Pacemaker After TAVI: The Risk, and Why It's Falling

Across the whole history of TAVI, somewhere between one in twenty and one in five patients has left hospital with a new permanent pacemaker. The range is that wide because it depends heavily on which valve is used and how it is positioned. Older self-expanding valves sat at the high end; balloon-expandable valves have generally run at around 7 to 10 per cent. A pacemaker after TAVI is still the procedure's single most common complication — more frequent than stroke, major bleeding or vascular injury.

For a Singapore patient weighing TAVI against open surgery, this is worth putting in perspective: surgical valve replacement also carries a pacemaker risk, usually quoted at 3 to 7 per cent, so TAVI's figure is higher but not in a different league. And, as we will come to, the modern number is a good deal lower than the headline history suggests.

The heartbeat's instruction to squeeze travels from the atria to the ventricles through a single narrow bridge of specialised tissue: the atrioventricular node, then the His bundle, then the left and right bundle branches. That bridge runs immediately beneath the membranous septum, the thin fibrous patch at the base of the aortic valve where the right and non-coronary cusps meet.

Immediately below this thin septum, the conduction axis splits into its branches. The left bundle branch — which drives the heart's main pumping chamber — emerges superficially, almost completely exposed, along the muscular ridge just millimetres below the base of the aortic valve leaflets. Anatomical studies put the distance between the bottom of the leaflet and these critical pathways at as little as 2 to 6 millimetres. It is the same few millimetres whether the procedure is done in Singapore, London or New York, and any device expanding in that landing zone places immediate mechanical pressure right on top of the nerve.

Three things happen when the valve frame opens against that ridge. First, direct mechanical compression: the metal stent pushes into the septal crest and squeezes the left bundle branch against unyielding tissue. Second, the trauma triggers local swelling — oedema and small haematomas — which keeps the pressure on for days after the procedure. Third, tiny feeding vessels to the conduction tissue can be pinched, causing a patch of ischaemia.

The first electrical sign is usually new left bundle branch block on the ECG, meaning the left bundle has been stunned. If the injury reaches the His bundle itself, the signal from top to bottom can fail completely — complete heart block — and the ventricles are left to beat on their own slow rhythm. That is the situation a pacemaker after TAVI is designed to rescue, and it is why, in Singapore as everywhere, the first 48 hours after the procedure are spent watching the ECG closely.

Balloon-expandable valves (the SAPIEN family) are deployed with one quick balloon inflation, sit relatively high in the valve, and have a short frame that clears the septal ridge. Self-expanding valves (CoreValve, then Evolut) are made of nitinol that keeps pushing outward for hours to days after release, and older versions were often implanted deeper into the outflow tract — right over the conduction tissue.

The difference showed up clearly in trials. The CHOICE study recorded new pacemakers in 37.6 per cent of self-expanding cases versus 17.3 per cent with balloon-expandable. In the low-risk trials, pacemaker after TAVI rates were 19.4 per cent for Evolut against 7.5 per cent for SAPIEN 3 at thirty days. This is one reason your Singapore heart team's choice of valve is not a technicality — it is weighed against your anatomy, your baseline ECG and your other risks.

The single biggest gain has come from a change in how the valve is aimed. In the cusp-overlap technique, the X-ray tube is angled so the right and left coronary cusps line up and the non-coronary cusp stands alone, stretching the outflow tract out on the screen. The operator can then see the true depth of the valve as it is released and deliberately sit it higher, away from the left bundle branch.

Pooled analyses put new pacemaker rates at about 8 per cent with cusp overlap versus roughly 17 per cent with the older three-cusp view. Add pre-procedure CT measurement of the membranous septum, smaller delivery catheters and a deliberately high implant, and several Singapore and international centres now report single-digit pacemaker after TAVI rates even with self-expanding valves. The history books say one in five; current practice is closer to one in twelve.

Some of the risk is set before the procedure begins, and a good pre-TAVI assessment in Singapore looks specifically for it. The strongest single predictor is a pre-existing right bundle branch block: if the right bundle is already down, injuring the left bundle leaves nothing conducting, and the odds of needing a pacemaker rise roughly four-fold.

None of these rules a patient out of TAVI — they change the odds, the choice of valve, and how closely the rhythm is watched afterwards. Other markers we weigh:

Most conduction problems declare themselves early. You will be on continuous heart monitoring for at least 24 hours, and longer — 48 to 72 hours — if a self-expanding valve was used or the ECG changed during the procedure. New left bundle branch block that appears and then settles within a day or two is usually watched rather than paced.

If complete or high-grade heart block appears and does not recover, a permanent pacemaker is implanted before you go home, typically adding a day or two to the stay. Delayed block is less common but real, which is why some Singapore centres send borderline patients home with an ambulatory ECG monitor for a couple of weeks. TAVI itself is performed at centres such as the National Heart Centre Singapore and the National University Heart Centre, with several private hospitals near Orchard Road also offering it — expect total costs from around SGD 40,000 in the subsidised system to SGD 80,000 or more privately, with Medisave and insurance applicable for eligible patients.

A pacemaker is a reliable fix for heart block, but it is not free of consequence. Pacing the right ventricle for most of the day makes the two ventricles contract slightly out of step, and over years this can nudge the pumping function down in some patients. Large registry data link a pacemaker after TAVI to a modest rise in later heart failure admissions and around a 13 per cent relative increase in long-term mortality — small at the level of the individual, but reason enough to avoid an unnecessary one.

Where a pacemaker is genuinely needed it is the right call, and newer conduction-system pacing methods aim to preserve a more natural beat. If you are being assessed for TAVI in Singapore, ask for your personal pacemaker risk based on your ECG, your CT and the valve proposed; at our clinic at Paragon Medical Centre we give patients that number before they decide.