Download Heart rate variability / QT

Heart rate variability / QT-dispersion
245 Altered RR Interval dynamics and vulnerability to
29
QT-DISPERSION
life-threatening arrhythmias: fractal analysis
T.H. Makikallio, M.J. Kotetinen, K.E.J. Airaksinen, T. Seppanen, C.-K. Peng,
A L GoMberger, H.V. Hulkuri. Drv. of Cardiology, Dept of Mod., University of
Oulu; Merikoski Rehabilitation and Research Center, Oulu, Finland;
Cardiovascular Dtv., Harvard Medical School, Boston, MA, USA
Fractal analysis techniques can reveal abnormalities In heart rate (HR) behavfour that are not detected by conventional summary measures of HR
variability. Detrended Fluctuation Analysis (DFA) technique quantifies the presence or absence of fractal correlation properties of non-stationary time series.
Short-term (<8 beats, a-,) and long-term (>8 beats, a2) correlations of RR
interval data were compared between 45 postinfarction patients with a recent
history of ventricular tachyarrhytmia (VT) and Induclble VT by programmed
electrical stimulation (VT-group) and 45 postinfarction patients without clinical
VT events or incuable VT (Ml control group). The patient groups were matched
by age and ejection fraction, and 45 age-matched healthy subjects served as
normal controls, a, was significantly smaller in VT-group (0.90 ± 0.26) than
In Ml controls (1.04 ± 0.17, p < 0.01) or healthy controls (1.11 ± 0.20, p <
0.001). a2 was higher (p < 0.05) In the postinfarction patients than in healthy
controls, but did not differ between the VT-group and Ml control group. Total
RR Interval variance was also smaller in VT-group (63 ± 29 ms) and in Ml
control group (71 ± 30 ms) than in the healthy subjects (83 ± 28 ms, p < 0.01
for both), but the high frequency spectral component did not differ between the
groups. In stepwise multiple regression analysis Including the DFA measures
and conventional time- and frequency domain measures of HRV the a, was
the strongest independent predictor of vulnerability to VT.
Short-term correlation properties of RR Interval dynamics arealtered in postinfarction patients with vulnerability to VT. Fractal analysis techniques can detect
subtle abnormalities In HR dynamics that may be related to VT susceptibility.
| 246 | Heart rate variability after myocardial Infarction: a
useful tool for predicting life-threatening ventricular
arrhythmias In the thrombolytlc era
R F.E. PedrettJ, S. Sarzi Braga, A. Laporta, E. Colombo, F. Maslowsky,
S. Landonl, O. Catalano, R. Tramarin. 'Salvatore Maugen' Foundation,
IRCCS, Rehabilitation Institute of Tmdate, Division of Cardiology, Italy
Aim of the study was to assess the clinical relevance of HRV in predicting
arrhythmic events in Ml survivors in the thrombofytic era.
Methods: We prospecttvely studied 530 consecutive post-MI pts admitted to
our hospital for rehabilitation: mean age 55 ± 9 yrs, 456 males, anterior Ml in
259, thrombotysis In 279. Exercise testing (ET), 24 h Hotter recording, signalaveraged ECG (SA-ECG) and 2D-Echo were performed for risk stratification
on day 20-25 after Ml We performed Cox proportional hazards analyses when
testing hypothesis about association between one or more risk predictors and
arrhythmic events. For HRV measures and filtered QRS complex duration on
SA-ECG we sought the cutoff points that maximized the hazard ratio.
Results: 28 (5.2%) pts had an arrhythmic event (sustained VT, sudden death,
nonfatal cardiac arrest) during 2-year period. Univariate analysis identified as
factors related to arrhythmic events: 1) ET: eligibility for ET (RR: 0.10, p <
0.001), ET termination because of dyspnea and/or pressure drop (RR: 8.2, p
< 0.001) 2) 2D-Echo: LVEF from 30% to 40% (RR: 3.6, p < 0 01), LVEF <
30% (RR: 9.3, p < 0.001) 3) Signal-averaged ECG: ventricular late potentials
(RR: 4.8, p < 0.001), filtered QRS complex duration > 110 msec (RR: 7.2, p <
0.001); 4) Hotter monitoring: ventricular couplets (RR: 2.9, p < 0.01), all time
and frequency domain measures of HRV (p < 0.001); 6) Clinical variables: age
> 60 yrs (RR: 2.8, p < 0.05), previous Ml (RR: 5.8, p < 0.001), no thrombofysls
(RR: 2.4, p < 0.05) 7) Therapy at hospital discharge: diuretic agents (RR: 9.6,
p < 0.001), ACE-inhibitors (RR: 32, p < 001). A Cox proportional hazards
model identified LVEF < 30% (RR: 11.9, p < 0.001), ET termination because
of dyspnea and/or pressure drop (RR: 9.2, p < 0.001), LVEF from 30% to 40%
(RR: 6.5, p < 0.001), filtered QRS complex duration > 110 msec (RR: 5.6,
p < 0.001), low (IF) to high frequency (HF) ratio < 2.0 on spectral analysis
(RR: 2.7, p < 0.05), ventricular couplets (RR: 2.4, p < 0.1) as independent
predictors oi post-MI arrhythmic events.
In the thrombotytic era HRV Is an independent predictor of arrhythmic events
after Ml and frequency domain analysis seems to be a more powerful tool
than time domain approach for prognostic evaluation. A low LF to HF ratio was
present in pts with arrhythmic events, suggesting a loss of the physiological
modulation of sympathetic activity in pts with poor prognosis.
| 2 4 7 [ Prognostic value of increased repolarlzatJon dispersion
In patients with coronary heart disease
M. Trusz-Gluza, I. Wozntek-Skowerska, L Glee, K. Szydto. / Clinic of
Cardiology, Institute of Cardiology, Silesian School of Medicine, Katowice,
Poland
Increased dispersion of QT Interval (QTd) reflects Inhomogenity of ventricular
action potentials and has been related to sudden cardiac death (SCD) in a
variety of heart disorders. However, clinical and prognostic importance is still
controvertial. To study the effect of QTd on the survival the relation to 33
traditionally accepted clinical predictors such as history, Qtc, Hoiter, exercise
test and echocardiographic variables to subsequent cardiac death (CD) and
SCD was examined In 162 pts with coronary heart disease (CHD).
QTd was defined as QT maximum minus QT minimum as measured from
12 lead ECG and was > 60 ms in 40 pts (25%). The clinical outcome during a
follow-up of 25 ± 11 months was assessed in all pts, 17 CD and 9 SCD were
recorded. There was a significant difference In CD (p < 0 001 In log rang test)
and In SCD (p < 0.01). The 1 and 3 year survivals were 87.5% and 76.5% vs
98% and 93.5%, respectively.
A stepwise Cox regression analysis revealed that increased QTd has been
Independent risk factor of CD and SCD. The optimum cut-off for QTd was
found to be 60 ms. The sensitivity and specificity CO were 53% and 79%,
respectively. Positive and negative prognostic values were 23% and 93%.
Our finding supports the hypothesis that Increased QTd have a prognostic
value In pts with CHD Independent of the other known prognostic factors. It
seems that thanks to QTd very tow risk pts can be better Identified.
2 4 8 QT Interval dispersion In survivors of sudden cardiac
death: a 24-hour assessment
J. Molnar1, J.S.Weiss 2 , J.E. Rosenthal2, J.C. Somberg 1 . 1 The Chicago
Medical School, North Chicago;2 Northwestern University Medical School,
Chicago, IL, USA
QT dispersion (QTd) measured from the 12 lead EKG may be associated
with electrical instability. Twenty-four hour acquisition of QTd from the Hoiter
and the clrcadian variation of QTd were evaluated In 21 survivors of sudden
cardiac death (SCD) (9F/12M, age =. 53 ± 12 y) and 21 healthy subjects
(H) (10F/11M, age = 57 ± 13 y) Computer-assisted QT measurement was
performed on 24-hour Hoiter recording; each recording for each subject was
divided into 288 5 minute segments and templates representing the average
QRST were generated by QTMDK software (Marquette Electronics, Wl). Onset
and offset of the QT Interval were visually determinated. QTd was calculated
as the difference between QT Intervals In leads V1 and V5 for each template
on Hoiter and as the difference between the longest and shortest QT Interval
on 12 lead EKG. Hoiter and 12 lead EKG showed close correlation In QTd (r
= 0.739 p < 0.001). The mean QTd was 28 ± 18 ms on Hoiter and 61 ± 30
ms on 12 lead EKG. The 24-hour mean QT dispersion was significantty longer
In SCD patients than In H group (46 ± 6 ms v. 19 ± 5 ms p < 0.001). QT
dispersion was larger at night (0-6AM) than daytime (10AM-4PM) in H (25 ±
2 ms v. 15 ± 2 ms, p < 0.001) and in SCD patients (51 ± 4 v. 44 ± 3 ms, p
< 0.01). The magnitude of clrcadian variation in hourly means was 19.5 ms in
SCD and 16 ms In H. We concluded that: QTd measured by Hoiter Is greater In
SCD than In H subjects. QTd has a clrcadian variation with greater dispersion
at night than during the day. There Is an increase in QTd variability in the earty
morning hours. Hoiter monitoring of QTd may be a valuable tool in Identifying
patients at high risk for sudden cardiac death.
30
QT-dispersion
2 4 9 Increased QTc dispersion: a new marker predicting
Induction of post-myocardlal Infarction ventricular
tachycardia
251
Lack of prognostic value of QT dispersion at discharge
in patients recovering from acute myocardial infarction:
a case-control study from the GISSI database
Q. Fang, J.P. Bourke, E. Simeonidou, A. Arya, R.W.F. Campbell. Academic
Cardiology, Freeman Hospital and University of Newcastte-upon-Tyne, UK
A. Milletich, R. Lattru, G. Garrido, A.P. Maggioni, F. Mauri, G. Zuanetti.
GISSI-ECG Collaborative Group, Milan, Italy
QTc dispersion (QTcd), (the difference between QTc-max and QTc-mln In
a 12 lead ECG), Is a measurement of ventricular heterogeneity. In many
situations, increased QTcd Is an arrhythmia risk. The Implication of increased
QTcd In patients surviving a myocardlal Infarction (Ml) has been explored. This
study sought to correlate QTcd and the Indudbflity of sustained monomorphlc
ventricular tachycardia (VT) by programmed stimulation.
Methods: Thirty-six patients with prior Q wave Ml were studied. Patients with
bundle branch block or with a 'non-specific' result of programmed stimulation
(ventricular flutter or fibrillation) were excluded. Sustained monomorphlc VT
was induced in 25 patients (VT (+)), but not In the remaining 11 (VT (-)). QT
was measured by dlgltiser and corrected for heart rate. The results between
VT (+) and VT (-) were compared.
Results:
Several studies suggested that QT dispersion may be a marker of electrical
Instability leading to sudden death in post-MI patients, but the significance
of these findings is still debated. We performed a case-control study from
the GISSI-2 ECG database. A total of 88 patients surviving the in-hosprtal
phase who died suddenly (within 1 hr from onset of symptoms, n = 70) or
developed sustained tachyarrhythmlas (n = 18) during the 6-month follow-up
were identified retrospectively and carefully 2 1 matched for age, sex, site of Ml
and presence of congestive heart failure (n = 176). Twelve lead ECG obtained
at discharge were analyzed. Data for QT and JT dispersion (>9 leads with end
of T wave measurable) were obtained In 74 cases and 154 controls.
Data (msec) are shown in the table, p = NS for all comparisons
VT(+)
VT(-)
P
QTcd
P-QTcd**
QTc-max
59
39
<0.01
42
28
NS*«
471
443
0.04
•AD data wane expressed as mean values (ms) "P-QTcd is defined as maximum 01c difference between any two of the preconfial leads. ""Statistically not significant
When a QTcd value of 50 ms was used as cut-off for the prediction of the
sustained monomorphic VT initiation the sensitivity and specificity were 72%
and 73% respectively. A cut-off QTc-max value of 460 ms had sensitivity of
60% and specificity of 73%.
Conclusions: Both an Increased QTcd and QTc prolongation correlated with
the Induction of VT by programmed stimulation In patients with pnor Q wave Ml.
QTcd, like signal averaging, can predict post Ml VT induciblllty. This has clinical
implication and it shed new light on the mechanism of post Ml arrhythmogenesis.
2 5 0 I QT dispersion Is a good predictor of cardiac death after
anterior myocardlal infarction
M. Del Greco, M.T. Delia Mea, C. Cemln, P. Pessano, G. Nollo 1 , M. Dlsertori.
Cardiology Department, Ftovereto Hospital;' Centro Material! Btoffstea
MecBca, ITC, Trento, Italy
It is still unclear whether QT dispersion indexes can predict death after acute
myocardial infarction (AMI) or not We evaluated QT dispersion (QTcD) as
the maximum difference between QT correct (Qtc) values (Bazetfs formula)
In at least 10 toads put of a standard 12 lead electrocardiogram (ECG). We
measured QT values manually by using a specific software Interfaced with a
flatbed scanner. OTcO estimation was performed In 165 patients (pts) (mean
age 68.6 ± 1 £; 484 males and 31 females) dudog toe secood week after AMI.
Five pts were excluded because of a bundle branch block. In our population
54 pts suffered anterior, 80 pts inferior and 21 non-Q AMI. During a mean
follow-up of 24 months, 13 pts died of cardiac death. The mean QTcD value
was significantly higher in pts with anterior AMI who died (4 pts) of cardiac
causes compared to survtvors (50 pts) (151.9 ± 15 vs 99.4 ± 30, p •= 0.001).
The difference was not statistically significant In the group with Inferior and
non-Q AMI (102.6 ± 33 vs 87.6 ± 27, p = 0.23; 98.7 ± 10 vs 96.8 ± 24, NS,
respectively). In the anterior AMI group, a QTcD > 125 showed a sensitivity of
100%, specificity of 78% and a predictive accuracy of 26% for cardiac death.
Conclusions. A QTcD greater than 125, measured on standard ECG during
the second week after anterior AMI, provides an extremefy sensitive method
for predicting cardiac death during the follow-up.
Rfl
Cases
Controls
QTcmax - QTcmin
888±155 101±40
827±155 100±35
SO QTc
JTcmax - JTcmtn
SO JTc
32±13
31 ±11
101 ±49
96 ±34
31 ±15
28 ±10
Similar results were obtained with uncorrected data.
In conclusion: 1) reliable data for duration and dispersion of repolarlzatlons
are obtained7in approximately 85% of all pts discharge alive from hospital 2)
dispersion of repolarlzation of pts prone to sudden death or tachyarrhythmlc
events post-discharge is similar to control patients 3) QTc and JTc dispersion
appear of limited use in risk stratification of post-MI pts at discharge.
252
QT Interval dispersion is not useful for predicting
arrhythmic events in myocardlal Infarction survivors
with left left ventricular dysfunction
R.F.E. Pedretti, O. Catalano, L Ballardinl', E. Radlce', A. Laporta, D.P. de
Bono 2 , R. Tramarin. Cardiology Dept;' Bloenglneering Dept, 'Salvatore
Maugeri' Foundation, IRCCS, Rehab. Inst. of Tradata, Italy;2 Cardiology
Dept, University of Leicester, Leicester, UK
Is still unclear If QT Interval dispersion may provide additional prognostic
information to low LVEF. In order to evaluate this point we performed the
following retrospective study.
Methods:B1 pts who survived an AMI and who had left ventricular dysfunction
(2D echo LVEF < 40%) were included In the study group: mean age 56 ±
8 yrs, 53 males, anterior AMI In 48, previous AMI in 16, Q-wave AMI In 52,
thrombotysis in 33. Mean LVEF was 35 ± 4%. Standard 12 lead ECGs from day
14 ± t3 of AMI were arjatyzed. ECGs were scanned, and the Image divided
into 12 files corresponding to the 12 leads. Specially designed software was
used to analyze ECGs providing automatic measurement of QT interval. Rate
corrected QT (QTc) duration, dispersion (QTc max minus QTc mln) and adjusted
dispersion (QTefRax mtaus-QTsmiadhddod hy toasquaiaioot ol the number
of leads with a measureable QT interval) were calculated. Conventional risk
markers (clinical variables, signal-averaged ECG for QRS complex duration
and Hotter recording for HRV) were also collected in all pts.
Results: 15 (24.6%) pts had an arrhythmic event during 2-year period.
Concerning QT interval measures no significant dfllerence was found between
pts with and without arrhythmic events: QTc (490 ± 140 vs 515 ± 38 msec,
p = 0.3), QTc dispersion (93 ± 42 vs 109 ± 45 msec, p = 0.2), adjusted QTc
tflspersion (29 ± 12 vs 33 ± 15 msec, p = 0.3). Amiodarone (13 vs 11 %, p o 1.0)
and ft Mocker (7 vs 19%, p = 0.4J prapojtio/is were not significantly different
between pts with and without arrhythmic events. In order to evaluate the clinical
relevance of the study group, the additional (to LVEF < 40%) prognostic power
of conventional risk markers was also assessed: thrombotysis (31 vs 63%, p <
0.05), previous AMI (47 vs 19%, p < 0.05), filtered QRS complex duration (115
± 12 vs 102 ± 12, p < 0.001), mean RR interval (720 ± 97 vs 790 ± 99, p <
0.05) and SD of normal RR Intervals (75 ± 33 vs 100 ± 33, p = 0.01) were all
significantly different between pts with and without arrhythmic events.
No significant relationship was found between the risk of arrhythmic events
and QTc interval duration and dispersion in pts with low LVEF after AMI.
QT interval measures do not seem useful for predicting ventricular electrical
Instability In patients wtth post-AMI left ventricular dysfunction.