Differentiating the QRS Morphology of Posterior Fascicular Ventricular Tachycardia From Right Bundle Branch Block and Left Anterior Hemiblock Aberrancy

Diverse QRS morphology reflecting variations in lead placement for left bundle branch area pacing

AIMS

Left bundle branch area pacing (LBBAP) is a potential alternative to His bundle pacing. This study aimed to investigate the impact of different septal locations of pacing leads on the diversity of QRS morphology during non-selective LBBAP.

METHODS AND RESULTS

Non-selective LBBAP and left ventricular septal pacing (LVSP) were achieved in 50 and 21 patients with atrioventricular block, respectively. The electrophysiological properties of LBBAP and their relationship with the lead location were investigated. QRS morphology and axis showed broad variations during LBBAP. Echocardiography demonstrated a widespread distribution of LBBAP leads in the septum. During non-selective LBBAP, the qR-wave in lead V1 indicated that the primary location for pacing lead was the inferior septum (93%). The non-selective LBBAP lead was deployed deeper than the LVSP lead in the inferior septum. The Qr-wave in lead V1 with the inferior axis in aVF suggested pacing lead placement in the anterior septum. The penetration depth of the non-selective LBBAP lead in the anterior septum was significantly shallower than that in the inferior septum (72 ± 11 and 87 ± 8%, respectively). In lead V6, the deep S-wave indicated the time lag between the R-wave peak and the latest ventricular activation in the coronary sinus trunk, with pacemaker leads deployed closer to the left ventricular apex.

CONCLUSION

Different QRS morphologies and axes were linked to the location of the non-selective LBBAP lead in the septum. Various lead deployments are feasible for LBBAP, allowing diversity in the conduction system capture in patients with atrioventricular block.

Palpitations in a Young Woman With Breast Cancer

This case report describes a woman in her 20s who had a 1-day history of palpitations and dyspnea. Her medical history was significant for breast cancer.

Belhassen Tachycardia in a Pediatric Patient: A Simulation for Pediatric Emergency Medicine Fellows

Ventricular tachycardia in pediatric emergency department patients is a high-risk, low-frequency event well suited for education through simulation. This technical report describes a simulation-based curriculum for Pediatric Emergency Medicine fellows and senior residents involving the evaluation and management of a 10-year-old female presenting with palpitations who is ultimately diagnosed with Belhassen tachycardia. The curriculum highlights the features that differentiate Belhassen tachycardia (idiopathic left posterior fascicular ventricular tachycardia) from supraventricular or other tachycardias, building upon foundational pediatric resuscitation skills and Pediatric Advanced Life Support (PALS) algorithms for advanced learners.

Magnetic Resonance Features of a Recent Catheter Ablation of Left Posterior Fascicular Ventricular Tachycardia

A 71-year-old male patient with a past medical history of hypertension, hyperlipidemia, and chronic kidney disease stage II presented with a complaint of intermittent palpitations for three months and was found to have wide complex tachycardia on the electrocardiogram (ECG). The patient was given adenosine and amiodarone, following which he underwent synchronized cardioversion at 150 Joules followed by 200 Joules without successful conversion. He was subsequently initiated on lidocaine drip at the rate of 1 to 4 mg/minute to maintain adequate rhythm control, which converted him to sinus rhythm and relieved his symptoms. An eventual assessment with an electrophysiology study identified the presence of incessant left ventricular tachycardia (VT). The mechanism was confirmed to be left posterior fascicular ventricular tachycardia (LPF-VT). Successful mapping and ablation for the LPF-VT were achieved. Post-procedure cardiac MRI showed two small areas of near-transmural delayed enhancement. These areas are associated with nulled areas in the inferolateral wall at the left posterior His-Purkinje fascicle. This case highlights fascicular VT as a separate clinical entity, with its characteristic ECG features and acute MRI features after ablation.

Differential Diagnosis of Wide QRS Tachycardias

In this article, the authors discuss the differential diagnostic methods used in clinical practice to identify types of wide QRS tachycardias (QRS duration >120 ms). A correct diagnosis is critical to management, as misdiagnosis and the administration of drugs usually utilised for supraventricular tachycardia can be harmful for patients with ventricular tachycardia.

Right bundle branch block-type wide QRS complex tachycardia with a reversed R/S complex in lead V6: Development and validation of electrocardiographic differentiation criteria

BACKGROUND

Differentiation of supraventricular tachycardia (SVT) with a right bundle branch block (RBBB) pattern from ventricular tachycardia (VT) is difficult, particularly when the R/S ratio in lead V₆ is below 1.0.

OBJECTIVE

We sought to investigate the electrocardiographic criteria for distinguishing between these arrhythmias.

METHODS

We investigated electrocardiographic parameters from 111 consecutive patients who had RBBB pattern wide QRS complex tachycardia with a reversed R/S ratio in lead V₆ (72 VTs, 39 SVTs). Diagnostic criteria from the previous algorithms were compared with our new criterion, the RS/QRS ratio, which was defined as the ratio of the interval from the onset of the QRS complex to the nadir of the S wave, divided by the QRS width in lead V₆. The RS/QRS ratio was further tested in a prospective population (31 fascicular VTs, 29 SVTs).

RESULTS

The diagnostic accuracy of previous criteria (Brugada algorithm, Vereckei algorithm, and R-wave peak time criterion) was only modest. However, the RS/QRS ratio in lead V₆ was significantly lower in SVT than in VT (0.36 ± 0.04 vs 0.50 ± 0.08; P < .001). A cutoff value of the RS/QRS ratio >0.41 differentiated VT from SVT with a high diagnostic accuracy (sensitivity 97.2%; specificity 89.7%). When tested in a prospective population with fascicular VT, the diagnostic accuracy of the criteria was maintained (sensitivity 90.3%; specificity 86.2%).

CONCLUSION

The RS/QRS ratio >0.41 in lead V₆ is a simple and reliable index for distinguishing VT from SVT in RBBB pattern wide QRS complex tachycardia with a reversed R/S complex in lead V₆. This criterion was particularly useful for the differential diagnosis of fascicular VT from RBBB pattern SVT.

Prognostic impact of right bundle branch block in hospitalized patients with idiopathic dilated cardiomyopathy: a single-center cohort study

Objective

Idiopathic dilated cardiomyopathy (IDCM) is a primary myocardial disease resulting in symptoms of heart failure. Right bundle branch block (RBBB) is associated with increased cardiovascular risk and all-cause mortality. Therefore, the present study was performed to identify the prognostic impact of RBBB in patients with IDCM.

Methods

In total, 165 hospitalized patients with IDCM were evaluated. Receiver operating characteristic curve analysis was used to determine the cutoff point, and Cox regression was used to assess risk factors.

Results

After a median follow-up of 73.1 months (interquartile range, 36.1–88.7 months), 59 (35.8%) patients had died. All-cause mortality was significantly higher in patients with than without RBBB (log-rank χ2 = 9.400), P<0.05. Significant independent predictors of all-cause mortality in patients with IDCM were RBBB (hazard ratio, 2.898; 95% confidence interval, 1.201–6.995) and the left ventricular end-diastolic dimension (LVEDD) (hazard ratio, 1.034; 95% confidence interval, 1.004–1.066) at admission. Patients with RBBB and an LVEDD of ≥63 mm had the highest mortality (log-rank χ2 = 14.854), P<0.05.

Conclusion

RBBB was an independent predictor of all-cause mortality, and the combination of RBBB and LVEDD provided more clinically relevant information than RBBB alone for assessing the risk of all-cause mortality in patients with IDCM.

New Insights on Verapamil-Sensitive Idiopathic Left Fascicular Tachycardia

Verapamil-sensitive left fascicular monomorphic ventricular tachycardia (LF-VT) was first described ~4 decades ago. Our knowledge regarding this arrhythmia is evolving continuously. The current review aims to highlight up to date aspects of this arrhythmia focusing on its ECG recognition, new considerations of the reentrant circuit, ablation targets in inducible and non-inducible patients and the approach to LF-VT with multiform morphology.