In invasive hemodynamics, which unit is used to report pressures such as those in the aorta and left ventricle?

In invasive hemodynamics, which unit is used to report pressures such as those in the aorta and left ventricle?

• A. mmHg
• B. kPa
• C. psi
• D. cmH2O

Answer: (A)

Pressures measured inside the cardiovascular system, like in the aorta and left ventricle, are reported in millimeters of mercury (mmHg) because this unit comes from the historic mercury manometer still used as a reference standard. The idea is straightforward: the pressure is balanced by a column of mercury, and the height needed to balance that pressure gives you the reading in millimeters. That scale matches the typical arterial pressure range clinicians deal with, making numbers like about 120 systolic or around 80 diastolic easy to interpret at a glance. Other units exist, but they’re not the standard for invasive cardiac pressures. Kilopascals, pounds per square inch, or centimeters of water can be used in some contexts, but they require conversions to interpret the usual arterial and ventricular pressures, which can introduce confusion in fast decision-making. For perspective, 1 mmHg is about 133 pascals, 1 kPa is about 7.5 mmHg, 1 cmH2O is about 0.7356 mmHg, and 1 psi is about 68.95 mmHg. Keeping to mmHg keeps readings consistent with the long-standing clinical literature and practice.

Pressures measured inside the cardiovascular system, like in the aorta and left ventricle, are reported in millimeters of mercury (mmHg) because this unit comes from the historic mercury manometer still used as a reference standard. The idea is straightforward: the pressure is balanced by a column of mercury, and the height needed to balance that pressure gives you the reading in millimeters. That scale matches the typical arterial pressure range clinicians deal with, making numbers like about 120 systolic or around 80 diastolic easy to interpret at a glance.

Other units exist, but they’re not the standard for invasive cardiac pressures. Kilopascals, pounds per square inch, or centimeters of water can be used in some contexts, but they require conversions to interpret the usual arterial and ventricular pressures, which can introduce confusion in fast decision-making. For perspective, 1 mmHg is about 133 pascals, 1 kPa is about 7.5 mmHg, 1 cmH2O is about 0.7356 mmHg, and 1 psi is about 68.95 mmHg. Keeping to mmHg keeps readings consistent with the long-standing clinical literature and practice.