“A Song of Ice and Fire”—another verse from the world of ablation

The debate between the use of radiofrequency (RF) or cryoenergy for ablation near the atrioventricular (AV) conducting system or small coronaries has been fueled by the relative efficacies and risks of the two technologies, particularly in smaller hearts. The manuscript by Schneider et al adds another chapter to that ongoing debate.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150576/1/jce13987.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150576/2/jce13987_am.pd

Adenosine Mapping for Adenosine‐Dependent Accessory Pathway Ablation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106956/1/pace12324.pd

Utility of Intrathoracic Impedance Monitoring in Pediatric and Congenital Heart Disease

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99042/1/pace12134.pd

Patient and Procedural Correlates of Fluoroscopy Use During Catheter Ablation in the Pediatric and Congenital Electrophysiology Lab

ObjectiveTo identify factors associated with fluoroscopy use in pediatric and congenital heart disease (CHD) patients.DesignRetrospective cohort.SettingPediatric electrophysiology lab in a single tertiary‐care children's hospital.PatientsThree hundred eighty‐three patients who underwent electrophysiology study and ablation between January 2010 and December 2012.MethodsAblation procedures in which nonfluoroscopic navigation was employed were reviewed. Procedures using ≥10 minutes of fluoroscopy (high‐fluoroscopy time; HF) were compared with those using <10 minutes (low‐fluoroscopy time; LF). Group comparison of characteristics was made in the entire cohort and in CHD and anatomically normal heart subsets.ResultsDuring the study period, 416 ablation procedures were performed involving 471 substrates in 383 patients. Median fluoroscopy time was 6.7 minutes overall and 5.1 minutes with anatomically normal hearts. LF comprised 61% of all ablation and 69% of anatomically normal hearts. LF procedures were associated with anatomically normal hearts (93% vs. 63%; P < .0001). In anatomically normal hearts, HF was associated with accessory pathways (64% vs. 47%; P = .01), posteroseptal substrates (22% vs. 9%; P = .002), and ventricular substrates (12% vs. 1%; P < .0001). All cases of intra‐atrial reentrant tachycardia were HF. HF was associated with trans‐septal puncture (47% vs. 23%; P < .0001) though not when controlling for atrioventricular nodal reentrant tachycardia. LF was associated with cryoablation (56% vs. 17%; P < .0001).ConclusionsIn pediatric and congenital EP, ablation procedures using cryoablation and in patients with anatomically normal hearts are associated with LF. In accessory pathway ablation, HF was not associated with trans‐septal puncture.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111901/1/chd12213.pd

Frequency of CIED remote monitoring: A quality improvement follow‐up study

BackgroundBased on the findings of a prior study of CIED (Cardiac Implantable Electrical Device) remote monitoring (RM) frequency at the same center, the University of Michigan Congenital Heart Center (UMCHC) instituted a quality improvement (QI) change to reduce the frequency of routine CIED RM from every 2 months to every 3 months. The objective of this study is to determine the impact of this QI initiative to reduce workload without compromising patient care.MethodsThis is a single‐center, retrospective cohort study of all UMCHC patients with CIEDs followed via Medtronic CareLink CIED remote monitoring system from July 2015 to June 2017, after the QI change in 2014. The primary outcome was success of transition to new monitoring schedule. Secondary outcomes included complications, incidence of actionable events (AES), patient compliance, and change in workload. Outcomes were compared to the prior study.ResultsThere were 325 patients (mean age was 24  ±  14 years) included, of who 293 (90%) completely transitioned to the new RM schedule. During the study period, 96 transmissions included AES (4% of total), of which 50 (52%) were asymptomatic and discovered on routine monitoring. No patient experienced a complication attributable to decreased RM frequency. The mean number of interrogations decreased by 1.6 per patient over the 2‐year period compared to prior study.ConclusionsThis study demonstrated successful implementation of a QI initiative to reduce CIED monitoring frequency at a single center with no patient adverse events. The intervention reduced workload and potentially improved patient compliance with routine RM.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150575/1/pace13707_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150575/2/pace13707.pd

Antitachycardia Pacemakers in Congenital Heart Disease

BackgroundMany patients with congenital heart disease (CHD) acquire rhythm abnormalities related to their repair, most commonly intraatrial reentrant tachycardia (IART). Treatment of IART in CHD is often multifaceted, and may include medication, ablation, and pacing. Evidence regarding the use of antitachycardia pacing therapies is limited.ObjectiveThe aim of the study is to define the use and efficacy of antitachycardia pacing in patients with CHD at a single center.ResultsEighty implants were performed on 72 patients between 2000 and 2010. Follow‐up data of more than 3 months were available for 56 patients; median follow‐up time was 2.8 years. Twenty (36%) patients received successful antitachycardia pacing at a median 1.3 years postimplant. For those patients with IART after implant, antitachycardia pacing was successful in 57%. Patients with two‐ventricle repairs were more likely to have successful antitachycardia pacing than those with one‐ventricle palliation (45% vs. 17%, P = .04). Patients with documented IART had more successful antitachycardia pacing than those with no documented atrial tachycardia prior to implant (46% vs. 7%, P = .006). Early complications of antitachycardia pacemaker implant occurred in six patients (11%); late complications after implant occurred in three patients (5.6%). Of the initial 72 patients implanted, there were six deaths (8%).ConclusionsAntitachycardia pacing therapies were successful in the majority of CHD patients who had IART after implant. Patients without documented atrial tachycardia prior to implant were unlikely to require or receive successful therapy from antitachycardia pacemaker. Those patients postatrial switch procedure who had documented IART prior to implant had the highest incidence of successful antitachycardia pacing therapies. Antitachycardia pacemaker implantation is an adjunct to the management of IART in CHD patients, but may not benefit patients who have not yet demonstrated IART.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111221/1/chd12230.pd

Polyclonal architecture of the mammalian head

While much of modern developmental biology has focussed upon molecularly defined cell populations, relatively little is understood about how clonal groups within these broad cell populations organise complex tissues. In this thesis, I explore the clonal architecture of the jaws and teeth, and of the dermal bones of the calvaria, revealing cryptic modules as novel developmental features in both. I combine Confetti multicolour genetic lineage labelling with novel analytical techniques in order to map clonal populations in 3D and provide quantitative parameters for clonal expansions. Tooth identity within the mandible is thought to be encoded by the an initial proximodistal position within the branchial arch, which implies that cells do not undergo migration. I observe distal Hand2-Cre labelled cells in the proximal territory, which necessitates migration. These distal cells give rise to the mandible, alveolar bone and a small proportion of odontoblasts, while unlabelled proximal cells were found in the distal territory of the incisors in different proportions. The clonal composition of teeth and jaw bones is dissected by novel analysis of mixed cell populations. I find odontogenic and alveolar bone populations to share a common lineage, comprising a cryptic developmental unit distinct from the mandible, a feature that I can also verify in another transgenic for the upper jaw. I also find that the initial tooth composition radically changes in ontogenetic time. Starting from similar compositions of distal and proximal cells I find that in incisors the distal population expands while the proximal wanes, while in molars the opposite occurs. This is the first evidence for a temporally changing cell population structure underlying the well defined heterodonty between incisors and molars and allows a reinterpretation of early tooth specification events. The dermal bones of the calvaria are thought to grow in thickness by static osteoblasts depositing matrix appositionally and growth is supposed to occur exclusively at sutures. Whole calvaria single-cell clonal lineage analysis of cranial neural crest cells with Wnt1-Cre and Confetti labelling reveals an extensively dynamic program of invasive growth distributed throughout all parts of the dermal bone. Cryptic clonal modules grow laterally, with invasion through and into the bone primarily organised around the centres of these `patches'. The process of bone maturation is revealed to consist of a series of invasions between the three layers of the bone, with the innermost compacta layer driving initial thickness growth by invasion into the middle spongy layer, and the outermost (dermis-adjacent) compacta layer driving later growth. Conversely there is no evidence to suggest that the sutures are principal generative regions, as they do not share a common clonal lineage with adjacent bone. I also investigate muscle attachment regions and find that the same clones traverse tissue boundaries from bone into muscle connective tissues, thus a clonal model predicated on joint 'attachment point precursor cells' can now explain patterns of skeletomuscular connectivity previously found at the population level by my supervisor. A novel generative model of bone growth from cryptic clonal patch modules is proposed, allowing us for the first time to understand thickness growth and the evolutionary transition from a micromeric to a macromeric dermal bone condition, events first visible in crown gnathostomes (placoderms)

Implantable Cardioverter Defibrillator Outcomes in Pediatric and Congenital Heart Disease: Time to System Revision

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122425/1/pace12878.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/122425/2/pace12878_am.pd

Explicit solution for vibrating bar with viscous boundaries and internal damper

We investigate longitudinal vibrations of a bar subjected to viscous boundary conditions at each end, and an internal damper at an arbitrary point along the bar's length. The system is described by four independent parameters and exhibits a variety of behaviors including rigid motion, super stability/instability and zero damping. The solution is obtained by applying the Laplace transform to the equation of motion and computing the Green's function of the transformed problem. This leads to an unconventional eigenvalue-like problem with the spectral variable in the boundary conditions. The eigenmodes of the problem are necessarily complex-valued and are not orthogonal in the usual inner product. Nonetheless, in generic cases we obtain an explicit eigenmode expansion for the response of the bar to initial conditions and external force. For some special values of parameters the system of eigenmodes may become incomplete, or no non-trivial eigenmodes may exist at all. We thoroughly analyze physical and mathematical reasons for this behavior and explicitly identify the corresponding parameter values. In particular, when no eigenmodes exist, we obtain closed form solutions. Theoretical analysis is complemented by numerical simulations, and analytic solutions are compared to computations using finite elements.Comment: 29 pages, 6 figure