Cerebral thromboembolism: 0.24% (4/1,657 patients)

A pre-existing blood clot in the heart or attached to the catheter may flow into and clog a cerebral vessel and cause a cerebral infarction during or after  surgery.
To prevent thromboembolism, patients take warfarin  for at least for 1 month before surgery to thin the blood, heparin is injected during surgery to thin the blood,   and  another medicine is taken by patients to stimulate cardiac activities and prevent the formation of blood clots. 
Warfarin should be discontinued immediately before hospitalization.
(This method was developed by the manager of our department and was presented to the Japanese Circulatory Society in 2006.)

Cardiac tamponade: 0.6% (10/1,657 patients)

When the cardiac muscle becomes weaker because of  cauterization, blood can leak from the heart and accumulate nearby.  This can  result in a lower blood pressure, a slower pulse, and ultimately a shock state.
If shock occurs  ,the accumulated blood is extracted to release the pressure on the heart .
In most cases ,the bleeding stops spontaneously and no problems remain. 
(Cases of cardiac tamponade  at our institution were summarized and reported to the Japanese Circulatory Society in 2008.)

Esophageal vagal afferent disorder: 0.24% (4/1,657 patients)

In three patients, the heat generated during cauterization of the heart was transmitted to the esophageal vagal afferents just behind the heart.  Nerve damage occurred, and the patients’ stomachs became inactive.
Three of the  four patients spontaneously recovered from the symptoms, whereas the stomach of the fourth patient was  surgically removed after the patient did not recover. 
We now  insert a thermometer in the esophagus to measure the temperature during cauterization and stop the electric current temporarily when the temperature increases.  (This preventive measure is used by our department exclusively  and was presented by our director, Kuwahara, at  the General Meeting of the Japanese Circulatory Society from 2005 to 2007.)

Pulmonary artery thrombotic embolism: 0.06% (1/1,657 patients)
Femoral vein thrombosis: 0.06% (1/1,657 patients)

One patient experienced  clots in a leg vein and then in a pulmonary artery on the day after surgery while resting in bed.  Thus, ablation surgery can generate the same symptoms associated with the “ economy-class syndrome,” which sometimes occurs in airplane passengers confined to small areas.
We prevent the formation of blood clots by having our patients wear elastic stockings or a Kendall electric massaging device on the lower thighs.

Diaphragmatic paralysis: 0.36% (6/1,657 patients)

In some case, nerve that moves the right diaphragm passes near the right pulmonary vein.  When this vein is cauterized,  some patients may experience immobility of the right diaphragm.
Whereas most cases are temporary and resolve without symptoms, rare cases of prolonged paralysis do occur.
As a preventive measure, we confirm the location of the phrenic nerve with the electric impulse when cauterizing near the right pulmonary vein. 

Allergy to contrast media: 2-3%

The contrast media used during dissection of the pulmonary vein causes . sickness in 2-3% of patients, a reduced blood pressure or breathing difficulty in 1/2,500 of patients, or death from anaphylactic shock in 1/200,000 of patients  .

Concealed hemorrhage at  a puncture site: 5%

The insertion of a catheter into a femoral vein at the groin and its removal after surgery can result in an internal hemorrhage on the thigh 2-7 days after surgery. The hemorrhage usually disappears completely in a short amount of time.