Article review by Dr Anthony Branco
- In patients without structural heart disease, is the presence of J-point elevation a marker for arrhythmic risk?
- Does the presence of J-point elevation, either with or without ST-segment elevation, in leads other than V1 to V3, exist as an innocent finding, or is this a marker associated with a history of VF in patients without structural heart disease?
- Is J-point elevation more prevalent in younger individuals?
Although J-point elevation is found more frequently among patients with idiopathic VF than among healthy controls, its presence should not be interpreted as a marker for increased risk when incidentally detected via screening.
- J-point elevation is considered an innocent finding among healthy young individuals, but recently this finding has increasingly being associated with occurrence of idiopathic VF
- this study aimed to define whether the presence of J-point elevation is a marker of arrhythmic risk
- EKGs of 45 patients with idiopathic VF were compared with those of 124 healthy controls (age/gender matched), as well as to those second control group of young athletes
- J-point elevation in 42% of VF patients and 13% of matched controls; with J-point elevation ≥0.1 mV cutoff, 31% vs. 9% (p ≧002); in comparison, 22% of “young athletes” had J-point elevation
- Could not determine a cut-off for J-point elevation to reliably distinguish between idiopathic VF patients and control
- Case-control study
- VF group (N=45)
- 14 – 69 years, mean age 38 ± 15 years; 71% male
- clinical diagnosis of idiopathic VF
- diagnosed by exclusion in cardiac arrest survivors when a complete work-up for alternative etiologies was negative
- diagnosed in patients with syncope or cardiac arrest when spontaneous polymorphic VT/VF
- no patient with Southeast Asian heritage, family hx of ventricular arrhythmia, related to one another
- 2 patients eventually dx with Brugada, despite lack of Brugada pattern at baseline
- Match control (N=124)
- Age: 24 to 70
- Selected from 3,500 adults participants from Tel Aviv medical screening program in 2007
- Inclusion criteria
- “no history of syncope” and “no history of heart disease”
- ECG was reported as normal (J-point elevation would not be considered abnormal in this screening program)
- Screening did not reveal heart disease.
- for each VF patient, 3 control subjects selected to match age (±2 years) and gender
- younger control subjects selected from healthy medical personnel or their offspring
- 11 controls excluded
- Young athletes (N=121)
- noncompetitive athletes randomly selected from pre-participation medical screening program
- 17 – 19 years old
- 11 excluded
- EKGs grade by consensus (3 investigators); blinded; assessed for “J-point elevation” or “J waves”, “slurring”, as well as for the height of the J-point and/or ST-segment elevation from the baseline
- J-point elevation / J waves were defined as positive “hump-like” deflections immediately after a positive QRS complex at the onset of the ST-segment
- transition from the QRS complex to the ST-segment was defined as “slurred” when the R-wave gradually became the ST-segment with upright concavity and as J-point elevation when a sharp and well-defined hump was noted immediately after the R-wave
- J-point elevation more common among patients with idiopathic VF than among matched-controls (42% vs. 13%, p = 0.001).
- In particular, true in inferior leads (27% vs. 8%, p = 0.006) and in leads I to aVL (13% vs. 1%, p = 0.009).
- In contrast, J-point elevation in V4to V6 occurred with equal frequency between patients and matched-controls (6.7% vs. 7.3%, p = 0.86).
- J-point elevation >0.05 mV (or >0.1 mV) also more frequent among idiopathic VF patients
- When J-point elevation present, it tended to be higher for VF patients than among controls; difference did not reach statistical significance (0.14 vs. 0.09 mV, p = 0.099).
- Investigators could not identify a cut-off value of J-point elevation to distinguish VF patients from controls
- QRS slurring (slurring of the descending limb of the R wave) was commonly among both groups (31% vs. 24%, p = 0.4).
- presence of “slurring” was not useful for identifying VF patients regardless of the lead
- “QRS slurring and/or J-point elevation” did not add diagnostic value to J-point elevation alone
- ST-segment elevation was commonly observed among VF patients and controls (33% vs. 24%, p = 0.35).
- presence of ST-segment elevation was not useful for identifying patients with idiopathic VF regardless of its magnitude or the leads where it was observed
- the combination of “ST-segment elevation and J-point elevation” or the presence of “ST-segment elevation or J-point elevation” did not add diagnostic value to the presence of J-point elevation alone
- Within each of the 3 patient groups, male subjects had J waves more often than female subjects
- difference remained significant even after correcting for gender-related differences in heart rate
- Particularly strong when only large J waves (>0.1 mV) were counted
- Comparison with young athletes showed two key findings
- the frequency of J waves among young athletes was intermediate between that observed among healthy adults and that observed in the VF group
- the distribution of J-point elevation differed between patient groups
- healthy control subjects: leads V4to V6 and/or in the inferior leads
- idiopathic VF patients: mainly in the inferior leads, less commonly in I to aVL and least commonly in leads V4to V6
- From this study, the probability J-point elevation is 0.42 for VF patients and 0.13 for controls.
- applying Bayesian formula of conditional probabilities: finding a J-wave in the ECG of an individual in the 35 to 45 years age range increases the chances of having idiopathic VF from 3.4 of 100,000 individuals to only 11 of 100,000
- estimated risk for idiopathic VF in the general population (age 35 to 45 years), is roughly 3.4 of 100,000 individuals