<s> [INST] <<SYS>> You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, say that you don't know. Please don't share false information. <</SYS>>What are the TOP 10 TAKE-HOME MESSAGES FOR THE
MANAGEMENT OF BRADYCARDIA AND
CARDIAC CONDUCTION DELAY? [/INST] 
1. Sinus node dysfunction is most often related to agedependent 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
various bradycardic or pause-related syndromes.
JACC VOL. 74, NO. 7, 2019 Kusumoto et al.
AUGUST 20, 2019:e51 – 156 2018 Bradycardia Guideline
e53
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,
beginning with solicitation of suspicious symptoms.
However, nocturnal bradycardia is not in itself an
indication for permanent pacing.
3. The presence of left bundle branch block on electrocardiogram markedly increases the likelihood of underlying structural heart disease and of diagnosing
left ventricular systolic dysfunction. Echocardiography is usually the most appropriate initial screening
test for structural heart disease, including left ventricular systolic dysfunction.
4. In sinus node dysfunction, there is no established
minimum heart rate or pause duration where permanent pacing is recommended. Establishing temporal
correlation between symptoms and bradycardia is
important when determining whether permanent
pacing is needed.
5. In patients with acquired second-degree Mobitz type
II atrioventricular block, high-grade atrioventricular
block, or third-degree atrioventricular block not
caused by reversible or physiologic causes, permanent
pacing is recommended regardless of symptoms. For
all other types of atrioventricular block, in the
absence of conditions associated with progressive
atrioventricular conduction abnormalities, permanent
pacing should generally be considered only in the
presence of symptoms that correlate with atrioventricular block.
6. In patients with a left ventricular ejection fraction
between 36% to 50% and atrioventricular block, who
have an indication for permanent pacing and are expected to require ventricular pacing >40% of the time,
techniques that provide more physiologic ventricular
activation (e.g., cardiac resynchronization therapy,
His bundle pacing) are preferred to right ventricular
pacing to prevent heart failure.
7. Because conduction system abnormalities are common after transcatheter aortic valve replacement,
recommendations on postprocedure surveillance and
pacemaker implantation are made in this guideline.
8. In patients with bradycardia who have indications for
pacemaker implantation, shared decision-making and
patient-centered care are endorsed and emphasized in
this guideline. Treatment decisions are based on the
best available evidence and on the patient’s goals of
care and preferences.
9. Using the principles of shared decision-making and
informed consent/refusal, patients with decisionmaking 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, and not physician-assisted suicide.
However, any decision is complex, should involve all
stakeholders, and will always be patient specific.
10. Identifying patient populations that will benefit the
most from emerging pacing technologies (e.g., His
bundle pacing, transcatheter leadless pacing systems)
will require further investigation as these modalities
are incorporated into clinical practice. </s>