Abstract
At this time, we find ourselves with an abundance of guidelines for management of
patients with manifest ventricular tachyarrhythmias, or at risk for such arrhythmias,
in patients with coronary heart disease (CHD). The guidelines are focused primarily
on the “appropriate use” of the implantable cardioverter/defibrillator (ICD). Unfortunately,
the bulk of the guidelines have very little basis in the underlying pathophysiology
responsible for sudden cardiac death (SCD) in patients with CHD. Rather, they are
based primarily on the results of randomized clinical trials that merely sought to
take broad populations at elevated total mortality risk and determining whether the
ICD can reduce overall mortality. The trials were not aimed at elucidating or exploiting
the varying pathophysiology responsible for the ventricular arrhythmias responsible
for most sudden deaths in this setting. The goal of the trials is appropriate – to
improve the survival. The problem with promoting trials that solely determine whether
a broad-based population (identified by one parameter such as ejection fraction that
bears no direct relation to the pathogenesis of arrhythmias) derives a survival benefit
from a therapy such as the ICD, is that many patients that could benefit from the
ICD are missed (not covered by the guidelines), and many patients that will never
benefit from the ICD are exposed to its risks and costs.
How can we advance the use of potent, but expensive therapies that carry risk such
as the ICD to improve survival of patients with CHD today? There are several avenues
worth pursuing, both for short-term as well as long-term gain. First, there are several
models shown to have the potential to identify patients currently covered by the guidelines
for ICD use, that are highly unlikely to benefit, because of the existing co-morbidities.
These models are likely to be valid because there is significant overlap in the parameters
identified in each model, and they have been tested retrospectively in a variety of
study populations. These models are not likely to be incorporated into use guidelines,
until they have been tested prospectively in a randomized trial in a contemporary
patient population. This can, and should be done. Use of such a model, based on noninvasive,
readily available clinical markers offers the possibility of improving the efficiency
with which ICDs are used to reduce the risk of SCD in CHD patients.
Second, we need to recognize the fact that SCD in this population is a result of multiple
potential mechanisms. And, the electrophysiologic substrates underlying these mechanisms
are influenced by interactions with the autonomic nervous system and hemodynamic conditions.
While most out-of-hospital cardiac arrests do not occur in persons with overt heart
failure, the presence of heart failure clearly increases the risk for SCD, likely
by a variety of mechanisms. There is increasing evidence that altered left ventricular
geometry may not only reduce LV mechanical efficiency, but may also have direct effects
on the electrophysiologic substrate. Although there is an abundance of evidence supporting
the importance of autonomic interactions in the genesis of spontaneous arrhythmias,
the utility of prospectively measuring autonomic indices to predict future arrhythmic
events has to date not proven to be useful. Of course, that is not to discount the
significant impact of beta-adrenergic blockade on survival and reducing arrhythmic
events. Future works must focus more on both animal models of post-infarction arrhythmias,
as well as integrating findings from such studies into human physiology, with subsequent
testing in the form of randomized clinical trials.
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to International Journal of CardiologyAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- Limitations of ejection fraction for prediction of sudden death risk in patients with coronary artery disease. Lessons from the MUSTT study.J. Am. Coll. Cardiol. 2007; 50: 1150-1157
- Risk stratification for primary implantation of a cardioverter-defibrillator in patients with ischemic left ventricular dysfunction.J. Am. Coll. Cardiol. 2008; 51: 288-296
- Maximizing survival benefit with primary prevention implantable cardioverter-defibrillator therapy in a heart failure population.Circulation. 2009; 120: 835-842
- Prediction of mortality in clinical practice for Medicare patients undergoing defibrillator implantation for primary prevention of sudden cardiac death.J. Am. Coll. Cardiol. 2012; 60: 1647-1655
- Electrophysiologic testing to identify patients with coronary artery disease who are at risk for sudden death.N. Engl. J. Med. 2000; 342: 1937-1945
- B-type natriuretic peptide is a major predictor of ventricular tachyarrhythmias.Heart Rhythm. 2014; 11: 1109-1116
- Pathogenesis of mitral regurgitation in acute myocardial infarction: importance of changes in left ventricular shape and regional function.Am. Heart J. 1996; 131: 865-871
- Early identification of left ventricular remodelling after myocardial infarction, assessed by transthoracic 3D echocardiography.Eur. Heart J. 2004; 25: 680-687
- Left ventricular sphericity independently predicts appropriate implantable cardioverter-defibrillator therapy.Heart Rhythm. 2016; 13: 490-497
- Electrophysiological effects of myocardial stretch and mechanical determinants of stretch-activated arrhythmias.Circulation. 1992; 86: 968-978
- Sensing pressure in the cardiovascular system: Gq-coupled mechanoreceptors and TRP channels.J. Mol. Cell. Cardiol. 2010; 48: 83-89
- Increased intraventricular pressures are as harmful as the electrophysiological substrate of heart failure in favoring sustained reentry in the swine heart.Heart Rhythm. 2015; 12: 2172-2183
- Influence of intracardiac pressure on spontaneous ventricular arrhythmias in patients with systolic heart failure: insights from the REDUCEhf trial.Circ. Arrhythm. Electrophysiol. 2013; 6: 272-278
Article info
Publication history
Published online: March 10, 2017
Accepted:
March 9,
2017
Received:
March 7,
2017
Identification
Copyright
© 2017 Elsevier B.V. All rights reserved.
