Complex Atrial Substrate in Hypertrophic Cardiomyopathy Presenting as Right Pulmonary Vein–Related Atypical Atrial Flutter

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  Figure 1. A: Incessant atrial flutter (AFL) with a tachycardia cycle length (TCL) of 240 ms was observed. The flutter wave morphology suggested a right inferior pulmonary vein origin, characterized by positive deflections in leads I, aVL, and II. biphasic waves in leads III and aVF, and predominantly positive waves in lead V1 across the precordial leads, along with low amplitude in lead II. B: Cardiovascular magnetic resonance (CMR) imaging demonstrates left ventricular hypertrophy and mild pericardial effusions on the cine image, elevated extracellular volume (ECV) on ECV mapping, and prominent patchy late gadolinium enhancement (LGE) within the left ventricle (LV) (red arrowheads). C: LGE is identified at the interatrial septum (red arrows), and the right inferior pulmonary vein (RIPV) (orange arrows) extending to the carina as depicted on the 3-dimensional left atrial (LA) LGE-CMR model. D: Local fractionated electrograms (EGMs) at the septal region of the right atrium (RA) are identified. The cycle length histogram of the RA during AFL demonstrates incomplete mapping coverage, suggesting that the reentrant circuit is not confined to the RA. E–G: LA electroanatomic mapping (EAM)…