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 ß-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 (ß-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 ß-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.

Risks of inappropriate use of an algorithm favouring intrinsic conduction.

An 80-year-old woman received a dual chamber pacemaker (Boston Scientific Accolade MRI DR) for pre-syncopal episodes associated with transient II-degree atrioventricular block type 1 and 2:1, recorded in 24-h Holter monitoring. Due to residual AV conduction with I-degree AV block, the pacemaker was set with the RYTHMIQ® algorithm, in order to reduce inappropriate ventricular pacing. A month later the patient started to complain of severe asthenia and bradycardia (46-48 bpm). Telemetry-supported pacemaker control revealed III-degree AV block with junctional escape rhythm, unmasking missed switch of RYTHMIQ® algorithm.

Kounis syndrome in a patient with multivessel coronary artery disease and DRESS.

A 68-year-old man was admitted with ST-elevation myocardial infarction and intense rash. He was diagnosed with type 2 Kounis syndrome elicited by drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome and received complete revascularization with percutaneous coronary intervention. This case highlights the complex pathophysiology of acute coronary syndrome, and the elusive link between coronary occlusion and ST-segment deviations at ECG.