Ventricular Pre-excitation Syndrome Research Articles

Cardiovascular system damage in the late-onset Pompe disease

The article presents a clinical case of metabolic hypertrophic cardiomyopathy against the background of a late-onset form of Pompe disease, illustrating the difficulties of differential diagnostic search for the cause of the disease. The clinical, laboratory and genetic aspects of the diagnosis of Pompe disease are highlighted. The features of laboratory diagnostics, the difficult path to the correct diagnosis and the appointment of enzyme replacement therapy are discussed. Much attention is paid to the clinical symptoms of the disease — the most significant damage to the cardiovascular system, there is no damage to the musculoskeletal sphere. Clinical picture of late Pompe disease is presented: cardiac rhythm and conduction disorders (ventricular preexcitation syndrome — multiple additional atrioventricular fenestrations), unstable ventricular tachycardia, supraventricular tachycardia, sinus node weakness syndrome. Considered approaches to the prevention of sudden cardiac death the patient underwent surgical treatment: radiofrequency ablation, endocardial implantation of a cardioverter defibrillator. Pathogenetic therapy for Pompe disease has been started.

Evaluation of left atrial and left ventricular functions in patients with Wolff-Parkinson-White syndrome before and after radiofrequency catheter ablation using three-dimensional speckle tracking echocardiography.

Wolff-Parkinson-White (WPW) syndrome is one of the most common congenital cardiac abnormalities among ventricular pre-excitation syndromes. Radiofrequency catheter ablation (RFCA) treatment of accessory pathways (APs) in WPW patients is an established curative therapy restoring normal atrioventricular conduction. We have not encountered any studies evaluating both the LA and LV functions of these patients before and after RFCA with three dimensional-speckle tracking echocardiography (3D-speckle tracking echocardiography (STE)). The purpose of the current study was to assess the LA and LV functions in patients with WPW syndrome before and after RFCA using 3D-STE. A total of 21 patients with WPW syndrome who had been scheduled for RFCA were prospectively recruited for this study. 3D-STE examinations of the patients were performed 12-24h before ablation and 1 month after ablation. The LV-global longitudinal strain (LV-GLS) and LV-global circumferential strain (LV-GCS) were significantly depressed in the pre-RFCA WPW group than in the control group (-14.3±2.1vs. -21.5±2.2, p<.001; -12.6±1.8vs. -20.4±1.8, p<.001, respectively). The left atrial strain-reservoir (LAS-r) and LAS-active were significantly decreased in the pre-RFCA WPW group than in the control group (31.9±2.4vs. 48.8±2.6, p<.001; 11.7±2vs. 26.5±2.1, p<.001, respectively). The LV-GLS, LV-GCS, LAS-r, and LAS-active values improved after RFCA compared to before. The results of our study indicated that there are subclinical impairments in LV and LA myocardial dynamics in the apparently healthy WPW patients, and these deteriorations improve after RFCA of AP.

Wolff-Parkinson-White syndrome in pregnancy: a case report

Wolff-Parkinson-White (WPW) syndrome is a rare congenital cardiac pre-ex citation syndrome encountered during pregnancy. However, WPW under this physiological process might be responsible for life threatening arrthymias leading to dangerous outcomes for both mother and the fetus. It is a ventricular pre-excitation syndrome of anterograde activation of the ventricle resulting from aberrant conduction pathway as well as the AV node. Very small percent of patients with WPW syndrome that is less than 1% are at risk of sudden cardiac death. Most of the antiarrthymic drugs are a threat to the fetus therefore careful choice of drug has to be made. Digoxin is the drug that is contraindicated in adults with WPW syndrome and some drugs like verapamil increase danger of ventricular fibrillation and therefore use of drugs are a topic of concern. We present a case of 25-year-old primi gravida 31 weeks 5 days woman was admitted with oligohydramnios. Patient known case of WPW syndrome not on treatment showing ECG changes of short PR interval and delta wave slurring along the QRS complex with heart rate of 98 beats/ min and echo demonstrated mild tricuspid regurgitation (TR) and mild pulmonary arterial hypertension (PAH). Patient was taken for emergency LSCS in view of Doppler changes (CPR less than 1) and delivered an alive preterm baby.

&lt;I&gt;PRKAG2&lt;/I&gt;-associated hypertrophic cardiomyopathy

Mutations in the PRKAG2 gene lead to hypertrophic cardiomyopathy in combination with Wolff—Parkinson—White syndrome. The cause of the development of heart damage is the deposition of glycogen in the myocardium and the conduction system of the heart with a violation of the metabolism of adenosine monophosphate-activated protein kinase. A feature of PRKAG2 hypertrophic cardiomyopathy is progressive conduction disturbances with the development of atrioventricular blockade and ventricular preexcitation syndrome with a high frequency of paroxysmal supraventricular tachycardia against the background of additional atrioventricular fenestrations (Wolff—Parkinson—White syndrome). Progressive heart failure, high frequency of sudden cardiac death at a young age are characteristic. The features of diagnosis and treatment are considered.

Echocardiographic characteristics of PRKAG2 syndrome: a research using three-dimensional speckle tracking echocardiography compared with sarcomeric hypertrophic cardiomyopathy

BackgroundPRKAG2 syndrome is a rare disease characterized as left ventricular hypertrophy (LVH), ventricular preexcitation syndrome, and sudden cardiac death. Its natural course, treatment, and prognosis were significantly different from sarcomeric hypertrophic cardiomyopathy (HCM). However, it is often clinically misdiagnosed as sarcomeric HCM. PRKAG2 patients tend to experience delayed treatment. The delay may lead to adverse outcomes. This study aimed to identify the echocardiographic parameters which can differentiate PRKAG2 syndrome from sarcomeric HCM.MethodsNine PRKAG2 patients with LVH, 41 HCM patients with sarcomere gene mutations, and 202 healthy volunteers were enrolled. Clinical characteristics, conventional echocardiography, and three-dimensional images were recorded, and reviewed by an attending cardiologist. We evaluated the parameters of left ventricular strains from three-dimensional speckle tracking echocardiography (3D STE) by TomTec software. Receiver operating characteristic (ROC) curves analysis was used to assess clinical and echocardiographic parameters’ differential diagnosis potential.ResultsThe heart rate (HR) of the PRKAG2 group was significantly lower than both the healthy group (53.11 ± 10.14 vs. 69.22 ± 10.48 bpm, P < 0.001) and the sarcomeric HCM group (53.11 ± 10.14 vs. 67.23 ± 10.32 bpm, P = 0.001). The PRKAG2 group had similar interventricular septal thickness (IVS), posterior wall thickness (PWT), and maximum wall thickness (MWT) to the HCM group (P > 0.05). The absolute value of GLS in the PRKAG2 group was significantly higher than HCM patients (-18.92 ± 4.98 vs. -13.43 ± 4.30%, P = 0.004). SV calculated from EDV and ESV in PRKAG2 syndrome showed a higher value than sarcomeric HCM (61.83 ± 13.52 vs. 44.96 ± 17.53%, P = 0.020). The area under the ROC curve (AUC) for HR + GLS was 0.911 (0.803 -1). For HR + GLS, the sensitivity and specificity of the best cut-off value (0.114) were 69.0% and 100%, respectively.ConclusionsPRKAG2 patients present deteriorated LV diastolic function and preserved LV systolic function. Bradycardia and preserved GLS are useful to identify PRKAG2 syndrome from sarcomeric HCM, which may be beneficial for clinical decision-making.

Antipsychotics in Wolff-Parkinson-White Syndrome

Wolff-Parkinson-White Syndrome (WPW) is a rare ventricular pre-excitation syndrome due to the presence of an atrioventricular accessory pathway. WPW patients are prone to fatal arrhythmias. Antipsychotics are FDA-approved for various psychiatric illnesses which increases the possibility of patients with WPW receiving such medications. Currently, there is scarce evidence on the safety of antipsychotics in WPW patients.

Ipsilateral block or can a single ECGbe used for the diagnosis?

Background: Pre-excitation syndrome (premature excitation of the ventricles) is a congenital anomaly in the structure of the cardiac conduction system and consists in the presence of an additional atrioventricular connection. The possibility to assume the presence of pre-excitation syndrome accompanied by tachycardia based on an electrocardiogram provides a clue to the correct diagnosis and subsequent treatment of the patient. Clinical case description: A clinical case of a 56-year-old patient is presented, who was admitted to the FRCC of the FMBA of Russia in January, 2021 with paroxysms of previously undiagnosed tachycardia. During Holter monitoring, an episode of heart palpitations was recorded. When analyzing an ECG fragment, it was possible, by calculating the tachycardia cycle length, to suspect the presence of a latent ventricular pre-excitation syndrome, which was accompanied by the development of orthodromic atrioventricular reciprocal tachycardia with a bundle branch block on the side of the additional atrioventricular connection (ipsilateral block). The patient underwent endocardial electrophysiological examination to confirm the presence of the bundle, followed by the catheter treatment of the atrioventricular connection. A good postoperative clinical result was obtained. Conclusion: It is important to be able to make a differential diagnosis between the presence of a latent pre-excitation syndrome with the development of orthodromic atrioventricular reciprocal tachycardia with the bundle branch block on the side of the extra atrioventricular junction (ipsilateral block) and other supraventricular tachycardias with an aberration along one of the bundle branches, in order to determine the tactics of the patient management and to control the effectiveness of the treatment.

A Brief review of the risks and the stratification of sudden death in the ventricular Pre-excitation syndrome.

Objective: The diagnosis of ventricular preexcitation syndromes is often occasional and with underestimated risk, showing controversies in its stratification and indication of prophylactic ablation. This work aims to explore and summarize the data in the literature, exposing the authors’ conclusions regarding this review. Methods: The authors prepared this work based on the latest guideline of the European Society of Cardiology plus a search for articles published in MEDLINE whose titles related to sudden death from ventricular fibrillation in patients with ventricular preexcitation. Discussion: Sudden death secondary to preexcited atrial fibrillation with degeneration to ventricular fibrillation is the most feared event in Wolff-Parkinson-White syndrome, has an average annual incidence of 0.15 to 0.39%, affecting individuals with structurally normal heart. The noninvasive stratification methods do not demonstrate adequate efficacy, and an electrophysiological study is recommended for all cases at the time of diagnosis. The most severe criteria for sudden death are shortest preexcited RR interval ≤ 250 ms (SPERRI or SPRRI); accessory pathway effective refractory period (APERP) ≤ 250 ms; presence of multiple accessory bundles; shortest paced cycle length with preexcitation during atrial pacing ≤ 250ms (SPPCL); Ebstein anomaly; induction of sustained supraventricular tachycardia. Conclusion: The low rate of complications during the diagnostic exam as well as in the therapeutic procedure, added to the high percentage of success of radiofrequency ablation, leads to indicate early the execution of electrophysiological study as a more diligent and accurate measure in the reduction of sudden death events in patients with ventricular preexcitation syndromes.

Emergency care for life-threatening arrhythmias

Background. Sepsis is often accompanied by arrhythmias and conduction disorders. It can be assumed that pacemaker cells of the sinoatrial node, strongly sensitized by massive stimulation with β1-adrenergic catecholamines, tend to trigger arrhythmias. The importance of the inflammatory component in the development of new atrial fibrillation (AF) events is also confirmed by the existence of a strong correlation between increased levels of C-reactive protein, interleukin-6 and tumor necrosis factor and the onset of fibrillation. Under the conditions of the new-onset AF, the hospital mortality of patients of general profile in the intensive care unit (ICU) significantly exceeds that for people without AF.&#x0D; Objective. To describe the features of treatment of life-threatening arrhythmias.&#x0D; Materials and methods. Analysis of literature data on this issue.&#x0D; Results and discussion. Amiodarone, diltiazem and lidocaine are the most commonly used treatments for life-threatening arrhythmias. According to a UK-wide study, amiodarone is used to treat new-onset AF in ICU in 80.94 % of cases, β-blockers (BB) – in 11.60 %, other antiarrhythmic drugs (AAD) – in 3.87 %, and digoxin – in 3.31 %. However, this tactic is not in line with the existing guidelines. According to the recommendations for the heart rate (HR) control in emergency care for AF (Bokeria L.A. et al., 2017), in an acute situation in the absence of ventricular pre-excitation syndrome intravenous administration of BB or non-dihydropyridine calcium channel blockers (CCB) is recommended to slow ventricular rhythm in patients with AF. Caution should be taken in patients with hypotension or heart failure. For the last group of patients intravenous administration of cardiac glycosides or amiodarone is recommended. In patients with ventricular pre-excitation syndrome, class I AAD or amiodarone are the drugs of choice. In presence of the pre-excitation syndrome and AF BB, non-dihydropyridine CCB, digoxin and adenosine are contraindicated. The guidelines for the management of AF patients, developed in 2017 by the European Society of Cardiology in collaboration with the European Association of Cardiothoracic Surgery, recommend to use different management tactics depending on the left ventricular ejection fraction (LV EF). In case of LV EF &lt;40 % or signs of heart failure, the lowest effective dose of BB should be prescribed to achieve rhythm control. Amiodarone is prescribed to hemodynamically unstable patients or to individuals with severely reduced LV EF. The primary goal of treatment is to achieve a HR &lt;110 beats/min. In the absence of this result, digoxin should be added. In case of LV EF ≥40 %, BB, or diltiazem, or verapamil should be administered. In the absence of clinical result, digoxin should be added. Practical models of AF treatment in sepsis have demonstrated the superiority of BB over CCB, digoxin and amiodarone (Walkey A.J. et al., 2016). BB weaken the stimulating effect of the sympathetic part of the autonomic nervous system on the myocardium, have a negative chronotropic effect, improve the contractility of ischemized cardiomyocytes, slow atrioventricular conduction, reduce myocardial oxygen demand, and apoptosis. Esmolol (Biblok, “Yuria-Pharm”) is indicated for supraventricular tachycardia (except for ventricular pre-excitation syndrome) and for the rapid control of ventricular rhythm in patients with AF or atrial flutter in the pre- and postoperative periods or in other circumstances when it is necessary to normalize ventricular rhythm with a short-acting drug. Studies show that esmolol inhibits inflammation in sepsis by increasing the expression of the antimicrobial peptide cathelicidin. Kaplan – Mayer analysis shows better survival for experimental animals with sepsis receiving esmolol compared to animals in the 0.9 % NaCl group (Ibrahim-Zada I. et al., 2014).&#x0D; Conclusions. 1. Sepsis is often accompanied by arrhythmias and conduction disorders. 2. Under the conditions of new-onset AF, the hospital mortality of patients of general somatic profile in ICU significantly exceeds the number for people without AF. 3. In case of AF and LV EF &lt;40 % or signs of heart failure, the lowest effective dose of BB should be prescribed to achieve rhythm control. 4. In case of LV EF ≥40 %, BB, or diltiazem, or verapamil should be administered. 5. Esmolol is indicated for supraventricular tachycardia and for the rapid control of ventricular rhythm in patients with AF or atrial flutter. 6. Esmolol inhibits inflammation in sepsis by increasing the expression of the antimicrobial peptide cathelicidin.

Unresolved questions associated with the management of ventricular preexcitation syndrome.

Many recent recommendations concern the management of preexcitation syndrome. In clinical practice, they are sometimes difficult to use. The purpose of the authors was to discuss the main problems associated with this management. Three problems are encountered: (1) the reality of the absence of symptoms or the interpretation of atypical symptoms, (2) the electrocardiographic diagnosis of preexcitation syndrome that can be missed, and (3) the exact electrophysiological protocol and its interpretation used for the evaluation of the prognosis. Because of significant progress largely related to the development of curative treatment, it seems easy to propose ablation in many patients despite the related risks of invasive studies and to minimize the invasive risk by only performing ablation for patients with at-risk pathways. However, there is a low risk of spontaneous events in truly asymptomatic patients and the indication of accessory pathway ablation should be discussed case by case.

Study on a pedigree of mitochondrial diabetes with acute pancreatitis

Objective To investigate the clinical features and molecular genetic characteristics of mitochondrial diabetes with acute pancreatitis in a pedigree. Methods The clinical data were collected from a family of nine members. The genomic DNA was extracted from the peripheral blood, and the mtDNA3243 mutation was detected. Results There were five diabetic patients having different degrees of hearing impairment, the mean age of onset of diabetes was(32.4±9.2)years old, the average duration of diabetes was(8.2±6.1)years, the mean body mass index was(18.85±1.48)kg/m2, the average fasting plasma C-peptide was(1.07±0.64)ng/ml, and the C-peptide at 120 min was(3.02±1.28)ng/ml. Of these five members, four had osteopenia or osteoporosis, electrocardiograph showed depressed ST segment or ventricular pre-excitation syndrome. Three members were diagnosd with acute pancreatitis at the same time or after the diagnosis of diabetes was made, without any definite etiology. The mtDNA3243A>G mutation was found in 8 members, only one of the paternal offspring(Ⅲ-3)did not have the mutation that conforms to maternal genetic characteristics. Among the 3 carriers with the average age of(11.7±10.3)years old, two cases showed ST segment depression or ventricular pre-excitation syndrome on the electrocardiograph. Conclusion We reported a mitochondrial tRNALeu(UUR)A3243G mutation in the mitochondrial diabetes with acute pancreatitis. Early detection of this mutation is of a certain clinical value, as it may help in timely manangement of those affected, and also aid in better understanding of this mitochondrial gene mutation and the spectrum of mitochondrial diabetes. (Chin J Endocrinol Metab, 2016, 32: 734-738) Key words: Mitochondrion; Gene mutation; Diabetes mellitus; Pancreatitis

ROLE OF FIBROUS MYOCARDIAL DISORGANIZATION IN FORMATION OF RHYTHM DISTURBANCE IN PREMATURE VENTRICULAR EXCITATION SYNDROMES

Aim. The aim of the study was to assess the markers of synthesis and degradation of collagen, the parameters of structural-functional status of myocardium in patients with Wolff-Parkinson-White (WPW) syndrome and phenomenon, as well as idiopathic atrial fibrillation (AF) and to evaluate their predictor value in the development of tachyarrythmias. Materials and methods. Seventy three patients were examined. The main group included 43 patients with premature ventricular excitation syndromes (16 with WPW phenomenon and 27 with WPW syndrome, mean age 25 ± 9,15 years, 29 (67 %) men and 14 (33 %) women). The comparison group joined 30 patients with “idiopathic” AF (mean age 28,8 ± 4,25 years, 67 % of men and 33 % of women) and practically healthy persons of the same age. To assess disturbance of fibrous matrix of the myocardium, quantitative value of tissue inhibitor of metalloproteinase-1 (TIMP-1), matrix metalloproteinase-9 (MMP-9) and carboxyterminal propeptide (PIP) - blood serum type I procollagen was studied. Structural-functional status of myocardium was investigated with echocardiographic method. Results. The study indicated participation of matrix metalloproteinases and their inhibitors in formation of structural-functional changes in the myocardium among WPW syndrome and phenomenon patients, with maximum dysbalance of type I collagen exchange registered in patients suffering from WPW syndrome combined with AF. When carrying out statistical processing, reliable difference between the indices of extracellular matrix status depending on WPW syndrome and phenomenon, as well as on the presence or absence of AF paroxysms against he background of ventricular preexcitation syndrome were found out. Conclusions. Presence of dysbalance of the fibrosis seromarkers, which correlate with geometry of the left atrium and have a predictor value for the development of atrial fibrillation with WPW, was stated.

Post-traumatic Wolff-Parkinson-White syndrome description and case presentation

The ventricular pre-excitation syndrome (Wolff-Parkinson-White syndrome) is defined as a premature activation of the entire ventricular myocardium by a super-ventricular impulse. The premature activation is made by accessory conduction pathways that produce a short circuit in the normal nodo-hisian pathway. The accessory pathways are made of atrial myocardial fibers that have a higher conduction velocity and a refractory period shorter than the nodo-hisian structures. The accessory bundle can be single or multiple; it refers to congenital structures that can be dormant and they are often activated under the action of different agents. We present the case of a male aged 34 who was the victim of an aggression being hit with fists and feet. In this case, the Wolff-Parkinson-White syndrome has appeared as a sudden atrial fibrillation and left ventricular failure that appeared immediately after a traumatism of the face and legs. In this case the patient suffered from severe symptoms due to the appearance of the Wolff-Parkinson-White and required immediate hospitalization, medical treatment and ablation of the Paladino-Kent bundle. Key W ords: WPW syndrome, accessory pathways, traumatism

Electrocardiographic Screening in Children With Attention-Deficit Hyperactivity Disorder

Some investigators have suggested that children receiving stimulant medications to manage attention-deficit hyperactivity disorder should undergo screening electrocardiography to identify asymptomatic cardiac disease. However, no study to date has examined the efficacy and costs of this strategy. In the present study we sought to determine the utility of electrocardiographic screening in children with attention-deficit hyperactivity disorder. We reviewed the clinical experience of electrocardiographic screening of subjects with attention-deficit hyperactivity disorder <21 years of age from April to September 2008. Additional cardiac care and testing that resulted from an abnormal initial electrocardiogram were recorded. Screening electrocardiograms were obtained in 1,470 children with attention-deficit hyperactivity disorder and were interpreted as abnormal in 119 subjects (8.1%). Further evaluation of these 119 subjects included 63 transthoracic echocardiograms, 5 stress tests, and 9 Holter monitor studies. Cardiac disease was identified in 5 subjects (0.3% of entire cohort), yielding a positive predictive value of 4.2%. Cardiac diagnoses included ventricular pre-excitation syndrome (n = 2), bicuspid aortic valve (n = 2), and moderate secundum atrial septal defect (n = 1). The mean cost of electrocardiographic screening including further testing for subjects with abnormal initial screen results was $58 per child. The mean cost to identify a true-positive result was $17,162. In conclusion, electrocardiographic screening for children with attention-deficit hyperactivity disorder can successfully identify cardiac disease in otherwise asymptomatic subjects, although the positive predictive value is low. Ongoing studies are needed to know what role electrocardiographic screening should play in the management of children with attention-deficit hyperactivity disorder.

Akuttherapie lebensbedrohlicher tachykarder Rhythmusstörungen

Life-threatening supraventricular tachyarrhythmias include atrial fibrillation, atrial flutter, AV-nodal reentrant tachycardia with rapid ventricular response and preexcitation syndromes combined with atrial fibrillation. Ventricular tachyarrhythmias still remain one of the leading causes of death; these arrhythmias include monomorphic and polymorphic ventricular tachycardia, torsade de pointes tachycardia, ventricular fibrillation and ventricular flutter. In all patients with tachycardias, an attempt should be made to differentiate between narrow (QRS duration < 0.12 s) or wide QRS complex (QRS duration ≥ 0.12 s) tachycardias. In the assessment of patients (pts) with supraventricular/ventricular tachyarrhythmias, attention should be given to identify whether the tachycardia is associated with worsening angina or low cardiac output. In pts with narrow QRS complex tachycardias or pts with atrial fibrillation and preexcitation syndromes immediate synchronized cardioversion should be performed if signs or symptoms of instability (hypotension, evidence of end-organ dysfunction, worsening angina) exist. In pts with a stable hemodynamic situation, vagal maneuvers, adenosine or calcium channel blockers can be used. Management of atrial flutter usually centers on cardioversion or rapid atrial pacing to normal sinus rhythm. In the treatment of patients with deemed unstable ventricular tachycardia (VT), electrical cardioversion is the treatment of choice. In more stable patients, ajmaline is the preferred agent after myocardial infarction and lidocaine if myocardial ischemia is present. In pts with torsade de pointes tachycardias aggressive steps must be taken to prevent degeneration of this rhythm to ventricular fibrillation (VF). Magnesium sulfate has recently been demonstrated efficacious and is currently considered first-line drug therapy. Transcutaneous overdrive pacing should be attempted if magnesium is unsuccessful. The pt with pulseless VT or VF demands early electrical countershock.

Ventricular preexcitation in children and young adults: atrial myocarditis as a possible trigger of sudden death.

Sudden death (SD) in ventricular preexcitation (VP) syndrome is believed to be the result of atrial fibrillation with rapid ventricular response over the accessory pathway. Previous reports are anecdotal and often lack autopsy validation. Prevalence and clinicopathological features of VP were investigated in a series of 273 SDs in children and young adults (aged <or=35 years). Site of accessory atrioventricular (AV) connection was predicted by 12-lead ECG. Right and left AV ring together with the sinoatrial and AV septal junction were studied in serial histological sections. Ten patients (3.6%; male, mean age 24+/-7 years) had VP: 8 had Wolff-Parkinson-White (WPW) and 2 had Lown-Ganong-Levine (LGL) syndrome. Six patients had previous symptoms, and SD occurred at rest in all but 1. Pathological substrates of LGL consisted of AV-node hypoplasia and right-sided atrio-Hisian tract, respectively. In the 8 WPW patients, 10 total accessory AV pathways consisting of ordinary myocardium were found (7 left lateral, 2 right posterolateral, and 1 septal). These pathways were close to the endocardium (mean distance, 750+/-530 microm) and 310+/-190 microm thick. In 4 WPW patients (50%), isolated acute atrial myocarditis was found, which was polymorphous in 1 and lymphocytic in 3. VP accounted for 3.6% of SD in young people and was not preceded by warning symptoms in 40%. A left accessory pathway was the most frequent substrate, and its subendocardial location supports the feasibility of catheter ablation. Isolated atrial myocarditis may act as a trigger of paroxysmal atrial fibrillation that leads to SD.

Electrocardiographic observation on spontaneously occurring arrhythmias in chickens.

In order to clarify the spontaneous occurrence of arrhythmias in chickens, electrocardiograms using standard bipolar limb leads were recorded for 461 chickens of 7 breeds, including 3 pure breeds: Rhode Island Red (RIR, n = 125), Japanese Game (JG, n = 101), and White Leghorn (WL, n = 52); and 4 crossbreeds of RIR: the first filial generation (F1) obtained by mating RIR with JG (RIR x JG, n = 44), the backcross obtained by mating the Fl of RIR x JG with the parental JG ((RIR x JG) x JG, n = 10), the F1 obtained by mating RIR with WL (RIR x WL, n = 73), and the F1 obtained by mating RIR with the commercial hybrid chicken, Dekalb Amber Link (DAL)(RIR x DAL, n = 56). Nine types of arrhythmias were observed in 107 chickens (23.2%, 107/461): 66 had sinus arrhythmia, 19 had atrial premature contraction, 9 had ventricular preexcitation syndrome, 7 had ventricular premature contraction, 2 had second-degree atrioventricular block. 1 had atrial fibrillation, I had aberrant ventricular conduction. I had intraventricular conduction disturbance, and 1 had ventricular electrical alternans. Except for sinus arrhythmia, the incidence of other arrhythmias in RIR was significantly high, compared with that in pure breeds other than RIR (p < 0.001) and that in crossbreeds of RIR (p < 0.01). Arrhythmias other than ventricular premature contraction and sinus arrhythmia will be the first to be described as spontaneously occurring arrhythmias in chicken. Although the reason for both the highest incidence of sinus arrhythmia in WL and the predominance of other arrhythmias in RIR were obscure, the present results suggest the possibility of using chickens, especially RIR which shows a high incidence of arrhythmias, as a relevant animal for studying arrhythmias.

Resolution of pace mapping stimulus site separation using body surface potentials.

Several studies have related 12-lead ECG waveform during ventricular tachycardia to ECG waveform during ventricular pacing to identify ablation sites for therapy of ventricular tachycardia. QRS isopotential maps and QRS isointegral maps derived from body surface isopotential maps have also been correlated with left ventricular pacing sites with the same objective. The comparison process used is subjective and only semiquantitative. Improved accuracy of catheter placement may improve success rates of ablation therapy. This animal study was performed to determine the spatial resolution with which left ventricular pacing sites could be distinguished by body surface isopotential mapping. Potentials were recorded from 64 evenly spaced thoracic leads. Hexapolar or octapolar pacing catheters with 2-mm interelectrode spacing were placed percutaneously in the left ventricle in each of six dogs, and bipolar endocardial pacing was performed using each pair of adjacent electrodes. QRS isopotential maps of each pacing site for each catheter placement were cross-correlated by computer. Difference maps for each pair of pacing sites were calculated lead by lead and time instant by time instant, and root-mean-square voltage differences were calculated. Results indicated that correlation coefficients and root-mean-square error of voltage differences monotonically decrease and increase, respectively, with stimulus site separation. Both measures were significantly different (P < .05) for separations of 4 mm or more. A method of quantitative comparison of body surface potential maps can be used in normal hearts to localize ventricular pacing sites within a 4-mm range. The method may have utility in determining potential ablation sites for therapy of ventricular tachycardia or preexcitation syndromes.

Rhabdomyoma and Ventricular Preexcitation Syndrome

A description of two infants with ventricular preexcitation syndrome and supraventricular tachycardia associated with rhabdomyoma and review of the literature. A review of two patients who were seen between 1981 and 1986 in the cardiology department. Pediatric Heart Institute at St Christopher's Hospital for Children, Philadelphia, Pa. Two newborn female infants with ventricular preexcitation syndrome, supraventricular tachycardia, rhabdomyomatous tumor of the heart, and tuberous sclerosis are described. The first patient had unsuccessful partial resection of the rhabdomyomatous tumors obstructing the tricuspid valve and right ventricular cavity and died immediately after surgery. By histologic examination, no direct accessory connection was noted between the myocardial fibers of atria and ventricles through annulus fibrosus. By gross examination, the tumor extended from the right atrium through the tricuspid valve to the right ventricular cavity, suggestive of macroscopic accessory connection. The second patient presented with unsustained ventricular tachycardia and obstructive subaortic rhabdomyoma, requiring emergency surgery. One week later, reentrant supraventricular tachycardia developed and she required digoxin therapy for 15 months. Infants with rhabdomyomatous tumor of the heart and ventricular preexcitation syndrome may have microscopic or macroscopic accessory connections. Cardiac tumors like rhabdomyoma and oncocytic tumors should be suspected in infants with ventricular preexcitation syndrome or supraventricular tachycardia.

INTERVENTIONAL DYSRHYTHMIA MANAGEMENT AND THE ROLE OF LASER

Drug-resistant dysrhythmias may require interventional management. Laser energy can be used for interruption or destruction of dysrhythmia-generating foci or conductive pathways. Lasers may, therefore, be useful tools for interventional management of supraventricular or ventricular dysrhythmias and preexcitation syndromes. Although the role of lasers in interventional dysrhythmia management is not clearly defined, the advantages may be substantial.