Answers

• 1.
  

  The 2017 ISHNE-HRS expert consensus statement on ambulatory ECG and external cardiac monitoring/telemetry is a useful resource when deliberating the various modalities for arrhythmia detection in unexplained syncope. There are several options, with varying advantages and disadvantages, and the choice should be tailored to the individual case.

  
  

  A 24- to 48-h Holter monitor is the traditional ambulatory electrocardiogram usually giving three leads of information using five electrodes. The yield in detecting arrhythmias for syncope is generally low (<10%–20%), but higher risk features such as prior heart disease, low ejection fraction, and older age seem to increase diagnostic yield with some studies suggesting male gender. However, the device is bulky and limits activities such as showering, bathing, and swimming, as well as proximity to large magnets or high-voltage areas. Additionally, in certain populations, such as in the described case, compliance related to “wearing” the device may be suboptimal. Newer models can extend to 30 days, allowing for longer periods of monitoring.

  
  

  Intermittent external loop recorders remain a staple for arrhythmia detection, and later models have automatic detection (rather than patient-triggered) for tachyarrhythmia and bradyarrhythmias, which would be necessary in patients with developmental delay or in those who are noncommunicative. These may be smaller than a standard Holter but are still bulkier than patch technology and should be worn continuously. Patch technology was devised to alleviate the size of a recording device to improve compliance and allow for water exposure. From iRhythm Technologies, the ZIO Patch is a single-use, water-resistant 14-day continuous rhythm monitor and has data in adult and pediatric patients with very good patient compliance and excellent quality of recordings. Mobile Cardiac Telemetry combines the benefits of Holter monitoring and loop recording and the Medtronic SEEQ remains a popular option, although temperature >80°F might be associated with discomfort and degraded performance. In certain populations, where existing external recorders are considered too cumbersome, the smaller patches may be a reasonable alternative.

  
  

  Finally, the implantable loop recorder is completely implanted and can be utilized for up to 3 years. It thus has the advantage of documenting events that are infrequent and difficult to capture, and once inserted, has minimal issues with patient compliance. Although more invasive, its longer duration of detection has been utilized to increase the diagnostic yield in atrial fibrillation. The insertable/injectable loop recorder (Medtronic LINQ) might offer a minimally invasive approach requiring less sedation and shorter hospital times, particularly when concerned about incision healing. High success with low complications has been demonstrated for advanced practice providers using this device.

  
  

  In this patient, we would consider starting with patch monitoring therapy (SEEQ or ZIO patch), and if index of suspicion remains high but no clear-cut indication for permanent pacing is detected, a LINQ injectable loop recorder would be considered. Given the patient’s noncommunicative state and issues with compliance, as well as the relative infrequency of events, an implantable, durable monitor with automatic detection may be considered ideal.

  
  
• 2.
  

  Catheter ablation has become a mainstay of treatment for arrhythmias of all types over the past several years. The ultimate goal of these procedures is elimination of the mechanism for arrhythmias, and this holds true for IART. Functionally, however, the primary role for catheter ablation in IART is for treating patient symptoms, controlling the arrhythmia with a less intense antiarrhythmic regimen, or desire for a drug-free lifestyle. For all adult congenital heart disease (ACHD) patients, procedural success for these ablations is estimated to be ∼75% with a 5-year recurrence rate between 30% and 50% (higher based on the complexity of the congenital heart disease).

  
  

  The tachy-brady syndrome is traditionally related to sinus node dysfunction, rather than progressive AV node dysfunction. In its most common descriptions, it is thought to result from progressive atrial fibrosis and apoptosis caused by atrial fibrillation. AV node dysfunction in congenital heart disease is more likely related to postoperative changes or intrinsic disease. Although rare, late development of postoperative AV block has been noted. In recent years, genetic contributions to progressive AV block in congenital heart disease have been recognized, and there are reported murine models in congenital heart disease that exhibit progressive AV node dysfunction. If the pathology is genetically predisposed or related to intrinsic disease or postoperative changes, it is unlikely that catheter ablation would alter the course toward advanced AV block requiring permanent pacing.

  
  

  In the described patient, the potential role of catheter ablation of the tachyarrhythmia should be considered and discussed. As is typically the case, the risks of an invasive procedure should be weighed against the patient’s quality of life, frequency of symptoms, and indication for anticoagulation. In hopes of staying off amiodarone, an antiarrhythmic with fewer side effects (e.g., sotalol, dronedarone, or dofetilide) might be offered. If tachycardia breaks through on antiarrhythmic therapy, or if the patient’s family prefers an attempt at more definitive therapy, catheter ablation should be offered. It is likely that the procedural success rate would be relatively high considering the biventricular physiology, although the potential for recurrence would have to be addressed. Given the high association of Trisomy 21 with obstructive sleep apnea, and the decreased success of catheter ablation for atrial arrhythmia in patients with untreated sleep apnea, polysomnography might be considered as well. In any case, extensive discussions with the family and caregivers should play a large role in the decision.

  
  
• 3.
  

  In this case, the patient would meet the ACC/AHA/HRS class I indication for permanent pacing consideration due to symptomatic bradycardia and complete heart block. The 2012 ACCF/AHA/HRS focused update on the guidelines highlights the role CRT might play in specific patient populations. In adults, when the left ventricular ejection fraction is <35% with NYHA II, III, or ambulatory IV symptoms and a left bundle branch block pattern with QRS duration >150 ms, there is significant likelihood of response with reduced hospitalizations and mortality. In children, given the heterogeneity of disease, the results can be more varied. With chronic epicardial ventricular pacing, a QRS duration wider than 150 ms would likely be expected as would an element of electromechanical dyssynchrony. Prophylactic multisite epicardial pacing has not, however, been the norm and there are no data to yet suggest a change in paradigm. Subsequent reoperation to place another lead would also be an invasive strategy with potential risk for morbidity given his prior difficulty with extubation and perioperative complications.

  
  

  In this patient, the etiology of depressed left ventricular systolic function is likely multifactorial from volume load of mitral regurgitation, dyssynchrony of epicardial pacing, and underlying nonischemic cardiomyopathy exacerbated by prior interventions or possibly associated with sleep apnea. If he is already optimized on medical therapy, the most aggressive option would be to redo the left AV valve repair or replacement with addition of a second epicardial lead for cardiac resynchronization. A less invasive approach that does not involve repairing the valve and could be considered would be catheter-based closure of intracardiac shunts and placement of a transvenous biventricular pacing system. Cardiac resynchronization has been shown to benefit dilated cardiomyopathy with functional mitral regurgitation at high risk for surgical operation with roughly half improving their mitral regurgitation (grade improvement > or =1) and better survival in improvers than nonimprovers. If the coronary sinus is not accessible for biventricular pacing, His bundle pacing has also been shown to be equivalent in outcomes with narrowing of the QRS duration. If intracardiac shunts are not addressed, a transvenous system would pose a 1%–2%/year risk of stroke and an upgrade of the epicardial system will be preferred.

  
  

  Again, with regard to CRT, the risks, benefits, and alternatives of an invasive procedure should be weighed against the patient’s desires and quality of life. The inability to reliably predict responders in the setting of congenital heart disease does have a tendency to make these discussions more difficult, although pacing-induced dyssynchrony is a subgroup that appears to be more likely to benefit. Thus, it should, at minimum, be brought up in discussions. If the intracardiac shunts can be easily closed, cardiac resynchronization may be useful for restoring ejection fraction and reducing the volume load of mitral regurgitation.