Source: https://guthlabs.ai/docs/instruments/qtc-interval-calculator-education/

instrument / verified-clean

# QTc Interval Calculator (education)

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/qtc-interval-calculator-education/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/qtc-interval-calculator-education/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/qtc-interval-calculator-education/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/qtc-interval-calculator-education/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Biology, Medicine & Pharmacology (educational estimates only — every panel labeled not-medical-advice)

**Tranche**: tranche-5

**Evidence ID**: t5-024

**Ledger rows**: 1

No ledger note is attached.

## Review findings

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.

### Formula and scope findings

- 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.

### Unit assumptions

- 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).

## Boundary hardening

**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.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "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."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

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

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`