Recovery from sudden death in a young patient with intermittent and asymptomatic ventricular preexcitation. Should we be more invasive in the diagnosis and treatment?
GABRIEL SALICA, JAVIER BONACINA
Instituto Tucumán de Enfermedades del Corazón (ITEC), Hospital Ángel C. Padilla.
(4000) San Miguel de Tucuman, Argentina. E-mail
Recibido 06-MAY-2018 – ACEPTADO después de revisión el 27-MAYO-2018.
There are no conflicts of interest to disclose.
In intermittent ventricular preexcitation, evaluated by supplementary non-invasive methods, such as 24-h Holter and graded ergometer test, these provide information on the anterograde conduction capacity of the accessory pathway. For years it has been the subject of study, publications and discussions on the management, follow-up and treatment that should be performed on these patients. There are conservative schools that choose not to be invasive with the patient, while others consider that invasive electrophysiology is the only tool capable of inexorably preventing the appearance of arrhythmias in which the pathway plays a leading role. The aim in reporting this infrequent case of an adolescent with intermittent and asymptomatic preexcitation, with non-invasive follow-up for 10 years, in another center, who debuted with a syncopal episode and sudden death from which he successfully recovered, then ablating successfully the left lateral accessory pathway without complications is to review the literature about the true "benignity" of accessory pathways.
In Wolff-Parkinson-White (WPW) syndrome, there is an anomalous connection between the atria and the ventricles, enabling atrial impulses to exit the ventricles before what is expected, indicating a conduction alternative to the normal one, which is what is known as accessory pathway. The presence of accessory pathway may produce, by reentry mechanisms, different types of supraventricular tachyarrhythmias, which are considered of low risk of death; however, the coexistence of these pathways with other atrial rhythms, particularly atrial fibrillation (AF), may cause a high ventricular rate and lead to ventricular fibrillation (VF) with the subsequent risk of death. The incidence of sudden cardiac death (SCD) is 3.3 per each 10,000 patients per year .
Different evaluation methods, both invasive and noninvasive, attempt to know the risk in these patients. A proportion of asymptomatic patients, close to 50%, may present a high risk marker, but epidemiological tests state that the risk of SCD is low [2,3,4].
We present the case of a patient with intermittent ventricular preexcitation, with no symptoms, diagnosed 10 years ago, who is admitted into the ER due to palpitations and syncope, and finally VF requiring cardiac reanimation and electrical cardioversion (ECV).
Male, 14-year-old patient, who consulted in his hometown, due to frequent palpitations that at the time of consultation, had a 30-minute evolution. ECG was made (Figure 1) that showed tachycardia with irregular wide QRS, compatible with preexcited AF, with RR interval of 300 ms. At the time of the evaluation in the medical center where he consulted, he suffered syncope symptoms, with recording of ventricular fibrillation in the monitor, so cardiopulmonary resuscitation maneuvers and ECV were applied, with recovery of sinus rhythm.
Figura 1.ECG in admission. In D1-D2-D3-aVR, preexcited atrial fibrillation. In V3-V4,
preexcited atrial fibrillation is observed with RR interval of less than 300 ms.
Post-cardioversion ECG does not show ventricular preexcitation. The patient remained hospitalized, and ECGs during that period show repeated minimum ventricular preexcitation (Figure 2).
Figure 2. ECG post ECV for ventricular fibrillation.
Minimum preexcitation is observed.
He was referred to our service for an electrophysiology evaluation. In admission, the patient was asymptomatic. Previous follow-up tests with Holter reported intermittent preexcitation with disappearance of it at a 130 bpm rate (Figure 3). An ergometer test yielded similar results, while he had not received antiarrhythmic treatment previously.
Figure 3. Holter before the atrial fibrillation event,
where intermittent ventricular preexcitation is observed.
The electrophysiology study was conducted, which was carried out under local anesthesia, placing 2 venous introducer sheaths in the right femoral vein, to place a diagnostic decapolar catheter in the coronary sinus and a quadripolar catheter in the His bundle. Right ventricular stimulation showed eccentric conduction with ventriculo-atrial interval earlier in the distal coronary sinus. Anterograde stimulation showed an effective refractory period of the pathway of 380 ms. Left lateral accessory pathway was verified, so radiofrequency ablation was performed by radiofrequency by retrograde aortic approach. Ablation catheter of 4 mm was placed in the lateral region of the mitral annulus, a site where RF application was successful, observing delta wave disappearance (Figure 4). The patient was discharged with no complications.
Figure 4. Electrograms during the application of radiofrequency,
showing the disappearance of ventricular preexcitation.
A significant number of population studies have evaluated the follow-up of patients with ventricular preexcitation. One of the oldest ones is from 1968, which evaluated 2251 patients for 28 years. Thirteen percent had presented tachycardia and 3 patients died with no clear relation to ventricular preexcitation . In a more recent Greek study with 157 patients, 77 of them were asymptomatic, followed for 55 months, and none presented sudden cardiac death . Fitzsimmons included in an 11-year follow-up, 238 individuals with ventricular preexcitation, with follow-up between 1 and 7 years, in whom an electrophysiology study (EPS) was made to determine which electrophysiological parameters predict risk of sudden cardiac death or of suffering tachyarrhythmias, and none presented sudden cardiac death .
In different publications, among them, those of the Maastricht group, a cooperative series of 7 European hospitals, and Klein observed that VF in patients with ventricular preexcitation as first symptom was very rare, although the risk is not completely ruled out, and in most the appearance of VF was predicted from previous arrhythmias [7,8,9,10].
The invasive evaluation of the electrophysiological properties of accessory pathways, such as anterograde refractory period and ventricular response during AF could be different between patients with VF and those that do not present it, which is considered of great interest in risk stratification . Papone et al, in a study of 212 patients with a 5-year follow-up, found that the induction of reentry arrhythmias, AF or the presence of multiple pathways are related to fatal arrhythmic events, so they propose EPS as a valuable tool in the risk stratification of symptomatic and fatal arrhythmic events .
The latter may not be extended to the pediatric population. Brembilla et al, studying 47 patients with an average age of 12 years, who underwent EPS initially and a second EPS during follow-up, did not show changes after 6.3 years of follow-up and induced AF presented a relatively low prognostic value for the prediction of adverse events . However, Santinelli in a study in children with an average age of 10 years, followed for 57 months observed that patients with short anterograde effective refractory period (AERP) and multiple accessory pathways were indicators of major risk for the development of arrhythmias risky for life .
Noninvasive evaluation has been based on its correlation to invasive evaluation. Findings like intermittent preexcitation, disappearance of preexcitation during ergometer test, were correlated to “low risk” electrophysiology findings. Also, the absence of syncope is considered of “low risk” as its presence is associated to the appearance of atrial fibrillation with rapid ventricular response (64% sensitivity and 100% specificity) .
These risk indicators were never assessed in a prospective epidemiological context, and its study did not go beyond the comparison of risk substitutes . Timmermans, in a population of 650 patients, besides the classical criteria, added the presence of emotional stress situations or exercise contributing to the development of VF .
The asymptomatic patient presented had intermittent ventricular preexcitation, so it was in the “low risk” group; however, the first episode was SCD.
A question to be asked is, Why an accessory pathway with a poor anterograde conduction capacity, as in the case of the patient presented, suddenly improves its conduction capacity?
A possible answer is supernormal conduction. Rosenbaum’s group published that a significant percentage of patients with anomalous pathways that presented prolonged AERP maintain the capacity to conduct atrial impulses during an early RR interval and a brief diastole within a refractoriness period. This unexpected and paradoxical conduction of the impulse is what is known as supernormal conduction . The supernormal (SN) phase of conduction of accessory pathways may facilitate the presence of VF during an episode of AF. The gradual increase of heart rate at a given cycle length would allow atrial impulses to reach the accessory pathway during the supernormal conductivity phase; in this sense AF irregularity may facilitate for many atrial impulses to reach the accessory pathway and go through to the ventricle, thus facilitating the appearance of VF .
Levi et al, proposed in electrophysiological terms, that for supernormal conduction to occur, certain conditions should be present: 1) abnormal PR prolongation; 2) immersion of excitability within the RP through two possible mechanisms of exteriorized cathodal supernormality through a depolarizing current, or anodal supernormality generated by hyperpolarizing current originating at the adjacent myocardial repolarization . Occasionally, SN conduction may be the only manifestation of anterograde conduction by accessory pathway with an impaired conduction. The identification of SN conduction would allow us to identify the patients in high risk of VF; precisely those presenting intermittent ventricular preexcitation.
A second question that comes up is, Within the group of patients considered to be in low risk by a noninvasive evaluation, are there some patients in high risk? It is believed that the answer is yes, and maybe noninvasive evaluation is not enough to assess the true risk of VF in a patient with ventricular preexcitation. Intermittent preexcitation in a Holter recording or the disappearance of ventricular preexcitation in an ergometer test may have a relative value, since catecholamines cause an improvement in atrioventricular node conduction, thus decreasing the passage of impulses through the accessory pathway, and it does not necessarily indicate that it is a low-risk pathway.
Invasive evaluation could be the next step; however, taking some studies as reference, 45% of asymptomatic patients do not present retrograde conduction and just 27% may have orthodromic tachycardia induced [21-22], and in pediatric patients, only in 32% tachycardia is inducible . One of the electrophysiological parameters considered to be significant as risk maker is AERP of the accessory pathway <250 ms in symptomatic patients with no history of SCD, which is only present in 50% of cases, in contrast to the low incidence of SCD in this group of patients . In spite of this, as we previously mentioned, there are those that propose EPS as a valuable tool . An element to take into account is also that most SCD occur between 20 and 30 years of age, with a second peak at 50 .
In pediatric patients, with no structural heart disease, as in the case presented here, atrial fibrillation is uncommon, mainly before 10 years of age . This incidence slightly increases in teenagers, mainly associated to alcohol consumption, obesity, and the administration of drugs like oral and inhaled corticosteroids [26-27], as in the presented case.
A third question, that is controversial, is: Should all asymptomatic patients with ventricular preexcitation, who are in low risk or are considered to be in low risk, receive RF ablation?
Dorantes et al, mentioned that the impossibility of inducing arrhythmias in these patients does not guarantee they may not happen at another time . This mechanism could occur since there are regional variations in excitability modulated by the concentration of intracellular calcium . Under the argument that asymptomatic patients with intermittent ventricular preexcitation are in low risk and should not undergo the risk of RF ablation, some of them may be exposed to SCD.
In the case of the patient presented here, considered to be in low risk, his first symptom was sudden cardiac death. Because of what we commented here, it is evident that there are patients with ventricular preexcitation of high risk that cannot be identified in a noninvasive manner, and even EPS does not offer a reliable enough negative predictive value .
If the electrophysiology study is performed to assess the electrophysiological characteristics of the accessory pathway, it should be made along with RF ablation in the same act, as this procedure in expert hands has a high percentage of success and a low rate of complications, as shown by different registries . Also, it should be taken into account that ventricular preexcitation patients, asymptomatic at a given moment, over their life will develop heart diseases, receive drugs or present risk factors that may favor atrial arrhythmias and condition the appearance of VF.
Another element to take into account is age. In an artificial model where the risk of SCD was evaluated, as well as RF ablation therapy, they observed that risk is low before age 8, and the benefit of ablation is greater after 8 years of age . This could be due to what was mentioned above, since AF is very rare before age 10 .
CONCLUSIONS Patients carriers of intermittent WPW syndrome and asymptomatic are not exempt from presenting an episode of sudden cardiac death by ventricular fibrillation, so it would be convenient and reasonable to perform an electrophysiological study and if possible, to ablate the accessory pathway by radiofrequency.
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