Biomedical Engineering Reference
In-Depth Information
Table 6.1
Recommendation classi fi cations
Recommendations for Acquired Atrioventricular Block in
Adults
Third-degree and advanced second-degree AV block at
Class I
Conditions for which there is evidence, general agreement,
or both that a given procedure or treatment is useful and
effective
•
any anatomic level associated with bradycardia with
symptoms (including heart failure) or ventricular arrhyth-
mias presumed to be due to AV block
Third-degree and advanced second-degree AV block at
Class II
Conditions for which there is conflicting evidence, a
divergence of opinion, or both about the usefulness/
efficacy of a procedure or treatment
•
Class IIa
Weight of evidence/opinion is in favor of usefulness/efficacy
any anatomic level associated with arrhythmias and other
medical conditions that require drug therapy that results
in symptomatic bradycardia
Third-degree and advanced second-degree AV block at
Class IIb
Usefulness/efficacy less well-established by evidence/opinion
Class III
Conditions for which there is evidence, general agreement,
or both that the procedure/treatment is not useful/effective
and in some cases may be harmful
•
any anatomic level in awake, symptom-free patients in
sinus rhythm, with documented periods of asystole greater
than or equal to 3.0 s, or any escape rate less than 40 beats/
min, or an escape rhythm that is below the AV node
Third-degree and advanced second-degree AV block at
Table 6.2
Levels of evidenc
e
Level of evidence
Basis of recommendations
A
Evidence from multiple randomized trials
or meta-analyses
•
any anatomic level in awake, symptom-free patients with
atrial fibrillation and bradycardia with one or more pauses
of at least 5 s or longer
Third-degree and advanced second-degree AV block at
B
Evidence from a single randomized trial
or nonrandomized studies
C
Expert opinion, case studies, or standards
of care
•
any anatomic level after catheter ablation of the AV
junction
Third-degree and advanced second-degree AV block at
•
Conduction disorders that require restoration of AV syn-
•
chrony, including varying degrees of AV block
VVI intolerance (e.g., pacemaker syndrome) in the pres-
any anatomic level associated with postoperative AV
block that is not expected to resolve after cardiac surgery
Third-degree and advanced second-degree AV block at
•
ence of a persistent sinus rhythm
Low cardiac output or congestive heart failure secondary
•
•
any anatomic level associated with neuromuscular dis-
eases with AV block, such as myotonic muscular dystro-
phy, Kearns-Sayre syndrome, Erb dystrophy (limb-girdle
muscular dystrophy), and peroneal muscular atrophy,
with or without symptoms
Second-degree AV block with associated symptomatic
to bradycardia
According to actual American College of Cardiology
(ACC)/American Heart Association (AHA)/Heart Rhythm
Society (HRS) 2008 Guidelines for Device-Based Therapy
of Cardiac Rhythm Abnormalities [ 34, 35 ] , the indications
(class I and class IIa) for permanent pacing are described in
the following paragraphs.
•
bradycardia, regardless of type or site of block
Asymptomatic, persistent third-degree AV block at any
•
anatomic site with average awake ventricular rates of
40 beats/min or faster if cardiomegaly or LV dysfunction
is present or if the site of block is below the AV node
Second- or third-degree AV block during exercise in the
Recommendations for Permanent Pacing in Sinus Node
Dysfunction
Sinus node dysfunction (SND) with documented symptom-
•
•
atic bradycardia, including frequent sinus pauses that pro-
duce symptoms. For some patients this is the result of
necessary long-term pharmaceutical therapy without the
possibility of a dose change or use of an alternative therapy.
Symptomatic sinus bradycardia that results from required
absence of myocardial ischemia
Persistent third-degree AV block with an escape rate
•
greater than 40 beats/min in asymptomatic adult patients
without cardiomegaly
Asymptomatic second-degree AV block at intra- or infra-
•
•
drug therapy for medical conditions.
Symptomatic chronotropic incompetence (inability to
His levels found during electrophysiologic testing
First- or second-degree AV block with symptoms similar
•
•
increase the heart rate with increased physical activity or
other demand of the patient).
SND with heart rate less than 40 beats/min when a clear
to those of pacemaker syndrome or hemodynamic
compromise
Asymptomatic type II second-degree AV block with a
•
•
association between significant symptoms consistent with
bradycardia and the actual presence of bradycardia has
not been documented.
Syncope of unexplained origin when clinically significant
narrow QRS
Recommendations for Permanent Pacing After the Acute
Phase of Myocardial Infarction
Persistent second-degree AV block in the His-Purkinje
•
abnormalities of sinus node function are discovered or
provoked in electrophysiologic testing.
•
system with alternating bundle branch block or third-degree
