Methods and apparatus for estimation of ventricular afterload based on ventricular pressure measurements

A method of deriving an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• determining the peak positive pressure value Pb, the peak negative derivative pressure dP/dtNP, and the decreasing pressure Pc associated with the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• determining the sample time tb of peak positive pressure, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• and
• calculating an index β of the slope of the early ejection pressure in the blood ejection phase in accordance with the formula β=(Pc−Pb)/(tc−tb), wherein the severity of ventricular afterload is proportional to the magnitude of the index β.

In an implantable heart monitor adapted to be implanted in a patient's body and comprising a pressure sensor coupled with pressure signal processing circuitry and memory for data storage, a method of deriving an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• operating the pressure sensor to obtain a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• determining the peak positive pressure value Pb, the peak positive derivative pressure dP/dtPP and the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• determining the sample time tb of peak positive pressure, the sample time ta of the peak positive derivative pressure dP/dtPP, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• calculating an index α of the relative timing of peak positive pressure Pb in the blood ejection phase in accordance with the formula α=(tb−ta)/(tc−ta), wherein the severity of ventricular afterload is proportional to the value of index α in the range between 0 and 1;
• and
• storing the calculated index α in data storage memory.

In an implantable heart monitor adapted to be implanted in a patient's body and comprising a pressure sensor coupled with pressure signal processing circuitry and memory for data storage, a method of deriving an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• determining the peak positive pressure value Pb, the peak negative derivative pressure dP/dtNP, and the decreasing pressure Pc associated with the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• determining the sample time tb of peak positive pressure, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• and
• calculating an index β of the slope of the early ejection pressure in the blood ejection phase in accordance with the formula β=(Pc−Pb)/(tc−tb), wherein the severity of ventricular afterload is proportional to the magnitude of the index β;
• and storing the calculated index β in data storage memory.

In an implantable medical device adapted to be implanted in a patient's body for delivering a therapy in accordance with adjustable therapy delivery operating modes and parameters comprising a pressure sensor coupled with pressure signal processing circuitry and therapy delivery means for delivering a therapy, a method of deriving an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• determining the peak positive pressure value Pb, the peak positive derivative pressure dP/dtPP and the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• determining the sample time tb of peak positive pressure, the sample time ta of the peak positive derivative pressure dP/dtPP, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• calculating an index α of the relative timing of peak positive pressure Pb in the blood ejection phase in accordance with the formula α=(tb−ta)/(tc−ta), wherein the severity of ventricular afterload is proportional to the value of index α in the range between 0 and 1;
• and
• adjusting one of a therapy delivery operating mode or parameter to minimize the value of index α.

In an implantable medical device adapted to be implanted in a patient's body for delivering a therapy in accordance with adjustable therapy delivery operating modes and parameters comprising a pressure sensor coupled with pressure signal processing circuitry and therapy delivery means for delivering a therapy, a method of deriving an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• determining the peak positive pressure value Pb, the peak negative derivative pressure dP/dtNP, and the decreasing pressure Pc associated with the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• determining the sample time tb of peak positive pressure, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• and
• calculating an index β of the slope of the early ejection pressure in the blood ejection phase in accordance with the formula β=(Pc−Pb)/(tc−tb), wherein the severity of ventricular afterload is proportional to the magnitude of the index β;
• and
• adjusting one of a therapy delivery operating mode or parameter to minimize the magnitude of index β.

Apparatus that derives an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• means for obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• means for determining the peak positive pressure value Pb, the peak positive derivative pressure dP/dtPP and the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• means for determining the sample time tb of peak positive pressure, the sample time ta of the peak positive derivative pressure dP/dtPP, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• and
• means for calculating an index α of the relative timing of peak positive pressure Pb in the blood ejection phase in accordance with the formula α=(tb−ta)/(tc−ta), wherein the severity of ventricular afterload is proportional to the value of index α in the range between 0 and 1.

Apparatus that derives an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• means for obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• means for determining the peak positive pressure value Pb, the peak negative derivative pressure dP/dtNP, and the decreasing pressure Pc associated with the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• means for determining the sample time tb of peak positive pressure, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• and
• means for calculating an index β of the slope of the early ejection pressure in the blood ejection phase in accordance with the formula β=(Pc−Pb)/(tc−tb), wherein the severity of ventricular afterload is proportional to the magnitude of the index β.

In an implantable heart monitor adapted to be implanted in a patient's body and comprising a pressure sensor coupled with pressure signal processing circuitry and memory for data storage, apparatus that derives an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• means for operating the pressure sensor to obtain a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• means for determining the peak positive pressure value Pb, the peak positive derivative pressure dP/dtPP and the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• means for determining the sample time tb of peak positive pressure, the sample time ta of the peak positive derivative pressure dP/dtPP, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• means for calculating an index α of the relative timing of peak positive pressure Pb in the blood ejection phase in accordance with the formula α=(tb−ta)/(tc−ta), wherein the severity of ventricular afterload is proportional to the value of index α in the range between 0 and 1;
• and
• means for storing the calculated index α in data storage memory.

In an implantable heart monitor adapted to be implanted in a patient's body and comprising a pressure sensor coupled with pressure signal processing circuitry and memory for data storage, apparatus that derives an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• means for obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• means for determining the peak positive pressure value Pb, the peak negative derivative pressure dP/dtNP, and the decreasing pressure Pc associated with the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• means for determining the sample time tb of peak positive pressure, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• means for calculating an index β of the slope of the early ejection pressure in the blood ejection phase in accordance with the formula β=(Pc −Pb)/(tc−tb), wherein the severity of ventricular afterload is proportional to the magnitude of the index β;
• and
• means for storing the calculated index β in data storage memory.

In an implantable medical device adapted to be implanted in a patient's body for delivering a therapy in accordance with adjustable therapy delivery operating modes and parameters comprising a pressure sensor coupled with pressure signal processing circuitry and therapy delivery means for delivering a therapy, apparatus that derives an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• means for obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• means for determining the peak positive pressure value Pb, the peak positive derivative pressure dP/dtPP and the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• means for determining the sample time tb of peak positive pressure, the sample time ta of the peak positive derivative pressure dP/dtPP, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• means for calculating an index α of the relative timing of peak positive pressure Pb in the blood ejection phase in accordance with the formula α=(tb−ta)/(tc −ta), wherein the severity of ventricular afterload is proportional to the value of index α in the range between 0 and 1;
• and
• means for adjusting one of a therapy delivery operating mode or parameter to minimize the value of index β.

In an implantable medical device adapted to be implanted in a patient's body for delivering a therapy in accordance with adjustable therapy delivery operating modes and parameters comprising a pressure sensor coupled with pressure signal processing circuitry and therapy delivery means for delivering a therapy, apparatus that derives an index of ventricular afterload presenting resistance to ejection of blood from a ventricle during a blood ejection phase comprising:

• means for obtaining a set of ventricular pressure values of blood pressure within a ventricle at sample times during the blood ejection phase of the ventricle;
• means for determining the peak positive pressure value Pb, the peak negative derivative pressure dP/dtNP, and the decreasing pressure Pc associated with the peak negative derivative pressure dP/dtNP from the set of ventricular pressure values;
• means for determining the sample time tb of peak positive pressure, and the sample time tc of the peak negative derivative pressure dP/dtNP from the sample times associated with the set of ventricular pressure values;
• means for calculating an index β of the slope of the early ejection pressure in the blood ejection phase in accordance with the formula β=(Pc −Pb)/(tc −tb), wherein the severity of ventricular afterload is proportional to the magnitude of the index β;
• and
• means for adjusting one of a therapy delivery operating mode or parameter to minimize the magnitude of index β.