Biomedical subjects

C L Johnsrude

Publications and source records attributed to C L Johnsrude.

13 recordsLinked to original sources

PubMed2000

Simultaneous transcatheter closure of an atrial septal defect with an amplatzer septal occluder and radiofrequency ablation of an accessory connection.

This report describes the first case of simultaneous transcatheter closure of an atrial septal defect and radiofrequency ablation of an accessory connection. This was performed successfully on an 8-year-old boy and represents an attractive therapeutic alternative to surgical repair in this combination of relatively common cardiac conditions.

Catheter Ablation↗

PubMed1999

Impact of arrhythmia circuit cryoablation during Fontan conversion for refractory atrial tachycardia.

Refractory atrial arrhythmias in late postoperative Fontan patients are usually associated with residual hemodynamic abnormalities and result in significant morbidity and mortality. Surgical revision of the Fontan anastomosis may improve hemodynamics without eliminating tachycardia. This study sought to assess the impact of surgical cryoablation of the arrhythmia circuit at the time of Fontan conversion on the clinical recurrence of tachycardia. Sixteen consecutive atriopulmonary Fontan patients with refractory atrial arrhythmias underwent surgical conversion to lateral tunnel total cavopulmonary anastomosis (15) or Fontan revision (1 patient). The initial 4 patients underwent Fontan conversions alone, without specific arrhythmia surgery. The subsequent 12 patients underwent electrophysiologically guided cryoablation of the tachycardia circuits at the time of surgical conversion. The mean age at Fontan revision was 15.6 +/- 3.8 years. Cryoablation was directed to 3 identified major tachycardia circuits: the inferomedial right atrium, the superior rim of the prior atrial septal defect patch, and along the lateral right atrial wall. Transmural antitachycardia pacemakers were implanted in 11 of the 16 patients. There was no surgical mortality in either group, and all patients improved in functional classification. All patients not undergoing cryoablation experienced recurrent symptomatic tachycardia requiring antiarrhythmic therapy (median follow-up, 54 months) versus 2 of 12 patients receiving cryoablation (median follow-up, 25 months; p <0.02). Thus, surgical cryoablation of the arrhythmia circuit at the time of Fontan conversion is highly effective in the management of refractory atrial arrhythmias, and is superior to Fontan conversion alone.

Adolescent↗

PubMed1999

Transmural atrial pacing in patients with postoperative congenital heart disease.

INTRODUCTION: Some patients with postoperative congenital heart disease require permanent cardiac pacing, but the use of transvenous or epicardial pacing leads may be limited by type of cardiac malformation, venous connections, body size, or fibrosis. Transmural atrial pacing may provide an alternative in difficult patients, but to date has been described in only a few articles with small patient numbers, and data from lead performance are lacking. METHODS AND RESULTS: Records were reviewed in 18 consecutive patients (4 months to 21 years old) with postoperative congenital heart disease receiving transmural atrial pacing leads from July 1994 to December 1996. Implantation materials and techniques were described. Lead sensing and capture thresholds obtained acutely and during short-term follow-up (mean: 11.0 months) were evaluated, and comparisons were made between patients with postoperative Fontan anatomy and non-Fontan patients, and between patients receiving steroid-eluting and nonsteroid leads. Overall, the median acute sensing and capture thresholds of transmural leads were 4.1 m V and 0.7 V at 0.5 msec, respectively. Median follow-up thresholds were 2.8 m V and 0.8 V, respectively. Performance of leads in Fontan patients was similar to those in non-Fontan patients. Steroid-eluting leads had a chronic capture threshold of 0.6 V versus 0.9 V for nonsteroid leads (P = 0.038). CONCLUSION: Transmural atrial pacing leads were successfully implanted in patients with diverse ages and types of postoperative congenital heart disease. Lead performance was acceptable both acutely and during the first year of follow-up.

Adolescent↗

PubMed1998

Fontan conversion to cavopulmonary connection and arrhythmia circuit cryoblation.

OBJECTIVES: We review our surgical experience patients with atriopulmonary Fontan operations who had obstructive or arrhythmia indications for conversion to total cavopulmonary artery connections, arrhythmia circuit cryoablation, and placement of atrial antitachycardia pacemaker. METHODS: Fourteen patients (mean age 14 +/- 4 years) had conversion to total cavopulmonary artery connection 8 +/- 3 years after the original atriopulmonary Fontan operation primarily for atrial arrhythmias in 11, obstructive lesions in 2, and bradycardia with cyanosis in 1. Arrhythmia circuit cryoablation was performed on 11 patients and 10 had atrial antitachycardia pacemakers. Preoperative functional New York Heart Association class was IV in 9, III in 4, and II in 1. RESULTS: One patient had brain death (7%) presumably caused by resternotomy complications despite an excellent hemodynamic result. Another required reoperation for a maldeployed clamshell device after attempted fenestration closure. Average length of stay was 10 +/- 3 days; chest tubes were removed on day 7 +/- 3. There were no long-term deaths (mean follow-up 1.7 years, range 5 months to 5 years). Postoperative arrhythmias occurred in five patients, three of whom had successful termination by antitachycardia pacemaker and two who had pharmacologic control of their respective junctional ectopic and slow atrial tachycardia. All patients have improved to New York Heart Association class I or II. CONCLUSIONS: Total cavopulmonary artery conversion in association with arrhythmia circuit cryoablation and atrial antitachycardia pacemaker placement can be accomplished with low morbidity and mortality, oftentimes resulting in dramatic increases in functional class and control of life-threatening arrhythmias.

Adolescent↗

PubMed1995

Effect of age and surgical technique on symptomatic arrhythmias after the Fontan procedure.

The purpose of this study was to determine the effects of newer Fontan modifications (lateral tunnel with or without fenestration) and patient's age at surgery on the incidence and impact of symptomatic postoperative early and intermediate arrhythmias. Modifications to the Fontan procedure are used to decrease postoperative complications, and the Fontan procedure is now being performed on younger patients to reduce age-related changes in ventricular function. A retrospective review was done of the medical records of 151 consecutive patients, ranging in age from 1 to 49 years, who underwent a Fontan procedure at Texas Children's Hospital between 1987 and 1993. Risk factors were identified for early and intermediate arrhythmias. Age at time of the procedure was an independent predictor of early atrial arrhythmias (p = 0.03), ventricular arrhythmias (p = 0.003), and junctional ectopic tachycardia (JET) (p = 0.05). We found that the older the patient at surgery, the higher the incidence of atrial and ventricular arrhythmias, whereas the younger the patient, the higher the incidence of JET. Using Cox's proportional-hazards model, the risk of intermediate atrial arrhythmias after lateral tunnel modification was 1/3 that after atriopulmonary connection. Younger patients who underwent the Fontan procedure had a lower risk for early atrial and ventricular arrhythmia but an increased risk for JET. The lateral tunnel modification can be performed in order to reduce the risk of intermediate atrial arrhythmias.

Adolescent↗

PubMed1995

Differentiating anomalous left main coronary artery originating from the pulmonary artery in infants from myocarditis and dilated cardiomyopathy by electrocardiogram.

Anomalous left main coronary artery (ALMCA) originating from the pulmonary artery is an important cause of morbidity from heart failure and mortality in infants. Discriminating ALMCA from myocarditis or other forms of dilated cardiomyopathy (DC) in infants is critical for proper early management of this treatable disease. This study was performed to characterize electrocardiographic (ECG) patterns in infants with ALMCA, and to identify features that would allow differentiation of these infants from those with myocarditis/DC. Presenting electrocardiograms from 28 patients with ALMCA < 2 years of age were analyzed for 103 variables, and compared with electrocardiograms from 28 aged-matched infants with myocarditis/DC using the t test, Fisher's exact test, and discriminant analysis using stepwise logistic regression techniques. ECG findings characteristic of infants with ALMCA were confirmed, including deep (> or = 3 mm) and wide (> or = 30 ms) Q waves and a QR pattern in at least 1 of the following leads: I, aVL, V5 to V7. Also, the complete absence of Q waves from leads II, III, and aVF in all infants with ALMCA was noted. These and other ECG patterns were more common in infants with ALMCA than in those with myocarditis/DC (p < 0.05), but were also noted in some patients with myocarditis/DC. Stepwise logistic regression analysis identified 3 ECG variables that best discriminated ALMCA from myocarditis/DC, including Q wave width (w) in lead I, and Q-wave depth (d) and ST-segment amplitude (s) in lead aVL.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathy, Dilated↗

PubMed1995

Postinfarction ventricular arrhythmias in children.

Because limited information is available on significant arrhythmias after myocardial infarction in pediatric patients, this study was performed to determine the incidence and impact of ventricular tachycardia or fibrillation on the postinfarction course in patients aged 1 day to 16 years. Review of 96 such children showed a wide range of underlying heart disease (56 patients with congenital heart disease, 12 with cardiomyopathy, and 28 with acquired heart disease). Postinfarction ventricular tachycardia/fibrillation occurred commonly (28% of patients with acute myocardial infarction) and early (84% by 2 days after diagnosis). Postinfarction mortality was high in patients with acute myocardial infarction (61%) and appeared to be independent of type of associated heart disease. Ventricular tachycardia/fibrillation was associated with higher mortality rates (approximately 80%) in patients with acute or remote myocardial infarction. The 61 postinfarction survivors were monitored for an average of 4.9 years, and none had significant recurrent ventricular arrhythmias or late sudden death.

Adolescent↗

PubMed1985

Mechanical properties of the myotomal musculo-skeletal system of rainbow trout, Salmo gairdneri.

Net forces and velocities resulting from in situ contractions of the myotomal musculature on one side of the body were measured at the hypural bones. Forces, velocities and power were determined with the body bent into a range of postures typical of those observed during fast-start swimming. For trout averaging 0.178 m in length and 0.0605 kg in body mass, the muscle system exerts a maximum normal force of 2.2N at the base of the caudal fin. This force is equivalent to 11.8 kN m-2 based on the mean cross-sectional area of the myotomal muscle. The maximum velocity was 1.11 m s-1, and the maximum mechanical power output, 0.64 W, or 42.4 W kg-1 muscle. Based on estimates of swimming resistance, these results would suggest acceleration rates of 7.5 to 16.5 m s-2, similar to averages observed during fast-starts. Maximum sprint speeds would range from 6.5 to 17.8 body lengths s-1, spanning the range of maximum speeds reported in the literature. It is suggested that maximum speed is limited by interactions between muscle contraction frequency and endurance. Losses in the mechanical linkages between muscle fibres and propulsive surfaces were estimated at about 50% for power with possibly greater losses in force transmission. Maximum force and power did not vary over the range of postures tested, supporting Alexander's (1969) suggestions that white muscle should contract over a small portion of the resting length of the fibres.

Animals↗

PubMedDate not supplied

Can pediatric residents interpret electrocardiograms?

The purpose of this study was to assess the electrocardiogram (ECG) interpretation skills of pediatric residents in a controlled environment and determine if the level of residency training (intern vs senior) improves accuracy. A list of ECG diagnoses was provided to four pediatric residency educators with instructions to categorize each diagnosis as follows: I, all residents; II, the majority of residents, including all senior residents; III, less than the majority of residents; and IV, few residents should be able to interpret correctly. Only those categories that the entire panel believed all residents (category I) or all senior residents (category II) should be able to interpret correctly were included. The test included 17 ECGs: 14 category I and 3 category II. A total of 132 residents participated: 78 interns and 54 seniors. Both groups scored below expected levels. Mean correct score among seniors was 10.9 out of the expected 17 (p < 0.001). Mean correct score for interns was 7.7 out of the expected 14 (p < 0.00l). No difference in ECG interpretation accuracy was found between residency programs. In general, pediatric residents' ECG interpretation skills are less accurate than expected. Although there is a trend toward improvement during training, senior residents fell short of the expectations of the panel. We speculate that focused education in this area will improve resident ECG interpretation and benefit patient care by (1) facilitating referral and treatment of patients with cardiovascular disease and (2) decreasing referrals for erroneous interpretations.

Clinical Competence↗

PubMedDate not supplied

Current approach to pediatric syncope.

Syncope is the abrupt loss of consciousness and postural tone that reverses without intervention. Typically, syncopal episodes in pediatric patients are brief, lasting seconds (rarely minutes), and are followed by complete recovery without residual neurological sequelae. Syncopal presentations may be dramatic and lead family members and primary care providers to suspect a malignant cardiac condition, prompting referral to a pediatric cardiologist. Significant advances in the understanding of syncope in infants, children, and adolescents have occurred in the past decade. This review emphasizes neurally mediated syncope, but other etiologies are reviewed to complete the spectrum encountered by pediatric cardiologists. Some clues are provided to distinguish the more common and benign forms of syncope from those due to significant underlying heart disease.

Adolescent↗

PubMedDate not supplied

New directions in surgical therapy of arrhythmias.

The success of the radiofrequency catheter ablation procedure for most types of supraventricular and ventricular tachycardia, particularly in young patients, largely eliminated the role of surgical therapy of arrhythmias. However, there remains a subset of arrhythmia patients in whom the catheter approach has not been successful and types of arrhythmias with high recurrence rates following initially successful catheter ablation procedures where surgery can provide more definitive therapy. In addition, the concepts of ablation therapy can be successfully incorporated into the concomitant repair of complex congenital heart disease, resulting in single-stage therapy for structural and rhythm abnormalities. Prospectively, knowledge of the role of anatomic barriers as substrates for future reentrant arrhythmia circuits provides the opportunity to alter these circuits prophylactically at the time of initial surgical repair of congenital heart disease in an attempt to avoid the late development of tachycardia. This article describes our experience during the past decade with 71 patients undergoing arrhythmia surgery using this approach.

Arrhythmias, Cardiac↗

PubMedDate not supplied

Novel approach to transvenous pacemaker implantation in a post-fontan adolescent.

Postoperative bradycardia is not uncommon following the Fontan procedure in patients with a functional single ventricle. The surgical connections created with various Fontan modifications may complicate access to the atria for transvenous implantation of a permanent pacemaker. We describe approaches to overcoming problems with atrial access in an adolescent with complex congenital heart disease who required permanent transvenous atrial pacing for tachycardia-bradycardia after Fontan surgery.

Adolescent↗

PubMedDate not supplied

A comparison of steroid-eluting epicardial versus transvenous pacing leads in children.

OBJECTIVE: To evaluate the acute and chronic performance of steroid-eluting (SE) epicardial (EPI) pacing leads as compared to SE transvenous (TV) pacing leads in children. METHODS: From 1989 through 1997, 55 children with congenital heart disease received a total of 85 SE pacing leads, of which 38 were EPI and 47 TV. The mean age of children receiving EPI leads was younger than those receiving TV leads (7.7 months vs 15.1 years, p = 0.001), and they had shorter follow-up (17.2 months vs 36.2 months, p < 0.001). All leads were evaluated for acute and chronic sensing and capture thresholds, and impedance. RESULTS: Acute and in particular chronic atrial and ventricular sensing and capture thresholds in SE EPI and TV leads were essentially equivalent. [table: see text]. The chronic impedance of TV leads (atrial 525 ohms, ventricular 520 ohms) was consistently higher than EPI leads (atrial 404 ohms, ventricular 386 ohms). CONCLUSION: At intermediate follow-up, SE EPI leads are functionally equivalent to SE TV leads. We recommend the use of SE EPI leads as long as practically feasible prior to using the TV approach in children who will require a life-time of pacing.

Adolescent↗