Extended Reality in Medical Practice.

PURPOSE OF REVIEW: Advances in display technology and computing have led to new devices capable of overlaying digital information onto the physical world or incorporating aspects of the physical world into virtual scenes. These combinations of digital and physical environments are referred to as extended realities. Extended reality (XR) devices offer many advantages for medical applications including realistic 3D visualization and touch-free interfaces that can be used in sterile environments. This review introduces extended reality and describes how it can be applied to medical practice. RECENT FINDINGS: The 3D displays of extended reality devices are valuable in situations where spatial information such as patient anatomy and medical instrument position is important. Applications that take advantage of these 3D capabilities include teaching and pre-operative planning. The utility of extended reality during interventional procedures has been demonstrated with through 3D visualizations of patient anatomy, scar visualization, and real-time catheter tracking with touch-free software control. Extended reality devices have been applied to education, pre-procedural planning, and cardiac interventions. These devices excel in settings where traditional devices are difficult to use, such as in the cardiac catheterization lab. New applications of extended reality in cardiology will continue to emerge as the technology improves.

Emerging Applications of Virtual Reality in Cardiovascular Medicine.

Recently, rapid development in the mobile computing arena has allowed extended reality technologies to achieve performance levels that remove longstanding barriers to medical adoption. Importantly, head-mounted displays have become untethered and are light enough to be worn for extended periods of time, see-through displays allow the user to remain in his or her environment while interacting with digital content, and processing power has allowed displays to keep up with human perception to prevent motion sickness. Across cardiology, many groups are taking advantage of these advances for education, pre-procedural planning, intraprocedural visualization, and patient rehabilitation. Here, we detail these applications and the advances that have made them possible.

A Clinical Risk Score to Improve the Diagnosis of Tachycardia-Induced Cardiomyopathy in Childhood.

Tachycardia-induced cardiomyopathy (TIC) is a treatable cause of heart failure in children, but there is little information as to which clinical variables best discriminate TIC from other forms of cardiomyopathy. TIC cases with dilated cardiomyopathy (DC) from 16 participating centers were identified and compared with controls with other forms of DC. Presenting clinical, echocardiographic, and electrocardiographic characteristics were collected. Heart rate (HR) percentile was defined as HR/median HR for age, and PR index as the PR/RR interval. P-wave morphology (PWM) was defined as possible sinus or nonsinus based on a predefined algorithm. Eighty TIC cases and 135 controls were identified. Cases demonstrated lower LV end-diastolic diameter and LV end-systolic diameter than DC controls (4.3 vs 6.5, p <0.001; 7.4 vs 10.9, p <0.001) and were less likely to receive inotropic medication at presentation (p <0.001 for both). Multivariable logistic regression identified HR percentile (OR 2.1 per 10% increase, CI 1.3 to 4.6; p = 0.014), PR index (OR 1.2, CI 1.1 to 1.4; p = 0.004), and nonsinus PWM (OR 104.9, CI 15.2 to 1,659.8; p <0.001) as predictive of TIC status. A risk score using HR percentile >130%, PR index >30%, and nonsinus PWM was associated with a sensitivity of 100% and specificity of 87% for the diagnosis of TIC. Model training and validation area under the curves were similar at 0.97 and 0.94, respectively. In conclusion, pediatric TIC may be accurately discriminated from other forms of DC using simple electrocardiographic parameters. This may allow for rapid diagnosis and early treatment of this condition.

Use of smartphone technology in cardiology.

Smartphone-based technologies along with broadband connectivity are changing the way modern cardiology is practiced. The ever broadening connectivity and increasing capabilities of smartphone-based technologies can better monitor, diagnose, and prevent cardiovascular diseases. Researchers can leverage the ubiquitous use of smartphone-based technologies and their constant stream of biometric data to establish large community-based clinical research studies. Patient engagement is enhanced with constant and on-demand access to physicians, daily self-monitoring, and expanding social networks. On the other hand, the exponential growth of smartphone-based technologies invariably disrupts the traditional healthcare model and leaves a vacuum in the infrastructure, medico-legal apparatus, and reimbursement systems that need to be addressed. In this review, we present a comprehensive discussion of the various applications utilizing smartphone-based technologies in cardiology.

SPEAR Trial: Smartphone Pediatric ElectrocARdiogram Trial.

OBJECTIVES: Smartphone-enabled ECG devices have the potential to improve patient care by enabling remote ECG assessment of patients with potential and diagnosed arrhythmias. This prospective study aimed to assess the usefulness of pediatric ECG tracings generated by the AliveCor device (Oklahoma City, OK) and to assess user satisfaction. STUDY DESIGN: Enrolled pediatric patients with documented paroxysmal arrhythmia used the AliveCor device over a yearlong study period. Pediatric electrophysiologists reviewed all transmitted ECG tracings. Patient completed surveys were analyzed to assess user satisfaction. RESULTS: 35 patients were enrolled with the following diagnoses: supraventricular tachycardia (SVT, 57%), atrial fibrillation (AF, 11%), ectopic atrial tachycardia (EAT, 6%), atrial tachycardia (AT, 3%), and ventricular tachycardia (VT, 23%). A total of 238 tracings were received from 20 patients, 96% of which were of diagnostic quality for sinus rhythm, sinus tachycardia, SVT, and AF. 126 patient satisfaction surveys (64% from parents) were completed. 98% of the survey responses indicated that it was easy to obtain tracings, 93% found it easy to transmit the tracings, 98% showed added comfort in managing arrhythmia by having the device, and 93% showed interest in continued use of the device after the study period ended. CONCLUSIONS: Smartphone-enabled ECG devices can generate tracings of diagnostic quality in children. User satisfaction was extremely positive. Use of the device to manage certain patients with AF and SVT showcases the future role of remote ECGs in the successful outpatient management of arrhythmias in children by potentially reducing Emergency Department visits and healthcare costs.

Pediatric electrocardiographic imaging applications.

Noninvasive electrocardiographic imaging (ECGI) has been used in pediatric and congenital heart patients to better understand their electrophysiologic substrates. In this article we focus on the 4 subjects related to pediatric ECGI: (1) ECGI in patients with congenital heart disease and Wolff­Parkinson­White syndrome, (2) ECGI in patients with hypertrophic cardiomyopathy and preexcitation, (3) ECGI in pediatric patients with Wolff­Parkinson­White syndrome, and (4) ECGI for pediatric cardiac resynchronization therapy.

Electrophysiologic substrate in congenital Long QT syndrome: noninvasive mapping with electrocardiographic imaging (ECGI).

BACKGROUND: Congenital Long QT syndrome (LQTS) is an arrhythmogenic disorder that causes syncope and sudden death. Although its genetic basis has become well-understood, the mechanisms whereby mutations translate to arrhythmia susceptibility in the in situ human heart have not been fully defined. We used noninvasive ECG imaging to map the cardiac electrophysiological substrate and examine whether LQTS patients display regional heterogeneities in repolarization, a substrate that promotes arrhythmogenesis. METHODS AND RESULTS: Twenty-five subjects (9 LQT1, 9 LQT2, 5 LQT3, and 2 LQT5) with genotype and phenotype positive LQTS underwent ECG imaging. Seven normal subjects provided control. Epicardial maps of activation, recovery times, activation-recovery intervals, and repolarization dispersion were constructed. Activation was normal in all patients. However, recovery times and activation-recovery intervals were prolonged relative to control, indicating delayed repolarization and abnormally long action potential duration (312±30 ms versus 235±21 ms in control). Activation-recovery interval prolongation was spatially heterogeneous, with repolarization gradients much steeper than control (119±19 ms/cm versus 2.0±2.0 ms/cm). There was variability in steepness and distribution of repolarization gradients between and within LQTS types. Repolarization gradients were steeper in symptomatic patients (130±27 ms/cm in 12 symptomatic patients versus 98±19 ms/cm in 13 asymptomatic patients; P<0.05). CONCLUSIONS: LQTS patients display regions with steep repolarization dispersion caused by localized action potential duration prolongation. This defines a substrate for reentrant arrhythmias, not detectable by surface ECG. Steeper dispersion in symptomatic patients suggests a possible role for ECG imaging in risk stratification.

Management of pediatric tachyarrhythmias on mechanical support.

BACKGROUND: Pediatric patients with persistent arrhythmias may require mechanical cardiopulmonary support. We sought to classify the population, spectrum, and success of current treatment strategies. METHODS AND RESULTS: A multicenter retrospective chart review was undertaken at 11 sites. Inclusion criteria were (1) patients <21 years, (2) initiation of mechanical support for a primary diagnosis of arrhythmias, and (3) actively treated on mechanical support. A total of 39 patients were identified with a median age of 5.5 months and median weight of 6 kg. A total of 69% of patients were cannulated for supraventricular tachycardia with a median rate of 230 beats per minute. A total of 90% of patients were supported with extracorporeal membrane oxygenation for an average of 5 days. The remaining 10% were supported with ventricular assist devices for an average of 38 (20-60) days. A total of 95% of patients were treated with antiarrhythmics, with 43% requiring >1 antiarrhythmic. Amiodarone was the most frequently used medication alone or in combination. A total of 33% patients underwent electrophysiology study/transcatheter ablation. Radiofrequency ablation was successful in 9 patients on full flow extracorporeal membrane oxygenation with 3 radiofrequency-failures/conversion to cryoablation. One patient underwent primary cryoablation. A total of 15% of complications were related to electrophysiology study/ablation. At follow-up, 23 patients were alive, 8 expired, and 8 transplanted. CONCLUSIONS: Younger patients were more likely to require support in the presented population. Most patients were treated with antiarrhythmics and one third required electrophysiology study/ablation. Radiofrequency ablation is feasible without altering extracorporeal membrane oxygenation flows. There was a low frequency of acute adverse events in patients undergoing electrophysiology study/ablation, while on extracorporeal membrane oxygenation.

Predictors of myocardial recovery in pediatric tachycardia-induced cardiomyopathy.

BACKGROUND: Tachycardia-induced cardiomyopathy (TIC) carries significant risk of morbidity and mortality, although full recovery is possible. Little is known about the myocardial recovery pattern. OBJECTIVE: The purpose of this study was to determine the time course and predictors of myocardial recovery in pediatric TIC. METHODS: An international multicenter study of pediatric TIC was conducted. Children ≤18 years with incessant tachyarrhythmia, cardiac dysfunction (left ventricular ejection fraction [LVEF] <50%), and left ventricular (LV) dilation (left ventricular end-diastolic dimension [LVEDD] z-score ≥2) were included. Children with congenital heart disease or suspected primary cardiomyopathy were excluded. Primary end-points were time to LV systolic functional recovery (LVEF ≥55%) and normal LV size (LVEDD z-score <2). RESULTS: Eighty-one children from 17 centers met inclusion criteria: median age 4.0 years (range 0.0-17.5 years) and baseline LVEF 28% (interquartile range 19-39). The most common arrhythmias were ectopic atrial tachycardia (59%), permanent junctional reciprocating tachycardia (23%), and ventricular tachycardia (7%). Thirteen required extracorporeal membrane oxygenation (n = 11) or ventricular assist device (n = 2) support. Median time to recovery was 51 days for LVEF and 71 days for LVEDD. Two (4%) underwent heart transplantation, and 1 died (1%). Multivariate predictors of LV systolic functional recovery were age (hazard ratio [HR] 0.61, P = .040), standardized tachycardia rate (HR 1.16, P = .015), mechanical circulatory support (HR 2.61, P = .044), and LVEF (HR 1.33 per 10% increase, p=0.005). For normalization of LV size, only baseline LVEDD (HR 0.86, P = .008) was predictive. CONCLUSION: Pediatric TIC resolves in a predictable fashion. Factors associated with faster recovery include younger age, higher presenting heart rate, use of mechanical circulatory support, and higher LVEF, whereas only smaller baseline LV size predicts reverse remodeling. This knowledge may be useful for clinical evaluation and follow-up of affected children.

Assessment of intrathoracic impedance algorithm in the pediatric and adult congenital population.

BACKGROUND: Decreased intrathoracic impedance has been used in adults to predict heart failure (HF) exacerbations. A commercial algorithm, OptiVol® (Medtronic Inc., Minneapolis, MN, USA), identifies patients with decreased impedance. We sought to determine the specificity, sensitivity, and positive predictive value (PPV) of OptiVol for predicting HF exacerbation or increased arrhythmia burden in pediatric and adult congenital heart disease (CHD) patients. METHODS: A multicenter retrospective chart review was undertaken. Inclusion criteria were: (1) <19 years or CHD adults, (2) an implanted device with OptiVol capability, (3) implanted between April 9 and September 6, and (4) follow-up of >30 days postimplant. Clinical events were defined as clinical HF exacerbation/hospital admission, initiation/uptitration of medication, or increased arrhythmia burden. RESULTS: Seventy-two patients (19 ± 9 years) were identified with the following indications: 20% dilated cardiomyopathy (DCM), 11% hypertrophic cardiomyopathy (HCM), 43% CHD, 15% channelopathy, and 11% other. Thirty-nine had 122 OptiVol crossings (median 2, range 1-11); 30% were linked to a cause. The remaining 33 had no crossing, though 17 had 89 clinical events. The clinical event rate was 19% greater in patients with crossings, though not statistically significant (P = 0.4). The algorithm had a 59% sensitivity, 52% specificity, and 62% PPV. Clinical HF exacerbation and arrhythmia burden did not significantly correlate with decreased impedance though uptitration or initiation of HF medication did correlate significantly (P = 0.03). CONCLUSION: The algorithm sensitivity for pediatric DCM, HCM, CHD, and adult CHD was equivalent to the general adult population. Further studies are warranted to assess whether inaccuracy in prediction is secondary to the algorithm or to differences in the clinical response of pediatric/CHD patients.

Duplication of 20p12.3 associated with familial Wolff-Parkinson-White syndrome.

Wolff-Parkinson-White (WPW) syndrome is caused by preexcitation of the ventricular myocardium via an accessory pathway which increases the risk for paroxysmal supraventricular tachycardia. The condition is often sporadic and of unknown etiology in the majority of cases. Autosomal dominant inheritance and association with congenital heart defects or ventricular hypertrophy were described. Microdeletions of 20p12.3 have been associated with WPW syndrome with either cognitive dysfunction or Alagille syndrome. Here, we describe the association of 20p12.3 duplication with WPW syndrome in a patient who presented with non-immune hydrops. Her paternal uncle carries the duplication and has attention-deficit hyperactivity disorder and electrocardiographic findings consistent with WPW. The 769 kb duplication was detected by the Affymetrix Whole Genome-Human SNP Array 6.0 and encompasses two genes and the first two exons of a third gene. We discuss the potential role of the genes in the duplicated region in the pathogenesis of WPW and possible neurobehavioral abnormalities. Our data provide additional support for a significant role of 20p12.3 chromosomal rearrangements in the etiology of WPW syndrome.

Updates on the inherited cardiac ion channelopathies: from cell to clinical.

OPINION STATEMENT: The inherited channelopathies are a rare, heterogeneous group of diseases with widely variable clinical presentations and courses. Systematic clinical and experimental work has led to identification of disease-causing genetic mutations and their biophysical manifestation. The process by which the knowledge base is developed, from genetic mutation, to cardiac myocyte, to whole heart, and finally to clinical presentation, has dramatically expanded our understanding of these diseases. Most importantly, we can now begin to comprehend how small changes at the genetic level can dramatically influence a patient's clinical course.

Unusually high association of hypertrophic cardiomyopathy and complex heart defects in children with fasciculoventricular pathways.

INTRODUCTION: Fasciculoventricular pathways (FVPs) are rare causes of preexcitation that do not mediate tachycardias. We report a two-center experience of pediatric patients with FVP and an unexpectedly high association of complex congenital heart defects (CHDs), chromosomal anomalies, and hypertrophic cardiomyopathy. METHODS: A retrospective review of the electrophysiology database at two institutions was performed to identify patients with FVP from January 2000 to January 2011. Medical records of these patients were reviewed for clinical history and course, presence of comorbidities, and details of intracardiac electrophysiology (EP) study. RESULTS: A total of 17 patients were identified. The primary indication for EP study was a preexcitation pattern on electrocardiogram. The majority of patients, 12/17 (71%), were found to have associated cardiac and genetic anomalies. Hypertrophic cardiomyopathy was found in 5/17 (29%) patients, with genetic testing in two patients demonstrating the lysosomal-associated membrane protein 2 mutation (Danon syndrome). Underlying complex CHDs were present in 3/17 (18%) patients. One patient (6%) was status post (s/p) cardiac transplant, one patient had hypertension, and another had Trisomy 21. Other electrophysiologic substrates mediating tachycardia were found in 3/17 (18%) patients. Only 5/17 patients (29%) were otherwise healthy with structurally normal hearts. CONCLUSIONS: In this largest reported series of FVP in children, there is an unusually high association of FVP with complex CHDs, chromosomal anomalies, and hypertrophic cardiomyopathy. Any patient with such disorders and manifest preexcitation should be evaluated with a high index of suspicion for a FVP.

Electrophysiologic substrate and intraventricular left ventricular dyssynchrony in nonischemic heart failure patients undergoing cardiac resynchronization therapy.

BACKGROUND: Electrocardiographic imaging (ECGI) is a method for noninvasive epicardial electrophysiologic mapping. ECGI previously has been used to characterize the electrophysiologic substrate and electrical synchrony in a very heterogeneous group of patients with varying degrees of coronary disease and ischemic cardiomyopathy. OBJECTIVE: The purpose of this study was to characterize the left ventricular electrophysiologic substrate and electrical dyssynchrony using ECGI in a homogeneous group of nonischemic cardiomyopathy patients who were previously implanted with a cardiac resynchronization therapy (CRT) device. METHODS: ECGI was performed during different rhythms in 25 patients by programming their devices to biventricular pacing, single-chamber (left ventricular or right ventricular) pacing, and native rhythm. The electrical dyssynchrony index (ED) was computed as the standard deviation of activation times at 500 sites on the LV epicardium. RESULTS: In all patients, native rhythm activation was characterized by lines of conduction block in a region with steep activation-recovery interval (ARI) gradients between the epicardial aspect of the septum and LV lateral wall. A native QRS duration (QRSd) >130 ms was associated with high ED (≥30 ms), whereas QRSd <130 ms was associated with minimal (25 ms) to large (40 ms) ED. CRT responders had very high dyssynchrony (ED = 35.5 ± 3.9 ms) in native rhythm, which was significantly lowered (ED = 23.2 ± 4.4 ms) during CRT. All four nonresponders in the study did not show significant difference in ED between native and CRT rhythms. CONCLUSION: The electrophysiologic substrate in nonischemic cardiomyopathy is consistent among all patients, with steep ARI gradients co-localizing with conduction block lines between the epicardial aspect of the septum and the LV lateral wall. QRSd wider than 130 ms is indicative of substantial LV electrical dyssynchrony; however, among patients with QRSd <130 ms, LV dyssynchrony may vary widely.

Outcomes of heart transplantation using donor hearts from infants with sudden infant death syndrome.

BACKGROUND: Uncertainty exists whether hearts from infants who have died of sudden infant death syndrome (SIDS) are acceptable for transplantation because the mechanism of death in SIDS remains unclear. We analyzed post-transplant outcomes in infants who received a heart from a donor where SIDS was the primary cause of brain death. METHODS: This retrospective multicenter cohort study used data from the Organ Procurement and Transplant Network (OPTN). All infants aged < 12 months undergoing heart transplant between 1994 and 2008 were included. A Cox proportional hazards model was used to determine whether donor SIDS was independently associated with post-transplant graft loss (death or retransplant). RESULTS: During the study period, 66 of 1033 infants (6.4%) who underwent heart transplant received an allograft from a SIDS donor. These infants were similar to the remaining infants with respect to age, diagnosis, blood type, and invasive support. In multivariable analysis, graft loss was associated with congenital heart disease (hazard ratio [HR], 1.6; 95% confidence interval [CI], 1.2-2.1), ventilator (HR, 1.4; 95% CI, 1.1-1.9), and extracorporeal membrane oxygenation support (HR, 3.0; 95% CI, 2.2-4.3), but not donor SIDS (HR, 1.0; 95% CI, 0.6-1.5), suggesting graft survival in SIDS-donor heart recipients was similar to the remaining infants. Primary causes of post-transplant death in infants receiving SIDS-donor hearts and the remaining infants were similar. CONCLUSIONS: Graft survival was similar in infants who received SIDS-donor hearts compared with those who received hearts from donors who died of other causes. There was no increase in incidence of non-rejection-related cardiac deaths after transplant in these children.

Use of a wearable automated defibrillator in children compared to young adults.

BACKGROUND: A wearable automated external defibrillator has been shown to be efficacious in the prevention of sudden death in adults who had a history of cardiac arrest but who did not have a permanent internal cardioverter/defibrillator (ICD) placed. The use of a wearable defibrillator has not been established in the pediatric population. METHODS: We retrospectively reviewed the clinical database for the wearable external defibrillator from ZOLL Lifecor Corporation (Pittsburgh, PA, USA). We compared the use of the wearable defibrillator in patients ≤18 years of age to those aged 19-21 years. RESULTS: There were 81 patients ≤18 years of age (median age = 16.5 years [9-18] and 52% male). There were 103 patients aged 19-21 years (median age = 20 years [19-21] and 47% male). There was no difference between groups in average hours/day or in total number of days the patients wore the defibrillator. In patients ≤18 years of age, there was one inappropriate therapy and one withholding of therapy due to a device-device interaction. In patients aged 19-21 years, there were five appropriate discharges in two patients and one inappropriate discharge in a single patient. CONCLUSION: It is reasonable to consider the wearable automated external defibrillator as a therapy for pediatric patients who are at high risk of sudden cardiac arrest but who have contraindications to or would like to defer placement of a permanent ICD. As there were no appropriate shocks in our patients ≤18 years of age, this study cannot address efficacy of the therapy.

Cryoablation with an 8-mm tip catheter for pediatric atrioventricular nodal reentrant tachycardia is safe and efficacious with a low incidence of recurrence.

BACKGROUND: Cryoablation with 4- and 6-mm tip ablation catheters has been demonstrated to be safe and effective in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) in pediatric patients, albeit with a higher rate of clinical recurrence. Limited information is available regarding efficacy, mid-term outcomes, and complications related to the use of the 8-mm Freezor Max Cryoablation catheter (Medtronic, Minneapolis, MN, USA) in pediatric patients. METHODS: We performed a retrospective review of all pediatric patients with normal cardiac anatomy who underwent an ablation procedure for treatment of AVNRT using the 8-mm tip Cryoablation catheter at three large pediatric academic arrhythmia centers. RESULTS: Cryoablation with an 8-mm tip catheter was performed in 77 patients for treatment of AVNRT (female n = 40 [52%], age 14.8 +/- 2.2 years, weight 62.0 +/- 13.9 kg). Initial procedural success was achieved in 69 patients (69/76, 91%). Transient second- or third-degree atrioventricular (AV) block was noted in five patients (6.5%). There was no permanent AV block. Of the patients successfully ablated with Cryotherapy, there were two recurrences (2/70, 2.8%) over a follow-up of 11.6 +/- 3.3 months. CONCLUSION: Cryoablation with an 8-mm tip ablation catheter is both safe and effective with a low risk of recurrence for the treatment of AVNRT in pediatric patients.

Current management of pediatric dilated cardiomyopathy.

PURPOSE OF REVIEW: American and European guidelines for treatment of adult heart failure have been recently revised. This review will reconcile those guidelines to recent studies and experience in the treatment of pediatric dilated cardiomyopathy. RECENT FINDINGS: Therapy for pediatric dilated cardiomyopathy includes establishing a diagnosis for diagnostic-specific therapies as well as preventive strategies for anthracycline toxicity and muscular dystrophy. Pediatric studies demonstrate safety and efficacy for use of angiotensin-converting enzyme inhibition and beta-blockers in dilated cardiomyopathy. Cardiac resynchronization and mitral annuloplasty represent potential nonpharmacologic therapies. Implantable defibrillator therapy may be of less import in children as compared with adults. Ventricular assist devices (VADs) are now available for all ages, which can improve survival and potentially can lead to recovery. SUMMARY: The robust development of new therapies for adult heart failure has been successfully applied to children with dilated cardiomyopathy. Therapies for severe, intractable heart failure have been more widely utilized than therapies for mild-to-moderate heart failure.