The r'-Wave Algorithm: A New Diagnostic Tool to Predict the Diagnosis of Brugada Syndrome after a Sodium Channel Blocker Provocation Test

A diagnosis of Brugada syndrome (BrS) is based on the presence of a type 1 electrocardiogram (ECG) pattern, either spontaneously or after a Sodium Channel Blocker Provocation Test (SCBPT). Several ECG criteria have been evaluated as predictors of a positive SCBPT, such as the β-angle, the α-angle, the duration of the base of the triangle at 5 mm from the r'-wave (DBT- 5 mm), the duration of the base of the triangle at the isoelectric line (DBT- iso), and the triangle base/height ratio. The aim of our study was to test all previously proposed ECG criteria in a large cohort study and to evaluate an r'-wave algorithm for predicting a BrS diagnosis after an SCBPT. We enrolled all patients who consecutively underwent SCBPT using flecainide from January 2010 to December 2015 in the test cohort and from January 2016 to December 2021 in the validation cohort. We included the ECG criteria with the best diagnostic accuracy in relation to the test cohort in the development of the r'-wave algorithm (β-angle, α-angle, DBT- 5 mm, and DBT- iso.) Of the total of 395 patients enrolled, 72.4% were male and the average age was 44.7 ± 13.5 years. Following the SCBPTs, 24.1% of patients (n = 95) were positive and 75.9% (n = 300) were negative. ROC analysis of the validation cohort showed that the AUC of the r'-wave algorithm (AUC: 0.92; CI 0.85-0.99) was significantly better than the AUC of the β-angle (AUC: 0.82; 95% CI 0.71-0.92), the α-angle (AUC: 0.77; 95% CI 0.66-0.90), the DBT- 5 mm (AUC: 0.75; 95% CI 0.64-0.87), the DBT- iso (AUC: 0.79; 95% CI 0.67-0.91), and the triangle base/height (AUC: 0.61; 95% CI 0.48-0.75) (p < 0.001), making it the best predictor of a BrS diagnosis after an SCBPT. The r'-wave algorithm with a cut-off value of ≥2 showed a sensitivity of 90% and a specificity of 83%. In our study, the r'-wave algorithm was proved to have the best diagnostic accuracy, compared with single electrocardiographic criteria, in predicting the diagnosis of BrS after provocative testing with flecainide.

The β-angle can help guide clinical decisions in the diagnostic work-up of patients suspected of Brugada syndrome: a validation study of the β-angle in determining the outcome of a sodium channel provocation test

AIMS

In patients with Brugada syndrome (BrS) but without spontaneous Type-1 electrocardiogram, several electrocardiographic characteristics have been studied, including the β-angle. Previous studies suggested that the β-angle might be useful in distinguishing BrS-patients from patients with only suggestive repolarization patterns without performing sodium channel blocker provocation testing. In this study, we aimed to determine the diagnostic value of the β-angle in patients suspected of BrS.

METHODS AND RESULTS

A large cohort (n = 1430) of consecutive patients who underwent provocation testing was evaluated. β-angles were measured in leads V1, V2, and their corresponding positions over the second and third intercostal space. Receiver-operating characteristic curves were constructed and the diagnostic accuracy of previously reported β-angle cut-offs were calculated and evaluated. The importance of the β-angle for predicting the provocation test outcome was determined using a prediction model constructed with logistic regression. The optimum β-angle cut-off in our cohort for ruling out a positive provocation test was 15°; sensitivities were 80-98% and negative predictive values were 79-96% among the right precordial leads. Previously reported β-angle cut-offs performed less well, indicated by lower Youden indices. In the optimism-corrected prediction model [C-statistic: 0.78 (95% CI: 0.75-0.81)], the β-angle had large value (Z-score: 2.1-10.3) and aided construction of a nomogram to predict test outcome.

CONCLUSION

To predict the outcome of provocation testing for BrS, the β-angle alone does not demonstrate strong diagnostic characteristics. However, the β-angle is an important variable to predict provocation test outcome and thus has added value.

The relationship between glenoid inclination and instability following primary reverse shoulder arthroplasty

PURPOSE

Despite advances in implant design and surgical technique, instability remains the most common early complication and reason for early revision after reverse shoulder arthroplasty (RSA). The purpose of this study is to evaluate the glenoid implant inclination, as measured by the β-angle, as an independent risk factor for instability after primary RSA.

METHODS

A retrospective case-control study was conducted matching cases with instability after primary RSA using a single implant to controls without instability. Controls were matched to age, sex, body mass index, and baseplate type (1:3 ratio of cases to controls). The preoperative, postoperative, and the change in pre- to postoperative glenoid inclination (β-angle) were compared between groups.

RESULTS

Thirty-four cases (mean age, 66.2 years) were matched to 102 controls (mean age, 67.0 years). There was a wide range of postoperative (63° to 100°) and pre- to postoperative change (-16.5° to +30.5°) in β-angles collectively. There was no significant difference in the postoperative β-angle (mean, 80.8° vs. 82.7°, P = .19) or the change in β-angle (mean, +1.7° vs. +3.4°, P = .35) between cases and controls, respectively. Regression analysis demonstrated no increased odds of instability with the postoperative β-angle, odds ratio 0.965 (confidence interval [CI] = 0.916-1.02, P = .19). Likewise, for the preoperative to postoperative change in β-angle, there was no significantly increased odds of instability, odds ratio 0.978 (CI = 0.934-1.03, P = .35). Finally, there was no difference in risk of instability in patients whose implant positioning resulted in a net superior increase in inclination, relative risk 0.85 (95% CI = 0.46-1.56, P = .28).

CONCLUSIONS

Neither the final prosthetic glenoid inclination nor the change in glenoid inclination, as measured by the β-angle, significantly influences the risk of prosthetic instability after primary RSA.

Comparison of glenoid inclination angle using different clinical imaging modalities

BACKGROUND

The β-angle, formed by the intersection of a line on the floor of the supraspinatus fossa and glenoid fossa line, has been described as a reliable measurement tool in the clinical setting to analyze glenoid inclination on the anteroposterior (AP) view of the shoulder. The purpose of this study was to compare the accuracy of the β-angle measurement using different imaging modalities with a validated 3-dimensional (3D) software tool.

MATERIALS AND METHODS

The β-angle was measured on AP radiographs, unformatted 2-dimensional (2D) computed tomography (CT) scan, and reformatted 2D CT scan in the scapular plane for 51 shoulders of 49 patients undergoing primary total shoulder arthroplasty. Comparison to the glenoid inclination angle calculated by the 3D software was performed.

RESULTS

The β-angle measured on reformatted CT scan was found to be the most accurate measurement method, with a mean difference of 1° (standard deviation [SD], 0.5°) with respect to 3D measurement. On AP radiographs, the β-angle was not as accurate, with a mean difference of 3° (SD, 0.7°; P < .006). The β-angle on unformatted 2D CT scan was not a reliable method to measure glenoid inclination, with a mean difference of 10° (SD, 0.9°; P < .0001).

CONCLUSION

The β-angle measured with 2D CT scan formatted in the scapular plane was the most accurate method for measuring glenoid inclination. The β-angle on the AP radiograph is less accurate and reliable. Measurement of the β-angle on an unformatted 2D CT scan is not an acceptable method to determine glenoid inclination.