The present study supports previous observations of the association between WPW syndrome and MELAS syndrome. Furthermore, the present case shows successful catheter ablation of an accessory pathway and periinterventional management including capnography-monitored deep analgosedation.
Recently, the case of a 44-year old female with a diagnosis of MELAS syndrome with the associated cardiac manifestations of left ventricular hypertrophy and atrial tachycardia was reported. That case also demonstrated cardiac involvement in MELAS syndrome. Furthermore, a larger series of 30 MELAS patients showed that 13% (4/30 patients) of the patients had signs of ventricular preexcitation on the surface ECG. Another series (Hirano et al.) noted a WPW syndrome in six of 43 patients, and in addition, cardiac conduction disturbances in three of 43 MELAS patients. In general, WPW syndrome occurs in 1.5 to 3.1 per 1000 persons in Western countries, which is substantially less than the reported incidence in MELAS syndrome. Interestingly, mutations in genes related to cellular energy metabolism, like the PRKAG2 gene (an adenosine monophosphate-activated protein kinase), have been linked to the development of WPW syndrome. During fetal development, altered cellular energy metabolism appears as a possible mechanism underlying the pathogenesis of abnormalities of the conduction system. Thus, MELAS syndrome including the concomitant mitochondrial pathologies may create a sort of energy depleted state, preventing normal maturation of the insulating ring, leading to persistence of abnormal conductive pathways. Nevertheless, a precise understanding of how mitochondrial diseases cause the development of WPW syndrome at molecular and cellular levels remains to be determined [1, 3, 5].
Cases of general anesthesia combined with mechanical ventilation have been described in MELAS syndrome using infusion of propofol, ramifentanyl as well as muscle relaxants. In those cases, muscle relaxant effects were antagonized with glycopyrrolate (0.4 mg) and pyridostigmine (15 mg) [1, 4,5,6]. In contrast to procedures in general anesthesia, the authors used conscious sedation in their case using midazolam and fentanyl. Since respiration was preserved throughout the intervention, there was no need to antagonize drug effects. In addition, pH levels remained constant without any need for an intervention. Thus, regular conscious sedation can be used in patients with MELAS syndrome. However, pH, lactate, respiration (O2 saturation and CO2 levels) should be monitored in such patients.
Thus, this is a report about successful catheter ablation of WPW syndrome including a left posterolateral accessory pathway using analgosedation in a patient with MELAS syndrome.