The Prevalence of Brugada ECG in Adult Patients in a Large University Hospital in the Western United States

Authors

  • Daniel Donohue MD,

    1. From the Department of Medicine, Division of Cardiology, University of California, Irvine, CA;1 and the Department of Medicine, Section of Cardiology, University of Arizona Sarver Heart Center, Tucson, AZ2
    Search for more papers by this author
  • 1 Faramarz Tehrani BS,

    1. From the Department of Medicine, Division of Cardiology, University of California, Irvine, CA;1 and the Department of Medicine, Section of Cardiology, University of Arizona Sarver Heart Center, Tucson, AZ2
    Search for more papers by this author
  • 1 Reza Jamehdor MD,

    1. From the Department of Medicine, Division of Cardiology, University of California, Irvine, CA;1 and the Department of Medicine, Section of Cardiology, University of Arizona Sarver Heart Center, Tucson, AZ2
    Search for more papers by this author
  • 1 Cuong Lam BS,

    1. From the Department of Medicine, Division of Cardiology, University of California, Irvine, CA;1 and the Department of Medicine, Section of Cardiology, University of Arizona Sarver Heart Center, Tucson, AZ2
    Search for more papers by this author
  • and 1 Mohammad-Reza Movahed MD, PhD 2

    1. From the Department of Medicine, Division of Cardiology, University of California, Irvine, CA;1 and the Department of Medicine, Section of Cardiology, University of Arizona Sarver Heart Center, Tucson, AZ2
    Search for more papers by this author

Mohammad-Reza Movahed, MD, PhD, Associate Professor of Medicine, Director of Coronary Care Unit, University of Arizona Sarver Heart Center, Department of Medicine, Section of Cardiology, 1501 North Campbell Avenue, Tucson, AZ, 85724; e-mail: rmovahed@email.arizona.edu

Abstract

The prevalence of Brugada ECG in the United States is controversial and has not been studied in the western United States. The goal of this study is to evaluate the prevalence of Brugada syndrome appearing on ECGs in a large university hospital located in California. A total of 1348 ECGs performed at a university hospital in southern California in 1995 were randomly selected and reviewed for fulfilling 1 of the 3 types of Brugada criteria. Patients' baseline data were recorded, including age, sex, and race. Only 2 (0.14%) ECGs were consistent with 1 of the 3 types of Brugada syndrome. Both were classified as type 2. One of the patients was an Asian woman and the second was a Hispanic man. The mean age of study population was 52.7±16.2 years and consisted of 55% Caucasian patients followed by 20.8% Hispanic patients. The incidence of Brugada is rare among adult patients at a university hospital in the western United States.

Brugada syndrome was first described in a group of 8 patients in 1992.1 This entity was found on electrocardiography showing right bundle branch block, normal QT interval, and persistent ST-segment elevation in the right precordial leads in a structurally normal heart. This condition was also associated with sudden death. At that time, the cause was unknown. There are now 3 recognized patterns in the right precordial leads.2 Type 1 displays a coved ST-segment elevation >2 mm, followed by a negative T wave. Type 2 ST-segment elevation has a saddleback appearance with a high takeoff ST-segment elevation >2 mm, a trough ST elevation >1 mm, and either a positive or biphasic T wave. Type 3 demonstrates an ST segment with either a saddleback or coved appearance of <1 mm. The presence of type 1 is diagnostic of Brugada syndrome, while types 2 and 3 are not. The administration of a sodium channel blocker, vagotonic agents, or a febrile state can reveal the electrocardiographic (ECG) manifestations of Brugada syndrome in patients in whom it is concealed.

Brugada syndrome is an inherited disorder through an autosomal dominant mode. The only gene identified to date is SCN5A, which encodes for the α subunit of the cardiac sodium channel gene.3 The mutation causes a loss of function disorder. The SCN5A mutations are found in about 20% to 30% of Brugada syndrome cases.

The disease typically occurs in adulthood, with a reported age of sudden death of 41±15 years.2 The youngest reported patient was 2 days old and the oldest was 84 years old. Because the ECG pattern can be concealed, the true prevalence is unknown. More appears to be known about the prevalence in South East Asia, where it is thought to be more common. There are few published manuscripts evaluating the prevalence of Brugada syndrome in Western countries, and there are no prevalence studies in the population residing in the western United States. The purpose of this study was to define the prevalence of Brugada appearing on ECGs in a group of adult patients who obtained an ECG for unknown clinical reasons in a large university hospital located in the western United States.

Methods

A total of 1348 randomly selected ECGs performed at the University of California, Irvine, in 1995 were reviewed for fulfilling 1 of the 3 types of Brugada criteria. Baseline data on the patients were recorded, including age, sex, and race. These patients included both inpatients and outpatients. The reason for the ECG was not specified. Two cardiologists reviewed the ECGs. The prevalence of Brugada ECGs and demographics of the study population were studied. The ECGs were analyzed for type 1 (a coved ST-segment elevation >2 mm followed by a negative T wave), type 2 (ST-segment elevation has a saddleback appearance with a high takeoff ST-segment elevation >2 mm, a trough >1 mm ST elevation, and either a positive or biphasic T wave), or type 3 (ST-segment with either a saddleback or coved appearance of <1 mm). The appearance of the 3 types of Brugada ECGs is illustrated in Figure 1. This study was approved by the institutional review board.

Figure 1.

Three electrocardiograms (ECGs) showing Brugada syndrome. Arrows show the important features of Brugada ECGs. Type 1: a coved ST-segment elevation >2 mm followed by a negative T wave; type 2: ST-segment elevation has a saddleback appearance with a high takeoff ST-segment elevation >2 mm, a trough >1 mm ST elevation, and either a positive or biphasic T wave; and type 3: ST-segment with either a saddleback or coved appearance of <1 mm. Adapted with permission from Wilde et al.13

Results

Baseline data are displayed in the Table. There were a total of 1348 ECGs reviewed. The largest proportion of patients was Caucasian, totaling 55.4%, followed by Hispanic (20.8%), Asian (18.3%), and African American (2.9%). The sexes were equally represented, with 52.6% of men and 47.4% of women. The average age was 52.7±16.2 years (range, 18–99 years). Only 2 patients had ECGs that met criteria for Brugada type, of which both were of the type 2 variety. One patient was a 40-year-old Asian woman and the other was a 59-year-old Hispanic man. Both patients were still alive 10 years after the detection of a Brugada-type ECG. The ECGs of these 2 patients are illustrated in Figure 2.

Table Table.  Demographics of the Study Population
VariableBaseline DataElectrocardiograms Showing Brugada Syndrome No. (%)
 No.
Age, y52.7±16.213482 (0.15)
Race, %
 Caucasian55.47470
 Hispanic20.82811 (0.36)
 Asian18.32471 (0.40)
 African American2.9390
 Other2.5340
Sex, %
 Male52.67091 (0.14)
 Female47.46391 (0.16)
Figure 2.

Arrows show ST-segment elevation as a saddleback appearance with a high takeoff ST-segment elevation >2 mm in 2 patients with electrocardiograms (ECGs) showing type 2 Brugada ECG found in our study.

Discussion

Brugada-appearing ECGs appear to be a rarity in an adult population of patients in the western United States who had ECGs performed for clinical reasons. This could indicate a low prevalence of this condition in Caucasians, which made up 55.4% of the study population. Most prevalence studies are from Japan, where there is a wide range of prevalence of Brugada (0.006% to 0.15%).4–8 Prevalence studies in Western countries are consistent with our study. For example, the prevalence of saddleback-shape Brugada was found to be only 0.2% and classic Brugada was not found in any patients in a large hospital in New York City with a large African American and Hispanic population.9 The prevalence of Brugada ECG in a Finnish and French population was found to be 0.5% and 0.3%, respectively.10,11 A large population study in New Orleans found a prevalence of only 0.0006%.12 The rarity could be related to the selected population in the western United States or it may indicate that patients with Brugada, if not caught early in life, may have died at a young age.

Conclusions

The prevalence of Bruguda-appearing ECG appears to be very rare in the older adult population living in the western United States. The cause of this low prevalence is not known. It may be related to the population studied or the deadly nature of this disease in early life, preventing the detection of the disease in older adults.

Study Limitations

The study is limited in that it is strictly observational. There is the possibility that there are patients in the population who have concealed Brugada that escapes ECG detection. Furthermore, diagnosis of Brugada ECG is challenging and dynamic in nature, leading to possible underestimation of this disease. Our study population was selected from patients who were referred for ECG testing for unknown clinical reasons and not from a healthy asymptomatic population, which limits our results.

Ancillary