January 13, 2012
Dear Mayo Clinic:
I was just diagnosed with atrial fibrillation and am on medication for the time being but was told I may need surgery. I have read about a new treatment option called cryoablation. Is this a safe option? How effective is the procedure?
Cryoablation can be used to control atrial fibrillation when medication and other treatments do not successfully restore normal heart rhythm. Although heat ablation has been used for more than a decade to treat atrial fibrillation, cryoablation — which freezes the affected tissue — has only recently been approved as an atrial fibrillation treatment. As with any medical procedure, some risks are associated with cryoablation. But, overall, studies have shown it to be safe and effective.
When the heart beats, the electrical signals that cause it to contract must follow a precise pathway through the heart. Any interruption in these signals can cause an abnormal heartbeat, or arrhythmia. Atrial fibrillation is a common form of arrhythmia that results in fast and chaotic heartbeats when the atria, the upper chambers of the heart, "wiggle" due to irregular electrical signals.
Because the heart pumps blood less efficiently to the rest of the body during atrial fibrillation, many people with this disorder have decreased blood pressure and suffer from weakness, fatigue, light-headedness and shortness of breath. Atrial fibrillation also raises a person's stroke risk.
Atrial fibrillation often gets worse over time if left untreated. Fortunately, in many cases, medication and procedures designed to reset or control the heart's rate and rhythm and prevent future episodes of irregular heartbeat are sufficient to treat atrial fibrillation.
For some people, however, those efforts are not enough. In such cases, cardiac ablation may be used to destroy the tissue that is producing the unpredictable electrical signals. During heat ablation, radiofrequency energy is directed at the pulmonary vein where it connects to the heart's left atrium. The treatment is delivered through a catheter inserted in an artery near the groin and threaded up to the heart. The heat creates lesions that scar the tissue, blocking the erratic electrical signals from reaching the atria.
During cryoablation, a coolant rather than heat is used to create a circle of lesions around the pulmonary vein to block the irregular electrical signals. This minimally invasive procedure also involves inserting a catheter through an artery and placing it near the heart. A deflated balloon is inserted through the catheter and then inflated and frozen in the treatment area.
Cryoablation has several advantages over heat ablation. First, heat ablation requires that multiple lesions be created to keep the electrical signals from reaching the atria. Between the lesions, there may be areas where a pathway can still exist for the abnormal signal to travel to the atria. If that happens, heat ablation needs to be repeated. In contrast, the frozen balloon used in cryoablation creates a full circle of lesions that the signals are less likely to break through.
Second, heat ablation can sometimes cause a complication known as pulmonary vein stenosis, a narrowing of the vein due to the development of scar tissue. Pulmonary vein stenosis does not appear to happen with cryoablation.
An uncommon complication associated with cryoablation is phrenic nerve injury. The phrenic nerve controls movement of the diaphragm, which is the muscle that separates the chest from the abdomen and plays an important role in breathing. Because the nerve is located behind the pulmonary vein, cryoablation may damage the phrenic nerve. The likelihood of nerve injury is reduced by careful surgical technique. Fortunately, when nerve injury occurs, it often resolves on its own.
In many cases, cryoablation can safely and effectively be used to treat atrial fibrillation. If medication does not control your atrial fibrillation, cryoablation may be an appropriate treatment option.
—Fred Kusumoto, M.D., Cardiovascular Diseases, Mayo Clinic, Jacksonville, Fla.