[CRT-FORUM] 12E. Dispersion of ventricular repolarization changes. Dr. Perez Riera

[CRT-INFO]

Dearest friend Yunlong: there are few reports of transmural dispersion of
repolarization in dilated cardiomyopathy in indexed literature, in spite of
Santangelo et al(1) demonstrated in a study population with severe heart
failure secondary to dilated cardiomiopathy that permanent biventricular
pacemaker implantation  causes a statistically significant reduction of
ventricular heterogeneity of repolarization and has an electrophysiological
anti-arrhythmic influence on the arrhythmogenic substrate.
In dog model a prolongation of the monophasic action potential duration of
subendocardial, subepicardial and mid-layer myocardium and increase in
transmural dispersion of repolarization during pacing participating of LV
(left ventricular epicardial  pacing, BiV) may contribute to the formation
of unidirectional block and reentry, which play roles or at least are the
high risk factors in the development of malignant ventricular arrhythmia,
especially in case of structural heart disease(2).
Left ventricular epicardial  pacing and Bi-V pacing result in prolongation
of ventricular repolarization time, and increase of transmural dispersion of
repolarization accounted for a parallel augmentation of the T(p-e) interval,
which provides evidence that T(p-e) interval accurately represents
transmural dispersion of repolarization. These effects are magnified in the
LQTS and dilated cardiomyopathy-CHF canine models in addition to their
intrinsic transmural heterogeneity in the intact heart. This mechanism may
contribute to the development of malignant ventricular arrhythmias, such as
Torsades in CHF patients treated with cardiac resynchronization therapy(3).
Here in Brazil(4), from a cohort (39 patients: 26 Obstructive HCM and 12
Non-obstructive) with 24 years of follow-up cardiac pacing in hypertrophic
cardiomyopathy was successful, with evidence of symptoms relief only in
obstructive HCM patients.

Major indications for implant were:
1)    Spontaneous or induced AV block (54%);
2)    Refractoriness to therapeutic conduct associated to high gradient
(33%),
3)    Support for drug therapy to treat bradychardia (8%)
4)    Atrial fibrillation prevention (5%).

Complications: (6 patients--15.4%). Three deaths occurred in the follow-up
period--the three of them were atrial fibrillation female patients, with
evidence of functional deterioration.

References

1)    Santangelo L, Ammendola E, Russo V, Cavallaro C, Vecchione F,
Garofalo S, D'Onofrio A, Calabrò R.Influence of biventricular pacing on
myocardial dispersion of repolarization in dilated cardiomyopathy patients.
Eupace. 2006;8: 502-505.
2)    Bai R, Pu J, Liu N, Lu JG, Zhou Q, Ruan YF, Niu HY, Wang LInfluence
of pacing site on myocardial transmural dispersion of repolarization in
intact normal and dilated cardiomyopathy dogsSheng Li Xue Bao. 2003 Dec
25;55:722-730.
3)    Bai R, Lü J, Pu J, Liu N, Zhou Q, Ruan Y, Niu H, Zhang C, Wang L,
Kam R. Left ventricular epicardial activation increases transmural
dispersion of repolarization in healthy, long QT, and dilated cardiomyopathy
dogs. Pacing Clin Electrophysiol. 2005 Oct;28:1098-1106.
4)    Silva LA, Fernández EA, Martinelli Filho M, Costa R, Siqueira S,
Ianni BM, Mady C. Cardiac pacing in hypertrophic cardiomyopathy: a cohort
with 24 years of follow-up. Arq Bras Cardiol. 2008 Oct;91:250-6, 274-280.

All the best
Andrés Ricardo Pérez Riera MD, chief of electrovectorcardiology sector
ABC Faculty of Medicine (FMABC), Discipline of Cardiology, Foundation of ABC
(FUABC), Santo André, São Paulo, Brazil.
> Dear Dr Pérez Riera
>
> Thanks for the kind words. Your Chinese friends are also missing you
> here, and welcome back to China in the near future.
>
> I will read in detail of the two papers you mentioned. As we know, the
> increased dispersion of ventricular repolarization was associated with
> ventricular tachyarrhythmias. Such increase might be due to different
> activation sequence, and autonomic nerval influence. But on the other
> hand, theoretically the dispersion of repolarization, transmurally or
> globally, might also be changed dramatically. But I have not found the
> related studies on the changes of transmural dispersion in dilated
> cardiomyopathy, hypertrophic cardiomyopathy, or heart failure. Do you
> know any related studies under these situations?
> Kind regards
>
> Yunlong
>
>> Dearest friend Yunlong Xia, from the beautiful Dalian, China. I’m 
>> very happy
>> to chat with you.  Are you fine? I miss you and the cleaver Chinese 
>> people a
>> lot!
>>
>> Answer: Very recently, (the last Month) Dr Zhou et al (1) from  
>> Department of
>> Internal Medicine, Division of Cardiology, Second Affiliated Hospital 
>> of Sun
>> Yat-Sen University, Guangzhou, People's Republic of China in a canine
>> congestive heart failure (CHF)  model ventricular electrophysiological
>> characteristics correlated with abnormal autonomic nerve function may 
>> have
>> important effects on SCD. In the CHF dog group, significant 
>> differences from
>> the control group in ventricular effective refractory period, monophasic
>> action potential  duration, ventricular late repolarization duration, 
>> the
>> ratio of ventricular effective refractory period to monophasic action
>> potential  duration, dispersion of ventricular recovery time, and
>> ventricular fibrillation threshold were noted. Both baroreflex 
>> sensitivity
>> and the time and power domain parameters of heart rate variability were
>> significantly decreased in the CHF group compared with the control 
>> group,
>> and a significant, positive correlation between heart rate 
>> variability and
>> baroreflex sensitivity was identified in the CHF group. Heart rate
>> variability and baroreflex sensitivity were negatively and significantly
>> correlated with ventricular late repolarization duration and 
>> dispersion of
>> ventricular recovery time, and were positively correlated with 
>> ventricular
>> effective refractory period / monophasic action potential duration and
>> ventricular fibrillation threshold in the CHF canine group.
>> Additionally, in human explanted hearts from patients with CHF 
>> Rotigaptide
>> (an enhancer of gap junctional conductance drug) applied to hearts of
>> patients with end-stage CHF shortened refractory periods   normalized
>> conduction curves and increased conduction parallel to fiber direction.
>> However, in 50% of the hearts local slowing of conduction with
>> destabilization of conduction (curves) occurs at sites close to the
>> stimulation site, when activation is perpendicular to fiber direction.
>>
>> Reference
>> 1)    Zhou SX, Lei J, Fang C, Zhang YL, Wang JF. Ventricular
>> electrophysiology in congestive heart failure and its correlation 
>> with heart
>> rate variability and baroreflex sensitivity: a canine model study. 
>> Europace.
>> 2009 Feb;11(2):245-251.
>>
>> 2)    Wiegerinck RF, de Bakker JM, Opthof T, de Jonge N, Kirkels H,
>> Wilms-Schopman FJ, Coronel R The effect of enhanced gap junctional
>> conductance on ventricular conduction in explanted hearts from 
>> patients with
>> heart failureBasic Res Cardiol. 2009 Jan 12. [Epub ahead of prin]
>>
>> All the best
>> Andrés Ricardo Pérez Riera MD, chief of electrovectorcardiology 
>> sector ABC
>> Faculty of Medicine (FMABC), Discipline of Cardiology, Foundation of ABC
>> (FUABC), Santo André, São Paulo, Brazil.
>> Riera at uol.com.br
>>
>> CRT-INFO escribió:
>>> Eu tenho aqui uma questão: Como ocorre a dispersão das mudanças na 
>>> repolarização ventricular nos pacientes com insuficiência cardíaca? 
>>> Como é a relação com as taquiarritmias ventriculares malignas?
>>>
>>> Atenciosamente,
>>>
>>> Dr. Yunlong Xia, PhD
>>> Dalian, China
>>>
>>
>>
>
>


-- 
Dr. Sergio Dubner
President of Scientific Committee

Dr. Edgardo Schapachnik
President of Steering Committee