ECG Findings in Active Patients: Differentiating the Benign From the Serious

ECGs and cardiac rhythms of normal athletes can vary widely. The heightened vagal tone from athletic conditioning can result in variant ECG findings that may mimic serious disorders. ECG patterns of long-QT syndrome, arrhythmogenic right ventricular dysplasia, Wolff-Parkinson-White syndrome, and hypertrophic cardiomyopathy signal the need for further evaluation, therapy, and possible participation restriction. Radiofrequency ablation may be appropriate when symptomatic supraventricular arrhythmias or Wolff-Parkinson-White syndrome is present. Further research is needed to effectively distinguish normal ECG changes in the athlete from changes that underlie cardiac disease. Improvements in identifying athletes at risk of serious or life-threatening arrhythmias are also needed.

Effect of low estrogen states in healthy women on dispersion of ventricular repolarization

Our data show that although estrogen does not seem to affect the QT interval in healthy women, it significantly decreases the QT dispersion. This finding could provide an explanation to the gender differences in susceptibility to ventricular arrhythmias, besides the difference in the incidence of coronary artery disease.

Use of correlation waveform analysis in discrimination between anterograde and retrograde atrial electrograms during ventricular tachycardia

INTRODUCTION

Discriminating between ventricular tachycardia (VT) with 1:1 ventriculoatrial association and sinus tachycardia can be difficult, even when assisted by intracardiac tracings. In this study, we used a new computer algorithm to perform correlation waveform analyses on intracardiac atrial electrograms to help distinguish between VT and sinus tachycardia.

METHODS AND RESULTS

Electrophysiologic studies of 28 patients (22 men; age 66 +/- 14 years) with inducible VT and mean ejection fraction of 37% +/- 16% were analyzed. A template of an intracardiac high right atrial electrogram was obtained during sinus rhythm (SR). Atrial electrograms during SR and VT were compared with the template using the new algorithm, and correlation coefficients (rho) were generated. The correlation coefficient of SR beats with the template was 96.4% +/- 3.4%. During VT with AV dissociation and persistent SR, rho was 94.5% +/- 3.7% (P = NS). During VT with 1:1 retrograde conduction, rho was 70.6% +/- 11.3% (P < 0.0001). At a cutoff of 85%, rho had positive and negative predictive values of 99% and 96%, respectively.

CONCLUSION

Our findings indicate that the new algorithm can reliably separate between anterograde and retrograde atrial activation during VT. It can, therefore, discriminate between sinus tachycardia and VT with 1:1 ventriculoatrial conduction and may be useful in preventing inappropriate shocks from dual chamber defibrillators.

Impact directly over the cardiac silhouette is necessary to produce ventricular fibrillation in an experimental model of commotio cordis

OBJECTIVES

In an experimental model of sudden death from chest wall impact (commotio cordis), we sought to define the chest wall areas important in the initiation of ventricular fibrillation (VF).

BACKGROUND

Sudden death can result from an innocent chest blow by a baseball or other projectile. Observations in humans suggest that these lethal blows occur over the precordium. However, the precise location of impact relative to the risk of sudden death is unknown.

METHODS

Fifteen swine received 178 chest impacts with a regulation baseball delivered at 30 mph at three sites over the cardiac silhouette (i.e., directly over the center, base or apex of the left ventricle [LV]) and four noncardiac sites on the left and right chest wall. Chest blows were gated to the vulnerable portion of the cardiac cycle for the induction of VF.

RESULTS

Only chest impacts directly over the heart triggered VF (12 of 78: 15% vs. 0 of 100 for noncardiac sites: p < 0.0001). Blows over the center of the heart (7 of 23; 30%) were more likely to initiate VF than impacts at other precordial sites (5 of 55; 9%, p = 0.02). Peak LV pressures generated instantaneously by the chest impact were directly related to the risk of VF (p < 0.0006).

CONCLUSIONS

For nonpenetrating, low-energy chest blows to cause sudden death, impact must occur directly over the heart. Initiation of VF may be mediated by an abrupt and substantial increase in intracardiac pressure. Prevention of sudden death from chest blows during sports requires that protective equipment be designed to cover all portions of the chest wall that overlie the heart, even during body movements and positional changes that may occur with athletic activities.

Epileptic seizures and electroencephalographic evolution in genetic leukodystrophies

The purpose of this study is to explore and compare epileptic seizures and EEG evolution in the various types of genetic leukodystrophy (GL). The authors reviewed the medical records and analyzed 69 serial EEGs in 27 patients with GLs: 13 with late infantile metachromatic leukodystrophy, one with juvenile metachromatic leukodystrophy, one with globoid cell leukodystrophy, six with X-linked childhood adrenoleukodystrophy, one with neonatal adrenoleukodystrophy, four with classic Pelizaeus-Merzbacher disease (PMD), and 1 with connatal Pelizaeus-Merzbacher disease. The diagnoses were made by biochemical and molecular studies. Two or more EEG studies with both awake and sleep traces were recorded during the varying clinical stages for each patient. At the beginning of the GLs, the EEGs were normal or showed mild slowing of background activity. Clinical seizures, mainly of focal origin, with progressive slowing and paroxysmal discharges on EEGs, usually appeared during the later stages of metachromatic leukodystrophy, X-linked childhood adrenoleukodystrophy, and classic Pelizaeus-Merzbacher disease. However, intractable seizures, mainly generalized in nature, and more severe slowing and abundant paroxysmal discharges on EEGs, with commensurate neurologic deterioration, were observed during the earlier course of globoid cell leukodystrophy, neonatal adrenoleukodystrophy, and connatal Pelizaeus-Merzbacher disease. These results indicate that GLs involve not only white matter, but gray matter as well. In all types of GL, there is good correlation between the severity of EEG changes, the severity of the diseases, and the clinical state of the patient.

Ventricular arrhythmias in the athlete

Life-threatening ventricular arrhythmias in the athlete nearly always occur in the presence of structural heart disease. In the last few years, 2 new causes of life-threatening arrhythmias have been described in patients with normal hearts-that of the Brugada syndrome and that of commotio cordis. Non-life-threatening premature ventricular beats and even nonsustained ventricular tachycardia are not rare, and although usually benign, can be secondary to cardiomyopathies. Athletes with symptoms of syncope, especially if exertional, warrant a complete evaluation. The treatment of athletes and other individuals with life-threatening ventricular arrhythmias has been revolutionized by the implantable cardioverter defibrillator, a device that affords excellent protection from sudden death. Defining those athletes who would benefit from the implantable defibrillator is not always clear. Furthermore, participation in competitive athletics for athletes with life-threatening arrhythmias or structural heart disease known to put the athlete at risk for life-threatening arrhythmias is usually prohibited.

Cardiac arrhythmias in the athlete

Cardiac arrhythmias in the athlete are a frequent cause for concern. Some arrhythmias may be benign and asymptomatic, but others may be life threatening and a sign that serious cardiovascular disease is present. Physicians often are consulted with regard to arrhythmias, or symptoms consistent with arrhythmias, in athletes. Sinus bradyarrhythmias are common and even expected in athletes. These bradyarrhythmias are rarely a cause for concern. Heart block is unusual and merits a thorough workup. Atrial fibrillation may be more common in the athlete. Supraventricular tachycardias other than atrial fibrillation generally warrant consideration of radiofrequency ablation for cure of the tachyarrhythmia. Ventricular arrhythmias in the athlete generally occur in the setting of structural heart disease that is genetically determined (hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, anomalous coronary arteries) or acquired (coronary artery disease, myocarditis, idiopathic dilated cardiomyopathies). In these conditions, the arrhythmia generally is life threatening. Ventricular arrhythmias that occur in the athlete without structural heart disease are not thought to be life threatening. Athletes with structural heart disease and syncope and those with exertional syncope merit a complete evaluation.

Connexin40-deficient mice exhibit atrioventricular nodal and infra-Hisian conduction abnormalities

INTRODUCTION

Previous electrophysiologic investigations have described AV conduction disturbances in connexin40 (Cx40)-deficient mice. Because expression of Cx40 occurs predominantly in the atria and His-Purkinje system of the mouse heart, the AV conduction disturbances were thought to be secondary to disruption in His-Purkinje function. However, the lack of a His-bundle electrogram recording in the mouse has limited further investigation of the importance of Cx40. Using a novel technique to record His-bundle recordings in Cx40-deficient mice, we define the physiologic importance of deficiencies in Cx40.

METHODS AND RESULTS

Ten Cx40-/- mice and 11 Cx40+/+ controls underwent a blinded, in vivo, closed chest electrophysiology study at 9 to 12 weeks of age. In the Cx40-/- mice, the PR interval was significantly longer compared with Cx40+/+ mice (44.6+/-6.4 msec vs 36.0+/-4.1 msec, P = 0.002). Not only the HV interval (14.0+/-3.0 msec vs 10.4+/-1.2 msec, P = 0.003) but also the AH interval (33.2+/-4.8 msec vs 27.1+/-3.7 msec, P = 0.006), AV Wenckebach cycle lengths, and AV nodal effective and functional refractory periods were prolonged in Cx40-/- compared with Cx40+/+ mice.

CONCLUSION

Cx40-deficient mice exhibit significant delay not only in infra-Hisian conduction, as would be expected from the expression of Cx40 in the His-Purkinje system but also in the electrophysiologic parameters that reflect AV nodal conduction. Our data suggest a significant role of Cx40 in atrionodal conduction and/or in proximal His-bundle conduction.

Invasive cardiac electrophysiology in the mouse: techniques and applications

As the genetic nature of a wide spectrum of cardiovascular diseases is being elucidated, it is increasingly important to understand the functional role of specific genes on cardiac arrhythmia and conduction disturbances. The progress made in molecular genetics has allowed the creation of mice with targeted gene overexpression or elimination. These animals are valuable tools for researchers who have adapted their clinical and technical skills to the mouse, in order to extract information on the phenotypic consequences of the specific genetic disruption. In this review, we summarize the progress made in the field of invasive murine electrophysiology, focusing on the recent technical advances in in vivo electrophysiologic testing and its application to various genetically engineered mouse models. The authors' views on the future needs and trends in the field are also presented.

Effect of saline irrigation flow rate on temperature profile during cooled radiofrequency ablation

INTRODUCTION

Cooled radiofrequency ablation has been developed clinically for the treatment of ventricular tachycardia. Although clinical studies employ a constant saline flow rate for cooling, we hypothesized that varying the flow rates might optimize the temperature profile at depth.

METHODS

In excised ovine left ventricle, we compared the temperature profile from a catheter tip electrode thermocouple to those placed at depths of 0.0 mm, 1.0 mm, and 2.0 mm. We compared the following settings: 20 Watts without flow, 20 Watts with 0.3 cc/sec flow, 20 Watts with 0.5cc/sec flow, and 70C surface temperature without flow (temperature control).

RESULTS

The temperatures decreased from 77.5 +/-10.5 degrees C, 91.7+/-6.3 degrees C, 65.5 +/- 11.8 degrees C, and 52.5 +/- 11.8 degrees C at 20W without saline irrigation at the tip, 0.0mm, 1.0mm, and 2.0 mm, respectively, to 33.0+/-1.4 degrees C, 63.4 +/- 7.0 degrees C, 57.1+/-5.8 degrees C, 49.9+/-5.8 degrees C+ at 20W with 0.5 ml/sec flow (*p<0.01, +p = 0.09). The lesion volumes were 79.6mm3 for 20W without flow, 64.1 mm3 for 20W with 0.3 ml/sec flow, 47.5 mm3 for 20W with 0.5 ml/sec flow, and 28.6 mm3 for temperature control.

CONCLUSIONS

We conclude that 1) the temperature profile greatly depends upon the rate of saline flow for cooling; 2) at high flow rates, the 0.0 mm and 1.0 mm temperatures are similar; 3) even at high irrigation rates, lesion size is greater than for temperature control; 4) the tip temperature significantly underestimates the surface temperature and improved methods of measuring temperature are needed.

Microwave radiometric thermometry and its potential applicability to ablative therapy

INTRODUCTION

[corrected] Current techniques for estimating catheter tip temperature in ablative therapy for cardiac arrhythmias rely on thermocouples or thermistors attached to or embedded in the tip electrode. These methods may reflect the electrode temperature rather than the tissue temperature during electrode cooling so that the highest temperature away from the ablation site may go undetected. A microwave radiometer is capable of detecting microwave radiation as a result of molecular motion. In this study, we evaluated microwave radiometric thermometry as a new technique to monitor temperature away from the electrode tip during ablative therapy utilizing a saline model.

METHODS AND RESULTS

A microwave radiometer antenna and fluoroptic thermometer were inserted in a test tube with circulating room temperature saline kept constant at 23.5 degrees C while the surrounding saline bath was heated from 37 degrees C to 70 degrees C. For every degree rise in the warm saline bath placed either 5 mm or 8 mm from the radiometer antenna, the radiometer temperature changed 0.26 degrees C and 0.14 degrees C respectively while the fluoroptic temperature probe remained constant at 23.5 degrees C. The radiometer temperature was highly correlated with the warm saline bath temperature (R(2)=0.997 for warm saline 5 mm from the antenna, R(2)=0.991 for warm saline 8 mm from the antenna).

CONCLUSIONS

Microwave radiometry can estimate distant temperatures by detecting microwave electromagnetic radiation. The sensitivity of the microwave radiometer is also distance-dependent. The microwave radiometer thus serves as a promising instrument for monitoring temperatures at depth away from the catheter-electrode tip in ablative therapy for cardiac arrhythmias.

Analysis of intracardiac electrograms showing monomorphic ventricular tachycardia in patients with implantable cardioverter-defibrillators

Ventricular tachycardia (VT) initiation and its relation to various clinical factors was studied by reviewing intracardiac electrograms from patients with implantable cardioverter-defibrillators. Events were divided into (1) sudden onset without preceding ventricular premature complexes (VPCs), (2) extrasystolic onset with VPCs, or (3) paced, depending on the type and morphology of the last 5 beats before initiation of VT. Prematurity index, sinus rate, cycle length, and presence of short-long-short sequence for each episode was noted. A total of 268 episodes of VT among 52 patients were analyzed. Extrasystolic initiation was the most frequent pattern (177; 66%) followed by sudden onset (75; 28%) and paced (16; 6%). Among extrasystolic onset, 99 episodes (56%) were due to multiple VPCs and 149 episodes (84%) had different VPC morphology than the subsequent VT. Among pacing-induced VT, 13 of 16 episodes were due to inappropriate pacing due to undersensing of prior R waves. Sudden-onset episodes were slower (mean cycle length 383+/-97 ms) than extrasystolic (mean cycle length 336+/-88 ms, p = 0.002) and paced (mean cycle length 313+/-85 ms, p = 0.01) onset. Patients in the sudden-onset group had better left ventricular ejection fraction (33+/-15%) than the extrasystolic (29+/-11%, p<0.001) and paced (28+/-14%, p<0.01) groups. Extrasystolic onset with multiple, late coupled VPCs was the most common pattern of VT initiation and was associated with lower ejection fraction. Sudden-onset initiation was more common with better preserved systolic function.

Safety and efficacy of a steerable temperature monitoring microwave catheter system for ventricular myocardial ablation

INTRODUCTION

Radiofrequency current delivered during cardiac ablation is limited by a rise in impedance secondary to coagulum formation on the ablation electrode. Microwave antennas continue to deliver energy despite the presence of coagulum; thus, temperature control of the ablation electrode may be even more important for microwave than for radiofrequency ablations to avoid thromboembolic risks. The purpose of this study was to test the safety and efficacy of an ablation system utilizing a feedback control system to maintain a fixed target temperature for creating lesions with multiple applications of microwave energy.

METHODS AND RESULTS

Microwave ablation was assessed using an 8.5-French catheter at 2 to 4 sites in 11 dogs. Microwave energy delivery was performed for 60 seconds three times at the same site. Power was regulated using a feedback control mechanism to maintain a target temperature of 75 degrees C. Ambulatory ECG monitoring was performed before and after ablation to assess arrhythmia occurrence. After follow-up, the dogs were euthanized, and lesion dimensions measured after fixation. The mean power applied to achieve the target temperature of 75 degrees C was 9.3+/-44 W. The mean depth of the lesions was 8.8+/-4.2 mm. The mean volume of the lesions was 304+/-240 mm3. Forty-four percent of the lesions were transmural. No endocardial thrombus was found. Ventricular tachycardia was observed acutely but resolved after 1 week.

CONCLUSION

Temperature feedback control systems for microwave ablation using a temperature-controlled system is feasible for myocardial ablation and creates uniform and large lesions; however, such large lesions can be acutely proarrhythmic.

Role of the amino acid 45 residue in reduced folate carrier function and ion-dependent transport as characterized by site-directed mutagenesis

In previous reports, an E45K mutation in reduced folate carrier (RFC1) resulted in marked substrate-specific changes in folate binding and the induction of an obligatory inorganic anion requirement for carrier function. In this study, site-directed mutagenesis was employed to further characterize the role of glutamate-45 in carrier function by replacement with glutamine, arginine, aspartate, leucine, or tryptophan followed by tranfection of the mutated cDNAs into the MTX(r)A line, which lacks a functional endogenous carrier. Alterations in transport function with amino acid substitutions at this residue were not charge related. Hence, E45Q, E45R, and E45K all 1) increased carrier affinity for 5-formyltetrahydrofolate approximately 4-fold, 2) increased affinity for folic acid approximately 6- to 10-fold, 3) did not change affinity for 5-methyltetrahydrofolate, and 4) except for E45R decreased affinity for methotrexate (2- to 3-fold). In contrast, mutations E45D, E45L, and E45W generally reduced affinity for all these folates except for folic acid. Finally, chloride-dependent influx was only noted in the E45R mutant. These data further substantiate the important role that glutamate-45 plays in the selectivity of binding of folates to RFC1 and establish that it is the addition of a positive charge at this site and not the loss of a negative charge that results in the induced anion dependence. These and other studies indicate that mutations in the first transmembrane domain can have a markedly selective impact on the affinity of RFC1 for folate compounds and in particularly a highly salutary effect on binding of the oxidized folate, folic acid.

Microwave ablation using a spiral antenna design in a porcine thigh muscle preparation: in vivo assessment of temperature profile and lesion geometry

INTRODUCTION

Theoretical studies have suggested that microwave energy can increase the depth of heating compared with radiofrequency energy. A spiral microwave antenna design may have advantages over previous designs using smaller designs because the resulting power deposition pattern is considerably larger than the catheter diameter. We tested the efficacy of a spiral antenna using microwave energy in a porcine thigh muscle preparation.

METHODS AND RESULTS

In five anesthetized pigs, the thigh muscle was exposed and bathed in heparinized bovine blood (36 degrees to 37 degrees C). A helical microwave catheter with a fiberoptic thermometer attached to the distal end was positioned perpendicular to the thigh muscle. The antenna-tissue interface and tissue temperatures at depths of 3.0 and 6.0 mm were measured. A 915-MHz microwave generator delivered energy at one of three power outputs (50, 100, or 150 W) for 60 seconds. Seventy lesions were created: 50 W (n = 23), 100 W (n = 24), and 150 W (n = 23). The mean depths at 50, 100, and 150 W were 4.3 +/- 1.8 mm, 7.2 +/- 1.7 mm, and 9.4 +/- 0.9 mm, respectively. Lesion depth (R = 0.96, P = 0.05), maximum surface dimension (R = 0.99, P = 0.06), and volume (R = 0.99, P = 0.04) were closely correlated to the power applied.

CONCLUSION

Power is an important determinant of lesion size using a spiral microwave antenna. A novel, spiral microwave antenna design can create lesions of significant depth that may be applicable for the ablative therapy of ventricular tachycardia.

Down-regulation by extracellular ATP of rat hepatocyte organic anion transport is mediated by serine phosphorylation of oatp1

Recent studies implicate a role in hepatocyte organic anion transport of a plasma membrane protein that has been termed oatp1 (organic anion transport protein 1). Little is known regarding mechanisms by which its transport activity is modulated in vivo. In previous studies (Campbell, C. G., Spray, D. C., and Wolkoff, A. W. (1993) J. Biol. Chem. 268, 15399-15404), we demonstrated that hepatocyte uptake of sulfobromophthalein was down-regulated by extracellular ATP. We have now found that extracellular ATP reduces the V(max) for transport of sulfobromophthalein by rat hepatocytes; K(m) remains unaltered. Reduced transport also results from incubation of hepatocytes with the phosphatase inhibitors okadaic acid and calyculin A. Immunoprecipitation of biotinylated cell surface proteins indicates that oatp1 remains on the cell surface after exposure of cells to ATP or phosphatase inhibitor, suggesting that loss of transport activity is not caused by transporter internalization. Exposure of (32)P-loaded hepatocytes to extracellular ATP results in serine phosphorylation of oatp1 with the appearance of a single major tryptic phosphopeptide; oatp1 from control cells is not phosphorylated. This phosphopeptide comigrates with one of four phosphopeptides resulting from incubation of cells with okadaic acid. These studies indicate that the phosphorylation state of oatp1 must be an important consideration when assessing alterations of its functional expression in pathobiological states.

A 2 1/4-turn spiral antenna for catheter cardiac ablation

To investigate the delivery of microwave energy by a catheter positioned inside the heart for ablating small abnormal regions producing cardiac arrhythmias, a 2 1/4-turn spiral catheter-based microwave antenna applicator has been developed. The antenna consists of the center conductor with continuous insulating material extending from the coaxial feed cable formed into a spiral antenna. The insulator completely isolates the center conductor from tissue. Phantom experiments were performed on homogeneous tissue equivalent medium. The reflection coefficient of the antenna at different frequencies and for different spiral lengths, the time course and temperature profile of an ablation, and the dosimetry of power versus temperature, all indicate that the high-power heating patterns from this antenna are both wider and deeper than with the other microwave antenna systems and radio-frequency electrodes.

Persistent hypertransaminasemia as the presenting findings of muscular dystrophy in childhood

Prolonged elevation of the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) is often attributed to hepatic diseases. However, these enzymes are also present in a variety of extrahepatic tissues, including skeletal muscle. Five children (all boys) were referred to the pediatric department of the National Taiwan University Hospital because of persistent elevation of serum aminotransferase activities. The ages of these children were between 4 months and 5.5 years. The neurological findings were all not remarkable. The initial ALT and AST values were 114-581 U/L and 183-700 U/L, respectively. Serum creatine kinase was checked first after 0 to 30 months follow-up and found to be markedly elevated (range, 10,557 U/L to 62,508 U/L). Muscle biopsies in the five cases all showed degenerating and regenerating myofibers with interstitial fibrosis. In Cases 3, 4 and 5, complete absence of dystrophin immunoreactivity was found. Genetic studies showed deletions in the DMD gene (exons 45-48 in case 2 and 49-50 in case 4). This experience indicates that occult muscle diseases should be taken into account in patients with unexplained long-lasting hypertransaminasemia and therefore measurement of serum creatine kinase activity and muscle biopsy should be done early for the correct diagnosis of muscular dystrophy.

Assessment of atrioventricular nodal physiology in the mouse

Transgenic mice are increasingly being utilized for understanding cardiac electrophysiologic abnormalities. However, little is known about the normal atrioventricular nodal and infraHisian physiology in the mouse because of the prior inability to record a His-bundle deflection. We present the first comprehensive examination of the murine atrioventricular nodal and His-Purkinje systems employing His-bundle recordings. Normal, healthy, male C57BL/6J mice (n = 48) underwent an in vivo electrophysiology study using a 2 F octapolar electrode catheter. Effective refractory periods were determined during premature atrial and ventricular stimulation. The PR interval measured 44 +/- 6 ms with a mean sinus cycle length of 185 +/- 42 ms. Baseline AH intervals were 36 +/- 5 ms and HV intervals were 10 +/- 2 ms. At a pacing cycle length of 140 ms the atrioventricular nodal effective refractory period (AVNERP) and atrial effective refractory period (AERP) were 86 +/- 19 ms and 57 +/- 17 ms, respectively. The mean AV Wenckebach and 2:1 paced cycle length were 103 +/- 14 ms and 84 +/- 13 ms, respectively. Premature atrial stimulation curves were asymptotic without discontinuity. A subset of nine mice was studied after administration of isoproterenol. The sinus cycle length, AVNERP and AERP decreased significantly from baseline measurements. This method establishes a practical and feasible technique to record in vivo His-bundle electrograms in the mouse to assess atrioventricular nodal and infraHisian physiology. Use of this model will allow for the examination of abnormalities of atrioventricular nodal and infraHisian conduction in transgenic murine models.

What is commotio cordis?

Although thought to be rare, sudden deaths caused by nonpenetrating chest wall impact in the absence of structural injury to the ribs, sternum, and heart (commotio cordis) are reported with increasing frequency. This phenomenon is described in individuals when they are struck by relatively innocent blows to the chest wall. Young male athletes aged 5 to 18 years are particularly at risk for this catastrophe. It has been described after blows to the chest from baseballs, softballs, hockey pucks, and other objects. Death is usually instantaneous, and successful resuscitation is uncommon. A recently reported experimental model provides clues to the mechanisms and inferences for the prevention and treatment of this devastating condition. This swine model shows that a) ventricular fibrillation results from low-energy chest wall impacts during a vulnerable period of repolarization, b) the risk of this event can be decreased with softer-than-standard baseballs, and c) prompt defibrillation is crucial for resuscitation to be successful.

Localization of the sites of conduction abnormalities in a mouse model of myotonic dystrophy

INTRODUCTION

A mouse strain lacking functional myotonic dystrophy protein kinase (DMPK) has recently been developed. DMPK-/- mice exhibit muscular and conduction abnormalities consistent with the disease; however, the site of abnormal cardiac conduction is unknown.

METHODS AND RESULTS

Nine homozygous DMPK-/- mice and seven age matched wild-type (WT) controls underwent in vivo electrophysiologic studies using an endocardial 2-French catheter. Baseline intervals as well as Wenckebach and 2:1 cycle lengths were measured to assess AV and ventriculoatrial (VA) conduction. Effective refractory periods (ERP) and functional refractory periods were determined during atrial and ventricular premature stimulation. His-bundle recordings were obtained on all the studied animals (16/16). DMPK-/- mice had significantly prolonged PR (48.1 +/- 5.5 vs 40.9 +/- 3.9 msec, P = 0.010) and AH (36.7 +/- 4.0 vs 31.6 +/- 4.8 msec, P = 0.037) intervals compared to WT controls. HV intervals were very significantly prolonged as well (14.7 +/- 2.0 vs 10.3 +/- 0.8 msec; P < 0.0001). Three of 9 DMPK-/- and 1 of 7 WT mice exhibited VA block. Atrial ERP was reached before AV node ERP in 2 (22%) of 9 of the knockout mice and 5 (71%) of 7 of the controls (P = 0.06). Only one mouse (DMPK-/-) exhibited infra-Hisian block on premature atrial stimulation.

CONCLUSION

In this mouse model of myotonic dystrophy, AV conduction abnormalities were localized to the supra-Hisian and infra-Hisian conduction tissues, with a higher predilection to the latter, a finding similar to the human form of the disease.

Dopa-responsive dystonia induced by a recessive GTP cyclohydrolase I mutation

GTP cyclohydrolase I (GTPCH) catalyzes the rate-limiting step of tetrahydrobiopterin (BH4) biosynthesis. GTPCH has been associated with two clinically distinct human diseases: the recessive hyperphenylalaninemia (HPA) and the dominant dopa-responsive dystonia (DRD). We found a recessive GTPCH mutation (R249S, 747C-->G in a dystonia patient. Her PHA-stimulated mononuclear blood cells had a normal amount of GTPCH mRNA, but low GTPCH activity. Arginine 249 is located at the C-terminus of GTPCH, outside the catalytic site. E. coli expressed recombinant R249S mutant protein possessed normal enzyme activity and kinetics. However, in transfected eukaryotic cells, R249S mutant protein expression level was lower than the wild-type protein. Therefore, this is suspected to be a destabilizing mutation. Our data suggest that DRD could be either dominantly or recessively inherited, and the inheritance might be determined by the mechanism of mutation.

Correlation waveform analysis to discriminate monomorphic ventricular tachycardia from sinus rhythm using stored electrograms from implantable defibrillators

In order to examine whether a template-matching program utilizing correlation waveform analysis (CWA) might be used to discriminate monomorphic ventricular tachycardia (MMVT) from sinus rhythm (SR) in patients with implantable cardioverter defibrillators (ICDs), we studied stored episodes of induced MMVT in 25 patients and compared them to corresponding stored SR electrograms. We calculated mean correlation coefficients for SR beats against an SR template chosen within each sinus episode, induced MMVT beats against an induced MMVT template within each ventricular tachycardia episode, and induced MMVT beats against the original SR template. For each patient, the 99.5% lower confidence limit for the mean correlation coefficient of SR beats versus an SR template (patient-specific method) or the empirical correlation coefficient value 0.9 were selected as threshold values to discriminate induced MMVT from SR. The mean correlation coefficient for induced MMVT beats versus the original SR template for each patient was subtracted from both threshold values. A positive value is defined as accurate discrimination of induced MMVT from SR. Using 0.9 for a threshold cut off, 21 of 25 episodes of induced MMVT were accurately labeled with a sensitivity of 84%. Using the patient-specific method, we were able to correctly distinguish 23 of 25 episodes of induced MMVT from SR with a sensitivity of 92%. There was no statistically significant difference between the patient-specific or empirical methods in detecting MMVT (P 50.4). This is the first demonstration using stored intracardiac electrograms from ICDs that CWA is able to discriminate MMVT from SR with high sensitivity. Such a template-matching system may be used for off-line analysis or real-time rhythm discrimination.

Selective activation of the K(+)(ATP) channel is a mechanism by which sudden death is produced by low-energy chest-wall impact (Commotio cordis)

BACKGROUND

Sudden death due to relatively innocent chest-wall impact has been described in young individuals (commotio cordis). In our previously reported swine model of commotio cordis, ventricular fibrillation (with T-wave strikes) and ST-segment elevation (with QRS strikes) were produced by 30-mph baseball impacts to the precordium. Because activation of the K(+)(ATP) channel has been implicated in the pathogenesis of ST elevation and ventricular fibrillation in myocardial ischemia, we hypothesized that this channel could be responsible for the electrophysiologic findings in our experimental model and in victims of commotio cordis.

METHODS AND RESULTS

In the initial experiment, 6 juvenile swine were given 0.5 mg/kg IV glibenclamide, a selective inhibitor of the K(+)(ATP) channel, and chest impact was given on the QRS. The results of these strikes were compared with animals in which no glibenclamide was given. In the second phase, 20 swine were randomized to receive glibenclamide or a control vehicle (in a double-blind fashion), with chest impact delivered just before the T-wave peak. With QRS impacts, the maximal ST elevation was significantly less in those animals given glibenclamide (0.16+/-0.10 mV) than in controls (0.35+/-0.20 mV; P=0.004). With T-wave impacts, the animals that received glibenclamide had significantly fewer occurrences of ventricular fibrillation (1 episode in 27 impacts; 4%) than controls (6 episodes in 18 impacts; 33%; P=0.01).

CONCLUSIONS

In this experimental model of commotio cordis, blockade of the K(+)(ATP) channel reduced the incidence of ventricular fibrillation and the magnitude of ST-segment elevation. Therefore, selective K(+)(ATP) channel activation may be a pivotal mechanism in sudden death resulting from low-energy chest-wall trauma in young people during sporting activities.

Alternate energy sources for catheter ablation

Because of the limitations of conventional radiofrequency ablation in creating large or linear lesions, alternative energy sources have been used as possible methods of catheter ablation. Modified radiofrequency energy, cryoablation, and microwave, laser, and ultrasound technologies may be able to create longer, deeper, and more controlled lesions and may be particularly suited for the treatment of ventricular tachycardias and for linear atrial ablation. Future studies will establish the efficacy of these new and promising technologies.

Long-term outcome of patients with syncope associated with coronary artery disease and a nondiagnostic electrophysiologic evaluation

Syncope in the patient with structural heart disease and a nondiagnostic noninvasive workup is a generally accepted indication for an invasive electrophysiologic study. However, if the electrophysiologic evaluation is not highly sensitive, arrhythmic causes of syncope may not be discovered. In these patients, recurrent syncope and even sudden death may be observed at follow-up. Thus, we evaluated long-term follow-up in 68 consecutive patients who presented with syncope, coronary artery disease, and who had a negative invasive electrophysiologic evaluation. At a mean follow-up of 30 +/- 18 months (range 1 to 65), there have been 2 sudden deaths and 1 episode each of ventricular fibrillation and ventricular tachycardia in patients treated with an implantable cardioverter-defibrillator. All 4 arrhythmias occurred in patients with left ventricular fractions < or = 25%. Seventeen patients had recurrent presyncope or syncope. Bradycardia causing syncope was found in 8 of these patients. A bundle branch block at the initial evaluation predicted for the occurrence of bradycardia at follow-up. We conclude that in patients with coronary artery disease and syncope, noninducibility at electrophysiologic study predicts a lower risk of sudden death and ventricular arrhythmias. However, in patients with a reduced ejection fraction, the risk of sudden death and ventricular arrhythmias remains up to 10%/year and these patients may warrant treatment with implantable cardioverter-defibrillators. Recurrent syncope is common, and frequently a bradyarrhythmia is found to be the cause. Treatment of selected patients (especially those with bundle branch blocks) with permanent pacemakers may be justified.

Neonatal type of nonketotic hyperglycinemia

Two infants with the neonatal type of nonketotic hyperglycinemia that had manifested as early neonatal consciousness disturbance are presented. Transient hyperammonemia had been detected in both initially. High levels of glycine in plasma and cerebrospinal fluid disturb the nervous system, causing variable manifestations of this disease. Both cases were complicated by intracranial hemorrhage, which has never before been reported. After treatment with sodium benzoate and dextromethorphan, some neurologic improvement was observed, although the glycine levels did not lower. Recent clinical trials are reviewed, and because of the unfavorable outcomes, the special need for prenatal diagnosis is highlighted.

Evaluation of coronary revascularization to prevent tachycardia recurrences in survivors of ventricular fibrillation

Long-term follow-up of 29 consecutive survivors of ventricular fibrillation who underwent revascularization demonstrated that recurrent arrhythmics events were common. Because revascularization alone does not prevent arrhythmia recurrence, treatment with an implantable defibrillator should be considered in these patients.

Muscle phosphofructokinase deficiency (Tarui's disease): report of a case

A 14-year-old girl had an acute episode of rhabdomyolysis after vigorous exercise and seizures. Laboratory studies revealed elevated creatine phosphokinase (CPK) activity and myoglobinuria without acute renal failure, as well as mild indirect hyperbilirubinemia, and hyperuricemia. The elevated CPK activity, mild indirect hyperbilirubinemia, and hyperuricemia persisted during a 10-month follow-up period, during which chronic hemolysis without overt anemia was also noted. A muscle biopsy specimen from the left biceps muscle revealed occasional muscle fiber necrosis and mild excess of glycogen accumulation on periodic acid-Schiff staining. Histochemical reactions were negative with phosphofructokinase (PFK) stain when fructose-6-phosphate was used as the substrate, but positive when fructose 1,6-bisphosphate was used as the substrate. These findings confirmed the diagnosis of muscle PFK deficiency (Tarui's disease), which is a defect of glycolysis in muscles and erythrocytes. Less than 40 such patients have been reported to date. When a specific metabolic myopathy is suspected in children with rhabdomyolysis, symptoms of hemolysis should also be sought to identify Tarui's disease. To the best of our knowledge, this is the first case of Tarui's disease identified in Taiwan.

Vocal cord paralysis and hypoventilation in a patient with suspected Leigh disease

The authors report the case of a 16-month-old male with suspected Leigh disease, which was diagnosed on the basis of the clinical manifestations, abnormal lactate stimulation test, proton magnetic resonance spectroscopy, and neuroradiologic findings. Progressive stridor resulting from bilateral vocal cord paralysis and hypoventilation was evident. The authors suggest that for infants or children who exhibit vocal cord paralysis, mitochondrial disorders, such as Leigh disease, should be considered.

Comparison of frequency of complications of implantable cardioverter-defibrillators in children versus adults

Compared with adults patients (n = 309) receiving implantable cardioverter-defibrillators at the same institution, pediatric patients (n = 11) exhibited a trend toward lower defibrillation thresholds. At follow-up of 29 +/- 17 months, the incidence of recurrent arrhythmias was similar, but lead revisions and device infections were more common in the pediatric patients.

Technologic advances in implantable cardioverter defibrillators

Multiple technologic advances in the implantable cardioverter defibrillator (ICD) have resulted in smaller size, easier implantation, and improved detection, therapy, and stored diagnostic information. Advanced dual-chamber ICDs are currently available that allow dual-chamber rate-responsive pacing with mode switching, enhanced detection algorithms, antitachycardia pacing, low-energy cardioversion, high-energy shocks, and extensive diagnostics. Based on improvements in lead systems and improved energy waveforms, almost all devices are being implanted with nonthoracotomy leads in the pectoralis area. The results of recent clinical trials have expanded indications for the ICD for primary and secondary prevention of sudden cardiac death. With advances in capacitor and battery technology coupled with improved lead systems and waveform resulting in lower defibrillation thresholds, it is likely that lower-output, smaller devices will be developed. In the future, ICDs may have expanded indications and may incorporate physiologic sensors to access hemodynamic significance of arrhythmias and algorithms for prediction and prevention of cardiac arrhythmias.

Clinical profile of commotio cordis: an under appreciated cause of sudden death in the young during sports and other activities

Not particularly well recognized are athletic field catastrophes in which virtually instantaneous cardiac arrest is produced by nonpenetrating chest blows in the absence of heart disease or identifiable morphologic injury to the chest wall or heart (commotio cordis). To better characterize the clinical profile of this syndrome, we have assembled 70 cases, including 34 occurring during organized competitive athletics and 36 others that occurred during informal recreational sports at home, school or the playground, or during nonsporting activities. Ages were 2 to 38 (mean age: 12) with 70% < 16 years old. Most common sports involved were youth baseball (n = 40), softball (n = 7), and ice hockey (n = 7). Seven (10%) of the 70 commotio cordis victims, including six with documented ventricular fibrillation, have survived the consequences of their chest blow. Eleven of the events (16%) occurred despite the presence of chest padding believed to be potentially protective. Four victims experienced modest chest blows while in circumstances completely unrelated to sports activities; three of the four individuals who delivered these blows were ultimately convicted of criminal acts within the justice system. An experimental model of low-energy chest wall impact demonstrates that commotio cordis events are due largely to the exquisite timing of blows during a narrow window within the repolarization phase of the cardiac cycle, 15 to 30 msec prior to the peak of the T wave.

Intracardiac echocardiographic guidance during microwave catheter ablation

The purpose of this study was to explore the potential of intracardiac echocardiography in monitoring lesion formation and assisting with the assessment of ablative lesions using microwave energy. Microwave energy is a promising modality for catheter ablation. Because microwave lesions may have considerable variability in dimension, the ability to assess them may be particularly useful. One hundred twenty-five microwave lesions were created in vitro in ovine left ventricles. Correct assessment of catheter-endocardial contact was possible in virtually all cases. Intracardiac imaging always identified correctly whether or not an ablation was performed. During ablation, gas formation was observed in all instances. Sensitivity, specificity, and predictive values for identification of ablation lesions were 88% to 92%. Although the correlations with pathology for lesion dimensions were relatively poor, intracardiac imaging had a predictive accuracy of 80% to 85% to discriminate small from large lesions. Intracardiac guidance for microwave ablation is useful for verifying tissue-electrode contact, monitoring lesion formation, and localizing lesions. It is also a useful tool for the assessment of lesion size. These attributes, combined with the ability to facilitate transseptal catheterization and to identify complications such as hemopericardium, make intracardiac echocardiography a potentially useful method for guiding microwave ablation of arrhythmic foci.

Spinal fusion and pedicle screw instrumentation in the treatment of spondylolisthesis over the age of 60

BACKGROUND

Spinal fusion or instrumentation for the treatment of spondylolisthesis in elderly people is still an issue of controversy. The purpose of this study was to assess the clinical results of laminectomy, posterolateral fusion, and pedicle screw instrumentation in patients over age 60.

MATERIALS AND METHODS

From 1993 through 1994, 94 spondylolisthesis patients over age 60 underwent laminectomy, posterolateral fusion and pedicle screw instrumentation. All the patients had follow-up examinations 3 months, 6 months, 1 year and then annually after the operation. At each follow-up visit, the clinical results and complications were evaluated and a radiographic assessment was performed. The follow-up period ranged from 2 to 4 years. At the final follow-up visit, we administered a questionnaire designed for clinical evaluation.

RESULTS

Seventy-five patients (80%) obtained improvement in back pain, 75 patients (80%) got improvement in leg pain, and 65 patients (69%) needed no medications. The average distance the patients were able to walk, at one time was 2.2 km. Sixty-seven patients (71%) could walk more than 500 m at a time. Seventy-four patients (79%) showed solid fusion, 20 patients inadequate fusion, and no psuedoarthrosis was found. Complications were rare.

CONCLUSION

Laminectomy with spinal fusion and instrumentation is a good method for the treatment of spondylolisthesis in elderly people, and it can achieve a satisfactory clinical outcome.

The modified dipeptide, enalapril, an angiotensin-converting enzyme inhibitor, is transported by the rat liver organic anion transport protein

Oatp1, the organic anion transport polypeptide, is an integral membrane protein cloned from rat liver that mediates the uptake of various organic anions such as bromosulfophthalein (BSP) and taurocholate (TCA). Recent studies by others revealed that the thrombin inhibitor, CRC 220, a modified dipeptide, was transported by oatp1. The present study was designed to examine whether another modified peptide, enalapril, an angiotensin-converting enzyme inhibitor, was also a substrate. Transport was studied with enalapril (1 to 800 micromol/L, with [3H]enalapril) in a HeLa cell line stably transfected with oatp1-cDNA under the regulation of a Zn2+-inducible promoter. Noninduced transfected cells (without zinc) that did not express oatp1 failed to take up enalapril. In contrast, cells expressing oatp1 transported enalapril, estrone sulfate (E1S), taurolithocholic acid sulfate (TLCAS), and the glutathione conjugate of BSP (BSPGSH). Uptake of enalapril by oatp1 at 37 degreesC was substantially higher than that at 4 degreesC. The rate at 37 degreesC (uptake rates for induced - noninduced, transfected cells) was linear over 5 minutes and was concentration-dependent, characterized by a Km of 214 +/- 67 micromol/L and a Vmax of 0.51 +/- 0.15 nmol/min/mg protein. Enalapril uptake was inhibited competitively by BSP (at 1, 5, 10, and 50 micromol/L) and TCA (at 5, 25, and 100 micromol/L) with inhibition constants (Ki) of 2 and 32 micromol/L, respectively. The metabolite enalaprilat was, however, not transported by oatp1. That oatp1 is not a general transporter of anionic compounds was further shown by the lack of transport of harmol sulfate, benzoate, and hippurate. These observations attest to the role of oatp1 as a specific transporter for at least two classes of pharmacologically important peptides.

The controversy regarding diagnostic criteria for early myoclonic encephalopathy

To re-evaluate the diagnostic criteria for early myoclonic encephalopathy (EME), the following study was done. During the past 2 years, five patients with erratic, fragmentary myoclonus of neonatal onset, in association with other types of seizures, were analyzed with regard to etiologies, electroclinical features and their evolution, using a series of examinations including electroencephalographies (EEGs) and metabolic investigations. Of these five patients, three were diagnosed to have non-ketotic hyperglycinemia (NKH); one was pyridoxine-dependent; the other was cryptogenic. Only two cases (one NKH and one cryptogenic) had initial typical suppression-burst (S-B) EEG pattern, which subsequently evolved into multiple paroxysmal abnormalities with random asynchronous attenuation (MP-AA) pattern. The other two cases with NKH had MP-AA EEG pattern throughout both awake and sleep recordings in two consecutive EEG studies. All three cases with NKH survived with increasing microcephaly, muscle tonicity; all developed infantile spasm with hypsarrhythmia on EEGs. The patient with pyridoxine-dependency had an initial MP-AA EEG pattern, which converted into S-B pattern after the first use of pyridoxine, eventually becoming normal after a supplement with the second-dose of pyridoxine. In conclusion, either S-B or MP-AA pattern may reflect the severity of the underlying pathologies or the disease stages. These results suggest that, from both etiological and electroclinical viewpoints, EME may represent a broader spectrum than previously recognized. The still ongoing controversy regarding whether the S-B pattern should be recognized as the sole EEG criteria for the diagnosis of EME needs further experience to clarify.

The human tail

The human tail is a congenital anomaly with a protruding lesion from the lumbosacrococcygeal region. A newborn with a tail-like structure over the coccygeal area observed since birth is presented. Lipoma accompanied by tethered spinal cord were found. In reviewing the literature from 1960 to 1997, 59 cases were described. Higher incidences of spinal dysraphism (49.15%) and tethered spinal cord (20.34%) compared with previous reports were evident. This fact plays an important role in understanding the disturbance of development and regression of human tails. A new classification according to whether the anomaly appears in combination with spinal dysraphism is proposed for clinical usage. Preoperative detailed image studies are needed to clarify the possibility of tethered spinal cord syndrome developing in the future and thus prevent it. Magnetic resonance imaging is the modality of choice if available. Long-term follow-up for possible sequelae after operation, especially in cases with spinal dysraphism, is necessary.

Intracranial arachnoid cysts in children: related signs and associated anomalies

Intracranial arachnoid cysts are benign development anomalies that may be clinically asymptomatic. The authors describe 30 children with intracranial arachnoid cysts in terms of clinical manifestations and relations to the associated brain anomalies or lesions. The mean age at onset of clinical manifestations was 4 years, 7 months (range 1 day to 14 years). The mean age at diagnosis was 6 years, 2 months (range 10 days to 16 years). Most patients with nonprogressive symptoms, such as seizures and headache, had focal epileptiform discharges on electroencephalogram, and they benefited from antiepileptic drugs. Surgery resulted in only partial reduction in both cyst size and seizure frequency in patients with intractable seizures, and it also failed to improve some neurologic signs, such as sexual precocity or cranial neuropathy resulting from long-term compression of arachnoid cysts. We conclude that the only absolute indication for surgery is the presence of progressive hydrocephalus or intracranial hypertension. The associated anomalies or lesions include brain tumors, giant nevocellular nevi, achondroplasia, microphthalmia, intracystic hemorrhage, dysgenesis of the corpus callosum, and heterotopia.

Sonographically guided microwave coagulation treatment of liver cancer: an experimental and clinical study

OBJECTIVE

Percutaneous microwave coagulation was performed with a modified system in animal experiments and in a clinical study to evaluate this technique as a treatment option for liver cancer.

SUBJECTS AND METHODS

As an in vitro study, a microwave electrode was inserted 5-6 cm into separated egg white, homogenate of pig liver, and pig liver, with different power outputs and different lengths of inner conductors. In the animal experiment, the sonographically guided coagulation was performed percutaneously nine times and at laparotomy 43 times on 17 adult dogs. The thermal needles were placed parallel to and 5 mm, 8-12 mm, and 15 mm from the electrode. Clinically, 41 patients with hepatocellular carcinoma and 10 patients with hepatic metastases were treated with a 60-W microwave emission for 240-300 sec.

RESULTS

Microwave coagulation using the modified system at 60 W for 300 sec produced a necrosis volume of 3.7 x 2.6 x 2.6 cm. The coagulated volume was elliptic when the exposed inner conductor of the electrode was 27 mm. The temperature at the periphery was 62.0 +/- 5.8 degrees C. During a mean follow-up period of 23 months, in 41 patients with hepatocellular carcinoma, 79% (46/58) of lesions became smaller, and the intratumoral blood flow disappeared in 89% (47/53). All tumors showed decreased density on unenhanced CT, and 84% (32/38) of tumors showed no enhancement on contrast-enhanced CT. In 21 patients with an elevated alpha-fetoprotein level, the level decreased in all 21 and was normalized in 17. A second biopsy on 19 patients showed complete destruction of tumor in 18. In 10 patients with hepatic metastases, the mean follow-up period was 13 months. Shrinkage of lesions occurred in 84% (21/25), and the blood flow inside the tumor disappeared in 75% (12/16) of lesions. Seventy-three percent (8/11) of the nodules showed no enhancement. A second biopsy on six patients showed complete necrosis in five.

CONCLUSION

Sonographically guided microwave coagulation performed with this modified system was an effective and safe treatment for liver cancer.

Clinical application of the measurement of cord plasma lactate and pyruvate in the assessment of high-risk neonates

Lactate levels in combination with lactate/pyruvate (L/P) ratio have been used to measure altered cellular redox states. We measured the cord plasma lactate levels and L/P ratios in 70 normal neonates (40 full-term and 30 preterm neonates) to set up the normal (control) ranges. The control cord plasma lactate levels and L/P ratios were 2660 [700 (SD)] micromol/l, 16 (3) in full-term neonates and 2750 (740) micromol/l, 17 (3) in preterm neonates, respectively. We also measured the lactate levels and L/P ratios in the high-risk full-term (n = 23) and preterm (n = 35) neonates, the results were 4500 (2600) micromol/l, 19 (13), and 5100 (2700) micromol/l, 26 (12), respectively. With the aid of elevated lactate levels and L/P ratios, the occurrence of neonatal encephalopathy can be predicted with a sensitivity of 100% and a specificity of 94.5% in this patient group. In our study, the six cases with abnormal neurodevelopment at 6-9 months of age all had both elevated lactate levels and L/P ratios at birth. We conclude that the measurement of lactate levels in combination with L/P ratios is a useful quantitative tool in assessing the existence and severity of perinatal hypoxia in the high-risk neonates.

Commotio cordis: cardiovascular manifestations of a rare survivor

Death due to low-energy chest wall trauma, commotio cordis, may occur in young athletes. Death is sudden and usually refractory to even immediate resuscitation efforts. Herein are described the clinical, angiographic, and hemodynamic data of a rare survivor. These observations suggest that commotio cordis not only may be secondary to ventricular fibrillation, but also may be associated with coronary vasospasm or segmental changes in myocardial contractility.

Transplantation for adrenoleukodystrophy with HLA-A and B nonidentical paternal marrow: report of one case

We report the result of allogeneic bone marrow transplantation (BMT) in a 14-year-old boy who was neurologically severely involved with the childhood form of adrenoleukodystrophy (ALD) and received marrow from his HLA-A and B nonidentical, MLC-nonreactive paternal donor without T-cell depletion processing. Bone marrow transplantation corrected the excess content of very long chain fatty acid in plasma but did not arrest the deterioration of the neurological status during 3.5-year post-transplant follow-up period. Since partially matched or unrelated donors have been applied to clinical BMT successfully with current new techniques, ALD patients will have a better prognosis when they are transplanted in status of mild and early involvement. Our first experience may be helpful in more trials of BMT for genetic leukodystrophy in Taiwan.

Prospective comparison of temperature guided microwave and radiofrequency catheter ablation in the swine heart

Microwave energy has been proposed as an alternative to radiofrequency energy for use during catheter ablation procedures. The purpose of this study was to prospectively compare, in an animal model, the lesion size associated with temperature guided catheter ablation using either microwave or radiofrequency energy. Eleven swine underwent catheter ablation with either radiofrequency (N = 4) or microwave energy (N = 7). In each animal catheter ablation was performed at 7-15 sites. At each site energy was delivered for 60 seconds using closed loop feedback temperature control to achieve a target temperature of 70 degrees C. Cardiac catheterization was performed before and after ablation. Animals were sacrificed approximately one month following the ablation procedure. Analysis of lesion size demonstrated that overall lesions created using radiofrequency energy were larger than those created using microwave energy. In the ventricle, lesions created using microwave energy were longer, but had a similar width and depth as those created using radiofrequency energy. An important relation was observed between the depth of lesions created using microwave energy and catheter stability, as evidenced by the temperature profile. Overall, lesions created using microwave energy are smaller than those created using radiofrequency energy. Catheter stability has an important impact on lesion size.

Strokes in children: a medical center-based study

Stroke is an important cause of mortality and morbidity in children. Cases of pediatric stroke admitted to National Taiwan University Hospital from January 1985 to December 1995 were reviewed. Patients whose stroke was obviously caused by premature birth, birth trauma or head injury were excluded. Totally 65 patients were enrolled, including 37 boys and 28 girls. Their ages ranged from birth to 18 years old. They were classified into two groups: ischemic stroke (38 patients) and hemorrhagic stroke (27 patients), according to the pathogenesis. The ages of onset, clinical manifestation, underlying diseases and treatment of these two groups were systematically analyzed. The major presenting symptoms of both ischemic and hemorrhagic strokes were motor deficit (65.8%) and consciousness disturbance (55.6%). A wide variety of diseases predisposing to strokes was identified. The major causes of hemorrhagic stroke were vascular malformation and oncologic conditions, with the latter, the most frequently encountered underlying diseases associated with childhood ischemic stroke. The mortality rate for hemorrhagic stroke was 37% and, for ischemic stroke, 21.1%. There was male predominance in pediatric stroke. Although the clinical symptoms and signs might provide some guidelines to differentiate between hemorrhagic and ischemic strokes, neuroimaging studies were crucial to more exact diagnosis. A variety of diseases may contribute to pediatric stroke. Early diagnosis determine treatability, then aggressive treatment are important.

An experimental model of sudden death due to low-energy chest-wall impact (commotio cordis)

BACKGROUND

The syndrome of sudden death due to low-energy trauma to the chest wall (commotio cordis) has been described in young sports participants, but the mechanism is unknown.

METHODS

We developed a swine model of commotio cordis in which a low-energy impact to the chest wall was produced by a wooden object the size and weight of a regulation baseball. This projectile was thrust at a velocity of 30 miles per hour and was timed to the cardiac cycle.

RESULTS

We first studied 18 young pigs, 6 subjected to multiple chest impacts and 12 to single impacts. Of the 10 impacts occurring within the window from 30 to 15 msec before the peak of the T wave on the electrocardiogram, 9 produced ventricular fibrillation. Ventricular fibrillation was not produced by impacts at any other time during the cardiac cycle. Of the 10 impacts sustained during the QRS complex, 4 resulted in transient complete heart block. We also studied whether the use of safety baseballs, which are softer than standard ones, would reduce the risk of arrhythmia. A total of 48 additional animals sustained up to three impacts during the T-wave window of vulnerability to ventricular fibrillation with a regulation baseball and safety baseballs of three degrees of hardness. We found that the likelihood of ventricular fibrillation was proportional to the hardness of the ball, with the softest balls associated with the lowest risk (two instances of ventricular fibrillation after 26 impacts, as compared with eight instances after 23 impacts with regulation baseballs).

CONCLUSIONS

This experimental model of commotio cordis closely resembles the clinical profile of this catastrophic event. Whether ventricular fibrillation occurred depended on the precise timing of the impact. Safety baseballs, as compared with regulation balls, may reduce the risk of commotio cordis.

Complications of dual chamber pacemaker implantation in the elderly. Pacemaker Selection in the Elderly (PASE) Investigators

Pacemakers are frequently implanted, yet accurate prospective data on implant complications are limited. Elderly patients may be at increased risk of implant complications and are increasingly being referred for pacemaker implantation. The purpose of the present analysis was to define the incidence and possible predictors of serious complications of dual chamber permanent pacemaker implantation in the elderly. Therefore, we sought to prospectively identify the incidence and predictors of pacemaker implant complications in a large multicenter trial involving patients receiving a dual chamber pacemaker. The Pacemaker Selection in the Elderly (PASE) study was a prospective trial designed to evaluate quality of life in dual chamber pacemaker recipients age 65 years or older randomized to DDDR versus VVIR programming. In addition to being age 65 years or older, patients enrolled in this study were in normal sinus rhythm, and had standard indications for permanent pacemaker implantation. All patients received dual chamber pacemakers and were randomized to DDDR versus VVIR pacing. Pacemaker implant complications were collected on standardized forms which were completed at pacemaker implantation and during follow-up appointments. In this study of 407 patients, there were 26 complications occurring in 25 patients (6.1%). The most frequent complication was lead dislodgment which occurred in 9 patients. This was followed by pneumothorax (8 patients) and cardiac perforations (4 patients). In 18 patients (4.4%) repeat surgical procedures (including chest tubes) were required. Complications were noted prior to discharge in only 18 patients. There were no significant predictors of overall complications. Pneumothorax was more frequent in patients > or = 75 years old, and was observed only in patients with subclavian venous access. In conclusion, complications from pacemaker implantation in the elderly are seen in 6.1% of patients and 4.4% of patients require a repeat surgical procedure. Other than advanced age and lower weight predicting for pneumothorax, there are no significant clinical predictors of complications.

Transcoronary ethanol ablation of the atrioventricular node in a young patient with tricuspid atresia

Catheter ablation of AV conduction with radiofrequency energy can be challenging in the presence of structural abnormalities of the AV junction, either congenitally or after reconstructive surgery. We used transcoronary ethanol to ablate the AV node in a patient with classic tricuspid atresia and refractory intraatrial reentry tachycardia. This approach provides an alternative means of creating complete heart block with catheter-based techniques, when radiofrequency catheter ablation is technically impossible or ineffective.

Neonatal radiofrequency catheter ablation of junctional tachycardias

Junctional tachycardias comprise several arrhythmia types with differing mechanisms, principally involving the region of the atrioventricular (A-V) junction. Neonatal radiofrequency catheter ablation has typically been reserved for life-threatening, drug-refractory cases due to the unique concerns regarding patient size and development. We performed radiofrequency catheter ablation on two neonates with incessant, rapid junctional tachycardias and hemodynamic compromise after failing conventional medical therapy. This report describes 2 neonates who underwent emergent radiofrequency catheter ablation, and compares these two patients to a larger pediatric catheter ablation patient cohort. Both neonates had an acutely successful outcome and were able to be discharged within a week of the ablation procedure. Fluoroscopy time and total procedure time were shorter in these two patients than in the course of the average pediatric catheter ablation. Though long-term developmental consequences of neonatal catheter ablation are yet unknown, in unique extreme situations, radiofrequency catheter ablation can be performed in neonates, as in older children and adults, without excessive acute morbidity.