Background: Isoproterenol, a non-specific beta agonist,
is commonly used during electrophysiology studies (EPS). However, with
the significant increase in the price of isoproterenol in 2015 and the
increasing number of catheter ablations performed, the cost implications
cannot be ignored. Dobutamine is a less expensive synthetic compound
developed from isoproterenol with a similar mechanism to enhance cardiac
conduction and shorten refractoriness, thus making it a feasible
substitute with a lower cost. However, the use of dobutamine for EPS has
not been well-reported in the literature.
Objective: To determine the site-specific effects of
various doses of dobutamine on cardiac conduction and refractoriness and
assess its safety during EPS.
Methods: From February 2020 to October 2020, 40
non-consecutive patients scheduled for elective EPS, supraventricular
tachycardia, atrial fibrillation, and premature ventricular contraction
ablations at a single center were consented and prospectively enrolled
to assess the effect of dobutamine on the cardiac conduction system. At
the end of each ablation procedure, measures of cardiac conduction and
refractoriness were recorded at baseline and with incremental doses of
dobutamine at 5, 10, 15, and 20 mcg/kg/min. For the primary analysis,
the change per dose of dobutamine from baseline to each dosing level of
dobutamine received by the patients, comparing atrioventricular node
block cycle length (AVNBCL), ventricular atrial block cycle length
(VABCL) and sinus cycle length (SCL), was tested using mixed-effect
regression. For the secondary analysis, dobutamine dose level was tested
for association with relative changes from baseline of each
electrophysiologic parameter (SCL, AVNBCL, VABCL, atrioventricular node
effective refractory period (AVNERP), AH, QRS, QT, atrial effective
refractory period (AERP), ventricular effective refractory period
(VERP), using mixed-effect regression. Changes in systolic and diastolic
blood pressures were also assessed. The Holm-Bonferroni method was used
to adjust for multiple testing.
Results: For the primary analysis there was no
statistically significant change of AVNBCL and VABCL relative to SCL
from baseline to each dose level of dobutamine. The SCL, AVNBCL, VABCL,
AVNERP, AERP, VERP and the AH, and QT intervals all demonstrated a
statistically significant decrease from baseline to at least one dose
level with incremental dobutamine dosing. Two patients (5%) developed
hypotension during the study and one patient (2.5%) received a
vasopressor. Two patients (5%) had induced arrhythmias but otherwise no
major adverse events were noted.
Conclusion: In this study, there was no statistically
significant change of AVNBCL and VABCL relative to SCL from baseline to
any dose level of dobutamine. As expected, the AH and QT intervals, and
the VABCL, VERP, AERP and AVNERP all significantly decreased from
baseline to at least one dose level with an escalation in dobutamine
dose. Dobutamine was well-tolerated and safe to use during EPS.
Key words: Dobutamine, electrophysiology study, supraventricular
tachycardia, cardiac conduction, cost analysis