Vibration was the most effective stimulus for detaching the otoconia from the cupula in these experimental models of cupulolithiasis.

No abstract

The otoconia of the utricle were dislodged into the semicircular canal after applying vibration. The time to dislodgement was significantly shorter in the vestibular dysfunction models than in the normal models; the utricular macula sustained significant morphological damage.

IntroductionLittle is known about the impact of blood‐pool local impedance (LI) on lesion characteristics and the incidence of steam pops.MethodsRadiofrequency applications at a range of powers (30, 40, and 50 W), contact forces (CF) (5, 15, and 25 g), and durations (15, 30, 45, and 120 s) using perpendicular/parallel catheter orientation were performed in 40 excised porcine preparations, using a catheter capable of monitoring LI (StablePoint©, Boston Scientific). To simulate the variability in blood‐pool impedance, the saline‐pool LI was modulated by calibrating saline concentrations. Lesion characteristics were compared under three values of saline‐pool LI: 120, 160, and 200 Ω.ResultsOf 648 lesions created, steam pops occurred in 175 (27.0%). When power, CF, time, and catheter orientation were adjusted, ablation at a saline‐pool impedance of 160 or 200 Ω more than doubled the risk of steam pops compared with a saline‐pool impedance of 120 Ω (Odds ratio = 2.31; p = .0002). Lesions in a saline‐pool impedance of 120 Ω were significantly larger in surface area (50 [38–62], 45 [34–56], and 41 [34–60] mm2 for 120, 160, and 200 Ω, p < .05), but shallower in depth (4.0 [3–5], 4.4 [3.2–5.3], and 4.5 [3.8–5.5] mmfor 120, 160, and 200 Ω, respectively, p < .05) compared with the other two settings. The correlation between the absolute LI‐drop and lesion size weakened as the saline‐pool LI became higher (e.g., 120 Ω group (r2 = .30, r2 = .18, and r2 = .16, respectively for 120, 160, and 200 Ω), but the usage of %LI‐drop (= absolute LI‐drop/initial LI) instead of absolute LI‐drop may minimize this effect.ConclusionsIn an experimental model, baseline saline‐pool impedance significantly affects the lesion metrics and the risk of steam pops.

Background Although the mechanism of an AT can usually be elucidated using modern high-resolution mapping systems, it would be helpful if the AT mechanism and circuit could be predicted before initiating mapping. Objective We examined if information gathered from the cycle length (CL) of the tachycardia can help predict AT-mechanism and its localization. Methods 138 activation maps of ATs including 8 focal-ATs, 94 macroreentrant-ATs and 36 localized-ATs in 95 patients were retrospectively reviewed. Maximal CL (MCL) and minimal CL (mCL) over a minute period were measured via a decapolar catheter in the coronary sinus. CL-variation and beat-by-beat CL-alternation were examined. Additionally, CL-respiration correlation was analyzed by the RhythmiaTM system. Results Both MCL and mCL were significantly shorter in macroreentrant-ATs (MCL = 288[253-348]ms, p = 0.0001; mCL = 283[243-341]ms, p = 0.0012), and also shorter in localized-ATs (MCL = 314[261-349]ms, p = 0.0016; mCL = 295[248-340]ms, p = 0.0047) compared to focal-ATs (MCL = 506[421-555]ms, mCL = 427[347-508]ms). An absolute CL-variation (MCL-mCL) &lt; 24 ms significantly differentiated reentrant ATs from focal-ATs with a sensitivity = 96.9%, specificity = 100%, positive predictive value (PPV) = 100% and negative predictive value (NPV) = 66.7%. The beat-by-beat CL-alternation was observed in 10/138 (7.2%), all of which showed the reentrant mechanism, meaning that beat-by-beat CL-alternation was the strong sign of reentrant mechanism (PPV = 100%). Although the CL-respiration correlation was observed in 28/138 (20.3%) of ATs, this was predominantly in right-atrium (RA)-ATs (24/41, 85.7%), rather than left atrium (LA)-ATs (4/97, 4.1%). A positive CL-respiration correlation highly predicted RA-ATs (PPV = 85.7%), and negative CL-respiration correlation probably suggested LA-ATs (NPV = 84.5%). Conclusion Detailed analysis of the tachycardia CL helps predict the AT-mechanism and the active AT chamber before an initial mapping.