How to do it Article
A 61-year-old male patient (170 cm, 59 kg, body mass index 22.1) was admitted to our hospital with recurrent sustained ventricular tachycardias (VTs). He suffered from a dilated cardiomyopathy (first diagnosed in 2014) most likely because of long-term abuse of alcohol with abstention since 2 years. Concomitant diseases were a one vessel coronary artery disease, chronic obstructive bronchitis, and Bechterews disease. Furthermore, a loss of hemoglobin was documented because of gastrointestinal bleedings from angiodysplasia. In 2015, a cardiac resynchronization therapy (CRT) system had been implanted (Medtronic Maximo II, Medtronic, Minneapolis), and in March 2017, the patient underwent implantation of a left ventricular assist device (LVAD [HVAD, Heartware, Massachusetts]). On admission, the patient presented in a condition of periodic dizziness and with recurrent episodes of VTs. Mean arterial pressure was 80 mmHg, the LVAD worked with estimated flow of 4.5 l/min, 2700 rpm, and a power of 3.5 W. Breathing frequency was 17/min and pulse 73/min. The medication consisted of atorvastatin, carvedilol, pantoprazol, acetylsalicylic acid, potassium capsules, sacubitril/valsartan, amiodarone, phenprocoumon, torasemide, and ranolazine. Amiodarone had to be stopped because of QT-interval prolongation.
The ablation was performed under general anesthesia. The right femoral vein was punctured four times with one 8 F and three 6 F sheaths. Transseptal approach was performed with a BRK needle (SJM, St. Paul, Minnesota) via a LAMP 45 sheath (SJM). The fixed sheath was exchanged for a steerable sheath (SJM Aegilis). After introducing a mapping and ablation catheter (ThermoCool SmartTouch, Biosense Webster, Diamond Bar) into the left ventricle (LV), a three-dimensional mapping system (CARTO 3, BiosenseWebster) was initialized using the UNIVU function. UNIVU has been shown to facilitate navigation and saving fluoroscopy by integrating fluoroscopic data into the mapping system.1 We administered heparin to maintain an activated clotting time of more than 300 s. This value was determined every 15 minutes.
Our intention was to perform both a fast anatomical mapping (FAM) and a bipolar voltage map of the LV. Because of an interference of the LVAD system with CARTO, we were unable to derive an intracardiac ECG with the ablation catheter. Thus, we were unable to perform the voltage mapping (Figure 1). By chance, we observed that this interference was stopped on application of radiofrequency (RF) energy to the myocardium of the LV. Therefore, we reduced ablation power settings down to 5 W, enabling us to create an FAM and voltage map with a clear ECG under a continuous mode of ablation. Reducing the power of ablation below 5 W (e.g., 3 W) did not show the effect of overcoming the interference. We avoided resting the catheter at a specific location during mapping to prevent significant RF delivery at unwanted sites. After adequate mapping, inferobasal low-voltage areas colocalizing with a perfectly matching pace map (of the clinical VT at a cycle length of 500 ms) could be identified (Figure 2). Furthermore, sites of slow conduction were identified by detection of fractionated electrograms. Ablation of these regions was performed by application of RF impulses with a maximum of 40 W from an irrigated catheter. At the end of the ablation, no VT was inducible during programmed decremental right ventricular stimulation with a basic cycle length of 600 ms, as well as 500 ms and S4 coupling.
A few days after the ablation, the patient developed again sustained VTs with slight dizziness and with longer VT-free intervals. The morphology of this VT was identical with the one before ablation, showing a marginally different cycle length of 530 ms. We first added prajmalin as an antiarrhythmic drug, then, in a second step, we reduced the LVADs flow from 2700 to 2400 rpm to avoid potential suction. Beneath this, the patient still suffered from an increasing amount of VTs. We then changed the antiarrhythmic medication to flecainide twice a day, which lowered the VT load. One week later, the patient was discharged in stable conditions. We saw him recently, 6 months after ablation, in our CRT ambulance in adequate clinical condition, without any new episode of VT. Although he was still complaining about paroxysmal dizziness without the presence of VTs, this grievance may have another origin.
The clinical presentation of patients with LVAD who develop VTs is heterogeneous and ranges from palpitations, ICD shock, and dyspnea to dizziness, syncope, and chest pain.2 Here we report on a case with ablation of VT in a patient with a LVAD, despite interference of the LVAD with the three-dimensional mapping system. Only a small number of studies and case reports have been published yet on this topic.3–5 Boudghène-Stambouli et al.6 and other groups reported on interferences of LVAD systems and implanted cardioverter defibrillators. In 2015, Sacher et al. 7 reported on electromagnetic interference between the LVAD system and a three-dimensional mapping system. To the best of our knowledge, this is the first report on how to successfully overcome this interference by a “hot mapping” FAM and voltage map by pretending an ablation with only 5 W. Technically, the energy to rotate the LVADs impeller is provided by electromagnets. This leads to electromagnetic interference with the CARTO system, which itself utilizes electromagnetic technology for navigation. At the moment of energy delivery with the ablation catheter, this electromagnetic interference of the two technologies seems to be interrupted for the time of ablation, without known technical reason (personal communication with the supplier of the three-dimensional mapping system). Of note, the time of energy delivery should be kept as short as possible to prevent harm from healthy tissue. However, the size and depth of a lesion created by ablation is dependent on the magnitude of applied power. Thus, we do not expect harmful lesions in areas experiencing brief 5 W exposures. As is the standard for left-sided procedures, we used an irrigated catheter. During ablation with more than 30 W, 30 ml/min of fluid was administered, 17 ml/min while ablating below 30 W. During periods without ablation, this flow amounts to 2 ml/min. In our case, the total ablation time was 18.33 min. The time of “hot mapping” at 5 W was 5.25 minutes, accounting for an additional fluid of approximately 90 ml. In our opinion, this is an acceptable amount, even in LVAD patients. Activated clotting time was maintained over 300 s the whole time during ablation; we therefore do not expect an elevated risk of embolic phenomena, for example, device thrombosis because of this extra time of RF delivery. The patient developed a recurrent VT a few days after ablation, which showed the same morphology with a slightly different cycle length. As the patient was arrhythmia-free 6 months post ablation, we do not think that hot mapping was responsible for this recurrent VT.
Interferences between LVAD and mapping systems seem to be rare. “Hot mapping” may be a successful approach to perform a mapping procedure under these circumstances, especially near the cannula of the LVAD.
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Keywords:Copyright © 2018 by the American Society for Artificial Internal Organs
left ventricular assist device; ventricular tachycardia; three-dimensional mapping system; ablation