Pulmonary Arterial Hypertension: Better on Paper, Unresolved at the Bedside
Fourteen months into treatment, her numbers show she's winning. Whether her symptoms match depends on which functional class you believe — and the two readings point toward genuinely different next steps.
M.R., a 43-year-old woman, became a grandmother eight months ago and set out, half as a promise to herself and half as a test, to build back enough stamina to keep up with a toddler on the floor. She had been previously healthy apart from longstanding hypothyroidism, well controlled for over a decade on a stable dose of levothyroxine, so when she found herself stopping on the stairs at her daughter's apartment to catch her breath, she assumed it was simple deconditioning. It wasn't. A year of progressive exertional dyspnea led to an echocardiogram showing a markedly elevated estimated pulmonary artery pressure, and a right heart catheterization fourteen months ago confirmed pre-capillary pulmonary hypertension — mean PAP 42 mmHg, PVR 6.8 Wood units, wedge pressure 10 mmHg — with a full secondary-cause workup (connective-tissue serologies, HIV testing, a ventilation- perfusion scan for chronic thromboembolic disease, left heart imaging) returning negative and acute vasoreactivity testing negative. The diagnosis was idiopathic PAH, WHO Group 1, and at that first assessment she carried enough intermediate-risk features — WHO-FC III, a 6MWD of 320 meters, an NT-proBNP of 850 pg/mL — that she was started on initial oral combination therapy, ambrisentan and tadalafil together, rather than either drug alone.
Fourteen months later, most of what can be measured has moved in the right direction. Her 6MWD is now 445 meters. Her NT-proBNP has fallen to 210 pg/mL, comfortably inside the low-risk range. A repeat RHC shows a mean PAP of 34 mmHg and an improved cardiac index — real hemodynamic progress, though her PVR, at 4.2 Wood units, is still well above normal and is not one of the variables the follow-up risk score actually counts. What resists easy classification is the one variable that isn't a number: asked directly, she describes gardening for twenty minutes without trouble but still needing to stop partway up the same stairs that first brought her in, and she isn't sure herself whether that counts as an occasional limitation or a real one. WHO-FC assessment turns on exactly this kind of self-report, and her answer sits close enough to the II/III boundary that two clinicians examining her the same week could reasonably write down different letters — and under the current risk-stratification model, that letter alone is enough to move her between continuing what's working and adding a third drug.
Reassessment at fourteen months
The follow-up score has three variables — functional class, walk distance, and natriuretic peptide — and two of them have moved cleanly into low-risk territory. Her PVR has fallen from 6.8 to 4.2 Wood units on top of that, which is real hemodynamic improvement, though it isn't one of the three. I'd call her WHO-FC II. "Stops on stairs" is not the same complaint as the class III limitation she described at diagnosis, when she couldn't get through a grocery trip without resting twice. Functional class is the softest of the three, precisely because it's the one most sensitive to how the question gets asked, and I'm not ready to let one ambiguous stairs comment overturn two objective signals that both point the same direction.
I'd weight it differently. The registry data behind the treat-to-target approach here are explicit that patients who fall short of clearly low-risk at first reassessment carry a measurably worse long-term survival curve than patients who reach it — and by the numbers on her repeat RHC alone, she hasn't reached it. I know the four-strata tool doesn't count PVR — but the guideline that recommends the tool says in the same breath to take additional variables into account as necessary, and a PVR still north of four Wood units is exactly the kind of variable that clause exists for. I don't think we need her stairs comment to justify escalating — the hemodynamics already do that on their own.
I'd push back on treating the functional-class question as the deciding vote here at all. Grant her WHO-FC II and the tool does call her low risk — I'm saying the tool was built as a simplification, and it discards the one measurement we went to the trouble of a right heart catheterization to obtain.
Before either of you commits her to a direction: riociguat is off the table regardless of how this resolves. It's specifically contraindicated in combination with a PDE5 inhibitor, and she's already on tadalafil — the combination has produced clinically significant hypotension in trial data, not just a theoretical concern. If escalation is the answer, the actual next drug is a prostacyclin-pathway agent. Oral selexipag is the least burdensome entry point, but it needs a slow uptitration, because the class-wide side effects — headache, jaw pain, flushing, diarrhea — are dose-limiting for a real fraction of patients, not a formality. That's not a small addition to hand her on the strength of one ambiguous sentence about stairs.
I'd rather get one more objective read before either of us decides anything. CPET gives a peak oxygen consumption and a ventilatory-efficiency number that doesn't depend on how she describes her own symptoms — and I'd guess you'd each accept it as tie-breaking evidence in a way neither of you is going to accept the other's read of the same stairs comment.
Agreed within the visit: order CPET, continue ambrisentan and tadalafil unchanged in the meantime, and reconvene once the result is back rather than deciding from the stairs comment alone.
Not agreed, and the reason the plan carries a branch point rather than a single expectation:
A reduced peak oxygen consumption or a clearly abnormal ventilatory-efficiency slope corroborates WHO-FC III, and oral selexipag is added — beginning at the lowest dose, with a structured titration schedule to manage the class-wide side effects.
A normal or near-normal exercise test argues for WHO-FC II despite the isolated stairs complaint, and the current regimen continues unchanged, with reassessment — including repeat hemodynamics — at three to four months rather than immediately.
The cardiologist's position — that the PVR alone, independent of functional class, already argues for escalation — didn't fully carry the room; the pulmonary hypertension specialist and the pharmacologist held that one hemodynamic parameter sitting just outside a threshold isn't the same order of evidence as a symptom-limited exercise test, and that a drug carrying this much day-to-day burden deserves that higher bar before it's added. Nobody set a preference between the two functional-class readings; the CPET result was made the tie-breaker instead.