The impact of conscious sedation on induced cardiac arrhythmia prior to catheter ablation

Catheter ablation has become the standard treatment for many arrhythmias. Despite the possible patient discomfort, many centers perform an electrophysiologic study (EPS) for ablation of documented or suspected supraventricular tachycardia (SVT) without sedation, for the fear to hamper tachycardia inducibility and ablation success.

To test the hypothesis that during an EPS, a regimen of sedation with ketamine and midazolam is non-inferior to an EPS without sedation with respect to inducibility of sustained SVT prior to catheter ablation.

A total of 54 patients undergoing EPS for documented or suspected SVT were studied (24 female, age 54±years, hypertension, N=16, diabetes, N=3, coronary artery disease, N=3). Each patient was serving as his own control. A standard programmed stimulation protocol was performed without sedation and repeated, following conscious sedation with ketamine and midazolam. The protocol included, in a stepwise, more aggressive fashion, until a sustained SVT could be induced or refractoriness was reached: atrial pacing at fixed, increasing rates (S1), pacing at a drive cycle length of 500ms for 8 beats, then inducing an extra stimulus with a decreasing coupling interval until refractory period is reached (S2), inducing a second extra stimulus with a decreasing coupling interval (S3). If no arrhythmia could be induced by then, isoprenaline was administered. In some patients, SVT was mechanically induced (sinus rhythm). Data are presented as absolute numbers (%). A RMLE analysis was used to assess non-inferiority (arrhythmia inducible while being conscious and while been sedated). A Stuart-Maxwell test was used for comparison of paired ordinal data. Patient comfort was assessed for the conscious and the sedated state, using a scale from 1-7 (1: perfect; 7: horror).

Arrhythmia was inducible in 51 (94.4%) patients without sedation and in 52 (96.3%) patients while being sedated. Accepting a - 8% non-inferiority margin, the non-inferiority assumption is met (mean difference 0.019 [95% CI -0.019 -0.056]). On average, a dose of 4.7±2.8 mg midazolam and 26.3±15.9 mg ketamine was administered.

Indication for ablation was AV nodal reentry reentry tachycardia (N=42, 78%), AV reentry (retrogradely conducting accessory pathway; N=3, 5.6%) and atrial tachycardia (N=8, 15%). No ablation: N=1 (1.9%); unsuccessful ablation (focal atrial tachycardia): N=3 (5.6%).

A sedation regimen with ketamine and midazolam during EPS was non-inferior to a conscious state with respect to inducibility of sustained SVT. If confirmed for a larger patient cohort, this protocol may improve patient comfort without hampering SVT inducibility.

Induction