Key result
Parasympathetic blockade with atropine revealed preserved parasympathetic effects on sinus cycle length at rest (320 ms, P=0.0001), exercise (105 ms, P=0.0003), and recovery (155 ms, P=0.0002).
Why the study?
Does parasympathetic blockade with atropine alter cardiac electrophysiology during rest, exercise, and recovery in patients with left ventricular dysfunction?
Observational (n=10)
Does parasympathetic blockade with atropine alter cardiac electrophysiology during rest, exercise, and recovery in patients with left ventricular dysfunction?
Parasympathetic effects on cardiac electrophysiology are preserved during rest, exercise, and recovery in patients with left ventricular dysfunction, suggesting the role of autonomic changes in sudden death pathophysiology requires further exploration.
Answers are grounded in this paper and cite their sources.
Preserved parasympathetic effects in LV dysfunction warrant no practice change; leaves open their role in sudden death risk.
Depressed parasympathetic activity has been proposed to be associated with an increased risk of sudden death. Parasympathetic effects (PE) on cardiac electrophysiology during exercise and recovery have not been studied in patients with left ventricular dysfunction. We performed noninvasive electrophysiological studies (NI-EPS) and characterized the electrophysiological properties of the sinus node, atrioventricular (AV) node, and ventricle in subjects with depressed left ventricular ejection fraction and dual-chamber defibrillators. NI-EPS were performed during rest, exercise, and recovery at baseline and after parasympathetic blockade with atropine to assess PE (the difference between parameter values in the 2 conditions). Ten subjects (9 men: age, 60 +/- 9 yr; and left ventricular ejection fraction, 29 +/- 8%) completed the study. All NI-EPS parameters decreased during exercise and trended toward rest values during recovery. PE at rest, during exercise, and during recovery, respectively, were on sinus cycle length, 320 +/- 71 (P = 0.0001), 105 +/- 60 (P = 0.0003), and 155 +/- 82 ms (P = 0.0002); on AV block cycle length, 137 +/- 136 (P = 0.09), 37 +/- 19 (P = 0.002), and 61 +/- 39 ms (P = 0.006); on AV interval, 58 +/- 32 (P = 0.035), 22 +/- 13 (P = 0.002), and 36 +/- 20 ms (P = 0.001); on ventricular effective refractory period, 15.8 +/- 11.3 (P = 0.02), 4.7 +/- 15.2 (P = 0.38), and 6.8 +/- 15.5 ms (P = 0.20); and on QT interval, 13 +/- 12 (P = 0.13), 3 +/- 17 (P = 0.6), and 20 +/- 23 (P = 0.04). In conclusion, we describe for the first time the changes in cardiac electrophysiology and PE during rest, exercise, and recovery in subjects with left ventricular dysfunction. PEs are preserved in these patients. Thus the role of autonomic changes in the pathophysiology of sudden death requires further exploration.
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Chicos et al. (2009) conducted an observational in Left ventricular dysfunction (n=10). Parasympathetic blockade with atropine vs. Baseline was evaluated on Parasympathetic effects on sinus cycle length at rest (320 ms, p=0.0001). Parasympathetic blockade with atropine revealed preserved parasympathetic effects on sinus cycle length at rest (320 ms, P=0.0001), exercise (105 ms, P=0.0003), and recovery (155 ms, P=0.0002).
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