Philip M. Chang

Wireless Smartphone ECG Enables Large-Scale Screening in Diverse Populations

The ubiquitous presence of internet‐connected phones and tablets presents a new opportunity for cost‐effective and efficient electrocardiogram (ECG) screening and on‐demand diagnosis. Wireless, single‐lead real‐time ECG monitoring supported by iOS and android devices can be obtained quickly and on‐demand. ECGs can be immediately downloaded and reviewed using any internet browser.

Amiodarone Versus Procainamide for the Acute Treatment of Recurrent Supraventricular Tachycardia in Pediatric Patients

Background—Intravenous amiodarone and procainamide are both used as therapies for refractory supraventricular tachycardia (SVT). However, no studies have compared the efficacy and safety of these agents in pediatric patients. Methods and Results—All patients treated with intravenous amiodarone or procainamide during 25 consecutive months for the following mechanisms of SVT were included: orthodromic reciprocating tachycardia, intra-atrial reentrant tachycardia, and ectopic atrial tachycardia; junctional ectopic tachycardia was excluded. Treatment response was categorized as full success, partial success, or failure. Partial success was defined as clinical improvement and/or arrhythmia control but not meeting full success criteria. Adverse events were classified as major (requiring resuscitation) or minor (management changes). There were 40 episodes of SVT in 37 patients (median age, 34 days; 24 with congenital heart disease). Amiodarone was the initial therapy in 26 cases and procainamide in 14 cases. If partial and full success are combined, procainamide was successful in 71% of cases compared with 34% for amiodarone (P=0.046). If partial success is considered a treatment failure, procainamide was successful in 50% compared with 15% for amiodarone (P=0.029). Ten patients received the second medication after the first failed. Success was achieved in 5 of 8 amiodarone-to-procainamide crossovers compared with 1 of 2 procainamide-to-amiodarone crossovers. One major and 10 minor adverse events occurred in amiodarone patients versus 6 minor adverse events in procainamide patients (P=NS). Conclusions—In this cohort, procainamide achieved greater success compared with amiodarone in the management of recurrent SVT without statistically significant differences in adverse event frequency.

Electrocardiographic patch devices and contemporary wireless cardiac monitoring

Cardiac electrophysiologic derangements often coexist with disorders of the circulatory system. Capturing and diagnosing arrhythmias and conduction system disease may lead to a change in diagnosis, clinical management and patient outcomes. Standard 12-lead electrocardiogram (ECG), Holter monitors and event recorders have served as useful diagnostic tools over the last few decades. However, their shortcomings are only recently being addressed by emerging technologies. With advances in device miniaturization and wireless technologies, and changing consumer expectations, wearable “on-body” ECG patch devices have evolved to meet contemporary needs. These devices are unobtrusive and easy to use, leading to increased device wear time and diagnostic yield. While becoming the standard for detecting arrhythmias and conduction system disorders in the outpatient setting where continuous ECG monitoring in the short to medium term (days to weeks) is indicated, these cardiac devices and related digital mobile health technologies are reshaping the clinician-patient interface with important implications for future healthcare delivery.

Subcutaneous Implantable Cardioverter-Defibrillator

For nearly 3 decades, the implantable cardioverter-defibrillator (ICD) has been available to patients who survived life-threatening rapid heart rhythms or are at risk of experiencing them. The ICD comprises a device generator coupled with a defibrillation lead. Traditional ICDs are implanted under the skin with the generator positioned beneath the collar bone. The defibrillation lead is inserted through the veins in the chest that course to the heart, permitting direct attachment to the inside of the heart, specifically the right ventricle. Figure (A) shows an x-ray of an ICD and leads. The subcutaneous ICD (SICD) is a novel defibrillator developed over the past decade that has become available to patients in the United States this year. The SICD provides an alternative option for patients whose physicians are recommending an ICD. Manufactured by Boston Scientific, Inc, a company that makes and sells ICDs, the SICD consists of an ICD generator and a defibrillation lead, similar to a traditional ICD. However, the defibrillation lead remains completely outside the chest cavity. Figure (B) shows an x-ray of the SICD. The SICD is implanted under the left breast, and the lead is placed under the skin along the left side of the breastbone. Early experience with the SICD has shown that it can terminate life-threatening rapid heart rhythms within seconds of their detection. Patients who are candidates for an ICD should understand the differences between a traditional ICD and the SICD. The greatest advantage of the SICD …

Unoperated Congenitally Corrected Transposition of the Great Arteries, Nonrestrictive Ventricular Septal Defect, and Pulmonary Stenosis in Middle Adulthood Do Multiple Wrongs Make a Right?

Submitted May 6, 2011; Accepted August 3, 2011. The survival into adulthood of patients with unoperated complex congenital heart disease with anomalies often considered life threatening in infancy and childhood requires a complex interplay of “balanced” defects allowing for cardiovascular physiology compatible with long-term survival. We report on a series of three cases from our advanced imaging database of middle-aged adults presenting with multiple similar defects providing a hemodynamically balanced circulation. The constellation of defects seen in each of these patients included congenitally corrected transposition of the great arteries, a large nonrestrictive ventricular septal defect, valvular pulmonary stenosis, and in two cases anomalous coronary arteries. Cardiovascular computed tomographic angiography (CCTA) and cardiovascular magnetic resonance imaging (CMR) were important to the characterization of the multiple defects and their three-dimensional relationships in these cases. Treatment decisions in patients with this constellation of findings are challenging, given the limited data due to the rarity of survival of patients with these defects into middle adulthood and the paucity of data related to decisions and approaches to medical management, surgical correction, or transplantation.

Predictors of Elevated Defibrillation Threshold with the Subcutaneous Implantable Cardioverter-defibrillator

There are limited data regarding defibrillation thresholds (DFTs) for the subcutaneous implantable cardioverter-defibrillator (S-ICD), and factors associated with elevated DFTs remain incompletely understood. The objective of this study was to determine the factors associated with elevated DFTs in patients undergoing S-ICD implantation. A retrospective cross-sectional analysis of all patients undergoing S-ICD implantation at our institution between 2013 and 2016 who underwent step-down DFT testing was performed. Factors associated with a higher DFT were analyzed. In total, 56 patients (mean age: 49.3 ± 13.1 years, mean left ventricular ejection rate: 31.1% ± 13.7%) underwent S-ICD implantation in the study period. Full DFT testing was performed in 31 of the 56 patients (55%), with an average DFT of 46.4 joules (J) ± 25.9 J found among this cohort. The DFT was > 65 J in five of the 31 patients (16%). A high DFT was associated with increased body mass index (BMI) (37.7 kg/m2 versus 29.4 kg/m2; p = 0.02) and either increased septal or posterior wall thickness (1.5 cm versus 1.0 cm; p = 0.0003 and 1.4 cm versus 1.1 cm; p= 0.003, respectively). Patients with high DFTs also had higher failed shock impedance values (138 Ω versus 71 Ω; p = 0.005). Renal failure did not appear to affect DFT (51.4 J versus 51.7 J; p = 0.99). BMI, body surface area (BSA), and septal and posterior left ventricular wall thickness predicted elevated DFT on univariate analysis, although findings were not significant with multivariate analysis due to the small sample size. Thus, elevated S-ICD DFT appears to be associated with increased BMI, BSA, and septal or posterior wall thickness. In contrast, dialysis-dependent renal failure is not associated with elevated DFT. Further investigation is necessary in order to better characterize and predict which patients are at-risk for high DFTs.

Bradyarrhythmias in Congenital Heart Disease

Bradyarrhythmias in adults with congenital heart disease (CHD) comprise a complex group of arrhythmia disorders with congenital and acquired origins, highly variable long-term sequelae, and complicated treatment options. They can develop across the spectrum of CHD defects and can be encountered at all ages. Although permanent pacing is effective in treating bradyarrhythmias, it is associated with many complications and morbidity, where it is often used early in life. This section discusses the incidence and prevalence of bradyarrhythmias in the CHD population, their timing of occurrence with respect to specific disease entities and interventions, and their short- and long-term clinical sequelae.

Implantation of a leadless cardiac pacemaker for recurrent pocket infections

Infections involving cardiovascular implantable electronic devices (CIEDs) remain an unfortunate indication for repeated device-related procedures, including extractions and reimplantations. Recurrent infections involving transvenous leads and superficial device pockets may eventually lead to epicardial lead implantation and generator placement in deeper tissue planes, both of which require a more invasive surgical approach. We present a unique case of a patient with recurrent CIED-related pocket infections involving both transvenous and epicardial pacing systems that was ultimately addressed with implantation of an investigational leadless cardiac pacemaker.

Cardiovascular Magnetic Resonance of the Ross II Procedure: Long-Term Postoperative Imaging

The Ross II procedure involves replacement of the mitral valve with a pulmonary artery autograft and placement of a bioprosthetic valve in the pulmonary position. Although the first eight cases were performed by Dr Donald N. Ross in 1967, more were not performed until 1997 due to the interim advent of other mechanical and xenograft options. From 1997 to 2004, a total of 103 Ross II procedures have been reported. We present cardiovascular magnetic resonance images demonstrating a satisfactory long-term result 11 years after Ross II operation. A 30-year-old patient with a history of rheumatic heart disease who underwent a Ross II procedure at age 19 presented for evaluation of the status of her surgical procedure. Cardiovascular magnetic resonance imaging demonstrated no evidence of stenosis or regurgitation of the autograft in the mitral position (Figures 1-3) and mild regurgitation of the bioprosthetic pulmonary valve. The complex anatomy and pathophysiology of the mitral valve has led to multiple approaches to valve repair or replacement. In the Ross II procedure, the native pulmonary valve is mounted in a Dacron graft and placed in the mitral position. In young patients with mitral valve disease not amenable to valve repair, the challenges of lifelong anticoagulation and limited longevity of bioprosthetic valves have led to occasional and selective consideration of this procedure. In congenital heart disease, it is important to understand the unique anatomy and physiology of rarely performed surgeries such as the Ross II procedure.

Isolated Double Chambered Right Ventricle in an Adult Imaged With Magnetic Resonance.

A 45-year-old male presented with congestive heart failure to an outside hospital where transthoracic echocardiography (TTE) reportedly revealed a ventricular septal defect (VSD), severe tricuspid regurgitation (TR), and pulmonary artery hypertension. Following transfer to our center, physical examination showed jugular venous distension, hepatomegaly, peripheral edema, and a loud (4 of 6), harsh systolic ejection murmur with palpable thrill at the left midsternal border. On TTE, severe right heart enlargement with TR and midcavitary obstruction within the right ventricle (RV) were seen (Figure 1). No VSD was identified. Cardiac catheterization revealed severe RV intracavitary obstruction (peak and mean gradients 110 and 60 mm Hg). Coronary angiography demonstrated no obstructive disease. Cardiac magnetic resonance imaging confirmed severe RV dilation (end-diastolic volume 231 mL) and hypertrophy with reduced ejection fraction of 40%. An anomalous muscle bundle extending from the interventricular septum to the RV free wall confirmed the diagnosis of double chambered right ventricle (DCRV; Figure 2). Surgical intervention involved anomalous muscle bundle resection, patch repair of the free wall, tricuspid valve repair, and atrial reduction (Figure 3). A VSD was not identified during intraoperative transesophageal echocardiogram or direct visual inspection. In DCRV, anomalous muscle bundles divide the RV into proximal high-pressure and distal low-pressure chambers. A rare form of congenital heart disease and typically associated with other lesions, most frequently VSD, isolated DCRV is extremely rare in adults and can present with heart failure, syncope, and chest pain. Right ventricular dysfunction, as seen in this case, may develop from long-standing and excessive pressure overload. Findings in DCRV may be confused with those associated with pulmonary arterial hypertension (PAH) in the absence of structural heart disease (Table 1). Echocardiography remains the mainstay for diagnosis but may be limited in adults. Though more invasive, cardiac catheterization provides direct hemodynamic information. 1 Departments of Internal Medicine and Pediatrics, Los Angeles County, University of Southern California Medical Center, Keck School of Medicine of USC, Los Angeles, CA, USA 2 Division of Cardiovascular Medicine, Los Angeles County, University of Southern California Medical Center, Keck School of Medicine of USC, Los Angeles, CA, USA