Download Clinical implications of QT internal measurements

EUROPACE 2005
showed cardiomegaly on chest X-ray. NYHA functional class>2 was
found in 42.2% of T G A pts (NYHA class 3 in 9.3%) and in 50.0% of
ccTGA pts (NYHA class 3 in 10.0%). Full criteria for CRT were met
in 3.1% of the T G A pts and 5.0% of the ccTGA pts. Including pts in
NYHA class 2 and without considering ventricular dilatation (ie. criteria
similar to CONTAK CD) 6.3% of TGA and 5.0% of ccTGA pts would
have been eligible for CRT.
Conclusion: in unselected pts with a systemic right ventricle, 3.1%
to 6.3% are potential candidates for CRT. If antibradycardia pacing is
indicated, electrical resynchronization may also need to be considered.
Prospective studies assessing the logistical and anatomical feasibility of
CRT in ACHD cohorts with failing ventricles are warranted.
SUNDAY,26 JUNE 2005, 15:45-17:15
ROOM 2.B
Clinical implications of QT internal
measurements
63
Corrected QT interval predicts mortality in patients with
non-Q-wave anterior wall myocardial infarction
T.Y. Burak 1, S.A. Boldueva 2
1State Medical Academy, Department of lnternal Diseases,
Saint-Petersburg, Russian Federation; 2Saint-Petersburg State Medical
Academy, Saint-Petersburg, Russian Federation
Some studies have demonstrated a relationship between the duration of
the corrected QT interval (QTc) and prognosis in patients with acute
myocardial infarction. However in other studies these relations were
weak or absent. Besides, it's unclear whether prognostic value of QTc
depends on the variant of myocardial infarction.
The aim of this study was to estimate the prognostic significance of QTc
in patients with Q-wave and non-Q-wave myocardial infarction.
Methods: 203 patients on the 10-14th day of myocardial infarction were
examined. The first group consisted of 96 patients with non-Q-wave
myocardial infarction (NQMI) and the second group consisted of 107
patients with Q-wave myocardial infarction (QMI). The control group
included 30 men without heart diseases. The QT interval was measured
on ECG recordings at rest and corrected using Bazett's formula. The
median follow-up lasted 20.1 months (range: 1.8-36.7). End points
included all cases of deaths; sudden (SM), cardiac (CM) and all-cause
mortality (ACM) was evaluated separately.
Results: QTc didn't differ between the NQMI group and QMI group
(417.54-31.0 ms and 421.24-29.7 ms, respectively, p=0.38), but in both
groups it was significantly greater than in the control group (400.54-17.4
ms, p<0.05). During the follow-up 23 patients died (11 in the NQMI
group and 12 in the QMI group), 16 from them died suddenly (7 and
9, respectively), 3 more cases were due to other cardiac causes. In
the NQMI group in a Kaplan-Meier survival analysis surviving curves
differed significantly between the patients with QTc greater and less then
440 ms for all end points (p<0.01 for SM, p<0.005 for CM and p<0.001
for ACM), in contrast to the QMI group where surviving didn't depend
on a value of QTc. In patients with NQMI who had anterior location
of the infarction (N=74) QTc>440 ms was an independent predictor of
all-cause mortality in a mukivariate Cox-analysis.
Conclusions: The study has demonstrated that corrected QT interval
carries an independent prognostic information in patients with non-Qwave anterior myocardial infarction, thus this parameter can be useful
when estimating a risk in such group of patients.
Sunday, 26 June 2005
64
QT interval variability and QT/RR relationship in patients with
postinfarction impairment of the left ventricle function and
different types of ventricular arrhythmias
K. Szydlo 1, M. Trusz-Gluza 2, W. Orszulak 2, D. Urbanczyk 2,
A. Filipecki 2, K. Wita 2 , J. Krauze 2
1Sosnowiec, Poland; 21 Dept. of Cardiology, Silesian Medical Academy,
Katowice, Poland
Circadian variability of QT interval, describing repolarization process
of myocardium, and QT/RR relationship, presenting short-time adaptation of QT into the changes of the heart rate are still under intensive
investigation.
The purpose of the study was to analyze if the variability of QT interval
parameters and QT/RR relationship may be helpful in differentiation of
postinfarction (MI) patients with impaired function of the left ventricle
and different types of ventricular arrhythmias.
The study population consisted of 100 pts with previous MI (>30 days)
with PVC, episodes of non-sustained ventricular tachycardia (nsVT),
sustained VT (sVT) or documented ventricular fibrillation (VF). Patients
were divided into two groups. Fifty pts without sVT or VF (NoVT/VF)
(36 males, 634-10 yrs, EF- 414-9%) and 50 pts with sVT or VF (VT/VF)
who underwent ICD implantation (37 males, 614-10 yrs, EF- 374-11%).
QT duration was calculated beat after beat from the Holter recordings
and after that had been processed with QT/RR Tools Special Analyses
(Reynolds). All recordings were analyzed in two periods- day: 6 a.m.9 a.m and 2 p.m.- 10 p.m.; night: 10 p.m.- 6 a.m. The following data
were used: the average of QT interval (QT), QT corrected to the heart
rate with the Bazzet's formula (QTc), QT variability-standard deviation
of all successive intervals (QTSD) and QT/RR regression slope (slope).
Results: groups had not been differentiated by age, gender, EF, size of MI
and extent of coronary artery lesions. Comparison of parameters revealed
differences between NoVT/VF and VT/VF groups: at daily period- QT
3864-39 vs 4214-36 ms (p<0.01), QTSD 184-4 vs 224-4 ms (p=0.05),
QTc 4144-22 vs 4464-31 ms (p<0.001), slope 0.144-0.05 vs 0.214-0.05
(p<0.05); at night period- QT 4014-44 vs 4304-35 ms (p<0.05), QTSD
154-5 vs 184-8 ms (p=ns), QTc 4124-24 vs 4424-30 ms (p<0.001), slope
0.154-0.04 vs 0.194-0.05 p<0.05; respectively. Parameters did not differ
between themselves at day and night periods.
Conclusion: both day and night parameters of repolarization were significantly higher in VT/VF indicating greater heterogeneity of this process.
Moreover, higher QT/RR slope in VT/VF may suggest increased, inappropriate QT adaptation to heart rate changes. QT/RR slope may
be useful tool in stratification of patients at higher risk of malignant
arrhythmic events.
65
Repolarization parameters in patients with acute anterior
myocardial infarction treated with primary PTCA: relationship
with the myocardial perfusion
K. Szydlo 1, D. Urbanczyk 2 , Z. Tabor 2, W. Kwasniewski 2 , J. Myszor 2,
M. Turski 2, K. Wita 2 , M. Trusz-Gluza 2
1Sosnowiec, Poland; 21 Dept. of Cardiology, Silesian Medical Academy,
Katowice, Poland
The purpose of the study was to analyse if any differences in repolarization parameters might be found in pts with acute anterior myocardial
infarction (AMI) treated with primary PTCA depending on the presence
of microvascular integrity of the left ventricle.
Methods: the study population consisted of 50 pts with first anterior
AMI treated with primary PTCA (<6 hours from the onset of AMI
symptoms) with TIMI III flow in LAD artery after the procedure. They
were divided into two groups according to the presence of the myocardial
perfusion assessed by contrast echocardiography (MCE) performed in
the 2nd day after procedure. There were 24 pts (P-) without perfusion
in the risk area (18 males, age: 594-9 yrs, EF: 394-7%) and 26 pts (P+)
with the presence of perfusion (16 males, age: 554-11 yrs, EF: 454-8%).
Europace Supplements, Vol. 7, June 2005
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There were no differences in gender, age, treatment, time from the onset
of symptoms of AMI to PTCA and extent of lesions in coronary arteries
in both groups. Electrocardiographic data were obtained from 3-channel
24h Holter monitoring performed in the 5th day after AMI during
awaking period (5-7 a.m). All repolarization parameters were corrected
according to the Bazzet's formula: QT interval duration (QTc), dispersion
of QT (QTdc), QTapex (QTapexc)and TapexTend (TapexTendc). QTd
without correction was also used to evaluated the number of pts with
QTd>30 ms.
Results: the comparison of parameters revealed the differences between
P- and P+ groups: for QTd (364-11 vs 264-7 ms, p<0.001), QTdc
(404-12 vs 274-8 ms, p<0.001), QTapexc (3324-30 vs 3324-34 ms, NS),
TapexTend (1084-13 vs 974-10 ms, p<0.005). Moreover, QTd>30 ms
differentiated P- and P+ pts, there were 13 pts in P- and 3 pts in P+
group (p<0.005).
Conclusions: patients with the presence of microvascular integrity of
the left ventricle were characterized by significantly lower values of
all repolarization parameters. Lower QTd, QTdc and TapexTendc might
indicate higher spatial and transmural homogeneity of this process
after successful primary PTCA. Prospective follow-up will indicate the
prognostic value of these findings.
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Increased dispersion of the repolarization during recovery f r o m
exercise
H.H.M. Draisma 1, C.A. Swenne 2, B. Hooft van Huysduynen 1,
A.C. M a i n 1, E.E. Van der Wall 1, M.J. Schalij 1
1Leiden University Medical Centec Cardiology Dept., Leiden,
Netherlands; 2Leiden University Medical Center (LUMC), Cardiology
Dept., Leiden, Netherlands
Background: Frequent ectopy during recovery (R) from exercise (X)
bears increased risk for death, while frequent ectopy during X does
not (NEJM 2003;348:781). One possible explanation for arrhythmia
facilitation during R is increased dispersion of the repolarization (DOR).
We compared DOR indexes in the X-ECGs and R-ECGs obtained during
a maximal exercise test to corroborate this hypothesis.
Methods: We analyzed 10-s ECGs recorded during VO2max tests in 55
healthy male subjects, age 334-11 years, of whom 34 did not participate
in competitive sports (normal group, N) while 21 were athletes (A). We
selected for every R-ECG the best heart-rate matched X-ECG in the same
subject. Each thus matched ECG pair was assigned the corresponding
recovery time (RCT, time after peak exercise) and percent heart rate
reserve (HRR). DOR parameters were T-vector magnitude (Tvec) and
T-wave symmetry ratio (Tsym). We tested on statistical differences
between Tvec(R) and Tvec(X) and between Tsym(R) and Tsym(X).
Paired t-tests were done at the 5% significance level in seven 1-minute
RCT bins (1, 2, ... 7 minutes after peak exercise) and in six 10% HRR
bins (40, 50, ... 90% of HRR).
Results: When statistically different, Tvec(R) was always larger than
Tvec(X) and Tsym(R) was always larger than Tsym(X). Tvec(R) vs
Tvec(X). Tvec(R) was larger than Tvec(X) in all RCT bins and in all but
the 40% HRR bin. Maximal Tvec(R) to Tvec(X) ratios were 1.74 (group
N, in the 2-min RCT bin), 1.73 (A, 1-min RCT), 1.81 (N, 80% HRR)
and 1.70 (A, 80% HRR). Tsym(R) vs Tsym(X). Tsym(R) was smaller
than Tsym(X) in RCT bins 1-4 and in all HRR bins except 40% (N and
A), 60% (N) and 90% (A). Maximal Tsym(R) to Tsym(X) ratios were
0.85 (N, 1-min RCT), 0.75 (A, 2-min RCT), 0.84 (N, 90% HRR) and
0.78 (A, 70% HRR).
Discussion: Our study demonstrates considerable DOR hysteresis in
both groups N and A, with the maximum early in the recovery episode.
Increased DOR during R can be explained by parasympathetic reactivation (Am J Physiol Heart Circ Physiol 2002;282:2091) in combination
with the still present humoral adrenergic stimulation. In conclusion,
it is conceivable that increased DOR is mechanistically involved in
arrhythmogenesis/sudden death early after vigorous exercise.
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67
Individual QT/RR relationship: average stability over time does not
rule out an individual residual variability implication for the
assessment of drug effect on the QT interval
F. Extramiana 1, P. Maison-Blanche:, E Badilini 3, P. Beaufils:,
A. Leenhardt 2
1Lariboisi re Hospital, Cardiology Dept., Paris, France; 2Lariboisi re
Hospital, Cardiology, Paris, France; 3AMPS LLC, NewYork, United
States of America
Background: Universal QT correction formulae have been shown to under or over-correct the QT interval duration. Individual QT/RR modeling
has been proposed as a preferable solution for heart rate correction of
QT intervals. However, the QT/RR relationship stability over time needs
to be evaluated.
Methods: The present report is part of randomized, double-dummy and
placebo-controlled 4-way crossover phase 1 study (48 healthy volunteers). Each randomized period included a run-in placebo day followed
the day after by drug administration, with moxifloxacin as a positive control for QT interval measurement. Digital Hoker ECG data were analyzed
using the "bin" approach. For each period individual QT/RR relationship
were calculated using 2 different models (linear and parabolic log/log
models).
Results: The mean intra-subject variability for the alpha coefficient
of the linear modeling (SDintra = 0.0114-0.005) reached 28.64-10.2%.
When the parabolic model was considered, the SDintra was 0.0264-0.009
for the alpha coefficient. The QT/RR relationship variability was in part
related to long term RR changes (R2=30%, p<0.05). However, no
significant time effect (ANOVA) was evidenced for QT/RR coefficients.
Moxifloxacin significantly increased the alpha coefficient of the QT/RR
relationship from 0.07+0.018 to 0.0854-0.019, p<0.05 (linear model).
Conclusions: The individual QT/RR relationship shows a residual variability in part related to long term autonomic changes. In addition, the
QT/RR relationship might be modulated by the drug tested. As a consequence pre-therapy QT/RR relationship obtained in a given patient
cannot be used as a fingerprint throughout a drug trial.
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C o m p a r i s o n of the effects of a selective If current inhibitor
ivabradine and atenolol on the QT interval in patients with
coronary artery disease
I.V. Savelieva 1, J. Camm 2
1St. George's Hospital Medical School, Dept Cardiological Sciences,
London, United Kingdom; 2St George's Hospital Medical School,
Cardiac and Vascular Sciences, London, United Kingdom
Ivabradine (IVA) is a novel antianginal agent which reduces the heart
rate by selectively blocking the If ion current implicated in the slow
depolarisation phase of the sinus node action potential. Prolongation of
the uncorrected QT interval with IVA is associated with reduction in
heart rate. Objective: to investigate whether changes in the QT interval
observed with IVA are entirely due to bradycardia or also to the direct
effects of IVA on ventricular repolarisation.
Methods: Because the non-linear relationship between the QT interval
and the heart rate may often result in under- or overestimation of the
corrected QTc interval by the conventional Bazett (QTcB) and Fridericia
(QTcF) formulae, respectively, a population correction formula (QTcP)
was used. The QTcP formula was developed and validated in 23,997
QT/RR paired values from the ECGs in 1216 patients with coronary
artery disease randomised to the placebo arm of several IVA efficacy
studies. The QTcP formula was then used for rate correction of the QT
interval in 995 patients randomised to treatment with IVA 10 mg bid.
Eighty-three patients treated with atenolol 100 mg od served as active
controls.
Results: Based on the analysis of the QT/RR values in the placebo
group, the QTcP formula resulted in a correction exponent of 0.384. Prolongation of the uncorrected QT interval was observed in patients treated