[SCD-FORUM] EXPERTS ASK, EXPERTS ANSWER

[SCD Symposium]

Dr. Leonid Makarov from Russia asks

- If there was a need to perform ECG screening in the healthy  
population to detect patients in high risk of noncoronary  
arrhythmogenic sudden death, which and how many electrocardiographic  
signs would you use for this purpose?
Dr. Wojciech Zareba from U.S.A. answers

- Identification of the SCD risk in general population is of major  
interest and there is no single test that could be considered as a  
gold standard due to a complexity of mechanisms leading to SCD. ECG  
screening is an attractive and easily obtained option. In particular,  
a standard 12-lead ECG could be considered useful. Evaluating step-by- 
step prognostic information coming from an ECG, one has to focus  
first on:


1.      Rhythm – presence of non-sinus rhythm in otherwise healthy  
population is rather infrequent, nevertheless, in cohorts of elderly  
healthy it is likely to find at least few percent of subjects with  
undiagnosed atrial fibrillation. Atrial fibrillation is first risk  
factor which is associated with an increased (at least 2-fold) risk  
of cardiac death and increased risk of SCD.


2.       Rate of heart rate – tendency to resting tachycardia,  
especially >80bpm usually indicates additional underlying medical  
problem and should also be considered as a risk factor. The  
association between elevated resting heart rate and mortality is  
observed in postinfarction patients and patients with heart failure,  
but data on healthy subjects are less convincing.  Increased heart  
rate should prompt physicians to investigate further the reason for  
this finding.


3.       QRS – conduction abnormalities, namely left bundle branch  
block, are associated with increased risk of cardiac events and SCD  
in healthy cohorts with hazard ratios >2.0. Data on RBBB do not show  
significant association with mortality. QRS prolongation is  
associated with increased risk of death and SCD in healthy cohorts.  
LVH is of lesser prognostic importance assuming that QRS duration is  
analyzed.


4.      QT-T wave – repolarization parameters are considered as an  
important marker of increased risk in healthy subjects. Elevated QTc  
(>0.44 sec) in healthy cohort, especially in elderly subjects, was  
reported to be associated with significantly increased risk of  
cardiac death and SCD. Abnormal T wave morphology (usually inverted  
or flat T wave or abnormal T wave axis) also serves as a sign of  
increased risk for cardiac death and SCD in cohorts of healthy subjects.

Therefore patients with atrial fibrillation and those in sinus rhythm  
with wide QRS complex (LBBB) or patients with abnormal repolarization  
(either prolonged QTc or abnormal T wave morphology) are at increased  
risk of cardiac death and SCD. Such subjects identified in the  
screening process require further attention to elucidate causes of  
the abnormalities and to consider preventive/therapeutic measures.

It is worth adding that exercise ECG testing with analysis of heart  
rhythm recovery (difference between heart rate at peak exercise and  
heart rate at 1-minute recovery) seems to be useful in identifying  
high-risk healthy individuals. The heart rate recovery <12bpm was  
reported as indicator of SCD in healthy cohorts.

Electrocardiology has a limited option in identifying patients with a  
vulnerable plaque, and ischemic incidents are the major causes of  
SCD. Therefore, the above screening should be combined with  
additional measures reflecting an increased risk of atherosclerotic  
changes including lipid profile and some inflammatory markers  
(sedimentation rate, CRP, etc…) while we are awaiting novel more  
specific markers of plaque vulnerability.

--
Dr. Sergio Dubner
President of Scientific Committee

Dr. Edgardo Schapachnik
President of Steering Committee




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