as a possible embodiment , fig1 shows a single - chamber icd system . the housing 110 thereof , including the components provided therein , is connected to a flexible , implantable electrode lead 120 . at the distal end thereof , the lead has a bipolar perception and stimulation pole , comprising a right ventricular tip electrode 130 and a right ventricular ring electrode 140 . for delivering the defibrillation shock , a distal shock coil 150 , and optionally a proximal shock coil 160 , are provided at the electrode lead 120 as the respective defibrillation or shock electrode . the electrocardiograms required for the determination of the p - wave dispersion as claimed can in principle be derived from the following electrode combinations : variant a : right ventricular tip electrode — icd housing variant b : right ventricular ring electrode — icd housing variant c : distal shock coil — icd housing variant d : proximal shock coil — icd housing the preferred derivations , however , are variant d , if a proximal shock coil is present , and variant c , if no proximal shock coil is present , since in these derivations the imaging of the atrial excitation ( p - wave ) is the most favorable . since several derivations are possible for determining the p - wave , in the exemplary embodiment a selection matrix is provided , which selects the most favorable derivation of the p - wave determination , either manually and programmably by the user , or automatically on the basis of electrode impedances and signal quality . in the version as a pacemaker , the illustrated shock coils 150 and 160 are eliminated . instead , the electrocardiogram derivation is performed by way of an atrial pacemaker electrode ( optionally tip electrode or ring electrode ), or by way of a floating atrial electrode , which additionally is accommodated as a ring electrode on the feed line of the ventricular electrode ( a + or vdd principle ). fig2 shows the results of signal averaging for detection of a p - wave in the far - field electrocardiogram . the upper curve 210 shows an input signal having an amplitude of 0 . 1 mv in order to simulate a very small p - wave . in addition , the input signal is slightly noisy in order to simulate the actual conditions of the far - field electrocardiogram derivation . in the second curve 220 , the derivation of these p - waves in the far - field electrocardiogram is shown , derived with an icd between the proximal shock coil and the housing of the icd . the interference signals illustrated next to the p - wave do not allow any automatic p - wave detection by the icd . in the third curve 230 , the signal is shown after it has been averaged over 24 cardiac cycles . signal averaging is synchronized for a particular detected atrial cardiac action ( atrial sense event ). the atrial cardiac action in this embodiment is detected in an electrocardiogram which was recorded by the proximal shock electrode 160 and the housing of the implant 110 . alternatively , a separate right atrial electrode can be used for atrial sensing . after 24 averagings ( signal 230 ), the signal quality is already sufficient to be able to achieve automatic detection the p - wave , including the components thereof ( right - left atria ), in the icd . based on the sufficiently averaged signal 230 , it is now possible to determine parameters which correlate with the p - wave dispersion . the most important parameter is the duration ( t ) ( also referred to as width ) of the p - wave , which is determined in the implant and stored . if the derivation vector and number of averaged cycles are sufficient , the duration of the averaged p - wave corresponds to the p - wave dispersion from the 12 - channel surface electrocardiogram . further improvement in the diagnostic meaningfulness — particularly for unmasking several focuses of the atrial excitation — is achieved by counting the points of irregularities ( s 1 . . . s 4 ) in the averaged p - wave 230 . fig3 shows several components of an icd , which is designed for a p - wave dispersion analysis described according to one or more embodiments of the invention , shown in the form of a block diagram . the icd here is additionally connected to a right atrial perception and stimulation electrode 310 . the intracardiac electrocardiogram ( iegm ) recorded ( derived ) with the help of this electrode is analyzed in a conventional icd sensing stage 320 , and the detected atrial cardiac actions ( atrial events , p - sense ) are subsequently supplied to an icd timer 330 for therapy control and rhythm diagnostic 340 . not shown is the ventricular perception and stimulation channel , because it is not changed compared to the prior art for the implementation according to embodiments of the invention . the shock electrodes 391 and 392 connected to a shock generator 390 of the icd , and the electrically conductive housing 300 of the icd , are additionally connected to a far - field electrocardiogram selection matrix 350 . this selection matrix 350 establishes which of the electrodes are used for the derivation ( recording ) of a far - field electrocardiogram for the p - wave dispersion analysis . the selection is made either manually by programming by the physician , or automatically by a signal quality analysis conducted in the icd ( 380 : “ signal quality analysis ”). this far - field electrocardiogram is subsequently preprocessed ( amplified , digitized , filtered ) in an electrocardiogram signal processing unit 360 and then fed to an average value forming device 370 as the averaging unit . the far - field electrocardiogram selection matrix 350 and the electrocardiogram signal processing unit 360 together form a far - field electrocardiogram capturing unit . the average value forming device 370 connected thereto conducts triggered signal averaging for a particular detected atrial cardiac action ( atrial event 320 ), and supplies these averaged p - wave recordings to a morphology classifier 380 . this morphology classifier 380 measures these averaged p - wave with respect to the signal duration ( signal width ) thereof , optionally with respect to the number of points of irregularities and optionally other morphological characteristics . this information is then supplied to a diagnostic memory 340 , wherein an association with the atrial rhythm ( 330 -& gt ; 340 ) is maintained . the information on the p - wave dispersion and on the atrial rhythm available in the diagnostic memory 340 can then be transmitted and displayed to the physician by way of near - field or far - field telemetry 321 . fig4 shows an expanded overall system for continuous monitoring of the p - wave dispersion . here , the electronic implant 410 described above is connected to a relay station or a base station 420 by way of rf telemetry ( preferably in the mics band ) and periodically transmits this information relating to the absence of atrial fibrillation to this relay station 420 . this station in turn transmits the information via a data transmission network 430 to a remote monitoring server 440 to which the physician 450 has access , for example via internet , and therefore has the option to care for the patient by telemedicine ( such as drug monitoring , scheduling for ablation therapy ). optionally , following a renewed occurrence of atrial fibrillation , or a period during which the criteria for the verification of the absence of atrial fibrillation are not met , the implant can immediately send a message to the remote monitoring system , and the remote monitoring server then sends a special message to the attending physician ( such as in the form of sms , fax , e - mail , or particularly striking identification of the patient in the remote continuing care database ). in order to ensure correct analysis of the classified rhythm by the physician , during the events classified as periods not free of atrial fibrillation a stored iegm is also sent to the remote monitoring server . in fig5 , a multichannel determination of the p - wave width (“ dispersion ”) is illustrated by way of example . in this example , a first far - field electrocardiogram derivation 510 is recorded and averaged , and simultaneously a second far - field electrocardiogram derivation 530 is recorded and averaged . both far - field electrocardiogram derivations are selected such that the atrial electrocardiogram can be depicted well . in addition , the right ventricular ( alternatively the left ventricular ) derived intracardiac electrocardiogram 520 is also recorded . the p - wave duration is now determined such that the earliest onset 540 of atrial excitation is searched for in both averaged atrial derivations . subsequently , the end 550 of the atrial excitation in the two averaged atrial electrocardiograms is determined . since typically also the ventricular excitation is visible in the atrial far - field electrocardiogram , additionally the analysis window for the atrial excitations is limited to the back . for this purpose , the information from the ventricular iegm is used . the atrial analysis window is limited at the earliest verifiable ventricular excitation 560 . fig6 shows a multichannel detector for determining the p - wave width according to the method illustrated in fig5 . this detector is connected to a right ventricular electrode ( 600 : rv ), electrodes for a first far - field derivation ( 630 : ff 1 ), and electrodes for a second far - field derivation ( 660 : ff 2 ). the electrodes for the first far - field derivation can be , for example , the proximal shock coil of an icd electrode and the icd housing . the electrodes for the second far - field derivation can be , for example , the proximal ring of a coronary sinus electrode and the icd housing . the right ventricular electrode connection is connected to a conventional sensing stage 610 for iegm signal processing . this unit in turn forwards the processed iegm signals to an r - wave detector , which is designed such that it detects the earliest onset of the r - wave and then forwards it to the connected r - wave width detector 690 . the two far - field connections 630 and 660 are connected to an electrocardiogram signal processing unit 640 and 670 , respectively . these electrocardiogram signal processing units 640 and 670 are designed such that they maximally amplify the atrial signals to be captured and subject them to broadband filtration , so that the entire atrial excitation can be captured . for the electrocardiogram signal processing of the first far - field channel 640 , other parameters can be set than for the electrocardiogram signal processing unit of the second far - field channel 670 . optionally , the electrocardiogram signal processing units may contain algorithms , which conduct automatic beat - to - beat adjustment of the parameters in order to optimally capture the recorded electrocardiogram signals . the far - field electrocardiogram signal processing units are associated with a p - wave averaging unit 650 and 680 . these units average the atrial electrocardiogram over a defined number of cardiac cycles , wherein this number is either fixed and preset or automatically determined by a signal quality analysis ( such as based on the evaluation of the signal - to - noise ratio ). the results of the p - wave averaging ( 650 , 680 ) are likewise supplied to the p - wave width detector ( 690 ). this p - wave width detector then determines the duration of the p - wave in accordance with the description of fig5 . it will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching . the disclosed examples and embodiments are presented for purposes of illustration only . therefore , it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention .
an electromedical implant , having a far - field electrocardiogram capturing unit for recording a far - field electrocardiogram signal , which is connected or can be connected to at least two electrodes for recording electric signals reflecting the curve of the far - field electrocardiogram of the right and left atria , a detection unit , which is designed to detect signal features characterizing atrial cardiac actions in an electrocardiogram signal , an averaging unit , which is connected to the recording unit and the detection unit and designed to generate an averaged p - wave signal in that the averaging unit averages a plurality of signal sections of the electrocardiogram signal associated with a particular detected atrial cardiac action , and an evaluation unit , which is connected to the averaging unit and designed to determine the duration of an averaged p - wave in the particular averaged p - wave signal .