The Study of Antiarrhythmic Medications in Infancy (SAMIS)

Background—

Supraventricular tachycardia (SVT) is one of the most common conditions requiring emergent cardiac care in children, yet its management has never been subjected to a randomized controlled clinical trial. The purpose of this study was to compare the efficacy and safety of the 2 most commonly used medications for antiarrhythmic prophylaxis of SVT in infants: digoxin and propranolol.

Methods and Results—

This was a randomized, double-blind, multicenter study of infants <4 months with SVT (atrioventricular reciprocating tachycardia or atrioventricular nodal reentrant tachycardia), excluding Wolff-Parkinson-White, comparing digoxin with propranolol. The primary end point was recurrence of SVT requiring medical intervention. Time to recurrence and adverse events were secondary outcomes. Sixty-one patients completed the study, 27 randomized to digoxin and 34 to propranolol. SVT recurred in 19% of patients on digoxin and 31% of patients on propranolol ( P =0.25). No first recurrence occurred after 110 days of treatment. The 6-month recurrence-free status was 79% for patients on digoxin and 67% for patients on propranolol ( P =0.34), and there were no first recurrences in either group between 6 and 12 months. There were no deaths and no serious adverse events related to study medication.

Conclusions—

There was no difference in SVT recurrence in infants treated with digoxin versus propranolol. The current standard practice may be treating infants longer than required and indicates the need for a placebo-controlled trial.

Clinical Trial Registration Information—

http://clinicaltrials.gov ; NCT-00390546.

Successful stent treatment of pulmonary vein stenosis following atrial fibrillation radiofrequency ablation

Pulmonary vein stenosis is a known complication of radiofrequency ablation of atrial fibrillation foci. We report a case of severe unilateral pulmonary vein stenosis following radiofrequency ablation resulting in no perfusion to the right lung. Simple balloon dilation was unsuccessful in this patient. Stent placement in the stenotic right pulmonary veins resulted in reperfusion of the lung as documented by follow-up lung scan at one year.

Milk of calcium in the breast: appearance on prone stereotactic imaging

Microcalcifications discovered by mammography require careful analysis, occasionally leading to core biopsy to exclude associated breast cancer. We report unrecognized milk of calcium layering on small field of view prone digital stereotactic images. We illustrate important features on prone digital images attributed to milk of calcium which can exclude breast neoplasm, suggest this diagnosis, and prevent unnecessary biopsy.

Unenhanced helical CT for suspected acute appendicitis

OBJECTIVE

The purpose of this study was to determine the diagnostic accuracy of unenhanced helical CT scans in patients with a suspected acute appendicitis.

SUBJECTS AND METHODS

Over a 20-month period, 109 adult patients with suspected acute appendicitis were referred by the emergency department for an unenhanced helical CT scan. Each scan was obtained in a single breath-hold from the T12 vertebral body to the public symphysis using a 5-mm collimation and a pitch of 1.6. No patients were given oral or IV contrast media. The primary CT criteria for diagnosing acute appendicitis was the identification of an appendix with a transverse diameter larger than 6 mm with associated periappendiceal inflammatory changes. The presence of an appendicolith was considered a secondary finding as was isolated periappendiceal inflammation; however, appendicitis was not diagnosed in such patients unless an enlarged appendix was definitely identified. Final diagnoses were established by surgical or clinical follow-up and were compared with the original CT reports.

RESULTS

We found 66 true-negatives, 37 true-positives, four false-negatives, and two false-positives that yielded a sensitivity of 90%, a specificity of 97%, a positive predictive value of 95%, a negative predictive value of 95%, and an accuracy of 94%. An alternative diagnosis was established by an unenhanced helical CT scan in 24 patients (22%), which included cecal diverticulitis (seven patients), urinary tract disease (five patients), adnexal pathology (four patients), sigmoid diverticulitis (two patients), small bowel disease (three patients), right lower quadrant tumor (two patients), and an infected dialysis catheter (one patient).

CONCLUSION

Unenhanced thin-section helical CT is an accurate, effective technique for diagnosing acute appendicitis.

Inadvertent atrioventricular block during radiofrequency catheter ablation. Results of the Pediatric Radiofrequency Ablation Registry. Pediatric Electrophysiology Society

BACKGROUND

Inadvertent atrioventricular block is a complication of radiofrequency ablation. The present study is an analysis of the incidence, significance, and factors associated with inadvertent atrioventricular block during radiofrequency catheter ablation in childhood and adolescence.

METHODS AND RESULTS

The records of the Pediatric Radiofrequency Ablation Registry were reviewed. Between January 1, 1991, and April 1, 1994, atrioventricular block occurred in 23 of 1964 radiofrequency ablations (1.2%): 14 as third-degree block (3 transient) and 9 as second-degree block (5 transient). Atrioventricular block occurred from 5 seconds to 2 months (mean, 4.1 days; median, 15 seconds) after the onset of the energy application. Eight transient cases lasted 1 hour to 1 month (mean, 9.4 days; median, 7 days). Inadvertent atrioventricular block was related to the ablation anatomic site: 3 of 111 (2.7%) anteroseptal, 11 of 106 (10.4%) midseptal, and 2 of 197 (1.0%) right posteroseptal sites (P = .0007) for anteroseptal, P = .0001 for midseptal, and P = .17 for right posteroseptal versus nonright septal sites). Five of 314 (1.6%) ablations for atrioventricular nodal reentrant tachycardia resulted in atrioventricular block (P = .004 versus nonright septal sites). Compared with a matched subgroup, radiofrequency ablation experience was the only significant risk factor (32.7 versus 106.6, P = .002) for the occurrence of atrioventricular block.

CONCLUSIONS

Inadvertent atrioventricular block may occur during or late after radiofrequency catheter ablation. It is associated with ablations for (1) anterior and midseptal accessory pathways and atrioventricular nodal reentry and (2) relative institutional inexperience.

Mapping and radiofrequency ablation of intraatrial reentrant tachycardia after the Senning or Mustard procedure for transposition ofthe great arteries

The Senning and Mustard procedures are often associated with the development of atrial tachyarrhythmias, which may be a cause of sudden death. We hypothesized that atrial surgery creates barriers to impulse propagation, establishing potential routes for atrial reentry, and that mapping combined with knowledge of the surgical anatomy could identify zones that are critical to the tachycardia to be targeted for radiofrequency catheter ablation. Patients underwent mapping to identify early sites of atrial activation that were related to anatomic or surgically created obstacles, with confirmation by pacing to demonstrate concealed entrainment. Radiofrequency lesions were placed to connect these obstacles, while observing for tachycardia termination. Thirteen tachycardias were attempted in 10 patients, 10 successfully. Three patients had 2 distinct tachycardias. Successful sites were in right atrial tissue, although in many, a retrograde approach to the pulmonary venous atrium was necessary. Ablation of the clinically documented tachycardia was successful in 9 of 10 patients. The most common successful site was the region of the coronary sinus mouth, approached antegrade or retrograde. Ablation of intraatrial reentrant tachycardias after the Senning or Mustard procedure is feasible using concealed entrainment mapping techniques, but requires a detailed knowledge of the individual surgical anatomy and the ability to approach the pulmonary venous atrium. Radiofrequency ablation offers significant advantages over other management modalities in this patient group.

Normal variations in the lateral contour of the head and neck of the pancreas mimicking neoplasm: evaluation with dual-phase helical CT

OBJECTIVE

The purpose of this study was to analyze variations in the lateral contour of the head and neck of the pancreas that can mimic pancreatic masses on CT imaging.

MATERIALS AND METHODS

We retrospectively reviewed dual-phase helical CT examinations of 119 patients who had no clinical or CT evidence of pancreatic disease. Contour variations of the head and neck of the pancreas were analyzed and were classified according to their anatomic orientation.

RESULTS

Forty-one (34.5%) of the 119 patients had discrete lobulations of pancreatic tissue greater than 1 cm lateral to the gastroduodenal or anterior superior pancreaticoduodenal artery. These lobulations showed normal pancreatic density on both predominantly arterial and portal venous phase images. Contour variants of the pancreatic head and neck were categorized as three main types: anterior (type I), posterior (type II), and horizontal (type III). In the 119 patients, we found 12 type I variants (10%), 23 type II variants (19%), and six type III variants (5%).

CONCLUSION

Variations in the lateral contour of the normal head and neck of the pancreas are common. Recognition of the different types of contours may help avoid misinterpretation of normal variants as pancreatic masses.

A comparison of omeprazole and ranitidine in the prevention of recurrence of benign esophageal stricture. Restore Investigator Group

BACKGROUND/AIMS

Dilatation combined with subsequent pharmacological control of gastroesophageal reflux represents a logical but poorly documented approach to the management of benign esophageal stricture. This large trial (366 patients) aimed to assess whether omeprazole as the most effective available medication for gastroesophageal reflux disease prevents recurrent stricture formation.

METHODS

Patients (n = 366) were randomized in a double-blind study to undergo either omeprazole (20 mg once daily; 180 evaluable patients) or ranitidine therapy (150 mg twice daily; 185 evaluable patients) for 1 year after dilatation to 12-18-mm diameter (36-54F gauge). Subsequently, endoscopy and dilatation were performed when clinically indicated and endoscopy on completion. Symptoms were assessed at clinic visits every 3 months and using weekly diary cards.

RESULTS

Fewer patients undergoing omeprazole therapy required redilatation compared with those on ranitidine (43 of 143 [30%] vs. 66 of 143 [46%] by 12 months; P < 0.01), and patients in the omeprazole group needed fewer redilatations during the year (0.48 vs. 1.08; P < 0.01). On completion, symptom relief favored omeprazole: 76% of patients in the omeprazole group were free of dysphagia (compared with 64% in the ranitidine group; P < 0.05); 83% were able to accept a normal diet (69%; P < 0.01); and 65% were completely asymptomatic (43%; P < 0.001).

CONCLUSIONS

Omeprazole, 20 mg once daily, was more effective than ranitidine, 150 mg twice daily, as prophylaxis against stricture recurrence and in providing symptom relief.

Differences in leucocyte-endothelium interactions between normal and adenocarcinoma bearing tissues in response to radiation

Previously, we demonstrated that the interaction between leucocytes and endothelial cells in tumour tissues is greatly diminished compared with normal tissues under several induced inflammatory conditions. Radiation has been reported to cause release of inflammatory mediators and to promote neutrophil adhesions to cultured endothelial monolayers. In this study, we tested the hypothesis that radiation would cause increased leucocyte rolling and adhesion in both tumour and normal tissues. We examined these two parameters in response to 6 Gy of gamma-radiation in mammary adenocarcinomas implanted into rat skinfold window chambers as well as normal (i.e. non-tumour-bearing) preparations. Leucocyte rolling and adhesion were measured in terms of flux of rolling leucocytes (F(rolling)) and density of adhering leucocytes (D(adhering)) in microvessels. F(rolling) and D(adhering) were measured in two groups of preparations: irradiated and control. In normal preparations, F(rolling) and D(adhering) were both increased significantly by radiation. In contrast, in adenocarcinoma-bearing preparations, F(rolling) and D(adhering) were either unchanged (in the tumour centre) or reduced (in tumour periphery and the normal tissue surrounding the tumour) by radiation. Radiation did not cause changes in haemodynamics in these preparations, thus the observed changes in leucocyte rolling and adhesion could not be accounted for by haemodynamic factors. These results indicate that: (1) in normal preparations, radiation could cause inflammation as manifested by increased leucocyte rolling and adhesion; and (2) in tumour-bearing preparations, radiation caused changes in the vascular surface properties such that they became less adhesive to leucocytes. Such differences in radiation response may have important implications for radiation therapy and provide new insights into the unique features of tumours.

Use of a database for managing qualitative research data

In this article, a process for handling text data in qualitative research projects by using existing word-processing and database programs is described. When qualitative data are managed using this method, the information is more readily available and the coding and organization of the data are enhanced. Furthermore, the narrative always remains intact regardless of how it is arranged or re-arranged, and there is a concomitant time savings and increased accuracy. The author hopes that this article will inspire some readers to explore additional methods and processes for computer-aided, nonstatistical data management. The study referred to in this article (Ross, 1991) was a qualitative research project which sought to find out how teaching faculty in nursing and education used computers in their professional work. Ajzen and Fishbein's (1980) Theory of Reasoned Action formed the theoretical basis for this work. This theory proposes that behavior, in this study the use of computers, is the result of intentions and that intentions are the result of attitudes and social norms. The study found that although computer use was sometimes the result of attitudes, more often it seemed to be the result of subjective (perceived) norms or intervening variables. Teaching faculty apparently did not initially make reasoned judgments about the computers or the programs they used, but chose to use whatever was required or available.

Collaboration in task analysis for developing a database to record the essential clinical behaviors of nursing students

This database for recording the Essential Clinical Behaviors of nursing students is the result of collaboration between nursing faculty and an instructional designer at Ball State University in Muncie, Indiana. The database was developed to aid nursing instructors in recording and tracking those student behaviors and skills essential to nursing education. The developers of the database are continuing to work toward the goal of having students record data and prepare reports. This would enable the students to be more self-directed in seeking appropriate and essential clinical experiences.

The effect of exercise on the atrial electrogram voltage in young patients

Atrial electrogram sensing is an important function in active individuals with permanently implanted bipolar dual chamber pacing systems. We undertook to determine the effect of vigorous exercise on the atrial electrogram size in 11 children and young adults (average age 12 years). Using a telemetry signal through a handheld programming wand, nine tracings were completely and clearly recorded for analysis. Six patients had tined/passive fixation atrial leads and three patients had screw-in/active fixation lead systems. All leads were bipolar. The atrial electrogram size for each patient was measured at rest and at each minute of exercise. The atrial electrogram size decreased with exercise from a mean of 5.08 mV to 3.44 mV (range 0.9-4.25 mV) (P = 0.002). The 1.64 mV mean decrease represented a 33.8% reduction (range 19%-56%) (P less than 0.001). There was no difference in the change in atrial electrogram size between the two lead types. Treadmill exercise testing with telemetric data of atrial electrograms showed a decrease in atrial electrogram size produced by exercise and may be helpful in determining appropriate atrial sensitivity settings in selected individuals. Because of the documented decrease in atrial electrogram size produced by exercise, we recommend obtaining maximal atrial electrograms at the time of implant and use of pacing systems that allow maximal flexibility in atrial sensing especially in athletically active individuals.

Abnormal responses to orthostatic testing in children and adolescents with recurrent unexplained syncope

Syncope in the pediatric age group is a frequent event. Most often the cause is readily apparent--i.e., orthostatic hypotension or a vasovagal event. However, there are a large number of children with frequent recurrent unexplained syncope. Neither history, physical examination, nor standard testing reveals a cause. One hundred four consecutive patients were evaluated by orthostatic testing after standard methods found no cause for the recurrent syncope. Forty-seven (44%) of these 104 patients had syncope produced by orthostatic testing. Twenty-six of the 47 (55%) became syncopal within 5 minutes of testing initiation and 21 of the 47 (45%) after 5 to 11 minutes of testing. These patients had an average decrease of 81.5 mm Hg in blood pressure and a 25 beat/min decrease in heart rate. Of 12 control subjects, none lost consciousness with standing times as long as 14 minutes. Pacing was ineffective in preventing syncope, as two patients with a previously implanted normally functioning pacemaker had recurrent syncope clinically. Syncope was also induced by orthostatic testing, with the pacemaker showing a normal response with pacing as the patient became bradycardic. The syncopal event produced by orthostatic testing occurred with a downward blood pressure trend and a narrowing of the pulse pressure without a significant increase in heart rate. This was followed by a sudden drop in blood pressure and then by bradycardia. There is a group of children and adolescents with recurrent unexplained syncope due to abnormal orthostatic control mechanisms. Orthostatic testing appears helpful in identifying these patients.

Cellular electrophysiology of neonatal and adult rabbit atrioventricular node

Adult and neonatal rabbit atrioventricular node (AVN) preparations were studied using transmembrane and surface electrogram recordings. Action potentials were categorized into four types, atrionodal (AN), nodal (N), "high" nodo-His (NH) (HNH), and "low" NH (LNH), according to their action potential characteristics and their location within the A-H interval. The electrophysiological parameters of the lower three regions were identical between the two age groups. Action potentials from the neonatal AN region were lower in amplitude and maximum diastolic potential than they were in the adult. The N cell action potential parameters did not differ between the two age groups, however, there did appear to be qualitative differences. AVN conduction times (A-H intervals) were the same in both age groups, as were the antegrade and retrograde refractory periods, and the Wenckebach intervals. Pacemaker activity was significantly greater in the neonates than in the adults and, in 11 of 13 neonatal preparations, originated in the AN region or higher. In 13 of 14 adult preparations, pacemaker activity resided within the AVN.

Congenital complete atrioventricular block

The various etiologies, pathologic findings, clinical concerns, and features of congenital complete atrioventricular block are presented and discussed. In addition, prenatal and antenatal diagnostic techniques are explained and analyzed. Lastly, treatment and the issues involved in deciding proper treatment are discussed in such a way that the general pediatrician can help the family to understand and handle the problem.

Management strategies for surgical treatment of dysrhythmias in infants and children

To elucidate the role of surgery in the management of refractory pediatric dysrhythmias, the investigators' 1987 experience with this therapy was reviewed. Sixteen patients (8 male, 8 female) had surgery. Age ranged from 3 months to 21 years (mean 7.7 years) with 2 being younger than 1 year of age. Eight patients had Wolff-Parkinson-White syndrome with supraventricular tachycardia (SVT), 6 had SVT alone and 2 had ventricular tachycardia. Patient symptoms fell into 3 distinct categories. Nine patients had frequent non-life-threatening tachycardia episodes despite aggressive medical management, 4 patients had life-threatening symptoms either related to frequent tachycardia episodes or due to side effects of drugs and 3 patients had minimal tachycardia symptoms but were judged to be at risk for sudden death. The mechanisms of the tachycardias included reentrant SVT using an accessory atrioventricular connection in 9, the permanent form of junctional reciprocating tachycardia in 2, atrioventricular node reentrant SVT in 2, atrial ectopic focus in 1 and ventricular ectopic foci in 2. Ablation techniques involved either surgical dissection or cryoablation of the arrhythmogenic substrates. There was no surgical mortality and follow-up shows 15 of 16 patients to have had no recurrence of symptomatic tachycardia without any therapy. Based on this experience, management strategies for surgical control of recalcitrant pediatric dysrhythmias are proposed. Surgery for infant dysrhythmias should be performed only for life-threatening symptoms. Beyond the first year of life, after failing 2 medications, surgical options for SVT should be considered. For patients with ventricular tachycardia, aggressive medical management with class II, IC and III agents should be attempted before surgical therapy.

Neonatal cardiac arrhythmias and their potential role in sudden infant death syndrome

A broad spectrum of dysrhythmias effects neonates. With modern monitoring techniques, we are detecting more of them. Modern treatment techniques should allow virtually all infants to be treated successfully and to lead normal lives.

Flecainide for supraventricular tachycardia in children

The clinical efficacy, adverse effects and pharmacokinetics of flecainide were evaluated in 16 pediatric and young adult patients with supraventricular tachycardia (SVT). Patients had received an average of 2.8 drugs before flecainide was tried. The following mechanisms of supraventricular arrhythmias were determined in patients by intracardiac electrophysiologic studies: atrioventricular node reentry, 4; reentry through an accessory connection, 7; atrial automatic focus, 2; atrial flutter, 3. Twelve patients had normal cardiac anatomy and 4 had congenital heart disease. Each patient received 2.8 mg/kg/day of flecainide divided into 2 doses 12 hours apart. After 3 days, the dose was increased to 5.6 mg/kg/day if necessary. In 14 patients, serum flecainide concentrations measured 3 to 4 days after beginning therapy ranged from 0.1 to 0.8 micrograms/ml (mean 0.40). Flecainide successfully controlled SVT in 8 of 16 patients. SVT in 3 of 7 patients with accessory connections and in 3 of 4 patients with atrioventricular node reentry was successfully controlled. In 1 of 2 patients with atrial automatic tachycardia, SVT had been completely controlled over 16 months. Only 1 of 3 patients treated for atrial flutter responded. Follow-up for successfully treated patients ranged from 4 to 16 months (median 9). Seven patients continue to take flecainide. None of the patients had clinical congestive heart failure. No drug-related adverse effects were noted on the resting surface electrocardiogram. Flecainide rarely produced proarrhythmic effects in this series. The 2 that were observed were mild and caused no clinical problems. Noncardiovascular side effects also occurred infrequently.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial automatic ectopic tachycardia due to an atrial tumor

A dilated cardiomyopathy picture has been produced by rapid atrial and ventricular rates sustained for a long period of time in some patients. The ventricular tachycardias have in some instances been associated with ventricular tumors as the cause of the tachycardia. Once the tumor is removed, the tachycardia stops and the heart function improves. Atrial ectopic tachycardias also produce a similar picture, but have not been associated with atrial tumors. Such a case is presented with an atrial rhabdomyoma producing atrial ectopic tachycardia and a dilated, poorly contracting myocardium. The tumor was resected and the tachycardia was immediately abolished. Cardiac function quickly returned to normal.

The Blalock-Taussig shunt in infants: standard versus modified

In recent years, the modified Blalock-Taussig shunt--a polytetrafluoroethylene graft from the subclavian artery to the pulmonary artery--has been preferred over the standard shunt by some surgeons because (1) it requires less dissection and (2) length of native vessels is not critical. From January, 1979, to June, 1985, we operated on 51 infants less than 1 year of age, including 26 less than 1 week of age, to palliate severe complex cyanotic congenital cardiac malformations. Twenty-four modified Blalock-Taussig shunts and 29 standard Blalock-Taussig shunts were created. The groups were concurrent. We reviewed all available cineangiograms and measured branch pulmonary and subclavian arteries. Pulmonary artery index was not different preoperatively in patients given a modified versus a standard Blalock-Taussig shunt (144 +/- 118 and 118 +/- 59 mm2/m2, respectively), but it was greater postoperatively in patients with a modified shunt (431 +/- 188 and 189 +/- 106 mm2/m2) (p = 0.07). Distortion of the pulmonary artery occurred less often after a modified Blalock-Taussig shunt (4/11) than a standard Blalock-Taussig shunt (6/8) (p = 0.06), though none of the distortions was severe. Early and late shunt failure occurred less often with a modified shunt (5/24) than with a standard shunt (15/29) (p less than 0.05). The modified Blalock-Taussig shunt had advantages over the standard Blalock-Taussig shunt in our series: pulmonary artery growth was greater, distortion of pulmonary arteries was less commonly seen, and shunt failure occurred less often. Thus, in infants, we believe the modified Blalock-Taussig shunt should be considered a reasonable alternative to the standard Blalock-Taussig shunt.

Role of cryoanalgesia in the control of pain after thoracotomy

Thoracotomy causes severe postoperative pain, which is difficult to manage since the use of systemic analgesics often causes respiratory depression. Cryoanalgesia of the intercostal nerves has been advocated as an effective means of local analgesia without serious side effects. A prospective randomised blind trial to investigate the efficacy of the technique was carried out. A total of 53 patients undergoing thoracotomy were allocated to either the trial or a control group. At thoracotomy the surgeon was informed of the patient's trial allocation. The trial group received one minute of direct cryotherapy to at least five intercostal nerves related to the incision. All patients received methadone via the lumbar epidural route in a dose calculated according to their weight. A linear analogue assessment of postoperative pain was made by the patients as soon as they were sufficiently awake. An independent record of all postoperative analgesia was kept. After discharge from hospital further assessments were made at least six weeks after operation. Statistical analysis of the scores of postoperative pain and analgesic consumption showed that there was no significant difference between the trial and the control group. There was, however, a suggestion of an increase in the long term morbidity, although these figures were not amenable to statistical analysis. Thus is has not been possible to demonstrate a role for cryoanalgesia in the control of post thoracotomy pain.

High-yield criteria for urgent cranial computed tomography scans

We conducted a study to establish high-yield criteria for urgent cranial computed tomography (CT) scanning in both medical and surgical conditions. Patients were scanned on an emergency basis and were entered in the study if they met preestablished criteria. The clinical findings of the 407 patients in this study were correlated with CT findings. The majority were scanned on an emergency basis for the following reasons: trauma, seizures, altered mental status, hemiparesis, headache, and coma. The yield for CT scans that altered patient management was moderate to high for each of the following categories: coma, 46%; trauma, 30%; seizures, 23%; hemiparesis, 22%; and headache, 21%. The yield for altered mental status and reasons outside the established criteria were fairly low, 8% and 7%, respectively. The specific clinical correlation with CT results in each category is discussed.

Ventricular arrhythmias and sudden death in children

In children, sudden death related to ventricular arrhythmias occurs virtually always in a patient with an abnormal heart. Therefore, children with ventricular tachycardia should be thoroughly investigated by anatomic cardiac catheterization and possibly electrophysiologic study. Sudden death may occur in a patient who had been relatively asymptomatic. This especially occurs in patients after repair of congenital heart disease. The patient may also never have had documented ventricular tachycardia, although most have had at least premature ventricular complexes on a Holter monitor recording. Finally, sudden death related to ventricular arrhythmias can often be prevented with vigorous medical and surgical therapy.

The incidence of retrograde conduction in children

With the increasing use of "physiological" pacemakers in the pediatric age group, retrograde conduction in children has become of clinical importance. Pacemakers which sense atrial depolarization may sense "retrograde" P waves. The pacemaker may then act as the antegrade limb of a reciprocating tachycardia circuit, while the patient's own conduction system acts as the retrograde limb. We reviewed the data of 127 patients who underwent antegrade and retrograde electrophysiologic study at Texas Children's Hospital, with regard to retrograde conduction. Sixty percent of the patients had ventriculo-atrial conduction through the A-V node; the incidence of retrograde conduction in patients after surgical correction of a tetralogy of Fallot was significantly lower (33%). None of the patients with third-degree A-V block had retrograde conduction. The mean retrograde conduction time was 162 ms (range 70-335 ms) at the slowest pacing rate and 257 ms (range 80-475 ms) at the fastest pacing rate. This high incidence of retrograde conduction and the variability of conduction times must be taken into account when "physiological" pacemakers are to be implanted.

Late results of valvoplasty for mitral regurgitation due to rupture of chordae of the posterior (mural) cusp

Nine patients with rupture of chordae tendinea of the posterior cusp of the mitral valve are presented. All have been treated by plication of the posterior cusp and atrial wall. The presenting postoperative features have been described: 89 per cent are markedly improved; two patients have normal heart sounds with no murmurs; 6 patients have only a Grade 1 pansystolic apical murmur. The advantages of this procedure compared with mitral valve replacement for the same condition have been presented.