QTc Interval Calculator (education) mechanism

Model scope

The mathematical formulas are standard, but the specification needs an explicit input contract for heart rate versus RR, a required unit/conversion rule, valid ranges, and defined QTc reference thresholds. The existing educational/not-medical-advice label is appropriate and should remain prominent; QTc output must not be presented as a clinical interpretation.

• The Bazett and Fridericia formulas are standard when QT and RR are expressed in the same time units, but the specification does not define how a heart-rate input is converted to RR.
• The output claims a prolonged-flag reference, but no threshold definition is provided; thresholds can depend on sex, age, methodology, and clinical convention.

Units and conventions

• QT and RR must use the same time unit; using milliseconds for both is valid because the ratio is dimensionless, and the resulting QTc is reported in milliseconds.
• If heart rate is supplied in beats per minute, RR must be calculated as RR(ms)=60000/heart_rate or RR(s)=60/heart_rate before applying either formula.
• The square-root and cube-root operations apply to the dimensionless RR ratio after normalizing RR to 1 second: Bazett QTc=QT(s)/sqrt(RR(s)) and Fridericia QTc=QT(s)/RR(s)^(1/3).

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "QT_ms": 400,
    "RR_ms": 1000
  },
  "expected_outputs": {
    "QTc_Bazett_ms": 400,
    "QTc_Fridericia_ms": 400
  },
  "working": "Convert: QT=400 ms=0.400 s; RR=1000 ms=1.000 s. Bazett: 0.400/sqrt(1.000)=0.400/1.000=0.400 s=400 ms. Fridericia: 0.400/(1.000)^(1/3)=0.400/1.000=0.400 s=400 ms."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The zero-RR input produces undefined results and must be rejected. The specification also leaves QT/RR unit conventions and prolonged-reference thresholds insufficiently defined, allowing materially different results or an indeterminate prolonged flag.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json