Method and system for determining physiological variables

Details Method and system for determining physiological variables Method and system for determining physiological variables

2001-08-24

2003-05-20

Nasser, Robert L. (Department: 3736)

Surgery

Diagnostic testing

Cardiovascular

C600S485000, C600S561000

Reexamination Certificate

active

06565514

ABSTRACT:

The present invention relates to monitoring of physiological variables, and in particular it relates to a method, a system and an arrangement for monitoring, determining by measurement and calculation and graphically displaying physiological variables related to blood pressure. A user interface system, including a monitor having an interactive graphical display for presentation of said physiological parameters and selectable functions, is provided.
BACKGROUND OF THE INVENTION
For the purpose of monitoring physiological variables, such as arterial blood pressure, there are monitoring systems available comprising graphical displays, on which variations of the parameter of interest over time can be displayed and analyzed.
For determining the so called Myocordial Fractional Flow Reserve, FFR
myo
, two pressures must be measured, namely the arterial pressure before a stenosis, and the pressure distally of the stensosis.
FFR
myo
is defined as maximum myocordial flow in the presence of a stenosis in the supplying epicardial coronary artery, divided by normal maximum flow. FFR
myo
is calculated by means of the formula:
FFR
myo
=(
P
d
−P
v
)/(
P
a
−P
v
)=
P
d
/P
a
, wherein
P
d
=arterial pressure at maximum hyperemia;
P
a
=distal coronary pressure at maximum hyperemia;
P
v
=central venous pressure at maximum hyperemia.
It is a lesion-specific index of the functional severity of the stenosis and can be obtained by intracoronary pressure measurement by the guidewire-mounted pressure sensor. During PTCA, balloon angioplastic or Percutaneaus Transluminal Coronary Angioplastic, the separate contributions of coronary and collateral blood flow to maximum myocordial perfusion can be obtained.
FFR
myo
has unique features:
Independent of changes in blood pressure, heart rate and contractility.
Clear breakpoint of 0.75 between significant and non-significant stenoses.
No control artery is needed: applicable in multivessel disease.
Easily and rapidly obtained by intracoronary pressure measurements at maximum vasodilation.
There are monitor systems available for the determination of FFR
myo
(e.g. WaveMap, Cardiometrics Inc. USA), but they do not have a graphical interface, only numerical displays showing measured values.
SUMMARY OF THE INVENTION
Thus, an object of the invention is to provide improved systems for monitoring physiological variables, in particular for pressure measurements in the coronary vessels, and especially for the reliable determination of Fractional Flow Reserve, FFR
myo
.
Another object is to provide methods for calculation of average pressure values and detection of heart beat using pressure signals from the measurements.
The present invention monitors, determines by measuring and calculation physiological variables related to blood pressure, wherein at least two physiological variables, arterial pressure P
a
and distal coronary pressure P
d
, is detected by and derived from a guidewire-mounted pressure sensor. Myocordial Fractional Flow Reserve (FFR
myo
) is determined by calculating a ratio P
d
/P
a
from said measured physiological variables (P
a
, P
d
) and a graph is formed and displayed of the data resulting from said calculation. The invention also provides an Interactive graphical User Interface system for controlling the performance of and for displaying, in at least one screen on a display in a monitoring unit, intermediate and final results of said invented method.
One advantages of the present invention are that the FFR
myo
-value has a clear breakpoint of 0.75 between significant and non-significant stenoses. This value is easily and rapidly obtained by intracoronary pressure measurements at maximum vasodilation by use of the invented method and system.
Another advantage is that the Interactive graphical User Interface system provides a user-friendly handling.


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