Registries and ongoing research have broadened our understanding of abnormal heart rhythms. Today, much more is known about the etiology of arrhythmias, as well as options for best therapies. Cardiovascular Business spoke with the incoming and outgoing presidents of the Heart Rhythm Society (HRS) about advances in our knowledge of these disease states.
Flutter & ablation
Five years ago, the relationship between atrial flutter and underlying heart disease was hazy. The prevailing notion was that atrial flutter might occur and then deteriorate into atrial fibrillation (AF). Today, electrophysiologists (EPs) recognize that flutter is its own abnormal rhythm, separate from AF, but with perhaps common origins, says Douglas Packer, MD, president of the HRS and director of heart rhythm services at the Mayo Clinic in Rochester, Minn.
Most atrial flutter seen by EPs is the result of underlying disease. It is unusual for a patient with a normal heart to have atrial flutter. "It's possible, but it is more likely that atrial flutter will occur in the setting of concomitant atrial fibrillation, so it tends to have the same risk factors such as hypertension, diabetes, hypertrophic cardiomyopathy, underlying obstructive coronary artery disease with infarction or heart failure," Packer says.
The specialty's understanding of patients with congenital heart disease also has advanced. These patients are at a substantially increased risk of developing atrial flutter, particularly those who undergo surgical correction. "Patients with congenital heart disease may do very well with the plumbing following surgery only to have increasing electrical problems later on," Packer says. Knowing this allows EPs to be better prepared to either reduce the occurrence of flutter or properly treat it following surgery.
In the setting of atrial flutter with concomitant AF, ablating the isthmus between the tricuspid valve and the inferior vena cava generally eliminates the flutter, but does not cure the AF. Consequently, it is important to monitor patients with atrial flutter to determine whether they also have AF. If not, ablation of the flutter is straightforward.
"On other hand, if a patient had several episodes of AF, even if atrial flutter had been the predominant arrhythmia, particularly in the setting of underlying disease, then we would ablate both arrhythmias in the same procedure," Packer says. "Most of the decisions regarding treatment options come down to whether there is the presence or absence of underlying disease and the presence or absence of AF in addition to flutter or vice versa."
In the past, however, EPs would have taken care of the flutter hoping that the AF would resolve itself. "We know that is not the case today, especially in the presence of underlying disease," Packer says.
Still, flutter can remain after ablating AF. There are several mechanisms for this. First, the heart has only so many ways to respond post-AF ablation. One of those manifestations is atrial flutter. Second, a gap in the linear ablation line could cause flutter and even be aggravated by the presence of that gap. "When we re-ablate, we may have to specifically localize the gap or gaps and ablate them," Packer says.
He suggests that fluoroscopy guidance may be sufficient to ablate around the pulmonary veins for AF. If flutter develops, particularly in the presence of prior ablation, 3D mapping systems help identify and localize specific gaps. "In these cases, mapping is almost mandatory," Packer says. Merging CT or MRI datasets also is particularly helpful to show the three-dimensionality of the cardiac chambers, but the images must be appropriately registered and point-to-point confirmation made.
The use of ablation as a first-line treatment for flutter is neither supported nor refuted by available guidelines, Packer says. In his opinion, however, ablative intervention is "very reasonable" for a patient with classic isthmus-dependent flutter who is highly symptomatic. One problem, however, is that EPs may not know if it is classic isthmus-dependent flutter from the ECG alone. Another problem is that flutter with coexisting AF calls for anti-arrhythmic drug therapy first, and ablation as the second choice when symptoms are persistent.