Prevalence of asymptomatic ST segment elevation in right precordial leads with right bundle branch block (Brugada-type ST shift) among the general Japanese population

Abstract

Objective: To examine the modality and morbidity of asymptomatic ST segment elevation in leads V1 to V3 with right bundle branch block (Brugada-type ST shift).

Methods: 8612 Japanese subjects (5987 men and 2625 women, mean age 49.2 years) who underwent a health check up in 1997 were investigated. Those with Brugada-type ST shift underwent the following further examinations over a two year period after the initial check up: ECG, echocardiogram, 24 hour Holter monitoring, treadmill exercise testing, signal averaged ECG, and slow kinetic sodium channel blocker loading test (cibenzoline, 1.4 mg/kg).

Results: Asymptomatic Brugada-type ST shift was found in 12 of 8612 (0.14%) subjects. Eleven of these 12 subjects were followed up. Follow up ECG exhibited persistent Brugada-type ST shift in seven of 11 (63.6%) subjects. ST shift was transformed from a saddle back to a coved type in three subjects. None of the subjects had morphological abnormalities or abnormal tachyarrhythmias. Positive late potentials were found in seven of 11 (63.6%) subjects. Augmentation of ST shift was shown by both submaximal exercise and drug administration in one of the 11 subjects (9.1%).

Conclusions: Asymptomatic subjects with Brugada-type ST shift were not unusual, at a rate of 0.14% in the general Japanese population. Almost all of the subjects had some abnormalities in non-invasive secondary examinations. Additional and prospective studies are needed to confirm the clinical significance and the prognosis of asymptomatic Brugada-type ST shift.

Figure 1

Bar graph showing age distribution of 8612 Japanese subjects in this study. Open and closed bars represent the male and female population in each generation, respectively. The number at the top of each bar is the percentage of the total population. Open and closed circles represent the subjects with saddle back and coved type ST shift, respectively. The number at the top of each circle is the percentage of the population by generation.

Figure 2

Diagnostic flow chart of Brugada-type ST shift in 8612 Japanese subjects. Values are the number (the percentage of the total population). RBBB; right bundle branch block.

Figure 3

Serial transformation of Brugada-type ST shift in follow up ECG. Persistent ST shift was confirmed in seven (63.6%) of 11 subjects followed up. However, Brugada-type ST shift changed from the saddle back type into the coved type in three subjects.

Figure 4

Representative cases of serial transformation. (A) Transformation of the coved type to no Brugada-type ST shift without right bundle branch block. (B) Transformation of the saddle back type to no Brugada-type ST shift without right bundle branch block. Transformation of the saddle back type to the coved type. (D) Transformation of the saddle back type to the coved type with prolonged QRS duration.