Accelerometer-based method for cardiac function and therapy assessment

Abstract

A method for determining a change in function of a patient's heart that includes the steps of collecting seismocardiographic (SCG) data corresponding to a heart motion of the patient's heart; determining a hemodynamic parameter based on the SCG data; and comparing the parameter with a predetermined measure of cardiac performance. The system used with the method includes one or more accelerometer sensors, a computer data analysis module, and may also include a 2D and 3D visual graphic display of analytic results, i.e. a Ventricular Contraction Map.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part of, and claims priority to, U.S. patent application Ser. No. 10 / 629,881, filed on Jul. 29, 2003, which claims priority to U.S. Provisional Patent Application Ser. No. 60 / 399,028, which was filed on Jul. 29, 2002 by the same inventors.BACKGROUND OF INVENTION [0002] 1. Field of Invention [0003] The present invention relates generally to accelerometer use and to methods for determining a change in function of a patient's heart. [0004] 2. Description of Related Art [0005] Heart failure afflicts about twenty-five million people worldwide, with about two million new cases diagnosed each year. In the United States, hospitalization for heart failure amounts to more than 6.8 million days a year, and the total cost of treatment is more than $38 billion annually, which is increasing as the population ages. The prevalence of congestive cardiac failure is also increasing due to improved survival from both m...

AI Technical Summary

Benefits of technology

[0021] An additional objective of the present invention is to determine the optimal site(s) of lead implantation for cardiac resynchronization therapy, and, therefore, enhance the effectiveness of the therapy.

[0025] The second expected change is in the wave that represents early filling of the ventricle. Normally the amplitude of this wave does not change because the heart muscle adapts and can accept the increase in blood with exercise readily. With marked narrowing or blockage of one or more coronary artery, the amplitude of this wave, called the rapid filling wave, becomes larger.

[0026] Moreover, continuous monitoring with an accelerometer can be used to assess a change in cardiac contractility as an indication of decreased cardiac function, cardiac instability or infarction during anesthesia or other surgical events. Continuous monitoring with an accelerometer could also be used in patients with suspected or acute myocardial infarction for detection of decrease in heart function so that pharmacological or other measures can be promptly instituted to prevent further deterioration in cardiac function that could result in an extension of the area of heart muscle damage or even prevent cardiac arrest.

[0027] It also is possible that accelerometer patterns will help identify patients who would be likely to benefit from CRT by showing a recognizable pattern of no or minimal desynchronization (in which case CRT would not be beneficial) or marked desynchronization (in which case CRT would be most helpful).

[0028] The invention also may be used during an electrophysiology study (EPS) to help determine if CRT is an effective treatment for a particular patient. During an EPS, catheters are placed in the heart and electrically stimulate different areas to identify abnormalities in the heart's conductive system. According to the present invention, an accelerometer measures the seismocardiographic behavior at different stimulation locations. The resulting data is analyzed to determine whether the patient only needs left ventricular or biventricular pacing or if CRT would be beneficial at all. If CRT is found to be an effective treatment, the cardiac pacing device could be implanted during the same procedure with the leads placed at an optimal location. Since one third of patients who have left ventricular or biventricular pacing do not improve with this procedure, the accelerometer-guided ventricular pacing could diminish this high incidence of ineffectiveness. Thus, the method and system of the invention can provide reliable prediction whether the patients would be candidates for CRT as well as provide optimal location for pacing lead placement during the implantation. Also, optimal settings for delay between onset of right and left ventricular contraction could be determined.

Problems solved by technology

Nevertheless, many patients remain markedly symptomatic despite maximal medical therapy.

Furthermore, patients with left ventricular failure are at an increased risk of progressive heart failure or sudden death.

In some heart patients, congestive cardiac failure affects the synchronous beating of the ventricles.

Accordingly, the left ventricle is not able to pump blood efficiently to supply the body with needed oxygen and nutrients.

This greatly reduces the efficiency of the left ventricle in patients whose hearts are already damaged.

Many patients with heart failure have poor electrical conduction in the heart that results in a pattern called left bundle branch block (LBBB) or intraventricular conduction delay.

The delay in aortic valve closure leads to a relative decrease in the duration of left ventricle diastole.

In patients with LBBB, prolonged depolarization or abnormal depolarization may result in regional myocardial contraction into early diastole, causing a delay of mitral valve opening with prolongation of left ventricle isovolumic relaxation time of up to 300% and shortened left ventricle filling time.

Further, left ventricle intraventricular conduction delay may add significantly to dyssynchrony, particularly in ischemic heart disease.

While the results have been positive, most studies have shown that approximately 30% of patients do not obtain any measurable benefit from the therapy.

Yet, the exact and best position for each catheter position is difficult to determine at the time of insertion.

In fact, there are no physiological means to determine the best site at the time of lead placement except possibly the use of echocardiography, which is time consuming and poses a problem in keeping the operative field sterile.

In addition, it is difficult to predict the effectiveness of CRT before the insertion of the cardiac pacing device.

However, the decrease in the QRS duration does not correlate well with the improvement of cardiac function in some patients.

However, these parameters cannot be evaluated in real time and do not provide information that physicians need to know at the time of lead and device implantation to determine if the patient will benefit from CRT.

Another problem encountered, particularly with the use of dual-chamber pacemakers, is the proper setting of the so-called “A-V delay interval.” Basically, the A-V delay interval refers to the time interval between a ventricular stimulation pulse and a preceding atrial depolarization.

Because the sequence of atrial and ventricular pacing is vital to the efficiency of the heart as a pump, a non-optimal A-V delay interval can seriously impact heart performance.

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