Prosthetic Heart Valve Assessment in PACES

How it presents in PACES

This is a frequently appearing case in the cardiovascular station, and it announces itself before you touch the patient. You approach the bed, hear a sharp metallic click audible to the naked ear, and see a midline sternotomy scar. That combination — an audible click plus a sternotomy — is a functioning mechanical prosthesis until proven otherwise, and the audible click is always the *closure* click.

The examiners want a candidate who works through four bedside tasks in order: recognise that the valve is prosthetic, identify *which* valve has been replaced, state the likely underlying native lesion, and then actively look for complications and anticoagulation status. Get those four right, calmly, and you have passed the case. The trap is treating it as a subtle auscultation problem and getting lost in soft flow murmurs that mean nothing.

Not every replaced valve clicks. A bioprosthesis (tissue valve) produces native-quality sounds with no click, so you recognise it from the scar, the patient's age, and a soft flow murmur rather than a metallic sound. Spotting a silent bioprosthesis in an elderly patient in sinus rhythm with no bruising is a discriminating move.

Signs to look for

Run a focused checklist rather than free-form listening. These are the discriminating signs:

• Midline sternotomy scar plus a metallic closure click audible without the stethoscope — a functioning mechanical valve.
• Localise by timing the click against the carotid upstroke: a click *after* the upstroke is a prosthetic S2, so an AVR; a click *before or with* the upstroke is a prosthetic S1, so an MVR. Two closure clicks means dual valve replacement.
• Read the apex for the original lesion: an undisplaced apex suggests a replaced *stenotic* valve (AS or MS); a displaced, thrusting apex suggests a replaced *regurgitant* valve (AR or MR).
• Valve-type cues: a ball-and-cage (Starr-Edwards) design adds an opening click and a low-pitched flow rumble and is the most thrombogenic; a tilting-disc gives a single crisp click and no rumble; a bioprosthesis gives no click at all.
• Anticoagulation clues: look for ecchymoses or bruising — this is over-anticoagulation, the commonest visible complication of a mechanical valve.
• Judge function by the crispness of the sounds: muffled, non-crisp metallic sounds suggest thrombosis or pannus.
• Don't-miss negatives: a saphenous-vein-harvest scar (concomitant CABG), a second native-valve murmur, and a marfanoid habitus that would explain a young patient needing an AVR for root disease.

Confirming the diagnosis and differential

The core judgement is well-functioning versus dysfunctional. A well-functioning prosthesis gives crisp sounds, at most a soft flow murmur, and — importantly — no regurgitant murmur and no collapsing pulse. A soft systolic flow murmur across an AVR is normal (turbulent flow through the prosthesis), as is a soft diastolic rumble across a mitral bioprosthesis. Do not label either as a leak.

The rule that saves marks: a *systolic* murmur over a *mitral* prosthesis is regurgitant until proven otherwise — never hand-wave it as flow before excluding a paravalvular leak and functional TR. A paravalvular (paraprosthetic) leak or partial dehiscence is the commonest cause of new prosthetic regurgitation and is strongly linked to prosthetic valve endocarditis, so always exclude infection. An AVR leak gives an early diastolic murmur at the left sternal edge with a collapsing pulse, Corrigan's sign and a displaced thrusting apex; an MVR leak gives a new loud apical pansystolic murmur radiating to the axilla, sometimes with heart failure or haemolysis.

Other threads on the differential are valve thrombosis or pannus (muffled, obstructive sounds), structural degeneration of a bioprosthesis at around ten to fifteen years, haemolysis (pallor and jaundice), valve failure driving heart failure, and endocarditis. If the patient is anaemic, the causes to offer are mechanical haemolysis, endocarditis, and anticoagulant-related bleeding.

The viva: what examiners ask

Expect to be pushed on investigations, anticoagulation and complications. Have crisp answers ready:

• Investigations: PT/INR on every prosthesis; a haemolysis screen (FBC, LDH, bilirubin, haptoglobin, reticulocytes and a blood film for schistocytes); cinefluoroscopy as a rapid first-line look at disc or leaflet motion; TOE, which is the key test for paravalvular leak, dehiscence or abscess because transthoracic echo is limited by metal reverberation; blood cultures and TOE if endocarditis is suspected.
• Mechanical versus bioprosthetic: the bedside discriminator is the click. Mechanical valves click, need lifelong warfarin and show bruising; bioprostheses are silent and off warfarin. Durability is roughly 20–30 years for mechanical valves versus 10–15 years for tissue valves, which is why the latter are chosen in the elderly, in high bleeding risk, and in women of childbearing potential.
• INR targets: an aortic tilting-disc valve targets 2–3, a mitral tilting-disc valve 2.5–3.5, and a ball-and-cage (Starr-Edwards) valve the highest at 3.5–4.5 because it is the most thrombogenic design. Bioprostheses need only about three to six months of anticoagulation post-operatively, then long-term antiplatelet, with no warfarin unless there is another indication such as AF.
• Anticoagulation rules: DOACs are contraindicated in mechanical valves — always warfarin. Periprocedural bridging is generally required (the exception being a bileaflet aortic valve with no other risk factors). In pregnancy, weigh warfarin's teratogenicity and late foetal loss against the higher thrombosis risk of LMWH.
• Complications and management: lifelong warfarin with dietitian input and echo follow-up; valve thrombosis treated with IV heparin if small or fibrinolysis/surgery if large; significant paravalvular leak closed percutaneously or by redo surgery; prosthetic valve endocarditis needing prolonged antibiotics with surgery for dehiscence or abscess; endocarditis prophylaxis, since a prosthetic valve is the highest-risk group; and valve-in-valve TAVI as an option for a failing bioprosthesis.

Common pitfalls and how to score

Most failures here are self-inflicted. Mis-timing the click against the carotid gives the wrong valve, so slow down and palpate deliberately. Calling a normal AVR flow murmur a leak or new stenosis loses credibility fast, as does dismissing an MVR systolic murmur as flow when it is a leak until proven otherwise. Forgetting to comment on anticoagulation status (bruising) and on the crispness of the sounds signals a candidate who recognised the valve but did not assess it.

In the viva, never suggest a DOAC for a mechanical valve, never miss endocarditis as the cause of a new leak, and don't overlook the vein-graft harvest scar or a marfanoid habitus. Score by narrating your logic out loud: 'audible closure click after the carotid upstroke with a midline scar, so a mechanical aortic valve replacement; the apex is undisplaced, suggesting the original lesion was stenotic; sounds are crisp with only a soft flow murmur and no collapsing pulse, so this valve appears to be functioning well; I would confirm with the INR and echo.' That structure is what separates a clear pass from a scrambled one.