective refractory periods and supraventricular tachycardia inducibility in recent invasive electrophysiologic studies. The first attempt at prospective evaluation of the use of ablation therapy in asymptomatic adult and pediatric patients with the condition has sparked a debate as to the definition of a high-risk patient and the utility of ablation in the asymptomatic patient.

SUMMARY

It is still controversial whether the established criteria for risk stratification in adults can be confidently applied to the pediatric patient. The majority of pediatric electrophysiologists use invasive electrophysiologic studies for risk stratification and selection of appropriate therapy. This clinical practice reflects the increasing prevalence and safety of electrophysiologic study and ablation. Further studies to better define indications for study and ablation are still necessary, however, to define accurate criteria for risk stratification in this difficult pediatric problem.

Etiology of pediatric out-of-hospital cardiac arrest by coroner's diagnosis

OBJECTIVES

To determine etiology of pediatric OHCA in a population-based sample from autopsy and coroner's diagnosis.

DESIGN

As part of the Ontario Pre-hospital Advanced Life Support (OPALS) study, we conducted a prospective cohort study including children below age 19 years with OHCA in an 11-year period. Deaths were matched with provincial coroner's office records and autopsies and investigation notes were reviewed.

RESULTS

From 1992 to 2002, there were 474 cardiac arrests in children below 19 years of age giving an annual incidence of 59.7 per million children. Mean age was 5.8 (S.D. 6.3), 43.0% were <1 year of age, males were 59.1%. 25.1% were bystander witnessed and 20.3% received bystander CPR. 1.9% survived to discharge. Four hundred and thirty nine matched to coroner's office records. Annual incidence rates per million by age groups were: 175.0 (age 1-4 years), 33.0 (age 5-14 years) and 61.6 (age 15-18). Annual incidence rates per million according to coroner's cause of death were: natural (26.2), accidental (17.4), suicide (3.7) and homicide (1.9). Post-mortem rate was 84.3% and Mean Injury Severity Score was 31.4 (S.D. 16.5). The commonest causes of natural death were SIDS (30.3%), cardiovascular (19.2) and respiratory (18.3%). The commonest causes of accidental death were drowning (27.5%), residential accidents (18.8%), fire (13.0%) and motor vehicle collisions (12.3%).

CONCLUSION

The highest mortality rates were among children age <4 years. 52.6% of deaths were from 'unnatural' causes (accidental, suicide, homicide, undetermined). Our findings will be useful for planning prevention, treatment and future research of pediatric OHCA.

Out-of-hospital cardiac arrest in a child without overt cardiac disease: emergency department management

This case report describes the successful resuscitation of a 7-year-old girl who had no previous history of cardiac disease other than one episode of syncope. She developed ventricular fibrillation for 10 min. External chest compressions, early defibrillation and orotracheal intubation were used with a successful outcome.

QT dispersion predicts ventricular arrhythmia in pediatric cardiomyopathy patients referred for heart transplantation

BACKGROUND

QT dispersion has been used in stratifying risk for sudden death in adults with dilated cardiomyopathy, but its role in the pediatric population has not been delineated.

METHODS

We reviewed electrocardiograms in pediatric patients with dilated cardiomyopathy referred for heart transplantation, to evaluate the role of QT dispersion in predicting malignant arrhythmias in these patients. Three groups were defined: Group I (n = 13) had dilated cardiomyopathy and malignant ventricular arrhythmias, Group II (n = 13) had dilated cardiomyopathy with no ventricular arrhythmias and Group III (n = 30) consisted of normals. QT dispersion was defined as the duration of the shortest QT subtracted from that of the longest. In addition, the standard deviation of the QT intervals was calculated for each ECG, using 12 leads.

RESULTS

QT dispersion was significantly prolonged in Group I (97 +/- 33 msec) compared to Group II (74 +/- 19 msec) and Group III (42 +/- 17 msec). QT standard deviation was also prolonged in Group I (30 +/- 11 msec) vs Group II (22 +/- 5 msec) and Group III (13 +/- 4 msec). Using a threshold value of 90 msec for QT dispersion or 25 msec for QT standard deviation, a sensitivity of 78% and a specificity of 70% was obtained for identifying patients who would subsequently develop ventricular arrhythmias.

CONCLUSIONS

In pediatric heart transplant candidates with dilated cardiomyopathy, QT dispersion and QT standard deviation identify patients at higher risk for the development of malignant ventricular arrhythmia. This simple test can be helpful in the evaluation and management of these patients awaiting transplantation.

A population-based prospective evaluation of risk of sudden cardiac death after operation for common congenital heart defects

OBJECTIVES

This study sought to define 1) the risk of sudden death after operation for common congenital heart defects; and 2) factors associated with an increased risk of sudden death.

BACKGROUND

Although the prognosis for patients with congenital heart defects is improved by surgical treatment, they remain at a well recognized but poorly defined risk of late sudden death.

METHODS

This population-based study evaluated all patients < 19 years old undergoing surgical treatment of common forms of congenital heart disease in the state of Oregon between 1958 and 1996. Patients were identified retrospectively through 1958, with prospective biannual follow-up beginning in 1982. The incidence and cause of late sudden death were evaluated for 3,589 patients surviving operation for the following defects: atrial, ventricular and atrioventricular septal defects; patent ductus arteriosus; pulmonary stenosis; aortic stenosis; coarctation of the aorta; tetralogy of Fallot; and D-transposition of the great arteries.

RESULTS

There were 41 unexpected late sudden deaths during 45,857 patient-years of follow-up, an overall event rate of 1/1,118 patient-years. Thirty-seven of the 41 late sudden deaths occurred in patients with aortic stenosis, coarctation, transposition of the great arteries or tetralogy of Fallot, an event rate of 1/454 patients-years. In contrast, only four sudden deaths occurred among the other defects, an event rate of 1/7,154 patient-years (p < 0.01). The risk of late sudden death increased incrementally 20 years after operation for tetralogy of Fallot, aortic stenosis and coarctation. However, risk was not dependent on patient age at operation or surgical era. The causes of sudden death were arrhythmia in 30 patients, circulatory (embolic or aneurysm rupture) in 7 and acute heart failure in 4.

CONCLUSIONS

The risk of late sudden death for patients surviving operation for common congenital heart defects is 25 to 100 times greater than an age-matched control population. This increased risk is primarily represented by patients with cyanotic or left heart obstructive lesions. The risk of sudden death appears to be time dependent, increasing primarily after the second postoperative decade.

Studies on vasorelaxation by tetrapentylammonium ions in rat aortic rings

Tetrapentylammonium ions (TPA+) relaxed the isolated rat aortic rings precontracted with phenylephrine and high extracellular K+ in a concentration-dependent manner with respective IC50 values of 38.9 +/- 3.9 microM and 40.2 +/- 2.9 microM. Other quaternary ammonium ions with a carbon side chain of varying length did not induce relaxation. The relaxant effect of TPA+ was independent of the presence of the endothelium, and was unaffected by various putative blockers of K+ channels such as iberiotoxin (100 nM), glibenclamide (3 microM) and 4-aminopyridine (1 mM). In addition, tetrodotoxin (3 microM), indomethacin (10 microM) and methylene blue (10 microM) had no effect on the TPA+-induced relaxation. TPA+ (50 microM) and procaine (10 mM) completely abolished the phasic contractile response to caffeine in Ca2+-free solution. In the absence of extracellular Ca2+, phorbol 12,13-diacetate (PDA) evoked a sustained tension and TPA+ concentration-dependently reduced the contraction with IC50 of 30.7 +/- 3.1 microM. TPA+ reduced the sustained tension of the similar magnitude induced by phenylephrine, 60 mM K+ and active phorbol ester with similar potencies. These results indicate that TPA+ could act as a non-selective relaxant in arterial smooth muscle. This vasorelaxant effect is unique for TPA+ since other quaternary ammonium ions did not show the similar action in the rat aorta.

Unexplained syncope: clinical management

The management of unexplained syncope begins with the patient's history and physical examination, which are oriented to help separate benign from serious causes. Malignant etiologies are more likely to occur with exertional syncope. Cardiac causes should be considered, particularly cardiomyopathy, postoperative congenital heart disease, right ventricular dysplasia, anomalous coronary artery, pulmonary artery hypertension, myocarditis, long QT syndrome, and Wolff-Parkinson-White syndrome. Neurological and metabolic disorders may underlie a syncope episode. After malignant causes of syncope have been excluded and the diagnosis of neurocardiac syncope has been established, treatment strategies include behavior modification, salt and increased fluids, and pharmacological agents. Efficacious agents include beta-blockers, dysopyramide, fludrocortisones, and alpha agents. Yet, behavior modification alone may be as effective as salt or pharmacological therapy. Because the natural history of neurocardiac syncope in children is spontaneous resolution, it is appropriate to try the simple measures before introducing drug therapy.

Additive impact of in-hospital cardiac arrest on the functioning of children with heart disease

OBJECTIVE

This study examined the impact of a sudden cardiac arrest (CA) on the neurodevelopmental and adaptive functioning of young children with congenital heart disease (CHD).

METHODOLOGY

Sixteen children with CHD who had sustained an in-hospital CA were compared with a medically similar group of children with CHD who had not incurred a CA. The contribution of CA, disease severity, and family socioeconomic status on the prediction of developmental outcome variables was evaluated.

RESULTS

Children in the CA group displayed more impairments in general cognitive, motor, and adaptive behavior functioning as well as greater disease severity as measured by a cumulative medical risk index. With respect to all children in the study, a higher socioeconomic status was related to higher scores on cognitive functioning, lower levels of child maladjustment, and lower levels of stress within the parent-child relationship. Although the occurrence of a CA alone did not contribute to the prediction of outcome measures, a significant interactional effect between CA and cumulative medical risk index was found. Specifically, among children who had incurred a CA, as disease severity increased, decrements in abilities were observed. Few significant correlations between specific CA-related variables (eg, length of CA) and outcome indices were found.

CONCLUSIONS

Results from this study indicate that the impact of cardiac arrest on neuropsychological functioning may be mediated by the child's overall disease severity. These findings have implications for the identification of CA survivors at greatest risk for developmental difficulties.

Congenital heart disease and sudden death in the young

Sudden death is a frequent mode of fatal outcome in cardiac disease and does not exclude young people. The aim of this investigation was to establish whether and to what extent sudden death in the young may be ascribable to the substrate of underlying congenital heart disease. Among 182 young people (< or = 35 years) who died of cardiac sudden death and underwent postmortem examination, 58 (32%) had congenital heart disease. Seven showed an intrapericardial rupture of aortic dissection, in the setting of Marfan syndrome in two, isolated bicuspid aortic valve in two, and bicuspid aortic valve and isthmic coarctation in three; all exhibited equally severe degeneration of the aortic wall. Sixteen cases had conduction system anomalies, mostly bypass tracts; 15 coronary artery anomalies (three ostial valve-like stenosis, five origin from the wrong aortic sinus, and seven deep intramyocardial course); 12 hypertrophic cardiomyopathy; five postoperative congenital heart disease including scar following ventriculotomy, conduction system injury, and defects left unrepaired; and three congenital aortic valve stenosis. One third of sudden deaths in the young was ascribable to structural defects present since birth. A large spectrum of congenital heart disease involves the risk of sudden death, but most structural defects are usually not considered to be life threatening. Some of these concealed defects are potentially detectable in life by clinical imaging techniques.

Myocardial preconditioning: a model or a phenomenon?

A brief ischemic episode (ischemic preconditioning) limits myocardial necrosis produced by a prolonged period of coronary artery occlusion and reperfusion. In absence of infarction, lack of cumulative ATP depletion, and ventricular arrhythmias and dysfunction "stunning" in models of intermittent ischemia and reperfusion also could be a component of an adaptive response to brief ischemia (preconditioning). Nonischemic stimuli also precondition the myocardium against ventricular arrhythmias and infarction by activating endogenous mechanism(s) of protection similar to that induced by ischemic preconditioning. Preservation of myocardial ATP, abolishing purine release, attenuation of free radical production, activation of adenosine receptors and KATP channels, and induction of heat shock proteins are common responses to ischemic and nonischemic stimuli of preconditioning. Although a significant reduction in myocardial infarction is critical to myocardial salvage and patient survival, it is equally important to have a functioning heart that can sustain systemic pressure without inotropic support or assist devices. It is scientifically challenging and clinically important to elucidate the mechanisms of myocardial preconditioning. However, it is necessary to expand the definition of myocardial preconditioning to include nonischemic stimuli of preconditioning and other important monitors of myocardial protection such as ventricular function and electrophysiological stability in addition to that of infarction.

Dilated cardiomyopathy in children: determinants of outcome

OBJECTIVE

To determine the outcome of dilated cardiomyopathy presenting in childhood and the features that might be useful for prognostic stratification.

SETTING

Supraregional paediatric cardiology unit.

DESIGN

Retrospective analysis.

BACKGROUND

The natural history of dilated cardiomyopathy in children is not well characterised. Previous studies have shown a variable relation between age at presentation and outcome, and sudden death has been infrequent.

METHODS

Retrospective study of 63 consecutive patients with idiopathic dilated cardiomyopathy presenting between 1979 and 1992. Survival curves were constructed by the Kaplan-Meier method.

RESULTS

Age at diagnosis ranged from 1 day to 15 years (median 12 months) and follow up ranged from 1 day to 13 years (median 19 months). Actuarial survival from presentation was 79% at one year (95% confidence interval (95% CI) 66%-88%) and 61% (44%-74%) at five years. Univariate analysis showed that mural thrombus, left ventricular end diastolic pressure > 20 mm Hg, and age at presentation > 2 years were predictors of adverse outcome, but on multivariate analysis only age at presentation was significant. Left ventricular echocardiographic indices either did not improve or deteriorated in 36 children (17 of whom died, four suddenly, and three were transplanted), partially improved in 16 (three of whom died, all suddenly), and returned to normal in 11 (all of whom have survived).

CONCLUSIONS

Older age at presentation and lack of improvement in systolic function are associated with an adverse outcome, and early transplantation should be considered in these patients. There is a persistent risk of late sudden death in those children in whom echocardiographic dimensions remain abnormal.

Future cardioprotective considerations

Remarkable strides have been made in perioperative myocardial protection for heart operations. Recent advances in understanding the physiology of myocardial ischemia and its protective responses suggest that there is a possibility for further improvement. Some of these strategies are discussed in this article, which updates current thinking in regard to operative developments contributing to myocardial protection, preconditioning, inhibition of adenosine triphosphate catabolism, the critical role of adenosine, management of myocardial edema, antioxidant therapy, endothelial cell injury, and the interaction between activated leukocytes and the endothelium. Some potential new directions for cardioprotection are identified.

Acceleration of ventricular response to atrial flutter after intravenous adenosine

Adenosine may be of therapeutic and diagnostic value in the emergency management of arrhythmias. It causes transient atrioventricular nodal block and thus ends paroxysmal supraventricular tachycardias that involve the atrioventricular node. Also, it may uncover underlying atrial arrhythmias by slowing the ventricular response. Its duration of action is brief and serious adverse effects have not been reported. A 12 year old patient with atrial flutter is presented, in whom intravenous adenosine was followed by acceleration of the heart rate to a potentially dangerous arrhythmia.

Pathophysiology and mediators of ischemia-reperfusion injury with special reference to cardiac surgery. A review

Although necessary for the ultimate tissue survival, reperfusion may paradoxically exacerbate the ischemic injury. Ischemia and reperfusion injury is intimately woven together. The relative role of reperfusion injury is not clarified and probably varies with the ischemic insult: Reperfusion is always preceded by ischemia, and some of the reperfusion-related events may represent a process continuing from the ischemic period; thus the proper designation should be ischemia-reperfusion injury. The reperfusion-related events are: arrhythmias, myocardial stunning with both systolic and diastolic dysfunction, and low reflow and microvascular stunning. Of pathogenetic importance are the mode and speed of reperfusion as well as the initiation of an intracoronary inflammatory reaction during reperfusion, including endothelium-leukocyte interaction, platelets, generation of oxygen free radical, generation and release of arachidonic acid metabolites, platelet activating factor, endothelium derived relaxing factor, endothelins, kinins, and histamine, complement activation, disturbances in calcium homeostasis, and disturbances in lipid and fatty acid metabolism.

Supraventricular tachyarrhythmias, congenital heart disease, and sudden cardiac death

The etiologies of sudden cardiac death following the surgical treatment of congenital heart defects remain uncertain. A young patient with prior repair of partial anomalous pulmonary venous return is presented, in whom brief episodes of a supraventricular tachyarrhythmia (rate 170/min) were documented to result in ventricular fibrillation. This unusual sequence may represent a basis for unexplained sudden cardiac death in other patients following atrial surgical procedures for the treatment of congenital heart disease.

Hydrogen peroxide-induced oxidative stress to the mammalian heart-muscle cell (cardiomyocyte): lethal peroxidative membrane injury

Oxidative stress induced by hydrogen peroxide (H2O2) may contribute to the pathogenesis of ischemic-reperfusion injury in the heart. For the purpose of investigating directly the injury potential of H2O2 on heart muscle, a cellular model of H2O2-induced myocardial oxidative stress was developed. This model employed primary monolayer cultures of intact, beating neonatal-rat cardiomyocytes and discrete concentrations of reagent H2O2 in defined, supplement-free culture medium. Cardiomyocytes challenged with H2O2 readily metabolized it such that the culture content of H2O2 diminished over time, but was not depleted. The consequent H2O2-induced oxidative stress caused lethal sarcolemmal disruption (as measured by lactate dehydrogenase release), and cardiomyocyte integrity could be preserved by catalase. During oxidative stress, a spectrum of cellular derangements developed, including membrane phospholipid peroxidation, thiol oxidation, consumption of the major chain-breaking membrane antiperoxidant (alpha-tocopherol), and ATP loss. No net change in the protein or phospholipid contents of cardiomyocyte membranes accompanied H2O2-induced oxidative stress, but an increased turnover of these membrane constituents occurred in response to H2O2. Development of lethal cardiomyocyte injury during H2O2-induced oxidative stress did not require the presence of H2O2 itself; a brief "pulse" exposure of the cardiomyocytes to H2O2 was sufficient to incite the pathogenic mechanism leading to cell disruption. Cardiomyocyte disruption was dependent upon an intracellular source of redox-active iron and the iron-dependent transformation of internalized H2O2 into products (e.g., the hydroxyl radical) capable of initiating lipid peroxidation, since iron chelators and hydroxyl-radical scavengers were cytoprotective. The accelerated turnover of cardiomyocyte-membrane protein and phospholipid was inhibited by antiperoxidants, suggesting that the turnover reflected molecular repair of oxidized membrane constitutents. Likewise, the consumption of alpha-tocopherol and the oxidation of cellular thiols appeared to be epiphenomena of peroxidation. Antiperoxidant interventions coordinately abolished both H2O2-induced lipid peroxidation and sarcolemmal disruption, demonstrating that an intimate pathogenic relationship exists between sarcolemmal peroxidation and lethal compromise of cardiomyocyte integrity in response to H2O2-induced oxidative stress. Although sarcolemmal peroxidation was causally related to cardiomyocyte disruption during H2O2-induced oxidative stress, a nonperoxidative route of H2O2 cytotoxicity was also identified, which was expressed in the complete absence of cardiomyocyte-membrane peroxidation. The latter mode of H2O2-induced cardiomyocyte injury involved ATP loss such that membrane peroxidation and cardiomyocyte disruption on the one hand and cellular de-energization on the other could be completely dissociated.(ABSTRACT TRUNCATED AT 400 WORDS)

The automatic implantable cardioverter-defibrillator in young patients

An international survey identified 40 patients less than 20 years old who underwent surgical implantation of an automatic implantable cardioverter-defibrillator (AICD). There was a history of aborted sudden cardiac death or sustained ventricular tachycardia in 92.5% of these patients. Twenty-two patients (55%) had structural heart disease; dilated and hypertrophic cardiomyopathy were the most common diagnoses. Eighteen patients (45%) had primary electrical abnormalities including seven with the congenital long QT syndrome. There were no perioperative deaths associated with device implantation. Concomitant drug therapy was administered to 75% of the patients. Defibrillator discharge occurred in 70% of the patients, with 17 patients (42.5%) receiving at least one appropriate shock. There were two sudden and two nonsudden deaths at 28.2 months' median follow-up. Sudden death-free survival rates by life table analysis at 12 and 33 months were 0.94 and 0.88, respectively. Total survival rates at 12 and 33 months were 0.94 and 0.82, respectively. The AICD represents an effective treatment approach for young patients with life-threatening ventricular tachyarrhythmias.