EUROPACE
Results: During this extended follow-up in 61 pts the IDL continued to
function normally. In 8 pts (11.6%) lead related problems were encountered.
In two pts oversensing due to lead fracture was noted resulting in inappropriate
shocks. In another pt oversensing occurred only after defibrillator shock. In
one pt high pacing threshold, low pacing impedance and low defibrillation
impedance developed 34 months after implantation. In one pt exteriorization
of the lead occurred 36 months after implantation. In one pt high defibrillation
threshold and oversensing after the shock was found at replacement. Finally
two pts had a unipolar ventricular pacing and sensing IDL which was not
compatible with the generators available at replacement. In one pt a new pacing
and defibrillator lead had to be implanted and in the other only a bipolar
pace-sense lead was implanted.
Conclusions: In a significant number of pts despite a normal IDL performance during the first two years after implantation, at extended follow-up lead
related problems can occur Regular follow-up including detailed evaluation fo
IDL system is important in order to ensure the proper function of the implanted
defibrillator and the safety of pts.
I
P 348
ANALYSES OF INTRACARDIAC
ELECTROGRAMS
FROM IMPLANTABLE
CARDIOVERTER
DEFIBRILLATOR:
THE IMPORTANCE OF THE MODE
OF RECORDING
P. Rossi’, A. Casaleggioz, A. Faini3, T. Guidot&, G. Sartori’, G. Musso4,
Division
R. Mureddu4, E. Casali5, V. Malavasi5, S. Chierchia’. ‘Cardiology
San Martino
“Cardiology
Hospital,
Division
Geneva;
Imperia;
211@31; Geneva; 3St Jude Medical It&a;
Cardiology
Division,
Modem,
Italy
Aim: Implantable Cardioverter Defibrillators (ICDs) allow storage of intracardiac electrograms (EGMs) in bipolar (local heart activity) and far-field (global
heart activity) modes. We study EGMs obtained from ICDs using Power Spectral Density, quantified by the frequency of the 50% of the signal power (fso),
and Correlation Dimension monitored by its Most Probable Value (MPDV).
We address two questions: (i) do far-field (FF) and bipolar (BIP) EGMs give
similar results for the same cardiac rhythm (Ho)?, and (ii) is it equally difficult
to discriminate between cardiac electrical activity underlying sinus rhythm (SR)
or ventricular tachycardia (VTJ from FF or BIP EGMs (HI)?
Method: We considered 191 EGMs from 26 patients with ICDs (11 with
BIP and 15 with FF EGMs). 87 EGMs are spontaneous VTs, the other are SR
recorded immediately before VT onset, or at the follow up. To answer Ho we
compared fso and MPDV from the whole BIP and FF groups. H1 requires to
distinguish between VT and SR EGMs using fso and MPDV This is obtained
comparing fso and MPDV of VT and SR EGM subgroups within the FF and the
BIP populations, separately. Statistically significant differences are accepted
using T-test with P<O.Ol.
Result: Answer to Ho: FF and BIP EGMs are signiiicantly different using
fso (6.4 vs. 21.9; t=-12.3, P<O.OOl) and MPDV (1.2 vs. 0.7; t=3.27, P<O.O05).
Answer to HI for SR and VT EGMs of FF group: fso (7.5 vs. 5.3; t=3.57,
P<O.O05), and MPDV (0.95 vs. 1.37; t=-3.45, P-zO.005) are signiiicantly different. BIP EGMs during SR and VT are not signiiicantly different: fso is 30.1
in SR and 19.8 in VT, but t=1.87 and the P>O.O5. MPDV is unreliable. Thus
it is easier to distinguish cardiac dynamics underlying SR from VT within FF
population, and also HI can be rejected.
Conclusion: FF and BIP EGM recordings monitor different cardiac dynamics, in other words, the information-content is different even when the cardiac
rhythm is similar; FF EGMs allow better distinction between different rhythm
conditions using fso and MPDV statistical parameters.
I
P 349
WHAT CAN WE EXPECT FROM SVT/VT
DISCRIMINATION
IN DUAL CHAMBER ICDS?
M. M&e’,
G. Groenefeldz, .I. Heintze3, H.J. Trappe’. For the MDII Study
Group; ‘Department
of Cardiology and Angiology, University Hospital Heme,
Ruhr-University,
Bochum, Germany;
21Jniversity Hospital,
Frankjirt,
Germany;
3Heart Ch: North Rhine-Westfalia,
Bad Oeynhawen,
Ruhr-University
Bochm,
Germany
Objectives: The advantage of dual chamber ICD’s is the discrimination of
tachyarrhythmias by comparing the atria1 rate (A) with the ventricular rate (v).
The single chamber SVT/VT discrimination criteria (morphology, stability, and
sudden onset) are only used when the A is equal or higher than the V The aim
of the study was to investigate the best programming of SVT/VT discrimination
criteria in dual chamber ICD’s.
Method: 178 patients (pts) (144 men, age 66&10 years) were implanted a
dual chamber ICD (Photon DR, Atlas DR, St. Jude Medical) in 14 centres. The
stored electrograms of 819 tachymhythmias were analysed and the details of
the tachymhythmias were entered into a database. Based on this clinical data
the best programming was evaluated.
B148
Europace Supplements,
Vol. 4, December
2003
Results: 514 VT and 305 SVT were detected by the ICD’s. 430 (84%) VT
episodes had a V>A. Only 84 (16%) VT’s and all SVT’s were detected in the
V=A or V<A rate branches and required further discrimination. A sensitivity
of 99% and a specificity of 94% was attained by the following programming:
A stability of 40 ms with AV association (80 ms) and a morphology of 45% in
the rate branch “V < A” when both criteria had to be fuliilled for the diagnose
“VT” and only morphology < 45% in the “V = A” rate branch. A sensitivity of
100% was achieved by a safety timer “maximum time to diagnose” (MTD).
Conclusion: We can expect a specificity of 94% for the SVTIVT discrimination in dual chamber ICD’s and keep a sensitivity of 100% by programming
a “safety timei’.
I
P 350
EFFICACY OF LOW ENERGY T WAVE SHOCK AS
REGARDS THE INDUCTION OF VENTRICULAR
FIBRILLATION
IN PATIENTS WITH AN IMPLANTED
DEFIBRILLATOR
RELATIONSHIP
BETWEEN
VULNERABILITY
AND VENTRICULAR
WITHDRAWAL
E. CastelImos, P. Hemandez-Simon, L. Mateos, C. Aguado, E. Lazaro,
Hospital
Virgen De La S&d.
L. Rodriguez Padial. Servicio De Cardiologia.
Toledo.
Spain
The normal method for determining the defibrillation threshold in patients
(P) with an automatic implanted defibrillator (AID) entails the induction of
ventricular fibrillation (VF). This is achieved through the administration of a
shock in the vulnerability area.
The objective of the study is to compare the efficacy of the induction of VF
through low energy T wave with a iixed coupling interval (CI) as compared
with a CI based on the ventricular refmctary period (VRP).
This was evaluated in 31 P during the implanting of AIDS (average age 68;
men: 84%, women: 16%), the majority had ischaemic heart disease (80%). A
crossed clinical trial was carried out with two induction procedures in each P
(62 inductions) with a random sequence. Sequence A:: the first induction of
VF by ventricular stimulation with a train of 8 stimulations (Sl-Sl) and a low
energy (1 jul) shock (S2) liberated by the AID with an CI iixed at 310 ms
(S2-310). The second induction by a train of 8 stimulations followed by an S2
with an CI resulting from adding 40 ms (SZVRP) to the VRP Sequence B: The
inverse order of sequence A (first induction SZVRP and secondly S2-310).
The SUCCESS
rate of VF induction through S2-310 was 68% and for the
S2-VRP method 45.2% (NS). We found no significant statistically differential
residual effects. When the SZVRP was used in the second induction of VF of a
P (sequence A), the success rate of induction of VF was 37.5%, compared with
a SUCCESS
rate of 86.7% for the S2-310 method applied as the second attempt
(sequence B) at induction of VF (p < 0.01).
To conclude, the efficacy of the low energy T wave shocks in order to induce
VF does not improve if the CI of the shock is adjusted to the VRP. In addition,
this method is less effective after ventricular defibrillation.
I P 351
INITIAL ZONES OF THE ATRIOVENTRICULAR
REALLY NEGLECTED ANATOMIC FEATURE
POTENTIAL CLINICAL SIGNIFICANCE?
NODE
OF
D. Kozlowski, P. Wozniak, G. Piwko, M. Grzybiak 2nd Department
Cardiac
Clinical
Diseases,
Anatomy,
Medical
Medical
University
University
of Gdaiisk,
of Gdaiisk,
Poland,
Poland
Department
of
of
Amongst the large amount of studies considering the a-v junction rarely did
they focuse on so called posterior extensions or the initial zones. Some authors
suggest that posterior extensions are not stable stmchm. Taking this under
consideration we decided to examine the morphology of the initial zones of the
node and to find the answer to the question of its existence.
The study was carried out on the material of 150 human hearts of both
sexes, 22-93 years of age, free from any macroscopic pathological changes or
congenital heart disease. The specimens of the whole triangle of Koch were
taken and were sectioned at 10 micrometer of thickness. Every 5th section was
stained with Mason-Goldner’s method. The length of the examined part of
the conduction system and its shape was estimated on basis of microscopic
observations.
Every one of the 150 examined hearts contained the atrio-ventricular node
and its initial parts. We observed that the initial zone of the atrioventricular node
is created by assembly of cells typical for conduction system that can create
initially independent from each other groups always mnged around atrioventricular nodal artery. Depending on their relation to the artery we have divided
them to: superior group located above the artery, to the left and supported
by right fibrous body; inferior group localized below the artery and supported
on the lower part of the attachment of septal letiet of tricuspid valve; and the
middle one localized below the nodal artery. In all examined hearts we stated
the presence of at least two initial parts of the node: superior and inferior. Those
E UROPACE
two groups were present in 45 hearts (90%). In the last 5 cases (10%) there
was also a middle group. Neither a single initial group nor any case without
any initial groups were found. In the examined sections, in 27 hearts (54%) the
superior group appeared as the first, in 23 cases (46%) the inferior group. The
length of each group was measured from the first appearence to the first solid
contact with the second part. The length of the superiorpart oscillated from 0,15
to 2,91 m m (an 0,90&0,6 mm), inferior from 0,ll to 2,41 m m (am. 0,88&0,6
mm)(table 2) and the middle from 0,67 to 2,21 m m (am 1,04&0,7 mm).
Based on OUTstudy we could conclude that the prevalence of at least two
initial zones of the node: superior and inferior one, is constant and occurs in
each examined heart. Our data suggest that the middle group is additional one.
I
P 352
THE SPECIFIC BIMODAL DISTRIBUTION PATTERN IN
RR INTERVAL HISTOGRAM PREDICTS EARLY
RECURRENCE OF ATRIAL FIBRILLATION
FOLLOWING EXTERNAL ELECTRICAL
CARDIOVERSION
X.H. Guo, J.M. Bland, M.M. Gallagher, A.J. Camm. St George’sHospita2
Medical
School,
UK
Background: W e hypothesize that abnormal AV nodal electrophysiological
behaviour as assessed by the presence of a bimodal RR histogram in atria1
fibrillation (AF) may contribute to vulnerability to recurrent AF postexternal
electrical cardioversion (ECV).
Methods: RR interval histograms were constructed from 24hour ECGs
recorded before ECVon 98 patients (68 men, age 65.3&10.3 years) with persistent AF. A 48.hour recording was obtained from each of 20 patients for
evaluating the reproducibility of RR histograms. RR histograms were classified as either unimodal or bimodal, including multi-modal RR histograms, by
3 observers according to predefined criteria. All patients were prospectively
followed-up during ECV, one-week and one-month later.
Results: Out of total 98 patients, 13 (13.2%) patients failed ECV and a total
of 52 (53%) patients were in AF at one-week and 66 (67%) at one-month post
ECV A bimodal RR interval distribution during AF was found in 17 (18%) of
the 98 patients and 8 (47%) of these 17 patients exhibited a speciiicbimodal RR
histogram. Inter- observed identification of bimodality was excellent (k= 0.966,
p<O.OOOl). The reproducibility of bimodality on consecutive days was good
(k= 0.56, p=O.O04). Compared to the patients with non- specific bimodality,
patients with the specific bimodal RR histogram were more likely to have recurrent AF within one-week and one-month (88 vs. 33%, 100 vs. 33%, p=O.Ol,
p=O.O09,respectively) with sensitivity: 78.73%; specificity: 88.100%; positive
predictive accuracy: 88.100% respectively.
Conclusion: A specific bimodal RR histogram is associated with low probability of maintaining sinus rhythm following ECV.
I P 353
P W A V E PARAMETERS IN PACEMAKERBIOTRONIK
AXIOS D ELECTROPHYSIOLOGY
TEST - STUDY IN
BRADYCARDIA-TACHYCARDIA
SYNDROME PATIENTS
M. Rosiak, M. Chudzik, K. Bartuak, .I. Kawinski, H. Bolinska, .I. Ruta.
Institute
of Cardiology,
Medical
of Lodz,
University
Poland
Atria1 fibrillation (AF) is the common arrhythmia observed in patients with
bradycardia-tachycardia syndrome (BTS). Inter&al conduction disturbances
represented by P-wave duration prolongation, and effective refractory period
shortening are proposed as the electrophysiologic substrate for AF. It has
been demonstrated that AAI/DDD pacing reduce supraventricular arrhythmia
(AFISVT) incidence in BTS patients.
Aim: The aim of the study was to document the changes of the P-wave
parameters in BTS patients (pts) after DDD pacemaker @cm) implantation.
Methods: Study population: 7 patients (4 women and 4 men aged 66,8&12,3)
with BTS (AF vs. sinus bradycardia) who hadBiotronikAxiosD
pcm implanted.
All pts were in DDD 60 bpm pacing mode. Pts had measured on l-day (l-d), 2
weeks (2-w) and 3 months (3-m) after implantation the following parameters: 1.
Measured by BiotronikAxios
D pcm electrophysiology program: Paced P-wave
duration (pP), sinus P-wave duration (sP), atria1 effective refractory period
(ERPA); 2. P-wave duration (PWD) from SAECG.
Results (p<O,O5):
Friedman
test
Pd
sPd
ERM
PWD
l-d vs. Z-w
NS
NS
NS
NS
l-d vs. 3-m
0,015s
NS
0,036
NS
Conclusion: In the group of OUTpts treated by DDD 60 bpm pacing we
observed the shortening of pPd and lengthening of ERPA (l-d vs. 3-m) mea-
2003
ERPA
ERR43-m I
P
sued by pcm electrophysiology program. These tendency should be beneficial
in lowering the number of AF episodes. Further studies with larger group and
different pacing rates are necessary to evaluate pacing rate optimal for P-wave
shortening and ERPA lengthening.
IP
354
CHRONAXIE TIMES ARE THE SAME FOR INDUCTION
OF VENTRICULAR FIBRILLATION
AND
DEFIBRILLATION
BUT DIFFERENT FOR STIMULATION
T. Lawo, B. Wenzel, S.M. Wagner, M. Buddensiek, J.H. Fischer, M. Bose,
A. Muegge, B. Lemke. University Hospital Bergmanmheil,
Bochum,
Germany;
University
of Cologne,
Germany;
Biohmik,
Erlangq
Germany
The strength-duration curve for cardiac stimulation is described by the hyperbolic chronaxie-rheobase relationship. Studies on the strength-duration relation
for the defibrillation threshold (DFT) are limited and show conflicting results.
In addition, no such data are available regarding the induction of ventricular
fibrillation (VF) by a T-wave shock. W e therefore assessedthe hypothesis that
the strength-duration curve for VF induction follows a hyperbolic relation with
a chronaxie (&) different from the t, for stimulation but identical to the t, for
defibrillation.
Twelve pigs were implanted with an ICD lead in the right ventricle. Three
single-coil leads served as the common anode. Fairly rectangular monophasic
shocks were applied by a custom made external defibrillator. Pacing thresholds
(via shock coil) were determined at stimulus durations of 0.02-20 ms. The lower
and upper VF induction threshold (LVr, UVT) and the DFT were determined
for different shock durations (0.1-100 ms). Chronaxies were derived from the
strength-duration curves of each single experiment.
The strength-duration curves for the LVT and the UVT followed a hyperbolic
function (r=O.96 for LVT and r=0.78 for UVT. The mean k for stimulation
was 0.22 ms (&0.12 ms, n=12) and was signiiicantly (p<O.OOl, t-test) shorter
than the k for the LVT (2.4&1.7 ms, n=lO), the UVT (2.5&1.3 ms, n=7) and
the DFT (2.2&1.3 ms, n=ll), respectively.
W e conclude, that not only the time constants but also the underlying cellular mechanisms are identical for T-wave induction and defibrillation (“graded
response”) but different from stimulation (“all-or-nothing response”).
I P 355
ORGANIZATION
OF MULTIPLE REENTRANT W A V E
FRONTS DURING ATRIAL FIBRILLATION
BY A PURE
IKR CHANNEL BLOCKER IN CANINE ATRIA
T. Ikeda, A. Kawase, K. Nakazawa, T. Ashihara, T. Namba, T. Yao, S. Yusu,
H. Yoshino. Kyorin University Mitaka, Japan and Japanese Working Group
On Cardiac
Simulation
and Mapping,
To&w, Japan
Background: Effects of II+ channel blocker on wave front dynamics during
atria1 fibrillation (AF) is unknown. This study aimed to assess the effects of
nifekalant, a pure II+ channel blocker on the characteristics of activation waves
during AF using mapping technique.
Methods: W e used an isolated, coronary perfused canine biatrial model
(n=7). The endocardium was mapped using computerized mapping system
(2.mm resolution). AF was induced by an extrastimulus method in the presence
of 5 u M acetylcholine. After coniirming sustained AF, 5 u M nifekalant was
added to the perfusing Tyrode’s solution. Effective refractory period (ERP),
conduction velocity (Cv), and excitable gap (EG) were determined during
AF.
Results: At baseline, multiple nonstationary wave fronts were observed
leading to meandering, breakups, and the generation of new wave fronts. After
perfusing the drug, multiple wave fronts were completely organized into a
single stationary reentrant wave front in all 7 preparations, anchoring to a large
pectinate muscle (5 preparations), to or&x of inferior vena cava (1 preparaEuropace Supplements,
Vol. 4, December 2003
B149