Structural heart intervention often defines success by the magnitude of correction achieved: greater valve area, lower residual gradient, and closer approximation to normal anatomy. Degenerative mitral stenosis (DMS) may require a different calculus. In a heavily calcified mitral apparatus, pursuing maximal expansion can exchange one difficult lesion for another - stenosis for severe iatrogenic regurgitation. The report by Inácio Cazeiro et al. in this issue brings this trade-off into sharp focus.1 For patients without a satisfactory surgical or transcatheter replacement option, the clinically relevant question may be not how widely the valve can be opened, but how much haemodynamic relief can be achieved without compromising valve competence.

DMS is not simply rheumatic mitral stenosis occurring in older patients. Its substrate is typically annular and basal leaflet calcification, producing a rigid, tunnel-like inflow obstruction without commissural fusion.2 This distinction explains both the limited role of conventional balloon commissurotomy and the difficulty of quantifying disease severity: transmitral gradient is flow-dependent, while direct planimetry and pressure half-time may be unreliable. DMS also clusters with advanced age, chronic kidney disease, and multimorbidity, and severe disease carries a poor prognosis.3 Surgery may be technically hazardous, whereas transcatheter mitral valve replacement in mitral annular calcification may be precluded by inadequate anchoring, excessive annular dimensions, or a prohibitive risk of left ventricular outflow tract obstruction.2,4 It is precisely because these anatomical contraindications to replacement leave no definitive alternative that a strategy aiming only to modify calcium, rather than replace the valve, becomes the relevant option. For these patients, an incomplete but safer result may be preferable to an anatomically ambitious but hazardous one.

The development of lithotripsy-assisted mitral valvuloplasty has gradually shifted the procedural objective. The first-in-human report by Eng et al. used peripheral intravascular lithotripsy (IVL) balloons to modify calcium before conventional balloon valvuloplasty.5 Subsequent reports, including that of Kassar et al., followed the same sequence: small peripheral IVL balloons prepared the calcified apparatus, after which a larger non-compliant balloon provided the definitive mechanical dilatation.6 In this first phase, IVL was an enabling technology rather than the treatment itself.

Alnasser et al. provided the most informative early clinical series of this strategy.7 Among 15 inoperable patients, the invasive mean transmitral gradient decreased from 14 to 6mmHg, and 14 of 15 evaluable patients reported symptomatic improvement at a median of 90 days. Yet only 53% met the prespecified endpoint of at least 50% gradient reduction without significant mitral regurgitation. More importantly, the gradient fell only from 14 to 12mmHg after IVL alone; most of the acute haemodynamic gain followed non-compliant balloon dilatation. Patients with at least moderate baseline regurgitation were excluded. The study therefore supported IVL-facilitated valvuloplasty in a stenosis-dominant but did not establish calcium modification alone as a sufficient intervention. Subsequent series broadened the feasibility data,8 and this early literature was later consolidated in a systematic review that also documented lower rates of new regurgitation with a lithotripsy-based approach.9

The MATRIX procedure then marked a second phase: larger and usually three simultaneous IVL balloons were used to maximise contact with the mitral annulus and dispense with conventional post-dilatation.10 In seven extreme-risk patients, the median gradient decreased from 9 to 3mmHg without worsening regurgitation or having major periprocedural complications. At 30 days, however, echocardiographic data were available in only six patients, and residual gradients ranged from below 5 to 13mmHg. This variability is instructive: technical feasibility does not guarantee a uniform haemodynamic response, and an asymptomatic patient may still have a substantial residual gradient.

Inácio Cazeiro et al. add a technically thoughtful Portuguese experience to this evolving field.1 Three patients underwent parallel IVL with two 12-mm balloons delivered through two deflectable sheaths across a single transseptal puncture, under conscious sedation and intracardiac echocardiographic guidance, without non-compliant balloon post-dilatation. Median echocardiographic gradient decreased from 16 to 7mmHg, invasive gradient from 11 to 7mmHg, and left atrial pressure from 32 to 17mmHg. No patient had an increase in mitral regurgitation grade, and two improved from New York Heart Association class III to II at 30 days. One transient junctional rhythm required temporary pacing; the third patient died after admission with a respiratory infection, an event adjudicated as unrelated to the procedure.

These observations are encouraging, but their meaning must be framed precisely. Three procedures without a major complication provide evidence of feasibility, not an estimate of safety. Likewise, acute gradient reduction is a biological signal, not proof of durable clinical effectiveness. The importance of the report lies elsewhere: it supports a procedural philosophy in which the operator stops after achieving an adequate haemodynamic result rather than pursuing maximal anatomical expansion with a high-pressure balloon.

This is not commissurotomy in the conventional sense. IVL does not remove calcium, restore normal leaflet architecture, or abolish the fixed annular component of obstruction. It modifies the mechanical properties of the calcified apparatus. The appropriate target is therefore not normality, but sufficiency: enough reduction in obstruction and left atrial pressure to improve the patient's clinical state, without causing severe regurgitation, annular injury, or haemodynamic collapse. In this context, haemodynamic palliation should not be regarded as therapeutic failure. For a patient with disabling symptoms and no definitive alternative, a partial but durable benefit may represent meaningful therapeutic success.

The difficult question is how to define’enough’. The lowest attainable gradient is unlikely to be the correct target. Mean transmitral gradient varies with heart rate, rhythm, cardiac output, regurgitant volume, and atrioventricular compliance. A fall in left atrial pressure is complementary but is also influenced by volume status and left atrial compliance. Assessment should therefore integrate standardised invasive and echocardiographic measurements, mitral regurgitation, pulmonary pressures, symptoms, and functional capacity. The possibility of a stiff left atrial phenotype is particularly relevant: reducing valvular resistance may lower the gradient without meaningfully reducing left atrial pressure or relieving symptoms when abnormal atrial compliance is the dominant contributor. Notably, the residual mean gradient of 7mmHg achieved in the present series still lies within the range compatible with significant stenosis, which underscores that the threshold defining an adequate result remains empirically unestablished — a question to be resolved by prospective data rather than a shortcoming of the approach.

Patient selection may ultimately matter more than the precise balloon configuration. The responsive phenotype is likely to depend on the distribution and depth of annular, leaflet, commissural, and subvalvular calcium; residual leaflet mobility; baseline flow; pulmonary vascular disease; right ventricular function; and competing comorbidities. Baseline regurgitation deserves scrutiny. Alnasser et al. excluded at least moderate regurgitation, whereas the series by Inácio Cazeiro et al. included one patient classified as having severe regurgitation before treatment.1,7 The absence of worsening in that patient is noteworthy but cannot establish safety in mixed mitral disease. In a systematic review pooling 40 lithotripsy-facilitated and 44 conventional valvuloplasty cases, new mitral regurgitation occurred in 2.5% versus 9.1% and reintervention in 2.5% versus 13.6%, respectively, consistent with the hypothesis that calcium modification, rather than high-pressure mechanical dilatation, better preserves valve competence.9

Less aggressive must not be confused with simple. The Inácio Cazeiro et al. procedure remained an off-label, technically demanding structural intervention requiring multiple vascular accesses, transseptal expertise, two steerable sheaths, cerebral protection, and a median procedural time of 184minutes.1 Optimal balloon number and sizing, the stopping rule for IVL, the selective role of adjunctive dilatation, cerebral embolic protection, management of a residual atrial septal defect, and surveillance for conduction disturbances all remain unsettled.

The next stage should therefore move from procedural ingenuity to disciplined evaluation. Prospective multicentre registries should apply a standardised anatomical classification, core-laboratory imaging, and prespecified haemodynamic conditions. Outcomes should extend beyond technical success and hospital discharge to validated health status, exercise capacity, heart-failure hospitalisation, days alive and out of hospital, reintervention, and survival. Serial imaging is needed to determine whether calcium microfracture produces durable compliance or merely temporary fissuring followed by restenosis. These data should clarify whether the procedure is best understood as destination therapy, a bridge to a later intervention, or symptom-oriented treatment when replacement is unrealistic.

Inácio Cazeiro et al. do not prove that less is more. They advance a more useful proposition: in carefully selected DMS, less may be enough. The field must now define what’enough’ means, identify the patients for whom it matters, and establish how long the benefit lasts.