Cardiology Unit Converter

Cardiology evolved through contributions from multiple disciplines — classical physiology used CGS units (dyne, cm, s); clinical medicine adopted mmHg for pressure (atmospheric convention); European scientific literature adopted SI units (kPa, Pa); the catheterisation lab adopted Wood Units for convenience (they are directly computed from measured haemodynamic variables without unit conversion); biochemistry labs in different countries standardised to different measurement frameworks. Globalisation of medical literature and digital health records is gradually increasing pressure to standardise, but the diversity remains clinically important for the foreseeable future.

Exactly: 1 mmHg = 133.3224 Pa = 0.1333224 kPa. For clinical purposes: 1 kPa = 7.5006 mmHg (≈ 7.5 mmHg). Practical rule: multiply mmHg by 0.133 to get kPa; multiply kPa by 7.5 to get mmHg. For blood pressure, the maximum rounding error using these approximations is less than 1 mmHg at clinically relevant values.

Wood Units (WU or Harvey Cushing Units in older literature) are a pulmonary vascular resistance unit defined as (mPAP - PCWP) / CO where mPAP is mean pulmonary artery pressure in mmHg, PCWP is pulmonary capillary wedge pressure in mmHg, and CO is cardiac output in L/min. Because CO is already measured in L/min and pressures in mmHg, WU requires no unit conversion — making it convenient in the catheterisation laboratory. Normal PVR is 0.5–2.5 WU; PVR > 3 WU is significant; PVR > 5 WU with poor vasoreactivity may preclude cardiac transplantation.

Triglycerides have a molecular weight of approximately 885.4 g/mol (based on a typical mixed triglyceride). The conversion factor is: mg/dL = mmol/L x 88.57; mmol/L = mg/dL / 88.57. Normal triglycerides < 1.7 mmol/L = <150 mg/dL; borderline high 1.7–5.65 mmol/L = 150–500 mg/dL; very high >5.65 mmol/L = >500 mg/dL (risk of pancreatitis). Do not use the cholesterol factor (38.67) for triglycerides.

High-sensitivity troponin assays (introduced from approximately 2010) report in ng/L (nanograms per litre), which is numerically 1000 times smaller than the ng/mL values from conventional assays. A hsTnT of 52 ng/L = 0.052 ng/mL. If a clinician reads '52' and assumes ng/mL (the old unit), they will believe the troponin is 1000-fold higher than it is. Conversely, a conventional troponin of 0.5 ng/mL = 500 ng/L — far above the high-sensitivity assay upper reference limit. Always confirm units with your laboratory and verify against the assay-specific reference range.

Pulmonary capillary wedge pressure (PCWP, also called pulmonary artery occlusion pressure, PAOP) is measured by inflating the balloon of a pulmonary artery catheter, occluding a pulmonary artery branch and thus measuring back-pressure approximating left atrial pressure. Normal PCWP is 6–12 mmHg = 0.8–1.6 kPa = 8.2–16.3 cmH2O. PCWP >18 mmHg indicates elevated left atrial pressure (pulmonary oedema threshold); >25 mmHg is severe. PCWP is used in the haemodynamic classification of pulmonary hypertension: pre-capillary PH has PCWP ≤15 mmHg; post-capillary PH has PCWP >15 mmHg.

1 mmHg = 1.3596 cmH2O. Therefore: cmH2O / 1.36 = mmHg; mmHg x 1.36 = cmH2O. Normal CVP is 2–8 mmHg = 2.7–10.9 cmH2O. Older bedside CVP manometers read in cmH2O (water column); electronic transducers read in mmHg. A CVP of 10 cmH2O = 7.35 mmHg. This distinction matters when comparing readings from different monitoring systems or interpreting older literature.

Cholesterol has a molecular weight of 386.65 g/mol. The mmol/L to mg/dL conversion for any substance is: mg/dL = mmol/L x (molecular weight / 10). For cholesterol: mmol/L x 386.65/10 = mmol/L x 38.665 ≈ 38.67. This same factor applies to LDL-C, HDL-C, non-HDL-C, and total cholesterol because they are all measured as cholesterol mass. Lipoprotein particles themselves are much larger molecules, but the mass reported is the cholesterol content of those lipoproteins.