THE OCCURRENCE OF ISOLATED LEFT SEPTAL FASCICULAR BLOCK CRITERIA DURING ROUTINE EXERCISE TESTS
Introduction: The presence of the left bundle branch septal fascicle has been confirmed by morphological and electrophysiological studies. However, there are no standards for its recognition. Because of that, the prevalence and significance of conductivity related disorders in the septal fascicle are unknown. Case reports suggest that the isolated left septal fascicular block (LSFB) may be the only indicator of ischemia.
Aim: To assess the occurrence of specific electrocardiographic criteria of LSFB during exercise tests (ET).
Test group and methodology: The analysis covered 999 exercise tests performed by 999 patients on a cycloergometr or treadmill according to different protocols, depending on a patient’s clinical condition and indications for the test. The patients with any used in publications criterion of LSFB in rest standard ECG were excluded from the analysis. A detailed analysis was performed on top of physical exercise or during recovery time. LSFB was suspected if at least one of the following criteria was met:
- Disappearance of septal q (I, V5, V6)
- In V5-V6 QRS duration widened but < 120ms
- Ventricular activation time to peak R: in V5-V6 > 60ms, in aVL or aVF >45ms.
- Slurring or notching on R upstroke in I, V5-V6
- Presence of any Q in V1 and V2 or in V2 and V3
- R in V1 5 mm
- R/S in V2 >2
- S in V2 < 5 mm
- RS or Rs in V2 and V3.
Results: 492 (49%) of 999 patients met the criteria of admission to a detailed analysis. Based on the criteria of appearance of q wave in V1 and V2, LSFB was suspected in 2 patients. This represents 0.2% of all investigated and 0.4% of those admitted to the detailed analysis.
Conclusion: Electrocardiographic criteria of LSFB appear very rarely in the course of routine ET.