The left ventricular (LV) summit, a seemingly small anatomical region, plays a disproportionately significant role in the genesis of certain types of ventricular arrhythmias. Understanding its anatomy, the characteristic morphology of arrhythmias originating from this site, and the implications for ablation procedures is crucial for accurate diagnosis and effective treatment. This article provides a comprehensive overview of the LV summit, focusing on its anatomical location, the morphology of premature ventricular contractions (PVCs) originating from this region, the clinical presentation of LV summit PVCs and VT, and the strategies employed in catheter ablation procedures targeting this site.
LV Summit Anatomy:
The left ventricle, the heart's primary pumping chamber, possesses a complex three-dimensional structure. The LV summit, also referred to as the LV apex, is the most superior aspect of the LV, situated at the intersection of the anterior, lateral, and septal walls. Precise anatomical localization is challenging, and its definition can vary slightly depending on the imaging modality used (e.g., echocardiography, cardiac magnetic resonance imaging (CMR), or electroanatomical mapping). However, it's generally accepted as the most apical portion of the LV, often situated just below the mitral annulus and anterior papillary muscle, though sometimes extending slightly beyond this point. The precise location within the LV summit that gives rise to arrhythmias can vary, contributing to the challenges in ablation. The intricate network of Purkinje fibers in this region plays a critical role in the initiation and propagation of arrhythmias. These fibers, responsible for rapid conduction within the ventricular myocardium, can become susceptible to abnormal electrical activity, leading to the genesis of PVCs and, in some cases, ventricular tachycardia (VT). The proximity to the mitral valve and other cardiac structures requires careful consideration during ablation procedures.
LV Summit PVC Morphology:
Premature ventricular contractions (PVCs) originating from the LV summit exhibit characteristic electrocardiographic (ECG) features that aid in their identification. The most striking feature is the presence of either a right bundle branch block (RBBB) or left bundle branch block (LBBB) morphology. The specific morphology depends on the exact location within the LV summit and the direction of electrical propagation.
* RBBB morphology: In PVCs with RBBB morphology, the QRS complex is widened (>120 ms), with a characteristic rsR' pattern in lead V1 and a broad, notched S wave in the lateral leads (V5-V6). This pattern reflects the delayed activation of the right ventricle.
* LBBB morphology: Conversely, PVCs with LBBB morphology show a widened QRS complex, a monophasic R wave in V1, and a deep S wave in V6. This indicates delayed activation of the left ventricle.
The early precordial transition is another key characteristic. The transition zone, representing the shift from predominantly negative to predominantly positive QRS complexes, occurs between leads V1 and V3. This rapid transition is a consequence of the activation sequence originating from the LV summit. This contrasts with PVCs originating from other locations, which often display a more gradual transition zone. The combination of a bundle branch block morphology and an early transition zone strongly suggests an LV summit origin. However, it's important to note that these morphological features are not always definitive, and other diagnostic tools may be necessary for precise localization.
current url：https://cjowlp.e798c.com/all/lv-summit-12042