Effect of heart rate and pacing mode on QRS fragmentation

BACKGROUND: The study was designed to investigate the effect of heart rate and pacing mode on QRS fragmentation (f‐QRS). Moreover, the usefulness of f‐QRS in distinguishing patients with impaired left ventricular ejection function (EF) and ventricular tachycardia (VT) from patients with normal EF was assessed. METHODS: Three hundred and six recipients, with dual‐chamber device, with intrinsic narrow or wide QRS complex and preserved atrioventricular conduction were grouped into normal‐EF or impaired‐EF VT. We analyzed intrinsic narrow f‐QRS and wide f‐QRS as well as ventricular‐paced f‐QRS following different heart rates (baseline, 100 bpm) and pacing modes. RESULTS: In the baseline state, overall, patients with impaired‐EF VT (35 ± 9%), compared to those with normal‐EF, had more f‐QRS (56% vs 27%, P < .001) and ventricular‐paced f‐QRS (62% vs 16%, P < .0001). Ventricular pacing conferred both at baseline and at higher heart rate more ventricular‐paced f‐QRS in patients with impaired‐EF VT than in normal‐EF (P < .001). Detection of ventricular‐paced f‐QRS markedly improved overall specificity (84%) and positive predictive value (91%) in identifying patients with impaired‐EF VT. CONCLUSIONS: Increased heart rate or/and ventricular pacing uncover QRS fragmentations. Detection of ventricular‐paced f‐QRS adds value toward noninvasive identification of patients with impaired‐EF VT.