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Fractionated endocardial electrograms are associated with slow conduction in humans: evidence from pace-mapping
W G Stevenson1, J N Weiss, I Wiener
1Department of Internal Medicine, University of California, Los Angeles School of Medicine 90024.
Insights
Fractionated ventricular electrograms often indicate slow conduction in the heart, a key factor in reentrant ventricular tachycardia. This finding helps identify substrates for dangerous arrhythmias during catheter mapping.
Area of Science:
- Electrophysiology
- Cardiology
Background:
- Fractionated ventricular electrograms during catheter mapping can indicate abnormal heart rhythms.
- These electrograms may represent slow conduction, a substrate for reentrant ventricular tachycardia, or be nonspecific findings.
Purpose of the Study:
- To investigate the association between fractionated sinus rhythm electrograms and slow conduction in humans.
- To determine if fractionated electrograms can predict the presence of slow conduction, a substrate for ventricular tachycardia.
Main Methods:
- Endocardial catheter mapping and pacing were performed at 133 sites in 13 patients.
- Slow conduction was assessed by measuring the stimulus-QRS interval (S-QRS) after pacing at each site.
- Patients included those with sustained monomorphic ventricular tachycardia and those with old myocardial infarction.
Main Results:
- Pacing at sites with fractionated electrograms showed a significantly longer S-QRS interval (>40 ms) in 49% of cases compared to non-fractionated sites (p < 0.001).
- A long S-QRS interval during pacing was often located near ventricular tachycardia circuits in patients with tachycardia.
- Fractionated electrograms were frequently associated with slow conduction, suggesting they are not merely nonspecific abnormalities.
Conclusions:
- Fractionated sinus rhythm electrograms are often indicative of slow conduction in the ventricles.
- This slow conduction identified by fractionated electrograms may serve as the substrate for reentrant ventricular tachycardia.
- The findings support the use of fractionated electrograms in identifying arrhythmogenic substrates during electrophysiological studies.
Abstract:
Fractionated ventricular electrograms recorded during catheter mapping may arise from areas of asynchronous depolarization associated with slow conduction, the substrate for reentrant ventricular tachycardia, but can also be a nonspecific abnormality or even artifact. To determine whether fractionated sinus rhythm electrograms are associated with slow conduction in humans, the results of endocardial catheter mapping and pacing at 133 endocardial sites in 13 patients were analyzed. Eleven patients had sustained monomorphic ventricular tachycardia and two patients had old myocardial infarction without ventricular tachycardia. Functional evidence of slow conduction at the recording site was assessed by pacing at that site and measuring the interval between the stimulus artifact (S) and the onset of the QRS complex in the 12 lead electrocardiogram (ECG). During pacing at 89 of 90 sites without fractionated sinus rhythm electrograms, the S-QRS interval was less than 40 ms, a value consistent with rapid propagation of the stimulated wave front away from the pacing site. During pacing at 21 (49%) of 43 sites with fractionated sinus rhythm electrograms, the S-QRS interval was greater than 40 ms (range 40 to 140), consistent with slow conduction at the pacing site (p less than 0.001 versus nonfractionated sites). In 9 of the 11 patients with ventricular tachycardia analysis of the paced QRS configuration, electrograms during induced ventricular tachycardia or programmed stimulation during tachycardia suggested that a site with a long S-QRS interval during pacing was located at or near a ventricular tachycardia circuit. Therefore, fractionated sinus rhythm electrograms are often associated with slow conduction, which may be the substrate for reentrant ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)