The following are key expert perspectives from the 2018 American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay, based on the Top Ten Take Home Messages selected by the Writing Committee:

1. Sinus node dysfunction (SND) is most often related to age-dependent progressive fibrosis of the sinus nodal tissue and surrounding atrial myocardium leading to abnormalities of sinus node and atrial impulse formation and propagation, and will therefore result in an array of different bradycardia or pause-related syndromes.
   
   Expert Perspective: By and large, the sole reason for considering any treatment for SND is the presence of symptoms. Asymptomatic sinus bradycardia has not been associated with adverse outcomes. On the other hand, patients with symptoms attributable to SND have a high risk of cardiovascular events including syncope, atrial fibrillation, and heart failure.
2. Both sleep disorders of breathing and nocturnal bradycardias are relatively common, and treatment of sleep apnea not only reduces the frequency of these arrhythmias, but also may offer cardiovascular benefits. The presence of nocturnal bradycardias should prompt consideration for screening for sleep apnea, starting with solicitation of suspicious symptoms, but is not in itself an indication for permanent pacing.
   
   Expert Perspective: Treating the underlying sleep apnea not only alleviates apnea-related symptoms and improves cardiovascular outcome, it also eliminates the need for pacemaker implantation in the vast majority of patients. In patients with sleep-related sinus bradycardia or transient sinus pauses occurring during sleep, permanent pacing should not be performed unless other indications for pacing are present.
3. The presence of left bundle branch block (LBBB) on electrocardiogram markedly increases the likelihood of underlying structural heart disease and of diagnosing left ventricular systolic dysfunction, and echocardiography is usually the most appropriate initial screening test for structural heart disease, including left ventricular systolic dysfunction.
   
   Expert Perspective: Excluding associated structural heart disease in all patients with LBBB is prudent, as the conduction disorder may not only be a harbinger of occult structural or ischemic heart disease, but also connotes an elevated risk should they be present, and may influence management in some forms of structural heart disease. Patients with LBBB may also present with heart failure that may be due to cardiac dyssynchrony or because of an underlying cardiomyopathy.
4. In SND, there is no established minimum heart rate or pause duration where permanent pacing is recommended; therefore, establishing temporal correlation between symptoms and bradycardia is important when deciding on the necessity of permanent pacing.
   
   Expert Perspective: External loop recorders and adhesive patch recorders provide a higher diagnostic yield than 24- or 48-hour Holter monitoring due to the longer period of monitoring. In populations with nonspecific symptoms felt to be potentially arrhythmic, one third of the population will manifest their presenting symptoms during continuous ambulatory monitoring without associated arrhythmia, a useful observation that often arrhythmia or conduction disorder is the source.
5. In patients with acquired second-degree Mobitz type II atrioventricular (AV) block, high-grade AV block, or third-degree AV block not due to reversible or physiologic causes, permanent pacing is recommended regardless of symptoms. For all other types of AV block, in the absence of conditions associated with progressive AV conduction abnormalities, permanent pacing should generally be considered only in the presence of symptoms that correlate with AV block.
   
   Expert Perspective: Bradycardia and conduction system disease in appropriate patient populations should lead to increased index of suspicion for sarcoidosis, amyloidosis, or hemochromatosis. Chagas disease should be considered in patients who have arrived from Trypanosoma cruzi endemic areas in Central and South America. Exercise testing can be helpful in distinguishing AV nodal versus conduction disturbances in the His Purkinje system below the AV node (infranodal) in the setting of 2:1 AV nodal conduction.
6. In patients with a left ventricular ejection fraction between 36% to 50% and AV block, who have an indication for permanent pacing and are expected to require ventricular pacing >40% of the time, techniques which provide more physiologic ventricular activation (cardiac resynchronization therapy or His bundle pacing) are reasonable in preference to right ventricular pacing to prevent heart failure.
   
   Expert Perspective: While some studies showed benefit of biventricular pacing with pacing burden of 40% or more, some studies suggest a benefit at pacing burden as low at 20%.
7. Since conduction system abnormalities are common after transcatheter aortic valve replacement (TAVR), recommendations on post-procedure surveillance and pacemaker implantation are made in this guideline.
   
   Expert Perspective: After TAVR, new right bundle branch block is associated with increased risk of permanent pacemaker implant and increased late all-cause mortality and cardiac mortality independent of whether a new permanent pacemaker was implanted. In patients with new persistent LBBB after TAVR, implantation of a permanent pacemaker may be considered, although it is unclear whether patients with new bundle branch block that persists when the patient is ready for discharge, will benefit from pacemaker implantation. Careful surveillance is reasonable, but it is not clear how and for how long it should be considered.
8. In patients with bradycardia and indications for pacemaker implantation, the importance of shared decision making and patient-centered care is endorsed and emphasized in this guideline in which treatment decisions are based not only on the best available evidence, but also on the patient’s goals of care and preferences. Patients should be referred to trusted material to aid in their understanding and awareness of the consequences and risks of any proposed action.
   
   Expert Perspective: A recommendation based both on the evidence as well as an understanding of the patients’ health goals, preferences, and values is essential to achieving true shared decision making.
9. Using the principles of shared decision making and informed consent/refusal, a patient with decision making capacity or his/her legally-defined surrogate has the right to refuse or request withdrawal of pacemaker therapy, even if the patient is pacemaker dependent, which should be considered palliative, end of life care, not physician-assisted suicide or euthanasia. However, any decision is complex, should involve all stakeholders, and will always be patient specific.
   
   Expert Perspective: While controversial among some, this recommendation is consistent with prior guidelines, in which patients who are pacemaker dependent have the right to request termination of pacing therapy.
10. Identifying patient populations that will benefit the most from emerging pacing technologies, such as His bundle pacing and transcatheter leadless pacing systems, will require further investigation as these modalities are incorporated into clinical practice.
    
    Expert Perspective: The relative merits of His bundle pacing, cardiac resynchronization, or other pacing strategies for maintaining or improving left ventricular function in patients with AV block are unknown.

Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Bradycardia, Bundle-Branch Block, Cardiac Electrophysiology, Cardiac Resynchronization Therapy, Cardiovascular Surgical Procedures, Decision Making, Diagnostic Imaging, Echocardiography, Electrocardiography, Electrocardiography, Ambulatory, Electrophysiologic Techniques, Cardiac, Exercise Test, Genetic Diseases, Inborn, Heart Failure, Heart Defects, Congenital, Heart Valve Diseases, Myocardial Infarction, Pacemaker, Artificial, Perioperative Period, Quality of Life, Secondary Prevention, Sick Sinus Syndrome, Sleep Apnea Syndromes, Subcutaneous Tissue, Syncope, Transcatheter Aortic Valve Replacement

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