WO1997039798A1

WO1997039798A1 - Implantable heart stimulator

Info

Publication number: WO1997039798A1
Application number: PCT/EP1997/001989
Authority: WO
Inventors: Dietmar Wietholt
Original assignee: Dietmar Wietholt
Priority date: 1996-04-20
Filing date: 1997-04-19
Publication date: 1997-10-30
Also published as: DE19615844A1; DE19615844B4

Abstract

The invention relates to a heart stimulator with an electric circuit which can be used to produce a sequence of stimulation pulses (SI) of the frequency fs(t) when one or the last of a plurality of successive extra systole(s) (ES) not observing the natural frequency fe is detected. After the extra systole occurs, said sequence starts at a higher frequency fsi in relation to the earlier natural frequency fe detected after a programmable period ti which is between 50 and 100 % of an average period tmean between two natural frequency systoles, and the frequency fs subsequently falls steadily until the frequency fs(t) falls below the natural frequency fe to a frequency fsub or ends with the frequency fe.

Description

Implantable cardiac stimulation device

The invention relates to an implantable cardioverter defibrillator and / or pacemaker for stimulating the heart muscle (cardiac stimulation device), with at least one electrode to be connected to the heart muscle, a programmable electrical circuit for generating stimulation pulse sequences with which the electrode can be acted upon, and with an electronic memory connected to the said circuit, with which the electrical processes inherent in the heartbeat, in particular the systoles and their natural frequency f, can be registered and stored over several periods of the heartbeat, the electrical circuit evaluating the stored electrical processes and corresponding sequences of delivers antitachycardial and antibradycardial stimulation pulses.

The two main types of cardiac stimulation devices, namely cardioverter-defibrillators and so-called cardiac pacemakers (Pacer), traditionally work with types of stimulation which are used after the occurrence of tachyarrhythmias and cardiac flutter.

Such cardiac stimulation devices in the form of cardioverter defibrillators and / or pacers with anti-tachycardial or anti-bradycardial stimulation modes are known, for example according to US Pat. No. 4,052,991 and US Pat. No. 3,857,399. The stimulation devices according to the aforementioned state of the art _However, technology emits stimulation impulses which start with the antitachycardial function after the occurrence of tachycardia with a time delay (delay) of approx. 1 s.

5

They act in unison, i.e. the period of the

The stimulation pulse sequence is shorter than the period of the

Systoles in tachycardia. This shortened pulse sequence is intended to "intercept" the extrasystoles ₀ that start with tachycardia. When considering the systole frequencies occurring in tachycardia, the "delay" time is followed by a continuous stimulation with a frequency f that is higher than the natural frequency f.

This frequency f is mainly kept constant. 5

The task is to specify a cardiac stimulation device that can prevent the occurrence of tachycardia in advance.

_Q This object is achieved by a cardiac stimulation device, namely a cardioverter defibrillator or a cardiac pacemaker of the type mentioned at the outset, which is characterized in that the electrical circuit upon detection of one or the last of 5 several consecutive ones which do not comply with the natural frequency f Extrasystole (n) a sequence of stimulation pulses of the frequency f (t) can be generated, which after the occurrence of the extrasystole compared to the determined previous natural frequency f after a programmable time interval 0, which measures between 50 and 100% of an average time interval t between two natural frequency systoles, starts at a higher frequency f and then decreases continuously in frequency f until frequency f (t) falls below a natural frequency f to a frequency fsub 5 or ends at frequency f.

This type of generation of a sequence of stimulation pulses is carried out in a heart stimulation known per se. Device as characterized in the preamble of claim 1.

The cardiac stimulation device according to the invention generates a sequence of stimulation pulses with a higher frequency f than the frequency f (natural frequency), which is initially faster following an extra beat. A slowdown then takes place until the frequency f (t) corresponds to or falls below the natural frequency f. The

Frequency f preferably ends when the

Natural frequency f.

In addition to the aforementioned and still available stimulation modes, the stimulation device according to the invention can therefore generate a further stimulation mode which intervenes after each extrasystole or after the last of a sequence of extrasystoles, which is followed by a longer "compensatory" pause without a delay beforehand for the first stimulation pulse of the order of 1 s, as in the prior art.

It is proposed that the time interval t between the occurred extrasystole and the first stimulation pulse be programmable with the frequency f, the time interval t between the occurred extrasystole and the first stimulation pulse preferably being between 60 and 90% of the mean time interval t between two natural-frequency systoles is. The percentage can be programmed according to the premature nature of the extrasystole.

The frequency reduction can be carried out, for example, in such a way that the time interval of the stimulation pulses increases from pulse to pulse by at least 3%, preferably 6-18%.

An average time interval tmβan between two natural-frequency systoles for determining the frequency is considered to be a sliding one Average determined over several, for example 2-5 heartbeat periods.

If two extrasystoles ES occur at different time intervals, the frequency determination starts at the last systole corresponding to the natural frequency.

The decrease in the initially higher frequency can be linear, for example according to the equation

takes place, where t 2 is the end point in time of the stimulation sequence at which f = f or - in the absence of a proper rhythm - remains on the set lower frequency of the pacemaker.

The decrease in the initially higher frequency f can also be exponential, for example according to the equation

take place, where α = (1 / t) -ln (f / f).

A further advantageous property of the cardiac stimulation device is if, when a further extrasystole is detected, the currently running stimulation sequence can be broken off and restarted after the extrasystole. This also ensures that normal heart systoles are not contrast-stimulated.

The cardiac stimulation device mentioned is further characterized in that it can be stimulated in the cardiac atrium or in the cardiac ventricle.

An application example is explained using two schematic cardiograms. The figures show: Fig. 1 shows an electrocardiogram of an untreated

Tachycardia with previous extrasystoles;

2 shows a stimulation sequence when extrasystoles occur for the prophylaxis of tachycardia.

Figure 1 shows a schematic representation with the time t as the X axis, the occurrence of systoles S 1, S2, S3, S Λ, SS at natural frequency, normal spacing. Shown in dashed lines is ^the time at which another own "normal"

Systole S is expected. In this case, however, an extrasystole ES occurs. The distance between S and ES is shorter than the normal distance between two systoles.

At the expected point in time when a natural frequency f is used, a further systole S occurs, which in turn is followed by an extrasystole ES, which has a shorter time interval from the systole than would be expected if a normal frequency (natural frequency) were maintained. An expected normal systole S, however, fails. The so-called compensatory pause arises until another systole S occurs, which in many cases is followed by a so-called tachycardia (increase in heart rate to over 100 beats per minute). Such a tachycardia has an "unfavorable prognosis" (cf. PSCHYREMBEL, Clinical Dictionary, 255th edition, article "Tachycardia").

Figure 2 shows the same initial situation. The systoles with ^the normal frequency f S - S occur at the same time and normal intervals. An extrasystole ES then occurs, namely at a shorter time interval than the frequency f. Systole S (dashed) fails. In the compensatory pause that then sets in, the cardiac stimulation device according to the invention in the cardiac atrium or cardiac ventricle after the extrasystole ES or the last extrasystole causes a sequence of extrasystoles shorter or equal time interval (50 - 100%) than the distance between the two normal systoles S 1, S2, ... S! triggered a stimulation pulse SI, followed by a second stimulation pulse SI and a third SI.

Depending on the delay of the extrasystole in the range of, for example, 200 ms to 600 ms, there is a variation of t between 50 and 100% of the mean time interval t, for example according to the following table:

Prematurity ti. in% of tπean the ES

<200 ms 60

<300 ms 70

<400 ms 80

<500 ms 90

<600 ms 100

The intervals of the stimulation pulses are each drawn 10% larger than the previous one in FIG. In reality, the magnification is only about 3-5%. Stimulation pulses are emitted over such a long period of time until normal self-systole S occurs again.

If an extrasystole occurs, the current stimulation pulse sequence is also terminated and restarted after the occurrence of the extrasystole or a sequence of extrasystoles.

It turns out that tachycardia can obviously be prevented in many cases by the pulse sequences generated by the cardiac stimulation device.

Claims

PATENT CLAIMS

1. Implantable cardioverter defibrillator and / or pacemaker for stimulating the heart muscle (cardiac stimulation device), with at least one electrode to be connected to the heart muscle, a programmable electrical circuit for generating stimulation pulse sequences with which the electrode can be acted upon, and with an electronic memory connected to the said circuit, with which the electrical processes inherent in the heartbeat, in particular the systoles and their natural frequency f, can be registered and stored over several periods of the heartbeat, the electrical circuit evaluating the stored electrical processes and corresponding sequences of delivers antitachycardial and antibradycardial stimulation pulses, characterized in that with the electrical circuit upon detection of one or the last of several successive extrasystoles (s) which do not obey the natural frequency f (ES) a sequence of stimulation pulses (SI) of the frequency f (t) can be generated, which after the occurrence of the extrasystole compared to the determined previous natural frequency f after a programmable time interval t which is between 50 and 100% of an average time interval t between two natural frequencies Systole is, begins with a higher frequency f Bi and then decreases steadily in the frequency fS until the frequency f (t) falls below the natural frequency f to a frequency f or ends with the frequency f.

2. Cardiac stimulation device according to claim 1, characterized in that the time interval t between the individual extrasystole (ES) that has occurred or the last of several successive extrasystoles and the first stimulation pulse (SI1) is between 60 and 90% of the mean time interval t between two natural-frequency systoles.

3. Cardiac stimulation device according to claim 1 or 2, characterized in that the time interval t is variable according to the time t between the occurrence of an extrasystole (ES) and the last intrinsic systole (S).

4. cardiac stimulation device according to claim 1, characterized in that the mean time interval t TTΛβeiπ between two natural-frequency systoles as sliding

Average over several, e.g. 2 to 5 heartbeat periods.

5. cardiac stimulation device according to claim 1, characterized in that the decrease in the initially higher frequency f Si linear, i.e. according to the equation

fs (t) = fsi [1 + t. (fe - fsi) / t21

takes place, where t is the end point in time of the stimulation sequence at which f = f or - in the absence of a proper rhythm - remains on the set lower frequency of the pacemaker.

6. cardiac stimulation device according to claim 1, characterized in that the decrease in the initially higher frequency f exponentially, i.e. according to the equation

takes place, where α = (1 / t 2) -ln (fα / fsi).

7. Cardiac stimulation device according to one of the preceding claims, characterized in that if a further extrasystole or a further sequence of extrasystoles occurs, the currently running stimulation pulse sequence can be terminated and restarted after the extrasystole or sequence of extrasystoles.

8. Cardiac stimulation device according to one of the preceding claims, characterized in that it can be stimulated with this in the cardiac atrium or in the cardiac ventricle.