**7. Bradyarrhythmias after cardiac surgery**

Bradyarrhythmias include sinus pauses, sinus bradycardia and various blocks depending on the site of abnormal conduction including SA node, AV node or parts of HIS bundle. Bundle branch blocks are common and are not only transient but also harmless in most cases. Various bundle branch blocks can occur in up to 50 – 60% of cases after CABG but are usually transient. (60, 61, 62, 63) Symptomatic blocks needing permanent pacemaker (PPM) insertion complicate 0.8 – 3.4% of CABG operations and up to 2 – 4% of valve surgeries. (64, 65) The incidence of symptomatic bradyarrhythmias is higher after aortic or tricuspid valve surgeries. Repeat surgeries are complicated by blocks needing pacing more often. (65) Heart transplantation is complicated by sinus node dysfunction needing a pacemaker in 21% of cases while AV node blocks needing pacemaker can happen in 4-5% of cases. (53)

Risk factors include increased age, prior Left bundle branch block (LBBB), valve calcification, left main coronary blockage, longer cardiopulmonary bypass time, higher number of bypassed arteries during surgery, associated Left Ventricular aneurysmectomy etc. Valve surgeries seem to be more of a risk than CABG. Increased vagal tone due to surgery, the type of anesthesia used or occurrence of postoperative pain seem to be important underlying factor as well.

Specific factors involved in increasing the risk of bradyarrhythmias after heart transplantation include Biatrial rather than bicaval transplant, older donor age, longer donor ischemic time, longer aortic cross clamp time.

### **Treatment:**

It is prudent to stop all unnecessary medications that can cause increased AV block like beta blockers or calcium channel blockers. Atropine can reverse symptomatic bradycardia. Aminophylline and Theophylline can be used to increase the heart rate during sinus node dysfunction or high grade AV blocks. (66, 67) Readers are also referred to the AHA 2010 guidelines on advanced ACLS for dealing with unstable bradycardia. (75)

Patients with complete heart block, symptomatic AV block or sinus node dysfunction need to have a temporary pacer inserted. It is advisable to wait for 5 – 7 days post op so that any possible edema of the conduction system of the heart resolves before a permanent pacemaker is inserted if still indicated. (68)

Patients who already have a permanent pacemaker or ICD prior to surgery pose a challenge for the surgeons and anesthetists. Electrocautery-induced electromagnetic interference can

pacing via epicardial leads placed during surgery can be used sometimes to provide overdrive pacing to get the heart out of the arrhythmia. Emergency bypass surgery can be considered in some situations. (59) Readers are also referred to the American Heart Association (AHA) 2010 guidelines on advanced cardiovascular life support (ACLS) for

If the patient does survive and is back in sinus it is prudent to initiate them on long term beta blocker and ACE inhibitor therapy according to current ACC guidelines. For those who sustained VT/VF and have recovered, if there are no underlying risk factors mentioned prior, a cardiac electrophysiological study can be considered and an implantable cardiac defibrillator (ICD) is advised if there is any inducible VT or VF. If the patient is deemed to have an underlying heart disease that is unlikely to respond to medical therapy, an ICD may

Bradyarrhythmias include sinus pauses, sinus bradycardia and various blocks depending on the site of abnormal conduction including SA node, AV node or parts of HIS bundle. Bundle branch blocks are common and are not only transient but also harmless in most cases. Various bundle branch blocks can occur in up to 50 – 60% of cases after CABG but are usually transient. (60, 61, 62, 63) Symptomatic blocks needing permanent pacemaker (PPM) insertion complicate 0.8 – 3.4% of CABG operations and up to 2 – 4% of valve surgeries. (64, 65) The incidence of symptomatic bradyarrhythmias is higher after aortic or tricuspid valve surgeries. Repeat surgeries are complicated by blocks needing pacing more often. (65) Heart transplantation is complicated by sinus node dysfunction needing a pacemaker in 21% of cases while AV node blocks needing pacemaker can happen in 4-5%

Risk factors include increased age, prior Left bundle branch block (LBBB), valve calcification, left main coronary blockage, longer cardiopulmonary bypass time, higher number of bypassed arteries during surgery, associated Left Ventricular aneurysmectomy etc. Valve surgeries seem to be more of a risk than CABG. Increased vagal tone due to surgery, the type of anesthesia used or occurrence of postoperative pain seem to be

Specific factors involved in increasing the risk of bradyarrhythmias after heart transplantation include Biatrial rather than bicaval transplant, older donor age, longer donor

It is prudent to stop all unnecessary medications that can cause increased AV block like beta blockers or calcium channel blockers. Atropine can reverse symptomatic bradycardia. Aminophylline and Theophylline can be used to increase the heart rate during sinus node dysfunction or high grade AV blocks. (66, 67) Readers are also referred to the AHA 2010

Patients with complete heart block, symptomatic AV block or sinus node dysfunction need to have a temporary pacer inserted. It is advisable to wait for 5 – 7 days post op so that any possible edema of the conduction system of the heart resolves before a permanent

Patients who already have a permanent pacemaker or ICD prior to surgery pose a challenge for the surgeons and anesthetists. Electrocautery-induced electromagnetic interference can

guidelines on advanced ACLS for dealing with unstable bradycardia. (75)

dealing with unstable tachycardia. (75)

of cases. (53)

**Treatment:** 

important underlying factor as well.

ischemic time, longer aortic cross clamp time.

pacemaker is inserted if still indicated. (68)

be indicated without electrophysiological study.

**7. Bradyarrhythmias after cardiac surgery** 

cause problems during the surgery. The cautery can inhibit the pacer and may cause inappropriate discharge of the ICD if the sensing function is not disabled. A comprehensive evaluation of the patient prior to surgery by an electrophysiologist is indicated. A magnet can be placed on top to disable the devices during the surgery so as to not cause any interference. Another option is to switch the pacer/ICD to asynchronous mode so that the cautery does not influence its function. However, patients need to be continuously monitored while the devices are in asynchronous mode as any malignant arrhythmias need to be treated via external defibrillator. (76)
