Growing up with a heart that beats differently
Decades ago, many babies born with complex heart defects didn't survive childhood.
Today, they do — and they're growing into adults who face a new challenge: heart failure that can start earlier and progress differently than in people born with typical hearts.
Treating these patients is tricky. Their hearts don't always fit the guidebook.
Adult congenital heart disease (ACHD) is a growing population.
Better surgeries and care in childhood mean more of these patients are living into middle age and beyond. But as they age, many develop heart failure — often because the heart's chambers never pumped the way a "standard" heart does.
Doctors have long wondered whether cardiac resynchronization therapy (CRT) — a pacemaker that times both ventricles to beat together — helps these patients the way it helps people with traditional heart failure.
The problem: most CRT studies excluded people with congenital defects.
The old way vs. the new evidence
For decades, guidelines for CRT have been based on patients with "acquired" heart failure, usually from heart attacks or high blood pressure.
Doctors extrapolated — meaning they guessed — that CRT would help ACHD patients too.
Here's what's different this time: a team of researchers systematically pulled together 25 studies with nearly 800 ACHD patients to see whether the guesses actually held up.
How it works, in simple terms
Think of your heart as a two-pump system where both pumps must squeeze together in perfect rhythm.
When the electrical signal between them gets out of sync, it's like two rowers on a boat paddling at different speeds. The boat still moves, but inefficiently — and eventually, the rowers tire.
CRT places small wires (leads) to help both pumps fire in unison again. In regular heart failure, this restores teamwork and gives the heart a rest.
In ACHD, the anatomy can be scrambled — sometimes the "wrong" chamber does the hard work, or the electrical pathways are rerouted by past surgeries. The question was: can CRT still help?
The study at a glance
Researchers followed standardized review methods to pool data from 25 studies covering 796 ACHD patients.
Of those, 723 received the traditional form of CRT called biventricular pacing (BiV), and 73 received a newer approach called conduction system pacing (CSP).
They tracked changes in QRS duration (a marker on the ECG showing how coordinated the heartbeat is), ventricular function, and symptoms rated on the New York Heart Association (NYHA) scale.
The numbers were encouraging.
QRS duration shortened by about 23 milliseconds — a meaningful narrowing that means the heart's electrical signals got back in sync. Ventricular function improved by nearly 8 percentage points. NYHA class dropped by nearly one full level, which typically means patients went from being noticeably short of breath to being more comfortable with daily activity.
Even more striking: the benefits held up in patients with a systemic right ventricle — a setup where the right ventricle (normally a lighter-duty chamber) has to pump blood to the whole body. That group traditionally responds poorly to many heart failure treatments.
This doesn't mean every ACHD patient with heart failure should rush to get CRT.
It means the door is now wider open for individualized discussions with a specialist.
A new kid on the block
The newer technique — conduction system pacing — looked promising in early data.
Instead of pacing both ventricles through separate leads, CSP places a lead along the heart's natural electrical highway. It achieved similar narrowing of the QRS as traditional BiV pacing.
But the CSP group was small (only 73 patients), and long-term outcomes are still unknown.
This meta-analysis won't rewrite guidelines overnight. But it's a meaningful step.
For years, ACHD patients have been underrepresented in cardiac research — leaving their care largely a matter of expert judgment. Pooled evidence like this gives specialists firmer ground to stand on when recommending CRT for this group.
Many ACHD specialists may now feel more confident offering CRT, especially in patients with visible electrical dyssynchrony and declining function.
If you or a loved one has adult congenital heart disease and is developing heart failure symptoms, ask about an evaluation by an ACHD-focused electrophysiologist.
CRT isn't right for everyone — it depends on heart anatomy, QRS pattern, and symptoms. But it's a treatment option worth discussing rather than assuming it doesn't apply.
Conduction system pacing may also be offered in some centers as an alternative.
Honest limitations
Most of the 25 pooled studies were observational — meaning they watched what happened without random comparisons.
That design can exaggerate benefits because the sickest patients may not have been selected for CRT in the first place. Sample sizes for CSP were small. Studies also came from different hospitals with varying definitions of success, making comparisons imperfect.
Prospective, phenotype-specific studies are needed next — meaning trials that match the treatment to the specific type of congenital heart anatomy.
Standardized outcome reporting would also help future meta-analyses be more conclusive. Over time, researchers hope to refine which ACHD patients benefit most from which pacing strategy.
The takeaway: hearts that are built differently may still respond to the same rhythmic fix — if we give them a chance.