Critical Care & Hemodynamics
Aortic Pulsatility Index (API) Calculator
Calculate API by relating systemic pulse pressure to mean left-sided filling pressure.Need the full picture? Open the combined Swan-Ganz calculator →Enter measurements
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Calculated result
(SBP − DBP) / PAWP
Enter the required measurements to calculate a result.
Educational use only. This tool and its outputs do not constitute medical advice, diagnosis, or treatment and do not replace clinical judgment. Independently verify the inputs, equations, assumptions, units, and outputs, and confirm that the tool is appropriate for your intended use before relying on a result.
Watch: Aortic pulsatility index (API)
eddyjoemd · 2023 · 16 min
A video explanation of API, its calculation, proposed prognostic cutoffs, and limitations in cardiogenic shock and decompensated heart failure. Pair this 2023 discussion with the clinical context and references on this page.
What is Aortic pulsatility index (API)?
Aortic pulsatility index is systemic pulse pressure divided by mean PAWP. It has been investigated as a surrogate of LV performance and ventricular–arterial coupling in heart failure; it is not a direct pressure–volume-loop measurement.
How is it calculated?
(SBP − DBP) / PAWP
SBP and DBP are systemic systolic and diastolic blood pressures in mmHg. PAWP is mean pulmonary artery wedge pressure in mmHg, also called mean PCWP. The result is a ratio.
Result units: ratio.
Clinical interpretation
API below 1.45 has been associated with adverse outcomes in selected decompensated-HF, cardiogenic-shock, and transplant-waitlist populations. Other studies used different cutoffs, including 2.9. Interpret the threshold within the source cohort rather than calling all values below it abnormal.
Clinical considerations
API cannot be calculated at PAWP zero and becomes unstable when PAWP is very low. A large V wave, inaccurate wedge, or non-simultaneous blood pressure can materially change the result.
Arterial compliance, valve disease, and mechanical support influence pulse pressure. An increased API does not establish normal systolic function or adequate systemic perfusion.
References
- Belkin MN, Fudim M, Baratto C, et al. Standardization of Baseline and Provocative Invasive Hemodynamic Protocols for the Evaluation of Heart Failure and Pulmonary Hypertension. Circulation: Heart Failure. 2026;19:e000088. ↗
- Supplemental Table 1 — Advanced Hemodynamic Parameters (page 1; references on page 2) ↗
- Belkin MN, et al. Aortic Pulsatility Index: A Novel Hemodynamic Variable for Evaluation of Decompensated Heart Failure. J Card Fail. 2021;27:1045–1052. ↗
- Grinstein J. Advanced hemodynamics for prognostication in heart failure: the pursuit of the patient-specific tipping point. Front Cardiovasc Med. 2024. ↗
- Dynamic assessment of left ventricular coupling and myocardial reserve in patients with cardiogenic shock. ESC Heart Fail. 2024. ↗
- Belkin MN, et al. Association between listing hemodynamics and heart transplantation waitlist outcomes: an analysis of the Scientific Registry of Transplant Recipients. J Heart Lung Transplant. 2026;45:350–362. Published online November 21, 2025. ↗
Independently created by MendelMD. These educational calculators are not provided, endorsed, or independently validated by the American Heart Association.