One of the most resonant educational pieces on ECG interpretation I have ever read. It takes a term that has generated confusion for decades and clarifies it with remarkable precision. It demonstrates how precise language improves clinical thinking and, ultimately, patient care.
I am getting a pacemaker for AV block mobitz II with two leads. The device can be extended in situ to a third lead. I figure one lead will do to the sinoatrial node. Where does the second go?
Thanks for reading. The specifics really need to come from the team responsible for fitting your device.
In general, pacemaker leads don't go to the sinoatrial node itself. The SA node is a small region at the top of the right atrium, near the superior vena cava.
In a typical dual-chamber pacemaker:
- the first lead sits in the right atrium (more broadly than the SA node)
- the second sits in the right ventricle
A third lead, if added, is usually passed through the coronary sinus to reach the surface of the left ventricle. That setup (with the three leads) is called cardiac resynchronisation therapy.
Yes, and the SA node doesn't just energise the atria. It triggers the whole heart.
The heart muscle has two types of cells:
1. Contractile cells do the actual squeezing. They can only depolarise (and contract) when something else triggers them.
2. Conducting cells can depolarise themselves, with no external trigger.
The SA node is a small cluster of conducting cells at the top of the right atrium. It self-fires automatically. That's why it's the heart's natural pacemaker.
From there, the signal travels through the rest of the conducting system: across the atria, down to the AV node, through the His bundle, into the left and right bundle branches, and out along the Purkinje fibres. This network is the heart's wiring. Its job is to deliver the SA node's trigger to every contractile cell in the right sequence (atria first, then ventricles).
When a contractile cell receives that trigger, it depolarises and contracts. Atrial cells get the signal early, so the atria contract first. Ventricular cells get it a fraction of a second later, so the ventricles contract next. That's a normal heartbeat.
One of the most resonant educational pieces on ECG interpretation I have ever read. It takes a term that has generated confusion for decades and clarifies it with remarkable precision. It demonstrates how precise language improves clinical thinking and, ultimately, patient care.
I am getting a pacemaker for AV block mobitz II with two leads. The device can be extended in situ to a third lead. I figure one lead will do to the sinoatrial node. Where does the second go?
Thanks for reading. The specifics really need to come from the team responsible for fitting your device.
In general, pacemaker leads don't go to the sinoatrial node itself. The SA node is a small region at the top of the right atrium, near the superior vena cava.
In a typical dual-chamber pacemaker:
- the first lead sits in the right atrium (more broadly than the SA node)
- the second sits in the right ventricle
A third lead, if added, is usually passed through the coronary sinus to reach the surface of the left ventricle. That setup (with the three leads) is called cardiac resynchronisation therapy.
After a few YouTube dives:
The SA node seems to energize the two Atria… does that energy cause Atria contractions?
I REALLY appreciate the explanations. Somehow knowing the process reduces anxiety.
Yes, and the SA node doesn't just energise the atria. It triggers the whole heart.
The heart muscle has two types of cells:
1. Contractile cells do the actual squeezing. They can only depolarise (and contract) when something else triggers them.
2. Conducting cells can depolarise themselves, with no external trigger.
The SA node is a small cluster of conducting cells at the top of the right atrium. It self-fires automatically. That's why it's the heart's natural pacemaker.
From there, the signal travels through the rest of the conducting system: across the atria, down to the AV node, through the His bundle, into the left and right bundle branches, and out along the Purkinje fibres. This network is the heart's wiring. Its job is to deliver the SA node's trigger to every contractile cell in the right sequence (atria first, then ventricles).
When a contractile cell receives that trigger, it depolarises and contracts. Atrial cells get the signal early, so the atria contract first. Ventricular cells get it a fraction of a second later, so the ventricles contract next. That's a normal heartbeat.
Glad the explanations help!