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Biomedical subjects

P C Gillette

Publications and source records attributed to P C Gillette.

At least 37 records · Page 2Linked to original sources
PubMed1996

Learning curve for radiofrequency catheter ablation in pediatrics at a single institution.

We examined the learning curve for radiofrequency ablation in pediatrics at a single institution. The first 146 cases were retrospectively reviewed, including patients < or = 21 years old with a single tachycardia diagnosis who were undergoing radiofrequency ablation for the first time. Data regarding demographics, electrophysiologic properties of the tachycardia, and procedural characteristics were tabulated. Data were then analyzed for evidence of association between these characteristics, success, and experience. Results revealed that success rates improved significantly with experience, reaching 85% success for all cases after < 100 cases attempted. Success for accessory pathway tachycardias alone reached > 93%. The number of cases of nonpathway tachycardias undertaken significantly increased as experience was gained. Fluoroscopy time improved to 34 +/- 27 minutes after < 100 cases. In conclusion, as experience was gained, (1) success rates showed a steep improvement; (2) the population undergoing radiofrequency ablation clearly shifted to include more difficult diagnoses; and (3) fluoroscopy time significantly decreased.

Adolescent↗
PubMed1996

Interatrial septal aneurysms and atrial arrhythmias in infants.

Studies have suggested that interatrial septal aneurysms (IASAs) may be the initiating mechanism of supraventricular tachycardia (SVT) in newborns and infants. A retrospective study was performed to determine the incidence of IASAs in 30 infants with atrial arrhythmias (SVT, atrial flutter, or frequent premature atrial contractions) and their possible relation to the mechanism of atrial arrhythmias. An IASA was defined as dilation of the septum > 5 mm beyond the plane of the atrial septum and associated with redundant tissue and abnormal mobility. The study patients were compared with age and sex-matched control subjects. Four (13%) of the 30 study patients and 2 (7%) of 30 control subjects had an IASA (difference not significant). In contrast to previous reports, this study demonstrates that there is not a significant relation between the presence of IASAs and the onset and recurrence of atrial arrhythmias.

Atrial Flutter↗
PubMed1996

Lack of proarrhythmia as assessed by Holter monitor after atrial radiofrequency ablation of supraventricular tachycardia in children.

The purpose of this study was to assess the short-term arrhythmogenicity of atrial radiofrequency (RF) ablation lesions in children. Patients with the greatest exposure to RF energy comprised the study group. Holter data on 35 RF ablation procedures in 31 patients with a median age of 13.2 years (range 3 months to 20 years) was retrospectively analyzed. Patients received an average of 19.9 (SD = 13.6) RF lesions, all delivered by an atrial approach. Supraventricular ectopy and ventricular ectopy were compared immediately before and after and 4 to 9 weeks after RF ablation by serial Holter monitoring. Factors thought to possibly predispose patients to a proarrhythmic effect were used to define subgroups for separate analysis. No increase in ambient supraventricular ectopy or ventricular ectopy was observed either immediately after or 4 to 9 weeks after RF ablation compared with the baseline Holter recordings. Children exposed to relatively large doses of RF energy may demonstrate transient and asymptomatic nonsustained tachycardias in the short term. However, no new sustained tachycardias and no increase in supraventricular or ventricular ambient ectopy are detected by short-term Holter monitoring.

Adolescent↗
PubMed1996

Developmental differences in myocyte contractile response after cardioplegic arrest.

Although developmental differences in left ventricular function after cardioplegic arrest and rewarming have been postulated, whether differences exist at the level of the myocyte remains unexplored. This project tested the hypothesis that there is a differential effect of hypothermic hyperkalemic cardioplegic arrest with subsequent rewarming on contractile function of immature compared with adult ventricular myocytes. Myocytes were isolated from the left ventricular free wall of five immature and five adult rabbits and incubated for 2 hours in hyperkalemic modified Ringer's solution at 4 degrees C (cardioplegia) or for 2 hours in cell culture medium at 37 degrees C (normothermia). Myocytes were resuspended ("rewarmed") in 37 degrees C cell culture medium after the incubation protocol. Normothermic baseline contractile performance was lower in immature, compared with adult, myocytes. Specifically, myocyte shortening velocity was 62 +/- 4 microm/sec in immature and 112 +/-6 microm/sec in adult myocytes (p < 0.01). After cardioplegia and rewarming, immature myocyte contractile function was unchanged, whereas adult myocyte contractile function was significantly diminished. For example, myocyte shortening velocity was 65 +/- 4 microm/sec in immature and 58 +/- 3 microm/sec in adult myocytes (p < 0.01 versus normothermic). Myocyte surface area, which reflects myocyte volume, was increased after cardioplegia and rewarming in adults (3582 +/- 55 versus 3316 +/- 46 microm2, p < 0.01), but remained unchanged in immature myocytes (2212 +/- 27 versus 2285 +/- 28 microm2, P = not significant). These unique findings demonstrate a preservation of myocyte contractile function and volume regulation in immature myocytes after cardioplegic arrest and rewarming. Thus this study directly demonstrates that developmental differences exist in myocyte responses to hypothermic hyperkalemic cardioplegic arrest with subsequent rewarming.

Animals↗
PubMed1996

Right ventricular volume estimation using an ellipsoidal shell model and single-plane magnetic resonance imaging.

RATIONALE AND OBJECTIVES: To investigate whether accurate right ventricular volumes could be obtained using an ellipsoidal shell model with magnetic resonance (MR) image measurements from a single imaging plane. METHODS: An initial retrospective patient study included 10 patients with congenital cardiac defects who had undergone same-day or next-day radiographic contrast ventriculography. An expanded study included MR scans of a total of 29 patients with congenital cardiac defects. Magnetic resonance scans of 10 healthy volunteers were also included in part of the study. Right ventricular volumes were calculated from (1) model-based calculations using single-plane cine MR imaging, and (2) multislice calculations based on contrast angiography. RESULTS: Regression of angiography-based volumes against MR-based volumes showed high correlation (r = 0.97, see = 12.5 mL) and slope near unity. Regression of right against left stroke volumes, both calculated from MR data, showed excellent correlation (r = 0.90, see = 11.6 ml) and slope near unity. CONCLUSIONS: The ellipsoidal shell model can be used to reliably estimate right ventricular volume using single-plane MR images.

Adolescent↗
PubMed1996

Late endocardial pacing lead body migration compromising Fontan physiology.

Migration of intracardiac transvenous pacing leads may occur. There is a known risk of intrapulmonary ventricular pacing lead migration in patients with endocardial lead systems. In the current report we present the late intrapulmonary migration of an endocardial atrial pacing lead body. The patient had undergone antitachycardia pacemaker placement to control recurrent atrial tachyarrhythmias following the Fontan procedure. Although the lead electrode remained in place and continued to pace, the lead body migrated, causing severe obstruction to blood flow. This resulted in severe cardiac decompensation, which was ultimately ameliorated by lead repositioning.

Adult↗
PubMed1996

Developmental effects of d-sotalol on anterograde and retrograde atrioventricular conduction in the rabbit.

INTRODUCTION: These experiments investigate the developmental effects of d-sotalol on standard electrophysiologic parameters of anterograde and retrograde AV conduction in the rabbit. METHODS AND RESULTS: Using bipolar electrograms and standard pacing techniques, the effects of graded concentrations of d-sotalol on anterograde and retrograde conduction in mature and immature perfused rabbit hearts were compared. Also, a quantitative assessment of the drug's effects on a rate-dependent property of anterograde AV node (AVN) conduction, termed the "recovery process," was compared in mature and immature rabbit hearts. The main developmental electrophysiologic findings of this investigation are: (1) in both the mature and immature rabbit heart, d-sotalol increases the anterograde conduction time and prolongs refractoriness of the AVN, yet the minimal concentrations of d-sotalol that produce these changes are lower in the neonate; (2) d-sotalol increases the anterograde refractory period of the His-Purkinje system in both age groups, but increases anterograde infra-Hisian conduction only in the neonate; (3) 1 x 10-4 M d-sotalol significantly changes the time constant of the AVN recovery process in the neonate, but not in the adult; (4) for retrograde conduction, slow conduction through the AVN (HAmax) and infra-Hisian region (VHmax) are increased by d-sotalol in the neonate, but not in the adult. CONCLUSIONS: The findings of this study illustrate that d-sotalol has different effects on parameters of the developing AV conduction system. This implies that there may be maturational changes in the ionic currents that are responsible for anterograde and retrograde AVN and His-Purkinje conduction.

Aging↗
PubMed1996

Fetal surgical protocols in Yucatan miniature swine.

Thirty-nine Yucatan miniature swine were used in three fetal surgical experimental protocols. They involved antiarrhythmic administration, pacemaker implantation, and in-utero diagnosis of ventricular septal defect by intraoperative echocardiography. Because of problems encountered with surgical protocols in the initial stages, modifications were made to prevent fetal hypothermia and intraoperative mortality. These modifications included environmental temperature support, staple surgical techniques to reduce operative time, and development of fetal catheters designed to facilitate cannulation of small vessels. Postoperative care protocols were intensive and included antibiotics, analgesics, and supportive care designed to reduce discomfort and prevent abortion and sepsis. Thirty-seven of 39 sows survived the surgical procedures; experiments were performed on 117 fetuses. Twenty-two fetuses died either intraoperatively or postoperatively because of complications related to the experimental protocols. Modification of surgical and postsurgical protocols for these projects demonstrates the feasibility of using miniature swine as a model for fetal surgery, when their use was appropriate for anatomic and physiologic reasons.

Animals↗
PubMed1996

Right and left ventricular geometry and myocyte contractile processes with dilated cardiomyopathy: myocyte growth and beta-adrenergic responsiveness.

OBJECTIVES: Comparison of the effects of supraventricular tachycardia-induced dilated cardiomyopathy on left and right ventricular isolated myocyte geometry and function. BACKGROUND: Chronic ventricular tachycardia and supraventricular tachycardia cause left ventricular dilation and dysfunction in humans. However, it is unknown whether supraventricular tachycardia-induced dilated cardiomyopathy is a homogenous process for both the left and right ventricles. METHODS: Dilated cardiomyopathy was induced by rapid atrial pacing (240 beats/min, 3 weeks) in 5 pigs. Five age- and weight-matched pigs served as controls. Ventricular mass was measured, myocyte dimensions were obtained, and isolated right and left ventricular myocyte contractile performance was evaluated at baseline and after beta-adrenergic receptor stimulation. RESULTS: With the development of dilated cardiomyopathy, there was no change in left ventricular mass. In contrast, right ventricular mass was increased, as was right ventricular myocyte cross-sectional area. In the control group, baseline right ventricular myocyte contractile function was increased compared to left ventricular myocytes. beta-adrenergic receptor stimulation increased myocyte contractile function in both left and right ventricular myocytes. With supraventricular tachycardia-induced cardiomyopathy, both left and right ventricular myocyte contractile function and beta-adrenergic responsiveness were reduced. CONCLUSIONS: This study demonstrated differences in left and right ventricular myocyte growth with supraventricular tachycardia-induced dilated cardiomyopathy and this differential growth response was associated with changes in contractile performance. Thus, in this model of cardiomyopathic disease, left and right ventricular growth and changes in contractile performance are not a homogenous process.

Adrenergic beta-Agonists↗
PubMed1995

Right ventricular volume estimation with an ellipsoidal shell model and two-plane magnetic resonance imaging.

In patients with congenital and other heart disease, measurement of right ventricular (RV) volumes would be as useful as left ventricular (LV) volume measurement has been for diseases of the LV. Model-based techniques have had limited success. Simpson's rule (multislice) techniques require lengthy data collection and reduction. We investigated a technique for volume estimation with a new but simple geometric model. A retrospective patient study compared RV volumes from model-based calculations with dual-plane cine magnetic resonance (MR) imaging and multislice calculations with biplane cineangiography. Linear regression showed high correlation (r = 0.98, standard error of the estimate = 11.8 ml) between the two techniques, with a slope near unity. Comparison of calculated right and left stroke volumes also showed an excellent correlation (r = 0.93, standard error of the estimate = 10.4 ml) and a slope near unity. It is concluded that the ellipsoidal shell model can be used to estimate RV volume reliably and practically with dual-plane MR imaging.

Adolescent↗
PubMed1995

The JT interval as a depolarization independent measurement of repolarization: lessons from catheter ablation of the Wolff-Parkinson-White syndrome.

In patients with Wolff-Parkinson-White syndrome (WPW), preexcitation precludes accurate assessment of the ventricular repolarization by the QTc. In patients with long QT syndrome, it has been demonstrated that the JTc does not change when depolarization abnormalities develop. We hypothesized that this phenomenon should also be applicable to WPW patients. To test this, we assessed the surface ECG of 29 patients (16 males, 13 females) with WPW pre- and postablation. The QRS, QT, and JT intervals were measured pre- and postablation at 50 mm/s paper speed in leads II and V2. QTc and JTc were calculated according to Bazett's formula. The average age was 12.8 +/- 4.9 years (range 1.5-21). All patients had no residual preexcitation on postablation ECG. Early and late follow-up ECGs were obtained at 32 +/- 34 days and 388 +/- 197 days postablation, respectively. Both the QRS and the QTc intervals shortened significantly on the postablation versus preablation ECGs (QRS: 115 +/- 23 ms vs 89 +/- 15 ms, respectively; P < 0.0001), QTc: 454 +/- 26 vs 423 +/- 23, respectively; P < 0.0001). The preablation JTc interval did not change, postablation (319 +/- 21 vs 323 +/- 23, respectively; P > 0.2). Also, the JTc interval did not change between early and late follow-up, postablation. JTc is an independent measure of repolarization, not related to depolarization. JTc may be a useful tool in assessing repolarization in patients with WPW and other depolarization abnormalities.

Adolescent↗