Correspondence *Thorax Institute, Hospital Clínic, University of Barcelona, Villarroel 170, 08036 Barcelona, Spain

Email jbrugada@clinic.ub.es

The case

A 55-year-old man presented at a secondary hospital having had two episodes of syncope over the previous 3 months. Both episodes occurred while the patient was sitting down and lasted for about 2 min. The patient did not have any prodromic symptoms and did not report having had any palpitations, dizziness or chest pain before, during or after the syncopal episodes. He had recovered completely on each occasion without neurological sequelae or transient confusion. He had no notable medical history, was not taking any medications, and had no family history of either syncope or sudden death.

An initial physical examination did not reveal any abnormalities. The patient's supine blood pressure was 130/80 mmHg, with no postural drop. Electrocardiography revealed a sinus rhythm with an incomplete right bundle branch block (Figure 1A), and no abnormalities were detected on a transthoracic echocardiogram or cerebral CT scan. A carotid sinus massage (CSM) revealed a sinus pause of almost 7 s when pressure was applied to the patient's left side (Figure 2). During the course of this examination, the patient experienced a presyncopal episode, but he recovered rapidly without significant change in blood pressure, indicating a cardioinhibitory response.

Figure 1 A baseline 12-lead electrocardiogram taken when the patient initially presented at (A) a secondary hospital and (B) the arrhythmia unit of our hospital.

Both electrocardiograms show a sinus rhythm with incomplete right bundle branch block (rSr´ in the V1 lead). The repeat electrocardiogram (B) also showed a slight elevation of the J point from V1 to V3, which was considered to be early repolarization.

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Figure 2 An electrocardiogram recorded during a carotid sinus massage on the patient's left side.

The arrow shows the end of the previous T wave and a sinus pause of almost 7 s is evident.

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The patient was diagnosed with symptomatic carotid sinus hypersensitivity, and referred for implantation of a pacemaker. Repeat electrocardiography showed a sinus rhythm, incomplete right bundle branch block and slight elevation of the J point from V1 to V3, which was considered to be early repolarization (Figure 1B). A dual-chamber, rate-modulated pacemaker was implanted in the patient's left pectoral region without complications. At follow-up the patient was diagnosed with hypertension and began -blocker therapy. Subsequent electrocardiograms revealed a basal rhythm upon pacemaker stimulation. Several months later, the patient presented at hospital having had two new syncopal episodes. Electrocardiography carried out at presentation showed a sinus rhythm with continuous ventricular stimulation by the pacemaker. An interview with the patient confirmed that his syncopal episodes were sudden and always occurred while resting or supine. These characteristics suggested a high-risk condition, possibly with a cardiac-related cause, prompting re-evaluation of all data previously collected. Investigation of the pacemaker device confirmed that it was working properly; none of the recordings available indicated tachyarrhythmia. Re-examination of the patient's initial electrocardiograms revealed that leads V1 and V2 had a wide R wave with a slow descending component, resembling the coved and saddle-back patterns seen in Brugada syndrome (Figure 1A,B). After the patient's pacemaker rate had been reduced to avoid interference with intrinsic rhythm, repeat electrocardiography revealed a spontaneous pattern characteristic of Brugada syndrome (Figure 3): an incomplete right bundle branch block with descendant ST-segment elevation (2 mm) in leads V1 to V3 (a coved-type electrocardiogram). These findings confirmed a diagnosis of Brugada syndrome without the need for additional clinical investigations.

Figure 3 A baseline electrocardiogram taken 2 years after the patient's initial presentation, when he was admitted to hospital for a second time.

The electrocardiogram was recorded with standard right precordial leads V1 and V2 (at the fourth intercostal space) and shows a type 1 Brugada pattern (a coved ST-segment elevation of 0.2 mV), followed by a negative T wave in leads V1 and V2 (arrows), diagnostic of Brugada syndrome.

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Discussion of diagnosis

Identification of the underlying cause of syncope is difficult and might not be established in up to 18% of cases.¹ A diagnosis is important, however, to determine the prognosis for each patient, which can vary from benign cases of vasovagal syncope to cardiac syncope, which is associated with a more than twofold increase in mortality rate.² Although cardiac-related causes only account of a relatively small proportion of cases (14%), they should always be excluded because affected individuals have a worse prognosis.³

Careful evaluation of a patient's clinical history and physical examination can help establish the underlying cause of syncope in more than 25% of cases, and can guide investigation strategies in the remainder of patients.^{1, 4} Detailed descriptions of the patient's syncopal episodes (regarding circumstances prior to syncope, the onset, the attack itself, the end of the episode and details about personal and familial background) can help differentiate between vasovagal and cardiac syncope.^{3, 5} Characteristics of different causes of syncope are summarized in Box 1.

Although electrocardiography is an important part of the initial assessment of a patient with syncope, it is diagnostic in only 5% of cases and suggests a potential cause in a further 5% of patients.⁶ Any abnormalities in a baseline electrocardiogram, however, are predictive for an increased risk of sudden death, emphasizing the importance of investigating possible cardiac defects.³ Conduction disturbances, pre-excited QRS complexes, a prolonged or shortened QT interval, epsilon waves, Q waves or a Brugada pattern are all indicative of arrhythmic syncope.³

Syncopal episodes in the present case were sudden without prodromic symptomatology, and usually occurred while the patient was supine. These characteristics suggested a possible cardiac origin and the patient's first electrocardiogram showed an incomplete right bundle branch block and a slightly elevated J point (<1 mm) from V1 to V3 (Figure 1). Although these findings were nondiagnostic, such abnormalities should prompt a physician to suspect a Brugada pattern, particularly when the patient has severe syncope symptomatology. An exhaustive cardiac examination should, therefore, have been included in this patient's initial workup, including electrocardiography with elevated right precordial leads (V1 and V2) at the second or third intercostal space, which might have unmasked Brugada syndrome with more sensitivity than standard leads. A test with sodium channel blockers such as ajmaline, flecainide or procainamide would probably also have been useful.⁷ Brugada syndrome should be included in the differential diagnosis of a patient with syncope, particularly if symptoms are severe, if the electrocardiogram indicates a Brugada pattern, or when risk factors such as a family history of sudden death are present.

CSM can help to identify some forms of reflex syncope and assists diagnosis in almost 20% of cases that might otherwise have been classified as unknown origin.^{3, 6} A patient's response to CSM is considered positive and defined as carotid sinus hypersensitivity when asystole lasts longer than 3 s, blood pressure decreases by more than 50 mmHg, or both. Carotid sinus hypersensitivity has been described in up to 6.6–10% of asymptomatic patients, and is probably even more frequent among older patients.¹ Current guidelines, therefore, recommend cautious interpretation of a patient's response to CSM and exclusion of other causes of syncope before making a diagnosis.^{3, 8} In this case, CSM was performed because initial electrocardiographic findings were not considered significant, and other investigations such as the cerebral CT scan were normal. The patient's severe positive response led to a diagnosis of hypersensitive carotid sinus syndrome, illustrating how CSM can lead to confounding diagnoses and the importance of excluding competing diagnoses before using this technique.³

Treatment and management

Since the patient described had a high risk of malignant arrhythmias, an implantable cardioverter-defibrillator (ICD) was indicated and implanted. This is the only effective treatment currently available for patients with Brugada syndrome. In the present case, up to 12 episodes of ventricular arrhythmia were successfully reverted by the device over 3 years (Figure 4).

Figure 4 An electrocardiogram recording of ventricular fibrillation taken during follow-up.

The arrow on the left shows the onset of ventricular fibrillation and the arrow on the right shows its appropriate termination by the device.

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Syncope in Brugada syndrome is usually produced by rapid polymorphic ventricular tachycardia that terminates spontaneously, so cerebral perfusion is only transiently impaired. The presence of a syncope in a patient with Brugada syndrome is associated with an increased risk of sudden death or ventricular fibrillation, as well as a spontaneous pattern on an electrocardiogram (Tables 1 and 2).⁹ Patients who fulfill these two criteria require an ICD even if an electrophysiological study does not induce malignant arrhythmias.¹⁰ The multiple episodes of ventricular fibrillation treated by the ICD therapy during follow-up of this patient confirmed that this therapy was appropriate.

Table 1 Probability of sudden death or ventricular fibrillation during lifetime of patients with Brugada syndrome.

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Table 2 Probability of events during lifetime of patients with Brugada syndrome according to combination of risk factors.

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Conclusions

Here we describe a patient with recurrent syncope at rest who was initially diagnosed with hypersensitive carotid sinus syndrome associated with a cardioinhibitory response, according to the results of a CSM. Despite cardiac pacing, the patient had two more syncopal episodes, prompting a re-evaluation of his diagnosis. After additional clinical investigations, the patient was diagnosed with Brugada syndrome, which is associated with a high risk of sudden death. He received an ICD that successfully reverted several life-threatening ventricular arrhythmias during a 3-year follow-up. This case illustrates how syncope and slight abnormalities on electrocardiogram can be early signs of Brugada syndrome. It also highlights the importance of carrying out a complete cardiac evaluation as part of the diagnostic work-up in a patient with recurrent syncope.

References

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