AF and the pulmonary veins

Nikhil Ahluwalia

Oct 7, 2022 • 2 min read

A lot of Cardiologists don't understand this so buckle up for this one...

What are the pulmonary veins?

Four blood vessels bring blood back from the lungs to the left atrium (the top left chamber of the heart. These are called the pulmonary veins. They're approximately 1cm in diameter and are made up of smooth muscle cells. Importantly, interlacing lines of heart cells can extend into the veins where the veins connect to the heart. These are called sleeves which have 'automaticity' i.e. can trigger extra beats that can activate the heart.

Two pulmonary veins come into the left atrium of the heart from each lung. Images adapted from here. The 4 openings represent the area of connection between the veins and the heart.

The relationship between the pulmonary veins and AF was born out in Bordeaux. In 1998, Michele Haïssaguerre published a seminal paper entitled "Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins". The team studied 45 patients with paroxysmal (on-off) AF by placing catheters with multiple electrode sensors into the heart. They found the earliest electrical activity during the beats that initiated AF originated from the pulmonary vein structures in most cases. They went on to apply ablation treatment to these areas which immediately stopped the AF

The image is taken from the Haïssaguerre study and represents the upper heart chambers (the right and left atrium). It shows the 69 AF origin sites were seen amongst the 45 patients. Each black dot represents an origin site.

The pulmonary veins play an important role in initiating AF. Adrenaline can stimulate the automaticity of the pulmonary veins whereas anti-arrhythmic medications can suppress this.

Electrical isolation of the pulmonary veins or "PVI" has become the cornerstone of AF catheter ablation and directly targets this troublesome area. Whether that's done using freezing or heating, with an ablation catheter or a balloon, all these treatments are designed to be able to stop electrical stimulation from coming into the heart from the pulmonary veins. At the moment, we have no evidence that additional ablation on the first sitting will produce added benefit although studies of additional ablation treatments on top of PVI are ongoing.

Haïssaguerre M, Jaïs P, Shah DC, Takahashi A, Hocini M, Quiniou G, Garrigue S, Le Mouroux A, Le Métayer P, Clémenty J. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med. 1998 Sep 3;339(10):659-66. doi: 10.1056/NEJM199809033391003. PMID: 9725923.

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