This heart health applet calculates the Flutter Instability Parameter (FIP).

Example Image

The FIP is a metric that has been shown to forecast abnormal aneurysm growth in the thoracic aorta. It acts by pinpointing the presence of a 'flutter' instability in the cardiovascular tract. This instability is akin to the oscillation of a bridge in the wind - see the Tacoma Bridge Collapse or Humen Bridge for examples.

Flutter instability can kick in as high blood pressure drives flow through a very compliant vessel. This amplifies vibration modes at higher frequencies of the heartbeat cycle, analogous to how gusts of wind resonate with a rolling bridge. See this Nature Biomed Publication for more details.

Entering the relevant physiological properties in the form below and hitting the 'Calculate the FIP' button will return a rough estimate of the corresponding numerical FIP. FIP ≤ 0 indicates that no instability is detected - the flow through the blood vessel is stable. FIP > 0 denotes the presence of a flutter instability.

FIP > 0 has been clinically and experimentally associated with the abnormal, rapid growth of aortic aneurysms (see this arXiv paper). FIP > 0 has also been indicated in arrhythmia, left ventricular dysfunction, and general heart failure.

The graphic above visualizes the FIP for 3469 healthy volunteers who underwent a medical checkup between 2006 and 2009. One person exhibited FIP > 0, showcasing the utility of this metric as a screening tool for heart disease.

The FIP only measures the presence of flutter instability, which appears to be one important physical phenomenon associated with cardiovascular disease progression. This means that FIP < 0 does not rule out the presence of other factors which may also advance heart disease.

Normal
(< 120 mmHg) Elevated
(120 to 129 mmHg) Hypertension
(> 129 mmHg)

Reference range for humans

The Systolic Blood Pressure (SBP) is the max blood pressure in the arterial system measured during contraction of the left ventricle (systole). It is the larger, 'top number' reported typically in millimeters of mercury (120/80 mmHg). Noninvasive methods to measure the SBP include the upper arm cuff, volume clamp, or arterial tonometry: Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.

Normal
(< 80 mmHg) Hypertension
(≥ 80 mmHg)

Reference range for humans

The Diastolic Blood Pressure (DBP) is the minimum blood pressure in the arterial system measured during the rest phase when the left ventricle fills with blood (diastole). It is the 'bottom number' reported typically in millimeters of mercury (120/80 mmHg).

Bradycardia
(< 60 bpm) Normal resting HR
(60 to 100 bpm) Tachycardia
(> 100 bpm)

Reference range for humans

Heart Rate (HR) is the number of heart beats in a minute: Heart rate monitor

Normal
(≤ 4 cm) Aneurysmal
(> 4 cm) Average before repair
(> 5 cm)

Reference range for human ascending aorta

The Blood Vessel Diameter (BVD) is the diameter of the relevant, at-risk blood vessel or blood flow tract. Typically, BVD is measured via clinical imaging (echo, MRI, etc.): Arteries

Height is the distance from sole (bottom of feet) to crown (top of head). It is often measured during routine checkups: Physical Examination

Example Image

Reference range for humans - 4D Flow MRI - Mean: 6 to 7 m/s

PWV is the speed with which blood pulse waves travel through the arterial system. It is a well established surrogate marker for arterial wall stiffness. The arterial wall tends to stiffen (PWV increases) over time as people age. The PWV can be measured clinically from 4-D Flow MRI or via other commercial devices: Local Pulse Wave Velocity

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