Combined local impedance and contact force for radiofrequency ablation assessment.

BACKGROUND: The combination of contact force (CF) and local impedance (LI) may improve tissue characterization and lesion prediction during radiofrequency (RF) ablation. OBJECTIVE: The purpose of this study was to evaluate the utility of LI combined with CF in assessing RF ablation efficacy. METHODS: An LI catheter with CF sensing was evaluated in swine (n = 11) and in vitro (n = 14). The relationship between LI and CF in different tissue types was evaluated in vivo. Discrete lesions were created in vitro and in vivo at a range of forces, powers, and durations. Finally, an intercaval line was created in 3 groups at 30 W: 30s, Δ20Ω, and Δ30Ω. In the Δ20Ω and Δ30Ω groups, the user ablated until a 20 or 30 Ω LI drop. In the 30s group, the user was blinded to LI. RESULTS: In vivo, distinction in LI was found between the blood pool and the myocardium (blood pool: 122 ± 7.02 Ω; perpendicular contact: 220 ± 29 Ω; parallel contact: 207 ± 31 Ω). LI drop correlated with lesion depth both in vitro (R = 0.84) and in vivo (R = 0.79), informing sufficient lesion creation (LI drop >20 Ω) and warning of excessive heating (LI drop >65 Ω). When creating an intercaval line, the total RF time was significantly reduced when using LI guidance (6.4 ± 2 minutes in Δ20Ω and 8.1 ± 1 minutes in Δ30Ω) compared with a standard 30-second workflow (18 ± 7 minutes). Acute conduction block was achieved in all Δ30Ω and 30s lines. CONCLUSION: The addition of LI to CF provides feedback on both electrical and mechanical loads. This provides information on tissue type and catheter-tissue coupling; provides feedback on whether volumetric tissue heating is inadequate, sufficient, or excessive; and reduces ablation time.

Noninvasive assessment of dofetilide plasma concentration using a deep learning (neural network) analysis of the surface electrocardiogram: A proof of concept study.

BACKGROUND: Dofetilide is an effective antiarrhythmic medication for rhythm control in atrial fibrillation, but carries a significant risk of pro-arrhythmia and requires meticulous dosing and monitoring. The cornerstone of this monitoring, measurement of the QT/QTc interval, is an imperfect surrogate for plasma concentration, efficacy, and risk of pro-arrhythmic potential. OBJECTIVE: The aim of our study was to test the application of a deep learning approach (using a convolutional neural network) to assess morphological changes on the surface ECG (beyond the QT interval) in relation to dofetilide plasma concentrations. METHODS: We obtained publically available serial ECGs and plasma drug concentrations from 42 healthy subjects who received dofetilide or placebo in a placebo-controlled cross-over randomized controlled clinical trial. Three replicate 10-s ECGs were extracted at predefined time-points with simultaneous measurement of dofetilide plasma concentration We developed a deep learning algorithm to predict dofetilide plasma concentration in 30 subjects and then tested the model in the remaining 12 subjects. We compared the deep leaning approach to a linear model based only on QTc. RESULTS: Fourty two healthy subjects (21 females, 21 males) were studied with a mean age of 26.9 ± 5.5 years. A linear model of the QTc correlated reasonably well with dofetilide drug levels (r = 0.64). The best correlation to dofetilide level was achieved with the deep learning model (r = 0.85). CONCLUSION: This proof of concept study suggests that artificial intelligence (deep learning/neural network) applied to the surface ECG is superior to analysis of the QT interval alone in predicting plasma dofetilide concentration.

Mobile thrombus on cardiac implantable electronic device leads of patients undergoing cardiac ablation: incidence, management, and outcomes.

PURPOSE: The rates of cardiovascular implantable electronic device (CIED) implantations and cardiac ablation procedures are increasing worldwide. To date, the management of CIED lead thrombi in the peri-ablation period remains undefined and key clinical management questions remained unanswered. We sought to describe the clinical course and management strategies of patients with a CIED lead thrombus detected in the peri-ablative setting. METHODS: We performed a retrospective analysis of all patients who underwent a cardiac ablation procedure at Mayo Clinic Rochester from 2000 to 2014. Patients were included in our study cohort if they had documented CIED lead thrombus noted on peri-ablation imaging studies. Electronic medical records were reviewed to determine the overall management strategy, outcomes, and embolic complications in these patients. RESULTS: Our overall cohort included 1833 patients, with 27 (1.4 %) having both cardiac ablation procedures as well as CIED lead thrombus detected on imaging. Of these 27 patients, 21 were male (77 %), and the mean age was 59.2 years. The mean duration of follow-up was 16.5 months (range 3 days-48.3 months). Anticoagulation was an effective therapeutic strategy, with 11/14 (78.6 %) patients experiencing either resolution of the thrombus or reduction in size on re-imaging. For atrial fibrillation ablation, the most common management strategy was a deferment in ablation with initiation/intensification of anticoagulation medication. For ventricular tachycardia ablations, most procedures involved a modified approach with the use of a retrograde aortic approach to access the left ventricle. No patient had any documented embolic complications. CONCLUSIONS: The incidence of lead thrombi in patients undergoing an ablation was small in our study cohort (1.4 %). Anticoagulation and deferral of ablation represented successful management strategies for atrial fibrillation ablation. For patients undergoing ventricular tachycardia ablation, a modified approach using retrograde aortic access to the ventricle was successful. In patients who are not on warfarin anticoagulation at the time of thrombus detection, we recommend initiation of this medication, with a goal INR of 2-3. For patients on warfarin at the time of thrombus detection, we recommend an intensification of anticoagulation with a goal INR of 3.0.