Third degree AV block surgery

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Raviteja Guddeti, M.B.B.S. [3] Soroush Seifirad, M.D.[4] Qasim Khurshid, M.B.B.S [5]

Overview

Cardiac pacemakers are effective treatments for a variety of cardiac conduction abnormalities and can reestablish adequate circulation by generating appropriate heart rate and cardiac response. Two main factors guide the majority of decisions regarding permanent pacemaker insertion. First is the association of symptoms with arrhythmia, and second is the potential for progression of the rhythm disturbance.

Recommendation for placement of permanent pacing

• Symptoms related to atrioventricular block are determining factor of placing permanent pacemaker, regardless of the level of atrioventricular block.
• Permanent pacemaker is warranted if the site of atrioventricular block is Infranodal, regardless of the presence or absence of symptoms.
• Varied degree of atrioventricular block from first degree atrioventricular block to complete atrioventricular block may develope over the time in neuromuscular disorders such as muscular dystrophies or Kearns-Sayre syndrome.
• Intermittent second-degree or third-degree atrioventricular block on 24-hour ambulatory electrocardiographic monitoring or atrioventricular block on resting ECG was found in 20% of patients with myotonic dystrophy type 1.
• In the presence of atrial fibrillation and slow regular ventricular response and wide QRS and pauses >3 seconds, infranodal atrioventricular block may be suspected.
• Atrioventricular block may develop by using betablocker for MI or heartfailure and amiodarone and sotalol for atrial fibrillation patients.
• The benefit of using these medications should be balanced over the side effects of right ventricular pacing.
• Atrioventricular block in the setting of cardiac sarcoidosis may resolve by using corticosteroids for 30 days.
• Evidence of prolonged HV interval (>55 ms) despite a narrow QRS was found in AL cardiac amyloidosis.
• Mutations in the lamin A/C gene can present with atrioventricular block, atrial arrhythmias, and ventricular arrhythmia.
• Risk of atrioventricular block and sudden cardiac death may increase in the setting of lamin A/C mutation.
• In one study, the risk of ventricular arrhythmias increased in the presence of first-degree atrioventricular block.
• Pseudo-pacemaker syndrome may develop in the setting of severe first-degree atrioventricular block with very long PR interval , atrial contraction during the closed atrioventricular valves leading to an increase in wedge pressure and a decrease in cardiac output.

Recommendations for permanent pacing for chronic management of Bradycardia Attributable to Atrioventricular Block

(Class I, Level of Evidence B):

❑Permanent pacing is recommended in patients with acquired second degree mobitz type2 atrioventricular block, high grade atrioventricular block, third degree atrioventricular block, regardless of symptoms that are not related to reversible causes ❑ permanent pacing with additional defibrillator capacity is needed in patients with neuromuscular disease associated conduction disorder such as myotonic dystrophy type1 or kearn sayre syndrome and presence of second degree atrioventricular block, third degree atioventricular block, HV interval of 70 ms or greater, regardless of symptoms if life expectancy>1 year

( Class I, Level of Evidence C) :

❑ Permanent pacing is recommended in patients with permanent atrial fibrillation and symptomatic bradycardia ❑ In patients with symptomatic atrioventricular block associated with necessary medications which there is not alternative treatment, permanent pacing is needed

(Class IIa, Level of Evidence B)

❑ In patients with cardiac sarcoidosis and amyloidosis and evidence of mobitz type 2 atrioventricular block, high grade atrioventricular block, third degree atrioventricular block , permanent pacing with additional defibrillator capacity is reasonable if life expectancy>1 year ❑ In patients with lamin A/C mutation such as limb girdle, emery driefuss muscular dystrophies with PR interval>240 ms and LBBB, permanent pacing with additional defibrillator capacity is reasonable if life expectancy >1 year

(Class IIa, Level of Evidence C)

❑ In patients with symptomatic first degree atrioventricular block or motitz tyoe 1 atrioventricular block, permanent pacing is recommended

(Class IIb, Level of Evidence C)

❑ Permanent pacing with additional defibrillator capacity is recommended in patients with neuromuscular disease including myotonic dystrophy type1 with PR interval >240ms , QRS duration >120 ms, fascicular block if life expectancy>1 year

The above table adopted from 2018 AHA/ACC/HRS Guideline

Management of bradycardia or pauses attributable to chronic atrioventricular block algorithm

Atrioventricular block

Complete heart block (aquired) Advanced AV block, Mobitz type2 Evidence for infranodal block

Permanent pacing (class1)

Consider risk for ventricular arrhythmia (class1)

Cardiac resynchronization therapy Is LVEF<35%?

NO Infrequent pacing? Other comorbidities?

Yes Medical therapy

Yes Single chamber ventricular pacing (class1)

N0 Permanent atrial fibrillation

Yes Single chamber ventricular pacing (class1)

NO Dual chamber pacing (class1)

LVEF>50%

Yes Right ventricular pacing lead (class 2a)

NO Is predicted pacing <40%

NO Pacing to reach physiologic activation of left ventricle (class2a)

Yes Righr ventricular pacing (class2a)

His bundle pacing (class2b)

The above algorithm adopted from 2018 AHA/ACC/HRS Guideline

Recommendations for temporary pacing for bradycardia associated atrioventricular block

Medical therapy (Class IIa, Level of Evidence B):

❑ In patients with symptomatic bradycardia associated second or third degree atrioventricular block, refractory to medications, temporary transvenous pacing is recommended to increase heart rate and improve symptoms

Surgery

A permanent pacemaker insertion is a minimally invasive procedure. The procedure is typically performed in a cardiac catheterization lab or an operating room. Transvenous access to the heart chambers under local anesthesia is the preferred technique, most commonly via the subclavian vein, the cephalic vein, or the internal jugular vein or the femoral vein.The pacing generator is most commonly placed subcutaneously in the pre-pectoral region. Placement of pacemaker leads, surgically via thoracotomy, is rarely used these days.

Types of permanent pacemaker systems

All cardiac pacemakers consist of two components: a pulse generator that provides the electrical impulse for myocardial stimulation; and one or more electrodes that deliver the electrical impulse to the myocardium. The original cardiac pacing system was used to place surgically in the abdomen. Over time, pacemaker systems evolved to predominantly placing the pulse generator in the infraclavicular region of the chest with transvenous-placed endocardial leads. Transvenous leads have potential long-term complications, including venous thrombosis, infection, and lead malfunction. Leadless cardiac pacing systems are currently in development and offer the promise of long-term pacing capability without lead-associated complications.

Transvenous systems

The majority of cardiac pacing systems use transvenous electrodes to transmit pacing impulses from the generator to the myocardium. Transvenous leads are usually placed percutaneously or with a cephalic cutdown, without the need for intrathoracic surgery. Long term complications of transvenous electrodes include infection,venous thrombosis, lead malfunction, and tricuspid valve injury.

Epicardial systems

Epicardial cardiac pacemaker systems utilize a pulse generator with leads attached surgically directly to the epicardial surface of the heart. These systems are occasionally used in patients with vascular access problems and have been replaced by transvenous systems.

Leadless systems

In response to the limitations of existing pacings systems, leadless systems are developed. Leadless systems consist of a self-contained system that includes both the pulse generator and the electrode within a single unit that is placed into the right ventricle via a transvenous approach. Leadless cardiac pacing system was approved in April 2016 in the United States