ECG interval · LIVE

QTc Bazett vs Fridericia

QTc

Compute heart-rate-corrected QT using Bazett or Fridericia. The formula argument is required.

LIVE $0.005 USDC GET /api/calc/qtc

Markdown: /docs/qtc.md · Canonical: https://magentlab.com/docs/qtc

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Compute heart-rate-corrected QT using Bazett or Fridericia. The formula argument is required.

When to use

When an agent must not apply Bazett silently. Callers must choose formula=bazett or formula=fridericia.

When not to use

• Not a diagnosis and not a drug-safety recommendation.
• formula is required. magent does not pick Bazett or Fridericia.
• Fridericia has no verified DOI in this record; citation is the 1920 Acta Med Scand paper.

Formula

QTc_ms = QT_ms / sqrt(RR_s)

Citation

Title

An analysis of the time-relations of electrocardiograms

Authors

Bazett HC

Source

Heart. 1920;7:353-370

DOI

none

Worked example

Also searched as

• QTc Bazett vs Fridericia
• Bazett formula
• Fridericia QTc
• corrected QT

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/qtc?qt_ms=400&heart_rate_bpm=80&formula=bazett

Full URL: https://api.magentlab.com/api/calc/qtc?qt_ms=400&heart_rate_bpm=80&formula=bazett

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/qtc?qt_ms=400&heart_rate_bpm=80&formula=bazett"

Parameters

Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/qtc Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 PREVIEW

• 1 to 25 items. Each item uses the same keys as the GET query parameters.
• POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
• The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
• HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
• Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
• x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request (fixture)

{
  "items": [
    {
      "formula": "bazett",
      "heart_rate_bpm": "80",
      "qt_ms": "400"
    },
    {
      "formula": "bazett",
      "heart_rate_bpm": "80",
      "qt_ms": "400"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/qtc",
  "items": [
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Bazett HC",
        "doi": null,
        "id": "bazett-1920",
        "source": "Heart. 1920;7:353-370",
        "title": "An analysis of the time-relations of electrocardiograms"
      },
      "formula": "bazett",
      "formula_expression": "QTc_ms = QT_ms / sqrt(RR_s)",
      "heart_rate_bpm": 80,
      "qtc_ms": 461.9,
      "qt_ms": 400.0,
      "rr_s": 0.75
    },
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Bazett HC",
        "doi": null,
        "id": "bazett-1920",
        "source": "Heart. 1920;7:353-370",
        "title": "An analysis of the time-relations of electrocardiograms"
      },
      "formula": "bazett",
      "formula_expression": "QTc_ms = QT_ms / sqrt(RR_s)",
      "heart_rate_bpm": 80,
      "qtc_ms": 461.9,
      "qt_ms": 400.0,
      "rr_s": 0.75
    }
  ]
}

Response

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Bazett HC",
    "doi": null,
    "id": "bazett-1920",
    "source": "Heart. 1920;7:353-370",
    "title": "An analysis of the time-relations of electrocardiograms"
  },
  "formula": "bazett",
  "formula_expression": "QTc_ms = QT_ms / sqrt(RR_s)",
  "heart_rate_bpm": 80,
  "qtc_ms": 461.9,
  "qt_ms": 400.0,
  "rr_s": 0.75
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• Corrected calcium — Compute Payne albumin-corrected calcium from total calcium and albumin.

Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /docs/mcp.

Guarantees

• HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON.
• exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
• HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
• Execution is timeout-bounded and concurrency-capped.
• Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.