Voltage and Activation Mapping

BACKGROUND

Endocardial mapping is mandatory before radiofrequency catheter ablation (RFCA). Mapping can be performed with either unipolar or bipolar recordings. Impact of the recording technique used was studied in patients with and without structural heart disease using the 3D electroanatomic CARTO mapping system.

METHODS AND RESULTS

Patients (n=44; 16 males; age 43+/-16 years) referred for RFCA of atrial flutter (AFL, n=18), focal atrial tachycardia (FAT, n=4), AV nodal reentrant tachycardia (AVNRT, n=5), or scar-related atrial reentrant tachycardia (IART, n=17) were studied. Voltage and activation maps were constructed. Unipolar and bipolar voltage distribution in the different groups was studied to establish a cutoff voltage value to facilitate delineation of scar tissue. Electrograms were recorded during tachycardia (FAT: n=246, cycle length [CL]=449+/-35 ms; AVNRT: n=182, CL=359+/-47 ms; AFL: n=1164, CL=255+/-56 ms; IART: n=2431, CL=280+/-74 ms). Unipolar voltages were greater than bipolar voltages (P<0.001). Unipolar voltages < or =1.0 mV were equally distributed in both AFL and IART patients. Bipolar voltages < or =0.1 mV were only found in patients with IART, and subsequently 0.1 mV was used as the cutoff value to delineate scar tissue. No unipolar cutoff value could be established. Timing of unipolar and bipolar local activation was correlated in all patient groups.

CONCLUSIONS

The recording technique used has considerable impact on reconstruction of reentrant pathways and on the outcome of RFCA. In general, unipolar and bipolar recordings provide complementary information; however, only bipolar recordings allow voltage-based scar tissue delineation in patients with congenital heart disease.

Pericardial cystic mass with fetal tachycardia

A pericardial cystic mass is a rare congenital anomaly and may be mistaken for other pericardial and pleural masses. A 31-year-old pregnant woman at 38 weeks of gestation presented with fetal pericardial cyst and fetal tachycardia, which were confirmed by transthoracal echocardiography after delivery. Tachycardia did not persist after delivery. The case is being followed up without any clinical problems at the pediatric cardiology clinic.

Familial neonatal atrial tachycardia

A father and his two sons each presented with atrial tachycardia in the newborn period. The father went on to develop dilated cardiomyopathy. The first son (who also had transposition of the great arteries) died from the arrhythmia after surgery. The second son is currently successfully managed pharmacologically.

Diagnosis and treatment of structural fetal cardiac abnormality and dysrhythmia

Although a great deal of controversy surrounds the concept of routine ultrasound screening, 70% of pregnant women in this country undergo ultrasound examination. Assessment of the fetal heart including a four-chamber view is recommended when ultrasound scans in the second and third trimester are performed. The accurate diagnosis of structural heart disease and cardiac dysrhythmias is now possible with advances in ultrasound and fetal echocardiography. Increased prenatal screening and genetic counseling have improved the management of these complicated pregnancies. It is hoped that the detection of significant congenital heart disease will continue to increase leading to further advances in medical and surgical treatment, improved patient care, and favorable perinatal outcomes.

Fetal arrhythmias

The increased awareness of fetal arrhythmias by obstetricians and the development of sophisticated fetal echocardiography have established the basis for identification and treatment of these arrhythmias. The development of fetal hydrops is a recognized link to the severity of the arrhythmia. Fetal tachycardias have been diagnosed relatively early in gestation. They may be differentiated into sinus tachycardia, supraventricular tachycardia, atrial flutter or fibrillation, and ventricular tachycardia. The need for prenatal treatment is widely accepted and various modes of therapy are advocated. Oral maternal antiarrhythmic medication is often used, is considered convenient and safe, and provides adequate conversion. The drugs of choice at various centers have included digoxin, flecainide, amiodarone, and a host of combinations, as well as sotalol, which is gaining popularity. At birth, reentry mechanisms are often documented, with frequent relapses of tachycardia, warranting postpartum continuation of treatment. Fetal bradycardias consist of sinus bradycardia (generally related to obstetric pathology) and atrioventricular block. Atrioventricular block may occur secondary to severe congenital heart disease in the fetus or as an isolated phenomenon. The development of isolated total atrioventricular block has been seen to occur from a gestational age of 18 weeks up to term. It is invariably accompanied by the presence of SS-A and SS-B autoantibodies in the mother. Passage of these antibodies across the placenta causes inflammatory disease of fetal atrioventricular node tissue, resulting in fibrosis and atrioventricular block.(ABSTRACT TRUNCATED AT 250 WORDS)

[Fetal arrhythmias--new immunologic studies and results]

The etiology of fetal arrhythmias is still unknown. We therefore did a research for immunologic causes: antimyolemmal antibodies (AMLA) in mothers and umbilical cord serum resulting from secondary immunopathogenesis caused by myocarditis of the mother. Is there a correlation between immunological and clinical findings giving a possible explanation for fetal arrhythmias? In 21 cases mothers and umbilical cord serum was investigated for AMLA; 16 with fetal atrial premature beats, 4 with fetal tachycardia and 1 with fetal bradyarrhythmia. From 16 mothers with fetal atrial premature beats had 12 AMLA, from these were in 4 cases in the umbilical cord serum AMLA. In 4 cases of fetal tachycardia we found in 1 case AMLA in mothers and umbilical cord serum. In the other 3 cases accessory pathways have been the cause for tachycardia. From 19 healthy persons were found in 3 cases AMLA in mothers serum, umbilical cord serum was negative.

Pediatric electrophysiology

Our understanding of pediatric arrhythmias continues to evolve through natural history studies of paroxysmal supraventricular tachycardia, the congenital long QT syndrome, and postoperative atrial and ventricular tachyarrhythmias. The influence of the autonomic nervous system on cardiovascular function may play a role in the sudden infant death syndrome, pallid breath-holding spells, and neurally mediated syncope; much work is necessary to understand these entities better. Therapeutic approaches to pediatric arrhythmias are extending beyond newer antiarrhythmic drugs and now include ablative therapy for many supraventricular tachyarrhythmias, both surgical and transcatheter. Advances in pacemaker therapy include novel implantation sites, down-sizing of devices, and the application of antitachycardia and rate-adaptive technologies.

Evaluation of fetal cardiac arrhythmias. Ultrasound findings and neonatal outcome

During a four-year period, 3,882 fetal diagnostic ultrasounds were performed and 162 patients (4% of all patients scanned) were referred to our perinatal center for evaluation of fetal cardiac arrhythmia. Fetal echocardiography subsequently revealed an arrhythmia in 80 (49%) of these patients. The rhythm disturbances noted were premature atrial or ventricular contractions (n = 65, 81%), tachyarrhythmia (n = 8, 10%), and bradyarrhythmia (n = 7, 9%). Three of the bradycardic fetuses evaluated had complete heart block associated with anatomic abnormalities. In seven tachycardic fetuses, the finding of fetal compromise was followed by intervention. The majority of fetuses with cardiac rhythm disturbance will have premature atrial or ventricular contractions and will have normal echocardiographic evaluation and neonatal outcome. Sustained tachyarrhythmias and bradyarrhythmias are more likely to be associated with fetal morbidity. Based upon the findings of this study and others, we propose a scheme for follow-up of the fetus referred with an irregular cardiac rhythm.

[Malignant ventricular arrhythmia in congenital aneurysms of the left ventricle in adulthood]

Congenital aneurysms of the left ventricle (ALV) are rare cardiac lesions. Beyond that an association with malignant ventricular arrhythmias (MVA, symptomatic ventricular tachycardia--VT or ventricular fibrillation--VF) is reported only in sporadic cases. Since 1988 we had the opportunity to study 5 patients (pts) with MVA (4 sustained VT, 1 VF; 1 female, 4 males; mean age 38 years) without cardiovascular risk factors, history of myocardial infarction, trauma or inflammatory disease. Left ventricular contrast angiography and echocardiography disclosed ALV's. At programmed electrical stimulation clinically documented MVA (4 VT, 1 resuscitated VF) were reproducible in all 5 cases, the respective VT was located in the area of the ALV in 4 cases. In 2 pts aneurysmectomy combined with subendocardial resection and cryotherapy (1 apical, 1 posterobasal ALV) was performed. In both pts histopathology confirmed a congenital disorder, without evidence of inflammatory lesions. In 2 pts MVA was controlled with antiarrhythmic therapy. The pt with VF and an ALV adjacent to the anulus of the aortic valve received an implantable cardioverter defibrillator. In congenital aneurysms of the left ventricle complicated by malignant ventricular arrhythmias surgical intervention offers a potential cure in selected cases.

Successful treatment of chaotic atrial tachycardia with oral flecainide

Two infants with chaotic atrial tachycardia diagnosed at birth and at 11 weeks of life, were treated successfully with oral flecainide. Both patients were in heart failure at initiation of therapy. Six months and 17 months later, respectively, they have had no recurrence of chaotic atrial tachycardia, left ventricular function returned to normal and therapy was stopped in both.

[Arrhythmogenic dysplasia of the right ventricle in a 16-month-old child]

The clinical history of a 16-month old child with an arrhythmogenic right ventricular dysplasia is reported. This is one of the youngest patients described in the literature. The pitfalls of the diagnosis and the particularities of the treatment of recurrent ventricular tachycardias are underlined.

Complete atrioventricular dissociation and His bundle tachycardia in a newborn: problems in prenatal diagnosis and postnatal management

A newborn infant with complete atrioventricular dissociation and infranodal tachycardia, detected at 33 weeks gestation by fetal echocardiography, is described. In the perinatal period, infra or juxta-nodal tachycardia was noted, compromising the hemodynamic state of the newborn. A combination of flecainide and propranolol terminated the arrhythmia.

[Fetal torsades de pointe and the long QT syndrome]

The authors report a case of pregnancy interrupted by caesarian section at 38 weeks' gestation for attacks of fetal ventricular tachycardia. The recording of a long QT interval at birth indicated a diagnosis of fetal torsades de pointe. These attacks recurred 2 hours after birth leading to cardiac arrest. The arrhythmia was immediately controlled by betablockers therapy. The diagnostic, epidemiological and physiopathological features of the long QT syndrome are reviewed. The links with maturation of the sympathetic nervous system are recalled. Finally, a diagnostic and therapeutic strategy is proposed, based on the results of fetal echocardiography.

[Polymorphic familial incessant ventricular rhythm disorders with ventricular repolarization abnormalities: borderline form of the congenital long QT syndrome?]

Two cases of polymorphic ventricular tachycardia (VT) are reported in siblings: the elder sister (18 years) was admitted to hospital because of syncope and ECG showed incessant attacks of VT. There was no obvious cardiac disease on echocardiography or cardiac catheterisation. A second syncopal attack occurred during Holter monitoring: this showed prolonged torsades de pointe which terminated spontaneously after a few minutes. Both syncopal attacks occurred at moments of intense emotional stress. Concomitantly, the duration of ventricular repolarisation was also observed to be increased. The attacks of polymorphic VT disappeared when the atrial rhythm accelerated, for example during exercise of isoprenaline infusion. It was not possible to induce VT by ventricular extrastimulation. The arrhythmia was controlled by nadolol and propafenone or flecainide. A familial investigation revealed that a younger brother had attacks of incessant VT with a long QT interval. The mother had frequent polymorphic ventricular extrasystoles and abnormal ST-T wave changes. The association of familial ventricular arrhythmias and long QT interval is suggestive of the Romano-Ward syndrome, but in this condition the intercritical ECG is normal except for the long QT. Conversely, in benign VT, the arrhythmia disappears during atrial pacing and exercise but there have been a few reports of sudden death. Our two cases could represent an intermediary form between these two pathological entities.

Afterdepolarizations as a mechanism for the long QT syndrome: electrophysiologic studies of a case

A young woman with palpitation and syncope was found to have ventricular tachyarrhythmia and a congenital long QT interval. The QT interval was shortened and the arrhythmia suppressed by propranolol. Electrograms recorded at various sites in both ventricles revealed a distinct diastolic slow wave that followed the T wave and measured 1.1 mV. Epinephrine infusion and emotion augumented this diastolic wave and induced ventricular ectopic complexes arising from this potential. Similar endocardial recordings in eight patients without a long QT interval showed diastolic slow waves that never exceeded 0.28 mV. In normal canine myocardium, afterdepolarizations can be induced by norepinephrine and blocked by propranolol. These findings suggest that the long QT syndrome is associated with abnormally large afterdepolarizations in ventricular myocardial cells, which are enhanced by beta-adrenergic stimulation to attain threshold and produce firing.

Surface electrocardiographic clues suggesting presence of a nodofascicular Mahaim fiber

Standard electrocardiograms from 87 consecutive patients with tachycardia of left bundle branch block configuration were analyzed retrospectively for features that might be characteristic of tachycardia utilizing a nodofascicular Mahaim fiber. The study group consisted of 13 patients with nodofascicular tachycardia, 34 with supraventricular tachycardia and aberrant conduction over the His-Purkinje system, 22 with ventricular tachycardia and 18 with antidromic tachycardia utilizing a right-sided accessory atrioventricular pathway. Six variables present during tachycardia of left bundle branch block configuration were predictive of a nodofascicular fiber: cycle length between 220 and 450 ms, QRS axis of 0 to -75 degrees, QRS duration 0.15 second or less, R wave in lead I, rS wave in precordial lead V1 and a precordial transition from a negative to a positive QRS complex after lead V4. All six criteria were present in 16 of the 87 patients. No patient with ventricular tachycardia satisfied these criteria, whereas 3 of 34 with supraventricular tachycardia, 1 of 18 with antidromic tachycardia and 12 of 13 with tachycardia using a nodofascicular fiber did. It is concluded that analysis of the surface electrocardiogram during tachycardia may suggest the presence of a nodofascicular fiber.

[Congenital bundle-of-his focal tachycardias. Cooperative study of 7 cases]

The authors described seven cases of supraventricular tachycardia with atrio-ventricular dissociation, associated with the activity of an automatic focus in the bundle of His. These tachycardias, which appear at birth or are discovered at a very young age, appear to be congenital and sometimes familial, and are always isolated, having no associated cardiac abnormality. They give rise to cardiac failure, which is more marked when the rate is high (180-260/mn) and particularly resistant to treatment. The most effective form of treatment is amiodarone, almost always used in combination with digitalis. The anatomical abnormality, which was studied in the first case, is a contricting fibrosis around the main trunk of the bundle of His, and the appearances are reminiscent of those found in conditions of congenital atrio-ventricular block.

Familial partial trisomy of the long arm of chromosome 10 (q24-26)

Two fourth cousins with a strikingly similar pattern of malformation and who have an unbalanced translocation (46, XY, -17, +t (17p; 10q) are described. From an analysis of the phenotypes of these patients and others reported with 10q trisomy, we propose that the trisomy 10q 24-26 syndrome includes: growth and mental retardation, a characteristic facies (microcephaly, flat face with spacious forehead, small nose, depressed nasal bridge, arched wide-spaced eyebrows, blepharophimosis, microphthalmia, low-set ears, bow-shaped mouth with prominent upper lip, micrognathia), palate anomalies (high-arched cleft or agenesis), congenital heart disease, and anomalies of the hands and feet. Anomalies common to the cousins, but not described in other patients with trisomy 10q, are believed to be expressions of a partial monosomy of 17p.